Column leaching behaviour of limonitic and saprolitic nickel laterite ores
Date
2014
Authors
Quaicoe, I.
Nosrati, A.
Addai Mensah, J.
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Conference paper
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UMat Biennaial International Mining and Mineral Conference 2014, 2014, pp.378-384
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UMat Biennial International Mining and Mineral Conference 2014 (30 Jul 2014 - 2 Aug 2014 : Tarkwa, Ghana)
Abstract
Despite technological flexibility and economic competitiveness of heap leaching (HL) for extraction of metals (e.g., gold,copper and silver) from their low grade ores, its successful application for processing complex, low grade nickel (Ni) lateriteores is very limited. This is mainly due to difficulty of forming a heap of run-of-mine or agglomerated ores with desirable porosity, permeability and long-term geotechnical stability. This work presents some highlights of laboratory column leaching studies undertaken to characterize and evaluate sulphuric acid leaching behaviour of agglomerated limonitic orgoethitic (G) and saprolitic (SAP) Ni laterites and their mixed/blended ores. The main focus was to investigate agglomerate strength and their column leaching behaviour for -2 mm G and -15 mm SAP feed ores as well as their blends comprising (i) -2 mm G (60%)/-15 mm SAP (40%) (Blend 1) and (ii) -2 mm G (79%)/-15 mm SAP (21%) (Blend 2), under industrially relevant,continuous acid irrigation conditions (acid strength of 200 g/l metered at a rate of 8.5 l/m2/h) for 100 days. Whilst the G agglomerates' compressive strength appeared greater than that of SAP agglomerates, the former displayed lower bed stability during column leaching. The high G content blend 2 agglomerates also displayed greater bed stability than those produced from blend 1, however, both exhibited substantially similar single agglomerate compressive strength. At a given column leaching conditions, the Ni/Co extractions were higher for -15 mm SAP agglomerates compared with -2 mm G butthe acid consumption for the latter was marginally greater. High SAP content blend 1 agglomerates also displayed greater Ni/Co extractions than blend 2 agglomerates while their acid consumption was almost the same. Comparatively, oreblending did not impact on the Ni/Co extraction rates or overall acid consumptions. However, it led to better agglomerate bed stability compared with that of -2 mm G ore agglomerates. The findings underscore the better column leaching performance of saprolites in contrast with limonites when ore mineralogy/chemistry is considered in designing Ni laterites heap leach operations. The results also suggest that blending of limonitic Ni laterite ores with high clay/silicate containing saprolitic ores could enhance agglomerate bed stability and hence, improve the HL performance of the former.
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Copyright 2014 the authors