Modification of UNIFAC parameter table Revision 5 for representation of aqueous solubility and 1-octanol/water partition coefficient for POPs

In order to represent aqueous solubility and 1-octanol/water partition coefficient for POPs (persistent organic pollutants) by the UNIFAC model, two pairs of group interaction parameters in Revision 5 of the UNIFAC parameter table were modified. First, the pair of interaction parameters between the aromatic carbon–chloride (ACCl) and water (H2O) groups were corrected by minimizing the deviation between the experimental and calculated values of these properties for chlorinated benzenes, polychlorinated biphenyls, and polychlorinated dibenzo-p-dioxins and dibenzofurans. The corrected interaction parameters provided a better representation of both properties than the calculation results obtained in early works using the UNIFAC model. Second, the unknown pair of interaction parameters between the chloroalkene (Cl(Cdouble bond; length as m-dashC)) and H2O groups, which are required for calculating those properties of the other five POPs (aldrin, chlordane, endrin, dieldrin, and heptachlor), were newly determined from the experimental data on their properties. Finally, this study shows that Revision 5 could also predict solubility of POPs in some organic solvents. The modified parameter table is first suggested as the UNIFAC parameter table applicable to various phase equilibria including aqueous or nonaqueous solubility and partition coefficient of POPs.