Degradation of methyl tertiary-butyl ether (MTBE) by anodic Fenton treatment

Abstract

Degradation of MTBE, a common fuel oxygenate, was investigated using anodic Fenton treatment (AFT) and by comparison with classic Fenton treatment (CFT). The AFT system provided an ideal pH environment (2.5–3.5) for the Fenton reaction and utilized gradual delivery of ferrous iron and hydrogen peroxide, which was more efficient than batch CFT to degrade MTBE and its breakdown products. The optimized ratio of ferrous iron to hydrogen peroxide for AFT was determined to be 1:5 (in mmol). Depending on the initial concentration, MTBE was completely degraded by the optimized AFT in 4–8 min. The breakdown products found during the treatment of MTBE were acetone, t-butyl formate, t-butanol, methyl acetate, acetic acid, and formic acid, which were all completely degraded by the optimized AFT in 32 min. Based on the experimental results and other work reported in the literature, degradation mechanisms of MTBE and its breakdown products in AFT and CFT were proposed. Generally, reactions are initiated by H-abstraction by OH, generating carbon-centered radicals which undergo various reactions including α/β-scission within the radical, combination with oxygen, oxidation by ferric ion, and reduction by ferrous ion before generating the final oxidation products. Radical combination with oxygen (and the reactions thereafter) and radical oxidation by ferric ion are believed to be the most important pathways in the overall fate of the generated radicals, while radical reduction by ferrous ion is the least important. By elucidating the reaction kinetics and mechanisms of MTBE degradation in the anodic Fenton system, this study offers a potential remediation technique for treating MTBE-contaminated wastewater.