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

Abstract

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 N2 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 O3 process and CTAB-NiO/O3 process, especially in the decomposition of O3 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/O3 system, about 98 % ammonia mainly converted to N2 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/O3 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 (·OH) generated by ozonolysis.