Researchers from the Faculty of Science and Technology of the University of Coimbra (FCTUC) developed, for the first time, natural flocculants from residues of eucalyptus wood for wastewater treatment, this Monday was announced.
“Flocculation is an essential step in the traditional treatment of effluents, widely used in wastewater treatment plants (WWTP)” of domestic or industrial origin, but continues to be promoted by flocculants of fossil origin (petroleum) – “the most common based on polyacrylamides ”- says the University of Coimbra (UC), in a note sent this Monday to the Lusa agency.
Coagulation consists of “aggregation of small particles, forming flakes (clusters of particles) that then allow the removal of contaminants”.
In addition to not being biodegradable, traditional flocculants "have several disadvantages, making the search for ecological approaches for the development of new flocculants existing in nature, especially based on natural by-products, pressing."
Considering the amount of eucalyptus waste that is produced, as a result of the activity of the pulp industry in Portugal, the team of researchers, led by Graça Rasteiro, from the Chemical Engineering Department of FCTUC, decided to bet on this by-product.
The research was carried out within the scope of the European project ECOFLOC, in the type of doctorate in European business environment (Marie Curie – People), and also involved the University of Leeds (United Kingdom) and a Swiss company specialized in recycling and wastewater treatment.
“From the transformation of materials extracted from eucalyptus residues, the researchers developed a set of cellulosic-based“ eco-flocculants ”with different characteristics that fit different applications”, explains the UC.
“Our‘ ecofriendly ’approach consisted of purifying and modifying these lignocellulosic residues to produce naturally-based polyelectrolytes (charged polymers) that promote flocculation,” reports Graça Rasteiro.
It was a complex process, because cellulose is not soluble, which is a major obstacle, because polyelectrolytes have to be soluble to act as flocculants. Therefore, we had to make extractions of the initial raw material that we optimized to be as mild as possible and several modifications so that the final product was soluble ”, adds, quoted by UC, the researcher.
Having overcome this first challenge, the team, which also had as researcher José Gamelas, from the Research Center for Engineering of Chemical Processes and Forest Products (CIEPQPF), developed a wide range of natural, biodegradable flocculants, suitable for different applications beyond effluent treatment (the focus of the project), such as in the cosmetics or food industry.
The products obtained were extensively characterized in terms of their chemical composition, structure and morphology.
Then, the “eco-flocculants” were successfully tested, first on model effluents and later on real effluents supplied by a textile industry (Rosários 4) in Mira de Aire ”, and“ as intended, allowed to increase color removal and turbidity ”.
“Compared to the use of commercial polyacrylamides, the performances obtained using the natural-based flocculants were as good or better than the traditional ones. In addition, we managed to reduce the chemical oxygen demand of effluents by up to 80% ”, describes Graça Rasteiro. This result “represents a great advance in relation to traditional flocculants (of fossil origin)”, he highlights.
“We also carried out tests on oily effluents from oil mills, and the first results are promising. It should be noted that both effluents (dyes and oily) are very difficult to treat ”, underlines the project coordinator.
The chemical oxygen deficiency is a parameter that allows to evaluate if the treated effluent meets the necessary conditions to be reused or discharged to aquatic environments.
In view of the good results obtained with the eucalyptus wood residues, the researchers decided to extend the investigation to wood from invasive species, namely acacia-mimosa wood, under another project, called MATIS.
The developed flocculants are now being tested.
Despite not having yet carried out an economic study, the FCTUC professor and researcher believes that the results of this project “can have very positive impacts, since it is an ecological approach not only for the treatment of effluents, but also for application in different sectors of activity".
“These cellulose-based flocculants have proved to be very promising alternatives to traditional oil-based agents”. If the industry so desires, “eco-flocculants” can enter the market in a relatively short period after undergoing pilot scale tests.