Original scientific paper

Electrokinetic Behaviour and Interaction with Oxalic Acid of Different Hydrous Chromium(III) Oxides

Graciela E. Magaz ; Unidad de Actividad Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Avenida del Libertador 8250, (1429) Buenos Aires, Argentina
Luis García Rodenas ; Unidad de Actividad Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Avenida del Libertador 8250, (1429) Buenos Aires, Argentina
Pedro J. Morando ; Unidad de Actividad Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Avenida del Libertador 8250, (1429) Buenos Aires, Argentina
Miguel A. Blesa ; Unidad de Actividad Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Avenida del Libertador 8250, (1429) Buenos Aires, Argentina

Abstract

Three samples of hydrous chromium(III) oxide have been prepared by different procedures, and their electrokinetic mobilities have been measured. In mineral media, isoelectric points were found to be 8.45 ±0.15. This value is shifted from the solution isoelectric point by –0.35 ±0.15, due to the contribution of solvation energy to the energy of ionic adsorption. On the basis of a simple model, it is suggested that the two successive surface acidity constants of hydrous chromium(III) oxide are pKS a1 = 7.17 and pKS a2 = 9.72. The influence of oxalic acidity on mobility may be described in terms of two successive adsorption equilibria, the first one conducive to the neutralization of positive protonic charge, and the second one originating a charge reversal. It is shown that the apparent affinity for this latter mode is lower in one of the samples, suggesting that surface complexation constants may in fact be sensitive to the history of hydrous chromium(III) oxide particles. The three samples show similar dissolution behaviour but the specific rates differ, in one case by two orders of magnitude. This difference is explained in terms of the influence of crosslinking on the reactivity.

Keywords

Hrčak ID:

132429

URI

https://hrcak.srce.hr/132429

Publication date:

1.12.1998.

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