Mn doped magnetic biochar as persulfate activator for the degradation of tetracycline

Recently, biochar (BC) has been frequently used to degrade organic contaminants in advanced oxidation processes (AOPs). In this study, Mn doped magnetic biochar (MMBC) was prepared to activate persulfate (PS) for the degradation of tetracycline (TC). The activation of PS by MMBC was affected by the doping amount of Mn, pyrolysis temperature and residence time. The degree of defects and the formation of metal oxides of MMBC were mainly affected by the pyrolysis temperature. The removal efficiency of TC reached 93%, which was much higher than that of the original BC (64%). Electron spin resonance (ESR) and quenching results showed that SO4− and OH were generated in MMBC-PS system and the dominated free radical was OH. In addition, the results of linear sweep voltammetry (LSV) proved that MMBC was highly conductive and the existence of electron transport in the degradation. X-ray diffractometer (XRD), Raman, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrum (FT-IR) analysis jointly implied that surface oxygen-containing functional groups, the defect structure of the material and iron-manganese oxide provided active sites for activation of PS with MMBC. In addition, MMBC exhibited an excellent reusability and did not cause secondary pollution to the environment due to its excellent magnetic properties. This study confirmed that the presence of transition metals can promote the activation of PS by BC, and the pyrolysis temperature can affect its catalytic performance by affecting the properties of carbon materials (oxygen functional groups, degree of defects, etc.), providing a new idea for the application of carbon materials in AOPs.