Enhanced solar light photodegradation of brilliant black bis-azo dye in aqueous solution by F, Sm³⁺ codoped TiO₂

This research focuses on improving the photocatalytic efficiency of TiO₂ during the photo-mineralisation of brilliant black (BN) bis-azo dye pollutant in aqueous solution. This was achieved by improving the visible light activity of TiO₂ photocatalyst semiconductor through co-doping of fluorine (F) and trivalent samarium ions (Sm³⁺) into a TiO₂ matrix using a modified sol-gel synthesis method. Structural, morphological, and textural properties were evaluated using ultra-violet /visible spectroscopy (UV-visible), Raman spectroscopy, scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction spectroscopy (XRD). Photocatalytic and degradation efficiencies were assessed by decolourisation of BN dye in aqueous solution. Complete degradation of BN was attained after an irradiation time of 3 h using F, Sm³⁺-TiO₂ (0.6% Sm³⁺) compared to 73.4% achieved using pristine TiO₂. Pseudo first order kinetics rate constants (K_a) were 2.73×10^-2 and 6.6×10^-3 min^-1 for Sm³⁺-TiO₂ (0.6%Sm³⁺) and pristine TiO₂, respectively, which translates to a remarkably high enhancement factor of 4. The results obtained established that doping of TiO₂ by F and Sm³⁺ enhances the photocatalytic performance of TiO₂ during solar light radiation which enables the utilisation of freely available and clean solar energy.