Efficient electrocatalytic oxidation of tetracycline in water using a SnO2-Sb/FTO electrode

Tetracycline (TC) has been emerged as a recalcitrant pollutant in water environment, and how to efficiently remove it has become a recent research focus. In this study, a low-cost SnO2-Sb/FTO electrode has been successfully constructed using fluorine-doped tin oxide (FTO) conductive glass as the substrate by simple sol-gel and calcination method, and was utilized in the electrocatalytic oxidation of TC in aqueous solution. The surface morphology and crystal structure of the SnO2-Sb/FTO electrode were characterized by various techniques. Electrochemical characterization indicated that SnO2-Sb/FTO electrode has good conductivity, excellent electrocatalytic activity and high oxygen evolution potential. In a 50 mM Na2SO4 solution, 5 mg.L-1 TC was completely removed within 25 min at 1.25 mA.cm(-2) with no pH adjustment (pH 6), and the first-order reaction rate constant was obtained as 0.144 min(-1) with the energy consumption of 13.63 kW.h.kg(-1). Electron paramagnetic resonance measurement (EPR) and free radical quenching experiments indicated the crucial role of .OH in the electrocatalytic oxidation process. By identifying the degradation products and DFT calculations, the possible degradation pathways of TC were proposed, and the reaction regions of TC were analyzed. Moreover, the electrode exhibited outstanding stability and reusability. It is promising to efficiently remove TC in wastewater by using the SnO2-Sb/FTO electrode.