正十六烷光催化降解的羟自由基测定及其反应速率常数  

EPR Measurement of Hydroxyl Radicals and Rate Constant of n-Hexadecane Photocatalytic Degradation

作　　者：钟萍[1] 孔令仁[1] 刘光明[1] 眭云霞[1] 

机构地区：[1]南京大学环境学院,污染控制与资源化研究国家重点实验室,南京210093

出　　处：《高等学校化学学报》2002年第12期2313-2316,共4页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金 (批准号 :2 98770 11)资助

摘　　要：以 5 ,5 -二甲基 -1 -吡咯啉 -N-氧化物 ( DMPO)为自旋捕集剂 ,采用电子顺磁共振 ( EPR)方法 ,在光照的Ti O2 磷酸缓冲水溶液 ( p H=7.4 )中检测到羟自由基的自旋加合物 ( DMPO-OH) ,其强度随光照时间增加而加大 .在 1 min时达到稳态 ,此时 DMPO-OH的产生和猝灭达到平衡 .根据已知的羟自由基 ( HO· )与 DMPO结合的速率常数 k0 ,推导出纳米级 Ti O2 光催化生成羟自由基氧化正十六烷 ( n-C1 6H3 4 )的速率常数 k=5 .0×1 0 1 1 mol- 1 · L· s- 1 .Spin trapping technique was used to detect the free radicals formed upon light irradiation of TiO 2 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 TiO 2, 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 TiO 2 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=5.0×10 11 mol -1·L·s -1 for the reaction of hydroxyl radicals with n-hexadecane could be obtained. In conclusions, TiO 2 photocatalytic reaction proceeded in a free radical mechanism.

关 键 词：正十六烷 测定 反应速率常数 光催化降解 羟自由基 电子顺磁共振 纳米TiO2 环境污染物 

分 类 号：X131[环境科学与工程—环境科学] D643.32[政治法律—政治学]