Degradation of aqueous organic pollutants by dual oxidant advanced oxidation processes: A comprehensive review

The advanced oxidation process (AOP) has been extensively studied for treatment of aqueous organic pollutants, and various oxidants have been utilized in AOP. In some cases, the combinations of two oxidants can help to boost the performance of AOP. In this review, the recent works concerning the applications of dual oxidant AOP for the degradation of organic pollutants have been summarized comprehensively. Various dual oxidant systems have been discussed, including O₃/peroxides, O₃/persulfates, peroxides/persulfates, periodate/peroxides, permanganate-based, ferrate-based and others. For each dual oxidant system, the reaction mechanisms and synergy effects as well as the effects of oxidant dosage and pH have been discussed in detail. Catalysts and/or external energy sources helped to enhance the performance of dual oxidant systems, which have also been summarized and discussed systematically. This review further highlights the current achievements and hurdles for dual oxidant AOPs, and also proposes recommendations for future works, such as more attentions on pollutant-specific performances of these systems and applications for real wastewater treatment, further investigations on the performances of new catalysts and cost analysis as well as more focus on the specific properties of dual oxidant systems.