Metal Extraction and Recycling Division, CSIR-National Metallurgical Laboratory, Jamshedpur, 831007, India; Department of Applied Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad, 826004, India.
Metal Extraction and Recycling Division, CSIR-National Metallurgical Laboratory, Jamshedpur, 831007, India.
J Environ Manage. 2020 Nov 1;273:111063. doi: 10.1016/j.jenvman.2020.111063. Epub 2020 Aug 27.
Strict environmental regulations as well as requirement of conservation of natural resources compelled the researchers to recycle the metal values from secondary resources. The scrap magnets found to be a potential alternative resource to extract rare earth metal, Nd. Present paper reports a novel process flow-sheet for the recycling of scrap Nd-Fe-B magnets to recover Nd as marketable salt and other valuable by-products. The Nd-Fe-B magnets were demagnetized, crushed and charged to atmospheric leaching resulting in ~99.99% recovery of REMs (Nd, Pr, Dy) and Fe using 1 M HSO solution at room temperature for 90 min and pulp density 50 g/L. The obtained leach liquor was subjected to acid extraction procedure by mixing the liquor with 70% TEHA diluted in kerosene for 10 min, which requires five stages for complete extraction of acid from the liquor having O/A ratio 2:1. Ammonia solution was used to increase the pH of acid free leach liquor to 1.65 for the precipitation of Nd (with minor amount of Pr and Dy) and above that to precipitate Fe. Further, processing of these valuables make them industrially applicable. The leached residue was checked using Toxicity Characteristics Leachability Procedure (TCLP) test and found the remained metals within the permissible limit. This process offers a simple and efficient means to reduce the toxicological effect by recovering Nd from magnets of computer hard disks.
严格的环境法规以及自然资源保护的要求迫使研究人员从二次资源中回收金属价值。发现报废磁铁是提取稀土金属钕的潜在替代资源。本文介绍了一种从报废 Nd-Fe-B 磁铁中回收 Nd 作为可销售盐和其他有价值副产品的新工艺流程图。将 Nd-Fe-B 磁铁退磁、粉碎并装入大气浸出中，在室温下使用 1 M HSO4 溶液浸出 90 分钟，固液比为 50 g/L，可实现约 99.99%的 REMs（Nd、Pr、Dy）和 Fe 的回收。将得到的浸出液与 70%TEHA 在煤油中稀释后进行酸萃取，在 O/A 比为 2:1 的情况下，需要五个阶段才能从浸出液中完全提取酸。用氨溶液将无酸浸出液的 pH 值提高到 1.65，以沉淀 Nd（少量 Pr 和 Dy），超过该值则沉淀 Fe。进一步处理这些有价值的物质，使它们在工业上具有应用价值。用毒性特征浸出程序 (TCLP) 测试检查浸出残渣，发现残留金属在允许范围内。该工艺提供了一种简单有效的方法，可从计算机硬盘的磁铁中回收 Nd，从而减少其毒理学影响。
