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Received October 16, 2013
Accepted November 27, 2013
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Leaching kinetics of neodymium in sulfuric acid from E-scrap of NdFeB permanent magnet
Ho-Sung Yoon
Chul-Joo Kim
Kyeong Woo Chung
Su-Jeong Lee1
A-Ram Joe1
Yang-Ho Shin1
Se-Il Lee1
Seung-Joon Yoo1†
Jin-Geol Kim2
Korea Institute of Geoscience & Mineral Resources (KIGAM), 124, Gwahang-ro, Yuseong-gu, Daejeon 305-350, Korea 1Department of Environmental and Chemical Engineering, Asan Seonam University, 7-111, Pyeongchon-gil, Songak, Asan 336-922, Korea 2Department of Chemical Engineering, Soonchunhyang University, Shinchang, Asan 336-745, Korea
Korean Journal of Chemical Engineering, April 2014, 31(4), 706-711(6), 10.1007/s11814-013-0259-5
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Abstract
The leaching kinetics of neodymium in NdFeB permanent magnet powder was analyzed for the purpose of recovery of neodymium in sulfuric acid (H2SO4) from E-scrap (electric scrap) of NdFeB permanent magnet powder treated by oxidation roasting to form a reactant. The reaction was conducted with H2SO4 concentrations ranging from 2.5 to 3.5M, a pulp density of 110.8 g/L, an agitation speed of 750 rpm, and a temperature range of 30 to 70 ℃. After 4 h of leaching, the neodymium content in the E-scrap powders was completely converted into a neodymium sulfate_x000D_
(Nd2(SO4)3) solution phase in H2SO4 in the condition of 70 oC and 3.0M H2SO4. Based on a shrinking core model with sphere shape, the leaching mechanism of neodymium was determined by the rate-determining step of the ash layer diffusion. Generally, the solubility of pure rare earth elements in H2SO4 is decreased with an increase in leaching temperatures. However, the leaching rate of the neodymium in E-scrap powders increased with the leaching temperatures in this study because the ash layer included in the E-scrap powder provided resistance against the leaching. Using the Arrhenius expression, the apparent activation energy values were determined to be 2.26 kJmol^(-1) in 2.5M H2SO4 and 2.77 kJmol^(-1) in 3.0 M H2SO4.
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