Characteristics of the synthetic heulandite-clinoptilolite family of zeolites

Heulandite-clinoptilolite zeolites can be synthesized over the complete range of Si/Al ratio (2.5 to 6) found for the natural minerals. The unit cell parameters, framework infrared vibrational characteristics and thermal properties are similar to those of their natural counterparts. Results of environmental studies involving the removal of toxic metal ions such as lead, strontium and cesium from solution show that though natural clinoptilolite efficiently removes these ions from solution, the higher aluminum content of heulandite results in an improvement in the capacity of this topology for divalent cations. The ability to readily prepare synthetic heulandite and clinoptilolite using environmentally benign methods is expected to lead to improvements in the use of this family of zeolites for similar environmental applications.