Slags from the metallurgical recycling process are an important source of resources classified as critical elements by the EU. One example is lithium from Li-ion battery recycling. In this context, the thermodynamic properties of the recycled component system play a significant role in the formation of the Li-bearing phases in the slag, in this case, LiAlO₂. LiAlO₂ crystal formation could be engineered and result in varying sizes and occurrences by different metallurgical processing conditions. This study uses pure ingredients to provide a synthetic model material which can be used to generate the valuable phase in the slag, or so-called engineered artificial minerals (EnAMs). The aim is to investigate the crystallisation of LiAlO₂ as an EnAM by controlling the cooling conditions of the model slag to optimise the EnAM formed during crystallisation. Characterisation of the EnAMs is an important step before further mechanically processing the material to recover the valuable element Li, the Li-bearing species, respectively. Investigations are conducted using powder X-ray diffraction (XRD), X-ray fluorescence (µXRF), and X-ray Computer Tomography (XCT) on two different artificial lithium slags from MnO-Al₂O₃-SiO₂-CaO systems with different cooling temperature gradients. The result shows the different EnAM morphology along the height of the slag, which is formed under different slag production conditions in a semi-pilot scale experiment of 5 kg. Based on the different EnAM morphologies, three defined qualities of the EnAM are identified: granular, dendritic, and irregular-shape EnAM.

Displacement washing of filter cakes is a critical process in various filtration applications and the presence of a top layer of fine particles from preceding cake filtration may influence washing efficiency. To investigate the effect of such a top layer on the displacement washing process, filter cakes with solid volume fractions ranging from 15 % to 33 % are formed from crushed, irregularly shaped limestone particles of about 10 to 250 µm to minimize or induce segregation effects due to sedimentation superimposed on cake filtration. The structural properties of the filter cakes are measured using X‐ray microscopy and dynamic image analysis. To predict the influence of cake structure on displacement washing, an advection–dispersion model is employed. Comparison between prediction and experimental data shows good agreement, highlighting the impact of cake structure on washing efficiency and providing valuable insights for optimizing displacement washing processes in industrial applications.

A more thorough understanding of the properties of bulk material structures in solid–liquid separation processes is essential to understand better and optimize industrially established processes, such as cake filtration, whose process outcome is mainly dependent on the properties of the bulk material structure. Here, changes of bulk properties like porosity and permeability can originate from local variations in particle size, especially for non-spherical particles. In this study, we mix self-similar fractions of crushed, irregularly shaped Al₂O₃ particles (20 to 90 µm and 55 to 300 µm) to bimodal distributions. These mixtures vary in volume fraction of fines (0, 20, 30, 40, 50, 60 and 100 vol.%). The self-similarity of both systems serves the improved parameter correlation in the case of multimodal distributed particle systems. We use nondestructive 3D X-ray microscopy to capture the filter cake microstructure directly after mechanical dewatering, whereby we give particular attention to packing structure and particle–particle relationships (porosity, coordination number, particle size and corresponding hydraulic isolated liquid areas). Our results reveal widely varying distributions of local porosity and particle contact points. An average coordination number (here 5.84 to 6.04) is no longer a sufficient measure to describe the significant bulk porosity variation (in our case, 40 and 49%). Therefore, the explanation of the correlation is provided on a discrete particle level. While individual particles < 90 µm had only two or three contacts, others > 100 µm took up to 25. Due to this higher local coordination number, the liquid load of corresponding particles (liquid volume/particle volume) after mechanical dewatering increases from 0.48 to 1.47.