Extraction Of Precious Metals Research Articles

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.

Oxidation Behavior of Copper Concentrate, Gold Concentrate, and Their Mixtures Between 1173 K (900 °C) and 1373 K (1100 °C)

Gold is typically extracted from ores using a cyanidation process. However, environmental regulations and low productivity are the main drawbacks of cyanide usage. Alternative technologies for gold extraction are being studied although development of any new technology necessitates additional investments. In South Korea, recovery of gold and silver is performed by the local copper producer by feeding gold concentrate into a smelter. An integrated copper-making process might be an efficient and feasible alternative for the extraction of precious metals without the use of toxic cyanide. Installed exhaust gas cleaning system of copper smelter would minimize the toxic effects of hazardous elements (arsenic, bismuth, antimony, etc.) contained in gold concentrates. A kinetic and thermodynamic understanding of the effects of gold concentrates on copper metallurgy is necessary for the operation. The effects of various parameters on the oxidation kinetics of sulfides were investigated.

Improving processes of gold-silver refractory ores treatment at the complex deposit of precious metals

The paper considers the results obtained in the study of the prospective gold-silver complex deposit at the Eriksky ore cluster (Khabarovsk Territory) with refractory pofycomponent ores. Energy dispersive, atomic emission, grain size and dispersive analysis of rock samples were carried out. Samples contained microelements of a wide range including gold, silver, bismuth, cobalt, chromium, manganese, molybdenum, nickel, lead, vanadium, tungsten, zinc, copper, etc. It was found that pofycomponent and dispersed composition of mineral raw materials at the deposit defines it as a complex object to extract valuable components. It was proposed to use systems based on methods that reduce consumption of reagents to address the issue of precious metal extraction with more environmentally and technologically efficient tools. It is achieved by creating conditions for a sustainable process of preparation for leaching of mineral components containing gold and platinum through destruction of the mineral component of refractory polycomponent ores by increasing micro disintegration fields using ultrasound. Providing sustainability of mineral crystal lattice destruction by regrinding the solid phase formed during cavitation is a fundamental factor when preparing for the extraction of microparticles of valuable components.

Wendy L. Queen

Abstract“We have designed a method to make new MOF‐polymer composites and found that these materials are highly selective for the extraction of heavy metals and precious metals from aqueous media ...” Find out more about this author's research at https://doi.org/10.1002/ejic.201801253.

Effluents Treatment Generated by Biolixiviation in the Extraction of Precious Metals through Selective Recovery of Iron, Copper and Zinc

Bioleaching comprises the use of microorganisms for metal-extraction processes from sulphide ores. During these complex processes, sulphides are oxidized to sulphates with the generation of heat. As a result, gold, silver, and other precious metals are liberated from the sulphide matrix, improving their recovery after further processing. A drawback of bioleaching processes is the generation of significant amounts of acid solutions with high heavy metal concentrations. If untreated, these acid solutions may alter the physical and chemical characteristics of water and its surroundings, with high impact to aquatic ecosystems. High heavy metal concentrations in solution may also result in pollution to living organisms. A feasible method to treat bioleaching-generated solutions is selective precipitation. This investigation presents the conditions for a successful individual recovery of the main base metals contained in a bioleaching solution with high copper, zinc, and iron concentrations by pH-based selective precipitation. Tests were made with standard solutions of known concentrations of copper, iron, lead and zinc and by titration the concentrations were checked; which allowed to validate the volumetric titration method. The selective precipitation of heavy metals was carried out in three phases using real acid main drainage and bioleaching solutions generated at the laboratory. The first phase in a pH range of 2 to 4 to recover iron; the second phase in a pH range of 4 to 6 to recover copper; and the third phase in a pH range of 6 to 10 to recover zinc. The selective precipitation allowed the heavy metals to be completely removed from the solution or to achieve concentrations below the maximum allowable limit to be discharged to a body of water or public sewer. Results portray that the variation of pH is an effective method, easy to use and not expensive, feasible to be used in the purification of waters that have been polluted with heavy metals.

Kell hydrometallurgical extraction of precious and base metals from flotation concentrates - Piloting, engineering, and implementation advances

Kell hydrometallurgical extraction of precious and base metals from flotation concentrates - Piloting, engineering, and implementation advances

Recent Advances in the Direct Synthesis of H2O2

AbstractHydrogen peroxide (H2O2) is a highly effective, green oxidant that has found application in sectors ranging from the synthesis of fine chemicals and waste stream treatment to the extraction of precious metals and the bleaching of paper pulp and textiles. The growing demand for H2O2 has seen it become one of the 100 most important chemicals in the world. The direct synthesis of H2O2 from H2 and O2 has been a challenge for the scientific community for over 100 years and represents an attractive alternative to the current means of production. Herein we discuss the historical perspective of the direct synthesis process, the recent literature regarding catalyst design and the role of additives as well as the application of H2O2 as an in situ oxidant. We discuss the key problems that remain and conclude that although there has been progress with respect to the selectivity of hydrogen utilisation, there is a need to now concentrate on catalyst activity as the key remaining problem requiring a solution is the concentration of H2O2 that can be achieved, especially in flow reactors.

Numerical Solution of Rare Metal Leaching Problem

It is well known that a lot of chemical and physical processes take place on the surfaces of interaction between solid and liquid substances. These processes include a very important technological process of uranium, nickel, copper, precious metal and other solid compound extraction - in-situ leaching. In this article we will rely on the mathematical description of these complex systems proposed by A.M. Meirmanov, where the main idea is the presence of new conditions on a free (unknown) boundary between liquid and solid phases (“pore space - solid skeleton”). These conditions express the usual laws of mass conservation of mass and the development of the mathematical model describing the processes at the macroscopic level. The method proposed in the book allows us to study numerically the dependence ways of free boundary dynamics on a heterogeneous solution distribution velocity and external parameters (reagent temperature, pressure and concentration).

Simulation and economic analysis of a hydrometallurgical approach developed for the treatment of waste printed circuit boards (WPCB)

<p>This paper presents the main achievements of a hydrometallurgical process to recover base and precious metals from waste printed circuit boards (WPCB). The technology comprises a first leaching process performed in a two-step counter current way with sulfuric acid and hydrogen peroxide for base metals solubilization and a consecutive cross leaching process with thiourea, ferric sulfate and sulfuric acid to extract precious metals. Furthermore, the reach solutions are subjected to cementation procedure with zinc powder to recover the elements of interests as metal powders. The spent solution achieved after cementation of precious metals is partially recycled within the process and the other part is treated by Fenton process and then neutralized with lime. Considering the achieved results at the laboratory level, the entire procedure was simulated using SuperPro Designer software to determine the process economy for an industrial plant. Besides this, the use of this software allows achieving the material balance of a process and the design of the plant. As a result, the process implementation at a larger scale is simulated and the main issues that can result in such a case can be determined and solved.</p>

Challenges in the Recycling of Precious Metals

Precious metals from industrial scraps generated by manufacturing processes have been extensively recycled. For these recycles, it is necessary to ensure confidentiality when dealing with the scraps and to perform the recycling operation in an isolated lot with a high recovery ratio, short operation time, and low treatment cost. In recent years, three challenges have emerged in scrap recycling. The first is the decrease in the precious metal content in the scrap, owing to the substitution of precious metals with other non-ferrous metals. The second is the contamination of the scrap with metals that are not present in natural ores. These contaminations pose challenges in the extraction and purification of precious metals. The third challenge is the adherence to Japan’s environmental regulations, which have been tightened recently, restricting the continuous use of some chemicals such as nitric acid. In this report, some efforts of precious metal recycling companies to overcome these challenges are discussed.

The process of liquid phase reduction of calcine obtained from gold-containing mattes

The results of researches on the direct restoring of refractory ores of gold and pyrometallurgy enrichment of the collector mattes of gold have been introduced in the article. The tests for gold containing calcine restoring at the temperature range of 1350-1450 ° C were performed in the laboratory. At the results of testing of temperature effect on the degree of gold containing calcine restoring it became known the process of restoring is much overall at the temperatures of 1400-1450 ° C. At this, the yield of a metalized phase is at 13-15% range, and iron content is 71% on the average. The effect of coke consumption on the rate of calcine restoring under the effective temperature of 1400 ° C has been studied. The coke consumption on the calcine restoring rate made by experiment have shown the possibility of regular control of metals content in the metalized alloy by changing its content in the feed stock. The basic parameters of liquid phase gold containing calcine restoring with obtaining copper-ferrous alloy and mattes enriched by gold and silver have been determined. The research results can be applied for the development and creation of the new methods of gold and other metals extraction from a collector sulphide mattes-CPS (contracted pyrometallurgical selection) process consisting of direct melting of ledge ores persistent to opening and gold concentrates. The roasting of collector gold containing sulphide mattes with further separating of gold-copper-iron alloys will enable to create a complete pyrometallurgy technology of processing of refractory ledge gold ores escaping the enrichment processes and cyanidation, with 98-99% of gold extraction. In case of providing a high-scale of precious metals extraction in finale products and the positive technical and economical characteristics of recovery melting the transfer of collector gold contained metal alloys for the copper mattes converting of copper plants is possible.

Investigation on the recovery of gold and silver from cyanide tailings using chlorination roasting process

In this work, a chlorination roasting method for the extraction of precious metals (gold and silver) from the cyanide tailings (CT) was investigated. The decomposition mechanism of the CaCl2 used as chloride agent was presented during the chlorination roasting. The Au and Ag recovery as high as 91.6% and 54.7% under the optimum experiment conditions would be achieved. The optimal process conditions were identified to be a CaCl2 content 4%, chlorination temperature 1323 K and chlorination duration of 2 h. The microstructures of CT before and after roasting were examined by using scanning electron microscopy (SEM), and the volatilization process of the chloride of Au and Ag was assessed. The chlorination behaviors of all the phases in the CT in air atmosphere was analyzed using the thermogravimetric analysis (TGA), and the phase transformation of the main phase during roasting were analyzed by using X-ray diffraction (XRD). The chlorination roasting process shows unique advantage for treating the secondary sources of CT, additionally being environmentally benign.

Effects of intermittent liquid addition on heap hydrodynamics

Heap leaching is a well-known mineral processing technique, whereby crushed low grade ore is used for valuable metal extraction. The technique is typically used to extract precious and base metals, however, the metal extraction efficiency is relatively low. Even though reaction kinetics are extensively studied in heap leaching, the detailed hydrodynamic studies are still required to understand the underlying flow aspects. Heap hydrodynamics plays an important role in the transport of both leaching reagents and dissolved metal species and thus uniform liquid distribution through the ore mass is required. However, liquid channelling within the heaps has been identified as one of the main contributing factors for non-uniform liquid distribution. Since liquid channelling is supposed to be an inherent property in heap leaching systems, this work was primarily designed to explore the suitable techniques to improve liquid distribution and minimise liquid channelling in heaps. Intermittent liquid addition is employed and its effect on liquid channelling is studied, which has not been reported in the literature despite the application of it in industrial heaps. Both narrowly sized ore (16–20 cm) and realistic ore mixtures (2.36–25 cm) were studied in a pseudo 2-D Perspex column and the effect of rest period in intermittent leaching on liquid channelling was studied using out-flow liquid distribution measurements. The experimental results showed improved out-flow liquid distribution profiles and less channelling flow features in intermittent liquid addition conditions. The liquid out-flow profiles in both the packed bed systems were improved by resulting more flow paths through the particles and reduced features of liquid channelling. The narrowly sized fraction formed a near-Gaussian liquid distribution, which is the expected continuous probability based theoretical flow profile with drip emitter based liquid addition in heaps.

Electrochemical Characteristics of Acid Solutions of Spent Saline Chemical Current Sources

By the cyclic voltammetry method, we study acid solutions of saline chemical current sources, analyze their qualitative and quantitative compositions, and perform theoretical analysis of the possibility of extraction of precious metals from the solutions with analyzed compositions. The possibility and expediency of utilization metals with the use of the chemical and electrochemical methods is demonstrated.

Methods and Equipment for Breaking Down Gold-Containing Concentrates from Lean Ores and Mining Industry Waste

Exhaustion of rich or readily enriched precious metal ores leads to involvement in operation of stubborn ores from which effective extraction of precious metals by traditional methods is impossible. Within stubborn ores, a considerable part of gold is finely associated with sulphide minerals, generally with arsenopyrite and pyrite, and remains inaccessible for leaching even with fi ne comminution. Presence of an active carbonaceous agent occluding cyanide complexes of gold from solutions is another reason for stubbornness of gold-bearing ores. The joint negative effect of both factors on enrichment gives rise to doubly stubborn ores. A reduction in gold extraction indicators during hydrometallurgical processing for ores and concentrates with sorption and active organic carbon is overcome in most cases by using ion-exchange resins and activated carbon, whereas recovery of gold bonded in sulfides requires breakdown of the mineral crystal lattice. For this purpose, oxidizing roasting, and autoclave or bacterial oxidation of sulfides in a pulp are usually applied. The last two methods are now the most widespread. At the same time, roasting gold ores and concentrates is applied at a number of the overseas enterprises. This shows that hightemperature processes remain the main methods for preparing gold-bearing ores and concentrates for leaching. On the basis of results of calculations, research, and design and engineering development, and industrial tests the authors conclude that it is possible to increase extraction of gold and silver in products from the Mai and Badran fields after pyrolysis in a rotary drum furnace. Compared with oxidizing roasting environmental protection issues are resolved. Procedures and production equipment schemes are developed.

Extraction and separation of nonferrous and precious metals from waste of electrical and electronic equipment through ferric sulfate leaching and electrolysis

AbstractBACKGROUNDThe continuous generation of waste electrical and electronic equipment (WEEE) causes serious environmental problems as it is disposed in landfills, because of its hazardous content. In most electronic equipment, there are important components which contain large amounts of nonferrous metals and precious metals.RESULTSSeparation of silver using sieving proved to be efficient; silver was almost entirely collected in the finer fraction (<0.5 mm size). Separating gold from silver and palladium was achieved through leaching the metallic fraction in a 0.5 mol L–1 aqueous ferric sulfate solution at room temperature. A good yield of metal extraction was obtained after leaching using ferrous sulfate. The composition of the cathode deposits points to an almost complete recovery of silver and copper by electrolysis and a partial recovery of tin. Also, cyclic voltammetry tests in the solution (pH adjusted at 0.5) identified cathode peaks at ∼ −0.3 V Ag−1 ref. ascribable to Cu reduction, at ∼ − 0.783 V Ag−1 ref. ascribable to Ni reduction, as well as a plateau in the range −0.75 ↔ −1.0 V Ag−1 ref. ascribable to a simultaneous reduction of several ionic species.CONCLUSIONLeaching from WEEE was carried out by an environmentally friendly procedure using nonpolluting ferric sulfate, and using electrolysis some metals were extracted in good condition. © 2018 Society of Chemical Industry

Urban Mining of E-Waste is Becoming More Cost-Effective Than Virgin Mining.

Stocks of virgin-mined materials utilized in linear economic flows continue to present enormous challenges. E-waste is one of the fastest growing waste streams, and threatens to grow into a global problem of unmanageable proportions. An effective form of management of resource recycling and environmental improvement is available, in the form of extraction and purification of precious metals taken from waste streams, in a process known as urban mining. In this work, we demonstrate utilizing real cost data from e-waste processors in China that ingots of pure copper and gold could be recovered from e-waste streams at costs that are comparable to those encountered in virgin mining of ores. Our results are confined to the cases of copper and gold extracted and processed from e-waste streams made up of recycled TV sets, but these results indicate a trend and potential if applied across a broader range of e-waste sources and metals extracted. If these results can be extended to other metals and countries, they promise to have positive impact on waste disposal and mining activities globally, as the circular economy comes to displace linear economic pathways.

ВЛИЯНИЕ ПРИРОДЫ И ПОЛОЖЕНИЯ КАРБОФУНКЦИОНАЛЬНОГО ЗАМЕСТИТЕЛЯ НА СОРБЦИОННУЮ АКТИВНОСТЬ ПОЛИАЛКИЛСИЛСЕСКВИОКСАНОВ

An extensive number of organic sorbents can be used for extraction of precious metals from solutions, among which organosilicon sorbents deserve a particular attention. The sorption activity of organosilicon sorbents is determined by the nature of the functional group and its position in the polymer chain. In this study, the effect of the nature and position of the functional substituent on the sorption activity of polyalkylsilsesquioxanes with respect to Ag (I) and Au (III) ions is analyzed for polymer homologues and polymer analogs with sulfhydril, sulphonic, thioalkylamine, guanidine, biguanidine, malonodiamide and phthalamide groups. It is shown that the sorption activity of the com-pounds under study increases during a transition from polyalkylsilsesquioxanes, containing chemically active groups in the a-position, to their polymer homologues, containing these groups in the b- и g-position. The sorption activity of complexing polymers is determined by the stability of the chelate compounds formed, the number of donor-active atoms in the functional groups and their spatial position facilitating the formation of complexes.

Biosorbents based on pine sawdust and malt sprouts for preconcentration and ICP-OES determination of nonferrous, heavy, and precious metals in the environmental samples

ABSTRACTPine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.

Extraction of precious metals from industrial solutions by the pine (Pinus sylvestris) sawdust-based biosorbent modified with thiourea groups

A novel biosorbent based on pine (Pinus sylvestris) sawdust with chemical grafted thiourea groups was proposed for preconcentration of precious metals. A simple procedure was proposed for the synthesis of biosorbent by treating of sawdust with ammonium thiocyanate solution and a subsequent heat treatment at 160 °C. The biosorbent has been studied by thermogravimetry/differential scanning calorimetry (TGA/DSC), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The adsorption properties for precious metals ions (Au3+, Pd2+, Pt2+, Pt4+, Ir4+, Rh3+, Ru4+) extraction have been studied. Biosorbent quantitatively extracted precious metals from dilute solutions of hydrochloric acid (0.5–4.0 M). Iron and non-ferrous metals were not extracted in these conditions. The adsorbent showed high adsorption capacity for precious metals: 0.4 (Au3+), 1.7 (Pd2+), 1.0 (Pt2+), 0.8 (Pt4+), 0.45 (Ru4+), 0.55 (Rh3+), 0.4 (Ir4+) mmol/g.Biosorbent was used for extraction and preconcentration of precious metals from industrial solutions of refinery. Enriched for precious metals desorbing solution was obtained as a result. It is possible to obtain precious metals powder by combustion of biosorbent after adsorption of precious metals.