Cerium-Doped TiO2 and Sepiolite Nanocomposites for Tetracycline Inactivation in Water Treatment

The increasing contamination of water resources by pharmaceutical compounds, such as Tetracycline (TC), has been a significant environmental concern due to the problems it can cause to humans and the environment. This study addressed the effectiveness of TC removal through an efficient approach that combines adsorption and photocatalysis, using Cerium-doped TiO2 and Sepiolite (Sep) nanocomposites as a supporting material. The wt % Ce was varied (0, 1, 2.5, and 5%), designating the samples as TiO2–Sep, 1CeTiO2–Sep, 2.5CeTiO2–Sep, and 5CeTiO2–Sep, respectively. Characteristic peaks of Sep were found in the X-ray diffraction (XRD) of the photocatalysts. FTIR analysis revealed characteristic bands for Sepiolite, such as the Mg–OH and Si–O–Si stretching located at 3689 and 1028 cm–1, respectively. Additionally, the nanocomposites exhibited mesoporous characteristics, with a Type IV isotherm and H3 hysteresis. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) images and XPS confirmed the presence of Ce-TiO2 in the clay mineral. From EDX-STEM images, titania is preferentially located at the edges of the clayey material, while Ce is more homogeneously dispersed in the clay mineral, with a smaller particle size. Photocatalytic studies demonstrated that the 1CeTiO2–Sep sample achieved higher efficiency in TC removal (40 ppm), with 70.45% removal, 35.34% being adsorption, and 35.11% photocatalysis. In the TOC test, there was a decrease in Total Organic Carbon from 22.90 to 10.56 mg L–1 and an increase in Inorganic Carbon from 0.084 to 3.627 mg L–1, indicating photodegradation of the TC molecule. In the inactivation test, using the growth of Escherichia coli as an indicator confirmed the inactivation of the drug in the solution, reducing the inhibitory effect to 83.12% with 180 min and 45.63% with 600 min of irradiation. Suppressor tests revealed that the hole (h+) is the primary radical for drug degradation, with only 1.35% removal efficiency when its suppressor is added. Thus, the synergistic effect between adsorption and photocatalysis proved an efficient strategy for removing organic toxins.