INTERLAYER WATER-MOLECULES IN VANADIUM PENTAOXIDE HYDRATE .2. EFFECT OF INTERCALATED METAL-IONS ON THE ADSORBABILITY OF WATER-MOLECULES

The effect of intercalated metal ions on the adsorption of H2O molecules in vanadium pentaoxide hydrate xerogel, V2O5.nH2O, was studied by measuring adsorption of H2O, X-ray diffraction, differential scanning calorimetry, and thermal gravimetric analysis. Intercalation of Li+ had little effect on the adsorption of H2O due to its low electric charge and strong hydrating property to form much hydrated species. Other ions, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+, Cr3+, and La3+, had an effect through two processes on the adsorption of H2O. (1) The hydrophilicity of ions facilitates the adsorption of H2O molecules at lower vapor pressure. (2) Introduced metal ions bring in additional crystal energy stemming from increased electrostatic charge between the layers, which depresses the expansion of the layers, i.e., adsorption of H2O molecules.