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In response to the problem of additive zinc concentrate consumption and inefficient reduction of ferric ion (Fe3+) in the acid-leaching solution of zinc hydrometallurgy when employing zinc sulfide concentrate, various parameters were examined. These included particle size, temperature, addition coefficient of the concentrate, and sulfuric acid concentration, all aimed at enhancing the rate of Fe3+ reduction. The results indicated that increasing the temperature from 80 to 120°C enhanced the Fe3+ reduction rate from 93.3 to 98%, reducing the time from 180 to 60 min. Furthermore, enlarging the particle size of the concentrate from below − 58/+ 48 μm to − 246/+ 150 μm, lowering the Fe3+ concentration in the reduction solution to < 0.5 g/L, and decreasing the addition coefficient from 1.8 to 1.5 further enhanced the reduction process. Additionally, employing a pressure process to increase the reduction temperature proved to be an effective strategy for enhancing the utilization rate of the zinc sulfide concentrates and the Fe3+ reduction rate, thereby reducing the amount of reduction residue and facilitating its subsequent treatment. [ABSTRACT FROM AUTHOR]

The re-dissolution of unstable iron oxides during the low-temperature hematite process significantly increases the iron ions concentration in solution after iron removal in zinc hydrometallurgy. The reason for the re-dissolution of precipitated hematite was determined through simulated iron removal experiments in an autoclave. It was caused by e.g., weak acid solubility resistance in high acidity and the poor crystallinity of hematite. In order to solve the problem of re-dissolution of hematite precipitated in a short time, three improving methods, namely increasing the reaction temperature, extending the reaction time in the autoclave, and reducing the acidity of hematite process, have been systematically studied. Increasing the reaction temperature is not economical from the perspective of industrial production, and extending the reaction time does not meet the original intention of the zinc smelter to increase production capacity. Although zinc sulfide concentrate as a neutralizing agent can increase the pH of the slurry, the hematite produced does not have the potential for sales. When 12 g/L zinc calcine was added, the residual Fe concentration in solution after iron removal within 90 min can be controlled below 1 g/L, and high-grade hematite with Fe, Zn, and S contents of 56.62%, 2.09%, and 2.78% can be produced. [ABSTRACT FROM AUTHOR]

Nickel catalysts are widely applied in the chemical and petrochemical industry due to high catalytic activity and low cost. However, these catalysts are often irreversibly deactivated, leading to residue generation. For this reason, recycling is necessary to reduce the environmental impact of landfills and to obtain valuable metal from the secondary source. Hydrometallurgical recycling routes have been investigated to provide nickel from secondary sources. A catalyst from the petrochemical process contained 44.5% Ni and was calcined at 600°C for 3 h to remove organic compounds. Then, the material was ground, and leaching experiments were performed using H2SO4. The effects of temperature, concentration, solid-liquid ratio, particle size, and time were evaluated. The best leaching conditions were 100°C, 2 mol/L H2SO4, solid-liquid ratio 1/5, d50 8.5 µm in 8 h with 97.4% of nickel leaching (116 g/L). The leach solution was purified using chelating ion exchange resins. Three resins were studied with different functional groups: iminodiacetate, HPPA, and aminophosphonic. The effect of pH in the batch and removing contaminants in a continuous system were evaluated. Iron removal achieved 92.2% efficiency using aminophosphonic resin in a continuous process using four columns. The recovery of nickel in the process reached 94.3%. [ABSTRACT FROM AUTHOR]

In this paper, according to the reaction principle and material balance, the coefficient calculation rule is established to construct the valuable element allocation model with Java programs in the hydrometallurgy process of cobalt-rich slag. Thus, the ratio of distribution in each process containing acid leaching, copper deposition, ferromanganese precipitation, and cobalt deposition are forecast quantitatively, accompanied by the recovery rate of the valuable element. Compared with the expanding process of cobalt-rich slag, the correctness and applicability of the model for the distribution and ratio of the valuable element are investigated, and the weak link can be improved according to the specific situation of the process. The recovery rate of cobalt is 95.38 %, and the content of cobalt in the cobalt product is 44.93 % in the cobalt deposition. Ultimately, the valuable element allocation model can quantitatively predict the experimental results, indicating that it can be used for simulating and optimizing the control of the hydrometallurgy process of cobalt-rich slag. This can improve the recovery rate of valuable elements in such hydrometallurgical processes. [ABSTRACT FROM AUTHOR]

Electronic waste (e-waste) has emerged as a valuable secondary source of metals, including precious metals (PMs), surpassing those found in natural ores. The objective of this study is to explore the use of cellulose-based adsorbents, specifically dithiocarbamate-modified cellulose (DMC) and proline-incorporated DMC with epoxy-cross-linkage (DMC-Pro-Epo6), in the recovery of Au from e-waste, particularly under harsh aqua regia (AR) conditions. DMC adsorption behavior in AR is influenced by several factors, such as AR dilution, pre-adsorption phenomena, contact time, and AuIII concentration. DMCs displayed competitive adsorption across varied AR dilutions, benefiting from diluted AR due to hindered adsorption in undiluted AR. Contact time analysis demonstrated rapid AuIII adsorption, with equilibrium achieved in approximately 30 min. Four anion exchange-type commercial resins (Lewatit MonoPlus TP 214, Diaion WA30, Dowex 1X8, and AmberChrom 1X8) and one chelating CR (Q-10R) were tested for comparison, and their adsorption capacities were evaluated. Both the DMC and DMC-Pro-Epo6 have higher adsorption capacities for AuIII than commercial resins, which can be attributed to their sorption-active dithiocarbamate functional groups. The study also outlined a step-by-step Au extraction from printed circuit boards (PCBs), and the effective recovery of metallic Au from PCBs using DMCs was demonstrated. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature 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.)

Waste from electrical and electronic equipment exponentially increased due to the innovation and the ever-increasing demand for electronic products in our life. The quantities of electronic waste (e-waste) produced are expected to reach 44.4 million metric tons over the next five years. Consequently, the global market for electronics recycling is expected to reach $65.8 billion by 2026. However, electronic waste management in developing countries is not appropriately handled, as only 17.4% has been collected and recycled. The inadequate electronic waste treatment causes significant environmental and health issues and a systematic depletion of natural resources in secondary material recycling and extracting valuable materials. Electronic waste contains numerous valuable materials that can be recovered and reused to create renewable energy technologies to overcome the shortage of raw materials and the adverse effects of using non-renewable energy resources. Several approaches were devoted to mitigate the impact of climate change. The cooperate social responsibilities supported integrating informal collection and recycling agencies into a well-structured management program. Moreover, the emission reductions resulting from recycling and proper management systems significantly impact climate change solutions. This emission reduction will create a channel in carbon market mechanisms by trading the CO2 emission reductions. This review provides an up-to-date overview and discussion of the different categories of electronic waste, the recycling methods, and the use of high recycled value-added (HAV) materials from various e-waste components in green renewable energy technologies. [ABSTRACT FROM AUTHOR]

Hydrometallurgy recycling of heavy metals from electroplating sludge is of hot spot in recent decades. Such recycling was tedious in the separation of impure Fe/Al prior to heavy metals from acid leachate after sludge dissolution. Herein, a facile hydrothermal route was developed to separate Fe/Al from Cu-bearing leachate. The results showed that when the leachate was directly hydrothermally treated at 160 °C in the presence of nitrate and ethanol, Al/Cu were stable in the leachate, but nearly 100% Fe was removed as hematite nanoparticles. With the addition of chloridion, the removal efficiencies of Fe/Al/Cu did not change apparently, but the corresponding precipitate was akageneite, not hematite. By replacing chloridion with sulfate, nearly 100% Fe and 98.6% Al were separated as natrojarosite/natroalunite block, while the Cu loss was only 1.7%. However, with the supplementary of phosphate, the Fe/Al removal achieved nearly 100%, but the Cu removal also achieved by 92.6%. The thermodynamic analysis showed that Cu was precipitated rapidly via the phosphate/Cu oxyhydroxide route by adding phosphate but removed slightly via the coordination route on the Fe/Al precipitates with the addition of nitrate, chloridion, and sulfate. In summary, Fe was effectively separated as hematite, akageneite, natrojarosite, and phosphate halite, in the presence of nitrate, chloridion, sulfate, and phosphate, separately. But the removal of Al as natroalunite and AlPO4 only started by adding sulfate and phosphate, respectively. Such results enabled a short hydrometallurgy process to effectively recycle heavy metals from electroplating sludge. [ABSTRACT FROM AUTHOR]

This study aimed to recover waste with other waste as a sustainable and environmentally friendly approach. Following this purpose, iron recovery from waste steel slag using different agricultural and forestry wastes was investigated. This study was carried out mainly in three stages: torrefaction of biomasses, leaching of Fe from waste steel slag with nitric acid, and adsorption of Fe with torrefied biomasses. Each biomass was used as an adsorbent for recovery studies after the torrefaction process at 270 °C for 60 min. According to the results of acidic leaching studies, it was stated that Fe leaching efficiency was between 38.5 and 140%. The effects of contact time and adsorbent dose were investigated in adsorption studies carried out with a leaching solution (Fe concentration 3682 mg/L, pH 0.60). The results showed that with 2 g/L torrefied pine needle, green walnut shell, and pomegranate seed biomasses (at 20 °C, 150 rpm, and 120 min contact time), 87.94%, 89.22%, and 87.09% Fe recovery was obtained respectively. Torrefied biomass could be a promising adsorbent and iron could be recovered in an environmental friendly way from steel slag. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) have a wide range of applications from electronic products to electric mobility and space exploration rovers. This results in an increase in the demand for LIBs, driven primarily by the growth in the number of electric vehicles (EVs). This growing demand will eventually lead to large amounts of waste LIBs dumped into landfills which can cause serious environmental problems. To reduce this environmental impact, the need for efficient recycling technology emerges. Furthermore, it has been proven that recycling waste LIBs consume less material and energy than producing new ones from virgin materials. Therefore, this paper aims to review different recycling technologies including hydrometallurgy, pyrometallurgy, direct recycling, and precise separation. The review concludes that hydrometallurgy might be the most efficient method of recycling waste LIBs on an industrial scale. [ABSTRACT FROM AUTHOR]

With the shortage of high-quality raw materials and increasingly strict environmental regulations, the recovery of metals from copper slag and pyrolusite has become a research hotspot. A novel method for simultaneously extracting Mn and Fe from pyrolusite and copper slag has been proposed. Under the optimal conditions (Copper slag / Pyrolusite = 2, H2SO4 = 2 M, liquid—solid ratio = 10, T = 90 ℃, holding time = 60 min), the leaching efficiencies of Mn and Fe can reach 98.28% and 99.04%, respectively. In addition, the treated residue containing 60.04 wt% SiO2 can be used as a raw building material. Through chemical kinetics and mineralogical transformation analyses, Fe2SiO4 in copper slag decomposes to release Fe2+, which can reduce and leach Mn from pyrolusite. The unreacted shrinkage nuclear reaction model under the control of the surface chemical reaction is the most suitable model to describe the process, and when the apparent activation energy is 35.50 kJ/mol, the apparent rate equation is: 1 - 1 - × 1 / 3 = 979.65 CS / Pyrolusite 2.6072 H 4 SO 4 1.3143 L / S 0.5649 e xp - 35.50 / RT [ABSTRACT FROM AUTHOR]

This report analyzes various methods of disposal and processing of exhaust from complex chemical current sources, subdivided into pyrometallurgical, hydrometallurgical, and combined. The complex technology for processing lithium-cobalt current sources (LCCS), developed at the National Research Center Kurchatov Institute, is described, including the stages of discharge, opening in an inert atmosphere, crushing, grinding (with mechanical activation), and leaching with extraction. The data from additional studies on the alkaline leaching process of the LCCS cathode are presented. In this case, the degree of aluminum extraction from the LCCS cathode reached 94.2%. Data on a comprehensive study of the distribution of metal components in fractions after grinding and milling in blade and ball mills were analyzed. The results showed that Co, Li compounds, and graphite are contained in powders of size 50–1000 pm, and fractions of size 1000–2500 pm contain Cu, Al compounds, and polymer particles. A fractional (staged) technology is proposed for separating valuable metal components from LCCS with water separation and leaching. The results of leaching mechanically activated powders with inorganic acids are presented. A comparative analysis of the results obtained with data from international authors on the efficiency of LCCS leaching was performed, and a mathematical description of the process kinetics was proposed. A modernized block diagram of combined mechanical processes with leaching and extraction processes was developed. [ABSTRACT FROM AUTHOR]

Lithium–titanate anodes are increasingly being used in the manufacturing of lithium-ion batteries due to their advantages in charge/discharge speed and safety of use relative to graphite anodes. The addition of titanium to the battery composition, along with the high content of cobalt and lithium, results in a further growth of their cost, and the reprocessing of such batteries becomes an extremely topical problem. In the framework of the present article, a comparative analysis of the hydrometallurgical reprocessing of batteries containing a lithium-titanate anode and a nickel–manganese–cobalt cathode by leaching with mineral acids (sulfuric and hydrochloric acids) is performed. In the work, the dependences of the leaching degree of the metals from real samples of the anode and cathode in their mixture on the mineral acid concentration, auxiliary additives, and solid : liquid ratio are demonstrated and the temperature and kinetic dependences for this process are obtained. Based on the results of qualitative and quantitative analysis of the leaching solutions, conditions for processing of the leaching process are proposed for further extractive separation. It is demonstrated that two-step successive leaching with hydrochloric and then sulfuric acid with the release of titanium concentrate is optimal. An important aspect of the work is the study of the joint leaching of the cathode and anode, since in the known processes of mechanical processing the stage of their separation is absent. [ABSTRACT FROM AUTHOR]

The work presented here focused on the extraction of gold (Au), silver (Ag) and palladium (Pd) from electronic waste using a solution of ammonium thiosulfate. Thiosulfate was used as a valid alternative to cyanide for precious metal extractions, due to its non-toxicity and high selectivity. The interactions between sodium thiosulfate, total ammonia/ammonium, precious metal concentrations and the particle size of the waste printed circuit boards (WPCBs) were studied by the response surface methodology (RSM) and the principal component analysis (PCA) to maximize precious metal mobilization. Au extraction reached a high efficiency with a granulometry of less than 0.25 mm, but the consumption of reagents was high. On the other hand, Ag extraction depended neither on thiosulfate/ammonia concentration nor granulometry of WPCBs and it showed efficiency of 90% also with the biggest particle size (0.50 < Ø < 1.00 mm). Pd extraction, similarly to Au, showed the best efficiency with the smallest and the medium WPCB sizes, but required less reagents compared to Au. The results showed that precious metal leaching is a complex process (mainly for Au, which requires more severe conditions in order to achieve high extraction efficiencies) correlated with reagent concentrations, precious metal concentrations and WPCB particle sizes. These results have great potentiality, suggesting the possibility of a more selective recovery of precious metals based on the different granulometry of the WPCBs. Furthermore, the high extraction efficiencies obtained for all the metals bode well in the perspective of large-scale applications. [ABSTRACT FROM AUTHOR]

Domestic and world tendencies of involvement in the processing of ores of rare metals (RMs) and rare-earth metals (REMs) are shown. It is shown that the main direction of innovative activity is the development and application of modern breakthrough technologies for complex processing of mineral raw materials with the production of high-quality products while minimizing environmental damage. The main deposits of rare and rare-earth metals are systematized from the standpoint of the content of the main components, concentrator minerals and the main enrichment methods. The main principal technological schemes of processing of some deposits of RMs and REMs in Russia (Lovozer, Tomtor, and Afrikand deposits) are given. Options for involving technogenic and off-balance raw materials in the processing in order to extract strategic metals are considered. It is substantiated that innovative environmentally friendly processes for the extraction of rare and rare-earth metals from complex ores of complex material composition are being actively developed in Russia at present. [ABSTRACT FROM AUTHOR]

An alternative, integrated method for processing sulfide molybdenum concentrate to recover molybdenum and associated rhenium is proposed. The method involves oxidizing roasting without the release of sulfur dioxide, dust entrainment, and loss of valuable metals and two-stage leaching with selective dissolution of rhenium and, then, molybdenum. Molybdenum concentrate from the Yuzhno-Shameisky deposit was used as the feedstock. The concentrate was mixed with calcium hydroxide in a ratio of 1:1 by weight. Then the mixture was granulated and covered with a layer of calcium hydroxide. Oxidizing roasting was carried out in a tubular furnace at T = 600°C for 80 min. After that, rhenium was recovered from the cinder using an aqueous solution. Further, molybdenum was recovered from the cake using sodium carbonate solutions at the following optimal parameters: T = 95°C, τ = 180 min, S:L = 1:6, C Na 2 CO 3 = 200 g/dm3, n = 8.3 sec–1 (500 min–1). The main phases of the resulting cinder and cake were established. The optimal parameters of processing molybdenum concentrate at which the recovery of rhenium and molybdenum is 81% and 98%, respectively, were determined. The proposed technology is applicable to any grades of molybdenum concentrate. [ABSTRACT FROM AUTHOR]

The physical and chemical properties of gold promote its application, such as in the high-tech, electronic products, and aerospace industries. The easily leachable ore is gradually depleted. Thus, it becomes necessary to extract gold from other resources such as refractory ore and electrical and electronic equipment. The normal method of leaching for gold is cyanide leaching, but it is very dangerous for both environment and operator. Non-cyanide leaching methods, including thiourea leaching, halide leaching, and sulfate leaching have been developed to substitute cyanide leaching. A variety of methods to enrich gold from leaching solutions are described in this paper, including solvent extraction, electrowinning, activated carbon adsorption, and ion exchange resins. Among those methods, ion exchange resins can adsorb gold with high adsorption efficiency and regenerate easily as well. This paper focuses on the research progress of the recovery of gold from non-cyanide leachates by ion exchange resins, summarizes the existing resin types and elution processes, points out the limitations in the application of current ion exchange resins, and discusses possible solutions. [ABSTRACT FROM AUTHOR]

An increasing attention to biomining technologies has emerged in the mining industry as a result of stricter environmental regulations and economic concerns to process ores with more complex mineralogy having high sulfur and carbon content. The application of bacteria and archaea in biomining has been broadly investigated. Nevertheless, to overcome the present challenges in biomining, there is a potential opportunity for fungi to be employed for the treatment of double/refractory sulfidic ores. This review, for the first time, provides a detailed investigation of the reported fungi used as biological engines to alter numerous sulfur and carbon matrices, including low and high-rank coals, organic and inorganic sulfur, as well as sulfide and carbon minerals. This study illustrates the potential applicability of fungi in biomining technologies, and summarizes microorganisms that have been successfully used with different sulfur and carbon sources. The fundamentals of fungi and their applications have been discussed in detail. Future directions that require further research to foster biomining technologies assisted by fungi have also been provided. [ABSTRACT FROM AUTHOR]

There have been several strategies developed to increase the diversified supply of energy so that it can meet all of the future demands for energy. As a result, to ensure a healthy and sustainable energy future, it is imperative to warrant reliable and diverse energy supply sources if the "green energy economy" is to be realized. The purpose of developing and deploying clean energy technologies is to improve our overall energy security, reduce our carbon footprint, and ensure that the generation of energy is secure and reliable in the future, making sure that we can spur economic growth in the future. In this paper, advancements in alternative sources of energy sustainability and strategies will be examined to ensure there will be enough fuel to supply all the future demands for energy. Several emerging clean energy technologies rely heavily on the availability of materials that exhibit unique properties that are necessary for their development. This paper examines the roles that rare earth and other energy-critical materials play in securing a clean energy economy and the development of clean energy economies in general. For the development of these technologies to be successful and sustainable, a number of these energy-critical materials are at risk of becoming unavailable. This is due to their limited availability, disruptions in supply, and a lack of suitable resources for their development. An action plan focusing on producing energy-critical materials in energy-efficient ways is discussed as part of an initiative to advance the development of clean and sustainable energy. [ABSTRACT FROM AUTHOR]

The authors developed a pilot project to test different preparations of cemented rock fill, determine the appropriate mix design, and check necessary mix strength. The article presents the required resistance studies and the research method used to determine feasibility, cost performance and increased mine productivity and safety. The study achieved a resistance peak of 1.6 MPa, reduced dilution of the ore, and increased pillar stability. [ABSTRACT FROM AUTHOR]

In the present study, ZnS was recovered from ferrochrome ash (FCA) waste using a hydrometallurgical process for the first time in the scientific literature, and it was utilized as an electrode material for asymmetric-type coin cell supercapacitors. FCA was initially leached with H2SO4 and HNO3 solutions with varying liquid: solid (L: S) ratios, acid concentrations, and leaching times. The optimal leaching parameters were 0.25 M as HNO3 concentration, 50:1 as L: S ratio, and the shortest leaching period of 5 min obtained, which resulted in 70.71% wt. Zn leaching efficiency (LE). Then, the pregnant liqueur was mixed with Na2S solutions, to precipitate ZnS. Afterward, an anode to be used in coin cell type supercapacitor was produced by mixing ZnS, carbon black, and PVDF in varying compositions. The obtained coin cell was characterized by electrochemical techniques. The highest specific capacitance value was determined as 71 mF.cm−2 at a scanning rate of 10 mV/s in a supercapacitor containing 70% wt. ZnS anode, however the highest capacitance retention (92.82%) was obtained after 1000 cycles of CV test for the 60% wt. ZnS including anode. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature 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 BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature 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 formulated problem of the raw-material base of non-ferrous metallurgy comprises the recovery of valuable components lost in concentration tailings by mechanochemical technology. The wastes of non-ferrous metallurgy sub-branches form exploitable resources, which, in addition to economic damage from incomplete metal extraction, cause environmental problems. The primary technologies for processing complex ores, which fail to provide waste-free concentration, cause an imbalance between raw material extraction and processing indicators since all the applied methods do not provide waste-free concentration processes. It is possible to increase the extraction of metals up to the background level by treating them with chemical reagent solutions at the time of formation of active mineral surfaces. There is also a tendency to involve metal leaching technologies in the exploitation of waste storages. The possibility of improving recovery rates during ore concentration provides a combination of traditional technologies with new technologies by supplementing the traditional technological chain with activator devices. The combination of traditional and new low-waste technologies will strengthen mineral safety through the rational use of the existing mineral resource base. [ABSTRACT FROM AUTHOR]

This study presents the mathematical modelling and estimates the kinetic parameters of red mud leaching using the Markov chain Monte Carlo method with the Metropolis–Hastings algorithm. The red mud used in this study comes from the Amazon region in Brazil and was characterised and leached with 20 and 30% (v/v) sulphuric acid at 60, 80 and 90 ºC through calcined and uncalcined hydrometallurgical routes. During leaching, samples were collected every 30 min and centrifuged to separate the leachate from the concentrate. The mathematical model for the leaching kinetics of red mud is a system of coupled differential equations and was based on the shrinking core model. The maximum iron and aluminium oxides leached averaged 96 and 91%, respectively, while the maximum recovery of titanium in the sulphuric acid solution has not exceeded 26%. The leaching kinetics of iron, titanium and aluminium oxides had average reaction order values of 1.52, 2.96 and 2.05, respectively. The activation energy values ranged from 64 to 176 kJ/mol. The proposed mathematical model was properly validated, enabling its application in other leaching processes and in the estimation of the kinetic parameters of other chemical elements present in the red mud. [ABSTRACT FROM AUTHOR]

We propose a novel integrated model for the recovery of tantalum from tantalum-rich waste using a combination of hydrometallurgical and bio-metallurgical processes. To this end, leaching experiments with heterotrophs (Pseudomonas putida, Bacillus subtilis and Penicillium simplicissimum) were carried out. The heterotrophic fungal strain leached manganese with an efficiency of 98%; however, no tantalum was detected in the leachate. An unidentified species did mobilise 16% tantalum in 28 days in an experiment with non-sterile tantalum capacitor scrap. Attempts to cultivate isolate and identify these species failed. The results of a range of leaching trials resulted in an effective strategy for Ta recovery. A bulk sample of homogenised Ta capacitor scrap was first subjected to microbial leaching using Penicillium simplicissimum, which solubilised manganese and base metals. The residue was subjected to the second leach using 4 M HNO3. This effectively solubilised silver and other impurities. The residue collected after the second leach was pure tantalum in concentrated form. The hybrid model produced derives from observations from previous independent studies and shows that we can effectively recover tantalum along with silver and manganese in an efficient and environmentally friendly manner from tantalum capacitor scrap. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature 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.)

In this work, a collaborative strategy for the aluminum and iron industry based on red mud recycling through the hydrometallurgy method was proposed. In this method, Fe3+ and Al3+ were firstly separated from the red mud by using H2SO4 as a leaching agent, which was by-produced from the sintering process of an iron and steel industry. Multiple influence factors on the leaching process were investigated, with the H2SO4 addition amount showing the strongest influence on the leaching rates of Al and Fe. The main components of the filter residue were CaSO4, TiO2, and SiO2, which could be reused as additives in the building materials. Subsequently, the final Fe recovery product was obtained through the co-precipitation, Fe/Al separation, and Fe(OH)3 calcination. In the final product, the content of Fe2O3 reached 82.87%, and the iron grade was 58.01%, meeting the requirement being raw materials for sinter production. [ABSTRACT FROM AUTHOR]

The increase in technology has increased the consumption and waste of electrical and electronic equipment, especially cell phones (smartphones). The waste printed circuit board (WPCBs) contained in this waste include metals that can be recovered, adding value to this waste and minimizing environmental impacts with its incorrect disposal or treatment. The present work applies the concepts of circular economy, the silver was recovered from WPCBs obsolete cell phones (smartphones) through hydrometallurgical processing in two stages of leaching. After the leaching process, the silver was recovered as AgCl, using a selective precipitation process. For the synthesis of AgNPs, the green synthesis was used at a temperature of 60 °C, using glucose as a reducing agent and the variation of two stabilizers: sodium citrate and polyvinylpyrrolidone (PVP). Synthesis of AgNPs using sodium citrate as a stabilizing agent, resulting in AgNPs with two diameter ranges of 47 and 2 nm. In the synthesis of AgNPs using PVP as a stabilizing agent, formed two diameters of 65 and 5 nm. The properties indicated polydispersed AgNPs predominantly spherical in shape. Antibacterial activity of AgNPs was evaluated on Escherichia coli bacteria growth, the results suggest that AgNPs are strong inhibitory agents for Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Thiosulfate is a lixiviant with potential applications for extraction of precious metals with lower environmental impact. As an alternative leaching reagent to cyanide, thiosulfate has promising gold extraction efficiency with much lower risk to operators and the environment. Thiosulfate is often produced at high temperatures via processes utilizing sulfide or sulfur and an oxidant. However, certain microorganisms can produce thiosulfate as the final product of their metabolism. This represents potential for lower emissions and costs in the manufacture of gold leaching reagents. Biotechnological applications of these processes have not been reported in the past and need to be investigated in depth. This review serves as a study of microorganisms to collect and analyze the reported species for potential utilization of biogenic thiosulfate in industrial applications, with a specific focus on precious metals extraction. Bacteria were identified and compared with respect to thiosulfate producing ability, feasibility for the mining industry, and cost of substrates. The future applications of biogenic thiosulfate and further direction of research on the topic have been identified. [ABSTRACT FROM AUTHOR]

Waste PCBs (WPCBs) contain many types of valuable but environmentally harmful metals. Thus, the recovery of metals from WPCBs has a high environmental consequence and is essential for resource conservation. The study aims to develop eco-friendly methods for the recovery of metals from WPCBs. Through this work, a systematic procedure for the separation of components and extraction of metals is demonstrated. PCB was disintegrated by sequentially dissolving the solder in methane sulfonic acid (MSA), epoxy in sodium hydroxide, N-Methyl-2-Pyrrolidone (NMP), and metal interconnects dissolved separately in citric acid, hydrochloric acid, and sulphuric acid. Various processing conditions were evaluated to enhance the extraction. ICP-AES analysis was done for all leaching solutions, and it was observed that the solution of 3.5 M MSA and 0.5 M H2O2 completely dissolves the solder (Sn and Pb) in 1.5 h at 28ºC. Both citric acid and HCl have shown more than 75% recovery of copper and metals like Ag, Al, Pb, Ni, and Fe in the leaching solution in 4 h and 24 h, respectively, at 28ºC. Similarly, leaching using 15wt% H2SO4 aqueous solution with 10 ml of H2O2 has shown more than 95% extraction of Ag, Al. Fe and Ni in the leachate. Citric acid has shown very competitive results among all three leachates with low extraction time. It was concluded that citric acid could be used as an eco-friendly replacement for inorganic acids. Subsequently, recovery of copper using iron powder was performed, and 95% recovery was achieved using 4 g of iron powder, which was deduced using ICP-AES analysis. The work demonstrates the feasibility of sequential delamination and removal of layers in a PCB without prior pulverization. A sustainable process for extracting copper and potentially other metallic components in PCB, in durations much shorter than those reported, is demonstrated. Notably, citric acid resulted in over 83% recovery of copper in less than 4 h, comparable and possibly better than some other inorganic acids. Additionally, there is no need for pre-crushing, and the non-metallic and polymeric components are obtained intact, which may potentially be used for different applications. [ABSTRACT FROM AUTHOR]

During zinc hydrometallurgy process, the chloride ions in the materials go into the leaching solution, which have abominable effects on equipment, electrowinning, and environment. So, it is necessary to remove chloride ions from zinc sulfate solution. The present review outlines the current research of removal methods of chlorine by holistically highlighting the advantages and mechanisms. The main techniques used to remove chloride ions from zinc sulfate solution are also discussed in detail. Among the methods, the precipitation method using copper slag to remove chlorine is widely used and the chlorine removal rate is up to 98%. In addition, the combination of electrochemistry and nanofiltration technology can form a closed-loop production process with less waste output and near-zero emissions. In addition, the challenges and possible future directions of chlorine removal from zinc sulfate solutions are also delineated. [ABSTRACT FROM AUTHOR]

It is expected that lithium sourcing from aqueous sources in the medium term will account for over half of worldwide production, since reserves in brines are more abundant than in hard rock ores. To produce high purity lithium products, the full abatement of both Mg2+ and Ca2+ cations is fundamental. Current practice involves the use of large volumes of chemicals, NaOH and Na2CO3, leaving behind only residues. We recently proposed to produce brine alkalinization via water reduction using a simple 2 compartment electrolyzer fitted with an anion exchange membrane. Here, we advanced the study of this system by correlating voltage drop, pH, and cation concentrations with the advancement of electrolysis. Results suggest that solids are not formed within the membrane, but only on its surface. We also propose a new strategy to avoid all together solid formation within the electrolyzer, arriving at very similar results regarding Mg2+ abatement and minimal Li+ depletion in the processed brine (average 99.6% Mg2+ depletion). However, Ca2+ concentrations remained at values between 30 and 44% of the original brine content. The voltage drop between electrodes in the new reactor setup was lower than that in the original setup (2 V lower at 200 A m−2). That difference suggests both that the membrane is not degrading at the more alkaline pH and that the electrical consumption for the electrolysis would be lower with the new setup. [ABSTRACT FROM AUTHOR]

This work proposes an integrated process flowsheet for the recovery of pure crystalline Si and Ag from end of life (EoL) Si photovoltaic (PV) panels consisting of a primary thermal treatment, followed by downstream hydrometallurgical processes. The proposed flowsheet resulted from extensive experimental work and comprises the following unit operations: Shredding the PV modules to − 4 mm, after the removal and recovery of aluminum frames, junction boxes and copper cables. Delamination of the Si cells from the front soda-lime protective glass, through a thermal treatment at 550 °C for 15 min, in excess of air, in order to disintegrate the encapsulating organic material (ethylene vinyl acetate (EVA)) and the polyvinyl fluoride (PVF) polymer backsheet (Tedlar®). Separation of the detached Si flakes from the front glass and the "ash residue" and classification via mechanical screening by a perforated trommel rotary screen equipped with square wire mesh sieves. Further grinding of the recovered Si flakes by ball milling to − 90 μm, in order to increase the specific surface area, prior to the downstream hydrometallurgical process. Quantitative leaching of Ag and Al from the Si flakes in one stage by HNO3 at ambient temperature. Alternatively, acid leaching in two stages can be applied: initially by H2SO4 for Al quantitative extraction and subsequently by HNO3 for Ag quantitative extraction at ambient temperature. In order to remove the anti-reflection coating, etching of the leached Si flakes by 2.5 M NaOH has been proven efficient and crystalline silicon of high purity was recovered. Separation and precipitation of Ag as AgCl or alternatively, Ag electrowinning from nitrate solutions and Al precipitation via solution neutralization. [ABSTRACT FROM AUTHOR]

Neodymium–iron–boron permanent magnets are increasingly used in green energy technologies, such as wind turbines and electric vehicles. In the near future, an increasing amount of magnets will reach their end-of-life stage, andtherefore, it is imperative to develop proper recycling routes aimed at the valorization of this waste fraction. In this work, a room temperature hydrometallurgical process was developed aimed at the recovery of both iron and rare earths contained in end-of-life wind turbine magnets. The process is based on a leaching step with nitric acid, followed by two precipitation steps and calcination. Iron hydroxide(III) and rare earth oxide with purity grade equal to 98% and 99%, respectively, were obtained. Based on these results, a process flowsheet was proposed for industrial implementation. [ABSTRACT FROM AUTHOR]

Decomposition hybrid algorithms with the recursive framework which recursively decompose the structural task into structural subtasks to reduce computational complexity are employed to learn Bayesian network (BN) structure. Merging rules are commonly adopted as the combination method in the combination step. The direction determination rule of merging rules has problems in using the idea of keeping v-structures unchanged before and after combination to determine directions of edges in the whole structure. It breaks down in one case due to appearances of wrong v-structures, and is hard to operate in practice. Therefore, we adopt a novel approach for direction determination and propose a two-stage combination method. In the first-stage combination method, we determine nodes, links of edges by merging rules and adopt the idea of permutation and combination to determine directions of contradictory edges. In the second-stage combination method, we restrict edges between nodes that do not satisfy the decomposition property and their parent nodes by determining the target domain according to the decomposition property. Simulation experiments on four networks show that the proposed algorithm can obtain BN structure with higher accuracy compared with other algorithms. Finally, the proposed algorithm is applied to the thickening process of gold hydrometallurgy to solve the practical problem. [ABSTRACT FROM AUTHOR]

A laboratory investigation on nickel and cobalt electrowinning procedure from dilute synthetic sulfate-based electrolytes (with concentrations less than 40 gr/l) in a non-circulating apparatus has been carried out in the presence of boric acid as a buffering agent. By perusing previous studies on the same subject, five levels were identified for the parameters, including initial pH, temperature, and current density. Experiments were carried out in two time groups. Deposit morphology, current efficiency, and specific energy consumption were discussed as the outcomes of the process. The results produced evidence that favorable conditions (low power consumption, appropriate deposit quality, and high efficiencies) were reached at 400 A/m2, 55 °C and initial pH 5 for nickel and at 600 A/m2, 70 °C, and initial pH 5 for cobalt electrolysis. In addition, higher current efficiencies (lower power consumptions) widely occurred above 400 A/m2 in nickel electrowinning, while cobalt constraint regions of high efficiencies were observed at 200 A/m2 and 600 A/m2. [ABSTRACT FROM AUTHOR]

Today's information-rich world has become more flexible, and its development trusts upon green technologies. Due to rise in demand for proficient transmission of worldwide information and communication, a portable podium is required. Small electronic devices such as portable computers, mobile phones and other electronic devices serve as encouraging entrants that have endorsed the swift progression of information handling and allocation. Attributable to the increased use of portable electronic devices, the batteries have become closely associated with human life and hardly there will be an area without its application. The devices used for these purposes are made of critical elements which have matchless properties inimitable by other materials. Such metals are in high ultimatum and head-on supply insecurity because of several hurdles in recycling technologies. For handling the supply challenges associated with these metals, new approaches have been adopted to isolate these elements from secondary sources. The discarding of voluminous spent batteries has produced a compulsion to discover ways to recover and recycle metals that exist for the development of recycling facility. This report is envisioned to be an appreciated reference for providing state of art of hydrometallurgical and pyrometallurgical treatments for the management of spent nickel metal hydride and lithium-ion batteries. It has been revealed that efficient hydrometallurgical recycling techniques proved to be helpful in terms of environmental defence and maintenance of resources. [ABSTRACT FROM AUTHOR]

In the neutral leaching process of zinc hydrometallurgy, exploring the characteristics of pH fluctuations in the reactor is an effective approach for improving the zinc leaching rate. A modeling method of the pH probability density distribution based on the Gaussian mixture model (GMM) has thus been proposed to describe the characteristics of pH fluctuation in the reactor. This method, based on the pH time series of the highest period of zinc leaching rate, extracts the pH probability density distribution characteristics, and then identifies the pH probability density distribution of the reactor by GMM, and finally combines an enhanced expectation-maximization (EEM) algorithm to estimate GMM parameters. The experimental result shows that the EEM algorithm improves the fitting accuracy of the model by 10 percentage points. Compared with single distribution models, the GMM is more suitable for the distribution characteristics of pH probability density. It provides a theoretical basis for pH optimization control. [ABSTRACT FROM AUTHOR]

Titanium dioxide is the most common titanium-containing product on the world market, with increasing demand. The global consumption of TiO2 is 7–7.5 million tons annually. Titanium dioxide is mainly obtained from ilmenite and rutile concentrates. China, USA, Germany, UK, Mexico, and Saudi Arabia are the largest TiO2 producers. Alongside with the natural sources of titanium, there are man-made sources. These sources include titanium-containing slag obtained as a result of pyrometallurgical processing of ores and concentrates containing titanium dioxide. These slags, in addition to titanium dioxide, contain silicon in the form of dioxide, silicates or aluminosilicates, whose chemical processing is difficult due to a high melting point thereof (higher than 2000°C) and to their chemical stability in mineral acids (sulfuric, nitric, hydrochloric ones). Processing of such raw materials is carried out by classical chlorine-based and sulfuric-acid-based methods. The fluorides in industry are used in the production of aluminum, zirconium, uranium, beryllium, niobium, etc., which indicates the possibility of using fluoride methods for titanium slag processing. The paper is devoted to the consideration of a method for producing titanium dioxide based on the use of ammonium hydrodifluoride NH4HF2 that exhibits a high reactivity with respect to a number of chemically resistant oxides (the oxides of silicon, titanium, aluminum, etc.). The fluoroammonium method for processing titanium slag using NH4HF2 involves slag decomposition in NH4HF2 melt followed by the sublimation of silicon admixture. The purification from iron, aluminum and other impurities is performed using a solution of NH4HF2. The further precipitation of titanium followed by the precipitate treatment with the use of AlCl3 and ZnCl2 solutions with the subsequent calcination makes it possible to obtain a rutile modification of titanium dioxide. [ABSTRACT FROM AUTHOR]

This study, which covered a set of leaching processes at a few stages, investigated the inclusion of iron found in mill scale, which is a waste of the iron-steel industry, in the solution as FeClx=2,3 in the presence of HCl and the conditions of using this solution with an oxidizing character in extraction of metals from chalcopyrite concentrate. Mill scale was treated with HCl, and an FeClx solution was obtained at a 100% Fe solubility and 83.43% Fe3+ conversion rate in the conditions of 60 min, 105 °C, 7 M HCl, and 1/10 solid-liquid ratio. This solution that was obtained was later used in copper extraction from a chalcopyrite concentrate. In the optimum conditions (120 min of leaching time, 105 °C of leaching temperature, 1/25 solid-liquid ratio, 400 rpm stirring speed), 95.04% of the copper was taken into the solution. In the leaching experiment in a medium containing mill scale + chalcopyrite and HCl at the same time, under the optimum conditions (120 min of leaching time, 105 °C of leaching temperature, 7 M HCl concentration, 1 g chalcopyrite concentrate, 1/25 solid-liquid ratio, 5 g mill scale, 400 rpm stirring speed), approximately 96% of copper was taken into the solution. [ABSTRACT FROM AUTHOR]

We demonstrate an end-to-end protocol for the recovery of Dy and Nd from used NdFeB magnets by following steps- crushing, roasting, grinding, leaching, liquid–liquid extraction and striping. The magnets were roasted over a temperature range of 923–1273 K. The influence of roasting temperature was studied by leaching the roasted samples with HCl solution. Roasting temperature, leaching temperature, leaching time, acid concentration, mixing speed, and pulp density were optimized to selectively leach Nd and Dy while most of the Fe was removed by the hydrolysis of Fe into Fe(OH)3. Nd and Dy were extracted from the leach liquor using D2EHPA in a two-stage process. First, ~ 95% of Dy was extracted at a pH = 2, and 0.05 M D2EHPA and then Nd was extracted at pH = 4, A/O = 1 with 0.2 M D2EHPA in the second stage. Dy and Nd were completely recovered from the metal-rich organic phase by stripping with varied concentrations of HCl. [ABSTRACT FROM AUTHOR]

The recovery of Pd from spent catalysts has been gaining attention due to its high economic value and limited availability in nature. To recover and reuse Pd, leaching in HCl–H2O2 media and recovery of Pd from the Pd/SiO2 catalyst were investigated. The Pd/SiO2 catalyst was leached using 3 M HCl solution with different concentrations of H2O2; then 0.5 M NaOH was added to precipitate the Pd ions. The leaching parameters were as follows: temperature, time, H2O2 concentration, and pulp density. A 100% leaching efficiency of Pd was obtained through the addition of 5 vol% H2O2 in 3 M HCl at pulp density of 50 g/L at 80 °C for 120 min. Complete recovery of Pd was obtained at a pH = 9 due to the hydrolysis of Pd. These results indicate that the leaching time and presence of H2O2 played a key role in the stable formation of aqueous Pd–Cl complexes and in improving the mass transfer efficiency. The palladium powder obtained was palladium oxide, and the purity of palladium oxide was 86.6%. Consequently, it is expected that the obtained PdO powder can be utilized in glass, ceramic, and catalyst applications. [ABSTRACT FROM AUTHOR]

Copper slags are solid by-products formed during the copper production process by pyrometallurgical method from sulfide copper ores. These slags usually contain significant quantities of valuable metals, such as cobalt, nickel, zinc and copper, in different forms. Extraction characteristics of Cu, Co, Zn, and Fe from Küre historical copper slag (KHS) by oxidative pressure leaching were investigated with sulfuric acid lixivant in this study. The phase composition of the studied slag was identified by the use of a combination of methods, including a mineral liberation analyzer (MLA), a scanning electron microscope coupled with an energy-dispersive spectrometer (SEM-EDS), and X-ray powder diffraction (XRD). Bornite, chalcopyrite, cuprospinel, brochantite, chalcocite, and metallic Cu are identified as copper-containing minerals. The samples used in leach tests contained averages of 0.84% Cu, 0.34% Co, 0.23% Zn, 2.90% Al, 0.70% Ca, 1.30% S, and 42.80% Fe. The factors affecting the performance and efficiency of the pressure leaching process, such as acid concentration, leaching time, solid/liquid ratio, oxygen partial pressure, particle size, and temperature, were investigated separately. It was found that metal extraction increased with temperature and sulfuric acid concentration. However, high acid concentrations led to gel formation that caused filtration problems. Under optimum conditions, the extraction efficiencies of cobalt, copper, and zinc from KHS were 96.82, 92.85, and 93.44%, respectively, while the extraction of iron was only 0.3%. [ABSTRACT FROM AUTHOR]

Poisoning of ion exchange resin often occurs in uranium hydrometallurgy processes, which reduces or even depletes the adsorption capacity of uranium adsorption. Many regeneration methods have been investigated but their static desorption efficiency is undesirable and only the recovery rate is considered in the selection of regenerant. In this paper, NaClO was selected as an antidote based on a series of investigation indexes. After detoxification by dynamic elution, all performance indexes of the regenerated resin are close to those of the new resin. Compared with static method, reagent consumption and detoxification time can be saved. At the same time of reducing the cost and waste liquid discharge, it also improves the work efficiency. [ABSTRACT FROM AUTHOR]

In zinc hydrometallurgy, hot-acidic leaching of calcines leads to Fe/Zn solutions in sulfuric acid medium. Three distinct processes have been previously developed to remove iron: jarosite, goethite and hematite. Each process displays their own drawbacks: important loss of zinc (jarosite, goethite), significant environmental impact of residue (jarosite) or economic cost (hematite). The work reported herein investigated the possibility of using phytic acid, a compound extractable from cereals, to remove iron. Precipitation was studied first at the laboratory-scale using DOE methodology and then with a laboratory pilot. At pH = 2.1, we showed that it is possible to remove up to 99.5% of iron with a loss of zinc equal to 0.6% and a residual concentration of FeIII of 130 mg L−1. Even if the amount of residue is more important than in the jarosite process, leaching tests showed that iron phytate could be stored in less drastic conditions than jarosite. [ABSTRACT FROM AUTHOR]

Zinc extraction from zinc-containing residual (ZCR) was examined with the leach of sulfuric acid of original materials and the materials milled in two different mill systems. For this purpose, vibrating ball mill (VBM) and ring mill (RM) were used. In chemical analysis of ZCR, it was determined that it contains a significant amount of zinc, lead, iron and silver and consisted of mostly CaSO4.2H2O, PbO, SiO2, Fe2O3, ZnFe2O4, Al2FeO4 and PbSO4 mineral phases. It was determined in XRD analysis of samples milled at both mills that peak intensity dramatically decreased when compared to original sample. According to comparative characterization analyses of the milled samples, it was determined that through the increasing grinding time, the particles became agglomerated and an increase in grain size occurred. This situation was also supported by N2-BET and SEM analyses. While zinc extraction value of the sample milled for 1 min, which was obtained at 0.5 M H2SO4 at leach temperature of 25 °C, at the solid–liquid rate of 100:1 and during the leach time of 30 min, was 90% and 60% for, respectively, VBM and RM, zinc of 54% was determined to be extracted in the leach of the original sample, under the same conditions. [ABSTRACT FROM AUTHOR]