Reactive species in nonthermal plasma-based advanced oxidation and reduction processes for micropollutants degradation: Generation, contribution and utilization

Nonthermal plasma wastewater treatment technology, which combines the advantages of advanced oxidation processes (AOPs) and advanced reduction processes (ARPs), has attracted increasing attention for remediating micropollutant-contaminated wastewater over the past few decades. This review article compiles and organizes peer-reviewed scientific publications from the last several years on the application of nonthermal plasma technologies for (waste)water treatment. Special focus is put on an in-depth discussion of (i) the processes of oxidative and reductive species generated by discharge plasma, (ii) the role of reactive species in various micropollutants degradation, and (iii) the possibilities to improve the degradation of micropollutants by scale up the technology and combining plasma with other methods, including catalysis. The analysis reveals that enhancing the utilization of reactive species can be achieved through two main approaches: (i) enhancing the mass transfer of reactive species, and (ii) improving the generation of reactive species with strong redox potential (such as center dot OH and eaq-). The maximum utilization of reactive species can reduce the energy consumption of nonthermal plasma technology and promote its industrial application. This review offers a comprehensive exploration of the generation, contribution and utilization of reactive species in plasma technology for micropollutant degradation, addressing gaps in existing literature by focusing on the scalability of nonthermal plasma in industrial applications.