Synthesis of sodalitehydrate from clays

Abstract

Synthesis of zeolites from clays requires more than stoichiometric quantity of caustic soda. It has been believed that apart from solubilising alumina and silica, excess sodium ions in caustic soda are involved as templates in the synthesis of zeolite. Clays (kaolin, bentonite and pyrophillite) have: been examined for the preparation of sodalitehydrate using caustic soda. Extents of sodalitehydrate formation is different for different clays (~38% for bentonite, 50% for pyrophillite and about <em>Q5% </em>each with kaolinite. and metakaolinite). It is found that sodium ions of electrolytes (NaCl and Na2S04) in fact template the zeolite synthesis, and can be used to replace a major part of the alkali. Thus, the system with 0.5 N NaOH and electrolyte produces about 85% sodalitehydrate. In the absence of electrolyte, it is necessary to have 8 <em>N </em>NaOH. This substantiates the templation of zeolites by sodium ions.