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Separation of zirconium and hafnium using Diphonix® chelating ion-exchange resin
Hydrometallurgy 95 (2009) 350–353
Contents lists available at ScienceDirect
Hydrometallurgy j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / h yd r o m e t
Technical note
Separation of zirconium and hafnium using Diphonix® chelating ion-exchange resin M. Smolik a,⁎, A. Jakóbik-Kolon a, M. Porański b a b
Department of Inorganic Chemistry and Technology, Faculty of Chemistry, Silesian University of Technology, 44-100 Gliwice, Poland Power Research & Testing Company “Energopomiar” Ltd, PO Box 402, 44-101 Gliwice, Poland
A R T I C L E
I N F O
Article history: Received 28 February 2008 Received in revised form 20 May 2008 Accepted 21 May 2008 Available online 28 May 2008 Keywords: Hafnium Zirconium Separation Ion exchange Diphonix®
A B S T R A C T The sorption behavior and possible separation of zirconium and hafnium from acid solution was studied on Diphonix® chelating resin containing diphosphonic, sulfonic and carboxylic acid groups. Sulfuric acid solution was selected and then used in dynamic studies. The effects of acid concentration, temperature and solution flow rate on the separation of Zr and Hf using Diphonix® ion-exchanger were investigated. The best separation of these elements was obtained in 0.5 M H2SO4 at 22 °C with a linear flow rate b 7.5 cm/h (b 0.79 BV/h). Results show Diphonix® resin to be very promising in the separation of zirconium from hafnium. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Hafnium occurs in all zirconium ores in the range of 2–3% but the use of these elements in the nuclear industry requires that reactor grade zirconium contains less than 100 ppm of hafnium, which is difficult because of their similar chemical properties resulting from almost identical atomic and ionic radii. Analytical problems also increase when the content of hafnium in zirconium compounds approaches the level of 100 ppm. Additionally zirconium minerals are the only sources of hafnium, which has many applications, e.g. semiconductors, anti-reflective covers, incandescent fibers. The best method of separating these metals and the most frequently used are: solvent extraction (Amer, 1981; Brown and Healy, 1978; Golub and Sergun'kin, 1971); ion exchange (Begovich and Sisson, 1983; Bonefeld and Umland, 1985; Charlot et al., 1960; Delons et al., 2006; Hague and Machlan, 1961; Hubicki, 1988; Hurst, 1983; Kozera et al., 1980; Kraus and Moore, 1949; Lister et al., 1956; Machlan and Hague, 1962; Marov et al., 1960; Poriel et al., 2006; Qureshi and Husain, 1971); and distillation of fused salts (Flengas and Dutrizac, 1977; Moulin et al., 1984; Salyulev et al., 1985). In the case of ion exchange, different anion and cation ion exchangers are employed. The most often used are strong-base anion exchange resins, where zirconium is adsorbed in preference to hafnium from concentrated hydrochloric acid or diluted sulfuric acid solutions (Charlot et al., 1960; Delons et al., 2006; Hague and Machlan, 1961; Kraus and Moore, 1949; Machlan and Hague, 1962; Poriel et al., 2006); and cation exchange resins where hafnium is preferentially adsorbed from diluted sulfuric acid solution (Begovich and Sisson, ⁎ Corresponding author. Fax: +48 32 237 22 77. E-mail address: [email protected] (M. Smolik). 0304-386X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2008.05.010
1983; Bonefeld and Umland, 1985; Hurst, 1983; Kozera et al., 1980; Lister et al., 1956). Moreover, only one paper presents the separation of Zr and Hf using chelating cation exchangers containing phosphonic acid groups (Hubicki, 1988). This information and the fact that the affinity of a chelating ion exchanger for specific metals depends on the reciprocal position of the functional groups, their spatial configuration, steric effects and other features related to the construction of resin (Hubicki, 1988), prompted to an investigation into the separation of hafnium and zirconium applying new resins with –PO3H2 groups and defined structure. Diphonix® resin is a commercially available chelating cation exchanger containing diphosphonic, sulfonic and carboxylic acid groups bonded to the polymer matrix [Horwitz et al., 1994 and 1995]. It has never been tested previously for Zr and Hf separation. In this paper the behavior of hafnium and zirconium on the Diphonix® resin has been investigated to appraise the possibility of separation of these metals in the selected system. 2. Experimental 2.1. Reagents and solutions Diphonix® and Monophos® resins were obtained from EiChrom Industries (France). Diphonix® and Monophos® were received in moist form and their moisture contents were determined to be 62.4 ± 0.3%, 60.2± 0.4%, respectively by drying at 105 °C to constant weight. High purity zirconium dichloride oxide octahydrate 99.9% (metal basis ~ 100 ppm Hf in relation to Zr), and hafnium dichloride oxide octahydrate 98%+ were purchased from Alfa Aesar (Germany) and used as received. Reagent grade hydrochloric, sulfuric and nitric acids, ethylene diamine tetraacetic acid (EDTA) disodium salt and Eriochrome
M. Smolik et al. / Hydrometallurgy 95 (2009) 350–353
351
Table 1 Weight distribution coefficients of Zr and Hf on Diphonix® in various acids solutions Medium 1.0 M H2SO4 1.0 M HNO3 1.0 M HCl
Hf
Zr
630 23000 9300
430 21000 8300
SF 0.68 0.91 0.89
black T supplied by POCh (Gliwice, Poland) were used without further purification. “Pure” zirconium dichloride oxide octahydrate (~2% Hf) and zirconium sulfate tetrahydrate (~2% Hf) were supplied by BDH LTD (England). Water was distilled and purified using a Millipore Elix 10 system. 2.2. Apparatus IRIS II ADVANTAGE RAD HR (serial no 7063) Thermo Jarrell Ash (USA) inductively coupled plasma emission spectrometer was used applying the instrument conditions and wavelengths reported in previous work (Smolik et al., 2007a). Four various emission lines of Hf were used. 2.3. Analytical methods In preliminary studies on weight distribution coefficients, the concentrations of metals in solutions were determined using ICP-AES (Smolik et al., 2007a). In dynamic studies, zirconium was determined by complexometric titration with EDTA in 2 M HCl solution in the presence of Eriochrome black T as indicator (Welcher, 1958). Each determination was realized thrice at a relative standard deviation not exceeding 1.5%. The minor component, hafnium was determined by ICP-AES from solutions containing 0.01 g Zr in 10 ml mL 2 M HCl solution (0.1% matrix of Zr) in the range of 1000–30,000 ppm Hf (Smolik et al., 2007b). Standards of the same concentrations of matrix (Zr with low ~100 ppm Hf) and corresponding acid solution were applied. Relative standard deviations of the results obtained were not greater than 1.6%.
Fig. 2. The breakthrough curves of zirconium and hafnium on Diphonix® resin at T = 22 °C (obtained in two simultaneous experiments) and at T = 5 °C. (cH2SO4 = 0.5 M; v = 2.64 BV/h).
contacted for 48 h and the concentrations of metals in solution were determined by ICP-AES. The weight distribution coefficient of Zr and Hf was calculated using the formula: λ¼
ðc0 −cs Þ V cs m
where: λ — weight distribution coefficient; c0 — initial concentration of metal in solution; cs — final concentration of metal in solution; m — dry ion-exchanger mass in H+ form [g]; V — total volume of the solution [mL]. Separation factor was also calculated applying the formula: SF ¼
λZr λHf
where: λZr, λHf — weight distribution coefficient of Zr and Hf respectively.
2.4.1. Selection of medium and determination of weight distribution coefficient (λ) To choose the best medium for zirconium and hafnium separation by continuous ion exchange, preliminary investigations were carried out in which the weight distribution coefficients of both elements were determined on Diphonix® resin in 1 M solutions of HCl, HNO3 and H2SO4. For this purpose 0.2 g resin and 10 mL solution were
2.4.2. Separation of Hf from Zr by frontal analysis All experiments concerning dynamic methods of Hf and Zr separation were performed utilizing a feed aqueous solution of zirconium sulfate containing the natural amount of hafnium of composition: [Zr] = 0.07 M (6.38 g/L); [Hf] = 8.63 ⁎ 10− 4 M (0.154 g/L); [Hf]/([Hf] + [Zr]) = 2.4% (m/m) and various concentrations of H2SO4 (0.2–1.0 M). Experiments were performed at least in duplicate at room temperature (22 ± 2 °C) and measured the effects of concentration of sulfuric acid, temperature and solution flow rate, using 9.1 mL (6.5 g)
Fig. 1. The breakthrough curves of zirconium and hafnium on Diphonix® resin: (cH2SO4 = 0.2 M, v = 2.64 BV/h, T = 22 °C).
Fig. 3. The breakthrough curves of zirconium and hafnium on Diphonix® resin: (cH2SO4 = 1.0 M, v = 2.64 BV/h, T = 22 °C).
2.4. Procedure
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M. Smolik et al. / Hydrometallurgy 95 (2009) 350–353
Diphonix® and 8.3 mL (6.5 g) Monophos® resin pre-equilibrated with sulfuric acid solution of proper concentration and placed in a glass column of 1.1 cm diameter. The above feed solution was then supplied to the column using a peristaltic pump at constant flow rate of 24 mL/h (2.64 BV/h and linear flow rate of 25.2 cm/h) or 7.2 mL/h (0.79 BV/h and linear flow rate of 7.5 cm/h). The effluent from the column was collected into fractions of 10 or 20 mL. Larger scale experiments were performed in a glass column of 1.9 cm diameter and 32.5 g (45.5 mL) of Diphonix® resin was used with a flow rate of 24 mL/h (0.53 BV/h and linear flow rate of 8.4 cm/h). The breakthrough curves were obtained as a dependence of fractions of initial concentration of metal (c / c0) and volumes of the collected effluent (in number of bed volumes [BVs]). 3. Results and discussion Table 1 shows the weight distribution coefficients of zirconium and hafnium determined separately for comparable amounts of both elements by equilibration on Diphonix® resin in HCl, HNO3, and H2SO4. These preliminary tests showed sulfuric acid to be the best medium for the separation of both metals and was therefore chosen for further dynamic studies. The breakthrough curves obtained for various concentrations of sulfuric acid are presented in Figs. 1–3 for 0.2, 0.5 and 1 M H2SO4, respectively. They show that the best separation occurs in 0.5 M sulfuric acid solution (Fig. 2) which worsens slightly when the concentration of sulfuric acid increases to 1 M (Fig. 3). The best concentration of H2SO4 (0.5 M) is consistent with that applied in Hf and Zr separation employing other chelating cation exchangers (Hubicki, 1988). The reproducibility of the process, shown in Fig. 2, indicates no significant difference between separations obtained in two simultaneous experiments. The breakthrough curves obtained at a flow rate of 7.2 mL/h (0.79 BV/h) are presented in Fig. 4. Comparison of Figs. 4 and 2 shows that the efficiency of separation of Zr and Hf increases with a decrease in the solution flow rate under the flow rate regimes tested. Fig. 2 also compares the breakthrough curves obtained at room temperature (22 °C) and at 5 °C and shows only a slight effect of temperature on the efficiency of Zr separation from Hf. The degree of separation at the same solution flow rate decreases as the temperature diminishes. However, kinetic factors may be the reason if the rate of zirconium ions displacement by hafnium ions at low temperature is lower. However this displacement cannot be confirmed since the zirconium concentration is over 40 times greater than that of hafnium. Some experiments were carried out on a larger scale (Fig. 4) utilizing the best tested conditions (t = 22 °C, 0.5 M H2SO4) at a slightly slower flow rate (0.53 BV/h) to obtain better results. In the collected fraction from 0–340 mL, the zirconium sulfate solution contained
Fig. 4. The breakthrough curves of zirconium and hafnium on Diphonix® resin: (S) small scale (v = 0.79 BV/h, mass of resin 6.5 g); (L) larger scale (v = 0.53 BV/h, mass of resin 32.5 g. T = 22 °C, cH2SO4 = 0.5 M).
Fig. 5. The breakthrough curves of zirconium and hafnium on Monophos® resin: (v = 2.89 BV/h, T = 22 °C, cH2SO4 = 0.5 M).
0.24% Hf in relation to Zr (which represents a tenfold decrease of initial Hf content) and 0.0107 mol Zr representing 45% Zr recovery efficiency. Fig. 5 presents the results of separation of Zr and Hf using Monophos® resin containing monophosphonic and sulfonic acid groups, which has never been applied yet in Hf and Zr separation. However the separation of zirconium and hafnium was significantly poorer than that obtained in the case of Diphonix® ion exchanger. This suggests that resins with similar functional groups but with various reciprocal positions differ significantly in separation performance. 4. Conclusions It is possible to utilize Diphonix® resin containing diphosphonic, sulfonic and carboxylic acid groups for separation zirconium and hafnium. The best medium for separation of hafnium and zirconium is 0.5 M sulfuric acid. A decrease in temperature from 22 °C to 5 °C lowers the degree of metals separation; while lower flow rates through the column increases zirconium and hafnium separation. Under the best examined conditions, a 10 fold decrease of initial content of hafnium in zirconium can be achieved, with an efficiency of zirconium recovery equal to 45%. These results prove that Diphonix® resin is very promising for the separation of zirconium from hafnium. References Amer, S., 1981. Solvent extraction applications in hydrometallurgy — 4: titanium, zirconium and hafnium. Revista de Metalurgia (Madrid) 17 (6), 377–395. Begovich, J.M., Sisson, W.G., 1983. Continuous ion exchange separation of zirconium and hafnium by using an annular chromatograph. Hydrometallurgy 10 (1), 11–20. Bonefeld, B., Umland, F., 1985. Separation of zirconium and hafnium complexes by means of ion exchangers. Fresenius' Zeitschrift fuer Analytische Chemie 322 (5), 495–498 (in German, with English Abstr.). Brown, A.E.P., Healy, T.V., 1978. Separation of zirconium from hafnium in nitric acid solutions by solvent extraction using dibutyl butyl-phosphonate. Hydrometallurgy 3 (3), 265–274. Charlot, G., Hure, J., Saint-James, M., Tremillon, B., 1960. Separation of zirconium and hafnium. Patent FR 19600419 (in French). Delons, L., Lagarde, S., Poriel, L., Lemaire, M., Favre Reguillon, A., Pellet Rostaing, S., 2006. Method for separating zirconium and hafnium. Patent WO 2006040458. Flengas, S.N., Dutrizac, J.E., 1977. New process for the separation of hafnium from zirconium. Metallurgical Transactions. B 8B (3), 377–385. Golub, A.M., Sergun'kin, V.N., 1971. Extraction of zirconium and hafnium thiocyanate complexes into cyclohexane. Zh. Prikl. Khim., vol. 43(6), pp. 1203–1209 (in Russian). Hague, J.L., Machlan, L.A., 1961. Separation of hafnium from zirconium by anion exchange. Journal of research, National Bureau of Standards 65A, 75–77. Horwitz, E.P., Alexandratos, S.D., Gatrone, R.C., Chiarizia, R., 1994 and 1995. Phosphonic acid based ion exchange resins. Patent US 5281631 and US 5449462. Hubicki, Z., 1988. Separation of zirconium(IV) from hafnium(IV) on various types of selective ion-exchangers. Solvent Extraction and Ion Exchange 6 (1), 183–205. Hurst, F.J., 1983. Separation of hafnium from zirconium in sulfuric acid solutions using pressurized ion exchange. Hydrometallurgy 10 (1), 1–10. Kozera, F., Dobrowolski, J., Kempa, A., Hubicki, Z., 1980. Ion-exchange separation of hafnium from zirconium. Effect of conditions of the process on the effectiveness of separation in sulfate solution. Zeszyty Naukowe Politechniki Śląskiej, Chemia 677 (96), 39–47 (in Polish).
M. Smolik et al. / Hydrometallurgy 95 (2009) 350–353 Kraus, K.A., Moore, G.E., 1949. Separation of zirconium and hafnium with anionexchange resins. Journal of the American Chemical Society 71, 3263. Lister, B.A.J., Duncan, J.F., Hutcheon, J.M., , 1956. Separation of hafnium from zirconium. Patent US 2759792. Machlan, L.A., Hague, J.L., 1962. Separation of hafnium from zirconium and their determination: separation by anion exchange. Journal of research, National Bureau of Standards A66, 517–520. Marov, I.N., Belyaeva, V.K., Ermakov, A.N., Ryabchikov, D.I., Vernadskii, V.I., 1960. Chromatographic separation of zirconium and hafnium. Zhurnal Neorganicheskoi Khimii, vol. 5, pp. 2844–2847 (in Russian). Moulin, L., Thouvenin, P., Brun, P., 1984. New process for zirconium and hafnium separation. ASTM Special Technical Publication 37–44. Poriel, L., Pellet-Rostaing, S., Lamotte, V., Lemaire, M., Favre-Reguillon, A., 2006. Zirconium and hafnium separation, Part 2. Solid/liquid extraction in hydrochloric acid aqueous solution with anion exchange resins. Separation Science and Technology 41 (12), 2711–2722.
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Qureshi, M., Husain, K., 1971. Quantitative cation exchange separation of zirconium and hafnium in formic acid media. Analytical Chemistry 43 (3), 447–449. Salyulev, A.B., Kudyakov, V. Ya., Smirnov, M.V., Moskalenko, N.I., 1985. Separation of hafnium and zirconium in solutions of their tetrachlorides in molten alkali-metal chlorides. Journal of Applied Chemistry of The USSR 57 (8), 1710–1713 (in Russian). Smolik, M., Jakóbik-Kolon, A., Porański, M., 2007a. Extraction of zirconium and hafnium in polyethylene glycol-based aqueous biphasic system. Separation Science and Technology 42, 1831–1841. Smolik, M., Jakóbik-Kolon, A., Porański, M., 2007b. Determination of hafnium in zirconium compounds using inductively coupled plasma atomic emission spectrometry. Annals of the Polish Chemical Society www.pg.gda.pl/chem/InneJednostki/ PTChem/ptch.htm. Welcher, F.J., 1958. The Analytical Uses of Ethylene Diamine Tetraacetic Acid. D. Van Nostrand Company, Inc., Princeton, New Jersey.
Contents lists available at ScienceDirect
Hydrometallurgy j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / h yd r o m e t
Technical note
Separation of zirconium and hafnium using Diphonix® chelating ion-exchange resin M. Smolik a,⁎, A. Jakóbik-Kolon a, M. Porański b a b
Department of Inorganic Chemistry and Technology, Faculty of Chemistry, Silesian University of Technology, 44-100 Gliwice, Poland Power Research & Testing Company “Energopomiar” Ltd, PO Box 402, 44-101 Gliwice, Poland
A R T I C L E
I N F O
Article history: Received 28 February 2008 Received in revised form 20 May 2008 Accepted 21 May 2008 Available online 28 May 2008 Keywords: Hafnium Zirconium Separation Ion exchange Diphonix®
A B S T R A C T The sorption behavior and possible separation of zirconium and hafnium from acid solution was studied on Diphonix® chelating resin containing diphosphonic, sulfonic and carboxylic acid groups. Sulfuric acid solution was selected and then used in dynamic studies. The effects of acid concentration, temperature and solution flow rate on the separation of Zr and Hf using Diphonix® ion-exchanger were investigated. The best separation of these elements was obtained in 0.5 M H2SO4 at 22 °C with a linear flow rate b 7.5 cm/h (b 0.79 BV/h). Results show Diphonix® resin to be very promising in the separation of zirconium from hafnium. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Hafnium occurs in all zirconium ores in the range of 2–3% but the use of these elements in the nuclear industry requires that reactor grade zirconium contains less than 100 ppm of hafnium, which is difficult because of their similar chemical properties resulting from almost identical atomic and ionic radii. Analytical problems also increase when the content of hafnium in zirconium compounds approaches the level of 100 ppm. Additionally zirconium minerals are the only sources of hafnium, which has many applications, e.g. semiconductors, anti-reflective covers, incandescent fibers. The best method of separating these metals and the most frequently used are: solvent extraction (Amer, 1981; Brown and Healy, 1978; Golub and Sergun'kin, 1971); ion exchange (Begovich and Sisson, 1983; Bonefeld and Umland, 1985; Charlot et al., 1960; Delons et al., 2006; Hague and Machlan, 1961; Hubicki, 1988; Hurst, 1983; Kozera et al., 1980; Kraus and Moore, 1949; Lister et al., 1956; Machlan and Hague, 1962; Marov et al., 1960; Poriel et al., 2006; Qureshi and Husain, 1971); and distillation of fused salts (Flengas and Dutrizac, 1977; Moulin et al., 1984; Salyulev et al., 1985). In the case of ion exchange, different anion and cation ion exchangers are employed. The most often used are strong-base anion exchange resins, where zirconium is adsorbed in preference to hafnium from concentrated hydrochloric acid or diluted sulfuric acid solutions (Charlot et al., 1960; Delons et al., 2006; Hague and Machlan, 1961; Kraus and Moore, 1949; Machlan and Hague, 1962; Poriel et al., 2006); and cation exchange resins where hafnium is preferentially adsorbed from diluted sulfuric acid solution (Begovich and Sisson, ⁎ Corresponding author. Fax: +48 32 237 22 77. E-mail address: [email protected] (M. Smolik). 0304-386X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2008.05.010
1983; Bonefeld and Umland, 1985; Hurst, 1983; Kozera et al., 1980; Lister et al., 1956). Moreover, only one paper presents the separation of Zr and Hf using chelating cation exchangers containing phosphonic acid groups (Hubicki, 1988). This information and the fact that the affinity of a chelating ion exchanger for specific metals depends on the reciprocal position of the functional groups, their spatial configuration, steric effects and other features related to the construction of resin (Hubicki, 1988), prompted to an investigation into the separation of hafnium and zirconium applying new resins with –PO3H2 groups and defined structure. Diphonix® resin is a commercially available chelating cation exchanger containing diphosphonic, sulfonic and carboxylic acid groups bonded to the polymer matrix [Horwitz et al., 1994 and 1995]. It has never been tested previously for Zr and Hf separation. In this paper the behavior of hafnium and zirconium on the Diphonix® resin has been investigated to appraise the possibility of separation of these metals in the selected system. 2. Experimental 2.1. Reagents and solutions Diphonix® and Monophos® resins were obtained from EiChrom Industries (France). Diphonix® and Monophos® were received in moist form and their moisture contents were determined to be 62.4 ± 0.3%, 60.2± 0.4%, respectively by drying at 105 °C to constant weight. High purity zirconium dichloride oxide octahydrate 99.9% (metal basis ~ 100 ppm Hf in relation to Zr), and hafnium dichloride oxide octahydrate 98%+ were purchased from Alfa Aesar (Germany) and used as received. Reagent grade hydrochloric, sulfuric and nitric acids, ethylene diamine tetraacetic acid (EDTA) disodium salt and Eriochrome
M. Smolik et al. / Hydrometallurgy 95 (2009) 350–353
351
Table 1 Weight distribution coefficients of Zr and Hf on Diphonix® in various acids solutions Medium 1.0 M H2SO4 1.0 M HNO3 1.0 M HCl
Hf
Zr
630 23000 9300
430 21000 8300
SF 0.68 0.91 0.89
black T supplied by POCh (Gliwice, Poland) were used without further purification. “Pure” zirconium dichloride oxide octahydrate (~2% Hf) and zirconium sulfate tetrahydrate (~2% Hf) were supplied by BDH LTD (England). Water was distilled and purified using a Millipore Elix 10 system. 2.2. Apparatus IRIS II ADVANTAGE RAD HR (serial no 7063) Thermo Jarrell Ash (USA) inductively coupled plasma emission spectrometer was used applying the instrument conditions and wavelengths reported in previous work (Smolik et al., 2007a). Four various emission lines of Hf were used. 2.3. Analytical methods In preliminary studies on weight distribution coefficients, the concentrations of metals in solutions were determined using ICP-AES (Smolik et al., 2007a). In dynamic studies, zirconium was determined by complexometric titration with EDTA in 2 M HCl solution in the presence of Eriochrome black T as indicator (Welcher, 1958). Each determination was realized thrice at a relative standard deviation not exceeding 1.5%. The minor component, hafnium was determined by ICP-AES from solutions containing 0.01 g Zr in 10 ml mL 2 M HCl solution (0.1% matrix of Zr) in the range of 1000–30,000 ppm Hf (Smolik et al., 2007b). Standards of the same concentrations of matrix (Zr with low ~100 ppm Hf) and corresponding acid solution were applied. Relative standard deviations of the results obtained were not greater than 1.6%.
Fig. 2. The breakthrough curves of zirconium and hafnium on Diphonix® resin at T = 22 °C (obtained in two simultaneous experiments) and at T = 5 °C. (cH2SO4 = 0.5 M; v = 2.64 BV/h).
contacted for 48 h and the concentrations of metals in solution were determined by ICP-AES. The weight distribution coefficient of Zr and Hf was calculated using the formula: λ¼
ðc0 −cs Þ V cs m
where: λ — weight distribution coefficient; c0 — initial concentration of metal in solution; cs — final concentration of metal in solution; m — dry ion-exchanger mass in H+ form [g]; V — total volume of the solution [mL]. Separation factor was also calculated applying the formula: SF ¼
λZr λHf
where: λZr, λHf — weight distribution coefficient of Zr and Hf respectively.
2.4.1. Selection of medium and determination of weight distribution coefficient (λ) To choose the best medium for zirconium and hafnium separation by continuous ion exchange, preliminary investigations were carried out in which the weight distribution coefficients of both elements were determined on Diphonix® resin in 1 M solutions of HCl, HNO3 and H2SO4. For this purpose 0.2 g resin and 10 mL solution were
2.4.2. Separation of Hf from Zr by frontal analysis All experiments concerning dynamic methods of Hf and Zr separation were performed utilizing a feed aqueous solution of zirconium sulfate containing the natural amount of hafnium of composition: [Zr] = 0.07 M (6.38 g/L); [Hf] = 8.63 ⁎ 10− 4 M (0.154 g/L); [Hf]/([Hf] + [Zr]) = 2.4% (m/m) and various concentrations of H2SO4 (0.2–1.0 M). Experiments were performed at least in duplicate at room temperature (22 ± 2 °C) and measured the effects of concentration of sulfuric acid, temperature and solution flow rate, using 9.1 mL (6.5 g)
Fig. 1. The breakthrough curves of zirconium and hafnium on Diphonix® resin: (cH2SO4 = 0.2 M, v = 2.64 BV/h, T = 22 °C).
Fig. 3. The breakthrough curves of zirconium and hafnium on Diphonix® resin: (cH2SO4 = 1.0 M, v = 2.64 BV/h, T = 22 °C).
2.4. Procedure
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M. Smolik et al. / Hydrometallurgy 95 (2009) 350–353
Diphonix® and 8.3 mL (6.5 g) Monophos® resin pre-equilibrated with sulfuric acid solution of proper concentration and placed in a glass column of 1.1 cm diameter. The above feed solution was then supplied to the column using a peristaltic pump at constant flow rate of 24 mL/h (2.64 BV/h and linear flow rate of 25.2 cm/h) or 7.2 mL/h (0.79 BV/h and linear flow rate of 7.5 cm/h). The effluent from the column was collected into fractions of 10 or 20 mL. Larger scale experiments were performed in a glass column of 1.9 cm diameter and 32.5 g (45.5 mL) of Diphonix® resin was used with a flow rate of 24 mL/h (0.53 BV/h and linear flow rate of 8.4 cm/h). The breakthrough curves were obtained as a dependence of fractions of initial concentration of metal (c / c0) and volumes of the collected effluent (in number of bed volumes [BVs]). 3. Results and discussion Table 1 shows the weight distribution coefficients of zirconium and hafnium determined separately for comparable amounts of both elements by equilibration on Diphonix® resin in HCl, HNO3, and H2SO4. These preliminary tests showed sulfuric acid to be the best medium for the separation of both metals and was therefore chosen for further dynamic studies. The breakthrough curves obtained for various concentrations of sulfuric acid are presented in Figs. 1–3 for 0.2, 0.5 and 1 M H2SO4, respectively. They show that the best separation occurs in 0.5 M sulfuric acid solution (Fig. 2) which worsens slightly when the concentration of sulfuric acid increases to 1 M (Fig. 3). The best concentration of H2SO4 (0.5 M) is consistent with that applied in Hf and Zr separation employing other chelating cation exchangers (Hubicki, 1988). The reproducibility of the process, shown in Fig. 2, indicates no significant difference between separations obtained in two simultaneous experiments. The breakthrough curves obtained at a flow rate of 7.2 mL/h (0.79 BV/h) are presented in Fig. 4. Comparison of Figs. 4 and 2 shows that the efficiency of separation of Zr and Hf increases with a decrease in the solution flow rate under the flow rate regimes tested. Fig. 2 also compares the breakthrough curves obtained at room temperature (22 °C) and at 5 °C and shows only a slight effect of temperature on the efficiency of Zr separation from Hf. The degree of separation at the same solution flow rate decreases as the temperature diminishes. However, kinetic factors may be the reason if the rate of zirconium ions displacement by hafnium ions at low temperature is lower. However this displacement cannot be confirmed since the zirconium concentration is over 40 times greater than that of hafnium. Some experiments were carried out on a larger scale (Fig. 4) utilizing the best tested conditions (t = 22 °C, 0.5 M H2SO4) at a slightly slower flow rate (0.53 BV/h) to obtain better results. In the collected fraction from 0–340 mL, the zirconium sulfate solution contained
Fig. 4. The breakthrough curves of zirconium and hafnium on Diphonix® resin: (S) small scale (v = 0.79 BV/h, mass of resin 6.5 g); (L) larger scale (v = 0.53 BV/h, mass of resin 32.5 g. T = 22 °C, cH2SO4 = 0.5 M).
Fig. 5. The breakthrough curves of zirconium and hafnium on Monophos® resin: (v = 2.89 BV/h, T = 22 °C, cH2SO4 = 0.5 M).
0.24% Hf in relation to Zr (which represents a tenfold decrease of initial Hf content) and 0.0107 mol Zr representing 45% Zr recovery efficiency. Fig. 5 presents the results of separation of Zr and Hf using Monophos® resin containing monophosphonic and sulfonic acid groups, which has never been applied yet in Hf and Zr separation. However the separation of zirconium and hafnium was significantly poorer than that obtained in the case of Diphonix® ion exchanger. This suggests that resins with similar functional groups but with various reciprocal positions differ significantly in separation performance. 4. Conclusions It is possible to utilize Diphonix® resin containing diphosphonic, sulfonic and carboxylic acid groups for separation zirconium and hafnium. The best medium for separation of hafnium and zirconium is 0.5 M sulfuric acid. A decrease in temperature from 22 °C to 5 °C lowers the degree of metals separation; while lower flow rates through the column increases zirconium and hafnium separation. Under the best examined conditions, a 10 fold decrease of initial content of hafnium in zirconium can be achieved, with an efficiency of zirconium recovery equal to 45%. These results prove that Diphonix® resin is very promising for the separation of zirconium from hafnium. References Amer, S., 1981. Solvent extraction applications in hydrometallurgy — 4: titanium, zirconium and hafnium. Revista de Metalurgia (Madrid) 17 (6), 377–395. Begovich, J.M., Sisson, W.G., 1983. Continuous ion exchange separation of zirconium and hafnium by using an annular chromatograph. Hydrometallurgy 10 (1), 11–20. Bonefeld, B., Umland, F., 1985. Separation of zirconium and hafnium complexes by means of ion exchangers. Fresenius' Zeitschrift fuer Analytische Chemie 322 (5), 495–498 (in German, with English Abstr.). Brown, A.E.P., Healy, T.V., 1978. Separation of zirconium from hafnium in nitric acid solutions by solvent extraction using dibutyl butyl-phosphonate. Hydrometallurgy 3 (3), 265–274. Charlot, G., Hure, J., Saint-James, M., Tremillon, B., 1960. Separation of zirconium and hafnium. Patent FR 19600419 (in French). Delons, L., Lagarde, S., Poriel, L., Lemaire, M., Favre Reguillon, A., Pellet Rostaing, S., 2006. Method for separating zirconium and hafnium. Patent WO 2006040458. Flengas, S.N., Dutrizac, J.E., 1977. New process for the separation of hafnium from zirconium. Metallurgical Transactions. B 8B (3), 377–385. Golub, A.M., Sergun'kin, V.N., 1971. Extraction of zirconium and hafnium thiocyanate complexes into cyclohexane. Zh. Prikl. Khim., vol. 43(6), pp. 1203–1209 (in Russian). Hague, J.L., Machlan, L.A., 1961. Separation of hafnium from zirconium by anion exchange. Journal of research, National Bureau of Standards 65A, 75–77. Horwitz, E.P., Alexandratos, S.D., Gatrone, R.C., Chiarizia, R., 1994 and 1995. Phosphonic acid based ion exchange resins. Patent US 5281631 and US 5449462. Hubicki, Z., 1988. Separation of zirconium(IV) from hafnium(IV) on various types of selective ion-exchangers. Solvent Extraction and Ion Exchange 6 (1), 183–205. Hurst, F.J., 1983. Separation of hafnium from zirconium in sulfuric acid solutions using pressurized ion exchange. Hydrometallurgy 10 (1), 1–10. Kozera, F., Dobrowolski, J., Kempa, A., Hubicki, Z., 1980. Ion-exchange separation of hafnium from zirconium. Effect of conditions of the process on the effectiveness of separation in sulfate solution. Zeszyty Naukowe Politechniki Śląskiej, Chemia 677 (96), 39–47 (in Polish).
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