Improved thiourea leaching of gold from a gold ore using additives

The global commercial drone market is experiencing rapid growth, particularly in precision agriculture applications such as crop spraying. This market is projected to expand at an 8.3% compound annual growth rate (CAGR), contributing to an overall drone market value of approximately $55.8 billion by 2030. Agricultural drones are made of various materials including electronic waste components such as circuit boards, connectors, and pins, containing significant amounts of gold. While gold cyanidation is the primary method for gold extraction, there is a growing interest in more environmentally friendly alternatives. This study focuses on extracting gold from pins using thiourea-based leaching with temperature variation and ultrasound agitation, comparing it to conventional cyanide processes. The process begins with the X-ray fluorescence analysis of drone components to detect gold. The gold concentration in pins is measured through aqua regia digestion (1:25 ratio, 70°C, 2 h). Cyanide leaching is conducted at 25°C for 2 h at pH 14, with a 1:25 mass ratio, while Thiourea leaching is performed at a 1:10 ratio for 2 h and pH 1, under different conditions: varying temperature and ultrasonic agitation. Cyanide digestion shows about 83 ppm of gold, setting a standard recovery benchmark of 100%. In contrast, aqua regia yields 66.8%. The thiourea leaching's efficiency, influenced by temperature and agitation, sees its highest gold recovery at 43.19% of the cyanide standard, with ultrasonic agitation, although overall performance is below cyanide yields. Further research is needed to enhance gold recovery through thiourea based leaching, focusing on optimizing the temperature parameters and leaching conditions.

Gold recovery enhancement from a refractory flotation concentrate by sequential bioleaching and thiourea leach

Thiourea leaching of gold in presence of jarosite and role of oxalate

To address the challenges of high reagent consumption and environmental risks in traditional cyanide gold extraction, this study investigated the leaching of gold from an oxide ore sourced from a gold mine in Laos using an iron ion-thiourea-thiocyanate additive system. The effects of key process parameters (thiourea concentration, iron ion concentration, thiocyanate ion concentration, pH, stirring speed, liquid-solid ratio, and leaching time) on gold leaching rate and thiourea consumption were systematically examined. Additionally, the mechanism of thiocyanate action and the evolution of mineral surface properties before and after leaching were analyzed via X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). The optimal leaching conditions were determined as follows: thiourea concentration 0.2 M, iron ion concentration 0.003 M, thiocyanate ion concentration 0.001 M, pH 1.5, stirring speed 250 rpm, liquid-solid ratio 4, and leaching time 6 h. Under these conditions, the gold leaching rate reached 93.1 %, which was higher than that of the cyanide process (91.6 %, 24 h) and thiosulfate process (86.4 %, 4 h). XPS results showed that thiocyanate complexed with Fe 3+ to regulate its electrode potential, reducing the oxidation of thiourea and inhibiting the formation of S 2− (a passivating species) on the ore surface. SEM observations confirmed that the leaching system corroded the ore surface, forming gullies and cracks that promoted mass transfer. Notably, the addition of thiocyanate significantly reduced thiourea consumption but slightly decreased the gold leaching rate, requiring a balance between reagent cost and extraction efficiency. This study provides a feasible and environmentally friendly non-cyanide gold extraction technology for oxide ores, offering theoretical and experimental support for industrial application.

Carbonaceous sulfidic gold ores are commonly double refractory and thus require pretreatment before gold extraction. In this paper, the capacity of pre-bio-oxidation can simultaneously decompose sulfides or deactivate carbonaceous matters (CM) from a double refractory gold ore (DRGO) using pure cultures of A. ferrooxidans or L. ferrooxidans, and a mixed culture containing A. ferrooxidans and L. ferrooxidans was investigated. The results showed that direct thiourea leaching of the as-received DRGO yielded only 28.7% gold extraction, which was due to the encapsulation of sulfides on gold and the gold adsorption of CM. After bio-oxidation, thiourea leaching of the DRGO resulted in gold extraction of over 75–80%. Moreover, bio-oxidation can effectively reduce the adsorption of carbon to gold. XRD, SEM-EDS and FTIR analysis showed that many oxygen-containing groups were introduced on the surface of DRGO during bio-oxidation, while the C=C bond was cleaved and the O–C–O and C–N bonds were degraded, causing a decrease in active sites for gold adsorption. Moreover, passivation materials such as jarosite were formed on the surface of DRGO, which might reduce the affinity of CM for gold in solutions. In addition, the cleavage of the S–S band indicated that sulfides were oxidized by bacteria. This work allows us to explain the applicability of pre-bio-oxidation for degrading both sulfides and CM and increasing gold recovery from DRGO in the thiourea system.

P.6.b.014 Alcohol misuse and eating disorders: a pilot study in a sample of Italian young adults

A novel non-cyanide extraction method of gold for high As-Sb-bearing refractory gold ore based on Mn-oxide ore acidic oxidation

The use of thiosulfate to extract gold from refractory ores is promising because of its non-toxicity and high selectivity. Sulfide minerals (i.e., pyrite, arsenopyrite, chalcopyrite), major gold carriers in refractory gold ores, however, hinder gold extraction due to the high consumption of a lixiviant. In this study, a new method to improve gold extraction from sulfide bearing gold ores is proposed based on the model experiments using a mixture of gold powder and arsenopyrite-bearing sulfide (HAsBS) ore. The effects of HAsBS ore on gold leaching in ammonium thiosulfate solutions were investigated, and it was found that gold extraction in the presence of HAsBS ore was suppressed because of the unwanted decomposition of thiosulfate on the surface of sulfide minerals. To improve gold extraction in the presence of the sulfide minerals, this study investigated the effects of the pretreatment of HAsBS ore using ammonium solutions containing cupric ions and confirmed that HAsBS ore was oxidized in the pretreatment and its surface was covered by the oxidation products. As a result, thiosulfate consumption was minimized in the subsequent gold leaching step using ammonium thiosulfate, resulting in an improvement in gold extraction from 10% to 79%.

This laboratory work demonstrates the ability to characterize and pre-treat Sudanese refractory gold ores at Ariab mines to extract the gold with optimal parameters. Characterization studies were performed by AAS, XRF and XRD analysis to assess the abundance of elements and mineral phases. In addition, the acidity of the ore was examined to estimate the effective amount of lime. The ore was subjected directly to cyanidation without any pre-treatment. High oxidation reagent processes were carried out to pre-treat the ore. Chemical analysis results show the gold grade to be 1.37 g/t. In addition, the ore contained 51.78% Fe2O3, 43.40% SO3, 2.39% CuO, 1.47% SiO2, 0.35% Cr2O3, 0.17% CaO, 0.08% As2O3, 0.06% ZnO and 0.06% MnO. The XRD result shows that the ore phases are Pyrite (FeS2), Chatkaite (Cu6Fe+2Sn2S2) and Quartz (SiO2). The investigations of direct cyanidation elucidated that the ore can consume a high amount of cyanide with unsatisfactory recoveries for gold (Exgold ≤39.41%). The influence of the cyanide concentration, pulp density (% by weight), leaching time hr, agitator speed and pH were examined in direct cyanidation experiments. In pre-treatment experiments, the effect of hydrogen peroxide (H2O2) and concentrations on gold recovery was studied. The pre-treatment of the ore with H2O2 achieved a good impact on the gold extraction performance. The higher gold extraction was obtained at hydrogen peroxide (H2O2) 300 ppm, cyanide concentration 3500 ppm, leaching time 10 hr, pH=10.5 and pulp density 40%.

Thiourea Bacillus combination for gold leaching from waste lithium-ion batteries

The leaching kinetics of an oxide gold ore with iodide/iodine solutions

Pongkor Gold Mining has been operated for almost twenty years and produced more than 50 ton of gold. One of important process to in gold processing plant at PT Antam (Persero) Tbk. Pongkor Gold Mining Business Unit is CIL (Carbon In Leach) Process which cyanidation process occur. Pongkor has epithermal low sulfide and clay ore which have its own difficulty to process to get high gold extraction levels. There are many several variables in cyanidation process that can be optimized to increase gold extraction. Variables like free cyanide concentration, dissolved oxygen level, viscosity, and residence time had play role in on gold dissolution rate and gold extraction. Optimization has done gradually and not simultaneously in 2013, some improvements done in Pongkor are decreasing level of viscosity and increasing dissolve of oxygen in CIL circuit by choosing and adding effective materials to increase gold dissolution rate and stabilize residence time for maximizing gold leaching time. Decreasing level. of viscosity and increasing dissolve oxygen means higher dissolution rate will achieved and will give higher gold extraction levels and also impact on getting higher throughput. By that improvements, average gold extraction in 2013 is increase 2.5 - 4 % compare to average gold extraction in 2012. This successful project will be utilized over 300,000 dmt ore/year.

In Tadzhikistan the volume of gold-containing waste converted to gold is 18 tons. This waste is products of amalgamation and cyaniding processes., and with respect to end component content they may be classified as a very rich type of raw material since they contain 1.7–8.5 g/ton of gold, whereas the average gold content in ores extracted for processing in one of the richest deposits of the republic, i.e., Tarror, comprises 2.4 g/ton. In addition, treatment of these dumps does not require crushing and refining since they have adequate coarseness of a finished class. In view of this the research object is goldcontaining waste of Tarror ore and a number of other adjacent deposits that have been accumulated over a long time. Results are provided for the raw material substance composition of the test raw material and the possibilities of using thiourea leaching for processing them. The main process parameters are optimized and the degree of gold extraction at the level of 80% is demonstrated. A fundamental production scheme is presented for processing dumps, including the following operations: preliminary acid treatment; sorption thiourea leaching; desorption; reactivation; electrolysis; melting.

Thermodynamics and technology of extracting gold from low-grade gold ore in system of NH4C1-NH3-H2O

This chapter tests the viability of solutions and holistic processing concepts for secondary raw materials processing via pilot actions, promotes socially acceptable, environmentally responsible and economically viable technologies, and reviews comprehensively the detailed assessment of the work carried out to date for the utilization of bauxite residue. The bauxite residue has been used to treat stockpiles of acid generating coal mining overburden in Western Pennsylvania. Bauxite waste mud can be used in the mining industry in gold extraction by the cyanide method, where it is a very efficient modifier of pH value that has to be kept elevated in the process, while gold, possibly adsorbed on bauxite residue, together with gold in ore, is separated by gravitational sedimentation. The sustainable use of bauxite residue for road construction as an embankment landfill is an attractive option with a high potential for large volume reuse.