In order to understand the kinetics of direct oxidation between ozone molecule and 2

4-dichlorophenoxyacetic acid(2

4-D)

the ozone oxidation of 2

4-D using sufficient tertbutyl alcohol as free radical inhibiting agent was studied in a bubbling reactor.The effect of initial pH on 2

4-D direct oxidation process was discussed.The results show that direct oxidation of 2

4-D and transfer of O3 are affected by initial pH.When the value of initial pH is lower than 3.3

the solution pH value maintains approximately constant during the process.When it is larger than 3.3

the solution pH value drops abruptly and reaches a steady value in a short period

while concentration of ozone increases rapidly and does a steady concentration.With the increasing of initial pH the steady ozone concentration and pseudofirstorder rate constant increase

and the time required to reach this steady value decreases.Hatta numbers are lower than 0.03 for different pH values.The 2

4-D degradation process by ozone molecule follows the slow rate kinetics.It shows that the direct reaction of 2

4-D and ozone molecule is a control step of whole kinetics process.