Optimization of electrocoagulation process for disperse and reactive dyes using the response surface method with reuse application

Abstract

In order to manufacture fabrics, clothing and other textile goods, huge amounts of water are used, generating highly contaminated effluents containing dyes. The focus of this study was the treatment of wastewater containing two textiles dyes (Danix Marinho S-2G 200% - disperse; Remazol Brilliant Blue R - reactive) by electrocoagulation (EC) using aluminum electrodes. The experimental runs were planned using the response surface methodology (RSM) with a Box-Behnken design (BBD) and complete factorial design (CFD). The effects of the operating parameters pH, current intensity (A) and electrolysis time (min) on the percentage of color removal (Rcor %) and operating cost ($/m3) were investigated. Several dyeing processes were also carried out, using polyester or cotton fabric, to evaluate the potential for the reuse of the treated water in the process. The best operating conditions were obtained by applying 4 A and 5 min for the effluent with the dispersed dye and 5–6 A and 30 min for the reactive dye. The influence of the initial pH on the removal of color and reduction in the operational cost of the process was only observed in the case of the effluent containing the reactive dye. The best results were obtained at pH 8. Maximum percentages of color removal of 92.48% and 91.34% and minimum operational costs of $ 0.47 and $ 2.99 were achieved simultaneously, under the optimum operating conditions, for the disperse and reactive dyes, respectively. This study showed that the EC process is an effective wastewater treatment method that is economically competitive. Also, it is a promising alternative for application in the textile industry, particularly since wastewater can be reused in the wash stages of the dyeing process.