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

This bench-scale study investigated the feasibility of activated persulfate (S 2 O 8 2− ) oxidation of methyl tert -butyl 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 α-hydrogen abstraction via attack of the SO 4 −• at the intermediate methoxy group.