Mechanisms of Sb(III) Photooxidation by the Excitation of Organic Fe(III) Complexes

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• 作者：Linghao Kong ; Mengchang He
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：July 5, 2016
• 年：2016
• 卷：50
• 期：13
• 页码：6974-6982
• 全文大小：519K
• 年卷期：0
• ISSN：1520-5851

文摘

Organic Fe(III) complexes are widely distributed in the aqueous environment, which can efficiently generate free radicals under light illumination, playing a significant role in heavy metal speciation. However, the potential importance of the photooxidation of Sb(III) by organic Fe(III) complexes remains unclear. Therefore, the photooxidation mechanisms of Sb(III) were comprehensively investigated in Fe(III)–oxalate, Fe(III)–citrate and Fe(III)–fulvic acid (FA) solutions by kinetic measurements and modeling. Rapid photooxidation of Sb(III) was observed in an Fe(III)–oxalate solution over the pH range of 3 to 7. The addition of tert-butyl alcohol (TBA) as an ·OH scavenger quenched the Sb(III) oxidation, suggesting that ·OH is an important oxidant for Sb(III). However, the incomplete quenching of Sb(III) oxidation indicated the existence of other oxidants, presumably an Fe(IV) species in irradiated Fe(III)–oxalate solution. In acidic solutions, ·OH may be formed by the reaction of Fe^II(C₂O₄) with H₂O₂, but a hypothetical Fe(IV) species may be generated by the reaction of Fe^II(C₂O₄)₂^2– with H₂O₂ at higher pH. Kinetic modeling provides a quantitative explanation of the results. Evidence for the existence of ·OH and hypothetical Fe(IV) was also observed in an irradiated Fe(III)–citrate and Fe(III)–FA system. This study demonstrated an important pathway of Sb(III) oxidation in surface waters.