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Recovery of indium from mining wastes, The
Tshijik Karumb, Evody
Tshijik Karumb, Evody
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2016
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Scarcity and high demand has placed an economic pressure on the supply of indium worldwide; therefore, there is a global interest in increasing the recycling capacity for indium. This project’s main goal is the identification of secondary raw material resources for indium production; investigations were conducted on three zinc processing wastes namely a “tailings” sample which is a waste from flotation plant, a “jarosite” sample which is a waste from a hydrometallurgical plant, and a “ferrite” sample which is a waste from pyro-hydrometallurgical plant. Characterization work conducted showed that the tailings sample was mainly comprised of silicates minerals such as quartz, muscovite, and feldspar, that the jarosite sample was mainly comprised of natrojarosite and sulfate minerals, and that the ferrite sample was mainly comprised of franklinite. Results from the chemical analysis showed that the indium content in the tailings, jarosite, and ferrite samples was 18.3, 246, and 783 ppm, respectively. Investigation on the potential for indium beneficiation via physical separation methods was conducted on all three samples; this project looked at gravity, magnetic, and electrostatic separation. It was concluded that physical separation did not achieved appreciable beneficiation. The indium head grade in the tailings sample was very low, and liberation of contained zinc minerals was also low; consequently this sample has a no economic incentive for processing. For the jarosite sample, it was concluded that a large portion of indium was contained in the lattice of natrojarosite; therefore, enrichment ratios were thought to be not high enough for commercial exploitation. It was determined that the sample should be leached as received. For the ferrite sample, it was concluded that physical separation would not work; however, it was determined that the sample could be screened at 297 um in to remove a portion of the coarser gangue minerals followed by leaching of the fines fraction. Indium was successfully extracted into solution via a sulfuric acid leach for both the jarosite (95% extraction) and the ferrite (90% extraction) samples. However, high acid consumption and high co-extraction of iron renders the process uneconomical. It is suggested for future work to employ a magnetizing roast process followed by a magnetic separation in order to separate out iron leaving a non-magnetic product possibly enriched in indium and perhaps more suitable for a low acid consuming leaching process, thus reducing the complexity of the purification step.
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