ADSORPTION OF HEAVY METALS AND DISSOLUTION OF STRUCTURAL ELEMENTS FROM CLAY MINERALS EFFECTED BY HEAT TREATMENT

Abstract

 Heavy metals are adsorbed on clay minerals and their adsorption capacities depend on the type of clay minerals. The physical and chemical characteristics of clay minerals are changed by heat treatment and the adsorption of heavy metals may be influenced by these changes. Therefore, in this study, the selected heavy metals were adsorbed on 1:1 layer silicates such as kaolinite, and 2:1 layer silicates such as hydrobiotite under different pH conditions. The results showed that the adsorption rates of heavy metals on kaolinite, dickite, and pyrophyllite decreased at 500℃, 500℃, and 1000℃, respectively, and that the adsorption rates of them except for Cs on hydrobiotite were approximately constant high levels regardless of heat temperature. The dissolution rates of structural elements from heated clay minerals were different and increased when the heavy metals were adsorbed on the heated clay minerals. The pH of clay minerals was changed because of heat treatment. However, the changes of pH were not related to the adsorption of the heavy metals or the dissolution of the structural elements. This study indicated that the structure and the adsorption capacities of clay minerals were changed by heat treatment and also that their changes effected on heavy metals adsorption on clay minerals.