Hydrothermal synthesis, cesium selectivity and water sorption property of V₂O₅·nH₂O gel

Layered vanadium pentaoxide gels, analogous to montmorillonite layered silicate can be synthesized under hydrothermal conditions at 200°C. The gel was characterized by x-ray diffraction and thermal analyses and electron microscopy. Water sorption isotherm of V₂O₅ gel indicated that the gel initially has micropores or cavities commensurate with the size of water molecules. At higher relative pressures of water, steps in sorption isotherm appeared indicating the montmorillonite type layer structure which expands and accommodates at least two layers of water molecules in between the layers. This gel is stable in aqueous media and hence could be used as an ion exchanger for several alkali, alkaline earth and transition metal cations. The gel exhibited high selectivity for cesium ion (K_d = 226-981) in the presence of highly concentrated solutions of metal (M) cations such as Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, and Sr²⁺ (M/Cs equivalent ratio = 250). Its cesium uptake and selectivity was investigated in detail at room temperature. This property could be useful in the separation of Cs from radioactive waste solutions or naturally occurring brines.