科研之友
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摘要
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-Vis 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-induced charge-carrier. The theoretically fit peak-shape curve of the intermediate with error-compensated algorithm parallel accorded with the experimental c similar to t curve. Thus we have got the rate constants of DBC-carboxyazo and TBC-CPA at 25 degrees C t being 0.170 (k(1)/min(-1)) and 2.96x10(-2)(k(2)/min(-1)) as well as 0.104(k(1)/min(-1)) and 9.56x10(-2)(k(2)/min(-1)), respectively. The effect of the initial pH value on the photo-degradation rate was tested. pH 3-7 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 TiO2 by 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 ate, 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.
- 出版日期1999-10
- 单位武汉大学
