Leachability of metals from fly ash: Leaching tests before and after extraction with supercritical CO2 and extractants

C. Kersch*, S. Peretó Ortiz, G. F. Woerlee, G. J. Witkamp

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Residues such as sewage sludge or fly ashes are usually contaminated with toxic heavy metals. These metals leach out after contact with water, thus polluting the groundwater. If aqueous concentrations of metals are exceeded, these residues require expensive disposal. Supercritical fluid extraction (SFE) is a promising method to reduce the metal content of contaminated particles to such an extent that leachability is reduced and the demands of legislation are observed. This paper focuses on the metal leachability and the effect after extraction in a 12-L revolving vessel with supercritical CO2 with fly ash from a municipal waste incinerator as model compound. Pre-leaching with water prior to SFE led to the removal of water-soluble compounds and structural changes on the ash surface. Standard leaching tests of fly ash after SFE with Cyanex 302, TBP, D2EHPA, or mixtures of TBP-D2EHPA focussed on metals such as Zn, Pb, Mn, Cd, Cu, V, Sb, Ni, Mo, Cr, and Co. The leaching test showed a leachability increase of Sb and the successful reduction in leachability of Zn, Pb, and Mn in particular.

Original languageEnglish (US)
Pages (from-to)119-127
Number of pages9
Issue number1-2
StatePublished - Feb 1 2004
Externally publishedYes


  • Extractant
  • Fly ash
  • Leaching

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geotechnical Engineering and Engineering Geology


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