Tungstate ion-alumina interaction in a ¹⁸⁸W → ¹⁸⁸Re biomedical generator

The surface interaction between WO₄² ions and the alumina support in the ¹⁸⁸W → ¹⁸⁸Re/Al₂O₃ biomedical generator system was examined by the dynamic adsorption method employing the ¹⁸⁷W tracer and by FT-IR, Raman, ²⁷Al MAS NMR, and XPS spectroscopic methods. These studies demonstrated the complex physical and chemical nature of WO₄^2- ion adsorption on alumina. The dynamic adsorption studies indicated that the adsorption process includes several stages from initial monolayer formation to almost complete saturation of the alumina surface. FTIR, Raman, and ²⁷Al MAS NMR data showed that adsorption of WO₄^2- on the Al₂O₃ surface in slightly acidic solutions proceeds via formation of thermodynamically stable complexes of tetrahedrally coordinated aluminum atoms and WO₄^2- tetrahedrons. Previously, these complexes were shown to form, and were identified, only under calcination conditions. Our conclusion on the nature of WO₄^2--Al₂O₃ complex in aqueous solutions was further 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.