Advances in the mechanism of deposition of MoO{sub 4}{sup 2{minus}} and Mo{sub 7}O{sub 24}{sup 6{minus}} species on the surface of titania consisted of anatase and rutile
- Univ. of Patras (Greece)
The mechanism of deposition of MoO{sub 4}{sup 2{minus}} and Mo{sub 7}O{sub 24}{sup 6{minus}} from electrolytic solution on the surface of industrial titania consisting of anatase and rutile patches was further investigated following a recently developed methodology. Comparison of the calculated parameters and variations with the corresponding ones obtained by deposition experiments, potentiometric titrations, and microelectrophoresis allows the authors to establish the mechanism of deposition of the Mo{sup (vi)} species on the surface of titania. According to this mechanism, in the pH range 9--7 the deposition takes place exclusively by reaction of the MoO{sub 4}{sup 2{minus}} ions located in the inner Helmholtz place (IHP) of the double layer developed between the support surface and the impregnating solution, and the neutral surface hydroxyls in the anatase regions of the support. The deposition through adsorption of the MOO{sub 4}{sup 2{minus}} and Mo{sub 7}O{sub 24}{sup 6{minus}} species, on the protonated surface hydroxyls of the support, starts at pH 7 and 6.4, respectively. The same equilibria are mainly responsible for the deposition on the rutile patches of the support, but the extent of deposition in this case is too small. A preference for deposition of MoO{sub 4}{sup 2{minus}} with respect to Mo{sub 7}O{sub 24}{sup 6{minus}} ions was observed in almost the whole pH range studied. This was attributed to the negative charge developed in the IHP, which inhibits the location in it of highly charged Mo{sub 7}O{sub 24}{sup 6{minus}} species. Lateral, attractive, interactions are exerted between the deposited Mo{sup (vi)} species through water molecules being in the IHP. The intensity of these interactions is proportional to the charge of the deposited Mo{sup (vi)} species.
- OSTI ID:
- 404607
- Journal Information:
- Journal of Colloid and Interface Science, Journal Name: Journal of Colloid and Interface Science Journal Issue: 1 Vol. 184; ISSN 0021-9797; ISSN JCISA5
- Country of Publication:
- United States
- Language:
- English
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