Lead and Zinc Partition Coefficients of Selected Soils Evaluated by Langmuir, Freundlich, and Linear Isotherms

Abstract

The paper outlines some approaches that should be considered in the calculation of partition coefficients based on Langmuir, Freundlich and Linear isotherms. It was found that the Langmuir partition coefficient (K _Lg ), whose calculation involved the maximal amount of lead (Pb) and zinc (Zn) adsorbed and their appropriate bonding term energy, seemed more “precise” than the Freundlich (K _F ) and Linear (K _Li ) based partition coefficients. The Freundlich partition coefficients were decidedly lower than the Langmuir and Linear ones and appeared to “resist” to changes of equilibrium lead and zinc equilibrium concentrations. This feature may lead to a potential underestimation of calculated K _F coefficients due to the heterogenic nature of soil adsorptive surface. The “adequate” Linear partition coefficient should unconditionally be obtained from the slope of the C‐type plot (isotherm) of the amount adsorbed versus its solution concentration. This step will occur when the Freundlich exponent n = 1. Langmuir partition coefficient (K _Lg ) as a convenient and reliable parameter to be applied for soil adsorption capacities assessment should be recommended.