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The optimum conditions for leaching the gold in the refractory gold concentrates pretreated with the pressure oxidation are as follows: 4 of pH, above V of the redox potential, 75 g/L of the NaCl concentration, and 40 °C of the leaching temperature, 3:1 of .
Table 1 Leaching rate of gold and goldsilver alloy in caustic sulphur solution at 60°C [13] Pure Au 5% Ag 20% Ag Leaching rate (× 10 5 mg/cm 2 ·s)
gold electrode (m2), and t is the time elapsed (s). Thus, the slope of the kinetic plot is a measure of the leaching rate. It can be seen from Figure 1 that the gold/silver leach rate increases as a function of time, eventually reaching a steady state value after 350s. At steady state, the leaching rate for gold/silver is
Most cyanide leaching is carried out at a alkaline pH of between 10 and 11, depending upon lab testing of individual ores and the optimum leaching/chemical use rates. The cyanide solution strength is also important in leaching gold, with the typical range of solution being in the % % NaCN.
for further gold leaching or further proce ssed with low ... part of the oxidation was due to oxidation of gold. EhpH diagrams were constructed and showed soluble Au(I)S(IV) species formed ...
(leaching). Basically gold and silver leaching involves spraying a cyanide so lution on the ore to dissolve the metal values, collecting the solution contain ing the dissolved metals, and recovering the metal from the solution. By elimi nating milling, leaching reduces .
The naturally occurring mineral leaching is very slow. The microbial bioleaching process can be optimized by creating ideal conditions— temperature, pH, and nutrient, O 2 and CO 2 supply etc. A diagrammatic representation of general bioleaching process is depicted in Fig.
In addition to elemental sulfur and gold–sulfur compounds, some oxygencontaining sulfur species were generated on the gold surface during the leaching process. For example, Baron et al. [ 126 ] reported that the decomposition of thiosulfate produced several intermediates such as tetrathionate, trithionate, elemental sulfur, and sulfide.
A process for recovering gold from goldbearing ores includes the steps of forming a slurry of ground ore and treating the ore with an oxidizing and complexing agent such as hydrogen sulfide or a sulfide salt. A chelating agent, SO 2, air, and an anion exchange resin are added to the slurry to subject the ore to a simultaneous sulfurous acid leaching and anion exchange resin adsorption step ...
The cheapest way to lower the soil pH is to add elemental sulfur to the soil. Soil bacteria change the sulfur to sulfuric acid, lowering the soil pH. If the soil pH is greater than, apply elemental sulfur (S) to decrease the soil pH to (see Table 1). Spring application and incorporation work best.
Gold cyanidation (also known as the cyanide process or the MacArthurForrest process) is a hydrometallurgical technique for extracting gold from lowgrade ore by converting the gold to a watersoluble coordination is the most commonly used leaching process for gold extraction.. Production of reagents for mineral processing to recover gold, copper, zinc and silver represents ...
In general, sulfides are first oxidized to elemental sulfur, whereas disulfides are oxidized to give thiosulfate, and the processes above can be applied to other sulfidic of nonsulfidic ores such as pitchblende also uses ferric iron as an oxidant (, UO 2 + 2 Fe 3+ ==> UO 2 2+ + 2 Fe 2+).In this case, the sole purpose of the bacterial step is the regeneration of Fe 3+.
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Thiosulfate leaching without additive was not effective to treat a refractory gold concentrate calcine with high iron, sulfur and arsenic due to its low gold extraction (%) and high ...
Dissolution of impurity elements (, copper and zinc) from their minerals results in excess reagent consumption and low gold recoveries in leaching as well as technical problems in downstream ...
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 and 3 at which most metal ions remain in solution.
The process of dissolution of metallic gold leaching is carried out in a system containing a ligand and an oxidizer, where the solubility of gold is increased by the addition of aromatic compounds containing ring sulfur or nitrogen. The leaching of gold using less corrosive fluids without significant losses in the dissolution rate of the metal ...
According to previous studies on bornite leaching, we found that the acidic ferric sulfate leaching was more efficient than the bioleaching in the ear.
place in an agitated leach process, automatic pH control is strongly recommended. pH is controlled between 11 and 12 during the leaching process. pH values below 11 favor the formation of HCN, hydrogen cyanide that interferes with reaction (1). Hydrogen cyanide is a colorless and poisonous gas that, if released due to lower pH values, can quickly
CN is required to leach gold and thus at decreasing pH''s the quantity of CN decreases due to the formation of HCN as pointed out above. Thus, the gold leach reaction can become cyanide limited if the CN concentration gets too low can compensate by having higher cyanide addition but also get higher HCN and hence HCN loss!
T /K Figure 5. Arrhenius plot for gold/silver leaching in a sulfide sulfur solution. The data for the caustic sulfur solution is also overlaid for comparison 52 10 r / mol m s1 Caustic Sulfide Bisulfide Sulfur Solution Figure 6. Comparison of gold/silver leaching in the caustic sulfur, sulfide sulfur, and bisulfide sulfur ...
Though the standard reduction potential of Fe(CN) 6 3− / Fe(CN) 6 4− is somewhat lower than that of oxygen in alkaline solution, theoretically ferrricyanide would be a potential oxidant to extract gold and silver in cyanide solution. In this research the stoichiometry reaction was first investigated through leaching of synthetic silver sulfide with ferricyanide–cyanide solution.
Many sulfide minerals also contain things like copper or antimony that can react with the cyanide, preventing the cyanide from leaching out the gold and silver. For information on methods to deal with and extract gold, silver and base metals from these refractory ores, I .
All cyanide leach experiments were conducted for 24 hours in a % sodium cyanide leach solution at a pH of approximately and pulp density of 15% solids. The thiourea leach experiments were conducted for 2 hours at a 10% pulp density, and at initial reagent concentrations of M thiourea, M ferric ion, and M sulfuric acid.
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