Simultaneous removal of sulfamethoxazole and Cr (Ⅵ) from water by pulsed discharge plasma

Since the actual composition of water bodies is complex, and the compound pollution of organic matter and heavy metals is serious, it is an urgent need for green and efficient technologies to simultaneously remove organic matter and heavy metals from water. The coexistence of oxidizing and reducing particles in plasma can synchronize the degradation of organic matter and the reduction of heavy metals. In this paper, the simultaneous degradation of SMX and reduction of Cr (Ⅵ) by pulsed discharge plasma (PDP) was investigated. The effects of electrical, solution and water quality parameters on the simultaneous removal effect were investigated. The results showed that the best degradation of SMX (50 mg·L−1) was achieved by adding 2 mg·L−1 of Cr (Ⅵ). Similarly, the best reduction of Cr (Ⅵ) (0.7 mg·L−1) was achieved by adding 15 mg·L−1 of SMX. Higher input power, frequency, duty cycle, flow rate, and lower pH and conductivity favored the simultaneous removal of SMX and Cr (Ⅵ). Cl−、HCO3−、SO42− and HA in natural water inhibited the simultaneous removal effect. In addition, through trap agent experiments, it was found that the formation and annihilation of ·OH、·O2−、1O2、e− and ·H in the system had a certain effect on the simultaneous removal of both SMX and Cr(Ⅵ). Finally, three transformation pathways of SMX in the PDP system were inferred by LC-MS and DFT. In addition, ECOSAR calculations showed that wastewater toxicity was greatly reduced. Therefore, this study demonstrated that the PDP technology is an effective means for simultaneous removal of SMX and Cr (Ⅵ).