A NEW ROUTE FOR THE PREPARATION OF HYDRATED ALKALI-METAL SILICATES

The novel use of solid-state chemical reactions for the synthesis of layered alkali-metal silicates from sodium metasilicate and silica has been investigated. Reactions were carried out using a conventional laboratory muffle furnace. Sodium octosilicate, kanemite and magadiite were obtained as pure phases, by controlling the reaction temperature between 50 and 800 degrees C. Magadiite is best prepared at temperatures below 200 degrees C, octosilicate at temperatures between 400 and 500 degrees C, and kanemite at temperatures between 600 and 800 degrees C. The purest products were obtained from equimolar mixtures of metasilicate and silica powders, which were carefully ground together. The new method yields materials with crystal morphologies very similar to those previously described; however, it offers significant practical advantages over other published procedures, which typically involve long hydrothermal crystallizations, at high pH and high temperatures.