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

Sulfite(SO_(3)^(2−))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 SO32−for removal of Methyl Orange in aqueous solution.The Co@NC catalysts were synthesized via pyrolysis of Co^(2+)-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 cobaltbased catalysts such as Co^(2+),Co_(3)O_(4) and CoFe_(2)O_(4),due to the synergistic effect of metallic Co and CoxOy.A series of chain reaction between Co species and dissolved oxygen was established,with the production and transformation of SO_(3)•−,SO_(5)^(2−),and subsequent active radicals SO_(4)•−and HO•.In addition,HCO_(3)−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 SO3_(2)−oxidation to promote organic pollutants degradation.