Comparative studies of various iron-mediated oxidative systems for the photochemical degradation of endosulfan in aqueous solution

This study investigated iron-mediated oxidative processes for the photochemical degradation of endosulfan, a chlorinated insecticide and central nervous system disruptor. At UV fluence of 360 ml/cm(2), 52.4% and 32.0% removal of 2.45 mu M initial endcisulfan was observed by UV/Fe3+ and UV/Fe2+ processes, respectively, at an initial concentration of 17.8 mu M iron. The degradation of endosulfan by UV/Fe3+ or UV/Fe2+ was dramatically enhanced by adding peroxide (i.e., H2O2, S2O82- or HSO5-). Among the UV/peroxide/Fe processes, the highest degradation efficiency of 99.0% at UV fluence of 360 mJ/cm(2) was observed by UV/HSO5-/Fe2+ with 2.45 mu M [endosulfan](0), 17.8 mu M [Fe2+](0), and 49.0 mu M [HSO5-](0). The observed degradation rate constant of endosulfan was promoted either by increasing [Fe2+](0) and/or [peroxidelo or by decreasing [endosulfan](0), while the initial degradation rate of endosulfan increased with increasing [Fe(2+)10, [peroxide]o, or [endosulfan]o. At UV fluence of 6000 mJ/cm(2), 45.0% mineralization as represented by the decrease in total organic carbon content was observed by UV/HSO5-/Fe2+ at 9.80 mu M [endosulfan](0), 980 mu M [HSO5-](0), and 17.8 mu M [Fe2+](0). The major by-product of endosulfan was observed in all cases to be endosulfan ether which was further degraded with an extended reaction time. The results suggest that iron-mediated advanced oxidation processes (AOP5) have a high potential for the removal of endosulfan and its by-product from contaminated water. (C) 2015 Elsevier B.V. All rights reserved.