Role of Fe2O3 in fly ash surrogate on PCDD/Fs formation from 2-monochlorophenol

Abstract

The correlation between the content and morphology of Fe 2 O 3 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 Fe 2 O 3 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 PCCD/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 monodentatebidentate surface species, resulting in formation of congeners with 1 chlorine more. This studies further confirm the propensity of iron oxide to predominantly form PCDFs. The iron content also defines PCDDs:PCDFs ratio.

A Comparative Study on the Formation of Environmentally Persistent Free Radicals (EPFRs) on Hematite and Goethite: Contribution of Various Catechol Degradation Byproducts

“…The bidentate configuration was more favored for accepting electrons and forming dimers than was the mononuclear configuration. 27,28 Thus, the M-B and B-B configurations for catechol adsorbed on HM and GT, respectively, were conducive to the dimer formation. The phenoxyl radical formed through the M-M configuration in GT may have been transformed back to catechol during extraction, resulting in a slower catechol degradation.…”

Promoted liquid-phase hydrodechlorination of chlorophenol over Raney Ni via controlling base: Performance, mechanism, and application

“…At present, numerous methods like physical method (Madannejad et al, 2018), biological method (Song et al, 2019), incineration (Peng et al, 2016), advanced oxidation processes (Li et al, 2019;Luo et al, 2018;Zhou et al, 2018), zero-valent metal reduction (Duan et al, 2016;Yang et al, 2017;Zheng et al, 2019), catalytic hydrodechlorination (HDC) (Jadbabaei et al, 2017;Ma et al, 2015;Xiong et al, 2018), etc have been applied for the elimination of chlorophenols. However, harsh reaction conditions and/or special facilities are often required in these methods, many of which are high-cost and will generate even more toxic byproducts (Guan et al, 2019;Madannejad et al, 2018;Zhao et al, 2018). Among these methods, catalytic HDC is a more prospective detoxifying technologies due to low-energy demands and the fact that the highly toxic chlorophenols are effectively transformed into less harmful products, reducing dramatically their ecotoxicity (Pizarro et al, 2017;Wu et al, 2012;Xiong et al, 2018).…”

Developmental Hazard of Environmentally Persistent Free Radicals and Protective Effect of TEMPOL in Zebrafish Model

“…Particles containing EPFRs were prepared as follows. The wetness impregnation method was applied to prepare Cab-o-sil/5% CuO particles [ 3 ]. EPFR-containing particles were acquired by dosing dichlorobenzene (DCB) vapor on the particles at 230 °C in vacuo.…”

“…Environmentally persistent free radicals (EPFRs) are primarily emitted from combustion and thermal processing of organic materials, in which the organic byproducts interact with transition metal-containing particles to form free radical particle pollutants in the cool and post-flame zones of combustion systems [ 1 , 2 , 3 ]. EPFRs can also be observed in ambient PM 2.5 [ 4 , 5 ], cigarette smoke [ 6 , 7 ], and soils from superfund sites [ 8 ].…”