Vol.1, No.3, 166-175 (2009)
Copyright © 2009 Openly accessible at http://www.scirp.org/journal/NS/
Natural Science
Ion exchange recovery of palladium (II) from nitrate
weak acidic solutions
Olga N. Kononova1*, Nataliya G. Goryaeva1, Olga V. Dychko1
1Department of Chemistry, Siberian Federal University, Krasnoyarsk, Russian Federation; cm2@bk.ru
Received 12 August 2009; revised 2 September 2009; accepted 4 September 2009.
Sorption recovery of palladium (II) from nitrate
weak acidic model solutions and solutions of
spent catalysts on some ion exchangers with
different physical and chemical structure has
been investigated. The palladium concentration
in contacting solutions was 5.0 · 10-5 1.0 · 10-3
mol/L at nitric acid and potassium nitrate con-
centrations 0.01 and 1.0 mol/L, respectively. It
was shown that anion exchangers AV-17-8 as
well as Purolite S 985 and A 500 possess the
best sorption and kinetic properties. These
sorbents can be recommended for selective
recovery of palladium from solutions of spent
Keywords: Palladium; Ion Exchange; Anion
Exchangers; Nitrate Solutions
As natural deposits of precious metals are being depleted,
the technologies for precious metals recovery from dif-
ferent secondary raw materials are becoming more im-
portant. The hydrometallurgical methods are success-
fully used for these purposes [1-3]. One of the most
promising methods for recovery of platinum group met-
als (in particular, of palladium) is sorption, characterized
by high efficiency and selectivity [1,3-5]. However, the
majority of investigations devoted to the sorption recov-
ery of palladium, deal with chloride or sulfate solutions
[6-14], and the studies of sorption of noble metals from
nitric acidic media are rather limited [1,15-20]. At the
same time, the recovery of palladium from some kinds
of secondary sources (e.g. electronic scrap and ex-
hausted nuclear fuel) requires its isolation from nitric
acidic and nitrate solutions [1,21].
Our previous investigations were focused on sorption
recovery of palladium from chloride model solutions
and solutions of spent catalysts by various ion ex-
changers and carbon adsorbents [9,22,23]. Apart from
this, we started the research of sorption concentration of
palladium on carbon adsorbents during its recovery from
model nitric acidic solutions [24]. We have revealed high
sorption abilities of some carbon adsorbents to palla-
dium (II) ions depending on initial concentrations of
nitric acid andPd .
The present paper is focused on sorption recovery of
palladium from nitrate weak acidic solutions (model and
of spent catalysts) by some ion exchangers with different
physical and chemical structure.
2.1. Characteristics of Ion Echangers
Some ion exchangers from various manufacturers were
taken for investigation. These sorbents possess different
physical and chemical structure. Their physical-chemical
characteristics are summarized in Table 1. It should be
noted that ion exchangers produced by Purolite Com-
pany for the first time were used for recovery of plati-
num group metals. However, these ion exchangers were
successfully applied in our previous investigations on
sorption recovery of gold and silver [25].
Before sorption all the ion exchangers were prepared
according to the standard procedures and then loaded
with 1 M solution, in order to convert them to
chloride form (anion exchangers) or to
,Na Cl
(amphoteric resin).
The acid-base properties of ion exchangers investi-
gated were studied by a potentiometric titration with the
glass electrode. Based on the experimental data obtained,
we have calculated the average apparent ionization con-
stants of functional groups of ion exchangers [5]. The
calculation procedure is described below and the values
of constants are presented in Table 1.
2.2. Preparation of Palladium Ntrate
The initial model stock solution of palladium was pre-
pared according to works [26,27]. The accurately
O. N. Kononova et al. / Natural Science 1 (2009) 166-175
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Table 1. Physical-chemical properties of ion exchangers investigated.
capacity to Cl-
ion (mmol/g)
K Manufacturer
A 500
Strong base
anion ex-
St – DVB MP QAB 1.2 15 2.31 Purolite, UK
A 530
Strong base
anion ex-
St – DVB MP QAB 0.60 12 1.15 Purolite, UK
S 985
Weak base
anion ex-
Ac – DVB MP PA 2.3 42 0.74 Purolite, UK
Strong base
anion ex-
St – DVB G QAB 3.6 23 0.99 TOKEM, Russia
Weak base
anion ex-
VP – DVB MP TAG, PN 5.3 10 1.78 Chercassy,
ion exchanger VP – DVB P PAG, TAG,
(2.6 to Na+) 22
St-styrene; DVB-divinylbenzene; Ac-acryl; VP-vinylpyridine; MP-macroporous; G-gel; P-porous; QAB-quaternary ammonium base;
PA-polyamine; TAG-tertiary aminogroups; PAG-phosphorylic acid groups; PN-pyridine nitrogen.
weighed metallic palladium (0.50 g) was dissolved under
heating in concentrated 3 (analytical grade) ac-
cording to the following reaction:
383()2 4PdHNOPdNONOH O 
The palladium concentration in initial stock solution
was 0.01 mol/L. The working solutions with palladium
concentrations 5.0 · 10-5 – 1.0 · 10-3 mol/L were prepared
from the stock solution. The nitric acid concentration in
these solutions was 0.01 mol/L and the constant ionic
strengths was made by means of 1.0 M 3
NO . Before
the preparation of working solutions, the palladium con-
centration in initial stock solution was controlled by gra-
vimetric method with dimethylglyoxime as a reagent
[26]. The palladium (II) concentration in working solu-
tions and in solutions after sorption was determined by
spectrophotometrical with nitroso-R-salt [27,28].
We chose the range of palladium and nitric acid con-
centrations for our experiment, aiming to make it closer
to real industrial conditions.
Apart from the model nitrate solutions of palladium,
we also used the solutions of spent palladium-containing
catalysts. These solutions were prepared as follows:
the catalyst quantities (0.20 g) were dissolved under
heating in concentrated nitric acid, similar to prepara-
tion of model solution. The working solutions of spent
catalysts with palladium concentrations 5.0 10-5–5.0
10-4 mol/L were prepared from the initial solution.
Before dissolution of spent catalysts samples in nitric
acid, we have determined their average composition by
X-ray-fluorescence method. The results are repre-
sented in Table 2.
2.3. Batch Studies
The sorption of palladium was studied under batch ex-
perimental conditions: resin mass–0.20 g, volume of
contacting solution–20.0 mL, stirring in a thermostat at
(20 ± 1) ºС. The equilibrium time determined by special
tests was about 24 h.
Sorption ability of ion exchangers investigated was
estimated by means of the recovery degree () and
distribution coefficient (, which were calcu-
lated from:
,/)DL g
where and are the initial and equilibrium mo-
lar concentrations of palladium solution; is the
exchange capacity of the resin for palladium, mmol/g.
The kinetics of sorption of palladium from weak
acidic nitrate solutions on ion exchangers investigated
was studied by the “limited bath” method [29,30] and
diffusion coefficients of (
()Pd II2
cms ) were
calculated. The kinetic experiment procedure is de-
scribed below.
The desorption of palladium was carried out by 1 M
thiourea solution in 0.01 M or in 1 M .
The mechanism of palladium sorption recovery by ion
exchangers from nitrate systems was studied by means
of IR-spectroscopy and diffuse reflectance spectroscopy.
The preparation procedures of samples are present be
O. N. Kononova et al. / Natural Science 1 (2009) 166-175
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Table 2. Average composition of initial sample of palla-
dium-containing spent catalyst.
All the results were statistically processed by standard
methods [31,32]. The average experimental error for 3-4
parallel runs was below 6 %.
2.4. Calculation of Apparent Constants of
Acid-Base Ionization of Ion
The constants values were calculated using potentiomet-
ric titration data. For each point of the titration curve, the
functional groups content was determined and the ap-
parent ionization degree (
) of the resin was calculated:
where []
is the equilibrium concentration of
ions in the ion exchanger phase, mmol/mL; is the
initial concentration of the titrant solution (0.1 M
Cl ).
Then a curve was plotted on the coordinates
(log )
pH f
and at 0.5
, the apparent
acid-base ionization constants of functional groups of
the ion exchangers (a
pK ) were calculated from Hen-
derson’s equation:
log( )
pKpH m
 (5)
where is the slope angle tangent of the curve. m
2.5. “Limited Bath” Method for Sorption
Kinetics of Palladium (Ii)
The quantities of preswollen resin (0.10 g) were stirred
with 25.0 mL of palladium nitrate solutions at (20 ± 1)ºС
over a period of 30 s to 24 h. The suspensions were in-
tensively stirred (more than 800 rev/min). After a certain
time period, the resins and solutions were quickly sepa-
rated and the concentration of was determined
in the solutions. Then the exchange degree (
()Pd II
calculated from
where and
are the amounts (in mmol) of the
palladium sorbed to the time (s) and to the equilib-
rium time.
According to the Boyd’s method [29,30,33], the ki-
netic coefficient was calculated from
The data obtained were plotted as a function()Btf t
If the process is controlled by gel diffusion [29,30,33],
this function should be linear. After that, the diffusion
coefficients (
D) were calculated according to the equa-
is the radius of the resin grain (cm).
The half-exchange time of the kinetic process () was
calculated as follows:
1/ 2
1/2 2
2.6. Preparation of Sample for
IR–spectra of ion exchangers investigated were recorded
by means of FT-IR- spectrometer Vector 22 (Bruker).
Before that, ion exchanger samples were dried during 4
h at 40ºС in convection drier. Then the samples were
held in a vacuum-desiccator over freshly calcinated cal-
cium chloride. The specimens were ground in a me-
chanical mill without air access and after that were
pressed with spectrally pure
Br to discs. The quanti-
ties of resin samples and potassium bromide were con-
stant (200 mg each of resin and
Br ).
2.7. Preparation of Samples for Diffuse
Reflectance Spectroscopy
The diffuse reflectance spectra were recorded by means
of spectrometer PULSAR (Russia). The resin quantities
(0.20 g) were preliminary saturated with palladium (II)
ions with concentration 5.0· 10-4 mol/L during 24 h. Af-
ter that, the resins were filtered and wet samples were
placed into cell. Then the diffuse reflectance spectra
Component Content (%)
Palladium 0.79
Sodium 0.41
Aluminum oxide ~ 84
Silicon 0.03
Sulfur 0.12
Chlorine 0.80
Iron 0.19
Nickel < 0.02
Zinc < 0.02
Gallium < 0.02
O. N. Kononova et al. / Natural Science 1 (2009) 166-175
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were recorded.
3.1. Ionic State of Palladium in Contacting
It is known from [26,27,34,35] that the ionic state of
platinum group metals in solutions depends on acidity
of contacting solution as well as on concentration of
chloride or nitrate ions (for chloride and nitrate systems,
respectively). It is determined at present that 32
()Pd NO
is formed after the dissolution of metallic palla-
dium in concentrated nitric acid according to reaction (1)
and subsequent diluting of the solution obtained [36,37].
It is also determined [38] that the hydrated palladium (II)
ions and their mononitrate complexes
[ are present in solution at mol/L.
With the increase in nitric acid con- centration, the
amount of different nitrate cationic and anionic com-
plexes as well as of neutral species is growing [19,20]:
[( )]PdH O
23 3
) ]
dHONO , ,
22 32
[()( )]PdHONO233
)()]O NO[(PdH
. When the nitric acid concentration dimin-
ishes from 1 mol/L to 0.01 – 0.001 mol/L, the formation
of hydroxocomplexes with the general formula
is observed in solution [36,38]. That
occurs due to the so-called “aging” of solutions, which
takes place in weak acidic media, and especially after
keeping of such solutions for longer than 24 h. This
phenomenon is typical for solutions of platinum group
metals [27,34,38]. At mol/L, the solution
does not contain aquatic ions and its nitrate
complexes, and only hydroxocomplexes of different
composition exist in this media [38].
(2 )
[(Pd NO
[(Pd OH
()Pd II
The above discussion concerns only the ()Pd II3
systems, i.e. without adding background electrolytes.
Our previous investigation [24] was focused on palla-
dium (II) recovery from strong acidic solutions
was 1, 2 and 5 mol/L) in the system sorbent
dIIHNO. However, the sorption of palladium
from weak acidic solutions in the presence of salt back-
ground is also of practical interest, since such media are
formed in number of technological schemes [1,3].
Therefore, we have also studied the following system:
ion exchanger –()
dII 0.01 M 1 M
NO . It
should be noted that data on ionic state of palladium in
such systems are not available at present and this prob-
lem requires a special study. However, we have at-
tempted to make some conclusions on this matter in the
present paper, as discussed below.
Before studying the palladium sorption recovery, we
have obtained electron absorption spectra of freshly
prepared palladium solutions in 1 M 3
NO and at
pH=2, presented in Figure 1. It should be noted that
palladium sorption was carried out from freshly prepared
solutions to minimize their “aging”. It can be seen from
Figure 1 that absorption maximum in spectrum 1 (Pd
1 M
NO is located at 390 nm and indicates the
presence of complexes [( as a pre-
vailing form [36-38]. However, the absorption maxima
in spectra 2 and 3 ( in 0.01 M in the pres-
ence of 1 M
NO ) are also located at 390 nm and
show presence of the same ()
dII complexes in solu-
tion. Probably, the formation of anionic nitrate com-
plexes of palla dium (II) is promoted by the high con-
centration of nitrate ions, despite the weak acidity of
solution (pH=2). Later, during our experiments on
sorption, we have not observed any precipita-
tion of metal specimens on a surface of resins, unlike
authors [20]. It means that there was no hydrolysis in the
investigated systems under chosen conditions (fresh
prepared weak acidic solutions and presence of 1 M
). However, the precipitation effect was clearly
observed when palladium sorption was carried out from
solutions kept more than 8 h or from freshly prepared
solutions with pH=4. This proves the formation of dif-
ferent hydroxocomplexes. Therefore, we can conclude
from the absorption spectra that complexes
prevail in contacting freshly prepared solutions
under the chosen conditions.
3.2. Sorption Recovery of Palladium from
Model Nitrate Solutions
The sorption properties of ion exchangers investigated to
palladium (II) are presented in Table 3. It can be seen
from these data that in general all the resins reveal high
sorption ability, since they recover on the level ~70
Figure 1. Absorption spectra of palladium (II) working solutions
in 1 M (1) and in the system 0.01 M + 1.0 M
(2,3), mol/L (1,2) and
mol/L (3).
KNO -3
(Pd)= 2.0×10-3
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% (ANKF-5) and more than 90 % (Purolite S 985). The
studied sorbents can be arranged by their affinity grade
to palladium in the following order: Purolite S 985 >
Purolite A 530 > Purolite A 500 ~ AV-17-8 > AN-251 >
It is interesting to note, that all ion exchangers except
Purolite S 985 possess approximately equal affinity to
, despite of their different physical and chemical
structure. The nature of functional groups of the ion ex-
changers investigated allows to form the following types
of chemical bonds during their contact with noble metal
ions [5,6,19,20]:
ionic, i.e. ion – ion interaction, which takes place
on strong basic anion exchangers;
coordination, forming as a result of conservation of
electron pair between ligand (electron-pair donor),
which is the nitrogen atom of resin functional
groups, and the metal (electron-pair acceptor); this
bond takes place on weak basic anion exchangers.
The fact that amphoteric ion exchanger ANKF-5 re-
covers ions from nitrate solutions on the same
level (and even less) than anion exchanger AN-251 (both
resins were synthesized on the basis of vinylpyridine),
unambiguously points out to ionic state of in
contacting solution. If cationic hydroxocomplexes or
hydrated ions were present in this solu-
tion, the degree of palladium (II) recovery would proba-
bly be above 69% due to the activity of phosphorylic
acid and pyridine nitrogen functional groups in weak
acidic media.
()Pd II
()Pd II
[( )]PdHO
Moreover, it is noteworthy that strong basic anion ex-
changers recover to a greater extent (Table 3),
although the additional complex formation of palladium
ions with functional groups of quaternary ammonium
base is impossible (unlike the weak basic anion ex-
changers). Therefore, we consider highly probable that
anionic palladium complexes
()Pd II
[()()]PdH ONO
exist in the systems investigated in the
presence of 1 M
[( )]Pd NO
NO .
Table 3. Sorption of palladium from nitrate model solutions
on ion exchangers investigated Initial concentration
is 5.0 · 10-4 mol/L, pH = 2.
D (%)R Trade
name log D (%)
Purolite A
500 2.79 86 AV-17-8 2.77 85
Purolite A
530 2.87 88 AN-251 2.54 78
Purolite S
985 3.23 94 ANKF-5 2.34 69
As for sorption recovery of palladium (II) on anion
exchanger Purolite S 985, which reaches 94%, there is
little doubt that this recovery proceeds according not
only to anion exchange, but also to complexation proc-
ess, taking into account the presence of polyamine
groups in the structure of this sorbent.
3.3. FT-IR Study of Palladium Sorption
To study the palladium recovery from nitrate solutions in
more detail, we have carried out IR-spectroscopic inves-
tigation. We have obtained IR-spectra of anion exchang-
ers Purolite S 985, AV-17-8 and AN-251, the fragments
of which are shown in Figure 2. IR-spectra of initial
samples of these resins in chloride form are presented
for comparison.
It can be seen from IR-spectra that appearance of in-
tensive peaks in the range of 1400–1300 cm-1 (1384,
1352 and 1300 cm-1) is observed for all the ion exchang-
ers, independently of their basicity and structure of
polymeric matrix. These peaks are assigned to vibrations
of N–O bonds of nitrate ion: peak at 1384 cm-1 corre-
sponds with stretching vibrations of free 3
whereas peaks at 1352 and 1300 cm-1 can be assigned to
the N–O stretching vibrations in palladium complex [39].
It should be noted that the greatest intensity of these
peaks is revealed in IR-spectrum of strong basic anion
exchanger AV-17-8 (Figure 2, spectrum 5). It was men-
tioned above that the functional groups of this resin
(quaternary ammonium base) cannot react with palla-
dium through additional coordination. Therefore, it can
be concluded that the anion exchange takes place in this
233 233
[()( )][()( )]RClPdHONOR PdHONOCl
 
Since the similar but less intensive peaks are re-
vealed in IR-spectra of weak basic anion exchangers
Purolite S 985 and AN-251 (Figure 2, spectra 1 and 3),
it can be concluded that the reaction (10) is to some ex-
tent attributable to these resins too.
However, in case of recovery on weak ba-
sic anion exchanger AN-251, the redistribution of the
intensities in the range of 1700 – 1400 cm-1, corre-
sponding to symmetric and asymmetric stretching vi-
brations of pyridine ring, is observed in IR-spectrum
of this resin (Figure 2, spectrum 3). The absorption
bands at 1600, 1558, 1494 and 1417 cm-1 are assigned
to С = С and C = N stretching in pyridine ring
[20,39,40]. The reduction of peak intensity at 1510
cm-1 and depression of that one at 1492 cm-1 points out
to the probable complexation between palladium and
pyridine nitrogen [5,40].
()Pd II
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Figure 2. IR-spectra fragments of anion ex-
changer samples Purolite S 985 (1), AN-251 (3),
AV-17-8 (5) saturated from nitrate solutions of
palladium (II) mol/ L;
mol/L; mol/L
Spectra (2), (4) and (6) correspond respectively to
initial samples of Purolite S 985, AN-251 and
AV-17-8 in chloride form.
C(Pd)= 5.0×10
C (HNO)= 0.01.0
Figure 3. IR-spectra fragments of samples of anion
exchanger Purolite S 985 saturated from nitrate pal-
ladium (II) solution (1) and of initial resin in chlo-
ride form (2) mol/L;
mol/L; mol/L.
C (Pd)= 5.0×10
C(KNO)= 1.0
C (HNO)= 0.01
The IR-spectrum of weak basic anion exchanger Puro-
lite S 985 saturated with palladium shows the greatest
changes compared to the spectrum of its initial sample in
chloride form (Figure 2, spectra 1 and 2). The peaks at
1384, 1352 and 1304 cm-1, which correspond to nitrate
ion and are characteristic for anion exchange in accor-
dance with reaction (10), also appear in the spectrum 1.
In the range of stretching vibrations of aminogroups
(1550 – 1530 cm-1), the reduction of peak intensities
takes place, and in the range of 1450–1420 cm-1, the
peak disappears, corresponding to vibrations of methyl-
ene groups [5,40]. Such changes indicate that complexa-
tion processes in the sorbent’s phase take place [5].
In case of Purolite S 985, special attention should be
paid to the short-wavelength fragments of IR-spectra,
shown in Figure 3. It contains an increase in peak inten-
sity at 771 cm-1 and appearance of bands at 822 and 711
cm-1. These changes correspond to deformation vibra-
tions of bond, which is characteristic for co-
ordination compounds [5,40,41].
Therefore, it can be concluded that palladium sorption
from nitrate weak acidic solutions on weak basic anion
exchangers proceeds not only according to anion ex-
change mechanism (reaction (10)), but also is accompa-
nied by coordination:
[][ ]
where 23
3.4. Sorption Isotherm Studies
The isotherms of palladium sorption from nitrate solu-
tions on anion exchangers Purolite S 985, A 500 and A
530 are represented in Figure 4. It is known [29,33] that
the shape of these curves is an evidence of sorption se-
lectivity. It can be seen from Figure 4 that all the iso-
therms are convex curves and they are classified to
Langmuir isotherms, which are described as follows:
eq eq
eq eq
 (12)
where EC
is the maximal equilibrium exchange ca-
pacity of the resin to palladium, mmol/g; eq
is the
apparent constant of ion exchange equilibrium, L/mmol.
By transforming the Eq. (12) to the linear form, we
calculated ion exchange equilibrium constants and de-
termination coefficients (r2), which are presented in Ta-
ble 4. It can be seen from these data that coefficients r2
are close to 1. This fact supports our hypothesis about
Langmuir-type isotherms for palladium sorption.
3.5. Kinetics Studies
The successful application of ion exchangers in indus-
trial conditions requires their good kinetic properties.
That is why the research on kinetics of ()Pd II sorp-
tion on Purolite ion exchangers in the investigated sys-
tems is both of theoretical and practical interest. The
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Figure 4. Isotherms of palladium sorption on anion exchangers
Purolite A 530 (1), A 500 (2) and S 985 (3)
mol/L; mol/L.
C (HNO)= 0.01
C(KNO)= 1.0
Table 4. Apparent constants of ion exchange equilibrium
) and determination coefficients (r2) during recovery
of palladium (II) from nitrate model solutions.
Trade name eq
Purolite A 500 135 0.894
Purolite A 530 34.4 0.991
Purolite S 985 588 0.975
Figure 5. Kinetic dependencies of function on time for
anion exchangers Purolite A 530 (1), S 985 (2) and A 500 (3).
Bt t
Table 5. Kinetic parameters of palladium (II) sorption
from nitrate model solutions mol/L;
C (Pd)= 5.0×10
C (HNO)= 0.01 mol/L; mol/L.
C(KNO)= 1.0
Trade name
1/ 2
Purolite A 500 11.70 8.26 1558
Purolite A 530 2.06 0.58 23164
Purolite S 985 9.26 5.94 2390
calculated main kinetic parameters are summarized in
Table 5 and Figure 5 contains the dependencies
. ()Btf t
It can be seen from Figure 5 that dependen-
cies ()Btf t
are the straight lines for all the resins
Purolite investigated and comply with criterion of gel
kinetics, i.e. the whole sorption process is controlled by
interdiffusion of the ions exchanged in a resin grain
[29,30,33]. As for the main kinetic parameters, it should
be noted that average rate of ion exchange process is
higher on strong basic anion exchanger Purolite A 500
(Table 5). Consequently, the value of average diffusion
coefficient for this resin exceeds such values for the
other sorbents and the half-exchange time is lesser. A
comparison of kinetic process between anion exchangers
Purolite S 985 and A 500 shows that such behavior of
these sorbents is in good consistence with our above-
mentioned assumptions about sorption mechanism.
Since the palladium sorption on Purolite A 500 is not
complicated by additional complexation (in contrast to
Purolite S 985), the rate of this process is higher and
diffusion coefficient values are also bigger, whereas the
half-exchange times are lesser for this resin. However, it
is interesting to note that the strong basic anion ex-
changer Purolite A 530, which is not practically distin-
guished from A 500 in its sorption properties (Table 3),
compares much unfavorably with A 500 in its kinetic
properties (Table 5). The average rate of ion exchange
process on Purolite A 530 is about 5 times lower than on
Purolite A 500. Also the average diffusion coefficient
values for A 530 are by one order smaller and the
half-exchange time is by one order greater (Table 5).
Such behavior of anion exchanger Purolite A 530 in
comparison with also strong basic resin A 500 can be
probably explained by its exchange capacity, which is
less by half than this value for A 500, and by its lesser
swelling as well (Table 1). Moreover, it can be assumed
that the sorbed complex ions of palladium (II), which
possess a square spatial configuration [42], have not
enough time to reach the active centers of the sorbent A
530, where the anion exchange occurs, because of its
small exchange capacity (there are few available ex-
change centers on a resin surface). Certainly this phe-
nomenon requires a special study, but from the practical
point of view the anion exchanger Purolite A 500 is
preferable than sorbent Purolite A 530 for recovery of
palladium (II) from nitrate solutions.
3.6. Sorption of Palladium from Nitrate
Solutions of Spent Catalysts
Further we have studied the sorption recovery of palla-
dium (II) from solutions of spent catalysts on some an-
ion exchangers chosen on the basis of their good sorp-
tion and kinetic properties. The results are summarized
in Table 6.
It can be seen from these data that the anion exchang-
ers in general possess good sorption ability to
ions, but this characteristic is slightly lower in compari-
()Pd II
0 102030405060708090100
CPd·10-6, mol/L
010002000 3000 4000 5000 60007000
t, s
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son with the data obtained for model solutions, exclud-
ing anion exchanger AV-17-8 (Table 3). Partly the de-
crease in recovery from real solutions can be
explained by complex composition of initial solution of
spent catalyst (Table 2), where a number of ions produce
a competing effect on palladium sorption process.
()Pd II
()Pd II
In order to determine the form of palladium in con-
tacting solution of spent catalyst as well as in the phase
of strong basic anion exchanger, we have obtained the
diffuse reflectance spectra presented in Figure 6. It can
be seen from these data that the maximum in diffuse
reflectance spectra is located at 410 nm. It corresponds
with the maximum in absorption spectrum at 390 nm
(Figure 1), since the bathochromic shift of maximum in
diffuse reflectance spectra is observed during sorption
concentration of noble metal ions in view of matrix ef-
fect of solid phase [43,44]. Therefore, the prevailing
form of existence in nitrate weak acidic solu-
tions of spent catalysts is its complex
[( )PdH O
It is known [2-5,15] that the desorption of noble
metals from highly selective ion exchangers is hardly
achievable process because of strong retention of ad-
sorbed metal ions by functional groups of resins. Due
to that, for the successful regeneration of these sor-
bents it is necessary to use the elution agents which
form more stable complexes with the recovered metal
ions than the complexes of these metals existing in the
resin phase. From this point of view, the acidic or ba-
sic thiourea solutions are widely applied as eluting
agent [1,15,19,22-24,27]. We have also used in the
present work the thiourea solutions for palladium de-
sorption after its sorption recovery. The results are
shown in Table 7. It can be seen from the presented
data that the palladium (II) elution degrees after its
recovery from model solutions reach the level of
78-82% – the result which is considered quite satis-
factory. However, the palladium desorption after its
recovery from solutions of spent catalysts proceeds on
the level of 22–25%. When carrying out this process,
we have changed thiourea concentration and used its
solutions in or , but the best result we
could reach was ~ 25% by palladium elution with 1 M
thiourea solution in 1 M
aOH. It should be noted
that the recovery of noble metals from industrial solu-
tions after their sorption on highly selective ion ex-
changers is often carried out by burning of such resins,
since the value of noble metals exceeds the costs of ion
exchange materials, even selective ones [2,4,24,45].
Therefore, it is necessary to continue the research for
improving the palladium recovery after its sorption on
selective ion exchangers from solutions of spent cata-
Figure 6. Diffuse reflectance spectra of anion exchangers’
samples AV-17-8 (1) and Purolite A 500 (2) saturated with
palladium (II) from nitrate solutions of spent catalysts.
mol/L; mol/L;
mol/L F(R) – diffuse reflectance coefficient.
C(Pd)= 5.0×10
C(KNO)= 1.0
C(HNO)= 0.01
Table 6. Sorption recovery of palladium (II) from nitrate
solutions of spent catalysts mol/L;
mol/L; mol/L.
C(Pd)= 5.0×10
(KNO)= 1.0
C(HNO)= 0.01C
Trade name log
Purolite A 500 2.31 65
Purolite S 985 2.86 88
AV-17-8 2.72 84
Table 7. Elution of palladium from anion exchangers in-
vestigated by thiourea solution (1.0 mol/L) in 0.01 M
after palladium sorption from nitrate weak acidic
model solutions.
Trade name Desorption degree (%)
Purolite S 985 78
Purolite A 500 82
Sorption recovery of palladium (II) from nitrate weak
acidic model solutions and solutions of spent catalysts
on some ion exchangers with different physical and
chemical structure was investigated. Based on electron
absorption spectra, it was determined that complexes
[()()]PdH ONO
prevail in contacting solutions. It
was shown that ion exchangers investigated possess
good sorption and kinetic properties.
The mechanism of palladium sorption recovery on
strong and weak basic anion exchangers from nitrate
weak acidic solution was outlined by means of
FT-IR-spectroscopy. It was shown that strong basic an-
ion exchangers sorb palladium according to anion ex-
change, whereas weak basic resins recover
()Pd II
380 400 420440 460480 500 520 540 560
, nm
O. N. Kononova et al. / Natural Science 1 (2009) 166-175
SciRes Copyright © 2009 Openly accessible at http://www.scirp.org/journal/NS/
complexes not only by anion exchange, but also by
means of additional coordination with nitrogen atoms of
functional groups.
The palladium (II) desorption after its recovery on se-
lective ion exchangers from model solutions and solu-
tions of spent catalysts was carried out using thiourea
solutions. It was shown that the degree of palladium
elution by 1 M thiourea solution in 0.01 M 3
NO after
its sorption from model solutions is on the level of 78 –
82 %, whereas this value does not exceed 25% after
sorption from solutions of spent catalysts. The
improvement of this process should be a subject for fur-
ther research.
()Pd II
Based on results of present investigation, the anion
exchangers AV-17-8 as well as Purolite S 985 and A 500
can be recommended for selective recovery of palladium
(II) from nitrate weak acidic solutions.
The authors would like to express profound gratitude to
the team of Moscow office of Purolite International Ltd,
who kindly provided us with ion exchanger samples.
[1] R. Pfrepper, (1988) Möglichkeiten Der Wiedergewin-
nung Von Pd Aus Sekundären Rohstoffquellen. ZFI-
Mitteilungen. Akademie-Verlag, Berlin, 3-292.
[2] I. F. Khudyakov, A. P. Doroshkevich, S. V. Karelov,
(1990) Metallurgy of the secondary non-ferrous heavy
metals. Nauka, Moscow, 15-25.
[3] M. A. Meretukov and A. M. Orlov, (1990) Metallurgy of
noble metals. Metallurgiya, Moscow, 27-30.
[4] A. G. Kholmogorov, (1986) Ion exchange in hydro-
metallurgical processing of palladium-containing spent
catalysts. Sibir, Krasnoyarsk, 150-151.
[5] K. M. Saldadze and V. D. Kopylova-Valova, (1980) Com-
plex-forming ion exchangers. Nauka, Moscow, 3- 336.
[6] S. A. Simanova, A. S. Tevlina, and I. S. Bazhanova,
(1994) Formation of palladium complexes during sorp-
tion on high permeable sorbents with heterocyclic nitro-
gen atoms. J. Inorg. Chem., Moscow, 39(1), 121-126.
[7] I. A. Kovalev, G. I. Tsyzin, and A. A. Formanovskiy,
(1995) Concentration of rhodium, palladium and plati-
num on sorbent with ethylenetriamine groups. J. Inorg.
Chem., Moscow, 40(5), 828-833.
[8] I. A. Tarkovskaya, L. P. Tikhonova, and N. V. Kulik,
(1997) Sorption of platinum group metals from aqueous
solutions on inorganic and synthetic ion exchange mate-
rials. Khimiya I Tekhnologiya Vody, 19(3), 227-239.
[9] A. G. Kholmogorov, O. N. Kononova, S. V. Kachin, and
S. V. Razvodovskaya, (1998) Sorption of palladium from
chloride solutions on anion exchangers with macro-re-
ticular and porous structure. J. Phys. Chem., Moscow,
72(2), 318-321.
[10] O. P. Shvoeva, V. P. Dedkova, and S. B. Savvin, (2004)
Effect of masking compounds on color reactions of di-
thizone with Pd (II), Hg (II) and Ag (I) after sorption
from chloride solutions on fibrous anion exchanger. J.
Anal. Chem., Moscow, 59(7), 704-709.
[11] V. P. Dedkova, O. P. Shvoeva, and S. B. Savvin, (2005)
Test-method for determination of palladium in chloride
solutions in solid phase of fibrous ion exchanger. J. Anal.
Chem., Moscow, 60(1), 85-89.
[12] Z. Hubicki and M. Leszczynska, (2005) Sorption of pal-
ladium (II) chloride complexes on weakly, intermediate
and strongly basic anion exchangers. Desalination, 175,
[13] Z. Hubicki and A. Wolowicz, (2009) Adsorption of pal-
ladium (II) from chloride solutions on Amberlyst A 29
and Amberlyst A 21 resins. Hydrometallurgy, 96, 159-
[14] Z. Hubicki and A. Wolowicz, (2009) A comparative study
of chelating and cationic ion exchange resins for removal
of palladium (II) complexes from acidic chloride media.
J. Hazard. Mater., 164, 1414-1419.
[15] V. V. Milyutin, S. V. Peskishev, and V. M. Gelis, (1994)
Sorption of palladium, ruthenium and rhodium from ni-
tric acidic solutions on different sorbents. Radiokhimiya,
36(1), 25-28.
[16] G. R. Anpilogova and E. V. Kondratieva, (1996) Study of
palladium (II) sorption on polyethylene-monosulfide
from nitric acidic solutions. J. Inorg. Chem., Moscow
41(3), 447-452.
[17] V. I. Skorokhodov, O. Y. Goryaeva, B. K. Radionov,
(2004) Choice of optimal structure of ion exchangers for
palladium sorption from nitric acidic solutions. Tsven-
naya Metallurgiya, 1, 31-33.
[18] Z. Hubicki, M. Leszczynska, B. Lodyga, and and A. Lo-
dyga, (2007) Recovery of palladium (II) from chloride
and chloride-nitrate solutions using ion exchange resins
with S-donor atoms. Desalination, 207, 80-86.
[19] K. A. Venkatesan, B. R. Selvan, M. P. Antony, T. G.
Srinivasan, and P. R. V. Rao, (2007) Extraction of palla-
dium (II) from nitric acid medium by imidazolium nitrate
immobilized resin. Hydrometallurgy, 86, 221-229.
[20] R. Kumaresan, K. N. Sabharval, T. G. Srinivasan, P. R. V.
Rao, and G. Dhekane, (2008) Studies on the sorption of
palladium using cross-linked poly(4-vinylpyridine- divi-
nylbenzene) resins in nitric acid medium. Solv. Extr. Ion
Exchange, 26, 643-671.
[21] A. V. Belyaev, (2003) Chemical-technological problems
of platinum group metals during processing of exhausted
nuclear fuel. Zhurnal Strukturnoy Khimii, 44(1), 39-47.
[22] O. N. Kononova, A. G. Kholmogorov, and E. V. Mikhlina,
(1998) Palladium sorption on vinylpyridine ion exchang-
ers from chloride solutions obtained from spent catalysts.
Hydrometallurgy, 48, 65-72.
[23] O. N. Kononova, N. G. Goryaeva, N. B. Dostovalova, S.
V. Kachin, and A. G. Kholmogorov, (2007) Recovery of
palladium from acidic solutions using carbon adsorbents.
Khimiya Tverdogo Topliva. 4, 71-75.
[24] O. N. Kononova, A. N. Lukianov, M. V. Derevyashkin, A.
G. Kholmogorov, S. V. Kachin, and N. G. Goryaeva,
(2008) Sorption of palladium on carbon adsorbents from
nitric acid solutions. J. Porous Mater. 15, 61-66.
[25] O. N. Kononova, K. A. Shatnykh, K. V. Prikhodiko, D.
M. Kashirin, and A. G. Kholmogorov, (2009) Sorption of
gold (I) and silver (I) from thiosulfate solutions on anion
O. N. Kononova et al. / Natural Science 1 (2009) 166-175
SciRes Copyright © 2009 http://www.scirp.org/journal/NS/
exchangers. Tsvetnye Metally, 1, 40-43. [36] R. A. Shoytsov, (1972) Spectrophotometrical investiga-
tion of palladium (2+) state in aqueous solutions. State
University, Moscow, Moscow, PhD-thesis.
[26] F. E. Beamish, (1966) The analytical chemistry of the
noble metals. Pergamon Press, Oxford, London, Edin-
burgh, New York, Toronto, Paris, Frankfurt, 41-45. [37] V. S. Shmidt, N. A. Shorokhov, A. A. Vashman, and V. E.
Samsonov, (1982) Study of complex 2223 )(). J.
Inorg. Chem., Moscow, 27(5), 1254-1256.
[27] S. I. Ginzburg, N. A. Ezerskaya, I. V. Prokofieva, N. V.
Fedorenko, Y. I. Shlenskaya, and N. K. Belskiy, (1972)
Analytical chemistry of platinum group metals. Nauka,
Moscow, 165-166. [38] P. I. Antyukhin, (1993) About correlation between solu-
bility constants of metal hydroxides and formation con-
stants of their neutral hydroxocomplexes. Sibirskiy
Khimicheskiy Zhurnal, 1, 21-25.
[28] F. Umland, A. Janssen, D. Thierig, and G. Wünsch, (1971)
Theorie und praktische Anwendung von Komplexbild-
nern. Akademische Verlagsgesellschaft, Frankfurt am
Main, 364-365. [39] L. Bellami, (1963) Infrared spectra of complex molecules.
Inostrannaya Literatura, Moscow, 383-590.
[29] F. Helfferich, (1962) Ion exchange. McGraw-Hill, New
York, 335-360. [40] V. A. Uglyanskaya, G. A. Chikin, V. F. Selemenev, and G.
A. Zavialova, (1989) Infrared spectroscopy of ion ex-
change materials. Izdatelstvo VGU, Voronezh, 150-207.
[30] F. Helfferich and J. A. Marinsky, (1966) Ion exchange
kinetics. (ed.) Ion exchange. A series of advances.
McGraw-Hill, Buffalo, New York, 281-331. [41] K. Nakamoto, (1986) Infrared and raman spectra of in-
organic and coordination compounds. Wiley, New York,
[31] D. C. Harris, (1996) Quantitative chemical analysis.
Freeman and Company, New York, 374-376. [42] F. A. Cotton and G. Wilkinson, (1969) Advanced inor-
ganic chemistry. A Comprehensive Text, Mir, Moscow,
[32] J. H. Pollard, (1977) A handbook of numerical and statis-
tical techniques. Cambridge University Press, Cambridge,
342-345. [43] P. Kubelka, and F. Munk, (1931) Ein Beitrag Zur Optik
Der Farbanstriche. Z. Techn. Phys., 12, 593 -601.
[33] Y. A. Kokotov, (1990) Ion exchangers and ion exchange.
Khimiya, Leningrad, 47-52. [44] G. D. Brykina, D. Y. Marchenko, and O. A. Shpigun,
(1995) Solid-phase spectrophotometry. J. Anal. Chem.,
Moscow, 50(5), 484-491.
[34] Y. A. Zolotov, G. M. Varshal, and V. M. Ivanov, (2003)
Analytical chemistry of platinum group metals. Editorial
URSS, Moscow, 16-88. [45] V. V. Barchenkov, (1982) Sorption technology of recov-
ery of gold and silver from ores. Nauka, Moscow,
[35] S. E. Livingstone, (1967) The chemistry of ruthenium,
rhodium, palladium, osmium, iridium and platinum. Per-
gamon Press, Oxford, New York, Toronto, Sydney, Paris,
Braunschweig, 178-211.
Openly accessible at