臭氧化降解除草剂2,4-D的机理研究(I):中间产物分析

苯氧羧酸类除草剂2,4-D是一种常见的农业污染物,具有较高的环境危害。将水中的除草剂2,4-D作为控制对象,采用臭氧、臭氧/过氧化氢两个氧化体系在实验室内进行降解。为了探讨2,4-D降解机理,分别采用气相色谱-质谱联机分析方法、高效液相色谱法、离子色谱法等方法对2,4-D的降解过程中可能产生的中间产物进行了检测。结果表明,2,4-D的臭氧化降解中间产物有芳香族化合物和有机酸等,主要包括:2,4-二氯苯酚、(氯)对苯二酚(邻苯二酚)、(氯)苯醌、顺丁烯二酸、反丁烯二酸、乙酸、草酸、甲酸等。并经过总有机碳分析可知,部分2,4-D经过臭氧、臭氧/过氧化氢体系氧化降解,在反应时间内能彻底降解为二氧化碳、水及某些无机物等终产物。对2,4-D降解中间产物的分析为臭氧化降解除草剂2,4-D降解路径的研究打下基础。

Mechanism of Herbicide 2,4-D Degradation by Ozonation I:Intermediate Product

2,4-dichlorophenoxyacetic acid (2,4-D), a member of the phenoxy family of herbicides, is a common contaminating agricultural herbicide. It is harmful to environment and is potentially toxic to humans. Degradation of 2,4-D using O3 and O3/H2O2 oxidation technologies was investigated in a cylindrical contact tower in the lab. In order to discuss the mechanism of 2,4-D degradation by O3 and O3/H2O2, many analytic methods such as Gas Chromatography-Mass Spectrometry (GC-MS), High Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC) were used to analyze the intermediate products formed during 2,4-D degradation process. The experiment results showed that the intermediate products of 2,4-D ozonation were mainly aromatic compounds and organic acids. The main intermediate products of 2,4-D degradation included 2,4-dichlophenol, (chloro-) hydroquinone (catechol), (chloro-) hydroquinone, maleic acid, fumaric acid, acetic acid, oxalic acid and formic acid and so on. Total organic carbon (TOC) in reaction solution was determined, and the result indicated that the mineralization of 2,4-D was obvious during the reaction process. Within the reaction time, a portion of 2,4-D was finally degraded to form carbon dioxide, water and some inorganic substances, which were the end products of 2,4-D degradation through ozonation. The analysis of intermediate products is the prior investigation needed to research the degradation pathway of 2,4-D.