Formation of polychlorinated dibenzo- p-dioxins/dibenzofurans from residual carbon on municipal solid waste incinerator fly ash using [formula omitted

Abstract

Na 37 Cl was used to study the role of chlorine in the formation of polychlorinated dibenzo- p-dioxins (PCDD) and dibenzofurans (PCDF) from carbon. Adding Na 37 Cl to fly ash showed that this compound was a (relatively) poor chloride source; chlorine naturally present on the ash – which could include both chlorine in residual carbon and (metal) chlorides – was found to be ca. 17 x more reactive. When both Na 37 Cl and CuCl 2 were added to aqueous extracted fly ash, the percentage of 37 Cl from Na 37 Cl included in PCDD/F increased, compared to the combination of Na 37 Cl/ fly ash. When Na 37 Cl and CuCl 2 were exchanged in water, followed by evaporation of the solvent, and mixed with aqueous extracted fly ash, the percentage of 37 Cl included in PCDD/F was much higher. Apparently, direct transfer of 37 Cl from CuCl 2 to carbon and PCDD/F was much faster than transfer of 37 Cl − from Na 37 Cl via a metal chloride (such as CuCl 2) to carbon and PCDD/F. In addition to chlorine in PCDD/F originating from exchanged NaCl/CuCl 2, chloride left on the fly ash after aqueous extraction and chlorine present in residual carbon could also have been incorporated in PCDD/F.