Recovery of Nd and Dy from rare earth magnetic waste sludge by hydrometallurgical process

This paper describes a hydrometallurgical process for recovering neodymium (Nd) and dysprosium (Dy) from a magnetic waste sludge generated from the Nd-Fe-B(-Dy) manufacturing process. Phase analysis by XRD study revealed Nd(OH)(3) and Fe2O3 as main mineral phases, and chemical analysis by ICP showed the contents of 35.1 wt% Nd, 29.5 wt% Fe, 1.1 wt% Dy and 0.5 wt% B. A solution of 1 M HNO3 + 0.3 M H2O2 was used to dissolve up to 98 % Nd and 81 % Dy, while keeping Fe dissolution below 15 % within 10 min. Fe dissolved in solution was completely removed as Fe(OH)(3) at pH 3 followed by precipitation of Nd and Dy with oxalic acid (H2C2O4) and recovered 91.5 % of Nd and 81.8 % of Dy from solution. The precipitate containing Nd and Dy was calcined at 800 A degrees C to obtain Nd2O3 as final product with 68 % purity, and final recovery of 69.7 % Nd and 51 % of Dy was reported in this process.