| Abstract
| - The relationship between the lattice parameter of the cubic unit cell and the ion-exchangeproperties was studied for a group of mixed metal oxides with the cubic pyrochlore structure,which had been prepared hydrothermally and by precipitation. The materials included binaryoxides antimony silicate, antimony titanate, and titanium tungstate and related compounds,which contained a third metal (W6+, Sb5+, Nb5+) in the framework structure that had beenincorporated in an attempt to improve their ion-exchange properties. The lattice parameterswere found to vary between 10.2440 and 10.4793 Å depending on the element combinationand the cationic form of the material. A clear increase in the trace strontium (89Sr) uptakein 0.1 M HNO3 and 0.1 M NaNO3 was observed when the lattice parameter was >10.34 Å.A similar increase was found for alkaline earth metals at macro concentrations, but theincrease was transcient as the cubic unit cell dimensions were affected by the nature of thein-going cation. Some of the materials showed high selectivity for the alkaline earths againstthe H+ ion making them suitable for removal of these cations from acidic solutions. However,the relative selectivity between the different alkaline earth cations was rather low in general,which does not allow for their selective individual separation. The three-dimensional tunnelstructure of the pyrochlore showed clear ion sieve property in the separation of the relativelylarge Cs+ cation from the other alkali metals.
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