Search

The cobalt removal process with arsenic salt of zinc hydrometallurgy has serious non‐linearity, uncertainty, and mutual coupling. Its accurate dynamic modelling has always been a challenging problem. On the basis of in‐depth analysis of cobalt removal process and reaction mechanism, considering the cascade relationship between the reactors, a dynamic synergistic continuously stirred tank reactor (SCSTR) mechanism model of the cobalt removal process was constructed. Aiming at the unknown parameters in the SCSTR model, the idea of the Kalman filter was introduced, and the unknown parameters were characterized as unknown states; a method of estimating the unknown model parameters was developed using the augmented state equation and the unscented Kalman filter (UKF) algorithm. Simulation results with industrial data of a zinc smeltery showed that the parameter estimation model has high accuracy, and the estimated parameters can be used in the SCSTR model. An intensive simulation analysis of the dynamic characteristics of the complete SCSTR model was carried out to verify the influence of different input disturbances on the output ion concentration of each reactor, which demonstrated the excellent dynamic performance and potential of the model. Ultimately, according to the industrial calculation analysis, the SCSTR model has a guiding effect on the addition of zinc powder in the reactors, overcomes the blindness in the production process, and provides a momentous basis for the optimization control of the cobalt removal process. [ABSTRACT FROM AUTHOR]

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]

Gold has important strategic significance and economic value.At present, cyanidation is mainly used to extract gold in the industry.However, cyanidation has a long production cycle and the cyanide used is highly toxic.If it is not well managed, there will be potential environmental pollution risks.Taking the gold-bearing acid residue of a gold smelter as the research object, the leaching of gold in a thiourea system was studied.The results show that the leaching rate of gold from gold-bearing acid residue is only 83.17 % under the condition of conventional intensified stirring thiourea leaching.Under the condition of ultra-fine grinding to enhance thiourea leaching, the gold leaching rate of gold-bearing acid residue reaches 89 %;it is recommended that the best experimental scheme is enhanced stirring leaching+one stage ultra-fine grinding leaching+two stage ultra-fine grinding leaching for three times+enhanced stirring leaching.The leaching rate of gold from gold-bearing acid residue can reach 95.04 %,which can realize the clean and deep extraction of gold from gold-bearing acid residue and provide theoretical and technical support for the industrial application of the non-cyanide gold extraction process. [ABSTRACT FROM AUTHOR]

Background. The kinetics of the oxidation of molybdenite concentrate in sodium hypochlorite solutions was previously studied. It was of interest to compare it with the behavior of pyrite concentrate under the same conditions. Purpose: to study the kinetics of oxidative leaching of gold and silver from pyrite concentrate, in hypochlorite electrolyte, using the rotating disk method. Methodology. Pyrite concentrate of Almalyk MMC JSC was used, pressed into tablet discs18 mm; sodium hypochlorite, controlled Au(I), Ag(I) in solutions (ААС Perkin-Elmer 3030В, ICP-Agilent 7500 IСP MS); solid phase SEM-EDS EVO-MA (Carl Zeiss, Instrum) and JCM-6000 Neoscope II (Jeol, Japan); FTIR Nicolet iS50 (Thermo Scientific, USA), XRD Empyrean (PANalytical). Originality. The parameters of the kinetic equation for the process of oxidative leaching: Au(I), Ag(I) from pyrite concentrate are obtained, the activation energy of the process of diffusion of Au, Ag from the solid into the liquid phase is calculated. Findings. Dependences of the leaching rate of Au, Ag from minerals in a hypochlorite electrolyte on a number of factors are constructed using the rotating disk method. [ABSTRACT FROM AUTHOR]

In this work the preparation of alumina from kaolinite by leaching with hydrochloric acid is studied. Crude kaolin was calcined at 850°C and then leached with 6 M hydrochloric acid at 90°C. Aluminum hydroxide was precipitated by adding 6 M HCl solution to the leaching water. Finally, the precipitated aluminum hydroxide was heated at 1100°C and converted to aluminum oxide. The materials were identified by XRF, XRD and SEM-EDX techniques. The percentage of alumina recovery was determined at different kaolin particle sizes (-200 to -400 standard Tyler sieve), different times (1, 2, 3 and 4 h), different leaching temperatures (80, 90, 100 and 104°C) and different concentrations of hydrochloric acid (20, 25, 30 and 37%). The phase changes of alumina were also investigated at two calcination temperatures (1100 and 1200°C). The purity of aluminum oxide obtained by this method is about 97% and the percentage of recovery is about 98%. It was observed that the kaolin granulation with dimensions smaller than 75 µm had no significant effect on the percentage of alumina recovery. It was also found that the percentage of alumina recovery increased with increasing leaching temperature. [ABSTRACT FROM AUTHOR]

At the end of their efficient functionality in energy production/storage applications, spent lithium-ion batteries need to be recycled. Recycling remains the most preferred economic option with benefits such as prevention/reduction of environmental issues due to landfilling and more efficient use of natural resources. In this paper, characteristics of lithium-ion battery components before and after being spent are presented, together with highlights of various extractive options suitable for recycling. The main emphasis of this review is on the direct recycling approach, which employs the physical separation of anode and cathode materials. Since flotation is the most common processing method successfully applied to the physical separation of minerals in the mining industry, researchers have given a lot of attention to this area. The success of recycling by flotation is mainly dependent on wettability differences between the anode (hydrophobic) and cathode (hydrophilic) components. However, such components are subjected to surface modifications due to the intimate organic coating introduced in battery production. As such, the hydrophobic entities of the solid electrolyte in battery assembly, which are so essential for the electrochemical functionality of the battery during its life cycle, present main challenges on the selectivity of flotation as a recycling option. Thus, the restoration of the original hydrophobicity/hydrophilicity level of each electrode has been the main focus area for many investigations. This paper also provides an up-to-date review of proposed pretreatment options. [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]

The importance of gold recovery from waste printed circuit boards is continuously increasing due to raising gold prices and demand as well as the need for innovative and flexible recycling methods for this complex waste stream. The state-of-the-art recycling process aims at the pyrometallurgical recovery of noble metals, mainly using a copper collector. Different technical limitations justify the application of a hydrometallurgical process alternative for recovering gold. The direct application of gold lixiviants on comminuted PCBs is hardly possible due to the high concentration of metal impurities. As a solution, most researchers propose hydrometallurgical separation of disturbing base metals prior to gold extraction. For this, different leaching systems with aggressive chemicals can be applied, often leaving residual base metal concentrations behind. Within this study, two different leaching parameter sets were investigated to separate base metals and determine the impact of residual base metals on subsequent gold recovery. The gold lixiviants that were applied for comparison were thiosulfate, thiourea, iodine-iodide, NBS, and cyanide. It was found that thiosulfate and thiourea are less sensitive than other lixiviants to metal impurities. When base metals are separated completely, gold recovery is strongly improved, and cyanide also achieves a good gold recovery. [ABSTRACT FROM AUTHOR]

Waste silicon powder produced during the production process of organosilicon materials is a major environmental concern that can lead to pollution and resource wastage. As a result, it is crucial to find efficient ways of recovering and utilizing this waste material. In this study, the morphology of waste silicon powder was systematically studied, and an optimized purification method was proposed based on a hydrometallurgical process and phase analysis. The complex composition of waste silicon powder presents a significant challenge during its recycling. However, the results of this study showed that metal-assisted chemical etching (MACE), followed by mixed acid system leaching, is the most effective method for removing impurities from the material. The superior order of different acid systems for removing metallic impurities was HCl < HF < HF + HCl < HF + H2O2 < CuACE. It is worth noting that CuACE treatment has a remarkable ability to remove more than 95% of Fe through hydrometallurgy. [ABSTRACT FROM AUTHOR]

Solid-state batteries (SSBs) are promising next-generation batteries due to their potential for achieving high energy densities and improved safety compared to conventional lithium-ion batteries (LIBs) with a flammable liquid electrolyte. Despite their huge market potential, very few studies have investigated SSB recycling processes to recover and reuse critical raw metals for a circular economy. For conventional LIBs, hydrometallurgical recycling has been proven to be able to produce high-quality products, with leaching being the first unit operation. Therefore, it is essential to establish a fundamental understanding of the leaching behavior of solid electrolytes as the key component of SSBs with different lixiviants. This work investigates the leaching of the most promising Al- and Ta-substituted Li7La3Zr2O12 (LLZO) solid electrolytes in mineral acids (H2SO4 and HCl), organic acids (formic, acetic, oxalic, and citric acid), and water. The leaching experiments were conducted using actual LLZO production waste in 1 M of acid at 1:20 S/L ratio at 25 °C for 24 h. The results showed that strong acids, such as H2SO4, almost completely dissolved LLZO. Encouraging selective leaching properties were observed with oxalic acid and water. This fundamental knowledge of LLZO leaching behavior will provide the basis for future optimization studies to develop innovative hydrometallurgical SSB recycling processes. [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]

Manganese dust generated during the production of ferroalloys contains iron and zinc oxides together with other minor oxides. Pure manganese compounds can be recovered from the leaching solution of the manganese dust by removing the impure ions. In this work, sulfuric acid and ferrous sulfate were employed as leaching and reducing agents for the manganese oxides in the dust. First, the leaching conditions for complete dissolution of the manganese oxides were investigated by varying the concentration of sulfuric acid and ferrous sulfate, and pulp density. Second, after oxidizing Fe(II) to Fe(III) by hydrogen peroxide, Fe(III) was removed from the solution by three stages of counter current extraction with D2EHPA. Third, Zn(II) was removed by two stages of cross current extraction with Cyanex 272. Stripping conditions for Fe(III) and Zn(II) were determined from the respective loaded organics. Fourth, Mn(OH)2 was precipitated from the raffinate by adjusting the pH of the solution to 10 with NaOH solution. The MnSO4 crystals with 99.5% purity were recovered by crystallization from the sulfuric acid solutions after the precipitates of Mn(OH)2 were dissolved. A comparison of the cost of the chemicals used to recover MnO2 and MnSO4 indicated that the current process was much more economical.

This article presents the results of a comparative study for the increase in the free finely dispersed gold recovery from the gold-bearing ore produced in a deposit in Kazakhstan. The following minerals were identified in the sample under X-ray phase analysis: chalcopyrite and pyrite, as well as in a finely disseminated state in silicate minerals. Gold in the ore is present mainly (40.09%) in the free form under the results of phase analysis. Flotation tests of ore beneficiation were performed in FML-1 and FML-3 flotation machines with chamber volumes of 1.0 and 3.0 liters. A flotation combined concentrate with a gold content of 15.3 g/t was obtained (concentrate yield 9.45%), with gold recovery into concentrate 82.79% in the optimal mode: the grind of 90% in the class -0.071 mm; consumption of reagents: C7foaming agent - 30 and 60 g/t, sodium butyl xanthate - 60 and 120 g/t; the time of the main flotation - 10 minutes, the control flotation - 7 minutes, at pH = 9. Flotation tailings contained 0.33 g/t of gold. The recovery showed a fairly high 84.42% (yield of the total concentrate 20.93%)with the gold content of 7.1 g/t with the use of a sulfidizing agent (Na2S) and additional dispersion of the pulp at pH = 9.0. A gold-bearing concentrate was obtained containing 4.0 g/t Au at a fineness of -0.05 mm and 6.8 g/t Au at a fineness of +0.05 mm. The beneficiation of the pulp with a fineness of +0.05 mm gave the recovery into the final concentrate equal to 89.94%.

In order to obtain PbO2 electrode with low cost, high catalytic activity and long life for manganese electrowinning, a carbon fiber/Ni - CoOx/Sn - SbOx/β - PbO2 - CNT composite electrode was prepared by adding bottom and intermediate layers on the carbon fiber substrate through electrochemical deposition and sintering. Galvanostatic polarization curve, Tafel curve and other electrochemical methods were employed to study the catalytic activity and corrosion resistance of the electrode. Results showed that the as - prepared carbon fiber electrode had a bottom layer of Ni - CoOx, an intermediate layer of Sn - SbOx, and a surface active layer of β - PbO2 - CNT. Adding Ni - CoOx bottom layer and Sn - SbOx intermediate layer made the connection between the PbO2 surface active layer and the carbon fiber closer, and adding carbon nanotubes into the β - PbO2 surface active layer improved the corrosion resistance, chlorine evolution potential and electrocatalysis activity of the electrode.

Recently, the depletion of nickel sulfide resources barely meet the increasing demand and laterite nickel ore gain a special attention as the main source of nickel in the future. Even laterite nickel ore has become a hot spot of research due to its rich reserves, easy mining, and convenient transportation, the effective treatment and efficient utilization of laterite nickel ore is still very appealing. In this article, we mainly introduces the smelting methods and technologies of different laterite nickel ore from different ore layers, summarizes the laterite nickel ore of different ore layers and their applicable smelting processes, analyzes the processing technology of different laterite nickel ore, and realizes different types of laterite comprehensive utilization of nickel ore.

[Display omitted] • A one-step leaching process for spent LiCoO 2 based on the mechanochemical method. • The new application of grape skins promotes the leaching of spent LiCoO 2. • Effect of mechanical activation on the interfacial reaction of spent LiCoO 2. • The mechanism of mechanochemical leaching was analyzed by BET, PSD, XRD, and XPS. A one-step system based on mechanochemical activation and the use of grape skins (GS) was proposed to recover metals from lithium-ion batteries (LIBs) cathode waste. The effects of the ball-milling (BM) speed, BM time, and quantity of added GS on the metal leaching rate were explored. The spent lithium cobalt oxide (LCO) and its leaching residue before and after mechanochemistry were characterized by SEM, BET, PSD, XRD, FT-IR, and XPS analysis. Our study shows that mechanochemistry promotes the leaching efficiency of metals from LIBs battery cathode waste by changing the cathode material properties (that is, reducing the LCO particle size (12.126 μm ∼ 0.0928 μm), increasing the specific surface area (0.123 m2/g ∼ 15.957 m2/g), enhancing the hydrophilicity and surface free energy (57.44 mN/m2 ∼ 66.18 mN/m2), promoting the generation of mesoporous structures, refining grains, disrupting the crystal structure, and increasing the microscopic strain, while deflecting the binding energy of the metal ions). A green, efficient and environmentally friendly process for the harmless and resource-friendly treatment of spent LIBs has been developed in this study. [ABSTRACT FROM AUTHOR]

The processing of zinc ore using hydrometallurgical methods leads to the formation and accumulation of a by-product called jarosite, which contains concentrated precious metals. In this study, we propose the recovery of In and its separation from Cu, Zn, Fe, Pb, and Ag. This study also presents a proposal for a new technological procedure for jarosite treatment. First we roasted the jarosite, and then the calcine collected was leached in water. The leaching extraction values obtained for Cu, Zn, Fe, and In were 91.07%, 91.97%, 9.60%, and 100.0%, respectively. Following the leaching of the roasted material in water, Pb, Ag, and most of the Fe obtained remained in the solid residue. The leaching solution was treated further by a precipitation process using NaOH, where In and Fe were precipitated and consequently separated from Cu and Zn. The In (OH)3 and Fe(OH)3 precipitates were dissolved further in a diluted H2SO4 solution, and then the cementation of In with Al was performed. We used HCl acid to remove Al from the In, after which unwrought In was obtained. [ABSTRACT FROM AUTHOR]

A selective extraction process for recovering vanadium (IV) over chromium was proposed with use of a mixed extractant consisting of di(2-ethylhexyl) phosphate (D2EHPA) and tri-n-butyl phosphate (TBP). The influence of various factors, which included the initial aqueous pH value, the concentration of leach solution and D2EHPA, phase ratio (O/A), extraction equilibrium time and extraction temperature in the extraction process on the separation of V and Cr was investigated. Under the condition of the optimum extraction, vanadium extraction was above 94.0%. Meanwhile, under the optimum stripping conditions, the vanadium stripping was above 93.0% utilizing 1.5 mol/L sulfuric acid as the effective stripping reagent. The regeneration and reusability of the loaded organic phases after stripping were discussed. In addition, continuous three-stage extraction and stripping strategy indicated that the aggregate loss of vanadium was 0.885% and that the purity of vanadium was more than 99.9%. Under the condition of the optimum precipitation, when the pH value of the stripping solution was adjusted to 7.0 with ammonia water, the precipitation efficiency reached 99.93%. The calcination conditions (above 680 °C in air) were finally determined by TG-DTA and TG-MS experiments, and the V2O5 obtained by calcination was characterized by XRD. Additionally, a method for detecting impurity elements in vanadium matrix without interference was established. The recovery technology has practical significance in enlarging production scale, reducing specific energy consumption and cost, and realizing automatic control in vanadium leaching process. [ABSTRACT FROM AUTHOR]

The rapidly increasing adoption of electric vehicles (EVs) worldwide is causing high demand for production of lithium‐ion batteries (LIBs). Tremendous efforts have been made to develop different components of LIBs in addition to design of battery pack architectures as well as manufacturing processes to make better batteries with affordable prices. Nonetheless, sustainable use of LIBs relies on the availability and cost of rare metals, which are naturally concentrated in a few countries. In addition, toxic electrolytes used in LIBs pose concerns on environmental impacts if LIBs are not handled properly after decommissioned from EVs. Therefore, it is paramount to realize effective utilization of spent LIBs, where their remaining capacities can be reused in less demanding applications. Finally, electrode materials and other valuable components of LIBs can be recovered via recycling, completing their circular life cycle. In this review, available options of LIBs after their retirement from EV applications, including battery second use, repair of electrode materials by direct regeneration, and material recovery by hydrometallurgical or pyrometallurgical processes are discussed. Throughout the review, the discussion is based around current available technologies, their environmental impacts, and economic feasibility as well as provided examples of pilot and industrial scale adoption of the processes. [ABSTRACT FROM AUTHOR]

With the development trend and technological progress of lithium batteries, the battery market is booming. This means that the demand for lithium batteries has increased significantly, resulting in a large number of discarded lithium batteries. The consumption of plenty of lithium batteries may lead to the scarcity and expending of relevant raw material metal resources, as well as serious heavy metal environmental pollution. Therefore, it is of great significance to recycle valuable metal resources from discarded lithium batteries. The proper recycling of these valuable metals can reduce the shortage of mineral resources and environmental hazards caused by a large number of scrapped vehicle batteries. Recently, different systematic approaches have been developed for spent lithium battery recovery. However, most of these approaches do not account for the hidden costs incurred from various processing steps. This work is determined by the concept of material flow cost accounting (MFCA). Hence, in this research, a MFCA-based approach is developed for the leaching process of spent lithium batteries recovery, taking into consideration the hidden costs embedded in process streams. In this study, hydrochloric acid had the worst leaching efficiency due to its high solid-to-liquid ratio and the lowest acid concentration, so it was excluded in the first stage selection. It takes TWD 16.03 and TWD 24.10 to leach 10 g of lithium battery powder with sulfuric acid and nitric acid, respectively. The final sulfuric acid was the acid solution with the highest leaching efficiency and relatively low cost among inorganic acids. [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.)

Copyright of Hydrometallurgy of China is the property of Hydrometallurgy of China 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.)

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]

Jarosite is an essential solid industrial waste material which is generated during the hydrometallurgical processing of zinc in smelters. Besides zinc and iron, Jarosite also contains toxic heavy metals like Pb, Cd, Al, Cr, Cu etc. due to which it is environmentally hazardous. Due to the presence of heavy metals, the useful Zn, Fe components cannot be utilized safely. Therefore, it is necessary to remove Pb(II), a major toxic element, to make it useful. In this report, a green process for immobilization of Pb(II) using phosphate materials (physiochemical adsorption) is discussed. Jarosite was used as a precursor for synthesis of the Zn−Fe binary nano‐composite. Mitigation of Pb(II) by this process was assessed by the batch experiments, which showed significant reduction in leaching of Pb(II). The mechanism of Pb(II) immobilization involve the dissolution of phosphate materials (KH2PO4, NH4H2PO4 and CaH2PO4) to a lower pH≤3 followed by precipitation of Pb(II) in the form of pyromorphite complex. The results indicated that the concentration of Pb(II) was reduced by 90–95 % which was pH dependent with a high uptake (325 ppm) of lead ion in the pH range of 5.5–6.0. This physicochemical process brings new perspectives for reuse of a polluting solid industrial waste. [ABSTRACT FROM AUTHOR]

The objective of this review is to critically evaluate important aspects of aluminium dross generation, classification, properties, applications, and its commercial recycling techniques. A by-product of aluminium industry, aluminium dross is recycled by pyrometallurgy, hydrometallurgy, and hydrothermal processes, leading to aluminium recovery and generation of valuable products. The dominance of pyrometallurgy on the industrial scale is evident, owing to the efficient metal recovery processes, namely, Rotary salt furnace (RSF) and salt-free technologies (SFT). On the laboratory research front, hydrometallurgy and hydrothermal processes emerge as promising routes of dross recycling. Production of zeolites, ion exchangers, molecular sieves, and layered double hydroxides is achieved by hydrothermal route and important aluminium-rich products, along with gases like H 2 , CH 4 , and NH 3 are produced by hydrometallurgical route. The advantages and disadvantages of each route govern the applicability of these processes. With a plethora of modern technologies emphasising on the recycling of aluminium dross, a detailed investigation of each route is vital. The recycling of dross also contributes to the judicious preservation of natural resources consumed during aluminium production. In addition, the adverse effects of improper dross disposal on human health and the environment have been discussed. Recovery of Al dross and its material cycle. [Display omitted] [ABSTRACT FROM AUTHOR]

Manganese plays a central role in lithium-ion batteries (LIBs) but its recycling is rarely addressed when compared to other valuable metals present in LIBs, such as Co and Ni. Thus, the main goal of this work was to study and achieve the separation of Mn from Co and Ni by solvent extraction from a leachate obtained from LIBs using hydrochloric acid in an upscaled reactor, which is an innovative aspect of this work. The results confirmed the high selectivity of D2EHPA towards Mn, which could be completely extracted in two stages (0.5 M D2EHPA at pH 2.5). The main co-extracted metals were Al, Cu and Co, but with lower concentrations than Mn. The behavior of minor impurities such as Zn and Mg was also monitored. Scrubbing using manganese chloride was crucial to remove impurities from the loaded organic and prevent their presence in the stripping product, and high O:A ratios negatively affected the scrubbing efficiency. Keeping the concentration of HCl up to 0.5 M in the stripping stage helped to limit the stripping of impurities. Manganese oxide was precipitated as a product with 99.5% purity (with traces of Zn, Cu and Co), which could be reused in the battery value chain. [ABSTRACT FROM AUTHOR]

The reaction mechanism of gold cyanide leaching process is complex, and there are many factors affecting leaching process. These will lead to some errors between process model and actual process. Therefore, the operation setting point acquired through model-based optimization is not the actual optimal one. As a result, it is difficult for the process to operate under the minimum material consumption required by the hydrometallurgy process. Therefore, a data-based compensation method for optimal operation setting of gold cyanide leaching process is proposed. Firstly, the optimal operation setting point is obtained through model-based optimization. Then, near the setting point, using the idea of Just-In-Time Learning (JITL), the model is established to describe the relationship between setting point deviation and material consumption reduction. On the basis of this model, the deviation of the setting point from the actual optimal one can be obtained by optimization. Furthermore, through iterative compensation, the setting point gradually converges to the actual optimal one, and the material consumption is further reduced. Finally, the gold cyanide leaching process in a smelter is taken as study object, the results prove this method is effective. [ABSTRACT FROM AUTHOR]

Recycling lithium-ion batteries (LIBs) is becoming an imperative task given the large flow of spent batteries that in the next future will have to be managed. Among the current three main recycling routes to convert spent LIBs into recycled products, that is, pyrometallurgy, hydrometallurgy, or direct recycling, the co-precipitation route lies between the last two routes: its key unit operations are the leaching of battery materials and the co- precipitation of a precursor for the re-synthesis of the cathode active material (CAM). High susceptibility to impurities in the leached solution and a strong link between high-quality CAM precursors and the composition of the dissolved metal salts, makes experimental analysis on spent LIBs a crucial step to find the best operating conditions. For this reason, we present an experimental campaign to study the co-precipitation and formation of the complex chemical compounds involved in the process. Moreover, we also exploit the support that rigorous models are giving in many industrial fields, also benefiting chemical engineering and laboratory analysis. Therefore, in this study we also present a rigorous simulation model on UniSim Design® with the thermodynamic package OLI® that enables the possibility to consider most of the different liquid-solid equilibria needed. A validation of the model is performed with experimental data and a sensitivity analysis on metal concentrations, pH, and chelating agent is performed to find the critical parameters that regulate the co-precipitation outcomes. The aim is to optimize the choice of operating conditions to limit the number of laboratory tests and complex analyses that are often expensive and time-consuming. [ABSTRACT FROM AUTHOR]

Due to the accumulation of waste mobile devices, the increasing production of electric vehicles, and the development of stationary energy storage systems, the recycling of end-of-life Li-ion batteries (EOL LIBs) has recently become an intensively emerging research field. The increasing number of LIBs produced accelerates the resources' depletion and provokes pollution. To prevent this, the global communities are concerned with expanding and improving the LIBs recycling industry, whose biggest problems are either large gaseous emissions and energy consumption or toxic reagents and low recycling yields. These issues are most likely solvable by upgrading or changing the core recycling technology, introducing effective benign chemicals, and reducing cathode losses. In this review, we analyze and discuss various LIB recycling approaches, emphasizing cathode processing. After a brief introduction (LIB's design, environmental impact, commercialized processes), we discuss the technological aspects of LIB's pretreatment, sorting and dissolving of the cathode, separation of leached elements, and obtaining high-purity materials. Covering the whole LIB recycling line, we analyze the proven and emerging approaches and compare pyrometallurgy, hydrometallurgy, and cathode's direct restoration methods. We believe that the comprehensive insight into the LIB recycling technologies made here will accelerate their further development and implementation in the large-scale battery industry. [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]

The exponential growth of electric and hybrid vehicles in the last five years forecasts a waste problem when their batteries achieve end-of-life. Li-ion batteries for vehicles have been assembled using materials from natural resources (as Li, Fe, Al, Cu Co, Mn and P). Among them, LiFePO4 cathode materials have demonstrated advantages such as charge–discharge cycles, thermal stability, surface area and raw materials availability (against Ni and Co systems). Due to the performance, LFP batteries stand out in heavy duty fleet, achieving 90% of new energy buses in China. To achieve the circular economy, the recycling of LFP batteries may be carried out by pyrometallurgy (thermal processing), hydrometallurgy (aqueous processing) or both in combination. Comparatively, hydrometallurgical processing is more advantageous due to its low energy consumption and CO2 emissions. In addition, Li may be recovered in a high-pure grade. This work is a literature review of the current alternatives for the recycling of LFP batteries by hydrometallurgy, comparing designed processes in the literature and indicating solutions towards a circular economy. The major recycling steps of hydrometallurgy routes such as pre-treatments, leaching and purification steps will be gathered and discussed in terms of efficiency and environmental impact. [ABSTRACT FROM AUTHOR]

An innovative cryo-mechano-hydrometallurgical process (named LIBAT) was demonstrated at pilot scale for the treatment of EOL lithium primary batteries with chemistry Li(0)-MnO2. The process allowed the recycling of steel scraps from external cases after cryomechanical dismantling, and the recovery of Mn and Li products after hydrometallurgical processing. During demonstration activities, about nine tons of batteries were treated in the cryomechanical section, and one ton of black mass was treated in the hydrometallurgical section for the recovery of Mn hydroxides and Li2CO3. The environmental impacts of the process were evaluated in comparison with an innovative pyrometallurgical approach allowing Li recovery, confirming the benefits of the proposed process due to a reduction in energy consumption. Process simulations were performed considering different mixture feeds (only Li primary, or mixture with Li-ion batteries) and process options (only the cryomechanical section of the integral process) to assess the lower limits of potentiality that would ensure economic sustainability. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite the large reserves of titanium ores, their treatment by basic approaches to obtain titanium products is not always economically feasible due to various factors. One of these problems is the high content of silicon in the ores. RESULTS: The paper considers the desiliconization of a leucoxene concentrate with an aqueous solution of ammonium bifluoride. It was found that at 80 °C the main impurities, such as silicon and iron, pass into solution in the form of corresponding ammonium–fluorine complex compounds. CONCLUSIONS: The degree of desiliconization was up to 99%. Aluminium reacts with ammonium bifluoride, but is almost not leached into solution due to its low solubility. Titanium does not react due to its relatively higher reaction Gibbs energy among other metals in reaction with ammonium bifluoride. The content of titanium oxide in the calcined leaching residue was 85.52 wt%. The resulting residue corresponds to the raw material used in industry for the production of titanium dioxide pigment or titanium metal by the chlorine method. Iron and silicon can be precipitated from the leaching solution. Furthermore, the resulting filtrate can be evaporated in order to regenerate and reuse ammonium bifluoride. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Hydrometallurgy is considered a promising method to produce solar-grade silicon (SOG-Si) from metallurgical-grade silicon (MG-Si) due to its advantages of low cost, simple operation, and easy control. In this paper, the effects of particle size of MG-Si, type of acid, leaching time, temperature, and liquid-to-solid ratio on the purification efficiency were investigated in an external field environment with the addition of ultrasound. The purification efficiencies of the two acid-leaching methods were compared. It was found that the simultaneous use of HCl + HNO3 was more effective than using only HCl for impurity removal in MG-Si: the extraction efficiencies of impurities Fe and Al were increased by 2.2% and 13.4%, respectively. The impurity contents in MG-Si before and after calcination pretreatment were also compared. This paper is expected to help researchers select the appropriate hydrometallurgical technique to reduce the impurity content in MG-Si. [ABSTRACT FROM AUTHOR]

Printed circuit boards are considered a secondary source of raw materials, such as precious or base metals. One of the most promising solutions for recovering these metals is certainly hydrometallurgy. However, the leaching of different metals from PCBs is hindered by the presence of an organic fraction that lowers the extraction yields. One solution to this problem is a pyrolysis pre-treatment which removes the organic fraction and enhances it through conversion into syngas. A steady-state simulation model was developed using ASPEN PLUS to describe the thermodynamic behavior of PCB pyrolysis. The pyrolysis reactor was modeled as a combination of the Yields reactor and the Gibbs reactor. The model has been validated using various data present in the literature. The composition of the different products was estimated through the minimization of Gibbs's free energy. A sensitivity analysis was performed to investigate the influence of different parameters on the conversion yield and the syngas quality produced. Thanks to the study, it was possible to describe and analyze the pyrolysis of PCBs without requiring numerous experimental tests. The results show how steam gasification appears to be the most efficient technology for the pre-treatment of PCBs within a hydrometallurgical process. [ABSTRACT FROM AUTHOR]

Due to the fast material reaction in zinc hydrometallurgy, the traditional national standard photometric method cannot capture the characteristic information of target substances in real time. Herein, a nitrogen protection device is built based on ultraviolet spectrophotometry, supplemented by a programmable logic controller (PLC), to form an automatic control system for the direct detection of target substances (SO42−, Pb2+ and S2−) in zinc hydrometallurgy. The baseline straightness comparison results show that the nitrogen atmosphere can effectively improve the stability of the instrument. Furthermore, the detection sensitivity of SO42−, Pb2+ and S2− under the nitrogen atmosphere is higher than that of the air atmosphere, manifesting in sensitivity increases of 16.23%, 18.05% and 17.91%, respectively. Additionally, devices based on PLC systems show advantages over manual control both in states feedback and information backtrack. Moreover, the regulation time and nitrogen consumption during the regulation process are reduced by 80% and 75%, respectively, which effectively reduces the test cost and improves the equipment utilization rate (from four cycles per day to six cycles per day). The device can meet the requirements of different target substances and different process conditions by changing the electronic control parts and air source, so it has great application potential in the automatic direct measurement of target substances in zinc hydrometallurgy. [ABSTRACT FROM AUTHOR]

The extraction of useful minerals or geological materials from the Earth's crust, most typically from various sources, is crucial to a country's development and progress. Mineral-rich countries use these resources to transform their economies and propel them toward long-term prosperity. There is an urgent need for the world to increase mineral exploration efforts, improve the recycling of important metal-containing resources, and extract them using upgraded hydrometallurgical procedures with high recovery efficiency. This review paper highlights the importance of strategic and critical metals in the economy and the role of nuclear techniques in the analysis, process optimization, and remediation of metals using solvent extraction, adsorption, and chromatographic resins. Radiotracer analysis, X-Ray Fluorescence spectrometry (XRF), Neutron Activation Analysis (NAA), and X-Ray Diffraction (XRD) are appropriate for improving laboratory-based hydrometallurgical processes, with future technical and economic benefits. The development and installation of novel instruments to provide the real-time control of mining and mineral processing plants for improved control have the potential to aid in the recovery of a broad range of metals. [ABSTRACT FROM AUTHOR]