Catalytic oxidation of contaminants by Fe0 activated peroxymonosulfate process: Fe(IV) involvement, degradation intermediates and toxicity evaluation

Abstract

In this study, the catalytic degradation of atrazine (ATZ) by peroxymonosulfate (PMS) activated with commercial Fe0 was investigated under different pH conditions. The degradation process was pH dependent, among which acidic and neutral conditions favored Fe0 corrosion and PMS decomposition. Electron spin resonance (ESR) tests and alcohol quenching experiments confirmed the simultaneous presence of sulfate radical (SO4−) and hydroxyl radical (OH) in the Fe0/PMS system, both of which were quantified via indirect monitoring of the generation of benzoquinone (BQ) and p-hydroxybenzoic acid (HBA), respectively. In addition, ferryl ion (Fe(IV)) was identified to be involved in the Fe0/PMS system based on the selective transformation from methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2). Coupled with SEM and XPS results, the activation mechanism of the Fe0/PMS system was thought to be that Fe(II) released from Fe0 corrosion decomposed PMS into SO4− and OH or reacted with PMS to yield Fe(IV), accompanied by the final conversion of Fe(II) to Fe(III). Furthermore, possible degradation pathways were proposed according to intermediates detected by LC-MS, and dechlorinated and dealkylated byproducts were quantitatively analyzed. Ultimately, toxicity tests based on luminescent bacteria Vibrio qinghaiensis sp.-Q67 suggested the detoxification of ATZ by the Fe0/PMS system.