HYDROTHERMAL SYNTHESIS OF SMECTITE FROM DICKITE

摘要

Dioctahedral smectite was prepared hydrothermally from dickite [Al_2Si_2O_5(OH)_4] as a starting material by autoclaving in a closed stainless steel vessel with variable temperature, pressure, time and pH conditions. Highly crystalline smectite can be obtained at 290℃ under a pressure of 69 bar for 48 h. The pH of the solution was an important factor and should be maintained at 10 to 11 for the successful formation of smectite. Characterization by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and the Greene-Kelly test showed that the smectite synthesized was Na-beidellite, mostly because of the heat treatment of the starting material and the stoichiometric batch composition.