Promotional effect of metal doping on nanostructured TiO2 during the photocatalytic degradation of 4-chlorophenol and naproxen sodium as pollutants

Abstract

Titania doped nanomaterials were prepared by the sol – gel method. Nickel, copper and iron were employed as doping cations. The as-prepared materials were characterized by X-ray diffraction, N2 physisorption and UV–vis DRS, EDS and XPS techniques. The TiO2-doped materials were evaluated during the photocatalytic degradation of 4-chlorophenol (4-CP) and naproxen (NPX) sodium as water pollutants under UV radiation. According to the photocatalytic activity and kinetic results, T-Cu 1.0 was the material with the best performance during the degradation of 4-CP, showing a degradation performance of 90% (0.1827 L g−1 min−1) after six reaction hours. T-Fe 1.0 was the photocatalyst with the best NPX degradation behavior, showing a degradation efficiency of 97% (0.1111 L g−1 min−1) also after 6 reaction hours. The photocatalytic degradations followed a pseudo-first-order behavior. The remarkable performance of the photocatalysts was due to a higher concentration of Ti3+ species and the presence of Ni2+, Cu2+ and Fe3+, which worked as TiO2 heterojunctions that allowed the degradation improvement of the organic compounds. The T-Cu 1.0 and T-Fe 1.0 materials were used in a reusability test for 4-CP and NPX compounds, showing around 20 and 30% of final deactivation, respectively. This deactivation was due to structural changes in the TiO2 framework and the oxidation state of the doping cation as a consequence of the constant exposure to UV radiation (18 h) and to the accumulation of carbonaceous species on the TiO2 surface. The systematic XPS analysis before and after the photocatalytic evaluation reveals its internal structure and gives insights about it photocatalytic behavior.