METHOD FOR LEACHING NICKELIFEROUS OXIDE ORES OF HIGH AND LOWMAGNESIUM LATERITES

摘要

A process is provided for the leaching of both the "limonite" (Fe approx. &g t;= 25 % and Mg approx. <= 6 %) and "saprolite" (Fe approx. <= 20 % and Mg approx. >= 10 %) fractions of typical nickel and cobalt bearing laterite ore. The low magnesium fraction of the laterite ore is leached with sulfuric acid at high pressure and temperature to solubilize the metal values while precipitating most of the solubilized iron as hematite or other iron compounds and a porti on of the dissolved aluminum as alunite or other aluminum compounds. After reducing the pressure of the leach slurry to approximately atmospheric pressure, the pregnant leach slurry or solution is contacted with the high magnesium fraction of the ore to solubilize most of the nickel contained in the high-magnesium ore fraction while dissolving only a small portion of the iron content of the high magnesium ore fraction. Further neutralization of t he leach slurry in the presence of an alkali metal or ammonium ion will allow t he precipitation of iron-bearing jarosite at ambient pressure. This process for incorporating the leaching of saprolite in the high pressure leaching proces s for limonite ores requires neither high temperature and pressure, nor specia l treatment of the saprolite ore fraction, nor the addition of special reagent s, e.g. reducing reagents.