A novel method of ultraviolet/NaClO2-NH4OH for NO removal: Mechanism and kinetics

• Published in: Journal of hazardous materials 2019-04, Vol.368, p.234-242
• Main Authors: Hao, Runlong, Mao, Xingzhou, Wang, Zheng, Zhao, Yi, Wang, Tianhao, Sun, Zhonghao, Yuan, Bo, Li, Yankun
• Format: Article
• Language: English
• Subjects: AOP method; Hydroxyl radical; Kinetics; NO removal; Oxychloride radical
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.01.042

[Display omitted] •A novel UV/NaClO2-NH4OH process for NO removal was proposed.•The removal efficiencies for SO2 and NO were 98.7% and 98.1% respectively.•HO, ClO and Cl2O2 were determined as the key species for NO oxidation.•The Hatta numbers are 229–403 and 730–780 corresponding to without and with UV.•NO3− is the final product of NO identified by XPS. The key step for nitric oxide (NO) removal using oxidation method is to efficiently oxidize NO. This study developed a novel advanced oxidation process (AOP) of ultraviolet light (UV) catalysis of chlorite (NaClO2) to oxidize NO. The production of nitric dioxide (NO2) and photo-production of chlorine dioxide (ClO2) were suppressed by adding ammonium hydroxide (NH4OH). The NO conversion efficiency was 98.1% using UV/NaClO2-NH4OH. Electron spin resonance (ESR) tests confirmed the roles of hydroxyl radical (HO) and oxychloride radical (ClO/Cl2O2) in the oxidation of NO. Kinetics analyses showed that NO flux was significantly enhanced by radical-induced (HO/ClO) oxidation of NO. In the presence of UV, the overall reaction rates (kov1*) were 3–8 times higher than those without UV. The Hatta number, namely the enhanced factor, was calculated in the range of 229–403 and 730–780 corresponding to without and with UV light, suggesting that NO oxidation belonged to fast and/or instantaneous reaction. Thus, the gas-film mass transfer resistance was the rate-determining step. N-containing product was determined as NH4+ and NO3− according to X-ray photoelectron spectroscopy (XPS).