TUNGSTATE ION-ALUMINA INTERACTION IN A W-188-]RE-188 BIOMEDICAL GENERATOR

The surface interaction between WO42- ions and the alumina support in the W-188 --> Re-188/Al2O3 biomedical generator system was examined by the dynamic adsorption method employing the W-187 tracer and by FT-LR , Raman; Al-27 MAS NMR, and XPS spectroscopic methods. These studies d emonstrated the complex physical and chemical nature of WO42- ion adso rption on alumina. The dynamic adsorption studies indicated that the a dsorption process includes several stages from initial monolayer forma tion to almost complete saturation of the alumina surface. FTIR, Raman , and Al-27 MAS NMR data showed that adsorption of WO42- on the Al2O3 surface in slightly acidic solutions proceeds via formation of thermod ynamically stable complexes of tetrahedrally coordinated aluminum atom s and WO42- tetrahedrons. Previously, these complexes were shown to fo rm, and were identified, only under calcination conditions. Our conclu sion on the nature of WO42--Al2O3 complex in aqueous solutions was fur ther supported by the results from XPS studies where it was shown that W-containing species are strongly attached to the surface of alumina via W-O bonds.