Revisiting the Oxidizing Capacity of the Periodate-H 2 O 2 Mixture: Identification of the Primary Oxidants and Their Formation Mechanisms

This study reexamined the mechanisms for oxidative organic degradation by the binary mixture of periodate and H O (PI/H O ) that was recently identified as a new advanced oxidation process. Our findings conflicted with the previous claims that (i) hydroxyl radical ( OH) and singlet oxygen ( O ) contributed as the primary oxidants, and (ii) OH production resulted from H O reduction by superoxide radical anion (O ). PI/H O exhibited substantial oxidizing capacity at pH < 5, decomposing organics predominantly by OH. The likelihood of a switch in the major oxidant under varying pH conditions was revealed. IO as the major PI form under acidic conditions underwent one-electron reduction by H O to yield radical intermediates, whereas H I O preferentially occurring at pH > 7 caused O generation through two-electron oxidation of H O . PI reduction by O was suggested to be a key reaction in OH production, on the basis of the electron paramagnetic resonance detection of methyl radicals in the dimethyl sulfoxide solutions containing PI and KO , and the absence of deuterated and O-labeled hydroxylated intermediates during PI activation using D O and H O . Finally, simple oxyanion mixing subsequent to electrochemical PI and H O production achieved organic oxidation, enabling a potential strategy to minimize the use of chemicals.