Selective Leaching Nickel from the Pre-Reduced Limonitic Laterite Ore at Atmospheric Pressure

In this paper a novel method for selective leaching nickel from pre-reduced laterite ore at atmospheric pressure was reported. The reduced calcine was leached in thin acid liquor to liberate the nickel and iron together firstly. By properly controlling the leaching condition, the leached iron ion could hydrolyze as goethite precipitate and regenerate the acid consumed in the leaching procedure. Finally, the nickel is selectively extracted into the leaching solution. The main factors in the leaching process, such as reduction degree of the laterite ore, acidity of the leaching solution were investigated as influence on the nickel extraction. The test results showed that selectively leaching of nickel could be achieved with an extraction degree up to 90% by reducing most of the iron in the lateritic ore to wuestite and controlling the pH value of the leaching solution below 2.5.