Efficient activation of sulfite for reductive-oxidative degradation of chloramphenicol by carbon-supported cobalt ferrite catalysts

Activation of (bi)sulfite (S(IV)) by metal oxides is strongly limited by low electrons utilization. In this study, two carbon-supported cobalt ferrites spinels (CoFe2O4 QDs-GO and CoFe2O4 MOFs-CNTs) have been successfully synthesized by one-step solvothermal method. It was found that both catalysts could efficiently activate S(IV), with rapid reductive dechlorination and then oxidative degradation of a recalcitrant antibiotic chloramphenicol (CAP). Characterizations revealed that CoFe2O4 spinels were tightly coated on the carbon bases (GO and CNTs), with effectiveness of the internal transfer of electrons. O2˙− was identified for the reductive dechlorination of CAP, with simultaneously detection of both •OH and SO4˙− responsible for further oxidative degradation. The sulfur oxygen radical conversion reactions and molecular oxygen activation would occur together upon the carbon-based spinels. Spatial-separated interfacial reductive-oxidation of CAP would occur with dechlorination of CAP by O2˙− on the carbon bases, and oxidative degradation of intermediates by SO4˙−/•OH upon the CoFe2O4 catalysts.