Precipitation of α-Fe2O3 and recovery of Ni and Co from synthetic laterite-leaching solutions

• Hydrolysis separated Fe from Ni and Co in synthetic laterite-leaching solutions.
• The effect of impurity ions on the hydrolysis of Fe was investigated.
• The growth model of α-Fe2O3 spheres was constructed.

Atmospheric hydrochloric-acid leaching of nickel laterite can produce a leaching solution containing a large amount of Fe. To recover Ni and Co, Fe should be separated from the laterite-leaching solutions. In this study, hydrolytic distillation was used to remove Fe from the synthetic laterite-leaching solutions; Ni and Co remained as soluble chlorides in the solutions, while most Fe was removed as Fe2O3. The conversion of Fe, recovery of Ni and Co, recovery of HCl, and the concentration of HCl, were investigated under various conditions. The results showed that the optimal output was obtained under the following process conditions: the hydrolysis temperature was 170 °C, the pressure was 0.03 MPa, the water flow rate was 1.67 mL/min, and the hydrolysis duration was 2 h. The effects of impurities under the optimized conditions were also studied, showing that as the amount of metal chlorides increased, the conversion of Fe decreased. The residues were characterized by X-ray diffraction analysis and scanning electron microscopy with X-ray energy-dispersive spectroscopy. Using the results, a growth model of α-Fe2O3 (hematite) spheres from the synthetic laterite-leaching solutions was constructed.