Abstract
Talc was treated with acid under a variety of conditions to obtain porous silica by selective leaching. Aliquots of the powder (1g) were leached with 50 ml of 2-4 M strong acids (HCl, HNO3 and H2SO4) at 80°and 150°C for 0.5 h-14 days. Since the chemical compositions of the resultant products showed little change after acid treatment at 80°C for 2 h, which conditions are generally sufficient to prepare a silica-rich product by selective leaching from a variety of other clay minerals, it is concluded that talc is more resistant to acid attack than other clays. The products obtained at 150°C using an autoclave showed an increased SiO2 content (up to>90 mass%) with longer leaching times. The specific surface areas of the resultant products were<40 m2/g and are lower than those from other clay minerals. This low surface area of the product is discussed with respect to the chemical compositions and structures of the various clay mineral reactants. Since the products preserved the original flaky particle shape after selective leaching and also after firing to 1000°C, the selective leaching of talc provides a method for preparing amorphous silica with a platy particle shape.
