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Measurements of Metal Adsorption in Oxide-Clay Mixtures: “Competitive-Additivity” Among Mixture Components

Published online by Cambridge University Press:  01 January 1992

V. S. Tripathi ,
M.D. Siegel  and
Z. S. Kooner
V. S. Tripathi
Affiliation:
Environmental and Earth Sciences Institute, McLean, Va 22101
M.D. Siegel
Affiliation:
Geoscience Assessment and Validation Division 6115, Sandia National Laboratories, Albuquerque, NM 87185
Z. S. Kooner
Affiliation:
Dept. of Geology, University of Tennessee, Knoxville, TN 37916
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Abstract

An important question concerning the transport of radionuclides from nuclear waste repositories is whether the adsorption of metals by rocks and soils can be predicted from the properties of the constituent minerals. Attempts by previous researchers to use sorption models based on linear adsorption or weighted "sorptive additivity" have met with limited success. In this study, a “competitive-additivity” model based on surface complexation theory was used to model the pH-dependent adsorption of lead by goethite/Ca-montmorillonite mixtures using complexation constants obtained from single sorbent systems. Measurements of lead adsorption by goethite, Ca-montmorillonite, and goethite-Ca-montmorillonite mixtures (and similar studies of copper and zinc adsorption) demonstrate that the two adsorbents compete for adsorption of metals over wide ranges of pH and concentrations of adsorbents and metals. The adsorption behaviors of the mixtures are determined by the relative concentrations of the adsorbents and their respective affinities for the adsorbate metal. Particle-particle interactions such as heterocoagulation of the oxide and clay do not appear to be significant for the majority of the adsorption sites in this system.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 294: Symposium V – Scientific Basis for Nuclear Waste Management XVI , 1992 , 791
Copyright
Copyright © Materials Research Society 1993

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References

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