Radiation Chemistry of Methyl tert-Butyl Ether in Aqueous Solution

• Published in: Environmental science & technology Vol. 38; no. 14; pp. 3994 - 4001
• Main Authors: Mezyk, Stephen P, Jones, Jace, Cooper, William J, Tobien, Thomas, Nickelsen, Michael G, Adams, J. Wesley, O'Shea, Kevin E, Bartels, David M, Wishart, James F, Tornatore, Paul M, Newman, Kimberley S, Gregoire, Kellie
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-07-2004; American Chemical Society (ACS)
• Subjects: Applied sciences; Aqueous solutions; Chemicals; Chemistry; Electrons; Exact sciences and technology; Groundwaters; Hydrogen-Ion Concentration; Hydroxyl Radical - chemistry; Kinetics; Methyl Ethers - analysis; Methyl Ethers - chemistry; MTBE; Natural water pollution; Oxidation-Reduction; Pollution; Pulse Radiolysis; Radiation; Solutions; Waste Disposal, Fluid; Water Pollutants, Chemical - analysis; Water treatment and pollution; Antiknock additive; Ether; Chemical degradation; Free radical reaction; Chemical reaction kinetics; Kinetic model; Additive; Decontamination; Electron irradiation; Oxygenator; Gasoline; Reaction mechanism; Radiochemical degradation; Radiolysis; Oxidation; Water pollution; Pulsed beam; Degradation product; Organic compounds; Ground water
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es034558t

The chemical kinetics of the free-radical-induced degradation of the gasoline oxygenate methyl tert-butyl ether (MTBE) in water have been investigated. Rate constants for the reaction of MTBE with the hydroxyl radical, hydrated electron, and hydrogen atom were determined in aqueous solution at room temperature, using electron pulse radiolysis and absorption spectroscopy (•OH and e- aq) and EPR free induction decay attenuation (•H) measurements. The rate constant for hydroxyl radical reaction of (1.71 ± 0.02) × 109 M-1 s-1 showed that the oxidative process was the dominant pathway, relative to MTBE reaction with hydrogen atoms, (3.49 ± 0.06) × 106 M-1 s-1, or hydrated electrons, <8.0 × 106 M-1 s-1. The hydroxyl radical reaction gives a transient carbon-centered radical which subsequently reacts with dissolved oxygen to form peroxyl radicals, the rate constant for this reaction was (2.17 ± 0.06) × 109 M-1 s-1. The second-order decay of the MTBE peroxyl radical was 2k = (6.0 ± 0.3) × 108 M-1 s-1. These rate constants, along with preliminary MTBE degradation product distribution measurements, were incorporated into a kinetic model that compared the predicted MTBE removal from water against experimental measure ments performed under large-scale electron beam treatment conditions.