The removal of hydrogen sulfide from gas streams using an aqueous metal sulfate absorbent

Aim of this study was to investigate the possibilities for a selective and efficient method to convert copper(II) sulfide (CuS) into copper(II) oxide (CuO). The oxidation of copper sulfide has been studied experimentally using a thermogravimetric analyzer (TGA) at temperatures ranging from 450 to 750 °C and oxygen concentrations of 5 and 10 vol.%. It appeared that the products formed upon the oxidation of copper sulfide depend on the reaction temperature. However, in all cases the conversion time using the powdered samples was much shorter than expected based on literature results (typically 3 min versus 1-3 h as mentioned in literature). The first reaction step in the oxidation of copper sulfide always was the fast decomposition of CuS into Cu2S and gaseous sulfur, which immediately was oxidized further to SO2. Subsequently, Cu2S was then oxidized, the route depending on the reaction conditions. Oxidation experiments carried out at various temperatures showed that Cu2S was oxidized selectively to CuO at temperatures above 650 °C, while at temperatures below 650 °C (basic) copper sulfate was also formed. The oxidation from Cu2S to CuO appeared to be the result of two consecutive reactions. Cu2S is first converted into Cu2O, which is subsequently oxidized to CuO. The experimental results allowed for the determination of the intrinsic kinetic rate expression and (Arrhenius) relation for the reaction rate constant of the conversion of Cu2S to Cu2O between 650 and 750 °C and oxygen concentrations between 5 and 10 vol.%.