Recovery of Neodymium from Waste Permanent Magnets by Hydrometallurgy Using Hollow Fibre Supported Liquid Membranes

Abstract

The recycling of the rare earth neodymium (Nd) is vital to providing greener technology for many industries. In this paper its recovery from waste permanent magnets (WPMs) is explored using a hydrometallurgical process involving separation using hollow fiber supported liquid membranes (HFSLMs). After demagnetization, the options for WPMs leaching were investigated by varying mineral acids, acid concentrations and solid/liquid (S/L) ratios. The separation Nd from iron (Fe) was carried out by precipitation using oxalic acid. Nd in WPMs was recovered by solvent extraction using D2EHPA in Isopar-L. The influence of various parameters such as pH and organic/aqueous (O/A) phase ratio were investigated. Optimum leaching was achieved using 3 M H2SO4 with an S/L ratio of 1 g/50 mL to obtain 485 g/kg of Nd. Nd-separation from Fe was successfully performed using 0.6 M D2EHPA with an O/A phase ratio of 3 at a pH of 1.26 – 2.0 resulting in Nd-recovery of 97.48%. The optimum stripping was achieved using 6 M HNO3. In the HFSLM experiments, the concentration of Nd in the aqueous strip solution was 4120 mg/L whilst that in the aqueous feed solutions was 658 mg/L. The HFSLM module used recovered 90.82% of the Nd within 35 min.