Combined treatment of a textile effluent containing reactive dyes by coagulation-flocculation and electroflotation
Textile effluents containing reactive dyes are often very complex and require intensive treatments. Nowadays, the combination of two or more techniques has become an interesting alternative, because of scientific progress allowing for a good control of the processes. Clays and clay minerals, because of their properties enabling them to be simultaneous adsorbents and flocculation additives, are of particular interest to researchers in industrial wastewater treatment. In this study, a textile effluent that represents the wastewater of a cotton dyeing plant (Denitex, Tlemcen, Algeria) was treated by a combined process. The treatment was divided into two stages: the first was a coagulation-flocculation (CF) stage using pre-neutralized aluminium salts, called Al13 polycations (AlO4Al12(OH)24(H2O)12), as a coagulant associated with an Algerian bentonite (B); in the second stage, an electroflotation technique (EF) was used. The EF technique was not only used as a solid-liquid separation operation, but also in the improvement of the effectiveness of the treatment. For the CF and EF treatments of wastewater, the effects of pH, reagent concentrations, contact times as well as electric current and energy consumption were investigated. The effluent treated by this combined method contained essentially no colour or COD: 99.7% and 99.1% elimination were obtained, respectively.