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Chemical Journal of Chinese Universities 2002, Vol. 23 Issue (12) :2313-2316    DOI:
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EPR Measurement of Hydroxyl Radicals and Rate Constant of n-Hexadecane Photocatalytic Degradation
ZHONG Ping, KONG Ling-Ren, LIU Guang-Ming, SUI Yun-Xia
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, China

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Abstract Spin trapping technique was used to detect the free radicals formed upon light irradiation of TiO2 in aqueous solutions. 5,5-dimethylpyrroline-N-oxide(DMPO) was used as a spin trapper. The Electron paramagnetic resonance( EPR) signal obtained 1 min after reaction initiated by 180 W mercury lamp irradiation with a mixture of 1 g/L TiO2, 0.05 mol/L DMPO in phosphate buffer(pH=7.4) gave the 1/2/2/1 quartet with hyperfine splittings of a N=a H=1.49×10-3 T, g=2.005 0, which were typical peaks of DMPO-OH. A model was used to speculate on the free radical mechanisms of n-hexadecane photodegradation by TiO2 in aqueous solutions. The intensity increased with increase of the irradiation time and the steady state was achieved at 1 min light irradiation. By employing the known rate constant for the reaction of hydroxyl radicals(HO ·) with the DMPO, the rate constant k=5.0×1011 mol-1·L·s-1 for the reaction of hydroxyl radicals with n-hexadecane could be obtained. In conclusions, TiO2 photocatalytic reaction proceeded in a free radical mechanism.
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KeywordsPhotocatalytic degradation   Hydroxyl radicals   EPR   Nano TiO2   n-Hexadecane     
Received 2002-01-10; published 2002-12-24
Cite this article:   
ZHONG Ping, KONG Ling-Ren, LIU Guang-Ming, SUI Yun-Xia .EPR Measurement of Hydroxyl Radicals and Rate Constant of n-Hexadecane Photocatalytic Degradation[J]  Chemical Journal of Chinese Universities, 2002,V23(12): 2313-2316
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http://www.cjcu.jlu.edu.cn//EN/     or     http://www.cjcu.jlu.edu.cn//EN/Y2002/V23/I12/2313
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