Selective Leaching Process for Neodymium Recovery from Scrap Nd-Fe-B Magnet
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NTRODUCTION
THE neodymium-iron-boron (Nd-Fe-B) magnet has superior magnetic properties such as magnetic power, easy processing, and cost compared to all other magnetic materials including the Alnico (Al-Ni-Co) and samarium cobalt (Sm-Co) series of magnets. Additionally, the amount of neodymium (Nd) in the mineral content of rare earth ore is rich, and it is easy to extract Nd from raw materials. Because of these advantages, Nd-Fe-B magnets are in demand and are suitable in magnetic field products or technology products such as various types of electronic components, computer equipment, medical equipment, petrochemicals, and audio equipment. According to the Walter et al. report on permanent magnets, the total estimation of Nd-Fe-B magnet production in the world was about 63,000 tons in 2007 and may increase to 120,000 tons by 2020.[1] The Nd magnets are the best option as a magnetic source for CHING-HWA LEE, Professor, and YU-JUNG CHEN, CHINGHUA LIAO, and CHI-EN HUNG, Students, are with the Department of Environmental Engineering, Da-Yeh University, Changhua 51591, Taiwan, ROC. Contact e-mail: [email protected] SRINIVASA R. POPURI, Lecturer, is with the Department of Biological and Chemical Sciences, The University of the West Indies, Cave Hill Campus, Bridgetown 11000, Barbados. SHANG-LIN TSAI, Consultant, is with Yung Yuan Chemical Materials Crop, Taoyuan 337, Taiwan, ROC. Manuscript submitted August 25, 2012 Article published online September 6, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A
electronic devices and home appliances.[2] Due to the enormous resources of Nd in China,[3] the domestic manufacturers of Nd-Fe-B magnets in Taiwan obtain Nd raw material from China. However, Nd-Fe-B magnet is a very brittle material, so there is often fracture during the manufacturing process. The production, processing, and cutting of Nd-Fe-B magnets in Taiwan by various manufacturers are generating a considerable amount of Nd-Fe-B scrap. One of the domestic magnet manufacturers estimated[4] that the amount of scrap from Nd-Fe-B magnet production in Taiwan is about 750 tons/year. With an approximately 20 pct annual increase of Nd-Fe-B magnet production in Taiwan (approximately 20 pct), more magnetic waste will be generated in the future. These waste magnetic products contain Nd and other valuable metals. If these metals are not recycled, it will be unfortunate as the overall production of magnetic waste resources may increase. Since Nd-Fe-B magnets are coupled with strong magnetic force, these can cause a qualitative change or damage of the nearest products after discard (e.g., debit cards and speakers). Additionally, Nd-Fe-B magnets are extremely powerful and can cause injury if not cautiously handled.[5] In terms of weight ratio, the Nd-Fe-B magnet scrap contains approximately 30 pct of high grade Nd and its value is about NT$ 280 to 20,000 per kilogram (purity 99 to 99.9999 pct);[3,6] this is quite expensive even compared to a recovery value. Therefore, research on recycling of waste Nd-Fe-B magnets will promote re
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