The global shift towards sustainable energy solutions has made lithium-ion battery recycling essential for circular economy, handling resource efficiency, waste reduction, and industry innovation, aligning with SDGs #9 and #12. However, battery recycling plants are not yet at relevant scales, and transition to a circular battery value chain needs to be accelerated. To that end, a comprehensive computational framework is presented coupling CFD with PBM to simulate NiSO4·6H2O crystallization via antisolvent method for sustainable metal recovery in battery recycling applications. This integrated model solves discretized PBE to predict crystal size distribution in a continuous 3D T-mixer crystallizer, analyzing crystal formation and growth under steady state laminar flow (). A novel kinetic growth model is also developed experimentally to determine kinetic parameters, and is supported by precise Ni solubility data and nucleation thresholds, to ensure the occurrence of seeded crystal growth (desupersaturation). Crystal polymorphs are further characterized using powder XRD, confirming the formation of α − NiSO4·6H2O crystals. Influence of flow dynamics and residence time on seeded crystal growth and particle size distribution is investigated numerically. Impact of impinging flow on local supersaturation levels highlights the role of mixing in crystallization, revealing radial mixing intensification with Re. Increasing Re reduces mean crystal size owing to shorter residence times, leading to less supersaturation utilization. Moreover, PSD narrows with the increase in Re, and peak shifts towards smaller crystal sizes, while PSD broadens and shifts right along the mixing channel length. Eventually, the efficacy of T-mixer in promoting uniform crystal growth, targeting narrow PSD, is evaluated—enabling energy-efficient continuous crystallization systems. Furthermore, this predictive simulation approach will help in designing innovative crystallization processes, contributing to a truly circular economy.

The development of processes for recycling spent lithium-ion batteries requires having a good knowledge of the battery components, skills in electrochemistry and physicochemistry applied to lithium-ion batteries, and obviously, thorough backgrounds in separation science and chemical engineering. On the other hand, the engineers involved in the development of the next generations of lithium-ion batteries should integrate very early special considerations to make recycling easier and economic as well as to minimize the environmental impacts of the batteries during its whole lifecycle (eco-design). Therefore, engineers must have a very good view of the recycling processes and the corresponding physicochemistry. This chapter provides fundamental skills in electrochemistry and physicochemistry to help the engineers to develop lithium-ion batteries and processes for recycling spent lithium-ion batteries. This chapter gives prerequisites to the reader on physicochemistry and electrochemistry applied to lithium-ion batteries. After giving a short view of the battery components in the first part of this chapter, the second part brings the backgrounds to understand the physicochemical and electrochemical phenomena taking place in lithium-ion batteries. In the third part of this chapter, each unit operations of hydrometallurgical processes implemented to produce raw materials for lithium-ion batteries and to recycle spent lithium-ion batteries are presented.

Microplastic residues originating from lithium-ion battery components, including hydrophobic binder-derived poly(vinylidene fluoride) (PVDF) and separator-derived polyethylene (PE), are increasingly encountered in hydrometallurgical recycling streams, yet their impact on downstream lithium recovery remains largely unexplored. This study systematically investigates their influence on the reactive crystallization of lithium carbonate (Li2CO3) from aqueous lithium sulfate (Li2SO4) solutions. Precipitation at 80 °C was conducted at controlled polymer loadings (0.01–1.0 wt%), and crystallization kinetics, particle size distribution, filtration behavior, yield, and crystal morphology were evaluated using in situ monitoring, laser diffraction, and microscopy.PVDF markedly modified crystallization behavior, slightly reducing the turbidity onset times and promoting the formation of significantly finer particles, which led to a pronounced deterioration in filtration performance at higher loadings. Microscopy revealed that Li2CO3 crystallites preferentially nucleated and grew on PVDF surfaces, forming dense agglomerated structures rather than the larger, well-defined individual crystals observed in polymer-free systems. In contrast, PE exhibited similar but substantially weaker effects, with no clear evidence of surface-mediated nucleation. Despite these pronounced changes in crystal size, morphology, and separation behavior, the final Li2CO3 yield remained within 68–80% across all systems, with only a modest non-monotonic dependence on polymer loading.These findings demonstrate that hydrophobic polymer microplastics can act as effective heterogeneous nucleation sites, fundamentally altering crystallization pathways and downstream solid–liquid separation without significantly affecting equilibrium yield. The results highlight an overlooked process-level impact of microplastic contaminants and underscore the necessity of accounting for such impurities in the design and optimization of lithium-ion battery recycling flowsheets.

The growing demand for sustainable energy has accelerated the recycling of critical materials from spent batteries. In this context, this study investigates eutectic freeze crystallization (EFC) in a synthetic aqueous NiSO₄–CoSO₄–H₂O system, with the long-term goal of applying the method to real industrial lithium-ion battery (LiB) leachate streams. Binary phase diagrams for NiSO₄-H₂O and CoSO₄-H₂O were identified experimentally at eutectic points. In mixed systems, eutectic points were determined from temperature–concentration variations by adding 1–12 wt% CoSO₄ to a ≈ 20 wt% NiSO₄ solution. Similarly, 1–12 wt% NiSO₄ was incrementally added to a ≈ 20 wt% CoSO₄ solution to examine the influence of nickel. The eutectic points of both systems converged as the concentration of the added metal increased.

Experimental analysis (XRD, SEM-EDS, ICP-OES) revealed the formation of separate NiSO₄·7H₂O and CoSO₄·7H₂O crystal phases, and notably, CoNi(SO₄)₂·12H₂O was detected for the first time at eutectic points. Comparative simulations deviated from experimental findings, highlighting the need for improved low-temperature models. After washing, the generated ice contained <0.2 wt% Ni and Co, enabling its reuse as process water. These findings demonstrate EFC's potential for high-purity metal salt recovery and provide the necessary thermodynamic framework for its application to real-world industrial battery recycling.

This chapter addresses the hydrometallurgical processes employed to recycle lithium-ion batteries, focusing on nickel–manganese–cobalt and lithium–iron phosphate chemistries. It begins by discussing the mechanical pretreatment steps to liberate the various battery components. Pyrometallurgical methods are briefly covered, but the emphasis is on hydrometallurgical techniques, which are increasingly relied upon in the industry. The leaching process is examined in detail, including the use of inorganic and organic acids, as well as ammonia-based solutions. Oxidative precipitation, liquid–liquid extraction, and crystallization-precipitation are then explored as downstream purification and separation steps. Emerging innovations are also reviewed, such as thermal treatments, mechanochemical processing, advanced liquid–liquid extraction, electrodialysis, and novel crystallization techniques. The production of battery-grade metal salts is highlighted, and the importance of managing impurities to meet strict specifications for cathode active material synthesis is discussed. Finally, the chapter provides an overview of the Li-cycle recycling process as an industry example.

This collection presents papers from a symposium on extraction of rare metals from primary and secondary materials and residues as well as rare extraction processing techniques used in metal production. Contributions cover the extraction of less common or minor metals including elements such as antimony, bismuth, barium, beryllium, boron, calcium, chromium, gallium, germanium, hafnium, indium, manganese, molybdenum, platinum group metals, rare earth metals, rhenium, scandium, selenium, sodium, strontium, tantalum, tellurium, and tungsten. Also covered are rare metals of low-tonnage sales compared to high-tonnage metals (iron, copper, nickel, lead, tin, zinc, or light metals such as aluminum, magnesium, or titanium and electronic metalloid silicon). The collection also covers bio-metallurgy, hydrometallurgy, and electrometallurgy while novel high-temperature processes such as microwave heating, solar-thermal reaction synthesis, and cold crucible synthesis of rare metals are also addressed.

Recycling of rare earth elements (REEs) has become of paramount importance for permanent magnets used in electric vehicles, wind turbines and motors. There is an imbalance in supply and demand of this commodity and the REE has been identified as critical raw materials by the European Union. This study focuses on the recovery of REEs (La, Pr, Nd, Dy, Y) from sulfuric acid leach solutions using antisolvent crystallization, scaling up the process by hybrid process modelling, and performing environmental impact assessment. Ethanol is used as an antisolvent to crystallize REE2(SO4)3∙8H2O. The impact of inorganic impurities including Cu(II), Co(II), Al(III), B(III), Fe(II) and Fe(III) on the quality of the crystal product, in terms of purity and morphology, has been investigated. Higher purity (above 99%) is obtained for seeded experiments, and the purity is higher for higher seed loading and lower antisolvent dosing rate. Furthermore, the REEs have a tendency to be precipitate as a mixed phase, i.e. REE2(SO4)3∙8H2O. By balancing the addition of antisolvent and seed loading the optimum conditions in terms of high purity and productivity can be found. Scale-up of the process to 100 kg/batch, with solvent recovery of ethanol and H2SO4 (aq.), waste heat reutilization and trade-off analysis, potentially reduces the global warming potential from 40 kg CO2 eq to 0.96 kg CO2 eq /kg REE2(SO4)3∙8H2O. The results can provide valuable insights to understand and optimize the recovery of REEs from sulfate media as a pure concentrate from impure leach liquors. The potential for scaling up the process is also demonstrated resulting in relatively low impacts on global warming.

The effect of various organic antisolvents on the solubility of lithium hydroxide monohydrate (LiOH·H2O) in water was systematically determined in order to obtain composition data for lithium hydroxide – water – antisolvent ternary systems. Based on these data, antisolvent crystallization of LiOH·H2O from a synthetic aqueous feed solution was investigated. A total of nine antisolvents were studied, including methanol, ethanol, acetone, 1-propanol, 2-propanol, 1,4-dioxane, 1,2-dimethoxyethane, acetonitrile and tetrahydrofuran (THF). LiOH·H2O showed high solubility in methanol and ethanol, and low solubility in 2-propanol, 1,4-dioxane and 1,2-dimethoxyethane aqueous solutions. The use of THF resulted in the formation of two liquid phases in all cases, while acetonitrile and 1-propanol also led to liquid phase separation at lower antisolvent mole fractions. In the acetone system, solvent decomposition was confirmed by 1H NMR, revealing aldol condensation. Crystallization of LiOH·H2O was confirmed for all antisolvents by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Among the tested solvents, 2-propanol was selected as the most promising antisolvent due to its favorable solubility behavior, environmental and human health profile, safety, and lower cost compared to 1,4-dioxane and 1,2-dimethoxyethane.

The thermodynamics and kinetics of ethanol antisolvent crystallization of rare earths from sulfate solutions has been explored, with a view towards separating the rare earths as part of a NdFeB magnet recycling process. The solubility of single and binary metal (Nd, Pr, Fe) phases in aqueous ethanol solutions has been determined. The impact of Fe and Pr on the crystallization of Nd is evaluated, the oxidation kinetics of Fe(II) to Fe(III) quantified, and the influence of Fe oxidation state on the thermodynamics and kinetics of crystallization investigated. Oxidation to Fe(III) is slow, with a half life of approx. 600 h. For pure Nd, the solubility of the obtained, stable sulphate octahydrate decreases exponentially with increased molar organic:aqueous (O/A) ratio, and is well described by the OLI model until O/A=0.2. Pr crystallizes as an isostructural octahydrate with similar solubility. Fe(II) precipitates as a mixed solid phase, with a solubility approximately 40 times higher than the rare earths at O/A=0.2. Fe(III) solutions exhibit liquid–liquid phase separation without precipitation at all evaluated concentrations. Nd and Pr coprecipitate together in proportion to their relative concentrations, with Pr precipitating at concentrations well below its pure component solubility. Fe(II) does not precipitate with Nd at O/A≤0.2 even at high concentration, with significant precipitation as separate particles at higher O/A for all concentrations. The crystallization kinetics and the morphology of the Nd phase is affected by the Fe oxidation state. The work highlights the potential of antisolvent crystallization for selective and efficient separation of REE from Fe.

Rare earth elements (REEs) are important for permanent magnets used in for example wind turbines and motors. There is an imbalance in supply and demand of this commodity and the REE have been identified as critical raw materials by the European Union. This study focuses on recovery of REEs from sulfuric acid solutions using antisolvent crystallization in recycling of magnet waste. Ethanol is used as an antisolvent to crystallize Nd2(SO4)3∙8H2O and (Nd/Dy)2(SO4)3∙8H2O. The impact of the presence of Fe in ferrous and ferric states, and of different seeding strategies, on the quality of the crystal product in terms of purity, crystal size, morphology and agglomeration has been investigated. Higher purity (above 99%) is obtained for seeded experiments and the purity is higher for higher seed loading and lower antisolvent dosing rate. Furthermore, Fe(III) has a higher tendency to be incorporated into the pure Nd phase compared to the Nd phase containing 10% of Dy, while Fe(II) is not detected in any of the phases. By balancing the addition of antisolvent and seed loading the optimum conditions in terms of high purity and productivity can be found. The results provide insights to improve the recovery of REEs as a pure concentrate.