1. Introduction In recent years, various studies have been carried out for sustainable energy sources that can replace fossil fuels and which do not have a negative impact on the environment. Among the proposals, biofuel produc- tion and use is probably the one that has the greatest potential to compensate the current need of fossil fuels. Biofuel can be easily generated from plants bio- mass resources and organic wastes which are abun- dant, cheap and renewable [1, 2]. Biodiesel has been highlighted due to its chemical and physical proper- ties that resemble to some extent those of diesel, as well as they can be blended with petroleum fuels in various compositions and used in regular engines with little or no modification [1]. Currently, more than 95% of commercial biodiesel has been produced by transesterification from edible oil (e.g., cottonseed, rapeseed, palm, sunflower and soybean) [3]. Transesterification is the triglycerides reaction with fatty acid alkyl esters and low molec- ular weight alcohols such as methanol and ethanol with or without a catalyst [4, 5]. After the transesterification reaction, biodiesel and glycerol are obtained as main phases. During the bio- diesel purification stage glycerol residues, soaps and fatty acids are removed. The large amount of biodiesel 504 Polymeric polyelectrolytes obtained from renewable sources for biodiesel wastewater treatment by dual-flocculation E. A. M. Ribeiro 1 , G. Rodrigues Filho 1* , N. S. Rozeno 1 , J. M. B. A. Nogueira 1 , M. A. Resende 1 , J. P. Thompson Junior 2 , J. G. Vieira 3 , S. C. Canobre 1 , F. A. Amaral 1 1 Instituto de Química, Universidade Federal de Uberlândia, Campus Santa Mônica, Av. João Naves de Ávila, 2121, Caixa Postal 593, 38.400-902 Uberlândia-MG, Brazil 2 Universidade São Francisco, Av. São Francisco de Assis, 218, 33495-870 Bragança Paulisa-SP, Brazil 3 Faculdade de Ciência Integradas do Pontal, Universidade Federal de Uberlândia, Campus do Pontal, Av. José João Dib, 2545, 38302-000 Ituiutaba-MG, Brazil Received 31 October 2016; accepted in revised form 24 January 2017 Abstract. Biodiesel wastewater generally contains high levels of oils, soaps and glycerol residues. This needs wastewater treatment. In this study, the biodiesel wastewater treatment was tested (industrial wastewater (EFID) and laboratory waste- water (EFLB) from biodiesel) by performing flocculation and dual-flocculation with renewable polymers. Tannin and cationic hemicellulose (CH) were used as cationic flocculant, and cellulose acetate sulfate (CAS) was used as an anionic flocculant. Polyacrylamide (PAM) was used as a reference anionic flocculant for result efficiencies analysis obtained with CAS (re- newable source flocculant). The treatment efficacy in wastewater was evaluated by: turbidity removal, sludge volume formed, chemical oxygen demand (COD) and total suspended solids (TSS). The obtained sludge was studied using thermogravimetric analysis (TG). The dual-flocculation application condition of the 25% proportion of tannin (T) and 75% proportion of cationic hemicelluloses (i.e., T25/CH75) showed EFLB turbidity removal of 89.1% and 89.5% for CAS and PAM additions respec- tively, and for EFID of 67% and 41% for CAS and PAM additions respectively. The dual-flocculation performance suggested that the polyelectrolytes obtained from renewable sources can be used for treating biodiesel wastewater. Keywords: biodegradable polymers, dual-flocculation, biodiesel wastewater, tannin, cellulose acetate sulfate eXPRESS Polymer Letters Vol.11, No.6 (2017) 504–517 Available online at www.expresspolymlett.com https://doi.org/10.3144/expresspolymlett.2017.47 * Corresponding author, e-mail: guimes.rodriguesfilho@gmail.com © BME-PT