Investigating the process of electrocoagulation in the removal of azo dye from synthetic textile effluents and the effects of acute toxicity on Daphnia magna test organisms

Abstract

Effluents generated by the textile industry can cause serious damage to receiving bodies of water, if not adequately treated. In this context, new treatment methods have been investigated, with great emphasis on electrocoagulation (EC). For this reason, the main objective of this research was to evaluate the efficiency of implementing the EC process in the treatment of synthetic textile effluents for removing azo dye, in relation to COD, TOC, true color and acute toxicity. Experimental tests were performed for the EC process to investigate the effects of current intensity (2 and 4 A), electrolyte concentration (2 and 4 g L-1) and dye concentration (0.05 e 0.10 g L-1) regarding the removal of the dye into the synthetic textile wastewater considering a 20-minute electrolysis time. The results of the EC process revealed the potential for the application of this technology in this type of treatment. Considering that the values found indicate color removal, TOC, and COD in the order of 96.5%, 93.5% and 85.0%, respectively, with a 4A current intensity applied. Still, acute toxicity tests with the bioindicator Daphnia magna showed high toxicity rates (EC50%), with amounts between 5.87% for synthetic textile effluent in the presence of azo dye and 40.24% in relation to treatment via EC. For these test bodies, a negative impact was observed in relation to the presence of azo dye in the synthetic textile effluent on the toxic effects observed, with high immobility/mortality in relation to textile effluent treated by the electrocoagulation process.