| Summary: | Rare earth elements (REEs) are strategically critical in the manufacture of advanced materials. Red mud and end-of-life NdFeB magnets can be good secondary sources for REEs, but recovery is difficult due to the high iron oxide content and small amount of REEs. Oxide mixtures whose composition of Fe, Nd, and Ga was similar to that in red mud were employed in experiments. In this study, a relatively inexpensive non-aqueous system was used to selectively dissolve Nd<sub>2</sub>O<sub>3</sub> in a mixture with Fe<sub>2</sub>O<sub>3</sub> and Ga<sub>2</sub>O<sub>3</sub>. The addition of ethylene glycol (EG) to HCl and H<sub>2</sub>SO<sub>4</sub> solution depressed the dissolution of Fe<sub>2</sub>O<sub>3</sub> and Ga<sub>2</sub>O<sub>3</sub> from the mixtures, and thus selective dissolution of Nd<sub>2</sub>O<sub>3</sub> was possible. The optimum conditions were as follows: (a) 1.0 M HCl in EG, 25 °C ± 1 °C, 50 g/L pulp density, 120 min, 200 rpm; and (b) 0.05 M H<sub>2</sub>SO<sub>4</sub> in EG, 25 °C ± 1 °C, 50 g/L pulp density, 60 min, 300 rpm. Under these conditions, Nd<sub>2</sub>O<sub>3</sub> was completely dissolved, whereas no Fe<sub>2</sub>O<sub>3</sub> or Ga<sub>2</sub>O<sub>3</sub> was dissolved by the H<sub>2</sub>SO<sub>4</sub> system, and the dissolution percentage of these two oxides by the HCl system was less than 1%. Due to the selective dissolution of Nd<sub>2</sub>O<sub>3</sub> from the oxide mixtures, it is simple to recover Nd. An efficient process can be developed for the recovery of REEs from red mud and end-of-life NdFeB magnets by applying our results.
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