Two mechanical extraction techniques were used for the extraction of
environmentaly interesting elements from coal fly ash: shaking, in which the
extraction process lasted from 6 to 24 hours, and ultrasonic sonication
during 15 to 60 minutes, with water as extractant. The concentration of
anions in fly ash extracts were determined by ion chromatography, while
atomic absorption spectrometry was used for determination of: As, Pb, Cd,
Ni, Cr, Zn, Cu, Fe, Mn and Al. The ultrasonic sonication yielded slightly
higher amounts of extracted anions and Pb, Al, Mn and Fe, while
shaking-assisted extraction was more efficient for the Cr, As, Zn and Ni
ions. The changes in pH value, particle size distribution in colloid, zeta
potential and conductivity during ultrasound-assisted extraction were
measured in order to explain changes on the surface of fly ash particles in
contact with water and different processes (adsorption, ion exchange,
flocculation) that occur in environmental conditions. Principal Component
Analysis were used for assessing the effect of observed process parameters.
Essential from a practical point of view is a quantitative evaluation of
these elements leachable from coal fly ash to surface waters in
environmental conditions and contamination of the environment.
Ultrasound and shacking-assisted water-leaching of anions and cations from fly ash
