Sb, combining with agitating by a magnetic stirrer, ika eurostpcus25. The gold industry has been seeking alternative reagents for leaching gold from lowgrade ores for the past 25 years. Us8597399b2 method for thiosulfate leaching of precious. The results for leaching gold with alternative reagents, sodium thiosulfate and ammonium hydroxide, show that the best extraction was achieved at 0. The results showed that pyrite catalyzed the decomposition and also significantly increased the consumption of thiosulfate. Barrick thiosulfate leaching of double refractory ore. Optimizing the thiosulfate leaching of gold from printed. This detrimental effect became more severe with increasing pyrite content. Thiosulfate leaching can be considered a nontoxic process, the gold dissolution rates can be faster than conventional cyanidation and, due to the decreased interference of foreign cations, high. Leaching of gold, silver and accompanying metals from circuit. Pdf leaching of gold from the waste mobile phone printed circuit. Gold leaching in thiosulfate solutions and its environmental. Ammonium thiosulfate ecological alternative to replace.
The modes of gold loss in the calcium thiosulfate leaching system. Please use one of the following formats to cite this article in your essay, paper or report. Leaching of middlerefractory gold ore show that both of the consumption of thiosulfate and leaching rate was decreased compare to the traditional copperammonia thiosulfate system. It is an important step in the gold mining industry, and widely receiving attention and congratulations. Results show that the anodic oxidation of thiosulfate ions is an inreversible reaction whose. Effects of ammon, copperammon ions, ph and sulphite on anodic oxidation of thiosulfate ions have been examined in details. In order to decrease the consumption of lixiviant, study on dissolution of pure gold and middlerefractory gold ore using a novel thiosulfate leaching system with ferricyanide as oxidant was carried out. The role of oxygen in thiosulphate leaching of gold. Roasting the sulphides increases the thiosdphate stability and gold extraction capacity. The influence of thiosulfate, ammonia and copper sulfate concentrations on the leaching of gold from pcbs of waste mobile phones was investigated. Leaching of gold, silver and accompanying metals from.
Chief metallurgists janet baron and averne flahartyescobar, director of strategic technology solutions yeonuk choi and senior director of strategic technology solutions peter kondos accept the metsoc innovation award on behalf of their team that developed the thiosulfate. The processes can employ lixiviants that include at most only small amounts of copper andor ammonia and operate at a relatively low ph, reduction of polythionates, inert atmospheres to control polythionate production, and electrolytic solutions which provide relatively high rates of. Effect of pyrite on thiosulfate leaching of gold and the. The results showed that the advantage of the novel system is that the thiosulfate consumption is negligible though the potential of ferricyanide is much higher than that of traditional cupric. As you may have heard barrick gold has recently published an article on their patented thiosulfate leaching process, entitled theres a first time for everything for the extraction of gold at their goldstrike mine in nevada, usa. Study on the leaching of mercuric oxide with thiosulfate solutions. Leaching of gold from the waste mobile phone printed circuit. Unlike cyanide, which is highly toxic, the chemicals used in the thiosulfate leaching process are benign. In artisanal gold mining, mercury is used to extract gold from ore, which always results in severe. Feng university of science and technology, liaoning, anshan, china received august 15, 2017, revised november 15, 2017 the effect of additives on gold leaching was investigated using ammonium thiosulfate or calcium thiosulfate. Although not as aggressive a leaching agent as cyanide, thiosulphate offers several technological advantages including its lower toxicity and greater efficiency with gold deposits associated with pregrobbing ores.
The effects of some associated minerals on thiosulfate gold leaching were. In this study, trioctylmethylammonium chloride tomac was used as an extractant to. Electrochemical study of the gold thiosulfate reduction. In the leaching test on the reference gold ore, about 93% of gold was extracted within 3. Once an experiment finished, the pulp was filtered in a press filter. Pretreatment enables to achieve for the ammonium thiosulphate leaching with ammonium 98 % gold and 93 % silver extraction after 48 hours of leaching fig. The leaching behavior of hgo in thiosulfate solutions under different experimental conditions temperature, thiosulfate concentration. Ammonium thiosulfate ecological alternative to replace sodium. Results show that the anodic oxidation of thiosulfate ions is an inreversible reaction whose oxidizing. The regularities of anodic oxidation of thiosulfate ions on a gold electrode have been investigated using electrochemical methods in order to improve gold extraction. The present work deals with the recovery of gold using ammonium thiosulfate as a leaching agent from waste mobile pcbs containing 0.
In the leaching test on the reference gold ore, about 93% of gold was extracted. Thiosulfate leaching of middlerefractory gold ore with. At full capacity,400 tons of ore can be processed daily, with leaching taking place simultaneously in two sets of seven tanks. The conventional cyanidation process in gold leaching has been used since 1887. Leaching of gold and silver from printed circuit board of. Leaching of sludge from the avr process with ammonium. Associated sulfide minerals in thiosulfate leaching of. However, gold cyanidation process has serious environmental risks if an accident occurs in the process because of the toxicity of cyanide. The processes can employ heap leaching or lixiviants that include one or more blinding agents. Treatment of a polysulphide ore by ammoniacal thiosulfate solutions and ion flotation for gold recovery 84 were added up to the iodine solution became colorless. During leaching ferric oxide, iron hydroxide and elemental sulfur will be in solids and copper in solution acting as oxidizer oxygen rejuvenating the cupric ion and gold will be left with the thiosulfate if this leach is working and if all conditions are maintained in solution, thiosulfate lixiviants. Processes are provided for recovering precious metals from refractory materials using thiosulfate lixiviants. Within the tanks, the slurry interacts with thiosulfate and a fine, beadlike material called resin that collects the gold.
An electrochemical and sers study of the goldthiosulfate. There exist encapsulated materials and gold present in microscopic pyrites and arsenopyrites. Jun 27, 2006 method for thiosulfate leaching of precious metalcontaining materials. In addition, thiosulfate can be cheaper than cyanide.
Oct 06, 2016 first time any company in the western world produces gold on a commercial scale using thiosulfate from left to right. Nioshtic2 publications search 10011646 coppercatalyzed. Thiosulfate leaching can be considered a nontoxic process, the gold dissolution rates can be faster than conventional cyanidation and, due to the decreased interference of foreign cations, high gold recoveries can be obtained from the thiosulfate leaching of complex and carbonaceoustype ores. The sodium metabisulphate lowers the ph of the solution, turning the gold liquid into gold powder. Treatment of a polysulphide ore by ammoniacal thiosulfate. Many researchers have identified that thiosulfate leaching is the most likely alternative to cyanidation due to nontoxicity, low cost and other benefits. Even though thiosulphate leaching has a potential in gold leaching, there is one major problem remaining and that is a high consumption of thiosulphate during gold leaching. Your browser doesnt seem to have a pdf viewer, please download the pdf to. Gold sodium thiosulfate is a fairly common sensitizer with elicitation of symptoms linked to gold in jewelry, occupational exposure to gold, dental restorations, gold plated intracoronary stents and previous rheumatoid arthritis treatment. The effect of cuii ions addition on silver leaching from solid residue after pressure leaching was investigated at thiosulfate and ammonia concentrations of 0. It confirms the possibility of thiosulfate leaching application for silver extraction. Us8097227b2 method for thiosulfate leaching of precious. The reduction voltammograms were obtained on a stationary gold electrode at ph 4. Effect of pyrite on thiosulfate leaching of gold and the role.
As one of the typical inorganic mercuric compounds, mercuric oxide was chosen for research in this paper. Study on the leaching of mercuric oxide with thiosulfate. Sulphide minerals were responsible for lower gold extraction and thiosulphate consumptioe the increase of oxlde minerais consumes more thiosulp hate. The proposed method of the gold recovery comprises leaching with a solution of a mixture of sodium and ammonium hydrosulfite and thiosulfate, by sorption of the thiosulfategold complex on a highly basic anion exchanger and by isolation of the highly basic anion exchanger, the sorption being carried out 210 hours after the leaching. The effect of pyrite and the role of ammonium alcohol polyvinyl phosphate aapp during gold leaching in ammoniacal thiosulfate solutions were investigated using pure gold foils. Reagent consumption is one of the major factors affecting the feasibility of the process to the actual operation yen et al. The effects of some associated minerals on thiosulfate gold leaching were studied through thermodynamic analysis and leaching experiments on composite ore samples containing various minerals and a reference silicate gold ore. Effect of additives on thiosulfate leaching of a gold ore. A method for leaching or dissolving gold from ores or. The role of ligands and oxidants in thiosulfate leaching. Thiosulfatecopperammonia leaching of pure gold and pressure. During leaching ferric oxide, iron hydroxide and elemental sulfur will be in solids and copper in solution acting as oxidizer oxygen rejuvenating the cupric ion and gold will be left with the thiosulfate if this leach is working and if all conditions are maintained in solution, thiosulfate leaching can be considered a nontoxic process, the gold dissolution rates can be faster than conventional cyanidation and, due to the decreased interference of foreign cations, high.
Anodic oxidation of thiosulfate ions in gold leaching. The gold leaching process followed the pseudosecond order kinetic model at the low concentration range of the reactants such as 4060 mm thiosulfate, 57 mm copperii and 0. Leaching of gold from the waste mobile phone printed. The models predicted 90pct gold extraction and a consumption of 0. Also, it was found that in thiosulfate solutions containing thiourea, the oxidation current of gold silver alloys decreased and the oxidation current from pure gold after the standard potential for gold oxidation 150 mv is higher than the total oxidation current from gold silver alloys. Method for thiosulfate leaching of precious metalcontaining. The proposed method of the gold recovery comprises leaching with a solution of a mixture of sodium and ammonium hydrosulfite and thiosulfate, by sorption of the thiosulfate gold complex on a highly basic anion exchanger and by isolation of the highly basic anion exchanger, the sorption being carried out 210 hours after the leaching. The mnieral content of the ore dso infiuenced the gold extraction capacity. Therefore, a method for leaching or dissolving gold from ores or precious. The effects of some associated minerals on thiosulfate gold leaching were studied through. For this pro pose, the gold leaching reagents are described and discussed in terms of their environmental and economical points of view. The reduction of gold thiosulfate was studied as an alternate gold complex for plating baths. Associated sulfide minerals in thiosulfate leaching of gold.
Process for the recovery of gold and silver from used refractory bricks. Chlorination, aqua regia, bromine, thiocyanate, thiosulfate and thiourea leaching. Electrochemical model for the leaching of gold using ammoniacal thiosulfate leach. It is currently the main gold leaching process in the world. Processing innovation nets metallurgy award barrick gold. The role of ligands and oxidants in thiosulfate leaching of gold. Thiosulphate leaching is a process that removes gold from gold bearing ores without the use of cyanide. Filter the water again using a fine gold filter and dump the water into another bucket and not onto the ground or down the drain. Gold sodium thiosulfate is a fairly common sensitizer with elicitation of symptoms linked to gold in jewelry, occupational exposure to gold, dental restorations, goldplated intracoronary stents and previous rheumatoid arthritis treatment. The cost and transport of cyanide, the poor recovery of gold from carbonaceous ores, the lack of selectivity of cyanide towards copper minerals and the cost of waste treatment are real factors which can make cyanide unattractive in some circumstances. Us8097227b2 us12683,967 us68396710a us8097227b2 us 8097227 b2 us8097227 b2 us 8097227b2 us 68396710 a us68396710 a us 68396710a us 8097227 b2 us8097227 b2 us 8097227b2 authority us united states prior art keywords precious metal thiosulfate calcium leach solution pregnant leach prior art date 20021115 legal status the legal status is an assumption and. Thiourea is not stable in base solution, but it was found that gold dissolution rates can be increased with a little thiourea,the mechanism is still unclear.
Effect of additives on thiosulfate leaching of a gold ore s. Leaching by thiosulfate decreases interference from these foreign cations. High consumption of reagents and the lack of a cheap process for recovering gold have made thiosulfate leaching. Therefore, by combining the expressions for the rate constants and the. Gold extraction was found to be enhanced with solutions containing 1520. Feb 26, 2019 please use one of the following formats to cite this article in your essay, paper or report. Thiosulfate leaching of gold ores has great potential to reduce the impact on the environment. Ammonium thiosulfate ecological alternative to replace sodium cyanide in gold and silver dissolution in lowgrade ores, m. Associated sulfide minerals in thiosulfate leaching of gold qspace. Pdf thiosulfate leaching of gold from waste mobile. Pdf thiosulphate leaching for gold hydrometallurgy. One such ewaste, the mobile phone printed circuit boards pcbs contain various precious metals which can be extracted by different hydrometallurgical routes. Ultimately, the processes of gold leaching from refractory ores and gold. Despite the fact that the gold mining industry accounts for only % of total cyanide consumption there is growing public concern over the use of toxic cyanide for gold extraction.