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Oxidative Roasting of Covellite With Minimal Retardation from the Cuo.cuso4 Film.
Met Trans AIME 1970 Aug; 1:2151-2156
Copper (II) sulfide can be efficiently converted to the oxide at lower temperatures than normally required in aerobic roasting by a new method involving programed environment roasting (per). When heating was conducted in absence of oxygen up to about 650 deg. C, and then nitrogen was replaced by air, the sulfide was easily converted to oxide without need for further increase in temperature. Traditional oxidative roasting of chalcocite required a temperature range of 800 deg. to 850 deg. C for conversion to tenorite. Unlike the situation with conventional roasting, cuso4 was not detected in the x-ray diffractogram of the product obtained with the per method above 625 deg. C. Also, the amount of cuo.Cuso4 significantly decreased as the halt temperature in the per process increased from 600 deg. to 700 deg. C. Apparently the shell of copper oxysulfate is impervious to oxygen and/or sulfur dioxide and delays the formation of tenorite until the sulfate and oxysulfate are decomposed. If the oxysulfate stage were bypassed with an inert atmosphere, then, even if small amounts of this salt were formed upon introducing the oxidant, it would decompose at an appreciable rate and the impedance of its thin film to gaseous transport would be considerably diminished. By contrast, the accelerating effect of externally added iron on the oxidative roasting of covellite was confined to the low temperature reactions and hence iron promoted the extent of sulfate formation. Iron did not, however, lower the thermal requirement for complete oxidation of cus or cu2s because it had virtually
Met. Trans., AIME, V.1, August 1970, PP. 2151-2156
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