Two step process for the preparation of zeolite A by hydrothermal treatment of clinoptilolite

Claim 1

A hydrothermal process for the preparation of a sodium cation form of zeolite A from natural clinoptilolite of the formula Na.sub.x (AlO.sub.2).sub.x (SiO.sub.2).sub.y.ZH.sub.2 O wherein x=5 to 7, y/x=4.5 to 5.5 and z=1 to 30 which comprises the steps of: (a) heating at a temperature of from about 60° C. to 110° C. said natural clinoptilolite in a 1 to 30 weight percent aqueous solution of sodium hydroxide to dissolve clinoptilolite, the clinoptilolite having a concentration of at least one gram clinoptilolite per 100 cc of aqueous sodium hydroxide solution; (b) filtering the clinoptilolite-sodium hydroxide solution to remove undissolved clinoptilolite and elemental impurities and form a filtrate; (c) reacting the filtrate at a temperature of from about 60° C. to 110° C. in the presence of up to 15 weight percent NaCl with at least 75 percent of a stoichiometric amount of sodium aluminate in an aqueous solution to precipitate and form zeolite A having a mean particle size of about 3 to 6 microns, said sodium aluminate having a concentration of from 1 to 16.5 weight percent in water; and recovering said zeolite A.