Kinetic Model for the Degradation of MTBE by Fenton's Oxidation

Abstract

Environmental Context.Since the early 1990s, methyl tert-butyl ether (MTBE), a possible human carcinogen, has been used as a gasoline oxygenate at concentrations of up to 15% by volume; however, a fraction of the MTBE produced has inevitably been released to the environment. And, spills at gasoline service stations have resulted in local groundwater contamination levels of MTBE over 100 mg L−1, because of its very high water solubility. Advanced oxidation is a common technique for mineralizing organic contaminants, but the reaction chemistry needs to be better understood to facilitate design of remediation systems. Abstract.A kinetic model for the degradation of methyl tert-butyl ether (MTBE) in batch reactors with Fenton’s oxidation (Fe2+/ H2O2) in aqueous solutions was developed. This kinetic model consists of equations accounting for (1) hydrogen peroxide chemistry in aqueous solution, (2) iron speciation, and (3) MTBE oxidation. The mechanisms of MTBE degradation, and the resultant pathways for the formation and degradation of the byproducts, were proposed on the basis of previous studies. A set of stiff nonlinear ordinary differential equations that describe the rate of formation of each species in this batch system was solved using Matlab (R13) software. The kinetic model was validated with published experimental data. The degradation of MTBE by Fenton’s oxidation is predicted well by the model, as are the formation and degradation of byproducts, especially methyl acetate (MA) and tert-butyl alcohol (TBA). Finally, a sensitivity analysis based on calculating the sum of the squares of the residuals (SSR) after making a perturbation of one rate constant at a time was applied to discern the effect of each reaction on MTBE disappearance.