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We examine the hedging and safe-haven characteristics of gold, silver, platinum, and palladium and three major indices in the US market. The metal markets are known for their hedging characteristics during financial distress. This article sheds new insights using high-frequency data into precious metals' hedging and safe-haven abilities under extreme market volatility conditions attributed to the COVID-19 crisis using the copula method. The results show that gold outperforms all other precious metals in hedging and as a safe haven under extreme stock market conditions, in both the pre-crisis and crisis periods, with silver as the next best alternative. JEL codes: G01, G11, G15, G19 [ABSTRACT FROM AUTHOR]

Traditionally, precious metals are processed by either lost-wax casting or the casting of semi-finished products followed by cold or hot working, machining, and surface finishing. Long process chains usually conclude in a high material input factor and a significant amount of new scrap to be refined. The maturing of Additive Manufacturing (AM) technologies is advantageous with regard to resources among other criteria by opening up new processing techniques like laser-based powder bed fusion (LPBF) for the production of near net shape metal products. This paper gives an insight into major advantages of the powder-based manufacturing of precious metal components over conventional methods focusing on product carbon footprints (PCF). Material Flow Cost Accounting (MFCA) for selected applications show energy and mass flows and inefficient recoverable losses in detail. An extended MFCA approach also shows the greenhouse gas (GHG) savings from avoiding recoverable material losses and provides PCF for the products. The PCF of the precious metals used is based on a detailed Life Cycle Assessment (LCA) of the refining process of end-of-use precious metals. In the best case, the refining of platinum from end-of-life recycling, for example, causes 60 kg CO2e per kg of platinum. This study reveals recommended actions for improvements in efficiency and gives guidance for a more sustainable production of luxury or technical goods made from precious metals. This exemplary study on the basis of an industrial application shows that the use of AM leads to a carbon footprint of 2.23 kg CO2e per piece in comparison with 3.17 kg CO2e by conventional manufacturing, which means about a 30 percent reduction in GHG emissions and also in energy, respectively. [ABSTRACT FROM AUTHOR]

Recycling precious metals with high-efficiency is undoubtedly beneficial to optimize resource utilization for environmental remediation and sustainable development. Herein, we report an efficient route to recycle the palladium (Pd) and platinum (Pt) electrocatalysts using a phase transfer method. This strategy involves acidic dissolution of deactivated precious metal (Pd/Pt) electrocatalysts from their loading substrates, mixing with an ethanolic solution of dodecylamine (DDA), subsequent extraction of metal ions into a non-polar organic phase, and final reduction by sodium borohydride to reproduce high-performance electrocatalysts towards typical electrochemical reactions, e.g., oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR). In specific, the transfer efficiencies are up to 98% and the final recovery rate is over 85% for Pd and Pt electrocatalysts in each cycle. This approach symbolizes a facile and efficient way to recover precious metals, which might be applied to recycling a wide range of metals in various realms after appropriate modifications.

Traditionally, precious metals are processed by either lost-wax casting or the casting of semi-finished products followed by cold or hot working, machining, and surface finishing. Long process chains usually conclude in a high material input factor and a significant amount of new scrap to be refined. The maturing of Additive Manufacturing (AM) technologies is advantageous with regard to resources among other criteria by opening up new processing techniques like laser-based powder bed fusion (LPBF) for the production of near net shape metal products. This paper gives an insight into major advantages of the powder-based manufacturing of precious metal components over conventional methods focusing on product carbon footprints (PCF). Material Flow Cost Accounting (MFCA) for selected applications show energy and mass flows and inefficient recoverable losses in detail. An extended MFCA approach also shows the greenhouse gas (GHG) savings from avoiding recoverable material losses and provides PCF for the products. The PCF of the precious metals used is based on a detailed Life Cycle Assessment (LCA) of the refining process of end-of-use precious metals. In the best case, the refining of platinum from end-of-life recycling, for example, causes 60 kg CO2e per kg of platinum. This study reveals recommended actions for improvements in efficiency and gives guidance for a more sustainable production of luxury or technical goods made from precious metals. This exemplary study on the basis of an industrial application shows that the use of AM leads to a carbon footprint of 2.23 kg CO2e per piece in comparison with 3.17 kg CO2e by conventional manufacturing, which means about a 30 percent reduction in GHG emissions and also in energy, respectively.

In this study, we designed a Pt/CoFe 2 O 4 /NC composite material as an excellent electrocatalyst for hydrogen evolution reaction (HER) and used the HER signal to construct an electrochemical immunosensor for carcinoembryonic antigen (CEA) detection. Remarkably, Pt/CoFe 2 O 4 /NC demonstrated superior HER performance compared to alternative Pt-based materials. It exhibited a low overpotential of only 42 mV and a Tafel slope of 253 mV dec−1 in acidic medium. Furthermore, due to the excellent conductivity, large surface area, and superior HER performance of Pt/CoFe 2 O 4 /NC, it was used as secondary antibody (Ab 2) label to achieve signal amplification in the electrochemical immunosensor. The results showed that this immunosensor possessed high selectivity and sensitivity. The linear detection range is 1.0 × 10−4–5.0 ng mL−1, and the detection limit is 0.0134 pg mL−1. It has potential applications in the clinical analysis field. Due to the excellent conductivity, large surface area, and superior HER performance of Pt/CoFe 2 O 4 /NC, it was used as an Ab 2 label to achieve signal amplification in the electrochemical immunosensor. The results showed that this immunosensor possessed high selectivity and sensitivity. The linear detection range is 1.0 × 10−4–5.0 ng mL−1, and the detection limit is 0.0134 pg mL−1. It has potential applications in the clinical analysis field. [Display omitted] • Pt is loaded onto the CoFe 2 O 4 /NC by photoreduction method. • The Pt/CoFe 2 O 4 /NC with low Pt loading presents low overpotential and Tafel slope in the HER. • A novel electrochemical immunosensor based on Pt/CoFe 2 O 4 /NC was constructed for CEA detection. [ABSTRACT FROM AUTHOR]

As a kind of energy conversion equipment with high energy conversion efficiency and green pollution-free characters, fuel cells are expected to improve the current situation of high fossil energy consumption and promote green development. The high cost and poor electrochemical performance of cathode oxygen reduction catalysts in fuel cells limit their commercialization. At present, researchers are actively developing new oxygen reduction catalysts with high catalytic activity and stability. The research progress of cathodic oxygen reduction catalysts is reviewed, and its future development direction and research progress are prospected. [ABSTRACT FROM AUTHOR]

The results of investigations into enrichment of precious metals in sphalerite and pyrite from the Maluntou epithermal gold deposit, China, are reported. The obtained data suggest intimate associations of Au- and Ag-bearing nanoparticles with chalcopyrite inclusions in sphalerite and pyrite. The origins of chalcopyrite inclusions involved different hydrothermal processes, including recrystallization-driven phase separation from parent chalcopyrite-sphalerite solid solutions and replacement of pre-existing pyrite in the presence of Cu-bearing fluids. The chalcopyrite blebs/lamellae follow sphalerite {111} planes, which define a shared sulfur layer for both chalcopyrite and sphalerite. This study indicates that mixing and boiling during the evolution of ore-forming fluids for the Maluntou deposit are key processes for the abnormal enrichment of precious metals in sphalerite and pyrite. The chalcopyrite micro/nano inclusions enhanced enrichment of precious metals in sphalerite provides new insights into the controls on the enrichment of precious metals in sulfides. [ABSTRACT FROM AUTHOR]

Pt/Ir thin film thermocouples were prepared on the surface of the GH5188 special-shaped high temperature superalloy，and the thin film thermocouples were placed on the flame flow table to test the transient temperature of the surface of the special-shaped high temperature superalloy. After four cycles of high temperature and high-speed flame burning，the total test time reached 8700 s，the Pt/Ir thin film thermocouple can still obtain stable temperature data. The success of this test indicated that Pt/Ir thin film thermocouples have taken an important step towards engineering application. Aiming at the engineering application of thin film thermocouples，the project team investigated the thin film preparation technology，interface control，integrated preparation，signal and system，etc.，broke through 13 key technologies，and realized the engineering application of Pt/Ir thin film thermocouples. The breakthrough of this experiment makes China have the ability of temperature measurement under the condition of blade simulation service.

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The noble metal Au is extensively used in jewelry, industry, and medicine. In order to mitigate the low sensitivity of the flame module atomic absorption spectrometer (FAAS) to determine the gold, zinc oxide (ZnO) nanomaterial were synthesized and used to pretreatment of the sample and preconcentrate gold ions in dispersive solid phase extraction (DSPE) process. Enrichment factor of the extraction method was enhanced by performing buffer solution type/volume, nanomaterial amount, mixing type/period, and desorption solvent concentration/volume optimizations. Calibration plot displayed good linearity and percent relative standard deviation recorded for the lowest concentration of the plot was adequately low (<7.0 %). Dynamic dynamic range for the proposed method was calculated between 30–400 μg/L. Regression coefficient (R2) of proposed method was found to be 0.9956. With an enrichment factor of 44.5‐folds, method recorded a detection limit (LOD) of 7.4 μg L−1 and quantification limit (LOQ) of 24.8 μg L−1. Flash gold plating bath solution was used to certify the quantification accuracy/applicability in complex matrix of the method. The obtained results (1.86±0.08 g L−1) were compatible with the results of the reference method (ICP‐OES) (1.87±0.08 g L−1). This is the first study for the extraction/preconcentration of gold using ZnO nanomaterial. [ABSTRACT FROM AUTHOR]

γ-Al2O3 is an enormously important industrial material, especially used as catalysts, catalyst supports, and adsorbents due to its attractive structural, surface, and dielectric properties. Particularly, catalytic reduction of pollutants such as nitric oxide, as well as oxidation of hydrocarbons, is accomplished with precious metals such as platinum or palladium dispersed on the γ-Al2O3 surface. γ-Al2O3 loaded with precious metals has an excellent catalytic degradation ability of organic matter and is widely used to treat exhaust gas from stationary and mobile sources. High-temperature sintering is a major cause of catalyst deactivation. For example, at higher treatment temperatures (>800 ℃), γ-Al2O3 transforms into δ-Al2O3 and θ-Al2O3, decreasing in surface area and a change in dielectric properties. Additionally, in the reaction environment, supported metal nanoparticles grow in size, leading to the loss of catalyst activity. How to improve the anti-sintering performance of catalysts is a particular concern of this field. This review analyzes the reason and mechanism of the high-temperature sintering of γ-Al2O3 loaded with precious metal. A high temperature leads to Ostwald ripening and particle migration, coalescence of precious metals, and phase transformation of γ-Al2O3, reducing the specific surface area and activity of the catalyst. On this basis, the approaches for improving the high-temperature thermal stability of catalysts were reviewed and sorted out from three aspects, namely, precious metals, supports, and the interaction between them. First, the focus is on precious metal modification, carrier modification, and changing the interaction between them to improve thermal stability. Additionally, other methods, such as the confinement method and crystal plane control, are thoroughly examined and explained. These strategies provide new insights into catalyst design. Finally, the developmental trends of γ-Al2O3-based oxidation catalysts are broadly forecasted.

There is no special standard for the determination of precious metal content in precious metal alloy electroplating wastewater. An ICP method for the determination of 5 precious metal elements in precious metal alloy electroplating wastewater was established in the study. By means of drying, dehydration, and roasting, the influence of impurities in electroplating wastewater was effectively avoided. The condition tests on roasting temperature, roasting time, and acid dosed for dissolution of the sample were conducted, which determined that the roasting temperature was 550 ℃,the roasting time was 2 h, and the dosage of acid（aqua regia） used for sample dissolution was 10 mL. The recovery rates were 97.33 %-102.67 %,and the relative standard deviation（RSD） was 0.58 %-2.58 %.The accuracy and precision are up to the requirements of analysis and testing. [ABSTRACT FROM AUTHOR]

With the development of the global economy, large amounts of fossil fuels are being burned, causing a severe energy crisis and climate change. Photocatalytic CO2 reduction is a clean and environmentally friendly method to convert CO2 into hydrocarbon fuel, providing a feasible solution to the global energy crisis and climate problems. Photocatalytic CO2 reduction has three key steps: solar energy absorption, electron transfer, and CO2 catalytic reduction. The previous literature has obtained many significant results around the first two steps, while in the third step, there are few results due to the need to add a co-catalyst. In general, the co-catalysts have three essential roles: (1) promoting the separation of photoexcited electron–hole pairs, (2) inhibiting side reactions, and (3) improving the selectivity of target products. This paper summarizes different types of photocatalysts for photocatalytic CO2 reduction, the reaction mechanisms are illustrated, and the application prospects are prospected. [ABSTRACT FROM AUTHOR]

Hydrogen energy, a green renewable energy, has shown great potential in developing new energy and alleviating environmental problems. Water electrolysis is an effective method to achieve large-scale clean hydrogen production, but this process needs to consume a huge amount of electric energy. It is urgent to develop high-activity, high-stability and low-cost catalysts to reduce the consumption of electric energy. At present, the noble metal catalyst is the star material in the hydrogen evolution reaction (HER), but its stability and high cost restrict its large-scale application. In this review, we comprehensively discussed the research progress on noble metal-based heterogeneous electrocatalysts used in water electrolysis for hydrogen production. Firstly, we analyzed the influence factors for hydrogen production performance, including the mass transfer process, the adsorption–desorption process, the catalytic process, and the influence of the working electrode and electrolyte. Then, we discussed the relationship between catalytic activity and electronic structure and chemical composition in view of theoretical calculations and summarized the strategies for developing efficient catalysts (alloying and interface engineering). Finally, we highlighted the challenges for the practical application of noble metal-based hydrogen evolution electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Small-sized Pt nanoclusters (PtNC) are synthesized and confined in the pores of HCS. • PtNC reveals excellent adsorption and catalytic ability while fixing S. • PtNC accelerates the transformation of polysulfides, and inhibit the shuttle effect. • PtNC@HCS as a host for Li-S cell cathode shows superior electrochemical performance. Sulfur (S) cathode is considered an ideal energy storage material for secondary batteries due to the high specific capacity and energy density. However, the insulating nature of S and lithium sulfide and slow electrochemical reaction kinetics, among many other issues, limit its power and energy output. Precious metals are vigorous catalytic materials and have been applied in various fields. However, the investigation of small-sized precious metal nanoclusters as the catalytic for polysulfide conversion in lithium-sulfur (Li-S) batteries has yet to be deepened. Herein, small-sized Pt nanoclusters are successfully synthesized and confined in the pores of hollow carbon spheres as the host for Li-S batteries cathode. The resultant PtNC@HCS provides the space for storing S and the electron transport network. Meanwhile, the Pt nanoclusters in the pores serve as catalytic sites for adsorbing and accelerating polysulfide conversion, thus effectively suppressing the shuttle effect. As a result, PtNC@HCS exhibits an initial capacity of 1460 mAh g−1 and a reversible capacity of 1316 mAh g−1 at 0.2C, with outstanding capacity retention, which confirms that such precious metal nanocluster catalytic material design effectively can optimize the electrochemical performance of Li-S batteries. [ABSTRACT FROM AUTHOR]

Over the last decade, Thailand imported approximately 21 million units of new mobile phones every year, equivalent to 262 million. While technology changes, consumers want the newest model to serve their lifestyle. These discarded mobile phones will be a challenging issue for waste management systems because of the metals in mobile phones, especially in printed circuit boards (PCBs). Sufficient and sustainable management is needed to maximize the benefits of recycling metals and minimize potential risks to public health. This study aims to estimate the possible range of DMP generation in Thailand (2012–2021) with the Approximation 2, Simple Delay, and Time Step methods using the government published data and a literature review. The results show that the discarded mobile phones ranged from approximately 1700 to 2500 tons/year, equivalent to 0.027 to 0.038 kg/year/capita over the last ten years. In 2021, more than half of the total mobile phone waste generated in the northeastern and central areas of Thailand was around 468.73 and 325.14 tons/year, respectively. Additionally, 1.28 tons of precious metals (Ag, Au), 5.33 tons of rare earth elements, and 7.26 tons of toxic metals (As, Cd, Cr, Pb) can be found in the PCB waste of DMPs. [ABSTRACT FROM AUTHOR]

Exploring the pathways for photocatalytic dissolution of precious metals (PMs) is crucial for optimizing recovery. In this work, we systematically investigated the selectivity and solvation effects observed for dissolution by focusing on photocatalysis, precious metals and solvents. By combining transient characterization, reaction kinetics, and density functional theory, we determined that the radicals generated in photocatalysis were the key active species in the entire reaction. The cyano functional group in the solvent was the driving factor for dissolution of gold, and the importance of chlorine radicals for dissolution of platinum group precious metals was further confirmed. In addition, the catalytic properties of different precious metals can promote different transformations of functional groups, leading to selective dissolution. The structures of photocatalytic precious metal leaches also precisely explains the special coordination forms of precious metals and functional group ligands. [ABSTRACT FROM AUTHOR]

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Precious metals occur naturally and have a high resistance to corrosion or oxidation. These natural resources are used as investment instruments to protect wealth values, such as gold, silver, and palladium. Price movements need to be understood when investing, and it is achieved through a time series model that predicts future prices. Also, autoregressive fractional integrated moving average (ARFIMA) is used to model price movements with long memory effects, while fuzzy time series Markov chain (FTSMC) is employed for performing numerical approach. It was observed that gold price movement has a long memory effect; therefore, it is eligible to be formed into the ARFIMA model. However, the silver and palladium prices do not contain a long memory effect, which means their movements are only formed through the FTSMC numerical model. The ARFIMA modeling results show that the gold price long memory model has the best accuracy with the smallest error value and also demonstrates excellent goodness of fit. Furthermore, the gold price long memory model movement has long-term stability compared to other precious metals. This provides an investment advantage because it is a stable asset, easy to liquidate in cash, free of interest, has an emergency fund role, and protects wealth’s value.

With the advancement of industrial development and urbanization, the indiscriminate discharge of industrial pollutants and wastes containing heavy metals and precious metals poses a significant threat to human health and ecosystems. Despite the widespread use of several traditional therapeutic procedures, these treatments frequently exhibit low efficacy and significant environmental consequences. The extraction and reuse of metal resources in pollutant treatment can effectively alleviate the current resource crisis; however, achieving a balance between recovery efficiency and environmental impact during the extraction process remains a major challenge. To tackle these challenges, emerging treatment materials along with advancements in thermal/photo/electrochemical methods offer additional possibilities for efficiently remediating/mineralizing heavy/precious metal pollution. This paper introduces traditional techniques for treating precious and heavy metals from water and soil while discussing the prospects of new treatment materials as well as effective thermal/photo/electrochemical methods for removing such metals. Furthermore, various strategies for recovering metals from municipal waste and wastewater containing heavy/precious metal are discussed, emphasizing sustainable approaches to enhance recycling performance. • The efficient utilization of heavy/precious metals is crucial for addressing pollution control. • Recent advances in new materials and technologies for the treatment of heavy/precious metal contaminants are evaluated. • Comprehensive evaluation of recycling strategies for various types of heavy/precious metal waste pollutants. • Challenges and prospects associated with the treatment of heavy/precious metal waste pollutants are discussed. [ABSTRACT FROM AUTHOR]

The article "Early Medieval Glass Smoothers as an Expression of the Spread of Christianity in Europe" examines the function of medieval hemispherical glass artifacts known as glass smoothers. The authors present new research findings that indicate that glass smoothers were primarily used for gilding wall paintings. The geographical distribution of glass smoothers is highest in Northern France, Belgium, and the Netherlands. It is noted that there are nearly a hundred graves containing glass smoothers, mainly found in Northern France and Belgium. The authors have analyzed various glass smoothers from the Czech Republic, dating from different periods. The study investigates early medieval glass grinders as an expression of the spread of Christianity. The chemical composition of the glass consists mainly of silicon, with low concentrations of calcium, sodium, and aluminum oxides. Anomalies of precious metals such as gold, silver, tin, copper, and brass were found on the surfaces of the artifacts. The authors analyze various glass artifacts from the 9th century and conclude that the most likely use of glass smoothers is in jewelry production. [Extracted from the article]

The suitability of assets-backed money has been the subject of considerable debate, although hampered in part by lack of theoretical and empirical evidence. Therefore, the motivation of this research is to investigate the perceptions of Shari'ah scholars and financial experts on the concepts and salient features of Shari'ah-compliant precious metal backed crypto-currency (PMC). To achieve this, this study adopted a qualitative method using semi-structured interview based on saturation technique. The results from Shari'ah advisors and financial experts indicated that the informants have differences of views on the assets-backed money, but they agreed that it ensures stability of money and adding the cryptocurrency technology is found to be desirable and recommendable. It is also found that PMC would be subjected to financial regulation challenges and using blockchain technology will increase the transparency. The informants agreed that PMC is closer to Maqāsid al-Shari'ah and there is some form of justice and equality compared to the current interest-based financial system. Therefore, the informants recommended the implementation of PMC. [ABSTRACT FROM AUTHOR]

Silicon-organic polymers containing thioacetamide, thiocarbamide, and dioxothiocarbamide groups were used in this investigation. The polymers were produced by the hydrolytic poly-condensation reaction of silicon-organic monomer, 3-triethoxysilylpropylamine. Au(III) sorption onto the polymers has been studied. The optimal condition of the sorption is confirmed by sorption experiments which were carried out at various times and in acidic solution conditions. Based on the result of the instrumental analysis and the values of thermodynamic parameters, such as ΔG°, ΔH°, and ΔS° can be concluded that Au(III) can be connected with the electro-donor nitrogen and sulfur atoms of the functional group of the polymer by chemical and coordination bonds. [ABSTRACT FROM AUTHOR]

Hydrogen energy, a green renewable energy, has shown great potential in developing new energy and alleviating environmental problems. Water electrolysis is an effective method to achieve large-scale clean hydrogen production, but this process needs to consume a huge amount of electric energy. It is urgent to develop high-activity, high-stability and low-cost catalysts to reduce the consumption of electric energy. At present, the noble metal catalyst is the star material in the hydrogen evolution reaction (HER), but its stability and high cost restrict its large-scale application. In this review, we comprehensively discussed the research progress on noble metal-based heterogeneous electrocatalysts used in water electrolysis for hydrogen production. Firstly, we analyzed the influence factors for hydrogen production performance, including the mass transfer process, the adsorption–desorption process, the catalytic process, and the influence of the working electrode and electrolyte. Then, we discussed the relationship between catalytic activity and electronic structure and chemical composition in view of theoretical calculations and summarized the strategies for developing efficient catalysts (alloying and interface engineering). Finally, we highlighted the challenges for the practical application of noble metal-based hydrogen evolution electrocatalysts.

This paper investigates the volatility spillovers across precious and industrial metal markets over the period 1993–2019 based on the DY and ​BK methods. Results are summarized as follows: (1) while volatility spillovers across industrial metals are higher than across precious metals, the opposite occurs during crisis periods where precious metals cause net volatility spillovers to industrial metals; (2) volatility spillovers of the two metal groups show different dynamics in the short‐, medium‐ and long‐term components, especially in the short‐ and medium‐term components. [ABSTRACT FROM AUTHOR]

Leaching of copper anode slime using hydrochloric acid (HCl) and hydrogen peroxide (H2O2) is performed to recover Au. It is imperative to reduce the amount of the costly oxidizing agent, H2O2, used in this leaching. In conventional conditions, the Se contained in the slime is oxidized and dissolved by the leachant as well as Au. If Au alone can be selectively leached, it should reduce the use of H2O2. The calculation of equilibrium potentials showed that when the concentration of HCl is high, it is possible for Au to be selectively leached, while the dissolution of Se is suppressed. The selective leaching of Au was demonstrated by experiments using 8 mol L-1 and 12 mol L-1 HCl solutions with various amounts of added H2O2. In the selective leaching, the increase in the leaching rate of Au with increasing amounts of H2O2 diminished after the leaching rate reached 80%. This may be because Au remained inside the Se particles, and the contact between Au and the leachant was physically inhibited by the Se layer encompassing the Au atoms. However, a leaching rate of Au of greater than 95% was achieved, even when the leaching rate of Se was less than 30%. From these results, it was confirmed that the use of H2O2 can be reduced by the selective leaching of Au compared to the cases in which all Se in the slime is dissolved.

This paper presents an overview of the various innovative methodologies used in the recovery of valuable metals and critical raw materials from secondary sources. The review also highlights the used varieties of application on large scale in real situations and hopes to provide insights into valorization of spent sources.

Rhodium films were deposited on 18k gold by magnetron sputtering and electroplating, respectively. The two processes were compared in terms of film properties, production efficiency, equipment cost, as well as material input and utilization efficiency. The results showed that as compared with the electroplated film, the magnetron-sputtered film has quite similar color and corrosion resistance, and a little better grain size and hardness, whose properties can meet the requirements of coatings on jewelry. The magnetron sputtering process is superior in overall production efficiency, safety, and environmental friendliness, but confronts with several problems, such as high initial investment on equipment and target material, low utilization efficiency of target material, high sensitivity to jewelry structure, and undesirable deposition on gem surface. Therefore, to apply magnetron sputtering in the production of precious metal jewelry, the utilization efficiency of target material should be improved by optimizing the design of moving magnetic field and the structure of target, some measures to improve the film uniformity should be considered in designing the product structure and developing the production process, and the gem surface should be shielded in advance for the inlaid jewelry. [ABSTRACT FROM AUTHOR]

Sukuk or Islamic bonds as new “Halal” securities had wildly expanded in Muslim and non-Muslim capital markets. So, this study aims to investigate the causal relationship between Islamic bonds (sukuk), oil and precious metals “silver and gold” prices in Asia pacific. This study used VAR model relying on daily data. The findings of Granger causality test and impulse-responses analysis results provide substantial evidence in favor of the relation between sukuk and the commodity market variables (oil, gold, and silver) meanwhile and unlike many empirical studies, don’t we have found that oil doesn’t cause changes in precious metals prices. Therefore, the idea that Islamic financial markets provide diversification benefits and they are safe havens during oil crisis cannot be supported empirically.DOI: 10.15408/aiq.v10i2.7171

The wet recovery methods for recovering precious metal palladium from different wastes were reviewed, and the important value of palladium recovery was clear, but there are problems of complex system components, extremely low content and direct discharge without treatment resulting in waste of resources. According to the different recovery mechanism of wet process, the wet recovery methods were classified and described by adsorption method, ion exchange method, complexation-extraction method，precipitation method and so on. Among the four methods, the application of the ad sorption method was gradually increasing，so the adsorption method was mainly introduced in detail. Adsorption materials could be divided into metal oxide composite adsorbent materials, carbon-based composite adsorbent materials, MOFs composite adsorbent materials and biomass composite adsorbent materials. The composite adsorbent was usually compounded with functional ligands and carriers by grafting or impregnation methods, so it had higher adsorption capacity and selectivity than ordinary adsorbents, and showed fast ad sorption. Tt pointed out that in the future development direction, in order to promote the high selectivity and high recovery rate of the noble metal palladium recovery, the adsorption method would become the first choice, and at the same time, the recycling could be green. [ABSTRACT FROM AUTHOR]

We conducted experiments using unit processes to prove the feasibility of the concept of an environmentally sound Au recovery process from waste electrical and electronic equipment (WEEE) using organic aqua regia, i.e., a propylene carbonate (PC) solution containing CuBr2 and KBr. First, the WEEE samples (memory card and mobile phone board) were finely ground. The samples were then carbonized and oxidized to decompose the polymers and oxidize the base metals. The leaching of Au from the oxidized samples was then carried out in a PC solution with 0.2 M of CuBr2 and 0.2 M of KBr over 353–373 K, followed by biphasic separation with sulfuric acid. The dissolved Au in the PC phase was recovered via ascorbic acid reduction. The mass balance of Au in the leaching was investigated. The maximum recovery ratios of Au from the memory card and mobile phone board were 79% and 83%, respectively. The cost of leaching was preliminarily estimated. [ABSTRACT FROM AUTHOR]

Recycling of waste electrical and electronic equipment has become an urgent global issue in recent years from the prospectives of resources recycling and environmental protection. In the present work, the recycling of waste memory modules (WMMs) through low-temperature alkali melts was investigated, based on the thermodynamic analysis of the nonmetallic reactions of brominated epoxy resin, glass fiber and memory chip with the molten mixed alkali. The effects of the reaction temperature and the ratio of alkali mixture on the removal rate of nonmetallic parts in WMMs were discussed under the condition of air atmosphere. The optimum process parameters were further confirmed by in-situ monitoring of the temperature during the whole reaction process. The mixtures with Cu, Fe and Ni as the main components were obtained after the treatment of WMMs in the molten alkali. These mixed metals were further separated into copper-rich and ferronickel-rich metals by physical magnetic separation. Moreover, the precious metals Au and Ag were enriched in Cu-rich alloys. This work provided an efficient and environment-friendly method for metal recycling from WMMs. [ABSTRACT FROM AUTHOR]

Secondary production of non-ferrous metals produced from waste can reduce the environmental burdens associated with primary production and contribute to achieving sustainable development goals. At the present condition, secondary metal manufacturers lack decision support system through an appropriate impact assessment framework. Thus, this paper presents an integrated impact assessment framework for primary and secondary metal production, using the material flow analysis and life cycle assessment. The non-ferrous metal analysed in this study is gold as a case study for the precious metal recovery from anode slime. The sensitivity analysis showed that using gold produced from combined primary and secondary sources generates significantly less environmental impact (e.g. climate change, freshwater ecotoxicity, and mineral resources depletion) in comparison with only primary metals. Further exploration of increasing separation and recovery efficiency of secondary production only suggested a marginal decrease in the overall impact. [ABSTRACT FROM AUTHOR]

Globally, continuous R & D efforts are being made to recuperate precious metals from wastes in order to conserve the natural resources as well as minimize environmental pollution. Keeping in view of the above, a process has been developed to recover gold from industrial effluent using hydrometallurgical route. Initially, the effluent was pre-treated using precipitation and solvent extraction techniques to remove impurities, i.e., iron and copper as value added products. Iron was removed up to 99.99% at pH ~ 3.5. Further, copper was extracted using 10% LIX 84IC maintaining phase ratio 1/1 in mixing time of 15 min and equilibrium (eq.). pH 2.2. Selective adsorption of gold was carried out using ionenaustauscher-II and resulted in 99% gold adsorption between pH 7 and 8 in contact time of 30 min. Experimental results obtained for the adsorption of gold was found to follow second order reaction and fitted well with the Freundlich isotherm. Gold from the loaded resin was eluted using a mixture of hydrochloric acid and thiourea. From the pure gold solution, metal could be produced using cementation/charcoal adsorption followed by heat treatment, respectively. [ABSTRACT FROM AUTHOR]

In the crypto world, there is a proverbial (and literal) gold rush now occurring. Currently, more than 37 gold‐backed cryptocurrency companies have now emerged. Interestingly, some of them also claim to be Sharīʿah‐compliant. Introducing precious metal‐backed cryptocurrencies is perceived to be an innovation among global payment systems, hampered in part by lack of supporting empirical evidence. Therefore, this research investigates potential users' tendency to adopt a Sharīʿah‐compliant precious metal‐backed cryptocurrency. As such, this study adopts an extended adoption model, which consists of eight factors. Partial least squares structural equation modeling (PLS‐SEM) analysis was conducted on data elicited from economic active residents in Klang Valley from questionnaires. Overall, it was found six out of the eight constructs specified to influence the adoption of precious metal‐backed cryptocurrency were statistically significant where 54.5% of the variation in adoption of PMBC can be explained by the structure model provided by this research. It was also found 63.55% of the respondents are willing to adopt precious metal‐backed cryptocurrency in their future transactions. [ABSTRACT FROM AUTHOR]

Methylimino-di-n-octylacetamide (MIDOA) was used to extract 57 metals from HCl into n-dodecane. MIDOA is a tridentate ligand with one N donor and two carbonyl O donors and can extract soft acid metals and metal oxonium anions. In the present work, Fe(III), Zr(IV), Ga(III), Mo(VI), Tc(VII), Pd(II), Cd(II), In(III), Sn(IV), W(VI), Re(VII), Os(III), Ir(III), Pt(IV), Au(III), Hg(II), Bi(III), and U(VI) had distribution ratios above 10 when using 0.1 M MIDOA/n-dodecane and 3 M HCl. The amount of metal ion (Mo(VI), Tc(VII), Re(VII), Pd(II), Pt(IV), and Au(III)) extracted from HCl was greater than that obtained using HNO3. [ABSTRACT FROM AUTHOR]