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Furthermore, ammonia leaching as a pretreatment process ahead of cyanide leaching was also examined. Only ~12% of gold was extracted by direct cyanide leaching of the ore. The addition of lead nitrate did not affect the leaching of gold. When ammoniacal cyanide leaching system was used, the extraction of gold was significantly improved to …
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Cyanidation is still the most common process for gold extraction because of its stability, high leaching ratio, and fast reaction rate. 1,2 The process of gold extraction by cyanidation inevitably produces a large amount of cyanide tailings, which, due to the specific nature of the process, has a tailing production ratio of nearly . For China …
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Gold is mainly extracted by cyanidation; however, cyanide is not only highly toxic to organisms but is also not a very effective lixiviant for refractory gold ores. Environmentally friendly leaching agents for gold include thiosulfate, thiourea, polysulfide, lime sulfur, halogens and their compounds, and alkaline amino acids.
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The effect of galvanic interactions and sulfide mineral dissolution on the gold leaching kinetics in aerated cyanide solutions is investigated. Gold leaching kinetics were measured using a ...
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The ongoing depletion of gold and silver-containing ore deposits demands a shift towards the processing of more complex sources. Leaching of gold or silver from these sources, which are named refractory and are typically low-grade, can be complicated due to one or more of the following effects: (1) kinetic or thermodynamic impediments on …
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1. Introduction. Gold is a precious strategic metal that is driving everyday life, the electronics industry, and the global economy (Zhan et al., 2021; Zhang et al., 2022a, Zhang et al., 2022b, Zhang et al., 2022c, Zhang et al., 2022).However, with the depletion of high-quality gold ore, refractory gold resources (gold recovery efficiency rate of <50% …
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1. Free cyanide and thiosulfate (Reaction 8) are preferentially oxidised prior to the oxidation of copper cyanide and thiocyanate which occur in parallel. 2. The control of pH is important since at low pH, HCN forms which is not readily oxidised and the rate of cyanate oxidation increases. 2 4 2-2 4 2-4H 2 5 S 2 3 HO →+ 5HSO (8) Hydrogen ...
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The head grade analysis of the sample indicated that it contained 13 g/t gold, 48.8% Iron and 37.7% Sulphur. The leach was performed in a small scale, 3L, reactor fitted with an overhead stirrer and compressed air/pure oxygen (Afrox 99%) sparger. The leach was carried out by using 1:1 concentrate: water ratio.
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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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The remaining 20% is used to manufacture sodium. cyanide, a solid form of cyanide, of which 90% (i.e. 18% of total production) is used in. mining operations around the world for gold recovery ...
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To avoid hydrolysis of cyanide [Eq.(26.2)], leaching must be carried out under alkaline conditions: (26.2) CN – + H 2 O → HCN + OH – However, in saline water, such as in many cyanidation plants in Western Australia, gold leaching is performed at a pH below 10 to reduce the high cost of lime under these buffering conditions.
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There is a vast amount of globally underutilized low-grade mine tailings and leach residues, including those from primary processing of gold. In this research, the target is to recover the remaining gold (10.9 g/t) from weathered refractory iron-rich residue that had previously been subject to autoclave oxidation, subsequent cyanidation in a …
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cyanide acces~ble gold being left in the residue, even after 24 hours. However, final gold extraction is already achieved after 6 hours when the PA-Lprocess is applied. 3 2 1 0 "L.—. —@— —. —o— . with H202 I [ 1 I I I 1 I 3 6 9 12 15 18 21 2.t I retention time (h) I Fig. 2 — Residual gold concentration in the Fairview ore as a ...
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The method consisted of two stages roasting for arsenic and sulfur removal, gold recovery by thiourea leaching, followed by an enhanced chlorination roasting for gold recovery in the presence of pyrite. In the two-stage roasting process, the phase transition of FeAsS and FeS 2 during the roasting process was analyzed. In the first stage ...
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Water containing cyanide ions is often treated with sulphur dioxide, chlorination process and/or aeration. ... chromatographic techniques are characterized by a low limit of detection at the level of milligrams per litre and high precision. ... The fate of cyanide in leach wastes at gold mines: an environmental perspective. Appl Geochem. …
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The formation of copper and silver cyanide complexes a ects the gold recovery in both the cyanide leaching process as well as the purification and refining stages [7]. These e ects mainly interfere with the gold cyanide reaction and the carbon adsorption. Most of the copper minerals react rapidly with cyanide, forming multiple cyanide complexes.
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The cyanidation of copper flotation tailings containing sulfides for gold recovery is an example of the formation of cyanide complexes with copper and silver during the leaching process [11,12]. Figure 4 shows the MLA Automated Minerology image of an ore sample from a copper mine in Mexico, containing chalcopyrite and bornite as copper …
DetailsComplex refractory gold ores, which have become a major raw material for global gold production (Bas et al., 2017), generally contain gold, silver, copper, sulfur and other valuable elements. The complex properties, many cyanide-consuming substances (Deschenes et al., 2000), and gold particles of fine size range (Bas et al., 2018) lead to …
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The extraction of gold increased from 9.7 to 82.1%. The sulfur conversion mechanism and the distribution of the gold phase as a function of leaching temperature during the pressure oxidation leaching process were investigated. ... an appropriate amount of non-cyanide gold leaching agent and activated carbon (60 g) were added to …
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cyanidation was 90.5% under the leaching condition of sodium cyanide 0.06 M, pH 11, pulp density of 20%, stirring speed of 300 rpm, 25 C and leaching time 24 h ( Dong et al., 2021a, 2021b ).
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The use of ammoniumâˆ'thiosulfate solutions to leach gold and silver from the oxidizing leaching residue of copper sulfide concentrates was reported by BEREZOWSKY and SEFTON in 1979 [25]. The authors claimed that the leaching rate of gold was higher than that by conventional cyanidation and halogen leaching method.
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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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Thiosulfate is also an efficient lixiviant for gold ores with high amounts of copper, which reacts with cyanide, reducing gold leaching efficiency (Sitando et al. 2018). Gold ore can be leached ...
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Abstract. The addition of lead to a gold leaching reactor can effectively accelerate or retard the gold cyanidation reaction. This study explored the effect of lead on the gold dissolution kinetics using cyclic voltammetry (CV) experiments. It was illustrated that the gold leaching kinetics in the cyanide solution enhanced with the addition of ...
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The detection standard is that the total cyanide content in the tailings toxic leaching solution is less than 0.05 mg/L, while the national standard GB/T 14848-2017 "Quality of Groundwater" The ...
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A sodium cyanide solution is commonly used to leach gold from ore. There are two types of leaching: Heap leaching: In the open, cyanide solution is sprayed over huge heaps of crushed ore spread atop giant …
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The further decomposition of formamidine disulfide to elemental sulfur has been proposed to reduce gold leaching efficiency as the sulfur forms a passivation layer ... In order to limit this effect and improve gold leaching ... (1999) The role of metal-cyanide species in leaching gold from a copper concentrate. Miner Eng 12:877–892. ...
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The gold extraction from the refractory sulphidic gold tailing by [Bmim + HSO 4− ]-water solution 20% (v/v)/thiourea/ferric ion was conducted at longer extraction times of 1 day, 2 days, 3 days and 5 days at pH = 1, temperature 60 °C and shaking speed of 250 rpm. Fig. 3 demonstrates the gold extraction at longer leaching times.
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The results obtained thus strongly suggest that the gold ore particle size is a more significant factor than cyanide concentration in determining the percentage dissolution of gold particles and that beyond a certain limit, an increase in cyanide concentration may not produce a corresponding rate in gold dissolution and may even retard it [10].
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In 10 mL of thiosulfate solution, 1 mol of thiosulfate extracts 0.4 g of Au. Therefore, thiosulfate levels in high pulp densities are not sufficient for efficient gold extraction [52]. It may be ...
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The detection of gold on the minerals may have been low due to the high detection limit of the experimental technique, which was ... The level of free cyanide could also be reduced by reaction with the elemental sulphur formed in Eq. (5 ... The role of metal–cyanide species in leaching gold from a copper concentrate. Minerals …
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A process called "Cyanidation", or cyanide leaching, has been the dominant gold extraction technology since the 1970s. In this process sodium cyanide, in a dilute solution of ranging from 100 ppm to 500 ppm or 0.01% to 0.05% cyanide, is used to selectively dissolve gold from ore. ... Again, local, state and national regulations limit the ...
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To avoid hydrolysis of cyanide (Eq. (2)), leaching must be carried out under basic conditions: (2) CN − +H 2 O⇒HCN+OH − However, in saline water, such as in many cyanidation plants in Western Australia, gold-leaching is performed at a pH below 10 to reduce the high cost of lime under these buffering conditions. Hydrocyanic acid (HCN) is …
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Gold leaching with thiourea has the advantages of fast speed (four to five times faster than that of cyanide leaching) and a high leaching rate for refractory gold ores (Choi et al., 2017, Lee et al., 2018). Thiourea is stable under acidic conditions and can form coordinating compounds with Au ions in the presence of an oxidizing agent.
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Briefly, the concentrations of HCN & free cyanide are equal in slurry/solution at pH -9.4; at pH 70% of cyanide is lost as HCN gas; the conversion of free CN to cyanate (CNO-) requires strong oxidizing conditions (Inco process, per oxygen chemicals, ozonation etc) & is therefore unlikely under CIL/CIP aeration conditions and yes, pH >11 will ...
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Cyanide lixiviant has been used as a leaching medium in the extraction of gold from the ore for more than a century due to the selectivity and chemical stability of the aurocyanide compound. The gold cyanide complexes such as [Au(CN) (]*and [Au(CN) +] * having stability constant of 2 x 1038 and ~1054, respectively (Marsden and House, 2006).
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Cyanidation is the main process in gold leaching. There are several parameters that affect gold recovery and cyanide consumption. In this paper, the effect of the oxidative pretreatment and lead nitrate addition on the cyanidation of Zarshuran refractory gold ore containing 3.32 ppm Au, 1.09% As, and 0.5% sulfur were …
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