Determination of Hydroxyl Radical Rate Constants for Fuel Oxygenates

Abstract

Advanced oxidation processes (AOP) are commonly used to treat contaminated groundwaters for a variety of synthetic organic chemicals (SOCs), including those contaminated with fuel oxygenates. To facilitate modeling oxygenate removal with advanced oxidation processes, kinetic rate constants are needed for hydroxyl radicals and specific oxygenates. In this work, hydroxyl radical rate constants were determined for a suite of fuel oxygenates and byproducts—methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), diisopropyl ether (DIPE), tert-butyl formate (TBF), and tert-butyl alcohol (TBA)—using a uniform methodology. Rate constants were determined with the competitive kinetic technique using para-chlorobenzoic acid (pCBA) as the radical probe and the UV/hydrogen peroxide AOP for radical generation. The second-order rate constants determined for MTBE, ETBE, TAME, DIPE, TBF, and TBA were 1.27 (±0.04) (10⁹), 2.46 (±0.8) (10⁹), 2.80 (±0.2) (10⁹), 3.01 (±0.06) (10⁹), 5.6 (±0.8) (10⁸), and 7.3 (±0.2) (10⁸) M⁻¹·s⁻¹, respectively.