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Final Report Summary - ECOFLOC OPTIMIZE (Combining an eco-friendly approach and a product performance approach to develop novel flocculation strategies)

Combining an eco-friendly approach and a product performance approach to develop novel flocculation strategies - ECOFLOC Optimize: http://www.uc.pt/fctuc/deq/ecofloc
Contact: coordinator – Prof. Maria G Rasteiro, University of Coimbra, mgr@eq.uc.pt
The main objectives of the project can be summarized as follows: development of new, more eco-friendly flocculants, and establishment of a map of product effectiveness versus flocculant characteristics to enable the development of predictive models for the flocculation process, which will enable more informed choices of flocculants for each specific process/application.
Regarding the first objective two approaches were proposed: development of polymers based on natural resources, namely cellulosic wastes or other natural materials (tannins) (WP2) and development of new synthetic polymers using either new, more eco-friendly monomers and/or synthesized using more health friendly oils, reducing the VOC component in the synthesis (WP3). The first topic of these objectives constitutes the theme of the research plan of ESR1, while the second one is the theme of the research work of ESR2.
As for WP5, "Developing a map of flocs structure versus flocculant characteristics", the ultimate objective of this WP is to construct a structure map to facilitate informed selection of flocculants to attain targeted flocs structures. The flocculants developed in WP 2 and 3 were tested in WP 5, regarding their performance in pre-selected systems. The construction of the map of flocs structure versus flocculant characteristics was based on an experimental design methodology. Performance was based on determining flocculation kinetics (including evolution of flocs size and structure with time) using the LDS (Laser Diffraction Spectroscopy) technique to monitor the flocculation process.
Also, the ultimate objective of the project was to graduate two PhD students, combining an academic with an industrial environment during training. Both ESRs registered for PhD in Chemical Engineering in the University of Coimbra, having completed several courses from the curricula of the Doctoral Program. Additionally, they were offered short courses on complementary skills, including courses at the University of Leeds (Associated Partner)
Still in relation to the training program foreseen in WP1, ESR2 submitted her PhD thesis to the University of Coimbra, under the topic “Development of novel flocculants to treat oily waters using health-friendly processes”, and has been awarded a PhD degree by the same University in April 13th, 2018. ESR1 is going to submit her PhD thesis entitled “Modification of natural polymers and natural by-products for coagulation and flocculation purposes” still in 2018.
Regarding the research work it is organized in 4 work packages: WP2 - Modifying natural polymers and natural by-products for coagulation and flocculation purposes; WP3 - Synthesis of novel flocculants based on oil-free processes or novel monomers; WP4 - Combination of natural and synthetic polymers to improve flocculation performance; WP5 - Developing a map of flocs structure versus flocculant characteristics.
In WP2 the work was directed to obtaining cheaper but effective, natural based flocculants from cellulose wastes and also performing modification on tannins to obtain natural coagulants for effluents treatment from different possible industries (with a main focus on textile industries). It was possible to modify tannins from different origins which were tested with positive results in decoloration of model coloured effluents and in an industrial water, including in a waste water pilot plant. One of the points which needs further consideration is the variability of the raw material, even when the origin is kept constant. Scale-up of the tannins modification process was also achieved with success, up to a 75 l pilot reactor. This part of the work was developed at A&T, Switzerland. Additionally, at UC, the main objective has been to obtain cellulosic polyelectrolytes for effluents treatment, the focus being again on polyelectrolytes which can be used for decoloration of industrial effluents. Modification of cellulose extracted from bleached pulp fibres or eucalyptus wood wastes was performed. The cationization route was optimized and cationization in aqueous medium was selected. It was possible to cationize with success cellulose extracted from the different sources, treated to lead to an initial raw material with different lignin content. In all cases, soluble polyelectrolytes (CDAC) were obtained. Reaction variables were tuned in order to synthesize flocculants with different characteristics, especially the degree of substitution and thus the charge. Also, anionization of the different raw materials, with different cellulose content, was performed by applying a two-step reaction procedure, which allowed obtaining highly charged anionic, water-soluble, cellulose-based polyelectrolytes (ADAC).
Those polyelectrolytes were tested with a range of dyes (model effluents), very good results having been obtained, mainly when compared with the use of traditional synthetic flocculants. Moreover, dual systems using bentonite followed by the polyelectrolyte (according to WP4), and adjustment of the pH level, were tested, allowing to increase colour removal and turbidity reduction. Performance tests in a real industrial coloured wastewater obtained from a textile company, were also conducted, good results having obtained when using the dual system (Bentonite/polymer) with both cationic and anionic cellulose based polyelectrolytes.
Regarding WP3 the work has been focussed on the development of new flocculants to treat oily waste waters, mostly organic in nature, using health-friendly processes in their synthesis. The goal is to produce specific products for this type of wastewaters, avoiding the problems of having to overdose polymers designed for other types of waters. New health-friendly oils with reduced VOC emissions were used as synthesis media. These oils were first used to synthesize well-known polymers (acrylamide co-polymers) synthesized in inverse-emulsion polymerization, which allowed us to choose the two health-friendly oils with better balance performance/cost. These oils were then used for the synthesis of new co-polymers expected to perform better in the treatment of oily waste waters. Both cationic and anionic polyelectrolytes, with a range of charge densities, have been produced. Hydrophobically-modified terpolymers, based on the co-polymers previously developed, have been also synthesized by inverse-emulsion polymerization with three different hydrophobic monomers varying in the length of the hydrophobic chain, and using different percentages of monomer. Evaluation of performance in flocculation of industrial effluents was accomplished for all polyelectrolytes using three different oily wastewaters from olive oil mill, dairy industry and potato crisps manufacturing industry. The obtained results proved a very good performance of the new polymers in flocculation applying low concentrations (below 100 ppm).
Regarding WP5 (Construction of a map of flocs structure versus flocculant characteristics), besides the jar tests, a specific test was developed to assess the characteristics of the flocs produced when the characteristics of the polymer change. That test was based on the assessment of the flocs characteristics (size and structure) using LDS, revealing that this technique is suitable for flocculation monitoring in real effluents, supplying information about the flocculation kinetics (evolution of flocs size and structure with time). This strategy was applied to monitor flocculation in oily effluents, using some of the polymers developed in WP3, as well as to monitor flocculation in coloured effluents using cellulose based polymers developed in WP2. Using data obtained from the LDS monitoring, a statistical model was developed, to identify the most important flocculant parameters influencing flocs properties.
Dissemination was another important task of the project, finalizing with the organization of a final project workshop under the topic “Ecofriendly Water Treatments”, at the University of Coimbra, on the 26th of January 2018, involving several invited speakers.
It is expected that the outputs of this project can have positive impacts in different European priorities. The first targeted impact is directed to the development of more eco-friendly aids for effluents and water treatment, which are essential to preserve water quality, one of the first line European priorities. Finally, the training of highly qualified human resources (PhD graduates) in a mixed environment, joining academic and private sector, constitutes a benchmark with a positive economic impact, since it will allow access of the private sector to skilled human resources.

Reported by

UNIVERSIDADE DE COIMBRA
Portugal

Subjects

Life Sciences
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