Immobilized hybrids between nitrogen-doped carbon and stainless steel derived Fe3O4 used as a heterogeneous activator of persulfate during the treatment of aqueous carbamazepine

Immobilized activators of persulfate (PS) with high activity and stability are highly desirable from an industrial and environmental point of view. In this work, nitrogen-doped carbon (CNx) was successfully hybridized with stainless steel (SS) derived Fe3O4 to construct a SS supported CNx/Fe3O4 heterogeneous catalyst (CNx/Fe3O4/ SS). When used in a sulfate radical (SO4 center dot-)-based advanced oxidation process (SR-AOP), CNx/Fe3O4/SS displayed significantly higher activity towards the degradation of aqueous carbamazepine (CBZ) when compared to the single Fe3O4 and CNx activators. The removal of CBZ had the most rapid progression, with an initial pH of 3.5, a temperature of 35 degrees C, an initially added PS concentration of 250 mg L-1 and an added amount of CNx/Fe3O4/SS of 0.30 g. The removal efficiency of CBZ was similar to 100% after 35 min of SR-AOPs. In addition, the CNx/Fe3O4/SS catalyst was stable, as demonstrated by six successive cycling experiments. The results obtained from the electron paramagnetic resonance (EPR) spectra and radical quenching experiments indicated that both SO4 center dot- and HO center dot contributed to the CBZ oxidation process. On the basis of X-ray photoelectron spectroscopy (XPS) and Fermi level analyses, it can be concluded that SO4 center dot- and HO center dot originated from the Fe3O4 catalyzed decomposition of aqueous PS. CNx facilitated the redox cycle of Fe(III)/Fe(II) in Fe3O4. This study demonstrated the potential application of SR-AOPs to efficiently degrade organic contaminants.