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

本文研究了利用熔融银和熔融镁直接从钕铁硼磁铁废料中提取和分离钕金属的方法，旨在开发一种新的回收工艺。首先，我们研究了用熔融银（Ag）作为萃取介质直接从Nd- fe - b磁铁废料中提取Nd金属的方法。在萃取实验之前，研究了Ag-Fe-Nd体系的相平衡，估计了理论萃取极限。结果表明，Fe/Nd_2Fe_<17>混合物与含50-52 mol% Nd（57-59质量% Nd）的Ag-Nd合金在1363K时达到平衡。实验结果与文献计算结果吻合较好。在1273K温度下，Nd- fe - b磁铁屑与熔银反应，提取出90%以上的钕，在1273 ~ 1573k温度下，获得了含Nd质量% 40 ~ 50的Ag-Nd合金。通过在空气中氧化得到的合金，将银中的钕以Nd_2O_3的形式分离出来。此外，还设计了一种从废料中提取Nd的环保型工艺，并对其可行性进行了论证。所研制的Nd萃取装置通过在反应容器内保持一定的温差，使Mg作为萃取介质循环，从而实现从废金属中连续提取金属Nd，从Mg-Nd合金中再提取Mg，最后回收纯Mg。结果表明，从废金属中直接回收出纯度为97.7%的纯钕金属。结果表明，萃取剂Mg可重复使用。结果证实了不经氧化过程直接提取纯金属Nd的可能性。

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.