Quantum chemistry study on the destruction mechanism of 2,3,7,8-TCDD by OH and O3 radicals

• The destruction mechanism of 2,3,7,8-TCDD by OH and O3 was investigated in detail.
• OH radical degraded 2,3,7,8-TCDD via substituting chlorine at the 2,3,7,8 positions.
• O3 radical degraded 2,3,7,8-TCDD via destructing CC bonds and aromatic ring.
• The rate constant of OH degrading 2,3,7,8-TCDD was much higher than that of O3.
• OH radical have much stronger ability to degrade 2,3,7,8-TCDD than O3 radical.

Due to its fundamental importance, the destruction mechanism of the dioxins, as exemplified by 2,3,7,8-TCDD, by OH and O3 radicals was investigated in detail employing Quantum Chemical Calculations in this paper. Theoretical results showed that, OH radical degraded 2,3,7,8-TCDD via substituting chlorine at the 2,3,7,8 positions, while O3 radical degraded 2,3,7,8-TCDD via destructing CC bonds and aromatic ring. Based on the mechanism study, the kinetic parameters of the reactions were also calculated by Transition State Theory. By comparing, the rate constant of the 2,3,7,8-TCDD destruction by OH was found to be much higher than that by O3, which indicated that OH radical have much stronger ability to degrade 2,3,7,8-TCDD than O3 radical. This finding was consistent with the standard electrode potential of OH and O3 radical. The theoretical results in this paper can be believed to supply important theory basis for the further investigation on dioxins removal by using the catalytic oxidation technology.