Activation of sulfite by metal-organic framework-derived cobalt nanoparticles for organic pollutants removal.

Sulfite (SO) activation is one of the most potential sulfate-radical-based advanced oxidation processes, and the catalysts with high efficiency and low-cost are greatly desired. In this study, the cobalt nanoparticles embedded in nitrogen-doped graphite layers (Co@NC), were used to activate SO for removal of Methyl Orange in aqueous solution. The Co@NC catalysts were synthesized via pyrolysis of Co-based metal-organic framework (Co-MOF), where CoO was firstly formed at 400℃ and then partially reduced to Co nanoparticles embedded in carbon layers at 800℃. The Co@NC catalysts were more active than other cobalt-based catalysts such as Co, CoO and CoFeO, due to the synergistic effect of metallic Co and CoO. A series of chain reaction between Co species and dissolved oxygen was established, with the production and transformation of SO, SO, and subsequent active radicals SO and HO•. In addition, HCO was found to play a key role in the reaction by complexing with Co species on the surface of the catalysts. The results provide a new promising strategy by using the Co@NC catalyst for SO oxidation to promote organic pollutants degradation.