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.