Fe(0)/Fe3O4 mediated hydrolysis of endosulfan and the further transformation of endosulfan diol

Abstract

Endosulfan, an insecticide containing six chlorine atoms, can be susceptible to reductive dechlorination by Fe(0). However, no reliable scientific reports have documented its abiotic dechlorination using Fe(0). In our study, we investigated the reaction between endosulfan and Fe(0) and found that endosulfan does not undergo reductive dehalogenation. Instead, it is hydrolyzed to yield equimolar quantities of endosulfan diol. This finding was verified using analytical methods, including GC–MS, IR and NMR, on the tentatively collected reaction product and by comparison with data for standard endosulfan diol. Iron oxide on the surface of Fe(0) we used was Fe₃O₄, which was verified by the XPS and Raman analysis. Acid-washed Fe(0) without Fe₃O₄ coating on the surface of Fe(0) could not hydrolyze endosulfan, nor could Fe₃O₄ alone without Fe(0), indicating that the combined roles of Fe(0) and the Fe₃O₄ coating are important. In contrast to previous studies showing alkaline hydrolysis of endosulfan at high pH, our results indicate that no hydrolysis occurred at pH 11 in the absence of Fe(0) over 48 h. Approximately 98% of the loss of endosulfan was accounted for by the hydrolytic formation of endosulfan diol, which was subsequently decomposed by Fe(0). This research provides the first evidence that Fe(0) and Fe₃O₄ on the surface of Fe(0) work together to create an alternative pathway for the breakdown of organochlorine pollutants.