水相中四氯化碳的激光闪光光解研究

利用激光闪光光解技术研究了水相中四氯化碳光分解和光氧化的微观机制,并且指证了水相中四氯化碳受光激发所产生的瞬态光谱中的一些瞬态物种的特征吸收峰。并对这些瞬态物种的行为和归宿进行了研究。研究表明在248nm激光作用下,四氯化碳受光激发将分解为CCl~3^.自由基和Cl^.自由基。CCl~3^.自由基在无氧/有氧条件下的反应途径是不同的:在无氧条件下CCl~3^.自由基将进行偶合反应生成更难于降解的C~2Cl~6;而在有氧条件下CCl~3^.自由基则与O~2反应生成CCl~3O~2^.自由基,而CCl~3O~2^.自由基最终转变为COCl~2,这意味着光氧化能够有效地降解CCl~4。Cl^.自由基基本上不受氧气存在的影响,其归宿是与水分子发生电荷转移反应。

Nanosecond laser flash photolysis (LFP) studies on aqueous CCl~4 solution

The dechlorinating microscopic mechanism and transient spectra of aqueous CCl~4 was studied by using nanosecond laser flash photolysis (LFP). The transient absorption band (λ~m~a~x<300nm) of aqueous CCl~4 solution deaerated by N~2 was attributed to trichloromethyl radical (CCl~3^.) which decayed following 2nd-order kinetics with (2k/εl) equal to 6.34×10^6s^-^1, and the transient absorption band (λ ~m~a~x<320nm) of same solution deaerated by O~2 was attributed to peroxytrichloromethyl radical (CCl~3O~2^.) which decayed following 1st-order reaction kinetics with a rate constant of 1.9×10^4s^-^1. The transient absorption band around 330nm was attributed to solvated chlorine atom. C~2Cl~6 as photolysis product of aqueous CCl~4 solution without oxygen showed that CCl~4 cannot be degraded by photolysis and free radical hydrolysis process. COCl~2 as photolysis product of aqueous CCl~4 solution in the presence of oxygen was observed directly in the transient absorption spectra, which means that CCl~4 can be degraded by photooxidation process.