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<p>Organic dyes used in the textile and plastic industries are among the most significant water pollutants when released into water bodies without proper treatment. This study presents an innovative solution for the degradation of toxic azo dyes Congo red (CR) and Eriochrome black T (EBT) using biosynthesized silver nanoparticles (AgNPs) under direct sunlight. The biosynthesized AgNPs were facilely synthesized using aqueous leaf extracts of <i>Ophiorrhiza mungos</i> (<i>Om</i>) as the reducing and stabilizing agent and confirmed by UV-Vis, FTIR, XRD, SEM, EDX and TEM techniques. The TEM images revealed that the <i>Om</i>-AgNPs were of 17 ± 5&#xa0;nm with spherical shapes. The effects of time, dye concentration, and catalyst amount on the dye degradation were studied. The maximum dye degradation was 82.35 ± 0.133% for CR and 92.88 ± 0.267% for EBT at 2&#xa0;mg/L dye concentration and 120&#xa0;mg/L <i>Om</i>-AgNPs, respectively, after 4&#xa0;h and 2&#xa0;h in sunlight. The degradation reactions followed first-order kinetics, with rate constants of 0.00798&#xa0;min<sup>− 1</sup> (correlation coefficient, 0.994) for CR and 0.01104&#xa0;min − 1 (correlation coefficient, 0.94041) for EBT. Furthermore, the trapping experiments with several scavengers displayed that the dye degradation mechanism in the AgNPs involves the generation of electrons (e<sup>−</sup>) and superoxide radicals (•O<sub>2</sub><sup>−</sup>) as key species in the photodegradation reaction. The catalyst could be recycled up to five cycles without significant loss of efficiency. Furthermore, XRD of the recovered catalyst demonstrated the high structural stability of the <i>Om</i>-AgNPs catalyst. This study provides an eco-friendly and effective solution for eliminating toxic dyes from contaminated water.</p> Graphical Abstract <p></p>

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Sunlight-driven photocatalytic degradation of dyes: a simple approach using ophiorrhiza mungos-derived silver nanoparticles

  • 期刊论文

  • 发表日期：

    2025年7月4日

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  • Sumon Ganguli,
  • Md. Imam Hossain Emon,
  • Aklima A Akhi,
  • Ummeh Sadia,
  • Abhijit Barua,
  • Farhana Rumzum Bhuiyan,
  • Samiran Bhattacharjee

摘要

Organic dyes used in the textile and plastic industries are among the most significant water pollutants when released into water bodies without proper treatment. This study presents an innovative solution for the degradation of toxic azo dyes Congo red (CR) and Eriochrome black T (EBT) using biosynthesized silver nanoparticles (AgNPs) under direct sunlight. The biosynthesized AgNPs were facilely synthesized using aqueous leaf extracts of Ophiorrhiza mungos (Om) as the reducing and stabilizing agent and confirmed by UV-Vis, FTIR, XRD, SEM, EDX and TEM techniques. The TEM images revealed that the Om-AgNPs were of 17 ± 5 nm with spherical shapes. The effects of time, dye concentration, and catalyst amount on the dye degradation were studied. The maximum dye degradation was 82.35 ± 0.133% for CR and 92.88 ± 0.267% for EBT at 2 mg/L dye concentration and 120 mg/L Om-AgNPs, respectively, after 4 h and 2 h in sunlight. The degradation reactions followed first-order kinetics, with rate constants of 0.00798 min− 1 (correlation coefficient, 0.994) for CR and 0.01104 min − 1 (correlation coefficient, 0.94041) for EBT. Furthermore, the trapping experiments with several scavengers displayed that the dye degradation mechanism in the AgNPs involves the generation of electrons (e−) and superoxide radicals (•O2−) as key species in the photodegradation reaction. The catalyst could be recycled up to five cycles without significant loss of efficiency. Furthermore, XRD of the recovered catalyst demonstrated the high structural stability of the Om-AgNPs catalyst. This study provides an eco-friendly and effective solution for eliminating toxic dyes from contaminated water.

Graphical Abstract