Recovery of Nd and Dy from rare earth magnetic waste sludge by hydrometallurgical process
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ORIGINAL ARTICLE
Recovery of Nd and Dy from rare earth magnetic waste sludge by hydrometallurgical process Jan Pana Rabatho • William Tongamp Yasushi Takasaki • Kazutoshi Haga • Atsushi Shibayama
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Received: 30 April 2009 / Accepted: 20 November 2012 / Published online: 11 December 2012 Ó Springer Japan 2012
Abstract This paper describes a hydrometallurgical process for recovering neodymium (Nd) and dysprosium (Dy) from a magnetic waste sludge generated from the Nd–Fe–B(–Dy) manufacturing process. Phase analysis by XRD study revealed Nd(OH)3 and Fe2O3 as main mineral phases, and chemical analysis by ICP showed the contents of 35.1 wt% Nd, 29.5 wt% Fe, 1.1 wt% Dy and 0.5 wt% B. A solution of 1 M HNO3 ? 0.3 M H2O2 was used to dissolve up to 98 % Nd and 81 % Dy, while keeping Fe dissolution below 15 % within 10 min. Fe dissolved in solution was completely removed as Fe(OH)3 at pH 3 followed by precipitation of Nd and Dy with oxalic acid (H2C2O4) and recovered 91.5 % of Nd and 81.8 % of Dy from solution. The precipitate containing Nd and Dy was calcined at 800 °C to obtain Nd2O3 as final product with 68 % purity, and final recovery of 69.7 % Nd and 51 % of Dy was reported in this process. Keywords Rare earth elements Magnetic waste sludge Hydrometallurgical processing
Introduction The importance of the application of rare earth elements (REE) to different industries is widely known and their significance in high technology continues to grow. The development of permanent magnetic magnets such as (RE)–Fe–B, where RE are Nd, Dy, or Pr, has opened up many new areas of
J. P. Rabatho W. Tongamp Y. Takasaki K. Haga A. Shibayama (&) Faculty of Engineering and Resource Science, Akita University, 1–1 Tegata-Gakuen-cho, Akita 010-8502, Japan e-mail: [email protected]
application to strategic use due to its excellent magnetic properties and functions with compact shapes and light weight. Many research papers discuss such applications including voice coil motors (VCMs), miniaturized multigigabyte portable disc drives, DVD drivers, magnetic resonance imaging (MRI), electrical motors, power hybrid vehicles and so on [1–8]. It has been reported recently that Nd–Fe–B sintered magnet production has grown globally to over 30 kt, and the annual production of Nd–Fe–B magnets in Japan alone is estimated at 10,000 tons [1–5]. It is noted in the literature that 20–30 % of the raw magnets are lost as waste during the production of Nd–Fe–B magnet [1, 9]. Many researchers note that due to lack of cost effective methods for recovery of rare earths, many wastes are stockpiled before being treated for the recovery of valuable metals [6–9]. Development of cost effective process to treat these wastes could contribute greatly to resource recovery and utilization, and reduce the resulting environmental burden. Many attempts have been made to develop a process to treat Nd–Fe–B wastes for recovery of Nd, which can be utilized in the production of rare earth magnets. These include processes such as carbonylation [1], chlorination
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