Investigation on Direct and Indirect Electrochemical Oxidation of Ammonia over Ru–Ir/TiO2 Anode

• Published in: Industrial & engineering chemistry research Vol. 54; no. 5; pp. 1447 - 1451
• Main Authors: He, Shilong, Huang, Qing, Zhang, Yong, Wang, Lizhang, Nie, Yulun
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.02.2015
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie503832t

Commercial Ru–Ir/TiO2 was used as the anode for electrochemical oxidation of ammonia at neutral pH in a continuous electrochemical quadrangular reactor. The reactor was packed with PAC to avoid short circuit and enhance electric efficiency, which could efficiently enhance the direct eletrooxidation. The contribution of indirect oxidation caused by active free chlorine to ammonia removal increased with the increase of chloride concentration. Moreover, the effects of inlet velocity, salinity, and current density on ammonia removal were also investigated in detail. On the basis of the CV scan and COD removal results, both direct and indirect oxidations were involved in ammonia removal. The results indicated that ammonia removal by direct oxidation occurs at a slower rate than that of COD, while indirect oxidation prefers removal of ammonia than that of COD. Ammonia could be oxidized by either •OH radicals or active free chlorine, and the removal of COD only comes from the oxidation by •OH radicals. Eighty percent of ammonia could be removed and mainly transferred to N2 in a PAC packed bed reactor under optimum conditions (pH = 6.5, I = 0.9 A, 2% Na2SO4, Cl– = 1500 mg/L, and inlet velocity = 0.8 L/h). Hence, the Ru–Ir/TiO2-based PAC packed bed reactor provides an alternative for treatment of ammonia wastewater with high chloride concentration.