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Alkaline cyanide leaching of refractory gold flotation ...

2018-8-1  Alkaline cyanide leaching is a conventional hydrometallurgical technique that involves selective leaching of gold (Au) from host ores using cyanide, a universal gold ligand, in a stepwise oxidative and complexation manner (Eq. ) (Deschênes, 2016; Menne, 1991; Nicol et al., 1987a).

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Alkaline-assisted leaching of iron-cyanide complex

2018-12-15  This study investigated the alkaline-assisted leaching behavior of iron-cyanide complexes from five cyanide-contaminated soils via batch leaching experiments spanning a wide pH range (10–14). The results showed that the leaching ratio of iron-cyanide complex (R) was highly dependent on pH.

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Alkaline cyanide leaching of refractory gold flotation ...

In this work, the mechanism and kinetics of alkaline cyanide leaching of the two refractory flotation gold concentrates and their bio-oxidised products, taken as surrogates, have been investigated under isothermal, batch conditions, together with a review of the cognate literature.

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Cyanide Leaching Chemistry Gold Cyanidation

2015-2-6  Most agree that the overall cyanide equation for leaching and cyanidation of gold is as follows: 4 Au + 8 NaCN + O2 + 2 H20 = 4 NaAu (CN)2 + 4 NaOH

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An Alkaline Glycine-Based Leach Process of Base and ...

2019-8-9  The metal extractions of three different alkaline leaching processes using (1) ammonia; (2) cyanide and (3) direct glycine–cyanide leaching were compared with the two-stage glycine and glycine–cyanide leach developed in this study. Table 3 shows the required stoichiometric amounts of each lixiviant to leach the targeted elements.

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Experimental study on cyanide-contaminated soil

2020-1-3  The removal of cyanide compounds in soil by leaching was investigated in flask and column tests. All the experiments were conducted under alkaline conditions to prevent loss of hydrogen cyanide. Results showed that leaching progressed rapidly when the leaching temperature or the initial cyanide concentration was high.

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Cyanide Leaching and Decomposition of Pyrrhotite

2015-10-14  Cyanide is then added to the charge and agitation and aeration continued. According to leaching metallurgists, too alkaline a solution may directly attack sulphides. The former suggests the equation: 12 Fe5S6 + 3Ca(OH)2 = 2 CaS5 + CaS2O3 + 60

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Effect of pH Alkalinity on Gold Leaching - 911

2015-2-8  In some instances, for specific purposes, protective alkalinity in the cyanide solution is maintained by the use of other alkalies such as sodium hydroxide and sodium carbonate. These alkalies, however, usually are not effective settling agents.

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A fundamental study of the alkaline sulfide leaching of gold

2015-12-27  It has been shown that the alkaline sulfide system leaching system is an effective means of recoveringgold from elemental sulfur formed during the partial oxidation of metal sulfides. When treated with eitherconcentrated hydroxide or sulfide solutions, the sulfur dissolves forming polysulfides and sulfide. Sulfide isable to act as a lixiviant for the process, and the polysulfide is the oxidant. The

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Treatment of copper-rich gold ore by cyanide leaching ...

2015-3-2  in cyanide leaching to mitigate the copper interference, allowing substantial reduction in cyanide consumption (by up to 90%) and selective leaching of gold with only limited dissolution of copper [3,4,22,23]. Ammoniacal cyanide leaching was successfully demonstrated for oxidised ores/tailings with selective extraction of

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Alkaline cyanide leaching of refractory gold flotation ...

In this work, the mechanism and kinetics of alkaline cyanide leaching of the two refractory flotation gold concentrates and their bio-oxidised products, taken as surrogates, have been investigated under isothermal, batch conditions, together with a review of the cognate literature.

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Pressure cyanide leaching for precious metals

2007-10-9  A novel method demonstrates that the oxidation and dissolution of gold and silver in alkaline cyanide solution can be conducted simultaneously in the same autoclave in less than 90 minutes with a recovery that exceeds 96%.

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An Alkaline Glycine-Based Leach Process of Base and ...

2019-8-9  The metal extractions of three different alkaline leaching processes using (1) ammonia; (2) cyanide and (3) direct glycine–cyanide leaching were compared with the two-stage glycine and glycine–cyanide leach developed in this study. Table 3 shows the required stoichiometric amounts of each lixiviant to leach the targeted elements.

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Cyanide Leaching and Decomposition of Pyrrhotite

2015-10-14  Cyanide is then added to the charge and agitation and aeration continued. According to leaching metallurgists, too alkaline a solution may directly attack sulphides. The former suggests the equation: 12 Fe5S6 + 3Ca(OH)2 = 2 CaS5 + CaS2O3 + 60

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Gold Metallurgy Leaching in Cyanicides

2016-7-14  The reason for the lower cyanide consumption obtained with intense aeration is probably connected with the reactions which take place when alkaline sulphide decomposes in cyanide solution. Alkaline sulphide is one of the initial products of the

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Cyanide and Other Lixiviant Leaching Systems for

2018-6-6  Alkaline lixiviant systems (pH > 10)include cyanide, ammonia-cyanide, ammonia, sulphide, nitriles, and a few other minor possibilities. Oxygen is the main oxidant. Cyanide, which is the main ligand in these systems, forms an anionic complex, “Au(CN)2”, with Au(I). Gold dissolution rates are controlled by oxygen solubility in solution.

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Effect of pH Alkalinity on Gold Leaching - 911

2015-2-8  These alkalies, however, usually are not effective settling agents. Although the use of an alkali is essential in cyanidation, many investigators have stated that alkalies such as sodium hydroxide, and particularly calcium hydroxide, retard the dissolution of

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Treatment of copper-rich gold ore by cyanide leaching ...

2015-3-2  Cyanide with its competency to form a strong complex with gold, is the most preferable reagent for leaching of gold from ores. Cyanide leaching is not inherently a selective process since many other metals/minerals present in the ore are also readily soluble under cyanide leaching conditions. In this regard, most copper minerals are highly soluble in cyanide solutions (Table 1) although chalcopyrite

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Characterization and availability of cyanide in solid

These results stress the necessity of performing a preliminary alkaline extraction prior to total cyanide determination. In summary, this study revealed a difference in physicochemical properties, cyanide concentration and speciation, viable bacterial populations and cyanide leaching behavior between aged and fresh solid mine tailings.

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Optimizing and evaluating the operational factors ...

2015-12-8  Conventionally, gold ores are treated with dilute alkaline cyanide solution in the presence of oxygen to solubilize the gold. The dissolved gold is then precipitated by zinc dust treatment. This is the well-known McArthur–Forrest–Merrill Crowe process .

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Pressure cyanide leaching for precious metals

2007-10-9  A novel method demonstrates that the oxidation and dissolution of gold and silver in alkaline cyanide solution can be conducted simultaneously in the same Pressure cyanide leaching for precious metals recovery SpringerLink

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Gold Metallurgy Leaching in Cyanicides

2016-7-14  The reason for the lower cyanide consumption obtained with intense aeration is probably connected with the reactions which take place when alkaline sulphide decomposes in cyanide solution. Alkaline sulphide is one of the initial products of the

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Cyanide and Other Lixiviant Leaching Systems for

2018-6-6  Alkaline lixiviant systems (pH > 10)include cyanide, ammonia-cyanide, ammonia, sulphide, nitriles, and a few other minor possibilities. Oxygen is the main oxidant. Cyanide, which is the main ligand in these systems, forms an anionic complex, “Au (CN)2”, with Au (I). Gold dissolution rates are controlled by oxygen solubility in solution.

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Cyanide hazards to plants and animals from gold

Cyanide extraction of gold through milling of high-grade ores and heap leaching of low-grade ores requires cycling of millions of liters of alkaline water containing high concentrations of potentially toxic sodium cyanide (NaCN), free cyanide, and metal-cyanide complexes. Some milling operations result in tailings ponds of 150 ha and larger.

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Technical Overview August 2019 - Metaleach

2020-10-21  The alkaline residue allows immediate application of cyanide leaching of gold and silver in ores where there is an economic precious metal content after removal of high cyanide consuming metals such as copper. Typical Capital and Operating Costs for Copper Heap Leaching

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The Case for Glycine Heap Leaching -

2020-12-11  The gold industry, by contrast, has been very successful in heap leaching a wide range of materials using cement agglomeration in an alkaline cyanide system. The ability to agglomerate with cement makes the process far more robust with respect to the physical properties of the ore, and recovery projections from test results are much more reliable.

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Characterization and availability of cyanide in solid

Following the standard acid reflux/distillation method, the total cyanide concentration (CN (T)) in fresh tailings was higher (average of 19.5 +/- 2.0 compared to 3.2 +/- 0.7 mg/kg) and the pH more alkaline (10.6 +/- 0.1 compared to 7.6 +/- 0.2) compared to aged ones.

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Treatment of copper-rich gold ore by cyanide leaching ...

2015-3-2  Cyanide with its competency to form a strong complex with gold, is the most preferable reagent for leaching of gold from ores. Cyanide leaching is not inherently a selective process since many other metals/minerals present in the ore are also readily soluble under cyanide leaching conditions. In this regard, most copper minerals are highly soluble in cyanide solutions (Table 1) although chalcopyrite

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TREATMENT OF CYANIDE HEAP LEACHES AND TAILINGS

efficiencies than heap leaching facilities, recovering from 85 to 98 percent of the gold contained in the ore. Generally, CIP or CIL methods are used for high grade ore. Oxide ores are typically beneficiated by grinding to 65 mesh and leaching with 0.05 percent sodium cyanide over a 4- to 24-hour period with a pulp density of 50 percent solids.

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ISOLATION OF CYANIDE HYDRATASE MUTANTS FROM ...

2021-5-15  compounds, or oxidation to cyanate. Because cyanide is volatile at a neutral pH environment, cyanide waste-waters are typically kept at highly alkaline pH levels, approximately between 10 and 11, to minimize the amount of cyanide that dissipates as HCN gas (Needham 1999). The

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alkaline gold cyanide process - fonmac.org

Alkaline cyanide leaching of refractory gold flotation Aug 01, 2018 Previous studies have shown that, the alkaline cyanide leaching efficacy of gold ores is mostly defined by: (1) gold leach-site availability; (2) gold-gangue mineralogy/chemistry; (3) degree of lixiviant (cyanide, oxygen and alkali) reactivity; and (4) process variables (e.g ...

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Cyanide and Other Lixiviant Leaching Systems for

2018-6-6  Alkaline lixiviant systems (pH > 10)include cyanide, ammonia-cyanide, ammonia, sulphide, nitriles, and a few other minor possibilities. Oxygen is the main oxidant. Cyanide, which is the main ligand in these systems, forms an anionic complex, “Au(CN)2”, with Au(I). Gold dissolution rates are controlled by oxygen solubility in solution.

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Cyanide hazards to plants and animals from gold

Cyanide extraction of gold through milling of high-grade ores and heap leaching of low-grade ores requires cycling of millions of liters of alkaline water containing high concentrations of potentially toxic sodium cyanide (NaCN), free cyanide, and metal-cyanide complexes. Some milling operations result in tailings ponds of 150 ha and larger.

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Experimental study on cyanide-contaminated soil

The removal of cyanide compounds in soil by leaching was investigated in flask and column tests. All the experiments were conducted under alkaline conditions to prevent loss of hydrogen cyanide. Results showed that leaching progressed rapidly when the leaching temperature or the initial cyanide conc

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THIOSULPHATE LEACHING – AN ALTERNATIVE TO

Like cyanide, thiosulphate leaching is an alkaline process (usually operated in the pH 8 to 10 range) so there are no concerns with corrosion and materials used in construction, and the process can be applied to heaps and dumps, or to stirred tanks. The thiosulphate process offers advantages over cyanide leaching in the following situations:

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Technical Overview August 2019 - Metaleach

2020-10-21  The alkaline residue allows immediate application of cyanide leaching of gold and silver in ores where there is an economic precious metal content after removal of high cyanide consuming metals such as copper. Typical Capital and Operating Costs for Copper Heap Leaching An analysis of the economics of the AmmLeach® process compared with

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How to Improve the Effect of Gold Cyanide Leaching?

2019-9-29  For this kind of problems, pre-aerated alkali leaching method is often adopted, that is, filling oxygen and agitating in the alkaline medium before the pulp cyanidation leaching, so that these minerals have enough oxidation and hydrolysis time to convert into the cyanide ferric hydroxide that cannot be dissolved by the cyanide, then adding the cyanide to effectively dissolve the gold.

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Characterization and availability of cyanide in solid

These results stress the necessity of performing a preliminary alkaline extraction prior to total cyanide determination. In summary, this study revealed a difference in physicochemical properties, cyanide concentration and speciation, viable bacterial populations and cyanide leaching behavior between aged and fresh solid mine tailings.

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TREATMENT OF CYANIDE HEAP LEACHES AND TAILINGS

efficiencies than heap leaching facilities, recovering from 85 to 98 percent of the gold contained in the ore. Generally, CIP or CIL methods are used for high grade ore. Oxide ores are typically beneficiated by grinding to 65 mesh and leaching with 0.05 percent sodium cyanide over a 4- to 24-hour period with a pulp density of 50 percent solids.

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INFLUENCE OF PRE-AERATION ON CYANIDE LEACHING

2015-5-6  The concentration of cyanide used varies depending on the mineralogical structure of the ore. Generally, the cyanide concentration practiced industrially is in the range of 0.15 to 0.5 g/dm3. However, the feed material may contain significant amounts of cyanide consumers and/or high silver content (i.e., >20 g/Mg). In such cases, higher

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