| Author: | Zhang, Zhuozhi |
| Title: | Combination of adsorption and catalytic oxidation on removal of formaldehyde in low concentration |
| Advisors: | Lee, S. C. (CEE) |
| Degree: | M.Sc. |
| Year: | 2016 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Formaldehyde -- Absorption and adsorption Formaldehyde -- Oxidation |
| Department: | Faculty of Construction and Environment |
| Pages: | xiv, 61 pages : color illustrations |
| Language: | English |
| Abstract: | Cobalt oxide impregnated activated charcoal were synthesized using wet impregnation method in this thesis, in order to realize the combination of adsorption and catalytic oxidation for removal of low concentration gas phase formaldehyde. Compared with the previous studies reviewed in the literature review section (treating with formaldehyde concentration over 100 ppm commonly, with reaction temperature higher than 70℃ in most cases), the impregnated charcoal materials showed good performance for low concentration formaldehyde (influent concentration of 175 ppb) under room temperature. In regard to the material characterization, impregnation of cobalt oxides has negative effects on the porous structure and the surface morphologies of the activated charcoal, according to the material characterization. Cobalt oxides precipitated outside the charcoal particles were observed, in which CoO and Co3O4 precipitation were identified by X-Ray Diffraction analysis, especially on the 15% Co/AC sample. In the study of effects of reaction temperature, a performance order of 25℃ > 45℃ > 35℃ was observed. It is concluded that lower temperature was suitable for formaldehyde adsorption, while higher temperature enhanced the catalytic oxidation. Desorption was observed on the higher temperature conditions, and saturation was also observed on raw activated charcoal in the long-term tests, indicating that the raw activated charcoal might not be suitable for long-term usage under relatively high temperature environment. Improvements were observed as the ozone is induced into the reaction in the study of effects of ozone concentration, especially on the cobalt oxide impregnated samples (approximately 4~5% increment with 14 ppb ozone input, and about 10% increment with 27 ppb ozone input were obtained). Different reaction mechanisms were proposed for reaction scenarios of no ozone input and with ozone input, since enhancement was also observed in the samples with no ozone input. In conclusion, optimum cobalt content weight-based ratio on the activated charcoal should be between 2% to 5% according to the formaldehyde removal tests. And under room temperature with low ozone input (approximately 15 ppb), the material showed good formaldehyde removal efficiency. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 991021952832303411.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 9.52 MB | Adobe PDF | View/Open |
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