Degradative and disinfective properties of carbon-doped anatase–rutile TiO2 mixtures under visible light irradiation

Carbon-doping of TiO2 was performed to improve the visible light response and photocatalytic activity of this catalyst. In this work, the high temperature annealing of TiC was studied and the anatase–rutile doped TiO2 mixtures created were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible light absorption spectrophotometry (UV–Vis). It was found that the TiC fully reacts at 400 °C. Transformation of the anatase to rutile phase was observed since the latter form is more heat stable. XPS analysis revealed that the carbon in the sample was present as carbonate species. The UV–Vis spectrum of the doped powders were red shifted compared to P25 TiO2, and a band gap narrowing of 0.2 eV was observed. The photocatalytic activity of the powders was quantified by the degradation of methylene blue under visible light irradiation. Langmuir–Hinshelwood kinetics were applied, and the maximum pseudo-first order degradation rate observed was 0.015 min−1 for the powder annealed at 400 °C for 8 h. Disinfection of Escherichia coli K12 was performed using the catalyst in an immobilized configuration under visible light, and up to 80% inactivation was observed, compared to negligible inactivation with P25. The modified Hom disinfection kinetic model was used to describe the data.