Hierarchical porous structured zeolite composite for removal of ionic contaminants from waste streams and effective encapsulation of hazardous waste.

A hierarchical structured composite made from clinoptilolite supported on date stones carbon is synthesized using two techniques. The composites are manufactured by fixing a natural zeolite (clinoptilolite) to the porous surface of date stones carbon or by direct hydrothermal synthesis on to the surface to provide a supported high surface area ion-exchange material for metal ion removal from aqueous streams. The fixing of the clinoptilolite is achieved using sucrose and citric acid as a binder. The composites and pure clinoptilolite were compared to test the efficacy for the removal of Sr 2+ ions from an aqueous phase. The encapsulation of the Sr 2+ using either vitrification or a geo-polymer addition was tested to ensure that the hazardous waste can be made safe for disposal. The hierarchical structured composites were shown to achieve a higher ion exchange capacity per gram of zeolite than the pure clinoptilolite (65 mg/g for the pure natural clinoptilolite and 72 mg/g for the pure synthesized clinoptilolite) with the synthesized composite (160 mg/g) having higher capacity than the natural clinoptilolite composite (95 mg/g). The rate at which the equilibria were established followed the same trend showing the composite structure facilitates diffusion to the ion-exchange sites in the zeolite. [ABSTRACT FROM AUTHOR]