Gold Cyanide Research Articles

Ore Characterization and Quality Control Aspects of Gold Cyanidation: The CIL Plant as a Case Study in Sudan

Mineralogical and chemical studies are key to mineral processing because they present the problem of low-grade ores to the metallurgist or mineral processing engineer. Quality control operations are also significant in obtaining good products by flowing the sequences of processes. In this study, the ore was characterized, and quality control issues were discussed. Results showed that the gold grade is 9.7 g/ton, the minerals are mainly silicates, and the pH of the ore is high, which means that without pre-treatment, i.e., roasting, oxidation, etc., it can be cyanided directly. Therefore, the CIL plant could recover more than 90% gold. In quality control of the plant, from each unit at a different time, a representative sample and an accumulative sample were collected and then subjected to analysis like fineness and solid percentage, moisture, and conditions of cyanidation. The results showed steady operation conditions for each unit.

Thiosulfate leaching in carbonaceous gold-bearing ores in Ethiopia

One of the main unit operations in metallurgical processing plant designs is gold leaching. The traditional cyanidation process was chosen and is currently in widespread use. However, the mining sector is looking for lixiviants other than cyanide. Cyanide’s effects on the environment have made it difficult for humans and other biotic creatures to survive. There is now research to discover a substitute for this cyanide. It is currently argued that thiosulfate is a preferable substitute for cyanide. The effectiveness of thiosulfate as a leaching agent in carbonaceous gold-bearing ores in Ethiopia is discussed in this paper compared to cyanide. The study has looked into the advantages of employing thiosulfate over cyanide from a technical, and economic standpoint. The leaching effects of both lixiviants on carbonaceous gold-bearing ores extracted from MIDROC Legadembi Open Pit mine in Southern Ethiopia, Oromia region, were examined in a laboratory experiment. After 48 h of leaching, it was discovered that thiosulfate has a better and quicker recovery of 91.54% over 61.70% of cyanide recovery. Tables and graphs are used to demonstrate thiosulfate’s technical advantage over cyanide. As a result, this paper provides evidence regarding the Legadembi gold mine in Ethiopia’s amenability to thiosulfate leaching on carbonaceous gold-bearing ores. A further research perspective is also sought for thiosulfate leaching in other refractory ores.

The adequacy of the current policy, legal and institutional frameworks in addressing social, environmental, and occupational safety & health impacts of gold cyanidation in Siaya County, Kenya

The adequacy of the current policy, legal and institutional frameworks in addressing social, environmental, and occupational safety & health impacts of gold cyanidation in Siaya County, Kenya

Cyanide and cyanidation wastes management in gold leaching plants in Siaya County, Kenya.

This study assesses cyanide and cyanidation wastes management practices among small, medium and large-scale gold leaching plants in Siaya County, Kenya. The socio-economic benefits of gold extraction through cyanidation of mercury-contaminated tailings notwithstanding, the study establishes inadequate cyanide and cyanidation wastes management practices which could potentially cause significant environmental and human health impacts. Through structured key-informant interviews with operators from 15 selected gold leaching plants of varying scales of operation, along with field observations, and quantitative analysis utilizing both bivariate and inferential statistical tools, the study reveals inadequacies in cyanide, cyanidation wastewater, and tailings management practices. Key findings highlight widespread contravention of the international cyanide management standards and lack of adoption of advanced cyanidation wastes treatment technologies. Moreover, the study examines Political, Economic, Social, Technological, Environmental, and Legal factors as external factors affecting the management of cyanidation wastes. Consequently, the study recommends adoption of comprehensive cyanide management practices as outlined in the Cyanide Code and technological upgrades to mitigate potential environmental and human health impacts, and enhance regulatory compliance in gold cyanidation. In a nutshell, this study underscores the urgent need for stringent enforcement of environmental and mining industry laws and regulations in order to protect the environment and public health in gold mining regions. These measures are vitally important to ensure responsible mining practices and uphold environmental stewardship while promoting economic growth.

The role of oxidants in the intensive cyanidation of gold. 1. Gold dissolution

In the intensive cyanidation of gravity gold concentrates, sodium m-nitrobenzene sulfonate (NBS) is often used to supplement dissolved oxygen as the oxidant in the process. This paper presents the results of a largely electrochemical study of the behaviour of NBS during cyanidation. The results have confirmed that NBS acts as an oxidant in the cyanidation of gold and that the mixed potential model can be applied to describe the mechanism of its action.The mixed potential is a good initial indicator of the rate of gold dissolution and, as expected, the anodic dissolution of pure gold in cyanide solutions is characterized by passivation at potentials above about −0.35 V.The reduction of oxygen under the conditions of the present study occurs in two 2-electron steps with peroxide as an intermediate. Dissolution of gold occurs at potentials in the diffusion-controlled region for the first step. The cathodic reduction of NBS occurs in the same potential region as the reduction of oxygen. The reaction is first order in the concentration of NBS and is largely independent of the pH. The stoichiometry of the reaction involves six moles of gold per mole of NBS confirming that the amine is the final product of reduction of NBS.Rates of gold dissolution in various solutions have been measured using a calibrated linear polarisation method. The rate increases approximately linearly with increasing NBS concentration and is independent of pH. The rate in 0.5 g/L NBS is approximately the same as in oxygenated solutions.A relatively simple titration has been adapted for use in determining NBS concentrations.

Research on Enhancing Copper-Ammonia-Thiosulfate Eco-Friendly Gold Leaching by Magnetization of Lixiviant Solution and Their Kinetic Mechanism

In thiosulfate leaching of gold, the copper-ammonia complex serves as an oxidant and catalyst. This study examined the impact of magnetizing the copper-ammonia thiosulphate lixiviant solution on gold leaching from refractory oxidized ores. Magnetization reduced surface tension, improved wettability and infiltration, and enhanced the diffusion of leaching agents. It also increased dissolved oxygen content and boosted the catalytic efficiency of copper-ammonia complexes. These changes led to more efficient gold extraction, with column leaching showing a 4.74% improvement in extraction rates compared to non-magnetized methods and a 3.67% improvement over cyanide processes. These findings suggest that magnetized copper-ammonia thiosulphate lixiviant is a promising, environmentally friendly alternative to cyanide for refractory oxidized gold ores.

Analisis Pendekatan Nilai %Ekstraksi Ore North Mainrigde Dengan Metode Bottle Roller Test Di PT. J Resources Bolaang Mongondow

The heap leach method is one of the cyanidation processes suitable for low-grade ore and PT J Resources Bolaang Mongondow uses this method in its processing. Column test is the most representative testwork of the heap leach process, but this testwork requires a long time so a faster testwork is needed and can provide %extraction value even though it is less representative and bottle roll test (BRT) is a solution for this. This study aims to estimate the % extraction obtained in cells by the BRT method. From the experimental results, it was obtained that the %extraction value of HG 01 samples at +12, +6, and -6 sizes was 67.1%, 79.2%, and 92.4%, respectively. for LG 02 samples of 68.3%, 81.5%, and 93.9%, for LG 03 samples of 54.5%, 90.6%, and 89.6%, respectively, these three samples are categorized as med-high extraction. While the LG 04 sample was 67.3%, 66.3%, 84.8% and categorized as low extraction.

Characterization of medium and small-scale gold processing operations, wastewaters, and tailings in the Arequipa region of Peru

Gold cyanidation facilities in the Arequipa Region of Peru are challenged by the availability and quality of water for processing in an arid environment. The facilities reuse decant water which recycles residual cyanide but also undesirable constituents. To understand the impact of intensive water recycling on cyanide and metals concentrations, we collected barren water, decant water, and tailings samples from six gold cyanidation facilities with ore capacities of 10–430 tons per day. Processing facilities in Arequipa recycle all effluents, with decant waters making up 58 ± 11 % of process waters. Decant water contained non-target metals: copper (394 ± 161 mg/L), iron (59 ± 34 mg/L), and zinc (74 ± 42 mg/L). In addition, decant water mean free and complexed cyanide concentrations were 534 ± 129 mg/L and 805 ± 297 mg/L, respectively. Complexed cyanide concentrations remained more constant than free cyanide concentrations with 786 ± 299 mg/L for barren water and 805 ± 297 mg/L for decant water. Cyanide mass balances showed between 21 % and 42 % of unaccounted free cyanide from the start of gold cyanidation and discharge to the tailings storage facility (TSF). Free cyanide estimated losses due to volatilization were 0.8 kg and 2.5 kg of hydrogen cyanide per ton of ore processed at barren water pH of 10.1 and 9.7. Together these results indicate two acute hazards: 1) volatilization of free cyanide during processing and 2) loading and retention of cyanides and metals into TSFs. This study elucidates the extent of uncontrolled vapor phase cyanide release during gold processing operation and contaminant concentrations in the tailings storage facilities. The data highlights the need for improvement oversight, accountability, and regulation of gold processing facilities practicing intensive recycling and zero discharge.

Evaluation of the Efficiency of Using an Oxidizer in the Leaching Process of Gold-Containing Concentrate

This article presents the results of cyanide leaching of gold-containing concentrate using the trichlorocyanuric acid (TCCA) oxidizer. Gold-containing concentrate was obtained from a gold tailings sample from a gold recovery factory (GRF) in one of the deposits of Kazakhstan that have not previously been studied for concentrability. According to X-ray phase analysis and energy dispersive spectrometry (DSM) data, the main compounds in the tailings sample under study are pyrite FeS2, quartz SiO2, calcite CaCO3, albite NaAlSi3O8, muscovite KAl2Si3AlO10(OH)8, dolomite CaMg(CO3)2, and oxidized iron compounds. Microscopic studies of the concentrate have established the presence of ultrafine gold with sizes from Au 0.9 to 10.2 μm in pyrite. Obtaining the gold-containing concentrate with a gold content of 15.95 g/t is possible according to the enrichment scheme, which includes centrifugal separation, classification according to the fineness class −0.05 mm, additional grinding of hydrocyclone sands to a fineness of 90.0–95.0% of the class finer than 0.050 mm, and control centrifugal separation. Since pyrite in technogenic raw materials is the main gold-containing mineral, this paper presents studies on the oxidizability of pyrite with the TCCA oxidizer. The results of studies on the oxidation of pyrite using the TCCA oxidizer show the products of its hydrolysis oxidize pyrite with the formation of various iron compounds on its surface. Pretreatment of gold-containing concentrate with oxidizer TCCA for 3 h before the cyanidation process (20 h) allows for an increase in the recovery of gold in the solution by 5.8%.

Gold recovery from waste fine carbon using acetone as solvent (Amesmessa gold mine, Algeria)

Purpose. The aim of this work at the first stage is to develop a new method to recover gold from waste fine loaded activated carbon. At the second stage, a new method is to be developed using less energy and less hazardous chemicals to recover gold from fine and coarse activated carbon in all the process of gold ore treatment. Methodology. The desorption of gold cyanide from the waste fine loaded activated carbon was processed by agitating the carbon on alkaline aqueous solution containing 20 % (v/v) of acetone (pH between 10 and 13) at room temperature. Findings. The application of the proposed method gave satisfactory results in terms of process efficiency, the time of operation and no use of hazardous chemicals such as cyanide. The efficiency is more than 96 %, the resident time – less than 3 h. As for the hazardous chemicals, there is no use of cyanide unlike in the conventional process. Originality. The use of acetone as an organic solvent makes the gold cyanide desorption from activated carbon operated at room temperature and in short time better than any other conventionel process. Practical value. This method allows to recover easily and economically the gold entrapped into waste activated carbon existing in a mining plant at room temperature in an agitating tank, pH = 10–13 with an efficiency over 96 %. This method can be a good alternative for all gold recovery processes from activated carbon used nowadays.

Gold cyanide leaching recovery prediction model based on neighbourhood component analysis and artificial intelligence technique

Gold cyanide leaching recovery prediction model based on neighbourhood component analysis and artificial intelligence technique

Electrochemistry of Molybdenum Single Crystals and Thin Wires in Cyanide and Gold Cyanide Electrolytes

Thin wires of molybdenum coated with gold are used for space applications and the adhesion of the gold layer is decisive for their use. The surface morphology of the wires is determined by the manufacturing process and preferential orientation of single crystal surfaces is expected. In this work three different single crystal surfaces were studied together with a 20 μm molybdenum wire to elucidate the importance of surface morphology on the electrodeposition process for gold. Electrochemical impedance spectroscopy was used to study the molybdenum samples in the absence and presence of gold cyanide complexes. The results show large pseudocapacitance prior to gold deposition, indicating the presence of a thin molybdenum oxide film on the surface. Thus, the electrodeposition takes place on the surface oxide and is afflicted with a nucleation overpotential. The overpotential is only slightly dependent on the single crystal orientation, while it is more negative for the wire. The adhesion of gold on the flat single crystal surfaces is weak but marginally better on the wire. This clearly shows that strong chemical binding to the surface is absent and that other processes, such as physical interlocking of the gold layer is necessary for good adhesion.

Study of Preg-Robbing with Quicklime in Gold Cyanide Solutions Analyzed by Time-of-Flight Secondary Ion Mass Spectrometry

Preg-robbing is a phenomenon in which minerals retain gold, especially due to the presence of species like carbonaceous matter and silicates in the mineral. This study demonstrates the impact of quicklime, used to adjust the pH of a gold cyanidation solution, on the retention of gold contained in pregnant cyanidation solutions and sorption mechanisms. The retention capacity of four quicklime solutions was evaluated using proportions of 200 g of lime in 800 mL of solution and 10 g of lime in 500 mL of solution. The concentrations of the gold cyanide solutions were 10, 15, and 25 ppm. The insoluble lime residue in the acetic acid solution was separated and analyzed by XRD, FTIR, elemental carbon, and Raman spectroscopy techniques. SEM and TOF-SIMS were used to analyze the lime samples after exposure to the gold cyanide solution. The results show that retention was attributable to quicklime due to the effects of its carbon and silicate content, although chemisorption and physisorption mechanisms may also be responsible.

A Comparative Analysis of Non-Cyanide and Cyanide Gold Leaching Technologies: Lessons Learned from the Failed CLINN GEM Facility and Promising Results of the REVIVE SSMB Project in Itogon, Benguet

This research paper presents a comparative analysis of a non-cyanide gold leaching technologies implemented in the small-scale mining community of Itogon Benguet against a potential gold recovery method with Free Cyanide decontamination and Sodium Cyanide recovery system. The study evaluates the failed CLINN GEM facility and the successful REVIVE SSMB project, focusing on technology readiness and acceptance, operational efficiency, and community engagement. The results demonstrate that the failure of the CLINN GEM facility was attributed to its low community acceptance, high operating costs, and complexity, hindering its practicality and scalability. In contrast, the REVIVE SSMB project achieved exceptional results through an alternative gold ore leaching process using Cyanidation CIP method, driven by strong community engagement, cost-effectiveness, sustainable wastewater/tailings discharge management system and simplified operation approach even for the recovery of gold from complex and low-grade Au ore from the locality. For a viability assessment, a stochastic model for the technology feasibility and project optional valuation under diverse uncertainty consideration for community adoption and expansion presentable to potential investors or for the option right to accept and manage the technology as demonstrated. This research simulated the viability of the REVIVE SSMB approach with a high predictability using Monte Carlo Model through Real Option Analysis; and under the worst-case scenario at 50th percentile (median) 74.53% recovery was achieved. Repeatedly with a similar 50th percentile simulation under an optimized condition with pulp density of 44- 50% and 3kg per ton of activated carbon loading during flotation yielded a gold recovery of 91%. Hence, it is arguably viable, coupling with the 98 to 99% free cyanide decontamination rate and the 55% NaCN recovery successful discharge management system under the REVIVE SSMB 6 months project model.

Cyanidation of tailings in artisanal small-scale gold mining at Arbaat Region in Red Sea State, Sudan

In this research, the processing of gold from artisanal small-scale gold mining was investigated by cyanidation using an agitation process. The sample's characterization shows that the silicate mineral exhibits the sample mineralogy, according to the results of the XRD examination. In XRF analysis, the mineralogical and chemical structure shows 77.1% SiO2, 8.08% Al2O3, 5.76% Fe2O3, 1.67% CaO, 0.97% K2O, 0.054% As2O3, 1.1% Na2O, 0.392% SO3, 0.454% TiO2, 0.049% MnO and 0.005% ZrO. The parameters of the experiments were stirring speed, NaCN concentration, solid-liquid ratio, temperature, and pH. The purpose of gold leaching in artisanal small-scale gold mining at Arbaat region is to find the appropriate conditions that will ensure maximum recovery. It was found that the gold dissolution decreases with increasing solid ratio. Furthermore, the cyanide concentration positively influences the range of 0.05–0.5 g/L. It is seen that the dissolution rate increases with the range of pH 10-10.30, while it starts to incline at pH after 10.30. However, the temperature and agitation speed have a significant effect on the gold dissolution. Cyanidation tests revealed that it is easy to apply the cyanidation process and recover about 87.52% Au content from the tailings of artisanal small-scale gold mining. The obtained recovery indicates the commercial and economic viability of the process that will be applied to extract Au from artisanal small-scale gold mining tailings in Arbaat.

Silver adsorption from gold leaching cyanide wastewater by a green functionalized magnetic graphene oxide Nano-adsorbent

A nanoadsorbent made of magnetic graphene oxide that was functionalized by glutathione (GSH/Fe3O4@GO NPs) was synthetized. Various characterization methods were employed to clarify the adsorbent's morphology and structure. The results confirmed the formation of nanosheets of graphene oxide with the homogenous coating of Fe3O4 nanoparticles and well conjugated glutathione (GSH) on its surface. This adsorbent was utilized to adsorb silver ion from synthetic AgCN solutions at pH = 10.5. A central composite design (CCD) was used to investigate the impact of silver and cyanide concentration. The significance of the concentration of cyanide and its interaction with silver concentration was confirmed. When the concentrations of silver and cyanide were 128 mg/L and 528 mg/L, respectively, the maximum adsorption capacity achieved was 586 mg/g. The successful fitting of the Freundlich isotherm explains the multilayer adsorption on the heterogeneous surface of the adsorbent. This adsorbent also showed significant efficiency in silver adsorption from a real cyanide wastewater sample as was predicted by the statistical model. The silver adsorption capacity of 123 mg/g were obtained from a gold cyanide leaching process wastewater (24.8 mg/L). The GSH/Fe3O4@GO NPs were found to be an effective adsorbent for extracting and separating silver ions from cyanide solutions.

Effect of Na2S+NaOH Pre-Identification Leaching on Oxidized Refractory Au-Ag Ores

This study was conducted to investigate the effect of the alkaline sulfide (Na2S+NaOH) pre-identification process on cyanide leaching performance in oxidized refractory gold-silver ores. The ore has intensive oxide, carbonate, and silicate content, and contains Au/Ag minerals containing electum, acanthite, and silver-bearing FePbZn Sulphate-Arsenate/Hydroxide minerals together with Fe, Pb, and Zn minerals. Niğde Ulukışla refractory Au/Ag ore has 8-9 g/T gold and 170-180 g/T silver grades. In mineralogical examinations, it was found that these metals were closed in minerals such as iron oxy/oxyhydroxide, calcite, and quartz or neighboring these minerals. In the cyanide soluble process after alkali sulfide preliminary procedure at room temperature, metal extraction yields were obtained as 62% for gold and 7% for silver. It is seen that silver is adversely affected by this process compared to the direct cyanidation process. However, after the hot alkali treatment process, metal extractions improved by approximately 25% of gold and 74% of silver. This increase in yield can be considered as converting Ag-oxyhydroxide into soluble Ag forms as a result of the effect of hot alkaline sulfur leaching on the cyanide process. The most important advantage of this decomposition process is to achieve high metal extraction efficiency in lower alkali concentrations.

Effect of Direct and Indirect Pre-Oxidation of Gold Ore from Doup North Sulawesi using Ozone Gas on the Gold Extraction in the Cyanidation Process

Refractory gold ore is a type of gold ore that is difficult to process when treated through a conventional cyanidation process. Pre-oxidation using ozone gas is one of the pre-treatment methods that can be used to improve gold recovery from sulfide-type refractory ore. This study used gold ore samples from Doup, North Sulawesi, Indonesia, to study the effect of direct and indirect pre-oxidation using ozone gas on gold recovery and subsequently treated by a cyanidation process. Direct and indirect pre-oxidation experiments were carried out at different pHs and using two raw materials for ozone generation (air and O2). The slurry obtained from the pre-oxidation experiments was filtered, and the filtrate was analyzed for the concentration of dissolved Cu, Fe, and Zn using atomic absorption spectroscopy (AAS); meanwhile, the residue from each pre-oxidation experiment was leached by cyanidation to obtain a pregnant leaching solution (PLS), which was analyzed for its gold concentration using AAS. The percentages of dissolved Cu, Fe, and Zn during pre-oxidation increased with the pre-oxidation time when the acidity was maintained at pH 2, using pure O2 as the ozone raw material. The direct pre-oxidation process at pH 2 using air as the ozone raw material increased gold extraction from 79.08% to 82.78% in the cyanidation process. The pre-oxidation experiments performed without controlling the pH resulted in lower gold dissolutions than the pre-oxidation conditions at pH 2. Possible causes of the lower gold dissolution were discussed.

Технология переработки сухих отходов сорбции и растворов хлоридов сурьмы

Reducing the loss of valuable components during the processing of complex gold-antimony ores, increasing the extraction of antimony during the flotation of sulfide minerals, is an urgent scientific problem. The aim of the study is to maximize the extraction of gold and antimony from dry sorption waste after gold cyanidation, and to improve the reagent regime of the antimony mineral flotation process. Research objectives are as follows: evaluation of the technology efficiency for processing dry sorption waste; extraction of gold from the cake of acidic leaching of antimony; production of various antimony-containing products from solutions of antimony chlorides; study of the possibility of replacing lead with a mixture of zinc and copper cations to hydrophobize the surface of antimony sulfide minerals during flotation. The object of the research is man-made and natural mineral raw materials containing gold and antimony. The following research methodology and methods are used: information analysis, evaluation of existing scientific developments, methods of theoretical and experimental research. A new technological solution has been proposed: acidic (a mixture of hydrochloric acid and hydrogen hydroxide) hydrometallurgical technology for processing dry sorption waste in order to extract gold and antimony. Acid treatment makes it possible to completely transfer antimony into solution, significantly improves the quality of the cake for subsequent cyanidation and gold extraction, reduces the volume of material for processing by cyanidation, and simplifies cyanidation technology. Sb2S3 activation and the possibility of lead (Pb(NO3) replacement have been studied 2) a mixture of zinc and copper (ZnSO4 and CuSO4) during the flotation of antimony ores from the Khipkoshinsky deposit in the Transbaikal Region. This has made it possible to create favorable conditions for interaction with xanthogenate and hydrophobize the surface of sulfide minerals. Theoretically, hydrogen sulfide substitutes such as NaCNS, KCNS, CuCNS for use in the flotation process were evaluated.

Review of gold cyanide leaching and the main factors affecting gold dissolution rate

This paper reviews the cyanide leaching technology and the influential parameters affecting the cyanidation process. In general, the factors influencing the degree of cyanide leaching of gold include particle size, NaCN concentration, the level of dissolved oxygen, pH, pulp density, and leaching time. Each of these parameters plays a significant role in gold cyanidation, and should be optimized respectively by conducting laboratory testing prior to production application.