UV-Vis Adsorption Spectra Tracing on Photodegradation of Azo Compounds on the Surface of Titanium Dioxide(é) The Discovery and Kinetic Behaviors Researching of Intermadiates

Abstract

Abstract: The kinetics and electron transfer of the photo-degradation procedure of five azo compounds, mainly DBC-carboxyazo, on the surface of titanium dioxide were studied by using UV-V is absorption and differential spectra. An intermediate with rather long life(t_1/2=8.86 min) formed and then destructed during the procedure of the capture of the photo-in-duced charge-carrier. The theoretically fit peak-shape curve of the intermediate with error compensated algorithm parallel accorded with the experimental c~t curve. Thus we have got the rate constants of DBC-carboxyazo and TBC-CPA at 25 ℃, being 0.170(k₁/min^-1) and 2.96×10^-2(k₂/min^-1) as well as 0.104(k₁/min^-1) and 9.56×10^-2(k₂/min^-1), respectively. The effect of the initial pH value on the photo-degradation rate was tested. pH3-7 was found to be the optimal pH range for the photo-degradation. In addition, the reaction solution without being buffered was found to tend to be weak acidic. The sensitization mechanism of TiO₂by azo was discussed. That is, electrons transferred from the excited azo to the conductive band of semiconductor TiO₂, which made the bandgap energy match the energy of visible light. The degradation course was presumed as that, after the electron injection and the self-oxidaiton of azo, the intermediate naphthoquinone was oxidized by O_2·-to produce phthalic acid, followed by the final mineralization of the phthalic acid to yield CO₂, H₂O and other inorganic compounds.

Key words: Photocatalyzed degradation, Azo compounds, TiO₂, UV-V is spectra tracing

CLC Number:

O643.1

TrendMD:

MA Wan-Hong, CAI Ru-Xiu, LIU Zhi-Hong, LIN Zhi-Xin . UV-Vis Adsorption Spectra Tracing on Photodegradation of Azo Compounds on the Surface of Titanium Dioxide(é) The Discovery and Kinetic Behaviors Researching of Intermadiates[J]. Chem. J. Chinese Universities, 1999, 20(10): 1542.

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