Preparation and application of cattail residue-based magnetic cellulose composites for tetracycline antibiotics adsorption

Tetracycline antibiotics (TCs) are widely present in wastewater and surface water due to their extensive use. Removal of TCs from water is urgent. In this study, magnetic cellulose (MC) composites were prepared from cattail residues to adsorb oxytetracycline hydrochloride (OTC center dot HCl), chlortetracycline hydrochloride (CTC center dot HCl), and tetracycline hydrochloride (TC center dot HCl) from water. The influence of Fe3O4 content on the antibiotics removal was studied. The synthesized MC composites were characterized using FTIR, XPS, zeta potential, SEM, and XRD. Adsorption mechanisms and characteristics were explored using classic isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models) and common kinetic models (pseudo-first-order, pseudo-secondorder, Elovich and Intraparticle diffusion models). Optimum adsorption capacity was achieved by MC2-1 (mass ratio of cellulose to Fe3O4 was 2:1), with a larger specific surface area (18.24 m2 g-1) and mesoporous structure. The adsorption processes were well described by the pseudo-second-order and Langmuir models. MC2-1 demonstrated maximum adsorption capacities of CTC center dot HCl (194.29 mg g-1), OTC center dot HCl (168.25 mg g-1), and TC center dot HCl (41.10 mg g-1). The results of models fitting and characterizations of the MC composites before and after the adsorption processes revealed that the main adsorption mechanisms were pore filling, hydrogen bonding, electrostatic interactions, and metal complexation. This study proposes a practical approach for utilizing wetland plant residues as an effective adsorbent for tetracycline antibiotics removal.