Ligand composition for zirconium and hafnium separation, and zirconium and hafnium separation method

Abstract

The present invention relates to a ligand composition for zirconium and hafnium separation and a zirconium and hafnium separation method, belonging to the technical field of metal solution extraction. The ligand composition for zirconium and hafnium separation of the present invention comprises at least two of persulfate ions, hydrogen persulfate ions, hydrogen monosulfate ions, hydrogen peroxide, perchlorate ions, hypochlorite ions, phosphate ions, and ammonium ions. The zirconium complex and hafnium complex formed by the combination of the ligand composition with zirconium and hafnium have a large difference in binding ability with an extractant, thereby realizing efficient separation of zirconium and hafnium.

Description

Technical Field

[0001] The invention relates to the technical field of metal solution extraction, and in particular to a ligand composition for zirconium and hafnium separation and a zirconium and hafnium separation method. Background Art

[0002] The thermal neutron absorption cross section of zirconium is only 0.18×10 -28 m 2 , which can effectively avoid the absorption of thermal neutrons and prevent nuclear leakage, and is often used as a nuclear reactor structural material or nuclear fuel cladding material; hafnium has a large thermal neutron absorption cross section (105×10 -28 m 2 ), high neutron absorption coefficient, and is often used as thermal neutron absorption material in nuclear reactors to control the reaction rate of nuclear reactors; it can be seen that zirconium and hafnium both play an important role in the nuclear industry and their roles are opposite. However, zirconium and hafnium coexist in nature, and because zirconium and hafnium have very similar physical and chemical properties other than nuclear properties, it is extremely difficult to separate the two.

[0003] At present, the separation methods of zirconium and hafnium mainly include pyrometallurgy and hydrometallurgy. Pyrometallurgy includes molten salt distillation and molten salt extraction. Molten salt distillation mainly uses the difference in solubility of ZrCl4 and HfCl4 in molten salt medium and combines with distillation tower to achieve separation of the two. Molten salt extraction mainly selects a specific molten salt system as an extractant, and uses the two-phase equilibrium between molten salt and liquid alloy of zirconium or hafnium to oxidize hafnium and enter the molten salt in the form of ions, and then separates it from the unreacted zirconium. However, pyrometallurgy has high operating temperature, high energy consumption, severe corrosion of high-temperature molten salt to equipment, and low production efficiency, which makes it difficult to meet the needs of large-scale industrial production.

[0004] Hydrometallurgy includes fractional crystallization, ion exchange and solvent extraction. The fractional crystallization method mainly uses the difference in solubility of K2HfF6 and K2ZrF6 in aqueous solution and the formation of K2ZrF6 crystals when the solubility decreases with temperature to achieve separation. However, the single-step zirconium-hafnium separation rate of this method is low, resulting in low separation efficiency. The ion exchange method uses specific cation exchange resins or anion exchange resins to separate zirconium and hafnium in solution, but the high cost of the resin and the limited adsorption capacity lead to low processing capacity. Compared with the fractional crystallization method or ion exchange method, the solvent extraction method mainly separates the two by selecting a suitable extractant and using the different distribution ratios of zirconium ions and hafnium ions in the organic phase and the aqueous phase. However, since the ionic radius of zirconium and hafnium differ by only 0.1Å and the electronegativity differs by only 0.1, the separation coefficient between the two is small, resulting in the separation effect of the existing zirconium-hafnium separation method to be improved. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a ligand composition for zirconium and hafnium separation and a zirconium and hafnium separation method.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a ligand composition for zirconium and hafnium separation, wherein the ligand composition comprises at least two of persulfate ions, hydrogen persulfate ions, hydrogen monosulfate ions, hydrogen peroxide, perchlorate ions, hypochlorite ions, phosphate ions, and ammonium ions.

[0008] The present invention has found that the 4f orbital of hafnium causes slight differences in chemical reactivity and coordination behavior between it and zirconium. By selecting specific ligands to combine with zirconium ions and hafnium ions, the coordination clusters of the formed zirconium complex and hafnium complex can have obvious charge differences, and the coordination structures of the two also have obvious size differences, which can significantly amplify the difference in binding ability between the zirconium complex and the hafnium complex and the extractant, so that more hafnium ions enter the organic phase, while most of the zirconium ions are retained in the aqueous phase. After multiple extractions, efficient separation of zirconium and hafnium can be achieved.

[0009] Optionally, the above-mentioned persulfate ion, hydrogen persulfate ion, hydrogen monopersulfate ion, perchlorate ion, hypochlorite ion, phosphate ion or ammonium ion can exist in the form of soluble (water-soluble) salts, such as sodium salts or potassium salts.

[0010] As a preferred embodiment of the ligand composition for zirconium and hafnium separation of the present invention, the ligand composition comprises persulfate ions and peroxymonosulfate ions, and the molar ratio of the persulfate ions to the peroxymonosulfate ions is (1~100):(1~100), preferably (40~60):(40~60), and more preferably (45~55):(45~55).

[0011] The study found that when persulfate ions combine with peroxymonosulfate ions, the zirconium and hafnium complexes will undergo varying degrees of oxidation or reconstruction of the coordination environment, thereby enhancing the binding ability of hafnium with the extractant and weakening the binding ability of zirconium with the extractant, thereby significantly improving the separation effect of zirconium and hafnium.

[0012] Optionally, in terms of molar fractions, the persulfate ions in the ligand composition may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts; the hydrogen permonosulfate ions may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts.

[0013] As a preferred embodiment of the ligand composition for zirconium and hafnium separation of the present invention, the ligand composition comprises a mixture of at least one of persulfate ions and peroxymonosulfate ions and hydrogen peroxide.

[0014] The study found that when persulfate ions or peroxymonosulfate ions are combined with hydrogen peroxide, the structural differences between the zirconium complex and the hafnium complex can be better enhanced, thereby changing the binding ability between the zirconium complex and the hafnium complex and the extractant, thereby significantly improving the separation effect of zirconium and hafnium.

[0015] As a preferred embodiment of the ligand composition for zirconium and hafnium separation of the present invention, the ligand composition comprises persulfate ions and hydrogen peroxide, and the molar ratio of the persulfate ions to the hydrogen peroxide is (1~100):(1~100), preferably (40~60):(40~60), and more preferably (45~55):(45~55).

[0016] Optionally, in terms of molar fractions, the persulfate ion in the ligand composition can be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts; the hydrogen peroxide can be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts.

[0017] As a preferred embodiment of the ligand composition for zirconium and hafnium separation according to the present invention, the ligand composition comprises peroxymonosulfate ions and hydrogen peroxide, and the molar ratio of the peroxymonosulfate ions to hydrogen peroxide is (1~100):(1~100), preferably (40~60):(40~60), and more preferably (45~55):(45~55).

[0018] Optionally, in terms of molar fractions, the amount of hydrogen permonosulfate ion in the ligand composition may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts; and the amount of hydrogen peroxide may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts.

[0019] As a preferred embodiment of the ligand composition for zirconium and hafnium separation of the present invention, the ligand composition comprises persulfate ion, peroxymonosulfate ion and hydrogen peroxide, and the molar ratio of the persulfate ion, peroxymonosulfate ion and hydrogen peroxide is (1-100): (1-100): (1-100), preferably (20-45): (20-45): (20-45), and more preferably (25-40): (25-40): (25-40).

[0020] Optionally, in terms of molar fractions, the persulfate ion in the ligand composition may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts; the hydrogen monopersulfate ion may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts; and the hydrogen peroxide may be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts.

[0021] In a second aspect, the present invention provides a method for separating zirconium and hafnium, comprising the following steps:

[0022] The mixed solution containing zirconium ions and hafnium ions is mixed with a ligand to obtain a solution containing a zirconium complex and a hafnium complex, and then an organic extractant is added thereto to perform solvent extraction treatment;

[0023] The ligand is the above-mentioned ligand composition for separation of zirconium and hafnium, or is selected from any one of persulfate ion, hydrogen persulfate ion, hydrogen monosulfate ion, hydrogen peroxide, perchlorate ion, hypochlorite ion, phosphate ion and ammonium ion.

[0024] As a preferred embodiment of the zirconium-hafnium separation method of the present invention, the molar ratio of the total amount of the zirconium ions and the hafnium ions to the ligand is (1-100):(1-100), preferably 1:(5-50).

[0025] The study found that the molar ratio of the total amount of zirconium ions and hafnium ions (i.e., the molar amount of zirconium ions + the molar amount of hafnium ions) to the ligand will affect the structure of the zirconium complex or hafnium complex (mono-nuclear, binuclear or poly-nuclear structure), and zirconium complexes or hafnium complexes with different structures have different geometric configurations and stabilities, which leads to significant differences in the binding ability with the extractant, thereby affecting the separation effect of zirconium and hafnium.

[0026] Optionally, the total amount of zirconium ions and hafnium ions can be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts by mole; the ligand can be 1 part, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 100 parts.

[0027] Optionally, the molar ratio of zirconium ions to hafnium ions in the mixed solution is (5-30): (1-10). Optionally, in terms of molar fractions, the zirconium ions in the mixed solution may be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, or 30 parts, and the hafnium ions may be 1 part, 2 parts, 4 parts, 6 parts, 8 parts, or 10 parts.

[0028] As a preferred embodiment of the zirconium and hafnium separation method of the present invention, the molar ratio of the total amount of zirconium ions and hafnium ions to the ligand is 1:(10-30). Optionally, the molar ratio of the total amount of zirconium ions and hafnium ions to the ligand can be any one of 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28, 1:30 or any two of the range values.

[0029] The study found that the zirconium-hafnium ions and ligands within the above molar ratio range can better enhance the selective coordination between the ligand and the zirconium-hafnium ions, thereby increasing the difference between the zirconium complex and the hafnium complex; moreover, it can also ensure that the ligand and the zirconium-hafnium ions are fully coordinated while avoiding the oversaturation or competitive coordination of the zirconium complex or the hafnium complex, thereby maintaining the binding efficiency with the extractant to achieve a good separation effect.

[0030] As a preferred embodiment of the zirconium and hafnium separation method of the present invention, the pH of the mixed solution containing zirconium ions and hafnium ions is 0.3 to 2.7, preferably 0.3 to 1.5. Optionally, the pH of the mixed solution containing zirconium ions and hafnium ions can be any one of 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7 or any two of the range values.

[0031] The study found that when the pH of the mixed solution containing zirconium ions and hafnium ions is 0.3~2.7, it can not only effectively avoid the precipitation of zirconium ions or hafnium ions, but also be beneficial to the change of the complex morphology, so as to better achieve efficient separation of zirconium and hafnium.

[0032] As a preferred embodiment of the zirconium and hafnium separation method of the present invention, the organic extractant includes at least one of MIBK (methyl isobutyl ketone), P507 (2-ethylhexyl phosphate-2-ethylhexyl ester), TBP (tributyl phosphate), and diisobutyl ketone.

[0033] As a preferred embodiment of the zirconium and hafnium separation method of the present invention, the temperature of the solvent extraction is 0-50°C and the time is ≥1min. Optionally, the temperature of the solvent extraction can be 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, and the time can be 1min, 5min, 10min, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention finds that the 4f orbital of hafnium causes slight differences in chemical reactivity and coordination behavior between it and zirconium. The coordination clusters of zirconium complexes and hafnium complexes formed by selecting specific ligands to combine with zirconium and hafnium have obvious charge differences, and the coordination structures of the two also have obvious size differences, thereby significantly amplifying the binding ability of the zirconium complexes and hafnium complexes with the extractant, thereby achieving efficient separation of zirconium and hafnium. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0037] Unless otherwise specified, other materials, reagents, etc. used in the examples can be obtained from commercial sources.

[0038] Example 1

[0039] This embodiment provides a zirconium and hafnium separation method, comprising the following steps:

[0040] S1. 0.6396 g of zirconium tetrachloride, 0.4509 g of hafnium tetrachloride and water are mixed to form a solution, and the pH of the solution is adjusted to 0.3 by hydrochloric acid to obtain a zirconium-hafnium ion mixed solution with a mass concentration of 500 ppm (the mass concentration of zirconium ions is 500 ppm, and the mass concentration of hafnium ions is 500 ppm);

[0041] S2. Mix the zirconium-hafnium ion mixture in S1 and the ligand (sodium persulfate) and stir for 10 minutes, then measure 10 mL of the mixed solution and add 10 mL of an organic extractant (methyl isobutyl ketone), extract at room temperature for 30 minutes (one extraction), and obtain an aqueous phase and an organic phase.

[0042] Embodiments 2 to 9

[0043] Embodiments 2 to 9 provide a method for separating zirconium and hafnium, comprising steps substantially the same as those of embodiment 1, except that the type of ligand and the amount of ligand added in step S2 are different.

[0044] Example 10

[0045] This embodiment provides a zirconium and hafnium separation method, comprising the following steps:

[0046] S1. 0.6396 g of zirconium tetrachloride, 0.4509 g of hafnium tetrachloride and water are mixed to form a solution, and the pH of the solution is adjusted to 1.5 by hydrochloric acid to obtain a zirconium-hafnium ion mixed solution with a mass concentration of 500 ppm (the mass concentration of zirconium ions is 500 ppm, and the mass concentration of hafnium ions is 500 ppm);

[0047] S2. Mix the zirconium-hafnium ion mixture in S1 and the ligand (sodium persulfate) and stir for 10 minutes. Take 10 mL of the mixed solution and add 10 mL of an organic extractant (tributyl phosphate). Extract at room temperature for 30 minutes (one extraction) to obtain an aqueous phase and an organic phase.

[0048] Comparative Example 1

[0049] This comparative example provides a method for separating zirconium and hafnium, comprising the following steps:

[0050] S1. 0.6396 g of zirconium tetrachloride, 0.4509 g of hafnium tetrachloride and water are mixed to form a solution, and the pH of the solution is adjusted to 0.3 by hydrochloric acid to obtain a zirconium-hafnium ion mixed solution with a mass concentration of 500 ppm (the mass concentration of zirconium ions is 500 ppm, and the mass concentration of hafnium ions is 500 ppm);

[0051] S2. Take 10 mL of the zirconium-hafnium ion mixed solution in S1, add 10 mL of an organic extractant (methyl isobutyl ketone), and extract at room temperature for 30 min (one extraction) to obtain an aqueous phase and an organic phase.

[0052] Comparative Examples 2 to 4

[0053] Comparative Examples 2 to 4 provide a method for separating zirconium and hafnium, comprising steps substantially the same as those of Example 1, except that the types of ligands in step S2 are different.

[0054] Table 1 Components and molar fractions of ligands in Examples 1 to 9 and Comparative Examples 1 to 4

[0055]

[0056] Performance Testing

[0057] The mass concentration (mg / L) of zirconium ions and the mass concentration (mg / L) of hafnium ions in the aqueous phase of each embodiment and comparative example were respectively measured by an inductively coupled plasma optical emission spectrometer (ICP-OES), and the mass m1 of zirconium ions and the mass n1 of hafnium ions in the aqueous phase were calculated; then, the mass m0 of zirconium ions and the mass n0 of hafnium ions in the same volume of the original solution (i.e., the zirconium and hafnium ion mixed solution in step S1) were calculated, and the zirconium extraction rate and the hafnium extraction rate were calculated by the following formula.

[0058] Zirconium extraction rate (%) = (m0-m1) / m0×100%;

[0059] Hafnium extraction rate (%) = (n0-n1) / n0×100%.

[0060] Table 2 Zirconium extraction rate and hafnium extraction rate of each embodiment and comparative example

[0061]

[0062] According to the data in Table 1, the zirconium extraction rates of Examples 1 to 10 are all greater than 10% (reaching 10.89% to 19.11%), and the hafnium extraction rates are all greater than 14% (reaching 14.55% to 30.01%), which indicates that the present invention uses specific ligands to form zirconium ligands and hafnium ligands with zirconium and hafnium, and then combines them with the extractant to achieve efficient separation of zirconium and hafnium.

[0063] At the same time, according to Examples 1 to 6, it can be found that compared with using sodium persulfate, hydrogen peroxide or potassium permonosulfate alone as a ligand, combining sodium persulfate with potassium permonosulfate as a ligand, or combining at least one of sodium persulfate and potassium permonosulfate with hydrogen peroxide as a ligand, both have a synergistic effect and can significantly improve the zirconium extraction rate and hafnium extraction rate. According to Examples 1 and 10, it can also be found that the ligand plays a key role in improving the zirconium extraction rate or hafnium extraction rate, and is the main factor affecting the zirconium and hafnium separation effect.

[0064] In addition, according to Example 1 and Comparative Example 1, it can be seen that compared with directly using solvent extraction to separate zirconium and hafnium, the zirconium extraction rate is increased by 75% and the hafnium extraction rate is increased by 131% after using specific ligands to form zirconium ligands and hafnium ligands with zirconium and hafnium and then using solvent extraction to separate zirconium and hafnium; according to Comparative Examples 2 to 4, it can be found that after conventional ligands such as glycine, serine or tyrosine are combined with zirconium and hafnium, the improvement of zirconium extraction rate and hafnium extraction rate is extremely limited, indicating that only when specific ligands are combined with zirconium and hafnium can efficient separation of zirconium and hafnium be achieved.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A ligand composition for separation of zirconium and hafnium, characterized in that: It includes at least two of persulfate ion, hydrogen persulfate ion, hydrogen monopersulfate ion, and hydrogen peroxide.

2. The ligand composition according to claim 1, characterized in that The ligand composition comprises persulfate ions and peroxymonosulfate ions, and the molar ratio of the persulfate ions to the peroxymonosulfate ions is (1-100): (1-100).

3. The ligand composition according to claim 1, characterized in that The ligand composition includes a mixture of at least one of persulfate ion and hydrogen monosulfate ion and hydrogen peroxide.

4. The ligand composition according to claim 3, characterized in that The ligand composition comprises persulfate ions and hydrogen peroxide, and the molar ratio of the persulfate ions to the hydrogen peroxide is (1-100): (1-100); Or, the ligand composition comprises peroxymonosulfate ions and hydrogen peroxide, and the molar ratio of the peroxymonosulfate ions to the hydrogen peroxide is (1-100):(1-100); Alternatively, the ligand composition comprises persulfate ion, peroxymonosulfate ion and hydrogen peroxide, and the molar ratio of the persulfate ion, peroxymonosulfate ion and hydrogen peroxide is (1-100):(1-100):(1-100).

5. A method for separating zirconium and hafnium, characterized in that: The following steps are involved: The mixed solution containing zirconium ions and hafnium ions is mixed with a ligand to obtain a solution containing a zirconium complex and a hafnium complex, and then an organic extractant is added thereto to perform solvent extraction treatment; The ligand is the ligand composition for zirconium and hafnium separation according to any one of claims 1 to 4, or is selected from any one of persulfate ion, hydrogen persulfate ion, monopersulfate ion, and hydrogen peroxide.

6. The zirconium and hafnium separation method according to claim 5, characterized in that: The molar ratio of the total amount of the zirconium ions and the hafnium ions to the ligand is (1-100): (1-100).

7. The zirconium and hafnium separation method according to claim 6, characterized in that: The molar ratio of the total amount of the zirconium ions and the hafnium ions to the ligand is 1:(10-30).

8. The zirconium and hafnium separation method according to claim 5, characterized in that: The pH of the mixed solution containing zirconium ions and hafnium ions is 0.3-2.

7.

9. The zirconium and hafnium separation method according to claim 5, characterized in that: The organic extractant includes at least one of methyl isobutyl ketone, 2-ethylhexyl phosphate-2-ethylhexyl ester, tributyl phosphate, and diisobutyl ketone.

10. The zirconium and hafnium separation method according to claim 5, characterized in that: The temperature of the solvent extraction treatment is 0-50°C and the time is ≥1min.

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