title: Importance of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans.
abstract: The role of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) has been studied thoroughly in an entrained flow reactor during simulated waste combustion. The effects of gas-phase chlorine species such as chlorine (Cl2), hydrogen chloride (HCl), and chlorine radicals (Cl*), as well as ash-bound chlorine, on PCDD/F de novo formation were isolated for investigation. The ash-bound chlorine alone was observed to be a sufficient chlorine source for PCDD/F formation. The addition of HCl to the system did not influence the yields of the PCDDs/Fs nor the degree of chlorination due to its poor chlorinating ability. Addition of 200 ppm of Cl2 to the ash-feed system resulted in increased PCDD/F yields, especially for the octa- and hepta-chlorinated congeners. Altering the reaction temperature to enable the presence of only Cl2 to the system did not change the yields of PCDD/F compared to those when both Cl2/Cl* were present. However, comparison between ash-bound and gas-phase chlorine, the latter at a concentration typical of a realistic combustion process, revealed ash-bound chlorine to be the more important chlorine source for de novo formation of PCDD/F in a full-scale incinerator.
authors.affiliation: National Risk Management Research Laboratory, Air Pollution Prevention and Control Division, Air Pollution Technology Branch, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
authors.forename: Evalena
authors.initials: E
authors.lastname: Wikström
authors.forename: Shawn
authors.initials: S
authors.lastname: Ryan
authors.forename: Abderrahmane
authors.initials: A
authors.lastname: Touati
authors.forename: Marnie
authors.initials: M
authors.lastname: Telfer
authors.forename: Dennis
authors.initials: D
authors.lastname: Tabor
authors.forename: Brian K
authors.initials: BK
authors.lastname: Gullett
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001572:Benzofurans / Q000737:chemistry*; D017606:Chlorine Compounds / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated; D004784:Environmental Monitoring; D017745:Incineration; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry*; D012037:Refuse Disposal; D013696:Temperature
chemical_list: D000393:Air Pollutants; D001572:Benzofurans; D017606:Chlorine Compounds; D000072338:Dibenzofurans, Polychlorinated; D000072317:Polychlorinated Dibenzodioxins