Seawater uranium extraction membrane material and preparation method thereof

Abstract

The invention relates to the field of materials for extracting uranium from seawater, in particular to a membrane material for extracting uranium from seawater and a preparation method thereof. The invention provides a seawater uranium extraction membrane material and a preparation method thereof.The preparation method comprises the steps that firstly, a copper pyrazole complex 1 with photocatalytic performance is synthesized and then added into a PAO solution, and the seawater uranium extraction membrane material with the photocatalytic performance is prepared through an electrostatic spinning method. The photocatalytic membrane prepared by the invention not only can be used for photocatalytic reduction of uranium, but also can be used for separation and reduction of uranium, and uranium can be separated and extracted while seawater desalination is performed; the method can be used for seawater pretreatment and saves cost.

Description

Technical Field

[0001] The invention relates to the field of materials for extracting uranium from seawater, and in particular to a membrane material for extracting uranium from seawater and a preparation method thereof. Background Art

[0002] my country is short of uranium resources on land, but has huge reserves of uranium resources in seawater. Extracting uranium from seawater is considered an important way to achieve sustainable development of nuclear energy in my country. The co-production of seawater desalination and uranium extraction from seawater can effectively reduce the cost of related equipment and power engineering, improve the efficiency of uranium extraction from seawater, and promote the industrialization of uranium extraction from seawater. First, the desalination power system is used to increase the external migration rate of the adsorption process. Secondly, the desalination pretreatment system is used to remove the corresponding interfering components, indirectly improving the adsorption selectivity effect. Thirdly, the co-production of seawater desalination and uranium extraction from seawater can reduce the cost of adsorbent placement. At the same time, it reduces marine biofouling, improves the recycling efficiency of materials, and indirectly reduces manufacturing costs.

[0003] In the process of seawater desalination, reverse osmosis membranes are prone to pollution and have a short service life. Since the composition of seawater is very complex, choosing appropriate pretreatment technology is conducive to reducing membrane pollution in the reverse osmosis process, reducing the number of membrane cleanings, extending the service life of the membrane, and further reducing the cost of water production. Traditional pretreatment methods mainly include coagulation sedimentation, coagulation flotation and particle media filtration. Compared with traditional pretreatment methods, membrane filtration produces better water quality and better retention of algae cells and bacteria. Therefore, it is also more conducive to reducing membrane pollution in the subsequent RO process and reducing the cost of water production in the SWRO process.

[0004] Although seawater uranium extraction and desalination co-production have obvious advantages in adsorption efficiency and extraction cost, the traditional adsorption uranium extraction method has many problems in its application in the field of seawater desalination-seawater uranium extraction co-production.

[0005] Problem 1: Adsorption selectivity limitation.

[0006] The composition of seawater is complex, with many + , K + , Ca 2+ Mg 2+ , Cu 2+ , Fe 3+ Competing ions are a huge challenge to the design and application of adsorption materials. The problem of competing ions is particularly prominent in the application of seawater desalination-uranium extraction. Therefore, in the process of seawater desalination-uranium extraction, higher requirements are placed on the selectivity of adsorption materials.

[0007] Problem 2: The core technical difficulty of photocatalytic uranium extraction from seawater is that the reduction product uranium dioxide and the adsorption material cannot be separated: Problem 2: The core technical difficulty of photocatalytic uranium extraction from seawater is that the reduction product uranium dioxide and the adsorption material cannot be separated.

[0008] A large number of studies have shown that the reduction product uranium dioxide is not stable and is easily oxidized into uranyl ions that dissolve in seawater. Since the uranium content in seawater is extremely low, the extraction process is a relatively long cycle. During this process, uranium dioxide is separated from the catalyst. Without the continuous supply of photoelectrons, it will further oxidize into uranyl ions that dissolve in seawater, thus losing its uranium extraction function. Therefore, it is necessary to continuously separate the reduction product uranium dioxide to prevent it from dissolving in seawater after oxidation. However, existing photocatalytic materials are mainly powder materials. After photocatalytic reduction, the insoluble uranium dioxide precipitated in the solution detaches from the surface of the material. Under the flushing and stirring of the water flow, uranium dioxide and the photocatalytic material are evenly mixed, making it difficult to separate uranium dioxide by existing means.

[0009] How to simultaneously achieve sterilization, photocatalysis, separation and a multifunctional separation membrane with certain mechanical properties requires the addition of multiple components. However, adding multiple components to the casting liquid has different compatibilities, and it is difficult to prepare a uniform casting liquid. It is difficult to prepare a membrane with certain separation functions, and the membrane preparation process has extremely high requirements. Summary of the invention

[0010] Based on the problems existing in the prior art, the present invention provides a membrane material for extracting uranium from seawater and a preparation method thereof. The technical concept of the present invention has the following characteristics:

[0011] In response to problem 1, the present invention modifies polyacrylonitrile by amine oxime to make it have better selective adsorption for uranium.

[0012] In response to question 2, the present invention adopts copper pyrazole complex as the photocatalytic active ingredient. The pyrazole ring can accelerate the electron transfer rate and the photocatalytic rate. The carbon cloth has photothermal properties and can increase the reaction rate. Photocatalysis can achieve adsorption limitation and has high selectivity. At the same time, pyrazole has good antibacterial ability, which is beneficial to extend the service life of the photocatalytic film.

[0013] In order to achieve multiple functions, multiple synergistic effects are used to achieve this. Among them, copper pyrazole can improve electron transfer and photocatalytic rate, improve reaction rate and kill bacteria at the same time; copper pyrazole can also photocatalytically reduce uranium, and produce oxygen free radicals to kill bacteria; polyacrylonitrile fixes copper pyrazole, making it evenly distributed, and at the same time intercepts and removes bacteria; amine oxime polyacrylonitrile plays a role in selectively adsorbing uranium. Multiple synergistic effects are achieved, sterilization helps to extract uranium, and sterilization consumes free radicals, thereby consuming holes, which helps to extract uranium. The three complement each other and interact with each other to form a whole, rather than a simple combination.

[0014] In order to achieve the purpose of the present invention, the present invention adopts the following technical solution:

[0015] Step 1: Preparation of pyrazole and copper complex: First, anhydrous copper chloride (0.94 g, 7 mmol) was completely dissolved in 40 mL of 25% concentrated ammonia water, and then pyrazole (1.021 g, 15 mmol) was completely dissolved in 40 mL of 25% concentrated ammonia water, and the two solutions were mixed under vigorous stirring. The resulting dark blue suspension was stirred for 20 minutes to obtain a blue precipitate. The precipitate was filtered, washed several times with 25% concentrated ammonia water and deionized water, and then dried in a vacuum oven at 40 ° C overnight to obtain copper pyrazole (CuPz) complex 1;

[0016] Step 2: Use commercial PAN powder containing 6.9% vinyl acetate; dissolve NH2OH-HCl in a mixed solvent consisting of ethanol and water in a volume ratio of 4:1 to prepare an NH2OH solution with a concentration of 1 g / L-50 g / L; adjust the pH value of the NH2OH solution to 7.0 by adding NaOH; carry out amide oxidation reaction in a 100 mL glass flask under a nitrogen atmosphere and electromagnetic stirring, wherein the reaction temperature is 20-80°C and the reaction time is 1-24 h; after the amide oxidation imine reaction is completed, repeatedly wash the obtained material with an ethanol / water mixed solvent (volume ratio of 4:1) to remove unreacted NH2OH; and vacuum dry the washed material at 20°C to obtain PAO powder 2;

[0017] Step 3: Dissolve the required amount of PAO in DMF and stir for 48 hours, disperse 1~5wt% of CuPz powder 1 in the DMF solution at a speed of 3000rpm, then ultrasonicate the suspension for 90 minutes and add it to the DMF solution of PAO powder 2, and then put it into an ultrasonic bath for 90 minutes; force-spin the prepared CuPz-PAO composite solution through a stainless steel needle with a diameter of 0.66 mm, and then collect the fibers on a stainless steel drum rotating at a speed of 10 revolutions per minute; the electrospun fabric is vacuum dried in a dryer at room temperature overnight to remove any possible residual solvent.

[0018] Technical description:

[0019] 1 Step 1: Copper pyrazole is selected as the photocatalytic active ingredient to improve the electron transport of the separation membrane, increase the photocatalytic rate, increase the reaction rate and kill bacteria at the same time.

[0020] 2 The amide oxidation reaction in step 2 is to introduce an amine oxime group into polyacrylonitrile, which is beneficial to the adsorption of uranium.

[0021] 3. The use of different ratios in step 2 for preparing amine oxime-treated polyacrylonitrile is to obtain amine oxime-treated polyacrylonitrile with different grafting rates; the copper pyrazole complex added in the ratio is for photocatalytic reduction of uranium and the generation of oxygen free radicals for sterilization. Beneficial Effects

[0022] 1. The photocatalytic film prepared by the present invention can not only photocatalytically reduce uranium, but also separate the reduced uranium, and can separate and extract uranium while desalinating seawater.

[0023] 2. The photocatalytic membrane prepared by the present invention can be used as a pretreatment of seawater before reverse osmosis to extend the service life of the reverse osmosis membrane.

[0024] 3. Sterilization helps to extract uranium. At the same time, sterilization consumes free radicals and then consumes holes, which helps to extract uranium. The prepared photocatalytic film can ensure the joint production of seawater desalination and seawater uranium extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : Infrared spectrum of the copper pyrazole complex prepared in Example 1.

[0026] Figure 2 : XRD pattern of the copper pyrazole complex prepared in Example 1.

[0027] Figure 3 : Schematic diagram of the synthesis of membrane materials in Example 1. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0029] Example 1

[0030] Step 1: Preparation of pyrazole and copper complex: First, anhydrous copper chloride (0.94 g, 7 mmol) was completely dissolved in 40 mL of 25% concentrated ammonia water, and then pyrazole (1.021 g, 15 mmol) was completely dissolved in 40 mL of 25% concentrated ammonia water, and the two solutions were mixed under vigorous stirring. The resulting dark blue suspension was stirred for 20 minutes to obtain a blue precipitate. The precipitate was filtered, washed several times with 25% concentrated ammonia water and deionized water, and then dried in a vacuum oven at 40 ° C overnight to obtain copper pyrazole (CuPz) complex 1;

[0031] Step 2: Use commercial PAN powder containing 6.9% vinyl acetate; dissolve NH2OH-HCl in a mixed solvent consisting of ethanol and water in a volume ratio of 4:1 to prepare an NH2OH solution with a concentration of 1 g / L-50 g / L; adjust the pH value of the NH2OH solution to 7.0 by adding NaOH; carry out amide oxidation reaction in a 100 mL glass flask under a nitrogen atmosphere and electromagnetic stirring, wherein the reaction temperature is 20-80°C and the reaction time is 1-24 h; after the amide oxidation imine reaction is completed, repeatedly wash the obtained material with an ethanol / water mixed solvent (volume ratio of 4:1) to remove unreacted NH2OH; vacuum dry the washed material at 20°C to obtain PAO powder 2;

[0032] Step 3: Dissolve the required amount of PAO in DMF and stir for 48 hours, disperse 1~5wt% of CuPz powder 1 in the DMF solution at a speed of 3000rpm, then ultrasonicate the suspension for 90 minutes and add it to the DMF solution of PAO powder 2, and then put it into an ultrasonic bath for 90 minutes; force-spin the prepared CuPz-PAO composite solution through a stainless steel needle with a diameter of 0.66 mm, and then collect the fibers on a stainless steel drum rotating at a speed of 10 revolutions per minute; the electrospun fabric is vacuum dried in a dryer at room temperature overnight to remove any possible residual solvent.

[0033] The seawater uranium extraction membrane material prepared in this embodiment is a membrane prepared by electrospinning with polyacrylonitrile as the skeleton and copper pyrazole complex as the filler. The infrared spectrum and XRD diagram of the copper pyrazole complex are shown as follows: Figure 1 and Figure 2 The schematic diagram of the synthesis of the seawater uranium extraction membrane prepared in this example is shown in Figure 3 shown.

[0034] Example 2

[0035] This embodiment is basically the same as the membrane material for extracting uranium from seawater and the preparation method thereof described in Example 1, except that NH2OH-HCl is dissolved in a mixed solvent consisting of ethanol and water in a volume ratio of 4:1, and the concentration of the prepared NH2OH solution is 30 g / L.

[0036] Example 3

[0037] The membrane for extracting uranium from seawater and the preparation method thereof described in this embodiment are basically the same as those described in Example 2, except that the reaction temperature of the amide oxidation imine reaction is 60° C. and the reaction time is 3 h.

[0038] Example 4

[0039] This embodiment is basically the same as the membrane for extracting uranium from seawater and the preparation method thereof described in Example 3, except that the amount of CuPz added in step 3 is 3 wt %.

Claims

1. A method for preparing a membrane material for extracting uranium from seawater, the method comprising the following steps: Step 1: Preparation of pyrazole and copper complex: First, anhydrous copper chloride (0.94 g, 7 mmol) was completely dissolved in 40 mL 25% concentrated ammonia water, and then pyrazole (1.021 g, 15 mmol) was completely dissolved in 40 mL 25% concentrated ammonia water, and the two solutions were mixed under vigorous stirring. The resulting dark blue suspension was stirred for 20 minutes to obtain a blue precipitate. The precipitate was filtered, washed several times with 25% concentrated ammonia water and deionized water, and then dried in a vacuum drying oven at 40 ° C overnight to obtain CuPz complex 1; Step 2: Use commercial PAN powder containing 6.9% vinyl acetate; dissolve NH2OH-HCl in a mixed solvent consisting of ethanol and water in a volume ratio of 4:1 to prepare an NH2OH solution with a concentration of 1g / L-50g / L; adjust the pH value of the NH2OH solution to 7.0 by adding NaOH; carry out amide oxidation reaction in a 100 mL glass flask under a nitrogen atmosphere and electromagnetic stirring, wherein the reaction temperature is 20-80°C and the reaction time is 1-24h; after the amide oxidation imine reaction is completed, repeatedly wash the obtained material with an ethanol / water mixed solvent (volume ratio of 4:1) to remove unreacted NH2OH; and vacuum dry the washed material at 20°C to obtain PAO powder 2; Step 3: Dissolve the required amount of PAO in DMF and stir for 48 hours, disperse 1~5wt% of CuPz powder 1 in the DMF solution at a speed of 3000rpm, then ultrasonicate the suspension for 90 minutes and add it to the DMF solution of PAO powder 2, and then put it into an ultrasonic bath for 90 minutes; force-spin the prepared CuPz-PAO composite solution through a stainless steel needle with a diameter of 0.66 mm, and then collect the fibers on a stainless steel drum rotating at a speed of 10 revolutions per minute; the electrospun fabric is vacuum dried in a dryer at room temperature overnight to remove any possible residual solvent.

2. A method for preparing a membrane material for extracting uranium from seawater as claimed in claim 1, characterized in that In step 2, NH2OH-HCl is dissolved in a mixed solvent consisting of ethanol and water in a volume ratio of 4:1 to prepare an NH2OH solution with a concentration of 30 g / L.

3. A method for preparing a membrane material for extracting uranium from seawater as claimed in claim 1 or 2, characterized in that The reaction temperature of the amide oxidation imine reaction in step 3 is 60° C. and the reaction time is 3 h.

4. A method for preparing a membrane material for extracting uranium from seawater as claimed in claim 1, 2 or 3, characterized in that The amount of CuPz added in step 3 is 3 wt %.

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