Alteration of perlite to calcium zeolites

Hydrothermal synthesis of calcium zeolites by alteration of perlite (a rhyolitic glass) is presented. Synthetic versions of the zeolites gismondine, epistilbite and heulandite are synthesized from perlite using calcium-containing solutions, and the effects of the solution phase, pH and temperature on the distribution of the zeolitic products obtained are discussed. Transient formation of a gismondine-type zeolite during transformation of perlite to heulandite suggests a novel synthesis route for the crystallization of heulandite-type zeolites from synthetic zeolite P1.