MECHANISTIC STEPS IN THE PRODUCTION OF PCDD AND PCDF DURING WASTE COMBUSTION

Research has shown that synthesis of polychlorinated dibenzo-p-dioxins (PCDDS) and polychlorinated dibenzofurans (PCDFs) during municipal waste combustion can proceed through a three step mechanism including 1) production of Cl. from a metal-catalyzed reaction of HCl and O2, 2) Cl2 chlorination of aromatic rings through substitution reactions, and 3) formation of dual ring structures by a second metal-catalyzed reaction. Formation of the dual ring PCDD structure, likely through condensation reactions of chlorophenols, is enhanced up to three orders of magnitude in the presence of metal catalysts, such as Cu(II), reaching a maximum around 400-degrees-C.