Modeling and optimizing electro-persulfate processes using Fe and Al electrodes for paper industry wastewater treatment

In this study, the treatment of paper industry wastewaters by the electrocoagulation (EC) process with a strong oxidant, persulfate addition, was investigated. Persulfate was activated by dissolution of Fe and Al from electrodes during the process. Central composite design method, being one of the response surface methods, was applied for the optimization of process parameters and the development of a mathematical model for chemical oxygen demand (COD) removal from paper industry wastewaters. The effects of S2O8-2/COD ratio, current, pH, and reaction time, being the variables of process, were assessed on the efficiency of contaminant removal. For COD removal in EC processes in which Fe and Al electrodes were used, the model's correlation coefficients (R-2) were determined as 90.14% and 87.46%, respectively. As the result of experimental study actualized under optimum conditions determined by the model in order to obtain maximum contaminant removal, COD removal efficiencies were determined as 63.5% and 72.8% respectively for the Fe electrode (S2O8-2/COD ratio: 1.25, current: 4.14 A, pH: 6, and reaction time: 5 minutes), and the Al electrode (S2O8-2/COD ratio: 0.5, current: 4.25 A, pH: 7.25, and reaction time: 25 minutes). Electro-activated persulfate process is an appropriate treatment alternative for COD removal from paper industry wastewaters.