A comparative study on the degradation of ciprofloxacin in wastewater by iron-visible bismuth vanadate and iron-activated carbon systems: Mechanisms, efficiency, and ecotoxicity assessment

This study investigates the activation mechanisms of hydrogen peroxide by iron-visible bismuth vanadate (Fe2+/ H2O2/BiVO4/Vis) and iron-activated carbon (Fe2+/H2O2/AC) for ciprofloxacin (CIP) degradation. The Fe2+/ H2O2/BiVO4/Vis system achieved 99.8 % removal efficiency within 30 min at pH 2, while the Fe2+/H2O2/AC system demonstrated 99 % efficiency at pH 4. The optimum conditions were determined to be 25 mol/L H2O2 and 1.0 g/L catalyst dosage at pH 2 for the BiVO4 system, and 200 mol/L H2O2and 0.5 g/L catalyst dosage at pH 4 for the AC system. Scavenger experiments revealed that h+ (non-radical holes) and center dot O2- were dominant in the BiVO4 system, while center dot OH and 1O2were primary in the AC system. Liquid chromatography high-resolution mass spectrometry identified by-products, confirming decarboxylation and piperazine ring opening as the primary degradation mechanisms. The electrical energy per order of magnitude (EEO) of the Fe2+/H2O2/BiVO4/Vis system was 210 kWh.m-3 in 30 min. Ecotoxicity tests indicated that the degradation products are less harmful to aquatic organisms. Kinetic analysis revealed that the degradation process follows pseudo-second-order kinetics (R2 = 0.93), while adsorption isotherms were best described by the Langmuir model (R2 = 0.97). Both systems maintained over 90 % efficiency through five consecutive treatment cycles, demonstrating good stability and offering an effective alternative for treating contaminated wastewater.