Extraction of gallium(III) by 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3- dioxolan-2-yl]methyl}-1H-1,2,4-triazole from hydrochloric acid solutions

Article abstract of DOI:10.1134/S0036023609120316

The extraction of gallium(III) with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1, 3-dioxolan-2- yl]methyl}-1H-1,2,4-triazole from hydrochloric acid solutions into toluene was studied. It was found that gallium( III) was efficiently extracted from 5-10 M solution

Full text of DOI:10.1134/S0036023609120316

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2009, Vol. 54, No. 12, pp. 2022–2026. © Pleiades Publishing, Inc., 2009.
Original Russian Text © G.R. Anpilogova, Yu.I. Murinov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 12, pp. 2104–2108.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Extraction of Gallium(III) by 1-{[2-(2,4-Dichlorophenyl)-4-
propyl-1,3-dioxolan-2-yl]methyl}-1H-1,2,4-Triazole from
Hydrochloric Acid Solutions
G. R. Anpilogova and Yu. I. Murinov
Institute of Organic Chemistry, Ufa Scientific Center, Russian Academy of Sciences, pr. Oktyabrya 71, Ufa, 450054
Bashkortostan, Russia
Received June 19, 2008
Abstract—The extraction of gallium(III) with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-
yl]methyl}-1H-1,2,4-triazole from hydrochloric acid solutions into toluene was studied. It was found that gal-
lium(III) was efficiently extracted from 5–10 M solutions of HCl by the anion-exchange mechanism. The fol-
lowing metal extraction order was determined in the above aqueous phase acidity range: Ga(III) > In(III) >
Al(III). The concentration constants and the thermodynamic parameters of the reaction of gallium(III) extrac-
tion from 6 M solutions of HCl at 25°C were calculated.
DOI: 10.1134/S0036023609120316
1-[[2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan- 342.2; Tm = 58°C; purity, no less than 98%) has the fol-
2-yl]methyl]-1H-1,2,4-triazole or Propiconazole (S) is
a commonly used systemic fungicide [1]. The availabil-
ity of this reagent, its low water solubility (0.1 g/L), and
weakly basic properties (ä‡ = 1.09) [1], as well as the
ability of 1,2,4-triazole and its derivatives to form com-
plexes with transition metals [2], are responsible for
interest expressed by researchers in the extraction prop-
erties of this reagent toward noble metals in hydrochlo-
ric acid solutions [3–6]. It was found that this reagent
lowing structural formula:
Cl
Cl
O
CH2 N N
N
O
C3H7
extracted the acid metal complexes AuCl–4, PdCl42–,
PtCl26– (toluene as a diluent) [3], IrCl26– [4], and
The identity and purity of the reagent were deter-
mined using elemental analysis, potentiometric titra-
tion in anhydrous acetic acid, thin-layer chromatogra-
phy, and gas–liquid chromatography. According to 13C
NMR-spectroscopic data, the reagent was a mixture
containing 55–65% cis- and 35–45% trans-diastereoi-
somers [3].
[RuCl4(H2O)2]– [5] (toluene and 15% decanol) by the
anion-exchange mechanism. It extracted rhodium(III)
as the ion associates SH+[RhCl4(H2O)S]– (p-xylene and
15% decanol) from 4 M HCl solutions [6]. With the use
of 1H and 13C NMR spectroscopy, it was found that, in
the cation of the extracted ion associates, the reagent is
protonated at a nitrogen atom in the 4-position. The
ability of the reagent to extract quantitatively the
anionic complexes of noble metals from strongly acidic
solutions allowed us to hypothesize that it can be effi-
ciently used for the extraction of rare metals that form
anionic species in hydrochloric acid solutions.
The stock solution of the reagent in toluene with a
concentration of 0.1 mol/L was prepared from an accu-
rately weighed amount, and the working solutions were
prepared by diluting the stock solution with toluene of
chemically pure grade.
The stock solutions of Ga(III) and In(III)
(0.1 mol/L) in 2 M HCl were prepared by dissolving the
weighed portions of corresponding oxides å2é3 (with
The aim of this work was to study the extraction of
Ga(III) with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3- a purity of no less than 99.9%) in a solution of HCl
dioxolan-2-yl]methyl}-1H-1,2,4-triazole in toluene (1 : 4) under weak heating followed by adjusting the
from hydrochloric acid solutions.
acidity and volume of the solution to required values.
The stock solution of Al(III) (0.1 mol/L) in 2 M HCl
was prepared by dissolving a weighed portion of
reagent-grade AlCl3 · 6ç2é in a solution with a required
HCl content. The working solutions containing 0.001–
EXPERIMENTAL
1-{[2-(2,4-Dichlorophenyl)-4-propyl-1,3-diox-
olan-2-yl]methyl}-1H-1,2,4-triazole
(molecular, 0.030 mol/L Ga(III) and 0.005 mol/L In(III) or Al(III)
2022

EXTRACTION OF GALLIUM(III)
2023
were prepared by diluting the stock solutions with the
solutions of HCl.
E, %
100
1
The concentrations of In(III) and Al(III) in solutions
were determined by complexometric titration with a
PAN indicator in the presence of a Cu(II) complexonate
[7] and by back titration with a solution of ZnSO4 with
a xylenol orange indicator [8], respectively. The stock
solution of Ga(III) was standardized complexometri-
cally with a PAN indicator [9]. The concentrations of
Ca(III) in working solutions, raffinates, and back
extracts were determined by a spectrophotometric
method with xylenol orange at pH 1.8 (hydrochloric
acid buffer solution of HCl–KCl) [10] on a Specord
M40 spectrophotometer in 2-cm glass cells. Before
analysis, an aliquot of the working solution or raffinate
containing Ga(III) and more than 1 mol/L HCl was
evaporated in a water bath to wet salts to remove hydro-
chloric acid. Then, the residue was dissolved in a 0.01
M solution of HCl.
80
60
40
20
2
3
10
, mol/L
0
2
4
6
8
HCl
c
Fig. 1. Dependence of the extraction efficiency of (1) gal-
lium(III) (c = 0.002 mol/L; c = 0.006 mol/L; τ= 5 min),
(2) indium(III) (c = 0.005 mol/L; c = 0.015 mol/L; τ =
30 min), and (3) aluminum(III) (c = 0.005 mol/L; c
Ga
S
Extraction was performed in thermostated glass
cells at the aqueous to organic phases volume ratio of
1 : 1 with intense stirring using MM 2A magnetic stir-
rers. The temperature was maintained to within 0.2°ë
using a U4 thermostat.
In
S
=
Al
S
0.015 mol/L; τ = 30 min) on the acidity of the aqueous
phase at 20°ë.
The IR spectra of the reagent, its hydrochloride, and
the extracted complex of Ga(III) in thin films were
measured on a Specord M80 spectrophotometer in the
region of 600–250 cm-1.
The dependence of the extraction of Ga(III) by the
reagent on the acidity of the aqueous phase was analo-
gous to the dependence of the extraction of Ga(III) by
weakly basic extractants—Primene 81-R branched pri-
mary amines in toluene [11] and 1-hexyl-3-meth-
ylpyrazol-5-one (HMP) in chloroform [12]—from
hydrochloric acid solutions. In this case, the extract-
ability of the test reagent in the optimum acidity range
was much higher than that of the above extractants. For
the quantitative extraction of Ga(III), the concentration
of HMP in the organic phase should be more than ten
times higher than the concentration of Ga(III) in the
aqueous phase. At a ratio of 1 : 7 between the initial
concentrations of Ga(III) and Primene 81-R in the
aqueous and organic phases, respectively, and an aque-
ous phase acidity of 8 mol/L HCl, the distribution coef-
ficient of Ga(III) was ~5.6. The test reagent extracted
Ga(III) from a 8 M solution of HCl with the distribution
coefficient D = 27.6 (96.5% recovery) at a ratio of 1 : 3
between the initial concentrations of Ga(III) and the
reagent in the aqueous and organic phases, respectively
(Fig. 1).
RESULTS AND DISCUSSION
The equilibration time of Ga(III) extraction from 4–
10 M solutions of HCl was no longer than 2 min regard-
less of the initial concentrations of Ga(III) and the
reagent; the phase separation time was 1–2 min. The
main regularities of Ga(III) extraction at 20–25°ë were
studied at the phase contact time τ = 5 min. Gallium(III)
was efficiently back extracted from the extracts with
0.01–0.1 M solutions of HCl; in this case, the degree of
back extraction decreased from 98.4 to 93.4% in accor-
dance with an increase in the acidity of the back extrac-
tant. The equilibration time of back extraction was
3 min.
To determine optimum conditions for the extraction
of Ga(III) and the selectivity of the extractant, we stud-
ied the dependence of the extraction efficiency of
Ga(III), In(III), andAl(III) on the acidity of the aqueous
phase (Fig. 1). We found that Ga(III) was efficiently
extracted in the region of >4 M HCl; in this case, its
recovery increased to a maximum at 8 mol/L HCl and
then insignificantly decreased as the acidity of solution
was increased to 10 mol/L. This was likely due to a shift
of the hypothetical anion-exchange equilibrium of
Ga(III) extraction to the left at high concentrations of
chloride ions:
An increase in the concentration of chloride ions in
the aqueous phase makes it possible to considerably
increase the extraction of Ga(III) from solutions with
an HCl concentration lower than an optimum as a result
of an increase in the concentration of the extracted
GaCl–4 complex (Fig. 2).
In the acidity range of 4–10 mol/L at the same ratio
between the initial metal and reagent concentrations,
the following metal extractability order was found:
Ga(III) (maximum distribution coefficient Dmax = 27.6) >
SHClorg + GaCl–4aq
SHGaCl4org + Cl–aq.
(1)
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 54 No. 12 2009

2024
ANPILOGOVA, MURINOV
D
2.0
y, mol/L
0.006
4
3
2
1.5
1.0
0.5
0.004
0.002
1
0
0.005 0.010 0.015 0.020 0.025
x, mol/L
0
0.5
1.0
, mol/L
1.5
2.0
c
NH4Cl
Fig. 2. Dependence of the distribution coefficient of Ga(III)
on the concentration of NH Cl in the aqueous phase at c
Fig. 3. Isotherms of Ga(III) extraction from 6 M solutions
of HCl at 25°ë and reagent concentrations of (1) 0.002, (2)
0.004, (3) 0.006, and (4) 0.008 mol/L.
=
çël
4
4 mol/L, c = 0.002 mol/L, c = 0.006 mol/L, and 20°ë.
Ga
S
In(III) (Dmax= 0.1) > Al(III) (Dmax = 0.01) (Fig. 1). This
order corresponds to a decrease in the concentration
and an increase in the hydration of anionic complexes
like MCl–4 in the aqueous phase, and it is analogous to
The rapid equilibration and easy back extraction of
Ga(III) from the organic phase with weakly acidic solu-
tions of HCl suggest the anion-exchange mechanism of
Ga(III) extraction by the test reagent from hydrochloric
acid solutions. We studied the mechanism of Ga(III)
extraction at an aqueous phase acidity of 6 mol/L HCl.
an extractability order for weakly basic extractants such
as HMP [12] and tertiary amines [13]. In the given
range of HCl concentrations, aluminum(III) does not
form anionic chloro complexes in detectable amounts;
therefore, it was almost not extracted by HMP, amine
salts, and the test reagent. Gallium(III) mainly occurs in
Cl–
In these solutions, Ga(III) occurred as Ga
[14].
4
Changes in the 1H and 13C NMR spectra of hydrochlo-
ric acid extracts obtained at an aqueous phase acidity of
1–4 mol/L indicate that the reagent was incompletely
protonated at a nitrogen atom in the 4-position upon
contact with solutions of < 4 mol/L HCl [3]. Using two-
phase titration of hydrochloric acid extracts with a
0.1 M solution of NaOH in the presence of bromothy-
mol blue, we found that the degree of protonation of the
test reagent in contact with 5 and 6 M solutions of HCl
was 98 and 100%, respectively.
these solutions as the tetrahedral GaCl–4 complex of íd
symmetry [14, 15], which is the species extracted with
the salts of secondary and tertiary amines and quater-
nary ammonium bases [16, 17]. The aquachloro com-
plexes [InCl4(H2O)2]– and [InCl5H2O]2– were the pre-
dominant In(III) species in the specified acidity range
of the aqueous phase [11, 15]. The IR spectra of In(III)
extracts containing a tertiary of quaternary amine in a
molar ratio of 1 : 1 or 2 : 1 with respect to In(III) suggest
The solvation number of Ga(III) was 1, as deter-
mined using organic phase saturation method (Fig. 3,
curves 1, 2). The solvation number determined from the
initial parts of equilibrium extraction isotherms by the
slope method was also close to unity (Fig. 4).
Cl–
that In(III) occurred in the form In
in ion associates
4
[16, 18]. Consequently, the transfer of In(III) into the
organic phase in the course of extraction with amines
was accompanied by the displacement of water mole-
cules from the inner coordination sphere of the
aquachloro complex anions of In(III), and this process
required an additional input energy. It is also well
known that the extractability of aliphatic amines for
In(III) decreases with decreasing the basicity of the
amine [11]. It is likely that the extractability of the test
reagent for In(III) was low for the above reasons. Thus,
Ga(III) can be selectively separated from Al(III) and
In(III) by extraction with this reagent from hydrochlo-
ric acid solutions.
To confirm the composition of SHGaCl4 ion associ-
ates formed in the organic phase during the extraction
of Ga(III) from 6 M HCl solutions, we obtained the
extracted complex of Ga(III) under conditions of the
full saturation of the organic phase (initial concentra-
tions, cGa = 0.3 mol/L and cS = 0.1 mol/L; volume ratio
of the aqueous to organic phases 3 : 2). The solvent (tol-
uene) was separated from the complex by evaporation.
The extracted complex was a reddish brown highly vis-
cous liquid. According to elemental analysis data, the
Ga(III) content of this complex was 12.56%, which is
consistent with the theoretical value (12.57%). The
molar ratio between the elements Ga : N : Cl = 1 : 3.2 :
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 54 No. 12 2009

EXTRACTION OF GALLIUM(III)
2025
The concentration constants of equilibrium for
anion-exchange extraction (1) were calculated from the
equation
logD
1.0
Kex
0.8
0.6
(2)
= [SHGaCl4org][Cl–aq]/([GaCl–4aq][SHClorg]),
where [SHGaCl4 org] = y, mol/L is the equilibrium con-
centration of Ga(III) in the organic phase, as calculated
from the difference between the concentrations of
Ga(III) in the initial aqueous solution and the raffinate;
[GaCl–4aq ] = ı, mol/L is the equilibrium concentration
of Ga(III) in the aqueous phase; [Cl–aq ] = [HClaq] –
0.4
[SHClorg]= 6 mol/L is the equilibrium concentration of
chloride ions in the aqueous phase (it can be taken
equal to the concentration of HCl in the aqueous phase
because the equilibrium concentration of the hydro-
chloric acid salt of the reagent in the organic phase
[SHClorg] is much lower than [HClaq]); and [SHClorg] =
[S]0 – y, mol/L, where [S]0 is the initial reagent concen-
tration in the organic phase.
–3.0
–2.8
–2.6
–2.4
logS
free
Fig. 4. Bilogarithmic dependence of the Ga(III) distribution
coefficient on free extractant concentration at c
6 mol/L and 25°ë. The least-squares estimate of the linear
correlation coefficient is r = 0.994; tanα = 1.11.
=
çël
The final equation for calculating the concentration
constants of extraction has the form
6.0 corresponds to the composition of the ion associate
SHGaCl4. The IR spectrum of the complex exhibited a
strong broad absorption band with a maximum at 381
cm–1 and a weak absorption band at 346 cm–1, which
were absent in the spectra of the reagent and its hydro-
chloride. The intense absorption band can be atributed
äex = 6y/{x ([S]0 – y)}.
(3)
The table summarizes the concentration constants
of anion-exchange extraction of Ga(III) from 6 M solu-
tions of HCl at 25°ë, as calculated from the initial por-
tions of extraction isotherms.
Cl–
to νd(Ga–Cl) of the tetrahedral Ga
complex with íd
4
symmetry [16, 17, 19], which was observed in the IR
Cl–
The study of the temperature dependence of the
Ga(III) extraction at the range of 10–45°ë demonstrated
that the concentration constant increased with tempera-
ture rise (Fig. 5). Consequently, the extraction is an
endothermic process. We evaluated the thermodynamic
parameters of the anion-exchange extraction of Ga(III)
from 6 M solutions of HCl. The value of ΔH = 7.0 kJ/mol
spectra of Ga
ion associates with aliphatic amine
4
cations [16, 17]. The appearance of a weak absorption
band due to νs(Ga–Cl), which is inactive in the IR spec-
tra of symmetrical tetrahedral complexes, suggests an
Cl–
insignificant deformation of the Ga
extracted complex [17].
ion in the
4
was calculated from the slope of the function logKex
=
Concentration constants of Ga(III) extraction with reagent S from 6 M solutions of HCl at 25°C
Equilibrium Ga(III) concentration, mol/L
Initial reagent concentration,
mol/L
Concentration constant
of extraction Kex × 10–4
x
y
0.004
0.004
0.004
0.006
0.006
0.006
0.008
0.008
0.008
0.00010
0.00016
0.00025
0.00009
0.00014
0.00025
0.00016
0.00027
0.00050
0.00095
0.00132
0.00168
0.00139
0.00179
0.00265
0.00274
0.00359
0.00475
1.79
1.89
1.74
2.00
1.89
1.90
1.95
1.84
1.75
Average value of Kex = (1.86 0.07) × 104
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 54 No. 12 2009

2026
ANPILOGOVA, MURINOV
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ex
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l/T, K
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Fig. 5. The temperature dependence of the concentration
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Ga
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from hydrochloric acid solutions occurs in accordance
with the anion-exchange mechanism. The reagent is
more efficient than the commercial extractant Primene
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