Thiocyanate Hydrometallurgy For the Recovery of Gold Part I: Chemical and Thermodynamic Considerations

Editor(s)

Petersen, Jochen

Abstract

Thiocyanate has been identified and studied as a promising alternative lixiviant for gold in acidic solutions. Eh-pH and ion species distribution diagrams for SCN-H2O, Au-SCN-H2O, Ag-SCN-H2O, Cu-SCN-H2O, and Fe-SCN-H2O systems were constructed to predict the behavior of each metal ion in the thiocyanate system and also to explain the experimental results. Thermodynamic analyses suggest that gold can be leached by thiocyanate under appropriate leaching potentials, forming aurous or auric complexes with thiocyanate, depending on the thiocyanate concentration and leaching potential. According to species distribution diagrams, silver (I) and copper (I) form insoluble salts at moderate thiocyanate concentrations and are soluble at low and high thiocyanate concentrations. Ferric ion forms a series of complexes with thiocyanate. The study of the ferric ion effect indicates that gold can be leached in acid thiocyanate solution with ferric sulfate as the oxidant. Also the presence of excess ferric ion reduces the apparent thiocyanate activity for copper (I) and silver (I) dissolution. The findings of this thermodynamic assessment are useful in the analysis of some of the phenomena encountered in the leaching and recovery of gold from thiocyanate solutions as discussed in subsequent papers.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Thiocyanate; Leaching; Gold; Thermodynamic; Silver; Copper; Eh-PH Diagrams; Distribution Diagrams

International Standard Serial Number (ISSN)

0304-386X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2012 Elsevier, All rights reserved.

Publication Date

01 Feb 2012

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