Electro-assisted catalytic oxidation of flue gas desulfurization-derived magnesium sulfite using cobalt ferrite as catalyst under moderate condition

Abstract

The catalysts were prepared by supporting cobalt ferrite (CoxFe3−xO4) on the surfaces of sphere mesoporous silica (MCM−41) nanoparticles. The electro-assisted catalytic oxidation of MgSO3 displayed an improved oxidation rate under moderate temperatures. Electric field and CoFe2O4/MCM−41 exhibited a beneficial synergistic effect because the associated MgSO3 oxidation rate is 3.38 times the oxidation rate when only the electric field was present, and 1.83 times the oxidation rate when only the catalyst was present. The cyclic voltammetry results proved that the catalysts reduced the oxidation potential of SO32− in the presence of an electric field, and increased the electron transfer rate in the oxidation. Both the X-ray photoelectron spectroscopy (XPS) characterization and free radical scavenging experiment results indicated that Co2+ served as the initiator in the generation of superoxide ions (O2−·), which was the primary active free radical responsible for the oxidation of SO32−. The electron spin resonance (ESR) spectra showed that the electric field and high current density expedited the production of O2−·. The XPS results convincingly demonstrated that the electric field effectively alleviated the catalyst deterioration, and, as a result, significantly improved the catalyst's recyclability. Lastly, the synergistic mechanism between the electric field and the catalyst in the catalytic oxidation of MgSO3 was explored.