Leaching Solution Research Articles

Selective recovery of antimony from Sb-bearing copper concentrates by integration of alkaline sulphide leaching solutions and microwave-assisted heating: A new sustainable processing route

The technical feasibility of leaching antimony from an antimony-bearing copper sulphide concentrate, using alkaline sulphide solutions and microwave-assisted and non-assisted heating technology, is investigated at a laboratory scale. The leaching test examines the influence of selective leaching reagent (Na2S and NaOH) concentrations, solid/liquid ratio, and temperature. The results indicate that antimony dissolution is highly selective (e.g. only Sb and As are leached), depending on the concentrations of leaching reagents and the leaching temperature. The influence of temperature on the mineral's dissolution, in the range 25–140 °C, is analysed from a thermochemical point of view using equilibrium databases. Under the optimal conditions: leaching agent: 250 g/L Na2S, 60 g/L NaOH, 2 h, 140 °C, with microwave assisted, the leaching efficiency of Sb reached 95.7 %. The antimony content in the copper concentrate is successfully reduced from 1.1 wt% to <0.2 wt% Sb, making it suitable for copper concentrate metallurgical processing. The study demonstrates that increasing temperature and NaOH/Na2S concentrations collectively enhance leaching efficiency, with a statistical significance, reducing both leaching time and the required temperature, compared to non-microwave-assisted leaching. Furthermore, it is established that excess free hydrogen sulphide ions ensure the efficient dissolution of the main impurities associated with penalties, such as antimony and arsenic, with limited copper and iron dissolution from the copper concentrate, predominantly chalcopyrite. Finally, an integrated hydrometallurgical process flowsheet for antimony removal and recovery from a sulphide copper concentrate is proposed.

Study on Column Leaching Behavior of Low-Grade High Calcium and Magnesium Copper Ore

This paper studies the process mineralogy, mechanism, and kinetics of column leaching behavior of low-grade high-calcium–magnesium copper ore. The effect of sulfuric acid concentration, leach solution spraying intensity, and material particle size on column leaching kinetics is discussed. The kinetic analysis of column leaching of copper indicates that sulfuric acid concentration has a significant impact. As sulfuric acid concentration increases, the limiting step of reaction shifts from chemical reaction control to a combination of chemical reaction and diffusion mixing control. Spraying intensity also affects copper column leaching; increasing intensity shifts the limiting step from diffusion control to mixing control, thereby mitigating the effects of diffusion control. Regarding other elements, it is found that iron leaching is primarily controlled by chemical reaction, while calcium leaching is mainly controlled by chemical reaction. As sulfuric acid concentration increases from 10 g/L to 20 g/L, the limiting step for calcium leaching shifts from chemical reaction control to chemical reaction and diffusion-mixing control.

Weak interaction induced selective separation of V/Mo/Co from spent hydrodesulfurization catalyst leaching solution: Mechanism and strategy

Spent hydrodesulfurization catalysts contain more than 10 ∼ 25 wt% V, Mo and Co, which are not only hazardous materials, but also can be considered as valuable secondary resources. The complete separation of these complex critical metals by solvent extraction still needs to be improved. Here, a selective extraction route for the separation of V/Mo/Co is proposed based on the weak interaction differences between extractants and metal, which is realized by theoretical calculation and experimental verification. This process does not require pretreatment of N1923 and Cyanex272 (C272), thus reduced the consume of acid and base as well as generation of waste water. With the preliminary results of V/Mo, Co/Mo, and V/Co separation, the weak interaction between extractants and metal molecules was revealed by quantum chemical calculations quantitatively. The molecular charge distribution, surface electrostatic potential distribution (ESP) and the average local ionization energy (ALIE) shows the priority reactivity of the metal molecules as: H6V10O28 > H2Mo4O13 > H4V4O12 > H3VO4 > H2MoO4. The independent gradient model based on Hirshfeld partition (IGMH) show differences in the weak interaction forces as: N1923-V>C272-Mo > C272-V>N1923-Mo > C272-Co. The selective separation process of V/Mo/Co was designed with the guide of above results. The combined recovery of the three metals V, Mo and Co amounted to 83.88 %, 87.08 %, and 99.01 %, respectively. The whole route reduces 3.92 t sulfuric acid and 7.83 t sodium hydroxide per solid, and reduces 1.99 t carbon emissions compared to the conventional route.

Selective removal of iron from sulfuric acid leaching solution of aerospace magnetic material scraps by jarosite process

Aerospace magnetic material scraps are abundant in cobalt and nickel. Sulfuric acid leaching process is an efficient method for extracting them. But it is a non-selective process, a significant amount of iron dissolves in the solution. This study focuses on the selective removal of iron from this solution using the jarosite process. Eh-pH diagram of K-S-Fe-H2O system was established. Based on thermodynamic analysis, H2O2 is used to oxidize Fe2+ into Fe3+, achieving efficient and selective removal of iron from the solution containing cobalt and nickel. The optimal conditions are as follows: temperature 95°C, K2SO4 dosage coefficient 1.5, seed dosage 10 g/L, time 90 min, pH 1.76, and endpoint pH controlled at approximately 3. Under these conditions, the iron removal efficiency is above 99%, while the loss ratios of cobalt and nickel are below 2%. The product is characterized by XRD and SEM-EDS. Results indicate that the product is jarosite ((K,H3O)Fe3(SO4)2(OH)6), exhibiting an ellipsoid structure with the mean particle size in the range of 0.2–5.0 μm. Temperature, pH value and seed dosage significantly affect reaction rate, particle size and crystallinity, and K2SO4 dosage mainly affects reaction rate and the morphology of jarosite. The jarosite crystallization kinetics can be described by the Avrami equation, with an Avrami index (n) of approximately 2.5 and the apparent activation energy of 42.68 kJ/mol.

Mine waste rock as a soil amendment for enhanced weathering, ecosystem services, and bioenergy production

Enhanced weathering of terrestrial rock material is a promising method for the removal of anthropogenic CO2 emissions from the atmosphere. Herein, we demonstrate that an ameliorated mining waste product can be effectively weathered in the soil environment when used as a soil amendment in conjunction with the cultivation of fast-growing willows (Salix matsudana Koidz. ⨯ S. alba L. “Austree”) in a pot study environment. Utilizing this locally sourced amendment minimizes emissions associated with grinding and transportation of enhanced weathering materials. Results showed that the willows were able to tolerate the relatively high metal concentrations of this amendment and sequester inorganic carbon (C) through the production of bicarbonate in soil solution. During the period of peak plant growth (10 weeks after planting), alkalinity measurements of soil solution from pots with willows and the addition of 25% by mass mine waste product indicated an additional 10 mg of inorganic C sequestration per liter of leached soil solution compared to unamended soils with willows. This represents 4.5 times the inorganic C sequestration rate of unamended soils. The addition of ameliorated mining waste also increased the pH of the soil solution by up to two units (pH of 6 in control vs. pH of 8 with the addition of 25% by mass mineral amendment). In addition to inorganic C sequestration, weathering of the ameliorated mining waste product may also provide base cations (such as calcium and magnesium) which could improve soil fertility. These results are encouraging for future investigation of ameliorated mine waste rock to sequester carbon and enhance the production of willows grown for ecosystem services and phytotechnologies.

A novel thermosensitive porous imprinted polymer for selectively separating ReO4− based on Pickering‐like emulsion polymerization

AbstractIn this study, we combined the imprinting technique, temperature‐sensitive polymer, and Pickering emulsion polymerization to prepare a temperature‐sensitive porous imprinted polymer. First, the temperature‐sensitive block polymer PDEA‐b‐P (DEA‐co‐AM) was prepared by reversible‐addition fragmentation chain transfer polymerization, and then a temperature‐sensitive porous ReO4− imprinted polymer (ReO4−‐TPIP) was prepared using the Pickering‐like polymerization technique, which was introduced to the preparation of the imprinted polymer. The structure and morphology of the polymer were characterized by FTIR, SEM‐EDS, and BET. The adsorption experiments showed that the maximum adsorption (Q), separation (R), and desorption (D) of ReO4−‐TPIP were 0.1568 mmol/g, 3.41, and 85.22%, respectively, and the adsorption equilibrium could be reached after 120 min, which decreased to 0.1212 mmol/g, 1.23, and 70.01% after repeated use for 11 times. These results indicate that ReO4−‐TPIP has good adsorption and reusability properties. The adsorption studies showed that ReO4−‐TPIP conformed to the zero‐level kinetic model in the pre‐adsorption stage, the quasi‐one‐level kinetic model in the late stage, and the isothermal adsorption process conformed more to the Langmuir model. In addition, in the secondary leach solution of high‐temperature alloys, the purity of rhenium in the solution increased from 35.4119% to 53.4812% after one adsorption/desorption cycle. The prepared ReO4−‐TPIP provides a new material and strategy for the selective separation and purification of rhenium in complex rhenium‐containing solutions for the industry.

A Large-Scale Electrometallurgical Treatment of Waste Printed Circuit Board (WPCB) in Ethylene Glycol for Metal Recovery

The accumulating generation of E-Waste is gaining more concern. This work reported an environmental-friendly approach, slurry electrolysis (SE), to highly effectively recover metals embedded in Waste Printed Circuit Board (WPCB). The reusable ethylene glycol (EG) is employed as the electrolyte, simple and cheap graphite rod, and copper strip function as anode and cathode, respectively. And it could operate at room temperature and pressure. EG can withstand for hours or days of electrolysis with no sign of degradation but evaporation. It has shown a good selectivity in the leaching solution with metal ions. The metals with high activity could be electrochemically oxidized but not reduced. The metals with low activity could undergo both. From the current results, the system has demonstrated a moderate faraday efficiency of the cathode of 67.7%, successfully recovered 95-97% copper from the real WPCB powder with 61% copper, 24% Al, 10% Zn, 3% Sn and some trace metals. Notably, the extracted metals are all in powder form and easily extractable, indicating that it requires only some facile treatments to make the powder eligible for replacement from mining. This study proved another novel approach to recovering metals from E-Waste on an industrial scale.

Recycling Process of Spent Alkaline and Zn-C Batteries for the Re-Utilization in Rechargeable Zn-Ion Battery

The Zn, Mn and C extraction processes from spent primary batteries and the synthesis of recycled Zn film, MnO2 and MnO2/C for Zn-ion battery application were developed in the project. The Zn, Mn and C extraction process involved the acid leaching of Zn and Mn ions from the spent alkaline and Zn-C battery electrodes in the lab-scale was initially investigated using various leaching conditions. The acid leaching using 0.5-2 M HCl and H2SO4 at ambient temperature providing Zn extraction efficiencies in a range of 72.3-95.3%. By introducing an inexpensive reducing agent namely sodium sulfide (Na2S), sodium metabisulfite (Na2S2O5) or hydrogen peroxide (H2O2) in 2M H2SO4, the Mn extraction efficiency for Mn was increased from 21.9% (with no reducing agent) up to 48.4%, 82.8% and 98.9%, respectively. The upscale leaching study was subsequently performed in a 100-L pilot scale reactor demonstrated the Zn and Mn extraction efficiencies of 71% and 65%, respectively. Using the leaching solutions from the upscale hydrometallurgical route, Zn-film fabrication via electrodeposition process, and the MnO2 and MnO2/C synthesis via hydrothermal techniques were performed. Additionally, the one-step synthesis of MnO2/C via one-step hydrothermal method with no acid leaching was also explored in this study. The recycled Zn, MnO2, MnO2/C and C residual were subsequently used as the anode and cathode main components in the CR2032 and pouch-cell rechargeable Zn-ion batteries. The recycled MnO2 and MnO2/C provided similar performance as the commercial products, which indicating the recycled MnO2, MnO2/C could be effectively utilized in the Zn-ion battery, while the utilization of recycled Zn-film provided slightly lower performance compared to that of the commercial Zn foil.

Modeling and Experimental Validation on a Bipolar Membrane Electrodialysis Stack for Lithium Sulfate Separation

Recycling lithium-ion battery materials is a crucial step to achieving a circular economy. Among a few methods for recycling spent battery materials, a novel hydrometallurgical recycling process with leaching by acids and precipitation by bases was proposed [1]. Lithium sulfate (Li2SO4) leachate solution is generated at the end of the closed-loop recycling process. Such Li2SO4 solution can be separated by electrodialysis (ED) to form H2SO4 and LiOH solutions, which are reused for leaching and precipitation of the recycling process. The present study attempts to model this ED process and validate the model with experimental data.An ED stack based on bipolar membranes (EDBM); see Fig. 1a, was built with repetitive unit cells, each consisting of a bipolar membrane, anion exchange membrane (AEM), and cation exchange membrane (CEM). Li2SO4 enters the dilute channel and splits into SO4 2- and Li+, which travel through the AEM and CEM, respectively. Water electrolysis occurs within the bipolar membrane to produce H+ and OH-, which react with SO4 2- and Li+ to form H2SO4 and LiOH, respectively; see Fig. 1b. A two-dimensional (2D) multiphysics model is developed to elucidate the coupled transport processes within the unit cell. Conservation equations for mass, momentum, and species are solved. The transport of ions is described by the Nernst-Planck equation. Electroneutrality equations are satisfied in these membranes and channels. Electro-osmotic water transport across the membranes is considered.The effective cross-sectional area of the stack was 121.8 cm2 (70mm×174mm). The flow channel between consecutive membranes was 0.8 mm, with a mesh inserted to facilitate mixing. Experiments were carried out with the EDBM stack over different conditions such as current density, number of cell pairs, and flow rates. All experiments were operated at constant current mode [2]. The feed, acid, and base solutions were recirculated through their tanks at initial concentrations of 1.1, 0.1, and 0.1 mol/L. The ion concentrations of the solutions were measured periodically with inductively coupled plasma (ICP) mass spectrometry. The weight and the pH value of the solution tanks were also recorded.The concentration of H2SO4 is found to increase with time linearly, whereas that of LiOH levels off due to a significant electro-osmosis that drags water through the CEM into the concentrate channel. This drag reduces the performance of EDBM due to the dilution of water into the concentrate compartment. However, electro-osmotic water transport also leads to a velocity increase in the concentrate channel, which is consistent with the simulation results in our previous ED model [3]. It is found that the voltage loss across the bipolar membrane ca. 1V accounts for a significant part of the unit cell of about 1.27V.The migration of ions in electrodialysis mainly relies on diffusion and electric drive. The streamlines and the concentration distribution of Li+ under different voltages indicate that increasing voltage accelerates ion migration, see Fig. 1(c). Furthermore, the effect of the potential and concentration variations on EDBM performance is also investigated. The effects of applied current density and inlet velocity are studied on species concentrations and fluxes. Increasing the stack current density accelerates the separation process, see Fig. 1(d). It is found that increasing the solution flow rate can increase LiOH solution concentration, ion recovery rate, and current efficiency. However, the impact of the flow rate is low.This work demonstrates that EDBM can be a simple and energy-saving alternative to the current chemical precipitation method to produce LiOH from Li2SO4. The present study provides new insights into optimal operation and design for Li2SO4 EDBM. The findings are helpful in determining how the stack can be scaled up for practical application.[1] A review of recycling spent lithium-ion battery cathode materials using hydrometallurgical treatments, JCY Jung, PC Sui, J Zhang, J. Energy Storage 35, 102217, 2021.[2] Electrodialysis of a Lithium Sulphate Solution: An Experimental Investigation. B Kang, D Kang, JCY Jung, A Asadi, PC Sui, J. Electrochem. Soc. 169 (6), 063515, 2022.[3] A Comprehensive Computational Fluid Dynamics Modeling of Lithium Sulphate Electrodialysis, A Asadi, HB Harandi, JCY Jung, PC Sui, J. Electrochem. Soc. 170(9), 093502, 2023. Figure 1

Exploiting Deep Eutectic Solvents in LiFePO4 Battery Recycling: From Cathode Leaching to Resynthesis

Nowadays, the increasing demand for electronic devices and electric vehicles influences the request for Lithium-Ion Batteries (LIBs), which are worldwide the most exploited electrochemical energy storage systems for portable devices and are expected to completely dominate also the sector of transportation soon. In particular, the use of LIBs with ordered-olivine structure LiFePO4 (LFP) cathodes stands out ever since their invention in 1997, being a valid solution in terms of durability, reliability, and safety, essential characteristics in the electric mobility application combined with the benefit of low content of critical raw materials, CRMs. Considering that the average life of LFP cathodes is about 5-8 years, the management of these materials as waste becomes essential: the growing number and volumes of LIBs that are currently produced is inevitably intended to correspond to the number of LIBs that will reach the end of their life, becoming waste that are accumulating, posing a staggering danger. [1,2] An also important consideration concerns the conditions required to synthesize LFP for electrochemical purposes, as it is necessary to coat the surface with conductive species, controlling the morphology and reducing the particle size, thus complicating the synthesis and making it economically more impactful. [3]In such a context, recycling combines the necessity to produce new LIBs with the need to cope with the increase in batteries’ waste accumulation: this can limit the disposal of waste batteries into landfills, thus decreasing the inevitable hazardous environmental consequences, while reducing the demand for new mining, re-assigning value to raw materials, in an attempt to minimize the costs that would be required to synthesize pristine LFP-based cathodes. Today, recycling is already implemented at the industrial level, exploiting the pyrometallurgy approach, which involves thermal treatments at very high temperatures (>1000°C) allowing for the recovery of only a fraction of valuable metals; nevertheless, this approach has a strong environmental impact due to the high energy demand and high carbon footprint. The hydrometallurgical approach is also employed, exploiting the leaching process with strong inorganic acids; however, this brings problematic issues, because producing such acids is itself a polluting process, and acidic wastewater management is a demanding problem. Moreover, today these processes involve the recycling of the most diffused cathode, LiCoO2, Li(Ni/Mn/Co)O2, LiMn2O4, and the sustainability of recycling relies on the possibility to recover valuable CRMs such as Co and Ni.In the proposed work we are currently investigating the degradation properties of Deep Eutectic Solvents (DESs), cheap and greener mixtures of compounds forming a eutectic system, liquid at room temperature. [4] In particular, the focus is on the leaching of LFP with a DES obtained by mixing different molar ratios of hydrogen bond acceptor and various hydrogen bond donors, in order to assess the best combination to leach the elements out of LFP structure. The key point of such approach is the design of a degradation system that can enable the conditions for the direct re-synthesis of new LFP material. Indeed, here the sustainability of the process cannot be driven by the recovery of CRMs, thus must rely on the close-loop recycling scheme. For this reason, we specifically designed DES compositions that allow for this process.The proposed DESs, which have been easily prepared at mild heating conditions, have been investigated through different techniques; the results obtained on the chemical-physical characterization (via FTIR spectroscopy, Solid-State NMR, viscosity, thermal analysis) will be presented. Among the different DESs, those with the best combination of properties (e.g. low viscosity, high thermal stability) have been explored for the leaching of LFP cathode. The leaching process has been optimized with respect to the temperature, duration, and cathode-to-DES ratio for different DESs, and the leaching yields have been evaluated through ICP-OES analysis. The obtained leached solution has been considered as the starting point for a sol-gel-like synthesis of new LFP material, finally characterized through XRD, TGA, ICP-OES, and SEM-EDX analysis. Tuning the parameters of the synthesis (temperature and duration of the heat treatment, ratio between LFP mass and conductive species to realize the coating) enables to control the morphology and the dimension of the synthesized particles, to find the best condition for the electrochemical application. The electrochemical performances of the resynthesized materials will also be presented.[1] Sun et al., J. Alloys Compd., 818 (2020)[2] Lv et al. ACS Sustain. Chem. Eng., 6 (2018)[3] Yuan et al., Energy Environ. Sci, 4 (2010)[4] Zhu et al., Resour. Conserv. Recycl., 188 (2023)

Selective Lithium Recovery from Spent Lithium Manganate Batteries Using Oxidative Stabilization Technique.

Using oxidizing compounds to handle the recycling of discarded lithium batteries has advanced significantly in recent years. One of the most prominent methods is the sintered electrode powder treatment using pre-used additives, with an aqueous solution of the oxidizing agent fueling highly selective lithium extraction and transition metals retention in the refractory material. Herein, phosphoric acid (H3PO4) was used as the exchanger and hydrogen ions provider, the oxidant (K2S2O8) activity was driven by heating, the raw material structure was deformed and adjusted by the oxidizing drive, and lithium was exhausted, while manganese was converted into manganese(III) phosphate hydrate and manganese dioxide insoluble material. The optimized conditions resulted in a lithium leaching rate of 94.16 % and a separation factor of 95.74 %, while the corresponding manganese leaching rate was limited to less than 5 %. The X-ray diffraction, X-ray spectroscopy, scanning electron microscopy, and inductively coupled plasma mass spectrometry measurements were used to investigate the influence of oxidation driving force and lithium leaching. Finally, the lithium leach solution was continuously stirred with sodium carbonate in boiling water to obtain the precipitate, which was separated and washed several times to obtain high-purity lithium carbonate.

Manufacturing of Fe-Ni Composite Oxide Powder and Leaching Process Optimization Via Nickel Pig Iron(NPI) Raw Materials

The lithium-ion battery industry is experiencing rapid growth in response to the widespread adoption of electric vehicles, leading to a significant increase in demand for high-purity nickel compounds, a critical raw material. As a result, ensuring a smooth supply of nickel resources poses a critical challenge not only for the battery industry but also for enhancing the competitiveness of future clean energy industries. High-purity nickel production is predominantly carried out via the high-pressure acid leach (HPAL) process, which extracts nickel from nickel laterite ores. However, this process involves substantial initial capital investment and consumes significant energy due to high temperatures, high pressure, and strong acids. Additionally, this method is associated with environmental concerns such as water and soil pollution. Furthermore, an alternative approach is proposed, which involves adding sulfur to low-grade nickel pig iron (NPI) to produce the nickel matte, followed by an iron removal process to generate high-purity nickel sulfide. However, this method presents challenges such as waste generation from the iron removal process, high carbon emissions, and the production of large amounts of greenhouse gases. This study explored using anodic oxidation to induce oxidative reactions in NPI to nano-powder. This approach improves nickel recovery efficiency by increasing the surface area compared to the bulk state, allowing leaching at room temperature and atmospheric pressure. As a result, the process becomes simpler, with lower initial capital investment, making it economically viable. Additionally, the process requires less energy consumption, allowing for achieving the breakeven point at an earlier stage. This study compared the characteristics of the nano-powderized NPI under different voltage and current ranges. Furthermore, the nickel leaching efficiency was assessed based on leaching solution conditions.

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.

Efficient extraction of Li and Rb from zinnwaldite via thermal activation and acid leaching

Lithium and its associated rubidium are regarded as the strategic metal resource, which have a wide use in many commercial products. Nowadays, the continuing growth in demand for Li resources, propelling the object of industrial exploitation will focus on low-grade, complex minerals composition and unwieldy ores. Zinnwaldite has received increasing attention as a potential lithium-containing resource in recent years. However, there are a lack of effective extraction processes for zinnwaldite. Hence, this paper proposes an effective method to extract metal cleanly and efficiently from zinnwaldite by using CaO and B2O3 as thermal activation additives and H2SO4 as the leaching agent. The results showed that the destruction of Fe-O and Si-O-Si bonds led to increased extraction efficiency. The breathing vibrations of oxygen atoms symmetric in 4- and 3-membered rings and Si-O symmetric stretch could influence the Li separation from silica skeleton. Ultimately, the 91.32 % Li, 93.09 % Rb, 81.14 % Fe, 95.00 % Al and 71.12 % K were recovered under the optimal conditions. Meanwhile, about 10 % F escaped into the air during thermal activation and the concentration of F in the leaching solution was lower than 2 mg/L. The use of B2O3 provides a valuable reference for the efficient and clean treatment of lepidolite using the salt roasting method.

Efficient Regeneration of Graphite from Spent Lithium-Ion Batteries through Combination of Thermal and Wet Metallurgical Approaches.

With the large-scale application of lithium-ion batteries (LIBs) in various fields, spent LIBs are considered one of the most important secondary resources. Few studies have focused on recycling anode materials despite their high value. Herein, a new efficient recycling and regeneration method of spent anode materials through the combination of thermal and wet metallurgical approaches and restored graphite performance is presented. Using this method, the lithium recycling ratio from spent anode materials reaches 87%, with no metal impurities detected in the leaching solution. The initial Coulombic efficiency of the recycled graphite (RG) materials is 90.5%, with a reversible capacity of 350.2 mAh/g. Moreover, RG shows better rate performance than commercial graphite. The proposed method is simple and efficient and does not involve toxic substances. Thus, it has high economic value and application potential in graphite recycling from spent LIBs.

Lithium recycling from artificial leachate of spent lithium-ion batteries using track-etched membranes for hybrid electrobaromembrane method

Lithium recycling is still poorly developed, but an important source of raw materials for the production of lithium salts. The hydrometallurgical technologies are usually employed to extract lithium from spent lithium-ion batteries. Reagent free membrane technologies such as electrobaromembrane method (EBM) can be used at this stage for the separation of Li+ ions and Co2+, Ni2+, Mn2+. The essence of the method is the simultaneous use of an opposing electric field and a pressure gradient in the device. Non-selective track-etched membrane with wide pores is used for ions separation. The selectivity of EBM separation is achieved due to the different mobility of the separated ions in the electric field. Under optimal conditions, this allows some of the more mobile ions to overcome the barrier of the oncoming convective flow, while others follow it. For the first time, the EBM method was used for long-term extraction of Li+ ions from an artificial leachate solution of spent LIBs. A solution containing the main macro components of typical leachate was processed at 0.3 bar and 125 A/m2 for 50 h. The fluxes of separated Li+, Co2+, Ni2+ and Mn2+ ions through the track-etched membrane were as follows 0.2, −0.02, −0.03 and − 0.08 mol/(m2 × h), respectively. A modification of the track-etched membrane with PDADMAC, which carries a positive charge, has been approved, which makes it possible to increase the rejection of doubly charged ions for more effective lithium isolation.

Eco-friendly solid waste-based cementitious material containing a large amount of phosphogypsum: Performance optimization, micro-mechanisms, and environmental properties

Reusing phosphogypsum (PG) waste to manufacture eco-cementitious materials is sustainable. However, PG faces the challenge of high stacking volume and low utilization rate, and the low-content PG in eco-cementitious materials currently limits its large-scale potential application. This study provides a solution to use high-content PG to fabricate eco-friendly solid waste-based cementitious material (PBC), associated with ground granulated blast furnace slag (GGBS), fly ash (FA), and hydrated lime. Respond surface methodology (RSM) was undertaken to optimize and discuss the influence of independent design factors of GGBS, FA, and hydrated lime content on the unconfined compressive strength (UCS). Besides, the micro-mechanisms and environmental properties of PBC were also investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and the leachate test. The results indicated that the optimal raw material contents were (by mass): 50.57% PG, 28% GGBS, 20% FA, and 1.43% hydrated lime. The UCS of the optimal PBC mixture is 23.57 MPa at 28 days, which was confirmed via experimental verification (24.65 MPa). Hence, the RSM is an effective method for optimizing PBC's UCS. The micro-mechanisms analysis shows that the ettringite is the primary hydration product within the reaction system of PBC, which is attributed to the substantial amount of PG. The leachate test results indicate that the fluoride ion concentration of the leaching solution of PBC remains below the PG, and the pH value falls within the range of 6–9. The leaching test results meet the Chinese environmental standard of GB 8978-1996. The cost and CO2 emission of the optimal PBC mixture could achieve a reduction of 71.25% and 99.98%, respectively, compared to Ordinary Portland cement (OPC). The findings of this study could serve as a theoretical foundation for the practical implementation of large-scale and efficient utilization of PG waste. The developed eco-friendly PBC has excellent potential to partially substitute conventional OPC binders and reduce engineering project costs.

Direct recovery of high-purity lithium via nanofiltration membranes from leaching solution of spent lithium batteries

The recycling of spent ternary lithium batteries (T-LIBs) promises scarce strategic resource recovery, however, efficient and selective recovery of Li+ from T-LIBs leaching solution with complex components is still a considerable challenge. Herein, we present a polyamide nanofiltration membrane based on the positively charged nanoscale dispersion interlayer for the first application in recycling lithium from the leaching solution of spent T-LIBs. The electronegativity is weakened by positive charge within the interlayer, which enhance the effect of Donnan exclusion. The pos-TFNi membrane can effectively permeate Li+ while the interfering divalent ions are almost completely separated, achieving the high purity (separation factor ≥ 93.5) and high recovery rate (79.2%) of Li+ from leaching solution simultaneously, with a 6.2-fold improvement in the separation factor over the pristine TFC membrane, and outperformed the majority of the NF membranes. This work represents a reference for the recycling of the massive accumulation of spent T-LIBs worldwide.

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting (SCS) dust using a sulfating roasting−water leaching process were investigated. The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl. Under the sulfating roasting conditions of the roasting temperature of 250 °C and the sulfuric acid excess coefficient of 1.8, over 74 wt.% of F and 98 wt.% of Cl were volatilized into flue gas. Approximately 98.6 wt.% of Zn and 96.5 wt.% of Cu in the roasting product were dissolved into the leaching solution after the water leaching process, while the leaching efficiencies of Pb and Sn were only 0.12% and 0.22%, respectively. The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.

Sustainable Hydroponics Using Zero-discharge Nutrient Management and Automated pH Control

Here we review the 400-year history of hydroponic culture and describe a unique management approach that does not require leaching or discarding solution between harvests. Nutrients are maintained at a low and steady concentration by daily additions of a dilute solution that replaces the transpired water along with the nutrients that were removed in growth each day. A stable pH and a low steady-state concentration of ammonium are maintained through automated additions of a solution of nitric acid and ammonium nitrate. Ample solution volume (at least 20 cm deep) stabilizes nutrient concentrations, reduces root density, and improves uniformity. Gentle aeration at ≈100 mL·min−1·L−1 maintains dissolved oxygen near saturation and increases uniformity throughout the rhizosphere. These practices facilitate a uniform, closed, root zone with rigorous pH control that provides the micromolar nutrient concentrations of N and P that are representative of field soils.