Ammonia leaching as a pre-treatment for the processing of oxidised PGM ores
Master Thesis
2015
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University of Cape Town
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Abstract
The exploitation of near-surface deposits has resulted in the need to adjust current conventional mineral processing technologies for the treatment of low grade oxidised PGM ores. The exposure of the ore to the atmosphere leads to the formation of an oxidation layer (consisting of base metal oxides) which inhibits the flotation process that requires a clean mineral surface to be effective. Previous studies have shown that an acid pre-treatment could lead to a 20% PGM recovery increase. Due to the corrosive nature of acid, such treatment would require additional equipment and a pre-wash. Therefore, this project investigates the use of ammonia as a pre-treatment of oxidised low grade PGM ores. Ammonia leaching has shown success in the extraction of base metals (94% and 91% Cu and Ni extraction) and is used as a wash reagent in an attempt to dissolve the oxidation layer and expose a cleaner mineral surface. Both column leaching of whole ore and batch stirred tank reactor leaching of milled ore were investigated as pre-treatment methods for varying length of process times, and the material was subsequently tested for its flotation behaviour. The total solids, base metal and PGM recoveries were monitored in order to determine the effect of the treatment.
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Includes bibliography.
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Musonda, K. 2015. Ammonia leaching as a pre-treatment for the processing of oxidised PGM ores. University of Cape Town.