Occurrence and removal of hydroxide precipitates on ion-exchanged faujasite-type zeolites: zinc molecular sieves

Abstract

Faujasitic zeolites have been shown to acquire a hydroxide surface deposit following ion exchange with zinc solutions. This phenomenon was studied using XRD and SEM techniques. The surface deposits can be removed by aqueous ammonia. The formation of the deposits can be explained in terms of the alkalinity of the zeolite surface, the acidity of the exchanging salt solution and the solubility of metal hydroxide. New procedures can prevent, or reduce, surface hydroxide deposits on zeolites A, X and Y.