Li-SATURATED KAOLINITE

Abstract--The ffect of heat treatments on the total charge and water adsorption by Ca-, Na- and Li-saturated kaolinite was studied using extraction techniques and thermal gravimetric analysis, respectively. Measurements of cation exchange capacity indicated that the total charge of Li-kaolinite was reduced by approximately 50 % after heating to 110 or 130 ~ In contrast, the total charge of Ca-kaolinite remained essentially constant while that of Na-kaolinite decreased slightly. Water adsorption and desorption on Ca- and Li-kaolinite following heat treatments at 150 ~ were consistent with the total charge of the respective kaolinites. Ion extraction of Li-kaolinite using NH4C1 revealed that only 6 % of the Li remained exchangeable after heating, while A1 and H were released. Thus, non-exchangeable Li ions not only reduced the total charge of the kaolinite but also displaced AI and H from the kaolinite structure. Infrared spectroscopy also indicated that Li migrated into the kaolinite structure and replaced aportion of the A1 from the octahedral sheet. The results presented here indicate that Li-kaolinite represents a surface of reduced charge rather than a surface free of cation-hydration effects. Therefore, Li-kaolinite is not rec-ommended as a reference for the study of vapor-phase adsorption, and conclusions based on such a reference material should be reevaluated. Key Words--Kaolinite, Cation exchange capacity, Water adsorption, Lithium retention