Extremely efficient catalytic ozonation of ammonia N to N2 using Co/Mg(OH)2 as catalysts

• Published in: Journal of hazardous materials 2024-12, Vol.480, p.136076, Article 136076
• Main Authors: Cao, Tingting, Xu, Jingtian, Fu, Shaozhu, Zeng, Qinghong, Cui, Bin, Cui, Han, Zhou, Dandan
• Format: Article
• Language: English
• Subjects: Ammonia nitrogen removal; Catalytic ozonation; Cobalt-doped magnesium hydroxide; Mechanisms
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.136076

The development of highly efficient and selective ozonation catalysts is crucial for enhancing the treatment of nitrogen-containing wastewater. In this study, a Co/Mg(OH)2 nano-hexagonal sheets ozonation catalyst was prepared by one-pot hydrothermal method, and the structural characteristics of this catalyst were comprehensively analyzed. The OSur/O ratio of this catalyst was 41.06 %. Under the optimal conditions (22 ℃, initial pH of 9.0, ozone dosage of 1.2 mg/L, catalyst dosage of 1.0 g/L, initial NH3-N concentration of 10.00 mg/L), NH3-N and total nitrogen (TN) removal efficiencies of 90.26 % and 63.44 % were respectively obtained, and the removal process exhibited pseudo-first-order kinetics. Moreover, at 4 ℃, the NH3-N and TN removal efficiencies reached 95.49 ± 1.14 % and 65.61 ± 1.13 %. In a co-degradation process for the removal of both N and C, the ammonia and most organic compounds competed for active substances, but both pollutants were effectively removed. Hydroxyl radicals (•OH) were the main active substance involved in NH3 removal. However, the massive loss of Mg2+ experienced after three cycles reduced the NH3-N and TN removal efficiencies to 31.83 % and 6.55 %, respectively. Finally, the electron transfer generated by the variable-valence Co ion was determined to promote the selectivity of the reaction toward gaseous N products. These findings offer promising avenues for the development of more energy-efficient and effective nitrogen removal processes. [Display omitted] •Nano Co/Mg(OH)2 catalysts were facilely synthesized via one-pot solvothermal method.•Co/Mg(OH)2 inspired by O3 showed great NH3 removal and selectivity to Gas-N.••OH was the dominant active species on NH3 degradation.•The production of Co3+/Co2+ increased the concentration and migration of electrons.•N transformation mechanism in the catalytic ozonation upon Co/Mg(OH)2 was proposed.