Recovery of rare earth elements from waste permanent magnet (WPMs) via selective leaching using the Taguchi method

Waste permanent magnets (WPMs) containing neodymium, praseodymium, and dysprosium are rare earth elements (REEs) that are in high demand in the global market. This study investigates the recovery of REEs in the WPMs through a leaching experiment using a variety of experimental parameters such as modification of sample, acid type, acid concentration, time, temperature, S/L ratio, stirring speed, and particle size. Recovery of REEs in WPMs has been conducted using pyro-hydrometallurgical process. Taguchi L18 orthogonal array was performed to identify the influential process parameters for higher rate of recovery With increased leaching of REEs from WPMs. The influential of parameters were examined by Analysis of variance (ANOVA) through the percentage of contribution. The investigation of the optimized REE's leaching is; unmodified WPMs, 5 M of HCl, 338 K temperature, 24 h, 2% S/L ratio, 800 rpm stirring speed, 0.250 mm particle size. Therefore, the result that acid type was the most influential factor with the percentage of contribution for leaching of rare earth elements 78% (Nd), 83% (Pr), and 76% (Dy) alongside p-values 0.007, 0.01 and 0.071, respectively. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.