Final Report Summary - LIMPID (Nanocomposite materials for photocatalytic degradation of pollutants)
Executive Summary:
"Nanocomposite materials for photocatalytic degradation of pollutants", LIMPID, has been a collaborative RTD European Project funded under NMP.2012.2.2-6 Photocatalytic materials for depollution.
LIMPID consortium has been designed to combine leading industrial partners in the field of inorganic nanomaterials and catalysts (Johnson Matthey), water purification systems (XYLEM SERV. and AQUAKIMIA), new polymer (SpPI, Solvay Specialty Polymers Italia S.p.A.) and photocatalytic construction materials (ACCIONA) with research groups experts on polymers (UPV/EHU), inorganic nanoparticles (CNR-IPCF, CU), hybrid coatings (ISC Fraunhofer), photocatalytic materials (EPFL, CNR IPCF), catalytic processes (CU, CNR IPCF, EPFL) and water purification technologies (CNR-IRSA, MGU, UTM), from Europe (8 partners), ASEAN Countries (3 partners) and Canada (1 partner). The consortium includes 8 partners from European Institutions and 4 partners from third countries, namely a partner from Canada and 3 from ASEAN countries, with specific expertise in degradation processes of organic pollutants, membrane technology for water treatments (UTM; CU and AQUAKIMIA), 5 leading industrial partners from sectors differently related to depollution applications (JM, materials, SpPI, polymers XYLEM SERV., water treatment, ACCIONA, building and infrastructures) including a leader water purification provider in South East Asian countries (AQUAKIMIA).
The proposal aims to foster an integrated approach to R&D focused on the development of photocatalytic materials, for environmental applications.
The main goal of LIMPID has been to develop fundamental materials and technologies based on the synergistic combination of different types of nanoparticles (NPs) into a polymer host to generate innovative nanocomposites, thus originating multifunctional nanostructured materials with enhanced photocatalytic properties, promptly processable, that can be applied onto a variety of supports, also unconventional in nature, integrated in photocatalytic reactors, photocatalytic filtration membranes, bactericide coatings, self-cleaning surfaces, active both in air and in water. At the same time such photocatalytic nanocomposites can prevent NP leaching into water and air phase, limit the potential threat associated to dispersion of NPs into the environment.
The prepared nanomaterials have been thoroughly characterized, their photocatalytic properties tested according to ISO standard and then fabricated as self-cleaning coatings, photocatalytic membrane reactors, UV e vis photocatalytic reactors, bactericidal films, able to remove pollutants from air and water matrix. Among the pollutants particular attention has been devoted to classes of compounds like contaminant of emerging concern, like pharmaceuticals and personal care products (PCPP) and endocrine disrupting chemicals (EDC), affecting both EU and ASEAN countries.
Within LIMPID an excellent cooperation between the EU, ASEAN and Canadian research groups and companies has been achieved, being all the beneficiaries working together, by exchanging materials, expertise and knowledge to design and develop innovative nanocomposite based materials and technologies to be used for purifying water and air.
A significant network of collaborations and exchanges between the different beneficiary has been reached and the intra- and inter-workpackage collaborations have been crucially exploited for the synthesis and the characterization of nanocomposites, their integration in the photocatalytic systems and devices for degradation of pollutants in water, for NOx and VOCs removal and for bacterial inactivation. The collaborative work and its critical evaluation have been crucial for the selection of suitable materials to be further developed in the last year of the project and then implemented in the proof of principle applications, for reactor set up and toxicity test evaluation.
Safety and risk assessment issues have been also taken into account, to watch out any possible health impact of the nanomaterial exposure.
LIMPID has generated knowledge and innovations, which resulted in 36 peer reviews papers, also on high impact journal in the fields of functional materials catalysis and environment, a large number of conference contributions and invited talks, 4 patents filed or under submission. Such a relevant output points out the fundamental impact of the LIMPID activities in the relevant scientific communities, but also their technological potential. Significant dissemination activities have been performed within the project, including a project website (http://www.limpid-fp7.eu/) which has been used also as one of the main vehicles of dissemination and interaction with the public seeking information on the project topics, workshops, project fliers, conference posters and presentations of LIMPID, interaction with other projects and platforms, training of students with projects on LIMPID topics.
Particularly relevant have been the two dissemination workshops held in Asia, namely
- "Workshop on Nanomaterials for photocatalytic depollution" that has been held in the frame of the ASEAN-EU STI Days in Bangkok (Thailand) on 22-23 January 2014.
- “International Workshop on Nanocomposite Materials for Photocatalytic Degradation of Pollutants: Advanced Opportunities for New Applications” in Kuala Lumpur (Malaysia) on 12 November 2015.
Project Context and Objectives:
In a time of increasing concern on environmental pollution, an enormous attention is paid to strategies and technologies able to clean and purify air and water.
Indeed in the last decades, with the worldwide growing population and the consequent growing demand of clean water resources, mankind is going to face serious issues regarding the decontamination of water from a series of pollutants. An even heavier situation has already been tackled with the air pollution. The development of cost-effective and stable materials, methods and technology for providing the fresh water in adequate amounts and clean air is a critical need for environmental protection.
Nanotechnology has been considered effective in solving water problems related to quality and quantity, however there are many aspects of nanotechnology that need to be addressed to solve the multiple problems of water and air quality in order to ensure the environmental stability.
The recent advances in nanoscale science and engineering suggest that several problems involving water and air quality could greatly benefit by using nanocatalysts, bioactive NPs, nanostructured catalytic membranes and NP enhanced filtration, among other products and processes resulting from the development of nanotechnology. Nanoscience developments facilitate a number of emerging technologies that could work to threat contaminants and develop products able to reduce concentration of toxic compounds, thus assisting the attainment of water quality standards and health advisories.
Improvement in performance has been strongly correlated to advances in nanotechnology. It is expected that both the technological and economic importance of photocatalytic materials can increase considerably in the future.
In this perspective inorganic-organic hybrid materials are considered to play a major role in the development of future oriented advanced functional materials. The LIMPID project has intended to contribute to such a development, supporting the research in functional materials by the opportunity to create new smart materials from the inorganic and organic components, and the possibility of their assembly using nanostructured phases.
The fundamental idea underlying LIMPID project has been to design, fabricate and exploit nanocomposite materials obtained by synergistically combining different types of catalytically active NPs within both organic and hybrid polymer, for (photo)catalytic degradation of pollutants and bacteria, in air or in aqueous solution. Such a unique synergistic combination of different catalytically active NPs, with peculiar size dependent optoelectronic and catalytic properties, within highly processable host polymers, provides a flexible and versatile tool to access an innovative class of multifunctional materials with superior photocatalytic properties in the UV and visible range.
While the concept of single component nanocomposites, including one particular type of inorganic oxide NPs such as TiO2, has been already reported and used in photocatalytic activities, LIMPID target is to go a step further, including in one nanocomposite different types of NPs. In particular, candidate NPs are combinations between semiconductor oxides, also doped in nature, and metals, whereas magnetic NPs or carbon nanotubes (CNTs) have been considered for bringing up further active surface area and include additional functionalities for recovery of photocatalysts.
At the same time the innovation brought by nanocomposite formulation is intended to prevent any NP leaching into water and air phase, thus strongly limiting the potential threat associated to dispersion of NPs into the environment.
In the perspective of resource consumption and reduced material usage, the development and application of multifunctional recoverable catalytic materials and coatings, active also under visible light irradiation, and, hence capable of utilizing a large portion of solar light, can represent a major advance.
These proposed ingenious combinations of functional oxides, metallic NPs and CNT is intended to open new vistas of material properties and new applications, able to generate a large potential both in EU and ASEAN countries. The use of such host polymers can envisage a large potential due to the multifunctionality deriving by the combination of diverse catalytically active NPs, but also due to their prompt processability, with film and coating forming properties.
Indeed nanocomposite materials could be in principle fabricated in products to use in catalytic degradation of pollutants in water and air, such as porous membranes for water treatment or re-usable photocatalytically active micro-particles, or in pollutant degradation reactors, and coating or paint to be deposited onto large surfaces, such as walls of buildings and facades.
In this perspective a careful selection of the host polymer has been fundamental and has represented one of the main challenges of this project. In fact, the host polymer to incorporate photocatalytic nanomaterials needs to sustain photocatalytic processes, as they can destroy any organic materials, including the organic matrix in which the NPs are embedded.
Therefore two classes of host materials have been identified, namely fluorinated polymers and organic-inorganic hybrid polymers, both can act as a medium dispersing NP and, at the same time, enable effective interactions with the catalytic substrate.
The use of these materials, as NP host, can burst the potential of such a combination of catalytically active NPs and can play a significant role for their integration in photocatalytic reactors, photocatalytic filtration membrane, bactericide coating, photocatalytic coating, self-cleaning surface, as it can enable fabrication of coatings, to be applied onto a variety of supports, also unconventional ones, as well as self-standing structures, active both in air and in water.
In addition, such integration ability can be applied in the fabrication of recoverable beads, based on magnetic NPs, able to further facilitate their recovery and provide alternative processing routes. Indeed magnetic beads coated with photocatalytic materials are easily recoverable after liquid phase photocatalytic reaction, by means of the magnetic separation, facilitating the practical running of pollutant clean-up process.
The nanocomposite materials obtained within LIMPID have been first bench-marked against reference and tested for the photocatalytic degradation of organic pollutants both in aqueous solutions and in gas phase. A careful material selection has been needed, in order to identify the most promising and most promptly accessible, in terms of scalability, materials.
UV and vis photocatalytic reactors and photocatalytic membrane reactors, with specific design, have been fabricated by using the most effective nanocomposites.
It is worth to point out that a large number of organic compounds is typically detected in completely untreated as well as pretreated wastewater. It is well known, in fact, that conventional wastewater treatment processes are not effective in the removal of pharmaceuticals, illicit drugs and other chemicals and that wastewater discharges in receiving water streams significantly contribute to the presence of contaminants of emerging concern in sources of drinking water
Therefore for the LIMPID activities a representative selection of organic pollutants designated among relevant classes of pollutants, including pharmaceuticals and personal care products (PPCP) and endocrine disrupting chemicals (EDC) and in general pollutants relevant both for European and ASEAN countries, have been investigated in order to test the performances of newly developed photocatalysts assisted degradation process. The degradation paths, the formation of by-products, their influence on the overall purification process have represented a relevant task in the project. The performance of the photoactive nanocomposite catalysts developed have been tested in both synthetic and real wastewaters, along with information obtained about the relative toxicity of the treated wastewaters, have been used to determine the presence of transformation products of greater concern which will then have undergone to different toxicity tests, at increasing trophic level.
The obtained nanocomposites have been also fabricated as film and coating products able to address needs of innovative façade building units. Photocatalytic performance of these coatings against classic organic pollutants such as VOCs, and NOx have been tested aiming at performance that can compete with the currently available commercial photocatalytic paints.
Films obtained by sputtering or co-sputtering TiO2, oxides and metal, with different composition and deposition conditions, onto polymers and textiles have been investigated on Escherichia coli (E. coli) for bacterial inactivation, both under UV and under low intensity simulated sunlight. This class of coating presents a large applicability, due to the their stability, the scalability of the sputtering process along with the great potential in answering issues related to infections in different critical environments, including hospitals.
In addition, the mechanisms behind the enhanced efficiency of the prepared materials, the scaling up of their preparation procedures, the toxicity of the investigated photocatalytic processes have been investigated and elucidated. Finally, the safety assessment on the nanomaterials synthesis, processing and usage, and the technological research towards end users applications have been carried out.
Within LIMPID project, EU and ASEAN research groups and companies have been working together to design and develop innovative nanocomposite materials and technologies, demonstrating a well-balanced scientific and technological cooperation in the consortium, where the roles of each beneficiary have been effective in covering the complete chain from materials, including nanomaterial synthesis, host polymer identification and investigation, and finally their integration in multifunctional nanocomposite photocatalytic structures.
As an essential part of the project, the industrial beneficiaries, along with the End User Advisory Board have played a crucial role to address the research efforts according to the market needs and/or opportunities. The industrial beneficiaries have been especially involved in the synthesis, up-scaling developments, reactors design, test and applications.
Among the main LIMPID scientific and technical objectives, it is worthwhile to highlight the following:
-Synthesis of metal oxide and metal doped oxide NPs and NCs with control on size, crystallinity, composition and shape by means of different routes, namely colloidal chemistry, solvothermal method and flame spray pyrolysis
- Synthesis of metal nanoparticles, magnetic oxides and multifunctional heterostructures
- Functionalization, surface engineering and characterization of the various nanomaterials especially inorganic oxide and NPs, such as TiO2, to make them suitable for integration in polymer matrices
- Structural, optical and surface characterization of nano-catalysts by means of spectroscopic, structural and microscopy techniques
- Photocatalytic tests on the prepared nanomaterials for degradation processes both in air and in aqueous matrix by using model molecules and their catalytic performances evaluated against commercial standard photocatalysts
- Synthesis of inorganic-organic hybrid coating materials by sol-gel technology
- Implementation of functional groups to facilitate adsorption of pollutants and to increase compatibility to functional nanoparticles
- Characterization of the coating materials
- Synthesis of polymer latexes based on perfluorinated polymers
- Polymers for membranes fabrication
- Optimization of nanoparticle incorporation and dispersion into hybrid matrices
- Sol-gel coating preparation and testing
- Preparation of nanocomposite photocatalytic paints
- Test of nanocomposite stability against ageing and photodegradation
- Fabrication of nanocomposite based membranes
- Fabrication of catalytically active magnetic beads
- Chemical and physical characterization of the photocatalytic nanocomposites
- Photocatalytic degradation of selected pollutants among PPCPs in wastewater
- Photocatalytic degradation of endocrine disruptor compounds (EDCs) in wastewater using PVDF/TiO2
- Test of novel photoactive nanocomposite membrane for degradation of EDCs in wastewater
- Investigation of the pollutant degradation in air with different types of coating and composites
- Photocatalytic bactericidal coatings
- Characterization of photodegradation products of pollutants
- Scale-up of nanomaterials and coating manufacture
- Evaluation of industrial coating application methods of the composites
- Preparation of test samples and devices
- Evaluation and test of tailored UV reactors, conventional low-pressure mercury and excimer lamps and lamps closely matching the UV-VIS solar spectrum for investigate visible light activated photocatalysis
- Design and scale-up the bench-scale membrane-based photocatalytic reactor system into pilot-scale system for degradation and separation of EDCs and NOMs from wastewater
- Development and validation of the technological applications of the products obtained in the LIMPID project.
- Hazard assessing for the investigated photocatalytic nanomaterials and nanostructures
- Coordinate the dissemination and exploitation of the knowledge generated in LIMPID
- Actively disseminate the knowledge generated in LIMPID beyond the Consortium
- Plan joint training and dissemination actions
- Establish relationship with end users.
Project Results:
Here, the main scientific and technical results are reported following the workprogramme structure that is based on workpackages (WPs) which define the distinct, consequent and tightly interrelated phases of the project. In particular WP1, WP2 and WP3 have been the materials-oriented WPs, and they have been devoted to synthesis of photocatalytic nanomaterials, host polymers and coatings, and photocatalytic nanocomposites and coatings, respectively, while WP4 and WP5 have been focused on photocatalytic degradation of water and air pollutants and bacteria. Technological applications aspects have been faced in WP6, while WP7 has taken care of dissemination, exploitation strategies. WP8 and WP9 have covered the scientific, administrative and financial aspects of LIMPID project.
WP1 Photocatalytic nanomaterials
In WP1 has been performed the synthesis, by means of different routes, namely colloidal chemistry, sol-gel chemistry, solvothermal method and flame spray pyrolysis of original nanomaterials able to attain enhanced photocatalytic performance, capability to absorb visible light to be active in the visible, suitable surface chemistry to be incorporated in different host matrices (Task 1.1).
A wide range of UV-Vis active photocatalysts, with tailored size, shape, chemical composition and crystallinity has been designed and obtained, including wide band gap semiconductors, doped semiconductors, heterostructured and coupled semiconductors have been obtained to increase visible light absorption and thus efficiency enhancement in this region for TiO2 based photocatalysts.
In particular flame spray pyrolysis (FSP) method has been used by JM to prepare different doped TiO2 with Fe, Si, Zr and has revealed flexible enough to access to segregated systems and ZrO2/TiO2, CeO2/TiO2 mixed oxides. The same method has been exploited at CU, where a range of doped TiO2 nanomaterials, included SiO2 doped TiO2, have been developed. Preparation of NPs according to solvothermal routes has been accomplished at ISC Fraunhofer to achieve in situ functionalized TiO2, SiO2/TiO2 core/shell structured NPs and hollow TiO2 spheres. Their in situ functionalization by aliphatic and aromatic surface agent has resulted in stable isolated NP dispersible in different solvent, that has demonstrated particularly suited for the incorporation into the ORMOCER® matrix, performed in WP3 as well as for their for their further processing in different polymer nanocomposites, as successfully accomplished by UTM and UPV/EHU, whom the NP have been also delivered.
It is worth to note that TiO2 nanoparticle produced at JM (namely TiO2_JM), by means of FSP has been agreed by the Consortium as common reference material for benchmarking LIMPID project activities.
Colloidal chemistry routes have been used at CNR IPCF for the preparation of TiO2 nanomaterials directly grown, in situ, at the surface of single walled carbon nanotubes (CNT) in a shape controlled (rod or sphere) anatase structure. Remarkably, the obtained SWCNTs/TiO2 heterostructures have resulted dispersible in organic solvents, leading to optically clear dispersions and their photocatalytic activity has demonstrates a significant enhancement, up to 3 times with respect to the commercially available standard TiO2 powder under UV light and up to 2 times under visible light.
The same colloidal chemistry routes have led to heterostructures based on TiO2 and noble metals (Ag and Au) with superior photocatalytic performance due to their unique properties deriving from the coupling of the semiconductor with a metal moiety able to perform multiple roles, including enhancement of charge carrier separation visible light sensitization and antenna effect. In addition it has been possible to achieve also heterostructures combining such photoactive heterostructures (TiO2/Ag) with a magnetic domain (Fe2O3), thus adding further functionality to the system, that can be magnetically separated in liquid media.
Heterostructured nanomaterials based on Ag/TiO2 and Au TiO2 have been also prepared by means of FSP at JM. A careful investigation on the role of synthetic parameters, including precursors nature and feed rate, on the resulting materials and their photocatalytic activity has been investigated.
Specific effort has been also devoted at JM in implementing a reliable scaling up of the FSP synthesis of TiO2 based photocatalysts, thus making available to beneficiaries relevant nanomaterial (up to several kilograms), for nanocomposite fabrication, testing and, finally for the use in the demonstrator implemented in WP6.
The different synthetic procedures have been throughout monitored by means of a set of physical and chemical characterization techniques (Task 1.3). A comprehensive investigation of the obtained nanomaterials by using complementary techniques, including microscopy techniques TEM, SEM, AFM, EDX, structural and surface chemical characterizations techniques such as XRD, XPS, FTIR has been performed. Optical properties have been assessed by UV-Vis and diffuse reflectance spectroscopy.
Surface chemistry of nanomaterials has been also investigated, as such a feature is not only important for the photocatalytic activity of the material, but it is also a key point to promote their integration in polymer matrices or immobilization onto specific surfaces. Surface engineering by silanization, ligand exchange or surface coating has turned particularly successful to enhance dispersibility, improve compatibility with matrix and stability over time (Task 1.2).
At M24, the data regarding characterization and photocatalytic activity evaluation of all nanomaterials prepared over the course of WP1 have been collected in a comprehensive a library of nanomaterials, including over 100 among nanomaterials and nanocomposites samples (Deliverable D1.6 and D1.7).
An accurate and systematic test of the photocatalytic activity, evaluated both in air and aqueous media, by assessing the degradation of a model pollutant/bacteria (toluene, Methylen blue –MB, Rhodamine B, E. coli), performed under UV and visible light irradiation and benchmarked against TiO2_JM, LIMPID reference material, and commercial Evonik (Degussa) P25, has allowed a judicious selection of the most promising photoactive materials and systems to be further incorporated in polymeric matrices and used in photocatalytic applications. (Task 1.4)
As far as photocatalytic performance evaluations, the LIMPID beneficiaries have agreed, following also PTA and EAB recommendation, to set up an experimental protocol to be used all over in the consortium to perform a preliminary test of the photocatalytic activity. Therefore a user-friendly, convenient and cost-effective protocol to compare the photocatalytic activity of newly developed materials, and to be proficiently carried out in the different labs, even when they are equipped with different experimental set up, has been implemented by CNR. Such a test is based on the comparison of the experimental data as a ratio of kinetic constants of the new catalytic material to be tested and the LIMPID reference standard, TiO2_JM, given same catalyst concentration in suspension.
Preliminary inter-laboratory validation runs carried out at CNR IPCF, CNR IRSA and MGU, by testing two different reference materials for degradation of MB as a model compound, has demonstrated that, irrespectively of the experimental conditions, the ratio of the kinetic constants is in the same range and, significantly, follows the same trend.
Preliminary tests have been performed on the whole series of novel nanomaterials (Task 1.4) showing some significant enhancement of performance, especially in the case of the metal semiconducting heterostructures (TiO2_Au, TiO2_Ag). Remarkably doped TiO2 nanomaterials developed at CU have been found significantly more (two times higher) photocatalytically efficient than the reference material.
Polyethylene-TiO2 films obtained at EPFL by direct current magnetron sputtering have been found to effectively discolour MB under low intensity solar/actinic light, demonstrating the critical role played by the preparative conditions on the discolouration kinetics. E. coli inactivation on TiO2, ZrO2 and TiO2-ZrO2 sputtered on polyester has been also demostrated under low intensity solar irradiation, thus suggesting a synergistic effect between the two oxides, aside a role of the sputtering conditions on the aggregation state of the sputtered particle. Also accelerated bacterial inactivation kinetics has been observed upon Cu-doping.
ACCIONA has also carried out preliminary test of photocatalytic activity on complete sets of different photocatalytic nanomaterials, both prepared in-house and by the different beneficiary in the consortium, by means of discolouration of Rhodamine B followed by colorimetry. This test has been performed according to the procedure described in the following paper: TiO2-containing cement pastes and mortars: measurements of the photocatalytic efficiency using a rhodamine B-based colourimetric test.
WP 2 - Polymers and coatings
In WP2 significant effort has been devoted to enhance fundamental understanding of structure-property relationships between hybrid film matrices and incorporated functional nanocomponents, and to, ultimately, bring to highly innovative products and technologies.
WP2 has been focusing on the synthesis of polymer materials, both organic and hybrid organic-inorganic, properly designed and realized to provide a suitable host for embedding the different NPs prepared in WP1. For this purpose, chemically stable polymers such as perfluorinated and siloxane polymers have been synthesized in the form of processable polymer latexes or dispersible pre-polymers. Functionalization of such polymers and development of specific NP functionalization has been carried out in order to optimize NPs dispersion. In addition, proper formulations have been designed to allow the chemical and physical access to the compounds to be degraded with specific photocatalytic reactions.
In particular, both ISC Fraunhofer and ACCIONA have applied sol-gel technology to incorporate functional NPs in a matrix and improving the film forming properties (Task 2.1). The hybrid material formulations and process conditions, thoroughly investigated, have resulted in high quality coating, promptly applicable onto different types of substrate of interest and with high compatibility to functional NPs. The adhesion of the coating matrix to the substrate as well as the compatibility to functional particles has been found to be enhanced by tailoring the polarity and incorporation of functional organic groups (Fraunhofer ISC).
In summary, in order to accomplish the requirements of the industrial applications in the project, for stainless steel reactor (Xylem) and on membranes for water treatment (UTM and Aquakimia), hybrid systems have been synthesized and preliminarily tested by Fraunhofer ISC (Task 2.3). The range cover UV and thermally curable coatings with a high degree of modifications in the structure (branched, non-branched, rigid, flexible, aliphatic, aromatic, polar, non-polar) which offer a great variability of applications on various substrate materials. Stainless steel and PVDF based substrate materials have been coated with different hybrid materials. On metal, the majority could be applied showing no tendency of delamination and decomposition after storage in water and under UV-light.
The coating of PVDF based membranes with various UV-curable hybrid compositions showed no evidence of incompatibility between substrate and coating, although some degree of porosity based inhomogeneous distribution in the membrane pore structure has prevented further test.
Alternatively, strategies based on synthesis of perfluorinated polymer latexes have been developed by UPV/EHU. Perfluorinated polymer and commercially available latexes (polytetrafluoroethylene, polyvinidene fluoride (PVDF) have been modified by post-polymerization of acrylic monomers, leading to latexes formed by core-shell NPs with a fluorinated core and a functional acrylic shell. (UPV/EHU and SpPI) (Task 2.2). Following this route substrates made by blending acrylic and PVDF/acrylic core-shell latexes have been successfully produced.
However, while in the case of the substrates prepared by blending a stratification of the TiO2 has been observed in the film, with a consequent segregation of most of the TiO2 NP at the bottom of the structure resulted in poor photocatalytic properties, different has been the case when Pickering miniemulsion polymerization has been used.
Indeed Pickering miniemulsion polymerization has allowed the production of polymer particles stabilized by TiO2 NPs (Task 2.4). Films prepared by these latexes have not shown a stratification of TiO2 but a homogenenous distribution along the film thickness.
Photocatalytic activity of the films made out of the TiO2 stabilized Pickering latexes demonstrated in the degradation of MB solutions, Rhodamine B (on coated concrete) (ACCIONA) and inactivation of E. coli (EPFL).
The Pickering stabilized polymeric dispersion has been used to coat different substrates, such as mesh, stainless steel, concrete, to degrade organic pollutants in water treatment systems (Task 2.3).
The Pickering stabilized polymeric dispersion has been also provided for implementation of the demonstrator to ACCIONA in WP6.
Novel multifunctional (magnetic and photoactive) polymer particle dispersions have ben also produced using the Pickering miniemulsion method (Task 2.4).
The composite multifunctional particles have been tested in the degradation of MB solutions under UV light. The composite particles demonstrated able to degrade the MB in five consecutive cycles and all the particles have been recovered by application of a magnetic field after each degradation cycle.
A patent has been filed on the method of preparation and application of the composite multifunctional polymer particle dispersion.
WP3 Photocatalytic nanocomposites materials and coatings
WP3 of the LIMPID project has been focused on the preparation of photocatalytically active nanocomposites, applied as coatings.
The following different technologies have been used to produce these materials:
- Wet chemical methods using either acrylic or fluoro polymer based or sol-gel derived inorganic-organic hybrid materials containing TiO2 nanoparticles, to coat surfaces like concrete, stainless steel and PVDF based membranes
- Deposition of TiO2 and metal doped TiO2 by sputtering techniques onto textiles of polymers like polyethylene and polyesters
- Chemical grafting of PMMA films and incorporation of nano-TiO2
- Fabrication of special structured porous membranes of PVDF with incorporated nano-TiO2.
Various nanocomposites consisting of organic polymers and TiO2 NP have been investigated (Task 3.1). In particular it has been found that, while the incorporation of reference materials like commercially available Evonik TiO2 NPs and LIMPID reference TiO2_JM NPs resulted in quite homogeneous and uniform surface, the incorporation of TiO2 NPs prepared by Fraunhofer ISC resulted in more inhomogenous surfaces indicating protruding features, and, hence beneficial effects in photocatalytic activity, that ask for accessible free TiO2 to accomplish the catalytic role.
The incorporation of photocatalytic NPs into sol-gel derived hybrid coating matrices has also proceeded via the surface functionalization with special sol-gel compatible components of NPs (Task 3.2) synthesized in WP1, like the TiO2 nanorods, a special type of particles manufactured by CNR-IPCF. Indeed the post-synthesis functionalization of TiO2 nanorods, originally prepared in the presence of oleic acid (OLEA) has been designed and performed to promote their incorporation into inorganic-organic hybrid coating system. The surface chemistry of OLEA-capped TiO2 nanorods has been modified, implementing capping exchange procedures with diverse capping molecules, with the aim to stabilize the NPs in typical organo-functional silane monomers used for formulating hybrid organic-inorganic resins. In this way a novel solvent-free, sunlight curable, hydrophobic, transparent and self-cleaning nanocomposite material has been manufactured by CNR IPCF. The nanocomposite consists of a methacrylic–siloxane resin loaded with 1 wt % TiO2 nanorods for use as structural coating, mainly intended for the protection of carbonate porous stones from (bio)deterioration. The embedded nanorods significantly increased the curing reactivity of the neat organic formulation both in air and inert atmosphere, since the photoactive nanocrystalline TiO2 acts as free radical donor photocatalyst in the curing reaction and they limit the inhibition effect of oxygen on photopolymerization.
The same nanocomposite formulation has been preliminarily tested as structural coating for the protection of porous carbonate stones. The results showed that the nanocomposite formulation forms a hydrophobic, durable, uniform and crack-free surface coating, able to reduce water penetration for capillarity effect and remove environmental organic pollutants, concomitantly preserving the original esthetical characteristics and vapor water permeability of the stone.
After a wide spread screening process of various compositions of cross-linkable inorganic-organic hybrid coating materials, two compositions have been identified at Fraunhofer ISC, which have been found suitable for application on devices for reactors and for polymer membranes (Task 3.2).
Interestingly, while the methacryl based system has been found suitable for UV-curing and for the epoxy based system the thermal curing has been demonstrated appropriate. Both curing methods can be applied in industrial coating processes. Both materials have been tested with various types of TiO2 NPs regarding the homogeneous agglomerate-free incorporation. The Fraunhofer ISC TiO2 NPs having an organic aliphatic or aromatic surface modification have definitely shown the best compatibility and the best homogeneous distribution in the selected hybrid coatings. Up to 50 wt-% of nano-TiO2 could be incorporated without agglomeration in the coating liquid and giving homogenous and uniform coatings.
A certain sensitivity to UV-pre-activation of the resulting composites has been observed in terms of increase of surface hydrophilicity, but with no influence on the photocatalytic activity. In general, the photocatalytic activity of the coatings containing the homogeneously distributed Fraunhofer nano-TiO2 particles has been observed higher than that obtained with other particles, which could be demonstrated by the discoloration of MB or Rhodamine B.
ACCIONA has developed sol-gel coatings for further incorporation of photocatalytic TiO2 NPs and a single step, acid-catalysed sol-gel process has been selected for the preparation of the sol to be applied as a coating materials by rolling on the cementitious substrate (mortar) realized by ACCIONA according to a specific standard procedure.
Tetraethylorthosilicate (TEOS) has been used as primary precursor and Triethoxymethylsilane (MTES) has been used as secondary precursor and silylation agent. Two different types of TiO2 NPs: commercial TiO2 P25 and TiO2_JM, have been incorporated into the sol-gel matrix in different quantities, namely 0 %, 5 %, 10 % and 15 wt% and photocatalytic activity test by means of discoloration of Rhodamine B on the photocatalytic films applied onto mortar substrates have shown that the samples with the best photocatalytic performance contained 10 wt-% TiO2 P25 and 15 wt-% TiO2 P25. The same test performed on the latex films developed by UPV/EHU and applied on mortar substrates by rolling and spraying has shown that the most suitable application method for the latex films has been spraying with an average percentage of Rhodamine B discoloration of 99 % and an index of photocatalytic activity of 0,96.
The deposition of TiO2 particles on PMMA grafted polymer films has been performed at CU by means of an original six-step synthesis procedure Task 3.2). Two different type of NPs, namely, Evonik P-25 and 1% SiO2/TiO2, produced by flame spray pyrolysis, have been attached to the PMMA film via reaction with the silanol groups to produce PMMA-TiO2 nanocomposite films. Various analytical techniques have confirmed the structure of the product and the presence of TiO2 on the nanocomposite films showing that the TiO2 NPs are well dispersed on the films. The photocatalytic activity of PMMA-TiO2 nanocomposite films has been tested for photodegradation of MB blue in aqueous phase under UV light irradiation and the two nanocomposite films have been found stable after 5 operation cycles, with average conversions of MB blue for film containing SiO2-TiO2 of 22% and with Evonik P-25 of 34%, respectively. No significant leaching of TiO2 NPs has been detected, indicating the stability of the manufactured nanocomposite. A comparison of various types of TiO2 NPs on the PMMA grafted film, tested in aqueous phase under UV-light and sun-light irradiation has revealed that in both cases a N-doped P25 load of the grafted films have showed the highest photoactivity in test periods of 8 weeks. The synthesis and grafting process has been transferred to PVDF membranes and again the N-doped TiO2 has shown the highest activity.
At EPFL the design, synthesis, and evaluation of photocatalytic nanocomposite films has been performed on flexible organic polymers or textiles by means of sputtering of different targets to obtain a wide range of catalysts (Task 3.3). The used substrates, PE and PES, have been pre-treated by RF-plasma and UV-C irradiation in order to enhance the photocatalyst attachment before sputtering of TiO2 photocatalyst on these non-polar substrates.
Whereas the TiO2/Cu-PES has shown almost no dependency on the light intensity for Staphylococcus aureus (MRSA) inactivation, the E. coli inactivation process has been found to be strongly dependent on the applied light dose. A stabilizing effect of TiO2 on the amounts of the Cu released during bacterial inactivation has been observed in co-sputtered surfaces compared to sequential sputtering of Ti and/or Cu on PES.
The antibacterial performance of PEpret-TiO2 transparent, non-scattering films has been found strongly dependent on (RF) plasma and ultraviolet light (UV-C) pre-treatment, that allows the PE to bind higher amounts of TiO2 necessary to induce E. coli inactivation in the minute time scale under simulated sunlight irradiation.
At UTM the focus has been on the preparation of nano-composite based membranes using PVDF as membrane and TiO2 as the photocatalyst (Task 3.4).
The first result has been a novel flat sheet membrane of titanium dioxide (TiO2)-halloysite nanotubes (HNTs) and PVDF as a photocatalytic separator for use in a photocatalytic membrane reactor (PMR). It has been found that 99.9% of hydrocarbons could be removed by the PMR within 8 h. In a second approach TiO2 photocatalysts in the form of nano-fibers have been immobilized on the membrane support. Hot pressing methods have been applied using a combination of heat and pressure to improve the attachment between fiber and membrane surface. The membrane prepared at 100 oC exhibited the highest photocatalytic activity in the degradation of Bisphenol A (BPA) under UV irradiation compared to 160 oC and 180 oC preparation temperatures. However, the pure water flux for the PVDF/e-TiO2 nanocomposite membrane has been reduced as the hot pressing temperature increased.
Furthermore, single layer hollow fiber membranes with TiO2 in the matrix have shown that PVP is a very good additive in improving the properties of PVDF-TiO2 composite membrane by enhancing permeability and selectivity, thus making the modified composite membrane a good candidate for a sustainable development of oily wastewater treatment. Also dual layer hollow fibre membranes, have been successfully fabricated by a single step co-extrusion technique and its properties have been found improved as of TiO2 NPs increasing their hydrophilicity, pore size and permeability, as demonstrated by the excellent performance in rejection (higher than 90 %.) towards nonylphenol.
As one objective of the project is the development of recoverable core/shell structured magnetic photocatalytic beads, suitable magnetic particles that could be used in fluorinated polymer synthesis have been identified by SpPI, the conditions for various synthesis routes have been evaluated and the synthesis has been tested and optimized by UPV/EHU (Task 3.5).
Recoverable catalytically active magnetic beads, based on multifunctional hybrid polymer particles containing both photocatalytically active NPs and magnetic particles, have been synthesized at UPV EHU. Magnetite particles have been encapsulated into acrylic latex particles during the latex polymerization and finally TiO2 NPs have been adsorbed on the polymer shell (Task 3.5).
It has been shown that the hybrid particles synthesized in this work presented superparamagnetism, and NP magnetic separation, redispersion and photocatalytic tests have been repeated several times. The hybrid polymer particles have shown a good photocatalytic activity towards MB degradation, which was up to 93.2 % in the 4th cycle and still 82.3 % in the 5th cycle of re-use, due to the large surface area of the hybrid polymer.
Overall, in the whole WP, a comprehensive set of physical and chemical characterization techniques, chemical, spectroscopic, morphological, structural, calorimetric chromatographic and mechanical has allowed not only to monitor the nanocomposite materials and coating preparation routes, but also to thoroughly investigate the relevant properties of the obtained functional materials.
WP4 Photocatalytic degradation of organic pollutants in water
The investigation on the efficiency of nanocomposite materials developed in LIMPID degrading selected types of pollutants in water and wastewater has been the main focus of Workpackage 4.
Several photocatalytic reactor designs, such as submerged membrane photocatalytic reactor, batch UV reactor with Hg-low pressure lamp, batch simulated-solar light reactor with Xenon lamp. Flow reactor, with UV and vis lamp and UV water disinfection test system, have been fabricated and tested in order to suit various nanocomposite configurations that have been synthesized in the previous WP (Task 4.1). The performance of these reactors together with developed photocatalytic medium (NPs and nanocomposite films and membrane) has been evaluated by using several types of pollutants and the findings have been compared with the commercial TiO2 P25 and with the LIMPID reference material TiO2_JM.
For the investigation of the photocatalytic degradation of organic pollutants in water and wastewater assisted by the developed nanocomposite photocatalysts (Task 4.2) CNR-IRSA and MGU have preliminarily set the composition of the emerging pollutants mixture to be employed in the different water matrixes for photocatalytic reaction with the new catalysts experimental activity, The mixture includes 22 organic pollutants selected among emerging pollutants not regulated by any European law, although, some of them are in the “watch list” of the European Commission, that has indeed started an obligation of monitoring in European surface water bodies.
These pollutants are recalcitrant to conventional wastewater treatment processes resulting in their detection in water supplies that receive inputs from wastewater treatment plants and include:
- pharmaceutical compounds (acetaminophen, mefenamic acid, gemfibrozil, warfarin, metoprolol, diclofenac sodium);
- iodinated X-ray contrast media (iopamidol, iopromide, diatrizoic acid);
- endocrine distruptor compounds (β-estradiol, estriol, triclosan);
- UV filters (2,4-Diydroxy-benzophenone , 2,2',4,4'-Tetrahydroxybenzophenone, 5-Benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, 2-Phenyl-5-benzimidazolesulfonic acid).
The experimental conditions, namely reactors and lamps, organic pollutants to be tested, the effect of operating conditions such as pH, light intensity and wastewater characteristic on pollutants degradation and water matrixes for organic pollutants degradation have been then identified. The analytical detection of the above reported emerging pollutants has been optimized based on liquid chromatography coupled to tandem mass spectrometry.
Under Task 4.3 EDC and palm oil mill effluent (POME) have been degraded by means of PVDF/TiO2 membranes by UTM jointly with AQUAKIMIA. The degradation of an EDC, i.e. nonylphenol, has been studied in a photocatalytic membrane reactor system where the TiO2 NP have been immobilized on the outer surface of dual-layer hollow fibres membrane. The presence of TiO2 NPs on the outer layer of dual-layer hollow fibre membranes greatly promotes the photocatalytic degradation of nonylphenol. Anaerobically treated palm oil mill effluent (AT-POME) degradation tests have been performed by using membrane prepared at different TiO2 loading, and using a submerged photo bioreactor. The results suggest the efficiency of the photocatalytic colour degradation. However a field test, in BBC Palm Oil Mill in Bintulu, Sarawak (Malaysia) by using a pilot plant purposely built by AQUAKIMIA, has shown that the highest percentage of colour reduction is obtained upon dilution of the effluent, probably due to the nature of the sample which is too dark to allow the efficient penetration of the UV light and in turn results in a poor effectiveness of the process.
A systematic investigation of different sets of LIMPID materials from JM, Fraunhofer ISC, CU and UTM, respectively, for degradation of real wastewaters has been performed in batch system equipped with i. 17 W Hg low-pressure UV lamp, ii. simulated-solar light, iii. excimer lamp, iv. flow system equipped with a 40 W Hg low pressure. The results of the photolytic treatments have revealed that the more recalcitrant pollutants are trimethoprim, metoprolol, carbamazepine, warfarin and gemfibrozil while the other have been removed efficiently by direct photolysis. A series of experiments has been than carried out in a secondary effluent (biologically treated wastewater) of a WWTP and in a less complex matrix i.e. groundwater, both spiked with the investigated organic pollutants.
Degradation kinetics of the mixture of the selected pollutants, including PPCP and EDC at low concentration (Task 4.5) have been investigated to assess the photocatalytic performance of the developed LIMPID nanocomposites. In particular it has been demonstrated that Degradation kinetics of the mixture of the selected pollutants, performed in presence of TiO2 NPs grown in situ onto the CNT surface (see WP1 Task 1.1) have shown that TiO2 NP/CNT nanocomposite is much more effective than commercial Evonik P25 in distilled water for degradation of few contaminants, while all the kinetics are slower, for real wastewater. However, since the amount of TiO2 in the CNT based nanocomposite is much lower (50%wt) than that of Evonik P25 TiO2 used as a reference, the investigated nanocatalyst presents a quite high specific efficiency and, in addition, can be easily removed from the aqueous solution by a mild centrifugation or a filtration step and, consequently, can be reused for a further photocatalytic treatment batch.
Results demonstrated that photocatalyst based on TiO2 NPs supported on PET (CU) is more effective than suspended TiO2 Evonik P25 and than LIMPID reference TiO2_JM in distilled water for degradation of iopamidol, iopromide, diatrizoic acid, diclofenac and sulfamethoxazole in UV photocatalytic treatments, although there is already a quite strong photolytic effect that contributes to the removal of the target pollutants. Finally, no adsorption of the target compounds on the photocatalyst surface was observed and no leaching of titanium dioxide in all the experiments performed employing TiO2 supported on PET (5% and 50%) was detected in solution.
At EPFL performance of Iron oxides supported on a flexible polymeric matrix have been tested under simulated solar light (Task 4.3) The effects of the Fenton reagents’ concentration on the Venlafaxine degradation time have been also identified, which found that fixing H2O2 between 35 – 60 ppm and FeSO4 between 7 - 25 ppm leads to 90 % of Venlafaxine degradation in less than one hour. Photocatalyic test of different TiO2-coated stainless steel plates and the collimated beam device (CBD) has been also examined showing a significant improvement in degrading MB in drinking water by factors of 7 -20 related to the percentaged reduction results. The study has also addressed the details of the photocatalyst performance during E. coli inactivation under visible light irradiation (> 400 nm), thus confirming the role of FeOx absorbing light in the visible region. The reaction rate constant k has been determined for each single pollutant present in aqueous matrix, thus allowing to compare the efficiency of the different newly synthesized nanocomposite catalysts. Overall, results clearly demonstrated that when performing the treatments in all the batch system in real wastewater, both suspended catalysts (reference TiO2_JM) and supported catalyst showed a very low performance in degrading the target pollutants probably due to a matrix effect that a real effluent can exercise against the catalyst. Toxicity investigation on treated water and wastewater (Task 4.6) has been performed at CNR IRSA In particular the tested catalyst that has resulted most effective (TiO2 deposited stainless steel) has been used for degrading the target pollutants in groundwater, under flow conditions system. Toxicity tests have been performed on samples collected during treatments performed in flow system, including also reference system for direct photolysis and for suspended referenceTiO2, by using selected standard tests. Namely Daphnia magna Strauss (Cladocera, Crustacea) – acute toxicity tests (UNI EN ISO 6341:2013), Vibrio fischeri – test with luminescent bacteria (UNI EN ISO 11348-3:2009), Green Alga Selenastrum capricornutum (UNI EN ISO 8692:2012), AMES test (mutagenicity test) and Fish embryo acute toxicity (FET) - the Zebra fish test. The limit test has provided that samples with a toxicity less than 10% for Daphnia test and less than 20% for Vibrio test are not toxic, results revealed that the investigated treatments do not increase the toxicity of the samples.
The results obtained by performing a more sensitive toxicity test, i.e. Green Alga Selenastrum capricornutum test and AMES test have revealed a decrease in toxicity value after 60 minutes of the treatments, clearly evident for the photocatalytic treatment in presence of the supported TiO2 on stainless steel in the AMES test. On the basis of the toxicity results a subsequent investigation about the chemical structures for the by-products formed under the oxidative conditions has been performed based on the data from liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) analysis. In particular LC-HRMS, the new instrumentation (high resolution quadrupole/time-of-flight/tandem mass spectrometer) recently acquired by CNR IRSA and profitably used within LIMPID activities, has revealed fundamental in the investigation of the chemical structure of the by-products, and, accordingly, of the degradation paths, fundamental for getting insight on the toxicity results.
WP5 Photocatalytic degradation of air pollutants and bacteria
WP5 reports the effective photodegradation of toluene in air taken as a VOC probe on several TiO2 catalysts under UV-A irradiation. The testing equipment/chamber has been described and the degradation test has been carried out according to the ISO22197-3 standard. The toluene removed reached about 1% under UV-A light within 24 hours. TiO2 NPs have been prepared by the ISC Fraunhofer and incorporated in a hybrid cross-linked sol-gel and finally supported on glass. The same photocatalyst has been also tested for NOx removal. The dynamics of NOx in air under UV-A light rendering NO + NOx has been investigated within 6 hours. The NOx removal has been also tested by catalysts prepared by ACCIONA using commercial P25 TiO2 Evonik and TiO2_JM incorporated in cross-linked hybrid composites prepared via sol-gel. The JM reference catalyst has degraded NOx up to 17% within 6h under UV-A, while the catalyst prepared using Evonik TiO2 P25 only reached a NOx 11%. CNR-IRSA reports preliminary tests for the NOx removal under UV-A light on TiO2 nanorods deposited on paper or cotton fabrics. CNR-IPCF has also reported reports self-cleaning ability on stone materials, by using methyl-red as a probe for discoloration under direct sunlight, demonstrating the possibility of using TiO2 nanorods for self-cleaning under daylight.
WP5 has been also devoted to investigation of pollutants degradation and bacteria inactivation in gas-phase. The investigation has been focused on relevant pollutants of selected industrial application. Such pollutants include simple aromatic-based compounds, namely benzene, toluene, xylenes and volatile alkyl-benzenes, as well as nitrogen-containing aromatic-based compounds, namely nitrobenzenes and, finally, inorganic pollutants like NOx.
Photocatalytic degradation of VOCs and NOx (Task 5.1) has been carried out by ACCIONA to investigate the pollutant degradation performance for the LIMPID nanocomposites developed in previous WPs. An in-house photocatalytic reactor, enabling the simulation of a wide range of indoor and outdoor air conditions, has been used to perform the VOCs degradation tests on different LIMPID material samples and evaluate their performance in degradation of pollutants under different conditions. The environmental conditions selected to perform the test are based on ISO 22197-3, describing the test method for air purification performance of semiconducting photocatalytic materials using toluene.
ACCIONA has focused on the fabrication and testing of the sol-gel formulations and has resulted that, as regard to Fraunhofer ISC formulations, the UV cured coating systems have shown enhanced degradation performance than the thermally cured coating systems, which did not exhibite, in fact, any significant photocatalytic activity.
Test on ACCIONA’s sol-gel systems has demonstrated for all the investigated formulations an effective photodegradation of VOCs under the applied experimental conditions. Among all the formulations, the coatings formulated with TiO2_JM reference material has been found to exhibit a slightly higher photocatalytic activity that the coatings using TiO2 P25 Evonik. ACCIONA’s best performing formulation has been the one containing 10% TiO2_JM.
Photocatalytic degradation of NOx by UV and/or visible light activated nanocomposite based coatings (Task 5.2) has been tested by ACCIONA for different nanocomposite based coatings developed by LIMPID beneficiary in LIMPID, to determine their ability to degrade NOx in air. As described in the first period report, the test has been performed according to the international ISO 22197-1 standard, which describes the method to obtain the air purification performance of photocatalytic materials by exposing a test piece to NOx polluted air under illumination by ultraviolet (UV) light. The most efficient NOx degradation has been those assisted by CNR and ACCIONA formulations. ACCIONA has also carried out the validation of the products obtained in the LIMPID project implanted in real work sites (WP6). In this context, NOx degradation tests of the nanocomposites have been carried out.
Most of the nanocomposites tested showed good NOx and toluene degradation capability, in some cases competitive with the currently available commercial photocatalytic paints
The conclusions of the tests performed are:
- Concerning VOC degradation, the best performing formulation has been the UV cured system by Fraunhofer ISC (39.3% of toluene degradation)
- Concerning NOx degradation, ACCIONA formulation, containing TiO2_JM NPs, has resulted in an overall NOx abatement of 22.7%
At comparison of fabrics, coated with TiO2 P25 NPs Evonik and TiO2 nanorods at CNR, have shown an interesting photocatalytic activity for the former sample, being 21,8% of NO and 7,9% of NOx converted. In both cases, the identification of a high surface area support has brought to a significant NOx abatement in spite of the very low amount of catalyst deposited (loading 0.05%wt – 0.25%wt), for this purpose XRF method has been assessed as a fast and accurate method to quantify titanium deposited on the support, and thus compare the performance.
Bacteria inactivation has been investigated by using selected bacterial model, such as Escherichia coli (E. coli K12) under daylight and dark conditions and onto different surfaces (polymers for medical applications, membranes for ultrafiltration, indoor walls) coated with nanocomposite materials set up in LIMPID. TiO2, Cu and Cu/TiO2 sputtered on polyester have been tested under actinic/sunlight to inactivate bacteria (E. coli) at the solid-air interface. The total inactivation has been observed for TiO2-polyester after 40 min, for Cu-polyester and Cu/TiO2 polyester after 10min. Thus this suggests that an interfacial charge transfer occurs between TiO2 and Cu based on the conduction and valence band positions of TiO2 and CuO. More important disinfection has also been observed in the dark for Cu-polyester and Cu/TiO2 polyester due to the high oxidation potential of the Cu-NPs, DC and High Power Impulse Magnetron Sputtering (HIPIMS) TiO2/Cu sputtered films have been compared with those obtained by HIPIMS using higher power. The latter resulted 15-16 times thinner compared to the DC sputtered films, thus allowing a significant saving of Cu and Ti, as they are non-renewable elements. Repeated disinfection cycles (8 cycles) have been performed on the Cu/TiO2 films.
Hybrid acrylic/TiO2 films inducing bacterial inactivation under low intensity simulated sunlight (Task 5.3) have been investigated at EPFL, by using nanocomposites provided by UPV/EHU and consisting of hybrid films prepared from TiO2 Pickering stabilized acrylic polymeric dispersion (WP2). Antibacterial performance of these hybrid acrylic/TiO2 films has been tested and stable repetitive bacterial inactivation has been reported for hybrid films with two different TiO2 loadings. Highly oxidative species (mainly OH•-radicals) have been quantitatively determined by fluorescence showing that higher concentration of OH• radicals results in a more effective bacterial inactivation. Bacterial adhesion experiments have confirmed qualitatively the beneficial effect of acrylic/TiO2 hybrid films compared to a pristine film, as a higher roughness results beneficial on E. coli inactivation.
Self-cleaning by Cu promoted semiconductor binary-oxides under low intensity sunlight irradiation has been found accelerated, as Cu acts as a promoter when added in very low amounts to the TiO2-ZrO2 matrix top most layers is shown to accelerate the MB-discoloration kinetics compared to the bare TiO2-ZrO2 matrix. A photo-induced interfacial charge transfer (IFCT) mechanism has been suggested to account for MB self-cleaning. The MB self-cleaning by the TiO2 is discussed considering the MB and the TiO2-ZrO2-Cu electronic band positions and generation of the OH°-radicals by TiO2-ZrO2-Cu under light.
WP 6 Technological application
The main objective of WP6 is to evaluate the technological viability of the investigated multifunctional materials, taking advantage by the peculiar process ability deriving from the characteristics of the polymeric matrix.
The systematic investigation on the scalability of the complex polymerization process to accomplish the complex polymerization process to prepare the PVDF/Acrylic hybrid materials, has allowed to identify, via multiple set of replicated experiments, the specifications of the reactors, temperature the precursors, reactant, initiator and stabilizers. Also, shelf life of final polymers has been assessed in an adiabatic chamber.
The pilot scale photocatalytic membrane reactor (PMR) manufactured by UTM in the first period of the project has been employed for degradation and separation of EDCs from wastewater. Under TASK 6.3 an integrated pilot scale photocatalytic membrane reactor (PMR) has been studied for oily ballast water and NP solution purification. From the investigational results, the following conclusions can be drawn:
1. The PMR has successfully photooxidized over~90% and less than ~5% of oily ballast water by 6 h UV irradiation on the surface nanocomposite photocatalytic membrane (M2) and surface of pure PVDF membrane (M1), respectively.
2. PMR filtration has rejected more than 99.5 % of oily ballast water during 1 h of membrane filtration process for M2.
3. The PMR has successfully photooxidized NP solution within 3 h of UV irradiation.
4. The nanocomposite photooxidation membrane has provided promising result on the water flux and antifouling property due to presence of an effective nanofiller (HNTs-TiO2).
Concerning the technological applications of the products obtained in the LIMPID project, efforts have been made for both air purification and water treatment. New UV lamps (based on UV-LEDs and excimer) have been successfully employed for the photocatalytic degradation of a mixture of emerging organic pollutants using the supported nano-sized catalysts prepared by the partners of the consortium. PET films have provided the most promising results with a removal of 80% of MB after 180min of UV-A exposition. Higher percentage of MB degradation has been obtained for all supported catalysts when using UV-C radiation. As for the activity with the new UV lamps (LEDs-UV based lamps and excimer lamps), tests have been performed in both MilliQ water (reference) and in wastewater using lab-scale reactors and larger reactors. Results showed that the specific efficiency of each lamp is compound-dependent and the specific efficiency of the pilot scale UV reactor (LBX3) is higher than the batch lab-scale system.
Also MB degradation experiments in drinking water have been carried out on several coated meshes using two different UV reactors, LBX3 (UV lamp centrally arranged) and E2 (UV lamps outer sphere arranged) in continuous flow. For all tests, the degradation of MB has been only significant in the presence of H2O2.The TiO2-containing coatings have not contributed to the UV/AOP degradation result. The LBX3 system performed better than the E2 system
Successfully application of two nanocomposites developed through the LIMPID project (sol-gel with 10wt% TiO2 provided by JM and acrylic latex with 10wt% TiO2 provided by Fraunhofer) in two street canyons has been performed. Although it has been difficult to analyse some of the results obtained, both nanocomposites tested have shown good Rhodamine B discoloration capability (75-88% of Rhodamine B discoloration and an index of photocatalytic activity greater than 0,1). Concerning the NO/NOx degradation capability of the testing core samples according to the ISO 22197-1 (feed flow rate=3,0 l/min and [Initial NO]=1 ppm), the sol-gel coating has shown a 15,17% of NO conversion and 10,17% of NOx conversion. In the case of the latex, 11,22% of NO and 6,71% of NOx has converted using and adaptation of the ISO 22197-1 (feed flow rate=1,5 l/min and [Initial NO]=500 ppbs)
Lastly, a risk assessment of the production of TiO2 nanopowder has been carried out using the control banding tool CB nanotool 2.0. The control banding tool CB nanotool 2.0 used in order to determine the overall nanomaterial exposure risk level, is based on the severity score and probability score. The current knowledge about potential negative impacts on human health of the manufactured nanomaterials and parent materials of TiO2 along with a proper estimation of the exposure conditions have been used. For the risk assessment, the methodology with the risk potential, the necessary measures and the remaining risk considering these measures have been used and the risk matrix has been produced. (Task 6.7)
WP7 Dissemination
WP7 has disseminated the knowledge generated in this project by different properly planned routes. Internal dissemination, among the beneficiaries, has been accomplished by realizing common databases, exploiting intranet facilities of LIMPID website, including a document-sharing platform and a LIMPID blog.
The webpage related to the project activity has provided a common platform to facilitate information exchange among beneficiaries and has been also one of the main vehicles of dissemination and interaction with the public seeking information about LIMPID, as demonstrated by the hi number of visitors counted for the webpage (Task 7.1).
Academic beneficiaries, both universities and research centers have been active in training students, at different levels of their career, Bachelor, Master and PhD degree in topics related to LIMPID activities. It is worth to point out that out of 34 students 12 were women, thus demonstrating the attention paid to gender equality issues, and that 8 PhD projects have been running dealing with subjects related to LIMPID topics (Task 7.2).
Actions for disseminating the results and the technological advance to relevant audience have been performed (Task 7.3) by organizing two Exploitation and Dissemination Workshop. Indeed to increase dissemination and networking opportunities, LIMPID consortium has set up a second workshop in the areas of nanomaterials for depollutions, beside the first "Workshop on Nanomaterials for photocatalytic depollution" that has been held in the frame of the ASEAN-EU STI Days in Bangkok (Thailand) on 22-23 January 2014, namely“International Workshop on Nanocomposite Materials for Photocatalytic Degradation of Pollutants: Advanced Opportunities for New Applications” in Kuala Lumpur (Malaysia) on 12 November 2015 and jointly organized by CU, UTM and AQUAKIMIA.
The event has pointed out that international cooperation dimension can be an increasingly important element of the environment research policy and the fields of nanomaterials and nanotechnology for depollution, as has been place in facts in LIMPID.
LIMPID has actively looked for links and interactions with other EC-funded projects in the areas of nanomaterials for environmental depollution, connections have been realized with the following projects: PCATDES “Photocatalytic materials for the destruction of recalcitrant industrial waste” (www.pcatdes.eu/) coordinated by Phil Davies, 4G-PHOTOCAT “Fourth generation photocatalysts: nano-engineered composites for water decontamination in low-cost paintable photoreactors (http://www.4g-photocat.eu/) coordinated by Radim Beranek, WATER “Winning application of nanotechnology for resolutive water hydropurification” (http://www.water.imm.cnr.it/) coordinated by Vittorio Privitera.
Also LIMPID has been pursuing active participation to the recently launched European Clusters: “European Cluster on Catalysis” (http://www.catalysiscluster.eu/) coordinated by Dr. Silvia Gross and Dr. Helge Wessel, Scientific Advisor Prof. Gabriele Centi and “Engineering & Upscaling Cluster” coordinated by Dr. Sophia Fantechi (EU Commission) Dr Gerhard Goldbeck, Goldbeck Consulting Ltd and Dr Bojan Boskovic,Cambridge Nanomaterials Technology Ltd.
The creation of an End Use Advisory Board (EAB) has represented an effective tool to obtain insights and advices to effectively address the project activities towards end-users and stakeholders needs.
The role of the EAB has been to contribute with the renowned competences and valuable expertise of its members to bringing advises and suggestions to LIMPID project Consortium to the decisions made by the Steering Committee itself. EAB Members have critically looked at the LIMPID activities and made comments and consideration on the issues specifically related to their own field of expertise and their comments, remarks and advise have been implemented during the project.
LIMPID activities have resulted in several relevant exploitable results, some of them have been filed or are in preparation to be presented.
WP8 Scientific Management and
WP9 Administrative and Financial management and coordination
The Scientific Management Workpackage (WP8) has satisfactorily succeeded to provide strategic vision of the project, a scientific management (Task 8.1) ensure a correct and consistent project development with respect to the project progress milestone, prepare scientific meeting (Task 8.2) and perform a quality check of technical performance versus Annex I Description of the work and Gantt Chart (Task 8.3). Research risk management has properly handled (Task 8.4)
The administrative and financial management and coordination (WP9) has adequately accomplished the administrative, financial and contractual coordination, reporting, financial and administrative management for the project, has appointed the EAB (Task 9.1) has coordinated the scheduling and organization of regular consortium meetings and Management Board and Advisory Board meeting (Task 9.2) coordinated communication among partners, the European Commission, and external institutions (Task 9.3). The management of three Amendments to the Annex 1, made necessary during the project, has been also properly performed.
Potential Impact:
Potential socio-economic impact
Significant contributions to functional nanomaterials design, and fabrication, understanding of their photocatalytic behaviour, both in air and in water, water purification reactors and coating for air pollutant removal, bacteria inactivation and self-cleaning have resulted from LIMPID.
The achievements reached in LIMPID project has allowed to progress beyond of the state-of-the-art in the field of functional nanomaterials and original technologies for air and water photocatalytically assisted depollution,
The development and usage of multifunctional catalytic materials and coatings along with highly efficient processes, accomplished in LIMPID, can provide original nanotechnology-based solutions with a potential economic impact. Indeed, while the scientific impact of LIMPID can be clearly inferred looking how well have been received the output of the project by the material, engineering and environmental science communities, as recognized by the high number of scientific publications on peer reviewed journals (36) and the concomitant presence of a few patents, already filed or under submission represents an effective indicator of the potential impact of the project achievements.
Potential impact for new materials and technologies for the environment, that is currently considered as one of the most important challenges for the society, can be, thus, anticipated.
In this context, LIMPID project has also served as starting point to create a high-level multidisciplinary and multisectorial consortium with cutting-edge expertise in the field of functional materials, including polymers and nanomaterials, environmental science and engineering.
The strong collaborative spirit and the scientific and technological skills shown by the consortium could be crucially exploited for further progresses towards a sustainable environmental solutions based on nanocomposites materials.
The close collaboration between academic and industrial partners, along with the advice of the EAB has been crucial to stir the project in order to reach the reported achievements.
The results of the scale-up activities, for instance, both for the complex polymerization process to prepare the PVDF/Acrylic hybrid material (SPpI) and for the nanomaterials synthesis via FSP may defnitely enhance the chance of industrial exploitation of the obtained functional materials, enabling, in principle, production lines for the realized photocatalytic nanocomposites.
Concerning the technological applications of the products obtained in the LIMPID project, significant results have been achieved both for air purification and water treatment. Some of the tested composites have also suggested a good potential for protection of cultural heritage stone artifacts.
Can be, thus, may be more clearly inferred how significant can be the economic potential of the developed nanocomposites and processes based on their application. Obviously, the time to market of some of the proposed products for the different applications can be variable.
It must be pointed out, however, that, the results obtained in LIMPID, although of large fundamental impact and the assessed technological viability, evidence also some limitation due to the intrinsic nature of the semiconductor assisted photocatalytic process. In fact, in spite of demonstrated enhancement in efficiency observed with the materials developed in the project, the overall process may still remain inadequate when compared with other more cost effective AOP processes, considering also the starting cost related to the setting of newly developed nanomaterials system in place of the existing ones. All these issues may still result limiting, if the new materials and technology are intended to provide, for instance, a single solution for any water purification problem.
For instance, a limitation could be given by at too long total residence time needed for the photocatalytic activities, while most applications for water treatment are normally continuous and with short residence time of a few minutes at most.
However, a realistic impact can be reasonably envisaged when the new nanocomposites and the related technologies are applied to answer to unique and specific air depollution problems, such as air purification and disinfection in restricted environment, or for solving specific needs in water degradation, related to a defined purification step, suitably integrated in a more complex treatment.
For instance, as pointed out by the EAB, interesting is the case of emerging substances with Endocrine Disrupting Chemicals properties that are usually poorly reduced by WWTP (waste water treatment plants), although for some of them, just for the pharmaceuticals evaluated in LIMPID, an obligation of monitoring in European surface water bodies, has been started by the European Commission.
Degradation of these recalcitrant contaminants of emerging concern in typical purification treatments may, in fact, become difficult and result in degradation path characterized by transformation products that retain their toxicity over time. In this perspective, the new photocatalytic nanocomposite materials could enable alternative degradation paths, finally resulting in a complete removal of toxicity. It must be also definitely highlighted that, as also recommended by the EAB, different treatments should rely on a wide spectrum of eco toxicity tests that can detect also chronic exposures and that are able to cover multiple trophic levels of the aquatic food chain. The potential toxicity could be caused both by the residual of the micropollutants treated and also by the nanomaterials present in the samples. Therefore, in LIMPID, valuable have demonstrated the toxicity tests acute and chronic performed on samples collected during photocatalytic treatments in flow system: - daphnia toxicity test, vibrio fischeri test, green Alga Selenastrum capricornutum, AMES test (mutagenicity test), the Zebrafish (Fish Embryo Toxicity Test-FET).
Another example is given be the case rising from a limitation, pointed out by the EAB, and related to the specific experience carried out in LIMPID by the intense color in organic wastewater, that, of course affect the light penetration, resulting in a reduced efficiency of the systems. In this case a possible solution would be, not just to dilute the wastewater, as it would be not that competitive, the realization of a hybrid system which includes a pre-oxidation step of the dark organics, to reduce color intensity and hence enhance light penetrations, so as to reduce the residence time needed for the photocatalytic applications, still maintaining the advantage of the nanocomposite system.
In summary, therefore the actual impact, like also addressed by the EAB members in their comments, stays in a judicious identification of the processes that can be effectively assisted by the prepared and, accordingly in a suitable and well-thought integration of the novel methods in proper processes.
The LIMPID proposal consortium as demonstrated able to build and strengthen reliable link of scientific and technological cooperation between beneficiaries in in Europe, South East Asia as well as the third country.
The strong complementarity in the expertise of the beneficiaries in Malaysia and Thailand, along with their well-known reputation for their work in the area of photocatalytic materials and catalytic processes (CU, Thailand) and water purification membranes technologies (UTM, Malaysia and AQUAKIMIA, Malaysia), respectively, has been of strong relevance. Furthermore, the consortium includes one partner from another third country (McGill University, Canada) with a unique expertise in water toxicity evaluation, which has effectively complemented the consortium, expanding the international dimension of the project. In addition, the four participating European industrial partners have commercial and, in some cases, industrial activities in ASEAN countries which will also benefit from the future economic interactions of the two geographic areas.
The LIMPID exploitation foreground, which is regulated by the Consortium Agreement, is represented by the results coming from the project and having a commercial potential significance, that can be exploited as a product, process, service. They can be identified in LIMPID catalytic nanomaterials (CNR IPCF, JM, CU, Fraunhofer ISC), nanocomposite materials for photocatalytic degradation of pollutants, both in air and water (Fraunhofer ISC, SpPI, UPV/EHU, UTM, CU ACCIONA, EPFL), characterization methods to evaluate the photocatalytic activity of the LIMPID nanocomposite materials in air (ACCIONA, EPFL, CNR IPCF, CU), novel photocatalytic systems and reactors (UTM, AQUAKIMIA, XYLEM, CNR IRSA, EPFL)
The results achieved within LIMPID, can also effectively affect the standardization issues, providing new methods and tools for standardization and certification, as the current limitation related to standardization test protocols for photocatalytic water purification has been clearly pinpointed in the project. In fact, more suitable standards would be amenable to properly and reliably assess the photocatalytic performance of the newly developed nanomaterials based photocatalytic systems, under conditions which necessarily need to be specifically identified for the original classes of materials, and that cannot be straightforwardly evaluated by using existing protocols.
Specifically for the industrial beneficiaries different commercial and exploitation interests have been defined. Namely for JM the main interest is in catalytic nanomaterials. The production of 80% industrially important chemicals involves catalysis. Catalysts are involved in more than $10 trillion in goods and services of the global GDP annually. Catalyst industry contributes around 2% of total investment in a chemical process. The global catalyst market for pharmaceutical and fine chemicals is around £90M, and of that around a half is in heterogeneous catalysis. In order to achieve a revenue growth, market share will have to be gained from JM’s international competitors by the introduction of new and innovative products offering performances and economic benefits.
For SpPI the main interest is linked to the fact that degradation of conventional polymers has been a limitation up to now for the development of a technology based on photocatalytic decontamination. Fluorinated materials could overcome this limitation and the possibility to synthesize fluorinated polymers via emulsion latex gives high flexibility to design the needed coating. Therefore, final market opportunities are related to needs of higher level of quality of the life of social communities. Then the final end-user are municipalities and companies interested in the level of pollution.
For XYLEM, the main interest in novel water purification photoreactors, as in this field the prospected yearly growth rate for disinfection systems are around 6 to 8% and for advanced oxidation systems 10 to 12% worldwide. The access to photocatalytic materials which can be used with existing reactors, as well as the use of modified lamp sources, enabling reduced energy consumption, would bring to the company grow sales volume by 10% in the first 3 years after market launch.
For ACCIONA new technological solutions for air purification represent the most relevant issue, as currently the limit of some pollutants is exceeding several times in the year, thus resulting in serious health problem for the citizens, with related assistance costs long with relevant fines from EU. Therefore, a market strategy devoted to application of photocatalytic materials in construction to avoid fines and health problems may result promising in the next future.
Also new technological solutions for water purification are appealing for AQUAKIMIA, as the Malaysian Government is now focusing on bringing potable water to rural communities and more than 5000 do not have access to drinking water, therefore AQUAKIMIA is looking at expanding the product range, including membrane technology and potable water applications.
LIMPID achievements have in principle a large strategic and economic impact as can increase the access to clean water, also in critical environment, where power supply for instance can be not a trivial issue, such as in remote areas or in developing countries. Therefore a strong impact can be given by the novel photocatalytic nanocomposite materials and processes, resulting in high efficiency and able to extend their activity beyond UV to the visible spectrum of natural sunlight for environmental application at a reasonable price.
Finally, LIMPID has pointed out the international cooperation dimension can be an increasingly important element of the environment research policy and the fields of nanomaterials and nanotechnology for depollution, and that has been place in facts in the project.
Societal implications
Although photocatalysis is not within the specific focus of the wider public, there are tangible impacts from the numerous applications. In particular results and developments achieved within LIMPID are focused towards applications of the functional nanomaterials in environmentally relevant application, as water and air purification. Therefore the advantages of the novel proposed technological solution for the environment, which can improve quality of air and water resource can likely arise a significant social interest and public acknowledgment. In addition, the effort made to disseminate the LIMPID topics to undergraduate and younger students as well as to general public can further increase the attention towards LIMPID achievements.
The photocatalytic nanomaterials and technologies resulting from LIMPID, as used for environmental, cleaning, depollution, can lead to reduction of pollutants and minimization of utilization of chemicals, resulting beneficial on the health of the general public and thus on the quality of life.
For the novel photocatalytic nanomaterials, coatings and systems which are outcome of LIMPID a significant technological potential can be envisaged, as they can stir different applications, such as bacterial deactivation in critical environment like in medical applications, hospitals, degradation of contaminant of emerging concern in specific treated waste waters, self-cleaning coating on building, facades or even cultural heritage artifacts.
Finally, nanocatalysts in host matrix are also expected to have little negative impact on human health and the environment, since they are usually immobilized in/on a substrate material (e.g. metals, tiles, or glass), as once integrated in a multifunctional nanocomposites, nanocatalysts are not likely to be released in amount that would result hazardous to humans or the environment. This aspect also may positive impact the social response to the outcome of the project.
The specific attention paid in LIMPID to the societal concerns includes a task devoted to risk assessment and occupational safety. Indeed a risk assessment on the production of TiO2 nanopowder has been carried out. The control banding tool CB nanotool 2.0 has used in order to determine the overall nanomaterial exposure risk level, based on the severity score and probability score.
Consideration of gender aspects
Gender issue have been constantly addressed within LIMPID project activities. The main goal has been to keep gender issue in the foreground, by improve attractiveness of scientific and technological themes and encourage woman participation to science and technological playground, providing space for discussion, along with the most fundamental gender equality opportunity.
In particular, throughout the project equal opportunity policy in hiring personnel, assistance for women in developing their career plans and sharing of experiences on career-development have been implemented.
The effectiveness of the measures has been reflected in the number of PhD, and Master/Bachelor students involved in LIMPID project related activities, as out of 34 students 12 are women.
All LIMPID beneficiaries have encouraged women to attend national and international conferences, schools and workshop and encouraged women to apply for positions and to get involved in project activities like meeting, workshops.
Also in LIMPID the coordination of the Project as well as of three out of the 8 workpackages has been performed by a woman.
List of Websites:
http://www.limpid-fp7.eu/
contact: M. Lucia Curri email: lucia.curri@ba,ipcf.cnr.it
webmaster: Claudio Capasso email: c.capasso@ba.ipcf.cnr.it
"Nanocomposite materials for photocatalytic degradation of pollutants", LIMPID, has been a collaborative RTD European Project funded under NMP.2012.2.2-6 Photocatalytic materials for depollution.
LIMPID consortium has been designed to combine leading industrial partners in the field of inorganic nanomaterials and catalysts (Johnson Matthey), water purification systems (XYLEM SERV. and AQUAKIMIA), new polymer (SpPI, Solvay Specialty Polymers Italia S.p.A.) and photocatalytic construction materials (ACCIONA) with research groups experts on polymers (UPV/EHU), inorganic nanoparticles (CNR-IPCF, CU), hybrid coatings (ISC Fraunhofer), photocatalytic materials (EPFL, CNR IPCF), catalytic processes (CU, CNR IPCF, EPFL) and water purification technologies (CNR-IRSA, MGU, UTM), from Europe (8 partners), ASEAN Countries (3 partners) and Canada (1 partner). The consortium includes 8 partners from European Institutions and 4 partners from third countries, namely a partner from Canada and 3 from ASEAN countries, with specific expertise in degradation processes of organic pollutants, membrane technology for water treatments (UTM; CU and AQUAKIMIA), 5 leading industrial partners from sectors differently related to depollution applications (JM, materials, SpPI, polymers XYLEM SERV., water treatment, ACCIONA, building and infrastructures) including a leader water purification provider in South East Asian countries (AQUAKIMIA).
The proposal aims to foster an integrated approach to R&D focused on the development of photocatalytic materials, for environmental applications.
The main goal of LIMPID has been to develop fundamental materials and technologies based on the synergistic combination of different types of nanoparticles (NPs) into a polymer host to generate innovative nanocomposites, thus originating multifunctional nanostructured materials with enhanced photocatalytic properties, promptly processable, that can be applied onto a variety of supports, also unconventional in nature, integrated in photocatalytic reactors, photocatalytic filtration membranes, bactericide coatings, self-cleaning surfaces, active both in air and in water. At the same time such photocatalytic nanocomposites can prevent NP leaching into water and air phase, limit the potential threat associated to dispersion of NPs into the environment.
The prepared nanomaterials have been thoroughly characterized, their photocatalytic properties tested according to ISO standard and then fabricated as self-cleaning coatings, photocatalytic membrane reactors, UV e vis photocatalytic reactors, bactericidal films, able to remove pollutants from air and water matrix. Among the pollutants particular attention has been devoted to classes of compounds like contaminant of emerging concern, like pharmaceuticals and personal care products (PCPP) and endocrine disrupting chemicals (EDC), affecting both EU and ASEAN countries.
Within LIMPID an excellent cooperation between the EU, ASEAN and Canadian research groups and companies has been achieved, being all the beneficiaries working together, by exchanging materials, expertise and knowledge to design and develop innovative nanocomposite based materials and technologies to be used for purifying water and air.
A significant network of collaborations and exchanges between the different beneficiary has been reached and the intra- and inter-workpackage collaborations have been crucially exploited for the synthesis and the characterization of nanocomposites, their integration in the photocatalytic systems and devices for degradation of pollutants in water, for NOx and VOCs removal and for bacterial inactivation. The collaborative work and its critical evaluation have been crucial for the selection of suitable materials to be further developed in the last year of the project and then implemented in the proof of principle applications, for reactor set up and toxicity test evaluation.
Safety and risk assessment issues have been also taken into account, to watch out any possible health impact of the nanomaterial exposure.
LIMPID has generated knowledge and innovations, which resulted in 36 peer reviews papers, also on high impact journal in the fields of functional materials catalysis and environment, a large number of conference contributions and invited talks, 4 patents filed or under submission. Such a relevant output points out the fundamental impact of the LIMPID activities in the relevant scientific communities, but also their technological potential. Significant dissemination activities have been performed within the project, including a project website (http://www.limpid-fp7.eu/) which has been used also as one of the main vehicles of dissemination and interaction with the public seeking information on the project topics, workshops, project fliers, conference posters and presentations of LIMPID, interaction with other projects and platforms, training of students with projects on LIMPID topics.
Particularly relevant have been the two dissemination workshops held in Asia, namely
- "Workshop on Nanomaterials for photocatalytic depollution" that has been held in the frame of the ASEAN-EU STI Days in Bangkok (Thailand) on 22-23 January 2014.
- “International Workshop on Nanocomposite Materials for Photocatalytic Degradation of Pollutants: Advanced Opportunities for New Applications” in Kuala Lumpur (Malaysia) on 12 November 2015.
Project Context and Objectives:
In a time of increasing concern on environmental pollution, an enormous attention is paid to strategies and technologies able to clean and purify air and water.
Indeed in the last decades, with the worldwide growing population and the consequent growing demand of clean water resources, mankind is going to face serious issues regarding the decontamination of water from a series of pollutants. An even heavier situation has already been tackled with the air pollution. The development of cost-effective and stable materials, methods and technology for providing the fresh water in adequate amounts and clean air is a critical need for environmental protection.
Nanotechnology has been considered effective in solving water problems related to quality and quantity, however there are many aspects of nanotechnology that need to be addressed to solve the multiple problems of water and air quality in order to ensure the environmental stability.
The recent advances in nanoscale science and engineering suggest that several problems involving water and air quality could greatly benefit by using nanocatalysts, bioactive NPs, nanostructured catalytic membranes and NP enhanced filtration, among other products and processes resulting from the development of nanotechnology. Nanoscience developments facilitate a number of emerging technologies that could work to threat contaminants and develop products able to reduce concentration of toxic compounds, thus assisting the attainment of water quality standards and health advisories.
Improvement in performance has been strongly correlated to advances in nanotechnology. It is expected that both the technological and economic importance of photocatalytic materials can increase considerably in the future.
In this perspective inorganic-organic hybrid materials are considered to play a major role in the development of future oriented advanced functional materials. The LIMPID project has intended to contribute to such a development, supporting the research in functional materials by the opportunity to create new smart materials from the inorganic and organic components, and the possibility of their assembly using nanostructured phases.
The fundamental idea underlying LIMPID project has been to design, fabricate and exploit nanocomposite materials obtained by synergistically combining different types of catalytically active NPs within both organic and hybrid polymer, for (photo)catalytic degradation of pollutants and bacteria, in air or in aqueous solution. Such a unique synergistic combination of different catalytically active NPs, with peculiar size dependent optoelectronic and catalytic properties, within highly processable host polymers, provides a flexible and versatile tool to access an innovative class of multifunctional materials with superior photocatalytic properties in the UV and visible range.
While the concept of single component nanocomposites, including one particular type of inorganic oxide NPs such as TiO2, has been already reported and used in photocatalytic activities, LIMPID target is to go a step further, including in one nanocomposite different types of NPs. In particular, candidate NPs are combinations between semiconductor oxides, also doped in nature, and metals, whereas magnetic NPs or carbon nanotubes (CNTs) have been considered for bringing up further active surface area and include additional functionalities for recovery of photocatalysts.
At the same time the innovation brought by nanocomposite formulation is intended to prevent any NP leaching into water and air phase, thus strongly limiting the potential threat associated to dispersion of NPs into the environment.
In the perspective of resource consumption and reduced material usage, the development and application of multifunctional recoverable catalytic materials and coatings, active also under visible light irradiation, and, hence capable of utilizing a large portion of solar light, can represent a major advance.
These proposed ingenious combinations of functional oxides, metallic NPs and CNT is intended to open new vistas of material properties and new applications, able to generate a large potential both in EU and ASEAN countries. The use of such host polymers can envisage a large potential due to the multifunctionality deriving by the combination of diverse catalytically active NPs, but also due to their prompt processability, with film and coating forming properties.
Indeed nanocomposite materials could be in principle fabricated in products to use in catalytic degradation of pollutants in water and air, such as porous membranes for water treatment or re-usable photocatalytically active micro-particles, or in pollutant degradation reactors, and coating or paint to be deposited onto large surfaces, such as walls of buildings and facades.
In this perspective a careful selection of the host polymer has been fundamental and has represented one of the main challenges of this project. In fact, the host polymer to incorporate photocatalytic nanomaterials needs to sustain photocatalytic processes, as they can destroy any organic materials, including the organic matrix in which the NPs are embedded.
Therefore two classes of host materials have been identified, namely fluorinated polymers and organic-inorganic hybrid polymers, both can act as a medium dispersing NP and, at the same time, enable effective interactions with the catalytic substrate.
The use of these materials, as NP host, can burst the potential of such a combination of catalytically active NPs and can play a significant role for their integration in photocatalytic reactors, photocatalytic filtration membrane, bactericide coating, photocatalytic coating, self-cleaning surface, as it can enable fabrication of coatings, to be applied onto a variety of supports, also unconventional ones, as well as self-standing structures, active both in air and in water.
In addition, such integration ability can be applied in the fabrication of recoverable beads, based on magnetic NPs, able to further facilitate their recovery and provide alternative processing routes. Indeed magnetic beads coated with photocatalytic materials are easily recoverable after liquid phase photocatalytic reaction, by means of the magnetic separation, facilitating the practical running of pollutant clean-up process.
The nanocomposite materials obtained within LIMPID have been first bench-marked against reference and tested for the photocatalytic degradation of organic pollutants both in aqueous solutions and in gas phase. A careful material selection has been needed, in order to identify the most promising and most promptly accessible, in terms of scalability, materials.
UV and vis photocatalytic reactors and photocatalytic membrane reactors, with specific design, have been fabricated by using the most effective nanocomposites.
It is worth to point out that a large number of organic compounds is typically detected in completely untreated as well as pretreated wastewater. It is well known, in fact, that conventional wastewater treatment processes are not effective in the removal of pharmaceuticals, illicit drugs and other chemicals and that wastewater discharges in receiving water streams significantly contribute to the presence of contaminants of emerging concern in sources of drinking water
Therefore for the LIMPID activities a representative selection of organic pollutants designated among relevant classes of pollutants, including pharmaceuticals and personal care products (PPCP) and endocrine disrupting chemicals (EDC) and in general pollutants relevant both for European and ASEAN countries, have been investigated in order to test the performances of newly developed photocatalysts assisted degradation process. The degradation paths, the formation of by-products, their influence on the overall purification process have represented a relevant task in the project. The performance of the photoactive nanocomposite catalysts developed have been tested in both synthetic and real wastewaters, along with information obtained about the relative toxicity of the treated wastewaters, have been used to determine the presence of transformation products of greater concern which will then have undergone to different toxicity tests, at increasing trophic level.
The obtained nanocomposites have been also fabricated as film and coating products able to address needs of innovative façade building units. Photocatalytic performance of these coatings against classic organic pollutants such as VOCs, and NOx have been tested aiming at performance that can compete with the currently available commercial photocatalytic paints.
Films obtained by sputtering or co-sputtering TiO2, oxides and metal, with different composition and deposition conditions, onto polymers and textiles have been investigated on Escherichia coli (E. coli) for bacterial inactivation, both under UV and under low intensity simulated sunlight. This class of coating presents a large applicability, due to the their stability, the scalability of the sputtering process along with the great potential in answering issues related to infections in different critical environments, including hospitals.
In addition, the mechanisms behind the enhanced efficiency of the prepared materials, the scaling up of their preparation procedures, the toxicity of the investigated photocatalytic processes have been investigated and elucidated. Finally, the safety assessment on the nanomaterials synthesis, processing and usage, and the technological research towards end users applications have been carried out.
Within LIMPID project, EU and ASEAN research groups and companies have been working together to design and develop innovative nanocomposite materials and technologies, demonstrating a well-balanced scientific and technological cooperation in the consortium, where the roles of each beneficiary have been effective in covering the complete chain from materials, including nanomaterial synthesis, host polymer identification and investigation, and finally their integration in multifunctional nanocomposite photocatalytic structures.
As an essential part of the project, the industrial beneficiaries, along with the End User Advisory Board have played a crucial role to address the research efforts according to the market needs and/or opportunities. The industrial beneficiaries have been especially involved in the synthesis, up-scaling developments, reactors design, test and applications.
Among the main LIMPID scientific and technical objectives, it is worthwhile to highlight the following:
-Synthesis of metal oxide and metal doped oxide NPs and NCs with control on size, crystallinity, composition and shape by means of different routes, namely colloidal chemistry, solvothermal method and flame spray pyrolysis
- Synthesis of metal nanoparticles, magnetic oxides and multifunctional heterostructures
- Functionalization, surface engineering and characterization of the various nanomaterials especially inorganic oxide and NPs, such as TiO2, to make them suitable for integration in polymer matrices
- Structural, optical and surface characterization of nano-catalysts by means of spectroscopic, structural and microscopy techniques
- Photocatalytic tests on the prepared nanomaterials for degradation processes both in air and in aqueous matrix by using model molecules and their catalytic performances evaluated against commercial standard photocatalysts
- Synthesis of inorganic-organic hybrid coating materials by sol-gel technology
- Implementation of functional groups to facilitate adsorption of pollutants and to increase compatibility to functional nanoparticles
- Characterization of the coating materials
- Synthesis of polymer latexes based on perfluorinated polymers
- Polymers for membranes fabrication
- Optimization of nanoparticle incorporation and dispersion into hybrid matrices
- Sol-gel coating preparation and testing
- Preparation of nanocomposite photocatalytic paints
- Test of nanocomposite stability against ageing and photodegradation
- Fabrication of nanocomposite based membranes
- Fabrication of catalytically active magnetic beads
- Chemical and physical characterization of the photocatalytic nanocomposites
- Photocatalytic degradation of selected pollutants among PPCPs in wastewater
- Photocatalytic degradation of endocrine disruptor compounds (EDCs) in wastewater using PVDF/TiO2
- Test of novel photoactive nanocomposite membrane for degradation of EDCs in wastewater
- Investigation of the pollutant degradation in air with different types of coating and composites
- Photocatalytic bactericidal coatings
- Characterization of photodegradation products of pollutants
- Scale-up of nanomaterials and coating manufacture
- Evaluation of industrial coating application methods of the composites
- Preparation of test samples and devices
- Evaluation and test of tailored UV reactors, conventional low-pressure mercury and excimer lamps and lamps closely matching the UV-VIS solar spectrum for investigate visible light activated photocatalysis
- Design and scale-up the bench-scale membrane-based photocatalytic reactor system into pilot-scale system for degradation and separation of EDCs and NOMs from wastewater
- Development and validation of the technological applications of the products obtained in the LIMPID project.
- Hazard assessing for the investigated photocatalytic nanomaterials and nanostructures
- Coordinate the dissemination and exploitation of the knowledge generated in LIMPID
- Actively disseminate the knowledge generated in LIMPID beyond the Consortium
- Plan joint training and dissemination actions
- Establish relationship with end users.
Project Results:
Here, the main scientific and technical results are reported following the workprogramme structure that is based on workpackages (WPs) which define the distinct, consequent and tightly interrelated phases of the project. In particular WP1, WP2 and WP3 have been the materials-oriented WPs, and they have been devoted to synthesis of photocatalytic nanomaterials, host polymers and coatings, and photocatalytic nanocomposites and coatings, respectively, while WP4 and WP5 have been focused on photocatalytic degradation of water and air pollutants and bacteria. Technological applications aspects have been faced in WP6, while WP7 has taken care of dissemination, exploitation strategies. WP8 and WP9 have covered the scientific, administrative and financial aspects of LIMPID project.
WP1 Photocatalytic nanomaterials
In WP1 has been performed the synthesis, by means of different routes, namely colloidal chemistry, sol-gel chemistry, solvothermal method and flame spray pyrolysis of original nanomaterials able to attain enhanced photocatalytic performance, capability to absorb visible light to be active in the visible, suitable surface chemistry to be incorporated in different host matrices (Task 1.1).
A wide range of UV-Vis active photocatalysts, with tailored size, shape, chemical composition and crystallinity has been designed and obtained, including wide band gap semiconductors, doped semiconductors, heterostructured and coupled semiconductors have been obtained to increase visible light absorption and thus efficiency enhancement in this region for TiO2 based photocatalysts.
In particular flame spray pyrolysis (FSP) method has been used by JM to prepare different doped TiO2 with Fe, Si, Zr and has revealed flexible enough to access to segregated systems and ZrO2/TiO2, CeO2/TiO2 mixed oxides. The same method has been exploited at CU, where a range of doped TiO2 nanomaterials, included SiO2 doped TiO2, have been developed. Preparation of NPs according to solvothermal routes has been accomplished at ISC Fraunhofer to achieve in situ functionalized TiO2, SiO2/TiO2 core/shell structured NPs and hollow TiO2 spheres. Their in situ functionalization by aliphatic and aromatic surface agent has resulted in stable isolated NP dispersible in different solvent, that has demonstrated particularly suited for the incorporation into the ORMOCER® matrix, performed in WP3 as well as for their for their further processing in different polymer nanocomposites, as successfully accomplished by UTM and UPV/EHU, whom the NP have been also delivered.
It is worth to note that TiO2 nanoparticle produced at JM (namely TiO2_JM), by means of FSP has been agreed by the Consortium as common reference material for benchmarking LIMPID project activities.
Colloidal chemistry routes have been used at CNR IPCF for the preparation of TiO2 nanomaterials directly grown, in situ, at the surface of single walled carbon nanotubes (CNT) in a shape controlled (rod or sphere) anatase structure. Remarkably, the obtained SWCNTs/TiO2 heterostructures have resulted dispersible in organic solvents, leading to optically clear dispersions and their photocatalytic activity has demonstrates a significant enhancement, up to 3 times with respect to the commercially available standard TiO2 powder under UV light and up to 2 times under visible light.
The same colloidal chemistry routes have led to heterostructures based on TiO2 and noble metals (Ag and Au) with superior photocatalytic performance due to their unique properties deriving from the coupling of the semiconductor with a metal moiety able to perform multiple roles, including enhancement of charge carrier separation visible light sensitization and antenna effect. In addition it has been possible to achieve also heterostructures combining such photoactive heterostructures (TiO2/Ag) with a magnetic domain (Fe2O3), thus adding further functionality to the system, that can be magnetically separated in liquid media.
Heterostructured nanomaterials based on Ag/TiO2 and Au TiO2 have been also prepared by means of FSP at JM. A careful investigation on the role of synthetic parameters, including precursors nature and feed rate, on the resulting materials and their photocatalytic activity has been investigated.
Specific effort has been also devoted at JM in implementing a reliable scaling up of the FSP synthesis of TiO2 based photocatalysts, thus making available to beneficiaries relevant nanomaterial (up to several kilograms), for nanocomposite fabrication, testing and, finally for the use in the demonstrator implemented in WP6.
The different synthetic procedures have been throughout monitored by means of a set of physical and chemical characterization techniques (Task 1.3). A comprehensive investigation of the obtained nanomaterials by using complementary techniques, including microscopy techniques TEM, SEM, AFM, EDX, structural and surface chemical characterizations techniques such as XRD, XPS, FTIR has been performed. Optical properties have been assessed by UV-Vis and diffuse reflectance spectroscopy.
Surface chemistry of nanomaterials has been also investigated, as such a feature is not only important for the photocatalytic activity of the material, but it is also a key point to promote their integration in polymer matrices or immobilization onto specific surfaces. Surface engineering by silanization, ligand exchange or surface coating has turned particularly successful to enhance dispersibility, improve compatibility with matrix and stability over time (Task 1.2).
At M24, the data regarding characterization and photocatalytic activity evaluation of all nanomaterials prepared over the course of WP1 have been collected in a comprehensive a library of nanomaterials, including over 100 among nanomaterials and nanocomposites samples (Deliverable D1.6 and D1.7).
An accurate and systematic test of the photocatalytic activity, evaluated both in air and aqueous media, by assessing the degradation of a model pollutant/bacteria (toluene, Methylen blue –MB, Rhodamine B, E. coli), performed under UV and visible light irradiation and benchmarked against TiO2_JM, LIMPID reference material, and commercial Evonik (Degussa) P25, has allowed a judicious selection of the most promising photoactive materials and systems to be further incorporated in polymeric matrices and used in photocatalytic applications. (Task 1.4)
As far as photocatalytic performance evaluations, the LIMPID beneficiaries have agreed, following also PTA and EAB recommendation, to set up an experimental protocol to be used all over in the consortium to perform a preliminary test of the photocatalytic activity. Therefore a user-friendly, convenient and cost-effective protocol to compare the photocatalytic activity of newly developed materials, and to be proficiently carried out in the different labs, even when they are equipped with different experimental set up, has been implemented by CNR. Such a test is based on the comparison of the experimental data as a ratio of kinetic constants of the new catalytic material to be tested and the LIMPID reference standard, TiO2_JM, given same catalyst concentration in suspension.
Preliminary inter-laboratory validation runs carried out at CNR IPCF, CNR IRSA and MGU, by testing two different reference materials for degradation of MB as a model compound, has demonstrated that, irrespectively of the experimental conditions, the ratio of the kinetic constants is in the same range and, significantly, follows the same trend.
Preliminary tests have been performed on the whole series of novel nanomaterials (Task 1.4) showing some significant enhancement of performance, especially in the case of the metal semiconducting heterostructures (TiO2_Au, TiO2_Ag). Remarkably doped TiO2 nanomaterials developed at CU have been found significantly more (two times higher) photocatalytically efficient than the reference material.
Polyethylene-TiO2 films obtained at EPFL by direct current magnetron sputtering have been found to effectively discolour MB under low intensity solar/actinic light, demonstrating the critical role played by the preparative conditions on the discolouration kinetics. E. coli inactivation on TiO2, ZrO2 and TiO2-ZrO2 sputtered on polyester has been also demostrated under low intensity solar irradiation, thus suggesting a synergistic effect between the two oxides, aside a role of the sputtering conditions on the aggregation state of the sputtered particle. Also accelerated bacterial inactivation kinetics has been observed upon Cu-doping.
ACCIONA has also carried out preliminary test of photocatalytic activity on complete sets of different photocatalytic nanomaterials, both prepared in-house and by the different beneficiary in the consortium, by means of discolouration of Rhodamine B followed by colorimetry. This test has been performed according to the procedure described in the following paper: TiO2-containing cement pastes and mortars: measurements of the photocatalytic efficiency using a rhodamine B-based colourimetric test.
WP 2 - Polymers and coatings
In WP2 significant effort has been devoted to enhance fundamental understanding of structure-property relationships between hybrid film matrices and incorporated functional nanocomponents, and to, ultimately, bring to highly innovative products and technologies.
WP2 has been focusing on the synthesis of polymer materials, both organic and hybrid organic-inorganic, properly designed and realized to provide a suitable host for embedding the different NPs prepared in WP1. For this purpose, chemically stable polymers such as perfluorinated and siloxane polymers have been synthesized in the form of processable polymer latexes or dispersible pre-polymers. Functionalization of such polymers and development of specific NP functionalization has been carried out in order to optimize NPs dispersion. In addition, proper formulations have been designed to allow the chemical and physical access to the compounds to be degraded with specific photocatalytic reactions.
In particular, both ISC Fraunhofer and ACCIONA have applied sol-gel technology to incorporate functional NPs in a matrix and improving the film forming properties (Task 2.1). The hybrid material formulations and process conditions, thoroughly investigated, have resulted in high quality coating, promptly applicable onto different types of substrate of interest and with high compatibility to functional NPs. The adhesion of the coating matrix to the substrate as well as the compatibility to functional particles has been found to be enhanced by tailoring the polarity and incorporation of functional organic groups (Fraunhofer ISC).
In summary, in order to accomplish the requirements of the industrial applications in the project, for stainless steel reactor (Xylem) and on membranes for water treatment (UTM and Aquakimia), hybrid systems have been synthesized and preliminarily tested by Fraunhofer ISC (Task 2.3). The range cover UV and thermally curable coatings with a high degree of modifications in the structure (branched, non-branched, rigid, flexible, aliphatic, aromatic, polar, non-polar) which offer a great variability of applications on various substrate materials. Stainless steel and PVDF based substrate materials have been coated with different hybrid materials. On metal, the majority could be applied showing no tendency of delamination and decomposition after storage in water and under UV-light.
The coating of PVDF based membranes with various UV-curable hybrid compositions showed no evidence of incompatibility between substrate and coating, although some degree of porosity based inhomogeneous distribution in the membrane pore structure has prevented further test.
Alternatively, strategies based on synthesis of perfluorinated polymer latexes have been developed by UPV/EHU. Perfluorinated polymer and commercially available latexes (polytetrafluoroethylene, polyvinidene fluoride (PVDF) have been modified by post-polymerization of acrylic monomers, leading to latexes formed by core-shell NPs with a fluorinated core and a functional acrylic shell. (UPV/EHU and SpPI) (Task 2.2). Following this route substrates made by blending acrylic and PVDF/acrylic core-shell latexes have been successfully produced.
However, while in the case of the substrates prepared by blending a stratification of the TiO2 has been observed in the film, with a consequent segregation of most of the TiO2 NP at the bottom of the structure resulted in poor photocatalytic properties, different has been the case when Pickering miniemulsion polymerization has been used.
Indeed Pickering miniemulsion polymerization has allowed the production of polymer particles stabilized by TiO2 NPs (Task 2.4). Films prepared by these latexes have not shown a stratification of TiO2 but a homogenenous distribution along the film thickness.
Photocatalytic activity of the films made out of the TiO2 stabilized Pickering latexes demonstrated in the degradation of MB solutions, Rhodamine B (on coated concrete) (ACCIONA) and inactivation of E. coli (EPFL).
The Pickering stabilized polymeric dispersion has been used to coat different substrates, such as mesh, stainless steel, concrete, to degrade organic pollutants in water treatment systems (Task 2.3).
The Pickering stabilized polymeric dispersion has been also provided for implementation of the demonstrator to ACCIONA in WP6.
Novel multifunctional (magnetic and photoactive) polymer particle dispersions have ben also produced using the Pickering miniemulsion method (Task 2.4).
The composite multifunctional particles have been tested in the degradation of MB solutions under UV light. The composite particles demonstrated able to degrade the MB in five consecutive cycles and all the particles have been recovered by application of a magnetic field after each degradation cycle.
A patent has been filed on the method of preparation and application of the composite multifunctional polymer particle dispersion.
WP3 Photocatalytic nanocomposites materials and coatings
WP3 of the LIMPID project has been focused on the preparation of photocatalytically active nanocomposites, applied as coatings.
The following different technologies have been used to produce these materials:
- Wet chemical methods using either acrylic or fluoro polymer based or sol-gel derived inorganic-organic hybrid materials containing TiO2 nanoparticles, to coat surfaces like concrete, stainless steel and PVDF based membranes
- Deposition of TiO2 and metal doped TiO2 by sputtering techniques onto textiles of polymers like polyethylene and polyesters
- Chemical grafting of PMMA films and incorporation of nano-TiO2
- Fabrication of special structured porous membranes of PVDF with incorporated nano-TiO2.
Various nanocomposites consisting of organic polymers and TiO2 NP have been investigated (Task 3.1). In particular it has been found that, while the incorporation of reference materials like commercially available Evonik TiO2 NPs and LIMPID reference TiO2_JM NPs resulted in quite homogeneous and uniform surface, the incorporation of TiO2 NPs prepared by Fraunhofer ISC resulted in more inhomogenous surfaces indicating protruding features, and, hence beneficial effects in photocatalytic activity, that ask for accessible free TiO2 to accomplish the catalytic role.
The incorporation of photocatalytic NPs into sol-gel derived hybrid coating matrices has also proceeded via the surface functionalization with special sol-gel compatible components of NPs (Task 3.2) synthesized in WP1, like the TiO2 nanorods, a special type of particles manufactured by CNR-IPCF. Indeed the post-synthesis functionalization of TiO2 nanorods, originally prepared in the presence of oleic acid (OLEA) has been designed and performed to promote their incorporation into inorganic-organic hybrid coating system. The surface chemistry of OLEA-capped TiO2 nanorods has been modified, implementing capping exchange procedures with diverse capping molecules, with the aim to stabilize the NPs in typical organo-functional silane monomers used for formulating hybrid organic-inorganic resins. In this way a novel solvent-free, sunlight curable, hydrophobic, transparent and self-cleaning nanocomposite material has been manufactured by CNR IPCF. The nanocomposite consists of a methacrylic–siloxane resin loaded with 1 wt % TiO2 nanorods for use as structural coating, mainly intended for the protection of carbonate porous stones from (bio)deterioration. The embedded nanorods significantly increased the curing reactivity of the neat organic formulation both in air and inert atmosphere, since the photoactive nanocrystalline TiO2 acts as free radical donor photocatalyst in the curing reaction and they limit the inhibition effect of oxygen on photopolymerization.
The same nanocomposite formulation has been preliminarily tested as structural coating for the protection of porous carbonate stones. The results showed that the nanocomposite formulation forms a hydrophobic, durable, uniform and crack-free surface coating, able to reduce water penetration for capillarity effect and remove environmental organic pollutants, concomitantly preserving the original esthetical characteristics and vapor water permeability of the stone.
After a wide spread screening process of various compositions of cross-linkable inorganic-organic hybrid coating materials, two compositions have been identified at Fraunhofer ISC, which have been found suitable for application on devices for reactors and for polymer membranes (Task 3.2).
Interestingly, while the methacryl based system has been found suitable for UV-curing and for the epoxy based system the thermal curing has been demonstrated appropriate. Both curing methods can be applied in industrial coating processes. Both materials have been tested with various types of TiO2 NPs regarding the homogeneous agglomerate-free incorporation. The Fraunhofer ISC TiO2 NPs having an organic aliphatic or aromatic surface modification have definitely shown the best compatibility and the best homogeneous distribution in the selected hybrid coatings. Up to 50 wt-% of nano-TiO2 could be incorporated without agglomeration in the coating liquid and giving homogenous and uniform coatings.
A certain sensitivity to UV-pre-activation of the resulting composites has been observed in terms of increase of surface hydrophilicity, but with no influence on the photocatalytic activity. In general, the photocatalytic activity of the coatings containing the homogeneously distributed Fraunhofer nano-TiO2 particles has been observed higher than that obtained with other particles, which could be demonstrated by the discoloration of MB or Rhodamine B.
ACCIONA has developed sol-gel coatings for further incorporation of photocatalytic TiO2 NPs and a single step, acid-catalysed sol-gel process has been selected for the preparation of the sol to be applied as a coating materials by rolling on the cementitious substrate (mortar) realized by ACCIONA according to a specific standard procedure.
Tetraethylorthosilicate (TEOS) has been used as primary precursor and Triethoxymethylsilane (MTES) has been used as secondary precursor and silylation agent. Two different types of TiO2 NPs: commercial TiO2 P25 and TiO2_JM, have been incorporated into the sol-gel matrix in different quantities, namely 0 %, 5 %, 10 % and 15 wt% and photocatalytic activity test by means of discoloration of Rhodamine B on the photocatalytic films applied onto mortar substrates have shown that the samples with the best photocatalytic performance contained 10 wt-% TiO2 P25 and 15 wt-% TiO2 P25. The same test performed on the latex films developed by UPV/EHU and applied on mortar substrates by rolling and spraying has shown that the most suitable application method for the latex films has been spraying with an average percentage of Rhodamine B discoloration of 99 % and an index of photocatalytic activity of 0,96.
The deposition of TiO2 particles on PMMA grafted polymer films has been performed at CU by means of an original six-step synthesis procedure Task 3.2). Two different type of NPs, namely, Evonik P-25 and 1% SiO2/TiO2, produced by flame spray pyrolysis, have been attached to the PMMA film via reaction with the silanol groups to produce PMMA-TiO2 nanocomposite films. Various analytical techniques have confirmed the structure of the product and the presence of TiO2 on the nanocomposite films showing that the TiO2 NPs are well dispersed on the films. The photocatalytic activity of PMMA-TiO2 nanocomposite films has been tested for photodegradation of MB blue in aqueous phase under UV light irradiation and the two nanocomposite films have been found stable after 5 operation cycles, with average conversions of MB blue for film containing SiO2-TiO2 of 22% and with Evonik P-25 of 34%, respectively. No significant leaching of TiO2 NPs has been detected, indicating the stability of the manufactured nanocomposite. A comparison of various types of TiO2 NPs on the PMMA grafted film, tested in aqueous phase under UV-light and sun-light irradiation has revealed that in both cases a N-doped P25 load of the grafted films have showed the highest photoactivity in test periods of 8 weeks. The synthesis and grafting process has been transferred to PVDF membranes and again the N-doped TiO2 has shown the highest activity.
At EPFL the design, synthesis, and evaluation of photocatalytic nanocomposite films has been performed on flexible organic polymers or textiles by means of sputtering of different targets to obtain a wide range of catalysts (Task 3.3). The used substrates, PE and PES, have been pre-treated by RF-plasma and UV-C irradiation in order to enhance the photocatalyst attachment before sputtering of TiO2 photocatalyst on these non-polar substrates.
Whereas the TiO2/Cu-PES has shown almost no dependency on the light intensity for Staphylococcus aureus (MRSA) inactivation, the E. coli inactivation process has been found to be strongly dependent on the applied light dose. A stabilizing effect of TiO2 on the amounts of the Cu released during bacterial inactivation has been observed in co-sputtered surfaces compared to sequential sputtering of Ti and/or Cu on PES.
The antibacterial performance of PEpret-TiO2 transparent, non-scattering films has been found strongly dependent on (RF) plasma and ultraviolet light (UV-C) pre-treatment, that allows the PE to bind higher amounts of TiO2 necessary to induce E. coli inactivation in the minute time scale under simulated sunlight irradiation.
At UTM the focus has been on the preparation of nano-composite based membranes using PVDF as membrane and TiO2 as the photocatalyst (Task 3.4).
The first result has been a novel flat sheet membrane of titanium dioxide (TiO2)-halloysite nanotubes (HNTs) and PVDF as a photocatalytic separator for use in a photocatalytic membrane reactor (PMR). It has been found that 99.9% of hydrocarbons could be removed by the PMR within 8 h. In a second approach TiO2 photocatalysts in the form of nano-fibers have been immobilized on the membrane support. Hot pressing methods have been applied using a combination of heat and pressure to improve the attachment between fiber and membrane surface. The membrane prepared at 100 oC exhibited the highest photocatalytic activity in the degradation of Bisphenol A (BPA) under UV irradiation compared to 160 oC and 180 oC preparation temperatures. However, the pure water flux for the PVDF/e-TiO2 nanocomposite membrane has been reduced as the hot pressing temperature increased.
Furthermore, single layer hollow fiber membranes with TiO2 in the matrix have shown that PVP is a very good additive in improving the properties of PVDF-TiO2 composite membrane by enhancing permeability and selectivity, thus making the modified composite membrane a good candidate for a sustainable development of oily wastewater treatment. Also dual layer hollow fibre membranes, have been successfully fabricated by a single step co-extrusion technique and its properties have been found improved as of TiO2 NPs increasing their hydrophilicity, pore size and permeability, as demonstrated by the excellent performance in rejection (higher than 90 %.) towards nonylphenol.
As one objective of the project is the development of recoverable core/shell structured magnetic photocatalytic beads, suitable magnetic particles that could be used in fluorinated polymer synthesis have been identified by SpPI, the conditions for various synthesis routes have been evaluated and the synthesis has been tested and optimized by UPV/EHU (Task 3.5).
Recoverable catalytically active magnetic beads, based on multifunctional hybrid polymer particles containing both photocatalytically active NPs and magnetic particles, have been synthesized at UPV EHU. Magnetite particles have been encapsulated into acrylic latex particles during the latex polymerization and finally TiO2 NPs have been adsorbed on the polymer shell (Task 3.5).
It has been shown that the hybrid particles synthesized in this work presented superparamagnetism, and NP magnetic separation, redispersion and photocatalytic tests have been repeated several times. The hybrid polymer particles have shown a good photocatalytic activity towards MB degradation, which was up to 93.2 % in the 4th cycle and still 82.3 % in the 5th cycle of re-use, due to the large surface area of the hybrid polymer.
Overall, in the whole WP, a comprehensive set of physical and chemical characterization techniques, chemical, spectroscopic, morphological, structural, calorimetric chromatographic and mechanical has allowed not only to monitor the nanocomposite materials and coating preparation routes, but also to thoroughly investigate the relevant properties of the obtained functional materials.
WP4 Photocatalytic degradation of organic pollutants in water
The investigation on the efficiency of nanocomposite materials developed in LIMPID degrading selected types of pollutants in water and wastewater has been the main focus of Workpackage 4.
Several photocatalytic reactor designs, such as submerged membrane photocatalytic reactor, batch UV reactor with Hg-low pressure lamp, batch simulated-solar light reactor with Xenon lamp. Flow reactor, with UV and vis lamp and UV water disinfection test system, have been fabricated and tested in order to suit various nanocomposite configurations that have been synthesized in the previous WP (Task 4.1). The performance of these reactors together with developed photocatalytic medium (NPs and nanocomposite films and membrane) has been evaluated by using several types of pollutants and the findings have been compared with the commercial TiO2 P25 and with the LIMPID reference material TiO2_JM.
For the investigation of the photocatalytic degradation of organic pollutants in water and wastewater assisted by the developed nanocomposite photocatalysts (Task 4.2) CNR-IRSA and MGU have preliminarily set the composition of the emerging pollutants mixture to be employed in the different water matrixes for photocatalytic reaction with the new catalysts experimental activity, The mixture includes 22 organic pollutants selected among emerging pollutants not regulated by any European law, although, some of them are in the “watch list” of the European Commission, that has indeed started an obligation of monitoring in European surface water bodies.
These pollutants are recalcitrant to conventional wastewater treatment processes resulting in their detection in water supplies that receive inputs from wastewater treatment plants and include:
- pharmaceutical compounds (acetaminophen, mefenamic acid, gemfibrozil, warfarin, metoprolol, diclofenac sodium);
- iodinated X-ray contrast media (iopamidol, iopromide, diatrizoic acid);
- endocrine distruptor compounds (β-estradiol, estriol, triclosan);
- UV filters (2,4-Diydroxy-benzophenone , 2,2',4,4'-Tetrahydroxybenzophenone, 5-Benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, 2-Phenyl-5-benzimidazolesulfonic acid).
The experimental conditions, namely reactors and lamps, organic pollutants to be tested, the effect of operating conditions such as pH, light intensity and wastewater characteristic on pollutants degradation and water matrixes for organic pollutants degradation have been then identified. The analytical detection of the above reported emerging pollutants has been optimized based on liquid chromatography coupled to tandem mass spectrometry.
Under Task 4.3 EDC and palm oil mill effluent (POME) have been degraded by means of PVDF/TiO2 membranes by UTM jointly with AQUAKIMIA. The degradation of an EDC, i.e. nonylphenol, has been studied in a photocatalytic membrane reactor system where the TiO2 NP have been immobilized on the outer surface of dual-layer hollow fibres membrane. The presence of TiO2 NPs on the outer layer of dual-layer hollow fibre membranes greatly promotes the photocatalytic degradation of nonylphenol. Anaerobically treated palm oil mill effluent (AT-POME) degradation tests have been performed by using membrane prepared at different TiO2 loading, and using a submerged photo bioreactor. The results suggest the efficiency of the photocatalytic colour degradation. However a field test, in BBC Palm Oil Mill in Bintulu, Sarawak (Malaysia) by using a pilot plant purposely built by AQUAKIMIA, has shown that the highest percentage of colour reduction is obtained upon dilution of the effluent, probably due to the nature of the sample which is too dark to allow the efficient penetration of the UV light and in turn results in a poor effectiveness of the process.
A systematic investigation of different sets of LIMPID materials from JM, Fraunhofer ISC, CU and UTM, respectively, for degradation of real wastewaters has been performed in batch system equipped with i. 17 W Hg low-pressure UV lamp, ii. simulated-solar light, iii. excimer lamp, iv. flow system equipped with a 40 W Hg low pressure. The results of the photolytic treatments have revealed that the more recalcitrant pollutants are trimethoprim, metoprolol, carbamazepine, warfarin and gemfibrozil while the other have been removed efficiently by direct photolysis. A series of experiments has been than carried out in a secondary effluent (biologically treated wastewater) of a WWTP and in a less complex matrix i.e. groundwater, both spiked with the investigated organic pollutants.
Degradation kinetics of the mixture of the selected pollutants, including PPCP and EDC at low concentration (Task 4.5) have been investigated to assess the photocatalytic performance of the developed LIMPID nanocomposites. In particular it has been demonstrated that Degradation kinetics of the mixture of the selected pollutants, performed in presence of TiO2 NPs grown in situ onto the CNT surface (see WP1 Task 1.1) have shown that TiO2 NP/CNT nanocomposite is much more effective than commercial Evonik P25 in distilled water for degradation of few contaminants, while all the kinetics are slower, for real wastewater. However, since the amount of TiO2 in the CNT based nanocomposite is much lower (50%wt) than that of Evonik P25 TiO2 used as a reference, the investigated nanocatalyst presents a quite high specific efficiency and, in addition, can be easily removed from the aqueous solution by a mild centrifugation or a filtration step and, consequently, can be reused for a further photocatalytic treatment batch.
Results demonstrated that photocatalyst based on TiO2 NPs supported on PET (CU) is more effective than suspended TiO2 Evonik P25 and than LIMPID reference TiO2_JM in distilled water for degradation of iopamidol, iopromide, diatrizoic acid, diclofenac and sulfamethoxazole in UV photocatalytic treatments, although there is already a quite strong photolytic effect that contributes to the removal of the target pollutants. Finally, no adsorption of the target compounds on the photocatalyst surface was observed and no leaching of titanium dioxide in all the experiments performed employing TiO2 supported on PET (5% and 50%) was detected in solution.
At EPFL performance of Iron oxides supported on a flexible polymeric matrix have been tested under simulated solar light (Task 4.3) The effects of the Fenton reagents’ concentration on the Venlafaxine degradation time have been also identified, which found that fixing H2O2 between 35 – 60 ppm and FeSO4 between 7 - 25 ppm leads to 90 % of Venlafaxine degradation in less than one hour. Photocatalyic test of different TiO2-coated stainless steel plates and the collimated beam device (CBD) has been also examined showing a significant improvement in degrading MB in drinking water by factors of 7 -20 related to the percentaged reduction results. The study has also addressed the details of the photocatalyst performance during E. coli inactivation under visible light irradiation (> 400 nm), thus confirming the role of FeOx absorbing light in the visible region. The reaction rate constant k has been determined for each single pollutant present in aqueous matrix, thus allowing to compare the efficiency of the different newly synthesized nanocomposite catalysts. Overall, results clearly demonstrated that when performing the treatments in all the batch system in real wastewater, both suspended catalysts (reference TiO2_JM) and supported catalyst showed a very low performance in degrading the target pollutants probably due to a matrix effect that a real effluent can exercise against the catalyst. Toxicity investigation on treated water and wastewater (Task 4.6) has been performed at CNR IRSA In particular the tested catalyst that has resulted most effective (TiO2 deposited stainless steel) has been used for degrading the target pollutants in groundwater, under flow conditions system. Toxicity tests have been performed on samples collected during treatments performed in flow system, including also reference system for direct photolysis and for suspended referenceTiO2, by using selected standard tests. Namely Daphnia magna Strauss (Cladocera, Crustacea) – acute toxicity tests (UNI EN ISO 6341:2013), Vibrio fischeri – test with luminescent bacteria (UNI EN ISO 11348-3:2009), Green Alga Selenastrum capricornutum (UNI EN ISO 8692:2012), AMES test (mutagenicity test) and Fish embryo acute toxicity (FET) - the Zebra fish test. The limit test has provided that samples with a toxicity less than 10% for Daphnia test and less than 20% for Vibrio test are not toxic, results revealed that the investigated treatments do not increase the toxicity of the samples.
The results obtained by performing a more sensitive toxicity test, i.e. Green Alga Selenastrum capricornutum test and AMES test have revealed a decrease in toxicity value after 60 minutes of the treatments, clearly evident for the photocatalytic treatment in presence of the supported TiO2 on stainless steel in the AMES test. On the basis of the toxicity results a subsequent investigation about the chemical structures for the by-products formed under the oxidative conditions has been performed based on the data from liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) analysis. In particular LC-HRMS, the new instrumentation (high resolution quadrupole/time-of-flight/tandem mass spectrometer) recently acquired by CNR IRSA and profitably used within LIMPID activities, has revealed fundamental in the investigation of the chemical structure of the by-products, and, accordingly, of the degradation paths, fundamental for getting insight on the toxicity results.
WP5 Photocatalytic degradation of air pollutants and bacteria
WP5 reports the effective photodegradation of toluene in air taken as a VOC probe on several TiO2 catalysts under UV-A irradiation. The testing equipment/chamber has been described and the degradation test has been carried out according to the ISO22197-3 standard. The toluene removed reached about 1% under UV-A light within 24 hours. TiO2 NPs have been prepared by the ISC Fraunhofer and incorporated in a hybrid cross-linked sol-gel and finally supported on glass. The same photocatalyst has been also tested for NOx removal. The dynamics of NOx in air under UV-A light rendering NO + NOx has been investigated within 6 hours. The NOx removal has been also tested by catalysts prepared by ACCIONA using commercial P25 TiO2 Evonik and TiO2_JM incorporated in cross-linked hybrid composites prepared via sol-gel. The JM reference catalyst has degraded NOx up to 17% within 6h under UV-A, while the catalyst prepared using Evonik TiO2 P25 only reached a NOx 11%. CNR-IRSA reports preliminary tests for the NOx removal under UV-A light on TiO2 nanorods deposited on paper or cotton fabrics. CNR-IPCF has also reported reports self-cleaning ability on stone materials, by using methyl-red as a probe for discoloration under direct sunlight, demonstrating the possibility of using TiO2 nanorods for self-cleaning under daylight.
WP5 has been also devoted to investigation of pollutants degradation and bacteria inactivation in gas-phase. The investigation has been focused on relevant pollutants of selected industrial application. Such pollutants include simple aromatic-based compounds, namely benzene, toluene, xylenes and volatile alkyl-benzenes, as well as nitrogen-containing aromatic-based compounds, namely nitrobenzenes and, finally, inorganic pollutants like NOx.
Photocatalytic degradation of VOCs and NOx (Task 5.1) has been carried out by ACCIONA to investigate the pollutant degradation performance for the LIMPID nanocomposites developed in previous WPs. An in-house photocatalytic reactor, enabling the simulation of a wide range of indoor and outdoor air conditions, has been used to perform the VOCs degradation tests on different LIMPID material samples and evaluate their performance in degradation of pollutants under different conditions. The environmental conditions selected to perform the test are based on ISO 22197-3, describing the test method for air purification performance of semiconducting photocatalytic materials using toluene.
ACCIONA has focused on the fabrication and testing of the sol-gel formulations and has resulted that, as regard to Fraunhofer ISC formulations, the UV cured coating systems have shown enhanced degradation performance than the thermally cured coating systems, which did not exhibite, in fact, any significant photocatalytic activity.
Test on ACCIONA’s sol-gel systems has demonstrated for all the investigated formulations an effective photodegradation of VOCs under the applied experimental conditions. Among all the formulations, the coatings formulated with TiO2_JM reference material has been found to exhibit a slightly higher photocatalytic activity that the coatings using TiO2 P25 Evonik. ACCIONA’s best performing formulation has been the one containing 10% TiO2_JM.
Photocatalytic degradation of NOx by UV and/or visible light activated nanocomposite based coatings (Task 5.2) has been tested by ACCIONA for different nanocomposite based coatings developed by LIMPID beneficiary in LIMPID, to determine their ability to degrade NOx in air. As described in the first period report, the test has been performed according to the international ISO 22197-1 standard, which describes the method to obtain the air purification performance of photocatalytic materials by exposing a test piece to NOx polluted air under illumination by ultraviolet (UV) light. The most efficient NOx degradation has been those assisted by CNR and ACCIONA formulations. ACCIONA has also carried out the validation of the products obtained in the LIMPID project implanted in real work sites (WP6). In this context, NOx degradation tests of the nanocomposites have been carried out.
Most of the nanocomposites tested showed good NOx and toluene degradation capability, in some cases competitive with the currently available commercial photocatalytic paints
The conclusions of the tests performed are:
- Concerning VOC degradation, the best performing formulation has been the UV cured system by Fraunhofer ISC (39.3% of toluene degradation)
- Concerning NOx degradation, ACCIONA formulation, containing TiO2_JM NPs, has resulted in an overall NOx abatement of 22.7%
At comparison of fabrics, coated with TiO2 P25 NPs Evonik and TiO2 nanorods at CNR, have shown an interesting photocatalytic activity for the former sample, being 21,8% of NO and 7,9% of NOx converted. In both cases, the identification of a high surface area support has brought to a significant NOx abatement in spite of the very low amount of catalyst deposited (loading 0.05%wt – 0.25%wt), for this purpose XRF method has been assessed as a fast and accurate method to quantify titanium deposited on the support, and thus compare the performance.
Bacteria inactivation has been investigated by using selected bacterial model, such as Escherichia coli (E. coli K12) under daylight and dark conditions and onto different surfaces (polymers for medical applications, membranes for ultrafiltration, indoor walls) coated with nanocomposite materials set up in LIMPID. TiO2, Cu and Cu/TiO2 sputtered on polyester have been tested under actinic/sunlight to inactivate bacteria (E. coli) at the solid-air interface. The total inactivation has been observed for TiO2-polyester after 40 min, for Cu-polyester and Cu/TiO2 polyester after 10min. Thus this suggests that an interfacial charge transfer occurs between TiO2 and Cu based on the conduction and valence band positions of TiO2 and CuO. More important disinfection has also been observed in the dark for Cu-polyester and Cu/TiO2 polyester due to the high oxidation potential of the Cu-NPs, DC and High Power Impulse Magnetron Sputtering (HIPIMS) TiO2/Cu sputtered films have been compared with those obtained by HIPIMS using higher power. The latter resulted 15-16 times thinner compared to the DC sputtered films, thus allowing a significant saving of Cu and Ti, as they are non-renewable elements. Repeated disinfection cycles (8 cycles) have been performed on the Cu/TiO2 films.
Hybrid acrylic/TiO2 films inducing bacterial inactivation under low intensity simulated sunlight (Task 5.3) have been investigated at EPFL, by using nanocomposites provided by UPV/EHU and consisting of hybrid films prepared from TiO2 Pickering stabilized acrylic polymeric dispersion (WP2). Antibacterial performance of these hybrid acrylic/TiO2 films has been tested and stable repetitive bacterial inactivation has been reported for hybrid films with two different TiO2 loadings. Highly oxidative species (mainly OH•-radicals) have been quantitatively determined by fluorescence showing that higher concentration of OH• radicals results in a more effective bacterial inactivation. Bacterial adhesion experiments have confirmed qualitatively the beneficial effect of acrylic/TiO2 hybrid films compared to a pristine film, as a higher roughness results beneficial on E. coli inactivation.
Self-cleaning by Cu promoted semiconductor binary-oxides under low intensity sunlight irradiation has been found accelerated, as Cu acts as a promoter when added in very low amounts to the TiO2-ZrO2 matrix top most layers is shown to accelerate the MB-discoloration kinetics compared to the bare TiO2-ZrO2 matrix. A photo-induced interfacial charge transfer (IFCT) mechanism has been suggested to account for MB self-cleaning. The MB self-cleaning by the TiO2 is discussed considering the MB and the TiO2-ZrO2-Cu electronic band positions and generation of the OH°-radicals by TiO2-ZrO2-Cu under light.
WP 6 Technological application
The main objective of WP6 is to evaluate the technological viability of the investigated multifunctional materials, taking advantage by the peculiar process ability deriving from the characteristics of the polymeric matrix.
The systematic investigation on the scalability of the complex polymerization process to accomplish the complex polymerization process to prepare the PVDF/Acrylic hybrid materials, has allowed to identify, via multiple set of replicated experiments, the specifications of the reactors, temperature the precursors, reactant, initiator and stabilizers. Also, shelf life of final polymers has been assessed in an adiabatic chamber.
The pilot scale photocatalytic membrane reactor (PMR) manufactured by UTM in the first period of the project has been employed for degradation and separation of EDCs from wastewater. Under TASK 6.3 an integrated pilot scale photocatalytic membrane reactor (PMR) has been studied for oily ballast water and NP solution purification. From the investigational results, the following conclusions can be drawn:
1. The PMR has successfully photooxidized over~90% and less than ~5% of oily ballast water by 6 h UV irradiation on the surface nanocomposite photocatalytic membrane (M2) and surface of pure PVDF membrane (M1), respectively.
2. PMR filtration has rejected more than 99.5 % of oily ballast water during 1 h of membrane filtration process for M2.
3. The PMR has successfully photooxidized NP solution within 3 h of UV irradiation.
4. The nanocomposite photooxidation membrane has provided promising result on the water flux and antifouling property due to presence of an effective nanofiller (HNTs-TiO2).
Concerning the technological applications of the products obtained in the LIMPID project, efforts have been made for both air purification and water treatment. New UV lamps (based on UV-LEDs and excimer) have been successfully employed for the photocatalytic degradation of a mixture of emerging organic pollutants using the supported nano-sized catalysts prepared by the partners of the consortium. PET films have provided the most promising results with a removal of 80% of MB after 180min of UV-A exposition. Higher percentage of MB degradation has been obtained for all supported catalysts when using UV-C radiation. As for the activity with the new UV lamps (LEDs-UV based lamps and excimer lamps), tests have been performed in both MilliQ water (reference) and in wastewater using lab-scale reactors and larger reactors. Results showed that the specific efficiency of each lamp is compound-dependent and the specific efficiency of the pilot scale UV reactor (LBX3) is higher than the batch lab-scale system.
Also MB degradation experiments in drinking water have been carried out on several coated meshes using two different UV reactors, LBX3 (UV lamp centrally arranged) and E2 (UV lamps outer sphere arranged) in continuous flow. For all tests, the degradation of MB has been only significant in the presence of H2O2.The TiO2-containing coatings have not contributed to the UV/AOP degradation result. The LBX3 system performed better than the E2 system
Successfully application of two nanocomposites developed through the LIMPID project (sol-gel with 10wt% TiO2 provided by JM and acrylic latex with 10wt% TiO2 provided by Fraunhofer) in two street canyons has been performed. Although it has been difficult to analyse some of the results obtained, both nanocomposites tested have shown good Rhodamine B discoloration capability (75-88% of Rhodamine B discoloration and an index of photocatalytic activity greater than 0,1). Concerning the NO/NOx degradation capability of the testing core samples according to the ISO 22197-1 (feed flow rate=3,0 l/min and [Initial NO]=1 ppm), the sol-gel coating has shown a 15,17% of NO conversion and 10,17% of NOx conversion. In the case of the latex, 11,22% of NO and 6,71% of NOx has converted using and adaptation of the ISO 22197-1 (feed flow rate=1,5 l/min and [Initial NO]=500 ppbs)
Lastly, a risk assessment of the production of TiO2 nanopowder has been carried out using the control banding tool CB nanotool 2.0. The control banding tool CB nanotool 2.0 used in order to determine the overall nanomaterial exposure risk level, is based on the severity score and probability score. The current knowledge about potential negative impacts on human health of the manufactured nanomaterials and parent materials of TiO2 along with a proper estimation of the exposure conditions have been used. For the risk assessment, the methodology with the risk potential, the necessary measures and the remaining risk considering these measures have been used and the risk matrix has been produced. (Task 6.7)
WP7 Dissemination
WP7 has disseminated the knowledge generated in this project by different properly planned routes. Internal dissemination, among the beneficiaries, has been accomplished by realizing common databases, exploiting intranet facilities of LIMPID website, including a document-sharing platform and a LIMPID blog.
The webpage related to the project activity has provided a common platform to facilitate information exchange among beneficiaries and has been also one of the main vehicles of dissemination and interaction with the public seeking information about LIMPID, as demonstrated by the hi number of visitors counted for the webpage (Task 7.1).
Academic beneficiaries, both universities and research centers have been active in training students, at different levels of their career, Bachelor, Master and PhD degree in topics related to LIMPID activities. It is worth to point out that out of 34 students 12 were women, thus demonstrating the attention paid to gender equality issues, and that 8 PhD projects have been running dealing with subjects related to LIMPID topics (Task 7.2).
Actions for disseminating the results and the technological advance to relevant audience have been performed (Task 7.3) by organizing two Exploitation and Dissemination Workshop. Indeed to increase dissemination and networking opportunities, LIMPID consortium has set up a second workshop in the areas of nanomaterials for depollutions, beside the first "Workshop on Nanomaterials for photocatalytic depollution" that has been held in the frame of the ASEAN-EU STI Days in Bangkok (Thailand) on 22-23 January 2014, namely“International Workshop on Nanocomposite Materials for Photocatalytic Degradation of Pollutants: Advanced Opportunities for New Applications” in Kuala Lumpur (Malaysia) on 12 November 2015 and jointly organized by CU, UTM and AQUAKIMIA.
The event has pointed out that international cooperation dimension can be an increasingly important element of the environment research policy and the fields of nanomaterials and nanotechnology for depollution, as has been place in facts in LIMPID.
LIMPID has actively looked for links and interactions with other EC-funded projects in the areas of nanomaterials for environmental depollution, connections have been realized with the following projects: PCATDES “Photocatalytic materials for the destruction of recalcitrant industrial waste” (www.pcatdes.eu/) coordinated by Phil Davies, 4G-PHOTOCAT “Fourth generation photocatalysts: nano-engineered composites for water decontamination in low-cost paintable photoreactors (http://www.4g-photocat.eu/) coordinated by Radim Beranek, WATER “Winning application of nanotechnology for resolutive water hydropurification” (http://www.water.imm.cnr.it/) coordinated by Vittorio Privitera.
Also LIMPID has been pursuing active participation to the recently launched European Clusters: “European Cluster on Catalysis” (http://www.catalysiscluster.eu/) coordinated by Dr. Silvia Gross and Dr. Helge Wessel, Scientific Advisor Prof. Gabriele Centi and “Engineering & Upscaling Cluster” coordinated by Dr. Sophia Fantechi (EU Commission) Dr Gerhard Goldbeck, Goldbeck Consulting Ltd and Dr Bojan Boskovic,Cambridge Nanomaterials Technology Ltd.
The creation of an End Use Advisory Board (EAB) has represented an effective tool to obtain insights and advices to effectively address the project activities towards end-users and stakeholders needs.
The role of the EAB has been to contribute with the renowned competences and valuable expertise of its members to bringing advises and suggestions to LIMPID project Consortium to the decisions made by the Steering Committee itself. EAB Members have critically looked at the LIMPID activities and made comments and consideration on the issues specifically related to their own field of expertise and their comments, remarks and advise have been implemented during the project.
LIMPID activities have resulted in several relevant exploitable results, some of them have been filed or are in preparation to be presented.
WP8 Scientific Management and
WP9 Administrative and Financial management and coordination
The Scientific Management Workpackage (WP8) has satisfactorily succeeded to provide strategic vision of the project, a scientific management (Task 8.1) ensure a correct and consistent project development with respect to the project progress milestone, prepare scientific meeting (Task 8.2) and perform a quality check of technical performance versus Annex I Description of the work and Gantt Chart (Task 8.3). Research risk management has properly handled (Task 8.4)
The administrative and financial management and coordination (WP9) has adequately accomplished the administrative, financial and contractual coordination, reporting, financial and administrative management for the project, has appointed the EAB (Task 9.1) has coordinated the scheduling and organization of regular consortium meetings and Management Board and Advisory Board meeting (Task 9.2) coordinated communication among partners, the European Commission, and external institutions (Task 9.3). The management of three Amendments to the Annex 1, made necessary during the project, has been also properly performed.
Potential Impact:
Potential socio-economic impact
Significant contributions to functional nanomaterials design, and fabrication, understanding of their photocatalytic behaviour, both in air and in water, water purification reactors and coating for air pollutant removal, bacteria inactivation and self-cleaning have resulted from LIMPID.
The achievements reached in LIMPID project has allowed to progress beyond of the state-of-the-art in the field of functional nanomaterials and original technologies for air and water photocatalytically assisted depollution,
The development and usage of multifunctional catalytic materials and coatings along with highly efficient processes, accomplished in LIMPID, can provide original nanotechnology-based solutions with a potential economic impact. Indeed, while the scientific impact of LIMPID can be clearly inferred looking how well have been received the output of the project by the material, engineering and environmental science communities, as recognized by the high number of scientific publications on peer reviewed journals (36) and the concomitant presence of a few patents, already filed or under submission represents an effective indicator of the potential impact of the project achievements.
Potential impact for new materials and technologies for the environment, that is currently considered as one of the most important challenges for the society, can be, thus, anticipated.
In this context, LIMPID project has also served as starting point to create a high-level multidisciplinary and multisectorial consortium with cutting-edge expertise in the field of functional materials, including polymers and nanomaterials, environmental science and engineering.
The strong collaborative spirit and the scientific and technological skills shown by the consortium could be crucially exploited for further progresses towards a sustainable environmental solutions based on nanocomposites materials.
The close collaboration between academic and industrial partners, along with the advice of the EAB has been crucial to stir the project in order to reach the reported achievements.
The results of the scale-up activities, for instance, both for the complex polymerization process to prepare the PVDF/Acrylic hybrid material (SPpI) and for the nanomaterials synthesis via FSP may defnitely enhance the chance of industrial exploitation of the obtained functional materials, enabling, in principle, production lines for the realized photocatalytic nanocomposites.
Concerning the technological applications of the products obtained in the LIMPID project, significant results have been achieved both for air purification and water treatment. Some of the tested composites have also suggested a good potential for protection of cultural heritage stone artifacts.
Can be, thus, may be more clearly inferred how significant can be the economic potential of the developed nanocomposites and processes based on their application. Obviously, the time to market of some of the proposed products for the different applications can be variable.
It must be pointed out, however, that, the results obtained in LIMPID, although of large fundamental impact and the assessed technological viability, evidence also some limitation due to the intrinsic nature of the semiconductor assisted photocatalytic process. In fact, in spite of demonstrated enhancement in efficiency observed with the materials developed in the project, the overall process may still remain inadequate when compared with other more cost effective AOP processes, considering also the starting cost related to the setting of newly developed nanomaterials system in place of the existing ones. All these issues may still result limiting, if the new materials and technology are intended to provide, for instance, a single solution for any water purification problem.
For instance, a limitation could be given by at too long total residence time needed for the photocatalytic activities, while most applications for water treatment are normally continuous and with short residence time of a few minutes at most.
However, a realistic impact can be reasonably envisaged when the new nanocomposites and the related technologies are applied to answer to unique and specific air depollution problems, such as air purification and disinfection in restricted environment, or for solving specific needs in water degradation, related to a defined purification step, suitably integrated in a more complex treatment.
For instance, as pointed out by the EAB, interesting is the case of emerging substances with Endocrine Disrupting Chemicals properties that are usually poorly reduced by WWTP (waste water treatment plants), although for some of them, just for the pharmaceuticals evaluated in LIMPID, an obligation of monitoring in European surface water bodies, has been started by the European Commission.
Degradation of these recalcitrant contaminants of emerging concern in typical purification treatments may, in fact, become difficult and result in degradation path characterized by transformation products that retain their toxicity over time. In this perspective, the new photocatalytic nanocomposite materials could enable alternative degradation paths, finally resulting in a complete removal of toxicity. It must be also definitely highlighted that, as also recommended by the EAB, different treatments should rely on a wide spectrum of eco toxicity tests that can detect also chronic exposures and that are able to cover multiple trophic levels of the aquatic food chain. The potential toxicity could be caused both by the residual of the micropollutants treated and also by the nanomaterials present in the samples. Therefore, in LIMPID, valuable have demonstrated the toxicity tests acute and chronic performed on samples collected during photocatalytic treatments in flow system: - daphnia toxicity test, vibrio fischeri test, green Alga Selenastrum capricornutum, AMES test (mutagenicity test), the Zebrafish (Fish Embryo Toxicity Test-FET).
Another example is given be the case rising from a limitation, pointed out by the EAB, and related to the specific experience carried out in LIMPID by the intense color in organic wastewater, that, of course affect the light penetration, resulting in a reduced efficiency of the systems. In this case a possible solution would be, not just to dilute the wastewater, as it would be not that competitive, the realization of a hybrid system which includes a pre-oxidation step of the dark organics, to reduce color intensity and hence enhance light penetrations, so as to reduce the residence time needed for the photocatalytic applications, still maintaining the advantage of the nanocomposite system.
In summary, therefore the actual impact, like also addressed by the EAB members in their comments, stays in a judicious identification of the processes that can be effectively assisted by the prepared and, accordingly in a suitable and well-thought integration of the novel methods in proper processes.
The LIMPID proposal consortium as demonstrated able to build and strengthen reliable link of scientific and technological cooperation between beneficiaries in in Europe, South East Asia as well as the third country.
The strong complementarity in the expertise of the beneficiaries in Malaysia and Thailand, along with their well-known reputation for their work in the area of photocatalytic materials and catalytic processes (CU, Thailand) and water purification membranes technologies (UTM, Malaysia and AQUAKIMIA, Malaysia), respectively, has been of strong relevance. Furthermore, the consortium includes one partner from another third country (McGill University, Canada) with a unique expertise in water toxicity evaluation, which has effectively complemented the consortium, expanding the international dimension of the project. In addition, the four participating European industrial partners have commercial and, in some cases, industrial activities in ASEAN countries which will also benefit from the future economic interactions of the two geographic areas.
The LIMPID exploitation foreground, which is regulated by the Consortium Agreement, is represented by the results coming from the project and having a commercial potential significance, that can be exploited as a product, process, service. They can be identified in LIMPID catalytic nanomaterials (CNR IPCF, JM, CU, Fraunhofer ISC), nanocomposite materials for photocatalytic degradation of pollutants, both in air and water (Fraunhofer ISC, SpPI, UPV/EHU, UTM, CU ACCIONA, EPFL), characterization methods to evaluate the photocatalytic activity of the LIMPID nanocomposite materials in air (ACCIONA, EPFL, CNR IPCF, CU), novel photocatalytic systems and reactors (UTM, AQUAKIMIA, XYLEM, CNR IRSA, EPFL)
The results achieved within LIMPID, can also effectively affect the standardization issues, providing new methods and tools for standardization and certification, as the current limitation related to standardization test protocols for photocatalytic water purification has been clearly pinpointed in the project. In fact, more suitable standards would be amenable to properly and reliably assess the photocatalytic performance of the newly developed nanomaterials based photocatalytic systems, under conditions which necessarily need to be specifically identified for the original classes of materials, and that cannot be straightforwardly evaluated by using existing protocols.
Specifically for the industrial beneficiaries different commercial and exploitation interests have been defined. Namely for JM the main interest is in catalytic nanomaterials. The production of 80% industrially important chemicals involves catalysis. Catalysts are involved in more than $10 trillion in goods and services of the global GDP annually. Catalyst industry contributes around 2% of total investment in a chemical process. The global catalyst market for pharmaceutical and fine chemicals is around £90M, and of that around a half is in heterogeneous catalysis. In order to achieve a revenue growth, market share will have to be gained from JM’s international competitors by the introduction of new and innovative products offering performances and economic benefits.
For SpPI the main interest is linked to the fact that degradation of conventional polymers has been a limitation up to now for the development of a technology based on photocatalytic decontamination. Fluorinated materials could overcome this limitation and the possibility to synthesize fluorinated polymers via emulsion latex gives high flexibility to design the needed coating. Therefore, final market opportunities are related to needs of higher level of quality of the life of social communities. Then the final end-user are municipalities and companies interested in the level of pollution.
For XYLEM, the main interest in novel water purification photoreactors, as in this field the prospected yearly growth rate for disinfection systems are around 6 to 8% and for advanced oxidation systems 10 to 12% worldwide. The access to photocatalytic materials which can be used with existing reactors, as well as the use of modified lamp sources, enabling reduced energy consumption, would bring to the company grow sales volume by 10% in the first 3 years after market launch.
For ACCIONA new technological solutions for air purification represent the most relevant issue, as currently the limit of some pollutants is exceeding several times in the year, thus resulting in serious health problem for the citizens, with related assistance costs long with relevant fines from EU. Therefore, a market strategy devoted to application of photocatalytic materials in construction to avoid fines and health problems may result promising in the next future.
Also new technological solutions for water purification are appealing for AQUAKIMIA, as the Malaysian Government is now focusing on bringing potable water to rural communities and more than 5000 do not have access to drinking water, therefore AQUAKIMIA is looking at expanding the product range, including membrane technology and potable water applications.
LIMPID achievements have in principle a large strategic and economic impact as can increase the access to clean water, also in critical environment, where power supply for instance can be not a trivial issue, such as in remote areas or in developing countries. Therefore a strong impact can be given by the novel photocatalytic nanocomposite materials and processes, resulting in high efficiency and able to extend their activity beyond UV to the visible spectrum of natural sunlight for environmental application at a reasonable price.
Finally, LIMPID has pointed out the international cooperation dimension can be an increasingly important element of the environment research policy and the fields of nanomaterials and nanotechnology for depollution, and that has been place in facts in the project.
Societal implications
Although photocatalysis is not within the specific focus of the wider public, there are tangible impacts from the numerous applications. In particular results and developments achieved within LIMPID are focused towards applications of the functional nanomaterials in environmentally relevant application, as water and air purification. Therefore the advantages of the novel proposed technological solution for the environment, which can improve quality of air and water resource can likely arise a significant social interest and public acknowledgment. In addition, the effort made to disseminate the LIMPID topics to undergraduate and younger students as well as to general public can further increase the attention towards LIMPID achievements.
The photocatalytic nanomaterials and technologies resulting from LIMPID, as used for environmental, cleaning, depollution, can lead to reduction of pollutants and minimization of utilization of chemicals, resulting beneficial on the health of the general public and thus on the quality of life.
For the novel photocatalytic nanomaterials, coatings and systems which are outcome of LIMPID a significant technological potential can be envisaged, as they can stir different applications, such as bacterial deactivation in critical environment like in medical applications, hospitals, degradation of contaminant of emerging concern in specific treated waste waters, self-cleaning coating on building, facades or even cultural heritage artifacts.
Finally, nanocatalysts in host matrix are also expected to have little negative impact on human health and the environment, since they are usually immobilized in/on a substrate material (e.g. metals, tiles, or glass), as once integrated in a multifunctional nanocomposites, nanocatalysts are not likely to be released in amount that would result hazardous to humans or the environment. This aspect also may positive impact the social response to the outcome of the project.
The specific attention paid in LIMPID to the societal concerns includes a task devoted to risk assessment and occupational safety. Indeed a risk assessment on the production of TiO2 nanopowder has been carried out. The control banding tool CB nanotool 2.0 has used in order to determine the overall nanomaterial exposure risk level, based on the severity score and probability score.
Consideration of gender aspects
Gender issue have been constantly addressed within LIMPID project activities. The main goal has been to keep gender issue in the foreground, by improve attractiveness of scientific and technological themes and encourage woman participation to science and technological playground, providing space for discussion, along with the most fundamental gender equality opportunity.
In particular, throughout the project equal opportunity policy in hiring personnel, assistance for women in developing their career plans and sharing of experiences on career-development have been implemented.
The effectiveness of the measures has been reflected in the number of PhD, and Master/Bachelor students involved in LIMPID project related activities, as out of 34 students 12 are women.
All LIMPID beneficiaries have encouraged women to attend national and international conferences, schools and workshop and encouraged women to apply for positions and to get involved in project activities like meeting, workshops.
Also in LIMPID the coordination of the Project as well as of three out of the 8 workpackages has been performed by a woman.
List of Websites:
http://www.limpid-fp7.eu/
contact: M. Lucia Curri email: lucia.curri@ba,ipcf.cnr.it
webmaster: Claudio Capasso email: c.capasso@ba.ipcf.cnr.it