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      Contribution of Aluminas and Aluminosilicates to the Formation of PCDD/Fs on Fly Ashes

      research-article
      1 , 1 , 2
      Chemosphere

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          Abstract

          Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200–600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process.

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          Author and article information

          Journal
          0320657
          8583
          Chemosphere
          Chemosphere
          Chemosphere
          0045-6535
          1879-1298
          27 November 2015
          23 November 2015
          February 2016
          01 February 2017
          : 144
          : 2421-2426
          Affiliations
          [1 ]Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana
          [2 ]Department of Environmental Sciences, Louisiana State University, Baton Rouge, Louisiana
          Author notes
          [* ]Phone: 225-578-8147. Fax: 225-578-3458. slomni1@ 123456lsu.edu
          Article
          PMC4695248 PMC4695248 4695248 nihpa740697
          10.1016/j.chemosphere.2015.11.009
          4695248
          26615490
          bb8e7cbc-ac81-41b4-a555-ac4dc1ba836a
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