Synergetic Hydroxyl Radical Oxidation with Atomic Hydrogen Reduction Lowers the Organochlorine Conversion Barrier and Potentiates Effective Contaminant Mineralization

For effective treatment and reuse of wastewater, removal of organo-chlorines is an important consideration. Oxidation or reduction of these compounds by one-component free radicals is difficult because of the high-energy barrier. Theoretical calculations predict that redox synergy can significantly lower the energy barriers. Hence, we developed an energy-efficient dual photoelectrode photoelectrochemical system wherein the oxidized and reduced radicals coexist. Taking p-chloroaniline as an example, the atomic hydrogen first initiates nucleophilic hydrodechlorination to form a critical intermediate followed by the electrophilic oxidation of the hydroxyl radical; the process shows stable free-energy changes. Compared to oxidation alone, the reaction rate and mineralization in the redox synergy system were similar to 4.5 and similar to 2.1 times higher, respectively. Nitrogen was also completely removed via this system. The full life cycle assessment with power consumption as the boundary showed that the proposed system was sustainable and highly energy efficient, ensuring its application in organochlorine wastewater treatment.

Automated summary

The study developed an energy-efficient photoelectrochemical system for the effective treatment and reuse of wastewater, specifically focusing on the removal of organo-chlorines. Redox synergy was found to significantly reduce energy barriers, increasing reaction rates and mineralization. The system was also shown to be sustainable and highly energy efficient, ensuring its application in organochlorine wastewater treatment.