活性艳红X-3B的Fenton氧化降解机理研究

采用UV-Vis、IR和GC-MS研究了X-3B的Fenton降解机理,结合X-3B的结构和亲电理论,提出了其Fenton氧化降解路径。染料分子首先在-N=N-C靠近萘环的C-N和C-NH两处断裂,产生三种中间产物:邻羟基重氮苯内盐、萘醌和4,6-二氯-1,3,5-三嗪-2-氨。邻羟基重氮苯内盐释放出N2,即偶氮基团的氮原子转化为N2,而其他氮原子被氧化为NO3-。染料中的C、H、S和Cl原子分别矿化为CO2、H2O、SO42-和Cl-,但部分有机碳仍存在于难以被.OH氧化降解的草酸-Fe3+络合物中。     

Self-catalytic degradation of ortho-chlorophenol with Fenton's reagent studied by chemiluminescence

The degradation of ortho-chlorophenol using Fenton's reagent was studied by chemiluminescence (CL). Without a special CL reagent, a weak CL emission from the mixture of ferrous ion and hydrogen peroxide was observed at room temperature. The CL intensity was increased by the addition of ortho-chlorophenol into the mixed solution. When the temperature was raised to 65℃, the CL intensity was enhanced strongly. The CL mechanisms for the system H₂O₂-Fe²⁺ with and without ortho-chlorophenol were studied by examining the CL spectrum, gas chromatography-mass spectrometry and electron spin resonance spectrum. The effects of various free radical scavengers, surfactants and fluorescence compounds on the CL intensity were also investigated. A self-catalytic oxidation mechanism was proposed. The results showed that singlet oxygen was the main emitter for the system H₂O₂-Fe²⁺. The strong CL from the system H₂O₂-Fe²⁺-ortho-chlorophenol was due to singlet oxygen and electronically excited quinone. The benzenediol-like intermediate product formed during the phenol oxidation process greatly promoted the Fenton's reaction and led to higher CL intensity. Chemiluninescence is a novel approach for the investigation of the oxidation of some organic pollutants by Fenton's reagent.