Facile modification of hydrochar derived from cotton straw with excellent sorption performance for antibiotics: Coupling DFT simulations with experiments

This study aimed to investigate the sorption of tetracycline (TC) and norfloxacin (NOR) by modified cotton straw hydrochars (CSHC), which would enable the agricultural waste to be processed and recycled. Three kinds of hydrochars were prepared by H2SO4, KOH and KMnO4 modification, showed obvious differences in structures and surface functional groups. The sorption processes contain film diffusion, intraparticle diffusion, and equilibrium. The interaction mechanism between hydrochar and antibiotics include pi-pi stacking, hydrogen bond, and electrostatic interaction. KMnO4-modified hydrochar had the largest sorption capacity for TC (58.09 mg/g), while H2SO4-modified hydrochar had the largest sorption capacity for NOR (49.64 mg/g). Density functional calculations (DFT) results confirmed that the sorption capacity between hydrochar (HC) and TC was larger than that between HC and NOR. During the sorption process, the TC and NOR were regarded as electron acceptor and electron donor. Generally, CSHC-KMnO4 and CSHC-H2SO4 may be simply prepared and have the potential to eliminate antibiotics from water. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the sorption of tetracycline and norfloxacin by modified cotton straw hydrochars, finding that KMnO4-modified hydrochar had the highest sorption capacity for tetracycline, while H2SO4-modified hydrochar had the highest sorption capacity for norfloxacin. The interaction mechanisms between hydrochars and antibiotics included pi-pi stacking, hydrogen bond, and electrostatic interaction during the sorption process.