Photoelectrocatalytic Degradation of Sulfonamide Antibiotics Using BiVO4/TiO2 Array Anode
The photoelectrocatalytic degradation of seven sulfonamide antibiotics—sulfathiazole (STZ), sulfadiazine (SDZ), sulfisoxazole (SIA), sulfamethoxazole (SMZ), sulfapyridine (SPD), sulfadimidine (SMT), and sulfaguanidine (SG)—was investigated using a bismuth vanadate-loaded titanium dioxide array (BiVO4/TiO2) as the anode under visible light irradiation. Systematic evaluation of BiVO4 loading, solution pH, current density, electrolyte type, and electrolyte concentration revealed optimal conditions of 50 mmol·L−1 Na2SO4, a current density of 1.67 mA·cm−2, and pH 2. Under these conditions, STZ removal and total organic carbon (TOC) removal reached 95.7% and 76.7%, respectively. Removal efficiencies for SDZ, SIA, SMZ, SPD, SMT, and SG were 94.9%, 80.9%, 79.1%, 57.7%, 52.3%, and 52.0%, with TOC removal ranging from 50% to 76.7%. Quenching experiments and electron paramagnetic resonance (EPR) identified hydroxyl radicals (·OH), singlet oxygen (1O2), and sulfate radicals (SO4−·) as dominant reactive species. The BiVO4/TiO2 composite exhibited a valence band edge at EVB = 2.775 V vs. RHE, enabling oxidation of H2O, OH−, and SO4^2− to generate these radicals. The heterostructure narrowed the bandgap to 2.12 eV and enhanced visible light response, facilitating efficient charge separation and transfer. Degradation pathways involved oxidation of aniline moieties to nitro groups, followed by hydroxylation and cleavage of S–N, N–C, or S–C bonds, ultimately mineralizing to CO2, H2O, SO4^2−, and NO3−. The system demonstrated high stability and catalytic efficiency across acidic and alkaline conditions, offering a promising approach for antibiotic removal from environmental waters.