Ultrasound and shacking-assisted water-leaching of anions and cations from fly ash

Abstract

Two mechanical extraction techniques were used for the extraction of
environmentaly interesting components of coal fly ash: shaking, during which
the extraction process lasted from 6 up to 24 h, and sonication that lasted
from15 up to 60 min, using water as extractant. The concentration of anions in
fly ash extracts was 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 ultrasonication yielded slightly higher amounts of extracted
anions as well as Pb, Al, Mn and Fe cations, while shaking-assisted
extraction was more efficient for the Cr, As, Zn and Ni ions. The changes in
pH value, particle size distribution within colloid solution, zeta potential and
conductivity during ultrasound-assisted extraction were measured in order to
explain changes that occur on the surface of fly ash particles contacting water
and different processes (adsorption, ion exchange and flocculation) that
develop under natural conditions. Principal Component Analysis was used for
assessing the effect of observed process parameters. It is essential to evaluate
quantity of these elements leachable from coal fly ash into the surface waters in
natural conditions in order to prevent contamination of the environment.