title: The rate-determining step in a low temperature PCDD/F formation from oxidative breakdown of native carbon in MSWI fly ash.
abstract: We developed a phenomenological approach to explain the kinetic experimental data of PCDD/F formation/destruction based on a reaction mechanism model at the congener group level. In the present work, we investigated the formation and destruction of PCDD/F on fly ash as a function of time at 280 °C, chlorine mass balance, evolution of the total equivalent toxicity and kinetic modelling. We determined that the volatilization process is negligible and that the reactive processes at short reaction times only become important above 300 °C. The results provide a substantial improvement on existing studies. We experimentally demonstrated, for the first time, that there is a correlation between the oxidative breakdown of native carbon and PCDD/F de novo synthesis. Data processing by our kinetic model showed that the formation of oxygen complexes C(O) was the determining step for de novo synthesis of PCDD/F. Indeed, the calculated reaction time at which the PCDD/F concentration was at a maximum (850 min) was greater than that calculated for the oxygen complexes C(O) (435 min). Moreover, the experimental carbon conversion efficiency for PCDD/F production (0.0032% at 600 min maximum) was in a very good agreement with the theoretical conversion (0.0041%).
authors.affiliation: Dept. of Earth and Environmental Sciences, Università degli Studi di Milano - Bicocca, Piazza della Scienza 1, 20126 Milano, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Collina
authors.affiliation: Dept. of Earth and Environmental Sciences, Università degli Studi di Milano - Bicocca, Piazza della Scienza 1, 20126 Milano, Italy. Electronic address: marina.lasagni@unimib.it.
authors.forename: Marina
authors.initials: M
authors.lastname: Lasagni
authors.affiliation: Dept. of Earth and Environmental Sciences, Università degli Studi di Milano - Bicocca, Piazza della Scienza 1, 20126 Milano, Italy.
authors.forename: Elsa
authors.initials: E
authors.lastname: Piccinelli
authors.affiliation: Dept. of Earth and Environmental Sciences, Università degli Studi di Milano - Bicocca, Piazza della Scienza 1, 20126 Milano, Italy.
authors.forename: Manuela Nadia
authors.initials: MN
authors.lastname: Anzano
authors.affiliation: Dept. of Earth and Environmental Sciences, Università degli Studi di Milano - Bicocca, Piazza della Scienza 1, 20126 Milano, Italy.
authors.forename: Demetrio
authors.initials: D
authors.lastname: Pitea
mesh_terms: D002244:Carbon / Q000737:chemistry*; D060729:Coal Ash / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated / Q000032:analysis* / Q000737:chemistry; D006358:Hot Temperature; D017745:Incineration / Q000379:methods*; D007700:Kinetics; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D052638:Particulate Matter; D000072317:Polychlorinated Dibenzodioxins / Q000032:analysis* / Q000737:chemistry; D062611:Solid Waste / Q000032:analysis
chemical_list: D060729:Coal Ash; D000072338:Dibenzofurans, Polychlorinated; D052638:Particulate Matter; D000072317:Polychlorinated Dibenzodioxins; D062611:Solid Waste; D002244:Carbon
keywords: Low temperature PCDD/F formation; MSWI fly ash; Oxidative breakdown mechanism