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.