Estimation of Surface Complex Structure of Cadmium Adsorbed on Clay Minerals

Abstract

It is important to know the behavior of Cd adsorption on clay minerals for the understanding of pollution mechanism in soils. The specific purpose of this study is to understand the pH dependence of Cd adsorption on clay minerals from a microscopic point of view. We investigated Cd adsorption on four different substrates: Montmorillonite (Kunipia-F), Kaolinite, Alumina, and Silica. Although Cd adsorption increased with pH, the degree of increase depended on the substrate species and background solution (NaNO₃) concentrations. We classified Cd adsorption on Montmorillonite into three pH ranges;(i) below pH 4, (ii) pH 4-7, and (iii) over pH 7 and discussed the behavior of Cd adsorption on clay minerals using the concept of ‘surface complex models’.