Electrooxidation assisted dual activation of in situ chemical oxidation for plasticizer wastewater treatment

Abstract

This study aimed to treat wastewater from the plasticizer chemical production industry by in situ chemical oxidation processes. Hydrogen peroxide (HP), peroxymonosulfate (PMS), peroxydisulfate (PS), sodium percarbonate (PC), and calcium peroxide (CP) were evaluated as oxidants, and Fe2+ was used as the activator. In the control experiments, chemical oxygen demand (COD) removal efficiencies of 38.0, 35.6, 35.0, 34.4, and 28.4% were obtained for the HP/Fe2+, PS/Fe2+, PMS/Fe2+, PC/Fe2+, and CP/Fe2+ processes, respectively. The COD removal efficiencies were close to each other; thus, green oxidants (PS and PC) were selected as sulfate and hydroxyl radical sources. Electrical current was applied for dual activation of the selected PS/Fe2+ and PC/Fe2+ processes. The optimum initial pH was determined as 7 for EO/PC/Fe2+ and EO/PS/Fe2+. To achieve maximum contaminant removal, the conditions of EO/PC/Fe2+ and EO/PS/Fe2+ were optimized by central composite design (CCD). With optimal variable terms obtained by numerical optimization (EO/PS/Fe2+: 0.93 A, 18.9 mM Fe2+, 98.7 mM PS, and 69.8 min; EO/PC/Fe2+: 1 A, 20 mM Fe2+, 100 mM PC, and 70 min), the predicted COD and UV254 removal were 65.9% and 92.0% for EO/PS/Fe2+ and 67.9% and 94.3% for EO/PC/Fe2+, respectively. Validation experiments performed under optimal conditions resulted in COD and UV254 removal of 63.5% and 91.0% for EO/PS/Fe2+; 65.5% and 92.5% for EO/PC/Fe2+, respectively. The difference between model predictions and validation experimental yields was found to be below 5%, indicating that the predictions obtained using CCD were highly accurate and reliable.