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Cyanide and copper cyanide recovery by activated carbon / X. Dai in Minerals engineering, Vol. 22 N° 5 (Avril 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 5 (Avril 2009) . - pp. 469–476 Titre : Cyanide and copper cyanide recovery by activated carbon Type de document : texte imprimé Auteurs : X. Dai, Auteur ; P. L. Breuer, Auteur Année de publication : 2009 Article en page(s) : pp. 469–476 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Gold  ores  Activated  carbon  Cyanidation  Hydrometallurgy Résumé : A process is proposed to recover the cyanide and copper cyanides following the leaching and recovery of gold from copper-containing gold ores. Metallic copper is dissolved into the tailings stream to convert the residual free cyanide to copper cyanides and to concurrently reduce the overall cyanide-to-copper ratio to facilitate copper and cyanide recovery by activated carbon. Metallic copper readily dissolves in both free cyanide and View the MathML source solutions to achieve a final cyanide-to-copper ratio below 3. The theoretical critical CN− and View the MathML source concentration for copper dissolution in air saturated solutions are 2.9 and 2.7 mM, respectively, matching well with the measured values of 3 mM. The copper dissolution rate decreases proportionately with concentration below these critical concentrations. The increase in pH due to oxygen reduction during copper dissolution may cause copper to precipitate as Cu(OH)2. The pH of precipitation decreases with increasing copper concentration and with decreasing cyanide-to-copper ratio. However, precipitation is not observed in the presence of carbon due to the simultaneous adsorption of copper onto carbon, which reduces the solution copper concentration. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687508002860 [article] Cyanide and copper cyanide recovery by activated carbon [texte imprimé] / X. Dai, Auteur ; P. L. Breuer, Auteur . - 2009 . - pp. 469–476. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 5 (Avril 2009) . - pp. 469–476 Mots-clés : Gold  ores  Activated  carbon  Cyanidation  Hydrometallurgy Résumé : A process is proposed to recover the cyanide and copper cyanides following the leaching and recovery of gold from copper-containing gold ores. Metallic copper is dissolved into the tailings stream to convert the residual free cyanide to copper cyanides and to concurrently reduce the overall cyanide-to-copper ratio to facilitate copper and cyanide recovery by activated carbon. Metallic copper readily dissolves in both free cyanide and View the MathML source solutions to achieve a final cyanide-to-copper ratio below 3. The theoretical critical CN− and View the MathML source concentration for copper dissolution in air saturated solutions are 2.9 and 2.7 mM, respectively, matching well with the measured values of 3 mM. The copper dissolution rate decreases proportionately with concentration below these critical concentrations. The increase in pH due to oxygen reduction during copper dissolution may cause copper to precipitate as Cu(OH)2. The pH of precipitation decreases with increasing copper concentration and with decreasing cyanide-to-copper ratio. However, precipitation is not observed in the presence of carbon due to the simultaneous adsorption of copper onto carbon, which reduces the solution copper concentration. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687508002860

Mechanisms of sulfide ion oxidation during cyanidation / D.M. Hewitt in Minerals engineering, Vol. 22 N° 13 (Octobre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 13 (Octobre 2009) . - pp. 1166–1172 Titre : Mechanisms of sulfide ion oxidation during cyanidation : Part II: Surface catalysis by pyrite Type de document : texte imprimé Auteurs : D.M. Hewitt, Auteur ; P. L. Breuer, Auteur ; M.I. Jeffrey, Auteur Année de publication : 2009 Article en page(s) : pp. 1166–1172 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Cyanidation  Sulfide  ores Résumé : The mechanisms and the reaction products for the oxidation of sulfide ions in the presence of pyrite have been established. When the leach solution contains free sulfide ions, oxidation occurs via electron transfer from the sulfide ion to dissolved oxygen on the pyrite mineral surface, with polysulfides being formed as an intermediate oxidation product. In the absence of cyanide, the polysulfides are further oxidised to thiosulfate, whilst with cyanide present, thiocyanate and sulfite are also formed from the reaction of polysulfides with cyanide and dissolved oxygen. Polysulfide chain length has been shown to affect the final reaction products of polysulfide oxidation by dissolved oxygen. The rate of pyrite catalysed sulfide ion oxidation was found to be slower in cyanide solutions compared to cyanide free solutions. Mixed potential measurements indicated that the reduction of oxygen at the pyrite surface is hindered in the presence of cyanide. The presence of sulfide ions was also found to activate the pyrite surface, increasing its rate of oxidation by oxygen. This effect was particularly evident in the presence of cyanide; in the presence of sulfide the increase in total sulfur from pyrite oxidation was 2.3 mM in 7 h, compared to an increase of <1 mM in the absence of sulfide over 24 h. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509001472 [article] Mechanisms of sulfide ion oxidation during cyanidation : Part II: Surface catalysis by pyrite [texte imprimé] / D.M. Hewitt, Auteur ; P. L. Breuer, Auteur ; M.I. Jeffrey, Auteur . - 2009 . - pp. 1166–1172. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 13 (Octobre 2009) . - pp. 1166–1172 Mots-clés : Cyanidation  Sulfide  ores Résumé : The mechanisms and the reaction products for the oxidation of sulfide ions in the presence of pyrite have been established. When the leach solution contains free sulfide ions, oxidation occurs via electron transfer from the sulfide ion to dissolved oxygen on the pyrite mineral surface, with polysulfides being formed as an intermediate oxidation product. In the absence of cyanide, the polysulfides are further oxidised to thiosulfate, whilst with cyanide present, thiocyanate and sulfite are also formed from the reaction of polysulfides with cyanide and dissolved oxygen. Polysulfide chain length has been shown to affect the final reaction products of polysulfide oxidation by dissolved oxygen. The rate of pyrite catalysed sulfide ion oxidation was found to be slower in cyanide solutions compared to cyanide free solutions. Mixed potential measurements indicated that the reduction of oxygen at the pyrite surface is hindered in the presence of cyanide. The presence of sulfide ions was also found to activate the pyrite surface, increasing its rate of oxidation by oxygen. This effect was particularly evident in the presence of cyanide; in the presence of sulfide the increase in total sulfur from pyrite oxidation was 2.3 mM in 7 h, compared to an increase of <1 mM in the absence of sulfide over 24 h. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509001472