Investigation of new microporous materials (metalphosphates) with high framework charges with regard to environmental applications

Research project P 13663 Investigation of new microporous materials Georg AMTHAUER 11.10.1999 The most important property of zeolites is their selective ion exchange behavior which lead to a broad range of applications to environmental problems like toxic and radioactive waste removal, treatment of industrial production pollution or water quality improvement. In the last years many new molecular sieves have been found which have similar topologies than the well known aluminosilicate zeolites but have metalphosphate frameworks with high framework charge densities. The new chemistry gives rise for new properties of these microporous compounds. The aim of the proposed project is to establish zeolitelike microporous materials with high framework charge densities to explore selective ion exchange properties for new applications. For that purpose synthesis conditions of microporous metalphosphates will be systematically investigated with help of modern computeraided syntheses procedures. Our main aspect is the investigation of phases in the zincophosphate system and the adjustment of the framework charge via the incorporation of iron during the hydrothermal synthesis. The ion exchange capability of the resulting microporous phases will be examined for mono-, di- and trivalent cations. Special emphasis will be given to ions, which are known to cause environmental problems like ammonium and heavy metal ions and cations of elements which have radioactive isotopes. The structural characterization of the crystalline products before and after the chemical modification using single crystal and powder diffraction and spectroscopic methods (Mössbauer) will be the main part of the investigation. The results will give informations about the flexibility of the frameworks and the specific bonding of the cations inside the zeolites and thus a better understanding of the ion exchange behavior will be achieved. Mössbauer spectroscopy will be used to detect trivalent iron ions which are incorporated as heteroatoms into the framework. We expect to get insight into the structural features and the sorption properties of zeolitelike microporous materials and to be able to give specifications concerning their suitability for the application in exchange processes.