Photocatalytic oxidation of ciprofloxacin by UV/ α-Fe2O3/sulfite: mechanism, kinetic, degradation pathway.

This study was aimed to investigate the synergistic effect of sulfite reducing agent on the UV/hematite (α-Fe2O3) photocatalytic process performance in the removal of ciprofloxacin from the aqueous solutions. For this purpose, influence of the operation parameters including initial antibiotic concentration, pH, sulfite to hematite molar ratio and the reaction time on the UV/hematite/sulfite (UHS) performance was evaluated. UV alone, UV/hematite (α-Fe2O3) (UH) and UV/sulfite (US) processes indicated to have little influence on the ciprofloxacin degradation. The simultaneous presence of hematite and sulfite in the reaction environment was significantly improved the degradation efficiency, as UHS process indicated an increase of 89%, 64% and 59% in the removal performance than that of UV alone, UH and US processes, respectively. Under the selected condition (pH of 7.0 and sulfite/hematite molar ratio of 1:3), 94% of ciprofloxacin (CFX) was degraded after 5 min of reaction. In addition, robs (mg L-1 min) value for UHS process was 25.26, 6 and 4.8 times that of UV alone, UH and US processes, respectively. The EEO and TCS values for UV alone, US, UH and UHS processes were (44.21 kWh/m-3 and 2.08 $ m-3), (10.5 kWh/m-3 and 1.1 $ m-3), (4.8 kWh/m-3 and 1.04 $ m-3) and (1.75 kWh/m-3 and 0.85 $ m-3), respectively. In addition, the study of the reaction mechanism showed hydroxyl and sulfate radicals play a vital role in the degradation of CFX by UHS process.