Leaching Method Research Articles

Surface oxidation using chlorine dioxide for cuprite and its oxidation leaching mechanism in sulfuric acid solution

Cuprite (Cu2O) is difficult to directly leach in acidic solutions. In the absence of oxygen, the acidic leaching process of cuprite occurs via a disproportionation reaction and can achieve a maximum cuprite leaching rate of only 50%. Furthermore, to improve the copper leaching rate, Cu(Ι) in cuprite must be oxidized via electrochemical reactions. In this study, chlorine dioxide (ClO2), a novel environmentally-friendly oxidant, was used to oxidize cuprite to enhance the leaching effect in sulfuric acid (H2SO4)solution. Leaching experiments, electrochemical measurements, atomic force microscopy (AFM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to analyze the oxidation leaching mechanism of cuprite under different reaction conditions. Under the condition of a leaching temperature of 50 °C, sulfuric acid concentration of 0.14 mol/L, average particle size of 60 μm, stirring speed of 800 rpm, and leaching time of 30 min, the leaching rate of cuprite reached 90.18% after adding 0.07 mol/L of ClO2. Electrochemical measurements demonstrated that a higher ClO2 concentration increased the corrosion rate of cuprite and oxidation efficiency. Moreover, the surface characterization results showed that with the addition of ClO2, monovalent copper on the cuprite surface was oxidized to divalent copper, which promoted the acidic leaching process of cuprite. In addition, once the cuprite surface was oxidized during oxidation leaching, sulfuric acid leached this layer until the end of the leaching process. The DFT calculation results further proved that with the participation of ClO2, the leaching reaction of cuprite in an acidic solution was more likely to occur. This oxidation leaching method might provide a reference for the effective leaching of cuprite.

Zn Extraction from Zinc-Containing Sludge Using Ultrasonic Treatment Leaching with ChCl-MA DES

The recovery of zinc from metallurgical dust sludge is a crucial component of using solid waste as a resource in the metallurgical process, and deep eutectic solvent–ultrasonic synergistic enhanced leaching is an efficient method of doing so with excellent economic effects. The leaching rate of zinc is used as the value of response in this study, along with the four process conditions of leaching temperature, leaching time, liquid–solid ratio, and ultrasonic power. By building a regression model, the relationship between the various parameter components is investigated, and a strategy for optimization is then chosen and confirmed. The findings indicate that, for the parameters of temperature 40 °C, ultrasonic power 90 W, liquid–solid ratio 7:1 g/L, stirring speed 250 rpm, and leaching duration 80 min, the prediction value of the regression model of the zinc leaching rate is 98.47%. The average zinc leaching rate obtained by the 3 parallel verification experiments was 98.49%; the deviation from the regression model’s predicted value was 0.02%. This demonstrated that the experimental results were consistent with those predicted by the regression model, the experimental results were reliable and trustworthy, and the optimization scheme was reasonable and accurate. Compared with the conventional leaching method (leaching rate: 91.61%), the method under ultrasound increased the zinc leaching rate by 6.88%.

Treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching

This research investigates the extraction of copper from copper-containing leaching residue, which includes 33.45% of copper, 14.14% of iron, 23.87% of sulfur and trace amounts of silver and other elements. Roasting the copper-containing residue under air and oxygen flow convert sulfides into sulfate, followed by water and acid leaching to extract copper. The process parameters, including leaching temperature, sulfuric acid concentration, leaching time, solid-to liquid ratio, and agitation speed, were optimized for both water and acid leaching methods. Results showed that the maximum copper dissolution efficiency was 93.12% with water leaching, and 97.16% with acid leaching. Chemical analysis revealed that the water and acid leaching residue contained 48.13% and 31.64% of iron, respectively. This study provides valuable insights into the process optimization for copper extraction from copper-containing leaching residue, which can inform the development of more efficient and sustainable methods for metal recovery.

Effect of nano silica on solidification/stabilization of heavy metal in alkali-activated MSWI fly ash solidified body

Municipal solid waste incineration fly ash (MSWIFA) containing considerable heavy metals is classified as a hazardous waste. Alkali-activated technology can effectively improve the environmental safety of MSWIFA. Due to the low silica content of MSWIFA, the addition of nano silica (NS) solves the problem to enhance the ability of solidification/stabilization (S/S) and maximize the utilization of MSWIFA. NS/MSWIFA solidified body was prepared by alkali-activated technology in this work. The mechanical and environmental properties of NS/MSWIFA solidified body with various dosages (0–3 wt%). NS were characterized by compressive strength, leaching concentration, and chemical speciation distribution of heavy metals. A comparative study of MSWIFA and solidified bodies for exploring S/S mechanisms was investigated using XRD, FTIR, TG/DTG, NMR, and SEM/EDS tests. The results showed that the leaching concentration of Pb in MSWIFA based on different leaching methods was 23.54 mg/L and 31.7 mg/L, 19.6 times higher than the standard of hazardous waste landfill and 126.8 times higher than the standard of landfill site of municipal solid waste, respectively. The total amount of Zn and Pb was 4739 mg/kg and 2451 mg/kg, respectively, exceeding other heavy metals by 1–2 orders of magnitude. When the addition of NS was 2 wt% and 3 wt%, the compressive strength and the leaching concentration of heavy metals in solidified bodies reached the highest and the lowest, respectively. Comparative analysis indicated that adding NS promoted heavy metals in MSWIFA to be converted into a stable state, and increased hydration product C-(A)-S-H gels formation, making the structure denser. On a broader perspective, NS/MSWIFA solidified body was developed as a low-carbon and environment-friendly binder.

Solvent casting‐particulate leaching synthesis of a nano‐SiO2/chitosan composite scaffold for potential use in bone tissue engineering

AbstractIn this work, a three‐dimensional (3D) scaffold comprised of chitosan and SiO2 nanoparticles (NPs) (CS/SiO2) was synthesized for bone tissue engineering. The scaffold was synthesized using a combination of solvent casting and salt leaching methods. The nanoparticle sizes were controlled by hydrothermal treatment with the aid of cetyltrimethylammonium bromide (CTAB), which was then used as a bio‐inorganic component of the composite scaffold. Various methods, such as SEM, FTIR, XRD, and liquid substitution, were conducted to determine the morphology, structure, pore sizes, and porosity of the synthesized scaffolds and the interaction between the SiO2 and CS phases. The mechanical properties of the composite scaffolds were evaluated by testing their tensile strength. The results showed that the synthesized 3D CS/SiO2 scaffolds exhibited porous structures with suitable average pore sizes ranging from 198 to 269 μm and porosities from 70.99 to 73.23%, respectively. The tensile strengths of the CS/SiO2 scaffolds were around 1.57‐1.83 MPa, matching well with those of cancellous bone. These appropriate values in terms of pore size, porosity, and tensile strength suggest that CS/SiO2 scaffolds could support cell migration, growth, and distribution. The synthesized CS/SiO2 scaffolds would be potential biomaterials for bone tissue engineering applications.

Improved Palladium Extraction from Spent Catalyst Using Ultrasound-Assisted Leaching and Sulfuric Acid–Sodium Chloride System

This paper presents a process for efficiently recovering palladium (Pd) from spent Pd/Al2O3 catalysts used for hydrogenation reactions, using ultrasound-assisted leaching (UAL). A system composed of H2SO4 and NaCl was investigated under ultrasound-enhanced conditions and compared to regular leaching methods to demonstrate the superiority of UAL. Single-factor experiments were conducted to determine the optimal conditions for leaching, which included an ultrasound power of 200 W, a liquid–solid ratio of 5:1, a leaching time of 1 h, a leaching temperature of 60 °C, H2SO4 concentration of 60%, and 0.1 mol of NaCl. The leaching rate under these conditions was found to be 99%. Additionally, kinetic analysis of the UAL process showed that the apparent activation energy of the Pd leaching reaction was 28.7 kJ/mol, and it was found that Pd leaching from spent catalysts was controlled by diffusion. The tailings were analyzed by SEM, revealing that during ultrasonic leaching, the specific surface area of the spent catalyst increased, the mass transfer rate of the solution was accelerated, the passivation film on the surface of the spent catalyst was peeled off, and a new reaction interface was formed. This improved the leaching rate of Pd and provided a new approach to efficiently leach precious metals such as Pd from spent catalysts.

Preparation of dual-use GPTES@ZnO photocatalyst from waste warm filter cake and evaluation of its synergic photocatalytic degradation for air-water purification

Organic pollutants are the most critical threats to the health of air and water resources. On this basis, fabricating a photocatalytic acrylic film with dual-use (i.e. removing benzene from air and MB/MO dyes from water) was aimed in this research. For this purpose, waste warm filter cake (WWFC) was used to extract zinc from it. Zinc element was separated from WWFC by a basic leaching method and acidified to prepare zinc oxide nanoparticles. In the following, a simple hydrothermal method was used to increase the surface functionality of the extracted ZnO nanoparticles in order to establish active reaction sites for reaction to silane coupling agent and increase in the holes that were prepared during photo-excitation. Thereafter, the nanoparticles were modified with 3-glycidoxypropyltriethoxysilane (GPTES) at different concentrations. The band gap of the modified nanoparticles decreased from 3.25 to 3.1 eV by surface modification. The photocatalytic performance of ZnO nanoparticles was assessed by degradation of MB and MO aqueous solution (50 ppm) under simulated UV/Visible irradiations. MB and MO were degraded 91 and 60% under UV light and 65 and 50% under visible light after 150 min of irradiation. The photo degradation rate increased after adding carboxy methyl cellulose (CMC) surfactant to methylene blue and adding cocamide-dea (CDE-G) surfactant to methyl orange. The results confirmed that the green surfactants improve the dispersion and surface interaction of the modified nanoparticles in the dyes solution and cause more electron charge transfer which creates effective photocatalytic sites. The prepared nanocomposite films were placed in a photo-reactor to remove gaseous benzene from air under UV/visible irradiation. Gas chromatography (GC) results showed that the modified nanoparticles removed up to 35.25 and 20.34% of benzene from air. Colorimetric analysis (ΔE*) showed that the acrylic film contained modified nanoparticles degraded 91 and 82% of MB, and 85 and 76% of MO under UV/visible lights, respectively. In the end, it can be said that these photocatalytic films are able to remove environmental pollution in air and water.

Process optimization and mechanism of high-efficiency germanium extracting from zinc oxide dust containing germanium enhanced by ultrasound

Aiming at the problem of low extraction efficiency of germanium in zinc oxide dust, a process of strengthening germanium leaching by ultrasonic wave in sulfuric acid leaching process was proposed. The effects of acidity, temperature, time, liquid-solid ratio, ultrasonic power and amount of iron powder on germanium leaching were investigated by response surface method, and the ultrasonic enhanced leaching process was optimized. Based on process mineralogy analysis, and germanium phase distribution analysis, which is obtained by self-establishment step-by-step extract method, the studied zinc oxide dust contains 94.1% germanium oxide and germanate, 5.13% germanium sulfide and 0.77% insoluble germanium. The results showed sulfuric acid concentration 131 g/L(1.34 mol/L), temperature 78 °C, time 22 min, liquid-solid ratio 7.6:1, ultrasonic power 270 W, iron powder content 0.71%. The leaching efficiency of germanium is 95.19%, which is 5.79% higher than that of conventional leaching method. It was found that ultrasound can destroy the particle size, reduce the cluster structure of leached products by 13.5%, inhibit the agglomeration of particles, and promote the leaching of germanate and germanium sulphide. This study is of great significance for the production of germanium.

RECOVERY OF MANGANESE FROM MANGANESE ORE REDUCTIVELY ACID LEACHING PROCESS USING REEDS (IMPERATA CYLINDRICA) AS REDUCING AGENT

Recovery of manganese from manganese ores was investigated by reductive leaching method using reeds as a reductant in the sulfuric acid medium. Cellulose, hemicellulose, and lignin are natural reducing agents which are widely used as reducing agents to recover manganese. Effects of calcination temperature and the holding time calcination on the leaching efficiency of manganese and impurities were examined. The calcination temperature and the holding time calcination have a significant effect on the extraction of manganese. The experimental results demonstrated that the higher the calcination temperature used, the higher the percentage of manganese obtained, namely 79.58% and 87.38%, respectively. The XRD (x-ray diffraction) pattern shows that the manganese phases formed at 700 and 800 °C are Mn3O4 (hausmannite) and Mn2O3 (bixbite), respectively. The morphology in the sample with calcination temperature at 700 °C showed agglomerate- shaped particles and unevenly dispersed. Meanwhile, the sample with calcination temperature at 800 °C exhibited agglomerated particles of inhomogeneous size and were more evenly distributed. Variation of holding time in the manganese ores recovery process also affects the results of manganese recovery. The composition of the manganese recovery in the samples using holding time calcination variations of 3 and 4 hours was 83.88% and 89.24%, respectively. The results of the XRD analysis showed that the manganese phase formed using 3 hours of calcination holding time was dominated by Mn3O4 (hausmannite). Meanwhile, the manganese phase formed using 4 hours of holding time of calcination was dominated by Mn2O3 (bixbite).

Recycling Strategy for Spent Lithium-Ion Batteries as an Ultra-efficiency Peroxymonosulfate Activator

In this study, a novel strategy was exploited to prepare an ultra-efficiency NiCoMn-layered double-hydroxide (NiCoMn-LDH) catalyst for the recycle of valuable elements in spent lithium-ion batteries. Based on the developed hydrometallurgical leaching method, avoiding the drawback of separation and purification procedures, it was stated that the elements of Ni, Co, and Mn could be synchronously extracted from the spent cathode powder in less than 20 min with leaching efficiencies exceeding 98.9%. NiCoMn-LDH with a uniform flake structure was synthesized successfully from the leaching solution by a co-precipitation method and the element precipitation efficiencies all exceeded 99% in the preparation process. NiCoMn-LDH exhibited a great tetrabromobisphenol S (TBBPS) degradation performance as a peroxymonosulfate (PMS) activator, TBBPS could be degraded completely in less than 100 s with an extremely low dosage (catalyst 10 mg/L and PMS 0.1 mmol/L, pH 5.6), and NiCoMn-LDH still kept a good stability after multiple reuse. Besides, ECOSAR predicted the toxicity of degradation products declined with the decrease of bromine substituents, reflecting the environmental friendliness of NiCoMn-LDH from spent lithium-ion batteries.

Eco-friendly strategy for advanced recycling waste copper from spent lithium-ion batteries: Preparation of micro-nano copper powder

Massive spent lithium-ion batteries (LIBs) were emerged worldwide as a consequence of the extensive use in energy storage applications. The recovery of cathode electrode materials from spent LIBs has received great attention due to economic benefits, which has led to the neglect of the deep utilization of low-value copper current. The present study focuses on the selective crushing of copper foil and the preparation of micro-nano copper powders through eco-friendly leaching and reduction processes. The occurrence characteristics of copper in the anode material obtained by disassembling the battery after discharge pretreatment were first analyzed, SEM + EDS detection shows that graphite with thickness of tens of microns is attached to the surface of copper foil. Subsequently, the application of mechanical force promoted the graphite to detach from the collector, and the results indicate that significant selective crushing leads to the enrichment of copper foil in coarse-grained particles. Further, an ammonia leaching method was used to leach copper gently. The leaching kinetic behavior of copper foil particles with different particle sizes was analyzed. The diffusion controlled shrinking core model can accurately describe the leaching behavior of copper foil particles in leaching process. The activation energies of +2 mm, 2–1 mm, and 1–0.5 mm are 15.04 kJ/mol, 11.61 kJ/mol, and 8.21 kJ/mol, respectively. Undissociated graphite has negative impact on the leaching behavior, and reduction in the particle size of the copper foil can enhance the leaching behavior. Finally, the glucose and ascorbic acid system reducing reaction promotes the transformation of the copper ions in the leaching solution into regular shaped copper nanoparticles. SEM and XRD results show that high purity copper nanoparticles with hundreds of nanometers was successfully prepared. This study provides an eco-strategy and value-added recovery approach to address the challenges of full component utilization of spent LIBs.

The effect of biochemical oxidation on the hydrometallurgical production of copper

The article presents the results of the use of the biochemical leaching method for copper-bearing non-commercial ore in a full hydrometallurgical cycle. The object of the study was the average copper-bearing ore of the Satbayev deposit, with an initial copper content of 0.26%. The experimental part of the full hydrometallurgical cycle included percolation leaching, extraction, and re-extraction tests, as well as electrodeposition tests and the production of finished cathode copper. Two variants of percolation leaching were performed as a comparison: a standard method using only sulfuric acid and a preliminary bacterial oxidation method for mineral raw materials with an adapted bacterial strain, Acidithiobacillus ferrooxidans. Percolation leaching experiments showed a significant reduction in sulfuric acid consumption when preliminary bacterial oxidation was used. Upon reaching the level of copper extraction from the ore of 86–87%, the final consumption of sulfuric acid for the standard leaching method was 15.5 kg per ton, while 9.4 kg per ton was required for the biochemical method. The productive solution obtained in the biochemical leaching process showed full suitability for all technological stages of hydrometallurgical copper production.

A sustainable process for selective recovery of metals from gallium-bearing waste generated from LED industry

With the rapid development of the LED industry, gallium (Ga)-bearing waste generated is regarded as one of the most hazardous as it typically contains heavy metals and combustible organics. Traditional technologies are characterized by long processing routes, complex metal separation processes and significant secondary pollution emission. In this study, we proposed an innovative and green strategy to selectively recovery Ga from Ga-bearing waste by using a quantitative phase-controlling transition process. In the phase-controlling transition process, the gallium nitride (GaN) and indium (In) are converted to alkali-soluble gallium (III) oxide (Ga2O3) and alkali-insoluble indium oxides (In2O3) by oxidation calcination, while nitrogen is converted into diatomic nitrogen gas instead of ammonia/ammonium (NH3/NH4+). By selective leaching with NaOH solution, nearly 92.65% of Ga can be recycled with a leaching selectivity of 99.3%, while little emissions of NH3/NH4+. Ga2O3 with a purity of 99.97% was obtained from the leachate which is also economy promising by economic assessment. Therefore, the proposed methodology compared to the conventional acid and alkali leaching methods is potentially greener and more efficient process for extracting valuable metals from nitrogen-bearing solid waste.

Subsurface irrigation with ceramic emitters improves the yield of wolfberry in saline soils by maintaining a stable low-salt environment in root zone

The high salt concentration in soils depresses crop growth and saline soil reclamation. An appropriate irrigation method is essential to alleviate water shortage and promote wolfberry (Lycium barbarum L.) cultivation in saline soils. Subsurface irrigation with ceramic emitters (SICE) is a novel technique that maintains a stable soil water environment through adaptive outflow and holds a beneficial impact on saving water and increasing yield. However, the effect of SICE on salt leaching remains to be investigated. A field experiment was executed to investigate the salt leaching process in SICE and subsurface drip irrigation (SDI) in saline soils and their effect on wolfberry yield. HYDRUS-2D was calibrated and validated using experimental data to investigate the spatial-temporal variation of soil salinity. Subsequently, the salt leaching efficiency with different emitter discharges (0.10, 0.15, 0.24, and 0.33 L h−1) was assessed via HYDRUS-2D. Results indicated that SICE leached soil salt below the stress threshold after 50 days of irrigation, while SDI required 148 days. At the end of irrigation, SICE formed a low-salt zone that occupied 74.14% of the main root zone, while the zone with SDI was 60.69%. Generally, SICE provided a stable low-salt environment for wolfberry root system for 117.5 days (69.9% duration of growth period). SICE improved the wolfberry yield and root-zone soil desalination efficiency (DE) by 0.17 t ha−1 and 0.41% cm−1 than SDI, respectively. When emitter discharge increased to 0.24 L h−1, the root zone of wolfberry was protected from salt stress, but DE decreased gradually. SICE with an emitter discharge of 0.24 L h−1 was recommended for wolfberry in saline soils of Ningxia. The results reveal that SICE is an efficient salt leaching method for saline soil management and crop yield improvement.

CO2 sequestration and CaCO3 recovery with steel slag by a novel two-step leaching and carbonation method

The steel smelting process produces extensive CO2 and Ca-containing steel slag (SS). Meanwhile, the low value utilization of steel slag results in the loss of Ca resources. CO2 sequestration utilizing SS can reduce carbon emissions while achieving Ca circulation. However, conventional SS carbon sequestration methods suffer from slow reaction rates, finite Ca usage efficiency, and difficulty separating the CaCO3 product from SS. Herein, an innovative two-step leaching (TSL) and carbonation method was presented based on the variations in leaching efficiency of activated Ca under different conditions, aiming at efficient leaching, carbon sequestration, and high-value reuse of SS. This method employed two NH4Cl solutions in sequence for two leaching operations on SS, allowing the Ca leaching rate to be effectively increased. According to the findings, TSL could increase the activated Ca leaching rate by 26.9 % and achieve 223.15 kg CO2/t SS sequestration compared to the conventional one-step leaching (CSL) method. If part of the CaCO3 is recovered as a slagging agent, about 34.1 % of the exogenous Ca introduction could be saved. In addition, the CO2 sequestration of TSL did not significantly decrease after 8 cycles. This work proposes a strategy that has the potential for recycling SS and reducing carbon emissions.

Bioleaching Modeling-A Review.

The leaching of minerals is one of the main unit operations in the metal dissolution process, and in turn it is a process that generates fewer environmental liabilities compared to pyrometallurgical processes. As an alternative to conventional leaching methods, the use of microorganisms in mineral treatment processes has become widespread in recent decades, due to advantages such as the non-production of emissions or pollution, energy savings, low process costs, products compatible with the environment, and increases in the benefit of low-grade mining deposits. The purpose of this work is to introduce the theoretical foundations associated with modeling the process of bioleaching, mainly the modeling of mineral recovery rates. The different models are collected from models based on conventional leaching dynamics modeling, based on the shrinking core model, where the oxidation process is controlled by diffusion, chemically, or by film diffusion until bioleaching models based on statistical analysis are presented, such as the surface response methodology or the application of machine learning algorithms. Although bioleaching modeling (independent of modeling techniques) of industrial (or large-scale mined) minerals is a fairly developed area, bioleaching modeling applied to rare earth elements is a field with great growth potential in the coming years, as in general bioleaching has the potential to be a more sustainable and environmentally friendly mining method than traditional mining methods.

1 Comparison of Ni Speciation Using Methods of Sequential Leaching and Quantitative Mineralogy for Workplace Aerosol at a Stainless Steel Plant

Abstract Based on epidemiological records of workers at Ni operations, regulatory guidelines often target specific Ni compounds for setting exposure limits. Thus, reliable methods of Ni speciation in airborne dust samples are required for effective monitoring of workplace exposure. In this study, Ni speciation of dust collected from a stainless steel operation was performed using a variety of methods: Zatka sequential leaching (original and modified protocols), soluble and insoluble Ni as described in ISO 15202, and quantitative mineralogy (QEMSCAN). Mineral characterization was also performed on bulk material collected from selected work areas at the plant. The quantitative mineralogical analysis determined that the Ni dust is composed of oxidic Ni (Ni in chromite and trevorite, > 80 % of the Ni in most samples) and metallic Ni (Ni-Fe alloy), and the results were validated against chemical assays and alternate methods of mineral characterization (Electron Probe Microanalysis, EPMA). In contrast, the original Zatka method erroneously identified soluble Ni as a major Ni contributor, whereas the modified Zatka method identified sulfidic Ni. The mineralogy identified ambient dust and grain sizes and textures of individual Ni compounds as potential factors that can affect leaching selectivity. Improving methods of sequential leaching is important because the resolution of quantitative mineralogical techniques diminishes at < 3 µm (respirable dust fraction). We recommend that quantitative mineralogy be performed in parallel with methods of sequential leaching to provide a robust system of characterization.

Separation of Zinc from Zinc Ferrite by Magnetization Roasting and Ammonia Leaching

Zinc ferrite can be found in zinc-bearing dust in ironmaking and steelmaking. It is difficult to be recovered due to its stable properties. The magnetization roasting and ammonia leaching method were used to separate iron and zinc from zinc ferrite in this study. Thermodynamic analysis showed that the key to the selective reduction of zinc ferrite to zinc oxide and ferric oxide is to control the appropriate temperature and atmosphere. The influences of the selective reduction roasting process of zinc ferrite on the conversion rate, phase change, and microevolution behavior were investigated. The microstructure analysis showed that the distribution area of iron was mainly gray, and the distribution area of zinc was mainly white grid lines. The zinc content in the white area was higher than that in the gray area. With the increase in temperature and PCO, the white area expanded and the migration of zinc and iron was accelerated, but the iron in the white area still existed. The ammonia leaching of the magnetization-roasted product showed that a zinc leaching rate of 78.12% was achieved under the following conditions: the roasting atmosphere of PCO/P(CO+CO2) = 25%, the roasting temperature of 750 °C, roasting duration for 45 min, n(NH3-H2O):n(NH4Cl) = 1:1, the solid–liquid ratio of 40 g/L, leachate concentration of 6 mol/L, leaching duration of 90 min, the leaching temperature of 50 °C, and the stirring rate of 200 rpm.

Influence of Leaching Solution on the Soil-Water Characteristics of Ion-Absorbed Rare Earth Minerals and Its Hysteresis Effect

The soil-water characteristic curve is the basic constitutive relation to express the water-holding characteristics of ion-absorbed rare earth. The simulated solution mining test and pressure plate apparatus tests were carried out, the relationship between matric suction and water content under different leaching actions was obtained. Using the Fredlund and Xing four-parameter model, the soil-water characteristic curves of ion-absorbed rare earth under different leaching actions were obtained, and the changing trend of each parameter was analyzed, and the influence of different leaching methods on the water-holding characteristic of soil was obtained. For different types of leaching solutions, the water-holding capacity of the soil varies from strong to weak for pure water, the 3% magnesium sulfate solution, and the 3% ammonium sulfate solution; as the concentration of the leaching solution increases, the water-holding capacity of the sample gradually decreases, and it decreases most significantly from 0% to 2%. Moreover, the saliency of the “hysteresis effect” of the soil-water characteristic curve was from high to low for pure water, the 3% magnesium sulfate solution, and the 3% ammonium sulfate solution, and the “hysteresis effect” showed a decreasing trend with the increase in the concentration.

Upcycling of Spent LiCoO2 Cathode to Lithium Dual‐Ion Battery Anode

AbstractOwing to the paradigm shift of the automobile industry toward the electrification of vehicles, the aftermath of batteries that power these devices at the end of their lives has to be addressed strenuously. Since upcycling strategies are hardly in the limelight, this paper focuses on giving a second life to LiCoO2 cathode as a dual‐ion battery (DIB) anode. Among many possible recovery approaches explored for cobalt, a microwave‐assisted green leaching method comprising mild leaching agents is chosen for this work. Cobalt is recovered as cobalt oxalate and converted to cobalt/cobalt oxide nanospheres embedded in a porous graphitic carbon matrix (Co3O4/Co@C). Due to the high working voltage, excellent safety, and environmental friendliness, DIBs are being considered as a replacement for lithium‐ion batteries in specific sectors. In an unconventional approach, the derived Co3O4/Co@C is effectively employed as an anode material for dual‐ion batteries. The half‐cell demonstrates a high discharge capacity of 550 mAh g−1 at 0.1 A g−1. A full‐cell DIB fabricated using Co3O4/Co@C, derived from upcycled LiCoO2 as an anode and graphite as a cathode, shows an appreciable capacity and remarkable cycling stability. This sustainable approach for upcycling exhausted LIBs can pave the way to improve the circular economy of batteries.