The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin(2,3,7,8-TCDD) is an efcient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H2 O are introduced in detail at the method of MPWB1K/6-31+G(d,p)//MPWB1K/6-311+G(3df,2p) level. In ozonolysis, H2O is an important source of OH radical formation and initiated the subsequent degradation reaction. The Rice-Ramsperger-Kassel-Marcus(RRKM) theory was applied to calculate rate constants with the temperature ranging from 200 to 600 K. The rate constant of reaction between 2,3,7,8-TCDD and O3 is 4.80 × 10 20cm3/(mole·sec) at 298 K and 760 Torr. The atmospheric lifetime of the reaction species was estimated according to rate constants, which is helpful for the atmospheric model study on the degradation and risk assessment of dioxin.
Dielectric barrier discharges(DBD) have been used in the degradation of dioxins due to the large number of excimers and free radicals produced in discharge process. In this article,the density functional theory(DFT) is used to study the degradation mechanism of octachlorinated dibenzo-p-dioxin(OCDD) with the atomic oxygen O(3P) in DBD reactor. The reactants, intermediates, transition states and products are optimized at the MPWB1K/6 –31 + G(d,p) level. The vibrational frequencies have been calculated at the same level. The reaction pathways and mechanisms are analyzed in detail. The effect of removing the chlorine atom on environment also has been discussed.
