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Effect of Metal Ions on Oxidation of Micropollutants by Ferrate(VI): Enhancing Role of FeIV Species

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journal contribution
posted on 16.12.2020, 19:09 by Xianbing Zhang, Mingbao Feng, Cong Luo, Nasri Nesnas, Ching-Hua Huang, Virender K. Sharma
This paper investigated the oxidation of recalcitrant micropollutants [i.e., atenolol (ATL), flumequine, aspartame, and diatrizoic acid] by combining ferrate­(VI) (FeVIO42–, FeVI) with a series of metal ions [i.e., Fe­(III), Ca­(II), Al­(III), Sc­(III), Co­(II), and Ni­(II)]. An addition of Fe­(III) to FeVI enhanced the oxidation of micropollutants compared solely to FeVI. The enhanced oxidation of studied micropollutants increased with increasing [Fe­(III)]/[FeVI] to 2.0. The complete conversion of phenyl methyl sulfoxide (PMSO), as a probe agent, to phenyl methyl sulfone (PMSO2) by the FeVI–Fe­(III) system suggested that the highly reactive intermediate FeIV/FeV species causes the increased oxidation of all four micropollutants. A kinetic modeling of the oxidation of ATL demonstrated that the major species causing the increase in ATL removal was FeIV, which had an estimated rate constant as (6.3 ± 0.2) × 104 M–1 s–1, much higher than that of FeVI [(5.0 ± 0.4) × 10–1 M–1 s–1]. Mechanisms of the formed oxidation products of ATL by FeIV, which included aromatic and/or benzylic oxidation, are delineated. The presence of natural organic matter significantly inhibited the removal of four pollutants by the FeVI–Fe­(III) system. The enhanced effect of the FeVI–Fe­(III) system was also seen in the oxidation of the micropollutants in river water and lake water.