Powdered activated coke for COD removal in the advanced treatment of mixed chemical wastewaters and regeneration by Fenton oxidation

Mixed chemical wastewaters in industrial parks contain a large number of non-degradable pollutants, and the advanced treatment process after biological treatment is required to meet the strict discharge requirement. In this study, the cost-effective powdered activated coke was used to remove chemical oxygen demand (COD) from the biological effluent in a chemical wastewater treatment plant in pilot-scale experiments. The powdered activated coke showed higher COD removal than different activated carbons, and the adsorption equilibrium was reached within 20 min. When the initial COD values in the biological effluent were in the range of 140–180 mg/L, the final COD in the treated wastewater decreased to below 80 mg/L with the powdered activated coke dose of 0.609 g/L. Moreover, the spent powdered activated coke was regenerated using Fenton oxidation and reused in the adsorption cycles. The spent activated coke was successfully regenerated at 150 mg/L H2O2 and 1.10 mmol/L Fe2+ at pH 4 for 30 min, and the activated coke still maintained 65.6% regeneration efficiency after six adsorption-regeneration cycles. This study demonstrated that activated coke adsorption was an effective and feasible advanced treatment method for the removal of COD from the mixed chemical wastewaters.