Enhanced degradation of antibiotic sulfamethoxazole by electrochemical activation of PDS using carbon anodes

In this study, electrochemical activation of peroxydisulfate (PDS) using carbon anodes including multi-walled carbon nannotube (MWCNT), graphite (GR), black carbon (BC) and granular activated carbon (GAC) for degradation of antibiotic sulfamethoxazole (SMX) was investigated for the first time. The degradation of SMX by electrochemical activation of PDS using carbon anodes showed dual kinetics: an induction stage followed by a quick decay stage. In the latter stage, the degradation rate of SMX by electrochemical activation of PDS using MWCNT, GR, BC and GAC anodes increased about 15–35 times of that by electrolysis alone and 30–130 times of that by carbon/PDS (without applying current). The results of degradation of radical probes (atrazine (ATZ) and nitrobenzene (NB)) and radical scavenging effect manifest that nonradical oxidation, hydroxyl radical (HO^[rad]) and sulfate radical (SO₄^[rad]−) jointly contributed to the degradation of SMX in electrochemical activation of PDS. The formation of transition state structure of PDS (activated PDS, PDS^∗) between PDS molecule and carbon anodes by applying current was proposed to be responsible for nonradical oxidation, and its further decomposition resulted in the generation of HO^[rad] and SO₄^[rad]−. Increasing PDS concentration (0.1–5 mM) or current density (10–200 A m⁻²) considerably promoted the degradation of SMX. Additionally, electrochemical activation of PDS using carbon anodes exhibited good resistance to water matrices.