Improving valuable metal ions capturing from spent Li-ion batteries with novel materials and approaches

Inclusive study of peanut shells derived activated carbon as an adsorbent for removal of lead and methylene blue from water

Green and efficient agro-waste-based activated carbon has been prepared utilizing peanut shells for adsorptive elimination of an industrial dye, methylene blue, and lead from polluted water. The carbonaceous biomass obtained from peanut shells was chemically activated using either NaOH, ZnCl2, or steam and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2 adsorption and desorption studies. The adsorption process was optimal for methylene blue at alkaline pH, while pH 4.5 was optimal for Pb (II) adsorption. The adsorption takes place through pseudo-second-order kinetic, and the rate-governing step of the adsorption procedure are intraparticle diffusion and film diffusion. Furthermore, the thermodynamics of the adsorption process has been studied, and the obtained Gibbs free energy (ΔG°) values are negative (- 35.90 to - 43.59 kJ mol-1) indicating the spontaneous adsorption of the investigated pollutants on the prepared activated carbon. As per the correlation coefficient, the obtained results were best fit by the Langmuir isotherm with maximum adsorption capacity of 303.03 mg g-1 for methylene blue and 130.89 mg g-1 for Pb (II). The activated carbon successfully removed methylene blue and Pb (II) with %removal exceeding 95%. The mechanisms of interaction of Pb (II) with the activated carbon is a combination of electrostatic interaction and ion exchange, while methylene blue interacts with the activated carbon via π-π interaction, hydrogen bonds, and electrostatic interaction. Thus, the prepared activated carbon has been employed to decontaminate wastewater and groundwater samples. The developed agro-waste-based activated carbon is a promising, cost-efficient, green, and accessible tool for water remediation.

Recovery of lithium and copper from anode electrode materials of spent LIBs by acidic leaching

In view of the importance of environmental protection and resource recovery, recycling of spent lithium ion batteries (LIBs) is quite necessary. In the present study, lithium and copper are recycled to lithium carbonate and copper oxide from anode electrode material of the spent LIBs. The anode electrode material is firstly treated with hydrochloric acid to leach lithium (96.6%) and then with nitric acid to leach copper (97.6%). Furthermore, lithium and copper are recovered as lithium carbonate and copper oxide from their respective solutions using precipitation and calcinations. These synthesized products are further characterized using XRD, FE-SEM, and EDX analysis. Finally, a simple process is proposed for the recovery of lithium and copper from anode electrode material of spent LIBs.

Synergistic Approach for Selective Leaching and Separation of Strategic Metals from Spent Lithium-Ion Batteries

Recycling spent Li-ion batteries (LIBs) is paramount to pursuing resource efficiency and environmental sustainability. This study introduces a synergistic approach for selectively leaching and separating strategic metals from waste LIBs, representing a more efficient alternative to traditional single-acid-based leaching methods. The research also thoroughly analyzes diverse extraction parameters, aiming to achieve clean metal separation through synergistic concepts rather than single-phase extraction. The outcome of this study is developing a comprehensive downstream process, advancing the cause of sustainable waste management in the LIB industry. Under specific conditions with 0.6 mol/L total acid content (0.5 mol/L tartaric acid + 0.1 mol/L ascorbic acid), 99.9% cobalt and 100% lithium were effectively leached. The subsequent extraction process achieved a clean separation, with 48.3% of cobalt extracted using a mixture of 0.1 mol/L Alamine-336-Cyanex-272 (A-336-Cy-272) from the leach liquor with no coextraction of lithium, and this efficiency was improved to 67.3% by adjusting the pH from 2.44 to 7.5. However, it is worth noting that increasing the extractant concentration led to an antagonistic effect. To further enhance cobalt enrichment in the organic phase, the McCabe-Thiele plot method was recommended, employing saponified Cy-272. Moreover, the regeneration of saponified Cy-272 was investigated, and the stripped solution was processed with NaOH to form Co(OH)2, subsequently converting it into cobalt oxide (Co3O4) through calcination.

The mechanism and behavior of cesium adsorption from aqueous solutions onto carbonated cement slurry powder

In this study, microstructural differences and changes in the adsorption capacity of cesium between cement and carbonated cement were investigated. Cement blocks were ground to powder for rapid carbonation, and microscopic variations were characterized by XRF, XRD, FT-IR, SEM, BET, and TGA. The characterization results show that the conversion of Ca(OH)2 and calcium silicate hydrate (C-S-H) gel to CaCO3 in cement after carbonation. And the component of Ca(OH)2 in the powder sample disappeared after three days of rapid carbonation. Batch experiments were used to investigate adsorption under the influence of time, initial cesium concentration, temperature, and ion coexistence. Pseudo-second-order kinetic and Langmuir isothermal model fitting could better describe the adsorption process and the results show that the maximum adsorption capacity of cement after carbonation surges from 29.6 μg‧g-1 to 1.58-5.89 mg‧g-1. (Different carbonating times lead to varying adsorption capacity.) The adsorption capacity decreases with increasing temperature. At temperatures of 293 K and 333 K, the calculated Gibbs free energy change values of cement with different carbonated degrees adsorbing cesium are -10.3 ∼ -14.9 kJ‧mol-1 and -8.03 ∼ -12.4 kJ‧mol-1. And the calculated values of enthalpy change and entropy change are -18.8 ∼ -23.8 kJ‧mol-1 and -27.9 ∼ -37.1 J‧mol-1‧K-1. Combining the characterization and adsorption results, the huge increase in cesium adsorption capacity is closely related to the conversion of Ca(OH)2 to CaCO3, which will provide a new perspective on the adsorption mechanism of cesium in cement.

Direct regeneration of spent LiFePO4 materials via a green and economical one-step hydrothermal process

The rapid development of electronic devices, electric vehicles and mobile energy storage devices, has increasingly emphasized the shortage of lithium resources for us in lithium-ion batteries are developing rapidly. The key to the disposal of spent lithium-ion batteries is to carry out green and efficient regeneration. Herein, we propose a one-step hydrothermal process for the direct regeneration of spent LiFePO4. To reduce the Fe3+ in the spent LiFePO4, the hydroxyl group was oxidized to an aldehyde group via a decarburization reaction, with DL-malic acid utilized as a low-cost and environmentally friendly reducing agent. The effects of various different Li concentrations, hydrothermal times and hydrothermal temperatures on the performance of regenerated LiFePO4 were investigated. The results revealed optimal electrochemical performance under a Li concentration of 1.2 mol L-1, a hydrothermal time of 6 h, and a hydrothermal temperature of 100 °C. The cycling stability of LiFePO4 regenerated under these conditions considerably improved. The initial discharge specific capacity and the discharge specific capacity of the regenerated LFP after 200 cycles were 138.4 mAh g-1 and 136.6 mAh g-1. All coulomb efficiencies of the regenerated LFP were above 97.2 %, and the capacity retention rate was 98.7%. This developed method can therefore be considered a green and feasible means for regeneration of LiFePO4.

Effective Adsorption and Removal of Doxorubicin from Aqueous Solutions Using Mesostructured Silica Nanospheres: Box-Behnken Design Optimization and Adsorption Performance Evaluation

The aim of this study is to evaluate the efficacy of mesoporous silica nanospheres as an adsorbent to remove doxorubicin (DOX) from aqueous solution. The surface and structural properties of mesoporous silica nanospheres were investigated using BET, SEM, XRD, TEM, ζ potential, and point of zero charge analysis. To optimize DOX removal from aqueous solution, a Box-Behnken surface statistical design (BBD) with four times factors, four levels, and response surface modeling (RSM) was used. A high amount of adsorptivity from DOX (804.84 mg/g) was successfully done under the following conditions: mesoporous silica nanospheres dose = 0.02 g/25 mL; pH = 6; shaking speed = 200 rpm; and adsorption time = 100 min. The study of isotherms demonstrated how well the Langmuir equation and the experimental data matched. According to thermodynamic characteristics, the adsorption of DOX on mesoporous silica nanospheres was endothermic and spontaneous. The increase in solution temperature also aided in the removal of DOX. The kinetic study showed that the model suited the pseudo-second-order. The suggested adsorption method could recycle mesoporous silica nanospheres five times, with a modest reduction in its ability for adsorption. The most important feature of our adsorbent is that it can be recycled five times without losing its efficiency.

Recover value metals from spent lithium-ion batteries via a combination of in-situ reduction pretreatment and facile acid leaching

The pretreatment of cathode material before leaching is crucial in the spent lithium-ion battery hydro-metallurgical recycling. Here research demonstrates that in-situ reduction pretreatment could dramatically improve the leaching efficiencies for valuable metals from cathodes. Specifically, calcination under 600 °C without oxygen using alkali treated cathode can induce in-situ reduction and collapse of oxygen framework, which is ascribed to the carbon inherently contained in the sample and promote the following efficient leaching without external reductants. The leaching efficiencies of Li, Mn, Co and Ni can remarkably reach 100%, 98.13%, 97.27% and 97.37% respectively. Characterization methods, such as XRD, XPS and SEM-EDS, were employed and revealed that during in-situ reduction, high valence metals such as Ni³⁺, Co³⁺, Mn⁴⁺ can be effectively reduced to lower valence states, conducive to subsequent leaching reactions. Moreover, leaching processes of Ni, Co and Mn fit well with the film diffusion control model, and the reaction barrier is in accordance with the order of Ni, Co and Mn. In comparison, it is observed that Li was leached with higher efficiency regardless of the various pretreatments. Lastly, an integral recovery process has been proposed and economic assessment demonstrates that in-situ reduction pretreatment increases the benefit with a negligible cost increase.

Two-step leaching of spent lithium-ion batteries and effective regeneration of critical metals and graphitic carbon employing hexuronic acid

Recovering precious metal ions like Co, Li, Mn, and Ni from discarded lithium-ion batteries (LIBs) has significant environmental and economic benefits. Also, graphite will be in high demand in the coming years due to the development of LIBs for use in electric vehicles (EVs) and the need for it for electrodes in a variety of energy storage devices. However, it has been overlooked during the recycling of used LIBs, which resulted in resource waste and environmental pollution. In this work, a comprehensive and environmentally friendly approach for recycling critical metals as well as graphitic carbon from discarded LIBs was proposed. To optimize the leaching process, various leaching parameters were investigated by employing hexuronic acid or ascorbic acid. The feed sample was analyzed using XRD, SEM-EDS, and a Laser Scattering Particle Size Distribution Analyzer to determine the phases, morphology, and particle size. 100% of Li and 99.5% of Co were leached at the optimum conditions of 0.8 mol L^-1 ascorbic acid, a particle size of -25 μm, 70 °C, 60 min of leaching time, and 50 g L^-1 of S/L ratio. A detailed study of the leaching kinetics was carried out. The leaching process was found to be well-fitted with the surface chemical reaction model based on the findings of temperature, acid concentration, and particle size variations. To obtain pure graphitic carbon after the initial leaching, the leached residue was subjected to further leaching with various acids (HCl, H₂SO₄, and HNO₃). The Raman spectra, XRD, TGA, and SEM-EDS analysis of the leached residues following the two-step leaching process were examined to exemplify the quality of the graphitic carbon.

Enhanced Adsorption and Evaluation of Tetracycline Removal in an Aquatic System by Modified Silica Nanotubes

In the present study, a nanocomposite adsorbent based on mesoporous silica nanotubes (MSNTs) loaded with 3-aminopropyltriethoxysilane (3-APTES@MSNTs) was synthesized. The nanocomposite was employed as an effective adsorbent for the adsorption of tetracycline (TC) antibiotics from aqueous media. It has an 848.80 mg/g maximal TC adsorption capability. The structure and properties of 3-APTES@MSNT nanoadsorbent were detected by TEM, XRD, SEM, FTIR, and N₂ adsorption-desorption isotherms. The later analysis suggested that the 3-APTES@MSNT nanoadsorbent has abundant surface functional groups, effective pore size distribution, a larger pore volume, and a relatively higher surface area. Furthermore, the influence of key adsorption parameters, including ambient temperature, ionic strength, initial TC concentration, contact time, initial pH, coexisting ions, and adsorbent dosage, had also been investigated. The 3-APTES@MSNT nanoadsorbent's ability to adsorb the TC molecules was found to be more compatible with Langmuir isothermal and pseudo-second-order kinetic models. Moreover, research on temperature profiles pointed to the process' endothermic character. In combination with the characterization findings, it was logically concluded that the 3-APTES@MSNT nanoadsorbent's primary adsorption processes involved interaction, electrostatic interaction, hydrogen bonding interaction, and the pore-fling effect. The synthesized 3-APTES@MSNT nanoadsorbent has an interestingly high recyclability of >84.6 percent up to the fifth cycle. The 3-APTES@MSNT nanoadsorbent, therefore, showed promise for TC removal and environmental cleanup.

Leaching NCM cathode materials of spent lithium-ion batteries with phosphate acid-based deep eutectic solvent

Deep eutectic solvents (DESs) play an important role in efficient recovery of spent lithium-ion batteries (LIBs). In this study, we proposed an efficient and safe method by using a choline chloride-phenylphosphinic acid DES as a lixiviant for the leaching of LiNi_xCo_yMn_zO₂ (NCM) cathode active materials of spent LIBs. The leaching conditions were optimized based on the leaching time, liquid-solid ratio, and leaching temperature. Under optimal experimental conditions, the leaching efficiencies of Li, Co, Ni, and Mn reached 97.7 %, 97.0 %, 96.4 %, and 93.0 %, respectively. The kinetics of the leaching process were well-fitted using the logarithmic law equation. The apparent activation energies for Li, Co, Ni, and Mn have been reported to be 60.3 kJ/mol, 78.9 kJ/mol, 99.3 kJ/mol, and 82.1 kJ/mol, respectively. UV-visible spectroscopy and Fourier transform infrared analysis revealed that the coordination configurations of Ni and Co in the leaching solution were octahedral and tetrahedral, respectively. In addition, the PO bond in phenylphosphinic acid was involved in coordination during leaching. This finding may provide an effective and safe approach for leaching valuable metals from spent LIBs.

One-step selective separation and efficient recovery of valuable metals from mixed spent lithium batteries in the phosphoric acid system

The recovery of valuable elements in spent lithium-ion batteries (LIBs) has attracted more and more attention. Efficient recovery of valuable elements from spent LIBs with lower consumption and shorter process is the target that people have been pursuing. In this study, the valuable metals (Ni, Co, Mn and Li) and FePO₄ products are simultaneously recovered from mixed spent LiNi_xCo_yMn_zO₂ and LiFePO₄ in one step under the optimized condition of 0.88 M H₃PO₄, a mass ratio of LFP/NCM of 2:1, a L/S ratio of 33:1 and 80 ℃ for 120 min without additional auxiliary reagents. Over 60 % of acid consumption is reduced and the process of adjusting pH is avoidable. The leaching efficiencies of the valuable elements reach up to 99.1 % for Ni, 98.9 % for Co, 99.6 % for Li and 97.3 % for Mn. Almost all of Fe is precipitated as FePO₄·2H₂O. By means of the empirical model, the research on leaching kinetics demonstrates that the leaching reaction is internal diffusion-controlled with the apparent activation energy of valuable metals less than 30 kJ/mol. Furthermore, the redox reaction mechanism between spent LiBs has been explored. And the intrinsic driving force in the phosphoric acid system is found out. This finding may provide an innovative and selective recycling method for valuable elements from mixed spent LIBs with high economic benefit and fewer environmental footprints.

Selective extraction of precious metals in the polar aprotic solvent system: Experiment and simulation

The traditional hydrometallurgical process is the mainstream technology to recover precious metals from e-waste, which usually adopts strong acid/base and strong oxide with high environmental cost and energy consumption. In the present study, the selective extraction of precious metals was simulated and experimented with DMF as the solvent and Cl^- ions provided by CaCl₂ and CuCl₂ (oxidizing agent). The leaching and precipitation rates of precious metals (Au, Ag, Pd) can reach more than 98% under optimization conditions. Kinetic data shows that the control model of the leaching process on precious metals was determined by linear fitting of the shrinkage model. The complex trace precious metals were extracted selectively using dimethylglyoxime and deionized water as precipitators by the leaching-precipitation-cycle method. Meanwhile, the waste liquid produced by this reaction process could be cyclically utilized. Furthermore, the leaching mechanism of precious metals was proposed. DMF could be complexed with the metals as well as coordination ions (Cl^-), which can reduce the redox potentials. Cu(II) could be easily reduced to Cu(I) in the DMF system due to the higher second ionization energy of copper, which is not influenced by the hydration effect, thus shifting the equilibrium to the metal leach side. Oppositely, the addition of water promoted the conversion of Cu(I) to Cu(II) since the higher hydration energy of Cu(II) compensates for the second ionization energy. This research opens up a new path of sustainable development and provides basic theory and practical experience for environmentally friendly recovery of precious metals from e-waste.

Functionalized layered double hydroxides composite bio-adsorbent for efficient copper(II) ion encapsulation from wastewater

In this study, naturally abundant and inexpensive bamboo was used to make cheaper activated charcoal for efficient encapsulation of toxic copper (Cu(II)) ion from wastewater. The functionalized bamboo charcoal-Layered double hydroxides (BC-LDHs) composite bio-adsorbent was prepared using co-precipitation method. The composite bio-adsorbent was exploited to eliminate Cu(II) ion with high sensitivity and selectivity from contaminated water. The adsorption parameters including the effect of pH, contact time, adsorbent dose, and effect of initial concentration were optimized in systematic way and the adsorption kinetics and isotherms were investigated for potential use in real sample treatment. The physicochemical properties and morphological structure of the adsorbent were examined using X-ray Diffraction, Scanning Electronic Microscopy, Fourier Transform Infrared Spectroscopy and Thermogravimetric Analysis to understand the Cu(II) ion adsorption mechanism. The adsorption results revealed that the BC-LDH could remove almost 100% of Cu(II) ion from aqueous solution at pH range between 3.0 and 6.0 within 30 min. The maximum monolayer adsorption capacity was determined to be 85.47 mg/g based on the Langmuir isotherm. The adsorption equilibrium data were well-fitted by the Langmuir isotherm model (R² = 0.998) and the experimental kinetic data were supported by the pseudo-second order model (R² = 0.999). The BC-LDH could be reused without losing its adsorption performance in several cycles after successful regeneration with 0.10 M HCl. The Cu(II) ion removal mechanism was postulated with intercalated ion exchange, surface precipitation and interaction between BC-LDH and surface functionalities. Therefore, the highly functional BC-LDH composite could be a promising adsorbent for efficient Cu(II) ion removal from wastewater.