Removal of tetracycline from wastewater using magnetic biochar: A comparative study of performance based on the preparation method

Abstract This study aimed to compare the removal effect of tetracycline (TC) by magnetic biochar, (BC) prepared via two magnetization methods: coprecipitation (MBC-1) and pyrolysis impregnation (MBC-2) The TC removal effects of MBC-1 and MBC-2 were compared. The samples were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET), and Zeta potential. Effects of contact time, initial TC concentration, pH, adsorption kinetics, and isotherms were studied. The results showed that the adsorption processes of TC with MBC-1 and MBC-2 were fitted with a pseudo-second-order kinetics model and that the Langmuir isotherm model was most suitable for the adsorption data of MBC-1 and MBC-2. The maximum adsorption capacities of MBC-1 (42.31 mg/g) and MBC-2 (24.31 mg/g) were greater than that of the primitive BC (PBC, 12.10 mg/g), indicating that magnetization effectively promotes the adsorption of TC. MBC-1 contains 2.3 times as much iron as MBC-2, and iron oxides provide –OH groups that act as donors and acceptors of hydrogen bonds, thus enhancing the hydrogen-bonding interactions between MBC-1 or MBC-2 and TC. Compared with MBC-2, MBC-1, could provide oxygen-containing functional groups as reactive sites. The prepared magnetic BCs using coprecipitation form an optimized method for removing TC from water to promote clean production. It also provides a new method of comprehensive utilization of waste mushroom matrix for the sustainable development of the edible mushroom industry.