Removing methyl-tert-butyl ether (MTBE) from water: The kinetics and mechanisms behind the electron beam advanced oxidation process

Free radical bimolecular rate constants for MTBE reaction with the hydroxyl radical (•OH), the solvated electron and the hydrogen atom (H•) and the subsequent reaction of the oxidized carbon-centered radicals with oxygen were measured. The measured reaction rate constants for hydrated electron (< 8 × 10⁶/M-sec) and hydrogen atom (3.49 × 10⁶/M-sec) reaction showed that these species would not be important in the removal of contaminated MTBE in natural waters. However, the competition-kinetics derived overall •OH reaction rate constant of K₂₊₃ = 1.71 × 10⁹/M-sec showed that this oxidative process was the dominant initial degradation pathway. The decay of these MTBE peroxyl radicals in solution was complex. The multiple decays of the three different tetroxides accounted for the mixture of major (TBF, tert-butyl alcohol, acetone, methyl acetate) and minor (formaldehyde, 2-methyl-2-methoxy propanal, pyruvaldehyde, hydroxy-iso-butyraldehyde, iso-butyraldehyde and hydroxy acetone) degradation products observed experimentally. These products would themselves undergo analogous free-radical-induced decomposition chemistry, until ultimately, mineralization of MTBE could be achieved. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).