Contribution of persulfate in UV-254Â nm activated systems for complete degradation of chloramphenicol antibiotic in water

In this work, we investigated the treatment of chloramphenicol (CAP) solution using a persulfate (PS)-based Advanced Oxidation Process (AOP) generating sulfate and hydroxyl radicals upon exposure to low intensity UV. Experiments were carried out at 20 °C in photo-reactors equipped with 4.9 Watt Low Pressure Mercury Lamp (LPHgL). Several experimental parameters were varied and evaluated to optimize the degradation process reaching therefore better mineralization of CAP and its degradation products. Parameters included: UV power, PS concentration, pH, dissolved ions e.g. HCO3−, Cl−, SO42−, nutrients e.g. NO3−, NO2−, HPO42− and organic acids e.g. fumaric acid, humic acids. Results showed that: (i) CAP degradation followed pseudo-first order kinetics with an optimized t1/2 lesser than 5 min under controlled conditions; (ii) CAP mineralization extent was proportional to the amount of PS used (0.25-5.0 mM) with no mineralization noticed in the absence of PS; (iii) The calculated % reaction stoichiometric efficiency (RSE) reached values up to 52% comparable to that of RSE obtained in thermally activated PS systems, however, exceeding by far RSE values in chemically activated systems; (iv) PS can be sustained in solution at high % RSE upon sequential CAP addition; (v) CAP partially disappeared along with coliforms in CAP-spiked non-treated wastewater samples using UV/PS system under moderate conditions; (vi) The optimized AOP showed an experimental break-even point between mineralization and CAP degradation at [PS] = 0.5 mM and a fluence of 330 J for 1 h reaction. CAP transformation products were identified by HPLC/MS and a CAP primary degradation reaction pathway was proposed. This study demonstrated that UV/PS system is much stronger than UV-only system for rapid and complete mineralization of CAP in water.