Comparing the electrochemical degradation of levofloxacin using the modified Ti/SnO2 electrode in different electrolytes

The purpose of this study is to develop an electrode material with high electrocatalytic activity, good stability and low price for the degradation of the new pollutant - antibiotic levofloxacin (LEV). A novel modified Ti/SnO₂ electrode is prepared using a sol–gel method combined with spraying. The morphology of the Ti/SnO₂-Sb-Ni/SiO₂ electrode was performed by field emission scanning electron microscopy, which revealed a smooth and flat surface. It can be seen from the results of X-ray diffraction and electrochemical tests, the electrode possessed finer grain size (2.68 nm) and slightly higher oxygen evolution potential (OEP, 1.87 V). Electrochemical degradation experiments show that the removal rate of LEV in Na₂SO₄ and NaNO₃ solutions reached 100% after 10 min reaction, while in NaCl solution the reaction time (LEV 100% removal) was shortened to 3 min, indicating a faster removal rate. An electrical energy consumption per order of magnitude (EE/O) of LEV degraded by Ti/SnO₂-Sb-Ni/SiO₂ electrode was only 0.59 kWh m⁻³ for an initial concentration of 20 mg/L LEV with a volume of 400 mL. According to the changes of UV–visible absorption spectra during the LEV degradation, the damage degree of conjugated structures in LEV molecules varies with different electrolytes. The existence of hydroxyl radical (•OH) and sulfate radical (SO₄^•−) was confirmed by radical quenching experiment and EPR text with 100 mM 5,5-Dimethyl-1-pyrrolidine N-oxide (DMPO). In different electrolytes, SO₄^•− (in Na₂SO₄ solution), •OH (in NaNO₃ solution) and active chlorine(in NaCl solution) played a leading role in LEV degradation, respectively.