Slow Pyrolysis Magnetization of Hydrochar for Effective and Highly Stable Removal of Tetracycline from Aqueous Solution

Although biochar has been intensively studied as an inexpensive adsorbent for diverse organic pollutants in aqueous solution, synchronously achieving high adsorption capacity, separability, and stability is still a challenge. Herein, we partially addressed this issue via an integrated activation and pyrolytic magnetization of sawdust hydrochar, during which the surface area of magnetic activated sawdust hydrochar (M-SDHA) increases from 1.7 to 1710 m(2) g(-1), and the weight loss decreases from 70 to 5% at 700 degrees C. Correspondingly, the maxmium adsorption capacity of M-SDHA toward tetracycline (TC) reaches 423.7 mg g(-1) and remains constant at pH 5-9. Multiple characterizations show that the fine pore structure and surface functional groups of M-SDHA were maintained during the pyrolysiS magnetization process, which is responsible for the high adsorption capacity.,In the pyrolysis magnetization process, the FeCl3 was reduced to Fe3O4 which endowed M-SDHA with magnetism and may simultaneously improve the thermostability of M-SDHA. In addition, acidic-basic stability of M-SDHA may be responsible for the stable adsorption toward TC at different pHs based on Fourier transform infrared spectroscopic results. These results along with the column adsorption experiment show that M-SDHA is an effective and practical adsorbent for TC removal.