Anomalies in the log freundlich equation resulting in deviations in adsorption k values of pesticides and other organic compounds when the system of units is changed

Abstract

Freundlich K values cannot be directly converted from one set of units to another unless the slope, N, is unity. Dimensional analysis of the Freundlich equation shows the units of K to be moles(1-N) L(N)g-1, instead of the commonly used units, moles/g. A mathematical relationship exists between the ratio of K values in two different sets of units, and N. The magnitude of K does not change by the same factor as the adsorption data (x/m, C) from which it was calculated, when units are changed, unless N = 1.0. To avoid problems associated with units of K, it is recommended that mole fraction ( a unitless quantity) be used to express equilibrium concentration, and that K no longer be used as an indicator of relative adsorption. An alternate means of assessing relative adsorption among pesticides is proposed.