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High-efficiency simultaneous extraction of rare earth elements and iron from ndfeb waste by oxalic acid leaching
Journal of Rare Earths ( IF 4.9 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.jre.2020.04.020
Qingsheng Liu , Tao Tu , Hao Guo , Huajin Cheng , Xuezhong Wang

Abstract Iron can not be recovered at high value because only rare earth elements are effectively recovered from NdFeB waste via oxidation roasting-hydrochloric acid leaching process. In this study, a new method for leaching NdFeB waste with oxalic acid was developed. The high-efficiency, simultaneous and high-value recovery of rare earth elements and iron was realized to simplify the process and improve the economic benefit. Results of the oxalic acid leaching experiments showed that under the optimum leaching conditions at 90°C for 6h in the aqueous solution of oxalic acid (2 mol/L) with a liquid-solid ratio of 60 mL/g, the iron leaching efficiency and precipitation rate of rare earth oxalate reached 93.89% and 93.17%, respectively. Rare earth oxalate and Fe(C2O4)33− were left in the residue and the leaching solution, respectively. The leaching mechanism was further analyzed by characterising the leach residues obtained through X-ray powder diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). Results of the leaching kinetics study indicated that the process of oxalic acid leaching followed the shrinking nucleus model, and the leaching kinetics model was controlled by the mixed factors of diffusion and chemical reaction. The leaching residue was calcined at 850°C for 3h and then decomposed into rare earth oxide, which could be directly used to prepare rare earth alloy via molten salt electrolysis. For the leaching solution, ferric oxalate solution was reduced using Fe powder to prepare the ferrous oxalate (FeC2O4·2H2O).

中文翻译:

草酸浸出高效同时提取钕铁硼废料中的稀土元素和铁

摘要 氧化焙烧-盐酸浸出工艺只能从NdFeB废料中有效回收稀土元素,无法高价值回收铁。在这项研究中,开发了一种用草酸浸出 NdFeB 废料的新方法。实现了稀土元素和铁的高效、同步、高值回收,简化了工艺流程,提高了经济效益。草酸浸出实验结果表明,在液固比为60 mL/g的草酸(2 mol/L)水溶液中,在90℃浸出6h的最佳浸出条件下,铁的浸出效率和稀土草酸盐沉淀率分别达到93.89%和93.17%。稀土草酸盐和 Fe(C2O4)33- 分别留在残渣和浸出液中。通过表征通过 X 射线粉末衍射 (XRD) 和扫描电子显微镜-能量色散 X 射线光谱 (SEM-EDS) 获得的浸出残留物,进一步分析了浸出机理。浸出动力学研究结果表明,草酸浸出过程遵循缩核模型,浸出动力学模型受扩散和化学反应混合因素控制。浸出渣在850℃下煅烧3h后分解为稀土氧化物,可直接用于熔盐电解制备稀土合金。对于浸出液,用铁粉还原草酸铁溶液制备草酸亚铁(FeC2O4·2H2O)。
更新日期:2020-05-01
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