Sorption kinetics of PAHs in methanol–water systems

The objectives of this study were to evaluate the relationships between the equilibrium sorption constant (Kp), the first-order desorption rate coefficient (k2), and the volumetric fraction of water miscible solvent (fc); and to utilize SPARC-calculated (SPARC Performs Automatic Reasoning in Chemistry) solubility and partitioning parameters with empirical measurements for a priori prediction of solute sorption kinetics in aqueous and mixed solvent systems. Soil column miscible displacement experiments were performed using naphthalene, phenanthrene, anthracene, pyrene and benzo(a)pyrene over an fc range from 0.0 to 0.8. Data from the miscible displacement studies were analyzed using a two-domain first-order mass transfer model to obtain Kp and k2. Results corroborated and extended the range of the validity of the log–log linear relationship between k2 and Kp and log–linear relationship between k2 and fc for mixed solvent systems. In addition, the slope of the log k2–log Kp relationship was found to be relatively solute independent. Predicted values of k2 in aqueous systems agreed well with experimentally measured values, thus, indicating the general applicability of the predictive approaches for predicting the sorption kinetics of hydrophobic organic compounds.