Iron Promoted TiO2-Activated Carbon Nanocomposites for Photocatalytic Degradation of Congo Red in Water

Nanocomposites containingTiO2 and activated carbon were obtained by the sol-gel method in the presence of Brij 58 surfactant. The sample with a higher surface area (185.6 m2/g) was promoted with Fe by impregnating it with aqueous solution of Fe(NO3)3. The obtained iron loadings, measured using X-ray fluorescence, were 0.83%, 3.30% and 7.17%. TiO2 anatase was identified in all the samples by X-ray diffraction and Raman spectroscopy, but the presence of iron oxides could not be detected. However, infrared spectroscopy indicated the existence of Fe-O and Fe-O-Ti bonds. X-ray photoelectron spectroscopy revealed the presence of Fe2+ for samples with a lower Fe content and a mixture of Fe2+ and Fe3+ in the sample with 7.17% Fe. UV-Vis and photoluminescence spectroscopy showed the presence of carbon and Fe alongside TiO2. This combination led to new properties due to the generation of intermediate energy levels and defects, contributing to an enhancement in the photocatalytic performance. The highest photodegradation efficiency of Congo red in solution (84.46%) was obtained for the sample with 7.17% Fe under visible light irradiation and acidic conditions. The synergistic contribution of dye adsorption and photodegradation was demonstrated, taking into account ZPC values of nanocomposites. Kinetic studies were completed with reaction mechanisms based on the results obtained in the presence of scavengers.