Reduction-Oxidation Coupling Mediated Decontamination and Detoxification of Persistent Organic Pollutants

Nitroaromatic and halogenated compounds are typical persistent organic pollutants (POPs) with high toxicity, poor biodegradability, and long-distance mobility. Traditional advanced oxidation processes (AOPs) cannot accomplish efficient mineralization of POPs because their strong electron-withdrawing groups decrease the electron cloud density of the benzene ring or adjacent carbon atoms, thereby enhancing the structures' stability. Although advanced reduction processes (ARPs) can effectively weaken the stubborn bonds of POPs and lower the ring-opening barriers of aromatic structures and halogenated aliphatic carbon skeletons, the generated high-toxicity intermediates in comparison to parent POPs might bring greater environmental risk. In this regard, the reduction-oxidation coupling (ROC) process might synchronously utilize the dual advantages of AOPs and ARPs to degrade POPs. However, the inherent mechanism of ROC-mediated POPs' decontamination and detoxification is still not fully understood. This review introduces the inherent mechanisms of AOPs, ARPs, and ROC process, summarizes the evidence of reactive species generation, and demonstrates that the ROC process can effectively eliminate and mineralize POPs via a barrier-decreasing and toxicity-attenuating pathway. We also discuss the challenges and perspectives of the ROC process for POP elimination in aspects of fundamental research and industrial application. We believe that a critical understanding of the ROC process can offer new perspectives and guidelines for POP elimination.