Molecular imprinting functionalization of magnetic biochar to adsorb sulfamethoxazole: Mechanism, regeneration and targeted adsorption

Sulfamethoxazole (SMX), a typical medical antibiotic, is regarded as a major risk in the surface hydrosphere because of its harmful biological reaction and potential to trigger bacterial resistance. Ameliorating the hydrosphere will become more convenient if the challenging adsorption and separation of SMX in hydrosphere are achieved. To reveal the mechanism, regeneration and targeted adsorption of SMX on a novel surface-imprinted polymer (MIP-MBC) and batch experiments were carried out in this study. MIP-MBC was prepared in organic solution using a Fe-Mn-modified biochar to selectively adsorb SMX in a water solution. Owing to the mesopores and oxygen-containing functional groups of MIP-MBC, imprinted cavities in pores are found to lead to a remarkable adsorption efficiency for SMX. The maximum adsorption capacity for SMX reaches up to 25.65 mg g−1, which is 1.34 times that of the non-molecularly imprinted magnetic biochar (NIP-MBC). The adsorption process matches well with the second-order kinetics and Freundlich thermodynamic model, which indicates that hydrogen bonds and electrostatic interactions are simultaneously involved in the adsorption process. After five cycles, the adsorption rate for MIP-MBC reaches 88.34%. Furthermore, MIP-MBC is applied to the binary system to remove SMX, and it can be used to accurately identify and adsorb SMX due to K`> 1 and being independent of the ion concentration. The high affinity site plays a major role in the imprinting process for SMX. This study furnishes a novel perspective for promoting the practical application and economic benefits of targeted biochar material to capture SMX in sewage purification.