| Jan 27, 2014 |
Small-scale imaging unlocks nickel ore value
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(Nanowerk News) Researchers are using a unique method of nano-material imaging to more effectively determine the highly variable acid leaching values of Western Australian nickel laterite ores.
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The study ("Acid resistance of goethite in nickel laterite ore from Western Australia. Part I. The relationship between goethite morphologies and acid leaching performance"), a joint project involving the Curtin University Centre for Materials Research and CSIRO Division of Process Science and Engineering, could have a far reaching impact on hydrometallurgical processing for these ores which have previously been difficult to characterise.
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Curtin PhD student and lead author Tony Wang applied his knowledge in materials science and applied material characterisation techniques on mineral analysis.
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Mr Wang used energy-filtered transmission electron microscopy (TEM) imaging to analyse the ores, a method relatively unfamiliar to metallurgists or geologists.
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| Mr Wang also found the goethite-silica cementation structure in some WA laterite ores explained why some goethitic laterite ores did not leach and release the nickel.
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“We know that TEM is an analysis tool for nano-materials and it has much better spatial resolution than normal scanning electron microscopy (SEM) based techniques,” Mr Wang says.
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“In TEM, electrons passing through [the] sample lose energy, different elements in samples grab characteristic amount of energy from the incident primary electron beam.
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“By detecting electrons with the amount of energy loss we are able to map where these elements present in a nano-scale particles/sample features.”
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Mr Wang says the ores analysed by Inductively Coupled Plasma (ICP) mass spectrometry or X-ray fluorescence (XRF) methods tell the practitioners how much nickel is present in the ores but not how much nickel can be extracted.
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“The difference can be surprisingly huge,” he says.
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“For example after same acid leaching time some ores can release 90 per cent of nickel while the other types can only give 10 per cent of nickel.
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“Therefore mineral processing scientists in CSIRO use X-Ray Diffraction to examine the mineralogy of these ores, hopefully a better correlation between types of ores and the acid leaching rates can be derived.
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“This is based on the fact that different minerals in the ore mixture have different chemical properties therefore different acid leaching rates.
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“The point I am emphasising in my paper is in the third levels, with the nano scale elemental imaging techniques, we are able to examine how the minerals are linked.”
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Mr Wang also found the goethite-silica cementation structure in some WA laterite ores explained why some goethitic laterite ores did not leach and release the nickel.
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“These goethite crystals are enveloped or covered by silica inside the cementation structures,” he says.
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“We found the cementation can be broken down by caustic digestion using potassium hydroxide liquors.
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“On the contrary, all the fast leaching ores in my sample suit contains ubiquitous discrete acicular or needle shaped goethite.
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