Leaching kinetics study of neodymium from the scrap magnet using acetic acid

Leaching kinetics of neodymium was investigated from Nd-Fe-B scrap magnet using green solvent as CH3COOH. The Characterization study of the scarp magnet was performed by XRD and SEM-EDAX to ascertain the phase as Nd2Fe14B (31.05% Nd, 65.15% Fe and 0.66% B). Influence of the factors such as CH3COOH concentrations (0.05-0.8 M), agitation speed (200-1000 rpm), particle size (45-150 mu m), temperature (308-353 K) and S/L ratio (1-5% (W/V)) affecting on leaching of Nd was investigated to obtain an optimum condition. Maximum yield (99.99%) of Nd along with definite extraction of Fe was resulted at the condition: Agitation speed: 800 rpm, S/L: 1% (W/V), temp. 353 K, 0.4 M CH3COOH and particle size: 106-150 mu m). The key factors such as CH3COOH concentration and temperature appears to be critical on effective dissolution of both Nd and Fe from the scrap magnet phase. Leaching kinetic results showed best fit with the shrinking-sphere model (1 - (1 - X)(1/3) = k(ap)t) ensuring the overall leaching process is governed by surface chemical control mechanism. The activation energy determined from the experimental study was of +17.13 kJ/mol further more supports the proposed chemical control leaching process. Thermodynamics variables like Delta G(0), Delta H-0 values determined from the Arrhenius plot at varied temperature indicating the feasibility of the leaching reaction of endothermic type. Linear dependence of the plot of log k(ap) on log 1/d(o) and a first order dependence of k(ap) with CH3COOH at 0.4 M was derived from the above proposed leaching model. (C) 2016 Elsevier B.V. All rights reserved.