Thermal roasting behavior and kinetics of African cobalt-rich copper sulfide ore in air atmosphere

African cobalt-rich copper sulfide ore (CRCS) is an important copper-cobalt resource. The CRCS mainly contains chalcopyrite (CuFeS2), pyrite (FeS2), and carrollite (CuCo2S4). In our previous study, activated roasting was used to treat CRCS, converting CuCo2S4 into sulfate that is easy to leach Cu and Co. It was found that the kinetics of CuCo2S4 in CRCS transformation was slow during roasting, which is a key factor affecting the subsequent increase in cobalt leaching rate. Therefore, it is of practical significance to explore the kinetics process in the activated roasting process of CRCS. In this study, thermal roasting kinetics of CRCS in the air atmosphere was studied by TG-DTG method at heating rates of 5, 10, 15, and 20 K min(-1), respectively. Meanwhile, the phase transformation behavior of major minerals, pyrite, and carrollite during roasting was studied. The results show that the roasting process of CRCS mainly goes through three stages: Stage I: removal of free water and crystal water; Stage II: oxidation of sulfide minerals to sulfate; and Stage III: decomposition of sulfate to oxide. Given Stage II, the deconvolution separation method was used to separate overlapping reaction peaks of FeS2 and CuCo2S4. The kinetic parameters were evaluated by Friedman method, KAS method, FWO method, and CR method, respectively. The most probable mechanism function and activation energy (E) were determined by comparing the model-free method with the model-fitting method. Results showed that the oxidation of FeS2 in CRCS conforms to the 2-D diffusion model; the oxidation of CuCo2S4 in CRCS accords with the Avrami-Erofeev model. Finally, thermodynamic parameters of the reaction including enthalpy, entropy, and Gibbs free energy were calculated. Kinetic analysis shows that the heating rate has a significant influence on the ore phase transition during the oxidation process of CRCS. The oxidation processes of different ore in CRCS conform to different kinetic mechanisms.

Automated summary

The study focuses on the kinetics process and thermodynamic parameters of African cobalt-rich copper sulfide ore in the activated roasting process, showing that the ore phase transition is significantly influenced by the heating rate, and the oxidation processes of different ore in CRCS conform to different kinetic mechanisms.