The main advantages of thiosulphate leaching compared with other methods are the low toxicity, high reaction selectivity, ability to recirculate the leaching solutions, lower reagent cost and the possibility to recover the dissolved gold by adsorption and electrodeposition [8, 33].
The new process also can be used to extract gold from consumer electronic waste. Current methods for gold recovery involve the use of highly poisonous cyanides, often leading to contamination of the environment. Nearly all gold-mining companies use this toxic gold leaching process to sequester the precious metal.
In a leach solution containing 20 % HCl and 20 g/L NaCl, 97 % of the gold was extracted in 6 hours with 90 kg/t available chlorine and 95 % of the gold was extracted in 18 hours with 45 kg/t available chlorine. For a refractory ore, pretreatment is required in order to expose the gold surface to the leach solution.
In this work, sodium dicyanamide (SD) was used as a leaching reagent for gold recovery, and the effects of the SD dosage and solution pH on the gold-leaching performance were investigated. A gold recovery of 34.8% was obtained when SD was used as the sole leaching reagent at a dosage of 15 kg/t. In the presence of a certain amount …
The recovery of gold by ore leaching is influenced by the size of the particles and the chemical environment. The effect of particle size on the dissolution of gold is usually studied using mono-size particles as the gold in solution comes from the ore of a unique leached particle size. This paper proposes a method to estimate the gold …
Researchers investigated the effect of calcium hydroxide and sodium hydroxide on the rate of dissolution of gold in cyanide solutions containing 0.10% NaCN. Their work was done on gold discs having a surface area of 10 sq. cm.; 100 ml. of cyanide solution was used and this was aerated continuously throughout the tests.
Gold Leaching Process Circuit NO. CY-1. This leach plant shows the continuous counter-current decantation system, in which all the ore is first reduced to a very fine state in the grinding mill-classifier circuit, in a Gold Leaching solution.
Thiosulfate leaching has been regarded as a promising alternative to cyanidation, but it still faces the challenge of the recovery of low content of gold from …
The consumption of cyanide during processing operations is a major economic cost in the extraction of gold from its ores, while the discharge of cyanide wastes may result in significant environmental pollution. Many factors influence the levels of consumption and discharge of cyanide, including ore mineralogy and lixiviant solution …
The heap leach cyanidation carbon adsorption electrowinning process developed has proved to be an economical method for exploiting low-grade gold ores and small isolated deposits not suitable for treatment by conventional cyanidation procedures.
The hot solution is allowed to cool (heat is recovered by heat exchangers for preheating feed to leaching) and Al(OH) 3 precipitates from solution. (Prior purification processes are needed as well, especially to remove silica, i.e. SiO 2, dissolved from clay minerals.
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 …
Cyanide is then used to separate the gold from the ore into the leached solution. With the new process, the leaching and recovery process is done with chloride, one of two elements in table salt ...
Leaching. Heap Leaching of Uranium; Solution Concentration and Purification; Metal Recovery; Contributors and Attributions; Hydrometallurgy involves the use of aqueous chemistry for the recovery of metals from ores, concentrates, and recycled or residual materials.This process is used in extraction of less electro positive or less …
The possibility of carbon-free recovery of gold from glycine leaching solution by the EDRR method was demonstrated for the first time in glycine media, using both synthetic solution and PLS obtained in optimum leaching conditions. The copper concentration in the final leach solution was relatively low (15 mg/L), and this can …
The use of citrate as an alternative reagent to ammonia in thiosulfate solutions offers an environmentally friendly, nontoxic, and cost-effective leaching method …
Thiosulfate leaching has been regarded as a promising alternative to cyanidation, but it still faces the challenge of the recovery of low content of gold from high concentrations of thiosulfate solutions. Liquid–liquid extraction is a method to address this issue but is still limited by the use of volatile and toxic organic solvents. To overcome …
Gold Leaching Through the Chloride-Hypochlorite Solutions. The effect of the sodium chloride (NaCl) concentration on the gold leaching through the sodium …
To concentrate and/or purify the leaching solutions loaded with PGMs, solvent extraction (SX) (or liquid–liquid extraction) is one of the unit operations mostly applied in hydrometallurgy to recover palladium and platinum from leaching solutions of spent catalysts . Accordingly, SX is the chosen unit operation to be explored in this review.
This article will focus on the alkaline leaching of gold-bearing tetrahedrite concentrate in a solution containing sodium sulfide and sodium hydroxide. This selective leaching is followed by the leaching of heavy and waste metals into the solution, which may influence the physical properties and quality of the desired product, possibly …
Dissolved gold is first separated from the impurities in leach solutions by selective adsorption onto activated carbon, or an ion exchange resin, or extracted into a water …
Figure 12b shows the leaching efficiency of gold at different leaching times with a constant sodium cyanide dosage of 1.75 kg/t. It can be seen from Figure 12a that the leaching efficiency of gold increases with increasing leaching time. When leaching time is more than 27 h, the leaching efficiency of gold does not significantly increase.
In recent years, the utilization of thiosulfate solutions (S 2 O 3 2− ) for gold leaching has been extensively researched as a substitute for the traditional cyanide leaching process [1][2][3][4 ...
Currently, the thiosulfate gold leaching operation at the Goldstrike mine, Nevada, of Barrick Gold Corp is the only large-scale gold extraction plant with an alternate lixiviant (Azizitorghabeh et al., 2021). Although research on sulfur-containing lixiviants has been the most common in gold hydrometallurgy in the past three decades, few ...
In simplified terms, the Effect of Oxygen on Gold Leaching can be summarized in saying: The dissolution rate of gold in alkaline cyanide solutions under atmospheric conditions, and at practical cyanide levels, is directly proportional to the dissolved oxygen concentration. The rate of dissolution of gold in alkaline cyanide …
The Process Flowsheet CCD CY-1 shows (below) the continuous counter-current decantation system, in which all the ore is first reduced to a very fine state in the grinding mill-classifier circuit, in a cyanide solution.The slime overflow of the classifier, usually 70%—200 mesh, or finer, is sent to the first thickener, known as the primary …
This paper aims to review the extraction of gold using alternatives to cyanide with focus on NESGLs. The paper starts with an overview on the non-cyanide gold lixiviants. Then it summarizes and discusses in detail the gold extraction efficacy, …
This review aims to provide an up-to-date evaluation of thiourea-gold leaching studies from electronic waste, with emphasis on the recent progression from the classic …
The substitutes for cyanide can be classified as traditional and novel non-cyanide gold leaching reagents. The traditional alternatives mainly include thiourea, halide, polysulfide, thiocyanate, lime sulfur synthetic solution (LSSS), and thiosulfate (Hilson and Monhemius, 2006, Sun et al., 2020, Xing et al., 2019).Although considerable …
Gold is mostly obtained through leaching operations from Au-bearing minerals using cyanide salts . Lately, with the development of the electronic industry, the recovery of gold from electronic waste has also gained attention . The traditional gold leaching method is cyanidation.