Clinoptilolite-heulandite: applications and basic research

Structural peculiarities of clinoptilolite and heulandite are reviewed. Special attention is given to partial Si, Al ordering within the tetrahedral framework structure. There is strong evidence that the Si, Al ordering pattern depends on the size, charge, and placing of the original extra framework cations.

Even if exchanged to  homoionic forms clinoptilolite and heulandite may display different properties depending on the degree and type of Si, Al ordering.

In some cation-exchanged heulandites symmetry lowering from the topological symmetry  C2/m to  Cm or  C1 has been observed due to partial Si, Al ordering  and low symmetry site preference of extra framework cations. Major applications of clinoptilolite are reviewed. In the field of pollution abatement not only the natural product but also surface modified clinoptilolites gain importance.

Source: http://www.krist.unibe.ch/pdf/2001/Clinoptilolite.pdf