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Download fileOverlooked Role of Peroxides as Free Radical Precursors in Advanced Oxidation Processes
journal contribution
posted on 2019-01-28, 00:00 authored by Zhihao Chen, Xuchun Li, Shujuan Zhang, Jiyuan Jin, Xiaojie Song, Xiaomeng Wang, Paul G. TratnyekResearch
efforts on advanced oxidation processes (AOPs) have long
been focused on the fundamental chemistry of activation processes
and free radical reactions. Little attention has been paid to the
chemistry of the precursor oxidants. Herein, we found that the precursor
oxidants could lead to quite different outcomes. A counterintuitive
result was observed in the photoreduction of bromate/iodate: the combination
of H2O2 and UV enhanced the reduction of bromate/iodate,
whereas the addition of persulfate to the UV system led to an inhibitory
effect. Thermodynamic and kinetic evidence suggests that the reduction
of bromate in UV/H2O2 was attributable to the
direct reaction between HOBr and H2O2. Both
experimental determination and kinetic simulation demonstrate that
the reaction between HOBr and H2O2 dominated
over the •OH-mediated reactions. These results suggest
that H2O2 possesses some particular redox properties
that distinguish it from other peroxides. The prototypical UV/H2O2 process is not always an AOP: it can also be
an enhanced reduction process for chemicals with intermediates that
are reducible by H2O2. Considering the increasing
interest in persulfate-based AOPs, the results of this study identify
some novel advantages of the classical H2O2-based
AOPs.