Degradation of carbamazepine by high-voltage direct current gas–liquid plasma with the addition of H2O2 and Fe2+

Carbamazepine (CBZ) is a typical psychotropic pharmaceutical which is one of the most commonly detected persistent pharmaceuticals in the environment. The degradation of CBZ in the aqueous solution was studied by a direct current (DC) gas–liquid phase discharge plasma combined with different catalysts (H 2 O 2 or Fe 2+ ) in this study. The concentrations of reactive species (H 2 O 2 , O 3 , and NO 3 − ) and •OH radical yield in the liquid were measured during the discharge process. The various parameters that affect the degradation of CBZ, such as discharge powers, initial concentrations, initial pH values, and addition of catalysts, were investigated. The energy efficiency was 25.2 mg·kW −1 ·h −1 at 35.7 W, and the discharge power at 35.7 W was selected to achieve the optimal balance on the degradation effect and energy efficiency. Both acidic and alkaline solution conditions were conducive to promoting the degradation of CBZ. Both H 2 O 2 and Fe 2+ at low concentration (10–100 mg/L of Fe 2+ , 0.05–2.0 mmol/L of H 2 O 2 ) were observed contributing to the improvement of the CBZ degradation rate, while the promotional effect of CBZ degradation was weakened even inhibition would occur at high concentrations (100–200 mg/L of Fe 2+ , 2.0–5.0 mmol/L of H 2 O 2 ). The degradation rate of CBZ was up to 99.1%, and the total organic carbon (TOC) removal efficiency of CBZ was up to 67.1% in the plasma/Fe 2+ (100 mg/L) system at 48 min, which suggested that high degradation rate and mineralization efficiency on CBZ could be achieved by employing Fe 2+ as a catalyst. Based on the intermediate products identified by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC–MS), the possible degradation pathways were proposed. Finally, the growth inhibition assay with Escherichia coli ( E. coli ) showed that the toxicity of plasma/Fe 2+ -treated CBZ solution decreased and a relatively low solution toxicity could be achieved. Thus, the plasma/catalyst could be an effective technology for the degradation of pharmaceuticals in aqueous solutions.