Recovery of scandium from laterite ore intermediate products: Efficient separation, selective extraction, and product preparation

Laterite ore is a promising source of Sc, and the recovery of Sc from it has garnered widespread interest. In this study, for Sc-bearing Al residue (SAR) produced in the HNO3 treatment process of laterite ore, the route of NaOH leaching to separate Al, HNO3 leaching to extract Sc, solvent extraction of Sc, and precipitation and roasting to prepare Sc2O3 product was proposed. First, the feasibility of Al-Sc separation was confirmed through Eh-pH diagram analysis. The results indicated that the Al leaching yield was up to 93.17% during NaOH leaching, with Sc being enriched in the leach residue, along with Ni, Co, and Mg. Then, over 99% of Sc, Ni, Co, and Mg in leach residues were further leached with HNO3. P204 and N1923 were used synergistically for selective Sc extraction from the HNO3 solutions. The formed hydrogen bond between N1923 and P204 promoted the dissociation of proton H in P204 and facilitated the extraction of Sc. 99.58% of Sc could be selectively extracted. After washing impurities with HNO3, 98.94% of Sc could be stripped as Sc(OH)4– via five-stage countercurrent extraction with NaOH solutions. Finally, the addition of H2C2O4 to the stripping liquor precipitated 94.36% Sc as Sc2(C2O4)3·6H2O and Sc(OH)3. After roasting at 700 °C, the block-like Sc2O3 product with a purity of 99.24% and micropores on the surface could be prepared.