Method of recovering nickel from laterite ores

Abstract

According to the present invention, processes are provided for recovery of nickel, cobalt and like metal values from laterite ores wherein the ores are separated into high and low magnesium containing fractions, the low magnesium fraction is leached with sulfuric acid at elevated temperatures and pressure to solubilize the metal values. The pregnant liquor resulting from the high pressure which also contains solubilized Fe, Al and acid is then contacted with a low magnesium fraction of the ore in a low pressure leach under conditions such that at least some of the acid is neutralized and substantially all of the solubilized Fe and Al is removed as hematite and alunite precipitate. In one embodiment, the pregnant liquor from the high pressure leach and the high magnesium fraction are contacted at atmospheric pressure and a temperature of about 80.degree. C. prior to low pressure leaching. In other embodiments, various process streams are separated by size and otherwise, and recycled to within the processes. In another embodiment, all leached values, including magnesium and sulfuric acid, are recovered, resulting in a dischargeless process which is environmentally and economically acceptable. Elimination of prior art iron and aluminum contaminants by the low pressure leach provides a simplified method of recovery of all elements in the leachate.

Dependencies are inferred from the claim text.