Uniform dispersion of cobalt nanoparticles over nonporous TiO₂ with low activation energy for magnesium sulfate recovery in a novel magnesia-based desulfurization process

The forced oxidation of magnesium sulfite (MgSO₃) aims to not only reclaim the by-product in the magnesia desulfurization, but also lower the risk of secondary pollution. The non-porous titanium dioxide nanoparticle was used as a support to prepare the cobalt catalyst (Co-TiO₂) in order to expedite the oxidation rate. This fabricated Co-TiO₂ was characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and energy dispersive spectroscopy (EDS) to figure out its catalytic mechanism. The results revealed that the cobalt nanoparticles were uniformly dispersed on the surface of the TiO₂ in forms of Co₃O₄ and Co₂O₃. The kinetics of the MgSO₃ oxidation catalyzed by the prepared Co-TiO₂ was investigated in a bubbling tank reactor, indicating that the oxidation rate was dependent on the catalyst concentration, oxygen partial pressure, pH value, and the reaction temperature. Compared with the reported porous catalyst (Co-CNTs), the activation energy with the Co-TiO₂ (17.29 kJ mol⁻¹) decreased by 50.9%, resulting in a good catalytic performance in sulfite oxidation. The findings will help advance the industrial application of the novel magnesia desulfurization process.