Synthesized TiO 2 /ZSM-5 composites used for the photocatalytic degradation of azo dye: Intermediates, reaction pathway, mechanism and bio-toxicity

Kefu Zhou, Xin Yan Hu, Bor Yann Chen, Chung Chuan Hsueh, Qian Zhang, Jiajie Wang, Yu Jung Lin, Chang Tang Chang

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)

Abstract

In this study, a one-step solid dispersion method was used to synthesize titanium dioxide (TiO 2 )/Zeolite Socony Mobil-5 (ZSM-5) composites with substantially reduced time and energy consumption. A degradation efficiency of more than 95% was achieved within 10 min using 50% PTZ (synthesized TiO 2 /ZSM-5 composites with TiO 2 contents of 50 wt% loaded on ZSM-5) at pH 7 and 25 °C. The possible degradation pathway of azo-dye Reactive Black 5 (RB5) was investigated using gas chromatography-mass spectrometry and ion chromatography (IC). The bonds between the N atoms and naphthalene groups are likely attacked first and cleaved by hydroxyl radicals, ultimately resulting in the decolorization and mineralization of the azo dye. A comparative assessment of the characteristics of abiotic and biotic dye decolorization was completed. In addition, the toxicity effects of the degradation intermediates of azo-dye RB5 on cellular respiratory activity were analyzed. The bio-toxicity results showed that the decay rate constants of CO 2 production from the azo-dye RB5 samples at different degradation times increased initially and subsequently decreased, indicating that intermediates of higher toxicity could adhere to the catalyst surface and gradually destroyed by further photocatalytic oxidation. Additionally, EDTA (hole scavengers) and t-BuOH (radical scavengers) were used to detect the main active oxidative species in the system. The results showed that the hydroxyl radicals are the main oxidation species in the photocatalytic process.

Original languageEnglish
Pages (from-to)300-309
Number of pages10
JournalApplied Surface Science
Volume383
DOIs
Publication statusPublished - 2016 Oct 15
Externally publishedYes

Keywords

  • Biotoxicity
  • Degradation pathway
  • Mechanism
  • Photocatalyst

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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