Aerobic and anaerobic regulation induced different degradation behaviors of parachloronitrobenzene in soil by microwave activated persulfate oxidation

Abstract

Persulfate (PS) oxidation is a promising soil remediation technology. Information regarding pollutant degradation in soil by PS-based technique under different oxidizing atmospheres is still lacking. In this study, p-chloronitrobenzene (p-CNB) degradation in soil in a microwave (MW) activated persulfate (MW/PS) system was evaluated under aerobic and anaerobic conditions. The experimental results demonstrated that anaerobic condition was more conducive to p-CNB degradation. Only 46% of p-CNB was degarded within 60 min treatment under aerobic conditions, but it increased to more than 80% under anaerobic conditions. The increase of PS dosage and MW temperature both promoted p-CNB degradation. SO4•− and •OH played important roles in p-CNB degradation under aerobic conditions, and p-CNB was mainly converted to hydroxylated byproducts including 4-nitrophenol and hydroquinone. The reductive radical S2O8•- was responsible for p-CNB degradation under anaerobic conditions, and aminated byproducts were generated. The residual toxicities of these byproducts were predicted to be decreased, compared with those of p-CNB. Furthermore, by regulating the aerobic and/or anaerobic conditions, other pollutants including pyrene and ethion were also effectively removed in the MW/PS system. Overall, this study highlighted new insights into degradation behaviors of pollutants by MW/PS treatment via aerobic and anaerobic regulation.