Copper(i) speciation in mixed thiosulfate-chloride and ammonia-chloride solutions: XAS and UV-Visible spectroscopic studiesElectronic Supplementary Information (ESI) available: composition of solutions for XAS and UV-Visible measurements (Tables S1-S4); results of principle component analysis and residual maps for the thiosulfate-chloride and ammonia-chloride data UV-Visible data (Figures S1-S4). See DOI: 10.1039/c1ra00708d
Thiosulfate and ammonia mixtures may be more environmentally benign alternatives to cyanide for leaching Au from ores. In this method, the Cu( i )/Cu( ii ) couple acts as a redox mediator aiding in the oxidative dissolution of metallic Au. Information about the speciation of Cu( i ) and Cu( ii ) in...
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| Main Authors | , , , , , , , |
|---|---|
| Format | Journal Article |
| Language | English |
| Published |
14.11.2011
|
| Online Access | Get full text |
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| Abstract | Thiosulfate and ammonia mixtures may be more environmentally benign alternatives to cyanide for leaching Au from ores. In this method, the Cu(
i
)/Cu(
ii
) couple acts as a redox mediator aiding in the oxidative dissolution of metallic Au. Information about the speciation of Cu(
i
) and Cu(
ii
) in these lixiviant solutions is paramount to the optimization of gold ore processing conditions. With this in mind, we have carried out XANES, EXAFS and UV-Vis spectroscopic studies of the speciation of Cu(
i
) in mixed thiosulfate-chloride and ammonia-chloride solutions. In thiosulfate-chloride solutions, the EXAFS studies indicate that the geometry of the predominant Cu(
i
) complex is distorted trigonal (triangular planar), with an average of 2 sulfur atoms + 1 oxygen atom occupying the coordination sphere. This indicates that the stability of the [Cu(S
2
O
3
)
3
]
5−
complex is lower than previously proposed. Formation constants for Cu(
i
) thiosulfate complexes have been derived on the basis of systematic UV-Vis measurements of solutions with varying [S
2
O
3
]/[Cl] ratios. Only one mixed chloride-thiosulfate complex, [Cu(H
2
O)(S
2
O
3
)Cl]
2−
, was found to predominate over the range of conditions investigated. For Cu(
i
) in ammonia-chloride solutions, our results confirm the broad stability of [Cu(NH
3
)
2
]
+
and we have also identified a stable mixed amminechlorocopper(
i
) complex, [CuCl(NH
3
)]
+
. XAS reveals that these two complexes share a linear geometry. This study demonstrates that combinations of methods are required to decipher the geometry and thermodynamic properties of transition metal complexes in mixed ligand chemical systems where many species may coexist. Our results allow more comprehensive predictions of solution speciation and contribute to efforts to design improved methods to process gold ore with thiosulfate and ammonia lixiviants.
The identity and thermodynamic properties of copper(
i
) complexes present in mixed thiosulfate- and ammonia-chloride systems have been determined using UV-Vis and XAS methods, allowing comprehensive modelling of gold-ore processing. |
|---|---|
| AbstractList | Thiosulfate and ammonia mixtures may be more environmentally benign alternatives to cyanide for leaching Au from ores. In this method, the Cu(
i
)/Cu(
ii
) couple acts as a redox mediator aiding in the oxidative dissolution of metallic Au. Information about the speciation of Cu(
i
) and Cu(
ii
) in these lixiviant solutions is paramount to the optimization of gold ore processing conditions. With this in mind, we have carried out XANES, EXAFS and UV-Vis spectroscopic studies of the speciation of Cu(
i
) in mixed thiosulfate-chloride and ammonia-chloride solutions. In thiosulfate-chloride solutions, the EXAFS studies indicate that the geometry of the predominant Cu(
i
) complex is distorted trigonal (triangular planar), with an average of 2 sulfur atoms + 1 oxygen atom occupying the coordination sphere. This indicates that the stability of the [Cu(S
2
O
3
)
3
]
5−
complex is lower than previously proposed. Formation constants for Cu(
i
) thiosulfate complexes have been derived on the basis of systematic UV-Vis measurements of solutions with varying [S
2
O
3
]/[Cl] ratios. Only one mixed chloride-thiosulfate complex, [Cu(H
2
O)(S
2
O
3
)Cl]
2−
, was found to predominate over the range of conditions investigated. For Cu(
i
) in ammonia-chloride solutions, our results confirm the broad stability of [Cu(NH
3
)
2
]
+
and we have also identified a stable mixed amminechlorocopper(
i
) complex, [CuCl(NH
3
)]
+
. XAS reveals that these two complexes share a linear geometry. This study demonstrates that combinations of methods are required to decipher the geometry and thermodynamic properties of transition metal complexes in mixed ligand chemical systems where many species may coexist. Our results allow more comprehensive predictions of solution speciation and contribute to efforts to design improved methods to process gold ore with thiosulfate and ammonia lixiviants.
The identity and thermodynamic properties of copper(
i
) complexes present in mixed thiosulfate- and ammonia-chloride systems have been determined using UV-Vis and XAS methods, allowing comprehensive modelling of gold-ore processing. |
| Author | Etschmann, Barbara E Grundler, Pascal V Brewe, Dale Brugger, Joël Spiccia, Leone McPhail, D. C Borg, Stacey Black, Jay R |
| AuthorAffiliation | The Australian National University Monash University School of Earth and Environmental Sciences Argonne National Laboratory University of California The University of Adelaide Advanced Photon Source Research School of Earth Sciences South Australian Museum North Terrace Institute for Geophysics and Planetary Physics School of Chemistry and Centre for Green Chemistry Division of Mineralogy CSIRO Exploration & Mining |
| AuthorAffiliation_xml | – name: North Terrace – name: Institute for Geophysics and Planetary Physics – name: Monash University – name: School of Earth and Environmental Sciences – name: Research School of Earth Sciences – name: The University of Adelaide – name: Division of Mineralogy – name: University of California – name: The Australian National University – name: Advanced Photon Source – name: Argonne National Laboratory – name: School of Chemistry and Centre for Green Chemistry – name: CSIRO Exploration & Mining – name: South Australian Museum |
| Author_xml | – sequence: 1 givenname: Barbara E surname: Etschmann fullname: Etschmann, Barbara E – sequence: 2 givenname: Jay R surname: Black fullname: Black, Jay R – sequence: 3 givenname: Pascal V surname: Grundler fullname: Grundler, Pascal V – sequence: 4 givenname: Stacey surname: Borg fullname: Borg, Stacey – sequence: 5 givenname: Dale surname: Brewe fullname: Brewe, Dale – sequence: 6 givenname: D. C surname: McPhail fullname: McPhail, D. C – sequence: 7 givenname: Leone surname: Spiccia fullname: Spiccia, Leone – sequence: 8 givenname: Joël surname: Brugger fullname: Brugger, Joël |
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| DOI | 10.1039/c1ra00708d |
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| Notes | 10.1039/c1ra00708d Electronic Supplementary Information (ESI) available: composition of solutions for XAS and UV-Visible measurements (Tables S1-S4); results of principle component analysis and residual maps for the thiosulfate-chloride and ammonia-chloride data UV-Visible data (Figures S1-S4). See DOI |
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| References_xml | – issn: 1978 publication-title: Vogel's Textbook of Quantitative Inorganic Analysis Including Elementary Instrumental Analysis doi: Vogel – issn: 1976 publication-title: Critical Stability Constants, Vol. 4: Inorganic Complexes doi: Smith Martell – issn: 1988 publication-title: Determination and Use of Stability Constants doi: Martell Motekaitis – issn: 2006 end-page: 261pp publication-title: The Thermodynamic Chemistry of the Aqueous Copper-Ammonia Thiosulfate System, PhD thesis doi: Black |
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| Snippet | Thiosulfate and ammonia mixtures may be more environmentally benign alternatives to cyanide for leaching Au from ores. In this method, the Cu(
i
)/Cu(
ii
)... |
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| Title | Copper(i) speciation in mixed thiosulfate-chloride and ammonia-chloride solutions: XAS and UV-Visible spectroscopic studiesElectronic Supplementary Information (ESI) available: composition of solutions for XAS and UV-Visible measurements (Tables S1-S4); results of principle component analysis and residual maps for the thiosulfate-chloride and ammonia-chloride data UV-Visible data (Figures S1-S4). See DOI: 10.1039/c1ra00708d |
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