Linear solvation energy relationship of the limiting partition coefficient of organic solutes between water and activated carbon

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A linear solvation energy relationship has been found for 353 values of the limiting adsorption coefficients of diverse chemicals: log K= -0.37 + 0.0341 V(i) 1.07β + D + 0.55P with R = 0.951, s = 0.51, n = 353, and F = 818.0, where V(i) is the intrinsic molar volume; β is a measure of the hydrogen bond acceptor strength of the solute; D is an index parameter for the research group which includes the effects of the different types of carbon used, the temperature, and the length of time allowed for the adsorption equilibrium to be established; and P is an index parameter for the flatness of the molecule. P is defined to be unity if there is an aromatic system in the molecule or if there is a double bond or series of conjugated double bonds with no more that one non-hydrogen atom beyond the double bond and zero otherwise. A slightly better fit is obtained if the two-thirds power of V(i) is used as a measure of the surface area in place of the volume term: leg K= -1.75 + 0.227V(2/3) - 1.10β + D + 0.60 P with R = 0.954, s = 0.49, n = 353, and F = 995.39. This is the first quantitative measure of the effect of the shape of the molecule on its tendency to be adsorbed on activated carbon.

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Environmental Science and Technology