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 show n that the model predicts relatively concentration-independent chi values f or rubbery matrices, concentration-dependent chi values for more glassy mat rices, and highly concentration-dependent, largely negative interaction par ameters for sorption of phenanthrene onto Green River kerogen, Ohio Shale I I kerogen, Illinois No. 6 and Wyoming coals, and poly(phenyl methacrylate). These greatly negative enthalpic contributions to the interaction paramete r are only to be expected where specific sorbate-sorbent interactions exist , such as in polar sorbate-polar sorbent systems. The failure of the nonlin ear partitioning model is explained in terms of its inability to predict th ese increased interactions of sorbing solutes within microvoids present wit hin glassy matrices. Calculations of sorbent solubility parameters through use of this model do, however, provide good agreement with literature solub ility parameter values for specific sorbents; it may thus prove useful for partial characterization of sorbents for which solubility parameters are un known.