Issue 6, 2000

The enhanced adsorption of cadmium on hydrous aluminium(III) hydroxide by ethylenediaminetetraacetate

Abstract

The adsorption of ca. millimolar concentrations of cadmium(II) on freshly precipitated aluminium(III) hydroxide is enhanced, at pH values of below 8, in the presence of ethylenediaminetetraacetate, EDTA, via stabilisation of the adsorbed cation. At levels where the hydroxide phase is in large excess to the cadmium(II), the addition of stoichiometrically equivalent concentrations of EDTA will enhance its adsorption to approximately 95%. In the presence of EDTA, cadmium adsorption increases with pH despite the fact that 99.9% of the dissolved cadmium is present as an anionic cadmium(II) EDTA complex. The adsorption observed has been modelled using the measured values of the solubility of aluminium hydroxide and its adsorption of EDTA, the normal and the EDTA-enhanced cationic binding of cadmium(II) and the accepted equilibrium constants for EDTA complexation of cadmium(II) and aluminium(III). The structures of the dissolved and adsorbed complexes have been inferred from XAFS and Al27 NMR spectroscopy.

Article information

Article type
Paper
Submitted
06 Dec 1999
Accepted
27 Jan 2000
First published
22 Feb 2000

Phys. Chem. Chem. Phys., 2000,2, 1273-1279

The enhanced adsorption of cadmium on hydrous aluminium(III) hydroxide by ethylenediaminetetraacetate

M. G. Burnett, C. Hardacre, J. M. Mallon, H. J. Mawhinney and R. Mark Ormerod, Phys. Chem. Chem. Phys., 2000, 2, 1273 DOI: 10.1039/A909612D

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