Hydrothermal formation of a kaolinite-like product from noncrystalline aluminosilicate g ls

Abstract--Noncrystalline aluminosilicate g ls with AI203/(AI203 + SiO2) weight ratios from 0.3 to 0.5 were reacted in 0.1 N KOH at temperatures varying from 125 ~ to 175 ~ The pH of the solutions dropped sharply with increasing el:solution ratios, indicating that the coordination umber of AI in the products changed from IV to VI. The degree of hydrolysis appeared to be higher with KOH than with NaOH. X-ray powder diffraction and infrared spectroscopy showed that disordered kaolinite was the only crystalline product formed. Thermal data and surface area measurements indicated that the kaolinite was formed by a con-densation process. Key Words---Aluminosilicate, G l, Infrared spectroscopy, Kaolinite, Synthesis, X-ray powder diffraction