Sulfite activation on a silica-supported well-dispersed cobalt catalyst via an electron transfer complex path

The metal activating sulfite system has attracted widespread attention as a novel advanced oxidation process recently. In this study, a silica-supported highly dispersed cobalt catalyst was prepared using Co ammine complex as precursor, characterized by transmission electron microscope, X-ray diffraction, Brunauer-Emmett-Teller surface area, X-ray photoelectron spectroscopy and so forth, and used to activate sulfite for the removal of organic pollutants. The as-prepared catalyst displayed a durable and remarkable catalytic activation of sulfite for organic degradation in sequential experiments. The mechanistic study corroborated the dual roles of sulfite as a complexing ligand on catalyst surface and a precursor of oxysulfur radicals. The surface-bound and free SO4 center dot- were found to be the dominating radicals responsible for organic degradation. The steady-state approximation of SO4 center dot- were examined and the apparent reaction rate constant of SO4 center dot- generation was 0.60 +/- 0.07 M-1 s(-1) at 0.25 g L-1 catalyst. The influencing factors and operating parameters, including catalyst dosage, sulfite/contaminant ratio, pH, temperature, anions and natural organic matter were investigated and optimized systematically. As conclusion, the as-prepared catalyst to efficient activation of sulfite can be proposed as a promising advanced oxidation process based on oxysulfur radicals for the treatment of wastewater. (C) 2020 Elsevier Ltd. All rights reserved.