Flotation Recovery of Molybdenite from Porphyry Copper Ores.
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Investigations were conducted to characterize the surface chemical and flotation properties of molybdenite in aqueous environments typical of those that exist in the copper circuits of plants that process prophyry copper ores. The investigations showed that molybdenite and quartz particles are negatively charged at the ph commonly used for bulk sulfide flotation. While the adsorption of calcium ions reduces the magnitude of negative charge on molybdenite, the adsorption can reverse the surface charge on quartz particles when the calcium concentration in solution exceeds 1 by 10- 3m. Heterocoagulation of molybdenite and quartz particles will thus be inevitable in solutions containing large amounts of lime and will impair the floatability of molybdenite. The deleterious effects of heterocoagulation can be somewhat overcome by an ultrasonic conditioning prior to flotation. Besides heterocoagulation, particle size is very critical for optimum molybdenite flotation. Coarse molybdenite particles float extremely rapidly and completely without being influenced by solution ph or heterocoagulation. The flotation of fine molybdenite particles is sensitive to the mean particle size and heterocoagulation. Results of tests conducted to assess the effects of overgrinding of molybdenite indicated that while there is no change in the crystal structure due to prolonged grinding, the floatability is significantly reduced due to the creation of rough surfaces.
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University of Arizona