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An Innovative Advanced Oxidation Technology for Effective Decomposition of Formaldehyde by Combining Iron Modified Nano-TiO2 (Fe/TiO2) Photocatalytic Degradation with Ozone Oxidation

Category: Control Techniques and Strategy

Article In Press
DOI: 10.4209/aaqr.2018.05.0156
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Su-Wen Cheng1, Yu-Hua Li2, Chung-Shin Yuan 1, Pei-Yi Tsai1, Hua-Zhen Shen3, Chung-Hsuang Hung4

  • 1 Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
  • 2 School of Resources and Environmental Science, Hubei University, Wuhan 430068, China
  • 3 College of Chemical Engineering, HuaQiao University, Xiamen 361021, China
  • 4 Department of Safety, Health and Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 81164, Taiwan

Highlights

Combine photocatalytic and ozonolytic technology effectively degrade indoor HCHO.
A novel nano-sized Fe/TiO2 photocatalysts was prepared and chemically characterized.
Optimal UV/TiO2 + O3 was operated at 0.15 ppm HCHO, 5% RH, 3.0 ppm O3, and 5%Fe/TiO2.


Abstract

Bench-scale experiments using iron modified and unmodified photocatalysts (Fe/TiO2 and TiO2) were conducted to compare their decomposition efficiencies with formaldehyde. The effects of operating parameters on the decomposition efficiency were further investigated. The grain size of iron doped photocatalysts ranged from 25 to 60 nm. The iron doped content of 1, 3, and 5% Fe/TiO2 photocatalysts was measured as 1.2, 3.1, and 4.7%, respectively. The UV-visible analytical results showed that a significant red shift was observed while the iron doping content of Fe/TiO2 increased from 0 to 5%. Two continuous-flow reaction systems, the ozonolytic and the photocatalytic reactors, were combined in series to investigate their capability to decompose formaldehyde by Fe/TiO2 photocatalysts with six operating parameters, namely, the influent formaldehyde concentrations (0.15, 0.30, and 0.45 ppm), the relative humidity (5, 35, and 55%), irradiation by light (visible, near-UV, and UV), the reaction temperatures (25, 30, and 35°C), the iron doping content (1, 3, and 5% Fe/TiO2), and the injected-ozone concentrations (2,000 and 3,000 ppb). The optimal operating parameters obtained in this study were an influent formaldehyde concentration of 0.15 ppm, a relative humidity of 5%, irradiation by UV light, a reaction temperature of 35°C, an iron doping content of 5% Fe/TiO2, and an injected-ozone concentration of 3,000 ppb. Overall, the efficiencies of different decomposition techniques for formaldehyde followed the sequence: UV/TiO2 + O3 > O3 + UV/TiO2 > UV/O3 ≈ O3. A maximum formaldehyde decomposition efficiency of 92% was obtained by using the UV/TiO2 + O3 technology.

Keywords

Indoor formaldehyde Fe/TiO2 photocatalyst Ozonolysis Decomposition efficiency of formaldehyde Operating parameters


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