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The reactions of hydroxyl radicals with methyl t -butyl ether (MTBE) were studied using gamma radiolysis. Aqueous solutions of 100 ppm MTBE were saturated with 4:1 N 2 O/O 2 gas mixture prior to irradiation. Under these conditions hydroxyl radical is the predominant reactive species generated during gamma radiolysis. Complete degradation of MTBE is achieved within ∼30 min of irradiation at a dose rate of 0.21 kGy/min. The major volatile organic compounds (VOCs) produced are t -butyl formate (TBF), t -butyl alcohol (TBA), acetone, and methyl acetate. Under the reaction conditions, TBF does not yield TBA, but rather acetone as the primary reaction product. The formation of TBA by hydrolysis of TBF and a hemiacetal formed during the initial oxidative processes of MTBE appear to be minor reaction pathways. Although 2-methyl-2-methoxyl-propionaldehyde (MMP) has been proposed as a reaction product, we were unable to confirm its existence and we therefore, propose a reaction pathway, which does not involve MMP, as the predominant path leading to the formation of methyl acetate. The overall yields of VOCs are low with maximum individual yields between 4% and 13%. Upon extended treatment with gamma radiolysis the VOCs can be completely degraded. These studies contribute to a better fundamental understanding of the reactions of hydroxyl radicals with MTBE, and the resulting oxidation products, TBF and TBA. |
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