Amidoximation phosphonate, preparation method and method for extracting uranium from seawater

Abstract

The invention discloses amidoximation phosphonate, a preparation method and a method for extracting uranium from seawater, and belongs to the technical field of extraction of uranium from seawater. The method specifically comprises the following steps: carrying out halogenation reaction on hydroxyl-containing phosphonic acid or hydroxyl-containing phosphonate to replace hydroxyl with chloride ions; and then adding a strong cyanation reagent to carry out a cyanation reaction so as to replace chloride ions with cyano groups, carrying out vacuum drying, and then carrying out an amidoximation reaction by adopting condensation reflux so as to obtain the amidoximated phosphonate. The amidoximation phosphonate and a surfactant are matched to generate an aqueous film-forming foam material, and uranyl ions in a water body can be selectively enriched and separated after the aqueous film-forming foam material is introduced into the uranium-containing water body. When the concentration of uranium and vanadium in the water body is 10-100 [mu] g / L, more than 90% of uranium can be selectively enriched within 90-120 seconds by the method provided by the invention, and the selectivity S (U / V) = Kd (U) / Kd (V) = 44.735. The invention provides a rapid, efficient and targeted solution for enrichment and separation of uranium in seawater.

Description

Technical Field

[0001] The present invention belongs to the technical field of uranium extraction from seawater, and particularly relates to an amidoximated phosphonate, a preparation method thereof, and a method for extracting uranium from seawater. Background Art

[0002] As the core fuel for nuclear power generation, the globally recoverable reserves of uranium on land can only meet the demand for the next hundred years. However, land uranium resources are not only limited but also unevenly distributed. Traditional uranium mining faces problems such as resource depletion, high costs, and environmental damage. In contrast, seawater contains abundant uranium resources, with a reserve of approximately 4.5 billion tons of uranium, more than 1000 times that of land uranium reserves, presenting great development potential. Therefore, the technology of extracting uranium from seawater is regarded as an important way to solve the shortage of uranium resources and ensure energy security.

[0003] The utilization of seawater uranium resources has become a strategic topic of global concern. However, there is a complex ionic competitive adsorption environment in natural seawater. Among them, vanadium, due to its similar hydrochemical properties to uranyl ions, has become the most serious interference factor during the uranium adsorption process. Existing amidoxime-based adsorbents rely on a single coordination mechanism, and the binding energy between them and uranyl (UO2 2+ ) (about -150 kJ / mol) only differs by 20 - 30 kJ / mol from that of vanadate (H2VO4 - ), resulting in a generally low uranium / vanadium selectivity coefficient in actual seawater, usually lower than 30. Especially in nuclear polluted sea areas, the vanadium concentration surges to 10 - 100 μg / L, and the proportion of vanadium competitive adsorption by traditional adsorbents exceeds 60%, resulting in a uranium recovery purity of less than 50%. The extraction of uranium from seawater needs to meet the economic requirements of a ten-thousand-ton treatment scale. However, due to the dependence on the passive diffusion mechanism of traditional adsorption materials, the uranium adsorption equilibrium time is as long as 48 - 72 hours, and the high salinity (3.5 wt% NaCl) leads to a shielding rate of effective adsorption sites exceeding 80%. Although conventional methods for accelerating mass transfer (such as mechanical stirring and fluidized beds) can shorten the time to 12 hours, they exacerbate the fragmentation of the material structure (wear rate > 15%) and cause an increase in the co-adsorption amount of vanadium by more than 30%. Uranium in seawater exists in the form of highly stable uranyl hydroxycarbonate complex ions ([UO2(CO3)3] 4- , logβ = 21.6), and the charge density (-4) of it is significantly different from that of vanadate (-1). However, due to the lack of interface charge matching design in traditional adsorbents, the binding efficiency of uranyl complex ions is less than 10%.

[0004] Therefore, there is an urgent need to provide a method that can achieve efficient capture, selective enrichment and separation of trace uranium in seawater. Summary of the Invention

[0005] The object of the present invention is to overcome the limitations of the existing uranium extraction technology from seawater, solve the problems of slow adsorption rate and poor selectivity in the existing technology, and provide an amidoximated phosphonate, a preparation method thereof, and a method for extracting uranium from seawater.

[0006] The specific technical solution adopted by the present invention is as follows:

[0007] The present invention provides a preparation method of an amidoximated phosphonate, and the specific steps are as follows:

[0008] S1: Dissolve the phosphonic acid containing hydroxyl or the phosphonate containing hydroxyl fully in a polar solvent, and then add a strong halogenating reagent and continuously stir for a halogenation reaction, so that the hydroxyl groups in the phosphonic acid containing hydroxyl or the phosphonate containing hydroxyl are replaced by chlorine ions, and a chlorinated modified phosphonate solution is obtained;

[0009] S2: Add a strong cyanating reagent to the chlorinated modified phosphonate solution obtained in step S1, and continuously stir for a cyanation reaction, so that the chlorine ions in the chlorinated modified phosphonate are replaced by cyanide groups; after the solution after the cyanation reaction is vacuum dried, a cyanated modified phosphonate is obtained;

[0010] S3: Place the cyanated modified phosphonate obtained in step S2 in an amidoximation solution, and carry out an amidoximation reaction by condensation reflux; after the solution after the amidoximation reaction is vacuum dried, an amidoximated phosphonate is obtained.

[0011] Preferably, in step S1, the phosphonic acid containing hydroxyl is 1-hydroxyethylidene-1,1-diphosphonic acid, and the phosphonate containing hydroxyl is tetrasodium 1-hydroxyethylidene-1,1-diphosphonate; the polar solvent is water, dichloromethane, tetrahydrofuran, dimethyl sulfoxide or N,N-dimethylformamide; the strong halogenating reagent is thionyl chloride or phosphorus trichloride.

[0012] Preferably, in step S1, the ratio of the tetrasodium 1-hydroxyethylidene-1,1-diphosphonate, the polar solvent and the strong halogenating reagent is (2-10) g: (50-150) mL: (1-5) mL; in step S1, the temperature during the continuous stirring process is set at -5 to 5 °C, and the stirring time is 4 to 8 h.

[0013] Preferably, in step S2, the strong cyanating reagent is potassium thiocyanate or potassium cyanide; the ratio of the chlorinated modified phosphonate solution to potassium thiocyanate is (50-150) g: (1-5) g.

[0014] Preferably, in step S2, the temperature during the continuous stirring process of the cyanation reaction is set at 0 to 5 °C, and the stirring time is 12 to 24 h; in step S2, the vacuum drying is carried out in a vacuum rotary evaporator, the temperature is set at 65 to 95 °C, and the drying time is 4 to 8 h.

[0015] Preferably, the solvent of the oximation solution in step S3 is methanol, and the solutes are hydroxylamine hydrochloride, hydroxylamine sulfate or hydroxylamine phosphonate; the solutes and the solvent are mixed at (1-5) g:(10-80) mL and then heated to 40-80 °C, adjusted to pH 6-8 with sodium hydroxide and then reacted for 0.5-1 h to obtain the oximation solution.

[0016] Preferably, the ratio of the cyanated modified phosphonate and the oximation solution in step S3 is (5-15) g:(20-60) mL; the temperature of the amidoximation reaction is set at 50-100 °C, and the reaction time is 12-24 h; the vacuum drying in step S3 is carried out in a vacuum rotary distillation, the temperature is set at 45-85 °C, and the drying time is 4-8 h.

[0017] In a second aspect, the present invention provides an amidoximated phosphonate prepared by using the preparation method described in the first aspect.

[0018] In a third aspect, the present invention provides a method for selectively enriching and separating uranium from seawater by using an amidoximated phosphonate, specifically as follows:

[0019] S1: After mixing the amidoximated phosphonate described in the second aspect and a surfactant, cutting is carried out at 3500-6500 rpm for 60-150 s to form an amidoximated phosphonate-containing aqueous film foam material, wherein the concentration of the amidoximated phosphonate is 0.2-1 mmol / L, and the concentration of the surfactant is 0.1-0.3 mmol / L;

[0020] S2: The amidoximated phosphonate-containing aqueous film foam material is introduced into the uranium-containing water body at a flow rate of 0.002-0.02 m 3 / min to selectively enrich and separate uranium; the volume ratio of the introduced amidoximated phosphonate-containing aqueous film foam material to the uranium-containing water body is 1:(3-5).

[0021] Preferably, the surfactant is tetradecyltrimethylammonium bromide, cetylpyridinium chloride, polyoxyethylene sorbitan fatty acid ester or rhamnolipid; the uranium concentration range in the uranium-containing water body is 0.01-1 mg / L.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention adopts chemical modification means, first performs a halogenation reaction on a phosphonic acid or phosphonate containing a hydroxyl group to introduce chloride ions, then performs a cyanation reaction to introduce a cyano group, and finally performs an amidoximation reaction to obtain an amidoximated phosphonate. The aqueous film foam material obtained by combining the amidoximated phosphonate prepared by the above method and a surfactant has excellent interfacial activity and selectivity, and can efficiently recognize and rapidly separate uranyl ions in the water body.

[0024] (2) Different from the traditional adsorbents used in the prior art that rely on surface functional groups to passively capture uranyl ions, the present invention can achieve highly specific adsorption and separation of uranium by introducing aqueous film-forming foam materials into uranium-containing polluted water bodies, significantly improving the efficiency and selectivity of uranium extraction from seawater. Through experiments, in a seawater environment with high salinity and complex ion composition (when the uranium and vanadium concentrations are 50 μg / L), the material provided by the present invention can selectively enrich more than 90% of uranium within 90 - 120 seconds, and the selectivity S(U / V) = Kd(U) / Kd(V) = 44.735.

[0025] (3) The method provided by the present invention does not require a large amount of chemical reagents for acid / alkali elution regeneration processes and does not pose a problem of secondary treatment of uranium-containing wastewater. It only needs to collect the upper-layer floating scum for calcination, and the lower-layer restored water body can also be reused. Description of the Drawings

[0026] Figure 1 Synthesis schematic diagram of the amidoximated phosphonate provided by the present invention;

[0027] Figure 2 Results graph of the capture of uranyl by different concentrations of amidoximated phosphonate in Example 2.

[0028] Figure 3 Results graph of the capture of uranyl by amidoximated phosphonate from solutions with different initial concentrations in Example 3.

[0029] Figure 4 Results graph of the capture of uranyl by amidoximated phosphonate from solutions with different pH values in Example 4.

[0030] Figure 5 Results graph of the capture of uranyl by amidoximated phosphonate from a binary mixed solution containing uranyl ions and metavanadate ions in Example 5.

[0031] Figure 6 Results graph of the capture of uranyl by amidoximated phosphonate from a binary simulated seawater solution containing uranyl ions and metavanadate ions in Example 6. Detailed Embodiments

[0032] The present invention will be further elaborated and described below in conjunction with the drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined correspondingly without conflict.

[0033] Example 1

[0034] In this example, an amidoximated phosphonate is prepared, and the process is as Figure 1 shown. The specific steps are as follows:

[0035] I. Preparation of chlorinated modified phosphonate solution

[0036] Measure 100 mL of tetrahydrofuran with a graduated cylinder and pour it into a 250 mL conical flask. Weigh 10 g of tetrasodium hydroxyethane-1,1-diphosphonate and pour it into the conical flask containing tetrahydrofuran. Then, place the conical flask in a constant-temperature water bath and stir magnetically at a speed of 900 revolutions per minute for half an hour. Pour 5 mL of thionyl chloride strong halogenating reagent into the conical flask and continue to stir for 6 h at a temperature of -5 to 5 °C for the halogenation reaction, so that the hydroxyl groups in tetrasodium hydroxyethane-1,1-diphosphonate are replaced by chloride ions. After the reaction is completed, quench the reaction by adding an appropriate amount of water or saturated sodium bicarbonate solution in batches to obtain a chlorinated modified phosphonate solution.

[0037] II. Preparation of cyanated modified phosphonate

[0038] Weigh 5 g of potassium thiocyanate strong cyanating reagent and 0.5 g of copper(I) iodide and add them to the conical flask after the reaction in step I is completed, where copper(I) iodide acts as a catalyst. Stir magnetically at a speed of 900 revolutions per minute in a constant-temperature water bath for 12 to 24 h until the cyanation reaction is completed. After the reaction is completed, transfer the solution in the conical flask to a 250 mL round-bottom flask. Connect the round-bottom flask to a vacuum rotary evaporator, adjust the rotation speed to 80 revolutions per minute, gradually adjust the temperature to 90 °C, and rotate and evaporate for 8 h. Transfer the product obtained by rotary evaporation to a beaker, wrap the beaker mouth with tin foil and make three holes, and place the beaker in an oven to dry for 8 h to obtain a cyanated modified phosphonate.

[0039] III. Preparation of amidoximated phosphonate

[0040] Measure 80 mL of methanol with a graduated cylinder and pour it into a 150 mL three-necked flask. Weigh 5 g of hydroxylamine hydrochloride and pour it into the three-necked flask containing methanol. Then, assemble the three-necked flask into a condensing reflux device, place it in a constant-temperature magnetic stirrer and heat and stir. Weigh 2 g of sodium hydroxide and add it to the three-necked flask in three portions (adjust the pH to 6 - 8), the stirring temperature is 45 °C, and the stirring time is 1 h. After the stirring is completed, add 2 g of anhydrous magnesium sulfate (to remove the water in the solvent) and continue to stir for 10 min until the end. Filter the solid-liquid mixture in the three-necked flask, and take the filtered solution to obtain a supersaturated hydroxylamine methanol solution, which is used as the oximation solution.

[0041] Place the hydroxylamine methanol solution and the cyanated modified phosphonate obtained in step II in a 150 mL single-necked flask, and use the single-necked flask to build a condensing reflux device and carry out the amidoximation reaction by condensing reflux at 80 °C for 12 h. After the reaction is completed, connect the single-necked flask to a vacuum rotary evaporator, adjust the rotation speed to 80 revolutions per minute, gradually heat the temperature from 35 °C to 60 °C and evaporate for 3 h. Finally, obtain a white solid of amidoximated phosphonate, that is, tetrasodium amidoxime-hydroxyethane-1,1-diphosphonate.

[0042] Example 2

[0043] In this example, uranyl ions in the amidoximated phosphonate capture solution prepared in Example 1 with different concentrations were used.

[0044] Weigh 0.06 g of surfactant cetyltrimethylammonium bromide and mix it with 25, 50, 100, 200, 300, and 500 mg of tetrasodium amidoxime hydroxylethylidene diphosphonate respectively, then add them to 1 L of water to form a mixed solution (the control group is 0.06 g of cetyltrimethylammonium bromide added to 1 L of water). Cut the mixed solution at a rotation speed of 5000 revolutions per minute to introduce air into the liquid and form a gas-liquid interface, obtaining an amidoximated phosphorus-containing aqueous film-forming foam material: cetyltrimethylammonium bromide quickly adsorbs on the gas-liquid interface to form a monolayer film, with the hydrophobic tail facing the air and the hydrophilic head facing the water to form stable bubbles, and a large amount of tetrasodium amidoxime hydroxylethylidene diphosphonate adheres to the gas-liquid interface. Pass the amidoximated phosphorus-containing aqueous film-forming foam material from the bottom of the water body with an initial uranium concentration of 200 μg / L and a pH of 8 to actively capture uranyl ions. After standing for 1 minute, take the supernatant of the water body, digest and filter it, and then measure the remaining uranium concentration by inductively coupled plasma mass spectrometry.

[0045] When the cut mixed solution is introduced into the graduated cylinder and stopped when the foam reaches the 100 mL scale at the upper end, and the graduated cylinder is left to stand until all the foam breaks, then observe the liquid scale to obtain the gas holdup.

[0046] Calculate the enrichment rate of uranyl ions according to Equation (1), and the results are as Figure 2 shown. When 100 mg of tetrasodium amidoxime hydroxylethylidene diphosphonate is weighed, the enrichment rate of uranyl ions is the highest, reaching 97.28%.

[0047] The calculation method of the enrichment rate of uranyl ions is as shown in Equation (1):

[0048]

[0049] In the formula, C0——Initial uranium concentration before adsorption (μg / L);

[0050] C e ——Remaining uranium concentration at adsorption equilibrium (μg / L);

[0051] V0——Volume of the initial uranium solution to be treated (mL);

[0052] V e ——Volume of the uranium solution at adsorption equilibrium (mL);

[0053] ∝——Gas holdup (%).

[0054] Example 3

[0055] In this example, the amidoximated phosphonate prepared in Example 1 was used to capture uranyl ions in solutions with different initial concentrations.

[0056] Prepare uranium solutions to be treated with uranyl nitrate at pH 8 and initial uranium concentrations of 10, 50, 100, and 200 μg / L respectively; weigh 0.06 g of tetradecyltrimethylammonium bromide and 100 mg of tetrasodium amide oxime hydroxylethylidene diphosphonate, mix them, and add them to 1 L of water to form a mixed solution; cut at 3500 - 6500 rpm for 60 - 150 s to form an interfacial-concentrated amidoximated phosphorus-containing aqueous film foam material, and introduce it from below the uranium solution to be treated to actively capture uranyl ions. After standing for 1 minute, take the supernatant of the water body, digest and filter it, and measure the remaining uranium concentration by inductively coupled plasma mass spectrometry. Calculate the enrichment rate of uranyl ions according to formula (1), and the results are as Figure 3 shown.

[0057] According to the results, when the initial concentration of the uranium solution is 100 μg / L, the enrichment rate of uranyl ions is the highest, reaching 97.82%.

[0058] Example 4

[0059] In this example, the amidoximated phosphonate prepared in Example 1 was used to capture uranyl ions in solutions with different pH values.

[0060] Prepare a uranyl solution with a concentration of 100 μg / L using uranyl nitrate, and then adjust the pH of the uranyl solution to 5, 6, 7, and 8 respectively with 2% nitric acid solution; weigh 0.06 g of tetradecyltrimethylammonium bromide and 100 mg of tetrasodium amide oxime hydroxylethylidene diphosphonate, mix them, and add them to 1 L of water to form a mixed solution; cut at 3500 - 6500 rpm for 60 - 150 s to form an interfacial-concentrated amidoximated phosphorus-containing aqueous film foam material, and introduce it from below the uranium solution to be treated to actively capture uranyl ions. After standing for 1 minute, take the supernatant of the water body, digest and filter it, and measure the remaining uranium concentration by inductively coupled plasma mass spectrometry. Calculate the enrichment rate of uranyl ions according to formula (1), and the results are as Figure 4 shown.

[0061] According to the results, different pH conditions have little effect on the enrichment efficiency of uranyl ions, and this amidoximated phosphonate has a good enrichment effect on uranyl ions in solutions with different pH values.

[0062] Example 5

[0063] In this example, the amidoximated phosphonate prepared in Example 1 was used to capture uranyl in a binary mixed solution containing uranyl ions and metavanadate ions.

[0064] Prepare a binary mixed solution of uranyl ions and vanadate ions with a concentration of 50 μg / L using uranyl nitrate and ammonium metavanadate, with a pH of 8; weigh 0.06 g of cetyltrimethylammonium bromide and 100 mg of tetrasodium amidoxime hydroxylethylidene diphosphonate, mix them and add to 1 L of water to form a mixed solution; cut at 3500 - 6500 rpm for 60 - 150 s to form an interfacial concentrated amidoximated phosphine-containing aqueous film foam material, and introduce it from below the uranium solution to be treated to actively capture uranyl ions. After standing for 1 minute, take the supernatant of the water body, digest and filter it, and measure the remaining uranium concentration by inductively coupled plasma mass spectrometry. Calculate the enrichment rates of uranyl ions and vanadate ions according to formula (1), and the results are as Figure 5 shown.

[0065] The results show that the enrichment rate of uranyl ions is still very high, 93.36%, and the distribution coefficient value Kd(U) = 983.666 L / g; while the enrichment rate of vanadate ions is only 23.90%, and the distribution coefficient value Kd(V) = 21.989 L / g; the selectivity S(U / V) = Kd(U) / Kd(V) = 44.735.

[0066] Example 6

[0067] In this example, the amidoximated phosphonate prepared in Example 1 was used to capture uranyl in a binary simulated seawater mixed solution containing uranyl ions and vanadate ions.

[0068] After the sea salt was fully dried, ultra-pure water was added to prepare a brine with a concentration of 35 g / kg. Use this brine to prepare a binary simulated seawater mixed solution containing 50 μg / L of uranyl ions and vanadate ions (pH = 8). Weigh 0.06 g of cetyltrimethylammonium bromide and 100 mg of tetrasodium amidoxime hydroxylethylidene diphosphonate, mix them and add to 1 L of water to form a mixed solution; cut at 3500 - 6500 rpm for 60 - 150 s to form an interfacial concentrated amidoximated phosphine-containing aqueous film foam material, and introduce it from below the uranium solution to be treated to actively capture uranyl ions. After standing for 1 minute, take the supernatant of the water body, digest and filter it, and measure the remaining uranium concentration by inductively coupled plasma mass spectrometry. Calculate the enrichment rates of uranyl ions and vanadate ions according to formula (1).

[0069] The results show that the enrichment rate of uranyl ions is still very high, 74.99%, and the distribution coefficient value Kd(U) = 209.841 L / g; while the enrichment rate of vanadate ions is only 28.05%, and the distribution coefficient value Kd(V) = 27.295 L / g; the selectivity S(U / V) = Kd(U) / Kd(V) = 7.688. It shows that the amidoximated phosphonate prepared by the present invention can selectively enrich and separate uranyl in seawater and achieve efficient capture.

[0070] The embodiments described above are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing amidoximated phosphonate, characterized in that, The specific steps are as follows: S1: Dissolve the phosphonic acid containing hydroxyl groups or the phosphonate containing hydroxyl groups in a polar solvent sufficiently, and then add a strong halogenating reagent and continuously stir for a halogenation reaction, so that the hydroxyl groups in the phosphonic acid containing hydroxyl groups or the phosphonate containing hydroxyl groups are replaced by chlorine ions, obtaining a chlorinated modified phosphonate solution; S2: Add a strong cyanating reagent to the chlorinated modified phosphonate solution obtained in step S1, and continuously stir for a cyanation reaction, so that the chlorine ions in the chlorinated modified phosphonate are replaced by cyanide groups; after vacuum drying the solution after the cyanation reaction, a cyanated modified phosphonate is obtained; S3: Place the cyanated modified phosphonate obtained in step S2 in an oximation solution, and carry out a geminal diamine oximation reaction by means of condensation reflux; after vacuum drying the solution after the geminal diamine oximation reaction, a geminal diamine oximated phosphonate is obtained.

2. The preparation method of the amidoximated phosphonate according to claim 1, wherein In step S1, the phosphonic acid containing hydroxyl groups uses hydroxyethylidene diphosphonic acid, and the phosphonate containing hydroxyl groups uses tetrasodium hydroxyethylidene diphosphonate; the polar solvent uses water, dichloromethane, tetrahydrofuran, dimethyl sulfoxide or N,N-dimethylformamide; the strong halogenating reagent uses thionyl chloride or phosphorus trichloride.

3. The preparation method of the amidoximated phosphonate according to claim 1, characterized in that, In step S1, the ratio of the tetrasodium hydroxyethylidene diphosphonate, the polar solvent and the strong halogenating reagent is (2 - 10) g : (50 - 150) mL : (1 - 5) mL; in step S1, the temperature during the continuous stirring process is set to -5 to 5 °C, and the stirring time is 4 to 8 h.

4. The preparation method of the amidoximated phosphonate according to claim 1, characterized in that, In step S2, the strong cyanating reagent uses potassium thiocyanate or potassium cyanide; the ratio of the chlorinated modified phosphonate solution to potassium thiocyanate is (50 - 150) g : (1 - 5) g.

5. The preparation method of the amidoximated phosphonate according to claim 1, characterized in that, In step S2, the temperature during the continuous stirring process of the cyanation reaction is set to 0 to 5 °C, and the stirring time is 12 to 24 h; in step S2, the vacuum drying is carried out in a vacuum rotary evaporator, the temperature is set to 65 to 95 °C, and the drying time is 4 to 8 h.

6. The preparation method of the amidoximated phosphonate according to claim 1, characterized in that, In step S3, the solvent of the oximation solution is methanol, and the solute is hydroxylamine hydrochloride, hydroxylamine sulfate or hydroxylamine phosphonate; after mixing the solute and the solvent according to (1 - 5) g : (10 - 80) mL and heating to 40 to 80 °C, adjust the pH to 6 to 8 with sodium hydroxide and react for 0.5 to 1 h to obtain the oximation solution.

7. The preparation method of the amidoximated phosphonate according to claim 1, characterized in that, In step S3, the ratio of the cyanated modified phosphonate to the oximation solution is (5 - 15) g : (20 - 60) mL; the temperature of the geminal diamine oximation reaction is set to 50 to 100 °C, and the reaction time is 12 to 24 h; in step S3, the vacuum drying is carried out in a vacuum rotary evaporator, the temperature is set to 45 to 85 °C, and the drying time is 4 to 8 h.

8. A geminal diamine oximated phosphonate prepared by using the preparation method according to any one of claims 1 to 7.

9. A method for extracting uranium from seawater by selective enrichment-separation using amidoximated phosphonate, characterized in that, Specifically as follows: S1: After mixing the geminal diamine oximated phosphonate according to claim 8 and a surfactant, cut at 3500 - 6500 rpm for 60 - 150 s to form a geminal diamine oximated phosphonate-containing aqueous film-forming foam material, wherein the concentration of the geminal diamine oximated phosphonate is 0.2 - 1 mmol / L, and the concentration of the surfactant is 0.1 - 0.3 mmol / L; S2: Feed the amidoximated phosphine-containing aqueous film-forming foam material into the uranium-containing water body at a flow rate of 0.002 - 0.02 m 3 / min for selective enrichment-separation of uranium; the volume ratio of the fed amidoximated phosphine-containing aqueous film-forming foam material to the uranium-containing water body is 1:(3 - 5).

10. The method for extracting uranium from seawater by selective enrichment-separation using amidoximated phosphonate, as claimed in claim 9, is characterized in that, The surfactant is selected from tetradecyl trimethyl ammonium bromide, cetylpyridinium chloride, polyoxyethylene sorbitan fatty acid ester or rhamnolipid; the uranium concentration range in the uranium-containing water body is 0.01-1 mg / L.

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