Enhanced electrochemical removal of sulfamethazine on Sm-doped Ti4O7 anode: Mechanisms and toxicity evaluation

Abstract

As one typical broad-spectrum antibiotics, the abuse of sulfonamide induce potential ecology risk to aquatic environment. Here, the novel Sm-doped Ti₄O₇ electrode (Sm-Ti₄O₇) were fabricated using a facile spark plasma sintering (SPS) method for anodic decomposition of recalcitrant pollutants of sulfamethazine (SMZ). Electrochemical degradation experiments demonstrated that the 0.25% Sm-Ti₄O₇ anode achieved a remarkable 91.2% removal SMZ (k_obs = 0.0158 min⁻¹), which the degradation kinetics was 3.16 times higher than that of the pristine Ti₄O₇ anode. Electron paramagnetic resonance (EPR) and quenching experiments confirmed that hydroxyl radicals (•OH) were the primary active species responsible for the SMZ degradation. Linear sweep voltammetry (LSV) revealed that the oxygen evolution potential (OEP) of 0.25% Sm-Ti₄O₇ anode was 2.23 V (vs. standard hydrogen electrode, SHE), which is higher than that of pristine Ti₄O₇ anode. Thus, the one-electron water oxidation reaction was boosted on 0.25% Sm-Ti₄O₇ anode for producing highly reactive of •OH. The degradation pathway and intermediate products were validated using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the toxicity analysis was also estimated. In summary, the doping of rare metal Sm in Ti₄O₇ could boosts the electro-generation of hydroxyl radical via H₂O oxidation, which make the electrochemical oxidation more effective and efficient.