Construction of core-shell FeO@GO-CoPc photo-Fenton catalyst for superior removal of tetracycline: The role of GO in promotion of HO to •OH conversion.

A novel core-shell structured FeO@GO-CoPc magnetic catalyst, which is with magnetite (FeO) as the core, graphene oxide (GO) as the interlayer and cobalt-phthalocyanine (CoPc) as the shell, was successfully prepared and used as a heterogeneous photo-Fenton catalyst for tetracycline (TC) degradation in this work. The core-shell structure of the catalyst was confirmed by XRD, FTIR, SEM and TEM. BET and magnetic hysteresis loops measurements indicated that FeO@GO-CoPc catalyst owned large specific surface area and could be easily recovered under an external magnetic field. Meanwhile, the experimental results of TC degradation demonstrated that the photo-Fenton efficiency of FeO@GO-CoPc was excellent. When the reaction time was 120 min, TC could be degraded almost completely in the photo-Fenton system with FeO@GO-CoPc. The high photo-Fenton catalytic activity of FeO@GO-CoPc could be resulted from the effective transfer of photo-generated electrons between CoPc and FeO by GO. Moreover, the main reaction species, •OH, O•-, O and h, were verified by the analysis of active species in this system. Finally, the mechanism analyses and quantitative analysis results of active species indicated that the introduction of GO accelerated the cycle between Fe(II) and Fe(III) as well as improved the effective utilization of HO (the efficiency of conversion of HO to •OH).