New recycling process of care earth metals using the formation of oxyhalide

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In this study, direct extraction and separation of neodymium (Nd) metal from Nd-Fe-B magnet scraps, using molten silver and magnesium, were investigated for the purpose of developing a new recycling process.Firstly, we examined the direct extraction of Nd metal from Nd-Fe-B magnet scraps using molten silver (Ag) as an extraction medium. Prior to the extraction experiment, the phase equilibrium of the system Ag-Fe-Nd was investigated to estimate the theoretical extraction limit. It was revealed that Fe/Nd_2Fe_<17> mixture equilibrates with the molten Ag-Nd alloy containing 50-52 mol% Nd(57-59 mass% Nd) at 1363K. The experimental results were in good agreement with the thermodynamic calculation based on literature values. By reacting Nd-Fe-B magnet scraps with molten silver at 1273K, more than 90% of the neodymium in the scraps was extracted and an Ag-Nd alloy containing 40-50 mass% Nd was obtained at 1273-1573K. The neodymium in the Ag-Nd alloy was separated from silver as Nd_2O_3 by oxidizing the obtained alloy in air.Furthermore, an environmentally sound process for the extraction of Nd from the scrap was devised and its feasibility was demonstrated. The developed Nd extraction apparatus circulates the Mg as an extraction medium by maintaining a temperature difference within the reaction vessel, thus achieving continuous extraction of metal Nd from the scrap, re-extraction of Mg from a Mg-Nd alloy, and finally, recovery of pure Mg. As a result, pure Nd metal with 97.7% purity was directly recovered from the scrap. It was also shown that the extraction agent, Mg, could be reused. The results confirmed the possibility of the direct extraction of pure Nd metal without the oxidization process.