Sorption kinetics of PAHs in methanol–water systems

Abstract

The objectives of this study were to evaluate the relationships between the equilibrium sorption constant ( K p), the first-order desorption rate coefficient ( k 2), and the volumetric fraction of water miscible solvent ( f c); 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 f c 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 K p and k 2. Results corroborated and extended the range of the validity of the log–log linear relationship between k 2 and K p and log–linear relationship between k 2 and f c for mixed solvent systems. In addition, the slope of the log k 2–log K p relationship was found to be relatively solute independent. Predicted values of k 2 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.