Platinum group metals (PGMs) are a group of six metals with high market value and key importance to many industrial sectors. Due to their low prevalence in the Earth’s crust and high demand, these metals have been recognized as critical materials for many years. Along with economic development, the natural resources of the platinum group metals are gradually depleting, which is accompanied by the need to recover PGMs from secondary sources. The solutions resulting from the processing of such materials are characterized by high content of impurities and low content of precious metals. For this reason, in order to obtain pure metals, it is extremely important to choose an effective, selective method for the recovery and separation of the platinum group metals. This review focuses on the most important aspects of the characteristics of the PGMs, including their properties and occurrence, the processing of natural and secondary raw materials and the role of liquid–liquid extraction in the selective separation of metals from this group, not only on a laboratory scale but, above all, on an industrial scale. In addition, this study collects information on the most commonly used, commercially available extractants, based on current reports, taken from the scientific literature.

This work presents the research results on the development of an innovative, hydrometallurgical technology for the production of manganese(II) perrhenate dihydrate from recycled waste. These wastes are scraps of Ni-based superalloys containing Re and scraps of Li–ion batteries containing Mn—specifically, solutions from the leaching of black mass. This work presents the conditions for the production of Mn(ReO₄)₂·2H₂O. Thus, to obtain Mn(ReO₄)₂·2H₂O, manganese(II) oxide was used, precipitated from the solutions obtained after the leaching of black mass from Li–ion batteries scrap and purified from Cu, Fe and Al (pH = 5.2). MnO₂ precipitation was carried out at a temperature < 50 °C for 30 min using a stoichiometric amount of KMnO₄ in the presence of H₂O₂. MnO₂ precipitated in this way was purified using a 20% H₂SO₄ solution and then H₂O. Purified MnO₂ was then added alternately with a 30% H₂O₂ solution to an aqueous HReO₄ solution. The reaction was conducted at room temperature for 30 min to obtain a pH of 6–7. Mn(ReO₄)₂·2H₂O precipitated by evaporating the solution to dryness was purified by recrystallization from H₂O with the addition of H₂O₂ at least twice. Purified Mn(ReO₄)₂·2H₂O was dried at a temperature of 100–110 °C. Using the described procedure, Mn(ReO₄)₂·2H₂O was obtained with a purity of >99.0%. This technology is an example of the green transformation method, taking into account the 6R principles.

This paper presents comparative experimental results for the single-stage and two-stage counter-current acid leaching of battery masses, with the addition of a booster, from different types of LIB waste. Three different types of battery masses were used in this research: Material I, module car; Material II, tablets and laptops; and Material III, mobile phones. These materials were obtained during the mechanical processing of Li-ion battery waste, which were dried at a temperature in the range of 80–180 °C. Leaching studies of these materials were carried out using the single-stage acid leaching method with the addition of hydrogen peroxide, and the innovative two-stage counter-current acid leaching method, also with the addition of hydrogen peroxide. The single-stage leaching of the battery mass (regardless of the composition of the material) in a 15% or 20% sulfuric acid solution with the addition of 30% H₂O₂ aqueous solution, for 2 h, with a solid-to-liquid-phase ratio of 1:5 or 1:4 at a temperature of 60 °C ensures the leaching of cobalt, nickel, copper and lithium with efficiencies above 95%. On the other hand, the use of an innovative method of two-stage counter-current leaching of the battery mass ensures the leaching of cobalt, nickel, copper and lithium at a level significantly greater than 95%, while obtaining a concentration of cobalt in the leaching solution at a level of nearly 50 g/dm³. It also reduces the leaching time of a single stage to 1 h and, importantly, reduces the amount of waste solutions and the consumption of H₂O₂ and sulfuric acid. The developed method of the two-stage counter-current leaching of battery masses is therefore characterized by high efficiency and low environmental impact, thanks to which it can be used in commercial processes for the recycling of lithium-ion batteries.

The work presents the research results regarding the development of an innovative technology for the production of lithium perrhenate. The new technology is based entirely on hydrometallurgical processes. The source of lithium was solutions created during the processing of Li-ion battery masses, and the source of rhenium was perrhenic acid, produced from the scraps of Ni-based superalloys. The research showed that with the use of lithium carbonate, obtained from post-leaching solutions of Li-ion battery waste and properly purified (by washing with water, alcohol, and cyclic purification with CO₂), and perrhenic acid, lithium perrhenate can be obtained. The following conditions: room temperature, time 1 h, 30% excess of lithium carbonate, and rhenium concentration in the acid from 20 g/dm³ to 300 g/dm³, allowed to produce a compound containing a total of 1000 ppm of metal impurities. The developed technology is characterized by the management of all aqueous waste solutions and solid waste and the lack of loss of valuable metals such as rhenium and lithium after the initial precipitation step of lithium carbonate.