Composition and formation kinetics of strontium polyvanadates in vanadium(IV,V) solutions

• Published in: Russian journal of inorganic chemistry 2011-12, Vol.56 (12), p.2013-2018
• Main Authors: Podval’naya, N. V., Volkov, V. L.
• Format: Article
• Language: English
• Subjects: Chemical composition; Chemistry; Chemistry and Materials Science; Forming; Inorganic Chemistry; Interlayers; Nanorods; Physical Chemistry of Solutions; Precipitates; Precipitation; Strontium
• ISSN: 0036-0236; 1531-8613
• DOI: 10.1134/S0036023611120436

The phase and chemical compositions of the precipitates forming in the Sr(VO 3 ) 2 -VOCl 2 -H 2 O system in the V 4+ /V 5+ = 0.11–9 range at 80–90°C are reported. At pH 1–3 and V 4+ /V 5+ = 0.25−9, the general formula of the precipitated compounds is Sr x V y 4+ V 12− y 5+ O 31−δ · n H 2 )(0.37 ≤ x ≤ 1.0, 1.7 ≤ y ≤ 3.0, 0.95 ≤ δ ≤ 2.1). Polyvanadates containing the largest amount of vanadium(IV) are obtained at an initial V 4+ /V 5+ ratio of 9 and pH 1.9. Precipitation from solutions at pH 3 takes place only in the presence of the VO 2+ ion, and the highest precipitation rate is observed at V 4+ /V 5+ = 0.11. The process is controlled by a second-order reaction on the polyvanadate surface. Under hydrothermal conditions at 180°C, Sr 0.25 V 2 O 5 ·1.5H 2 O nanorods are obtained from solutions with a V 4+ /V 5+ molar ratio of 0.1 at pH 3. The nanorods, 30–100 nm in diameter and up to 2–3 μm in length, have a layered structure with an interlayer spacing of 10.53 ± 0.08 Å.