Effective degradation of diatrizoate by electro-peroxone process using ferrite/carbon nanotubes based gas diffusion cathode

In this study, ferrite modified carbon nanotubes (MFe 2 O 4 /CNTs, M: Fe, Mn) were prepared and employed as cathodic catalysts to assist electro-peroxone (i.e., combined ozonation with electrolysis process using a carbon-polytetrafluoroethylene cathode) treatment of emerging pollutant diatrizoate (DTZ) in aqueous solution. The structural and surface property of synthesized catalysts was studied, and the performance of electro-peroxone process using MFe 2 O 4 /CNTs based gas diffusion cathode (GDC) was systematically investigated from the kinetic and mechanistic viewpoints. Results show that the combination of ozonation and electrolysis exhibited synergistic degradation of DTZ. Approximately 71.9% DTZ had been degraded with MFe 2 O 4 /CNTs based GDC after 10   min, 13.2% higher than with bare CNTs based GDC, implying that the combined treatment efficiency could be enhanced by the presence of MFe 2 O 4 . The performance of MFe 2 O 4 /CNTs catalytic electro-peroxone process was positively correlated with inlet ozone concentration (10–30   mg/L), and an increase in applied current stimulated DTZ degradation at a low cathodic current density (5–40   mA/cm 2 ) but inhibited the degradation at a high cathodic current density (40–60   mA/cm 2 ). The MFe 2 O 4 /CNTs catalytic electro-peroxone treatment also showed a significant dependence on initial pH and reaction temperature, but was little affected by supporting electrolyte concentration. Higher removal efficiency was obtained at a lower initial DTZ concentration. The comparison tests reveal that peroxone reaction was the main pathway of hydroxyl radicals (HO ) production in the present system, and the presence of MFe 2 O 4 at the cathode could promote HO generation. These observations suggest that electro-peroxone is efficient for DTZ degradation in aqueous solution, and MFe 2 O 4 /CNTs are good and promising cathodic materials and catalysts for this process.