The sustainable society requires the recycling of rare metals. Rare earth Nd is one of rare metals, accompanying huge consumption especially in Nd-Fe-B magnets. Although the wet process using acid is in practical use in the in-plant recycle of sludge, higher selectivity between Nd and Fe at room temperature is desired. We have proposed a pretreatment of corrosion before the dissolution into HCl and the oxalic acid precipitation. The corrosion produces $\gamma$-FeOOH and a Nd hydroxide, which have high selectivity for HCl solution at room temperature. Nd can be recovered as Mn$_{ 2}$O$_{ 3}$-type Nd$_{ 2}$O$_{ 3}$. The estimated recovery-ratio of Nd reaches to 97\%.
Categories: cond-mat.mtrl-sci