Quantitative evaluation of relative contribution of high-valent iron species and sulfate radical in Fe(VI) enhanced oxidation processes via sulfur reducing agents activation

Publication date: 1 May 2020Source: Chemical Engineering Journal, Volume 387Author(s): Yuan Gao, Yang Zhou, Su-Yan Pang, Zhen Wang, Yong-Ming Shen, Jin JiangAbstractRecently, it has been reported that sulfur reducing agents (e.g., sulfite and thiosulfate) can effectively activate Fe(VI), leading to a fast degradation of various contaminants. However, the reactive intermediates (i.e., high-valent iron species versus free radicals) involved in the Fe(VI)/sulfite and Fe(VI)/thiosulfate systems remain far from clear. In this work, by using methyl phenyl sulfoxide (PMSO) as a mechanistic probe, we quantitatively assessed the relative contribution of high-valent iron species versus sulfate radical in these two systems. High-valent iron species oxidized PMSO to methyl phenyl sulfone product (PMSO2), while sulfate radical oxidized PMSO to hydroxylated and/or polymeric products. The yield of PMSO2 (mole of PMSO2 formed per mole of PMSO consumed) was quantified to be in the range of 30–95% under various conditions. This finding suggested the contribution of both high-valent iron species and sulfate radical in the Fe(VI)/sulfite system, which was dependent on solution chemistry (i.e., solution pH and [Fe(VI)]:[sulfite] ratio). Comparatively, the yield of PMSO2 in the Fe(VI)/thiosulfate system remained as high as 90–100% under various conditions. This finding indicated that only high-valent iron species was involved in the Fe(VI)/thiosulfate system and the contribution of sulfate rad...

Source: Chemical Engineering Journal - January 22, 2020 Category: Chemistry Source Type: research