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The target of this review is to point out the best cyanide-free processes of following methods and reagents: Bioleaching, Chlorination, Aqua Regia, Bromine, Thiocyanate, Thiosulfate and Thiourea leaching. For this propose, the gold leaching reagents are described and discussed in terms of their environmental and economical points of view.

A process as claimed in claim 13, wherein the acidic solution is a leach solution obtained in the final recovery step of the acidified thiourea leaching of gold ore or concentrate in the presence of carbon followed by elution of the carbon by thiosulfate or thiocyanate.

Research Highlights Initial gold leaching rate of the order of 10 − 9 mol cm − 2 s − 1 was obtained in the mixed thiourea–thiocyanate solution and higher than either lixiviant alone. The synergistic effect was attributed to the formation of mixed ligand complex Au(Tu) 2 SCN. Open circuit potentials show that thiocyanate concentration has a great effect on the leaching …

Feb 01, 2011· The gold leaching rate decreases with time and ferric concentration has only a minor effect on the rate of gold dissolution. (2) A u + F e 3 + + 2 S C N − → A u (S C N) 2 − + F e 2 + In thiourea–thiocyanate solutions, the gold leaching rate remains constant with time, which means the mixed ligand exhibits behavior similar to thiourea ...

Thiocyanate gold leaching is an electrochemical reaction which occurs at pH 1.5–2.5 and electrochemical potential of 600–700 mV. The literature shows fast gold leaching kinetics in well ...

Keywords: boulangerite ore, gold leaching, ammonium thiocyanate Introduction The demand for gold is constantly increasing due to its widespread use in electronic devices, jewellery and as economy. Consequently, its recovery from the relevant ores has become more important over the last few decades. Solvent extraction of gold from leach liquors

Generally, gold leaching using thiocyanate (0.01–0.05 M) occurs at a potential of 0.4–0.45 V, pH 1–3, in the presence of an oxidant like ferric ions (2–5 g/L) or peroxide. It has been shown that, under optimal conditions, a gold extraction yield of 95% can be achieved . Thiocyanate concentrations in the range of 0.5 to 5 g/L and Fe (III ...

4.2.2 The gold leaching behavior 92 4.2.2.1 Gold head grade 95 4.2.3 The pH variation 97 4.2.4 Free cyanide concentration in the effluent solution 103 4.2.5 Thiocyanate in the effluent solution 110 4.2.6 The iron behavior 116 4.3 Conclusions 120 5 Experimental results and discussions - …

Thiocyanate gold leaching is an electrochemical reaction which occurs at pH 1.5–2.5 and electrochemical potential of 600–700 mV. The literature shows fast gold leaching kinetics in well ...

Thiocyanate gold leaching is an electrochemical reaction which occurs at pH 1.5–2.5 and electrochemical potential of 600–700 mV. The literature shows fast gold leaching kinetics in well ...

Commissioning milestone for First Gold successfully achieved Complex brownfield demolition, construction and tie-in works completed with minimal unplanned interruption to operations World's first use of resin in leach technology for thiocyanate leach

This study focused on evaluating sodium thiocyanate as an alternative reagent to the conventional cyanidation process for leaching of gold ores. Goldcorp's Coffee project in Yukon-Canada supplied three mineral samples namely, Supremo Oxide 68151, Supremo oxide 68151, Supremo Composite 72142 for this study. As a baseline for comparison with thiocyanate …

Generally, gold leaching using thiocyanate (0.01–0.05 M) occurs at a potential of 0.4–0.45 V, pH 1–3, in the presence of an oxidant like ferric ions (2–5 g/L) or peroxide. It has been shown that, under optimal conditions, a gold extraction yield of 95% can be achieved . Thiocyanate concentrations in the range of 0.5 to 5 g/L and Fe (III ...

Barbosa-Filho, O. and Monhemius, A.J. (1988) Thermochemistry of Thiocyanate Systems for Leaching Gold and Silver Ores. In Jha, M.C. and Hill, S.D., Eds., Precious ...

Provided is a method for regenerating cyanide from thiocyanate. The method comprises contacting the thiocyanate with an oxidizing gas containing ozone, generally a mixture of oxygen and ozone. The pH of the contacting medium is generally less than 7.0 to assure that HCN is the predominant species relative to CN - . The method has important applications to processes …

leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent accidental spills from contaminating soils as well as surface and ground waters. Various methods of cyanide remediation by separation and oxidation are ... cyanide, metal-cyanide complex, thiocyanate, oxidation, separation

leaching of gold and uranium, which would have obvious economic advan­ ... thiourea, thiosulphate, and thiocyanate complexes. These are the only ligands that are likely to compete with cyanide in the large-scale processing of gold ores, and they are likely to become more important, since increased atten­ ...

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Before leaching the gold, ore must be crushed and grinded into small particles, usually particle size varies between 30 and 180 μm. Free milling ores are ready for leaching after crushing and grinding whereas refractory ores need pretreatment. It is important to pretreat a refractory ore before leaching to achieve better gold extraction.

Keywords: gold leaching, ammonium thiosulfate, chloride, thiourea, thiocyanate Introduction The most common hydrometallurgical methods of primary raw material utilization in the production of gold are based on the use of cyanide (Hilson, 2006). In this method a weak sodium cyanide solution (NaCN) of 100-500 ppm is used. Since the Baia Mare

A process is disclosed for the direct recovery of gold from thiourea, thiocyanate or thiosulfate solutions or acidified thiourea leach liquor. The process comprises reduction precipitation of the gold from solution by the addition of stabilized alkali metal borohydride, preferably sodium or potassium borohydride, at ambient temperature and pressure.

The leaching of gold in thiourea-thiocyanate solutions has been studied by the rotating-disc technique using ferric sulfate as oxidant. The effects of initial concentrations of ferric, thiourea (Tu) and thiocyanate as well as temperature and pH on gold leaching rates were studied. An initial gold leaching rate in the order of 10− 9 mol cm ...