Understanding the Integrated Adsorption and Photocatalytic Processes of Tetracycline over TiO2@UiO-66-NH2 Heterojunctions

Semiconductor photocatalysis holds great potential for removing organic contaminants in wastewater, where pollutant adsorption onto photocatalysts is crucial for effective degradation. Herein, tetracycline (TC) was selected as a model pollutant to explore the integrated adsorption and photocatalytic processes of TiO₂@UiO-66-NH₂ (TUON). Structural characterizations confirm the successful formation of the TUON heterojunction, with uniform nanoparticles and a homogeneous elemental dispersion. BET analysis shows a surface area of 429.1 m² g^–1, and the micromesoporous structure (pore size: 1–3 nm) facilitates TC adsorption (saturated adsorption capacity of 131.6 mg g^–1 at 298.15 K). Adsorption follows the quasi-second-order model and the Langmuir isotherm. The absorption process is spontaneous, exothermic, and entropy-increasing. Under UV irradiation, TUON achieves almost complete TC removal within 60 min, with a rate constant of 0.04742 min^–1, outperforming pure TiO₂ (0.02004 min^–1) and UiO-66-NH₂ (0.00739 min^–1). This study brings light to comprehend the pollutant adsorption and photodegradation mechanisms, promoting efficient photocatalysts for environmental applications.