Pb extraction ability of EDTA
The extraction of Pb by the two different
concentrations of EDTA is presented in Table 3.
EDTA can extract a high level of the total available
Pb from the mine tailings in a dose dependent
manner. In general, EDTA showed a higher and more
stable extraction ability than that of the simulated
leachate. However, the leachates with a low pH
(initial and acidogenesis phase) showed a comparably
or higher degree of Pb extraction.
Table 3. The amount of extracted Pb and the proportion (%) of the total available Pb that was extracted
from the mine tailings by EDTA.
EDTA Pb extracted % Extracted
(ppm)
0.04 M 36.55 ± 2.07 61.09 ± 3.46
0.1 M 45.11 ± 3.26 75.4 ± 5.45
EDTA has a strong complexing ability and
forms soluble metal complexes, and so exhibits a
higher ability to leach metals in comparison with that
of HA. Although HA and FA also form rather strong
complexes with metals, their complex metal salts are
usually only sparingly soluble in water, which affects
their leaching ability.(12)
Fractions of heavy metals
The sequential extraction results of the Akra
mine tailings are summarized in Table 4. The release
of metals from the contaminated matrix depends not
only on the extraction conditions, such as the pH,
reagent concentration etc., but also on the modes of
metal retention within the soil. Consequently, metal
reactivity and behavior towards the extracting solution
also depend on the nature of the metal fixation on the
matrix particles, which can be operationally measured
by application of sequential extraction procedures.
Weakly sorbed fractions, such as exchangeable and
carbonate can be readily extracted, but an effective
extraction of strongly sorbed metals in oxide and
residual fractions was not always guaranteed within
different types of matrix and contamination sources.
Pb extraction ability of EDTAThe extraction of Pb by the two differentconcentrations of EDTA is presented in Table 3.EDTA can extract a high level of the total availablePb from the mine tailings in a dose dependentmanner. In general, EDTA showed a higher and morestable extraction ability than that of the simulatedleachate. However, the leachates with a low pH(initial and acidogenesis phase) showed a comparablyor higher degree of Pb extraction.Table 3. The amount of extracted Pb and the proportion (%) of the total available Pb that was extractedfrom the mine tailings by EDTA.EDTA Pb extracted % Extracted(ppm)0.04 M 36.55 ± 2.07 61.09 ± 3.460.1 M 45.11 ± 3.26 75.4 ± 5.45EDTA has a strong complexing ability andforms soluble metal complexes, and so exhibits ahigher ability to leach metals in comparison with thatof HA. Although HA and FA also form rather strongcomplexes with metals, their complex metal salts areusually only sparingly soluble in water, which affectstheir leaching ability.(12)Fractions of heavy metalsThe sequential extraction results of the Akramine tailings are summarized in Table 4. The releaseof metals from the contaminated matrix depends notonly on the extraction conditions, such as the pH,reagent concentration etc., but also on the modes ofmetal retention within the soil. Consequently, metalreactivity and behavior towards the extracting solutionalso depend on the nature of the metal fixation on thematrix particles, which can be operationally measuredby application of sequential extraction procedures.Weakly sorbed fractions, such as exchangeable andcarbonate can be readily extracted, but an effectiveextraction of strongly sorbed metals in oxide andresidual fractions was not always guaranteed withindifferent types of matrix and contamination sources.
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