Conversion of Freundlich Adsorption K Values to the Mole Fraction Format and the Use of SY Values to Express Relative Adsorption of Pesticides

Anomalies in the Freundlich isotherm equation prevent the simple conversion of K values to a common set of units for assessment of relative adsorption. Although there is a straightforward way to properly convert the units of K values, serious extrapolation errors can result because, in the new set of units, the K value may be evaluated considerably outside the concentration data range. In the mole fraction format, concentration is reported as a mole fraction, and adsorption as mol g −1 , giving units of mol g −1 for K . In this format, K loses any practical meaning since it is evaluated at log Z = 0, Z = 1. An improved and more flexible method of reporting relative adsorption using S Y values is presented as well as a procedure to convert existing data to this format.