Performance of lignin impregnated biochar on tetracycline hydrochloride adsorption: Governing factors and mechanisms

Corn stalk-based and wheat straw-based biochar were modified by lignin impregnation and applied to adsorb tetracycline hydrochloride (TCH) in wastewater. Porous properties of lignin impregnated biochar were improved and showed better adsorption performance for TCH. Lignin impregnated wheat straw biochar (WS-L) had the maximum adsorption capacity of 31.48 mg/g, which was 1.89 times compared to corresponding pristine biochar, because excellent pore structure developed via the lignin impregnation and carbonization. The adsorption behavior of TCH molecules on biochar could be interpreted well by two-step process, and it postulated to be a physical adsorption process based on pore filling, hydrogen bonding, pi-pi interaction, and electrostatic in-teractions. And cations including Na+, K+, Mg2+ and Al3+ could compete with TCH for adsorption, while Ca2+ could promote TCH adsorption by forming tetracycline-Ca2+ complexes. Maximum TCH adsorption occurred at pH of 7. The best performing lignin impregnated biochar was WS-L that demonstrated the biochar modulated by lignin had the potential to remove antibiotics from aqueous solutions.

Automated summary

Lignin impregnated biochar derived from corn stalk and wheat straw showed improved porous properties and exhibited excellent adsorption performance for tetracycline hydrochloride (TCH) in wastewater. The adsorption behavior of TCH on the biochar could be interpreted by a two-step process, involving pore filling, hydrogen bonding, pi-pi interaction, and electrostatic interactions. Cations such as Na+, K+, Mg2+, and Al3+ could compete with TCH for adsorption, while Ca2+ could enhance TCH adsorption through the formation of TCH-Ca2+ complexes. The best performing lignin impregnated biochar was WS-L, which illustrated the potential of lignin-modified biochar for antibiotics removal from aqueous solutions.