Photocatalytic Degradation of Pharmaceuticals through Bulk and Mesoporous g-C3N4/TiO2 Systems

Abstract

Background: In recent years, pharmaceutical pollutants have emerged as a growing threat to the environment. To mitigate this situation, heterogeneous photocatalysis has been considered a promising advanced oxidation technology, where TiO2-based systems have exhibited outstanding efficiency in the degradation of organic compounds. Objective: In this work, we have studied the photocatalytic performance of the coupled g-C3N4/TiO2 system in the degradation of the pharmaceuticals tetracycline, ciprofloxacin, and ibuprofen. Moreover, the effect of the graphitic carbon nitride (g-C3N4) was examined through the study of two different samples, a bulk g-C3N4 prepared from the direct calcination of melamine and a mesoporous g-C3N4 synthesized through a nanocasting process using SBA-15 silica as hard template. Methods: The hybrid photocatalysts were prepared by forced hydrolysis of titanium isopropoxide using two g-C3N4 samples, a bulk material and a mesoporous one. The samples were characterized by X-ray powder diffraction (XRD), Diffuse Reflectance Spectroscopy (DRS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and N2 adsorption-desorption measurements. The photocatalytic activity was examined through the degradation of tetracycline, ciprofloxacin, and ibuprofen under simulated solar irradiation. Results: The textural properties of g-C3N4 play a preponderant role in the photoactivity of the g- C3N4/TiO2 system. In this sense, high dispersion of the TiO2 nanoparticles could be obtained using a mesoporous g-C3N4 sample. All hybrid photocatalysts exhibit higher degradation rates than the pristine materials, including bare TiO2. In this regard, the samples with 1 wt.% g-C3N4 attained the highest photocatalytic performance in the degradation of tetracycline, ciprofloxacin, and ibuprofen. Conclusion: The coupling of TiO2 with graphitic carbon nitride leads to the formation of hybrid photocatalysts with outstanding photoactive properties in the degradation of pharmaceutical pollutants. In this way, the g-C3N4/TiO2 samples can be considered as excellent photocatalysts for the degradation of organic pollutants.