Effective Removal of Tetracycline by Using Biochar Supported Fe3O4 as a UV-Fenton Catalyst

Novel Fe3O4-decorate hierarchical porous carbon skeleton derived from maize straw(Fe3O4@MSC) was synthesized by a facile co-precipitation process and a calcination process, which was developed as a UV assisted heterogeneous Fenton-like catalyst. The as-synthesized catalysts were characterized via X-ray powder diffraction(XRD), scanning electron microscope(SEM), transmission electron microscope(TEM), Brunauer-Emmet-Teller(BET) and vibrating sample magnetometer(VSM) at room temperature. The morphology and structure analysis revealed that the as-prepared Fe3O4@MSC retained the original pore morphology of the maize straw material. The non-uniform polyhedral Fe3O4 grew on the whole surface of the MSC, which reduced the aggragation of Fe3O4 and provided more active sites to strengthen the UV-assisted Fenton-like reaction. As a result, the tetracycline(TC) degradation efficiency after 40 min reaction and total organic carbon(TOC) removal efficiency after 2 h reaction of Fe3O4@MSC catalyzing UV-Fenton system reached 99.2% and 72.1%, respectively, which were more substantial than those of Fe3O4@MSC/H2O2(31.5% and 2%), UV/H2O2 system(68% and 23.4%) and UV/Fe3O4/H2O2(80% and 37.5%). The electron spin resonance(ESR) results showed that the •OH played an important role in the catalytic reaction. A possible degradation pathway of TC was proposed on the basis of the identified intermediates. Overall, the UV assisted heterogeneous Fenton-like process in Fe3O4@MSC improved the cycle of Fe3+/Fe2+ and activated the interfacial catalytic site, which eventually realized the enhancement of degradation and mineralization to tetracycline.