Study on acid-modulated UiO-66-NH2 and its adsorption performance and mechanism for OTC

Abstract

In this study, UiO-66-NH₂ nanoparticles were synthesized via a hydrothermal method, using acetic acid and hydrochloric acid as modulators to optimize the specific surface area and pore width. Oxytetracycline (OTC) was chosen as the test compound to evaluate the adsorption efficiency of UiO-66-NH₂.The material was thoroughly characterized under varying conditions, and the adsorption mechanism was systematically explored through adsorption kinetics, isotherms, and thermodynamic analyses. The results demonstrated that UiO-66-NH₂ exhibited a high OTC adsorption capacity, achieving a maximum of 312.5 mg g⁻¹ under optimal conditions. XRD, TGA, and BET analyses revealed that acetic acid and hydrochloric acid significantly improved the crystallinity and thermal stability of UiO-66-NH₂, increasing the specific surface area from 8.023 m² g⁻¹ to 998.663 m² g⁻¹ and reducing the pore width from 18.783 nm to 2.129 nm. FTIR, XPS, adsorption kinetics, and isotherm studies indicated that the main forces driving OTC adsorption by CMC-Fe were hydrogen bonding, π–π stacking, weak electrostatic interactions, and pore filling. Cyclic adsorption experiments further demonstrated the excellent reusability of UiO-66-NH₂. In summary, the use of acetic acid and hydrochloric acid significantly increased the specific surface area of UiO-66-NH₂, exposing more adsorption sites and playing a critical role in pollutant removal.