Exchange adsorption by zeolite

The conversion of molecular sieve 4 A and zeolitic tuff with calcination and chemical treatment has been studied in reference to their exchange capacity and X-ray diffraction properties. Based on the experimental results, it was established that (1) The zeolitic structure is stable up to 800℃, but the exchange-adsorption capacity of zeolitic tuff decreases with the calcination temperature. This tendency seems to result from sintering of volcanic glass in the tuff. (2) The crystalline structure of molecular sieve 4 A collapses with acid treatment when the acid concentration is above 0.5 N. On the other hand, zeolitic tuff is stable against acid, because the zeolitic structure in the tuff is enclosed in a gelated material of volcanic glass. (3) Hydroxy sodalite is formed by alkali treatment of zeolite and volcanic glass when the alkali concentration is more than 5 N. The exchange-adsorption capacity increases as a result of the gelation of the volcanic glass, showing a maximum at 3 N concentration. (author)