LINEAR SOLVATION ENERGY RELATIONSHIP OF THE LIMITING PARTITION-COEFFICIENT OF ORGANIC SOLUTES BETWEEN WATER AND ACTIVATED CARBON

A linear solvation energy relationship has been found for 353 values o f the limiting adsorption coefficients of diverse chemicals: log K = - 0.37 + 0.0341 V-i - 1.07 beta + D + 0.65P with R = 0.951, s = 0.51, n = 353, and F = 818.0, where Vi is the intrinsic molar volume; beta is a measure of the hydrogen bond acceptor strength of the solute; D is a n index parameter for the research group which includes the effects of the different types of carbon used, the temperature, and the length o f 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 th at 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: log K = -1.75 + 0.227 V-2/3 - 1.10 beta + D + 0.60P with R = 0.954, s = 0.49, n = 353, and F = 895.39. This is the first quantitative measure of th e effect of the shape of the molecule on its tendency to be adsorbed o n activated carbon.