Preconcentration strategies in the processing of nickel laterite ores part 3: Flotation testing

• Results of previous studies of flotation testing of nickel laterites at laboratory scale are reported.
• Successful upgrading of nickel laterites is compromised by very complex mineralogy.
• Flotation testing aimed at producing either a high Fe and/or low Si containing product.
• Best separation obtained using starch and amine on a hydrocyclone underflow product.

The preconcentration of nickel (Ni) laterite ores ahead of Ni recovery by hydrometallurgical processing makes good economic sense. Since Ni-bearing minerals are often finely disseminated through laterite ores, liberation of minerals either high and/or low in Ni content is a prerequisite prior to any form of separation process. It is the purpose of this paper to investigate the use of flotation to generate products either high or low in Ni-bearing minerals from a sample of Ni laterite with the generic description of “siliceous goethitic”. Previous attempts showed that upgrading of Ni laterites has only been conducted in laboratory or pilot plant scale, not adopted commercially. A number of feed preparation techniques ahead of flotation were attempted at laboratory scale on a sample of Ni laterite containing predominantly goethite and quartz. Flotation tests even on closely sized particles (38–75 μm) failed to yield significant Ni upgrades using the reagents tested in this study, based on those used commercially for processing iron oxide ores. The best result was an increase in Ni content from 1.0% to 1.4% at a Ni recovery of 43%. This was obtained using 400 g/t of an amine collector and 300 g/t of starch at pH 10 on a sample of hydrocyclone underflow. This paper was designed to provide some lessons learnt for future researchers from laboratory flotation testing of a complex Ni laterite ore.