Extraction behaviors of aluminum and scandium from Sc-bearing aluminum residue by cascade leaching in NaOH and HNO3 aqueous solution

Aluminum and scandium are often associated with laterite nickel ore and have important extraction value. In the treatment process of laterite nickel ore, aluminum and scandium are enriched and precipitated in the form of Sc-bearing aluminum residue (ScAR). The extraction behaviors and phase transformations of aluminum and scandium from ScAR by cascade leaching in NaOH and HNO 3 aqueous solution were invested systematically in this work. Results indicated that 93.10 % of Al was successfully leached from ScAR into alkali leachate and Sc was enriched about 7 times in alkali leaching residue (ALR) and its content was 0.15 %. 97.38 % of Sc was extracted from the ALR into nitric acid leachate. The extraction behaviors of aluminum and scandium were confirmed by X-ray diffractometer (XRD) and scanning electronic microscopy/energy dispersive spectroscopy (SEM/EDS). The scandium dissolution kinetic followed the unreacted shrinking core model with a mixed control of diffusion and chemical reaction and the apparent activation energy was 19.07 kJ/mol. The proposed process was a good technique for extraction of aluminum and scandium with high leaching efficiency.