Agglomeration and column leaching behaviour of nickel laterite ores: Effect of ore mineralogy and particle size distribution

• Ni laterite acid agglomeration is an essential pre-treatment for heap leaching.
• Ore mineralogy and particle size impact on agglomeration and leaching behaviour.
• Ore blending is an option to enhance heap leaching performance of agglomerates.
• Up to 90% Ni and 70% Co recovery was achieved within 100 days of column leaching.

Nickel (Ni) laterites account for about 60–70% of the world's nickel mineralization. The processing of low grade (e.g., 1% Ni) laterite ores is favoured by the use of the more cost-effective hydrometallurgical techniques (e.g., atmospheric agitated tank or heap leaching) instead of smelting. Application of heap leaching which boasts of low capital and operating expenditures, however, is very limited due to intractable challenges such as poor heap porosity/permeability associated with most laterite feed ores. Feed particles' agglomeration into robust and porous agglomerates of right size range enables permeable and geotechnically stable bed required for successful heap leaching to be constructed. In this paper, several basic and applied studies of the agglomeration and column leaching behaviour of real Ni laterite ores are reported. The work involved isothermal, batch agglomeration tests carried out to produce 5–40 mm agglomerates which were characterized and subjected to > 100 days of laboratory column leaching. The effect of feed ore characteristics (e.g., mineralogy/chemistry and particle size distribution) on agglomeration behaviour and agglomerates' column leaching behaviour was investigated through several characterization techniques including agglomerate size, compressive strength, 3D micro-structure analyses and laboratory column leaching tests. Links between feed mineralogy/chemistry and size, binder dosage, agglomeration behaviour, agglomerate properties and leaching behaviour are established. The significance of the findings to Ni laterite plant agglomeration for enhanced heap leaching is discussed.