The crystal chemistry, dissolution kinetics and dehydroxylation of oxide-type lateritic Ni ore /cMatthew Landers

Matthew Landers

    Research output: ThesisDoctoral Thesis

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    The recent strong demand for Ni for steel production has significantly depleted the easily extractable Ni sulphide deposits, causing the mining industry to look towards the more abundant albeit complex, low-grade lateritic Ni deposits. There have been major difficulties in the extraction of Ni from lateritic Ni ores reflecting, inter alia, the limited knowledge of the location and distribution of Ni within minerals (particularly iron-oxides) in lateritic ores, as well as the limited understanding of the acid leaching kinetics of these minerals. A new method for improving the extraction of Ni from oxide-type (limonitic) lateritic Ni ores by means of shock heating has been investigated in this thesis utilising a combination of bulk and macroscopic techniques. Five oxide-type lateritic Ni ores from Indonesia (Weda Bay), Western Australia (Kalgoorlie and Ravensthorpe) and New Caledonia (Goro and Koiambo), composed mostly of acicular, nano-sized goethite crystals with minor amounts of quartz, talc, willemseite, maghemite, magnetite, asbolane, kaolinite, Mn oxides and various spinels. These minerals were identified using synchrotron X-ray diffraction (SXRD) and electron energy loss spectroscopy (EELS). The nickeliferous goethites were subjected to shock heating for 30 minutes at temperatures in the range 220-800°C. Goethite partially dehydroxylated to OH-hematite at 300-400°C and had completely altered to well ordered hematite at 800°C. OH-hematite has broad XRD reflections, structural water, high specific surface area, structural disorder and small crystal size. The high surface area (1.5-2.6 fold increase from that of goethite) is due to the formation of slit-shaped micropores (300°C), which further develop into elliptically-shaped micropores (400°C), and is partly responsible for a 9-34 fold increase in the dissolution rate constant k for the Kabai equation, measured from the dissolution of Fe in 2M H2SO4. The remaining 5-10 fold increase in the dissolution
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010


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