Silica gels doped with vanadium were prepared from tetra ethyl orthosi
licate and an aqueous solution of NH4VO3, at a final sol pH of 1.5-2.5
. Absorption and electron paramagnetic resonance (EPR) spectral studie
s establish that under ambient conditions the incorporated pentavalent
vanadium is stabilized as tetravalent vanadyl ion in the gel monolith
s. Dried gels were very stable under ambient conditions, however, tran
sformation of V4+ to V5+ was noted during gel densification. (C) 1998
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