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Dysprosium (Dy) Separation from Yttrium Concentrate in Nitric Acid Solution
Using Aliquat 336 Solvent
Conference Paper · April 2020
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Key Engineering Materials
ISSN: 1662-9795, Vol. 840, pp 573-579
© 2020 Trans Tech Publications Ltd, Switzerland
Submitted: 2019-03-19
Revised: 2019-10-28
Accepted: 2019-11-12
Online: 2020-04-24
Dysprosium (Dy) Separation from Yttrium Concentrate in Nitric Acid
Solution Using Aliquat 336 Solvent
Kris Tri Basuki1,a, Ridwan Arifudin1,b, Wahyu Rachmi Pusparini2,c
and Andri Saputra3,d*
1STTN-BATAN, Yogyakarta, Indonesia-55281
2PSTA-BATAN, Yogyakarta, Indonesia-55281
3Department of Chemical Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia-55284
akristri_basuki@batan.go.id (main contributor), bridwanarifudin1996@gmail.com,
crachmi_p@batan.go.id, dandrisaputra22@mail.ugm.ac.id
Keywords: Aliquat 336, dysprosium, extraction
Abstract. Similarity of chemical and physical properties between rare-earth elements (REEs) and
Dy is the main concern in order to get Dy with high purity, which it is necessary to do separation by
extraction process. The purpose of this research is to obtain the optimum condition of operation
(stirring time and rate, concentration of nitric acid, feed, and solvent) and determine the distribution
constant, separation factor, and extraction efficiency of Dy using Aliquat 336. This research was
conducted by varying stirring time (10, 15, 20, 30, 40 minutes), stirring rate (100, 150, 200, 250,
300 rpm), nitric acid concentration (2, 3, 4, 5, 6 N), feed concentration (25,000; 50,000; 100,000;
150,000; 200,000 ppm) and solvent concentration (10, 20, 30, 40, 50 % v/v). The optimum result is
achieved when operation is carried out at stirring 100 rpm about 15 minutes in nitric acid 3 N with
100,000 ppm of feed concentration using 30% solvent concentration (v/v) which extract more Dy
element than Yttrium (Y) and Godolinium (Gd). The highest distribution constant of Dy is 0.427,
separation factor of Dy-Y is 6.831, separation factor of Dy-Gd is 1.799, and extraction efficiency of
Dy is 31.604%.
Introduction
Rare-earth elements (REEs) are widely used in advanced technology. In the use of nuclear
science and technology, REEs such Y in the form of oxide (Y2O3) is used as a control rod dopant
material in nuclear reactors [1]. The maximum level of impurities such Dy is about 500 μg/g
powder of Y2O3 [2]. In the use of non-nuclear, Y2O3 is used as a superconductor material which has
the potential to produce super-fast trains [3‒5]. The purity level of Y2O3 for superconductors is
above 90% [6]. Rare-earth elements (REEs) are derivatives of lanthanide element that has similar
chemical and physical properties. Because of its similar properties, it is very difficult to separate
these REEs from main minerals [7‒9]. It is necessary to choose the most feasible and efficient
technology to obtain the maximum Dy in the range of desired operating conditions [8].
The separation of rare-earth elements is commonly processed by solvent extraction, ion
exchanger (resin), and solvent impregnated resins (SIR) methods. Liquid-liquid extraction method
is widely used because it has high selectivity. This method is very reliable for separation process
involving metals with similar chemical properties [10]. Liquid-liquid extraction method is a feasible
and efficient method to extract the elements (constituent) of rare-earth elements. This method has
some advantages that are more efficient, used to separate the elements with low to high quality,
more effective, selective to certain ions, reusable solvents, saver (lower) energy uses, and need
smaller equipment [11].
In an extraction process, the influenced variables process is stirring time and rate, concentration
of nitric acid, feed, and solvent. The success parameters of the process can be measured by looking
at the magnitude of distribution constant, separation factor, and extraction efficiency. This study
proposes to investigate the separation of rare-earth elements, especially the Dy elements by
extraction process using Aliquat 336 solvent, to study the effect of extraction process parameters,
and to obtain the optimum condition of operation.
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Symposium of Materials Science and Chemistry II
Experimental Section
Materials. Materials that used in this research are Aliquat 336, yttrium concentrate, distilled
water, 65% HNO3 (Merck), NaOH, NH4OH, 2 M NaNO3 and kerosene. The instruments that used
in this research are beaker as reactor for precipitation process, erlenmeyer as reactor for extraction
process, pH meter, XRF as instrument that used for quantitative and qualitative analysis, graduated
cylinder, watch glass, magnetic stirring bar, magnetic stirrer, stirring rod, mechanical shaker,
volumetric flask, pipette/dropper, volumetric pipette, analytical balance, and hotplate stirrer.
Feed solution preparation. Feed solution of REE(OH)3 was prepared by digesting the REEs
Oxalate 405 g in NaOH 405 g and then filtered by hot water until the pH of the filtrate is neutral.
The obtained REE(OH)3 was dissolved in HNO3 with ratio 1:3 (w/v) and evaporated at 120 °C until
the gas from HNO3 runs out and then added with distilled water 1.5 L. REE(NO3)3 was deposited
by NH4OH 15% until pH 6.5 then the sediment was filtered and dried by oven to form the solid
REE(OH)3. REE(OH)3 100,000 ppm about 10 mL was prepared by dissolving REE(OH)3 into
HNO3 with ratio 1:3 (w/v) and evaporated at 120 °C until the gas from HNO3 ran out, then make up
to the mark with 3 M HNO3 until 100 mL as a sample.
Solvent preparation. The solvent solution was prepared by mixing Aliquat 336 and 2 M NaNO3
(ratio 2:1) about 1 hour, then was left for a few minutes until 2 layers were formed. Upper layer was
taken as a solvent solution for next step.
Variation of stirring time and rate. The sample as water phase (WP) was extracted by 30%
Aliquat 336 in kerosene (v/v) as organic phase (OP) with ratio WP to FO is 1:1. The stirring process
was carried out at varied stirring rate 100, 150, 200, 250, and 300 rpm with varied stirring time 10,
15, 20, 30 and 40 minutes then the solution phase was allowed to stand for 1 hour until the water
phase and the organic phase were separated. The water phase was taken as much as 5 mL to be
analyzed by an X-ray fluorescent spectrophotometry. The stirring time which has the highest
separating factor (optimum) is used to optimize the nitric acid and feed concentration.
Variation of nitric acid and feed concentration. REE(OH)3 with varied concentration about
25,000; 50,000; 100,000; 150,000; 200,000 ppm was added by HNO3 with varied concentration
about 2, 3, 4, 5, and 6. Then, sample as water phase (WP) was extracted by 30% Aliquat 336 in
kerosene (v/v) as organic phase (OP) with ratio WP to FO is 1:1. The stirring process was carried
out at optimum stirring rate and stirring time then the solution phase was allowed to stand for 1 hour
until the water phase and the organic phase were separated. The water phase was taken as much as
5 mL to be analyzed by an X-ray fluorescent spectrophotometry. The stirring time which has the
highest separating factor (optimum) is used to optimize the solvent concentration.
Variation of solvent concentration. REE(OH)3 with optimum concentration was added by
HNO3 with optimum concentration as water phase (WP), then this sample was extracted by varied
concentration of solvent (10; 20; 30; 40; 50%) as organic phase (OP) with ratio WP to FO is 1:1.
The stirring process was carried out at optimum stirring rate and stirring time then the solution
phase was allowed to stand for 1 hour until the water phase and the organic phase were separated.
The water phase was taken as much as 5 mL to be analyzed by an X-ray fluorescent
spectrophotometry.
Results and Discussion
Preparation and characterization of feed solution. Feed solution was prepared from REEs
oxalate that produced from xenotime sand. Xenotime sand is a rare-earth phosphate mineral which
is obtained from side product of tine mining process of PT. Timah on Bangka Island. These REEs
oxalate consist of Y, Gd, and Dy about 19.30%, 10.17%, and 3.02%, respectively. In order to fulfill
the standard of application requirements, REEs oxalate must be processed into yttrium concentrate
through precipitation process. The result of REEs oxalate precipitation process shown in Table 1.
According to Table 1, deposited REE(OH)3 that produced by precipitation process has higher Y,
Gd, and Dy content than REEs oxalate. It proves that the deposition process can reduce the
impurities present in REE(OH)3 and increase the content of the yttrium concentrate.
Key Engineering Materials Vol. 840
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Table 1. Composition of REEs
Types of REEs
REEs oxalate
(before precipitation process)
REE(OH)3
(after precipitation process)
Y
Content (%)
Gd
Dy
19.30
10.17
3.02
60.14
13.90
4.22
Variation of Stirring Time. The varied stirring time gives different distribution constant (see
Fig. 1) and extraction efficiency (see Fig. 2) values for each extraction. Both distribution constant
and extraction efficiency of Dy increased from 10 to 15 minutes, which indicating more solutes
were extracted from organic phases.
30
0.3
0.2
Y
Gd
0.1
0
-0.1
Dy
0
10
20
30
40
50
Stirring time (minute)
Figure 1. Effect of stirring time to distribution
constant of Y, Gd, and Dy
Extraction Efficiency (%)
Distribution Constant
0.4
25
20
Y
Gd
Dy
15
10
5
0
-5
0
10
20
30
40
50
Stirring time (minute)
Figure 2. Effect of stirring time to extraction
efficiency of Y, Gd, and Dy
However, from 20 to 40 minutes the distribution constant and extraction efficiency tends to
decrease, which indicating extracted Dy is getting lower. This is because the solvent has a tendency
to bond Gd at a stirring speed of more than 15 minutes, so that the extracted Dy is getting lower.
These results are in line with the research that conducted by [6]. Based on Table 2, the stirring time
at 15 minute was used for the subsequent extraction process (varied stirring rate). This selection is
based on result that it has provided highest separation factor among others.
Table 2. Separation factor of Dy-Y and Dy-Gd on varied stirring time
Stirring time (min)
10
15
20
30
40
Separation factor
Dy-Gd
Dy-Y
3.940
0.990
5.619
1.544
0.826
0.159
∞
0.000
∞
0.000
Variation of stirring rate. Fig. 3 and Fig. 4 show that varied stirring rate gives different
distribution constant and extraction efficiency values for each extraction. The highest distribution
constant and extraction efficiency of Dy is at 100 rpm, which indicating more solutes were
extracted from organic phases.
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Symposium of Materials Science and Chemistry II
0.55
0.45
Distribution Constant
Gd
Dy
0.35
0.25
0.15
0.05
-0.05 50
100
150
200
250
300
350
Stirring Rate (rpm)
Figure 3. Effect of stirring rate to distribution
constant of Y, Gd, and Dy
Extraction Efficiency (%)
Y
35
Y
30
Gd
25
Dy
20
15
10
5
0
-5
50
100
150 200 250 300
Stirring Rate (rpm)
350
Figure 4. Effect of stirring rate to extraction
efficiency of Y, Gd, and Dy
According to Table 3, the stirring rate at 100 rpm was used for the subsequent extraction process
(varied nitric acid concentration). This selection is based on the result that at that rate it has
provided highest separation factor among others. Distribution constant, extraction efficiency, and
separation factor of Dy tend to decrease as a stirring rate more than 100 rpm. According to [12], it
happens because rapid stirring rate makes the mixing of water phase and organic phase into a stable
emulsion, so it is difficult to separate.
Table 3. Separation factor of Dy-Y and Dy-Gd on varied stirring rate
Stirring rate (rpm)
100
150
200
250
300
Separation factor
Dy-Gd
Dy-Y
6.831
1.799
5.619
1.544
4.174
1.000
0.000
0.000
0.981
0.533
Variation of nitric acid concentration. The distribution constant and extraction efficiency
tends to decrease by increasing concentration of HNO3 (See Fig. 5 and Fig. 6). Although the
increased concentration of HNO3 can increase the reactivity of the H+ ions formation, high acidity
will reduce the ability of solvent.
As a result, it will reduce the extraction efficiency of REE. This formed solvation reaction have
to avoided because if the reaction mechanism occurs in different reaction, it will produce different
elements product. At a relatively high acidity concentration, the reaction that occurs in
organophosphorus solvents is the formation of complexes, whereas at low concentrations the
reactions that occur are ion exchange [13]. According to Table 4, nitric acid with 3 M was used for
the subsequent extraction process (varied feed concentration). This selection is based on the result
that it has provided highest separation factor among others.
Variation of concentration of feed solution. Fig. 7 and Fig. 8 show that initially the
distribution constant and extraction efficiency tends to increase by increasing feed concentration
until 100,000 ppm. According to the Le Chatelier principle, when the concentration of one part
(reactant or product) is added, the reaction tends to shift towards the part that is not added, causing
the value of the distribution constant and extraction efficiency tend to increase [14].
Key Engineering Materials Vol. 840
0.5
35
Extraction Efficiency (%)
Distribution Constant
Dy
20
Dy
15
0.2
10
0.1
-0.1
Gd
25
Gd
0.3
Y
30
Y
0.4
0
577
1
3
5
7
5
0
-5
2
Concentration of Nitric Acid (N)
Figure 5. Effect of nitric acid concentration to
distribution constant of Y, Gd, and Dy
3
4
5
6
Concentration of Nitric Acid (N)
Figure 6. Effect of nitric acid concentration to
extraction efficiency of Y, Gd, and Dy
Table 4. Separation factor of Dy-Y and Dy-Gd on varied nitric acid concentration
2
3
4
5
6
Distribution Constant
0.5
Y
0.4
Gd
Dy
0.3
0.2
0.1
0
-0.1
25
50
100
150
200
Concentration of Feed Solution (103
ppm)
Figure 7. Effect of feed concentration to
distribution constant of Y, Gd, and Dy
Separation factor
Dy-Gd
Dy-Y
2.040
1.562
6.831
1.799
0.000
0.000
3.057
∞
0.221
0.319
Extraction Efficiency (%)
Nitric Acid Concentration (M)
35
30
25
20
15
10
5
0
-5 0
Y
Gd
Dy
50
100
150
200
Concentration of Feed Solution (103
ppm)
Figure 8. Effect of feed concentration to
extraction efficiency of Y, Gd, and Dy
Table 5. Separation factor of Dy-Y and Dy-Gd on varied concentration of feed solution
Concentration of Feed Solution
(×103 ppm)
25
50
100
150
200
Separation factor
Dy-Gd
Dy-Y
1.879
∞
∞
∞
6.831
1.799
0.863
0.771
0.000
0.000
However, the distribution constant and extraction efficiency tends to decrease by increasing feed
concentration over than 100,000 ppm. According to Biyantoro [15], more REE elements will be
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Symposium of Materials Science and Chemistry II
extracted to form complexes with organic phases by increasing feed concentration. But, the solvent
has maximum ability to bond REE element, so as a solvent concentration is constant, the ability of
solvents to bond REE elements is also limited to a certain amount. Feed concentration at
100,000 ppm was used for the subsequent extraction process (varied solvent concentration). This
selection is based on the result that it has provided highest separation factor among others (See
Table 5).
Variation of solvent concentration. Fig. 9 and Fig. 10 show that initially the distribution
constant and extraction efficiency tends to increase by increasing solvent concentration until 30%
(v/v). The complex formed to bond REE element is getting higher as the more solvents is used.
35
Y
0.4
Gd
Dy
0.3
0.2
0.1
0
10
-0.1
20
30
40
50
Concentration of Solvent (%)
Figure 9. Effect of solvent concentration to
distribution constant of Y, Gd, and Dy
Extraction Efficiency (%)
Distribution Constant
0.5
Y
Gd
Dy
30
25
20
15
10
5
0
-5
10
20
30
40
Concentration of Solvent (%)
50
Figure 10. Effect of solvent concentration to
extraction efficiency of Y, Gd, and Dy
Table 6. Separation factor of Dy-Y and Dy-Gd on varied solvent concentration
Solvent Concentration (%)
10
20
30
40
50
Separation factor
Dy-Gd
Dy-Y
0.547
∞
∞
0.246
6.831
1.799
0.000
0.000
0.000
∞
However, the distribution constant and extraction efficiency tends to decrease by increasing
solvent concentration over than 30% (v/v). This occurs because the higher solvent concentration,
the movement of solute from the water phase to the organic phase is tend to harder which can be
explained by the Stokes-Eintein. According to Stokes-Eintein, diffusion is inversely proportional to
the solvent viscosity and as the greater solvent viscosity, the more difficult to diffuse from the water
phase into the organic phase, thereby reducing the rate of mass transfer of metal ions from the water
phase to the organic phase [16]. Solvent concentration at 30% (v/v) was chosen for the extraction
process. This selection is based on the result that it has provided highest separation factor among
others (See Table 6).
Summary
According to the results of the research, it can be concluded that the optimum conditions of
separation of Dy from nitric acid solution were obtained at 100 rpm about 15 minutes with
100,000 ppm of feed concentration, 3 M of nitric acid and 30% (v/v) of Aliquat 336. That operation
condition can extracte more Dy than Y and Gd from the solutions. The highest distribution constant
for Dy is 0.427 and extraction efficiency for Dy is 31.60%. The highest separation factor for Dy-Y
is 6.831 and for Dy-Gd is 1.799.
Key Engineering Materials Vol. 840
579
Acknowledgments
This work was partially funded by Kris Tri Basuki, Ridwan Arifudin, and Wahyu Rachmi
Pusparini. The authors gratefully acknowledge the funding. Also, the authors gratefully
acknowledge to Mr Kris Tri Basuki as main (first) contributor for this research.
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