Synergetic\nHydroxyl Radical Oxidation with Atomic\nHydrogen Reduction Lowers the Organochlorine Conversion Barrier and\nPotentiates Effective Contaminant Mineralization

For effective treatment and reuse\nof wastewater, removal of organochlorines\nis an important consideration. Oxidation or reduction of these compounds\nby one-component free radicals is difficult because of the high-energy\nbarrier. Theoretical calculations predict that redox synergy can significantly\nlower the energy barriers. Hence, we developed an energy-efficient\ndual photoelectrode photoelectrochemical system wherein the oxidized\nand reduced radicals coexist. Taking <i>p</i>-chloroaniline\nas an example, the atomic hydrogen first initiates nucleophilic hydrodechlorination\nto form a critical intermediate followed by the electrophilic oxidation\nof the hydroxyl radical; the process shows stable free-energy changes.\nCompared to oxidation alone, the reaction rate and mineralization\nin the redox synergy system were ∼4.5 and ∼2.1 times\nhigher, respectively. Nitrogen was also completely removed via this\nsystem. The full life cycle assessment with power consumption as the\nboundary showed that the proposed system was sustainable and highly\nenergy efficient, ensuring its application in organochlorine wastewater\ntreatment.