Kinetics and products of reactions of MTBE with ozone and ozone/hydrogen peroxide in water

• Published in: Journal of hazardous materials 2002-01, Vol.89 (2), p.197-212
• Main Authors: Mitani, Marie M., Keller, Arturo A., Bunton, Clifford A., Rinker, Robert G., Sandall, Orville C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Byproducts; Carcinogens - chemistry; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Groundwaters; hydrogen peroxide; Hydrogen Peroxide - chemistry; Hydroxyl radical; Kinetics; Methyl Ethers - chemistry; MTBE; Natural water pollution; Oxidants - chemistry; Oxidants, Photochemical - chemistry; Ozone; Ozone - chemistry; Pollution; Pollution, environment geology; Reaction pathway; Soil Pollutants - analysis; TBA; TBF; Temperature; Water; Water treatment and pollution
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/S0304-3894(01)00309-0

Methyl- t-butyl-ether (MTBE) has become a prevalent groundwater pollutant due to its high volume use as a nationwide gasoline additive. Given its physicochemical properties, it requires new treatment approaches. Both aqueous O 3 and a combination of O 3/H 2O 2, which gives OH, can remove MTBE from water, making use of O 3 a viable technology for remediation of groundwater from fuel contaminated sites. Rate constants and temperature dependencies for reactions of MTBE with O 3 or with OH at pH 7.2, in a range of 21–45°C (294–318 K) were measured. The second-order rate constant for reaction of MTBE with O 3 is 1.4×10 18 exp(−95.4/ RT) (M −1 s −1), and for reaction of MTBE with OH produced by the combination of O 3/H 2O 2 is 8.0×10 9 exp(−4.6/ RT) (M −1 s −1), with the activation energy (kJ mol −1) in both cases. At 25°C, this corresponds to a rate constant of 27 M −1 s −1 for ozone alone, and 1.2×10 9 M −1 s −1 for O 3/H 2O 2. The concentration of OH was determined using benzene trapping. Products of reactions of O 3 and O 3/H 2O 2 with MTBE, including t-butyl-formate (TBF), t-butyl alcohol (TBA), methyl acetate, and acetone, were determined after oxidant depletion. A reaction pathway for mineralization of MTBE was also explored. Under continuously stirred flow reactor (CSTR) conditions, addition of H 2O 2 markedly increases the rate and degree of degradation of MTBE by O 3.