Degradation of benzotriazole by DBD plasma and peroxymonosulfate: Mechanism, degradation pathway and potential toxicity

Benzotriazole (BTA) is a widely used chemical in domestic and industrial products. BTA is bio-refractory and has become an emerging contaminant in the aquatic environment. In this study, a new approach for degradation of BTA is developed by coupling falling water film dielectric barrier discharge (DBD) plasma with peroxymonosulfate (PMS) or persulfate (PS). The degradation of BTA is significantly improved (by 47%) by the introduction of PMS into the DBD plasma system. In addition, the energy yield is increased by 84%. The enhanced degradation efficiency may be attributed to the activation of PMS enriches the active species and increases the oxidation potential of the DBD plasma system. Radical scavenger experiments show that both sulfate radical and hydroxyl radical contribute to the degradation of BTA, but the latter has greater direct impact on BTA degradation. In addition, superoxide radicals, singlet oxygen and electrons have also played an important role in the DBD-PMS system. Degradation intermediates of BTA are identified and reaction pathways, including hydroxylation, cleavage and coupling reactions, are proposed. Further toxicity analysis of intermediates demonstrates that the toxicity of oral rat LD 50 and the developmental toxicity of BTA are alleviated. Overall, the combination of DBD and PMS may be a promising technology for efficient, economical and environmentally friendly removal of refractory pollutants in water.