Environmental Engineering Reference
In-Depth Information
Among various methods of the sequential extraction, the Tessier [1, 2],
Rudd [3], BCR [4-7], Gatehouse [8], Kersten and Förstner [9], Psenner [10]
and Sposito [11] procedures are most often used for solid samples, described
from 3-rd to 6-th of metal fractions. The Cd distribution within fractions
differs among methods. Therefore, we have attempted to compare those
methods in order to establish optimal sequential method for maximum
extractability and reproducibility.
2.
C
OAL
F
LY
A
SH
P
REPARATION
AND
C
ONDITIONS OF
R
ESEARCHES
Surface coal fly ash (0-15 cm) growth from the Rzeszów Heat and Power
Plant (Poland) was used. The samples were collected according to BN-
81/0623-01 norm. A 0.5 kg subsample was obtained from the air-dried coal fly
ash samples (5 kg), Cd ashes in an agate mortar and a grain diameter
subsample of 10.00 g mass (0.25 mm) was utilized for chemical extraction.
3.
S
EQUENTIAL
E
XTRACTION
Coal fly ash was evaluated with a 30 ml portioning of extractant using
sequential extraction four replicates (n = 4). The sequential extraction of Cd
from coal fly ash was performed in order to determine of 3 (BCR method), 5
(Tessiera, Gatehousea, Psennera and Sposito methods) or 6 (Kerstena and
Förstnera method) fractions of Cd - Table 1. This was done for fractions
defined as: (1) exchangeable and soluble fraction including Cd forms soluble
in water, (2) acids soluble fraction (carbonate and adsorbed), (3) oxide
fraction, (4) fraction bound to sulfide and organic matter and (5) so called
residue including the most stable Cd forms. Metal included in this fraction is
chemical by passive and biologically inactive. There was investigated: the
sequential extraction time (t
extn
= 0.5 - 24 h), volume of the eluent (V
eluate
= 30
ml), temperature of carrying out the sequential extraction process (t = 20 -
96°C) and mass of fly ash (m = 10.00 g).
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