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

Abstract

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. 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. 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. 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. 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.