Enhanced degradation of PFOA in water by dielectric barrier discharge plasma in a coaxial cylindrical structure with the assistance of peroxymonosulfate

摘要

Perfluorooctanoic acid (PFOA) has been used as a dispersant in the fabrication of fluoropolymers and is classified as a "likely carcinogen" by the United States Environmental Protection Agency. In this work, the enhanced degradation of PFOA in water by dielectric barrier discharge (DBD) plasma in a coaxial cylindrical structure with the assistance of peroxymonosulfate (PMS) was explored. The effects of PMS dosage, input voltage and solution circulation rate on PFOA removal were studied and analysed. Further, the activation of PMS by O-3 (plasma) produced by discharge was conducted through a gas pump (gas flow rate) to realize O-3 (plasma) secondary utilization. The results showed that with the addition of 445 mg.L-1 of PMS, the degradation of PFOA was improved by 26.6% (from 54.4% to 81.0%), which was further increased to 94.8% through the secondary utilization of O-3 (plasma). The enhanced degradation efficiency could be attributed to the formation of SO4 center dot- and .OH through PMS activation. A possible degradation pathway of PFOA was proposed based on density functional theory (DFT) analysis and the related literatures. In addition, further toxicity analysis of the intermediates demonstrated that the toxicity at the oral 50% lethal dose (LD50) in rats and the bioaccumulation factor were reduced. The overall findings could provide new insight into wastewater treatment.