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Experimental results showed that average gold and silver recoveries increased by 13.3% and 28.8%, respectively at 500 ppm NaCN and 300 ppm SO32- concentration levels compared to the control experiments where no sulfite was added to the leach slurries. Additionally, higher sulfite concentrations in the leach slurries resulted in lower ...
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preparation prior to leaching. Gold and silver are dissolved by cyanide in solutions of high pH in the presence of oxygen. There are three general methods of contacting ores with leach solutions: (1) heap leaching, (2) vat leaching, and (3) agitation leaching. Cyanidation heap leaching and vat leaching account for most gold and silver recovery ...
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Apr 14, 2020 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 adaptability. In this paper, we summarized the research progress and remaining challenges in gold extraction using these noncyanide reagents.
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oxidative leaching with ozone is relevant in copper-iron sulphide and gold- and silver- containing sulphides. Moreover , oxidative leaching of coal-containing iron sulphide might also have a positive impact on coal cleaning prior to its use in energy related applications. The hydrometallurgy of different sulphide minerals will be treated.
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Gold Leaching( carbon in leach) process is widely used in the newly built gold leaching plants in recent years, and a lot of plants are changing into CIL as well.Gold Leaching CIL process is suitable for the treatment of oxidized gold ore with low sulfur content and mud content. It is unsuitable for the gold ore with high-grade silver.
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Aug 03, 2019 The leaching consumption of the material; and the combination of sulfur ions and cyanide (CN-) ions in the sulfide slurry; (3) Neutralize the acid formed by the oxidation of CO2 dissolved in water and sulfide ore, and prevent sodium cyanide from being decomposed by these acids.
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If this was reagent grade elemental sulphur then it can be fairly hydrophobic and therefore very slow to react. If you want to observe it in the lab then it helps if the pH is elevated and a surfactant to disperse the sulfur may also assist. I work for a gold mine using the Biox process for oxidation of gold bearing pyrite/arsenopyrite.
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Oct 04, 2016 All samples recorded low pH in the range of 2.4–3.2 and high concentrations of Fe, S and Cu . The concentrations of Fe, S and Cu in LS was 500, 8227 and 171 (ppm.) respectively.
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In the process of leaching maintain the pH of leach solution is not less than 7,0 using ammonia, the concentration of the sulfite ion in the solution supports not less than 0.05% by introducing sulfur dioxide (U.S. Patent N 4369061, CL SW 11/04, Jan.18, 1983).
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If soil pH is kept within the desirable range of 5.8 to 6.0 with dolomitic limestone, the available levels of calcium and magnesium will usually be high enough to meet the needs of the crop. Otherwise, 40 to 50 pounds of calcium (Ca) and 15 to 20 pounds of magnesium (Mg) per acre are needed from the N …
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Ammonium thiosulphate is an alternative gold leaching Laaviant used to replace cyanide. The current problem of thiosulphate gold leaching is the high reagent consumption, To understand the decomposition chemistry of thiosulphate, solution stability tests were conducted in open and sealed vessek mder ambient temperature
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the encapsulation of fine particles of gold in the ore host. A clear boundary between refractory and non-refractory ore in terms of gold recovery is not well defined, but several authors have pointed out that less than 60% gold recovery by direct cyanide leaching, after fine grinding of mineral indicates a refractory mineral [1]. The refrac-
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Jul 01, 1997 The energy derives from the oxidation of reduced or partially reduced sulfur compounds, including sulfides, elemental sulfur and thiosulfate, the final oxidation product being sulfate [2, 3]. Bacterial leaching is carried out in an acid environment at pH values between 1.5 and 3 at which most metal ions remain in solution.
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Feb 21, 2020 2. pH value, Temperature and Stirring Speed. pH, temperature and stirring speed affect the leaching of gold reason is that in cyanide pulp zhongyi reaction generated by hydrocyanic acid (HCN), hydrocyanic acid volatile and toxic, if the volatilization of hydrocyanic acid from pulp can lead to the loss of cyanide, also can cause environmental ...
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In the leaching solution, a decrease in total iron was mainly due to the transformation of Fe 3+ to jarosite. System C holds more sulfur-oxidizing bacteria and produced more SO 4 2−, which might drive the reaction between Fe 3+ and SO 4 2−. pH of the abiotic control increased gradually with the leaching …
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bromide leaching of not only gold, but also sulde minerals, encapsu - lating the gold. In future, this could have the way towards one-stage processing of refractory gold raw materials, avoiding the need of roasting, POX or bio-oxidation. 2. Materials and methods Leaching tests in the current work are carried out for one type of refractory gold ...
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Chemical leaching of the concentrate (slurry density at 200 g/L) by ferric sulfate biosolvent (initial concentration at 35.6 g/L), which was obtained by microbial oxidation of ferrous sulfate for 2 hours at 70 C at pH 1.4, was allowed to oxidize 20.4% ofarsenopyrite and 52.1% of sulfur.
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The leaching rate of copper reaches 91.54% and more than 99.8% of gold and silver are enriched in the slag for further recovery when the alkaline washed waste acid residues are subjected to the ...
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Feb 28, 2015 Thiobacillus bacteria are acidophilic aerobic chemolithotrophs which grow most rapidly at a pH in the range of 2-3. T. ferrooxidans derive their energy by oxidizing ferrous iron, elemental sulfur and reduced sulfur compounds and utilize carbon from carbon dioxide for biosynthesis (Hutchins et …
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In a method for leaching gold from copper sulfides, the sulfide ores are first subjected to leaching of copper, thereby producing a leaching residue having 7.9% or less of the copper content. This leaching residue is mixed with a leach liquor, which contains the chloride ion and ferric ion and has 1.9 or less of pH. Gold and copper can be effectively leached from the copper sulfide ores.
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Nov 01, 2001 Thiosulfate offers a nontoxic alternative to cyanide for processing gold ores. The mechanism of leaching gold using ammoniacal thiosulfate solution is driven by the Cu(II)-Cu(I) redox couple and is complicated by competing ligands such as NH3 and S2O32−. It is shown that an understanding of the copper speciation and sulfur speciation is required to optimize this system. This …
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INTRODUCTIONAs alkaline sulfide leaching of gold has its roots in the development and industrial application of nitrogen species catalyzed pressure leaching for partial oxidation of sulfides, a discourse in this topic is relevant. ... Figure 1 -1Equilibrium Eh-pH diagram for sulfur Figure 2 -2Meta-stable species Eh-pH diagram for sulfur Figure ...
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, the gold leaching rate is extremely low [18]. This suggests that Cu(CN)3 2 can provide sufficient cyanide ions for the leaching of gold or other minerals according to Equation (9) [18]. 4Au + 8Cu(CN)3 2 + O 2 + 2H2O !4Au(CN)2 + 8Cu(CN) 2 + 4OH (9) As the leaching of the ore proceeds, the concentrations of the major species change and so
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Pressure leaching of sulfide ores is complicated by many items such as sulfur viscosity and the passivation of reactive surfaces. “Low” temperature conditions (100o C to 140o C) are generally not used in sulfide pressure leaching as this temperature range is conducive to formation of liquid elemental sulfur. This liquid
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Aug 01, 2006 It has been previously proposed that a passive film of sulfur formed on the surface of gold may be responsible for the reduced gold leaching rates in sulfide containing solutions (Jeffrey and Breuer, 2000). If this is the case, then the role of the added lead is …
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Mar 01, 2007 Fig. 1 shows the dissolution of gold with the addition of sulphur species. For comparison, a parallel test was conducted under the standard condition without any sulphur species being added. The leaching curve showed an approximately linear relationship from about 3 h onwards under the standard condition.With the addition of 5 mM sulphur species, the overall gold dissolution increased.
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The best recommended method is CIL/CIP to recovery gold in a sulphide ore and you must design condition tanks for per treatment of sulfur, in this condition tanks you must dose lime of at least 12 pH, induced oxygen (either by having oxygen plant or dosing hydrogen peroxides.
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When the dilute concentration is 15%, the gold leaching rate reaches 73.42%. The mass ratio of sulfur to lime is the main reason affecting the sulfur conversion and pH value of mother solution....
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Jul 01, 2011 Gold mostly concentrates in high-sulphidation systems at 300 C at low pH ( 2) and high log f(O 2)(–28). For example, the concentration of Au in the vapor phase is 0.06 ppb at pH = 2 and log f(O 2) = −28 (Archibald et al., 2001). Under the condition of the same oxygen fugacity but at pH = 1, the Au concentration is 0.6 ppb.
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Sep 10, 2014 The Eh–pH diagram for the gold–thiosulfate–EDTA–copper–citrate shows that the gold is stable as Au(S 2 O 3) 2 3 − in the pH range above 7 and only in the narrow windows of potential (between − 0.2 and 0.02 V). Experimental results (not shown here) indicated that the recovery of gold in the absence of EDTA is very low (less than 10%).
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Feb 15, 2014 Direct leaching was performed with 10 g/dm 3 of waste with Cu-rich waste being added to the microbe culture once the pH reached 1.0. For indirect leaching, the biogenic acid was harvested and used in leaching the waste. Fig. 10 shows there is very little difference in the Cu mobilisation in both direct and in-direct leaching at 30 C.
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Feb 19, 2018 Pyrite Oxidation Kinetics – How Fast does Pyrite Oxidize. Pyrite oxidation has been studied extensively, in the past, because of its importance in sulfide mineral separations by flotation, in the generation of acid in mine waters and in leaching of pyrite. The oxidation of pyrite also plays key role in supergene alteration of ore deposits ...
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