The degradation of MTBE-BTEX mixtures by gamma radiolysis. A kinetic modeling study

Gamma radiolysis was used to degrade aqueous MTBE/BTEX mixtures and the results compared to kinetic modeling predictions. Under our experimental conditions all the BTEX compounds are degraded within 10 min while MTBE required irradiation times in excess of 30 min to accomplish complete decomposition. The initial simulation of the degradation kinetics based on a model containing the full set of water radiolysis reactions and rate constants of the reactions of the generated hydroxyl radicals, hydrated electrons, and hydrogen atoms with the MTBE, benzene, toluene, ethyl benzene and para-xylene, agreed well with the measured data, however, deviations at longer irradiation times were seen. A second simulation, involving the grouping of the MTBE/BTEX degradation products into a single class of N identical species and using a rate constant for the hydroxyl radical with this species of 5.0 x 10(9) N M(-1)s(-1), leads to excellent agreement with the observed experimental results even at longer irradiation time. (C) 2002 Elsevier Science Ltd. All rights reserved.