Recycling metals from wastes: a novel application of mechanochemistry

Mechanochemical degradation performance of lindane in different types of soils: The effects of soil properties and elemental components

Although mechanochemical remediation of organic-contaminated soil has received substantial attention in recent years, the effects of soil properties on soil remediation performance are not clear. In this work, the properties and elemental components of 16 soils were tested, and the mechanochemical degradation performance of lindane in these soils was investigated through experiments. Most importantly, the relationships between soil variables and the mechanochemical degradation rates of lindane in the additive-free and CaO systems were elucidated. The results showed that the mechanochemical degradation efficiencies of lindane in the 16 soils were significantly different without additives, with a range of 31.0 %-97.2 % after 4 h. The mechanochemical degradation rates of lindane in the 16 soils varied from 0.7 h-1 to 15 h-1 after the addition of 9 % CaO. Correlation analysis, redundancy analysis and the partial least squares path modeling results clearly showed that the main factors affecting the reaction rate (k1) without additives were organic matter (-) > clay (+) > bound water (-) > Si (+). After the addition of 9 % CaO, the order in which the main factors affected the reaction rate (k2) was organic matter (-) > bound water (-) > Ti/Fe/Al (-) > pH (+) > clay (+). The established and corrected multiple nonlinear regression equations can be used to accurately predict the mechanochemical degradation performance of hexachlorocyclohexanes in actual soils with and without additives.

Highly efficient recovery of Zn2+/Cu2+ from water by using hydrotalcite as crystal seeds

The efficient and waste-free recovery of heavy metals is critical for heavy metal wastewater treatment. In this work, we explored how heavy metals can be recovered as valuable chemicals in the presence of crystal seeds. Hydrotalcite (one kind of layered double hydroxides (LDHs)) was used as crystal seeds to recover Zn2+ in the presence of Al3+ from water (i.e., seed-Zn2+-Al3+ system), which was compared with the monometallic heterogeneous system (seed-Zn2+) and direct coprecipitation (Zn2+-Al3+) system. Our results demonstrated that the seed-Zn2+-Al3+ system possessed a recovery rate of 2.6-2.8 times and a recovery kinetic rate of 2.7-5.9 times higher than those of the other two systems. Differing from the latter two systems, hydrotalcite seeds could induce Zn2+ and Al3+ to form ZnAl-LDH in seed-Zn2+-Al3+. Interestingly, the ZnAl-LDH presents a compositional divalent/trivalent cation molar ratio of ca. 3, which is comparable with the value in the hydrotalcite. It was demonstrated that the hydrotalcite seeds could act as a template to significantly induce the formation of ZnAl-LDH complying with the seed's structure and compositional ratio. Similar induction effect of seeds as the Zn2+ system was further verified in Cu2+ systems. This work provides a novel strategy for efficient recovery of heavy metals with product selectivity.

Lead recovery from waste CRT funnel glass by mechanochemical reaction with reductive Al powder

The safe disposal of waste cathode ray tubes (CRTs) has always been a serious problem due to the stable microstructure of toxic lead (Pb) located in glass. Thousands of researches have been trying to explore environmental and efficient ways to dispose of waste CRTs. To recycle lead from waste CRT funnel glass effectively, a mechanochemical reduction method has been developed in this research. Aluminum was used as a reductant, and the hydrochloric acid solution was used in the leaching process to separate lead from the solution. After mechanochemical ball milling with aluminum, lead ion in CRT funnel glass was transferred into nano-sized element lead. Lead recovery from CRT funnel glass increased significantly as compared to non-activated leaded glass. Approximately 40 % of lead was leached after mechanical activation without aluminum, while over 96 % of lead in the CRT funnel glass could be recovered after mechanochemical reduction with aluminum. Lead chloride (PbCl2) can be recycled from the leaching solution after cooling crystallization. Nano-sized Pb formation and the structural changes of leaded CRT funnel glass by mechanochemical reduction process contributed to obvious improvement in lead recovery. This research provided a high-efficiency and feasible approach for recovering lead in form of PbCl2 crystal from leaded glass.

Recycling and reutilization of smelting dust as a secondary resource: A review

Smelting dust is a toxic waste produced in metal-mineral pyrometallurgical processes. To eliminate or reduce the adverse environmental impacts of smelting dust, valuable components need to be selectively separated from the toxic components present in the waste. This paper reviews the chemical composition, phase composition and particle size distribution characteristics of smelting dust, and the results show that smelting dust has excellent physicochemical characteristics for recovering valuable metals. The process flow, critical factors, development status, advantages and disadvantages of traditional technologies such as pyrometallurgy, hydrometallurgy and biometallurgy were discussed in depth. Conventional treatment methods typically prioritize separating and reclaiming specific elements with high concentrations. However, these methods face challenges such as excessive chemical usage and limited selectivity, which can hinder the sustainable utilization of smelting dust. With the increasing scarcity of resources and strict environmental requirements, a single treatment process can hardly fulfil the demand, and a physical field-enhanced technology for releasing and separating valuable metals is proposed. Through analysing the effect of electric field, microwave and ultrasound on recovering valuable metals from smelting dust, the enhancement mechanism of physical field on the extraction process was clarified. This paper aimed to provide reference for the resource utilization of smelting dust.

How Green are Redox Flow Batteries?

Providing sustainable energy storage is a challenge that must be overcome to replace fossil-based fuels. Redox flow batteries are a promising storage option that can compensate for fluctuations in energy generation from renewable energy production, as their main asset is their design flexibility in terms of storage capacity. Current commercial options for flow batteries are mostly limited to inorganic materials such as vanadium, zinc, and bromine. As environmental aspects are one of the main drivers for developing flow batteries, assessing their environmental performance is crucial. However, this topic is still underexplored, as researchers have mostly focused on single systems with defined use cases and system boundaries, making the assessments of the overall technology inaccurate. This review was conducted to summarize the main findings of life cycle assessment studies on flow batteries with respect to environmental hotspots and their performance as compared to that of other battery systems.

Universal and efficient extraction of lithium for lithium-ion battery recycling using mechanochemistry

The increasing lithium-ion battery production calls for profitable and ecologically benign technologies for their recycling. Unfortunately, all used recycling technologies are always associated with large energy consumption and utilization of corrosive reagents, which creates a risk to the environment. Herein we report a highly efficient mechanochemically induced acid-free process for recycling Li from cathode materials of different chemistries such as LiCoO₂, LiMn₂O₄, Li(CoNiMn)O₂, and LiFePO₄. The introduced technology uses Al as a reducing agent in the mechanochemical reaction. Two different processes have been developed to regenerate lithium and transform it into pure Li₂CO₃. The mechanisms of mechanochemical transformation, aqueous leaching, and lithium purification were investigated. The presented technology achieves a recovery rate for Li of up to 70% without applying any corrosive leachates or utilizing high temperatures. The key innovation is that the regeneration of lithium was successfully performed for all relevant cathode chemistries, including their mixture.

Selective Extraction of Critical Metals from Spent Lithium-Ion Batteries

Selective and highly efficient extraction technologies for the recovery of critical metals including lithium, nickel, cobalt, and manganese from spent lithium-ion battery (LIB) cathode materials are essential in driving circularity. The tailored deep eutectic solvent (DES) choline chloride-formic acid (ChCl-FA) demonstrated a high selectivity and efficiency in extracting critical metals from mixed cathode materials (LiFePO₄:Li(NiCoMn)_1/3O₂ mass ratio of 1:1) under mild conditions (80 °C, 120 min) with a solid-liquid mass ratio of 1:200. The leaching performance of critical metals could be further enhanced by mechanochemical processing because of particle size reduction, grain refinement, and internal energy storage. Furthermore, mechanochemical reactions effectively inhibited undesirable leaching of nontarget elements (iron and phosphorus), thus promoting the selectivity and leaching efficiency of critical metals. This was achieved through the preoxidation of Fe and the enhanced stability of iron phosphate framework, which significantly increased the separation factor of critical metals to nontarget elements from 56.9 to 1475. The proposed combination of ChCl-FA extraction and the mechanochemical reaction can achieve a highly selective extraction of critical metals from multisource spent LIBs under mild conditions.

Acid-free mechanochemical process to enhance the selective recycling of spent LiFePO4 batteries

With the large-scale application of LiFePO₄ (LFP) in energy storage and electric vehicles, the recycling of spent lithium LFP batteries has gained more attention. However, recycling spent LFP is less economically feasible owing to the poor economic value of Fe products, which causes a problem for both the efficiency and economy. This work proposes a highly economical acid-free mechanochemical approach for the efficient and selective extraction of lithium (Li) from spent LFP battery cathode materials. The selective release of 98.9 % of Li from the LFP crystal structure is achieved at a reaction time of 5 h, a rotational speed of 500 rpm, and sodium citrate (Na₃Cit) to LFP mass ratio of 10. Meanwhile, Fe is reserved in the form of FePO₄ in the olivine structure. The use of Na₃Cit as a co-milling agent ensures a pollution-free recovery process and efficient extraction of Li⁺. The chelation of Li⁺ with organic ligands (Cit^3-) is the key to the efficient selective recovery of Li⁺ from the olivine LFP structure via the mechanochemical process. The economic analysis indicates that the method is feasible and ensures industrial viability. The acid-free mechanochemical (MC) process reported in this work provides a novel route to selectively recover Li from spent LFP efficiently and highly economically.

A sustainable approach for selective recovery of lithium from cathode materials of spent lithium-ion batteries by induced phase transition

Recycling of spent lithium-ion batteries (LIBs) has attracted widespread attention because of their dual attributes to environmental protection and resource conservation. Utilization of strong corrosive acids is currently the preferred way to recover valuable metals from spent LIBs, but the extensive use of chemical reagents can pose serious environmental risks. Herein, this research proposes a green process for selective recovery of lithium using the material of spent LIBs itself without adding exogenous reagents, mechanochemistry induced phase transition. The leaching efficiency of Li can reach 94% by employing the copper foil separated from spent LIBs as the co-grinding additive during the mechanochemical reaction process. Then, the high value LiOH·H₂O can be prepared through direct evaporation and crystallization without adding any precipitant. Meanwhile, cobalt is almost remained in the leaching residue which can be recovered through a step-by-step separation process. XRD, XPS, and SEM-EDS characterizations show that LiCoO₂ and copper foil are transformed into the soluble Li₂O, and insoluble CuO and CoO under the mechanical force. Finally, the soluble Li₂O is dissolved in water to prepare the LiOH solution, and the insoluble CuO and CoO are transformed into Cu₂O and Co(OH)₂. On the basis of the experimental investigation, it is proven that the proposed process is suitable for selectively recovering Li from all types of cathode materials without generating salty wastewater or introducing chemical reagents. Thus, the proposed approach can ensure the efficient recovery of valuable metals from spent LIBs while avoiding the potential threat to the environment and human health.

Facile path for copper recovery from waste printed circuit boards via mechanochemical approach

Recycling copper (Cu⁰) from waste printed circuit boards (PCBs) is a prevalent challenge. Here, we propose a new pathway and reveal mechanisms for recovering Cu⁰ from waste PCBs via a mechanochemical approach. The successful application of mechanical force avoids using inorganic acid in the Cu⁰ recovery process. Our work demonstrates that ferric chloride (FeCl₃) was superior to ferric sulfate and ferric nitrate as a solid-phase reagent for Cu⁰ recovery due to chloride complexation. Under the induction of mechanical force, the Cu⁰ in the waste PCBs was oxidized by Fe³⁺ and complexed by Cl^¯ to form a meta-stable cuprous chloride, which was susceptible to leaching in an acidic liquid-phase system constructed by hydrolysis of ferric salt. Further mechanism analysis reveals that in the mechanochemical solid-phase reaction, Cu⁰, metallic impurities, metal oxides, and carbon materials from waste PCBs could also reduce Fe³⁺ to Fe²⁺. The optimum conditions for Cu⁰ recovery from waste PCB powder with FeCl₃ as a solid-phase reagent were: rotational speed of 500 rpm, Cu⁰:Fe³⁺ molar ratio of 1:20, and reaction time of 120 min, achieving the highest recovery of 99.6 wt%. This study presents a facile path for Cu⁰ recovery from waste PCBs for resource circulation.

Efficient recovery of rare earth elements from discarded NdFeB magnets by mechanical activation coupled with acid leaching

Due to the increasing demands and supply shortages for rare earth elements (REEs), the recovery of REEs from discarded NdFeB with high REE content has become extremely important. In this paper, a hydrometallurgical coupling process involving mechanical activation and selective acid leaching was proposed for the recovery of REEs from discarded NdFeB magnets. The effects of ball milling activation speed, hydrochloric acid concentration, and solid-liquid ratio on the leaching efficiencies of REEs in NdFeB magnets were studied. The results indicated that the ball milling activation method could enhance the reactivity of the samples through the action of mechanical force, which promoted the leaching efficiency and leaching speed of REEs. Under the optimum conditions (650-rpm activation speed, 0.4 M hydrochloric acid, 100 g/L solid-liquid ratio), the leaching efficiency of REEs increased up to 99% with low hydrochloric acid consumption and the leaching speed of REEs was triple than that of without activation. The final purity of recovered rare earth oxides reached up to 99.9%. All results demonstrated that ball milling activation coupled with selective leaching of hydrochloric acid could be an effective and environment-friendly strategy to achieve the recovery of REEs.

Analysis of Lanthanum and Cobalt Leaching Aimed at Effective Recycling Strategies of Solid Oxide Cells

Lanthanum and cobalt are Critical Raw Materials and components of Solid Oxide Cells—SOCs electrodes. This review analyses lanthanum and cobalt leaching from waste materials (e-waste, batteries, spent catalysts), aiming to provide a starting point for SOC recycling, not yet investigated. The literature was surveyed with a specific interest for leaching, the first phase of hydrometallurgy recycling. Most references (86%) were published after 2012, with an interest higher (85%) for cobalt. Inorganic acids were the prevailing (>80%) leaching agents, particularly for lanthanum, while leaching processes using organic acids mostly involved cobalt. The experimental conditions adopted more diluted organic acids (median 0.55 M for lanthanum and 1.4 M for cobalt) compared to inorganic acids (median value 2 M for both metals). Organic acids required a higher solid to liquid ratio (200 g/L), compared to inorganic ones (100 g/L) to solubilize lanthanum, while the opposite happened for cobalt (20 vs. 50 g/L). The process temperature didn’t change considerably with the solvent (45–75 °C for lanthanum, and 75–88 °C for cobalt). The contact time was higher for lanthanum than for cobalt (median 3–4 h vs. 75–85 min). Specific recycling processes are crucial to support SOCs value chain in Europe, and this review can help define the existing challenges and future perspectives.

Mechanochemically synthesized Fe-Mn binary oxides for efficient As(III) removal: Insight into the origin of synergy action from mutual Fe and Mn doping

Iron manganese oxide resources are widely derived from the geological structure, and their combinations play an important role in the migration and transformation of arsenic. Iron oxide and manganese oxide exist generally in a mixed state in Fe-Mn oxides synthesized via the well studied co-precipitation methods using potassium permanganate and manganese/iron sulfates. Herein, a newly designed Fe-Mn-O compositing oxide with Fe-MnO₂, Mn-Fe₂O₃, (Fe_0.67Mn_0.33)OOH solid solution and FeOOH as the main components, simply through solvent-free mechanical ball milling pyrolusite (MnO₂) and ferrihydrite (FeOOH) together has been reported. Atomic-scale integrations by doping Fe and Mn with each other were detected and an adsorption-oxidation bifunctionality was achieved, where Fe-doped MnO₂ served as oxidizer for As(III) and amorphous/ground FeOOH acted as adsorbent first for As(III) and then As(V) from the oxidization. The maximal adsorption for As(III) could reach 44.99 mg/g and over 82.5% of As(III) was converted to As(V). More importantly, high removal ability of arsenic worked in a wide pH range of 2-10.5%, and 87.2% of its initial adsorption-oxidation capacity could be kept even after 5-cycles reuse for treating 20 mg/L As(III) with a dosage at 1 g/L. Together with the enhanced adsorption capacity by the milled FeOOH, surface electron transfer efficiency of the developed Fe-MnO₂ surrounded with Mn-Fe₂O₃ has been studied for the first time to understand the oxidization effect to As(V). Besides the environment-friendliness of ball milling method, the prepared sample is quite stable without noticeable metal release into solution. Mechanism studies of arsenic removal by the as-prepared Fe-Mn-O oxide provide a new direction for improving the oxidation efficiency of MnO₂ to As(III) based on the widely available cheap Mn and Fe oxides, contributing to the development of advanced oxidization process in the treatment of waste water.

A process of leaching recovery for cobalt and lithium from spent lithium-ion batteries by citric acid and salicylic acid

There is great economic and environmental value in recovering valuable metal ions from spent lithium-ion batteries (LIBs). A novel method that employs organic acid recovery using citric acid and salicylic acid was used to enhance the leaching of metal ions from the cathode materials of spent LIBs. The effects of the acid concentration, reducing agent content, solid to liquid (S : L) ratio, temperature, and leaching time were systematically analyzed and the optimal acid leaching process condition was determined through the results. The kinetics of the leaching process with different temperatures was analyzed to explore and verify the relationship between the leaching mechanism and temperature. The results of TG/DSC analysis showed that the optimum calcination temperature was 500 °C for 1 h and 600 °C for 3 h. The XRD and micromorphology analysis results showed that cathode material powders without impurities were obtained after pretreatment. The experimental results demonstrated that the optimal leaching efficiencies of the metals ions were 99.5% Co and 97% Li and the optimal corresponding condition was 1.5 M citric acid, 0.2 M salicylic acid, a 15 g L⁻¹ S : L ratio, 6 vol% H₂O₂, 90 °C, and 90 min. Afterward, the infrared tests and SEM morphologies results indicated that only salicylic acid was present in the residue after filtration because of the microsolubility of the salicylic acid. Finally, it was obvious that the temperature had a great influence on the leaching process as observed through the kinetics and thermodynamics analyses, while the E_a values for Co and Li were obtained as 37.96 kJ mol⁻¹ and 25.82 kJ mol⁻¹ through the kinetics model. The whole process was found to be efficient and reasonable for recovering valuable metals from the industrial electrodes of spent LIBs.

A new mixed organic acid of citric acid and salicylic acid is proposed to recover valuable Co and Li ions from spent LIBs. Under the optimum leaching conditions, the leaching efficiencies of Co and Li ions can reach 99.5% and 97%.

Converting spent lithium cobalt oxide battery cathode materials into high-value products via a mechanochemical extraction and thermal reduction route

This study innovatively combines mechanochemistry and high-temperature thermal reduction to achieve the recovery of valuable metals from spent LIBs. First, under the action of mechanical force, the crystal structure of lithium cobalt oxide (LiCoO₂) found in the cathode materials of spent LIBs was destroyed and converted into lithium carbonate (Li₂CO₃) and Li-free residue (C/Co₃O₄) using dry ice as a co-grinding reagent. The optimum Li₂CO₃ recovery conditions were determined to be as follows: a ratio of dry ice: LiCoO₂ powder mass of 20:1; a rotation speed of 700 rpm, and a reaction time of 1.5 h. With these conditions the maximum percentage of Li₂CO₃ recovered was 95.04 wt%. The Co₃O₄ in Li-free residue was reduced to a high-value Co⁰ product via a high-temperature (800 °C) heat treatment. Gibbs free energy analysis confirmed that the carbon in the Li-free residue could be used as a self-reducing reagent for the thermal reduction of Co₃O₄. The reactants and products of each step were characterized by XRD, FT-IR, XPS and SEM techniques. The green route for recycling spent LIBs that this study proposes realizes the green and cost-effective conversion of LiCoO₂ to high-value products, which may become an outstanding example of recycling spent LIBs.

State-of-the-Art of Eggshell Waste in Materials Science: Recent Advances in Catalysis, Pharmaceutical Applications, and Mechanochemistry

Eggshell waste is among the most abundant waste materials coming from food processing technologies. Despite the unique properties that both its components (eggshell, ES, and eggshell membrane, ESM) possess, it is very often discarded without further use. This review article aims to summarize the recent reports utilizing eggshell waste for very diverse purposes, stressing the need to use a mechanochemical approach to broaden its applications. The most studied field with regards to the potential use of eggshell waste is catalysis. Upon proper treatment, it can be used for turning waste oils into biodiesel and moreover, the catalytic effect of eggshell-based material in organic synthesis is also very beneficial. In inorganic chemistry, the eggshell membrane is very often used as a templating agent for nanoparticles production. Such composites are suitable for application in photocatalysis. These bionanocomposites are also capable of heavy metal ions reduction and can be also used for the ozonation process. The eggshell and its membrane are applicable in electrochemistry as well. Due to the high protein content and the presence of functional groups on the surface, ESM can be easily converted to a high-performance electrode material. Finally, both ES and ESM are suitable for medical applications, as the former can be used as an inexpensive Ca2+ source for the development of medications, particles for drug delivery, organic matrix/mineral nanocomposites as potential tissue scaffolds, food supplements and the latter for the treatment of joint diseases, in reparative medicine and vascular graft producing. For the majority of the above-mentioned applications, the pretreatment of the eggshell waste is necessary. Among other options, the mechanochemical pretreatment has found an inevitable place. Since the publication of the last review paper devoted to the mechanochemical treatment of eggshell waste, a few new works have appeared, which are reviewed here to underline the sustainable character of the proposed methodology. The mechanochemical treatment of eggshell is capable of producing the nanoscale material which can be further used for bioceramics synthesis, dehalogenation processes, wastewater treatment, preparation of hydrophobic filters, lithium-ion batteries, dental materials, and in the building industry as cement.

Mechanochemical degradation of brominated flame retardants in waste printed circuit boards by Ball Milling

Degradation of brominated flame retardants (BFRs) in waste printed circuit boards (WPCBs) occurred due to mechanical force during the crushing process. In this study, a planetary ball-milling simulation experiment was designed to explore the mechanochemical debromination process of BFRs in WPCBs. The results showed that CaO had a better debromination performance than MgO and the mixture of Fe + SiO₂, and high revolution speed and low mass ratio of WPCBs to CaO promoted the degradation of BFRs. After milling for 1 h, the particle size distribution was stable while the debromination efficiency increased with the increase of milling time. Ball milling promoted the migration of bromine from the inside to the new surface of WPCBs powder, and submicron particles adhered to the micron size aggregates. The polybrominated diphenyl ethers (PBDEs) detection showed that the concentrations of most PBDE congeners decreased with the increase of milling time, and a possible degradation pathway was proposed according to the experimental results. All the results provided new data for the mechanism of degradation of BFRs in WPCBs during the mechanical crushing process.

Use mechanochemical activation to enhance interfacial contaminant removal: A review of recent developments and mainstream techniques

Interfacial processes, including adsorption and catalysis, play crucial roles in environmental contaminant removal. Mechanochemical activation (MCA) emerges as a competitive method to improve the performance of adsorbents and catalysts. The development and application of MCA in the last decades are thereby systematically reviewed, particularly highlighting its contribution to interfacial process modulation. Two typical apparatuses for MCA are ball milling (BaM) and bead milling (BeM). Compared to BaM, BeM is able to yield a much higher MCA intensity, because it could pulverize bulk solid particles to nearly 100 nm. Since MCA intensity on the adsorbents and catalysts is directly responsible for the contaminant removal afterwards, quantitative and qualitative determination methods for valid MCA intensity are introduced. MCA benefits both the adsorption kinetics and capacity of powdered activated carbon by increasing the specific surface area. Carbon oxidation should be given an additional attention, but potentially favors the adsorption of heavy metals. MCA favors the catalyst performance by providing abundant surface functional group and increasing the free energy in the near-surface region. Finally, the future research needs are identified.

A low-toxicity and high-efficiency deep eutectic solvent for the separation of aluminum foil and cathode materials from spent lithium-ion batteries

The separation of cathode materials from aluminum (Al) foil is a key issue worthy of attention in the process of resource utilization of spent lithium-ion batteries (LIBs). Traditional technologies for the Al foil and cathode materials separation have the disadvantages of the use of corrosive acid/alkali, release of HF hazards, and environment and healthy risks of the toxicity reagent. In this study, a low-toxicity, high-efficiency, and low-cost deep eutectic solvent (DES), choline chloride-glycerol, was synthesized and applied to solving the separation dilemma of Al foil and cathode materials in spent LIBs. The experimental results show that separation of the Al foil and cathode materials can be achieved under optimal conditions designed by the response surface method: heating temperature 190 ℃, choline chloride: glycerol molar ratio 2.3:1, and heating time 15.0 min; the peeling percentage of cathode material can reach 99.86 wt%. Mechanism analysis results confirm that the separation of Al foil and cathode materials was the result of the deactivation of the organic binder polyvinylidene fluoride (PVDF), which can be attributed to an alkali degradation process caused by the attack of the hydroxide of choline chloride on the acidic hydrogen atom in PVDF.

Acid-Free and Selective Extraction of Lithium from Spent Lithium Iron Phosphate Batteries via a Mechanochemically Induced Isomorphic Substitution

Lithium (Li) is the most valuable metal in spent lithium iron phosphate (LiFePO₄) batteries, but its recovery has become a challenge in electronic waste recovery because of its relatively low content and inconsistent quality. This study proposes an acid-free and selective Li extraction process to successfully achieve the isomorphic substitution of Li in LiFePO₄ crystals with sodium (Na). The method uses low-cost and nontoxic sodium chloride (NaCl) as a cogrinding reagent via a mechanical force-induced solid-phase reaction. X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), and X-ray photoelectron spectroscopy (XPS) characterizations demonstrated the evidence of Li/Na isomorphic substitution, while XPS spectra of Fe 2p, P 2p, and O 1s revealed that the coordination environment of these elements was not significantly altered. Density functional theory calculations further provided evidence that Na and Li share similar outer electron arrangements and coordination environments, favoring Na over Fe as a replacement for Li in LiFePO₄. Additionally, the regeneration of NaCl and the recovery of precipitated Li₂CO₃ were simultaneously achieved with Na₂CO₃ as the sole reagent. This concise and efficient acid-free mechanochemical process for Li extraction is a promising candidate for feasible recycling technology of Li from spent LiFePO₄ batteries. The proposed process is particularly appealing because of its high selectivity, considerable economic advantages, and environmental benefits.

Synthesis of Calcium Aluminates from Non-Saline Aluminum Dross

The present work examines the synthesis of tricalcium aluminate (for use as a synthetic slag) from the non-saline dross produced in the manufacture of metallic aluminum in holding furnaces. Three types of input drosses were used with Al₂O₃ contents ranging from 58 to 82 wt %. Calcium aluminates were formed via the mechanical activation (reactive milling) of different mixtures of dross and calcium carbonate, sintering at 1300 °C. The variables affecting the process, especially the milling time and the Al₂O₃/CaO molar ratio, were studied. The final products were examined via X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The reactive milling time used was 5 h in a ball mill, for a ball/dross mass ratio of 6.5. For a molar relationship of 1:3 (Al₂O₃/CaO), sintered products with calcium aluminate contents of over 90% were obtained, in which tricalcium aluminate (C₃A) was the majority compound (87%), followed by C₁₂A₇ (5%).

Comprehensive characterization on Ga (In)-bearing dust generated from semiconductor industry for effective recovery of critical metals

Gallium (indium)-bearing dust generated from semiconductor industry is an important secondary resource for critical metal recycling. However, the diverse and distinct physicochemical natures of such waste material have made its recycling less effective, e.g. low extraction rate and complex treatment procedures. This research is devoted to gaining in-depth knowledge of the physical and chemical properties of such waste, including the chemical composition, physical phases, particle size distribution and chemical-thermal properties with a series of technologies. As a consequence, the occurrence and distribution of GaN and metallic indium phases are found to be crucial to efficient metal recycling. The thermal-chemical behavior shows that continuous oxidation occurred in the air atmosphere, indicating that heat-treatment followed by acid leaching is feasible to improve their recycling efficiencies. This process is able to leach 80.35% of gallium and 95.78% of indium with one-step operation. Furthermore, different treatment strategies for the waste material are preliminarily evaluated and discussed for the aim of metal recovery. The results show that gallium can be selectively recycled with recycling rate of 89.59% using alkaline leaching. With this research, the understanding on the recyclability of different metals and possibilities of selective recovery can be improved. It provides guidelines during the stage of decision-making for critical metal recycling in order to achieve efficient resource circulation.

A novel process of extracting precious metals from waste printed circuit boards: Utilization of gold concentrate as a fluxing material

Waste printed circuit boards (PCBs) are highly toxic materials because of the hazardous substances that are incorporated into them. An advanced recycling technology based on pyrometallurgical treatment using Au concentrate as a flux material was developed in this study. The benefits of employing roasted gold concentrate (RGC) in the smelting process of waste PCBs were demonstrated through high-temperature experiments. The major oxide compositions of PCBs (CaO, Al₂O₃, and SiO₂) were fluxed using oxidized Au concentrate composed of Fe_tO and SiO₂. Quaternary slag systems (CaO-Fe_tO-Al₂O₃-SiO₂) were formed during the smelting process, which rendered the process of separation of oxide impurities from Cu-based alloys easier. Precious metals (Au and Ag) were effectively recovered from waste PCBs and Au concentrate in the form of a metal alloy that required further treatment by leaching and extraction. Residual S in the RGC significantly changed the alloy phases. A large quantity of S was formulated into a matte phase, while a small amount of S was dissolved into a Cu-Fe metal alloy. The subsequent hydrometallurgical process was optional. Electrorefining or pressure leaching could be applied depending on the type of Cu alloy.

Facile and Cost-Effective Approach for Copper Recovery from Waste Printed Circuit Boards via a Sequential Mechanochemical/Leaching/Recrystallization Process

The recovery of copper (Cu⁰) from waste printed circuit boards (WPCBs) is a great challenge as a result of its heterogeneous structural properties, with a mixture of metals, epoxy resin, and fiberglass. In this study, a three-step sequential process, including mechanochemical processing, water leaching, and recrystallization, for Cu⁰ recovery from WPCB powder is reported. Potassium persulfate (K₂S₂O₈), instead of acid/alkali reagents, was employed as the sole reagent in the cupric sulfate (CuSO₄) regeneration process. Complete oxidation of Cu⁰ in the WPCBs to copper oxide (CuO) and CuSO₄ was first achieved during mechanochemical processing with K₂S₂O₈ as the solid oxidant, and the K₂S₂O₈ was simultaneously converted to sulfate compounds [K₃H(SO₄)₂] via a solid-solid reaction with epoxy resin (C _nH _mO _y) as the hydrogen donator under mechanical force. The rapid leaching of Cu species in the forms of CuO and CuSO₄ was therefore easily realized with pure water as a nontoxic leaching reagent. The kinetics of the leaching process of Cu species was confirmed to follow the shrinking nucleus model controlled by solid-film diffusion. Finally, CuSO₄·5H₂O was successfully separated by cooling crystallization of the hot saturated solution of sulfate salt [K₂Cu(SO₄)₂·6H₂O]. An efficient conversion of Cu⁰ to CuSO₄·5H₂O product, for WPCB recycling, was therefore established.

Recycling of LiNi1/3Co1/3Mn1/3O2 cathode materials from spent lithium-ion batteries using mechanochemical activation and solid-state sintering

The production of lithium-ion battery is around 9100 million sets in 2016 and is believed to further increase consecutively. This fact triggers the generation of spent cathode materials which contain metals of both valuable and hazardous. Their recycling corresponding to life cycle sustainability of lithium-ion battery has attracted significant attention. However, most technologies for recycling waste lithium-ion batteries are dependent on metallurgical based processes where secondary pollution is inevitable. This research demonstrates a process to directly regenerate LiNi_1-x-yCo_xMn_yO₂ cathode material by incorporating methods of mechanochemical activation and solid-state sintering, which can restore the layered structure and improve the lithium ion diffusion without introducing extra impurities. By understanding the effects of sintering temperature, the optimal conditions for direct regeneration of cathode materials with obvious improvement on electrochemical performance can be obtained. As a result, this research proves the possibility of direct regeneration of nickel-containing waste cathode materials with minimized chemical consumption.

Diverse Architectures and Luminescence Properties of Group 11 Complexes Containing Pyrimidine-Based Phosphine, N-((Diphenylphosphine)methyl)pyrimidin-2-amine

In this article, the synthesis, structural studies, and luminescence properties of Cu^I, Ag^I, and Au^I complexes of pyrimidine-based phosphine [C₄H₃N₂-2-NH(CH₂PPh₂)] (1) are described. The reactions of 1 with CuX led to the isolation of one-dimensional (1D) chain, tetranuclear ladder, or cyclic derivatives. The structural features of these complexes are greatly influenced by the metal-to-ligand ratio, reaction conditions, and CuX (X = Cl, Br or I) employed. In the case of CuCl and CuBr, one-dimensional coordination polymers [{CuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (2) and [{CuBr}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (3) were obtained, whereas CuI afforded tetracopper complex [{CuI}₄{C₄H₃N₂-2-NH(CH₂PPh₂)}₂(NCCH₃)₂] (4) having Cu₄ ladder structure supported by P∩N-bridging coordination of 1. The reaction of 1 with AgOTf yielded unprecedented one-dimensional chain structure [{AgOTf}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (5), whereas the reaction with AgBF₄ produced a 12-membered dinuclear complex, [{Ag}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂[BF₄]₂ (6), with each silver atom having a linear geometry. Gold complex [{AuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂ (7) was synthesized by reacting 1 with [AuCl(SMe₂)]. Compounds 2-4 were also prepared using a pestle and mortar by grinding method in almost quantitative yield. Complex 4 with a Cu···Cu distance of 2.828(5) Å shows high luminescence due to the nonbonded metal···metal interactions.

Unveiling the Role and Mechanism of Mechanochemical Activation on Lithium Cobalt Oxide Powders from Spent Lithium-Ion Batteries

This research presented the impacts of mechanochemical activation (MCA) on the physiochemical properties of lithium cobalt oxide (LiCoO₂) powders of cathode materials from spent lithium-ion batteries, and analyzed the relevant effects of these changes on the leaching efficiency of lithium and cobalt and the leaching kinetics of LiCoO₂ powders. The results revealed the superiority of MCA in the following levels of changes in the LiCoO₂ powders: first, the physical properties included a decrease in the average particle size, an increase in the specific surface area, and the appearance of a mesoporous structure change; second, changes in crystal-phase structures were reflected in the grain refinement of LiCoO₂ powders, lattice distortions, lattice dislocations, and storage and increment of internal energy; third, the surface characteristics included a chemical shift of lithium element electrons, a reduction in Co³⁺ concentration, and an increment in the surface hydroxyl oxygen concentration. These changes in physiochemical properties and structures enhanced the hydrophilicity and interface reactivity of the activated LiCoO₂ powders and significantly improved the leaching efficiencies of Li and Co in organic acid solutions. The rate-limiting step of metal leaching was also altered from a surface chemical reaction-controlled one before MCA to an ash layer diffusion-controlled one after MCA.

Chelator-induced recovery of rare earths from end-of-life fluorescent lamps with the aid of mechano-chemical energy

Rare-earths (REs) are key components for the transition to a greener energy profile and low carbon society. The elements turn out to be of limited availability in the market, due to the supply-demand issues, exponential price rises, or geopolitics, which has led to a focus on the exploration of secondary sources for RE reclamation. End-of-life (EoL) nickel-metal hydride batteries, permanent magnets, and fluorescent lamps (FL) have been the primary sources for recyclable REs, while the recovery of REs in EoL FL (Ce, Eu, La, Tb, or Y) includes comparatively fewer processing steps than the other potential sources. In the current work, we proposed a simple, energy-efficient protocol for EoL FL processing, using chelators in combination with ball milling. The parameters for optimum chelator-assisted recovery (chelator concentration, solid-to-liquid ratio, solution pH), and milling variables (ball size, ball weight, milling speed, milling duration), were evaluated at room temperature (RT, 25 ± 2 °C). The dissolution of REs with ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid, methylglycinediacetic Acid, or 3-hydroxy-2,2'-iminodisuccinic acid, was compared at RT, while EDTA was used as the reference chelator throughout. Increasing the system temperature from 25 to 135 °C achieved at least double Eu and Y recovery, relative to that at RT, whereas the recovery rate improvement for Ce, La or Tb was insignificant. Mechano-chemical treatment at RT, via wet milling of EoL FL, with chelators, yielded a five order of magnitude increase in Ce, La and Tb recovery, however, plus a two-order increase for Eu or Y, compared with non-abetted operating conditions. It was also found that higher impact energy achieved improved recovery over a reduced milling duration with this technique having the added advantage of minimal acid consumption and reduced effluent production.

Lithium recovery from spent Li-ion batteries using coconut shell activated carbon

Lithium is one of scarce natural resources in the world that need to be preserve. One of the way in preserving the resource is by recovery the rich source of the lithium such as in the spent batteries. It is necessary to develop a recovery method which is efficient and low-cost to be able to recover the lithium in an economic scale. In this study, low-cost activated carbon (AC) from coconut shell charcoal was prepared by chemical and physical activation methods and tested for Li removal from Co, Mn, and Ni ions in semi-continuous columns adsorption experiments. The maximum surface area is 365 m²/g with the total pore volume is 0.148 cm³/g that can be produced by physical activation at 800 °C. In the same activation temperature, activation using KOH has larger ratio of micropore volume than physical activation. Then, the adsorption capacity and selectivity of metal ions were investigated. A very low adsorption capacity of AC for Li ions in batch adsorption mode provides an advantage in column applications for separating Li from other metal ions. The AC sample with chemical activation provided better separation than the samples with physical activation in the column adsorption method. During a certain period of early adsorption (lag time), solution collected from the column outlet was found to be rich in Li due to the fast travel time of this light element, while the other heavier metal ions were mostly retained in the AC bed. The maximum lag time is 97.3 min with AC by KOH activation at 750 °C.

Status of electronic waste recycling techniques: a review

The increasing use of electrical and electronic equipment leads to a huge generation of electronic waste (e-waste). It is the fastest growing waste stream in the world. Almost all electrical and electronic equipment contain printed circuit boards as an essential part. Improper handling of these electronic wastes could bring serious risk to human health and the environment. On the other hand, proper handling of this waste requires a sound management strategy for awareness, collection, recycling, and reuse. Nowadays, the effective recycling of this type of waste has been considered as a main challenge for any society. Printed circuit boards (PCBs), which are the base of many electronic industries, are rich in valuable heavy metals and toxic halogenated organic substances. In this review, the composition of different PCBs and their harmful effects are discussed. Various techniques in common use for recycling the most important metals from the metallic fractions of e-waste are illustrated. The recovery of metals from e-waste material after physical separation through pyrometallurgical, hydrometallurgical, or biohydrometallurgical routes is also discussed, along with alternative uses of non-metallic fraction. The data are explained and compared with the current e-waste management efforts done in Egypt. Future perspectives and challenges facing Egypt for proper e-waste recycling are also discussed.

Bioleaching of metals from WEEE shredding dust

A bioleaching process developed in two separate steps was investigated for the recovery of base metals, precious metals and rare earth elements from dusts generated by Waste Electrical and Electronic Equipment (WEEE) shredding. In the first step, base metals were almost completely leached from the dust in 8 days by Acidithiobacillus thiooxidans (DSM 9463) that lowered the pH of the leaching solution from 3.5 to 1.0. During this step, cerium, europium and neodymium were mobilized at high percentages (>99%), whereas lanthanum and yttrium reached an extraction yield of 80%. In the second step, the cyanide producing Pseudomonas putida WSC361 mobilized 48% of gold within 3 h from the A. thiooxidans leached shredding dust. This work demonstrated the potential application of biohydrometallurgy for resource recovery from WEEE shredding dust, destined to landfill disposal, and its effectiveness in the extraction of valuable substances, including elements at high supply risk as rare earths.

Mechanochemical Synthesis of Slow-release Fertilizers: A Review

Aims/Objective:

This review discusses the processes and applications associated with the mechanochemical synthesis of Slow-Release Fertilizers (SRF) from different resources.

Explanation:

The effect of mineral fertilizers on the environment and on living species will be discussed. Moreover, various aspects related to fertilizers production and applications are illustrated. It is found that solid-solid mechanical interaction initiates chemical reactions by lowering their energy of activation when compared to other thermochemical processes. Since milling is an important industrial operation, its contribution to materials processing is discussed.

Conclusion:

In general, SRFs increase the value of nutrient uptake in plants and reduces energy consumption and labor costs.

Lead recovery from waste CRT funnel glass by high-temperature melting process

In this research, a novel and effective process for waste CRT funnel glass treatment was developed. The key to this process is removal of lead from the CRT funnel glass by high-temperature melting process. Sodium carbonate powder was used as a fusion agent, sodium sulfide serves as a catalytic agent and carbon powder acts as reducing agent. Experimental results showed that lead recovery rate increased with an increase in the amount of added sodium carbonate, sodium sulfide, carbonate, temperature and holding time initially, and then reached a stable value. The maximum lead recovery rate was approximately 94%, when the optimum adding amount of sodium carbonate, sodium sulfide, carbonate, temperature and holding time were 25%, 8%, 3.6%, 1200°C and 120min, respectively. In the high-temperature melting process, lead silicate in the funnel glass was firstly reduced, and then removed. The glass slag can be made into sodium and potassium silicate by hydrolysis process. This study proposed a practical and economical process for recovery of lead and utilization of waste glass slag.

En masse pyrolysis of flexible printed circuit board wastes quantitatively yielding environmental resources

This paper reports the recycling of flexible printed circuit board (FPCB) waste through carbonization of polyimide by dual pyrolysis processes. The organic matter was recovered as pyrolyzed oil at low temperatures, while valuable metals and polyimide-derived carbon were effectively recovered through secondary high temperature pyrolysis. The major component of organics extracted from FPCB waste comprised of epoxy resins were identified as pyrolysis oils containing bisphenol-A. The valuable metals (Cu, Ni, Ag, Sn, Au, Pd) in waste FPCB were recovered as granular shape and quantitatively analyzed via ICP-OES. In attempt to produce carbonaceous material with increased degree of graphitization at low heat-treatment conditions, the catalytic effect of transition metals within FPCB waste was investigated for the efficient carbonization of polyimide films. The morphology of the carbon powder was observed by scanning electron microscopy and graphitic carbonization was investigated with X-ray analysis. The protocols outlined in this study may allow for propitious opportunities to salvage both organic and inorganic materials from FPCB waste products for a sustainable future.

An environmentally friendly ball milling process for recovery of valuable metals from e-waste scraps

The present study reports a mechanochemical (MC) process for effective recovery of copper (Cu) and precious metals (i.e. Pd and Ag) from e-waste scraps. Results indicated that the mixture of K₂S₂O₈ and NaCl (abbreviated as K₂S₂O₈/NaCl hereafter) was the most effective co-milling reagents in terms of high recovery rate. After co-milling with K₂S₂O₈/NaCl, soluble metallic compounds were produced and consequently benefit the subsequent leaching process. 99.9% of Cu and 95.5% of Pd in the e-waste particles could be recovered in 0.5mol/L diluted HCl in 15min. Ag was concentrated in the leaching residue as AgCl and then recovered in 1mol/L NH₃ solution. XRD and XPS analysis indicated that elemental metals in the raw materials were transformed into their corresponding oxidation state during ball milling process at low temperature, implying that solid-solid phase reactions is the reaction mechanism. Based on the results and thermodynamic parameters of the probable reactions, possible reaction pathways during ball milling were proposed. Suggestion on category of e-waste for ball milling process was put forward according to the experiment results. The designed metal recovery process of this study has the advantages of highly recovery rate and quick leaching speed. Thus, this study offers a promising and environmentally friendly method for recovering valuable metals from e-waste.

Extraction of lead from waste CRT funnel glass by generating lead sulfide - An approach for electronic waste management

Waste cathode ray tube (CRT) funnel glass is the key and difficult points in waste electrical and electronic equipment (WEEE) disposal. In this paper, a novel and effective process for the detoxification and reutilization of waste CRT funnel glass was developed by generating lead sulfide precipitate via a high-temperature melting process. The central function in this process was the generation of lead sulfide, which gathered at the bottom of the crucible and was then separated from the slag. Sodium carbonate was used as a flux and reaction agent, and sodium sulfide was used as a precipitating agent. The experimental results revealed that the lead sulfide recovery rate initially increased with an increase in the amount of added sodium carbonate, the amount of sodium sulfide, the temperature, and the holding time and then reached an equilibrium value. The maximum lead sulfide recovery rate was approximately 93%, at the optimum sodium carbonate level, sodium sulfide level, temperature, and holding time of 25%, 8%, 1200°C, and 2h, respectively. The glass slag can be made into sodium and potassium silicate by hydrolysis in an environmental and economical process.

Mechanochemical mechanism of rapid dechlorination of hexachlorobenzene

Recent researches indicate that mechanochemical treatment (MCT) is a promising method to degrade the environmental hazards, especially in the area of persistent organic pollutants (POPs) disposal. However, the mechanochemical dechlorination mechanism of POPs still needs to be further verified. In this mechanochemical process, hexachlorobenzene (HCB) was chosen as a model pollutant with aluminum and alumina (Al+Al₂O₃) powders as the co-milling regents. Both of the intermediate analysis and quantum chemical calculations were adopted to elucidate the free radical dechlorination mechanism of HCB. The solid residues were characterized by electron spin-resonance (ESR) spectroscopy, Fourier transform infrared (FTIR) spectra and X-ray photoelectron (XPS) spectra, which proposed that the radicals formed in the mechanochemical process were chlorinated phenoxyl radicals (CB-O). Four quantum chemical descriptors were selected in predicting the intermediates and reaction pathway: (i) atomic charge, (ii) electrostatic potential (ESP), (iii) frontier molecular orbitals (FMO) theory and (iv) dual descriptor. Then, a stepwise dechlorination mechanism based on CB-O was proposed. It was found that the intermediates and radical-related reactions in the mechanochemical dechlorination of HCB are quite different from that happen in a typical photocatalytic dechlorination process. Impacts of different radical reactions on the dechlorination of HCB were also compared at last.

Recent development of recycling lead from scrap CRTs: A technological review

Cathode ray tubes (CRTs) contain numerous harmful substances with different functions. Lead is found in the funnel glass of CRTs. Improperly treated toxic lead may pose significant risks to human health and the environment. This paper reviews and summarizes existing technological processes on the recycling of lead from waste CRTs, including pyrometallurgy, hydrometallurgy, and product-regeneration. The present situation, advantages, and disadvantages of these techniques are described in detail. Generally, pyrometallurgy shows better practicability in recovery lead from waste CRT than hydrometallurgy and hydrometallurgy, in view of environmental impact, energy-consumption, product formats and safety and maturity of technology. Moreover, the gaps in the existing technologies were identified and recommendations for future research were provided.

Innovative leaching of cobalt and lithium from spent lithium-ion batteries and simultaneous dechlorination of polyvinyl chloride in subcritical water

In this work, an effective and environmentally friendly process for the recovery of cobalt (Co) and lithium (Li) from spent lithium-ion batteries (LIBs) and simultaneously detoxification of polyvinyl chloride (PVC) in subcritical water was developed. Lithium cobalt oxide (LiCoO2) power from spent LIBs and PVC were co-treated by subcritical water oxidation, in which PVC served as a hydrochloric acid source to promote metal leaching. The dechlorination of PVC and metal leaching was achieved simultaneously under subcritical water oxidation. More than 95% Co and nearly 98% Li were recovered under the optimum conditions: temperature 350°C, PVC/LiCoO2 ratio 3:1, time 30min, and a solid/liquid ratio 16:1 (g/L), respectively. Moreover, PVC was completely dechlorinated at temperatures above 350°C without any release of toxic chlorinated organic compounds. Assessment on economical and environmental impacts revealed that the PVC and LiCoO2 subcritical co-treatment process had significant technical, economic and environmental benefits over the traditional hydrometallurgy and pyrometallurgy processes. This innovative co-treatment process is efficient, environmentally friendly and adequate for Co and Li recovery from spent LIBs and simultaneous dechlorination of PVC in subcritical water.

An environmental benign process for cobalt and lithium recovery from spent lithium-ion batteries by mechanochemical approach

In the current study, an environmental benign process namely mechanochemical approach was developed for cobalt and lithium recovery from spent lithium-ion batteries (LIBs). The main merit of the process was that neither corrosive acid nor strong oxidant was applied. In the proposed process, lithium cobalt oxide (obtained from spent LIBs) was firstly co-grinded with various additives in a hermetic ball milling system, then Co and Li could be easily recovered by a water leaching procedure. It was found that EDTA was the most suitable co-grinding reagent, and 98% of Co and 99% of Li were respectively recovered under optimum conditions: LiCoO2 to EDTA mass ratio 1:4, milling time 4h, rotary speed 600r/min and ball-to-powder mass ratio 80:1, respectively. Mechanisms study implied that lone pair electrons provided by two nitrogen atoms and four hydroxyl oxygen atoms of EDTA could enter the empty orbit of Co and Li by solid-solid reaction, thus forming stable and water-soluble metal chelates Li-EDTA and Co-EDTA. Moreover, the separation of Co and Li could be achieved through a chemical precipitation approach. This study provides a high efficiency and environmentally friendly process for Co and Li recovery from spent LIBs.

Innovative Application of Mechanical Activation for Rare Earth Elements Recovering: Process Optimization and Mechanism Exploration

With the rapidly expanding use of fluorescent lamps (FLs) and increasing interest in conservation and sustainable utilization of critical metals such as rare earth elements (REEs), the recovering of REEs from phosphors in waste FLs is becoming a critical environmental and economic issue. To effectively recycle REEs with metallurgical methods, mechanical activation by ball milling was introduced to pretreat the waste phosphors. This current study put the emphasis on the mechanical activation and leaching processes for REEs, and explored the feasibility of the method from both theoretical and practical standpoints. Results showed physicochemical changes of structural destruction and particle size reduction after mechanical activation, leading to the easy dissolution of REEs in the activated samples. Under optimal conditions, dissolution yields of 89.4%, 93.1% and 94.6% for Tb, Eu and Y, respectively, were achieved from activated waste phosphors using hydrochloric acid as the dissolution agent. The shrinking core model proved to be the most applicable for the leaching procedure, with an apparent activation energy of 10.96 ± 2.79 kJ/mol. This novel process indicates that mechanical activation is an efficient method for recovering REEs from waste phosphors, and it has promising potential for REE recovery with low cost and high efficiency.