Catalytic effects by metal oxides on the formation and degradation of chlorinated aromatic compounds in fly ash

• Published in: Chemosphere (Oxford) 2008-04, Vol.71 (6), p.1135-1143
• Main Authors: Öberg, T., Bergbäck, B., Filipsson, M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Carbon - chemistry; Catalysis; Catalytic reaction; Chemistry; Chlorobenzenes; Chlorobenzenes - chemistry; Coal Ash; Combustion and energy production; Design of experiments; Dioxin derivatives; Dioxins; Dioxins - chemistry; Environmental chemistry; Exact sciences and technology; Factorial design; Fly ash; Hexachlorobenzene; Incineration plant; Kemi; Metal Oxides; Metals - chemistry; Miljökemi; Models, Theoretical; NATURAL SCIENCES; NATURVETENSKAP; Organic chlorine compounds; Organic compounds; Oxidation; Oxides - chemistry; Particulate Matter - chemistry; Persistent organic pollutant; Pollutant formation; Pollution; Pollution sources. Measurement results; Reaction mechanism; Solid waste; Temperature; Thermal degradation; Urban waste; Waste combustion
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2007.10.033

Polychlorinated benzenes, dibenzo- p-dioxins (PCDD), and dibenzofurans (PCDF) may be formed below the combustion temperature in fly ash from municipal solid waste incinerators (MSWI). Copper catalyzes this formation, possibly by the Deacon reaction. Many other elements are also Deacon catalysts or promoters, and here we report results from a statistically designed experiment with 15 metal oxides added to fly ash and heated at 300 °C for 2 h in an air atmosphere. A resolution IV fractional factorial design with four replicates was completed in 36 runs with the oxides of magnesium, yttrium, titanium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc, and tin. All samples were analyzed for chlorinated benzenes and the results were evaluated by analysis of variance. The addition of copper significantly increased the amounts of the chlorinated benzenes, while cobalt, chromium and vanadium decreased the net formation. The oxides of zinc and iron seemed to have a slightly positive and negative effect respectively. The findings in this study seem to corroborate our previously reported results regarding the different catalytic effects of copper and chromium, and lack of a significant effect by nickel. Besides chromium, it also identifies cobalt and vanadium as potent catalysts for oxidative degradation of the chlorinated aromatic compounds found in MSWI fly ash.