Recovery of palladium from concentrated nitrate solutions with N,N 2-dimethyl-N,N 2-dioctyltetradecy lmalonamide as new extractant

Article abstract of DOI:10.13005/ojc/330530

The new unsymmetrical malonamide namely; N,N2-dimethyl-N,N 2-dioctyltetradecyl-malonamide (DMDOT DMA) was prepared and evaluated as agent for the extraction and separation of Pd (II) from nitrate media was studied. N,N 2-dimethyl-N,N 2-dioctylmalonamide (DMDO MA) was synthesized and used for comparison purpose. The effect of various parameters had been studied in details to explain the extraction properties of pd(II) by using DMDOTDMA in mixed diluents (75 vol.% n-dodecane-25 vol.% n-octanol) from nitrate media. The extraction equilibrium of Pd(II) with the investigated maloamides was reached within 10 minutes. Pd(II) showed remarkable extractability by DMDOTDMA and the maximum extraction percentage of Pd(II) is nearly reached at ~ 5 M HNO₃. Under similar extraction conditions Zn(II), Ni(II), Mn(II) Cu(II) and Pb(II) were found poorly extracted. The dominate extracted species of Pd(II) is Pd(NO₃)₂(MA)₂. The separation of Pd(II) from other studied metal ions was found to be effective in the range of nitric acid solution used. The stripping of Pd(II) was successfully carried out by single contact with 0.1M thiourea solution.

Full text of DOI:10.13005/ojc/330530

ISSN: 0970-020 X
CODEN: OJCHEG
2017, Vol. 33, No.(5):
Pg. 2377-2385
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Recovery of Palladium from Concentrated Nitrate Solutions
with N,N 2-Dimethyl-N,N 2-Dioctyltetradecy lmalonamide
as New Extractant
EMAD A. MOWAFY1,2,*, D. MOHAMED1
1 Faculty of science, Hail University, Hail, P.O. BOX 2240, Saudi Arabia.
2Hot Labs. Centre, Atomic Energy Authority, P. O. Box 13759, Cairo, Egypt.
*Corresponding author E-mail: mowafy 69@yahoo.com
http://dx.doi.org/10.13005/ojc/330530
(Received: April 01, 2017; Accepted: June 20, 2017)
ABSTRACT
The new unsymmetrical malonamide namely; N,N2-dimethyl-N,N 2-dioctyltetradecyl-
malonamide (DMDOT DMA) was prepared and evaluated as agent for the extraction and separation
of Pd (II) from nitrate media was studied. N,N 2-dimethyl-N,N 2-dioctylmalonamide (DMDO MA)
was synthesized and used for comparison purpose. The effect of various parameters had been
studied in details to explain the extraction properties of pd(II) by using DMDOTDMA in mixed
diluents (75 vol.% n-dodecane-25 vol.% n-octanol) from nitrate media. The extraction equilibrium
of Pd(II) with the investigated maloamides was reached within 10 minutes. Pd(II) showed remarkable
extractability by DMDOTDMA and the maximum extraction percentage of Pd(II) is nearly reached
at ~ 5 M HNO3. Under similar extraction conditions Zn(II), Ni(II), Mn(II) Cu(II) and Pb(II) were found
poorly extracted. The dominate extracted species of Pd(II) is Pd(NO3)2(MA)2. The separation of
Pd(II) from other studied metal ions was found to be effective in the range of nitric acid solution
used. The stripping of Pd(II) was successfully carried out by single contact with 0.1M
thiourea solution.
Key words: Novel extractant, Palladium, Base metal ions, Extraction/Separation, Nitric acid.
INTRODUCATION
of new secondary sources is mandatory for future
supply of palladium5,6. In fact, liquid-liquid extraction
is an important process in the recycling of the
platinum- group metals (PGMs), and thus there are
valuable efforts for the development of novel
effective extractant molecules2,7,8. Several reagents
have been used for the palladium extraction and
most of them were developed during the last three
decades and still in used today. Several classical
common and/or commercial extractants like; Cyphos®
IL-1019,dialkyl sulphoxides10,4-acylpyrazolone11,
2-hydroxy-4-sec-octanpyldiphenyl- ketoxime12,
Palladium is one of the most important of
the platinum group metals (PGMs) with high
corrosion resistance and catalytic properties. It has
different important applications in industrial fields
such as automobile catalytic converters1-4. In fact,
palladium is a very rare metal in the earth’s crust,
the world wide reserves being localized in very few
countries1,5. Since, the recycling of secondary
resources such as electronic scrap and catalytic
converters is very important. Therefore, the recycling

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Acorga® Cl x 50, 8-hydroxyquinoline, tributyl-
MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
To our knowledge, there is no available
phosphate (TBP), Aliquat 336, Cyanex 923, Cyanex work involving the use of DMDOTDMA in nitric acid
471X13,14 have been used for the extraction of pd(II) solution or hydrochloric acid solution for the
from hydrochloric acid solutions. In general, these extraction of Pd(II). No systematic investigation has
extractants have several problems like poor been reported on the extraction of Pd(II) with
solubility in aliphatic diluents, slow kinetics of DMDOTDMA from concentrated nitrate media. In a
extraction, chemical stability, and pH sensitivity, previous work1,2,23,28,29, we reported on the synthesis and
etc15-17. In view of these limitations, it becomes utilizations of different diamides, diglycolamides and
necessary to develop of new classes of ligands. cyanamides for the extraction and separation of selected
Many researchers have tried to improve and develop PGMs and base metal ions from various acid solutions.
novel extractants, which have high extraction
efficiency as well as selectivity for platinum group
In the present study, selective extraction of
metals (PGMs). During the last twenty years a Pd(II) with DMDOTDMA in mixed diluents (75 vol.%
several of amide bidentate ligands have been often n-dodecane-25 vol.% n-octanol) from nitric acid
proposed for the solvent extraction process, mainly medium in the presence of metal ions, such as
due to their faster kinetics, higher efficiency, Co(II), Zn(II),Ni(II), Mn(II) Cu(II) and Pb(II) was
selectivity, and complete incinerability18-22
.
carried out using binary and multicomponent
mixtures.The effective separation of Pd(II) from other
Very recently, a new class of ligands studied metal ions nitric acid solution was
namely; malonamides, have come to play an highlighted during this work. DMDOMA was studied
important role in this subject. Although malonamides for comparison purpose.
have been extensively investigated for the extraction
of lanthanide and actinide ions in nuclear
processing industry21-23, only a limited amount of
work reported involving the use of these ligands for
EXPERIMENTAL
DMDOMA and DMDOTDMA were
the extraction of Pd(II) from hydrochloric acid synthesized by using the method described below.
solutions3-8. No systematic studies have been The investigated metal ions aqueous solutions were
reported on the extraction of Pd(II) from prepared by dissolving the desired metal nitrate in
concentrated nitrate media. Therefore, the nitric acid solution. Different Pd(II) salt (palladium
development of new solvent extraction systems for chloride) and other aqueous medium (hydrochloric
the extraction and separation of Pd(II) from nitrate acid) were also used. The stock solutions of the
solutions is an important subject. The extraction investigated metal ions (Pd(II) Co(II), Zn(II), Ni(II),
properties of Pd(II) with malonamides from nitrate Mn(II) Cu(II) and Pb(II)) were diluted to obtain the
solutions have not yet been understood.
desired concentrations for working solutions. In this
study, all reagents of analytical grade purity and
Recently, a few malomamides derivatives have used without additional purification.
been planned for solvent extraction of PGMs from
hydrochloric acid solution3,24-27. Costa et al.,24 have used Synthesis of DMDOMA and DMDOTDMA
N,N’-dimethyl-N,N’-diccyclotetrade cylmaloamide
N, N 2-dimethyl-N,N2-dioctylmalonamide
(DMDCHTDMA) to effective extraction of platinum (DM DOMA) and N,N 2-dimethyl-N,N 2-dioctyl-
chloride solutions. Platinum, palladium and rhodium tetradecyl malonamide (DMDOTDMA) were
extraction from hydrochloric acid media has been synthesized and purified following the procedure
studied withN,N’-dimethyl-N,N’-diphenyltetrade that we described previously21,29
cylmalonamide(DMDPHTDMA)26. Poirot et al.5,
.
investigated the extraction behavior of N,N’–dimethyl,N,N’-
DMDOMA synthesized by adding a
dioctylhexylethoxymalonamide (DMDOHEMA)/ n-heptane stoichiometric quantity of malonyl dichloride with
system towards palladium from nitrate media. They N-metyloctylamine in presence of methylene
observed the formation of third phases due to the poor chloride and triethylamine as a basic medium. The
solubility of palladium complexes with DMDOHEMA/n- intermediate compound, malonyl dichloride, was
heptane system in different conditions.
prepared through the reaction of thionyl chloride

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MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
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,

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MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
100
mixture of 75 vol.% n-dodecane-25 vol.% n-octanol
was chosen as the diluent for the investigated
malonamidesextractants. For the both DMDOMA
and DMDOTDMA, no third phase formation was
obtained after extraction process; good and fast
phase separation was also observed for all the
extraction experiments system that was conducted.
80
60
40
20
0
Extraction equilibrium studies
DMDOTDMA
DMDOMA
The variation of percentage extraction
(%E) of palladium(II) with DMDOMA or
DMDOTDMA in 75 vol.% n-dodecane-25 vol.%
n-octanol as a function of shaking time was
investigated, Fig. 1. It was found that the extraction
of palladium from aqueous solution was obtained
in short period time ~ 10 minutes.
0
2
4
6
8
[HNO3], M
Fig. 2. Influence of nitric acid concentrations on
the extraction percentage (%E) of Pd(II) using
DMDOMA or DMDOTDMA in 75 vol.% n-dodecane -
25 vol.% n-octanol at 25 0.5oC
100
malonamides permits an easy back-extraction of
palladium(II) with lower HNO3 concentration
solution.
80
Figure. 3 showed the ability of DMDOMA
or DMDOTDMA to extract Pd(II) from HCl solution. It
can be seen that the extraction percentage of
palladium(II) with DMDOMA is slightly affected by
increasing HCl concentration from 0.5 to ~3 M, after
which a sharp increase was observed. The
extraction of Pd(II) with DMDOTDMA is decrease
with the hydrochloric acid concentration until ~2 M,
after which a sharp increase was obtained, as
shown in Figure.3.
60
40
20
0
DMDOTDMA
DMDOMA
0
10
20
30
40
50
Shaking time, min
Fig.1. Variation of the extraction percentage (%E) of
Pd(II) in 5 M HNO3 with 0.05 M DMDOMA or
100
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-
octanol as a function of the contact time at 25 0.5oC.
DMDOMA
DMDOTDMA
80
60
40
20
0
Influence of acid concentration on the extraction
of palladium
Figure. 2 shows the variation of the
percentage extraction of Pd(II) with DMDOMA or
DMDOTDMA as a function of HNO3 concentration.
It can be seen that the extraction of Pd(II) with
DMDOMA is dependent on the HNO3 concentration
until about 5 M, after which a slight decrease was
observed. For DMDOTDMA, the extraction of Pd(II)
increases with increase in the initial concentration
of HNO3 up to about 5 M.This followed by decrease
of extraction until the range of HNO3 concentration
studied, 7M.This may be attributed to the protonation
of the extractant at higher HNO3 concentrations.The
poor extraction of palladium in the very low
concentration region of HNO3 solution with these
0
2
4
6
8
[HCl], M
Fig.3: Influence of hydrochloric acid concentrations on
the extraction percentage (%E) of Pd(II) using
DMDOMA or DMDOTDMA in 75 vol.% n-dodecane-25
vol.% n-octanol at 25 0.5oC.
By comparison of the results obtained from
Fig. 2 and 3, it can be concluded that the extraction
of palladium increases when alkylation the central

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MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
carbon atom. The alkyl substituent in DMDOTDMA
was found to cause a noticeable increase in the
extraction ability for Pd(II) compared with the non-
central alkylated analogue (DMDOMA). This effect
was anticipated in our present work. So far, no
available work was reported on the influence of the
introduction of alkyl group on the central carbon
atom for the extraction of palladium(II) from nitric
acid solutions. In general, the extractability of the
malonamides can be attributed to both the
electroinductive influence as well as the steric
hindrance around the active binding site.Therefore,
the alkylation of central carbon atom in malonamide
could have play an important role for palladium
extraction from nitric acid or hydrochloric acid
solutions.
ionic strength. The concentration of nitrate ion was
adjusted by using NaNO3. Fig. 4 shows that the
relation between the distribution ratio of
palladium(II), Dpd, and nitrateion concentration is a
straight line relationship with slope equal to ~ 2 for
DMDOMA or DMDOTDMA. Therefore, two-nitrate
ion participates in complex formation.
Composition of Pd(II) extracted species
Attempts were done to know about the
nature of extracted complex species by studying
the distribution ratios of Pd(II) as a function of
DMDOMA or DMDOTDMA (MA) concentration.The
extracted species composition can be ascertained
from the relation between log DPd and log[MA] at 5
M HNO3, Fig.5.The graph of log DPd against log[MA]
in 75 vol.% n-dodecane - 25 vol.% n-octanol was
found to be liner, having a slope of 1.92 and 1.85
for DMDOMA and DMDOTDMA, respectively.
Hence, this result suggests that the composition
(metal:extractant) of the main extracted species of
pd(II) from 5 M HNO3 by DMDOMA and
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-
octanol are 1:2. The obtained results are in
agreement with those previously reported for the
extraction of Pd(II) using other diamides1,5.
In this concern, Mowafy and Aly29
investigated the extraction of iron(III) from HCl
solution with other malonamides. They found that
the alkylation of the central carbon atom
suppressed the extraction of iron from HCl medium.
However, further studies are required in this
important area using various structures of
malonamides to clarify the relationship between
structures and the extraction of Pd(II).
Pd2+(aq)+2 NO-3(aq)+2MA(o)=Pd(NO3)2(MA)2(o)
(3)
Effect of nitrate ion concentration on palladium(II)
extraction
Therefore, we can suggest that the
dominate extracted species of Pd(II) by DMDOMA
or DMDOTDMA (MA) in vol.% n-dodecane - 25
vol.% n-octanol at 5 M nitric acid are Pd(MA)2(NO3)2.
This can be represented by the following equilibrium .
In order to explain the role of nitrate ion in
the extraction reaction of Pd(II) with DMDOMA or
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-
octanol, the influence of nitrate ion on the distribution
ratio of palladium(II) ,DPd, was determined at fixed
100
100
DMDOTDMA
DMDOMA
10
10
1
1
DMDOTDMA
DMDOMA
0.1
0.02
0.1
0.2
[MA], M
0.8
1
8
Fig.5: Dependence of the distribution ratio
Pd(II) extraction in 5M HNO3 on DMDOMA or
DMDOTDMA concentrations in 75 vol.% n-
dodecane - 25 vol.% n-octanol at 25 0.5°C
[NO3-], M
Fig. 4. Dependence of palladium(II) extraction on
nitrate ion concentration with 0.05 M DMDOMA or
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-
octanol at 25 0.5 oC, [HNO3] = 1M.

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MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
where aq = aqueous phase, o = organic palladium(II) stripping in one single contact. The
phase, and MA denotes the malonamides recovered palladium(II) was found to be about
(DMDOMA or DMDOTDMA).
91% and 98% for DMDOMA and DMDOTDMA,
respectively.
Spectroscopic studies
To provide insight into the bonding of the Extraction of palladium(II) from binary solutions
extracted species of Pd(II) by DMDOMA and The separation of palladium(II) from
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n- different elements in binary mixtures was attempted
octanol, FT-IR spectra of the organic phase were using DMDOMA or DMDOTDMA in 75 vol.% n-
studied before and after metal ions extraction. dodecane - 25 vol.% n-octanol. Table 1 shows high
Comparison of the IR spectra of the organic phase extractability of pd(II) with almost negligible
loaded with palladium(II) and pure DMDOMA or extraction of Zn(II), Ni(II), Cu(II), Mn(II) and
DMDOTDMA have been carried out.
Pb(II).Thus, very high separation factor can be
obtained for pd(II) over these elements. The results
The absorption band at 1644 and 1645 showed that pd(II) was always extracted at nearly
cm–1 can be attributed to the carbonyl-stretching constant value in the presence of the above
mode in free DMDOMA and DMDOTDMA, elements for all the binary element mixtures
respectively. A new vibration bands at 1625 and systems, as shown in Table 1.
1622 cm-1 were observed in the IR spectra of the
extracted species.These two bands can be assigned
On the other hand, the extractability of Pd(II)
to DMDOMA and DMDOTDMA, respectively, with DMDOMA or DMDOTDMA in 75 vol.% n-
coordinated in the inner sphere, suggesting that dodecane - 25 vol.% n-octanol was not affected by
DMDOMA and DMDOTDMA are coordinated to the amount of elements in the binary mixtures used.
palladium through two carbonyl oxygen atoms. A
shift of 19 and 23 cm–1 in the carbonyl group Selectivity patterns
frequency for DMDOMA and DMDOTDMA,
Selectivity tests were carried out with
respectively, suggests stronger binding of these DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-
compounds with palladium, which is in agreement octanol, for separation of palladium(II) from
with the extraction results.
multicomponent mixtures. Table 2 shows the high
extraction of pd(II) from multicomponent mixtures of
The peaks at 1378 and 1370 cm–1 in the elements, viz. Zn(II),Ni(II), Mn(II) Cu(II) and Pb(II)
IR spectra of the extracted species suggest the with DMDOTDMA.
presence of free nitrate ions, which may exist in the
extracted molecules20,28.These results are consistent
On the other hand, the results indicated
with those reported previously by us and others for the superior extraction of palladium(II) over other
different diamides1,5,20,28
.
associated multi-component elements when
extracted with DMDOTDMA. The high selectivity of
DMDOTDMA is considered to have very interesting
Back-extraction
To strip Pd(II) from organic phase 0.05 M results in view of a practical application, considering
(DMDOMA or DMDOTDMA in 75 vol.% n-dodecane - that no significant contamination of the organic
25 vol.% n-octanol, water and different concentrations of phases occurs.
diluted nitric acid were tried. The back-extraction of
palladium(II) was found to be more difficult in all Reusing of DMDOTDMA
systems. On the other hand, water or dilute nitric
To evaluate the stability and feasibility of
acid are not sufficient as stripping agent for reusing DMDOTDMA in 75 vol.% n-dodecane - 25
Pd(II) from organic phase. A solutions of (0.01. vol.% n-octanol for the selective recovery of
0.05 and 0.1 M) thiourea in 0.5 M nitric acid palladium(II) from nitric acid for the adopted
was also used as the stripping agent for Pd(II) experimental conditions, experiments were also
from the organic phase. It was found that 0.01 carried out. Fig. 6 shows five successive extraction–
M thiourea was the most sufficient for stripping cycles done with 0.05M DMDOTDMA in

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MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
Table. 1: Binary separation of Palladium(II) from Zn(II),Ni(II), Mn(II) Cu(II) and Pb(II) by 0.05 M
DMDOMA or DMDOTDMA in vol.% n-dodecane - 25 vol.% n-octanol at 25 0.5oC; [HNO3] = 5 M
% Recovery of Pd(II) or M(II)
Composition
Molar
ratio
DMDOMA
Pd(II)
DMDOTDMA
Pd(II)
M(II)
M(II)
1:01
1:05
1:10
1:01
1:05
1:10
1:01
1:05
1:10
1:01
1:05
1:10
1:01
1:05
1:10
55.01
54.82
54.32
55.04
54.42
54.23
54.95
54.71
54.15
54.72
54.2
NE
<0.001
<0.01
<0.001
<0.01
<0.01
<0.001
<0.01
0.1
0.02
0.02
0.04
0.01
88.83
88.81
88.29
88.74
88.7
88.21
88.55
88.31
88.18
88.72
88.2
NE
NE
<0.001
NE
NE
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
~0.01
<0.002
0.003
0.02
Palladium(II) : Zinc(II)
Palladium(II) : Nickel(II)
Palladium(II) : Manganese(II)
Palladium(II) : Copper(II)
Palladium(II) : Lead(II)
54.16
54.92
54.48
54.13
88.06
88.92
88.68
88.31
0.03
0.04
Where 1:1 = 1.5x0.001M Pd(II): 1.5x0.001M M(II); 1: 5 = 1.5x0.001 M Pd(II): 7.5 x0.001M M(II); 1: 10=
1.5x0.001 M Pd(II):15x 0.001M M(II), M(II) = Zn(II),Ni(II), Mn(II) Cu(II) and Pb(II), NE= Not extraction.
Table. 2: Selective extraction of 0.001 M Pd(II) from multicomponent mixtures of 0.005 M of each
of Zn(II), Ni(II), Mn(II),Cu(II), Cu(II) and Pb(II) by 0.05 M DMDOTDMA in 75 vol.% n-dodecane - 25
vol.% n-octanol from different HNO3 concentrations
[HNO3],M
% Extraction
Pd
4.31
Zn
NE
Ni
NE
Mn
NE
Cu
ND
Pb
NE
0.5
1
3
5
7
13.90
69.43
92.21
81.60
NE
NE
NE
<0.001
<0.001
NE
ND
<0.001
<0.001
NE
ND
<0.001
~0.005
ND
<0.001
<0.001
<0.001
<0.001
~0.001
~0.003
where; NE= Not extraction and Nd= Not detection.
75 vol.% n-dodecane - 25 vol.% n-octanol followed
by striping with 0.1M thiourea in 0.5M nitric acid,
using fresh 5 M HNO3 aqueous solutions of 0.001
M Pd(II) extraction in each stage.
re-utilization is feasible. On the other hand, no
degradation of the DMDOTDMA in the used
experimental conditions seems to occur. In this
context, the results obtained in this study and that
reported by others3,5,18,25,26 reinforces the possibility
of successive reutilization of DMDOTDMA, which
can probably be extended to other unsymmetrical
malonamides derivatives, in view of their industrial
application.
It was found that the extraction percentage
of Pd(II) for five cyclic of extraction and stripping
remained almost constant at the original value of
DMDOTDMA. The obtained results clearly
demonstrate the stability of DMDOTDMA and that

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MOWAFY et al., Orient. J. Chem., Vol. 33(5), 2377-2385 (2017)
100
80
60
40
20
0
1
2
3
4
5
Extraction cycles
Fig. 6. Extraction of palladium(II) from 5 M HNO3 in five successive extraction- stripping cycles by
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-octanol
recovered from the organic phase by simple contact
with 0.1 M thiourea in 0.5 M nitric acid. The results
indicated that, the extractability of Pd(II) with
DMDOTDMA in 75 vol.% n-dodecane - 25 vol.% n-
octanol was not affected by the presence of
elements in binary or multicomponent mixtures.
Thus, this extractant (DMDOTDMA) could be a
potential candidate for the selective extraction and
separation of Pd(II) from other metal ions present in
the waste nitrate liquors and also as alternative to
commercial organophosphorousextractants.
CONCLUSIONS
The present study offer an insight about a
new solvent extraction application for
unsymmetrical malonamide derivative namely;
N, N’–dimethyl-N, N’– diotcyltetradecylmalonamide
(DMDOTDMA) as a promising extractant for
palladium(II). DMDOMA was investigated for
comparison purpose.The extractability of Pd(II) with
DMDOTDMA is higher than that of DMDOMA. The
extraction equilibrium was reached within 10
minutes. The maximum extraction percentage of
Pd(II) with DMDOTDMA is nearly reached at about
5 M HNO3.The composition (metal ion: extractant)
of the dominate extracted species of Pd(II) from 5
M HNO3 by DMDOMA or DMDOTDMA in 75 vol.%
n-dodecane-25 vol.% n-octanol are 1:2.
Palladium(II) is found to be nearly quantitatively
ACKNOWLEDGEMENTS
The financial support kindly provided by
Research Deanship, University of Hail, Saudi Arabia
(project#0150115) is gratefully acknowledged.
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