Optimization of electrocoagulation process for removal of an azo dye using response surface methodology and investigation on the occurrence of destructive side reactions

The optimization and modeling of the electrocoagulation process which conducted by means of iron (EC-Fe) and aluminum (EC-Al) anodes, in the removal of C.I. Reactive Red 43 were performed through the response surface methodology (RSM). Moreover, the occurrence of possible destructive reactions during both EC-Fe and EC-Al processes was investigated using UV–Vis spectrometry, total organic carbon (TOC) and GC–MS analyses. The electrocoagulation experiments were carried out in a monopolar batch reactor using two anodes and two cathodes in parallel connections. Current density, time, pH and chloride concentration were considered as input variables for RSM. The analysis of variance revealed a high coefficient of determination ( R EC-Fe 2 = 0.981     and     R EC-Al 2 = 0.934 ) between experimental removal efficiency and predicted one by RSM developed models. The optimum conditions proposed by RSM to reach the maximum RR43 removal through the EC-Fe were different from the ones proposed for the EC-Al. At the optimum conditions, the removal efficiency of dye was more than 99% for both processes, whereas 90.58% and 98.37% of initial TOC concentration decreased during EC-Fe and EC-Al processes, respectively. The analyses results confirmed that beside sweep flocculation mechanism, known as the main removal mechanism, the degradation of dye was occurred during EC-Fe as a minor pathway.