Degradation of ethyl paraben in aqueous medium using advanced oxidation processes: Efficiency evaluation of UV-C supported oxidants

Abstract

UV-C-mediated advanced oxidation processes (AOPs) for the enhanced degradation of ethyl paraben (EP) in the presence of oxidants such as persulfate (PS), hydrogen peroxide (H2O2) and peroxymonosulfate (PMS) were systematically investigated. The AOP treatments showed 98.1%, 97.0% and 81.3% degradation of EP with rates of 0.0373, 0.0339, and 0.0202 min(-1) within 90 min for UV/PS, UV/H2O2 and UV/PMS, respectively. Degradation rates of EP increased with higher initial dosages of oxidant(s), while the opposite trend was observed in the case of increasing initial EP concentration. Maximum EP removal was achieved at pH 6.5 for UV/PS and UV/PMS and at pH 3 for UV/H2O2. Humic acid significantly retarded the degradation of EP. Chloride (Cl-) and carbonate (CO32-) suppressed reaction rates using UV/PS and UV/H2O2 systems, whereas they elevated the degradation rates with UV/PMS treatment. Degradation of EP in each of the UV-C based AOPs followed pseudo-first-order kinetics. The use of ethanol and t-butyl alcohol as scavengers revealed that HO center dot and SO4 center dot- radicals were the major reactive radicals in UV/H2O2, UV/PS, and UV/PMS treatments. The efficiency (according to electrical energy per order and total cost per cubic meter) of the systems followed the order UV/PS > UV/H2O2 > UV/PMS. Thus, UV/PS process was more efficient and economical for EP degradation than the other processes examined in this study.