Patent ID: 7563421

Claim:
A hydrometallurgical process for recovering nickel and cobalt from nickel oxide ores, comprising: (1) a leaching stage which stirs the slurried ore in the presence of sulfuric acid at 220 to 280° C. to produce leached slurry, (2) a solid-liquid separation stage which washes the leached slurry in multi-stages to produce pregnant liquor and leached residue, the pregnant liquor containing nickel and cobalt, (3) a neutralization stage which treats the pregnant liquor in the presence of calcium carbonate incorporated to keep the pH level at 3.2 to 3.8, while suppressing oxidation of divalent iron present in the liquor, to produce neutralization precipitate slurry and mother liquor for nickel recovery, the neutralization precipitate slurry containing trivalent iron, and (4) a sulfide precipitation stage which blows hydrogen sulfide gas into the mother liquor to produce sulfide and barren liquor, the sulfide containing nickel and cobalt.