Leaching Efficiency Research Articles

Acid leaching of vivianite separated from sewage sludge for recovering phosphorus and iron

This paper examines the acid leaching efficiencies of Fe and P from vivianite slurry (VS, Fe3(PO4)2·8H2O), which is magnetically separated from anaerobic digested sludge, and elaborates on Fe and P reuse routes. The characteristics and dissolution behavior of raw VS in hydrochloric, sulfuric, phosphoric, oxalic, and citric acids are investigated. Results reveal that the primary impurities in VS are organic matter, other phosphate compounds, and Mg present in the vivianite crystal structure. Hydrochloric and sulfuric acids could effectively extract P (90%) from VS at an optimal hydrogen-to-phosphorus (H⁺/P) ratio of 2.5, compared with sewage sludge ash (SSA) that normally needs an H⁺/P ratio greater than 3. Hence, VS can be employed as an alternative P resource following a similar recovery route used with SSA. However, in comparison to SSA, VS use can decrease acid consumption in P extraction and the requirement for the extensive purification of cationic impurities. Furthermore, oxalic acid effectively facilitates the separation of P and Fe in VS by precipitating Fe as insoluble ferrous oxalate in acidic conditions, leading to a high Fe recovery rate of 95%. The recovery and reuse of Fe through the oxalic acid route further improves the feasibility of VS as an alternate resource.

Improvement of Salt Leaching Efficiency and Water Content of Soil through Irrigation with Electro-Magnetized Saline Water

While the advantageous effects of using magnetic and electromagnetic treatment (ET) of brackish and saline waters on soil salinity reduction in the root zone were largely reported, more studies are needed to answer questions about the soil salt leaching efficiency and the effect of the duration of the exposure to ET. For this aim, pot experiments were conducted using an Aqua-4DR physical water treatment device. The first experiment included two trials. The first trial considered five concentrations: C0:1.0; C1:4.5; C2:9; C3:13.5; and C4:18 dS m−1. The results revealed that the volume and the salt concentrations of the drained waters were significantly higher under irrigation with ET saline waters than those provided by untreated waters. The drained fraction of water varied from 20 to 26% under irrigation with untreated water and increased from 33 to 56% under irrigation with electro-magnetized water, indicating an improvement in the salt leaching. The second trial was carried out with different irrigation doses. The results showed that the higher the dose, the more obvious and significant the ET effect. The different treatment durations of water exposure revealed that the volume and salinity of drained water significantly increase as the ET duration increases. An increase in the ET duration also induces an increase in the soil water content of around 2.5%. Based on the experimental findings, we may conclude that the ET of saline water can reduce the adverse effect of salinity on the top soil, but these leached salts are carried away in depth and there is no concentration limit of water to the effect of the ET.

A Sequential Leaching Protocol for δ11B and Trace Element Analyses of Multi‐Phase Carbonate Rocks

AbstractBoron geochemistry from biogenic carbonates offer valuable information about ocean pH and CO2 chemistry. However, application to geological carbonate deposits suffers from analytical difficulties in obtaining geochemical signals exclusively from the carbonate phase. Sequential leaching with reagents and acids has the potential to overcome such an issue. There is, however, little systematic investigation about the efficiency of sequential leaching in isolating carbonate‐associated boron from siliciclastic matrix. Here, we developed a sequential leaching protocol and applied it to methane‐derived‐authigenic‐carbonate samples. Using the leachate δ11B signatures, elemental composition, and mineral composition of residues, we show that the sequential leaching is able to improve the separation of boron from different phases. Buffered hydrogen peroxide removes organic matter and also some silicate phases resulting low δ11B values. Leaching with NH4Ac removes adsorbed boron though may also partially leach some carbonate phases. The first few leaching steps with diluted acetic acid dissolve carbonate phases. Depending on the sample type, these may also capture some remaining adsorbed boron from the preceding NH4Ac leaching. Once the adsorbed boron is completely removed, as indicated by the progressively higher δ11B values during the following acid leaching steps, representative carbonate composition can be derived. The accuracy of this protocol is demonstrated with leaching experiments using artificial deep sea coral carbonate and clay mixtures that give the representative carbonate‐associated δ11B within error of the pure coral value. Our results provide insights into characteristic signatures derived from silicates and organic matter that need to be considered in boron isotope analyses of impure marine carbonates.

Leaching Efficacy of Ethylenediaminetetraacetic Acid (EDTA) to Extract Rare-Earth Elements from Monazite Concentrate

Alkaline EDTA solution has been previously identified as an effective leaching agent for solubilising rare-earth oxalates. These oxalates are the product of an oxalic acid conversion leach dissolving monazite and redepositing the salt. Pervious work suggested a significant increase in recovery was observed between pH 8 and 10; we have demonstrated that, in an excess of EDTA, this is not the case, and the dissolution is similar. While demonstrating that, at a nominal solid loading of 100 g/L, 0.2 M EDTA solution produced the highest dissolution, elevated solids require an equivalent increase in lixiviant concentration driven by consumption. Very-high-solution concentrations (>50 g/L dissolved TREEs) were achieved at a high solid loading, indicating both that a solution equilibrium is yet to be reached and that a build-up of oxalate in the system (estimated at ~1 M) does not impact the leach efficiency. We have also demonstrated the recycling of EDTA to use in multiple stages as well as the ability to recover oxalate from this solution.

Lithium-Ion Battery Recycling: Ternary Deep Eutectic Solvents Enable Efficient and Selective Electrochemical Recovery of Critical Component Metals

The growing demand for lithium-ion batteries (LIBs) in electric vehicles and energy storage systems has led to a rise in LIB waste. Efficient metal recovery from LIB waste is critical to meet the growing demand sustainably. However, traditional recycling methods, such as pyrometallurgy and hydrometallurgy, have limitations regarding energy consumption, efficiency, and environmental impact. In this work, we address these challenges by exploring the potential of Deep Eutectic Solvents (DESes) as an alternative. DESes are compounds formed by mixing hydrogen bond donors and acceptors and exhibit a high capability for metal dissolution. DES has a wide electrochemical stability window (1-2 V vs Ag), making it ideal for electrodeposition. While DES holds promise for sustainable LIB recycling, current applications are hindered by high leaching temperatures (140-220°C) and prolonged durations, extending even to days.In this study, we investigate the physical properties of a novel ternary DES and assess its leaching capabilities alongside electrodeposition studies. The leaching efficiency (LE) of metals using ternary DES is compared to the binary DES, composed of choline chloride and ethylene glycol (1:2 ChCl: EG). For the same leaching conditions (900C, 24 hr), the leaching efficiency (LE) of metals using binary DES, is 20%, whereas the LE of metals from ternary DES is nearly 100%. We optimized the leaching conditions and investigated the leaching kinetics. The electrochemical properties of the tailored, ternary DES are explored, revealing an electrochemical window of 2-3 V vs Ag. We analyze current density–time transients using the Scharifker–Hills model for instantaneous and progressive nucleation to study the early nucleation and growth mechanism of electrodeposition. Furthermore, we perform potentiostatic electrodeposition of metals from the leach liquor on different substrates, such as copper sheet and carbon at various constant potentials (-0.7 V to -1 V vs Ag). The effect of applied potential, stability of working and counter electrodes, and growth mechanism of deposited metals are studied. The electrodeposited metals are characterized using scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Our findings indicate that the proposed ternary DES holds significant promise for efficient and environmentally friendly metal recovery from LIB waste, paving the way for advancements in sustainable battery recycling technologies. Figure 1

A Sustainable Recycling Approach to Regenerate Graphite from Industrially Sourced Failed Anodes

Recycling graphite from Li-ion battery (LIB) waste plays an important role in increasing the accessibility of graphite resources and sustainable recovery. This presentation describes our work to purify graphite from failed (i.e., out-of-specification) anodes in LIB manufacturing by focusing on the most common contaminant: copper, used as the current collector in LIB anodes.A new, three-step scalable and environmentally friendly approach was used to provide a cost-effective and sustainable method in industrial settings to recycle failed anodes during the early stages of battery manufacturing.The study aimed to understand the differences between new, battery-grade graphite and recycled graphite from anode production waste. In particular, focus was placed on the effect of metallic Cu residues on electrochemical performance. The efficiency of Cu removal from graphite was quantified by Microwave Plasma – Atomic Emission Spectroscopy (MP-AES) analysis of leachates. The following experimental parameters were studied to maximize Cu leaching efficiency: solid-to-liquid ratio, temperature, acid concentration, time and stirring speed.The surface morphology and elemental composition of leached and thermally treated purified graphite were analysed by Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM-EDS) and Laser Induced Breakdown Spectroscopy (LIBS). The specific surface area and crystallographic parameters were measured by Braunauer–Emmett–Teller Analysis (BET) and X-Ray Diffraction (XRD), respectively. The electrochemical performance was evaluated by galvanostatic cycling with potential limitation versus Li+/Li. These five techniques were carried out on the solid residues after each stage of the regeneration procedure. The results were compared with battery-grade graphite to assess the effectiveness of our sustainable recycling approach to reuse graphite from failed anodes in LIBs.

Selective lithium recovery from pyrolyzed black mass through optimized caustic leaching

This study presents a new method for selectively extracting lithium (Li) from pyrolyzed lithium-ion batteries (LIBs) black mass (BM) using a novel caustic (NaOH) leaching process. The efficiency of the NaOH leaching has been evaluated by response surface methodology (RSM), and the effects of leaching parameters on Li leaching efficiency (LE) and selectivity have been discussed in terms of leaching mechanism based on thermodynamics and kinetics studies. The results show that caustic leaching has excellent selectivity towards Li with no detectable leaching for nickel (Ni), manganese (Mn), cobalt (Co), and copper (Cu), LE up to ∼81 % Li. However, caustic leaching coextracts aluminium with Li. Further, Li is recovered from leach solution as lithium hydroxide (LiOH) using evaporative crystallization or lithium carbonate (Li2CO3) with Na2CO3 addition and CO2 injection. Li2CO3 recovered via CO2 injection has the highest purity at ∼93 %, surpassing the Li2CO3 purity levels obtained through precipitation with Na2CO3 (∼82 %) and LiOH (∼21 %) retrieved via evaporative crystallization.

Simultaneously achieving high Li leaching efficiency and Li/Co selectivity from lithium-ion batteries cathode by using natural low-melting mixture solvents (LoMMSs) as green solvents

Simultaneously achieving high Li leaching efficiency and Li/Co selectivity from lithium-ion batteries cathode at mild condition with high sustainability is difficult up to now. To achieve this goal, we here utilize amino acid-based low-melting mixture solvents (LoMMSs) as green solvents. Representative LoMMSs valine:lactic acid (1:12) could leach nearly 100% Li with the high Li/Co selectivity of 48.39 from lithium cobalt oxide (LCO). Effect of temperature, time and leaching agent mass is investigated. Higher temperature continuously increases the Li leaching efficiency, while Co leaching efficiency first increases during the temperature from 25 °C to 60 °C and then decreases at higher temperature. Both Li and Co leaching efficiency when extending the time or adding the leaching agent mass. Mechanism study shows that acid-base interaction and coordination are the main interaction for the high efficiency of metal leach while redox reaction is negligible. This work would provide a useful guide for promoting the industrial application of selectively recycling lithium-ion batteries cathode with high sustainability and low cost.

Novel ternary deep eutectic solvents used for recycling lithium and cobalt from waste lithium-ion batteries

The escalating disposal of lithium-ion batteries (LIBs) poses significant environmental challenges but also offers substantial opportunities for resource recovery. In this work, we introduce a recycling strategy using a green, cost-effective ternary deep eutectic solvent (DES) composed of guanidine hydrochloride, ethylene glycol, and maleic acid. The DES can achieve >99.5 % leach efficiency of lithium (Li) and cobalt (Co) at 100 °C, 9h, and L/S=50. The kinetic study found that the chemical reaction rate at the interface was the key to controlling the leaching process. The study of leaching mechanisms found that the acidity and coordination ability of DES were the main driving forces of leaching. Co loaded in the DES phase can almost precipitate out by using oxalic acid, achieving the separation of Li and Co. After reusing three times, the maximum load of Li in the DES phase reached 4.1 mg/g. These outstanding performances, along with the avoidance of the use of hazardous chemicals and the reduction of high costs, confirmed that the DES possesses a promising prospect for sustainable, large-scale application in efficiently leaching valuable metals from LiCoO2.

Synergistic enzymatic mechanism of lepidolite leaching enhanced by a mixture of Bacillus mucilaginosus and Bacillus circulans

Numerous studies have demonstrated that the co-leaching of ores by different silicate bacteria significantly improves the performance of bioleaching systems. Nevertheless, the mechanism of different silicate bacteria synergistically or complementarily enhanced the leaching process of lithium-containing silicate remains unclear. This study discussed the leaching impact of the combined presence of two metabolically distinct silicate bacteria on lepidolite, with the aim of comprehending the synergistic effect resulting from the presence of Bacillus mucilaginosus and Bacillus circulans in the leaching process. The results indicated that the polysaccharides and proteins secreted by bacteria-containing functional groups such as -OH and -COOH, which played an important role in the complex decomposition of ores. Organic acids played the role of acid etching and complexation. Bacillus mucilaginosus and Bacillus circulans exhibited low individual leaching efficiency, primarily due to their weak organic acid secretion. Moreover, the prolific polysaccharide production by Bacillus mucilaginosus led to bacterial aggregation, diminishing contact capability with minerals. Bacillus circulans decomposed the excessive polysaccharides produced by Bacillus mucilaginosus through enzymatic hydrolysis in the co-bioleaching process, providing later nutrient supply for both strains. The symbiosis of the two strains enhanced the synthesis and metabolic capabilities of both strains, resulting in increased organic acid secretion. In addition, protein and humic acid production by Bacillus mucilaginosus intensified, collectively enhancing the leaching efficiency. These findings suggested that the primary metabolic products secreted by different bacterial strains in the leaching process differ. The improvement in bioleaching efficiency during co-leaching was attributed to their effective synergistic metabolism. This work contributes to the construction of an efficient engineering microbial community to improve the efficiency of silicate mineral leaching, and reveals the feasibility of microbial co-culture to improve bioleaching.

Recovery of valuable metal elements from spent lithium-ion battery via a low temperature ammonium persulfate roasting approach

A low-cost and eco-friendly recycling method is crucial for recovering valuable elements from end-of-life lithium-ion batteries (LIBs), which plays a vital role in addressing resource scarcity and reducing the environmental impact. This study aims to develop a low-temperature pyro-metallurgical combined process to recycle spent LiNi0.5Co0.2Mn0.3O2 (NCM523). Unlike traditional pyrometallurgy methods that generate liquid alloys and slags at temperatures exceeding 1000 °C, the (NH4)2S2O8 roasting approach operates at 350 °C and converts NCM523 to water-soluble sulfates, exhibiting remarkable leaching efficiencies of Li, Ni, Co, and Mn, with values of 99.43 %, 99.87 %, 98.88 %, and 99.19 %, respectively. Systematic studies were conducted to investigate the influence of roasting temperature, (NH4)2S2O8-to-NCM mass ratio, and roasting time on the sulfation process. Furthermore, the mechanism of sulfation reaction was identified by combining experiments with thermodynamic calculation. At temperatures above 160 °C, (NH4)2S2O8 decomposes into (NH4)2S2O7, which reacts with NCM. Lithium in a layered structure forms Li2SO4, while transition elements form MnSO4, Li2Co (SO4)2, and NiSO4. At around 350 °C, (NH4)2S2O8 further decomposes into NH4HSO4, releasing SO2 and NH3. SO2 reacts with remaining NCM or unsulfated transition metal oxides, converting them into MnSO4, Li2Co (SO4)2, and NiSO4. Above 800 °C, the metal sulfates decompose into stable oxides. This study presents a low-temperature sulfation method that effectively disintegrates the crystal structure of lithium metal oxides without the need for acids or reducing agents.

Efficient recovery of all valuable metals from spent HDS catalysts: Based on roasting mechanisms for enhanced selective leaching and separation

Recovery of all valuable metals such as Ni, Mo, V and Al from spent hydrodesulfurization (HDS) catalysts is beneficial to environmental protection and resource recycling. The current recycling process mostly considers the recovery of Mo and V than recovery of Ni and Al, and generates a large amount of difficult-to-decompose Ni-Al residue and wastewater. Aiming at the insufficiency of the current recycling process, in this study, a novel pyro-hydrometallurgical process for efficient and complete recovery of metals from spent HDS catalysts was proposed. The mechanisms of phase transformation during roasting and leaching are investigated by XRD, XPS and SEM in depth. The modulation of the phase transformation of the spent HDS catalyst in the oxidative roasting process is the key to the influence on the leaching of Ni and Al. Inhibition of θ-Al2O3 phase and Ni-Al spinel generation by controlled roasting can achieve efficient leaching of Mo, V, Ni and Al. Subsequently, Mo and V were selectively leached with 2 mol/L Na2CO3, and the alkaline leach residue obtained was treated with 6 mol/L HCl. The results showed that alkaline leaching efficiencies of Mo and V reached 99.73 % and 91.86 % while acid leaching efficiencies of Ni and Al reached 99.71 % and 90.27 %, respectively. The metals of acid leach solution were recovered by using N235, HBL110 and NaAlO2 stepwise. This new process has the advantages of high efficiency and comprehensive metal recovery, high product purity, and low amount of slag and wastewater, and has good prospects for industrial application.

Investigating the acidophilic microbial community's adaptation for enhancement indium bioleaching from high pulp density shredded discarded LCD panels

As part of electronic waste (e-waste), the fastest growing solid waste stream in the world, discarded liquid crystal displays (LCDs) contain substantial amounts of both valuable and potentially harmful metal, offering valuable opportunities for resource extraction but posing environmental threats. The present comprehensive study is an investigation into the bioleaching of indium from discarded LCD panels, with a particular focus on high pulp density shredded (Sh-LCDs) and powdered (P-LCDs) materials. This study involved an acidophilic consortium, with two pathways, namely the mixed sulfur-iron pathways and sulfur pathways, being explored to understand the bioleaching mechanisms. Indium bioleaching efficiencies through the mixed sulfur-iron pathway were approximately 60% and 100% for Sh-LCDs and P-LCDs, respectively. Three mechanisms were involved in the extraction of indium from LCD samples: acidolysis, complexolysis, and redoxolysis. The microbial community adapted to a pulp density of 32.5 g/L was streak-plated and it was revealed that sulfur-oxizing bacteria dominated, resulting in the minimum indium extraction of 10% and 55% for both Sh-LCDs and P-LCDs samples, respectively. It was generally accepted that ferric ions as oxidants were effective for indium bioleaching from both the Sh-LCDs and P-LCDs. This implies that the cooperation or interaction within the microbial community used in the bioleaching process had a beneficial impact, enhancing the overall effectiveness of extracting indium from LCD panels. The adapted consortium utilizes a combination of microbial transformation, efflux systems, and chelation through extracellular substances to detoxify heavy metals. The adapted microbial community demonstrated better indium leaching efficiency (50%) compared to the non-adapted microbial community which achieved a maximum of 29% and 5% respectively from Sh-LCDs and P-LCDs at a pulp density of 32.5 g/L. The advantages of an adapted microbial community for indium leaching efficiency, attributing this advantage to factors such as high metabolic activity and improved tolerance to heavy metals. Additionally, the protective role of the biofilm formed by the adapted microbial community is particularly noteworthy, as it contributes to the community's resilience in the presence of inhibitory substances. This information is valuable for understanding and optimizing bioleaching processes for indium recovery, and by extension to possibly other metals.

Irrigation expansion shows potential for increased maize yield and reduced nitrogen leaching in the Midwest US

CONTEXTYield gaps in Midwest US rainfed maize (Zea mays L.) are likely to continue to increase as the frequency of extreme weather events associated with future climate change increase (i.e., high temperatures, precipitation variability). One solution to closing this gap is the expansion of irrigation in regions that currently do not utilize this practice. While irrigation expansion has the potential to increase maize yields and crop productivity, there is also the potential to see improvement in nitrogen loss. However, it remains unclear at what point irrigation should be triggered (i.e., plant available water content (AWC) thresholds) to obtain a balance between crop productivity and environmental improvements. OBJECTIVEThe objective of this study is to assess the effects of irrigation management on maize yield, nitrogen leaching, and water use efficiency under the expansion of irrigation across the entire Midwest US and to determine the optimal plant AWC threshold to trigger irrigation for achieving a substantial increase in maize yield and reduction in nitrogen leaching while using the minimal amount of required irrigation. METHODSWe use an agroecosystem model, Agro-IBIS, to simulate both rainfed and irrigated maize production and nitrogen leaching under likely future climate conditions (i.e., wet-warm, dry-warm). To determine the optimal plant AWC threshold for irrigation, irrigation scenarios were conducted for a range of plant AWC thresholds (0.2 to 0.8) across the entire Midwest US. RESULTS AND CONCLUSIONSOur results show that Midwest US regions that do not currently utilize irrigation could experience an 11–37% increase in maize yield and a 12–32% decrease in nitrogen leaching when irrigation (39.0 to 96.8 mm yr−1) is triggered at the lower end of the plant AWC threshold (e.g., 0.3). Maize grown under dry-warm and wet-warm climate conditions will likely experience increased yields and reduced nitrogen loss with minimal irrigation. While these findings suggest that the expansion of irrigation could help close yield gaps while improving other ecosystem services, future work should focus on simulating these conditions under a wider range of precipitation extremes and fertilizer management to better understand the potential interactions under a changing climate. SIGNIFICANCEThis study outlines the optimal plant AWC threshold for irrigation to maximize maize yields in the Midwest while minimizing nitrogen loss and can provide valuable insights for making informed decisions about landscape management under future conditions.

Efficient Leaching of Metal Ions from Spent Li-Ion Battery Combined Electrode Coatings Using Hydroxy Acid Mixtures and Regeneration of Lithium Nickel Manganese Cobalt Oxide

Extensive use of Li-ion batteries in electric vehicles, electronics, and other energy storage applications has resulted in a need to recycle valuable metals Li, Mn, Ni, and Co in these devices. In this work, an aqueous mixture of glycolic and lactic acid is shown as an excellent leaching agent to recover these critical metals from spent Li-ion laptop batteries combined with cathode and anode coatings without adding hydrogen peroxide or other reducing agents. An aqueous acid mixture of 0.15 M in glycolic and 0.35 M in lactic acid showed the highest leaching efficiencies of 100, 100, 100, and 89% for Li, Ni, Mn, and Co, respectively, in an experiment at 120 °C for 6 h. Subsequently, the chelate solution was evaporated to give a mixed metal-hydroxy acid chelate gel. Pyrolysis of the dried chelate gel at 800 °C for 15 h could be used to burn off hydroxy acids, regenerating lithium nickel manganese cobalt oxide, and the novel method presented to avoid the precipitation of metals as hydroxide or carbonates. The Li, Ni, Mn, and Co ratio of regenerated lithium nickel manganese cobalt oxide is comparable to this metal ratio in pyrolyzed electrode coating and showed similar powder X-ray diffractograms, suggesting the suitability of α-hydroxy carboxylic acid mixtures as leaching agents and ligands in regeneration of mixed metal oxide via pyrolysis of the dried chelate gel.

Copper recovery from waste printed circuit boards using pyrite as the bioleaching substrate.

Waste printed circuit boards (WPCBs) can be bioleached for Cu recovery, but lack of substrate for the bioleaching culture. In this study, using pyrite as a bacterial substrate for bioleaching WPCBs and recovering Cu was explored. The results showed that the WPCBs bioleaching using pyrite as the bacterial substrate was feasible. Mechanical crushing was a suitable WPCBs pretreatment method. The optimal WPCBs and pyrite pulp densities were respectively found to be 1.25% (w/v) and 1.0% (w/v), and the suitable nitrogen source ratio ((NH4)2SO4: (NH4)2HPO4) was deemed as 2g/L: 2g/L, achieving a Cu2+ leaching efficiency of 95.60 ± 1.57% in 14 d. Copper in the bioleaching solution can be directly recovery via electrodeposition. The Cu recovery efficiency in 60min was up to 92.19 ± 1.35% under the optimal condition that the initial Cu2+ concentration and pH were respectively set at 7.34g/L and 2.75, and the current density was set at 200 A/m2. Copper was found as the dominant metal in the cathode deposits, existing in the form of Cu and Cu2O. This work provided a novel approach for bioleaching WPCBs and recovering Cu.

Accelerated carbonation of incineration fly ash (IFA) and its impact on inhibiting heavy metals leaching and removal of soluble salts

This study analysed the composition and leaching results for 12 IFA samples from a local incineration plant by XRF and leaching tests based on BS EN12457-1:2002. XRF results show that the main elements are Ca, Cl and S in all IFA samples. Leaching test results shows a high leachability of Na, Cl, Br, Pb, Zn and Cu. The accelerated carbonation with (NH4)2CO3 was attempted to inhibit heavy metals leaching and remove soluble salts. The effect of (NH4)2CO3 concentration on carbonation efficiency and inhibition of heavy metal leaching was systematically investigated. TGA and ICP-MS were used to determine carbonation capacity and heavy metal leaching, respectively. TGA results show the maximum carbonation capacity is achieved in one hour with 10 wt% (NH4)2CO3 and 76% carbonation occurs -in the first 10 min. Leaching test results reveal that Cu and Pb are efficiently immobilised when the concentration of (NH4)2CO3 is as low as 2 wt% with a s/l ratio of 1:5 within 1 hr. Increasing the concentration of (NH4)2CO3 to 4 wt%, the leaching rate of Zn is also below NEA RVs (National Environment Agency of Singapore). Carbonation is also effective to immobilise Cd and Ni, but not for Cr since it exists as CrO42- and cannot be carbonated. XRF results from a larger scale reaction confirm the significant removal of soluble salts, and lower leachability (except SO42-) is substantiated by leaching tests. By integrating the processes of CO2 capture with ammonia and accelerated carbonation, our work contributes to CO2 sequestration and IFA detoxification.

Ultra-low viscosity betaine hydrochloride-formic acid deep eutectic solvent for leaching critical metals from spent NCM lithium-ion batteries

With the rapid development of the electric vehicle market and increasing demand for lithium-ion batteries (LIBs), spent LIBs recycling has attracted extensive attention worldwide. Being environmentally friendly, deep eutectic solvents (DESs) have great potential for critical metal recycling from spent LIBs. In this study, a new type of DES, consisting of betaine hydrochloride (BeCl) and formic acid (FA) in a 1BeCl:9FA molar ratio, was designed to leach critical metals from spent LIBs cathode materials. The study found that the as-prepared DESs exhibited extremely low viscosities and strong coordination abilities, which are suitable for metal leaching. By properly regulating and controlling the leaching parameters, the Li, Mn, Co, and Ni leaching efficiencies from spent LiNi0.8Co0.1Mn0.1O2 LIBs reached 98.03, 96.01, 94.19, and 92.35%, respectively, whereas those of critical metals were all > 99.5% from either LiCoO2 or LiMn2O4. The leaching kinetics revealed that the leaching process was controlled by the interfacial chemical reaction, and the leaching mechanism indicated that the highly efficient critical metal leaching was the result of the strong coordination capacity (Cl-), acidity (H+), and reduction capacity (FA) synergistic effect in the DES. This study provides a novel, environmentally friendly, and efficient strategy for critical metals recovery from spent LIBs.

Comprehensive analysis of thermochemical phase evolution and strategic recovery of valuable elements from high-alumina coal fly ash at different thermal conditions

The evaluation of the application potential of high-alumina coal fly ash (HACFA) resources relies on the assessment of the phase composition and leaching behavior of valuable elements. Herein, we systematically investigated the particle size, specific surface area, and morphology of high-alumina high-temperature coal ash (HAHCA) produced under laboratory conditions at different temperatures and quantitatively analyzed phase transformations using the Rietveld method. The results revealed that the HAHCA particle size gradually increased, specific surface area gradually decreased, and pores became lesser with the increasing coal combustion temperature of high-alumina coal (HAC) from 400 °C to 1300 °C. Furthermore, HAHCA phases sequentially changed across various temperatures, its main phases at a coal combustion temperature of 400 °C included 29.8 % kaolinite, 6.9 % boehmite, and 5.4 % calcite, but the crystalline phases were the most abundant and turned into 41.2 % mullite, 13.7 % corundum, and 11.6 % plagioclase when the coal combustion temperature reached 1300 °C. Additionally, the leaching behavior of 28 major and trace valuable elements of HAHCA under acidic and alkaline conditions was investigated. Most metal elements easily leached from HAHCA under acidic conditions at coal combustion temperatures of 600 °C–800 °C: the optimal leaching efficiencies of Al, Li, K, Rb, Mg, Ca, Sr, and Ba were 67.64 %, 92.71 %, 76.67 %, 73.46 %, 86.74 %, 98.87 %, 98.42 %, and 61.19 %, respectively. Si, a nonmetallic element, achieved a high leaching efficiency of 48.27 % under alkaline conditions at a coal combustion temperature of 1300 °C. Interestingly, only Mo exhibited a high leaching efficiency of approximately 98 % under acidic and alkaline conditions.

Repurposing Kraft black Liquor as Reductant for Enhanced Lithium-Ion Battery Leaching.

The economic advantages of H2SO4 make it the acid of choice for the hydrometallurgical treatment of waste lithium-ion batteries (LIBs). However, to facilitate the full dissolution of the higher valency metal oxides present in the cathode black mass, a suitable reducing agent is required. Herein, the application of industrial black liquor (BL) obtained from the Kraft pulping for papermaking is investigated as a renewable reducing agent for the enhanced leaching of transition metals from LIB powder with H2SO4. The addition of acidified BL to H2SO4 significantly improved the leaching efficiency for a range of LIB cathode chemistries, with the strongest effect observed for manganese-rich active material. Focusing on NMC111 (LiMnxCoyNizO2) material, a linear correlation between the BL concentration and the leaching yield of Mn was obtained, with the best overall leaching efficiencies being achieved for 2.0 mol L-1 H2SO4 and 50 vol % of BL at 353 K. A quasi-total degradation of oxygenated and aromatic groups from the BL during NMC111 dissolution was observed after leaching, suggesting that these chemical groups are essential for LIB reduction. Finally, the leached transition metals could be easily recovered by pH adjustment and oxalic acid addition, closing the resource loop and fostering resource efficiency.