Bentonite supported cobalt catalyst prepared by blending method for the catalytic oxidation of desulfurization by-product sulfite: Catalytic performance and mechanism.

Wet flue gas desulfurization (WFGD) could effectively reduce sulfur dioxide emission. However, magnesium sulfite (MgSO3), a by-product of desulfurization, was easy to result in secondary pollution. In this study, the solid catalyst Co-Bent (bentonite supported cobalt) was prepared by blending method for MgSO3 oxidation with bentonite as the carrier and cobalt as the active component. At the calcination temperature of 550 °C and the Co loading level of 3 wt.%, the catalyst showed excellent catalytic performance for the oxidation of high concentration MgSO3 slurry, and the oxidation rate of MgSO3 was 0.13 mol/(L·h). The research indicated that the active component was uniformly distributed within porous structure of the catalyst as Co3O4, which facilitated the oxidation of SO32- catalyzed by Co3O4. Kinetic researches indicated the oxidation rate of MgSO3 was influenced by the catalyst dosage, the reaction temperature, the solution pH, the airflow rate, and the SO32- concentration. Additionally, after recycling experiments, the regenerated catalyst retained its high catalytic performance for the MgSO3 oxidation. The reaction mechanism for the catalytic oxidation of MgSO3 by Co-Bent catalyst was also proposed. The generation of active free radicals (OH·, SO4-·, SO3-·, SO5-·) accelerated the MgSO3 oxidation. These results provide theoretical support for the treatment of MgSO3 and the development of durable catalyst.