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concentration from the initial aqueous concentration
of the investigated metal ions. The concentrations
of Pd(II) Co(II), Zn(II),Ni(II), Mn(II) Cu(II) and Pb(II)
in the aqueous phases were determined before
and after extraction process by using ICP-AES
8100, Shimadzu and atomic absorption
spectrometry (AAS, Perkin– Elmer-400).The relative
error values associated with all measurements
were found to be about 2.5%. The extracted
species of Pd(II) in the organic phase were studied
by using FT-IR (Thermo Scientific Nicolet-6700),
with the spectra recorded in the range
400–4000 cm–1.
and malonic acid, with suffering immediately a
subsequent reaction with N-methyloctylamine at
about 5oC. The reaction was refluxed for about 5
hours. After purification and evaporation of the
diluents, the obtained crude product was distilled
under reduced pressure to get pure product. The
purity of the prepared DMDOMA was found to be
~99%.DMDOTDMA has been synthesized by taking
DMDOMA as a starting material. DMDOTDMA was
obtained by alkylation of the central carbon atom of
DMDOMA dissolved in toluene by the reaction with
sodium hydride, and finally with bromotetradecane.
The reaction mixture was refluxed for
about 30 hours. After completion of the reaction,
the crude product was separated and the diluent
was evaporated.The yield of the crude product was
found to be 92%. The two synthesized extractants
were characterized by using different analytical tools
like IR, elemental analysis, and H-NMR. The purity
of DMDOTDMA was found to be more than 98%.
Back extraction studies
For this study, the organic phase of
DMDOMA or DMDOTDMA was loaded with 1.5 ×
10−3 M Pd(II) in 5 M HNO3. Equal volumes of the
loaded organic phase and aqueous phase
containing the stripant agent were equilibrated in
separator funnel using a mechanical shaker for
30 minutes.
General extraction procedure
Re-utilization of DMDOTDMA
In order to prevent the co-extraction of
To gain insight on the stability or
regeneration characteristics and feasibility of
reusability of this extractant, an organic phase
containing DMDOTDMA in 75 vol.% n-dodecane-
25 vol.% n-octanol was subjected to five successive
extraction-stripping contacts with fresh solutions of
Pd(II) in 5 M HNO3 and with 0.1M thiourea in 0.5M
nitric acid, respectively.
HNO3, which may have occurred during the
extraction of metal ions, the solvents (organic
phases) were preequilibrated with the same nitric
acid concentrations as the aqueous phase studied.
Extraction process were carried out by shaking
equal volumes of aqueous and organic phases in
a thermostated water bath adjusted to the desired
temperature (25 1oC) for about 30 minutes. After
phase separation by centrifugation, known aliquots
of the aqueous phase was sampled for analysis.
The distribution ratio (DM) was determined as the
ratio between the concentration of metal ion in the
organic and aqueous phases,
RESULTS AND DISCUSSION
Certain preliminary experiments were
performed in order to explain the extraction
behavior of palladium(II) by DMDOMA and
DMDOTDMA in the absence of other the other
investigated metal ions. The optimum extraction
conditions of palladium(II) were established by
various the experimental parameters, such as HNO3
concentration, DMDOTDMA concentration, and the
extraction equilibration time. The formation of solid
third phases were obtained during the extraction of
palladium by using DMDOHEMA/ n-heptane/ nitric
acid system5.
DM = [M]org / [M]aq
(1)
Percentage extraction of element (%E) was
determined by using the following equation:
%E = DM / DM +1 x 100
(2)
whereM is the metal ion (Pd(II) Co(II),
Zn(II), Ni(II), Mn(II) Cu(II) or Pb(II)). All the extraction
experiments were conducted in triplicate. Normally
1.5 × 10−3 M of the desired metal nitrate at various
nitric acid concentrations was used as feed solution.
The concentration of the element in the organic
phase was determined by subtracting the aqueous
In general, to avoid the third phase
formation, a long-chain alcohol a polar reagent can
be added into the organic solution. In this study,