Effect of electrolyte addition on the colloidal stability of aqueous zeolite sols

Recovery of zeolites from aqueous media can be a very difficult operation. when the crystals have colloidal dimensions. The solid-liquid separation ca n be facilitated by processing at the respective isoelectric point (IEP) wh ere the sol is unstable and the crystals form aggregates. The addition of s alts results in a further improvement, because the zeolite agglomerates bec ome larger, and the pH range of flocculation is broadened. This wider opera tional window, in particular, is of importance for the recovery of zeolites that would dealuminate or collapse at their respective IEP.