Insights into the electrooxidation of florfenicol by a highly active La-doped Ti4O7 anode

In this study, a novel active La-doped Ti4O7 (La-Ti4O7) electrode was fabricated through a simple one-step spark plasma sintering method. Characterization results revealed that La was successfully incorporated into the crystal lattice of Ti4O7, leading to an increase in the surface oxygen vacancy content (from 26% to 31%), oxygen evolution potential (from 2.24 to 2.75 V vs SCE), hydroxyl radical yield [•OH, from 0.123 to 0.205 μmol/(min·cm2)] and interfacial charge-transfer rate compared to pristine Ti4O7. La-Ti4O7 electrodes achieved efficient anodic oxidation of florfenicol (FLO, one of the most widely used antibiotics), which mainly due to the indirect oxidation mediated by electro-generated •OH. The degradation of FLO by La-Ti4O7 electrodes fitted well with the pseudo-first-order kinetic model, and the optimal degradation rate constant (kFLO, 0.021 min−1) was achieved by 1.60% La-Ti4O7 electrode. In addition, the degradation efficiency of FLO increased with the increasing current density, decreasing pH and co-existing Cl-, while an opposite pattern was observed with co-existing NO3–. Seven degradation products of FLO were identified by UPLC-MS/MS. The main degradation pathways included hydrolysis, hydroxylation, dechlorination and C-N bonds cleavage. The energy consumption (EC) for FLO degradation ranged from 1.91 to 29.53 Wh/L, and the optimal practical conditions were obtained by the analysis of the calculated ratios of kFLO and EC. Moreover, La-Ti4O7 electrode maintained excellent removal efficiency of FLO (>93.5%) within 20 degradation cycles. This study suggested that La-Ti4O7 is a promising anodic material for the efficient treatment of FLO-polluted water.