A. Singhal, L. M. Toth, J. Lin
Nov 20, 1996
Citations
1
Influential Citations
155
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Journal
Journal of the American Chemical Society
Abstract
Small-angle X-ray scattering measurements were performed on zirconium acidic aqueous solutions to investigate the structure and the size of polynuclear species larger than the previously identified tetrameric species. Solutions with [H+]added and [OH-]added ranging from 0.0 to 1.0 M and 0.0 to 0.02 M, respectively, were analyzed. This study demonstrates that an octameric species, Zr8(OH)20(H2O)24Cl12, exists in equilibrium with the tetrameric species, Zr4(OH)8(H2O)16Cl62+, such that, for 0.05 M Zr(IV) in highly acidic solutions ([H+]added ≥ 0.6 M), the tetramer is the dominant species; and at conditions with [H+]added ≤ 0.05 M, the octameric species becomes predominant. The estimated value of the equilibrium quotient obtained for the tetramer/octamer equilibrium is 0.20 ± 0.05 M3. The tetramer and octamer have radii of gyration of 3.8 and 5.1 ± 0.2 A and a hydrolysis ratio of 2.0 and 2.5, respectively. The octamer forms by stacking two tetramers on top of each other. At conditions where small amounts of N...