In the current study the oxidation of CuS to CuO at temperatures in the range of 450–750 ◦C and oxygen concentration
as encountered during roasting (5–10 vol.%) has been studied experimentally using a thermogravimetric analyzer.
Thermodynamics show that the formation of CuO from CuS is possible if the SO2 partial pressure is sufficiently low. Besides CuO some by- or intermediate products like (basic) copper sulfate or Cu2O may be formed during the oxidation
of CuS. The stability of these byproducts depends on the process conditions like temperature, sulfur dioxide and oxygen
concentration. At temperatures up to 527 ◦C (basic) copper sulfate is a stable component. Experiments have shown that
the oxidation of CuS toCuOconsists of several reaction steps, the conversion of CuS to Cu2S being always the first step.
Since this reaction appeared to be a fast reaction compared to the other reactions that may occur, Cu2S was chosen as
starting material for the oxidation experiments carried out at temperatures above 400 ◦C (above this temperature CuS
reacts very fast to Cu2S both in the presence and absence of oxygen). The experimental results showed that the time
needed for a complete conversion of the copper sulfide to copper oxide was very short when compared to the reaction
times mentioned in literature. At temperatures above 650 ◦C the powdered Cu2S samples were completely converted to
CuO in less than approximately 3 min as compared to the 1–3 h reaction time typically mentioned in literature for the
conversion of Cu2S in a pelletized shape. The experimental results showed that at temperatures up to 550 ◦C CuS and
Cu2S may be converted (partially) into (basic) copper sulfate. Above this temperature it is possible to convert Cu2S selectively and completely to CuO. The oxidation of Cu2S to CuO appeared to be a two step process. The first reaction step is the oxidation of Cu2S toCu2O. The second step is the subsequent oxidation of Cu2O to CuO. The rate at which Cu2S is converted in to Cu2O increased with temperature. Both chemical reaction and mass transfer influenced the conversion rate. To derive the intrinsic kinetics from the experimental results a number of experiments were performed in which the temperature and amount of sample used were varied. The kinetics of the oxidation reaction of Cu2S to Cu2O have thus been determined as a function of temperature (Table 3).