A novel Fe-loaded porous hydrothermal biochar for removing tetracycline from wastewater: Performance, mechanism, and fixed-bed column

The novel Fe-loaded porous hydrothermal biochars (FeKHCs) were successfully prepared by two-step synthesis of hydrothermal pretreatment and pyrolysis at different temperatures and used to remove tetracycline (TC) from wastewater. The biochar synthesized at 900 °C (FeKHC900) showed the highest specific surface area (SSA) (1487.55 m2/g) and porosity volume (Vtotal) (0.9951 cm3/g), which was significantly affected by hydrothermal pretreatment and K2C2O4 activation. K2C2O4 favored the micropores formation, which was beneficial to TC adsorption. Thus, FeKHC900 had the largest sorption amount of 606.52 mg/g for TC and outstanding performance for the other three antibiotics. Moreover, Fixed-bed column adsorption experiments proved that FeKHC900 has good dynamic adsorption performance (425.93 mg/g). The slightly reduced sorption amounts in different initial pH, coexisting ions, and humic acid (HA) indicated that FeKHC900 has a high resistance to interference and selective adsorption ability. Batch experiments revealed that TC adsorption was dominated by chemisorption, and the main mechanism referred to π-π interactions, pore-filling, H-bonding, and complexation. This work shares a simple and effective strategy for fabricating magnetic porous hydrothermal biochar as an efficient adsorbent to treat antibiotics.