Environmental photochemistry on semiconductor surfaces: Photosensitized degradation of a textile azo dye, Acid Orange 7, on TiO{sub 2} particles using visible light

Journal Article · Wed May 01 00:00:00 EDT 1996 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es950655d· OSTI ID:249730

Vinodgopal, K; Wynkoop, D E ^[1]; Kamat, P V ^[2]

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1. Indiana Univ. Northwest, Gary, IN (United States)
2. Univ. of Notre Dame, IN (United States)

Photosensitized degradation of a textile azo dye, Acid Orange 7, has been carried out on TiO{sub 2} particles using visible light. Mechanistic details of the dye degradation have been elucidated using diffuse reflectance absorption and FTIR techniques. Degradation does not occur on Al{sub 2}O{sub 3} surface or in the absence of oxygen. The dependence of the dye degradation rate on the surface coverage shows the participation of excited dye and TiO{sub 2} semiconductor in the surface photochemical process. Diffuse reflectance laser flash photolysis confirms the charge injection from the excited dye molecule into the conduction band of the semiconductor as the primary mechanism for producing oxidized dye radical. The surface-adsorbed oxygen plays an important role in scavenging photogenerated electrons, thus preventing the recombination between the oxidized dye radical and the photoinjected electrons. Diffuse reflectance FTIR was used to make a tentative identification of reaction intermediates and end products of dye degradation. The intermediates, 1,2-naphthoquinone and phthalic acid, have been identified during the course of degradation. Though less explored in photocatalysis, the photosensitization approach could be an excellent choice for the degradation of colored pollutants using visible light. 51 refs., 10 figs.

• OSTI ID: 249730
• Journal Information: Environmental Science and Technology, Vol. 30, Issue 5; Other Information: PBD: May 1996
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
36 MATERIALS SCIENCE
AZO DYES
PHOTOCHEMICAL REACTIONS
DECOMPOSITION
OXYGEN
ADSORPTION
TITANIUM OXIDES
VISIBLE RADIATION
SEMICONDUCTOR MATERIALS
SURFACES
ABSORPTION SPECTRA
INFRARED SPECTRA
AIR POLLUTION CONTROL
PHOTOLYSIS
CHEMICAL REACTION KINETICS
ELECTRON TRANSFER