pH-Dependent Dye Protonation and the Effect of Iron on Dye Degradation During Fenton-Based Processes

ABSTRACT

This study investigated the degradation and removal efficiency of reactive and direct dyes using various treatment processes, including UV alone, peroxide alone, Fenton, photo-Fenton, and UV-peroxide. The decolorization results showed that UV and peroxide alone had limited performance, achieving only 8.8% to 14.4% decolorization for direct dyes DR28 and DB71. The Fenton and photo-Fenton processes exhibited rapid total organic carbon (TOC) degradation within the initial 30 minutes, reducing reactive dyes RBla5, RB19, and RO16 by 41.3% to 38.8%. However, the reaction stagnated due to the depletion of Fe2+ in the Fenton process. Interestingly, the UV-peroxide treatment demonstrated superior decolorization performance, achieving 72.9% to 99.2% decolorization for DR28 and DB71 at pH 3 and 7. In contrast, TOC removal efficiency fell below expectations for all processes. The iron-based processes, Fenton and photo-Fenton, resulted in low TOC removal values for both direct dyes, possibly caused by the mordanting phenomena between dyes and iron, shown by visible sediment formation Further research is needed to optimize TOC removal efficiency, especially for direct dyes, and to elucidate the mechanisms of protonation and mordant interactions in the dye degradation process.

KEYWORDS:

• Direct dyes
• mordant
• protonation
• reactive dyes
• UV peroxide

Acknowledgments

This work was supported by JSPS KAKENHI Grant Number JP22H01629. The authors have no competing interest to declare that are relevant to the content of this article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/01919512.2023.2285690

Additional information

Funding

The work was supported by the Japan Society for the Promotion of Science [22H01629].