SYNTHESIS OF SODALITEHYDRATE FROM CLAYS

Synthesis of zeolites fi om clays requires more than stoichiometric qu antity of caustic soda. It has been believed that apart from solubilis ing alumina and silica, excess sodium ions in caustic soda are involve d as templates in the synthesis of zeolite. Clays (kaolin, bentonite a nd pyrophillite) have been examined for the preparation of sodalitehyd rate using caustic soda. Extents of sodalitehydrate formation is diffe rent for different clays (similar to 38% for bentonite, 50% for pyroph illite and about 95% each with kaolinite and metakaolinite). It is fou nd that sodium ions of electrolytes (NaCl and Na2SO4) 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 abo ut 85% sodalitehydrate. In the absence of electrolyte, it is necessary to have 8 N NaOH. This substantiates the templation of zeolites by so dium ions.