This paper deals with the recovery of gold from waste printed circuit boards (WPCBs) ash by high-pressure oxidative leaching (HPOL) pre-treatment and iodide leaching followed by reduction precipitation. Base metals present in WPCB ash were removed via HPOL using a diluted sulfuric acid solution at elevated temperatures. Effects …

Groudev et al. (1999) used solutions that contained amino acids of microbial origin and thiosulphate to leach the gold and silver from oxide ores that contained 3.5 g/t of gold and 14 g/t of silver. First, an alkaline solution (pH 10–10.5) was irrigated on the top of the heap to stabilize the pH.

This study evaluated the ability of two IOB sourced from a commercial culture collection, Roseovarius (R.) tolerans DSM 11457 T and R. mucosus DSM 17069 T, to bioleach gold from electronic waste (e-waste) (1030 ppm gold) and sulfidic gold ore concentrate (45 ppm gold) using one-step, two-step and spent medium leaching at 1% …

Thiosulfate is a green gold leaching agent that shows great potential to replace the highly toxic cyanide. Ammonia is traditionally used as the copper ligand in thiosulfate solutions to reduce the reactivity of copper ions towards thiosulfate, but it is a toxic reagent. As a result, efforts to replace ammonia with another complexing agent …

Effect of different pH ranges in gold leaching by chloride —hypochlorite solutions ( a) as well as distribution of HClO species as a function of pH. Experimental conditions were 25 g/L of Ca (OCl) 2 and 15 g/L of NaCl, 10% of solids (w/v), −37.0 µm at room temperature. Full size image.

Following leaching, gold ions remain dissolved in the solution, together with other elements. It is necessary to recover gold ions from this solution, separating them from the other dissolved metals present. This section of the paper reviews some of the most common methods used to recover gold from leaching solution. 5.1. Activated carbon (AC)

In this study, the following leaching parameters were tested to optimize the gold recovery for the first time from an oxide ore using the response surface methodology: initial thiocyanate ...

The literature contains various information in processing complex gold-copper ores. For instance, the classification of complex gold ores into cyanide-consuming minerals, oxygen-consuming minerals, and preg-robbing materials was provided by the previous investigators [16, 17].The solubility of copper minerals in cyanide solution varies …

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 …

Two examples are cerric sulfate, i.e., Ce (IV) in sulfuric acid solution (E° = 1.44 V) and KMnO4 (E° = 1.51 V). However, experience confirms that both Au + and Au +3 are …

Cyanide-free mild chloride leaching was investigated. •. Gold could be recovered even at <520 mV vs. Ag/AgCl in carbon-in-chloride-leach mode. •. Copper was a stronger oxidant than iron in gold leaching. •. Gold was oxidized by in-situ dissolving impurities. •. Seawater contains enough chlorides to dissolve gold.

The nature of gold (Au) ore deposits plays an essential role in determining the best gold recovery method as an alternative to cyanidation, considering environmental concerns. Thiourea (Tu) leaching of gold is an alternative lixiviant for treating sulfide gold ores and concentrates. The present study investigated the leaching behavior of Au from sulfide …

Cyanide is a lixiviant, or reagent that is used to leach, often in tanks, gold from a solid matrix and form a gold cyanide complex. The gold cyanide complex is then extracted from the pulp or slurry by adsorption onto activated carbon. CIL stands for carbon-in-leach. This is a gold extraction process called cyanidation where ... Gold CIL …

Gold (Au), a precious and chemically inactive metal, occupies an essential position in jewelry, economy, and industrial technology due to its brilliant color, high …

The application of pressure oxidation (POX) followed by thiosulfate gold leaching is an efficient method used to extract gold from double refractory gold ores containing both sulfide and carbonaceous matter. This process is expected to result in high gold recovery rates, as it liberates gold from sulfides and eliminates the preg-robbing …

Gold leaching using thiourea (0.4 M thiourea, pH 1.5, 3 h) following pretreatment using HCl and Citrate and no pretreatment, M. Reprinted with perimission from [66]

The leaching of gold from copper leach residues reached 99 % efficiency at 40 °C for 90 min. Based on this, Lu et al. optimized the pretreatment of copper removal as well as parameters of gold leaching using a mixture of NaClO 3, H 2 SO 4, and NaCl for further separation and recovery of gold using liquid–liquid extraction (LLE) and ...

Gold leaching in iodine-iodide solution has been intensely researched in 1980s; while due to the high cost, it has not been applied in industry. Currently, as the drawbacks of other hydrometallurgies appearing such as aqua regia and cyanidation, mining and exploration companies are shifting their attention to the iodide leaching, …

Another method that is also used to separate gold from ore in industry and small-scale gold mining is the cyanide leaching method [7, 8]. Leaching is the process of separating a solid that is ...

A suitable replacement for cyanide leaching is thiourea leaching. Thiourea in an acidic solution dissolves gold to form a complex. The addition of a catalyst, ferric sulfate, increases the oxidation of gold. The reaction proceeds according to the equation: Au 0 + 2SC (NH 2) 2 → Au [SC (NH 2) 2] 2+ + e −.

The oxidation of gold by oxygen is a slow process in non-cyanide media and highlights the need for a redox mediator such as the copper(II)/(I) couple (Ritchie et al., 2001).However, the use of a mixed copper(II)–ammonia–thiosulphate–oxygen system poses a challenge on kinetic analysis, as it requires consideration of the reactions between …

This will facilitate the subsequent gold leaching process. 3.3. The Effects on Gold Leaching Efficiency. As mentioned above, the arsenic was removed in the first stage roasting process at temperature 550 ℃, air flow rate 0 L/min and roasting time 1 h. The sulfur was removed in the second roasting process at 700 °C, air flow 2.5 L/min with ...

The gold leaching reaction by thiosulfate without additives is shown in Eq. (4). (4) 4Au + 8S 2 O 3 2-+ O 2 + 2H 2 O → 4Au(S 2 O 3) 2 3-+ 4OH-Thiosulfate and oxygen act as ligands and oxidants, respectively. The leaching efficiency is low due to passivation in which catalysts are required (Zhang and Nicol, 2003). The copper …

10 interesting, and terrifying facts about cyanide: 1. Cyanide was used as a chemical weapon for the first time in World War I. 2. Low levels of cyanide are found in nature and in products we ...

Thiocyanate (SCN–) is a promising alternative to cyanide as a lixiviant for gold extraction and is 1000 times less toxic than cyanide. In this study, the following leaching parameters were tested to optimize the gold recovery for the first time from an oxide ore using the response surface methodology: initial thiocyanate concentration (10–500 mM), initial …

The disadvantages of using organic nitriles for gold leaching are volatility, toxicity, high cost, and difficulty in recovering gold from the leaching solution. Gold leaching using ionic liquids has become a research topic in recent years (Feng et al., 2021, Teimouri et al., 2020). Ionic liquids are composed of organic cations and inorganic or ...

Currently, leaching, particularly cyanide leaching, is the dominant extraction process for gold. More than 83 per cent of the world's gold is extracted via cyanidation …

Gold hydrometallurgy. Cyanidation. Alternative leaching reagents. Sustainable Mineral Processing. 1. Introduction. Gold is the most important precious …

Th e gold leaching reaction by thiosulfate without additives is shown in Eq. (4). 4Au + 8S 2 O 3 2-+ O 2 + 2H 2 O → 4Au(S 2 O 3) 2 3-+ 4OH-(4) Thiosulfate and oxygen act as ligands and oxidants ...

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-designed thiocyanate systems. The solubilized gold-thiocyanate species can be recovered from the pregnant leach solution by a variety of methods …

Nearly all gold-mining companies use this toxic gold leaching process to sequester the precious metal. "The elimination of cyanide from the gold industry is of the utmost importance environmentally," said Sir Fraser Stoddart, the Board of Trustees Professor of Chemistry in the Weinberg College of Arts and Sciences. "We have …

Abstract: Gold leaching is an important process to extract gold from ore. Conventional alkaline cyanide process and alternative nontoxic lixiviants including …

Gold leaching rate is fast, and the leaching usually finishes in 4–6 h. There are few interfering ions. Thiourea leaching has a good adaptability for various gold ores and are suitable to treat silver-rich gold ores, complex ores that are pretreated by bio-oxidation or hot-press oxidation, and gold ores that are difficult to be treated by ...

A gold ore sample originated from an epithermal deposit with a composition shown in Table 2 was used as a feed material in the leaching experiments. X-ray fluorescence and inductively coupled plasma optical emission spectrometry (ICP-OES; Thermo Scientific iCAP 6000, USA) were used to determine the chemical composition of …

Oxidative thiosulfate leaching using Cu(II)-NH3 has been explored for both mining and recycling applications as a promising method for Au extraction. This study seeks to understand the dissolution behavior of Au from waste RAM chips using a Cu(II)-NH3-S2O3 solution. In the course of this work, bimodal leaching and Au loss were observed …

Cyanide is a lixiviant, or reagent that is used to leach, often in tanks, gold from a solid matrix and form a gold cyanide complex. The gold cyanide complex is then extracted from the pulp or slurry by adsorption onto activated carbon. CIL stands for carbon-in-leach. See more

Gold leaching is an important process to extract gold from ore. Conventional alkaline cyanide process and alternative nontoxic lixiviants including thiosulfate, thiourea, thiocyanate, and halogen have been widely investigated. However, density functional theory (DFT) study on the gold complexes Au(CN)2−, Au(S2O3)23−, …

There are a considerable number of gold leaching methods which are currently tested or developed as pilot-scale studies, but only a few are available on …

The leaching behavior of gold from an oxide gold ore using copper–tartrate–thiosulfate solutions has been investigated. Experimental parameters, including temperature, initial pH, and concentrations of copper tartrate and thiosulfate, were systematically studied. The capability of gold leaching using copper–tartrate–thiosulfate …