Nitrogen selectivity upon catalytic ozonation of ammonia with CTAB-NiO catalyst

In this work, CTAB-NiO catalyst was prepared by solid-state method and employed for oxidizing ammonia (NH4+) in aqueous solution by catalytic ozonation. In order to obtain high N-2 selectivity, the effects of operating parameters on catalytic ozonation of ammonia were investigated in detail. Experimental results revealed that initial pH played a crucial role both in single O-3 process and CTAB-NiO/O-3 process, especially in the decomposition of O-3 and the pathway of ammonia being oxidized into final products. Meanwhile, CTAB-NiO catalyst exhibited good performance in treating low concentration NH4+-containing wastewater from rare earth smelting. The results of qualitative and quantitative analysis of the reaction product distribution showed that in the CTAB-NiO/O-3 system, about 98 % ammonia mainly converted to N-2 at 293 K and ambient atmospheric pressure, with a selectivity of 76 %. The mechanism of catalytic ozonation of ammonia in aqueous solution was investigated by adding tert-butanol to the CTAB-NiO/O-3 system. The catalytic ozonation of ammonia in aqueous solution was primarily due to the synergistic effect between the active ingredient from CTAB-NiO catalyst and hydroxyl radicals (center dot OH) generated by ozonolysis.