4-n-壬基酚的激光闪光光解和紫外光降解

The laser flash photolysis and UV photolytical degradation of 4-n-nonylphenol

采用266nm激光闪光光解瞬态吸收光谱和254nm紫外光降解,研究了乙腈及乙腈-水混合溶液中4-n-壬基酚(4-n-NP)的各种光解行为,考察了不同物理化学体系对4-n-NP光解行为的影响规律.实验发现,在266nm激光闪光光解下,4-n-NP既发生光电离又发生光激发,获得了4-n-NP光电离生成的阳离子自由基,以及光激发生成的激发三重态的瞬态特征吸收谱.由S2O82-光分解产生的SO4·-可快速氧化4-n-NP,测得反应速率常数为2.85×109M-1s-1,判定4-n-NP阳离子自由基在pH高于2.2条件下会转变成脱质子中性自由基.研究发现,使用254nm紫外光直接降解4-n-NP比较困难,UV结合添加H2O2可提高其降解效率,UV结合添加K2S2O8可极大提高4-n-NP降解效率,3.5min的光照即可使1×10-4M的4-n-NP完全降解.本文就4-n-NP在各种条件下的光解机理进行了探讨,为此类具有生物激素效应的非离子表面活性剂光降解奠定了基础.

The photolytical behavior of 4-n-NP,as a model of nonylphenol compounds,in acetonitrile and acetonitrile/water solution was investigated by use of 266 nm laser flash photolysis and 254 nm photolysis.And the effect of various physical chemical conditions on the degradation of 4-n-NP was also explored.It has been found that 4-n-NP can be either photoionized or photoexcited if exposed to 266 nm laser.The characteristic transient absorption spectra of radical cation formed from photoionization and excited triplet formed from photoexcitation of 4-n-NP were obtained.It has also confirmed that 4-n-NP can be oxidized by SO4·-,which produced from photo-decomposition of S2O82-exposed to 266 nm laser,to produce radical cation 4-n-NP·＋ and the rate constant for reaction of SO4·-and 4-n-NP is determined to be 2.85×109 M-1 s-1.The radical cation 4-n-NP·＋ will be transferred into its neutral radical 4-n-NP· via deprotonation over pH 2.2.With the 254 nm exposure it is difficult to photo-degrade 4-n-NP in the mixture solution of acetonitrile and water（1：1） while with addition of H2O2 the degraded efficiency of 4-n-NP can be improved.Accordingly,with addition of K2S2O8 the degraded efficiency of 4-n-NP reaches the highest and it can be degraded completely in 3.5 min.The photolytical mechanisms involved in photolysis of 4-n-NP have been proposed,which may be useful to further photo-degradation treatment for the non ionic surfactants with biologic hormone influence.