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Die struktuur en eienskappe van anorganiese ioonruilers en die toepassing daarvan in die behandeling van radioaktiewe afval

D.Sc. / The ion exchange properties of a number of synthetic inorganic ion exchangers and the natural zeolite, clinoptilolite, were evaluated with respect to the elements Na, Cs, Sr, Ba, Ce(III), Eu, Zr, U(VI), Np(V), PU(IV) and Am(III). The role of the structure of crystalline exchangers in determining the selectivity thereof, especially in the case of clinoptilolite, was also investigated. Hydrated antimony pentoxide and antimonic acid showed high sorption of a number of ions over a wide pH range (2 - 10). The selectivity order of hydrous oxides for the actinides was as follows: PU(IV) > Am(III) > U(VI) > Np(V). Titanium phosphate, zirconium phosphosilicate and sodium titanate, however, preferred U to Am. To predict the selectivity order of crystalline inorganic ion exchangers, the Eisenman theory could be used, but other factors such as ion sieve effects had to be taken into account. In such cases the parameters contributing to the change in free energy during ion exchange plays a major role. Samples containing clinootilolite from two deposits in South Africa were evaluated with respect to chemical composition, conversion to the sodium, calcium and cesium forms, as well as the sorption of Cs and Sr from various media. Similar trends to those:reported for clinoptilolite from other parts of the world were found. Rietveld refinement of the structure of Cs-exchanged clinoptilolite was carried out using powder diffraction data and the computer program WYRIET. The zeolite was not isolated from the natural matrix, which meant that a number of phases had to be included in the refinement process. The refinement confirmed the...

Identiferoai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:3729
Date10 February 2014
CreatorsDe Villiers, Wessel van Zyl
Source SetsSouth African National ETD Portal
Detected LanguageEnglish
TypeThesis
RightsUniversity of Johannesburg

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