Abstract
With the addition of sulfite, almost complete removal of seven out of eight tested contaminants, i.e. benzotriazole, phenol, ciprofloxacin, methyl blue, rhodamine B, methyl orange and sulfamethoxazole, was observed in 30 s except for sulfamethoxazole at pH 9.0, while Fe(VI) alone only resulted in less than 6% removal. In this study, the mechanism of sulfite/Fe(VI) process was explored for the first time. Firstly, sulfite attacks Fe(VI) via a 1-e− transfer forming the primary sulfite radical (SO3−), then SO3− reacts rapidly with oxygen in a diffusion controlled rate to form a much more reactive peroxyl radical SO5−, which further reacts with HSO3− and produces SO4−. All the signals of sulfite, sulfate and hydroxyl radicals were observed in the electron spin resonance (ESR) analysis. The DMPO and alcohol quenching experiments confirmed that sulfite/Fe(VI) process involves radicals as the plausible reactive species for decomposition of organic pollutants, and SO4·-/·OH instead of SO3−/SO5− are the major reactive oxygen species. Since oxygen participates in the formation of the secondary radicals, i.e. SO5−, SO4− and ·OH, the sulfite/Fe(VI) process open to air displayed better performance than that purged with nitrogen. Compared with previous sulfite/Cr(VI) and sulfite/Mn(VII) processes, which are only effective under acidic conditions, sulfite/Fe(VI) process provides an alternative under neutral and alkaline conditions. The extraordinarily fast oxidation of pollutants in sulfite/Fe(VI) process suggests that activation of sulfite by Fe(VI) might lead to a new class of advanced oxidation processes (AOPs) in water treatment.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.