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THE IMPORTANCE OF CHLORINE SPECIATION ON DE NOVO FORMATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND POLYCHLORINATED DIBENZOFURANS
Citation:
Wikstrom**, E., A. Touati, M. A. Telfer*, D. Tabor, AND B K. Gullett*. THE IMPORTANCE OF CHLORINE SPECIATION ON DE NOVO FORMATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND POLYCHLORINATED DIBENZOFURANS. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 37(6):1108-1113, (2003).
Description:
The role of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) has been thoroughly studied in an entrained flow reactor during simulated waste combustion. Namely, the affects of gas-phase chlorine species such as chlorine [Cl(2)], hydrogen chlorine (HCl), and chlorine radicals [Cl(n-)], as of well as solid-phase chlorine, ie., ash-bound, 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 enhanced neither the yields of the PCDDs/Fs nor the degree of chlorination due to its poor chlorinating ability. Addition of 200 ppm of C1(2) to the ash-feed system resulted in increased PCDD/F yields and especially for the octa-and hept-chlorinated congeners. Moreover, altering the reaction temperature to enable the addition of only C1(2) to the system did not change the yields of PCDD/F compared to when both C1(2)/Cl(n-) were present. Comparison between ash-bound and gas-phase chlorine, the latter at a concentration typical of a realistic combustion process, revealed that ash-bound chlorine was the most significant chlorine source for PCDD/F de novo formation in the current system.