TiO_2光催化降解2,4-二氯酚动力学及机理的研究

The Study on 2,4-dichlorophenol Photodegradation Kinetics and Reaction Mechanism by TiO_2

以TiO2作为催化剂,500 W汞灯作为光源,对水体中2,4-二氯酚(2,4-DCP)的光催化降解特性进行了研究。实验结果表明,TiO2光催化降解2,4-DCP效果较好,降解的最佳pH为7,催化剂的最佳投加量为200 mg·L-1。2,4-DCP的初始浓度越小,光催化的效率越高。在初始浓度为5 mg·L-1时,光催化1 h的降解率达90%。在实验的四种不同初始浓度(5 mg·L-1、10 mg·L-1、20 mg·L-1、40 mg·L-1)下,2,4-DCP的光降解速率常数近似与其初始质量浓度成一级反应动力学关系。结合高效液相色谱、气相色谱-质谱的测定结果以及Cl-、COD的变化,认为2,4-DCP的主要降解过程为:脱氯-开环-矿化、中间产物相互作用-进一步矿化。

Photocatalytic degradation characteristics of 2,4- DCP by TiO2 was studied under 500 W mercury lamp.The experimental results showed that TiO2 exhibited significantly photocatalytic action on 2,4- DCP. The optimal pH was about 7 and the best catalyst dosing quantity was 200 mg·L- 1. The initial mass concentration of 2,4- DCP presented negative effect to photocatalysis efficiency. When the initial concentration of 5mg·L- 1,photocatalytic degradation of 1 h rate was 90%. Four different initial concentrations were 5 mg·L- 1,10 mg·L- 1,20 mg·L- 1,and 40 mg·L- 1,the photodegradation rate constant approximation of 2,4- DCP and its initial mass concentration into a first order reaction kinetics. In combination with high performance liquid chromatography, gas chromatography- mass spectrometry determination results were as well as the change of Cl-and COD. The results showed that the main degradation process for2,4- DCP were dechlorination- open loop- mineralization,and the intermediate interaction- further mineralization.