The Effect of Soil Properties on Zinc Adsorption by Soils

Abstract

Abstract Solutions containing eight different concentrations of Zn were equilibrated with four soils sampled at two depths to determine whether Zn adsorption conformed to the Langmuir isotherm and to relate the Langmuir coefficients to soil properties. Zinc adsorption conformed to the Langmuir isotherm and two linear portions of the curve were found. The adsorption sites for the lower part had very high bonding energy coefficients and low adsorptive capacities compared with the adsorption sites of the part of the curve corresponding to higher Zn concentrations in the equilibrating solution. The CEC was related to the adsorptive capacity. The lower part was equivalent to 23% of the CEC and the upper part to 76% of the CEC. Soils high in clay or organic matter had higher adsorptive capacities and higher bonding energies for Zn than sandy soils low in organic matter. More differences in Zn adsorption were observed among soil types than between depths in each soil type. A study of the effect of pH on the adsorption of Zn revealed that low pH reduced Zn adsorption more for the sandy soils than for those high in colloidal‐size materials.