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Highly effective oxidation of roxarsone by ferrate and simultaneous arsenic removal with in situ formed ferric nanoparticles
- Yang, Tao, Liu, Yulei, Wang, Lu, Jiang, Jin, Huang, Zhuangsong, Pang, Su-Yan, Cheng, Haijun, Gao, Dawen, Ma, Jun
- Water research 2018 v.147 pp. 321-330
- arsenates, arsenic, benzoquinones, breeding, dominant species, industry, livestock, meat, nanoparticles, oxidation, pH, parasites, pigmentation, reaction kinetics, reaction mechanisms, roxarsone, water treatment
- Roxarsone (ROX) is used in breeding industry to prevent infection by parasites, stimulate livestock growth and improve pigmentation of livestock meat. After being released into environment, ROX could be bio-degraded with the formation of carcinogenic inorganic arsenic (As) species. Here, ferrate oxidation of ROX was reported, in which we studied total-As removal, determined reaction kinetics, identified oxidation products, and proposed a reaction mechanism. It was found that the apparent second-order rate constant (kapp) of ferrate with ROX was 305 M⁻¹s⁻¹ at pH 7.0, 25 °C, and over 95% of total As was removed within 10 min when ferrate/ROX molar ratio was 20:1. Species-specific rate constants analysis showed that HFeO4⁻ was the dominant species reacting with ROX. Ferrate initially attacked AsC bond of ROX and resulted in the formation of arsenate and 2-nitrohydroquinone. The arsenate was simultaneously removed by ferric nanoparticles formed in the reduction of ferrate, while 2-nitrohydroquinone was further oxidized into nitro-1,4-benzoquinone. These results suggest that ferrate treatment can be an effective method for the control of ROX in water treatment.