ABSTRACT

Recovery of rare earth elements (REEs) from spent NdFeB magnets is important to meet the increasing demand for magnets and high-tech applications. In general, pretreatments of spent NdFeB magnets are necessary to recover REEs such as Nd, Pr, and Ce from the magnets. In this work, a simple process was proposed to recover REEs without any pretreatment of NdFeB magnets by using precipitation of REE(III) double salt. The correlations among several variables on the precipitation of REE(III) double salt were investigated by using synthetic solutions such as the molar ratio of Na(I) and sulfuric acid to Nd(III), the concentration of Nd(III) and Fe(III). The REES and iron present in NdFeB magnets were completely dissolved in 2 M H₂SO₄ solution at room temperature. The dissolved REE(III) ions were then directly separated by precipitation of double salt when Na₂SO₄ was added at 80°C. After REEs precipitation, the addition of iron powder to the filtrate at room temperature reduced Fe(III) to Fe(II) and removed a small amount of Cu(II) and Co(II) by cementation. Then Fe(II) and Na₂SO₄ were separated by precipitation of Fe(OH)₂ when solution pH was adjusted to 8. The conditions for the precipitation of Nd(III) double salt were thermodynamically verified. Mass balance of continuous experiments indicated that it was possible to recover REEs and iron with high purity by the proposed process in this work.

摘要

从废 NdFeB 磁体中回收稀土元素 (REE) 对于满足磁体和高科技应用日益增长的需求非常重要。一般来说，需要对废 NdFeB 磁体进行预处理，以从磁体中回收稀土元素，例如 Nd、Pr 和 Ce。在这项工作中，提出了一种简单的工艺，通过使用 REE(III) 复盐沉淀来回收 REE，无需对 NdFeB 磁体进行任何预处理。通过合成溶液，如Na(I)和硫酸与Nd(III)的摩尔比、Nd(III)和Fe的浓度(三）。NdFeB 磁体中存在的 REES 和铁完全溶解在 2 MH ₂ SO _4中室温下的溶液。然后，当在80℃下添加Na ₂ SO ₄时，通过复盐沉淀直接分离溶解的REE(III)离子。稀土元素沉淀后，在室温下向滤液中添加铁粉，将 Fe(III) 还原为 Fe(II)，并通过胶结去除少量 Cu(II) 和 Co(II)。_{然后当溶液pH调节至8时，通过Fe(OH) 2}沉淀分离Fe (II)和Na ₂ SO ₄。热力学验证了Nd(III)复盐沉淀的条件。连续实验的质量平衡表明，通过本工作中提出的工艺可以回收高纯度的稀土元素和铁。