Oxidative Degradation of MTBE by Pyrite-Activated Persulfate: Proposed Reaction Pathways

Abstract

This bench-scale study investigated the feasibility of activated persulfate (S(2)O(8)(2-)) oxidation of methyl tertbutyl ether (MTBE), using pyrite (FeS(2)) as the source of ferrous ion activators. Under the FeS(2)-activated S(2)O(8)(2-) condition, the sulfate free radical (SO(4)) is the predominant reactive species generated. The oxidation reactions were able to completely degrade MTBE when given sufficient doses of FeS(2) and S(2)O(8)(2-) and sufficient reaction time (e.g., 3 g FeS(2)/L and 5 g Na(2)S(2)O(8)/L within 4 h) and exhibited generation and subsequent degradation of the primary MTBE degradation intermediate products including tert-butyl formate, tert-butyl alcohol, methyl acetate, and acetone. The detailed reaction mechanism proposed for a SO(4)(-)driven oxidation process in this paper indicates that the destruction of MTBE most likely happens through alpha-hydrogen abstraction via attack of the SO(4)(-) at the intermediate methoxy group.