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

The novel use of solid-state chemical reactions for the synthesis of l ayered alkali-metal silicates from sodium metasilicate and silica has been investigated. Reactions were carried out using a conventional lab oratory muffle furnace. Sodium octosilicate, kanemite and magadiite we re obtained as pure phases, by controlling the reaction temperature be tween 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 metasil icate and silica powders, which were carefully ground together. The ne w method yields materials with crystal morphologies very similar to th ose previously described; however, it offers significant practical adv antages over other published procedures, which typically involve long hydrothermal crystallizations, at high pH and high temperatures.