After mechanical pre-treatment, the typical hydrometallurgical route of NdFeB magnet recycling starts with leaching in acidic solutions. However, due to the high concentration of iron ions in the leaching solution, the selective recovery of rare earths from the solution is challenging. In our work, the selective precipitation of rare earth oxalates as a potential separation method was proposed. The precipitation of neodymium oxalate was first tested on model solutions, which was then followed by experimental tests carried out on real solutions after the leaching of NdFeB magnets. The recovery of rare earths in the form of oxalates was investigated with the use of different amounts of oxalic acid in relation to its stoichiometric amount. The most efficient separation of rare earths was observed in the case where sulfuric acid was used for leaching. The use of oxalic acid in stoichiometric amounts resulted in the precipitation of about 93% of all rare earths present in the solution, whereas the concentration of Fe and other elements (Ni, Co, and B) practically did not change. An increase in oxalic acid of 20% and 40% more than the stoichiometric amount (100%) led to the increase in the precipitation efficiency of rare earths to 96.7% and 98.1%, respectively. However, the use of oxalic acid in a 1.4 ratio caused a 7% decrease in Fe concentration, which suggests Fe co-precipitation. In order to investigate a possibility of further increasing the separation of rare earths from iron, an additional method was tested, in which iron was first oxidized from Fe²⁺ to Fe³⁺ before the precipitation of rare earth oxalates.

A simplified approach for rare earth elements leaching from NdFeB (neodymium-iron-boron) magnets was investigated. The possibility of simplifying the magnet recycling process by excluding grinding, milling and oxidative roasting unit operations was studied. Attempts to skip the demagnetization step were also conducted by using whole, non-demagnetized magnets in the leaching process. The presented experiments were conducted to optimize the operating conditions with respect to the leaching agent and its concentration, leaching time, leaching temperature and the form of the feed material. The use of hydrochloric and sulfuric acids as the leaching agents allowed selective leaching of NdFeB magnets to be achieved while leaving nickel, which is covering the magnets, in a solid state. The application of higher leaching temperatures (40 and 60 °C for sulfuric acid and 40 °C for hydrochloric acid) allowed us to shorten the leaching times. When using broken demagnetized magnets as the feed material, the resulting rare earth ion concentrations in the obtained solutions were significantly higher compared to using whole, non-demagnetized magnets.

In recent years, the demand for lithium, essential to the high-tech and battery sectors, has increased rapidly. The majority of lithium carbonate is now sourced from continental brines in Latin America, owing to the lower production costs and reduced environmental impact. In Europe, often overlooked but promising lithium resources could include highly mineralized underground waters. Therefore, this study investigates the enrichment of these low-grade solutions (<100 mg/L Li) through evaporation followed by solvent extraction (SX) processes under specific conditions. The effectiveness and the technical feasibility of lithium extraction were evaluated using binary synthetic, multicomponent semi-synthetic, and real brine samples. The popular tributyl phosphate/methyl isobutyl ketone (TBP/MIBK) system, supplemented with FeCl₃ and AlCl₃ as co-extractants, was employed as the organic phase. Evaporation resulted in significant lithium losses (up to 80%), reduced to ~10% by washing the crystallisate obtained during evaporation with ethanol. The results from SX tests revealed differences between the synthetic and real brines. While the synthetic brines exhibited satisfactory lithium extraction yields (91%), the real brines showed a significantly lower extraction efficiency (~32%), rendering the tested system ineffective. Solid phase precipitation during the SX trials was observed for both the synthetic and real brines, which were concentrated before the SX stage, highlighting the challenges in lithium-recovery processes. However, semi-synthetic brine trials yielded promising results, with a satisfactory extraction efficiency (76%), and the absence of physical problems (emulsion, long disengagement, etc.). This reveals the importance of the chemical composition of brines and emphasizes the need for varied procedural approaches in lithium-recovery processes.

New liquid crystalline thiophene esters, thiophene-3-yl 3,4,5-tris(n-dodecan-1-yloxy)benzoate (ThBz1) and thiophene-3-yl 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoate (ThBz2), were synthesized for use in lithium-ion batteries as safe, new solvent-free ionic conductors. Both compounds were synthesized in multi-step reactions and were characterized via¹H, ¹³C NMR and FT-IR spectroscopy, confirming the formation of the desired products. ThBz1 and ThBz2 showed good thermal stability and liquid crystalline behaviour. Electrochemical tests demonstrated a wide electrochemical window of 4 V for both tested ThBz compounds. Moreover, preliminary battery tests for new electrolytes in the LiCoO₂/Li₄Ti₅O₁₂ system confirmed their applicability in lithium-ion batteries.

Differential thermal analysis and differential scanning calorimetry were used to investigate phase equilibria in the AgCl–LnCl₃ (Ln = Ce, Sm, Gd) binary systems. It was found that systems under investigation represent typical examples of simple eutectic systems. The eutectic compositions and eutectic temperatures were found to be: x(CeCl₃) = 0.095, T_eut = 700 K (for AgCl–CeCl₃), x(SmCl₃) = 0.228, T_eut = 644 K (for AgCl–SmCl₃) and x(GdCl₃) = 0.288, T_eut = 609 K (for AgCl–GdCl₃). The thermodynamic functions of mixing in AgCl–LnCl₃ systems (Ln = Ce, Nd, Sm, Gd) were predicted on the basis of experimental data using the CALPHAD method by association model (AM) and Redlich–Kister model (RKM). The possibility of existence of the associates in the liquid phase was discussed.

Differential scanning calorimetry technique was used to investigate phase equilibria in the YbCl₂–MCl (M = Li, Na) binary systems. The YbCl₂–LiCl system exhibits an eutectic located at YbCl₂ mole fraction x = 0.415 (733 K) and a LiYb₂Cl₅ stoichiometric compound that is formed at 711 K and melts incongruently at 742 K. The YbCl₂–NaCl system exhibits an eutectic located at YbCl₂ mole fraction x = 0.559 (764 K). In both systems the formation of solid solutions in the MCl-rich side (M = Li, Na) has been found. The molar enthalpies of mixing (ΔH^MIX) in the liquid YbCl₂–MCl (M = Na, K) mixtures have been measured at 1085 K with a Calvet-type high temperature microcalorimeter in the entire range of composition. A negative value of mixing enthalpy was observed for all melts. The minimum value was of approximately: − 2.5, and − 7.5 kJ mol⁻¹, for systems with NaCl and KCl, respectively. All the experimental results along with the available literature data were used to optimize the thermodynamic properties of the investigated systems using the CALPHAD method.