Synergetic mechanism for basic and acid sites of MgMxOy (M = Fe, Mn) double oxides in catalytic ozonation of p-hydroxybenzoic acid and acetic acid

MgMxOy (M = Fe, Mn) powders prepared by the sol-gel method were used as the catalysts for ozonation of p-hydroxybenzoic acid (p-HBA) and acetic acid (AcOH) (20 mg/L) at a neutral pH for 9 min. The study aims to bring an insight into the synergetic mechanism for basic and acid sites of MgMxOy in heterogeneous catalytic ozonation. 84.8 %, 88.2 %, 86.7 % p-HBA were removed by ozonation catalyzed by MgFexOy, MgMnxOy and MgO, respectively. 49.3 %, 65.8 %, 64.3 % AcOH were removed by ozonation catalyzed by the three catalysts, respectively. MgMnxOy exhibited the highest catalytic activity in ozonation of p-HBA and AcOH owing to the action of acid sites of MgMnxOy for additional ozone decomposition. The increase of solution pH, the protonation of surface hydroxyl groups and the electron transfer on acid sites induce ozone decomposition into reactive oxygen species in MgMxOy catalytic ozonation.