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Kinetics and mechanism of the conversion of covellite (CuS) to digenite (Cu1.8S).
Shah ID; Khalafalla SE
Metall Trans 1971 Sep; 2(9):2637-2643
Rates of conversion of covellite (cus) to digenite (cu1.8S) in n2 and various partial pressures of o2 have been studied in the temperature range 260 deg to 400 deg c. The reaction is first order with respect to o2 concentration in n2-o2 mixtures at 1 atm. The experimental activation energy for the conversion of cus to cu1.8S is 23 +/- 3 kcal. In a nitrogen atmosphere, the conversion proceeds at a slower rate but with the same activation energy and leads to the formation of elemental sulfur instead of so2. An externally added small amount of iron powder (0.6 percent) increased the rate of conversion but had no effect on the apparent activation energy. The rate-controlling reaction in the conversion mechanism is postulated to be cu1.8S -> 1.8 Cu+ + 1.8 E- + s at the cu1.8S/gas interface. Reduction of cus by copper(I) ions and electrons occurs by a rapid reaction, 0.8 Cu+ + 0.8 E- + cus -> cu1.8S at the cus/cu1.8S interface, which steadily contracts with time.
Chemical-reactions; Chemical-properties; Chemical-kinetics; Gas-mixtures; Gases
OP; Journal Article
Metallurgical Transactions. B. Process Metallurgy
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