Speciation of Manganese in a Synthetic Recycling Slag Relevant for Lithium Recycling from Lithium-Ion Batteries

Photo-switchable Collectors for the Flotation of Lithium Aluminate for the Recycling of the Critical Raw Material Lithium

Flotation of the mineral lithium aluminate by application of the natural product punicine from Punica granatum and some derivatives as collectors is examined. Punicines, 1-(2',5'-dihydroxyphenyl)-pyridinium compounds, are switchable molecules whose properties can be changed reversibly. They exist as cations, neutral mesomeric betaines, anions, and dianions depending on the pH. In light, they form radicals. Five punicine derivatives were prepared which possess β-methyl, β-chlorine, γ-tert.-butyl, and γ-acetyl groups attached to the pyridinium ring, and a pyrogallol derivative. On the other hand, LiAlO2 reacts with water to give species such as LiAl2(OH)7 on its surface. Flotations were performed applying the punicines in daylight (3000 lux), in darkness (<40 lux) and under UV-irradiation (4500 lux, 390-400 nm). The pH of the suspension, the collector's concentration, the conditioning time as well as the flotation time were varied. The recovery rates strongly depend on these parameters. For example, the recovery rate of lithium aluminate was increased by 116 % on changing the lighting condition from daylight to darkness, when the pyrogallol derivative of punicine was applied. UV, FTIR, TGA and zeta potential measurements as well as DFT calculations were performed in order to gain insight into the chemistry of punicines on the surface of LiAlO2 and LiAl2(OH)7 in water which influence the flotation's results.

Pyrometallurgical Approach to Extracting Valuable Metals from a Combination of Diverse Li-Ion Batteries' Black Mass

Li-ion batteries (LIBs) are widely used nowadays. Because of their limited lifetimes and resource constraints in manufacturing them, it is essential to develop effective recycling routes to recover their valuable elements. This study focuses on the pyrometallurgical recycling of black mass (BM) from a mixture of different LIBs. In this study, the high-temperature behavior of two types of mixed BM is initially examined. Subsequently, the effect of mechanical activation on the BM reduction kinetics is investigated. Finally, hematite is added to the BM to first be reduced by the excess graphite in the BM and second to form an Fe-based alloy containing Co and Ni. This study demonstrates that mechanical activation does not necessarily affect the kinetics of BM high-temperature behavior. Furthermore, it demonstrates that alloy-making by the addition of hematite is a successful method to simultaneously utilize the graphite in the BM and recover Co and Ni, regardless of the LIB type.

Engineering Compounds for the Recovery of Critical Elements from Slags: Melt Characteristics of Li5AlO4, LiAlO2, and LiAl5O8

Engineered artificial minerals (EnAMs) are the core of a new concept of designing scavenger compounds for the recovery of critical elements from slags. It requires a fundamental understanding of solidification from complex oxide melts. Ion diffusivity and viscosity play vital roles in this process. In the melt, phase separations and ion transport give rise to gradients/increments in composition and, with it, to ion diffusivity, temperature, and viscosity. Due to this complexity, solidification phenomena are yet not well understood. If the melt is understood as increments of simple composition on a microscopic level, then the properties of these are more easily accessible from models and experiments. Here, we obtain these data for three stoichiometric lithium aluminum oxides. LiAlO2 is a promising EnAM for the recovery of lithium from lithium-ion battery pyrometallurgical processing. It is obtained through the addition of aluminum to the recycling slag melt. The high temperature properties spanning from below to above the liquidus temperature of three stoichiometric Li-Al-Oxides: Li5AlO4, LiAlO2, and LiAl5O8 are determined using molecular dynamic simulations. The compounds are also synthesized via the sol-gel route. The Li+ ion exhibits the largest diffusivity. They are quite mobile already below the liquidus temperature, i.e., for LiAlO2 at T = 1700 K, the diffusion coefficient of the lithium ion equals D = 3.0 × 10-9 m2 s-1. The other ions Al3+ and O2- do not move considerably at that temperature. The diffusivity of Li+ is largest in the lithium-rich compound Li5AlO4 with D = 32 × 10-9 m2 s-1 at 2500 K. The lower the viscosity, the higher the lithium content. The Li5AlO4 exhibits a viscosity of η = 2.2 mPa s at 1328 K which matches well with the experimentally determined 2.5 mPa s at this temperature. The viscosity of LiAlO2 at 1800 K is more than two times higher. These data sets can help to describe the melts on a microscopic level and understand how the melt properties will change due to gradients in the Li/Al concentration.

Experimental Study Based on Box-Behnken Design and Response Surface Methodology for Optimization Proportioning of Activated Lithium Slag Composite Cement-Based Cementitious Materials

Cement-based cementitious materials occupy a central position in the construction industry, but the problem of high carbon dioxide(CO2) emissions from cement production has attracted global attention. To meet this challenge, finding low-carbon alternative materials has become a top priority in the research of new building materials. At the same time, the problem of large amounts of lithium slag piling up needs to be solved, and resource utilization has become its potential way out. In this study, the volcanic ash activity of lithium slag was activated by composite activation means of high-temperature calcination and sodium silicate, and it was used as an alternative mix to cement. The Box-Behnken design and response surface method (BBD-RSM) was utilized to optimize the ratio of activated lithium slag composite cement-based cementitious materials, and high-performance new solid waste cementitious materials were prepared. The results show that activated lithium slag composite cementitious materials activated lithium slag exhibit excellent performance when activated lithium slag mass fraction is 7.3%, the sodium silicate dosage is 8.8%, and water-solid ratio is 0.6:1. The composite cementitious material under this ratio shows excellent performance, with fluidity 235.69 mm, gelation time 73.54 s, water evolution rate 1.123%, 3d and 28d compressive strengths, respectively, are 11.54 MPa and 22.9 MPa. Compared with ordinary Portland-cement-based cementing materials, the uniaxial compressive strength, modulus of elasticity, and tensile strength at break of activated lithium slag cementitious material solidified body were increased by 34.33%, 36.43%, and 34.98%, and the compressive deformation and tensile deformation were enhanced by 37.78% and 40%. This study not only provides a theoretical basis and experimental foundation for the preparation of new solid waste cementitious materials, but also provides a new solution for the reinforcement of crushed rock bodies in engineering practice, which is of great significance for promoting the low-carbon development of the construction industry.

Control of Interface Migration in Nonequilibrium Crystallization of Li2SiO3 from Li2O-SiO2 Melt by Spatiotemporal Temperature and Concentration Fields

During liquid-solid transformation, bulk mass and thermal diffusion, along with the evolved interfacial latent heat, work in tandem to generate interfacial thermodynamic and kinetic forces, the interplay of which decides the solidification velocity and consequently the solidified phase attributes. Hence, access to interface dynamics information in dependence of bulk transfer processes is pivotal to tailor the desired quantity of solid phases of unique compositions. It finds particular application for engineering concentrated Lithium (Li) phases out of Li-ion battery slags, thus generating a high value-added product from a conventional waste process stream. However, considerable challenge exists to predict the impact of the diverse external cooling rates on the evolving internal transfer processes and thus tuning solidification routes for achieving phases of interest. Hence, in this work, a thermodynamically consistent nonequilibrium model, by considering spatiotemporal temperature and concentration fields, is developed and applied to study solidification of Li2SiO3 from a Li2O-SiO2 melt that constitutes an important subsystem of the Li containing battery-recycling slags. The approach treats the sharp solid/liquid interface as a moving heat source. In the presence of different heat extraction profiles, it evaluates the spatial temperature heterogeneity and its implicit correlation to internal material fluxes resulting from maximization of dissipation and consequently the interrelation to interface velocities. Model calculations revealed that irrespective of the external cooling rate, for an initial short time duration, the magnitude of which increased with decreasing cooling rates, the interface velocities show a reducing trajectory directly relatable to the reducing thermodynamic forces due to localized interfacial temperature rise from the generated latent heat of fusion from the initial solidification. This is followed by a thermodynamically controlled regime, whereby for each cooling rate, the interface velocities increase until a maxima, the magnitude of which decreases with decreasing cooling rates. Finally, the interface propagation speeds decrease as controlled by the kinetic regime.

Lithium aluminate flotation by pH- and light-switchable collectors based on the natural product punicine

Derivatives of the natural product punicine [1-(2',5'-dihydroxyphenyl)pyridinium chloride] were developed as switchable collectors for the flotation of lithium-containing engineered artifical minerals (EnAMs). These EnAMs are e.g. formed by pyrometallurgical processing of end-of-life lithium-ion batteries. Depending on the pH value and the lighting conditions, punicines exist in water as cations, two different electrostatically neutral mesomeric betaines, anionic tripoles, radical cations or radical anions. The radical species form by photochemically induced disproportionation reactions. We prepared punicine derivatives introducing alkyl chains in the pyridinium moiety (4-methyl, 4-ethyl, 4-octyl and 4-undecanyl) to install hydrophobic groups and examined the recovery rates of the flotation of lithium aluminate (LiAlO2). We varied the lighting conditions (darkness, daylight, LED irradiation at λ = 390-400 nm) and the pH value, the collector's and frother's concentration, and the flotation time. With our collectors, recovery rates of lithium aluminate up to 90% were accomplished when the flotation was conducted in Hallimond tubes exposed to daylight at pH 11 in water.

Polyether-tethered imidazole-2-thiones, imidazole-2-selenones and imidazolium salts as collectors for the flotation of lithium aluminate and spodumene

Imidazolium salts were prepared which possess 2-ethoxyethyl pivalate or 2-(2-ethoxyethoxy)ethyl pivalate groups as amphiphilic side chains with oxygen donors as well as n-butyl substituents as hydrophobic groups. The N-heterocyclic carbenes of the salts, characterized by 7Li and 13C NMR spectroscopy as well as by Rh and Ir complex formation, were used as starting materials for the preparation of the corresponding imidazole-2-thiones and imidazole-2-selenones. Flotation experiments in Hallimond tubes under variation of the air flow, pH, concentration and flotation time were performed. The title compounds proved to be suitable collectors for the flotation of lithium aluminate and spodumene for lithium recovery. Recovery rates up to 88.9% were obtained when the imidazole-2-thione was used as collector.

Influencing the froth flotation of LiAlO2 and melilite solid solution with ionic liquids

In the present work experiments for single mineral flotation against LiAlO₂ and melilite s.s. were carried out for seven ionic liquids (ILs). From these, IL-1 with an imidazolium cation and a bromide anion and IL-7 with a pyridinium cation and a bromide anion were selected for further flotation experiments (dosage, pH). Flotation experiments were also conducted using naphthenic acid, a conventional flotation fatty acid-based collector, and FS-2, a commercial collector in order to compare the results with ILs. Moreover, the effects of different anions in the ILs on the flotation were evaluated and a significant influence on the hardness of anions was found on the flotation process. Finally, a pre-functionalization was also explored with modified cholesterol derivatives, comparing the effect of cholesterylsulfate and cholesterylphosphate on the flotation of LiAlO₂ and melilite s.s. This study is vital for the further optimization of lithium recovery from the pyrometallurgical recycling path of lithium-ion batteries and the flotation of primary minerals such as aluminosilicates.

Recovery of Graphite and Cathode Active Materials from Spent Lithium-Ion Batteries by Applying Two Pretreatment Methods and Flotation Combined with a Rapid Analysis Technique

This work investigates the comprehensive recycling of graphite and cathode active materials (LiNi0.6Mn0.2Co0.2O2, abbreviated as NMC) from spent lithium-ion batteries via pretreatment and flotation. Specific analytical methods (SPME-GC-MS and Py-GC-MS) were utilized to identify and trace the relevant influencing factors. Two different pretreatment methods, which are Fenton oxidation and roasting, were investigated with respect to their influence on the flotation effectiveness. As a result, for NMC cathode active materials, a recovery of 90% and a maximum grade of 83% were obtained by the optimized roasting and flotation. Meanwhile, a graphite grade of 77% in the froth product was achieved, with a graphite recovery of 75%. By using SPME-GC-MS and Py-GC-MS analyses, it could be shown that, in an optimized process, an effective destruction/removal of the electrolyte and binder residues can be reached. The applied analytical tools could be integrated into the workflow, which enabled process control in terms of the pretreatment sufficiency and achievable separation in the subsequent flotation.

Influence of P and Ti on Phase Formation at Solidification of Synthetic Slag Containing Li, Zr, La, and Ta

In the future, it will become increasingly important to recover critical elements from waste materials. For many of these elements, purely mechanical processing is not efficient enough. An already established method is pyrometallurgical processing, with which many of the technologically important elements, such as Cu or Co, can be recovered in the metal phase. Ignoble elements, such as Li, are known to be found in the slag. Even relatively base or highly redox-sensitive elements, such as Zr, REEs, or Ta, can be expected to accumulate in the slag. In this manuscript, the methods for determining the phase formation and the incorporation of these elements were developed and optimized, and the obtained results are discussed. For this purpose, oxide slags were synthesized with Al, Si, Ca, and the additives, P and Ti. To this synthetic slag were added the elements, Zr and La (which can be considered proxies for the light REEs), as well as Ta. On the basis of the obtained results, it can be concluded that Ti or P can have strong influences on the phase formation. In the presence of Ti, La, and Ta, predominantly scavenged by perovskite (Ca1-wLa2/3wTi1-(x+y+z)Al4/3xZryTa4/5zO3), and Zr predominantly as zirconate (Ca1-wLa2/3wZr4-(x+y+z)Al4/3xTiyTa4/5zO9), with the P having no effect on this behavior. Without Ti, the Zr and Ta are incorporated into the pyrochlore (La2-xCa3/2x-yZr2+2/4y-zTa4/5zO7), regardless of the presence of phosphorus. In addition to pyrochlore, La accumulates primarily in britholite-type La oxy- or phosphosilicates. Without P and Ti, similar behavior is observed, except that the britholite-like La silicates do not contain P, and the scavenging of La is less efficient. Lithium, on the other hand, forms its own compounds, such as LiAlO2(Si), LiAl5O8, eucryptite, and Li silicate. Additionally, in the presence of P, Li3PO4 is formed, and the eucryptite incorporates P, which indicates an additional P-rich eutectic melt.

HERMES - a GUI-based software tool for pre-processing of X-ray absorption spectroscopy data from laboratory Rowland circle spectrometers

HERMES, a graphical user interface software tool, is presented, for pre-processing X-ray absorption spectroscopy (XAS) data from laboratory Rowland circle spectrometers, to meet the data handling needs of a growing community of practice. HERMES enables laboratory XAS data to be displayed for quality assessment, merging of data sets, polynomial fitting of smoothly varying data, and correction of data to the true energy scale and for dead-time and leakage effects. The software is written in Java 15 programming language, and runs on major computer operating systems, with graphics implementation using the JFreeChart toolkit. HERMES is freely available and distributed under an open source licence.

Improvement of the froth flotation of LiAlO2 and melilite solid solution via pre-functionalization

In this work froth flotation studies with LiAlO₂ (lithium-containing phase) and Melilite solid solution (gangue phase) are presented. The system was optimized with standard collectors and with compounds so far not applied as collectors. Furthermore, the principle of self-assembled monolayers was introduced to a froth flotation process for the first time resulting in excellent yields and selectivities.