Cyanide Extraction Research Articles

Acidithiobacillus ferrooxidans Leaching of Silica-Sulfide Gold Ores from May-Hibey Deposits, Tigray, Ethiopia

Oxidative leaching is an inexpensive alternative to using chemical cyanide extraction methods for gold from low-grade gold sulfide. Oxidation of finely ground gold-bearing ore by Acidithiobacillus ferrooxidans was evaluated in terms of cell density, pH, and leaching efficiency of Fe and Au in shake flask experiments. The compositional and elemental analyses of the beneficiated ore were analyzed using XRD and EDXRF spectroscopy. The ore’s primary constituents are gold (4.356 mg/L), silicon, iron, and sulfur (62.456, 15.441, and 7.912 wt%, respectively). XRD spectra, the main phases of the concentrated ore, showed that the major components of the ore were quartz, syn, silicon sulfide, pyrite, and polymetallic elements such as silderenrite, gismondine, siderenikite, hematite, and syn. The experimental results, with Acidithiobacillus ferrooxidans bacteria and blank, were evaluated. The pH of the blank remained nearly constant, and the pH of the bioleached was occasionally lowered. The A. ferrooxidans strain always grew better throughout the bioleaching process. For the A. ferrooxidans strain, the cell density of cells reached a maximum of 90.00 × 106 cells/mL after the 11th week and decreased to 87.00 × 106 cells/mL after the 12th week. The decrease in cell density may be due to the presence of polymetallic elements such as Al, Cr, Ti, and Ni, leading to reduced metal tolerance of the A. ferrooxidans strain. In the A. ferrooxidans leaching process, the maximum total iron and gold extraction reached 92.16% (14.23 mg/L) and 99.97% (4.355 ppm), respectively, after the 11th week, and leaching tends to decrease up to 14 weeks, which may be due to the formation of secondary minerals. More research will be performed to optimize the procedure and leaching kinetic, examine the impact of metal content, and take into account the potential for bioleaching process pollution in addition to the amount of gold recovered.

Study on the performance of Anerinibacillus sp. in degrading cyanide wastewater and its metabolic mechanism

Cyanide extraction dominates the gold smelting industry, which leads to the generation of large amounts of cyanide-containing wastewater. In this study, Aneurinibacillus tyrosinisolvens strain named JK-1 was used for cyanide wastewater biodegradation. First, we tested the performance of JK-1 in degrading cyanide under different conditions. Then, we screened metabolic compounds and pathways associated with cyanide degradation by JK-1. Finally, we explored the potential JK-1–mediated cyanide degradation pathway. Our results showed that the optimal pH and temperature for cyanide biodegradation were 7.0 and 30 °C, respectively; under these conditions, a degradation rate of >98% was achieved within 48 h. Untargeted metabolomics results showed that increased cyanide concentration decreased the abundance of metabolic compounds by 71.1% but upregulated 32 metabolic pathways. The Kyoto Encyclopedia of Genes and Genomes enrichment results revealed significant changes in amino acid metabolism pathways during cyanide degradation by JK-1, including cyanoamino acid metabolism, β-alanine metabolism, and glutamate metabolism. Differential metabolic compounds included acetyl-CoA, l-asparagine, l-glutamic acid, l-phenylalanine, and l-glutamine. These results confirmed that cyanide degradation by JK-1 occurs through amino acid assimilation. This study provides new insights into the mechanism of cyanide biodegradation, which can be applied in the treatment of cyanide wastewater or tailings.

Experimental analysis on cyanide removal of gold tailings under medium-temperature roasting

The cyanide content of gold tailings exceeds the standard seriously due to the cyanide extraction process. In order to improve the resource utilization efficiency of gold tailings, a medium-temperature roasting experiment was carried out on the stock tailings of Paishanlou gold mine after washing and pressing filtration treatment. The thermal decomposition rule of cyanide in gold tailings was analyzed, and the effects of different roasting temperatures and roasting durations on cyanide removal efficiency were compared. The results show that when the roasting temperature reaches 150 °C, the weak cyanide compound and free cyanide in the tailings begin to decompose. When the calcination temperature reached 300 °C, the complex cyanide compound began to decompose. When the roasting temperature reaches the initial temperature of cyanide decomposition, the cyanide removal efficiency can be improved by prolonging the roasting time. After roasting at 250–300 °C for 30–40 min, the total cyanide content in the toxic leachate decreased from 3.27 to 0.01 mg/L, which met the water quality standard of III class in China. The research results provide a low-cost and efficient way for cyanide treatment, which is of great significance for promoting the resource utilization of gold tailings and other cyanide-containing wastes.

Науково-технологічні рішення щодо скорочення баластних солей при очищенні коксового газу.

The article deals with the causes of formation of ballast salts in circulating solutions of the absorption process during the purification of coke oven gas from hydrogen sulphide. The processes occurring during the hydrogen sulphide recovery from coke oven gas using the vacuum carbonate method, which consists in washing the coke oven gas with a soda solution, are considered in detail. In this process, acidic components are captured: hydrogen sulphide, carbon dioxide and hydrogen cyanide. The article analyses the causes and stages of ballast salt formation, provides equations and conditions for the relevant reactions The article analyses the causes and stages of ballast salt formation, provides equations for the relevant reactions, and indicates ways to reduce their formation. The advantages of a two-stage purification scheme are shown, which allow to reduce the content of unregenerated ballast salts at the second stage. At the same time, the potential of the first stage of purification is used for the selective extraction of hydrogen cyanide (HCN). It has been shown that the selective absorption of hydrogen cyanide in relation to hydrogen sulphide (H2S) at the first stage of purification leads to a significant reduction in the supply of hydrogen cyanide to the second stage of absorption, and, accordingly, to a reduction in the formation of unregenerated ballast salts in the second stage solution. The article calculates the consumption of soda products in the process of vacuum-carbonate desulphurisation with selective absorption of hydrogen cyanide in the first stage scrubber and hydrogen sulphide in the second stage scrubber, and also calculates the soda savings for the production of solutions of different concentrations. The possibility of integrating the used technical solutions into the existing scheme of two-stage desulphurisation is noted. The considered scheme of coke oven gas desulphurisation with isolated solution cycles of different concentrations can be applied in the perspective projects of SE GIPROKOKS for enterprises in Ukraine and abroad. Keywords: ballast salts, two-stage vacuum-carbonate desulphurisation, selective hydrogen cyanide extraction. Corresponding author: M.S. Solovyov, e-mail: solovjov.gpk.ua@gmail.com

The Mining Legacy of William S. Godbe

The Mining Legacy of William S. Godbe

Potentiometry for Cyanide Detection Applied to Fisheries Regulation

Illegal cyanide fishing is practiced by some fishers to capture agile and otherwise inaccessible reef fishes easily. Economic incentives had prevented discontinuation of the practice despite regulations present. Aside from the well-known toxicity of cyanide, it is a concern whether the fish is for ornamental purposes or human consumption that cyanide is being used because of the environmental damage it can cause by killing off non-target species. Currently, the cyanide content of fish is determined using an ion-selective electrode (ISE), with distillation as the mode of extraction of cyanide from tissues. This paper reports a modification of ASTM Method 500-CN-E, a method originally used to test for cyanide content in the wastewater. This paper outlines the process of determining the applicability of the method modification for analysis of fish tissue samples, in which no standard method was designed specifically for the matrix mentioned above. Although percent recoveries for cyanide at 0.05-10 mg/L range in spiked distilled water matrices are in line with the American Society of Testing and Materials (ASTM) results (90-105%), cyanide recoveries in spiked fish tissue matrices at the same concentration range are appreciably lower (~60-80%). For regulatory purposes, it serves as a temporarily acceptable method to detect cyanide-laden fish until a suitable method can be validated on international standards. However, to be accepted as a standard method, additional modifications may be needed or proven in inter-laboratory tests that the recovery of cyanide in fish is consistently low.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ЭФФЕКТИВНОСТИ ПРИМЕНЕНИЯ ВИХРЕВЫХ АППАРАТОВ ДЛЯ РЕГЕНЕРАЦИОННОГО ИЗВЛЕЧЕНИЯ ЦИАНИСТОГО НАТРИЯ ИЗ ОТРАБОТАННЫХ РАСТВОРОВ

The article presents the results of the study on the effectiveness of the use of vortex apparatuses for the regenerative extraction of sodium cyanide from spent solutions. The authors emphasize the main advantages and factors explaining the higher efficiency of vortex devices compared with traditional technologies for the regeneration of NaCN from spent solutions. The study also highlights the results of experiments according to which the average volumetric conversion rate of the starting compounds is 40-60 times higher than in conventional bubble columns, which clearly shows the advantage of vortex devices.

Ultrasound-assisted cyanide extraction of gold from gold concentrate at low temperature.

A sonochemical reactor was developed to study the ultrasound-assisted cyanide extraction of gold from gold ore at low temperature. The effects of ultrasound on gold leaching in low temperature and conventional conditions were investigated. At the low temperature of 10°C, ultrasound-assisted extraction increased extraction rate of gold by 0.6%-0.8% and reduced the gold content of cyanide tailings to 0.28g/t in the leaching of gold concentrate and cyanide tailings, respectively. At the conventional temperature of 25°C, ultrasound-assisted extraction obtained a 0.1% higher extraction rate of gold compared with conventional extraction, with the unit consumption of NaCN reduction of 15%. The analysis of kinetic model also demonstrated that sonication indeed improved the reaction of gold leaching greatly. The mineralogy and morphology of ore were further analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and particle size analyzer to explore the strengthening mechanism of gold leaching. The results showed that the ore particles were smashed, the ore particle surface was peeled, the passive film was destroyed and the reaction resistance decreased under ultrasonic processing. Therefore, the extraction rate of gold was improved and the extraction time was shortened significantly in ultrasound-assisted cyanide extraction.

Mg-Al-CO3 layered double hydroxide reinforced polymer inclusion membrane as an extractant phase for thin-film microextraction of cyanide from environmental water samples.

In this paper, a flexible and efficient nano-reinforced polymer inclusion membrane (PIM) was fabricated and used for cyanide (CN-) extraction from water samples. Aliquat 336 (a liquid anion exchanger) was embedded in poly(vinyl chloride) (PVC) support as the extractant. Mg-Al-CO3 layered double hydroxide (LDH) with high surface area and anion exchange ability was applied to promote the extraction efficiency of PIM. A PIM comprising 56% PVC, 40% Aliquat 336, and 4% Mg-Al-CO3 LDH showed the best extraction efficiency. A single beam ultraviolet-visible spectrophotometer was used for the detection of cyanide. Surface morphology of the PIM was studied by field emission scanning electron microscopy. The experimental parameters influencing the extraction process were investigated and optimized. The intra- and inter-day relative standard deviations at two different concentrations were in the range of 2.8-7.6%. The dynamic range of the method was in the range of 5-500μgL-1, and the detection limit was 1.4μgL-1. The LDH reinforced PIM showed proper characteristics for the extraction of cyanide from real water and wastewater samples with recoveries between 82 and 115%.

The mineralogy and processing potential of the Commonwealth project in the Molong Volcanic Belt, central eastern New South Wales, Australia

The Commonwealth prospect area comprises the base metal-gold Commonwealth Mine, Commonwealth South gold deposit and the Silica Hill deposit located 100 km north of Orange in New South Wales, Australia. Impact Minerals Limited has discovered high grade mineralization of gold, silver, zinc, lead and copper which occurs in massive sulfides with extensive pyrite, veins of sulfide and quartz, and disseminated sulfide in a variety of sedimentary and volcanic host rocks. The Inferred Resource comprises 720,000 tonnes at 2.8 g/t gold, 48 g/t silver, 1.5% zinc, 0.6% lead and 0.1% copper. The overall aim was to establish the metallurgical characteristics of these ores and develop an appropriate flow sheet to allow future mining operations at this prospect.The mineralogy of a suite of samples representative of the various ore types were characterised using advanced analytical microscopy and mass spectrometry techniques to identify metal deportment, mineral associations and liberation characteristics of both ore-bearing and gangue minerals. Leaching tests were carried out to determine the reactivity of minerals and the availability of metals to extraction processes by both conventional cyanide leaching and Curtin University’s patented glycine leach (GlyCat™) technologies. The benign nature of glycine and atmospheric leaching conditions make it a potential favourable leaching option in treating such ores, particularly in sensitive areas where cyanide usage is discouraged.The samples from three areas studied consisted of: (a) the massive sulfide deposit from Commonwealth Main with high gold (2.41–11.6 g/t), silver (545–1080 g/t), zinc (6.6–10 wt%) and lead (2.3–3.9 wt%) mineralisation associated with intergrowths of predominately pyrite with sphalerite, arsenopyrite and galena, barite and zincian siderite; (b) Commonwealth South porphyry rhyolite-rhyodacite with moderate gold (1.31, 10.9 g/t Au) and silver (29.4, 32.2 g/t Ag) grades consisting of a mixture of different mineral assemblages ranging from sulfide barren quartz and muscovite/sericite grains, to particles with enriched zones of sphalerite, pyrite and galena and a sulfide-rich sandstone-shale, which is predominately quartz with moderate amounts of pyrite, muscovite, baryte and quartz/mica mixture; (c) Silica Hill feldspar porphyry rhyolite-rhyodacite samples consist of low gold (0.58, 7.65 g/t Au) and medium silver (30.7, 172 g/t Ag) grades and made up of predominately siliceous intergrowths with disseminated pyrite and arsenopyrite as both coarse euhedral aggregates and fine discrete grains (10–200 µm).The massive sulfide samples were largely refractory to gold and silver extraction under all leach test conditions due to precious metals associated mainly with pyrite. With the exception of zincian siderite, the practical separation of finely disseminated sphalerite and galena for zinc and lead contents will be a challenge. Pressure oxidation or chloride based processes may be economical if further resources can be defined. Direct leaching for precious metal extraction by both cyanide and Glycat™ is possible for the porphyry rhyolite-rhyodacite and the sulfide-rich sandstone-shale samples where gold extraction ranged from 75% to 90%. Silver extraction ranged from 40 to 60% and is largely from leaching of fine grained electrum. Minor silver-bearing minerals, tetrahedrite, acanthite, pyrargyrite, and freibergite have limited solubility in cyanide extraction processes and will require more intensive conditions to leach. GlyCat™ show potential as a heap leach or tank leach process option where low cyanide additions can be managed and removed.

English

Cyanide is a very toxic substance, which occurs in various forms in environmental matrices and its determination requires a good extraction method. From the reference method of cyanide distillation by reflux heating under acidic conditions and entrainment of HCN gas collected as CN- ions with detection by UV-Visible spectrophotometry, an improved and complete procedure for total cyanide extraction in aqueous and solid matrices has been developed. The best conditions after optimization of complete recovery (≃ 100%) of total cyanide and elimination of interferences in natural waters and soils fortified are: heating at 181.75°C, saving of reflux time to 30 min, sulfuric acid concentration of 0.6 M, 2 to 4 times less acid, without catalyst and other special treatments of interferences relatively to existing techniques. Application to water samples (drinking, surface, underground) and effluents collected at the Samira gold mine (Niger) and its environs shows the impact of distillation extraction on total cyanide recovery. Waters, exempt of cyanide at the starting of mining activity, currently contain total cyanide contents of 1 to 5 μg L-1 and in effluents up to 37 times the discharge standard (1 mg L-1). Key words: Cyanide decomposition, distillation extraction, environmental matrices, Samira gold mine (Niger).

Recovery of Copper and Cyanide through Emulsion Liquid Membrane with Quaternary Amine Salt as the Mobile Carrier

ABSTRACTA fundamental study on using emulsion liquid membranes(ELMs) with modified quaternary amine salt to extract copper and cyanide from waste cyanide solutions has been conducted. Both copper and cyanide can be effectively extracted by ELMs. A low pH of the external phase favors copper and cyanide extraction. A high molar ratio of CN/Cu tends to suppress copper extraction and results in more extraction of free cyanide. A high copper concentration in the external phase results in high transport of copper and cyanide. ELMs formed with the recovered membrane materials can be effectively re-used for recovering copper and cyanide from waste cyanide solutions.

Optimization of cyanide extraction from wastewater using emulsion liquid membrane system by response surface methodology.

To solve the disposal problem of cyanide wastewater, removal of cyanide from wastewater using a water-in-oil emulsion type of emulsion liquid membrane (ELM) was studied in this work. Specifically, the effects of surfactant Span-80, carrier trioctylamine (TOA), stripping agent NaOH solution and the emulsion-to-external-phase-volume ratio on removal of cyanide were investigated. Removal of total cyanide was determined using the silver nitrate titration method. Regression analysis and optimization of the conditions were conducted using the Design-Expert software and response surface methodology (RSM). The actual cyanide removals and the removals predicted using RSM analysis were in close agreement, and the optimal conditions were determined to be as follows: the volume fraction of Span-80, 4% (v/v); the volume fraction of TOA, 4% (v/v); the concentration of NaOH, 1% (w/v); and the emulsion-to-external-phase volume ratio, 1:7. Under the optimum conditions, the removal of total cyanide was 95.07%, and the RSM predicted removal was 94.90%, with a small exception. The treatment of cyanide wastewater using an ELM is an effective technique for application in industry.

Headspace sorptive solid phase microextraction (HS-SPME) combined with a spectrophotometry system: A simple glass devise for extraction and simultaneous determination of cyanide and thiocyanate in environmental and biological samples

A simple, low cost and efficient headspace sorptive solid phase microextraction (HS-SPME) method for determination of cyanide has been developed. The system comprises of a glass tube with two valves and a moveable glass slide fixed at its centre. It includes an acceptor phase polyurethane foam treated mercury (II) dithizonate [Hg(HDz)2–PUF] complex fixed inside by a septum cap in a cylindrical configuration (5.0cm length and 1.0cm diameter). The extraction is based upon the contact of the acceptor phase to the headspace and subsequently measuring the absorbance of the recovered mercury (II) dithizonate from PUFs sorbent. Unlike other HSSE, extraction and back – extractions was carried out in a closed system, thereby improving the analytical performance by preventing the analyte loss. Under the optimized conditions, a linear calibration plot in the range of 1.0–50.0µmolL−1 was achieved with limits of detection (LOD) and quantification (LOQ) of 0.34, 1.2µmolL−1 CN−, respectively. Simultaneous analysis of cyanide and thiocyanate in saliva was also performed with satisfactory recoveries.

Treatment of cyanide wastes through bioremediation

<p class="p1">This document presents results of research in which an autochthonous consortium of cyanide-degrading microorganisms was developed for use in the biological treatment of hazardous cyanide waste. </p><p class="p1">These autochthonous microorganisms were lyophilized (freeze dried) in different protective media, such as gelatin and lactose broth, at different temperatures (-35,-45,-55 and -65 <span class="s1">o</span>C). </p><p class="p1">The preliminary treatment of cyanide wastes involved pretreatment of sludge for 3-5 days to leach the waste, and a subsequent treatment in aerated lagoons, where the consortium of lyophilized microorganisms was applied. </p><p class="p1">Eight different lyophilized samples were obtained at different temperatures using two protective media for lyophilization, which produced excellent results six months after lyophilization. </p><p class="p1">The consortium of lyophilized microorganisms showed 70% to 80% viability, with cyanide extraction percentages higher than 95%, and can be kept active for long periods of time (for years). </p><p class="p1">Lyophilized microorganisms can be used for biodegradation of cyanide wastes from gold mines or from any other cyanide waste such as that from metallic electroplating baths, or from the jewelry manufacturing industry. </p>

Copper and Cyanide Extraction with Emulsion Liquid Membrane with LIX 7950 as the Mobile Carrier: Part 1, Emulsion Stability

The potential use of emulsion liquid membranes (ELMs) with LIX 7950 as the mobile carrier to remove heavy metals from waste cyanide solutions has been proposed. Relatively stable ELMs with reasonable leakage and swelling can be formed under suitable mixing time and speed during emulsification. The concentration of LIX 7950 and Span 80 in the membrane phase, KOH in the internal phase and the volume ratio of membrane to internal phases are also critical to ELM formation. The efficiency of copper and cyanide removal from dilute cyanide solution by ELMs is related to ELM stability to some extent. More than 90% copper and cyanide can be removed from dilute cyanide solutions by ELMs formed under suitable experimental conditions.

Optimization of Auxiliary Solvent Demulsification Microextraction for Determination of Cyanide in Environmental Water and Biological Samples by Microvolume UV-Vis Spectrophotometry

A new, simple, rapid and efficient solvent terminated-auxiliary solvent-dispersive liquid-liquid microextraction (ST-AS-DLLME) technique for determination of cyanide ions by microvolume UV-Vis spectrophotometry was developed. Effective parameters on the extraction and absorbance of cyanide were optimized using two optimization methods: fractional factorial design (FFD) and central composite design (CCD). Zinc(II) tetraphenylporphyrine (ZnTPP) was used as a selective cyanide receptor agent. Methyl isobutyl ketone (MIBK), ethanol and 1-butanol were used as extraction solvent, dispersive solvent and demulsifier solvent, respectively. The method shows very good selectivity in presence of other species. The analytical curve was linear in the range of 4.0-130 μg L -1 with a limit of detection of 1.0 μg L -1 . Relative standard deviation (RSD) of the method for ten replicate measurements of 100 μg L -1 of cyanide was 1.1%. The method was successfully applied for determination of cyanide in natural water and plasma samples with good spike recoveries.

Cloud point extraction of trace cyanide from environmental waters for indirect flame atomic absorption spectrometric determination

A method has been developed for indirect determination of cyanide in environmental waters based on cloud point extraction (CPE), preconcentration and determination by flame atomic absorption spectrometry (FAAS). The method was based on reduction of Cu(II) to Cu(I) in the presence of cyanide and complexation of the produced Cu(I)(CN)2− with gallocyanin (GC+) as an ion-pairing reagent at pH 4.0, followed by its extraction into polyethyleneglycol mono-p-nonylphenylether (Ponpe 7.5). Selectivity was improved with the use of suitable masking agents. Various factors influencing separation and preconcentration of cyanide have been investigated, and conditions were optimized, allowing determination of cyanide in the range of up to 1.2 mg L−1 with a detection limit of 0.00045 mg L−1. The method has been applied to the determination of cyanide in environmental waters, the results being in agreement with those obtained by a reference method.

A novel process based on gas filled membrane absorption to recover cyanide in gold mining

In the last ten years, the operational costs in the gold and silver cyanidation processes have increased, fundamentally, due to the treatment of ores which contains high cyanide soluble metals, such as zinc, copper, and nickel, among others, increasing the cyanide consumption along with the increase in cyanide price. Additionally, the high cyanide consumptions in gold operations have increased the cyanide contents in leach tailings, forcing the inclusion of processes to recover or eliminate cyanide. For these reasons, a membrane contactor operation to recover cyanide from gold mining, using gas filled membrane absorption is proposed in this study, performing laboratory tests in order to determine the throughput of this process and the most relevant parameters, which affect the cyanide recovery. Gas Filled Membrane Absorption (GFMA) process can extract cyanide, using an absorption solution of NaOH. In this process, previously reported for wastewater treatment, a hydrophobic membrane with its pores filled with air separates an aqueous stream containing cyanide and receives a solution with a high pH value. These aqueous solutions cannot penetrate into the membrane pores, promoting the cyanide transfer from the cyanidation solution to the receiving solution. The experimental results show cyanide recoveries higher than 90% in extraction times of approximately 10min, achieving an average cyanide transfer rate of 0.01kgm−2h−1 and identifying the pH, feed flow rate and copper concentration as the most influential parameters on the performance of the process.Furthermore, a phenomenological transport model was developed in order to explain the critical steps of the cyanide transfer in the GFMA process. This model was validated by means of the comparison with the experimental results of cyanide extraction with the presence of Cu(I) and Zn(II) ions, obtaining a statistical error lower than 10%. Thus, the gas filled membrane absorption process can recover cyanide, with similar performance to the current cyanide recovery processes, and could involve a smaller size of the equipment due to the high transfer surface area per volume that membrane contactors have.

Experimental Research on Cyanidation Leaching of a Gold Ore

The gold ore is oxidized ores, and it is not suitable for flotation separation. The cyanide leaching is used for the recovery of gold. Experimental studies of cyanidation leaching for a oxidized gold ore were carried out. The factors that influence leaching such as grinding size, sodium cyanide quantity, pulp density, extraction time and segmentation leaching were conducted. And experiment pretreatment test with the copper ion which influences leaching. The results demonstrated that the good index of leaching rate 90.11% could be reach.