Degradation of ciprofloxacin by photocatalytic ozonation process under irradiation with UVA: Comparative study, performance and mechanism

The photocatalytic ozonation process (O-3/UVA/TiO2) was applied for the removal of ciprofloxacin antibiotic (CIP) from aqueous solutions. The influence of various operational factors such as solution pH, initial pollutant concentration, catalyst content, ozone dose and scavengers was studied on the process. The mineralization, biodegradability, kinetic models, catalyst recyclability, electrical energy consumption and cost estimation of the process were also performed. Various techniques of FE-SEM, EDS, FTIR, XRD and UV-vis were applied to characterize the catalyst. The highest CIP removal (98.5 %) was obtained in ozone and catalyst doses of 0.34 g/h and 1.0 g/L, respectively during 15 min reaction time at pH 9.0. The scavenging experiments approved the contribution of hydroxyl radicals ((OH)-O-center dot) and superoxide (O-2(center dot-) as the main active radical species in the process. The competition effect of various anions on the process efficiency was in the order of chloride > carbonate > bicarbonate > sulfate. The process kinetics followed the pseudo-first-order model. The catalyst efficiency was about 95 % of the original one after 6 recycling steps. It can be concluded that the photocatalytic ozonation process (O-3/UVA/TiO2), due to the low reaction time and high removal efficiency, can be considered as a suitable and practical technique for the removal of antibiotics from aqueous solutions. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.