Periodic Reporting for period 1 - Enhanced-MUMs (Enhanced MUlti-Functional Membranes for Water Treatment and Desalination)
Berichtszeitraum: 2018-06-25 bis 2020-06-24
Enhanced-MUMs addresses the problem of global shortage of freshwater sources and the consequent growing demand for alternative water resources. The project is aimed at providing a tool for cost effective alternatives to traditional water supplies, such as reuse and recycling of wastewater and seawater desalination.
The advancements of material science and engineering reveal the potentials to solve real-world practical problems and heighten the current technologies. The engagement of multidisciplinary research areas into the commercial membrane systems offers an opportunity to refine and optimize current techniques as well as to provide new insights and novel methods to handle the current challenges.
The main objective of Enhanced-MUMs is the development of advanced multifunctional low-cost polymeric membranes for water treatment and desalination. The ideal membrane should provide high water flux, improved stability and resistance to fouling and should retain a high rejection rate throughout its service life. The expected enhancements in membranes’ performances include:
1) high permeability (with reduced specific energy consumption);
2) suitable mechanical properties;
3) enhanced water treatment and desalination properties;
4) antifouling and antimicrobial characteristics.
The advancements of material science and engineering reveal the potentials to solve real-world practical problems and heighten the current technologies. The engagement of multidisciplinary research areas into the commercial membrane systems offers an opportunity to refine and optimize current techniques as well as to provide new insights and novel methods to handle the current challenges.
The main objective of Enhanced-MUMs is the development of advanced multifunctional low-cost polymeric membranes for water treatment and desalination. The ideal membrane should provide high water flux, improved stability and resistance to fouling and should retain a high rejection rate throughout its service life. The expected enhancements in membranes’ performances include:
1) high permeability (with reduced specific energy consumption);
2) suitable mechanical properties;
3) enhanced water treatment and desalination properties;
4) antifouling and antimicrobial characteristics.
Cellulose acetate was selected as a cost-effective and market available bio-based polymer.
A wide range of cellulose acetate membranes, differing in pore sizes and pore size distribution, was achieved by optimization of the fabrication conditions without chemical or structural modifications. The basic fabrication was carried out using phase inversion of casted membranes, in which pure deionized water was used as a main coagulation medium. The speed of the film applicator and the thickness of the casted films were found to be important parameters to be controlled during the fabrication process. The produced membranes were porous in their upper and lower surfaces. The fabrication conditions were found also to have a significant effect on the cross-section morphology of the membranes, which were found to be typically anisotropic, with different pore shapes and sizes in a finger like pattern.
Further modifications to control the microscopic structure of the produced membranes were carried out by mixing the polymer solution with a water-soluble surface-active agent (surfactant) before the casting of the membrane. The produced membranes presented a sponge like structure instead of a finger like one, in addition to a more uniform pore size distribution.
Another modification was introduced by using a salt coagulation bath instead of the fresh water bath: the result was a reduction of the pore sizes of the produced membranes, which widened their filtration range (ultrafiltration, nanofiltration).
The previously mentioned modifications were also combined together, providing an enhanced membrane with small pore sizes and a narrower pore size distribution in an overall more homogeneous microscopic structure.
All the produced membranes were structurally characterized and investigated for their water permeability and organic dye removal efficiency (using representative models for organic water pollutants).
The optimized preparation conditions, chosen on the bases of the previous results, were then employed to prepare membranes containing photosensitizers (PSs). The PS was added to the polymer solution prior to proceed with the casting and phase inversion procedure. Several PSs, differing in structure and charge/polarity were tested in different loadings, and the obtained membranes were optically characterized by means of steady-state and time-resolved photophysical techniques. The singlet oxygen production capacity of the PSs embedded in the polymeric membranes was analysed by means of an innovative method that makes use of a colorimetric singlet oxygen trap in a solid-liquid interface setup.
All the modified membranes were structurally characterized and investigated for their water permeability.
The outcomes of the project have been presented at five national and international conferences. At least two papers will be shortly submitted. Participation of the ER and the Supervisor to the European Researchers’ Night event in 2019 in Bologna with a stand, presentations and activities allowed dissemination to the large public of the innovation brought by the use of polymeric membranes to desalinate and remove pollutants from water. Moreover, the ER has been invited to present the project results at the “Aquatech 2019” Exhibition in Amsterdam, with a lecture at the “Meet the Expert Stage” of the InnovationLab and a poster at the EU Innovation Project Pavillon. The latter exhibition is a unique event in Europe with a 100% focus on water (process, drinking and wastewater), with an estimation of 25,000 visitors from 140 countries and over 1000 exhibitors.
A wide range of cellulose acetate membranes, differing in pore sizes and pore size distribution, was achieved by optimization of the fabrication conditions without chemical or structural modifications. The basic fabrication was carried out using phase inversion of casted membranes, in which pure deionized water was used as a main coagulation medium. The speed of the film applicator and the thickness of the casted films were found to be important parameters to be controlled during the fabrication process. The produced membranes were porous in their upper and lower surfaces. The fabrication conditions were found also to have a significant effect on the cross-section morphology of the membranes, which were found to be typically anisotropic, with different pore shapes and sizes in a finger like pattern.
Further modifications to control the microscopic structure of the produced membranes were carried out by mixing the polymer solution with a water-soluble surface-active agent (surfactant) before the casting of the membrane. The produced membranes presented a sponge like structure instead of a finger like one, in addition to a more uniform pore size distribution.
Another modification was introduced by using a salt coagulation bath instead of the fresh water bath: the result was a reduction of the pore sizes of the produced membranes, which widened their filtration range (ultrafiltration, nanofiltration).
The previously mentioned modifications were also combined together, providing an enhanced membrane with small pore sizes and a narrower pore size distribution in an overall more homogeneous microscopic structure.
All the produced membranes were structurally characterized and investigated for their water permeability and organic dye removal efficiency (using representative models for organic water pollutants).
The optimized preparation conditions, chosen on the bases of the previous results, were then employed to prepare membranes containing photosensitizers (PSs). The PS was added to the polymer solution prior to proceed with the casting and phase inversion procedure. Several PSs, differing in structure and charge/polarity were tested in different loadings, and the obtained membranes were optically characterized by means of steady-state and time-resolved photophysical techniques. The singlet oxygen production capacity of the PSs embedded in the polymeric membranes was analysed by means of an innovative method that makes use of a colorimetric singlet oxygen trap in a solid-liquid interface setup.
All the modified membranes were structurally characterized and investigated for their water permeability.
The outcomes of the project have been presented at five national and international conferences. At least two papers will be shortly submitted. Participation of the ER and the Supervisor to the European Researchers’ Night event in 2019 in Bologna with a stand, presentations and activities allowed dissemination to the large public of the innovation brought by the use of polymeric membranes to desalinate and remove pollutants from water. Moreover, the ER has been invited to present the project results at the “Aquatech 2019” Exhibition in Amsterdam, with a lecture at the “Meet the Expert Stage” of the InnovationLab and a poster at the EU Innovation Project Pavillon. The latter exhibition is a unique event in Europe with a 100% focus on water (process, drinking and wastewater), with an estimation of 25,000 visitors from 140 countries and over 1000 exhibitors.
Membrane-based desalination techniques are currently considered more environmentally friendly and energy-efficient than thermal desalination methods such as multistage and multiple-effect distillation.
Although synthetic polymeric materials are popular and cost-effective, unfortunately their inherently low stability greatly limits their applications. Moreover, poor compatibility between the polymeric materials and the additive that could enhance their properties usually results in formation of defects during membrane preparation which limits the possibility to improve the polymer characteristics. Currently, significant efforts are being paid to develop proper low-cost polymeric membranes from commercial polymers.
The project deals with research and development of cost-effective and environmentally-friendly composite membrane materials with enhanced intrinsic stability for efficient water treatment and desalination. The addition of photosensitizers to the polymeric material is the key point to impart photoinduced antifouling and antimicrobial characteristics to the membrane in order to achieve a “self-disinfection” function that prolong its lifetime and enhance its performances in view of application in filtration devices.
Although synthetic polymeric materials are popular and cost-effective, unfortunately their inherently low stability greatly limits their applications. Moreover, poor compatibility between the polymeric materials and the additive that could enhance their properties usually results in formation of defects during membrane preparation which limits the possibility to improve the polymer characteristics. Currently, significant efforts are being paid to develop proper low-cost polymeric membranes from commercial polymers.
The project deals with research and development of cost-effective and environmentally-friendly composite membrane materials with enhanced intrinsic stability for efficient water treatment and desalination. The addition of photosensitizers to the polymeric material is the key point to impart photoinduced antifouling and antimicrobial characteristics to the membrane in order to achieve a “self-disinfection” function that prolong its lifetime and enhance its performances in view of application in filtration devices.