Degradation of sulfamethoxazole in aqueous solution by dielectric barrier discharge plasma combined with Bi2WO6 -rMoS2 nanocomposite: Mechanism and degradation pathway

The feasibility of pollutant removal in aqueous solution by dielectric barrier discharge plasma in combination with Bi2WO6-rMoS2 composite photocatalyst was investigated by choosing sulfamethoxazole (SMZ) as the model pollutant. In this study, Bi2WO6-rMoS2 catalysts were synthesized by a modified hydrothermal method and characterized by TEM, XRD, XPS. The results showed that the Bi2WO6 was well loaded on the surface of MoS2. The influences of the main operating parameters including discharge voltage, initial concentration, initial pH, mass ratios and dosages of Bi2WO6-rMoS2 on the removal efficiency of SMZ were studied. The results revealed that the initial concentration of 20 mg L−1 SMZ solution (100 mL) could be degraded by 97.6% with the addition of 0.08 g L−1 Bi2WO6-rMoS2 (1 wt%) at 9 kV after 21 min, compared with 72.5% by single dielectric barrier discharge plasma. Even after four cycling runs, Bi2WO6-rMoS2 (1 wt%) still remained high removal efficiency of SMZ. Moreover, the yields of hydrogen peroxide (H2O2) and Ozone (O3) in plasma discharge process were also investigated, and the results exhibited that adding Bi2WO6-rMoS2 could notably influence the amount of O3 and H2O2. Finally, ten intermediates of SMZ degradation were identified, and the proposed SMZ degradation pathways were deduced based on the detected intermediates.