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The mining and metallurgical industry represents one of the leading causes of environmental pollution. In this context, the optimization of mineral waste management and the efficient extraction of metals of interest becomes an imperative priority for a sustainable future. Microorganisms such as Acidithiobacillus thiooxidans have represented a sustainable and economical alternative in recent years due to their capacity for environmental remediation in bioleaching processes because of their sulfur-oxidizing capacity and sulfuric acid generation. However, its use has been limited due to the reluctance of mine operators because of the constant reproduction of the bacterial culture in suitable media and the care that this entails. In this work, the central objective was to evaluate the functional characteristics of A. thiooxidans, microencapsulated and stored at room temperature for three years in vacuum bags, using a spray drying process with gum arabic as a wall vector. Growth kinetics showed a survival of 80 ± 0.52% after this long period of storage. Also, a qualitative fluorescence technique with a 5-cyano-2-3 ditolyl tetrazolium (CTC) marker was used to determine the respiratory activity of the microorganisms as soon as it was resuspended. On the other hand, the consumption of resuspended sulfur was evaluated to corroborate the correct metabolic functioning of the bacteria, with results of up to 50% sulfur reduction in 16 days and sulfate generation of 513.85 ± 0.4387 ppm and 524.15 ± 0.567 ppm for microencapsulated and non-microencapsulated cultures, respectively. These results demonstrate the success after three years of the microencapsulation process and give guidelines for its possible application in the mining-metallurgical industry. [ABSTRACT FROM AUTHOR]

The work describes the construction of lithium-ion batteries, with particular emphasis on metals that can be obtained as secondary raw materials. The work presents the latest trends in the recycling of lithium-ion batteries, using pyro- and hydrometallurgical methods, or their combination. The ecological aspect of the impact of the recycling processes on the environment is shown, as well as the challenges and expectations for the future in the field of recycling processes. [ABSTRACT FROM AUTHOR]

The overuse and exploitation of fossil fuels has triggered the energy crisis and caused tremendous issues for the society. Lithium‐ion batteries (LIBs), as one of the most important renewable energy storage technologies, have experienced booming progress, especially with the drastic growth of electric vehicles. To avoid massive mineral mining and the opening of new mines, battery recycling to extract valuable species from spent LIBs is essential for the development of renewable energy. Therefore, LIBs recycling needs to be widely promoted/applied and the advanced recycling technology with low energy consumption, low emission, and green reagents needs to be highlighted. In this review, the necessity for battery recycling is first discussed from several different aspects. Second, the various LIBs recycling technologies that are currently used, such as pyrometallurgical and hydrometallurgical methods, are summarized and evaluated. Then, based on the challenges of the above recycling methods, the authors look further forward to some of the cutting‐edge recycling technologies, such as direct repair and regeneration. In addition, the authors also discuss the prospects of selected recycling strategies for next‐generation LIBs such as solid‐state Li‐metal batteries. Finally, overall conclusions and future perspectives for the sustainability of energy storage devices are presented in the last chapter. [ABSTRACT FROM AUTHOR]

The work describes the construction of lithium-ion batteries, with particular emphasis on metals that can be obtained as secondary raw materials. The work presents the latest trends in the recycling of lithium-ion batteries, using pyro- and hydrometallurgical methods, or their combination. The ecological aspect of the impact of the recycling processes on the environment is shown, as well as the challenges and expectations for the future in the field of recycling processes.

Abstract The overuse and exploitation of fossil fuels has triggered the energy crisis and caused tremendous issues for the society. Lithium‐ion batteries (LIBs), as one of the most important renewable energy storage technologies, have experienced booming progress, especially with the drastic growth of electric vehicles. To avoid massive mineral mining and the opening of new mines, battery recycling to extract valuable species from spent LIBs is essential for the development of renewable energy. Therefore, LIBs recycling needs to be widely promoted/applied and the advanced recycling technology with low energy consumption, low emission, and green reagents needs to be highlighted. In this review, the necessity for battery recycling is first discussed from several different aspects. Second, the various LIBs recycling technologies that are currently used, such as pyrometallurgical and hydrometallurgical methods, are summarized and evaluated. Then, based on the challenges of the above recycling methods, the authors look further forward to some of the cutting‐edge recycling technologies, such as direct repair and regeneration. In addition, the authors also discuss the prospects of selected recycling strategies for next‐generation LIBs such as solid‐state Li‐metal batteries. Finally, overall conclusions and future perspectives for the sustainability of energy storage devices are presented in the last chapter.

Rapid technological modernization has accelerated the replacement of older electronic goods with newer ones, which has led to the generation of huge quantities of discarded electronic items at its end-of-life, known as electronic wastes (e-wastes). The growing quantity of e-wastes has become a major threat to the society as well as environment. On the other hand, e-wastes contain several valuable metals and materials of high economic value, which compels researchers to work in the area for secondary resources for metal recovery. Metal recovery from such secondary resources will not only preserve the primary resources but also reduce the loss of valuable metals/materials, protect the environment from their hazardous effects as well as reduce the demand-supply gap of metals up to some extent. In view of the above, present study is focused on the possible effort to figure out variety of metals present in the component of waste personal computers (WPCs) as well as different recycling processes implemented for the efficient recovery of metals. [ABSTRACT FROM AUTHOR]

The suitable electrochemical performance of lithium-ion batteries (LIBs) led to an increase in demand and the use of LIBs in electrical and electronic equipment. Naturally, increased demand will be accompanied by an enhancement in the supply of metals from mineral resources. On the other hand, the lithium metal supply scenario will not be able to meet market demand over the next few years. Spent LIBs include valuable metals like lithium, cobalt, nickel, manganese, etc., which can be considered as a secondary source for the recovery of valuable metals. LIBs also contain toxic and organic compounds whose lack of attention, causes irreparable damage to the public health and the environment. Therefore, two important perspectives on the recycling of spent LIBs are the recovery of valuable metals as secondary sources and compliance with environmental regulations. Among the recycling process of spent lithium-ion batteries, hydrometallurgical processes are a suitable technique for recovery of valuable metals from spent lithium-ion batteries, due to their advantages such as the high recovery of metals with high purity, low energy consumption, and very low gas emissions. In this paper, the main aspects of spent LIBs recycling (environmental and economic) and hydrometallurgical processes (pre-treatment, leaching by organic and inorganic acids with various reducing agents, precipitation, solvent extraction, electrochemical methods, ion exchange resin, and regeneration) used to recover valuable metals, have been investigated. [ABSTRACT FROM AUTHOR]

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We present the preparation and characterization of pure lead monoxide obtained through recycling of the lead paste recovered from exhausted lead acid batteries. The recycling is based on a hydrometallurgical procedure reported in a STC Patent, that includes simple chemical operations (desulphurisation, leaching, precipitation, filtration) and a final thermal conversion. Materials obtained by treatment at 600 °C consist predominantly of β-PbO. The electrochemical behaviour of Positive Active Mass (PAM) prepared from different materials (or mixtures) is then investigated and compared. An optimized oxide material, obtained by prolonged (8 h) thermal treatment at 600 °C, consists of pure β-PbO and appears suitable for preparation of battery elements, alone or in mixture with a small fraction (10%–30%) of traditional industrial leady oxide. The resulting battery performances are similar to those obtained from pure leady oxide. In comparison with traditional recycling processes, the proposed method guarantees lower energy consumption, limited environmental impact and reduced operating risk for industry workers. [ABSTRACT FROM AUTHOR]

The main objective of this manuscript is the description of a mobile demonstration plant designed and built for the recovery of metals from waste of electrical and electronic equipment and other waste such as spent batteries and exhausted industrial catalysts. The plant was designed within the European FP7 framework HydroWEEE-demo (2012–2016) and can offer an effective proposal to addressing the problem of the electronic waste, reducing the environmental impact of their not correct disposal, recovering critical materials as rare earths and precious elements, and giving economic benefits, moreover by it, it is possible to overcome the problem of moving hazardous wastes from one country to another one. Details about the process to recover rare earths from fluorescent materials are presented. Two alternative treatments are showed with and without recirculation of the residual solutions. Economic analysis shows that with the actual product price (14 €/kg) only the process, in which solution recirculation is present, provides a return on the investment. Positive gain is possible if the plant works at its highest capacity and if the price growths up to 20 €/kg the gain increases about 20% of operating costs (process with recirculation, 2 batch/day). In the process without recirculation of the solution, to obtain the same ratio between gain and operating cost it is necessary that the price increases up to 26 €/kg. About other e-wastes, economic analysis has shown that the highest gain is provided from the PCB treatment. [ABSTRACT FROM AUTHOR]

The paper deals with a possibility of zinc and cobalt extraction from refuse after sphalerite mineral leaching. It contains theoretic analysis of hydrometallurgical processes. Practical part describes samples and their leaching in 10 % and 20 % sulphuric acid. In the end of the paper it is evaluated under which conditions the highest yield of zinc and cobalt from refuse after sulphide ore leaching is reached.

This article presents a copper leaching process from chalcopyrite concentrates using a low-pressure reactor. The experiments were carried out in a 30 L batch reactor at an oxygen pressure of 1 kg/cm2 and solid concentration of 100 g/L. The temperature, particle size and initial acid concentration were varied based on a Taguchi L9 experimental design. The initial and final samples of the study were characterized by chemical analysis, X-ray diffraction and particle size distribution. The mass balance showed that 98% of copper was extracted from the chalcopyrite concentrate in 3 h under the following experimental conditions: 130 g/L of initial sulfuric acid concentration, temperature of 100 °C, oxygen pressure of 1 kg/cm2, solid concentration of 100 g/L and particle size of −105 + 75 μm. The ANOVA demonstrated that temperature had the greatest influence on copper extraction. The activation energy was 61.93 kJ/mol. The best fit to a linear correlation was the chemical reaction equation that controls the kinetics for the leaching copper from chalcopyrite. The images obtained by SEM showed evidence of shrinking in the core model with the formation of a porous elemental sulfur product layer.

The metals and industrial minerals contained in the tailings of mining and quarrying activities, can degrade natural environments as well as human health. The objective of this experimental work is the application of innovative and sustainable technologies for the treatment and exploitation of mining tailings from Romania. Within this approach, the recovery of high grade raw materials to be placed on the market is achieved and reduction of these wastes volume are achieved. The current study is focused on hydrometallurgical process for the recovery of gold. The innovative treatment chosen is the thiosulphate process that, compared with the conventional cyanide, has several advantages (e.g., it is more ecologically friendly and is not toxic to humans). The conventional cyanidation process shows operating limits in the case of auriferous refractory minerals, such as Romanian wastes, the object of the study. An important characteristic of thiosulphate leaching process it has the best selectivity towards gold; it does not attack the majority of the gangue mineral constituents. Gold extraction of 75% was obtained under ambient conditions of temperature. Moreover, the overall process achieved about 65⁻67% Au recovery, this being in line with the conventional cyanidation process. As these results are obtained by application of the thiosulfate process on a low gold content ore, they may be considered encouraging. The optimization of process parameters and operating conditions, should permit the best results in terms of process yields to be achieved.

The paper deals with a possibility of zinc and cobalt extraction from refuse after sphalerite mineral leaching. It contains theoretic analysis of hydrometallurgical processes. Practical part describes samples and their leaching in 10 % and 20 % sulphuric acid. In the end of the paper it is evaluated under which conditions the highest yield of zinc and cobalt from refuse after sulphide ore leaching is reached. [ABSTRACT FROM AUTHOR]

• Efficient and economic production process can mitigate criticality of germanium. • US germanium resources remain unused due to inefficiency in production. • Production processes including leaching, precipitation, and separation are reviewed. • Separation includes precipitation, solvent-extraction, ion-exchange, and adsorption. • Ge chemistry differs from other cations as it remains as neutral species in acidic pH. Germanium (Ge) is one of the critical elements of modern technologies, with supply risk, inefficient production, and increased demand. It is used in high technology applications such as infrared systems, fiber optics, polymer catalysis, electronics, and solar cells. Its demand is expected to increase due to lack of suitable substitutes, increasing demand for solar cells and 5G networks, and the continuous increasing trend of Ge demand for the past 20 years. Globally, 130 tonnes (t) of Ge are being produced (2020) primarily in China. Germanium is recovered as a byproduct from Zn-refineries and coal fly ash. Yet very low amount (<3%) of Ge contained in Zn-ores and fly ash is recovered worldwide, which suggests that the criticality of Ge is due to lack of economical and efficient extraction and recovery process rather than lack of resources. Worldwide, it is estimated that Zn-ores contain 7–13 kt Ge, and coal and coal fly ash, 25–112 kt. The production of Ge involves leaching followed by recovery of Ge by chlorination-distillation, precipitation, solvent extraction, ion flotation, supported liquid membranes, ion exchange, or solid-phase extraction. Leaching from Zn-refinery residues is primarily done with mineral acids, whereas from coal fly ash is achieved with organic ligands. Ge is different from common metal cations, as it exists as neutral species in acidic pH (1–7). Thus, organic ligands are used to form anionic germanium-ligand complexes in solvent extraction and ion-exchange processes so that the species can be separated through anion-exchange. Alternatively, chelating solvent extractants, chelating ion-exchange resins, and ligand functionalized adsorbents in solid-phase extraction (SPE) are used to recover Ge. The primary challenges in Ge hydrometallurgical production are high energy and chemical requirements in precipitation/chlorination-distillation, high chemical consumption, impurities co-extraction, and waste stream generation in solvent extraction, and lack of selective and high-capacity adsorbents in SPE. An improved, efficient, and economical production method, utilizing unconventional resources, can reduce Ge supply risk. SPE has various advantages over other processes, which makes it an attractive option to recover Ge efficiently and economically. [ABSTRACT FROM AUTHOR]

[Display omitted] • Valuable metals Mn, Ni, Co, and Li recovered from leaching solution of spent LIBs. • About 96.5% of Mn ions were separated under conditions MRMK: 2 and pH: 2. • pH, DMG, and MRND were identified as effective parameters in Ni ions extraction. • D2EHPA, TBP, pH and O/A ratio were investigated for cobalt SX operation. • Taguchi L 9 orthogonal array method was designed for the cobalt SX operation. • lithium separation reached 98.84% in specifically designed conditions. The process of recovering metals from spent lithium-ion batteries is difficult due to the complexity of the metal components. Therefore, the separation and extraction of metal ions from the leaching solution of spent lithium-ion batteries requires a set of hydrometallurgical processes. In this research, precipitation and solvent extraction processes have been used to the final recovery of metals. Initially, by applying potassium permanganate with molar ratio of manganese ions to potassium permanganate: 2 and pH: 2, 96.5% of manganese ions were precipitated and separated from the leaching solution. Then, via dimethylglyoxime in molar ratio of nickel ions to dimethylglyoxime: 0.5, and pH: 5, 96% nickel recovered, approximately. Subsequently, using 30 v/v% D2EHPA and 5 v/v% TBP respectively as an extractant and a modifier of the organic phase, and under optimal conditions of Vo/Va: 1, pH: 5, temperature 25 °C, time 20 min and mixing speed 400 rpm, it is possible to achieve 93.38% cobalt extraction efficiency and also control the loss of lithium at 16.74%. Finally, in the molar ratio of lithium ions to sodium carbonate: 0.7, temperature 100 °C, time 40 min, mixing speed 400 rpm and the pH: 12, the lithium precipitation efficiency reached to 98.84%. [ABSTRACT FROM AUTHOR]

Hydrometallurgical methods for preparation of refractory arsenopyrite concentrates to cyanidation using bacterial leaching and chemical decomposition have been investigated. After cyanide or non-cyanide gold dissolution, the complexes of gold can be selectively recovered on acrylic or styrene anion exchangers. [ABSTRACT FROM AUTHOR]

SEM and TEM images of microparticles of arabic gum encapsulating Acidithiobacillus thiooxidans obtained by Spray Drying. The viability of the bacterium is reported with a high survival rate after the spray drying process, aimed to be applied for the removal of Ag impurities in a bioleaching process. [Display omitted] • Acidithiobacillus thiooxidans encapsulation was achieved by the spray drying method. • The best wall material for encapsulation was Arabic gum. • Spherical microcapsules with modal particle size distribution were obtained. • Rehydrated powders showed flow stability and shear thinning behavior. • Obtained microcapsules could be effectively applied in bioleaching processes. Acidithiobacillus thiooxidans is a microorganism of great interest in bio-hydrometallurgical processes, as it is potentially capable of treating complex, low-grade (purity) sulfur minerals. However, there are concerns in the metallurgical industry regarding the microbial manipulation due to problems arising related to cellular integrity, metabolic activities, genetic stability and maintainability of a continuous generation of microbial cultures. In this work, a spray drying (SD) process (inlet temperature: 150 °C, feed flow: 1.2 L/h, and atomization rate: 27,500 rpm) was adopted to encapsulate Acidithiobacillus thiooxidans using different biopolymers as wall materials. The physicochemical properties of the powders obtained by SD reveal water activity (a w) below 0.55 with less than 10% moisture, which ensures better stability of the powders during storage with a trapping efficiency above 80%. Morphology studies by scanning electron microscopy (SEM) of the microparticles showed defined surfaces with no collapsing structures, quasi-modal size particles, low viscosity of the reconstituted powders and fast release profiles. Calorimetric analysis confirmed the viability of A. thiooxidans to withstand the SD process. By infrared analysis, the same peaks of the functional groups corresponding to the biopolymers after spray drying were observed, which evidences the microorganism encapsulation (whose signal disappeared after SD). The presence of A. thiooxidans in the microcapsules was confirmed by Transmission Electron Microscopy (TEM). Finally, viability was verified by respiratory assessment of the bacterium rendering high survival rate (1.4 × 109 Cells/mL) after the spray drying process. [ABSTRACT FROM AUTHOR]

The metals and industrial minerals contained in the tailings of mining and quarrying activities, can degrade natural environments as well as human health. The objective of this experimental work is the application of innovative and sustainable technologies for the treatment and exploitation of mining tailings from Romania. Within this approach, the recovery of high grade raw materials to be placed on the market is achieved and reduction of these wastes volume are achieved. The current study is focused on hydrometallurgical process for the recovery of gold. The innovative treatment chosen is the thiosulphate process that, compared with the conventional cyanide, has several advantages (e.g., it is more ecologically friendly and is not toxic to humans). The conventional cyanidation process shows operating limits in the case of auriferous refractory minerals, such as Romanian wastes, the object of the study. An important characteristic of thiosulphate leaching process it has the best selectivity towards gold; it does not attack the majority of the gangue mineral constituents. Gold extraction of 75% was obtained under ambient conditions of temperature. Moreover, the overall process achieved about 65–67% Au recovery, this being in line with the conventional cyanidation process. As these results are obtained by application of the thiosulfate process on a low gold content ore, they may be considered encouraging. The optimization of process parameters and operating conditions, should permit the best results in terms of process yields to be achieved. [ABSTRACT FROM AUTHOR]

This article presents a copper leaching process from chalcopyrite concentrates using a low-pressure reactor. The experiments were carried out in a 30 L batch reactor at an oxygen pressure of 1 kg/cm2 and solid concentration of 100 g/L. The temperature, particle size and initial acid concentration were varied based on a Taguchi L9 experimental design. The initial and final samples of the study were characterized by chemical analysis, X-ray diffraction and particle size distribution. The mass balance showed that 98% of copper was extracted from the chalcopyrite concentrate in 3 h under the following experimental conditions: 130 g/L of initial sulfuric acid concentration, temperature of 100 °C, oxygen pressure of 1 kg/cm2, solid concentration of 100 g/L and particle size of −105 + 75 μm. The ANOVA demonstrated that temperature had the greatest influence on copper extraction. The activation energy was 61.93 kJ/mol. The best fit to a linear correlation was the chemical reaction equation that controls the kinetics for the leaching copper from chalcopyrite. The images obtained by SEM showed evidence of shrinking in the core model with the formation of a porous elemental sulfur product layer. [ABSTRACT FROM AUTHOR]