Prediction of rate constants for radical degradation of aromatic pollutants in water matrix: A QSAR study

We present the results of the QSAR/QSPR study on the degradation rate constants of 78 aromatic compounds by the hydroxyl radicals in water. A genetic algorithm and multiple regression analysis were applied to select the descriptors and to generate the correlation models. Additionally to DRAGON descriptors, the parameters from quantum-chemical calculations at semiempirical and at density functional theory level (B3LYP/6-31 G(d,p)) were applied. The most predictive model is a four-variable model that had a good ratio of the number of variables and the predictive ability to avoid overfitting. As it was expected, the main contribution to the degradation rate was given by the E-HOMO parameter. Additionally, a number of topological descriptors in selected models showed an importance of polarizability term regarding the degradation rate of compounds. Overall, the applied GA-MLRA approach with the use of quantum-chemical and DRAGON generated descriptors showed good results in this study. The obtained statistically robust structure-degradation rate model can be used for future studies of the presence of organic compounds in the environment, and especially their degradation by hydroxyl radicals as a part of a water/wastewater treatment. (C) 2009 Elsevier Ltd. All rights reserved.