Degradation of chloramphenicol using a combination system of simulated solar light, Fe2+ and persulfate

Solar irradiation (λ ≥ 290 nm) has been introduced into a traditional Fe2+ activated persulfate (PS) system (Fe2+/PS). The combination system of solar light, Fe2+ and PS system (solar/Fe2+/PS) exhibited a rapid and continuous oxidation of chloramphenicol (CAP) in solution, and showed great advantages over the Fe2+/PS process by accelerated degradation efficiency. A presumed reason is that Fe2+ was slowly and continuously recycled by solar light, and the reductive photolysis Fe3+ to Fe2+ was promoted concomitantly with the production of additional hydroxyl radical (HO). The optimal dosages of PS and Fe2+ were determined by batch experiments. pH significantly influenced CAP degradation, and an acidic condition favored the reaction. Both HO and sulfate radical (SO4−) were considered to be the mainly oxidant to remove CAP, and HO had a higher contribution than SO4−. The presence of HCO3−, NO3−, NO2−, H2PO4−, HPO42− demonstrated adverse effects on CAP decay in solar/Fe2+/PS process. Coexisting Cl− ions slightly accelerated the CAP degradation rate at an appropriate concentration (0.6-6 mM) but gradually inhibited at a higher Cl− (12-36 mM) content. The results clearly showed that CAP presented the slowest degradation rate in wastewater, and the colloids should be taken into consideration prior to the application of solar/Fe2+/PS for wastewater treatment. Nonetheless, up to 89.7%, 94.7%, and 65.4% of CAP were removed from the filtrate, permeate, and retentate within 100 min, respectively. It is expected that the modified process could be applied for CAP removal from wastewater containing a considerable colloids/organic content. Finally, 8 major intermediate products were identified and the preliminary degradation pathways were proposed.