Neodymium-iron-boron (NdFeB) grinding slurries are the residual output of grinding as shaping process step in the production process of sintered NdFeB magnets. The treatment of the grinding slurries with the aim of recovering rare earth elements may lead to a reduced demand in primary raw materials like the rare earth elements neodymium, praseodymium and dysprosium. In this study, the possibility of recycling the contained rare earth elements, which account for up to 30 wt % in the alloy, through a pyrometallurgical process was investigated. The necessity of a thermal conditioning prior to the pyrometallurgical process is described.

Dumps in the Central German Mansfeld mining district have been investigated by a multi-disciplinary research team to develop a holistic concept for the recovery of base and trace metals from low-grade Kupferschiefer ore. Geochemical and mineralogical data from representative sampling indicate that the low-grade Kupferschiefer dumps contain significant amounts of Cu (0.6 %) and Ag (up to 800 ppm), besides exploitable grades of Pb and Zn. Additionally to flotation and hydrometallurgy, first shake flask bioleaching experiments on otherwise untreated Kupferschiefer ore yield Cu recovery rates of up to 95 %. A total of 900 t Cu and 5 t Ag contained in black copper can thus be produced from the pilot dump of 100 000 m 3 low-grade Kupferschiefer ore. Additionally, large volumes of limestone waste, separated from the dumps by sensor-based sorting, can be utilized as aggregate in the construction industry.Figure 6. Mass balance of Cu in different solvents with varying pretreatment of the material.

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