Influence of the surface hydroxyl groups of MnO_x/SBA-15 on heterogeneous catalytic ozonation of oxalic acid

摘要

Comparative ozonation experiments were carried out to investigate the catalytic ability and mechanism of SBA-15 supported manganese oxide (MnO_x/SBA-15) for the degradation of oxalic acid (OA) in aqueous solution. The results showed that MnO_x/SBA-15 possessed good catalytic capacity for the ozonation of OA. The influences of tert-butanol and phosphate on OA removal and ozone equilibrium concentration in aqueous solution demonstrated that initiation of hydroxyl radicals (OH) was involved and surface reaction played the major role in O3/MnO_x/SBA-15. The effects of manganese content and initial solution pH verified that surface hydroxyl groups affected by the pH of solution and the point of zero charge (pH_(PZC)) of catalysts, were closely related to OA adsorption and ~·OH initiation on the surface of MnO_x/SBA-15. The pre-ozonated catalyst improved its catalytic activity a little due to the enhancement of electron transfer in the presence of higher multivalent MnO_x (Mn(III)/Mn(IV)). It was concluded that the protonated surface hydroxyl groups were the main reaction sites and a possible catalytic ozonation mechanism of OA over MnO_x/SBA-15 was proposed.