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HEAVY AND TOXIC ELEMENTS DISTRIBUTION IN MAGNETICALLY SEPARATED FRACTIONS FROM COAL FLY ASHES

AUTHOR/S: A. SHOUMKOVA, V. STOYANOVA
Sunday 1 August 2010 by Libadmin2010

10th International Multidisciplinary Scientific GeoConference - SGEM2010, www.sgem.org, SGEM2010 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 20-26, 2010, Vol. 2, 597-604 pp

ABSTRACT

The analytical results for the concentration of about 50 elements in magnetic fractions,
obtained by wet low intensity magnetic separation of fly ashes from six coal burning
power plants in Bulgaria, have been compared to the data previously reported [1] for the
initial fly ashes. It has been found that the total content of heavy and toxic elements in
magnetic fractions is lower than that in the source materials. The concentrations of Cr,
Mn, Co, Ni, and, in some ashes, of V and Cu are almost proportional to the content of
Fe in magnetic fractions, indicating their presence in substituted magnetite or
maghemite. In some magnetic fractions a slight enrichment of Ce, Hf, Zn, etc. has been
also observed, but most of the trace elements (As, Pb, Pr, Rb, Sc, Sr, Sn, Tl, Zr, etc.) are
concentrated in non-magnetic fractions. The chemical compositions of about 900 single
particles, selected by brightness criterion in backscattering electrons mode, have been
determined by means of SEM-EDX. It has been confirmed that many heavy metals and
other toxic trace elements (Ba, Sr, Pb, Tl, Cd, etc.) exist predominantly in separate
particles - alone, in typical combinations, or accompanied by Al and Si. The statistic
data for the association of trace elements with iron and aluminosilicate matter, generally
confirm the conclusions made on the base of the bulk analyses.

Keywords: Coal fly ash, trace elements, magnetic fraction, SEM-EDX.