Effect of Organic Solvent on Sorption of Aromatic Solutes onto Soils

Abstract

Experiments and modeling activities are performed to determine the effect of polar solvent in the aqueous phase on the sorption of relatively hydrophobic solutes onto soils. The hydrophobic aromatic solutes generally display a semi‐logarithmic increase in solubility with increasing volume fraction of solvent in solvent/water mixtures. This results in a semi‐logarithmic decrease in the tendency for these solutes to sorb onto soil. A semi‐empirical model is developed in this investigation which supports these findings. However, the increase in solute solubility does not result in a directly proportional decrease in the sorption coefficient. This is believed to be a result of the solvent swelling the soil organic carbon material and thereby increasing the accessibility of the solute to this material. The effect of solvent on the increase in solute solubility and the decrease in soil sorption is much more pronounced for the more hydrophobic solutes. The findings from the investigation are useful to assess near‐source transport of hydrophobic aromatic solutes in soil systems in the event of a spill or discharge of solutes with a polar solvent.