article · Colloids and Surfaces A Physicochemical and Engineering Aspects
Water pollution remediation requires simple, economical and effective catalyst systems to remove organic contaminants. This study evaluated two visible-light active photocatalysts, bismuth oxyiodide (BiOI) and nitrogen-palladium co-doped titanium dioxide (N,Pd-TiO2), within a photocatalytic ozonation system to degrade methylene blue dye. While both catalysts exhibited similar initial dye degradation rates and improved ozonation mineralisation, BiOI achieved superior overall mineralisation. This difference arose because the band structure of BiOI enabled the generation of non-selective, highly oxidising hydroxyl radicals capable of thoroughly breaking down both the dye and its intermediate compounds. In contrast, the N,Pd-TiO2 system relied primarily on selective superoxide radicals, resulting in lower mineralisation of breakdown products. The findings demonstrate that single semiconductors such as BiOI provide a cheaper, highly efficient visible-light alternative to complex co-doped titanium dioxide for catalytic ozonation processes in water treatment.
Industrial pollutants such as synthetic dyes often persist in water supplies, posing significant environmental and public health concerns. Combining light-activated catalysts with ozone helps break down these resilient contaminants into harmless mineral components. Demonstrating that simpler, less expensive materials can outperform heavily modified catalysts helps reduce the economic barrier to deploying advanced oxidation systems in water treatment.
This research is relevant to wastewater treatment operators and environmental technology providers seeking efficient advanced oxidation processes to remove organic pollutants. It shows that simple BiOI semiconductors could serve as lower-cost alternatives to complex, precious-metal-doped catalysts. However, the technology is at an early research stage, having been tested at laboratory scale on a model dye, meaning pilot testing and validation on complex industrial effluents are still required.
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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 co-doped 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.
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DOI: 10.1016/j.colsurfa.2024.133167
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