Abstract Spent NdFeB magnets are highly appealing secondary resources for rare earth elements (REEs), especially for Nd. The goal of this study was to investigate electrochemical leaching of Fe and rare earths from NdFeB magnets with sulfuric and oxalic acids at different acid concentrations and current densities and reveal the mechanism of the leaching in varying conditions. The metals were leached from polished magnet surface and from crushed magnets using a 3D-printed Ti basket. Electron and atomic force microscopic analysis showed a highly heterogeneous structure of the magnets containing on average 60 wt-% of Fe and 25 wt-% of Nd. According to Kelvin probe force microscopy, the Volta potential difference between the matrix and the REE-rich grains was over 500 mV. Addition of oxalic acid (H2C2O4) in the sulfuric acid leach solution allows leaching at lower cell voltage and separation of the REE-oxalate precipitates. Some incorporation of rare-earth element oxalates in the cathodic sediment was also observed. Finally, the leaching mechanism is discussed.

中文翻译：

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从废钕铁硼磁体中电化学浸出稀土元素

摘要 废钕铁硼磁铁是非常有吸引力的稀土元素 (REE) 二次资源，尤其是 Nd。本研究的目的是研究在不同酸浓度和电流密度下用硫酸和草酸从 NdFeB 磁体中电化学浸出 Fe 和稀土，并揭示不同条件下浸出的机制。使用 3D 打印的钛篮从抛光的磁体表面和压碎的磁体中浸出金属。电子和原子力显微分析显示磁体的高度异质结构包含平均 60 wt% 的 Fe 和 25 wt% 的 Nd。根据开尔文探针力显微镜，基体和富含 REE 的颗粒之间的伏特电位差超过 500 mV。在硫酸浸出溶液中加入草酸 (H2C2O4) 可以在较低的电解槽电压下进行浸出并分离 REE 草酸盐沉淀物。还观察到在阴极沉积物中掺入了一些稀土元素草酸盐。最后讨论了浸出机理。