| Modeling the adsorption of Cd(II) onto goethite in the presence of citric acid. | |
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MedLine Citation:
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PMID: 14651893 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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The adsorption of cadmium onto goethite in the presence of citric acid was measured as a function of pH and cadmium concentration at 25 degrees C. Potentiometric titrations were also performed on the system. Cadmium adsorption onto goethite was enhanced above pH 4 in the presence of 50 microM, 100 microM and 1 mM citric acid. While there was little difference between the enhancements caused by 50 and 100 microM citric acid below pH 6, above pH 6 further enhancement is seen in the presence of 100 microM citric acid. When 1 mM citric acid was present, the enhancement of cadmium adsorption was greater below pH 6, with increased Cd(II) adsorption down to pH 3.5. However, above pH 6, 1 mM of citric acid caused slightly less enhancement than the lower citric acid concentrations. ATR-FTIR spectra of soluble and adsorbed citrate-cadmium species were measured as a function of pH. At pH 4.6 there was very little difference between the ternary Cd(II)-citric acid-goethite spectrum and the binary citric acid-goethite spectrum. However, spectra of the ternary system at pH 7.0 and 8.7 indicated the presence of additional surface species. Further analysis of the spectra suggested that these were metal-ligand outer-sphere complexes. Data from the adsorption experiments and potentiometric titrations of the ternary Cd(II)-citric acid-goethite system were fitted by an extended constant-capacitance surface complexation model. The spectroscopic data were used to inform the choice of surface species. Three reactions in addition to those for the binary Cd(II)-goethite and citric acid-goethite systems were required to describe all of the data. They were [formula in text], [formula in text], and [formula in text]. Neither the spectroscopy nor the modeling suggested the formation of a ternary inner-sphere complex or a surface precipitate under the conditions used in this study. |
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Authors:
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Kurt Lackovic; Michael J Angove; John D Wells; Bruce B Johnson |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Journal of colloid and interface science Volume: 269 ISSN: 0021-9797 ISO Abbreviation: J Colloid Interface Sci Publication Date: 2004 Jan |
Date Detail:
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Created Date: 2003-12-03 Completed Date: 2004-08-19 Revised Date: 2009-11-11 |
Medline Journal Info:
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Nlm Unique ID: 0043125 Medline TA: J Colloid Interface Sci Country: United States |
Other Details:
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Languages: eng Pagination: 37-45 Citation Subset: - |
Affiliation:
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Colloid and Environmental Chemistry Laboratory, La Trobe University, Bendigo, PO Box 199, Bendigo, Victoria 3552, Australia. kurt.lackovic@bendigo.latrobe.edu.au |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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