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:: Synchrotron Reveals Bioleaching Transformation
A combination of biology and chemistry is being used to extract minerals from sources that have traditionally been overlooked, including low-grade ores and mining waste.
Bioleaching is the use of microorganisms to leach target metals such as copper or zinc from sulfide ores.According CSIRO’s Dr Miao Chen this biotechnological method is potentially cheaper and more environmentally friendly than traditional high temperature processing, making it an economically viable option for lower grade ores.
Although bioleaching is already being used commercially to extract copper from secondary sulfide minerals such as chalcocite, the process has not been as successful in extracting copper from the primary copper sulphide chalcopyrite, CuFeS2. The slow dissolution of chalcopyrite during bioleaching is preventing commercial use of the technique.
Until recently little was known about how bioleaching worked exactly - only that it did. However Dr Chen has been working with scientists at the Australian Synchrotron in Melbourne, particularly Dr Qinfen Gu, to get a clearer picture of the process as it happens.
“We have our own x-ray diffraction (XRD) equipment at CSIRO, which is a powerful tool. But the resolution at the synchrotron is so much more powerful, due to the higher x-ray flux and better resolution." This in situ electrochemical XRD technology has allowed the phase mineralogy transformations during bio- and chemical leaching of chalcopyrite to be tracked.
Dr Chen’s research focuses on the extraction of copper from chalcopyrite, which contains up to 70 per cent of the world’s copper resources. Biochemists have developed effective strains of microbes; her task uses physics and new electrochemical technology to better define the process and to identify any factors that can be tweaked to make it more effective.
By studying the development of the microbes and the leaching process in situ at the synchrotron, Dr Chen has been able to identify the influence of pH and temperature on bioleaching. She has also studied the development of ‘passivation’ that slows down or prevents the leaching process. She says although conditions at the initiation of the process are critical, she has also been tracking changes midway through and late in the leaching process.
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