Hydroxyl and sulfate radical-based degradation of ciprofloxacin using UV-C and/or Fe2+-catalyzed peroxymonosulfate: Effects of process parameters and toxicity evaluation

Abstract

Ciprofloxacin (CIP) is a valuable antibiotic and discharged in huge quantities in aquatic environment. Different •OH and SO4•−-based advanced oxidation technologies (AOTs), e.g., Fe2+/PMS, UV-C/PMS, and UV-C/Fe2+/PMS are developed for treatment of CIP. The removal of CIP by Fe2+/PMS, UV-C/PMS and UV-C/Fe2+/PMS was 63, 77, and 87 %, respectively, under identical conditions which showed better performance of UV-C/Fe2+/PMS. The UV-C/Fe2+/PMS also caused high removal of total organic carbon of CIP. This high performance of UV-C/Fe2+/PMS-based AOTs possibly looked due to dual activation of PMS by UV-C and Fe2+. The removal of CIP by the three AOTs was found due to •OH and SO4•− and the later showed high reactivities with CIP, i.e., 2.45 × 109 and 2.35 × 109 M−1 s−1, respectively. The study of factors affecting the reactivities and/or yield of •OH and SO4•− diminished CIP degradation efficiency. The change in pH of solution and temperature and doses of Fe2+, PMS, and CIP exhibited significant impacts on the removal of CIP. The addition of inorganic ions showed strong inhibiting effects of NO2–, CO32–, and HCO3– while Cu2+ showed facilitating role. Analysis of degradation of CIP by GC–MS was used to develop proposed pathways. Acute and chronic toxicities of CIP and its products were measured by ECOSAR program and showed the resulting products to be non-toxic.