A method for separating zirconium and hafnium in solution

Abstract

The present invention discloses a method for separating zirconium and hafnium in a solution, and relates to the field of metal adsorption separation and purification. The method for separating zirconium and hafnium in a solution provided by the present invention first selects specific ligands such as persulfate and hydrogen persulfate to form zirconium and hafnium complexes with larger size differences through complexation, and then selects a specific porous material with a pore size of 1 to 50 nm under acidic conditions of pH ≤ 4.0 to adsorb the mixture of zirconium and hafnium complexes, thereby achieving the separation of zirconium and hafnium in a solution where zirconium and hafnium ions coexist, and the separation coefficient β Hf / Zr The value can be below 0.84 or above 1.49, and the method is environmentally friendly and simple.

Description

Technical Field

[0001] The invention relates to the field of metal adsorption separation and purification, and in particular to a method for separating zirconium and hafnium in a solution. Background Art

[0002] Zirconium and hafnium are key strategic metals that are widely used in various fields such as corrosion-resistant materials, nuclear reactors and ultra-high temperature materials due to their excellent physical properties. However, the nuclear properties of zirconium and hafnium are completely opposite, so in order not to affect their use, the two must be separated. However, zirconium and hafnium usually coexist in baddeleyite and zircon, and their physical and chemical properties are extremely similar, making the separation of zirconium and hafnium extremely difficult. At present, Chinese patent CN101039878A utilizes the difference in properties of zirconium and hafnium in aqueous phase, first hydrolyzes a mixture of ZrCl4 and HfCl4 in a strong inorganic acid aqueous solution, and then separates zirconium ions from hafnium ions through anion exchange resin; however, a large amount of acid is used in the prior art, and subsequent treatment is difficult. At the same time, although the prior art achieves a separation factor of 10.1, this is also closely related to the high mass ratio of zirconium and hafnium ions in the raw materials used, which is as high as 97.5 / 2.5. Therefore, how to separate zirconium and hafnium ions of similar concentrations in an environmentally friendly and simple way, and then achieve a higher separation factor and obtain high-purity two metal ions, is of great strategic significance. Summary of the invention

[0003] In order to solve the shortcomings of the prior art, the present invention provides a method for separating zirconium and hafnium in a solution. First, a specific ligand is selected to form zirconium and hafnium complexes with a larger size difference through complexation. Then, an appropriate porous material is selected to adsorb the mixture of the zirconium and hafnium complexes, thereby achieving the separation of zirconium and hafnium.

[0004] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0005] A method for separating zirconium and hafnium in a solution comprises the following steps:

[0006] After the ligand is added to a solution where zirconium and hafnium ions coexist for complexation reaction, a porous material is added to the resulting mixed solution for adsorption treatment, thereby achieving separation of zirconium and hafnium in the solution;

[0007] The ligand comprises at least one of persulfate, hydrogen persulfate, hydrogen monosulfate, sulfate, perchlorate, hypochlorite, phosphate, ammonium, thiocyanate, hydrogen peroxide, glycine, serine, tyrosine, aspartic acid and cysteine, and the molar ratio of the total amount of zirconium and hafnium ions in the solution in which the ligand coexists with zirconium and hafnium ions is (2-100):1;

[0008] The complex reaction is carried out under the condition that the solution pH is ≤4.0;

[0009] The pore size of the porous material is 1-50 nm.

[0010] The method for separating zirconium and hafnium provided by the present invention first adds a ligand to make zirconium ions and hafnium ions form zirconium complexes and hafnium complexes respectively, thereby amplifying the spatial size difference between the two ions (zirconium has a strong polymerization ability, and the size of the complex structure formed after combining with the ligand is significantly larger than the size of the complex formed by hafnium); then, the present invention adds a porous material with a pore size of 1 to 50 nm to the reaction system, and the hafnium complex with a smaller size can pass through the pores with a pore size of 1 to 50 nm and then be adsorbed by the porous material, while the zirconium complex with a larger size cannot pass through the pores of the porous material and therefore cannot be adsorbed. Based on this, the present invention can achieve the separation of zirconium and hafnium.

[0011] It should be noted that the inventors of the present application have experimentally confirmed that the ligand used in the complex reaction can be at least one of persulfate, hydrogen persulfate, hydrogen monosulfate, sulfate, perchlorate, hypochlorite, phosphate, ammonium, thiocyanate, hydrogen peroxide, glycine, serine, tyrosine, aspartic acid and cysteine, wherein the complex reaction is carried out under the condition of pH≤4.0 to ensure that the complex formed by zirconium and hafnium has a larger size difference sufficient to be separated. Specifically, the coordination ability of zirconium and hafnium with the above ligands is related to pH, wherein zirconium has a stronger ability to coordinate with the three ligands as the pH increases, while hafnium has a smaller change in the ability to complex with the ligands as the pH changes. In order to amplify the size difference of the zirconium and hafnium complexes, the pH of the solution in which zirconium and hafnium ions coexist needs to be increased, but too high a pH will cause zirconium and hafnium to form precipitation. Therefore, in order to ensure the effect of adsorption separation, the pH of the solution needs to be specially controlled when carrying out the complex reaction. At the same time, when the amount of ligand added is insufficient, zirconium and hafnium are difficult to fully complex, and the size difference of the formed complex is also insufficient. Therefore, the present invention should also ensure that the amount of ligand added is sufficient.

[0012] In a specific embodiment of the present invention, the solution in which zirconium and hafnium ions coexist is an aqueous solution of zirconium tetrachloride and hafnium tetrachloride. In a specific embodiment of the present invention, hydrochloric acid is used to adjust the pH of the solution in which zirconium and hafnium ions coexist.

[0013] In a specific embodiment of the present invention, the complexation reaction is carried out at room temperature.

[0014] Preferably, the ligand comprises at least one of peroxymonosulfate, persulfate, and hydrogen peroxide.

[0015] Using at least one of peroxymonosulfate, persulfate and hydrogen peroxide as a ligand can make the complex formed by zirconium and hafnium have a larger size difference and a better separation effect.

[0016] More preferably, the complexation reaction is carried out under the condition that the solution pH is ≤ 2.7.

[0017] At low pH values ​​(such as pH = 0.3), the size differences of the complexes formed by zirconium, hafnium and ligands are more significant and the structures are more differentiated, thus showing different affinities on the adsorbent surface, which helps to improve the separation efficiency of the two.

[0018] More preferably, when the ligand is persulfate, the complexation reaction is carried out under the condition of pH < 2.7.

[0019] When the ligand is persulfate, the complexes formed between zirconium and hafnium under the condition of pH < 2.7 are more different.

[0020] Preferably, the molar ratio of the total amount of zirconium and hafnium ions in the solution in which the ligand coexists with zirconium and hafnium ions is (15-25):1.

[0021] The inventors have experimentally confirmed that the separation effect is better when the molar ratio of the total amount of zirconium and hafnium ions in the solution where the ligand coexists with zirconium and hafnium ions is controlled within the range of (15-25):1. This is because the excess ligand can ensure that the zirconium and hafnium ions are fully complexed.

[0022] Preferably, the mass ratio of zirconium ions to hafnium ions in the solution in which zirconium and hafnium ions coexist is (0.5-3):1.

[0023] More preferably, the total mass concentration of zirconium and hafnium ions in the zirconium and hafnium ion coexisting solution is 2 mg / L to 100 g / L.

[0024] More preferably, the total mass concentration of zirconium and hafnium ions in the zirconium and hafnium ion coexisting solution is 2 mg / L to 1000 mg / L.

[0025] More preferably, the total mass concentration of zirconium and hafnium ions in the zirconium and hafnium ion coexisting solution is 50-200 mg / L.

[0026] More preferably, the solid-to-liquid ratio of the solution in which the porous material coexists with zirconium and hafnium ions is (0.005-100) g:100 mL.

[0027] More preferably, the solid-to-liquid ratio of the solution in which the porous material coexists with zirconium and hafnium ions is (0.005-2) g:100 mL.

[0028] More preferably, the solid-to-liquid ratio of the solution in which the porous material coexists with zirconium and hafnium ions is (0.05-0.2) g:100 mL.

[0029] More preferably, the porous material includes at least one of molecular sieve, activated carbon and adsorption resin.

[0030] Preferably, the pore size of the porous material is 2-15 nm.

[0031] More preferably, the pore size of the porous material is 3-8 nm.

[0032] By using a porous material with a pore size within the above range for the adsorption and separation of zirconium and hafnium, a more excellent adsorption and separation effect can be obtained.

[0033] More preferably, the porous material comprises SBA-15 molecular sieve.

[0034] The SBA-15 molecular sieve has a flexible and adjustable pore size. The inventor has experimentally confirmed that the SBA-15 molecular sieve has a better separation effect for the adsorption separation of zirconium and hafnium.

[0035] Preferably, the complexing reaction time is 0.05 to 48 h.

[0036] Preferably, the adsorption time is 20 to 28 h.

[0037] Controlling the adsorption time to 20-28 h can ensure the adsorption capacity and improve the separation effect.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The method for separating zirconium and hafnium provided by the present invention is used to treat a solution in which zirconium and hafnium ions coexist, and the size difference between zirconium and hafnium ions can be magnified to achieve full separation of zirconium and hafnium in the solution in which zirconium and hafnium ions coexist, and the separation coefficient β Hf / Zr The value can be below 0.84 or above 1.49, and the method is environmentally friendly and simple. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. Among them, the raw material information used in each embodiment and comparative example is as follows:

[0041] SBA-15 molecular sieve-1: pore size is 11nm.

[0042] SBA-15 molecular sieve-2: pore size is 4nm.

[0043] SBA-15 molecular sieve-3: pore size is 7nm.

[0044] SBA-15 molecular sieve-4: pore size is 9nm.

[0045] 5A molecular sieve: pore size ~0.5nm.

[0046] Example 1

[0047] A method for separating zirconium and hafnium in a solution comprises the following steps:

[0048] Using water as a solvent to dissolve hafnium tetrachloride and zirconium tetrachloride, a solution with a volume of 500 mL and a total mass concentration of 100 mg / L in which zirconium and hafnium ions coexist (the mass concentrations of zirconium ions and hafnium ions are both 50 mg / L, that is, the mass ratio of the two is 1:1) is prepared, the pH is adjusted to 2.7 by hydrochloric acid, hydrogen persulfate (the specific reagent added is potassium hydrogen persulfate) is added to the solution in which zirconium and hafnium ions coexist to carry out a complex reaction with a reaction time of 1 hour, and then SBA-15 molecular sieve-1 is added and adsorbed at 25°C for 24 hours to complete the adsorption separation of zirconium and hafnium;

[0049] The molar ratio of the total amount of zirconium and hafnium ions in the solution of potassium peroxymonosulfate and zirconium and hafnium ions is 20:1; the solid-liquid ratio of the solution of SBA-15 molecular sieve-1 and zirconium and hafnium ions is 0.1 g:100 mL.

[0050] Example 2

[0051] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0052] The ligand is hydrogen peroxide.

[0053] Example 3

[0054] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0055] The ligand is persulfate (specifically, the added reagent is sodium persulfate), and the complexation reaction is carried out at a pH of 0.3.

[0056] Example 4

[0057] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0058] The complexation reaction is carried out at a pH of 0.3.

[0059] Example 5

[0060] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0061] The ligand is hydrogen peroxide, and the complexation reaction is carried out at a pH of 0.3.

[0062] Example 6

[0063] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0064] The ligands are peroxymonosulfate, persulfate and hydrogen peroxide in a molar ratio of 1:1:1, and the complex reaction is carried out under a pH value of 0.3.

[0065] Example 7

[0066] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0067] The molar ratio of the total amount of zirconium and hafnium ions in the solution containing hydrogen persulfate, zirconium and hafnium ions is 100:1.

[0068] Example 8

[0069] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0070] The molar ratio of the total amount of zirconium and hafnium ions in the solution containing hydrogen persulfate, zirconium and hafnium ions is 15:1.

[0071] Example 9

[0072] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0073] The molar ratio of the total amount of zirconium and hafnium ions in the solution containing hydrogen persulfate, zirconium and hafnium ions is 25:1.

[0074] Example 10

[0075] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 3 is only that:

[0076] The complexation reaction was carried out at a pH of 2.7.

[0077] Embodiment 11

[0078] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0079] The ligand is glycine.

[0080] Example 12

[0081] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0082] The ligand is serine.

[0083] Example 13

[0084] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 5 is only that:

[0085] The SBA-15 molecular sieve-1 was replaced with SBA-15 molecular sieve-2.

[0086] Embodiment 14

[0087] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 5 is only that:

[0088] The SBA-15 molecular sieve-1 was replaced with SBA-15 molecular sieve-3.

[0089] Embodiment 15

[0090] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 5 is only that:

[0091] The SBA-15 molecular sieve-1 was replaced with SBA-15 molecular sieve-4.

[0092] Comparative Example 1

[0093] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0094] The pH of the solution in which zirconium and hafnium ions coexist is adjusted to 2.7 without adding a ligand for complexation reaction, and SBA-15 molecular sieve is directly added to adsorb the zirconium and hafnium ions.

[0095] Comparative Example 2

[0096] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0097] The mesoporous material is 5A molecular sieve.

[0098] Comparative Example 3

[0099] A method for separating zirconium and hafnium in a solution, wherein the difference from Comparative Example 2 is only that:

[0100] The complexation reaction was carried out at a pH of 0.3.

[0101] Comparative Example 4

[0102] A method for separating zirconium and hafnium in a solution, wherein the difference from Example 1 is only that:

[0103] The molar ratio of the total amount of zirconium and hafnium ions in the solution containing hydrogen persulfate and zirconium and hafnium ions is 1:1.

[0104] Performance Testing

[0105] Zirconium adsorption test: After the adsorption treatment is completed (adsorption reaches equilibrium), the solids in the reaction system are filtered to obtain a liquid sample. Next, standard solutions of zirconium and hafnium are prepared, and the emission light intensity at different concentrations is measured to establish a standard curve. Then, the sample is injected into the ICP-OES instrument, and the instrument calculates the equilibrium concentration of zirconium by measuring the emission light intensity of the sample and combining it with the standard curve. Finally, the adsorption amount is calculated based on the measured concentration data.

[0106] Hafnium adsorption test: After the adsorption treatment is completed (adsorption reaches equilibrium), the solids in the reaction system are filtered to obtain a liquid sample. Next, standard solutions of zirconium and hafnium are prepared, and the emission light intensity at different concentrations is measured to establish a standard curve. Then, the sample is injected into the ICP-OES instrument, and the instrument calculates the equilibrium concentration of hafnium by measuring the emission light intensity of the sample and combining it with the standard curve. Finally, the adsorption amount is calculated based on the measured concentration data.

[0107] Calculation of adsorption amount: Calculate the adsorption amount of the adsorbent based on the ion concentration in the initial solution and the ion concentration in the filtrate:

[0108]

[0109] Where q is the adsorption amount (mg / g), C0 is the initial concentration (mg / L), and C e is the equilibrium concentration (mg / L), V is the volume of the solution (L), and m is the mass of the adsorbent (g).

[0110] Separation factor: β Hf / Zr =Hf adsorption (mg / g) / Zr adsorption (mg / g). β Hf / Zr The greater the deviation from 1, the better the separation performance.

[0111] The specific performance test data is shown in Table 1 below:

[0112] Table 1. Adsorption and separation effects of zirconium and hafnium using the methods provided in the examples and comparative examples

[0113]

[0114] According to the data in Table 1 above, the method for separating zirconium and hafnium in a solution provided by the present invention is used to treat a solution where zirconium and hafnium ions coexist, and the separation coefficient β is 0.04. Hf / Zr Can reach below 0.84 or above 1.49.

[0115] From the data of Examples 1 to 6 and Examples 10 to 12, it can be seen that when the added ligand includes at least one of peroxymonosulfate, persulfate, and hydrogen peroxide (Examples 1 to 6 and Example 10), better separation effects can be obtained. Among them, when the ligand is hydrogen peroxide or persulfate (Examples 2 to 3, 5, and 10), the pH is lower (Examples 3 and 5), and the separation effect is better; and when the ligand is peroxymonosulfate (Examples 1 and 4), the complex formed by peroxymonosulfate and zirconium and hafnium ions has an enhanced adsorption effect on hafnium at a pH of 2.7, and a reduced adsorption effect on zirconium at a pH of 0.3. This is because the morphological structure of the complex and the binding energy with the adsorbent of the ligand at different pH values ​​are different, resulting in differences in adsorption capacity.

[0116] It can be seen from the data of Examples 1, 7-9 and Comparative Example 4 that in the method provided by the present invention, the amount of the ligand added in the complexation step should be within an appropriate range. When the molar ratio of the total amount of zirconium and hafnium ions in the solution in which the ligand coexists with zirconium and hafnium ions is within the preferred range of (15-25):1 of the present invention (Examples 1, 8-9), the separation effect is better.

[0117] From the data of Examples 5, 13-15, and Comparative Examples 2-3, it can be seen that when SBA-15 molecular sieves with a pore size of 2-15 nm are used for adsorption, especially when SBA-15 molecular sieves with a pore size in the more preferred range of 3-8 nm (Examples 13-14) of the present invention are used for adsorption, the adsorption and separation effect of zirconium and hafnium is better. When the pore size is further increased, the adsorption and separation effect shows a trend of first decreasing and then increasing, indicating that the porous material with a specific pore size has a certain interaction with the zirconium and hafnium complexes, which can promote the separation of zirconium and hafnium. However, too small a pore size will also lead to a decrease in the separation effect (Comparative Examples 2-3).

[0118] It can be seen from Comparative Example 1 that it is difficult to achieve a good separation effect by directly adding porous materials for adsorption without adding ligands for complexation.

[0119] 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 method for separating zirconium and hafnium in a solution, characterized in that: The steps include: After the ligand is added to a solution where zirconium and hafnium ions coexist for complexation reaction, a porous material is added to the resulting mixed solution for adsorption treatment, thereby achieving separation of zirconium and hafnium in the solution; The ligand comprises at least one of persulfate, monopersulfate, hydrogen peroxide, glycine, and serine, and the molar ratio of the total amount of zirconium and hafnium ions in the solution where the ligand coexists with zirconium and hafnium ions is (2-100):1; The complex reaction is carried out under the condition that the solution pH is ≤4.0; The pore size of the porous material is 1-50 nm.

2. The method for separating zirconium and hafnium in a solution according to claim 1, characterized in that: The ligand includes at least one of peroxymonosulfate, persulfate, and hydrogen peroxide.

3. The method for separating zirconium and hafnium in a solution according to claim 2, characterized in that: The complexation reaction is carried out under the condition that the solution pH is ≤2.

7.

4. The method for separating zirconium and hafnium in a solution according to claim 1, characterized in that: The molar ratio of the total amount of zirconium and hafnium ions in the solution where the ligand coexists with zirconium and hafnium ions is (15-25):

1.

5. The method for separating zirconium and hafnium in a solution according to claim 1, characterized in that: The mass ratio of zirconium ions to hafnium ions in the solution in which zirconium and hafnium ions coexist is (0.5-3):

1.

6. The method for separating zirconium and hafnium in a solution according to claim 5, characterized in that: The total mass concentration of zirconium and hafnium ions in the solution in which zirconium and hafnium ions coexist is 2 mg / L to 100 g / L.

7. The method for separating zirconium and hafnium in a solution according to claim 6, characterized in that: The solid-to-liquid ratio of the solution in which the porous material coexists with zirconium and hafnium ions is (0.005-100) g:100 mL.

8. The method for separating zirconium and hafnium in a solution according to claim 7, characterized in that: The porous material includes at least one of molecular sieve, activated carbon and adsorption resin.

9. The method for separating zirconium and hafnium in a solution according to claim 8, characterized in that: The pore size of the porous material is 2-15 nm.

10. The method for separating zirconium and hafnium in a solution according to claim 9, characterized in that: The porous material includes SBA-15 molecular sieve.

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