Comparative study of visible-light active BiOI and N,Pd-TiO2 photocatalysts: Catalytic ozonation for dye degradation

The increasing demand for clean water requires the development of simple, cheap, and efficient catalysts systems for water pollution remediation. To develop cheap yet efficient hybrid advanced oxidation processes for degradation of organic pollutants in water requires their systematic comparison under similar conditions to make informed decisions of economically feasible and sustainable systems. Visible light active single BiOI and N, Pd codoped TiO2 were investigated for photocatalytic ozonation (PCO) for methylene blue (MB) degradation. Metal and non-metal co-doping improved morphology, band structure and active sites on the surface of TiO2 to shift its light absorption into the visible region. The degradation of MB with BiOI PCO and N,Pd-TiO2 PCO was practically similar but showed improvement of the ozonation mineralization efficiency. However, mineralization of MB on BiOI PCO surpassed that of N,Pd-TiO2 PCO due to band structure that influenced generated free radicals during the PCO processes. BiOI PCO system progressed through the existence and involvement of strongly oxidizing and non-selective hydroxyl radicals towards enhanced mineralization of dye and intermediates while N,Pd-TiO2 PCO was steered by the superoxide radical that is selective and had lower mineralization efficiency of formed intermediates despite its high initial degradation efficacy. The work demonstrated cheap and efficient visible light active semiconductors like BiOI as potential candidates for application in photocatalytic ozonation for real applications with matching activities to that of co -doped UV active semiconductors like TiO2. This work advances the use of visible light active semiconductors towards PCO based processes for environmental pollution remediation.