The extraction of metals from metal containing catalysts by supercritical fluids
AuthorMcPartland, Jack Stuart
AdvisorBautista, Renato G.
Mining & Metallurgical Engineering
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Experiments were conducted to determine the feasibility of leaching cobalt from a hydrotreating catalyst material using supercritical aqueous ammonia solvents. Supercritical phase leaching conditions were attained using a modified Autoclave Engineers Supercritical Screening System. The effects on cobalt extraction caused by variations in solvent composition, pressure and temperature, including subcritical conditions, were investigated. Four series of experiments, each using various solvent compositions ranging from O to 30 percent ammonia at one temperature - pressure condition, were conducted. Cobalt in the catalyst material was leachable at supercritical and subcritical solvent phase conditions. Cobalt extraction at supercritical phase conditions was generally higher than extraction obtained at any of the other pressure – temperature conditions tested. Leaching enhancement at supercritical conditions was determined not to be solely the result of simple pressure or temperature effects. Rather, leaching enhancement is probably caused by the improved transport properties exhibited by supercritical fluid solvents. Cobalt extraction at supercritical conditions was enhanced by an average of 14.2 percent over extraction at supercritical pressure - elevated temperature conditions, 6.8 percent over extraction at low pressure - low temperature conditions, and 4.0 percent over extraction at supercritical pressure - low temperature conditions. Cobalt extraction generally increased with increasing ammonia concentration at all four temperature – pressure conditions tested.
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