Recycling Of Valuable Metals Research Articles

Recycling of valuable metals from spent lithium-ion batteries

فرآیند بازیابی فلزات از باتری‌های لیتیم – یون مصرف‌شده به دلیل پیچیدگی اجزای فلزات تشکیل‌دهنده آن دشوار است، بنابراین جداسازی و بازیابی یون‌های فلزی از محلول لیچینگ باتری‌های لیتیم – یون مصرف‌شده نیازمند بهره‌گیری از مجموعه‌ای از فرآیندهای هیدرومتالورژیکی است. در این تحقیق از فرآیندهای ترسیب و استخراج حلالی جهت بازیابی نهایی فلزات از محلول لیچینگ استفاده‌شده است. برای این منظور مقدمتا با به‌کارگیری پتاسیم پرمنگنات با نسبت مولی یون‌های منگنز به پتاسیم پرمنگنات:2 و 2:pH حدود 5/96% از یون‌های منگنز به فرم اکسیدی ترسیب و از محلول لیچینگ جداسازی شد. سپس در 5:pH با استفاده از دی متیل گلی‌اکسیم و نسبت مولی یون‌های نیکل به دی متیل گلی‌اکسیم: 5/0، نسبت به بازیابی تقریبا 96% نیکل اقدام گردید. متعاقبا با استفاده از غلظت 30 درصد حجمی D2EHPA به‌عنوان استخراج‌گر و غلظت 5 درصد حجمی TBP به‌عنوان تنظیم‌کننده فاز آلی و با عنایت به اثر سینرجیسم آن‌ها، تحت شرایط بهینه شامل سرعت هم‌زنی 400 دور بر دقیقه، مدت‌زمان 20 دقیقه، دما 25 درجه سانتی‌گراد، نسبت فاز آلی به فاز آبی 1 و 5:pH می‌توان به بازدهی استخراج 38/93% کبالت دست‌یافت و هم‌چنین میزان هدر رفت لیتیم را در مقدار 74/16% کنترل کرد. درنهایت، در نسبت مولی یون‌های لیتیم به سدیم کربنات:7/0 تحت شرایط دمای 100 درجه سانتی‌گراد، مدت‌زمان 40 دقیقه، سرعت همزنی 400 دور در دقیقه و 12:pH، نرخ ترسیب 84/98‌% لیتیم حاصل گردید.

One-step recovery of valuable metals from spent Lithium-ion batteries and synthesis of persulfate through paired electrolysis

• The paired electrolysis reduces energy consumption in the recycling of spent LIBs. • Synchronously recovering Co 2+ as cobalt metal and synthesizing persulfate. • Simultaneous desalting in the recycling process of spent LIBs. The application of electrochemical methods on the recycling of valuable metals from spent lithium-ion batteries, and the removing of pollutant from wastewater by persulfate have attracted widespread attention in recent years. However, high energy consumption resulting from side electrochemical reactions constrains its application. Herein, a paired electrolysis method was designed to achieve the recycling of valuable metals from the spent LIBs and the synthesis of persulfate synchronically. In the process, high purity cobalt metal (>99.9%) was obtained from the leachate (catholyte) of the spent LIBs, and valuable persulfate were synchronically synthesized anolyte through a diaphragm electrolyzer. The prepared persulfate was directly thermally activated for pollutant degradation. Two important synthesis process are conducted in one step. About 30% energy consumption is reduced through paired electrolysis to produce valuable products of equal quality and the cathodic current efficiency is also enhanced about 4% compared with the single cobalt electrolysis system at same stage. Additionally, Li + is recycled as Li 2 CO 3 through precipitation from the electrolyte. As a green method, paired electrolysis will own a wide application prospects in the waste recycling and other hydrometallurgical fields because of low energy consumption and high valuable products.

Sustainable and high-efficiency recycling of valuable metals from oily honing ferroalloy scrap via de-oiling and smelting separation

Oily ferroalloy scraps generated from machinery honing enterprises are typical hazardous municipal materials that release benzene-series volatile organic compounds (VOC), which endanger human physical and mental health. Therefore, harmless treatment and resource reuse for these hazardous materials is urgent. In this study, the VOC emission, and pyrolysis and de-oiling behaviors of oily honing scrap was first characterized to evaluate the environmental risks. Smelting separation was then proposed to economically and eco-friendly recover valuable metals from the de-oiled ferroalloy scraps. The thermodynamics of Al2O3-SiO2 and CaO-Al2O3-SiO2 systems was calculated to optimize the slag formation. Results showed that after de-oiling and smelting with CaO addition, the hazardous VOC are removed, and the valuable metals are recovered in ferroalloy state. Under optimum conditions, a crude Fe-Mo-Cu alloy with Fe, Mo and Cu recoveries of 98.5 wt%, 97.9 wt%, and 98.4 wt% were obtained. In addition, the slag containing few toxic elements and VOC can be used for silicate cement production. Pyrolysis, de-oiling behaviors and mechanism for slagging and growth of Fe-Mo-Cu alloy during smelting were discussed via various testing techniques, and leaching toxicity of the cleaned slag was also characterized in this work. This process is also applicative to recover metals from various honing ferroalloy scraps.

Recovery and Recycling of Valuable Metals from Low-Grade Ores Using Microorganisms: A Brief Review

The demand for metals is ever increasing with the advancement of the industrialized world. But the global reserve high levels of ores are adjacent to decline. However, there exists there is a vast reserve of metals inferior ore, and other subsidiary sources. Low category ores as well as metal recovery conventional strategies such as pyrometallurgy, hydrometallurgy, etc., require strong and asset inputs that are often environmentally friendly pollution. Accordingly, there is required for the utilization of more coherent technologies to the recuperation of metals. The utilization of microbes to recovery metal ions is considered a unique key optimistic and revolutionary field of environmental biotechnology. The components of this method are disintegrated in an aqueous solution, which provides them more effective in addition, treatment, and convalescence. Recycling giant metals is also very important to prevent pollution and to prevent wastage of sources. Biological means are also used to easily recycle metals from their secondary sources. In this research, various approaches using microbes to recover giant metals from primary (low-grade ore) and secondary (electronic wastes) sources are discussed. Future prospects of utilizing microbes are also granted here.

Removal of arsenic from “Dirty acid” wastewater via Waelz slag and the recovery of valuable metals

The use of Waelz slag produced during zinc (Zn) hydrometallurgical processes to treat “dirty acid” wastewater was investigated in this study. As(III) in the wastewater was oxidized by performing a pre-oxidation process, after which oxidation leaching, Fe-As co-precipitation, Cu-As cementation, neutralization-hydrolysis, and hematite precipitation processes were performed. The initial As concentration was 8.56 g/L, and the treatment processes decreased the concentration to 0.5 mg/L, which meets the integrated wastewater discharge standard stipulated by the Ministry of Ecology and Environment, P.R China. Most of the As was removed during the Fe-As co-precipitation process as crystalline scorodite at atmospheric pressure, and most of the copper in the Waelz slag was removed during the Cu-As cementation process as Cu3As and Cu2O, which could be used to remove Co from the zinc sulfate (ZnSO4) leaching solution used during Zn hydrometallurgical processes. Fe was precipitated as hematite, which could be used as a raw material to make iron at high temperatures and pressures. The proposed treatment process can effectively remove As from “dirty acid: wastewater and allow the recycling of valuable metals in Waelz slag. The treatment process is therefore efficient and inexpensive, and offers promise for industrial use.

Efficient computation of the magnetic polarizabiltiy tensor spectral signature using proper orthogonal decomposition

AbstractThe identification of hidden conducting permeable objects from measurements of the perturbed magnetic field taken over a range of low frequencies is important in metal detection. Applications include identifying threat items in security screening at transport hubs, location of unexploded ordnance, and antipersonnel landmines in areas of former conflict, searching for items of archeological significance and recycling of valuable metals. The solution of the inverse problem, or more generally locating and classifying objects, has attracted considerable attention recently using polarizability tensors. The magnetic polarizability tensor (MPT) provides a characterization of a conducting permeable object using a small number of coefficients, has an explicit formula for the calculation of their coefficients, and a well understood frequency behavior, which we call its spectral signature. However, to compute such signatures, and build a library of them for object classification, requires the repeated solution of a transmission problem, which is typically accomplished approximately using a finite element discretization. To reduce the computational cost, we propose an efficient reduced order model (ROM) that further reduces the problem using a proper orthogonal decomposition for the rapid computation of MPT spectral signatures. Our ROM benefits from a posteriori error estimates of the accuracy of the predicted MPT coefficients with respect to those obtained with finite element solutions. These estimates can be computed cheaply during the online stage of the ROM allowing the ROM prediction to be certified. To further increase the efficiency of the computation of the MPT spectral signature, we provide scaling results, which enable an immediate calculation of the signature under changes in the object size or conductivity. We illustrate our approach by application to a range of homogenous and inhomogeneous conducting permeable objects.

Screening for Microbial Metal-Chelating Siderophores for the Removal of Metal Ions from Solutions.

To guarantee the supply of critical elements in the future, the development of new technologies is essential. Siderophores have high potential in the recovery and recycling of valuable metals due to their metal-chelating properties. Using the Chrome azurol S assay, 75 bacterial strains were screened to obtain a high-yield siderophore with the ability to complex valuable critical metal ions. The siderophore production of the four selected strains Nocardioides simplex 3E, Pseudomonas chlororaphis DSM 50083, Variovorax paradoxus EPS, and Rhodococcus erythropolis B7g was optimized, resulting in significantly increased siderophore production of N. simplex and R. erythropolis. Produced siderophore amounts and velocities were highly dependent on the carbon source. The genomes of N. simplex and P. chlororaphis were sequenced. Bioinformatical analyses revealed the occurrence of an achromobactin and a pyoverdine gene cluster in P. chlororaphis, a heterobactin and a requichelin gene cluster in R. erythropolis, and a desferrioxamine gene cluster in N. simplex. Finally, the results of the previous metal-binding screening were validated by a proof-of-concept development for the recovery of metal ions from aqueous solutions utilizing C18 columns functionalized with siderophores. We demonstrated the recovery of the critical metal ions V(III), Ga(III), and In(III) from mixed metal solutions with immobilized siderophores of N. simplex and R. erythropolis.

Engineering a tandem leaching system for the highly selective recycling of valuable metals from spent Li-ion batteries

In this work, formic acid and its derived DESs are employed to engineer a tandem leaching system for the selective recovery of Li and Co/Mn valuable metals from spent LIBs.

Application of various processes to recycle lithium-ion batteries (LIBs): A brief review

The growing concern for portable devices and electric vehicles has led to an enormous rise in the demand for lithium-ion batteries. After the end of life, these LIBs act both as a secondary source for the recovery of valuable metals and simultaneously possess a threat to the environment. So they need to be recycled properly to gain economic benefits. This article focuses on several methods used for the recycling of valuable metals. It describes the structures, components, and state-of-the-art on spent LIBs. This article has summarized different recycling methods, their physiochemistry, and their applications to regenerate valued metals like cobalt, nickel, lithium, etc. The advantages and the problems linked with these technologies have also been put forward.

Regulating and regenerating the valuable metals from the cathode materials in lithium-ion batteries by nickel-cobalt-manganese co-extraction

Effective recycling of valuable metals from the spent lithium-ion batteries (LIBs) is conducive to the rational utilization of resources and environmental protection. To shorten the recovery process and directly obtain the high-pure regenerated products, solvent extraction (co-extraction) method was employed in this work. Here, 3 mol/L (M) hydrochloride (HCl) without reductant was used as leaching agent for the leaching of cathode material, resulting in the leaching efficiency of all metals exceeding 99%. Subsequently, di-(2-ethylhexyl) phosphinic acid (P227) was used to co-extract transition metals directly from the leachate and separate them from lithium (Li). The composition of nickel (Ni), cobalt (Co), and manganese (Mn) extracted into the organic phase can be controlled by changing the extraction conditions, and the type of the cathode material was also regulated simultaneously. Finally, the loaded organic phase with a Ni-Co-Mn ratio of 1:1:1 was completely stripping with 0.4 M HCl, and the LiNi1/3Co1/3Mn1/3O2 was regenerated by oxalic acid co-precipitation the stripping solution and high temperature calcination. The regenerated LiNi1/3Co1/3Mn1/3O2 exhibits excellent electrochemical performance with 150.0 mA h g−1 discharge capacity at 0.5 C. Therefore, the demonstrated separation and preparation integration process not only realizes the regeneration of the battery but also promotes the co-extraction technique to practical application.

Selective extraction of valuable metals from spent EV power batteries using sulfation roasting and two stage leaching process

Selective extraction of valuable metals from spent electric vehicles (EVs) power batteries was undertaken by a sulfation roasting-water leaching-acidic leaching process. After sulfation roasting (acid-to-lithium molar ratio (nH2SO4:nLi) = 0.95, 550 °C and 3 h), the roasted products were subject to the 1st stage of water leaching. Under optimum conditions (30 °C, 2 h and liquid-to-solid (L/S) ratio of 4 mL/g), the extraction of Li and Mn reached 90% and 10%, whereas extractions of Co and Ni were negligible. The water leaching residues were then treated by the 2nd stage of acidic leaching (2 mol/L H2SO4 solution with L/S ratio of 5 mL/g at 60 °C for 2 h) which resulted in an additional 98% Ni, 97% Co and 90% Mn being leached from the residue. An investigation of the phase transformation mechanism indicated that the extraction behaviors of valuable metals might be induced by the different reduction pathways of the metals while controlling the roasting conditions. With roasting temperature <550 °C and roasting time <2 h, Li within the crystalline LiCoxNiyMn1-x-yO2 was de-intercalated and transformed to soluble Li2SO4, while Ni, Co and Mn in the LiCoxNiyMn1-x-yO2 decomposed to MnCo2O4 and Ni6MnO8 because of the co-existence of sulfuric acid and carbon reductant from the graphite anode material. When nH2SO4:nLi was higher than 1.2, Li was further converted to Li2Mn2(SO4)3. Under the conditions of roasting temperature > 550 °C and roasting time >2 h, MnCo2O4 and Ni6MnO8 were further reduced into low-valence states CoO and (NiO)0.75(MnO)0.25. These results provide a fundamental basis for the development of an efficient and selective extraction strategy for the recycling of valuable metals from spent EV power batteries.

Ultrasonic-assisted leaching of valuable metals from spent lithium-ion batteries using organic additives

Sustainable recycling of valuable metals from spent lithium-ion batteries (LIBs) has been derived by the growing environmental issues and nonferrous metal resources scarcity. In this study, mixed organic acids (acetic and ascorbic acid) and bagasse pith were innovatively used as leachants and reductant in ultrasonic-assisted leaching of valuable metals from waste cathode materials of spent lithium-ion batteries. Based on the leaching results, over 95% of all valuable metals (Li, Ni, Co and Mn) can be dissolved under optimal leaching conditions. And leaching reactions of different metals fit well with Avrami equation with apparent energy of 40.6 kJ/mol, 42.2 kJ/mol, 42.8 kJ/mol and 43.8 kJ/mol for Li, Ni, Co and Mn, respectively, suggesting that the leaching of these metals was controlled by chemical reaction. Detailed analysis of leaching reaction mechanism indicates that the synergy of mixed acids can significantly reduce acid dosage, and bagasse pith can be hydrolyzed to reducing sugars and other soluble reductants that can be used as reductants to facilitate the leaching process in return. Ultrasonic can also promote the leaching of valuable metals. The current study can be a sustainable alternative for the efficient recycling of valuable metals from spent LIBs, featured with reduced acid consumption, mild leaching conditions and less environmental footprint.

Improved hydrometallurgical extraction of valuable metals from spent lithium-ion batteries via a closed-loop process

The increasing market size of high-energy storage systems due to the booming of not only portable electronic devices but also electrical vehicles and renewable energy sources has promoted battery technologies, resulting in many spent lithium-ion batteries (LIBs). This study focuses on proposing a closed-loop process to recycle the full valuable metals from spent LiNi1/3Co1/3Mn1/3O2 material. Reduction roasting and hydrometallurgy were combined and used for de-agglomeration of cathode composites and enhanced recycling of valuable metals. Experimental results showed the cathode material was reduced to Ni, Co, Li2CO3, and MnO under microwave carbothermic reduction, and lithium carbonate was directly recovered after dissolved in water with a high yield of 99%. Afterward, transition metals (Ni, Co, Mn) enriched residues can be dissolved in fumaric acid with leaching efficiencies of more than 96% under optimized leaching conditions, and finally recovered as single compounds by step-wise addition of chemicals. The mechanism of the nonthermal effect of microwave on the leaching of metals was analyzed by kinetic studies, and the decreased Ea values for metals demonstrate that microwave treatment is beneficial for metals leaching through decreasing their apparent energies. Besides, the characterization results of X-ray diffraction and scanning electron microscope indicate the destruction of the layered crystal structure and an increased liberation degree after microwave treatment, which is also beneficial for the enhancement of metals leaching. Therefore, the microwave reductive-assisted process is found in a green and effective industrial process to recycle valuable metals from spent LIBs.

Stepwise recycling of valuable metals from Ni-rich cathode material of spent lithium-ion batteries

A novel and efficient approach for stepwise recycling of valuable metals from Ni-rich cathode material is developed. First, the spent cathode materials are leached by H2SO4 + H2O2 solution. The leaching efficiencies of lithium, nickel, manganese and cobalt reach almost 100%, 100%, 94% and 100%, respectively, under the conditions of 2 M sulfuric acid, 0.97 M hydrogen peroxide, 10 ml·g−1 liquid-solid ratio, 30 min and 80 °C. Then, manganese and cobalt are co-extracted from the leaching liquor with PC88A, while almost 99% nickel and 100% lithium remain in the raffinate followed by being separated from each other by solvent extraction with neodecanoic acid (Versatic 10). The results show that 98% manganese and over 90% cobalt are co-extracted at pH = 5, 30 vol% PC88A and volume ratio of oil to water (O:A) = 2:1, while 100% nickel is separated from lithium under the optimum extraction conditions of initial pH = 4, O:A = 1:3 and 30 vol% Versatic 10. Finally, cobalt and manganese in the strip liquor of co-extraction are separated by selective precipitation method. Over 90% manganese is separated from cobalt under the conditions of pH = 0.5, 0.076 M KMnO4, 80 °C and 60 min.

Selective recovery of valuable metals from industrial waste lithium-ion batteries using citric acid under reductive conditions: Leaching optimization and kinetic analysis

Recycling of valuable metals from waste lithium-ion batteries (LIBs) has recently attracted significant attention due to the environmental and economical concerns. In this paper, a simple and economical leaching process based on citric acid system was developed for the leaching of metals from the industrial waste LIBs without the manual separation of current collectors, i.e. copper and aluminum foils. The results showed significantly higher leaching efficiencies of metals due to the presence of copper and aluminum. About 91% Li, 90% Co, 94% Ni and 89% Mn were leached under the optimum leaching conditions of 0.5 mol/L citric acid, solid to liquid (S/L) ratio of 80 g/L at 90 °C for 80 min. Furthermore, the effects of the addition time and species of reductant on the leaching of Li, Co, Ni, and Mn were investigated, and the selectivity over Cu and Al as well. The kinetics data revealed that the leaching of Li, Co, Ni and Mn fitted best to the Avrami equation controlled by the surface chemical reaction, whilst the leaching of Cu and Al corresponded to the surface chemical-controlled reaction based on shrinking core model. The leaching feed before and after leaching were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

A Citric Acid/Na2S2O3 System for the Efficient Leaching of Valuable Metals from Spent Lithium-Ion Batteries

Recycling of valuable metals from spent lithium-ion batteries (LIBs) appears inevitable for both environmental protection and resource recovery. In the present study, an efficient hydrometallurgical leaching of Co and Li from cathode materials of spent LIBs using a citric acid/sodium thiosulfate (Na2S2O3) system is explored. The effects of citric acid and Na2S2O3 concentrations, leaching time, temperature, and the solid/liquid (S/L) ratio on the leaching processes are also examined. With the exception of the S/L ratio, the increase of citric acid concentration, Na2S2O3 concentration, leaching time, and temperature all have positive effects on the leaching of Co and Li. Ultimately, approximately 96% of Co and 99% of Li are recycled from the spent LIBs in this citric acid/sodium thiosulfate system under the leaching conditions of an S/L ratio of 20 g l−1, concentration of Na2S2O3 of 0.3 M, concentration of citric acid of 1.2 M, leaching time of 30 min, and leaching temperature of 70°C. The Avrami equation is well fitted by the data of the leaching processes, and model equations are built to describe the leaching of Co and Li. Furthermore, pure sulfur can be obtained as a by-product during the leaching process, and SO2 produced during the reaction is easily collected as a raw material for industrial production of sulfuric acid. The present study represents a promising process for hydrometallurgical recovery of valuable metals from spent LIBs.

Novel extraction of valuable metals from circulating fluidized bed-derived high-alumina fly ash by acid–alkali–based alternate method

The recycling of valuable metals from circulating fluidized bed (CFB)-derived high-alumina fly ash (HAFA) paves the way for ash utilization with high economic benefits. However, obtaining an ideal extraction ratio for metals using a single acid treatment under moderate conditions is difficult. A moderate acid–alkali–based alternate method was used in this study to extract aluminum (Al) from CFB-derived HAFA. The dissolution behavior of lithium (Li), gallium (Ga), and rare earth elements (REY) was investigated. The characteristics of leaching residues were studied by XRD, 27Al and 29Si MAS NMR, BET, and SEM-EDS. Results show that Al in the units with low degree of polymerization distributed on the particle surface was preferentially dissolved in the HCl solution. HCl could not penetrate the particle interior and thus greatly limited the improvement of the Al extraction ratio. NaOH solution effectively removed SiO2 that accumulated on the particle surface and broke the Si–O–Al units in the residues. The exposed and liberated Al was further extracted with the HCl solution. Finally, 78% of Al2O3, 80% of Li, 72% of Ga, and 55% of REY in the ash were extracted with the HCl solution. Moreover, 63% of SiO2 in the ash was dissolved in the NaOH solution. The acid leaching residue presented abundant mesopores and a high specific surface area of 205 m2/g. The findings imply that the proposed method that combines the extraction of valuable metals and the preparation of mesoporous materials provides a new way to utilize CFB-derived HAFA.

Partition studies on cobalt and recycling of valuable metals from waste Li-ion batteries via solvent extraction and chemical precipitation

Present work addresses Co(II) extraction from chloride medium using toluene diluted Cyphos IL 102 as an innovative extractant for the recovery of cobalt. Effect of various parameters has been examined. Co(II) is transferred into the organic phase as [P66614+]2[CoCl42−] which can be efficiently stripped by 0.05 mol L−1 HCl. Loading capacity and recyclability have been assessed. Temperature effect confirmed that the extraction of Co(II) is endothermic in nature. Studies were further extended to recover cobalt, manganese and lithium from waste Li-ion batteries containing 2.915 g L−1, 0.576 g L−1, 3.370 g L−1, 0.407 g L−1, 0.014 g L−1, 0.033 g L−1, 0.019 g L−1 of cobalt, lithium, manganese, nickel, aluminium, iron and copper, respectively. The influence of the concentration of Cyphos IL 102 to extract cobalt from leach liquor has been investigated. The McCabe-Thiele plot suggested two theoretical stages of counter current extraction at A/O 1/1 with Cyphos IL 102 (0.2 mol L−1) for the quantitative extraction of Co(II) with negligible extraction of nickel and lithium. A stripping efficiency of around 99.9% for Co(II) was obtained using 0.05 mol L−1 HCl in a single stage at O/A 1/1. Cobalt is recovered as cobalt oxide from the loaded organic phase. Manganese and lithium were also recovered from leach liquor as MnO2 and Li2CO3 using the precipitation method. All the recovered products were identified using XRD, EDX as well as FE-SEM techniques.

Enhancement in leaching process of lithium and cobalt from spent lithium-ion batteries using benzenesulfonic acid system

Recycling of valuable metals from spent lithium ion batteries (LIBs) is of great significance considering the conservation of metal resources and the alleviation of potential hazardous effects on environment. Thus, the present work focuses on enhancing the efficiency of leaching process for the recovery of cobalt and lithium from the cathode active materials of spent LIBs. In this study, benzenesulfonic acid (C6H5SO3H) with a reducing agent hydrogen peroxide (H2O2) was innovatively used as leaching reagents, and the operating variables were optimized to obtain higher leaching efficiencies. Results show the optimized leaching recovery of 99.58% Li and 96.53% Co was obtained under the conditions of 0.75 M benzenesulfonic acid, 3 vol% H2O2, a solid to liquid (S/L) ratio of 15 g/L, 500 rpm stirring speed, and 80 min leaching time at 90 °C. Moreover, a new kinetic model was introduced to describe the leaching kinetics of LiCoO2 from the cathode material. The apparent activation energies Ea for leaching of lithium and cobalt are 41.06 and 35.21 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. Further, the proposed recovery mechanism for spent cathode material was raised by analyzing the experimental results and characterizing the morphological and chemical state (i.e. SEM-EDS, XPS and XRD) of raw material and leaching residues. In comparison with the previous leaching process, this research was found to be efficient, low energy consumption, and environmental friendly.

Metal Recovery from Spent Samarium-Cobalt Magnets Using a Trichloride Ionic Liquid.

Recycling of samarium–cobalt (SmCo) magnets is essential due to the limited resources of the mentioned metals and their high economic importance. The ionic liquid (IL) trihexyltetradecylphosphonium trichloride, [P666,14][Cl3], which can safely store chlorine gas in the form of the trichloride anion, was used as an oxidizing solvent for the recovery of metals from spent SmCo magnets. The dissolution was studied considering various mixtures of the ILs [P666,14][Cl3] and [P666,14]Cl, solid-to-liquid ratios and different temperatures. The results showed that the maximum capacity of [P666,14][Cl3] for SmCo magnets was 71 ± 1 mg/g of [P666,14][Cl3], in the presence of an extra source of coordinating chloride ions. The maximum loading of the IL could be reached within 3 h at 50 °C. Four stripping steps effectively removed all metals from the loaded IL, where sodium chloride solution (3 mol L–1), twice water and ammonia solution (3 mol L–1) were used consecutively as the stripping solvents. The regenerated IL showed a similar dissolution performance as fresh IL. Oxidative dissolution of metals in trichloride ILs is easily transferable to the recycling of valuable metals from other end-of-life products such as neodymium–iron–boron magnets and nickel metal hydride batteries.