Photodegradation of phenol red on a Ni-doped niobate/carbon composite

The photocatalytic activity of a new nanostructured Ni-doped niobate KSr2(Ni0.75Nb4.25)O15−δ was studied using the phenol red dye as a test molecule and the influence of amorphous carbon deposits upon the photoactivity of the niobate-based materials was also verified. KSr2(Ni0.75Nb4.25)O15−δ powder was prepared by a high energy ball milling method and the C-KSr2(Ni0.75Nb4.25)O15−δ composite by the partial pyrolysis of the niobate dispersed in a polyester matrix. Materials were characterized by FTIR spectroscopy and X-ray diffraction (XRD). The diffraction line profile and the refinement of the structural parameters of KSr2(Ni0.75Nb4.25)O15−δ were derived by the Rietveld method. Both samples showed similar phenol red photodegradation under steady-state kinetic conditions. However, amorphous carbon seems to beneficially affect the reaction mechanism which followed first order kinetics. In terms of KSr2(Ni0.75Nb4.25)O15−δ concentration a clear enhancement in the photoactivity of the niobate in the presence of amorphous carbon by a factor 4.7 was found suggesting a synergy effect between both solids. We conclude that C-KSr2(Ni0.75Nb4.25)O15−δ composite can be employed for the photocatalytic degradation of diluted pollutants.