Reevaluation of general partitioning model for sorption of hydrophobic organic contaminants by soil and sediment organic matter

This evaluation of the polymer-based Flory–Huggins sorption theory has shown that the model predicts relatively concentration-independent χ values for rubbery matrices, concentration-dependent χ values for more glassy matrices, and highly concentration-dependent, largely negative interaction parameters for sorption of phenanthrene onto Green River kerogen, Ohio Shale II kerogen, Illinois No. 6 and Wyoming coals, and poly(phenyl methacrylate). These greatly negative enthalpic contributions to the interaction parameter are only to be expected where specific sorbate-sorbent interactions exist, such as in polar sorbate–polar sorbent systems. The failure of the nonlinear partitioning model is explained in terms of its inability to predict these increased interactions of sorbing solutes within microvoids present within glassy matrices. Calculations of sorbent solubility parameters through use of this model do, however, provide good agreement with literature solubility parameter values for specific sorbents; it may thus prove useful for partial characterization of sorbents for which solubility parameters are unknown.