In Situ Formed Soot Deposit as a Carbon Source for Polychlorinated Dibenzo-p-dioxins and Dibenzofurans

• Published in: Environmental science & technology Vol. 38; no. 7; pp. 2097 - 2101
• Main Authors: Wikström, Evalena, Ryan, Shawn, Touati, Abderrahmane, Gullett, Brian K
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2004
• Subjects: Applied sciences; Benzofurans - chemistry; Carbon; Carbon - analysis; Carbon - chemistry; Chlorine; Dibenzofurans, Polychlorinated; Dioxins; Environmental Monitoring; Exact sciences and technology; Incineration; Other wastes and particular components of wastes; PCB; Pollution; Polychlorinated biphenyls; Polychlorinated Dibenzodioxins - analogs & derivatives; Polychlorinated Dibenzodioxins - chemistry; Soil contamination; Soil Pollutants - analysis; Wastes; Combustion residue; Heat treatment; Dioxin derivatives; Waste treatment; Soot; Pollutant formation; De novo; Persistent organic pollutant; Persistence; Fly ash; Incineration; Chlorine Organic compounds; Reaction mechanism; Homologous series; Kinetics; Organic compounds
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es034564p

The aim of this study was to investigate the role of in situ formed soot deposits generated during a combustion process for the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs). In situ formed soot deposits were generated in an entrained flow reactor by using a sooting methane (CH4) flame (sooting phase), with or without chlorine doped into the flame, and fly ash added into the gas phase. The presence of fly ash in the soot deposit was found to be critical, as a catalyst for formation and/or a chlorinating agent. The presence of chlorinated aromatic structures in the soot matrix was not enough to promote de novo formation of PCDDs/Fs without the presence of fly ash. PCDFs were formed via direct release of the molecule backbone structure from the soot. PCDDs were formed via a similar mechanism as well as an equally important formation pathway of condensation reactions of C6 compounds. The formation rate of the soot/ash deposit was still at half its original activity 34 h after the deposits were formed, suggesting a persistent de novo formation occurring for a long time after the sooting incidences (memory effect).