Degradation of sulfadiazine in a cyclic V-SDBD plasma system: Parameters analysis and degradation pathway

Abstract

A cyclic volume and surface dielectric barrier discharge (V-SDBD) plasma wastewater treatment system with stainless steel net as discharge electrode was established and applied to the sulfadiazine (SDZ) degradation. The discharge characteristics, active substance yield and relative emission spectra in different net electrode systems were compared. The SDZ degradation as well as the UV–vis spectra and COD removal of the SDZ solutions under different treatment conditions were investigated to achieve the appropriate mesh parameter of the net electrode and circulating velocity of the solution. The obtained results show that the SDZ had a better degradation in the cyclic V-SDBD system than that in the intermittent DBD system. 10-mesh stainless steel net and 333 mL min−1 circulating flow rate were the optimal reaction conditions for the SDZ degradation. Compared with the other three net electrodes (14, 20 and 40-mesh), the 10-mesh electrode system could produce more H2O2 and O3, and the relative emission spectrum had stronger intensity. The results of voltage and current waveform and Lissajous figures show that the air ionization in the V-SDBD system with 10-mesh electrode was higher, and more micro-discharge channels could be generated in the discharge space. UV–vis spectra and COD removal analysis of SDZ solutions also stated the SDZ degradation in the V-SDBD plasma system. According to the byproducts’ identification, SDZ degradation pathway was speculated and the change of solution toxicity was analyzed. The results verified that the total toxicity of the initial SDZ solution could be reduced after treating in the V-SDBD plasma system.