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Cyanide speciation at four gold leach operations undergoing remediation

Environmental Science and Technology

By:
, , , and
DOI: 10.1021/es702334n

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Abstract

Analyses have been made of 81 effluents from four gold leach operations in various stages of remediation to identify the most-persistent cyanide species. Total cyanide and weak acid-dissociable (WAD) cyanide were measured using improved methods, and metals known to form stable cyanocomplexes were also measured. Typically, total cyanide greatly exceeded WAD indicating that cyanide was predominantly in strong cyanometallic complexes. Iron was generally too low to accommodate the strongly complexed cyanide as Fe(CN)63- or Fe(CN)64-, but cobalt was abundant enough to implicate Co(CN)63- or its dissociation products (Co(CN)6-x(H2O)x(3-x)-). Supporting evidence for cobalt-cyanide complexation was found in tight correlations between cobalt and cyanide in some sample suites. Also, abundant free cyanide was produced upon UV illumination. Iron and cobalt cyanocomplexes both photodissociate; however, the iron concentration was insufficient to have carried the liberated cyanide, while the cobalt concentration was sufficient. Cobalt cyanocomplexes have not previously been recognized in cyanidation wastes. Their identification at four separate operations, which had treated ores that were not especially rich in cobalt, suggests that cobalt complexation may be a common source of cyanide persistence. There is a need for more information on the importance and behavior of cobalt cyanocomplexes in ore-processing wastes at gold mines.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Cyanide speciation at four gold leach operations undergoing remediation
Series title:
Environmental Science and Technology
DOI:
10.1021/es702334n
Volume
42
Issue:
4
Year Published:
2008
Language:
English
Publisher:
American Chemical Society
Publisher location:
Easton, PA
Contributing office(s):
Crustal Geophysics and Geochemistry Science Center
Description:
7 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
1038
Last page:
1044
Country:
United States
State:
California;Nevada;New Mexico