Mechanistic and kinetic aspects of silver dissolution in cyanide solutions

Hiskey, J. B.; Sánchez, Víctor Hugo

doi:10.1007/bf01076060

Cited by 42 publications

(25 citation statements)

References 11 publications

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“…This is in accordance with the literature findings that the gold surface becomes much more passive due to a tight AuCN film formation as compared to AgCN film on the silver surface. These findings contradict the reported literature of silver dissolution lagging behind the dissolution of gold …”

Section: Resultscontrasting

confidence: 99%

Effect of silver on gold cyanidation in mixed and segregated sulphidic minerals

Muhammad

Larachi

2016

Can J Chem Eng

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Gold is mostly found in nature in metallic form and is associated with sulphide minerals and other precious metals, most often silver. Pyrite, chalcopyrite, sphalerite, and stibnite are the sulphidic minerals investigated in the present gold‐silver cyanidation study by adopting the metal‐sulphide multi‐layer packed‐bed reactor approach. Gold leaching kinetics was enhanced remarkably for the pyrite and chalcopyrite sulphide minerals, with 94.5 % and 85 % recovery respectively. The influence of a bilayer sulphidic mineral system on the dissolution of gold was also investigated with a maximum gold dissolution of 87 % for the pyrite‐chalcopyrite bilayer system. The effect of silver on the dissolution of gold was investigated with the gold associated with sulphidic minerals in an arrangement of mixed as well as segregated mineral layers. Three sets of mineral systems were established: pyrite‐chalcopyrite‐silica, pyrite‐sphalerite‐silica, and pyrite‐stibnite‐silica systems. The addition of silver enhanced the gold dissolution for the pyrite‐sphalerite‐silica system, slightly lessened the gold dissolution with the pyrite‐stibnite‐silica system, and retarded gold dissolution severely in the case of the pyrite‐chalcopyrite‐silica system, irrespective of the dispersion of gold and silver in the same as well as in the segregated mineral layers.

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Section: Resultscontrasting

confidence: 99%

Effect of silver on gold cyanidation in mixed and segregated sulphidic minerals

Muhammad

Larachi

2016

Can J Chem Eng

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“…Also, these curves show a plateau on which the current depends on the sulfi te concentration and solution temperature. The run of the dependences is close to that of the voltammetric curves reported for thiocarbamide, thiosulfate, and cyanide electrolytes [23][24][25][26]. As noted in [26], the existence of a plateau indicates that the dissolution rate of silver becomes fully diffusion-controlled and directly proportional to the concentration of the complexing agent.…”

Section: Methodssupporting

confidence: 61%

“…The run of the dependences is close to that of the voltammetric curves reported for thiocarbamide, thiosulfate, and cyanide electrolytes [23][24][25][26]. As noted in [26], the existence of a plateau indicates that the dissolution rate of silver becomes fully diffusion-controlled and directly proportional to the concentration of the complexing agent. The shift of curves 2-5 relative to the curve 1 is 0.39 V, which is close to a value for [SO 3 2-] = 0.1 mol l -1 calculated by the following formula: According to [27], the [Ag(SO 3 ) 2 ] 3-complex is predominant under the given conditions.…”

Section: Methodssupporting

confidence: 61%

On anodic dissolution of silver coatings deposited on base metals

2012

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Potentiodynamic polarization and potentiostatic electrolysis techniques were employed to study the anodic oxidation of silver and a number of other metals (copper, iron, nickel, and tin) in sulfi te media, both individually and in Ag-M binary electrodes. The conditions in which silver is dissolved with a nearly 100% current effi ciency were found.It is known [1] that a considerable part of metallic silver used for technical and decorative purposes is in the form of surface fi lms deposited onto various substrates. The role of substrates is played by various metals and metal alloys, including copper, iron, nickel, brass, and tin. The optimal process for recovery of silver from scrap articles of this kind is that in which the substrate metal is not dissolved.The conventional methods for recovery of silver [2][3][4][5] are based on its dissolution in the presence of oxidants in solutions of acids or complexing agents, with the subsequent recovery of silver in the form of insoluble salts or its reduction to the metal. The main shortcomings of these methods are the gross expenditure of reagents and the dissolution nonselectivity: substrate metals pass into solution together with silver.A substantially lower expenditure is characteristic of techniques based on the anodic oxidation of silver. In processing of materials containing considerable amounts of base metals, selective transfer of silver into solution is possible in an alkaline medium in which many transition metals form insoluble hydroxides. An additional advantage of the electrolytic method is that the oxidation of silver may be accompanied by its deposition onto a cathode. The oxidation of silver in alkaline media in the presence of chlorides, nitrates, sulfates, and borates has been extensively studied [6][7][8][9][10][11][12]. However, the formation of passivating fi lms composed of silver oxides on the surface of the metallic phase has been frequently observed. Silver is commonly dissolved in special electrolytes [13], including those containing such complexing agents as thiourea [14], rhodanide [15,16], and amino acids [17].A promising complexing agent for these purposes is sodium sulfi te, because sulfi te complexes of silver(I) are rather stable [18]. Compared with the cyanide widely used in hydrometallurgy of silver, the sulfi te ion forms stable complexes with a substantially smaller number of metal ions [18]. In addition, the sulfi te by itself creates an alkaline medium (pH ≈ 9-10) in solution. All this gives reason to expect a high selectivity in recovery of silver(I) into solutions in the presence of other metals.It is known that sulfi te ions are unstable against atmospheric oxygen. The fi nal oxidation product is the sulfate ion (SO 3 2-+ 2OH --2e = SO 4 2-+ H 2 O, E 0 = -0.90 V [19]). Probably, just the widely accepted opinion about fast oxidation by oxygen has hindered development of methods using sulfi te ions as complexing agents, including those for recovery of silver. The kinetics of SO 3 2-oxidation in aqueous solutions was studied in [20,...

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“…Silver usually occurs as silver sulphide minerals in the ore, e.g. acanthite (Ag 2 S) and argentojarosites (AgFe 3 [SO 4 ] 2 (OH) 6 ), the low solubility of these silver sulphides was believed to limit the extraction of silver …”

Section: Resultsmentioning

confidence: 99%

Impact of silver sulphide on gold cyanidation with conductive sulphide minerals

2017

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Gold is mostly found in metallic form, while silver exists in various mineral forms. Pyrite, chalcopyrite, sphalerite, and stibnite were the sulphidic minerals investigated for the effect of silver sulphide on gold cyanidation. Four sets of mineral systems, pyrite‐silica, chalcopyrite‐silica, sphalerite‐silica, and stibnite‐silica, were established to investigate the effect of silver sulphide. Silver sulphide addition promoted gold dissolution for the pyrite‐silica and sphalerite‐silica systems. The gold dissolution was retarded with the chalcopyrite‐silica and stibnite‐silica systems, irrespective of the dispersion of gold and silver sulphide in the mineral as well as in the quartz layer. The surface characterization of the gold particles was attempted by using X‐ray photoelectron spectroscopy (XPS) in order to identify the surface obstructing species. XPS analysis showed that the passivation layers of silver sulphide (Ag2S), Cu2O/Cu(OH)2, and antimony oxide (Sb2O5) might form on the surface of goldparticles by the simultaneous dissolution of silver sulphide as well as sulphide minerals, resulting in the retardation of gold dissolution.

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Mechanistic and kinetic aspects of silver dissolution in cyanide solutions

Cited by 42 publications

References 11 publications

Effect of silver on gold cyanidation in mixed and segregated sulphidic minerals

Effect of silver on gold cyanidation in mixed and segregated sulphidic minerals

On anodic dissolution of silver coatings deposited on base metals

Impact of silver sulphide on gold cyanidation with conductive sulphide minerals

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