Treatment of wastewater from plasticizer chemical production industry by hybrid electrochemical technologies

Abstract

This study aimed to investigate the application of electrochemical methods to treat wastewater from the plasticizer chemical production industry. These methods are as follows: Electrocoagulation using Al electrodes (EC/Al), electrocoagulation using Fe electrodes (EC/Fe), electrooxidation (EO), electro-Fenton (EF), Fered-Fenton (FF), electrochemical peroxidation (ECP), and peroxicoagulation (PC). In the control studies, electrochemical processes are ranked in terms of chemical oxygen demand (COD) removal efficiency as FF>EF>ECP>PC>EC/Fe>EC/Al>EO. For the control experiments, the lowest energy consumption among the EF types was observed in the PC process at 5.7 kWh/kg COD, while energy consumptions of 10.6 kWh/kg COD and 12 kWh/kg COD were calculated for the EC/Fe and EC/Al processes, respectively. Based on COD removal and energy consumption, EC/Fe and PC were selected and optimized. Optimum conditions are: EC/Fe - pH 7, 0.25 A, inter-electrode distance (IED) 3 cm, 90 min; PC - pH 5, 0.75 A, IED 2 cm, 90 min. Under optimized conditions, the EC/Fe process (EC/Feopt) achieved removals of 50.5 % COD, 94.7 % total suspended solids (TSS), 65.9 % color, and 33.2 % UV254, while the PC process (PCopt) achieved 60.6 % COD, 91.2 % TSS, 79.6 % color, and 43.1 % UV254 removal. The two selected processes were then operated sequentially, achieving COD removals of 65.6 % and 72.3 % for the hybrid PCopt-EC/Feopt and EC/Feopt-PCopt processes, respectively. Energy consumptions were 4.1, 11.2, 6.3, and 5.3 kWh/kg COD for EC/Feopt, PCopt, and the hybrid PCopt-EC/Feopt and EC/Feopt-PCopt processes, respectively, with higher TSS, color, and UV254 removal efficiencies observed in the hybrid treatments compared to the individual processes.