Adsorption of OTC from Aqueous Solution by UiO-66-NH2: Kinetics, Isotherms, and Thermodynamics

Abstract In this study, UiO-66-NH2 nanoparticles were synthesized by a hydrothermal method, and subsequently, the adsorption performance of UiO-66-NH2 on oxytetracycline (OTC) was evaluated by batch adsorption experiments, in which the key parameters, such as the concentration of OTC, pH, reaction time, and temperature, were investigated. UiO-66-NH2 nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), BET specific surface area, and transmission electron microscopy (TEM). The results showed that the adsorption data conformed to the Sips model, indicating a maximum adsorption capacity of 322.48 mg·g− 1. Additionally, the quasi-primary kinetic equilibrium adsorption capacity was determined to be 314.61 mg·g− 1, while the quasi-secondary kinetic equilibrium adsorption capacity reached 365.69 mg·g− 1. The adsorption kinetics suggested that the process was influenced by physicochemical co-actions. Notably, the specific surface area of UiO-66-NH2 was measured at a high value of 998.663 m²·g⁻¹, potentially contributing to improved adsorption efficiency. Analyses using FT-IR, XRD and XPS confirmed the adsorption of OTC on the material surface. Overall, the main driving forces behind the adsorption process are weak electrostatic interactions, hydrogen bonding interactions and π-π stacking interactions.