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Application of annular centrifugal contactors in the extraction flowsheet for producing high purity yttrium
Hydrometallurgy 85 (2007) 154 – 162 www.elsevier.com/locate/hydromet
Application of annular centrifugal contactors in the extraction flowsheet for producing high purity yttrium Jiazhen Zhou, Wuhua Duan ⁎, Xiuzhu Zhou, Chengqun Zhang Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 102201, China Received 16 January 2006; received in revised form 30 May 2006; accepted 5 August 2006 Available online 18 October 2006
Abstract Compared with mixer-settlers applied widely in the hydrometallurgical industry of rare earths (RE), centrifugal contactors have several advantages such as low hold-up volume, excellent phase separation, high mass transfer efficiency, compact and short pieces of equipment, etc., and have been successfully used in some industrial fields. Yttrium (Y) is an important element and in great demand in many industries. For a variety of uses in many specialized areas, the high purity Y is often required. However, the separation and purification of Y by solvent extraction from RE mixture is widely known to be difficult due to their similar chemical properties. This paper studied both the separation factors of RE ions in the 32% HA (naphthenic acid) − 20% iso-octylalcohol–48% kerosene–RECl system and the distribution ratios of RE ions in the 32% HEHEHP (2-ethylhexyl phosphonic acid mono-2ethylhexyl ester) −68% kerosene–RECl system. Based on these studies, an extraction flowsheet for producing high purity Y with HA and HEHEHP as extractants has been developed. Both the bench scale test and the pilot-plant test of the flowsheet have been performed with ϕ20 mm and ϕ120 mm centrifugal contactors respectively. It is shown that Y2O3 with 99.99% purity was obtained, and the total recovery of Y was about 95%. © 2006 Elsevier B.V. All rights reserved. Keywords: Centrifugal contactor; Extraction; Rare earth; Yttrium; High purity; HEHEHP; Naphthenic acid
1. Introduction Yttrium (Y) is an important element and in great demand in astronavigation, luminescence, nuclear energy and metallurgical industries. For a variety of uses in these specialized areas, high purity Y is often required. For example, the fluorescent grade Y2O3 requires the content of relevant RE impurities should be lower than 1 × 10− 4 (weight fraction, National standards of China: ⁎ Corresponding author. Institute of Nuclear and New Energy Technology, Tsinghua University, P. O. Box 1021, Beijing 102201, China. Tel.: +86 10 8019038; fax: +86 10 62771740. E-mail address: [email protected] (W. Duan). 0304-386X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2006.08.010
GB3503-83). However, the separation and purification of Y from RE is widely known to be difficult due to their similar chemical properties (Wang et al., 2002; Xiaobo et al., 2005). Amongst different methods used for the purpose, such as chromatography, ion exchange, emulsified liquid membrane and solvent extraction, solvent extraction is one of the most popular and versatile techniques (Chunsheng et al., 2001). Over the years a number of extractants have been employed for the extraction separation of Y from other RE and more prominent among these are high molecular weight amines (HMWA), carboxylic acids, Cyanex 923, Cyanex 302, Cyanex 272, alkylphosphorus extractants (Gupta et al., 2003). HEHEHP (2-ethylhexyl phosphonic acid mono-
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Table 1 Composition of the mixture of RE oxides RE oxide
La2O3
Ce2O3
Pr6O11
Nd2O3
Sm2O3
Eu2O3
Gd2O3
Tb4O7
Percentage (wt.%) RE oxide Percentage (wt.%)
27.0 Dy2O3 4.41
0.6 Ho2O3 0.77
4.3 Er2O3 2.42
14.1 Tm2O3 b0.3
2.85 Yb2O3 1.78
0.8 Lu2O3 b0.3
4.66 Y2O3 35.0
0.86
2-ethylhexyl ester) and HA (naphthenic acid) have been reported to be better extractants in extraction separation of Y from other RE (Han et al., 1987; Yingli et al., 1980; Zheng et al., 1991). At present, mixer-settlers have been applied widely in the hydrometallurgical industry of RE (Guangxian, 2002). However, they have some disadvantages, such as high hold-up volume, large floor space requirement, and the escape of toxic and/or flammable vapors from the organics, etc. Annular centrifugal contactors are efficient extraction pieces of equipment in extraction processes. Compared with mixer-settlers, annular centrifugal contactors offer the following advantages (Leonard, 1988; Wuhua et al., 2005): • Low hold-up volume; • Excellent phase separation;
• High mass transfer efficiency; • Compact and short; • Rapid start-up, shut-down and wash out of the process liquors. The primary centrifugal contactor, which was the paddle type, had been successfully developed and operated for many years at Savannah River Plant (SRL). In the late 1960s, the paddle-type centrifugal contactor was modified into the annular type at Argonne National Laboratory (ANL), which was reliable, easy to operate and maintain (Bernstein et al., 1973a,b; Leonard et al., 1980). In the late 1970s, Institute of Nuclear and New Energy Technology, Tsinghua University, China (INET) started to develop its own annular centrifugal contactors. From that time on, a series of annular centrifugal contactors have been developed with the rotor diameter from 10 mm to
Fig. 1. Schematic of the annular centrifugal contactor.
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Fig. 2. The flow of two phases in the centrifugal contactor.
230 mm and used successfully in some industrial fields at INET (Jiazhen, 1984; Wuhua et al., 2001; Zhigeng et al., 1993; Xiuzhu et al., 1997). At present, the main material of the centrifugal contactors is the stainless steel or titanium that can be corroded by H2SO4 or HCl, so they cannot be applied in extraction systems containing these acids. In order to make the centrifugal contactor be applied in the industrial scale test for producing the high purity Y, which the extraction systems containing H2SO4 or/and HCl, a centrifugal contactor with 120 mm of the rotor diameter (ϕ120 mm) that the main material is the glass fibre reinforced plastic (GFRP) has been developed at INET. GFRP has many desirable properties including high corrosion resistance, high strength and stiffness to weight ratio, low cost, and can easily be optimized to suit any applied load. In this paper, an extraction flowsheet with annular centrifugal contactors for producing the high purity Y developed in our lab is described. Results of both the bench scale test and the pilot-plant test are presented.
including Ca, Si, and Pb in the mixture of RE oxides. Both HEHEHP and HA were kindly supplied by Shanghai Organic Factory, China, and were dissolved in sulfated kerosene to prepare the organic phase. The tertiary amine (N235) was also supplied by Shanghai Organic Factory, China, and its indicated formula is R3N (R = CnH2n+1, n = 8, or 9, or 10). These extractants (technical grade, N95 wt.%) were used without further purification. All other chemicals used were of analytical grade.
2. Experimental procedure 2.1. Materials The mixture of RE oxides was obtained from Shanghai Yuelong Chemical Plant, China. Its composition is shown in Table 1. There were about 0.1% of Fe, and 0.3% Al and less than 0.1% of other impurities
2.2. Apparatus The annular centrifugal contactor is shown in Fig. 1. The flow of two phases in the centrifugal contactor is Table 2 The specifications of annular centrifugal contactors Type
ϕ20 mm
ϕ120 mm
Rotor diameter (mm) Main material
20 Stainless steel
Total flow rate (L/h) (H2O–kerosene system) Hold-up volume (mL) Extr action stage efficiency Flow ratio (A/O) Suggested rotor speed (r/min)
0–5
120 Glass fibre reinforced plastic 0–1000
20
9000
N95%
N95%
1/10–10/1 3000–5000
1/10–10/1 2800
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Fig. 3. Flowsheet for separation Y and RE elements in the bench scale test.
the housing. Then each liquid leaves its collector ring through a tangential exit, and flows into an adjacent stage respectively. The extraction cascade is formed by linking the exit to its corresponding inlet of the neighbor contactors in the opposite direction. Two types of annular centrifugal contactors used in the tests were designed and manufactured at INET: a ϕ20 mm annular centrifugal contactor (with 20 mm of the rotor diameter) used in the bench scale test, and a ϕ120 mm annular centrifugal contactor (with 120 mm of the rotor inside diameter) in the pilot-plant test. The
shown in Fig. 2. Two immiscible liquids with different density are fed from the opposite sides into the annular mixing zone between the spinning rotor and the stationary housing. The liquid–liquid dispersion created by turbulent Couette flow in the annular mixing zone flows by gravity to the inlet in the bottom face of the rotor and thus into the centrifugal separating zone inside the rotor. Here the dispersion breaks and separates rapidly under the high centrifugal force. The separated phases flow separately through the heavy phase weir and the light phase weir of the rotor into their collector rings in
Table 3 The composition of the feed solution RE
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Mole fraction 0.3070 0.2326 0.0122 0.0573 0.2214 0.0414 0.0063 0.0438 0.0060 0.0344 0.0052 0.0159 0.0021 0.0125 0.0018
Table 4 Parameters of the extraction flowsheet in the bench scale test (25 °C) System HA section
HEHEHP section
Composition
Access to stage Flow rate (L/h) Composition Access to stage Flow rate (L/h)
Organic phase
Feed solution
Scrubbing acid
Stripping acid
Scrubbing acid
Scrubbing water
32% HA–20% iso-octylalcohol– 48% kerosene 1
Feed solution pH = 3
2.15 mol/L HCl
3.0 mol/L HCl
6.0 mol/L HCl
H2 O
45
55
60
63
64
1.5
0.15
0.39
0.07
1.0
1.0
32% HEHEHP– 68% kerosene 1
Y and La solution 5
1.0 mol/L HCl 12
4.0 mol/L HCl 17
6.0 mol/L HCl 19
H2 O 20
1.62
1.08
0.322
0.108
1.0
1.0
158
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Fig. 4. Flowsheet for separation Y and RE elements in the pilot-plant test.
specifications of both ϕ20 mm and ϕ120 mm annular centrifugal contactors under the normal condition are presented in Table 2. 2.3. Procedures 2.3.1. Distribution ratio and separation factor Both the distribution ratios and the separation factors were important for separation of RE ions, so the separation factors of RE ions in the 32%HA–20% isooctylalcohol–48% kerosene–RECl system must be determined, and the distribution ratios of RE ions in the 32% HEHEHP–68% kerosene–RECl system must also be determined. The distribution ratio was calculated by the following equation (Zhou et al., 1985): D ¼ ½REO;eq =½REA;eq
The separation factor was calculated by the following equation (Zhou et al., 1985): b ¼ D1 =D2
ð2Þ
Where β is the separation factor of two kinds of RE ions, D1 and D2 are the distribution ratios of two kinds of RE ions in the same system. The mixture of RE oxides was dissolved in hydrochloric acid, then the total concentration of RE was analyzed by EDTA titration using xylenol orange as an indicator. The concentration of each rare earth element in the aqueous phase was analyzed with ICP-AES (Inductive Coupled Plasma). The concentration of RE in the organic phase was determined by mass balance. A pH meter was used for pH measurement.
ð1Þ
Where D is the distribution ratio of RE ion, [RE]O,eq and [RE]A,eq are the equilibrium concentrations of RE ion in the organic phase and in the aqueous phase respectively (mol/L-1). Table 5 The composition of the solution after Y stripping Element
Y
La
Pr
Nd
Ho
Er
Ca
g/L
80
0.5 × 10− 3
b1 × 10− 3
b1 × 10− 3
2.7 × 10− 3
b0.2 × 10− 3
2.0 × 10− 3
2.3.2. The bench scale test The mixture of RE oxides was first dissolved with HCl to prepare solution. Then extraction separation of La + Y and other RE elements from the prepared solution after removing both Fe and Al with HA was carried out with the 32% HA–20% iso-octylalcohol– 48% kerosene. Because the distribution ratios of La and Y in the system were low, they remained in the aqueous phase. Then extraction separation of La and Y from the aqueous phase was carried out with the 32% HEHEHP–68% kerosene to obtain the high purity Y
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Table 6 Parameters of the extraction flowsheet in the pilot-plant test (25 °C) System HA section
HEHEHP section
N235 section
Composition
Access to stage Flow rate (L/h) Composition Access to stage Flow rate (L/h) Composition
Access to stage Flow rate (L/h)
Organic phase
Feed solution
Scrubbing acid
Stripping acid
Scrubbing acid
Scrubbing water
32% HA–20% iso-octylalcohol– 48% kerosene 1 412 50% HEHEHP– 50% kerosene 1 130 35% N235–20% iso-octyl alcohol– 45% kerosene 1 17.5
Feed solution pH = 3
2 mol/L HCl
3 mol/L HCl
6 mol/L HCl
H2 O
50 41.2 Y and La solution
65 82 1 mol/L HCl 19 37.5
72 20.1 4 mol/L HCl 26 17.5
75 40 6 mol/L HCl 30 40
78 40 H2 O
8 123 Solution after stripping Y
32 40 H2 O
3 17.5
solution. At last, Y2O3 with 99.99% of purity was obtained after stripping the organic phase containing Y with 4 mol/L HCl, precipitation with H 2 C 2 O 4 , filtration, and ignition (Jingming et al., 1995). In the precipitation process, when the H2C2O4/RECl3 molar ratio was higher than 2.0, the acidity of the solution was less than 0.5 mol/L, and the temperature was 25 °C, the yield of Y could reach 99%. The temperature of ignition was 900 °C. The extraction flowsheet for obtaining the high purity Y solution was developed on the basis of both separation factors and distribution ratios of RE elements in the 32% HA– 20% iso-octylalcohol–48% kerosene–RECl system and the 32% HEHEHP–68% kerosene–RECl system respectively. The extraction flowsheet is shown in Fig. 3. The oil in the raffinate was removed by skimming. The composition of the feed solution is shown in Table 3. Parameters of the extraction flowsheet are presented in Table 4 (Peijiong et al., 1995). 84 stages of ϕ20 mm annular centrifugal contactors were applied in the bench scale test of the extraction flowsheet. 2.3.3. The pilot-plant test On the basis of the bench scale test, the extraction flowsheet was improved to guarantee purity and yield of Y in the pilot-plant test. The new extraction flowsheet is shown in Fig. 4. The composition of the solution after Y stripping is shown in Table 5. Parameters of the extraction flowsheet are presented in Table 6. In the new extraction flowsheet, the section to remove Fe with tertiary amine (N235) as extractant was added. 118 stages of ϕ120 mm annular centrifugal contactors that their main material was glass fibre reinforced plastic was applied in the pilot-plant test of the extraction flowsheet.
8 3.0
3. Results and discussion 3.1. Distribution ratios and separation factors Variations of the separation factor of La and Y with the mole ratio of La/Y in the 32% HA–20% iso-octylalcohol–48% kerosene–RECl system are present in Table 7. It was shown that βLa/Y was greater than 1.10 when the mole ratio of La/Y was less than 0.4. The mole ratio of La/Y in the mixture of RE oxides in this paper was about 0.535, so βLa/Y was less than 1.0. Therefore it was very difficult to separate La and Y only with HA. Variations of the separation factors of lanthanide (Ln) ions to Y with temperature in the 32% HA–20% isooctylalcohol–48% kerosene–RECl system are presented in Table 8. It was shown that βLn/Y was greater than 1. 0 but βLa/Y was less than 1.0. Moreover the higher the temperature, the lower βRE/Y was. Therefore 25 °C was selected in these tests. Zizhong (1991) systematically studied variations of the separation factors of RE ions with the pH of the equilibrium aqueous phase in the 15%~20% HA–15%∼20% isooctylalcohol–60%–70% kerosene–RECl system. The experimental results showed that 4.7–5.1 of pH was good for separation of Ln and Y. Variations of the distribution ratios of some RE ions with the pH of the equilibrium aqueous phase in the 32%
Table 7 Variations of the separation factor of La and Y with the mole ratio of La/Y (25 °C) Mole ratio of La/Y
0.10
0.40
0.70
4.49
8.33
βLa/Y
1.25
1.10
0.77
0.59
0.40
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Table 8 Variations of separation factors between Y and RE elements with temperature (pH = 4.8) Temperature (°C)
βLa/Y
βCe/Y
βPr/Y
βNd/Y
βGd/Y
βHo/Y
βEr/Y
βSm/Y
βEu/Y
βDy/Y
26 35 40 45 50
0.637 0.601 0.548 0.519 0.507
1.71 1.60 1.58 1.50 1.43
1.90 1.74 1.66 1.60 1.54
1.97 1.85 1.76 1.65 1.62
2.54 2.39 2.27 2.05 1.95
2.28 2.22 2.19 2.06 2.00
2.21 2.22 2.20 2.19 2.09
3.20 3.12 2.81 2.54 2.42
3.22 3.10 2.81 2.55 2.41
2.40 2.30 1.90 1.80 1.55
HEHEHP–68% kerosene–RECl system are presented in Table 9. It was shown that the distribution ratio of Y was approximate to that of heavy RE ions, but was much greater than that of light RE ions, and the higher pH, the greater the distribution ratios of RE ions. From the above it was established that separation of Y and light RE was difficult with HA from the mixture of RE oxides however was easy with HEHEHP. So in this paper, both HA and HEHEHP were selected for producing high purity Y. 3.2. The bench scale test The concentrations of some RE elements in the raffinate of the extraction section with HA as extractant are shown in Table 10. The concentrations of Y and La in the outlet organic phase of the extraction section with HA as extractant are shown in Table 11. Both La and Y were successfully separated from other RE elements, and the recovery of Y was about 96%. Test results of the extraction section with HEHEHP as extractant are shown in Table 12. Y was successfully separated from La, and the recovery of Y was about 99%. Y2O3 with 99.99% of purity was obtained after stripping the organic phase containing Y with HCl, precipitation with H2C2O4, filtration, and ignition (see Table 9 Variations of distribution ratios of RE elements with pH (25 °C) pH
DY
DLa
DNd
DSm
DGd
DHo
0.35 0.45 0.56 0.67 0.79 1.29
8.05 10.1 16.0 51.9 78.8 87.1
b1 × 10− 4 5 × 10− 4 1 × 10− 3 0.002 0.004 0.074
0.005 0.01 0.02 0.02 0.05 1.37
0.1 0.1 0.1 0.3 0.3 0.7
0.1 0.2 0.4 0.9 1.4 12.8
2.4 4.4 3.5 12.5 12.5 43.5
Table 13). In addition, the purity of La in the raffinate could also reach 99%. 3.3. The pilot-plant test The pilot-plant tests were carried out for four times, with the continuous operation time 79 h, 80 h, 103 h, and 95 h respectively. Results of the pilot-plant test were similar to those of the bench scale test. Y2O3 with 99.99% of purity was also obtained, and the total recovery of Y was about 95%. Percentages by weight of other RE oxides in the final Y2O3 production are shown in Table 13, and the total percentage of other impurities such as Ca, Fe, Si, and Pb, etc. was less than 0.0015%. All centrifugal contactors have been operated for about 1400 h in all tests including the mechanical tests, the hydraulic tests and the mass transfer tests. When the rotor speed of the centrifugal contactors was 2200 r/min, the amplitude and the noise intensity of the centrifugal contactors were lower than 10 μm and 85 dB respectively. Meanwhile, the temperature of the centrifugal contactors was lower than 50 °C after 103 h of operation (25 °C of ambient temperature). Both the low temperature and the little amplitude are useful to maintain the normal lifetime of the centrifugal contactors. During the whole pilot-plant tests, other mechanical damages of
Table 11 Concentration of La and Y in the outlet organic phase Element
La
Y
Concentration (mg/L)
9.9
41.24
Table 12 Results of separating Y from La Element
Table 10 Constituents in the raffinate Element Concentration (mg/L)
Nd 1.03
Er 0.25
Ho 0.22
La
Y 3
9.3 × 10
10.1 × 103
Y
La
Nd
Er
Ho
Concentration in the raffinate 4.5 7200 1.0 0.02 0.02 (mg/L) Concentration in the outlet organic 6730 0.03 0.21 0.22 0.13 phase (mg/L)
b0.001 b0.0001 b0.0005 b0.0005 b0.0005 b0.001 b0.0005
b0.001
b0.001
b0.0005
b0.0005
b0.0005
b0.0005
b0.0005
b0.001 0.00041 b0.0003 0.0012 0.00069 0.0015 b0.001 b0.0003 b0.001
Bench scale test Pilot-plant test
0.00048
b0.0002
b0.00038
b0.0003
b0.0001
Tb4O7 Sm2O3 Nd2O3 Pr6O11 Ce2O3 La2O3 RE oxide
Table 13 Percentages by weight of other RE oxides in the final Y2O3 production (%)
Eu2O3
Gd2O3
Dy2O3
Ho2O3
Er2O3
Tm2O3
Yb2O3
Lu2O3
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the centrifugal contactors did not happen except that 28 shafts and 36 bearings were corroded by acid solutions because the seals were not tight; so the operation of all centrifugal contactors was stable and reliable. Moreover, the application of centrifugal contactors in the RE extraction flowsheet brought in obvious benefits for reducing the area of factory building and the liquid hold-up volume, and shortening the time required for reaching the steady-state operation. 4. Conclusion Based on study of both the separation factors of RE ions in the 32% HA–20% iso-octylalcohol–48% kerosene–RECl system and the distribution ratios of RE ions in the 32% HEHEHP–68% kerosene–RECl system, the extraction flowsheet for producing high purity Y was developed at INET. Both the bench scale test and the pilot-plant test of the flowsheet were performed with ϕ20 mm and ϕ120 mm annular centrifugal contactors respectively. It was shown that Y2O3 with 99.99% of purity could be obtained, and the total recovery of Y was about 95% in the pilot-plant test. All of results demonstrated the successful application of annular centrifugal contactors in the extraction flowsheet for producing high purity Y. References Bernstein, G.J., Grosvenor, D.E., Lenc, J.F., Levitz, N.M., 1973a. Development and Performance of a High-Speed, Long-rotor Centrifugal Contactor for Application to Reprocessing LMFBR Fuels. ANL-7968. Argonne National Laboratory, Argonne, IL. Bernstein, G.J., Grosvenor, D.E., Lenc, J.F., Levitz, N.M., 1973b. Development and Performance of a High-Speed Annular Centrifugal Contactor. ANL-7969. Argonne National Laboratory, Argonne, IL. Chunsheng, L., Jiangtao, J., Yi, Z., Guang, X., Chunhua, Y., Biaoguo, L., Guangxian, X., 2001. Extraction of scandium from ionadsorptive rare earth deposit by naphthenic acid. J. Alloys Compd. 323–324, 833–837. Guangxian, X., 2002. Rare Earths. Metallurgy Industry Press, Beijing, China, pp. 827–870 (in Chinese). Gupta, B., Malik, P., Deep, A., 2003. Solvent extraction and separation of tervalent lanthanides and yttrium using Cyanex 923. Solvent Extr. Ion Exch. 21 (2), 239–258. Han, L., Zhichuan, C., Shulan, M., 1987. Extraction equilibria of individual rare earth in HEHEHP–kerosene–HCl–RECl3 system. J. Chin. Rare Earth Soc. 5 (3), 71–74 (in Chinese). Jiazhen, Z., 1984. Study on performance of 10-mm miniature annular centrifugal extractor. Chin. Chem. Ind. Eng. 12 (6), 25–29 (in Chinese). Jingming, X., Fuyi, B., Xitai, G., Chengqun, Z., Peijiong, H., Jiazhen, Z., Derong, T., Junfu, L., Renxuan, X., 1995. Constraction of industrial scale test base for separating high purity rare earths. Rare Earths 16 (2), 1–8 (in Chinese). Leonard, R.A., 1988. Recent advances in centrifugal contactor design. Sep. Sci. Technol. 23 (12 and 13), 1473–1487.
162
J. Zhou et al. / Hydrometallurgy 85 (2007) 154–162
Leonard, R.A., Bernstein, G.J., Ziegler, A.A., Pelto, R.H., 1980. Annular centrifugal contactor for solvent extraction. Sep. Sci. Technol. 15 (4), 925–943. Peijiong, H., Yushun, Y., Jun, F., Fuyi, B., Mingde, Y., 1995. Producing high purity yttrium by two solvent extraction in Φ20 mm centrifugal extractor. Rare Earths 16 (2), 9–18 (in Chinese). Wang, Y.G., Yue, S.T., Li, D.Q., Jin, M.J., Li, C.Z., 2002. Solvent extraction of scandium (III), yttrium (III), lanthanides (III), and divalent metal ions with sec-nonylphenoxy acetic acid. Solvent Extr. Ion Exch. 20 (6), 701–716. Wuhua, D., Wendong, Y., Xiuzhu, Z., Fengqi, L., Jiazhen, Z., 2001. Performance of three-stage cascade ϕ70 mm centrifugal extractor used in nuclear industry. Chin. J. Nucl. Sci. Eng. 21 (3), 282–287 (in Chinese). Wuhua, D., Chongli, S., Qiulin, W., Xiuzhu, Z., Jiazhen, Z., 2005. Development and performance of a new annular centrifugal contactor for semi-industrial scale. Sep. Sci. Technol. 40 (9), 1871–1883. Xiaobo, S., Junmei, Z., Shulan, M., Deqian, L., 2005. Synergistic extraction and separation of yttrium from heavy rare earths using mixture of sec-octylphenoxy acetic acid and bis (2,4,4-trimethylpentyl) phosphinic acid. Anal. Chim. Acta 533, 83–88.
Xiuzhu, Z., Jiazhen, Z., Chengqun, Z., Wendong, Y., 1997. Application of annular centrifugal contactor on separating indium from iron. Sep. Sci. Technol. 32 (16), 2705–2713. Yingli, Z., Tienchung, F., Juwen, T., Chikuei, W., Yungli, M., Linfeng, C., Yunna, W., 1980. A research in the behaviour and mechanism of the extraction of the rare earths by means of mixed system of naphthenic acid and acetamide. J. Lanzhou Univ. (Sci. Technol.) 3, 67–77 (in Chinese). Zheng, D., Gray, N.B., Stevens, G.W., 1991. Comparison of naphthenic acid, versatic acid and D2EHPA for the separation of rare earths. Solvent Extr. Ion Exch. 9 (1), 85–102. Zhigeng, Z., Chengqun, Z., Jiazhen, Z., Fengqi, L., Xinmin, H., 1993. Study on the hydraulic performance of 230-mm annular centrifugal extractor. Chin. Chem. Eng. 21 (4), 21–28 (in Chinese). Zhou, L., Yigui, L., Weiyang, F., 1985. The Processes and Facilities of Liquid–Liquid Extraction. Nuclear Energy Press, Beijing, China, pp. 40–89 (in Chinese). Zizhong, F., 1991. Extraction separation and purification of yttrium oxide with naphthenic acid from hydrochloric acid solution. Uranium Min. Metall. 10 (2), 42–48 (in Chinese).
Application of annular centrifugal contactors in the extraction flowsheet for producing high purity yttrium Jiazhen Zhou, Wuhua Duan ⁎, Xiuzhu Zhou, Chengqun Zhang Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 102201, China Received 16 January 2006; received in revised form 30 May 2006; accepted 5 August 2006 Available online 18 October 2006
Abstract Compared with mixer-settlers applied widely in the hydrometallurgical industry of rare earths (RE), centrifugal contactors have several advantages such as low hold-up volume, excellent phase separation, high mass transfer efficiency, compact and short pieces of equipment, etc., and have been successfully used in some industrial fields. Yttrium (Y) is an important element and in great demand in many industries. For a variety of uses in many specialized areas, the high purity Y is often required. However, the separation and purification of Y by solvent extraction from RE mixture is widely known to be difficult due to their similar chemical properties. This paper studied both the separation factors of RE ions in the 32% HA (naphthenic acid) − 20% iso-octylalcohol–48% kerosene–RECl system and the distribution ratios of RE ions in the 32% HEHEHP (2-ethylhexyl phosphonic acid mono-2ethylhexyl ester) −68% kerosene–RECl system. Based on these studies, an extraction flowsheet for producing high purity Y with HA and HEHEHP as extractants has been developed. Both the bench scale test and the pilot-plant test of the flowsheet have been performed with ϕ20 mm and ϕ120 mm centrifugal contactors respectively. It is shown that Y2O3 with 99.99% purity was obtained, and the total recovery of Y was about 95%. © 2006 Elsevier B.V. All rights reserved. Keywords: Centrifugal contactor; Extraction; Rare earth; Yttrium; High purity; HEHEHP; Naphthenic acid
1. Introduction Yttrium (Y) is an important element and in great demand in astronavigation, luminescence, nuclear energy and metallurgical industries. For a variety of uses in these specialized areas, high purity Y is often required. For example, the fluorescent grade Y2O3 requires the content of relevant RE impurities should be lower than 1 × 10− 4 (weight fraction, National standards of China: ⁎ Corresponding author. Institute of Nuclear and New Energy Technology, Tsinghua University, P. O. Box 1021, Beijing 102201, China. Tel.: +86 10 8019038; fax: +86 10 62771740. E-mail address: [email protected] (W. Duan). 0304-386X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2006.08.010
GB3503-83). However, the separation and purification of Y from RE is widely known to be difficult due to their similar chemical properties (Wang et al., 2002; Xiaobo et al., 2005). Amongst different methods used for the purpose, such as chromatography, ion exchange, emulsified liquid membrane and solvent extraction, solvent extraction is one of the most popular and versatile techniques (Chunsheng et al., 2001). Over the years a number of extractants have been employed for the extraction separation of Y from other RE and more prominent among these are high molecular weight amines (HMWA), carboxylic acids, Cyanex 923, Cyanex 302, Cyanex 272, alkylphosphorus extractants (Gupta et al., 2003). HEHEHP (2-ethylhexyl phosphonic acid mono-
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Table 1 Composition of the mixture of RE oxides RE oxide
La2O3
Ce2O3
Pr6O11
Nd2O3
Sm2O3
Eu2O3
Gd2O3
Tb4O7
Percentage (wt.%) RE oxide Percentage (wt.%)
27.0 Dy2O3 4.41
0.6 Ho2O3 0.77
4.3 Er2O3 2.42
14.1 Tm2O3 b0.3
2.85 Yb2O3 1.78
0.8 Lu2O3 b0.3
4.66 Y2O3 35.0
0.86
2-ethylhexyl ester) and HA (naphthenic acid) have been reported to be better extractants in extraction separation of Y from other RE (Han et al., 1987; Yingli et al., 1980; Zheng et al., 1991). At present, mixer-settlers have been applied widely in the hydrometallurgical industry of RE (Guangxian, 2002). However, they have some disadvantages, such as high hold-up volume, large floor space requirement, and the escape of toxic and/or flammable vapors from the organics, etc. Annular centrifugal contactors are efficient extraction pieces of equipment in extraction processes. Compared with mixer-settlers, annular centrifugal contactors offer the following advantages (Leonard, 1988; Wuhua et al., 2005): • Low hold-up volume; • Excellent phase separation;
• High mass transfer efficiency; • Compact and short; • Rapid start-up, shut-down and wash out of the process liquors. The primary centrifugal contactor, which was the paddle type, had been successfully developed and operated for many years at Savannah River Plant (SRL). In the late 1960s, the paddle-type centrifugal contactor was modified into the annular type at Argonne National Laboratory (ANL), which was reliable, easy to operate and maintain (Bernstein et al., 1973a,b; Leonard et al., 1980). In the late 1970s, Institute of Nuclear and New Energy Technology, Tsinghua University, China (INET) started to develop its own annular centrifugal contactors. From that time on, a series of annular centrifugal contactors have been developed with the rotor diameter from 10 mm to
Fig. 1. Schematic of the annular centrifugal contactor.
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Fig. 2. The flow of two phases in the centrifugal contactor.
230 mm and used successfully in some industrial fields at INET (Jiazhen, 1984; Wuhua et al., 2001; Zhigeng et al., 1993; Xiuzhu et al., 1997). At present, the main material of the centrifugal contactors is the stainless steel or titanium that can be corroded by H2SO4 or HCl, so they cannot be applied in extraction systems containing these acids. In order to make the centrifugal contactor be applied in the industrial scale test for producing the high purity Y, which the extraction systems containing H2SO4 or/and HCl, a centrifugal contactor with 120 mm of the rotor diameter (ϕ120 mm) that the main material is the glass fibre reinforced plastic (GFRP) has been developed at INET. GFRP has many desirable properties including high corrosion resistance, high strength and stiffness to weight ratio, low cost, and can easily be optimized to suit any applied load. In this paper, an extraction flowsheet with annular centrifugal contactors for producing the high purity Y developed in our lab is described. Results of both the bench scale test and the pilot-plant test are presented.
including Ca, Si, and Pb in the mixture of RE oxides. Both HEHEHP and HA were kindly supplied by Shanghai Organic Factory, China, and were dissolved in sulfated kerosene to prepare the organic phase. The tertiary amine (N235) was also supplied by Shanghai Organic Factory, China, and its indicated formula is R3N (R = CnH2n+1, n = 8, or 9, or 10). These extractants (technical grade, N95 wt.%) were used without further purification. All other chemicals used were of analytical grade.
2. Experimental procedure 2.1. Materials The mixture of RE oxides was obtained from Shanghai Yuelong Chemical Plant, China. Its composition is shown in Table 1. There were about 0.1% of Fe, and 0.3% Al and less than 0.1% of other impurities
2.2. Apparatus The annular centrifugal contactor is shown in Fig. 1. The flow of two phases in the centrifugal contactor is Table 2 The specifications of annular centrifugal contactors Type
ϕ20 mm
ϕ120 mm
Rotor diameter (mm) Main material
20 Stainless steel
Total flow rate (L/h) (H2O–kerosene system) Hold-up volume (mL) Extr action stage efficiency Flow ratio (A/O) Suggested rotor speed (r/min)
0–5
120 Glass fibre reinforced plastic 0–1000
20
9000
N95%
N95%
1/10–10/1 3000–5000
1/10–10/1 2800
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Fig. 3. Flowsheet for separation Y and RE elements in the bench scale test.
the housing. Then each liquid leaves its collector ring through a tangential exit, and flows into an adjacent stage respectively. The extraction cascade is formed by linking the exit to its corresponding inlet of the neighbor contactors in the opposite direction. Two types of annular centrifugal contactors used in the tests were designed and manufactured at INET: a ϕ20 mm annular centrifugal contactor (with 20 mm of the rotor diameter) used in the bench scale test, and a ϕ120 mm annular centrifugal contactor (with 120 mm of the rotor inside diameter) in the pilot-plant test. The
shown in Fig. 2. Two immiscible liquids with different density are fed from the opposite sides into the annular mixing zone between the spinning rotor and the stationary housing. The liquid–liquid dispersion created by turbulent Couette flow in the annular mixing zone flows by gravity to the inlet in the bottom face of the rotor and thus into the centrifugal separating zone inside the rotor. Here the dispersion breaks and separates rapidly under the high centrifugal force. The separated phases flow separately through the heavy phase weir and the light phase weir of the rotor into their collector rings in
Table 3 The composition of the feed solution RE
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Mole fraction 0.3070 0.2326 0.0122 0.0573 0.2214 0.0414 0.0063 0.0438 0.0060 0.0344 0.0052 0.0159 0.0021 0.0125 0.0018
Table 4 Parameters of the extraction flowsheet in the bench scale test (25 °C) System HA section
HEHEHP section
Composition
Access to stage Flow rate (L/h) Composition Access to stage Flow rate (L/h)
Organic phase
Feed solution
Scrubbing acid
Stripping acid
Scrubbing acid
Scrubbing water
32% HA–20% iso-octylalcohol– 48% kerosene 1
Feed solution pH = 3
2.15 mol/L HCl
3.0 mol/L HCl
6.0 mol/L HCl
H2 O
45
55
60
63
64
1.5
0.15
0.39
0.07
1.0
1.0
32% HEHEHP– 68% kerosene 1
Y and La solution 5
1.0 mol/L HCl 12
4.0 mol/L HCl 17
6.0 mol/L HCl 19
H2 O 20
1.62
1.08
0.322
0.108
1.0
1.0
158
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Fig. 4. Flowsheet for separation Y and RE elements in the pilot-plant test.
specifications of both ϕ20 mm and ϕ120 mm annular centrifugal contactors under the normal condition are presented in Table 2. 2.3. Procedures 2.3.1. Distribution ratio and separation factor Both the distribution ratios and the separation factors were important for separation of RE ions, so the separation factors of RE ions in the 32%HA–20% isooctylalcohol–48% kerosene–RECl system must be determined, and the distribution ratios of RE ions in the 32% HEHEHP–68% kerosene–RECl system must also be determined. The distribution ratio was calculated by the following equation (Zhou et al., 1985): D ¼ ½REO;eq =½REA;eq
The separation factor was calculated by the following equation (Zhou et al., 1985): b ¼ D1 =D2
ð2Þ
Where β is the separation factor of two kinds of RE ions, D1 and D2 are the distribution ratios of two kinds of RE ions in the same system. The mixture of RE oxides was dissolved in hydrochloric acid, then the total concentration of RE was analyzed by EDTA titration using xylenol orange as an indicator. The concentration of each rare earth element in the aqueous phase was analyzed with ICP-AES (Inductive Coupled Plasma). The concentration of RE in the organic phase was determined by mass balance. A pH meter was used for pH measurement.
ð1Þ
Where D is the distribution ratio of RE ion, [RE]O,eq and [RE]A,eq are the equilibrium concentrations of RE ion in the organic phase and in the aqueous phase respectively (mol/L-1). Table 5 The composition of the solution after Y stripping Element
Y
La
Pr
Nd
Ho
Er
Ca
g/L
80
0.5 × 10− 3
b1 × 10− 3
b1 × 10− 3
2.7 × 10− 3
b0.2 × 10− 3
2.0 × 10− 3
2.3.2. The bench scale test The mixture of RE oxides was first dissolved with HCl to prepare solution. Then extraction separation of La + Y and other RE elements from the prepared solution after removing both Fe and Al with HA was carried out with the 32% HA–20% iso-octylalcohol– 48% kerosene. Because the distribution ratios of La and Y in the system were low, they remained in the aqueous phase. Then extraction separation of La and Y from the aqueous phase was carried out with the 32% HEHEHP–68% kerosene to obtain the high purity Y
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Table 6 Parameters of the extraction flowsheet in the pilot-plant test (25 °C) System HA section
HEHEHP section
N235 section
Composition
Access to stage Flow rate (L/h) Composition Access to stage Flow rate (L/h) Composition
Access to stage Flow rate (L/h)
Organic phase
Feed solution
Scrubbing acid
Stripping acid
Scrubbing acid
Scrubbing water
32% HA–20% iso-octylalcohol– 48% kerosene 1 412 50% HEHEHP– 50% kerosene 1 130 35% N235–20% iso-octyl alcohol– 45% kerosene 1 17.5
Feed solution pH = 3
2 mol/L HCl
3 mol/L HCl
6 mol/L HCl
H2 O
50 41.2 Y and La solution
65 82 1 mol/L HCl 19 37.5
72 20.1 4 mol/L HCl 26 17.5
75 40 6 mol/L HCl 30 40
78 40 H2 O
8 123 Solution after stripping Y
32 40 H2 O
3 17.5
solution. At last, Y2O3 with 99.99% of purity was obtained after stripping the organic phase containing Y with 4 mol/L HCl, precipitation with H 2 C 2 O 4 , filtration, and ignition (Jingming et al., 1995). In the precipitation process, when the H2C2O4/RECl3 molar ratio was higher than 2.0, the acidity of the solution was less than 0.5 mol/L, and the temperature was 25 °C, the yield of Y could reach 99%. The temperature of ignition was 900 °C. The extraction flowsheet for obtaining the high purity Y solution was developed on the basis of both separation factors and distribution ratios of RE elements in the 32% HA– 20% iso-octylalcohol–48% kerosene–RECl system and the 32% HEHEHP–68% kerosene–RECl system respectively. The extraction flowsheet is shown in Fig. 3. The oil in the raffinate was removed by skimming. The composition of the feed solution is shown in Table 3. Parameters of the extraction flowsheet are presented in Table 4 (Peijiong et al., 1995). 84 stages of ϕ20 mm annular centrifugal contactors were applied in the bench scale test of the extraction flowsheet. 2.3.3. The pilot-plant test On the basis of the bench scale test, the extraction flowsheet was improved to guarantee purity and yield of Y in the pilot-plant test. The new extraction flowsheet is shown in Fig. 4. The composition of the solution after Y stripping is shown in Table 5. Parameters of the extraction flowsheet are presented in Table 6. In the new extraction flowsheet, the section to remove Fe with tertiary amine (N235) as extractant was added. 118 stages of ϕ120 mm annular centrifugal contactors that their main material was glass fibre reinforced plastic was applied in the pilot-plant test of the extraction flowsheet.
8 3.0
3. Results and discussion 3.1. Distribution ratios and separation factors Variations of the separation factor of La and Y with the mole ratio of La/Y in the 32% HA–20% iso-octylalcohol–48% kerosene–RECl system are present in Table 7. It was shown that βLa/Y was greater than 1.10 when the mole ratio of La/Y was less than 0.4. The mole ratio of La/Y in the mixture of RE oxides in this paper was about 0.535, so βLa/Y was less than 1.0. Therefore it was very difficult to separate La and Y only with HA. Variations of the separation factors of lanthanide (Ln) ions to Y with temperature in the 32% HA–20% isooctylalcohol–48% kerosene–RECl system are presented in Table 8. It was shown that βLn/Y was greater than 1. 0 but βLa/Y was less than 1.0. Moreover the higher the temperature, the lower βRE/Y was. Therefore 25 °C was selected in these tests. Zizhong (1991) systematically studied variations of the separation factors of RE ions with the pH of the equilibrium aqueous phase in the 15%~20% HA–15%∼20% isooctylalcohol–60%–70% kerosene–RECl system. The experimental results showed that 4.7–5.1 of pH was good for separation of Ln and Y. Variations of the distribution ratios of some RE ions with the pH of the equilibrium aqueous phase in the 32%
Table 7 Variations of the separation factor of La and Y with the mole ratio of La/Y (25 °C) Mole ratio of La/Y
0.10
0.40
0.70
4.49
8.33
βLa/Y
1.25
1.10
0.77
0.59
0.40
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Table 8 Variations of separation factors between Y and RE elements with temperature (pH = 4.8) Temperature (°C)
βLa/Y
βCe/Y
βPr/Y
βNd/Y
βGd/Y
βHo/Y
βEr/Y
βSm/Y
βEu/Y
βDy/Y
26 35 40 45 50
0.637 0.601 0.548 0.519 0.507
1.71 1.60 1.58 1.50 1.43
1.90 1.74 1.66 1.60 1.54
1.97 1.85 1.76 1.65 1.62
2.54 2.39 2.27 2.05 1.95
2.28 2.22 2.19 2.06 2.00
2.21 2.22 2.20 2.19 2.09
3.20 3.12 2.81 2.54 2.42
3.22 3.10 2.81 2.55 2.41
2.40 2.30 1.90 1.80 1.55
HEHEHP–68% kerosene–RECl system are presented in Table 9. It was shown that the distribution ratio of Y was approximate to that of heavy RE ions, but was much greater than that of light RE ions, and the higher pH, the greater the distribution ratios of RE ions. From the above it was established that separation of Y and light RE was difficult with HA from the mixture of RE oxides however was easy with HEHEHP. So in this paper, both HA and HEHEHP were selected for producing high purity Y. 3.2. The bench scale test The concentrations of some RE elements in the raffinate of the extraction section with HA as extractant are shown in Table 10. The concentrations of Y and La in the outlet organic phase of the extraction section with HA as extractant are shown in Table 11. Both La and Y were successfully separated from other RE elements, and the recovery of Y was about 96%. Test results of the extraction section with HEHEHP as extractant are shown in Table 12. Y was successfully separated from La, and the recovery of Y was about 99%. Y2O3 with 99.99% of purity was obtained after stripping the organic phase containing Y with HCl, precipitation with H2C2O4, filtration, and ignition (see Table 9 Variations of distribution ratios of RE elements with pH (25 °C) pH
DY
DLa
DNd
DSm
DGd
DHo
0.35 0.45 0.56 0.67 0.79 1.29
8.05 10.1 16.0 51.9 78.8 87.1
b1 × 10− 4 5 × 10− 4 1 × 10− 3 0.002 0.004 0.074
0.005 0.01 0.02 0.02 0.05 1.37
0.1 0.1 0.1 0.3 0.3 0.7
0.1 0.2 0.4 0.9 1.4 12.8
2.4 4.4 3.5 12.5 12.5 43.5
Table 13). In addition, the purity of La in the raffinate could also reach 99%. 3.3. The pilot-plant test The pilot-plant tests were carried out for four times, with the continuous operation time 79 h, 80 h, 103 h, and 95 h respectively. Results of the pilot-plant test were similar to those of the bench scale test. Y2O3 with 99.99% of purity was also obtained, and the total recovery of Y was about 95%. Percentages by weight of other RE oxides in the final Y2O3 production are shown in Table 13, and the total percentage of other impurities such as Ca, Fe, Si, and Pb, etc. was less than 0.0015%. All centrifugal contactors have been operated for about 1400 h in all tests including the mechanical tests, the hydraulic tests and the mass transfer tests. When the rotor speed of the centrifugal contactors was 2200 r/min, the amplitude and the noise intensity of the centrifugal contactors were lower than 10 μm and 85 dB respectively. Meanwhile, the temperature of the centrifugal contactors was lower than 50 °C after 103 h of operation (25 °C of ambient temperature). Both the low temperature and the little amplitude are useful to maintain the normal lifetime of the centrifugal contactors. During the whole pilot-plant tests, other mechanical damages of
Table 11 Concentration of La and Y in the outlet organic phase Element
La
Y
Concentration (mg/L)
9.9
41.24
Table 12 Results of separating Y from La Element
Table 10 Constituents in the raffinate Element Concentration (mg/L)
Nd 1.03
Er 0.25
Ho 0.22
La
Y 3
9.3 × 10
10.1 × 103
Y
La
Nd
Er
Ho
Concentration in the raffinate 4.5 7200 1.0 0.02 0.02 (mg/L) Concentration in the outlet organic 6730 0.03 0.21 0.22 0.13 phase (mg/L)
b0.001 b0.0001 b0.0005 b0.0005 b0.0005 b0.001 b0.0005
b0.001
b0.001
b0.0005
b0.0005
b0.0005
b0.0005
b0.0005
b0.001 0.00041 b0.0003 0.0012 0.00069 0.0015 b0.001 b0.0003 b0.001
Bench scale test Pilot-plant test
0.00048
b0.0002
b0.00038
b0.0003
b0.0001
Tb4O7 Sm2O3 Nd2O3 Pr6O11 Ce2O3 La2O3 RE oxide
Table 13 Percentages by weight of other RE oxides in the final Y2O3 production (%)
Eu2O3
Gd2O3
Dy2O3
Ho2O3
Er2O3
Tm2O3
Yb2O3
Lu2O3
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the centrifugal contactors did not happen except that 28 shafts and 36 bearings were corroded by acid solutions because the seals were not tight; so the operation of all centrifugal contactors was stable and reliable. Moreover, the application of centrifugal contactors in the RE extraction flowsheet brought in obvious benefits for reducing the area of factory building and the liquid hold-up volume, and shortening the time required for reaching the steady-state operation. 4. Conclusion Based on study of both the separation factors of RE ions in the 32% HA–20% iso-octylalcohol–48% kerosene–RECl system and the distribution ratios of RE ions in the 32% HEHEHP–68% kerosene–RECl system, the extraction flowsheet for producing high purity Y was developed at INET. Both the bench scale test and the pilot-plant test of the flowsheet were performed with ϕ20 mm and ϕ120 mm annular centrifugal contactors respectively. It was shown that Y2O3 with 99.99% of purity could be obtained, and the total recovery of Y was about 95% in the pilot-plant test. All of results demonstrated the successful application of annular centrifugal contactors in the extraction flowsheet for producing high purity Y. References Bernstein, G.J., Grosvenor, D.E., Lenc, J.F., Levitz, N.M., 1973a. Development and Performance of a High-Speed, Long-rotor Centrifugal Contactor for Application to Reprocessing LMFBR Fuels. ANL-7968. Argonne National Laboratory, Argonne, IL. Bernstein, G.J., Grosvenor, D.E., Lenc, J.F., Levitz, N.M., 1973b. Development and Performance of a High-Speed Annular Centrifugal Contactor. ANL-7969. Argonne National Laboratory, Argonne, IL. Chunsheng, L., Jiangtao, J., Yi, Z., Guang, X., Chunhua, Y., Biaoguo, L., Guangxian, X., 2001. Extraction of scandium from ionadsorptive rare earth deposit by naphthenic acid. J. Alloys Compd. 323–324, 833–837. Guangxian, X., 2002. Rare Earths. Metallurgy Industry Press, Beijing, China, pp. 827–870 (in Chinese). Gupta, B., Malik, P., Deep, A., 2003. Solvent extraction and separation of tervalent lanthanides and yttrium using Cyanex 923. Solvent Extr. Ion Exch. 21 (2), 239–258. Han, L., Zhichuan, C., Shulan, M., 1987. Extraction equilibria of individual rare earth in HEHEHP–kerosene–HCl–RECl3 system. J. Chin. Rare Earth Soc. 5 (3), 71–74 (in Chinese). Jiazhen, Z., 1984. Study on performance of 10-mm miniature annular centrifugal extractor. Chin. Chem. Ind. Eng. 12 (6), 25–29 (in Chinese). Jingming, X., Fuyi, B., Xitai, G., Chengqun, Z., Peijiong, H., Jiazhen, Z., Derong, T., Junfu, L., Renxuan, X., 1995. Constraction of industrial scale test base for separating high purity rare earths. Rare Earths 16 (2), 1–8 (in Chinese). Leonard, R.A., 1988. Recent advances in centrifugal contactor design. Sep. Sci. Technol. 23 (12 and 13), 1473–1487.
162
J. Zhou et al. / Hydrometallurgy 85 (2007) 154–162
Leonard, R.A., Bernstein, G.J., Ziegler, A.A., Pelto, R.H., 1980. Annular centrifugal contactor for solvent extraction. Sep. Sci. Technol. 15 (4), 925–943. Peijiong, H., Yushun, Y., Jun, F., Fuyi, B., Mingde, Y., 1995. Producing high purity yttrium by two solvent extraction in Φ20 mm centrifugal extractor. Rare Earths 16 (2), 9–18 (in Chinese). Wang, Y.G., Yue, S.T., Li, D.Q., Jin, M.J., Li, C.Z., 2002. Solvent extraction of scandium (III), yttrium (III), lanthanides (III), and divalent metal ions with sec-nonylphenoxy acetic acid. Solvent Extr. Ion Exch. 20 (6), 701–716. Wuhua, D., Wendong, Y., Xiuzhu, Z., Fengqi, L., Jiazhen, Z., 2001. Performance of three-stage cascade ϕ70 mm centrifugal extractor used in nuclear industry. Chin. J. Nucl. Sci. Eng. 21 (3), 282–287 (in Chinese). Wuhua, D., Chongli, S., Qiulin, W., Xiuzhu, Z., Jiazhen, Z., 2005. Development and performance of a new annular centrifugal contactor for semi-industrial scale. Sep. Sci. Technol. 40 (9), 1871–1883. Xiaobo, S., Junmei, Z., Shulan, M., Deqian, L., 2005. Synergistic extraction and separation of yttrium from heavy rare earths using mixture of sec-octylphenoxy acetic acid and bis (2,4,4-trimethylpentyl) phosphinic acid. Anal. Chim. Acta 533, 83–88.
Xiuzhu, Z., Jiazhen, Z., Chengqun, Z., Wendong, Y., 1997. Application of annular centrifugal contactor on separating indium from iron. Sep. Sci. Technol. 32 (16), 2705–2713. Yingli, Z., Tienchung, F., Juwen, T., Chikuei, W., Yungli, M., Linfeng, C., Yunna, W., 1980. A research in the behaviour and mechanism of the extraction of the rare earths by means of mixed system of naphthenic acid and acetamide. J. Lanzhou Univ. (Sci. Technol.) 3, 67–77 (in Chinese). Zheng, D., Gray, N.B., Stevens, G.W., 1991. Comparison of naphthenic acid, versatic acid and D2EHPA for the separation of rare earths. Solvent Extr. Ion Exch. 9 (1), 85–102. Zhigeng, Z., Chengqun, Z., Jiazhen, Z., Fengqi, L., Xinmin, H., 1993. Study on the hydraulic performance of 230-mm annular centrifugal extractor. Chin. Chem. Eng. 21 (4), 21–28 (in Chinese). Zhou, L., Yigui, L., Weiyang, F., 1985. The Processes and Facilities of Liquid–Liquid Extraction. Nuclear Energy Press, Beijing, China, pp. 40–89 (in Chinese). Zizhong, F., 1991. Extraction separation and purification of yttrium oxide with naphthenic acid from hydrochloric acid solution. Uranium Min. Metall. 10 (2), 42–48 (in Chinese).