Adsorption of tetracycline on copper alginate-graphene oxide aerogels prepared by secondary lyophilization under CuSO4 crosslinking

To meet the challenge of antibiotic contamination in the aquatic environment, a novel copper alginate-graphene oxide (CA-GO) composite aerogel was developed in this study for the efficient removal of tetracycline (TC). The CA-GO aerogel was prepared by a two-step sol-gel method and the three-dimensional porous network structure was constructed with the help of freeze-drying technique. The microstructure, chemical composition and surface properties of the materials were systematically characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), mercury intrusion porosimetry (MIP), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDXS). The experimental results showed that CA-GO aerogel possessed high porosity (91.76%) and rich active sites. Compared with the single copper alginate aerogel, CA-GO showed significantly enhanced tetracycline adsorption performance (increased by 20%) and specific surface area (increased by 158.25%). The adsorption amount reached 238.15 mg·g −1 at a temperature of 45 ℃ and an initial concentration of TC of 70 mg·L −1 . In addition, the adsorption behavior of tetracycline on this aerogel conformed to the quasi-primary kinetic and Langmuir isothermal models, which indicated that the adsorption process was mainly chemisorption with monolayer adsorption. Furthermore, the introduction of Cu²⁺ not only enhances the mechanical strength of the aerogel, but also significantly improves the adsorption of tetracycline molecules through electrostatic interactions, ligand chelation, and π-π conjugation. What's more, the CA-GO aerogel exhibited a low Cu 2+ dissolution rate (14d, Cu 2+ concentration of 0.078 mg·L −1 ) and better regeneration performance (5 cycles, more than 50% of initial adsorption capacity).