Facile synthesis of boron-doped porous biochar as a metal-free adsorbent for efficient removal of aqueous tetracycline antibiotics

This study introduced a microwave-assisted pyrolysis method for the rapid and efficient preparation of boron-doped porous biochar. The resulting biochar exhibited a large specific surface area (933.39 m2/g), a rich porous structure (1.044 cm3/g), and abundant active sites. Consequently, the prepared boron-doped porous biochar exhibited higher efficiency in adsorbing tetracycline with a maximum adsorption capacity of 413.223 mg/g, which significantly exceeded that of unmodified biochar and most commercial and reported adsorbents. The correlation analysis between the adsorption capacity and adsorbent characteristics revealed that the formation of the –BCO2 group enhanced π–π electron donor–acceptor interactions between boron-doped porous biochar and tetracycline. This mechanism mainly contributed to the enhanced adsorption of tetracycline by boron-doped porous biochar. Additionally, the as-prepared boron-doped porous biochar exhibited broad applications in removing antibiotics (tetracycline), phenolics (bisphenol A), and dyes (methylene blue and rhodamine B). Moreover, the boron-doped porous biochar exhibited satisfactory stability, and its adsorption capacity can be nearly completely regenerated through simple heat treatment. This study provides new insights into the effectiveness of boron-doped carbonaceous materials in removing antibiotic contaminants.