Solubility and sorption of petroleum hydrocarbons in water and cosolvent systems

The solubility and sorption of oil by uncontaminated clay loam and silt loam soils were studied from water and cosolvent/water solutions using batch techniques. The data obtained from the dissolution and sorption experiments were used to evaluate the applicability of the cosolvent theory to oil as a complex mixture. Aqueous solubility and soil-water distribution coefficients (K(d,w), L/kg) were estimated by extrapolating from cosolvent data, with a log-linear cosolvency model, to the volume fraction of cosolvent (f(c)) 0, and were compared with direct aqueous measurements. The extrapolated water solubility was 3.16 mg/L, in good agreement with the directly measured value of 3.83 mg/L. Extrapolated values of K(d,w) for the two soils were close to each other but consistently higher than the values from direct aqueous measurements, because of the presence of dissolved organic carbon (DOC). The partition coefficient (K(DOC)) between the DOC and the freely dissolved phase and the OC-normalized sorption coefficient (K(OC)) were determined. The average values of logKD(OC) and logK(OC) were estimated as 4.34 and 3.32, respectively, giving insight into the possibility of oil becoming mobilized and/or of the soil being remedied. This study revealed that the cosolvency model can be applied to a broader range of hydrophobic organic chemicals (HOCs) than has been previously thought. The results aided in a reliable determination of water solubility and sorption coefficients and provide information about the fate of oil in solvent-contaminated environment.