A new insight into catalytic ozonation of ammonia by MgO/Co3O4 composite: The effects, reaction kinetics and mechanism

[Display omitted] •NH4+ was high-efficiently degraded to gaseous nitrogen by catalytic ozonation.•The oxygen vacancy of MgO/Co3O4 facilitated the indirect oxidation of NH4+ by ozone.•NH4+ and Cl− decreased linearly with reaction time and followed pseudo-zero kinetics.•The affecting factors for removal of NH4+ by catalytic ozonation were examined. It is highly concerned to explore heterogeneous catalysts of metal oxides to remove NH4+-N in the wastewater, in which NH4+-N can be greatly oxidized as gaseous nitrogen in the mild reaction conditions. Herein, the high-efficient catalyst cobalt oxide modified by Mg was prepared, and the structures of catalyst were thoroughly characterized by SEM, XRD, ICP, Raman and ESR. Furthermore, the reaction kinetics of ammonia and affecting ammonia removal factors were investigated. In addition, the mechanism of catalytic ozonation for degrading NH4+ to gaseous nitrogen was also clarified. At the condition of 30 °C, initial pH = 8.0 and catalyst dosage of 2.0 g/L, 30.00 mg/L NH4+-N (source: NH4Cl) was almost completely oxidized and TN removal efficiency was 84.26% after 60 min. The degradation of ammonia and the conversion of Cl− both followed pseudo-zero kinetics. The presence of SO42−, CO32− and PO43− inhibited the degradation of ammonia with the order: SO42−