Removal of ciprofloxacin using modified advanced oxidation processes: Kinetics, pathways and process optimization

Degradation of ciprofloxacin by using various advanced oxidation processes (AOPs) like UV, H2O2, UV/H2O2, modified Fenton (nZVI/H2O2) and modified photo-Fenton was studied at near neutral pH. The results revealed that direct photolysis (UV) resulted in 60% degradation with TOC removal of 4% in 120 min. Hydrogen peroxide (H2O2) resulted in 40% removal of ciprofloxacin in 100 min. However, different combinations of DV, H2O2 and nano zero valent iron particles (nZVI) resulted in 100% removal efficiency in 30-40 min with higher mineralization. Degradation of ciprofloxacin followed second order kinetics with highest rates for modified photo-Fenton process. Daughter products formed during the degradation were identified and pathways of degradation were established for different removal processes. Residual hydrogen peroxide concentrations were found to be very low when combined methods were applied. Response surface methodology (RSM) study shows that a nZVI:H2O2 ratio of 5:1 can achieve 99.30% removal in 120 min thus reducing the use of H2O2. The optimized combination in presence of UV light resulted in 100% degradation within 25 min. (C) 2017 Elsevier Ltd. All rights reserved.