Sequential Process Combination of Photocatalytic Oxidation and Dark Reduction for the Removal of Organic Pollutants and Cr(VI) using Ag/TiO2
SCIE
SCOPUS
- Title
- Sequential Process Combination of Photocatalytic Oxidation and Dark Reduction for the Removal of Organic Pollutants and Cr(VI) using Ag/TiO2
- Authors
- CHOI, YEOSEON; Min Seok Koo; Alok D. Bokare; Dong-hyo Kim; Detlef W. Bahnemann; CHOI, WONYONG
- Date Issued
- 2017-03
- Publisher
- AMER CHEMICAL SOC
- Abstract
- We investigated a sequential photocatalysis-dark reaction, wherein organic pollutants were degraded on Ag/TiO2 under UV irradiation and the dark reduction of hexavalent chromium (Cr(VI)) was subsequently followed. The photocatalytic oxidation of 4-chlorophenol (4-CP), a test organic substrate, induced the generation of degradation intermediates and the storage of electrons in Ag/TiO2 which were then utilized for reducing Cr(VI) in the postirradiation period. The dark reduction efficiency of Cr(VI) was much higher with Ag/TiO2 (87%), compared with bare TiO2 (27%) and Pt/TiO2 (22%). The Cr(VI) removal by Ag/TiO2 (87%) was contributed by adsorption (31%), chemical reduction by intermediates of 4-CP degradation (26%), and reduction by electrons stored in Ag (30%). When formic acid, humic acid or ethanol was used as an alternative organic substrate, the electron storage effect was also observed. The postirradiation removal of Cr(VI) on Ag/TiO2 continued for hours, which is consistent with the observation that a residual potential persisted on the Ag/TiO2 electrode in the dark whereas little residual potential was observed on bare TiO2 and Pt/TiO2 electrodes. The stored electrons in Ag/TiO2 and their transfer to Cr(VI) were also indicated by the UV–visible absorption spectral change. Moreover, the electrons stored in the preirradiated Ag/TiO2 reacted with O2 with showing a sign of low-level OH radical generation in the dark period.
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/41253
- DOI
- 10.1021/acs.est.6b06303
- ISSN
- 0013-936X
- Article Type
- Article
- Citation
- ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol. 51, no. 7, page. 3973 - 3981, 2017-03
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