Degradation of sulfamethoxazole in water by dielectric barrier discharge plasma jet: influencing parameters, degradation pathway, toxicity evaluation

Abstract

Sulfamethoxazole (SMX) is an antibiotic and widely present in aquatic environments, so it presents a serious threat to human health and sustainable development. A dielectric barrier discharge (DBD) plasma jet was utilized to degrade aqueous SMX, and the effects of various operating parameters (working gas, discharge power, etc) on SMX degradation performance were studied. The experimental results showed that the DBD plasma jet can obtain a relatively high degradation efficiency for SMX when the discharge power is high with an oxygen atmosphere, the initial concentration of SMX is low, and the aqueous solution is under acidic conditions. The reactive species produced in the liquid phase were detected, and OH radicals and O3 were found to play a significant role in the degradation of SMX. Moreover, the process of SMX degradation could be better fitted by the quasi-first-order reaction kinetic equation. The analysis of the SMX degradation process indicated that SMX was gradually decomposed and 4-amino benzene sulfonic acid, benzene sulfonamide, 4-nitro SMX, and phenylsulfinyl acid were detected, and thus three possible degradation pathways were finally proposed. The mineralization degree of SMX reached 90.04% after plasma treatment for 20 min, and the toxicity of the solution fluctuated with the discharge time but eventually decreased.