Transformation of Sepiolite into Kaolinite and Smectite by AlCl<SUB>3</SUB> Solution

Well crystallized sepiolite was treated by AlCl3 solution under hydrothermal conditions and at room temperature as well. The products were examined by X-ray, thermal, infrared absorption and electron microscopy methods. In addition, Si, Mg and Al in the solution were determined by atomic absorption analysis.In this experiment, kaolinite was formed by the treatment with 3.0N, 0.1N and 0.8N AlCl3 solution above 200°C, and dioctahedral smectite was obtained with 0.5 N and 0.2N solution above 200°C. Therefore, it has been made clear that in this experiment the Al concentration in the solution and the temperature play the most important role.The reaction may be considered to proceed in the following sequence:sepiolite→amorphous material→kaolinite→dioctahedral smectite