One-step separation and recovery of rare earth and iron from NdFeB slurry via phosphoric acid leaching

The recovery of rare earth elements (REEs) from NdFeB slurry by traditional hydrometallurgy has been limited becuase a large number of REEs are lost during separation together with iron. In this paper, a simple and sustainable method is proposed to efficiently separate and recover REEs and iron from NdFeB slurry. REEs were recovered by one-step selective precipitation in phosphoric acid, and the dissolved iron was recovered by oxalic acid. Phosphoric acid leaching results show that under the conditions of 4 mol/L phosphoric acid, 80 °C, L/S of 30:1 and 90 min, the leaching efficiencies of Fe and REEs reach 98.76% and 1.09%, respectively. While the rest of REEs remained in the leaching residue in the form of REEPO 4 · n H 2 O precipitation. Subsequently, the mixed rare earth oxide (rare earth oxalate roasted at 800 °C) and FeC 2 O 4 ·2H 2 O are obtained by oxalic acid precipitation with purities of 99.49% and 97.17% from the REEPO 4 · n H 2 O dissolving solution and the phosphoric acid leaching solution. Moreover, the phosphoric acid is regenerated while recovering iron, and it can be reused in the phosphoric acid leaching step after removing the impurity C 2 O 4 2− . In summary, this work provides an efficient and environmentally friendly method for recovering REEs and iron from NdFeB slurry waste. Phosphoric acid can effectively separate and recover rare earth and iron from NdFeB waste. Under the optimal conditions, the recovery and purity of iron and rare earth are very high. • Phosphoric acid can effectively separate and recover REEs and iron from NdFeB waste in one-step. • A flow sheet for producing high-purity FeC 2 O 4 ·2H 2 O and rare earth oxide is proposed. • Phosphoric acid can be reused after purification.