A process for the selective separation of molybdenum from nitric acid solutions containing uranium and fission products

Abstract

The application discloses a method for selectively separating molybdenum from a nitric acid solution containing uranium and fission element. The method comprises the following steps: chemically grafting 8-hydroxyquinoline to silica gel by using a silane coupling agent to prepare a hydroxyquinoline grafted silica gel material, and then using the material as an adsorbent to efficiently and selectively adsorb molybdenum from a nitric acid solution containing uranium and fission element. The method breaks the limitation that known silica gel grafts and single quinoline ligands cannot well realize the selective separation of molybdenum and other elements, adjusts the spatial configuration of the 8-hydroxyquinoline ligand by grafting 8-hydroxyquinoline on the silica gel, provides the selective adsorption effect of the 8-hydroxyquinoline ligand on molybdenum and uranium and the like, and improves the saturated adsorption amount of molybdenum.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for separating and purifying molybdenum, and particularly relates to a method for separating molybdenum from uranium and other fission elements by using a hydroxyquinoline grafted silica gel material. BACKGROUND

[0002] Silica gel (SiO2) is an optimal adsorption material due to its non-toxicity, good mechanical properties, low cost and easy chemical modification. However, the adsorption capacity and selectivity of unmodified silica gel is low. Therefore, there are studies on grafting organic functional groups on silica gel to provide more stable hybrid or composite materials through chemical bonds between silica gel material and organic molecules, and to use them for adsorption of metal ions. However, the known silica gel grafts cannot well achieve the separation of molybdenum from uranium and various fission elements, and the saturated adsorption capacity of molybdenum also needs to be further improved.

[0003] 8-hydroxyquinoline has good coordination with Mo(VI) under acidic conditions, and has great potential in the adsorption of Mo(VI) (Ramkumar, J.; Maiti, B. Transport of molybdenum across a bulk liquid membrane using 8-hydroxy quinoline as a carrier. Sep. Sci. Technol. 2004, 39, 449-457). However, 8-hydroxyquinoline alone can coordinate with uranium and other fission elements, and even be extracted or adsorbed, so the selective separation of molybdenum from elements such as uranium cannot be achieved by relying on 8-hydroxyquinoline alone. SUMMARY

[0004] The purpose of the present application is to provide a method for selectively separating molybdenum from uranium and other fission elements.

[0005] To achieve the above purpose, the present application grafts 8-hydroxyquinoline onto silica gel, and finds that cis-MoO2 2+ At about pH 1.0, 8-hydroxyquinoline can form a stable complex structure with the grafted hydroxyquinoline, and thus be adsorbed on the grafted silica gel material; for elements such as uranium, multiple quinoline groups need to be twisted to a specific angle to form a stable complex structure. However, since the quinoline groups are fixed on the silica gel and cannot move freely, it is difficult for them to coordinate with elements such as uranium, and finally the selective separation of molybdenum from elements such as uranium is achieved. The present application breaks the limitation that known silica gel grafts and quinoline ligands alone cannot well achieve the selective separation of molybdenum from other elements, and achieves the unexpected effect of separating molybdenum.

[0006] The technical scheme provided by the present application is: a method for selectively separating molybdenum from a nitric acid solution containing uranium and fission elements, first, 8-hydroxyquinoline is chemically grafted onto silica gel by using a silane coupling agent to prepare hydroxyquinoline grafted silica gel material, and then the material is used to efficiently and selectively adsorb molybdenum from a nitric acid solution containing uranium and fission elements.

[0007] Preferably, the specific surface area of the silica gel is 150-1500 m 2 / g.

[0008] Preferably, the hydroxyquinoline grafted silica gel material is prepared by using inorganic silica gel as a base material, and by two-step chemical grafting of (3-aminoalkyl)trialkoxysilane (AATAS) and 8-hydroxyquinoline (Quin) which has high selective coordination with Mo(VI), as shown in the following formula: Figure 1 The hydroxyquinoline grafted silica gel material (denoted as SiO2-AATAS-Quin) is prepared.

[0009] The chemical structure of the hydroxyquinoline grafted silica gel material prepared by the above method is shown in formula I:

[0010]

[0011] In the formula, a is an integer of 1-12, and b is an integer of 1-12. Preferably, a=3 and b=2, that is, (3-aminopropyl)triethoxysilane (APTES) is used as the grafting coupling agent.

[0012] The preparation method of the hydroxyquinoline grafted silica gel adsorption material (SiO2-AATAS-Quin) shown in formula I is as follows: silica gel (SiO2) is added to a hydrochloric acid solution and heated to reflux overnight to activate the surface of the silica gel; the activated silica gel is separated by filtration and dried; AATAS is added to the suspension of the activated silica gel, and heated to reflux under argon protection; after the reaction is completed, the mixture is cooled to room temperature, filtered, washed, and dried to obtain SiO2-AATAS; SiO2-AATAS and 8-hydroxyquinoline-2-carboxaldehyde are refluxed in an organic solvent (such as DMF); after the reaction is completed, the mixture is cooled to room temperature, filtered, washed, and dried to obtain SiO2-AATAS-Quin.

[0013] The hydroxyquinoline grafted silica gel material of the present application can be used to efficiently and selectively separate and purify molybdenum from a nitric acid solution containing uranium and zirconium, ruthenium, iodine, cesium, and / or cerium, etc. fission elements, and the nitric acid solution usually refers to a nitric acid solution of an irradiated uranium target.

[0014] Specifically, the method for separating and purifying molybdenum from a nitric acid solution containing uranium and zirconium, ruthenium, iodine, cesium, and / or cerium, etc. fission elements includes the following steps:

[0015] (1) using hydroxyquinoline grafted silica gel material as adsorbent, adsorbing molybdenum in nitric acid solution containing molybdenum, uranium and other fission elements, while uranium and other fission elements (such as zirconium, ruthenium, iodine, cesium and cerium, etc.) are not adsorbed;

[0016] (2) desorbing the adsorbent after step (1) to obtain a molybdenum-containing elution solution.

[0017] The adsorbent after desorption in step (2) can be recycled.

[0018] In the above step (1), the amount of hydroxyquinoline grafted silica gel material adsorbent is not particularly limited, and generally 0.01-1.5 g / L adsorbent is used per liter of the nitric acid solution. When the concentration of molybdenum in the nitric acid solution is high, the mass of the adsorbent can be increased to achieve efficient adsorption. The adsorption temperature can be 5-100℃, and there is no particular limitation on the adsorption process and equipment.

[0019] Preferably, the pH value of the nitric acid solution in step (1) is 1.0-2.0. The adsorption operation can be to add the hydroxyquinoline grafted silica gel material to the nitric acid solution, shake and mix, and then stand for a period of time, or make the nitric acid solution flow through the adsorption column filled with the hydroxyquinoline grafted silica gel material.

[0020] In the above step (2), the desorption solution of the hydroxyquinoline grafted silica gel material after adsorbing molybdenum can be an aqueous ammonia solution of ammonium carbonate, a guanidine carbonate solution and an ammonium carbonate solution. Preferably, the desorption solution used in step (2) is an aqueous ammonia solution containing 0.05 M ammonium carbonate.

[0021] The hydroxyquinoline grafted silica gel material adsorbent used in the present application has good radiation stability and thermal stability. When the total radiation dose is less than 800 kGy and the temperature is less than 300℃, it can maintain a very high adsorption efficiency.

[0022] The application provides a method for adsorbing and separating molybdenum from a nitric acid solution containing uranium, molybdenum, zirconium, ruthenium, iodine, cesium and cerium. The method uses a silica gel material grafted with hydroxyquinoline as an adsorbent, breaks the limitation that known silica gel grafts and single quinoline ligands cannot well achieve selective separation of molybdenum and other elements, adjusts the spatial configuration of the 8-hydroxyquinoline ligand by grafting 8-hydroxyquinoline on the silica gel, provides the selective adsorption effect of the 8-hydroxyquinoline ligand on elements such as molybdenum and uranium, and improves the saturated adsorption amount of molybdenum. The application finds through experiments that the adsorption process of SiO2-APTES-Quin on Mo(VI) conforms to the Langmuir adsorption isotherm, which is a single-layer chemical adsorption. The saturated adsorption amount of SiO2-APTES-Quin on Mo(VI) is 203 mg / g, which is more than 5 times that of commercial alumina. The adsorption process of SiO2-APTES-Quin on Mo(VI) conforms to the pseudo-second-order kinetics, indicating that the adsorption process is controlled by chemical interaction. Nearly 100% of Mo(VI) can be eluted at one time by using 0.05M ammonium carbonate aqueous solution. SiO2-APTES-Quin meets the thermal stability requirement at less than 300 DEG C. When the absorbed dose of irradiation reaches 800 kGy, the adsorption percentage of SiO2-APTES-Quin on Mo(VI) is reduced by not more than 1%, which can better meet the irradiation stability. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The synthesis route of the SiO2-AATAS-Quin adsorbent described in the application is shown.

[0024] Figure 2 The distribution ratio of SiO2-APTES-Quin on Mo(VI) under different pH values is shown, wherein the inner graph is the adsorption distribution ratio under higher acidity (adsorbent mass: 30.0 mg; initial Mo(VI) concentration: 1.0 mM; water phase volume: 0.5 mL; adsorption time: 2 h).

[0025] Figure 3 The (a) adsorption kinetics and (b) pseudo-second-order kinetics model fitting of the SiO2-APTES-Quin adsorbent on Mo(VI) are shown (adsorbent mass: 10.0 mg; water phase volume: 5 mL; nitric acid concentration: 0.10 M; initial Mo(VI) concentration: 1300 ppm).

[0026] Figure 4 The (a) adsorption isotherm and (b) Langmuir adsorption isotherm linear fitting of the SiO2-APTES-Quin adsorbent on Mo(VI) are shown (adsorbent mass: 10.0 mg; water phase volume: 10 mL; nitric acid concentration: 0.10 M; adsorption time: 2 h).

[0027] Figure 5 is the percentage of adsorption of SiO2-APTES-Quin to Mo(VI) at different adsorption doses (adsorbent mass: 30.0 mg; initial Mo(VI) concentration: 1.0 mM; aqueous phase volume: 1.0 mL; nitric acid concentration: 0.10 M; adsorption time: 2 h).

[0028] Figure 6 is the column chromatography elution curve of SiO2-APTES-Quin (aqueous phase: 0.50 mL of 0.10 M nitric acid solution containing 125.0 mg / L U(VI), 18.1 mg / L Mo(VI), 27.1 mg / L Zr(IV), 13.4 mg / L Ru(III), 20.3 mg / L Sr(II) and 26.1 mg / L Ce(III); stationary phase: 0.200 g of SiO2-APTES-Quin) DETAILED DESCRIPTION

[0029] The application will be described in detail below through specific experiments, but in no way limits the scope of the application.

[0030] Example 1

[0031] (I) Materials and methods

[0032] (1) Synthesis method of SiO2-APTES-Quin adsorbent

[0033] 20.0 g of commercial silica gel (SiO2) was added to 200 mL of hydrochloric acid solution (18.5%) and heated to reflux overnight to activate the surface of the silica gel. After the silica gel was separated by filtration, it was placed in a vacuum drying oven and dried overnight. To the suspension of 4.0 g of activated silica gel in 100 mL of toluene, 4 mL of (3-aminopropyl)triethoxysilane (APTES) was added, and the mixture was heated to reflux under argon protection for 72 hours to functionalize the surface of the silica gel, obtaining SiO2-APTES. After cooling to room temperature, the mixture was filtered, and the SiO2-APTES was washed with toluene, methanol and diethyl ether in sequence. It was placed in a vacuum drying oven and dried overnight. 2.0 g of SiO2-APTES was added to a DMF solution of 3.0 g of 8-hydroxyquinoline-2-carboxaldehyde, and the mixture was refluxed at 135°C for 12 hours. After cooling to room temperature, the mixture was filtered. The solid was washed with DMF, methanol and diethyl ether in sequence, and then placed in a vacuum drying oven and dried overnight to obtain the SiO2-APTES-Quin adsorbent. The synthesis route thereof is shown in Figure 1

[0034] (2) Test of adsorption effect of SiO2-APTES-Quin

[0035] ​Adsorption experiments were carried out by shaking 0.5 mL of aqueous solution containing uranium (1.0 mmol / L), molybdenum (1.0 mmol / L) and other siderophores ions (0.5 mmol / L) with 30 mg of SiO2-APTES-Quin adsorbent at 25 °C. The adsorption time was about 1 h to ensure the adsorption equilibrium. After the adsorption was completed, the aqueous solution was separated by centrifugation at 4500 rpm for 5 min, and the concentration of the corresponding element was determined by ICP-OES or ICP-MS after dilution to the appropriate concentration, 131 I concentration change was determined by a γ counter.

[0036] (3) Distribution ratio K d (mL·g -1 ), adsorption percentage E (%), selectivity coefficient SF

[0037] According to the following formula:

[0038]

[0039]

[0040]

[0041] wherein C0(mg·L -1 ) is the concentration of metal ions in the aqueous solution before separation, C(mg·L -1 ) is the concentration of metal ions in the aqueous solution after separation, V is the volume of the aqueous phase (mL), W is the mass of the adsorbent (g), K d (M) and K d (N) represent the distribution ratio of M and N elements, respectively. Each experiment was repeated more than 4 times.

[0042] (B) Results

[0043] (1) Effect of acidity

[0044] By changing the acidity of the aqueous phase, the optimal adsorption effect of SiO2-APTES-Quin on Mo(VI) under different acidity conditions was determined. After changing the concentration of nitric acid, the adsorption distribution ratio (K d ) of Mo(VI) was tested, as shown in Figure 2 . It was found that as the pH value increased from 0.3 to 8.0, the distribution ratio of Mo(VI) first increased and then decreased, and an optimal acidity condition appeared. At pH = 1.0 and 2.0, the highest distribution ratio was obtained, reaching 10 4 orders of magnitude.

[0045] (2) Adsorption kinetics and thermodynamics

[0046] The adsorption capacity of SiO2-APTES-Quin for Mo(VI) at different time points was tested. The adsorption kinetics results are shown in Figure 3 The adsorption process rate of SiO2-APTES-Quin for Mo(VI) is fast, and the adsorption equilibrium can be reached in about 1 hour. The adsorption kinetics data was fitted using the pseudo-first-order kinetic model and the pseudo-second-order kinetic model. As shown in Figure 3 , the adsorption kinetics conforms to the pseudo-second-order kinetic model (correlation coefficient R 2 = 0.999), indicating that the adsorption process is mainly controlled by chemical action, rather than mass transfer action.

[0047] As shown in Figure 4 , the adsorption isotherm curve of SiO2-APTES-Quin for Mo(VI) was tested by changing the Mo(IV) concentration in the mother liquor. The adsorption isotherm process was fitted with Langmuir and Freundlich adsorption models, and the fitting results showed that the adsorption process conforms to the Langmuir adsorption isotherm, indicating that the adsorption process is a single-layer chemical adsorption. The saturation adsorption capacity is about 228 mg·g -1 calculated by the grafting amount, the Langmuir adsorption isotherm predicts the saturation adsorption capacity to be 243 mg·g -1 , and the actual observed saturation adsorption capacity is 203 mg·g -1 . The saturation adsorption capacity of SiO2-APTES-Quin for Mo(VI) is more than 5 times that of commercial alumina, which can better meet the adsorption capacity requirements of the adsorbent.

[0048] Based on the above experimental data, the optimized related process parameters are:

[0049] (1) The best acidity of SiO2-APTES-Quin adsorbing Mo(VI) is a nitric acid solution with pH = 1.0-2.0, and the distribution ratio reaches 10 4 orders of magnitude.

[0050] (2) The actual observed saturation adsorption capacity of SiO2-APTES-Quin for Mo(VI) is 203 mg·g -1 , which is more than 5 times that of commercial alumina.

[0051] (3) The adsorption process rate of SiO2-APTES-Quin for Mo(VI) is fast, and the longest 1 hour can reach adsorption equilibrium.

[0052] Example 2

[0053] (I) Materials and methods

[0054] (1) The materials and adsorption process are the same as in Example 1;

[0055] (2) Desorption: 2.0 mL of eluent was added to the 30.0 mg of Si02-APTES-Quin adsorbent after adsorbing Mo(VI), and oscillated for 30 minutes. After oscillation, centrifugation was performed, 1.0 mL of aqueous phase was taken, and organic matter was removed by nitration, and then diluted to 5 mL for ICP-OES test. The aqueous phase containing ammonia water needs to be evaporated first, and then diluted to volume after nitration.

[0056] (II) Results

[0057] In order to realize the elution of Si02-APTES-Quin adsorbing Mo(VI), various elution conditions were tested, as shown in Table 1. In addition to adjusting the acidity and alkalinity, the salinity or complexing ability of the eluent also needs to be increased to improve the desorption capacity. The elution effect of the ammonia solution of ammonium carbonate is the best, and almost completely elutes Mo(VI) at one time. The elution effect of ammonium carbonate solution and guanidine carbonate solution is the second.

[0058] Table 1 Elution effect of Si02-APTES-Quin adsorbing Mo(VI) under different conditions

[0059]

[0060] Example 3

[0061] (I) Materials and methods

[0062] (1) The materials and methods are the same as those in Example 1;

[0063] (2) In the irradiation experiment, the adsorbent and the aqueous phase were subjected to 60 Co source irradiation, and the received irradiation dose was 200-800 kGy. After irradiation, the adsorption experiment was performed, and the operation of the adsorption experiment was the same as above.

[0064] (II) Results

[0065] In order to test the irradiation stability of Si02-APTES-Quin, 30.0 mg of Si02-APTES-Quin and 1.0 mL of 0.1M HNO3 solution containing 1.0 mM Mo(VI) were placed in 60 Co source irradiation. After absorbing different doses, the adsorption effect of Si02-APTES-Quin on Mo(VI) did not decrease obviously, as shown in Figure 5 At an absorption dose of 800 kGy, the adsorption percentage only decreased by about 1%. In addition, after absorbing a higher dose of irradiation (400 kGy), the aqueous phase remained colorless and transparent. This indicates that the adsorbent material has good irradiation stability and potential for the separation and purification of Mo(VI) in actual high irradiation environment.

[0066] Example 4

[0067] (I) Materials and Methods

[0068] (1) The same as Example 1;

[0069] (2) Column test of simulated uranium target dissolution solution, 0.200 g of SiO2-APTES-Quin adsorbent was taken, and after adding 0.1 M HNO3 solution, a chromatographic column was filled. The chromatographic column was a glass chromatographic column with a stopcock with an inner diameter of about 6 mm. 500 μL of simulated dissolution solution was taken and loaded onto the column. Among them, the 0.10 M HNO3 simulated uranium target dissolution solution contains 125.0 mg / L U(VI), 18.1 mg / L Mo(VI), 27.1 mg / L Zr(IV), 13.4 mg / L Ru(III), 20.3 mg / L Sr(II) and 26.1 mg / L Ce(III). After loading, 0.1 M HNO3 solution was used as the mobile phase to elute various impurity element ions. Then 0.05 M ammonium carbonate ammonia solution was used as the eluent to elute Mo(VI). The flow rate of the mobile phase was about 0.35 mL·min -1 .

[0070] (II) Results

[0071] In order to further explore the dynamic separation and purification effect of SiO2-APTES-Quin on Mo(VI), a chromatographic column separation test was carried out, as shown in Figure 6 After loading, 0.10 M HNO3 solution was first used as the mobile phase, at this time Mo(VI) was basically completely adsorbed on the column, while U(VI) and Sr(II), Ru(III) and Ce(III) were quickly eluted in large amounts. After about 8.0 mL of 0.10 M HNO3 eluent was used, U(VI) and Sr(II), Ru(III) and Ce(III) metal ions were completely eluted, and there were no metal ions in the eluent at this time.

[0072] Then 0.05 M ammonium carbonate ammonia solution was used to elute Mo(VI). During the whole process, Zr(IV) was not eluted. The main reason is that silica gel can adsorb Zr(IV) efficiently under acidic conditions, and Zr(IV) is easily hydrolyzed, and Zr(IV) is easily precipitated under alkaline conditions and cannot be effectively eluted and dissolved.

[0073] It should be noted that the purpose of publishing the examples is to help further understand the present application, but those skilled in the art can understand that various substitutions and modifications are possible without departing from the spirit and scope of the present application and the appended claims. Therefore, the present application should not be limited to the disclosed content of the examples, and the scope of protection claimed by the present application is defined by the scope defined by the claims.

Claims

1. A process for the separation of molybdenum from a nitric acid solution containing uranium and fission elements, by first chemically grafting 8-hydroxyquinoline onto silica gel through a silane coupling agent to prepare a hydroxyquinoline grafted silica gel material, and then using the material for the selective adsorption of molybdenum from a nitric acid solution containing uranium and fission elements; wherein, A hydroxyquinoline grafted silica material is prepared by two-step chemical grafting of (3-aminoalkyl) trialkoxysilane and 8-hydroxyquinoline on inorganic silica gel as a base material, and is denoted as SiO2-AATAS-Quin, and the chemical structure is shown as formula I: Formula I In formula I, a is an integer of 1-12, and b is an integer of 1-12. The preparation method of the hydroxyquinoline grafted silica material shown as formula I is as follows: the silica gel is added into a hydrochloric acid solution and heated to reflux overnight to activate the surface of the silica gel; the activated silica gel is separated by filtration and dried; (3-aminoalkyl) trialkoxysilane is added into a suspension of the activated silica gel, and heated to reflux under argon protection; after the reaction is completed, the mixture is cooled to room temperature, filtered, washed and dried to obtain a grafting product SiO2-AATAS; the grafting product SiO2-AATAS and 8-hydroxyquinoline-2-carboxaldehyde are refluxed in an organic solvent; after the reaction is completed, the mixture is cooled to room temperature, filtered, washed and dried to obtain the hydroxyquinoline grafted silica material shown as formula I.

2. The method of claim 1, wherein, The specific surface area of the silica gel is 150-1500 m² / g.

3. The method of claim 1, wherein, The (3-aminoalkyl) trialkoxysilane is (3-aminopropyl) triethoxysilane.

4. The method of claim 1, wherein, The suspension of the activated silica gel is a toluene suspension of the activated silica gel; and the reflux reaction of the grafting product SiO2-AATAS and 8-hydroxyquinoline-2-carboxaldehyde is carried out in N,N-dimethylformamide.

5. The method of claim 1, wherein, The hydroxyquinoline grafted silica material is used to separate molybdenum from a nitric acid solution containing uranium and fission elements, and the method comprises the following steps: 1) The hydroxyquinoline grafted silica material is used as an adsorbent to adsorb molybdenum in a nitric acid solution containing uranium and fission elements, while uranium and other fission elements are not adsorbed; 2) The adsorbent after step 1) is desorbed to obtain an elution solution containing molybdenum.

6. The method of claim 5, wherein, In step 1), 0.01-1.5 g / L of the adsorbent is used per liter of the nitric acid solution, and the pH value of the nitric acid solution is 1.0-2.

0.

7. The method of claim 5, wherein, The adsorption operation of step 1) is that the hydroxyquinoline grafted silica material is added into the nitric acid solution, mixed uniformly by oscillation, and then left to stand for a period of time, or the nitric acid solution is allowed to flow through an adsorption column filled with the hydroxyquinoline grafted silica material.

8. The method of claim 5, wherein, The desorption solution of step 2) is an aqueous ammonia solution of ammonium carbonate, a guanidinium carbonate solution or an ammonium carbonate solution.

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