Computer-based predictions of intermediates and byproducts in the aqueous phase advanced oxidation systems: First-principles studies with kinetic Monte Carlo techniques

We develop a computer-based first-principles kinetic model to predict degradation mechanisms and fates of intermediates and byproducts produced in the aqueous phase advanced oxidation processes (AOPs) for various organic compounds. The model is comprised of three modules: 1) a module that predicts degradation pathways using the graph theory; 2) a module that estimates hydroxyl radical reaction rate constants using a group contribution method (GCM), and 3) an algorithm that solves ordinary differential equations (ODEs). We generate the degradation mechanisms of acetone and trichloroethylene (TCE) for the UV photolysis and hydrogen peroxide AOP and validate the generated mechanism with experimental data. One problem that we encountered was trying to solving numerous stiff ODEs that predict the byproduct formation. To solve this problem we developed a kinetic Monte Carlo (KMC) technique that can simulate the degradation processes of complicated macromolecules in AOPs without solving a set of stiff ODEs. This KMC model also automatically predicts degradation pathways with the graph theory and estimates corresponding reaction rate constants with GCM. We predicted the reaction mechanism, the time-dependent profiles of averaged molecular weight and polydispersitivity for polyethylene glycol degradation in UV/H2O2 process. These predictions are in good agreement with experimental data. The model also provides detailed and quantitative insights into the time evolutions of molecular weight distribution and concentration profiles of low molecular weight products and functional groups