A model for metal adsorption on montmorillonite

Anne M.L. Kraepiel, Klaus Keller, François M.M. Morel

Research output: Contribution to journalArticle

178 Citations (Scopus)

Abstract

A consistent thermodynamic model is developed for metal sorption on expanding 2:1 layer clays such as montmorillonite. The particle of clay, including lamellae and interlayers, is represented as a porous solid bearing a permanent negative charge (resulting from isomorphic substitution) with an infinite plane interface (i.e., edges) with the solution. Cation exchange occurs inside the clay particle as the result of the negative potential of the clay. Surface complexation reactions take place at the interface whose surface charge and potential are pH dependent. The potential in the bulk of the clay and near the interface, as well as the surface potential-surface charge density relation, are calculated taking into account the effect of the permanent negative charge. The results are discussed and compared with the classic Gouy-Chapman theory. A subroutine (Clayeql) with the new potential- charge relationships is implemented in the thermodynamic equilibrium program Mineql +3.0 and is used to fit an extensive published experimental data set on adsorption of transition metals on montmorillonite. The model is shown not only to fit satisfactorily all the data, but also to explain specific features of adsorption on clays compared to oxides. In particular, the increase in the surface concentration of protons with decreasing ionic strength is successfully reproduced and the weaker dependence of metal sorption on pH compared to oxides is correctly fitted.

Original languageEnglish (US)
Pages (from-to)43-54
Number of pages12
JournalJournal of Colloid And Interface Science
Volume210
Issue number1
DOIs
StatePublished - Feb 1 1999

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Bentonite
Clay minerals
Clay
Metals
Adsorption
Surface potential
Surface charge
Oxides
Sorption
Bearings (structural)
Thermodynamics
Subroutines
Ionic strength
Charge density
Complexation
Transition metals
clay
Cations
Protons
Ion exchange

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

Cite this

Kraepiel, Anne M.L. ; Keller, Klaus ; Morel, François M.M. / A model for metal adsorption on montmorillonite. In: Journal of Colloid And Interface Science. 1999 ; Vol. 210, No. 1. pp. 43-54.
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A model for metal adsorption on montmorillonite. / Kraepiel, Anne M.L.; Keller, Klaus; Morel, François M.M.

In: Journal of Colloid And Interface Science, Vol. 210, No. 1, 01.02.1999, p. 43-54.

Research output: Contribution to journalArticle

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