[Kinetics and influencing factors of dimethyl phthalate degradation in aqueous solution by ozonation]

The rate constants for the reaction of higher concentrations of DMP with ozone and hydroxyl radical (*OH) were determined by competition kinetics method, in which nitrobenzene (NB) was selected as the reference organic compound. The effects of *OH inhibitor tert-butyl alcohol, pH and a variety of ions on the degradation of DMP were discussed. Experimental results showed that the degradation of DMP by ozonation followed pseudo-first-order kinetics. The rate constants of DMP with ozone and *OH were (0.064 +/- 0.014) L x (mol x s)(-1) and 3.59 x 10(9) L x (mol x s)(-1), respectively. The system pH decreased due to the carboxylic acids intermediates generated by ozonation at initial pH of 6.08 and 9.07, but the system pH was stabilized in strong alkali or acidic solution. A large number of intermediates resulted in the removal rate of COD lagging behind the degradation efficiency of DMP, and part of the intermediates were difficult to be mineralized. The reaction of DMP with *OH was not inhibited by lower concentrations of tert-butyl alcohol. But the reaction was inhibited when the concentration of tert-butyl alcohol was 90.21 times as high as that of DMP, and the degradation efficiency of DMP decreased from 98.7% to 8.8%. The degradation efficiency of DMP was higher with phosphate buffer solution for pH adjustment than NaOH/H2SO4 solution. Low concentrations of cations and anions had no effects on the degradation efficiency of DMP. High concentrations of SO4(2-), NO3(-) and HPO4(2-) had no remarkable effects on ozonation. But high concentrations of Cl(-) and HCO3(-) inhibited the degradation and the inhibitory effect of HCO3(-) was stronger than Cl(-). The degradation efficiency of DMP was only 50.5% and 26.2%, respectively, after 40 min under 7 097 mg x L(-1) of Cl(-) and 6 093 mg x L(-1) of HCO3(-).