A new dioxin decomposition process based on a hybrid density-functional calculation

Using hybrid density-functional theory, a new decomposition process for 2,3,7,8-tetrachlorinated dibenzo-p-dioxins (TCDD) is proposed. This hypothetical process is composed of two steps, combining the use of hydrogen radicals with proton irradiation of dioxins. The first step is to remove chlorine atoms bound to the dioxin ring by selective abstraction using hydrogen radicals. This leads to non-chlorinated dibenzo-p-dioxin (NCDD) which is much less toxic than 2,3,7,8-TCDD. In the second step, a dative bond is formed between an oxygen atom of an NCDD and an introduced proton; then further irradiation with hydrogen radicals results in the breaking of the C-O bond of the dioxin ring. The rate-determining step of the whole process is the chlorine abstractions, and their computed activation energies are less than 0.4 eV. (C) 1999 Elsevier Science B.V. All rights reserved.