Title: Role of Fe2O3 in fly ash surrogate on PCDD/Fs formation from 2-monochlorophenol.
Authors: Guan, Xia; Ghimire, Ajit; Potter, Phillip M; Lomnicki, Slawomir M
Published In Chemosphere, (2019 Jul)
Abstract: The correlation between the content and morphology of Fe2O3 and the yields of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was studied in this work. Three fly ash surrogates containing 1%, 2.5%, and 4% of Fe2O3 were prepared and their effects on PCDD/Fs formation were investigated and compared to our previously studied 5% iron oxide sample using 2-monochlorophenol precursor model. As the intermediate of PCDD/Fs, environmentally persistent free radical formation propensity was correlated with the PCDD/Fs formation yields for different iron oxide samples. PCDD/Fs yield increases exponentially with the increasing iron content under pyrolytic conditions. On the contrary, low iron oxide content promotes oxidation and lowers yields of PCDD/Fs. Changing iron oxide clusters' morphology (crystallinity and cluster size) affects the mechanism of PCDD/Fs formation - on larger crystallites, a bidentate chemisorption of precursor is preferred leading to lower chlorinated congeners, while smaller clusters promote formation of PCDFs through mixed monodentate-bidentate surface species, resulting in formation of congeners with 1 chlorine more. This study further confirms the propensity of iron oxide to predominantly form PCDFs. The iron content also defines PCDDs:PCDFs ratio.
PubMed ID: 30965252
MeSH Terms: Chlorophenols/chemistry*; Coal Ash/chemistry*; Dibenzofurans, Polychlorinated/analysis; Dibenzofurans, Polychlorinated/chemical synthesis*; Ferric Compounds/chemistry*; Incineration; Oxidation-Reduction; Polychlorinated Dibenzodioxins/analysis; Polychlorinated Dibenzodioxins/chemical synthesis*