Treatment Of 2, 4-dichlorophynoxyacetic Acid By Catalytic Ozonation

The physical chemistry properties and application in water treatment of ozone are reviewed and the research objective is proposed too. There are two parts in this paper: Kinetic and mechanism of ozonation of 2,4-Dichlorophenoxyacetic acid (2,4-D); Kinetic and mechanism of homogeneous catalytic ozonation of 2,4-D.During the ozonation of 2,4-D, the direct reaction between 2,4-D and ozone is the main reason of 2,4-D degradation in acidic solution. The remove rate of 2,4-D increase with increasing pH of solution owing to the dissociation of 2,4-D and the contribution of hydroxyl radical ( OH). The batch test showed that the stiochiometric factor ( ) is 2, the absolute oxidation reaction rate of ozone ( kO3 ) and 2,4-D ( k2,4-D)are 61.66 L mol-1 s-1 and 30.83 L mol-1 s-1.2,4-dichlorophenol, 2,4-Dichlorophenoxyformaldehyde are identified as intermediates by GC-MS. 2,4-dichlorophenol, 4-chlorophenol, benzoquinone, oxalic acid, maleic acid, fumaric acid are identified as intermediates by HPLC. The degradation pathway of 2,4-D is proposed during ozonation.Though the removal rate of 2,4-D is high, the removal of COD is low in ozonation of 2,4-D. In order to improve the removal of COD, experiments were done using catalytic ozonation with ferrous. The remove rate of 2,4-D decrease with increasing ferrous concentration in the beginning, and increase more quickly than ozonation of 2,4-D later. Catalytic ozonation showed higher remove rate of COD than ozonation because the hydroxyl radical has strong oxidation power with all organic compounds. The remove rate of 2,4-D decrease with increasing pH in acidic condition, and increase with increasing temperature.The TOC and COD remove rate are 34% and 67% respectively at a certain conditions during catalytic ozonation, much higher than ozonation, which can make up disadvantages of ozonation. 2,4-dichlorophenol, 4-chlorophenol, 2-chlorophenol are identified as intermediates both by GC-MS and HPLC. benzoquinone, maleic acid, are also identified as intermediates by HPLC. glycolic, glyoxylic and oxalic acid aredetected by IC chromatography. The degradation pathway of 2,4-D is proposed duringcatalytic ozonation.