Defective boron nitride aerogels by salt template synthesis: A green adsorbent for tetracycline removal

Hexagonal boron nitride (h-BN) exhibits unique application potential in water purification due to its large specific surface area, high porosity, and chemical inertness. Designing adsorbents with highly active adsorption sites is one effective method to improve their adsorption capacities. In this study, porous h-BN aerogels containing multiple defect types (DP-BN) were synthesized by using salt templates. The experimental results showed that DP-BN had an extremely low density. With outstanding adsorption capacity for tetracycline (TC), its maximum adsorption capacity was 1620.37 mg/g, which was 2.6 times higher than that reported in the known literature (623.018 mg/g). DP-BN adsorbed TC quickly, and its rate was influenced by liquid film diffusion, pore diffusion, and diffusion to the active adsorption site. The adsorption process was dominated by chemisorption and could take place spontaneously. The adsorption of TC by DP-BN was exothermic. As the environmental temperature increased, the adsorption capacity of DP-BN increased significantly. DP-BN exhibited excellent reusability. After five cycles, the adsorption removal rate remained up to 99.93%. Overall, the high adsorption capacity of DP-BN for TC was attributed to its abundant active adsorption sites, Π-Π interactions, and intermolecular interactions. This study provided a new idea to modulate the microstructure and improve the adsorption performance of h-BN, hoping to accelerate the application of h-BN in wastewater treatment.