Integrated hydrometallurgical investigation for extraction and recovery of neodymium (Nd) from waste permanent Nd-Fe-B magnet

The Nd-Fe-B permanent magnet was treated through integrated hydrometallurgical approach to recover neodymium. Leaching kinetics and process optimization using dilute HCl was investigated. The kinetics results ensures on following of leaching behaviour of Nd to Shrinking-Core model governed by diffusion control model (1-2X/3-(1-X) 2/3). The kinetic fitting result was strongly supported by the Ea of 13.79KJ/mole obtained from the Nd dissolution study while examined at varying temperatures. The leach liquor obtained at the optimum leaching condition contains Fe: 12.6 g/L, Nd: 9.167 g/L, Pr: 0.122 g/L and B: 0.202 g/L was subjected to the recovery of Fe2O3 using slaked lime at pH 4.0 and was confirmed from XRD analysis of precipitated product. The Bifunctional ionic liquid like R4NPC was introduced for extraction of REMs (Nd and Pr) from the leach solution. The Solvent extraction carried out at the condition; pH 4.0, R4NPC of 0.35 M and A: O = 1 showed high selectivity towards REM (Nd and Pr) leaving Boron in the raffinate. The association of 3-mole of Extractant was apprehend from the resulted slope of the plot logD against log[R4NPC]. Extraction isotherm results suggested on requirement of 2-numbers of stages for complete extraction of Nd at A: O = 2:1 and was validated in 6 cycles counter current study. First stage stripping was carried out at low concentration of oxalic acid to separate out Pr (0.243 g/L) and in which 2.357 g/L Nd was also stripped. In second stage of stripping remaining 15.975 g/L Nd was fed into stripping isotherm followed by simulation by 0.6 M oxalic acid. The obtained enriched (3.5 times) neodymium oxalate out of stripping circuit was calcined at 400 degrees C to yield Nd2O3 and confirmed from XRD analysis.

Automated summary

The Nd-Fe-B permanent magnet was processed using a hydrometallurgical approach to recover neodymium. The leaching kinetics of neodymium using dilute HCl was studied, and the process optimization was investigated. The obtained leach liquor was used for the recovery of Fe2O3 using slaked lime, and a bifunctional ionic liquid was introduced for the extraction of REMs (Nd and Pr) from the solution. The enriched neodymium oxalate was obtained through calcination of the stripping circuit product.