Efficient enrichment method for uranyl in fiber eluent for extracting uranium from seawater

Abstract

The invention discloses a method for efficiently enriching uranyl in a fiber eluent for extracting uranium from seawater, and belongs to the technical field of extracting uranium from seawater. According to the method, an ion exchange method and a chemical precipitation method are adopted for treating an eluent of seawater uranium extraction fibers, the fiber eluent is pretreated firstly, then D201 resin is used for concentrating and purifying the fiber eluent to obtain a uranium concentrated solution, finally, ammonia water is used for precipitating the uranium concentrated solution, precipitates are collected, and the precipitates are centrifugally dried to obtain the uranium compound. According to the method, uranyl in the fiber eluent can be efficiently enriched.

Description

Technical Field

[0001] The present invention relates to the technical field of uranium extraction from seawater, and particularly to an efficient enrichment method for uranyl in the eluate of seawater uranium extraction fibers. Background Art

[0002] Uranium, as a basic resource for nuclear energy production, is of strategic significance for the sustainability of the global nuclear industry. In recent years, the continuous expansion of nuclear power scale has driven a significant increase in the demand for uranium related to reactors. The uranium reserves on land are decreasing day by day, and it is estimated that they are only enough for one century's use. Therefore, people are preparing to identify and utilize unconventional uranium reserves. Uranium in seawater is an important unconventional uranium resource, with a reserve of about 4.5 billion tons, which is about a thousand times that of conventional sources such as land-based ores, and can ensure the long-term stable development of nuclear power.

[0003] The key to uranium extraction from seawater lies in the selection of methods and materials. Currently, the commonly used methods for uranium extraction from seawater include membrane separation, ion exchange, chemical precipitation, electrochemistry, and adsorption. In contrast, the adsorption method has become one of the most commonly used and effective technologies due to its advantages such as low cost, simple operation, practicality, environmental protection, and simple regeneration of the adsorbent. Whether the adsorption method is applicable depends on the design and structure of the material. Commonly used adsorbents include carbon-based materials, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), biopolymers, amidoxime-based materials, etc.

[0004] For adsorption materials, a lot of research has been done. The most promising one is the amidoxime-based fiber, which has good mechanical strength and high uranium adsorption capacity in seawater. The uranium collected by the amidoxime-based adsorption fiber is usually recovered by acid elution with 1M hydrochloric acid or the like. However, a serious disadvantage of the acid elution method is that the fiber deteriorates due to acid hydrolysis, limiting its reusability.

[0005] At the present stage, the relevant research work on uranium extraction from seawater mainly focuses on the development and performance research of uranium extraction materials. There is little research on purifying uranium from the eluate of adsorption materials into yellow cake, and more is on the treatment of uranium-containing wastewater and uranium ore leaching solution.

[0006] Therefore, it is necessary to develop an efficient enrichment method for uranyl in the eluate of seawater uranium extraction fibers. Summary of the Invention

[0007] In view of the above problems, the present invention overcomes at least one deficiency and provides an efficient enrichment method for uranyl in the eluate of seawater uranium extraction fibers.

[0008] An efficient enrichment method for uranyl in the eluate of seawater uranium extraction fibers includes the following steps:

[0009] (1) Pretreat the uranium-extracted fibers from seawater with an alkaline eluent to obtain a fiber eluent containing uranium-extracted fibers from seawater. Filter the fiber residues from the fiber eluent containing uranium-extracted fibers with a sieve and let it stand for a set time, then filter off the large particle precipitates with a sieve again. Then place the filtered fiber eluent under a heating device and heat it to 80 - 100 °C for flocculation to agglomerate smaller impurities and filter and separate them again with a sieve to obtain a clarified uranium-containing elution solution and uranium-containing precipitates.

[0010] (2) Filter and separate the uranium-containing precipitates. Add a 2 - 3 M ammonium carbonate solution to the uranium-containing precipitates separated in step (1) until the uranium-containing precipitates are completely submerged. Stir the resulting mixture at a temperature of 45 - 50 °C for 2 - 3 h. Then filter and separate the precipitates and the solution in the mixture, and mix the separated solution with the clarified uranium-containing elution solution in step (1) to obtain a uranium-containing solution to be concentrated.

[0011] (3) Measure the concentration of uranium in the uranium-containing solution obtained in step (2) by ICP. Then add ion exchange resin to the chromatography column according to the standard of the maximum adsorption capacity of 0.4 - 0.5 mg / g. Circulate the uranium-containing solution in the chromatography column through a peristaltic pump and regularly monitor the concentration of uranium in the uranium-containing solution until C(U) < 1 ppm in the uranium-containing solution.

[0012] (4) Prepare a 1 M hydrochloric acid solution with a volume of 1 / 20 - 1 / 10 of the uranium-containing elution solution obtained in step (2). Add the hydrochloric acid solution to the chromatography column through a peristaltic pump for circulation and monitor the concentration of uranium in the hydrochloric acid solution. Circulate for 1 - 2 h to obtain a uranium concentrate.

[0013] (5) Add ammonia water to the uranium concentrate to adjust the pH to 10 - 11 and regularly monitor the concentration of uranium in the solution until C(U) < 1 ppm in the uranium concentrate.

[0014] (6) Centrifuge and filter to collect the precipitates in the uranium concentrate obtained in step (5), then wash the precipitates with deionized water, and collect the uranium-containing compound after drying.

[0015] This application first concentrates and purifies uranium with a strongly basic anion exchange resin (partially purified by adsorption), and then precipitates uranium with ammonia water (as an eluent for uranium, capable of precipitating to obtain a uranium compound). The precipitates are centrifuged and separated, and then the uranium compound is obtained after washing and drying. This application can efficiently enrich uranyl in the fiber eluent.

[0016] The method of the present invention further collects uranium in the fiber eluent and improves the recycling of uranium-extracted fibers from seawater.

[0017] In this application, "M" refers to the amount-of-substance concentration (mol / L); ICP is an Inductively Coupled Plasma analysis technology that can be used for quantitative detection of elements.

[0018] In one embodiment of the present invention, the uranium-extracting fiber contained in the fiber eluent is a polyacrylonitrile fiber grafted with amidoxime groups.

[0019] In one embodiment of the present invention, the alkaline eluent used in the pretreatment of step (1) is Na2CO3-H2O2, and the stirring and elution time for the pretreatment is 30 - 45 min.

[0020] The polyacrylonitrile fiber grafted with amidoxime groups has good mechanical strength and high uranium adsorption capacity in seawater. Uranium collected by existing amidoxime-based adsorption fibers is usually recovered by acid elution with 1M hydrochloric acid or the like. However, a serious drawback of the acid elution method is that the fiber deteriorates due to acid hydrolysis, limiting its reusability. The alkaline eluent used in this application is Na2CO3-H2O2, which causes little damage to the fiber during the elution process, and the fiber can be regenerated for reuse only by rinsing with water.

[0021] In one embodiment of the present invention, in step (1), the liquid-solid ratio of the alkaline eluent to the wet fiber is 4 mL:1 g.

[0022] In one embodiment of the present invention, in step (1), the liquid-solid ratio of the alkaline eluent to the dry fiber is 20 mL:1 g.

[0023] In one embodiment of the present invention, the sieve used for filtration in step (1) is a sieve with 200 - 500 mesh.

[0024] In one embodiment of the present invention, in steps (3) and (4), the liquid inlet flow rate of the peristaltic pump is 2 - 3 L / min.

[0025] In one embodiment of the present invention, the ion exchange resin in step (3) is D201 resin;

[0026] It also includes a step of activating and recovering the D201 resin after elution in step (4), specifically including: first soaking the D201 resin in a 3 - 5% sodium hydroxide solution for 2 - 3 hours, washing it with deionized water until pH ≤ 8; then soaking the D201 resin in 3 - 5% hydrochloric acid for 2 - 3 hours, washing it with deionized water until pH ≥ 6, and then soaking the D201 resin in 3% - 5% sodium hydroxide for 0.5 - 1.5 h to regenerate the free base of the D201 resin again, and then rinsing it with deionized water until pH ≤ 8 to obtain the recovered D201 resin.

[0027] In one embodiment of the present invention, the set time in step (1) is 1 - 2 days.

[0028] The beneficial effects of the present invention are as follows: In this application, strongly basic anion exchange resin is first used to concentrate and purify uranium, and then ammonia water is used to precipitate uranium. The precipitate is centrifuged and separated, and then a uranium compound is obtained after washing and drying. The method of the present invention further collects uranium in the fiber eluate and improves the recycling of uranium extraction fibers from seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a process flow chart for the enrichment method of uranium compounds in the fiber eluate for uranium extraction from seawater;

[0030] Figure 2a is a curve showing the change of the uranium (U) concentration in the solution with time when the resin adsorbs the uranium-containing eluate in the current embodiment;

[0031] Figure 2b is a curve showing the change of the calcium (Ca) concentration in the solution with time when the resin adsorbs the uranium-containing eluate in the current embodiment;

[0032] Figure 2c is a curve showing the change of the magnesium (Mg) concentration in the solution with time when the resin adsorbs the uranium-containing eluate in the current embodiment;

[0033] Figure 2d is a curve showing the change of the vanadium (V) concentration in the solution with time when the resin adsorbs the uranium-containing eluate in the current embodiment;

[0034] Figure 3 is a curve showing the change of the concentrations of calcium, magnesium, uranium, and vanadium in the solution with time when the resin is eluted with hydrochloric acid in the current embodiment;

[0035] Figure 4a is a curve showing the change of the U concentration in the solution with time when the uranium concentrate is precipitated with ammonia water in the current embodiment;

[0036] Figure 4b is a curve showing the change of the Ca concentration in the solution with time when the uranium concentrate is precipitated with ammonia water in the current embodiment;

[0037] Figure 4c is a curve showing the change of the Mg concentration in the solution with time when the uranium concentrate is precipitated with ammonia water in the current embodiment;

[0038] Figure 4d is a curve showing the change of the V concentration in the solution with time when the uranium concentrate is precipitated with ammonia water in the current embodiment;

[0039] Figure 5It is a schematic diagram of the uranium compound finally obtained by the enrichment process according to the steps of the current embodiment;

[0040] Figure 6 It is a schematic diagram of the content ratio of the main elements in the uranium compound finally obtained in the current embodiment. Specific implementation manners

[0041] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

[0042] An embodiment of the present invention refers to Figure 1 the following processing steps are carried out according to the process flow:

[0043] (1) In this embodiment, the uranium extraction fiber after the actual sea trial is eluted and pretreated to obtain a fiber eluate, with a total of 11.04 kg. The pretreatment steps are as follows: The uranium extraction fiber is washed with clean water three times, 25 L each time, to wash away the sediment and shellfish on the surface, facilitating subsequent elution treatment.

[0044] After the fiber is washed, wet fiber is obtained, and it is stirred and eluted with an alkaline eluent at a solid-liquid ratio of 4 mL:1 g of the eluent to wet fiber for 45 - 50 min. In the current embodiment, 46 L of fiber eluate is obtained by stirring and eluting the uranium extraction fiber with 50 L of prepared Na2CO3-H2O2 alkaline eluent for 45 min. In other implementation manners, dry fiber can also be used for elution pretreatment to obtain fiber eluate, and the liquid-solid ratio of the alkaline eluent to dry fiber is 20 mL:1 g.

[0045] After the fiber eluate is obtained, the enrichment of uranium compound is carried out according to the method of the present invention, including the following steps:

[0046] First, the fiber eluate is preliminarily screened with a 200-mesh sieve to filter out the fiber residues dropped during the elution process. Then the fiber eluate is allowed to stand for one day to make it stratified, and then filtered through a 200-mesh sieve to filter out large sediment particles. Then the fiber eluate is placed on a heating device for heating and flocculation to make smaller impurities agglomerate and is filtered and separated again with a 200-mesh sieve to obtain uranium-containing precipitate and 33 L of clarified uranium-containing eluate. In this embodiment, the concentration of uranium in the uranium-containing eluate is 11.98 mg / L.

[0047] (2) Add 2 L of 3 M ammonium carbonate solution to the uranium-containing precipitate collected in step (1) to obtain a mixed solution. Heat the mixed solution at 50 °C for 2 h, and then filter and separate the precipitate and the solution in the mixed solution. The uranium concentration in the uranium-containing solution obtained through this step is about 10 mg / L, and in the current example, it is 9.6 mg / L. Mix the obtained uranium-containing solution with the clarified uranium-containing elution solution obtained in step (1) to form a new uranium-containing solution.

[0048] (3) Measure the uranium concentration in the uranium-containing solution obtained in step (2) by ICP, and calculate the amount of D201 resin required according to the standard of the maximum adsorption capacity of 0.4 - 0.5 mg / g. In the current example, it is 1 kg. Load 1 kg of D201 resin into the chromatography column, and circulate the uranium-containing solution through a peristaltic pump at a flow rate of 2 L / min for 7 days until C(U) < 1 ppm in the uranium-containing solution. In the current example, the uranium concentration in the uranium-containing elution solution is reduced to 0.73 mg / L. Figures 2a - 2d Respectively, it is possible to see the curve graphs of the concentration changes of the main elements (U, Ca, Mg, V) in the elution solution with time when the resin adsorbs the uranium-containing elution solution in the previous example. Among them, the abscissa represents time, and the ordinate represents the concentration of each element. Among them Figure 2a It is also possible to see the change in the state of the uranium-containing elution solution after resin adsorption.

[0049] (4) After the adsorption is completed, prepare 1 M hydrochloric acid solution with a volume of 1 / 20 - 1 / 10 of the uranium-containing solution obtained in step (2). In the current example, it is 3 L. Circulate 3 L of 1 M hydrochloric acid solution through the peristaltic pump at a flow rate of 2 L / min in the chromatography column for 2 h to obtain a uranium concentrate. After the elution in step (4) of the present invention is completed, the uranium concentration in the obtained uranium concentrate can reach about 120 mg / L. In the current example, the uranium concentration in the obtained uranium concentrate is 155.47 mg / L. The concentration has increased by 12.97 times.

[0050] Among them, to improve the utilization rate of the resin, the resin after elution in step (4) can be reused after activation. First, soak the D201 resin in a 3 - 5% sodium hydroxide solution for 2 - 3 hours, and wash it with deionized water until pH ≤ 8; then soak the D201 resin in 3 - 5% hydrochloric acid for 2 - 3 hours, and wash it with deionized water until pH ≥ 6. Then soak the D201 resin in 3% - 5% sodium hydroxide for 0.5 - 1.5 h to regenerate the free base of the D201 resin again, and then rinse it with deionized water until pH ≤ 8 to obtain the recycled D201 resin. As Figure 3 shown, the curve graphs of the concentration changes of calcium, magnesium, uranium, and vanadium in the solution with time when eluting the resin with hydrochloric acid.

[0051] (5) Slowly add ammonia water to the uranium concentrate to adjust the pH to 10 and carry out precipitation. During the precipitation, regularly monitor the concentration of uranium in the solution until C(U) < 1 ppm in the uranium concentrate. In the current embodiment, the precipitation was carried out for 10 h. After the precipitation was completed, the concentration of uranium in the uranium concentrate decreased to 0.88 mg / L. Figures 4a - 4d They are the curves of the concentrations of the main elements (U, Ca, Mg, V) in the uranium concentrate varying with time when ammonia water is added for precipitation in the current embodiment, where the abscissa represents time and the ordinate represents the concentrations of the respective elements. In Figure 4a it can also be seen the uranium concentrate before precipitation and the precipitate in the uranium concentrate after 10 h of precipitation.

[0052] (6) Collect the uranium compound from the uranium concentrate after the precipitation in step (5) by centrifugation, washing and drying. A total of 939 mg of uranium compound was collected, as Figure 5 shown. The content of uranium in the uranium compound obtained after step (6) of the present invention is about 30%, and the enrichment efficiency of uranium is about 90%. The content of uranium in the uranium compound of the current embodiment refers to Figure 5 , with a proportion of 33.1%. The enrichment efficiency of the entire enrichment process is 92.83%. Among them Figure 6 other in it represents the total proportion of other elements except the main elements (U, Ca, Mg, V).

[0053] Using the method of the present invention for the enrichment of uranium compounds improves the extraction rate of uranium and activates the uranium extraction fiber, thereby improving the recycling of the uranium extraction fiber.

[0054] The above are only the preferred embodiments of the present invention, and thus do not limit the patent protection scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, directly or indirectly applied in other related technical fields, shall be equally included in the protection scope of the present invention.

Claims

1. A method for efficiently enriching uranyl in seawater uranium extraction fiber eluate, characterized in that: The steps include: (1) pre-treating the seawater uranium extraction fiber with an alkaline eluent to obtain a fiber eluent containing the seawater uranium extraction fiber, filtering the fiber eluent containing the seawater uranium extraction fiber with a sieve to remove fiber residues, then letting it stand for a set time, and filtering out large particle precipitates with the sieve again; then placing the filtered fiber eluent under a heating device, heating it to 80-100° C. for flocculation, agglomerating smaller impurities, and filtering and separating them with a sieve again to obtain a clarified uranium-containing eluent and a uranium-containing precipitate; (2) filtering and separating the uranium-containing precipitate, adding a 2-3 M ammonium carbonate solution to the uranium-containing precipitate separated in step (1) until the uranium-containing precipitate is completely submerged, and stirring the resulting mixed solution at a temperature of 45-50° C. for 2-3 h; Then, the precipitate and the solution in the mixed solution are separated by filtration, and the separated solution is mixed with the clarified uranium-containing elution solution in step (1) to obtain a uranium-containing solution to be concentrated; (3) measuring the uranium concentration in the uranium-containing solution obtained in step (2) by ICP, then adding ion exchange resin into the chromatography column according to the standard of maximum adsorption capacity of 0.4-0.5 mg / g, circulating the uranium-containing solution in the chromatography column by a peristaltic pump and regularly monitoring the uranium concentration in the uranium-containing solution until the C(U) in the uranium-containing solution is less than 1 ppm; (4) preparing a 1 M hydrochloric acid solution with a volume of 1 / 20-1 / 10 of the uranium-containing elution solution obtained in step (2), adding the hydrochloric acid solution to the chromatography column by a peristaltic pump for circulation and monitoring the concentration of uranium in the hydrochloric acid solution, and continuing the circulation for 1-2 hours to obtain a uranium concentrate; (5) Adding ammonia water to the uranium concentrate to adjust the pH to 10-11, and regularly monitoring the uranium concentration in the solution until the C(U) in the uranium concentrate is less than 1 ppm; (6) Collecting the precipitate in the uranium concentrate obtained in step (5) by centrifugal filtration, washing the precipitate with deionized water, and collecting the uranium-containing compound after drying.

2. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater according to claim 1, characterized in that: The seawater uranium-extracted fiber contained in the fiber eluent is a polyacrylonitrile fiber grafted with amidoxime groups.

3. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater as claimed in claim 2, characterized in that: The alkaline eluent used in the pretreatment of step (1) is Na2CO3-H2O2, and the stirring elution time for the pretreatment is 30-45 minutes.

4. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater as claimed in claim 3, characterized in that: In step (1), the liquid-to-solid ratio of the alkaline eluent to the wet fiber is 4 mL:1 g.

5. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater as claimed in claim 3, characterized in that: In step (1), the liquid-to-solid ratio of the alkaline eluent to the dry fiber is 20 mL:1 g.

6. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater according to claim 1, characterized in that: The sieve used for filtering in step (1) is a sieve with a mesh size of 200-500.

7. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater according to claim 1, characterized in that: The liquid inlet flow rate of the peristaltic pump in step (3) and step (4) is 2-3 L / min.

8. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater according to claim 1, characterized in that: The ion exchange resin in step (3) is D201 resin.

9. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater as claimed in claim 8, characterized in that: The method further comprises the step of activating and recovering the D201 resin after the elution in step (4), specifically comprising: firstly soaking the D201 resin in a 3-5% sodium hydroxide solution for 2-3 hours, and washing with deionized water until the pH value is less than or equal to 8; then soaking the D201 resin in a 3-5% hydrochloric acid solution for 2-3 hours, and washing with deionized water until the pH value is greater than or equal to 6; then soaking the D201 resin in a 3%-5% sodium hydroxide solution for 0.5-1.5 hours to generate free alkali in the D201 resin again, and then washing with deionized water until the pH value is less than or equal to 8 to obtain the recovered D201 resin.

10. The method for efficiently enriching uranyl in the eluate of uranium extraction fiber from seawater according to claim 1, characterized in that: The set time in step (1) is 1-2 days.

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