Isopiestic measurement of salt imbibition in zeolites Na–X and Na–Y

Abstract

Factors affecting the reliability of the isopiestic method for the measurement o the imbibition of salts from aqueous solution by zeolites have been examined. It has been found that the sharp intersection of the isopiestic curves, which is essential to the accuracy of the method, does not occur when the zeolite crystals are so small that sorption of the salt on the external surface of the zeolite is substantial. Results for the occlusion of sodium nitrate by zeolite Na–X (ca. 6 µm crystals) and Na–Y (ca. 7 µm crystals) at 298.2, 313.2 and 328.2 K are reported. Those for sodium nitrate and sodium chlorate at 298.2 K are used to test the applicability of the Donnan equation.