PARTITION-COEFFICIENTS FOR ALCOHOL TRACERS BETWEEN NONAQUEOUS-PHASE LIQUIDS AND WATER FROM UNIFAC-SOLUBILITY METHOD

In this work, we have applied a group-contribution activity-coefficien t model, UNIFAC, and the solubility of alcohols in water to estimate p artition coefficients for alcohol tracers between water and nonaqueous -phase liquids (NAPLs). The effects of temperature and mutual solubili ty between NAPL and aqueous phases on the estimation of partition coef ficients were also investigated. By comparing the estimated results wi th experimental partition coefficients for 30 alcohol tracers between 10 NAPLs and water, we found that: i) the UNIFAC-solubility method, in which the UNIFAC model in its infinite-dilution form is applied to th e NAPL phase and the solubility of tracers in water is used for estima tion of the activity coefficient in the aqueous phase, works better th an the UNIFAC model; ii) a linear relation between the logarithm of pa rtition coefficients and the logarithm of tracer solubility in water i s observed for those tracers having a similar chemical structure (i.e. the same number of branched methyl groups). This can serve as a usefu l tool for quick selection of the tracers that exhibit the desired par tition coefficients; iii) the effect of mutual solubility between NAPL and aqueous phases can be neglected because such miscibility is very small, usually of the order of 10(-3) mole/mole unit; and iv) temperat ure variation between 15 degrees and 25 degrees C does not significant ly affect partition coefficients. Copyright (C) 1997 Elsevier Science Limited.