Highly efficient catalytic ozonation for ammonium in water upon ?-Al2O3@ Fe/Mg with acidic-basic sites and oxygen vacancies

Catalytic ozonation has prospects in the advanced treatment of nitrogen removal, and solid base MgO can efficiently catalyze the ozonation of ammonium nitrogen. However, it is necessary to improve the problem of easy loss, difficult recovery, and low percentage of gaseous products. Here, MgO, amorphous Fe2O3, and gamma-Al2O3 were selected as doping components and supports, respectively, to prepare gamma-Al2O3@Fe/Mg composite catalysts with abundant acidic-basic sites and oxygen vacancies. The results show that gamma-Al2O3@Fe/Mg5 can efficiently catalyze the ozonation of ammo-nium nitrogen (98.73%) with 67.82% gaseous product selectivity under the conditions of initial pH = 7, catalyst dos-age of 112.88 g/L, and ozone dosage of 2.4 mg/min. The doping of Fe(2)O(3 )and MgO with a weaker lattice oxygen binding energy improves the gaseous product selectivity. The mechanism of ammonium nitrogen removal for gamma- Al2O3@Fe/Mg5 is revealed, especially the intrinsic contribution of acidic-basic sites and oxygen vacancies. The pH and active sites play different roles in ozone decomposition for NH4+ removal. Surface hydroxyl protonation on basic sites and oxygen vacancies and electron transfer on acidic sites are responsible for ozone decomposition to hy-droxyl radicals. Moreover, gamma- Al2O3@Fe/Mg5 exhibits good stability, few leaching ions, and can be settled in water for easy recovery. This study suggests that gamma- Al2O3@Fe/Mg5 is a good candidate for the catalytic ozonation of ammo-nium nitrogen.

Automated summary

The study focuses on the catalytic ozonation of ammonium nitrogen using composite catalysts. The results show that the γ-Al2O3@Fe/Mg composite catalyst exhibits high efficiency and selectivity in the ozonation reaction. The mechanism of ammonium nitrogen removal is also explored, highlighting the role of acidic-basic sites and oxygen vacancies.