Effective Removal of Tetracycline by Using Biochar Supported Fe ₃ O ₄ as a UV-Fenton Catalyst

Novel Fe ₃ O ₄ -decorate hierarchical porous carbon skeleton derived from maize straw(Fe ₃ O ₄ @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 Fe ₃ O ₄ @MSC retained the original pore morphology of the maize straw material. The non-uniform polyhedral Fe ₃ O ₄ grew on the whole surface of the MSC, which reduced the aggragation of Fe ₃ O ₄ 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 Fe ₃ O ₄ @MSC catalyzing UV-Fenton system reached 99.2% and 72.1%, respectively, which were more substantial than those of Fe ₃ O ₄ @MSC/H ₂ O ₂ (31.5% and 2%), UV/H ₂ O ₂ system(68% and 23.4%) and UV/Fe ₃ O ₄ /H ₂ O ₂ (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 Fe ₃ O ₄ @MSC improved the cycle of Fe ³⁺ /Fe ²⁺ and activated the interfacial catalytic site, which eventually realized the enhancement of degradation and mineralization to tetracycline.