Removal of aqueous oxalic acid by heterogeneous catalytic ozonation with MnO_x/sewage sludge-derived activated carbon as catalysts

摘要

MnO_x/sewage sludge-derived activated carbon (MnO_x/SAC) was prepared as catalysts to improve the performance of aqueous oxalic acid degradation by ozonation. The results indicated that MnO_x/SAC had excellent catalytic activity in mineralization of oxalic acid during heterogeneous catalytic ozonation process. MnO_x/SAC with a manganese load of 30% exhibited the strongest catalytic activity under the condition of solution pH 3.5, which enhanced the oxalic acid removal from 10.3% to 92.2% in 60 min compared with that treated by ozone alone. Increase of catalyst dosage and aqueous ozone concentration was advantageous for oxalic acid removal from water. On the basis of catalyst characterization analysis and the observation of inhibitory effect induced by higher pH, less catalyst dosage as well as the presence of hydroxyl radical scavenger, it was deduced that the reaction mechanism involved both hydroxyl radicals attack and surface reactions.