基于Guassian、Multiwfn及ECOSAR的氮磷系阻燃剂在UV/PDS体系中的降解路径及产物毒性预测研究

Degradation pathway and product toxicity prediction of nitrogen phosphorus flame retardants in UV/PDS system based on Guassian,Multiwfn and ECOSAR

氮磷系阻燃剂作为一类新兴无卤阻燃剂被广泛应用,但其在环境中难降解,紫外活化过二硫酸钠(UV/PDS)高级氧化技术能有效降解结构复杂的有机污染物.为探究氮磷系阻燃剂在UV/PDS氧化体系的降解路径,本研究选取3种典型氮磷系阻燃剂9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)、三聚氰胺(Melamine)及磷酸三苯酯(TPP)为降解目标物.首先利用Guassian模型结合Fukui指数推测了UV/PDS体系中HO·和SO_(4)·^(-)自由基与阻燃剂发生反应的位点及其相应的降解路径,通过分析DOPO及其降解产物的质谱数据验证了所推测降解路径的合理性,并进一步利用ECOSAR模型进行降解产物的毒性预测.结果表明,各氮磷系阻燃剂键能较低的位点与Fukui指数较高的位点相吻合,UV/PDS反应体系中的自由基主要通过攻击苯环上的碳氢键(键能较低的位点)来降解氮磷系阻燃剂,DOPO降解的质谱分析数据表明,依据低键能位点推测的降解产物与质谱鉴定结果相一致.同时利用ECOSAR模型评估发现,降解产物毒性普遍低于阻燃剂母体.因此,本研究采用模型预测阻燃剂降解路径与产物毒性的方法便捷有效,可为光催化降解复杂结构有机物的研究提供理论依据.

Nitrogen phosphorus flame retardants were widely used as a new type of halogen-free flame retardant,but they were difficult to degrade in the environment.Ultraviolet activated sodium persulfate(UV/PDS)advanced oxidation process can effectively degrade organic pollutants with complex structures.In order to explore the pathway of oxidative degradation of nitrogen phosphorus flame retardants in UV/PDS,9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide(DOPO),Melamine and triphenyl phosphate(TPP)were selected as degradation targets in this study.Firstly,the bond energy calculated by Guassian model and the Fukui index calculated by Multiwfn program were used for speculating the reaction sites of HO·and SO_(4)·^(-)with flame retardants and the degradation pathways of flame retardants in UV/PDS system.The rationality of the speculated degradation pathway was verified by the mass spectrometry data of DOPO and its degradation products.The toxicity of degradation products was predicted by ECOSAR model as well.The results showed that the sites with lower bond energy of nitrogen phosphorus flame retardants were consistent with the sites with higher Fukui index.The free radicals in UV/PDS degraded nitrogen phosphorus flame retardants mainly by attacking the sites with lower bond energy,which were hydrocarbon bonds on benzene rings.The mass spectrum data showed that the predicted degradation products which based on breaking the low bond energy sites were consistent with the results identified by mass spectrometry.At the same time,it is found that the toxicity of degradation products is generally lower than that of flame retardants by using ECOSAR model.Therefore,the method of predicting the pathway and the toxicity of degradation products is convenient and effective,which provide a theoretical basis for the study of photocatalytic degradation of complex organic compounds.