Degradation of organic pollutants in hazardous spent sulfuric acid by catalytic oxidation reaction with agricultural waste-derived catalyst

The discharge of spent sulfuric acid generates significant toxic wastes and poses serious hazards to the environment. The effective treatment of spent sulfuric acid remains a great challenge because conventional thermochemical pyrolysis is limited by energy-intensive processing, high equipment investment, and severe equipment corrosion. In this study, we propose an energy-efficient and moderate catalytic oxidation reaction to treat spent sulfuric acid. During the catalytic oxidation reaction, the organic pollutants, especially refractory acid-soluble oil (ASO), in the conversion of spent sulfuric acid and ammonia wastewater were oxidized and degraded into CO2, H2O, and inorganic structures with H2O2 as the oxidant and ozone-treated activated carbon (OAC), derived from coconut shells, as a catalyst. The catalytic activity of OAC enhanced the degradation efficiency of organic pollutants under mild conditions, which was ascribed to the abundant acidic functional groups, and the anchored metal ions on the OAC promoted the generation of highly reactive radicals. The purified (NH4)2SO4 solution with an ASO removal of 96.4% and total organic carbon (TOC) removal of ~92% under the optimum conditions was used to prepare the qualified (NH4)2SO4 product. This work demonstrates the effective utilization of spent sulfuric acid and a cost-effective route to prepare catalysts from agricultural waste for the oxidative degradation of organic pollutants.