Eva Gerold

The growing demand for lithium-ion batteries (LIBs), particularly in the field of electromobility, is leading to an increasing need for efficient and sustainable recycling processes. In addition to the recovery of strategically important metals, such as lithium, nickel, cobalt, and manganese, the fluorine content also poses a challenge. Fluorine enters the battery system primarily via the conductive salt lithium hexafluorophosphate (LiPF₆) and via fluorine-containing binders, such as polyvinylidene fluoride (PVDF). During hydrometallurgical recycling, fluorine can transfer into the leaching solution, where it can negatively impact metal recovery and product quality, e.g., by forming stable fluoride compounds. Furthermore, this halogen exhibits environmentally problematic and health-hazardous properties. This study investigates the distribution of fluorine and the influence of defluorination strategies on hydrometallurgical recycling processes for end-of-life lithium-ion batteries. For this purpose, the fluorine content in each process step from two different black masses, one pyrolysed and one unpyrolysed sample, are analysed. To determine their behaviour and the effect of pretreatment, these experiments are also conducted with defluorinated black masses. Wet-chemical defluorination in an alcoholic potassium hydroxide solution was used as the defluorination method, which was then compared to the untreated variants as a reference. After pretreatment, the hydrometallurgical recycling process of the black masses starts by leaching with sulphuric acid, as well as the addition of hydrogen peroxide as a reducing agent. The pregnant leach solutions are further processed using multi-stage precipitation processes to selectively recover nickel, cobalt, manganese, and lithium. The fluorine content in the individual process steps is measured in order to evaluate the fluorine distribution throughout the process. In combination with the effects of the respective pretreatments on the fluorine distribution, a broader understanding of fluorine behaviour in hydrometallurgical recycling of lithium-ion batteries can be gained.

Selective lithium pre-leaching can separate an accessible lithium fraction before complete black-mass dissolution while limiting the co-dissolution of accompanying elements. However, comparative evidence across compositionally different, industrially pyrolyzed black masses under a consistent operating framework remains limited. To address this gap, three such black masses were systematically investigated using water and dilute inorganic and organic acids (0.1–0.5 mol·L⁻¹, 25–80 °C) without an external reducing agent. Water-leaching experiments were additionally performed to quantify the readily soluble lithium fraction. Lithium extraction after 120 min varied strongly with black mass origin and leaching conditions. Water leaching extracted 12–16% Li from BM1, 24–28% from BM2, and 36–47% from BM3. Under the most favourable water-leaching conditions, transition-metal dissolution remained negligible, resulting in substantially higher selectivity than in most acidic systems. Dilute acids increased lithium extraction in selected experiments, reaching up to 98%, but this was generally accompanied by increased dissolution of Co, Ni, Mn, Cu, and Al. The results demonstrate that lithium accessibility is governed more strongly by feed-specific phase composition and material history than by total lithium content. Selective pre-leaching should therefore be considered a feed-dependent conditioning step whose operating conditions must balance lithium removal against preservation of the transition-metal-rich solid fraction.

Heavy mineral sands (HMS) are the principal source of titanium feedstock. Yet their critical-element content is rarely resolved at the mineral scale, even though it determines whether these elements are recoverable. This study characterizes the run-of-mine feed of the operating Byrzulivske ilmenite deposit (Ukraine) using a multidimensional property-class analysis of particle size, density and magnetic susceptibility, with chemical and mineralogical analyses for each property class. The feed carries 9.8 wt% heavy minerals dominated by ilmenite, altered along the ilmenite–pseudorutile–leucoxene sequence, with accessory zircon, monazite and xenotime concentrated in the finer particle size classes. Because the assemblage is essentially fully liberated, each susceptibility class approximates a single-mineral population, and the element deportment maps directly onto the host minerals. The critical elements can be resolved into three routes. Vanadium, niobium and tantalum substitute in the altered ilmenite and would report to the commercial ilmenite concentrate, amounting to roughly 1100 t V2O5, 210 t Nb2O5 and 51 t Sc2O5 per year at current throughput. Hafnium and the rare earth elements are carried by zircon and phosphates and would report entirely to the non-magnetic tailings, together with about 1600 t ZrO2 and 16 t HfO2 annually. Scandium follows the ilmenite by mass but reaches its highest grades in zircon. The by-product potential lost under the present flowsheet is therefore concentrated in a single, fully liberated tailings stream, which is identified as the priority target for dedicated reprocessing.

The alteration of ilmenite controls its chemical composition, mineralogy, and physical properties, and thereby its behaviour during processing; yet the alteration state, magnetic susceptibility, and electrostatic charging are usually examined separately and remain insufficiently linked. This study characterises ilmenite from a weathering placer deposit using an integrated multi-property approach across defined particle-size and magnetic-susceptibility classes, combining X-ray fluorescence, iron redox titration, X-ray diffraction, polarized-light microscopy, scanning electron microscopy with energy-dispersive spectroscopy, specific surface area measurement and corona charging experiments. Progressive alteration follows a single continuous trajectory that combines the oxidation of Fe2+ to Fe3+ with the leaching of iron, accompanied by titanium enrichment and a gradual transformation from an ilmenite-dominated toward a rutile-dominated, partly amorphous Ti-rich assemblage, consistently across all particle size classes. The Fe2+/Fe3+ ratio is quantitatively related to both the apparent magnetic susceptibility and the specific surface area through well-defined power laws, with nearly identical exponents across the three size classes. Because oxidation and leaching advance together, the readily measured redox ratio reliably tracks the degree of alteration; the magnetic susceptibility, however, is governed primarily by the total iron content, so that the ratio serves as a convenient indirect proxy rather than the direct physical cause. In contrast, the electrostatic charging is not a simple function of the alteration state. Still, it is jointly governed by the alteration state and grain size, with the coarse and fine classes responding in opposite directions; the coarse class acquires the highest specific charge despite its larger size, contrary to the usual size–charge expectation. The results establish the Fe2+/Fe3+ ratio as a practical indicator of the alteration state and show that the individual separation properties respond to that state in distinct ways, with direct implications for the magnetic and hydrometallurgical processing of altered ilmenite.

Cemented carbides are essential materials for cutting and wear applications but rely on critical raw materials such as tungsten and cobalt, making efficient recycling routes increasingly important. The zinc process is an established recycling technology in which cemented carbides are first disintegrated by zinc infiltration and subsequently treated by vacuum distillation to remove incorporated zinc and recover reusable WC-Co powder. However, this distillation step is typically associated with deep vacuum conditions and extended treatment times, while systematic data on parameter dependencies remain limited. In this study, zinc removal from disintegrated WC-Co cemented carbides was experimentally investigated at an intermediate vacuum level of 150 mbar to assess distillation behavior under moderate vacuum conditions. Two industrially relevant cemented carbide grades were examined using a design-of-experiments approach to evaluate the influence of temperature (700–1000 °C) and holding time (30–180 min) on residual zinc content. Zinc removal exceeding 98% was achieved within the investigated parameter window, with temperature identified as the dominant parameter. Pronounced material-dependent differences were observed between the two grades. Thermodynamic calculations further showed that zinc volatility in the Co-Zn system is strongly composition dependent. These findings provide insight into composition-dependent zinc evaporation and vacuum-assisted separation behavior under reduced-pressure conditions.

Cemented carbides are essential for cutting and drilling applications but rely on critical raw materials such as tungsten and cobalt, making efficient recycling increasingly important. While zinc-based recycling is industrially established, the kinetics of zinc-induced disintegration under vapor-phase conditions remain insufficiently quantified. In this study, the disintegration kinetics of four industrial WC-Co cemented carbide grades with systematically varied WC grain size, cobalt binder content, and alloying and grain growth inhibitor additions were investigated under zinc vapor exposure. The evolution of disintegration yield was analyzed using a shrinking core framework, evaluating reaction-controlled and diffusion-controlled limiting cases. Neither regime alone described the full kinetic behavior, indicating mixed control governed by interfacial reaction and zinc transport through the product layer. Significant differences in effective kinetic parameters were observed between the grades, demonstrating a strong dependence on material composition. The results establish a quantitative link between microstructure and disintegration behavior, demonstrating that process durations can be adjusted to specific cemented carbide grades and providing a basis for material-informed optimization of zinc-based recycling processes.

The growing demand for lithium-ion batteries (LIBs) requires efficient and sustainable recycling solutions. This study investigates bioleaching as an alternative to conventional hydrometallurgical methods, focusing on (i) organic acid-mediated leaching with Gluconobacter oxydans and (ii) sulfuric acid bioleaching with Acidithiobacillus thiooxidans. Experiments were conducted at 26 °C with leaching durations of one to three weeks, depending on the microbial system, at pH 1.35 for sulfuric acid treatments, and with liquid-to-solid ratios equivalent to 100 mL g⁻¹ (A. thiooxidans) or 100 mL g⁻¹ in culture medium (G. oxydans). Results show that indirect bioleaching with G. oxydans achieved high recovery rates for cobalt (96%), manganese (100%), nickel (65%), and lithium (68%), while the direct approach was less effective due to microbial inhibition by black mass components. Similarly, biologically produced sulfuric acid exhibited moderate leaching efficiencies, but chemically synthesized sulfuric acid outperformed it, particularly for nickel (93%) and lithium (76%) after one week of leaching. These findings suggest that bioleaching is a promising, eco-friendly alternative for LIB recycling but requires further process optimization to improve metal recovery and industrial scalability. Future research should explore hybrid approaches combining bioleaching with conventional leaching techniques.