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The acid oxidation temperature should be above 175°C to prevent the formation of elemental sulfur, as it can absorb or encapsulate the gold, reducing gold recovery in the cyanidation step. In addition, sulfur can react with cyanide, forming thiocyanate, which increases operational costs (Thomas & Pearson, 2016).
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The reactions that take place during the dissolution of gold in cyanide solutions under normal conditions have been fairly definitely established. 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 . Cyanide Leaching Chemistry
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In the present paper, the alkaline sulfide system was studied as an alternative to cyanide for recovering gold from elemental sulfur. It was found that the dominant lixiviant for gold in this …
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Applying additives in leaching could also limit the reactivity of basic metals (Cu, Zn, etc) and ameliorate the cyanidation of ... Linda, L, Breuer, P and Chu, C, 2002. A kinetic and electrochemical study of the ammonia cyanide process for leaching gold in solutions containing copper, Minerals Engineering, 15:1173-1180. ... Pre-oxidation of ...
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Fig. 6 Effect of gold grade, a and cyanide production, b in the extraction of gold using biocyanidation leaching. Data obtained from (Baker 1973;Lawson et al. 1999;Aylmore and Muir 2001;Faramarzi ...
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Sulfide minerals are known to cause the following effects: (1) passivation of gold surfaces through the formation of gold sulfides (AuS x may be formed if gold surfaces are …
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The elemental sulfur has been identified as one of the main contributors to the formed passivated film both in the thiosulfate leaching of gold and the cyanide leaching of sulfide containing ores (Jeffrey and Breuer, 2000, Jeffrey, 2008, Baron, 2013). It has been suggested that the passivation film is a monolayer of AuS x (Grönbeck et al., 2006).
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Alkaline sulfur-containing lixiviants, including thiosulfate, polysulfides, and alkaline sulfide solutions, stand out as a promising class of alternatives to cyanide because of their low toxicity, high efficiency, and strong …
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In the following a brief description of used leaching reagents takes place 8-11. Cyanide and Alternative Gold Leaching Reagents The most commonly used cyanide salts are KCN and NaCN, which are easily soluble in water. Cyanide leaching is the dominating process for gold recovery from primary resources, due to its simplicity and high cost efficiency.
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From an environmental perspective, the most significant cyanide releases from gold leach operations have involved catastrophic spills of process solutions or leakage of effluent …
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Cyanide leaching is currently the dominant process used by the minerals industry to extract gold (and silver ) from geological ores. Gold extraction is accomplished through the selective dissolution of the gold by cyanide solutions, that is, the so-called process of cyanidation. This hydrometallurgical technique is so efficient that the mining ...
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The cyanidation results showed that the cyanide gold leaching rate of acid leaching residues was close to 100wt%. However, the maximum cyanide gold leaching rate of gold calcine was only 85.31wt%.
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Leaching gold from refractory ore faces obstacles, including kinetic or thermodynamic barriers to cyanide diffusion, readsorption of preg-robbing gold or silver, and high cyanide consumption ...
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Table XII.-Gold Concentrate Treated With Partial NSC Sulfide Oxidation Gold = 35 g/T Arsenic = 6.31 % Iron = 25.0 % Total Sulfur = 24.0 % Table XIII.-Nitrogen Species Catalyzed Partial Sulfide Oxidation Leach Conditions Initial Free Sulfuric Acid = 50 g/L Reactor Working Pressure = 620 kPag Slurry Solids Content = 100 g/L Solids Size = 80 % ...
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Salt Lake City, Utah have reported on mercury precipitation from gold cyanide leach solutions with caS and Na2S. They found that Na2S and CaS can serve as ... Electrochemical phase diagram for the mercury-sulfur-water system at 25°C. (Total dissolved sulfur = 8.6x1O-5 M, total dissolved mercury = 4.3x1O-5M)
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The total content of cyanide in typical cyanide tailings is much higher than the limit of toxicity characteristic leaching procedure (TCLP), which requires a further detoxification process.
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limitations are found to affect the rate of sulphide oxidation and the volume of materials that can be treated for gold leaching. ... which generally limits the oxidative gold dissolution rates (Mpinga et al., 2015 ... ores is the destabilisation of gold cyanide complex by sulphur metastable species such as hydrosulphide, polysulphide ...
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The paper presents an overview of bio-oxidation of sulphidic refractory gold ores prior to gold cyanidation. This review discusses several factors, more importantly, oxygen requirements and oxygen ...
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[54] WEBSTER J G. The solubility of gold and silver in the system goldâˆ'silverâˆ'sulfurâˆ'oxygenâˆ'water at 25 °C and 1 atm [J]. Geochimica et Cosmochimica Acta, 1986, 50(9): 1837âˆ'1845. [55] SENANAYAKE G. Gold leaching in non-cyanide lixiviant systems: critical issues on fundamentals and applications [J].
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of circulating fluidized-bed roasting to treat refractory sulfide ores with 1.2 g/t Au. The treatment capacity was 575 t/d and gold recovery was 80 to 85% [6].
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from a solution containing 0.02M potassium dicyanoaurate, 0.23M potassium cyanide, 0.086M potassium carbonate. The gold/silver alloy was prepared by the same procedure, with the exception that 0.5mM silver ... Kinetic plot showing the mass of the electrode during the leaching of gold/silver in a caustic sulfur solution at 60°C. Also shown is ...
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very finely distributed in the sulfides, and gold leaching was assumed to be comparable to the dissolution degree of the host sulfides. Almost linear dependencies between sulfide oxidation and gold leaching efficiency have been observed with several ores (Ahtiainen 2020; Linge and Welham 1997; Pangnum and Browner 1996).
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The literature contains various information in processing complex gold-copper ores. For instance, the classification of complex gold ores into cyanide-consuming minerals, oxygen-consuming minerals, and preg-robbing materials was provided by the previous investigators [16, 17].The solubility of copper minerals in cyanide solution varies from one …
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For the gold cyanidation leaching process in some hydrometallurgy plant, we established a dynamic mech- anism model. The Tikhonov regularization method was used to estimate the unavailable kinetic ...
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The most commonly used equation for the dissolution of gold in a cyanide solution, known as Elsner's equation, is (26.1) 4Au + 8NaCN + O 2 + 2H 2 O → 4NaAu(CN) 2 + 4NaOH Gold dissolution is an electrochemical reaction in which oxygen takes up electrons at one part of the metallic surface (the cathodic zone), while the metal gives them up at another (the anodic …
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Sulfur is likely generated and deposited or adsorbed on the surface of gold, which causes low gold extraction during leaching with sulfur-containing lixiviants (Bas et al., 2017). …
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the gold [2,3,4]. From the advent of the cyanide leaching process in 1880, the carbonaceous material ... Method Code - CSA03V,limits of detection - 0.01%. Sulphur analysis: Method Code - CSA08V, Method - Various, limits of detection - 0.01%. ... The process of leaching gold from its host minerals by cyanidation is widely used in the minerals
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Here is a list of methods to help you on how to manage gold leaching when cyanide consumers are present. Recovering Gold from Iron Sulphides While the oxidized iron minerals ordinarily have little effect in cyanidation, the sulphides—pyrite, marcasite and pyrrhotite—tend …
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Dissolution of elemental sulfur in sodium hydroxide is also used as a lixiviant for alkaline sulfide leaching. The combination of sodium hydroxide and elemental sulfur results in the formation of species other than just sulfide (S −2).Both sodium polysulfide (Na 2 S X) and sodium thiosulfate (Na 2 S 2 O 3) are created along with sulfide. Fig. 1 illustrates the equilibrium …
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determine the optimum conditions for the operational parameters (e.g. leaching time, cyanide strength, particles size etc.) to maximize gold recovery and gold grade. The traditional way of
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