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Metal ion coordination at the water-manganite (gamma-MnOOH) interface I. An EXAFS study of cadmium(II)

Author:
  • L. Bochatay
  • Per Persson
  • S. Sjoberg
Publishing year: 2000
Language: English
Pages: 584-592
Publication/Series: Journal of Colloid and Interface Science
Volume: 229
Document type: Journal article
Publisher: Elsevier
Additional info: 2

Abstract english

The local structure of Cd(II) surface complexes adsorbed onto manganite (gamma-MnOOH) has been investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. Adsorption experiments were carried out within the pH range 7.4-9.8 and with surface coverage from 2.2 to 8.9 mu mol/m(2). Quantitative analysis of the EXAFS spectra shows little difference in the local coordination environment of Cd regardless of the coverage. Analysis of the first shell required a third cumulant in an asymmetric distribution model (i.e., non-Gaussian distribution), indicating distorted CdO6 octahedra with an average Cd-O distance of 2.31 Angstrom. A single second shell of Mn neighbors at a constant distance of 3.33 Angstrom was detected. This comparatively short distance shows that inner-sphere complexes are formed. No Cd neighbor was found which means that cadmium hydroxide precipitation or cluster formation does not occur at the surface at the experimental conditions probed in this study. We assign the Cd-Mn distance to edge sharing between CdO6 and MnO6 octahedra, with a geometry similar to that in the mixed solid Cd2Mn3O8 This adsorption mode is possible on the {110} and {010} cleavage planes of manganite. (C) 2000 Academic Press.

Keywords

  • Earth and Related Environmental Sciences

Other

Published
  • ISSN: 1095-7103
Per Persson
E-mail: per [dot] persson [at] biol [dot] lu [dot] se

Professor

MEMEG

+46 46 222 17 96

+46 70 266 38 79

E-C350

50

Professor

Centre for Environmental and Climate Research (CEC)

+46 46 222 17 96

+46 70 266 38 79

D350

Ekologihuset, Sölvegatan 37, Lund

50