Catalysis of MnO2-cellulose acetate composite films in DBD plasma system and sulfamethoxazole degradation by the synergistic effect

Abstract

Herein, dielectric barrier discharge (DBD) plasma and MnO2-cellulose acetate (MnO2/CA) composite films was coupled together to degrade sulfamethoxazole (SMX) in water. The MnO2/CA composite films were firstly prepared successfully though heating blending method in this study and then characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectra, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TG). Catalytic effect of the MnO2/CA films was investigated by comparing the removal percentages, the kinetic constants, the energy utilization efficiencies (G50) as well as the COD and TOC removal during the SMX degradation in the DBD plasma system with or without the MnO2/CA films addition under different reaction conditions. The optimal catalytic performance was obtained by adding the 3% MnO2/CA films into the DBD plasma system and the alkaline solution condition was favorable for the SMX degradation. After four times using, the MnO2/CA composite films still maintained the catalytic activity. Catalytic mechanism of the MnO2/CA films was speculated by analyzing the changes of solution pH and conductivity during the reaction, concentrations of the formed O3 and H2O2 in water and the generated active species (1O2 and ·OH) in both the DBD plasma system and the DBD-MnO2/CA films system. The quenching test was also carried out to figure out the important effect of the ·O2−, 1O2 and ·OH for the SMX degradation in the synergistic system. Finally, LC-MS was used to analyze the main intermediates generated during the SMX degradation and the possible degradation pathways were accordingly speculated. The research could provide a new direction for the development and application of the DBD plasma technology as well we the composite films catalyst.