Patent ID: 8187360

Claim:
A process for the instantaneous control of the precipitation of Ni and Co present in a leach liquor resulting from the pressure acid leaching of laterite ores using pH adjustments to the solution, comprising: a. precipitating Al, ferric Fe, and Cr while minimizing the precipitation of Ni, Co, and Mn by making additions of lime and/or limestone to the solution while controlling the pH in the solution within a first pre-determined range; b. precipitating ferrous Fe while minimizing the precipitation of Ni, Co, and Mn by making additions of lime and/or limestone to the solution while controlling the pH in the solution within a second pre-determined range; c. separating the precipitated Al, ferric and ferrous Fe, and Cr from the solution; and d. precipitating Ni and Co by making additions of magnesia to the solution while controlling the pH of the solution within a third predetermined range, wherein the procedure for precipitating Ni and Co from the solution comprises the steps of: i. adding solid calcined magnesia to the solution while measuring the pH of the solution; ii. adding the magnesia in a controlled manner such that the pH of the solution is maintained between 7.0 and 8.0; iii. carrying out the precipitation over a period of time covering approximately three hours at a temperature of approximately 50° C.; iv. separating the precipitated product from the solution using equipment designed for that purpose; v. washing the precipitated material, thereby reducing or even eliminating the impregnated magnesium sulfate present therein; and vi. treating the filtered and washed product at refineries designed for the recovery of the contained Ni and Co.