Effects of sulfur dioxide, hydrogen peroxide and sulfuric acid on the de novo synthesis of PCDD/F and PCB under model laboratory conditions

Abstract

In a laboratory model system consisting of fly ash from municipal waste incinerator, CuCl 2 · 2H 2O, NaCl and activated carbon in N 2 + 10% O 2 atmosphere, the de novo synthetic reactions of formation of polychlorinated dibenzo- p-dioxins (PCDDs), dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) were studied under laboratory conditions in the presence of sulfur dioxide, hydrogen peroxide, and sulfuric acid. It has been found that the formation of PCDD is suppressed by sulfur dioxide more efficiently than the formation of PCDF. A similar effect has also been observed in the presence of hydrogen peroxide. The formation of PCDF is strongly suppressed in the presence of sulfuric acid. On the basis of the experimental results and thermodynamic calculations, the following mechanisms are proposed and discussed: oxidative destruction of PCDD and PCDF oxygen rings, conversion of cupric chloride and possibly also cupric oxide into the non-reactive sulfate, and the Deacon oxychlorination processes catalyzed by cupric chloride.