Precious Metal Content Research Articles

Influence of Α-Site Cations on Performance of Α2Ir2O7 Pyrochlore Oxygen Evolution Catalysts in Acidic Condition

The acidic nature of proton exchange membrane (PEM) electrolysis coupled with the highly oxidizing conditions of the oxygen evolution reaction (OER) greatly limits viable options for catalysts that are both active and stable. Precious metal catalysts, such as IrOx, are high performing OER materials, but scarcity and high cost may limit widespread implementation. Pyrochlore catalysts of the form A2B2O7 (where A is typically a rare-earth or alkaline-earth metal and B is a transition metal) have emerged as promising active candidates with reduced precious metal content and intriguing stability. For example, Y2Ir2O7 has demonstrated excellent activity and stability under acidic OER conditions despite some leaching of the Y cation, potentially leading to the in situ formation of a new active phase during catalysis1. In this work, the influence of the A-site cation on the activity and stability of Ir-based pyrochlore materials (A2Ir2O7) was systematically explored. Using a series of rare-earth metals, activity and stability were experimentally correlated with changes in the physical, chemical, and electronic properties to better understand the origin of the enhanced performance. This experimental work was supported by density functional theory (DFT) calculations. The fundamental insight gained will help to design OER catalysts with improved activity and reduced precious metal content, all without compromising stability. Cyclic voltammetry, chronoamperometry, chronopotentiometry, and double layer capacitance were used to determine the electrochemical performance of the catalysts. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify leaching of the A-site cations and Ir under acidic OER conditions and establish a relationship between the loss of material and the change in catalytic performance. This relationship was further investigated with DFT calculations. Additionally, the crystal structure, surface composition, and morphology of the catalysts before and after electrochemical testing were probed using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM).

Estimating flows and metal recovery values of waste printed circuit boards in Australian e-waste

This paper overviews current situation with e-waste management in Australia, focusing on material flows and metal recovery values of waste printed circuit boards (PCBs). PCBs often contain high concentrations of precious and other metals representing the most valuable material for recycling from e-waste. The amount of recovered PCBs from e-waste in Australia is estimated at up to 10 kt per year or 40% (2014), with potential metal recovery value of US$ 78 m or AUD 100 m (2014). However, most of collected PCBs are exported for recycling overseas, resulting in lost economic opportunities. The findings from this study represent the first comprehensive country-wide estimation of volumes, destiny and metal recovery values for waste PCBs. While many figures are indicative and expert opinion based, they help overcome the limitations of the official statistics for e-waste in Australia and provide important data for a feasibility study if the metal recovery operations for PCBs are to be considered in the country.

The mineralogy and mineral associations of platinum-group elements and precious metals in the Aurora Cu-Ni-Au-PGE deposit, Northern Limb, Bushveld Complex

Aurora is a platinum-group element (PGE) prospect hosted in the Northern Limb of the Bushveld Complex, South Africa. It is one of only three deposits discovered in the Northern Limb so far to be hosted in the melanocratic-leucocratic gabbroic cumulates of the Main Zone of the Rustenberg Layered Suite (Aurora, Moorddrift and Waterberg T Zone deposits), rather than in predominantly ultramafic rocks (e.g. Platreef). The host cumulates at Aurora have been divided into three principal units and they intrude the dolomites of the lower Transvaal Supergroup. Base metal sulphide (BMS) mineralisation with PGE is present in the leucogabbronorites and gabbronorites of Unit 2, and in coarse grained gabbronorite veins which intrude the peridotites of Unit 1. These veins contain up to 50% interstitial pyrrhotite-pentlandite-chalcopyrite ± pyrite. Unit 2 contains 1–3% pentlandite-pyrrhotite-chalcopyrite assemblages, and 1–5% chalcopyrite ± pyrite/pyrrhotite associated with hydrothermal alteration. The PGE content of Aurora however is predominantly controlled by the presence of platinum-group minerals (PGM), not BMS. LA-ICP-MS analysis of sulphides shows the BMS in Aurora have lower PGE concentrations than other Bushveld magmatic sulphides, with pentlandite carrying much lower concentrations of Pd (average 23 ppm) than the Platreef or the Merensky Reef. SEM-EDS analysis of 26 sections characterised 995 platinum-group minerals (PGM) and precious metal-bearing minerals (PMM), with a total area of 27850 μm2 and an average size of 28.2 μm2. Of the PGM and PMM identified in Aurora 85% (by area) are Pd-Te-Bi minerals, with 6% Pd-Te minerals, 4% electrum and 3% Ag-Te minerals, along with minor Pd-Bi, Pd-As, Pt-Te-Bi, Pt-As and Pt-S minerals that collectively comprise 2% of total area. Only 25% of the PGM and PMM in Aurora are BMS hosted, with the rest hosted in silicates. Of the total PGM and PMM area 22% are hosted in alteration-silicates (quartz, chlorite or actinolite) in an alteration halo around sulphides. Unusually, 52% of the PGM and PMM are spatially removed from BMS, instead hosted in alteration silicates and within cracks in primary silicates away from any BMS. This indicates a multi-stage ore genesis model, with hydrothermal remobilisation of PGE important for ore formation. The style and host rocks for mineralisation in the Aurora deposit are fundamentally different from other deposits in the Northern Limb of the Bushveld hosted in ultramafic rocks, such as the Platreef, GNPA member deposits and the F zone of the Waterberg deposit, all of which contain a greater diversity of PGM and BMS with higher precious metal contents. The mineralisation most similar to Aurora is the T Zone of the Waterberg deposit, located to the north of Aurora, which been suggested to be an along-strike equivalent of the Aurora Main Zone mineralisation. However, despite strong similarities in PGM mineralogy and S isotope signatures there are significant differences in BMS mineralisation and host lithology meaning it is unlikely they are directly linked stratigraphically. At present it seems more likely that Aurora and the Waterberg T Zone reflect similar fluid-influenced processes operating in different parts of the Main Zone, perhaps at different times and in different structural basins, rather than a continuous mineralised zone along strike.

Quality Increase in the Gold-Containing Cathode Sediment

The cathode sediments (CS), obtained as a result of industrial processing of gold-polymetallic raw material with complex chemical and mineral composition, contain a significant amount of impurity metals (copper, lead, zinc, iron, etc.), which leads to a significant increase in the cost of subsequent refining of these materials. The authors carried out experimental work on preliminary acid treatment of CS for the purpose of leaching impurities and increasing the share of precious metals in them. The objects of research were cathodic sediments (bypass solutions of the enterprise) containing copper and lead in the amount,% wt., respectively: 21.29 and 4.11. We tested nitric acid as a solvent in laboratory tests. For the selection of optimal leaching parameters, studies were carried out at various concentrations of the agent (from 50 to 350 kg/m3) and the ratio of L:S - (3-7):1. The duration of the experiments was 2 h, the experiments were carried out with vigorous stirring and standard ambient temperature (25°C). The experimental data processing was carried out with the help of STATISTICA 6.0 software; As factors of variation, we chose: concentration of acid, ratio of liquid and solid phases. It has been determined that nitric acid provides effective purification of CS from impurities. After the chemical enrichment, the content of precious metals in leaching cakes increased, the CS became compliant with the requirements of TU 117-2-3-78. When processing cathode sediments with nitric acid, 99% of silver passes into solution, which then allows it to be recovered from solutions by cementation and, consequently, to obtain alloys of gold and silver separately.

Flotacijska ispitivanja majdanpečke rude bakra u cilju poboljšanja iskorišćenja bakra i kvaliteta koncentrata primenom različitih kolektora

This paper presents the results of mineralogical and flotation studies on the copper ore from the deposit North Revir in the Copper Mine Majdanpek, using different collectors. XRD and ore mineralogical analysis showed that the most common minerals are pyrite and chalcopyrite. Chemical analysis confirm that it is a complex low-grade copper ore with average copper content of 0,273%. The content of precious metals (Au and Ag) was 0.2 g/t and 1.2 g/t, respectively. The main aim of flotation studies have been the effect of collector type on the recovery and concentrate grade in the copper flotation process. Various collectors and combinations of them were used in the rough flotation tests of copper ore. The copper recovery was in the range from 79.43% (test no. 4) to 84.96% (test no. 7). The best flotation results were obtained with mixture collectors of sodium isopropyl xanthate (Z11), dialkyl dithiophosphinates (Aerophine 3404) and SKIK BZ 2000. The collector's dosages of 20 g/t Z11, 8 g/t AP3404 and 8 g/t SKIK BZ 2000 produced the copper recovery (84.96 %) with copper concentrate grade of 1.52% .

Au-Ag-Pd-Pt mineralization in sedimentary rocks associated with Triassic carbonaceous silicites of Sikhote-Alin

Subject.The paper is devoted to the study of the gold-silver-palladium-platinum mineralization of the streaky systems in the sedimentary rocks associated within the Triassic carbonaceous silicites of the Taukhinsky and Samarkinsky terranes of the Sikhote-Alin.Materials and methods.In the process of investigations we studied the metamorphosed carbonaceous siliceous-clay rocks and systems of the mineralized fractures in the Triassic siliceous-clay and siliceous (including jaspers) rocks of Shirokopadninskaya, Vysokogorskaya and Gornaya areas, as well as in the sandstones (unclarified age) of Gornaya area. The samples for the analytical study were taken with the lump way. To estimate the content of precious metals in the rocks, cut by the systems of the mineralized fractures, we used the fire assay and atomic-absorption methods. The analyses of minerals (in polished sections) have been done using the JXA-5A and JXA8100 microanalysers.Results.The gold-silver-palladium-platinum mineralization in the siliceous and clay-siliceous rocks, as well as in the sandstones is restricted to the systems of the mineralized fractures and by many features are analogous to the precious-metal mineralization of the black-shale formations. It is represented by native forms, disordered solid solutions, and intermetallic compounds of different metals. The specificity of the Au-Ag-Pd-Pt mineralization is a wide distribution of copper gold, Ni-, Cu-, and Pbbearing gold, and Zn-bearing platinum. Native elements and intermetallic compounds, including those of precious metals, are not rarely associated with the organic matter testifying to the active participation of carbon and, probably, hydrogen that provided the high- and ultra-reduction character of the processes of mineral formation.Conclusions.The presence of the mineral forms of different maximum reduced metals is caused by the influence of the organic matter of the Triassic carbonaceous silicites. This consisted in the removal of the most volatile components, and first of all the poorly bound water and hydrocarbons from the carbonaceous rocks through the contact metamorphism related with the injection of the granitoid intrusions of Cretaceous plutonic and volcanoplutonic belts.

Geochemical and micro-textural fingerprints of boiling in pyrite

Abstract The chemical composition, textures and mineral associations of pyrite provide key information that help elucidate the evolution of hydrothermal systems. However, linking the compositional and micro-textural features of pyrite with a specific physico-chemical process, e.g., boiling versus non-boiling, remains elusive and challenging. In this study we examine pyrite geochemical and micro-textural features and relate these results to pyrite-forming processes at the active Cerro Pabellon Geothermal System (CPGS) in the Altiplano of the northern Chile. We integrate electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data with micro-textural observations of pyrite and associated gangue minerals recovered from a ∼500 m long drill core that crosscuts the argillic, sub-propylitic and propylitic alteration zones of the CPGS. Additionally, we carried out a Principal Component Analysis (PCA) in order to inspect and understand the main data structure of the pyrite geochemical dataset. The concentrations of precious metals (Au and Ag), metalloids (As, Sb, Se, Bi and Tl), and base and heavy metals (Cu, Co, Ni and Pb) in pyrite from the CPGS are significant. Among the elements analyzed, As, Cu and Pb are the most abundant with concentrations that vary from a few parts per million (ppm) to wt% levels (up to 4.4 wt% of As, 0.5 wt% of Cu and 0.2 wt% of Pb). Based on contemporaneous gangue mineral associations and textures, the mechanisms of pyrite precipitation in the CPGS were inferred. Pyrite formed during vigorous boiling is characterized by relatively high concentrations of As, Cu, Pb, Ag and Au and lower concentrations of Co and Ni compared to pyrite formed under different conditions. These anhedral to euhedral pyrite grains display zones with a porous texture and abundant mineral micro- to nano-inclusions (mainly galena and chalcopyrite) indicating a formation by rapid crystallization. In contrast, pyrite formed under gentle boiling (more gradual cooling and less abrupt physico-chemical variations than in vigorous boiling) to non-boiling conditions is characterized by a higher concentration of Co and Ni, and relatively low concentrations of As, Cu, Pb, Ag and Au. Texturally, these pyrites form aggregates of euhedral and pristine pyrite crystals with scarce pores and mineral inclusions suggesting formation under steadier physico-chemical conditions. Our results show that pyrite can not only record the chemical evolution of hydrothermal fluids, but can also provide critical information related to physico-chemical process such as boiling and phase separation. Since boiling of aqueous fluids is a common phenomenon occurring in a variety of pyrite-forming environments, e.g., active continental and seafloor hydrothermal systems, and porphyry Cu-epithermal Au-Ag deposits, pyrite compositional and textural features are a valuable complement for discriminating and tracking boiling events in modern and fossil hydrothermal systems.

Behavior of Waste Printed Circuit Board (WPCB) Materials in the Copper Matte Smelting Process

The amount of waste electrical and electronic equipment (WEEE) in the world has grown rapidly during recent decades, and with the depletion of primary ores, there is urgent need for industries to study new sources for metals. Waste printed circuit boards (WPCB) are a part of WEEE, which have a higher concentration of copper and precious metals when compared to primary ore sources. PCB materials can be processed using pyrometallurgical routes, and some industrial processes, such as copper flash smelting, have utilized this type of waste in limited amounts for years. For the purpose of recycling these materials through smelting processes, this work studied the behavior of WPCB scrap when dropped on top of molten slag. A series of experiments was carried out during this research at a temperature of 1350 °C, in an inert atmosphere with different melting times. The time required for complete melting of the PCB pieces was 2–5 min, after which molten alloy droplets containing Cu, Pb, Sn, Ni, Au, and Ag formed and started descending toward the bottom of the crucible. The ceramic fraction of the PCB material mixed with slag and the polymer fraction was pyrolyzed during the high-temperature experiments. The results give an understanding of PCB melting behavior and their use as a part of the smelting furnace feed mixture. However, more research is needed to fully understand how the different elements affect the process as the amount of PCB in the feed increases. The physical behavior and distribution of PCB materials in fayalite slag during the smelting process are outlined, and the results of this work form a basis for future studies about the chemical reaction behavior and kinetics when PCB materials are introduced into the copper smelting process.

ОПЫТ КОМПЛЕКСНОГО ИСПОЛЬЗОВАНИЯ ЗОЛОТОСОДЕРЖАЩЕГО СЫРЬЯ ПРИ ПРОИЗВОДСТВЕ ДРАГОЦЕННЫХ МЕТАЛЛОВ

С истощением богатых золотосодержащих руд в переработку все чаще стали вовлекаться полиметаллические руды, которые помимо драгоценных металлов содержат другие элементы, представляющие интерес для их извлечения. Проблема использования таких руд решается крайне трудно из-за высокой себестоимости доизвлечения сопутствующих ценных компонентов. В работе приведены результаты исследований по комплексному использованию добываемого золотосодержащего сырья на примере месторождения «Березитовое» (Амурская обл.), характеризующегося низким содержанием драгоценных металлов и наличием в значительном количестве тяжелых цветных металлов (меди, свинца). Были проведены экспериментальные работы по получению меди методом цементации из растворов, образующихся после выщелачивания соляной кислотой примесей золотосодержащих катодных осадков. Металлом-цементатором служила железная стружка (отходы токарного цеха предприятия). Далее было предложено использование цементационной меди в качестве коллектора при переплавке шлаков - отходов переработки бедных полиметаллических руд, содержащих драгоценные металлы. Авторами были получены слитки сплава лигатурного золота с массовой долей золота 16 %, отвечающие требованиям ТУ 117-2-7-75 по содержанию цветных металлов. Серебро, частично перешедшее в раствор при солянокислой обработке катодных осадков, также восстанавливается совместно с цементационной медью и при последующей плавке переходит в сплав лигатурного золота. Таким образом, предложенный авторами метод способствует снижению содержания драгоценных металлов в «незавершенном производстве» золотоизвлекательной фабрики. Показана возможность реализации полученной цементационной меди на предприятиях, специализирующихся на изготовлении ювелирных изделий; ожидаемый экономический эффект при этом составил более 1,8 млн руб.

Concentration of precious metals from waste printed circuit boards using supergravity separation

Printed circuit boards (PCBs) comprise valuable metals, precious metals, and hazardous materials. Thus, they are considered both attractive secondary sources of metals and environmental pollutants. This study is based on the selective separation of Pb-Sn, Sn-Cu, and Cu-Zn alloys, where supergravity separation was used to concentrate precious metals (i.e., Ag, Au, and Pd) from PCBs in Cu-Zn alloy and final residue. The temperature and gravity coefficient were found to have great influence on the concentration of precious metals in said alloy and residue. At the optimized temperature of 1300 °C, gravity coefficient of 1000, and separation time of 5 min, the Ag, Au, and Pd contents in the Cu-Zn alloy increased by 1.65, 2.05, and 1.54 times, respectively, compared to their concentrations in the original PCBs, while those in the final residue increased by 0.63, 1.02, and 2.62 times, respectively. By combining an appropriate hydrometallurgical process with the present supergravity separation and concentration of precious metals, this clean and efficient process provides a new pathway to recycle valuable metals and prevent environmental pollution by PCBs.

Exploration of the material distribution of complex components in waste electrical and electronic equipment

<p>Technological development combined with a rapid and global market penetration has led to high volumes of Waste Electrical and Electronic Equipment (WEEE). Simultaneously, the use-phase has become shorter resulting in an annual growth rate of WEEE between 3-5%, which makes WEEE one of the fastest growing waste streams. The high metal content of WEEE has been a driving force for behind the expansion of recycling industry. However, during the de-pollution process, a certain type of components is sorted out, which due to their diversity in shape, size, and material composition, cannot be assigned to any homogenous material. These components can generally be classified as complex components and include Printed Circuit Boards (PCB), Hard Disk Drives, Power Supply Units, etc. The aim of the present research is to provide an assessment of the material composition of complex components exemplified in more detail on PCBs. A set of minimal requirements has been developed in order to increase comparability of available data sets. Furthermore, a novel classification system has been designed for PCBs with according to the current recycling practices in EU. Finally, the paper provides a mapping of complex components with a particularly high content of precious metals and critical raw materials.</p>

Spanish and Portuguese Gilding Threads: Characterization Using Microscopic Techniques.

Gilding threads collected from Spanish and Portuguese palaces and from the embroideries and adornments of sculptures of the Virgin and Christ that form part of Sevillian Holy Week were analyzed and compared (20 artifacts were evaluated). The study covered a broad time period with examples from the 13th to 14th centuries, 18th to 20th centuries, and also including modern embroideries. A combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy was used. The knowledge of the layered structures of the threads has provided very valuable information regarding the manufacturing techniques. The different metal threads found in the embroidery studied consisted of gold, silver, copper, and alloys of these metals and aluminium. The fabrication procedures often differed in the different workshops and changed with time. In the modern embroideries, a decrease of precious metal concentration was detected. The threads were wound around a core of silk threads.

Experimental and numerical analysis of flow through catalytic converters for original part and WALKER’s replacement using reverse engineering and CFD

The paper describes results of experiments and CFD simulation for an original catalytic converter part and WALKER’s replacement. Pressure drop was measured for catalysts, which influences on exhaust backpressure, an important parameter affecting the engine power, fuel consumption, emission of harmful gases and wear components. First the pressure drops was examined in the original catalyst and in prototypes of WALKER’s. The prototypes differed in that their monoliths had different lengths, density of channels and contents of precious metals (PGM). In the next stage reverse engineering was applied, which included laser scanning of parts and then processing the point clouds in Leios2 program. Recreated 3D geometry of catalysts in Catia v5 program was prepared for computational fluid dynamics. For all studied cases the measured data were used to calculate coefficients of porous media model i.e. viscous and inertial resistances, which were used in the Ansys Fluent program. Static pressure drops on the monoliths were then predicted by the CFD model for different gas mass flow rates through the catalysts. Exhaust velocities and flow uniformity were also analysed. Comparison of the results for all parts allowed for stating, which prototype is better and which has operating parameters comparable to the original part.

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.

Anchoring Active Pt2+ /Pt0 Hybrid Nanodots on g-C3 N4 Nitrogen Vacancies for Photocatalytic H2 Evolution.

A Pt2+ /Pt0 hybrid nanodot-modified graphitic carbon nitride (CN) photocatalyst (CNV-P) was fabricated for the first time using a chemical reduction method, during which nitrogen vacancies in g-C3 N4 assist to stabilize Pt2+ species. It is elucidated that the coexistence of metallic Pt0 and Pt2+ species in the Pt nanodots loaded on g-C3 N4 results in superior photocatalytic H2 evolution performance with very low Pt loadings. The turnover frequencies (TOFs) are 265.91 and 116.38 h-1 for CNV-P-0.1 (0.1 wt % Pt) and CNV-P-0.5 (0.5 wt % Pt), respectively, which are much higher than for other g-C3 N4 -based photocatalysts with Pt co-catalyst reported previously. The excellent photocatalytic H2 evolution performance is a result of i) metallic Pt0 facilitating the electron transport and separation and Pt2+ species preventing the undesirable H2 backward reaction, ii) the strong interfacial contact between Pt2+ /Pt0 hybrid nanodots and nitrogen vacancies of CNV facilitating the interfacial electron transfer, and iii) the highly dispersed Pt2+ /Pt0 hybrid nanodots exposing more active sites for photocatalytic H2 evolution. Our findings are useful for the design of highly active semiconductor-based photocatalysts with extremely low precious metal content to reduce the catalyst cost while achieving good activity.

Waste electric and electronic equipment (WEEE) melting and resulting gases processing in microwave field

The recycling of waste electric and electronic equipment (WEEE) is of great interest due to the large amounts of such wastes and to their contents of useful and precious metals. After reaching the end of its service lifetime, WEEE is collected and recycled through various processing methods, depending on the waste type.Pyrometallurgy is currently the most used method for the recovery of the metallic fractions from WEEE such as printed circuit boards (PCBs). This type of processing raises major issues because of the generated gas emissions. The non-metallic fraction of the PCBs, which account for a large proportion (50-70 wt.%), contains brominated flame retardants, thermosetting resin, reinforced materials and other toxic and hazardous organic substances. The combustion of these chemicals during the pyrometallurgical processes may cause serious health-related and environmental problems. In this paper, the treatment in microwave field of the toxic gases resulted from the melting of crushed PCBs has been preliminarily investigated. During the waste melting in a microwave furnace, toxic compounds such as benzene (3.2-6.5 mg×m−3), toluene (15.3-17.8 mg×m−3), ethylbenzene (2.8-5.7 mg×m−3), styrene (21.5-24.3 mg×m−3), m/pXilen (1.4-2.8 mg×m−3), naphthalene (1.1-1.3 mg×m−3) and 1,3,5 trimethylbenzene (15.2-23.5 mg×m−3) have been detected in the effluent gases. The treatment was carried out by passing the resulting gases through a filter fabricated from a microwave susceptor granular material (SiC), placed in a microwave transparent tube (fused quartz, 5 cm diameter). For heating the filter, a number of 3 magnetrons (2.45 GHz frequency and 850 W power each) were mounted outside the fused quartz tube at an angle of 120 degrees and in different geometrical planes. The influence of the process parameters (heating response of the susceptor materials, temperature, gas flow, gas pressure) was investigated. It was observed that the temperature of the filter (i.e. the power density in the microwave susceptor material) has a major influence on the neutralization of the toxic compounds while the gas flow and pressure had a minor influence. At a temperature of 1350-1400°C (power density of 5000 W× kg−1), a gas flow of 150 m3 × h−1 and a pressure of 800-1000 mbar, the content of such substances in the gases was reduced below the legal limits. These results confirm the feasibility of the process of treating the gases resulting from the melting of e-waste in a microwave furnace.

Advanced Core-Shell Nanostructures for Electrocatalytic Applications

The electrocatalytic performance of Pt-bimetallic catalysts is usually limited by the lack of long-term durability, primarily due to leaching of the non-noble element under the harsh electrochemical conditions. We have recently developed cobalt-platinum core-shell nanostructures could sustain high catalytic activity for the oxygen reduction reaction, demonstrating 8 times of improvement in catalytic activity versus commercial Pt catalysts and no more than 13% of loss after 30,000 potential cycles. Furthermore, we have developed a series of core-shell nanostructures involving various transition metals, such as Co, Cu, Pd, Au, Ag, Rh and Pt. These materials have been found to exhibit superior catalytic performances in many electrochemical reactions, achieving enhanced catalytic activity and durability at reduced precious metal content. We have combined electron microscopic elemental mapping and electrochemical studies of CO stripping to follow the evolution of nanoscale and surface structures over the course of electrochemical reactions, which has allowed us to develop fundamental understanding of the interactions between the metals in the core-shell nanostructures.

Determination of Precious Metals in Geological Samples from Four Gold Ore Deposits of the North-East of Russia

Compositions of rare mineral phases containing precious metals (PMs) in samples from Natalka, Pavlik, Vetrenskoe, and Degdekan gold ore deposits (North-East of Russia) are studied by scintillation atomic emission spectrometry (SAES) and electron probe microanalysis (scanning electron microscopy and electron probe X-ray microanalysis, SEM–EPMA). The SAES method found dozens and hundreds of particles carrying gold, silver, and all platinum-group elements as native metals, intermetallides and solid solutions, arsenides, antimonites, sulfoarsenides, tellurides, selenides, etc. The variety of the elemental compositions of PM species (mineral phases) found by SAES significantly exceeds the list of minerals found previously by SEM–EPMA because of different natures of optical and X-ray spectra. The sizes of PM particles calculated by the SAES method and measured by SEM–EPMA are similar. The SAES data on the total concentrations of PMs satisfactorily agree with the results of inductively coupled plasma mass spectrometry.

Investigation of an alternative chemical agent to recover valuable metals from anode slime

Anode slime (AS) including high content of precious metals is a by-product obtained after the electro-refining stage in copper production. In this study, it is aimed to recover Cu, Au, and Ag from the AS by using 1-butyl-3-methyl-imidazolium hydrogen sulphate ([Bmim]HSO4) ionic liquid (IL) as a green solvent. The effects of IL concentration, temperature, reaction time and pulp density on recovery of valuable metals were statistically investigated. A high copper recovery of 87.52% was obtained under optimum condition as in 60% (v/v) [Bmim]HSO4 at 50 °C after 2 h, pulp density at 40 g/L (1/25 solid/liquid ratio). Also, a remarkable gold recovery as 97.32% has been achieved in 80% (v/v) [Bmim]HSO4 at 95 °C after 4 h, pulp density at 40 g/L. Temperature and IL concentration were detected as the most effective parameters for copper and gold recovery from AS, respectively. Silver could not be recovered from the AS due to the lower solubility in [Bmim]HSO4 IL media. According to experimental results, [Bmim]HSO4 could be offered as an alternative leaching agent, instead of conventional solvents, to recover valuable metals from copper anode slime.

Благороднометалльная геохимическая специализация мезопротерозойских магматических комплексов Башкирского мегантиклинория и восточной окраины Восточно-Европейской платформы

First described the noble metal (platinum group elements (PGE) and Au) geochemical specialization of magmatic rocks of Bashkirian meganticlinorium and the adjacent part of the East European Platform (EEP). Identity graphs of normalized PGE and Au contents in igneous rocks of the western slope of the Southern Urals and east EEP indicates the proximity of their formation and common mechanisms of formation of noble metal geochemical specialization during the formation of these bodies. It was found that the specific precious metal geochemical specialization (“rhodium anomaly”) magmatic complexes Bashkirian meganticlinorium and east EEP, due to the content of precious metals in sulphide minerals (pentlandite) has a “primary” nature. Variations contents Pt, Pd and Au, which are characteristic for different varieties of common species within the region, are the result of their redistribution during the formation of magmatic bodies and/or transformation by secondary processes. It is shown that the noble metal geochemical specialization of clastic rocks of Bashkirian meganticlinorium tectonic zones (presence of increased amounts of platinum and most importantly - “rhodium anomaly”) formed under the influence of magmatism with further redistribution and concentration of precious metals as a result of a later time metamorphism and local metasomatism.