Mar cobalt (SmCo) magnets use SmCo5 (1:5 series) or Sm2 […]
Mar cobalt (SmCo) magnets use SmCo5 (1:5 series) or Sm2Co17 (2:17 series) as the main phase, but the 2:17 series contains trace elements in addition to sa and cobalt, such as iron, copper, and zirconium due to SmCo Magnets High coercivity (anti-demagnetization), good corrosion resistance and excellent thermal stability, so they are mainly used for high-temperature applications. SmCo magnets account for less than 2% of the permanent magnet market because they have since 1985, Neodymium iron boron (NdFeB) magnets have been basically replaced. However, due to new applications in consumer electronics, automotive and medical technology, aerospace and military equipment, the global SmCo magnet market is growing.
The recycling of SmCo magnets can reduce the supply risk of sa and cobalt, reduce material recycling (circular economy), and reduce environmental problems related to primary mining and ore processing. 3 The easiest way to recycle SmCo permanent magnets is to recycle it directly. 5 It is only possible to convert the magnets into new ones when a waste stream with a fairly constant chemical composition is available and the magnets are not broken and oxidized on the surface. Alloy powder. 5 The more common method is indirect recovery, in which the metal is separated and recovered by hydrometallurgy. Oxidative dissolution is required to chemically recover metals in elemental state. This is usually achieved by dissolving the metal in a solution of strong mineral acids such as hydrochloric acid, sulfuric acid or nitric acid. 6-8 The disadvantage of this hydrometallurgical method is that it generates hydrogen and consumes a lot of acid. Other types of oxidants used for metal dissolution are solutions of chlorine, bromine or iodine in organic solvents. For example, a solution of chlorine in N,N-dimethylformamide has been used to chlorinate metal metallic and zirconium. 9,10 However, halogens and organic solvents are both volatile and harmful. Moreover, halogens can attack organic solvents and form undesirable decomposition products.
Ionic liquids (IL) composed entirely of ions are usually regarded as environmentally friendly solvents because of their negligible vapor pressure. They are used in the fields of synthesis, separation, catalysis and electrochemistry. IL also shows the potential to safely store halogens by forming trihalide or polyhalide anions (for example [Cl3]-, [Br3]-, [I3]- or [ClBr2]-). In recent years, trichloride ILs have been synthesized and used to dissolve various metals and alloys under mild conditions. In the traditional process, the use of trichloride ILs for the oxidative dissolution of metals is more environmentally friendly than the direct use of chlorine, because the ratio of the oxidant trichloride anion to the metal ion can be effectively consumed through quantitative control. In conventional methods, a large excess of chlorine is usually purged into the reactor to effectively chlorinate the metal.
The IL is selected according to the hydrophobicity of [P666,14] Cl, which makes it possible to use an aqueous solution for post-release treatment. The dissolution efficiency is studied by changing the volume fraction of [P666,14] [Cl3] in [P666,14] Cl (the latter as an additional source of coordinated chloride ions), the solid-liquid ratio and the temperature. The stripping of metals from the supported ionic liquid with different aqueous solutions was studied, and then the reusability of the ionic liquid was studied. Finally, a conceptual process flow diagram was proposed, in which iron, copper, cobalt and sa were separated in different streams.