Kinetic modeling and simulation of PCE and TCE removal in aqueous solutions by electron-beam irradiation

The irradiation of aqueous solutions of TCE and PCE using a high-energy electron-beam results in the rapid decomposition of both chemicals. It is known that both TCE and PCE react with the aqueous electron and the hydroxyl radical with bimolecular rate constants greater than 10(9) M-1 s(-1) for each reaction. The fact that high-energy electrons produce significant concentrations of both e(aq)(-) and .OH radicals in water makes it an effective process for the removal of TCE and PCE from aqueous solution. We have employed steady state and computer-based chemical kinetic models to simulate and better understand the chemistry and kinetics of e-beam irradiation when applied to natural water systems. Model results were benchmarked to experimental data, allowing for the optimization of the reaction of DOC with the .OH radical. Values for the associated second-order reaction rate constant were found to be 2.5 x 10(8) and 4.0 x 10(8) M-1 s(-1), consistent with reported values for k(OH,DOC). The models were also used to investigate the possibility of incomplete irradiation during treatment and the presence of proposed chemical reactions of by-products. The reactions involve radicals and radical-adduct species formed by the reaction of TCE and PCE with the hydroxyl radical. (C) 2002 Elsevier Science Ltd. All rights reserved.