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Desorption behavior of Cd, Zn and Pb sorbed on hydroxyaluminum- and hydroxyaluminosilicate-montmorillonite complexes

Uttam Kumar Saha, Kozo Iwasaki and Katsutoshi Sakurai
Desorption behavior of Cd, Zn and Pb sorbed on hydroxyaluminum- and hydroxyaluminosilicate-montmorillonite complexes
Clays and Clay Minerals (October 2003) 51 (5): 481-492

Abstract

There is a clear gap in the understanding of the desorption patterns of metals sorbed on soils and clays, despite their importance in the mobility, transport and fate of metals in natural environments. In this study, we investigated the desorption behavior of Cd, Zn and Pb sorbed on montmorillonite (Mt) and on hydroxyaluminum (HyA)- and hydroxyaluminosilicate (HAS)-Mt complexes. At pH 6.5, 2.5 g L (super -1) of HyA-Mt and HAS-Mt sorbed almost all of the 10 (super -6) M Cd, Zn or Pb, while Mt under the same condition sorbed approximately 48, 49 and 55% of the added Cd, Zn and Pb, respectively. Based on pH (sub 50) values, the selectivity of metal sorption on Mt was Pb>Zn>Cd, and on the complexes, it was Pb>>Zn = Cd. In general, larger fractions of sorbed metals were remobilized from Mt than from the complexes. Again, in comparison with Pb, larger fractions of sorbed Cd and Zn were remobilized from different clays. Reducing the pHs of the equilibrium sorption systems from a fixed point (6.5) to different points (6.0, 5.5, 5.0, 4.5, and 4.0) and from different points (6.5, 6.0, 5.5, 5.0, and 4.5) to a fixed point (4.0) both yielded hysteretic metal desorption patterns. The fractions of Cd and Zn desorbed through Na and Cu exchange from the clays, especially from the complexes, were very different, indicating the existence of cation exchangeable metal sorption sites of weak and strong affinities on the complexes. Based on the EDTA-extractable fractions of Cd and Zn from HAS-Mt and HyA-Mt, it appeared that HyA-metal bonds are stronger than the HAS-metal bonds. Compared with other agents, acetic acid remobilized the highest fractions of all metals irrespective of the type of clays, with a concomitant release of Al or Al + Si. The Pb-HyA/HAS-Mt bonds were, however, still much too strong to be broken substantially by this mechanism. The results accomplished in this study suggest further attention to the fundamental understanding of the mobility, fate, bioavailability and toxicity of the concerned metals in soils and related environments.


ISSN: 0009-8604
EISSN: 1552-8367
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 51
Serial Issue: 5
Title: Desorption behavior of Cd, Zn and Pb sorbed on hydroxyaluminum- and hydroxyaluminosilicate-montmorillonite complexes
Affiliation: University of Saskatchewan, Department of Soil Science, Saskatoon, SK, Canada
Pages: 481-492
Published: 200310
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 41
Accession Number: 2004-003217
Categories: Geochemistry of rocks, soils, and sedimentsSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Secondary Affiliation: Kochi University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200401
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