Etude de l'influence des complexants de l'aluminium et du broyage des hydroxydes d'aluminium sur la formation hydrothermale de la kaolinite

Abstract

We have studied the synthesis of kaolinite from crys-tallized aluminum hydroxide and amorphous silica in a domain of temperature between 125°C and 200°C. The aluminous clay mineral does not appear after a week's treatment of the mixture (molar ratio Si/Al = 1) at 200°C . But in the presence of organic aluminum complexing acids, aluminum becomes more rapidly mobile and kaolinite forms even at a temperature lower than 200°C. Reducing the size of the original hydroxide particles also lowers the temperature of synthesis. The reaction still takes place at 135°C which is the lower limit temperature for the transformation of gibbsite into boehmite.