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<p>Methylene blue (MB) dye exhibits pH-selective photodegradation properties when exposed to natural sunlight, even in the absence of a photocatalyst. The solar dye degradation efficiency can be effectively enhanced by tuning the appropriate pH and using titanium dioxide (TiO<sub>2</sub>) as a nanocatalyst. Due to high band gap energy, TiO<sub>2</sub> exhibits photocatalytic properties in UV radiation with significantly reduced efficiency under sunlight, which comprises more visible radiation. In the present work, the self-degradation property of MB coupled with TiO<sub>2</sub> nanoparticles is explored. The large surface area of TiO<sub>2</sub> nanoparticles allows for greater interaction with MB, facilitating the transfer of excited electrons from MB to the conduction band of TiO<sub>2</sub>. This process enhances the generation of hydroxyl radicals, thereby speeding up the degradation rate of MB. The degradation efficiency of MB was evaluated in the absence and presence of TiO<sub>2</sub> in the pH range 2–10, the weight of TiO<sub>2</sub> was varied between 1 and 4&#xa0;g L<sup>−1</sup>, and the concentration of MB was varied between 5 and 20&#xa0;mg L<sup>−1</sup>. The degradation of MB was confirmed using a UV–Visible spectrophotometer and chemical oxygen demand (COD). The COD values were high at acidic pH and linearly decreased from 57.7&#xa0;mg L<sup>−1</sup> at pH 2 to 11.5&#xa0;mg L<sup>−1</sup> at pH 10. Further, to explore the mechanism of degradation, the byproducts of degraded MB were analyzed using GC–MS. This approach can be used to design a reactor bed for the degradation of the MB class of dyes.</p>

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Enhanced Sunlight Driven Photocatalytic Degradation of Methylene Blue Dye Using TiO2: Exploiting the Self-dye Degradation Property and pH Specificity in a Novel Approach

  • 期刊论文

  • 发表日期：

    2025年2月3日

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  • Preeti S. Kulkarni,
  • Rachana D. Bamb,
  • Varuna S. Watwe,
  • Sunil D. Kulkarni

摘要

Methylene blue (MB) dye exhibits pH-selective photodegradation properties when exposed to natural sunlight, even in the absence of a photocatalyst. The solar dye degradation efficiency can be effectively enhanced by tuning the appropriate pH and using titanium dioxide (TiO2) as a nanocatalyst. Due to high band gap energy, TiO2 exhibits photocatalytic properties in UV radiation with significantly reduced efficiency under sunlight, which comprises more visible radiation. In the present work, the self-degradation property of MB coupled with TiO2 nanoparticles is explored. The large surface area of TiO2 nanoparticles allows for greater interaction with MB, facilitating the transfer of excited electrons from MB to the conduction band of TiO2. This process enhances the generation of hydroxyl radicals, thereby speeding up the degradation rate of MB. The degradation efficiency of MB was evaluated in the absence and presence of TiO2 in the pH range 2–10, the weight of TiO2 was varied between 1 and 4 g L−1, and the concentration of MB was varied between 5 and 20 mg L−1. The degradation of MB was confirmed using a UV–Visible spectrophotometer and chemical oxygen demand (COD). The COD values were high at acidic pH and linearly decreased from 57.7 mg L−1 at pH 2 to 11.5 mg L−1 at pH 10. Further, to explore the mechanism of degradation, the byproducts of degraded MB were analyzed using GC–MS. This approach can be used to design a reactor bed for the degradation of the MB class of dyes.