Correlating the photocatalytic activity and the optical properties of LiVMoO6 photocatalyst under the UV and the visible region of the solar radiation spectrum

Abstract

This study presents a simplified method for the evaluation of the optical properties of photocatalytic powders and in particular LiVMoO6, including the extinction (β), absorption (κ) and scattering (σ) coefficients. The optical properties of LiVMoO6 were determined by applying the six-flux radiation absorption–scattering model applied to a photocell geometry and through simple spectrophotometric measurements of diffuse reflectance, diffuse transmittance and collimated transmittance of aqueous suspensions of LiVMoO6. Once the optical properties were determined, the spatial distribution of the local volumetric rate of photon absorption (LVRPA) in an experimental reactor was calculated for the two cases when either ultraviolet light or visible light was used. X-ray diffraction and Raman spectroscopy of the LiVMoO6 resulted in a brannerite type structure of the catalyst. The optimum conditions and catalyst concentration for the degradation and mineralization of a model water contaminant in aqueous suspensions of LiVMoO6, under either UV or visible light irradiation in the experimental reactor, were predicted from the calculated optical properties and by applying the six-flux radiation absorption–scattering model. The photoactivity of LiVMoO6 was compared with that of commercial anatase TiO2 Degussa P25. The highest percentage of organic removal and mineralization was obtained when LiVMoO6 was irradiated with visible light.