Preparation method and application of functionalized graphene and graphene film for removing tritium from radioactive waste liquid

Abstract

The invention discloses functionalized graphene for removing tritium from radioactive waste liquid and a preparation method and application of a graphene film, the functionalized graphene is a flaky substance formed by stacking lamellar structures, and the distance between the stacked lamellar structures is 7.5-8.7. The preparation method comprises the following steps: preparing graphene oxide powder; performing sulfonation on the graphene oxide powder to obtain sulfonated graphene aerogel; performing carboxylation on the graphene oxide powder to obtain carboxylated graphene; and mixing and stirring the sulfonated graphene aerogel and carboxylated graphene to obtain the functionalized graphene. The tritium in the tritium-containing liquid is separated by utilizing the membrane formed by the functionalized graphene, and the tritium removal technology has the advantages of mild reaction conditions, low energy consumption, easiness in large-scale production and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radioactive waste treatment, in particular to a functionalized graphene for removing tritium from radioactive waste liquid and a preparation method and application of a graphene film. BACKGROUND

[0002] Tritium is an isotope of hydrogen and has beta radioactivity. The natural abundance of tritium in nature is very low, which is difficult to concentrate and utilize, and also does not pose a threat to the human body. However, nuclear facilities produce a large amount of tritium-containing liquid effluent every year, in addition, some extreme nuclear accidents also produce a large amount of tritium-containing wastewater, such as the Fukushima nuclear accident in Japan since 2013 has accumulated more than 1.3 million tons of tritium-containing wastewater with an activity concentration of about 106Bq / L. Even after purification by the three-waste treatment system, the tritium with radioactivity cannot be effectively removed. These tritium-containing wastewater has become the main source of tritium in nature and has caused great potential harm to human health and the environment.

[0003] Tritium participates in the biological cycle by isotopic exchange reaction with hydrogen in nature, and enters the human body through diet, respiratory inhalation, and skin penetration. Studies have shown that tritium can cause direct biological effects through beta-ray internal irradiation, leading to the occurrence of leukemia and other malignancies. Therefore, the treatment of tritium-containing wastewater and tritium-containing liquid effluent is urgent.

[0004] Current technologies for tritium removal include electrolysis, rectification, catalytic exchange, and other engineering technologies, as well as porous material adsorption and membrane separation methods. However, these engineering technologies generally have high energy consumption, low safety, limited processing efficiency, and other problems, and there is an urgent need to develop future-oriented high-efficiency, low-energy, and low-cost tritium removal technologies.

[0005] For example, for membrane separation methods, the patent document with publication number CN113600011A discloses a graphene solid electrolytic cell device for hydrogen isotope separation, which includes an electrolytic cell and a graphene composite membrane electrode arranged in the electrolytic cell. The graphene composite membrane electrode is composed of a hydrogen evolution catalyst layer, a graphene layer, an anion exchange layer, and an oxygen evolution catalyst layer. The device utilizes the selective permeability of graphene sub-atoms to the screening ability of hydrogen isotopes, thereby improving the separation efficiency of hydrogen isotopes, especially the treatment efficiency of tritium-containing wastewater. However, this method has a complex device, high energy consumption, and high cost.

[0006] Graphene oxide (GO) filter membrane is widely used in water treatment, seawater desalination, organic separation and other fields due to its two-dimensional sheet structure and rich oxygen functional groups. In the existing research, some people try to use GO or reduced GO filter membrane to separate water and heavy water (H2O / D2O) as a model system for isotope separation. However, the membrane with clear separation effect for H2O / D2O cannot be directly applied to the separation of tritium water. The reasons are as follows: First, the isotopic mass difference of tritium also exists, but tritium is radioactive, and the beta electrons produced by radioactivity may have a certain influence on the separation process; Second, there are differences in nuclear quantum effects in the graphene oxide microchannel confined space between H2O / D2O system and H2O / HTO system, and the separation mechanism is different. The existing membrane with clear separation effect for H2O / D2O is not clear about its tritium removal performance; Third, in terms of experimental safety and management, tritium water treatment involves radioactivity control, leakage risk and radiation protection, which requires strict environmental and process control. Therefore, many heavy water separation methods, whether physical penetration, distillation or membrane filtration, are difficult to be directly used for tritium water without special design.

[0007] Based on the above-mentioned blank and defects of the prior art, the present application is proposed. SUMMARY

[0008] In order to solve the problems proposed in the background art, the present application provides a functionalized graphene for removing tritium from radioactive waste liquid, and also provides a preparation method thereof. Meanwhile, a functionalized graphene membrane is prepared by using the functionalized graphene, and the membrane is applied to the removal of tritium from radioactive waste liquid. The functionalized graphene membrane capable of effectively separating tritium and water is prepared by using a mixture of carboxylated graphene and sulfonated graphene through a series of precise chemical reactions and physical treatment steps. The preparation of the membrane material considers the particle size and interlayer spacing of the graphene sheet, thereby improving the removal rate of tritium in the radioactive waste liquid, and obtaining a functionalized graphene membrane with stable structure and good tritium removal performance (tritium removal rate of 25.2%~54.5%).

[0009] The present application adopts the following technical solutions: The first object of the present application is to provide a functionalized graphene for removing tritium from radioactive waste liquid, which is a sheet-shaped substance formed by stacking sheet structures, and the spacing between the stacked sheet structures is 7.5Å~8.7Å.

[0010] The present application utilizes the difference between the dynamics and diffusion rate of H2O molecules and HTO molecules in the membrane, and the adsorption and isotope exchange of tritium and functional groups in the graphene oxide membrane, to realize the separation of tritium in the tritium-containing liquid by functionalized graphene oxide. When the interlayer spacing is between 7.5 Å and 8.7 Å, the transmembrane rate of H2O molecules is higher than that of HTO, and part of the HTO molecules are intercepted on the graphene membrane in the form of adsorption and isotope exchange, so as to realize the effective separation of tritium in the tritium-containing liquid.

[0011] As a preferred scheme, the lateral size of the sheet structure ranges from 1 μm to 5 μm, and the thickness ranges from 1 nm to 2.5 nm; the particle size of the sheet formed by stacking the sheet structure ranges from 40 μm to 75 μm. And / or, the sheet structure is twisted and has wrinkles.

[0012] The functionalized graphene obtained by the present application is a sheet structure, and the particle size ranges from 40 μm to 75 μm. In this particle size range, the separation effect is better. When the particle size is too small, the water flux of the prepared membrane may be small, and the separation effect may decrease. When the particle size is too large, the water flux of the prepared membrane may be too large, and the separation effect may also decrease.

[0013] The surface of the sheet structure of the present application is twisted and has wrinkles. A multi-stage, asymmetric three-dimensional network structure is formed by the wrinkles, bending and interlacing. The gaps between the sheets constitute numerous meandering nanoscale channels. At the same time, these wrinkles and corrugated structures exist as a kind of “prestress”, which can effectively buffer the deformation under external pressure or water flow shear force, prevent the interlayer structure of the membrane from being compacted and collapsed, and thus maintain the long-term stability of the channel structure. The exchange sites at the edges of the functionalized graphene sheets are more exposed to the fluid due to the wrinkled structure, increasing the contact opportunity with water molecules. HTO will undergo adsorption and isotope exchange with the functional groups in the graphene oxide membrane. These mechanisms work together to promote the high-selectivity separation of tritium.

[0014] The second object of the present application is to provide a preparation method of the functionalized graphene for removing tritium from radioactive waste liquid according to any one of the above, comprising the following steps: Preparation of graphene oxide powder; Sulfonation of the graphene oxide powder to obtain sulfonated graphene aerogel; Carboxylation of the graphene oxide powder to obtain carboxylated graphene; Mixing, stirring, ultrasonic dispersion and vacuum freeze-drying of the sulfonated graphene aerogel and the carboxylated graphene to obtain functionalized graphene.

[0015] Due to the swelling problem and poor structural stability of existing graphene oxide membranes in practical applications, for the swelling problem, the interlayer continuously absorbs water under wet conditions, causing the interlayer distance to expand, resulting in a decrease in selectivity and unstable tritium retention performance. For the problem of poor structural stability, layer slip, group shedding and structure damage may occur in long-term soaking, repeated wet-dry cycles, chemical environments (such as acids, bases, oxidizing and reducing agents in radioactive waste liquid, radioactive decomposition products, etc.). The graphene membrane prepared by the functionalized graphene of the application not only maintains structural stability in tritium-containing liquid, but also does not have swelling problems, which may be due to the strong hydrogen bonding between sulfonated graphene and carboxylated graphene effectively preventing the swelling effect of water molecules.

[0016] Specifically: through sulfonation (-SO3H) and carboxylation (-COOH) functionalization, polar groups that can form hydrogen bonds are introduced, forming a multiple hydrogen bond network between the layers. This hydrogen bond network can partially replace the role of water molecules in the interlayer space under wet conditions, thereby limiting the excessive expansion / loosening of the interlayer distance and maintaining the stable structure of the interlayer ion or molecular channel.

[0017] Functionalization often affects the separation channel structure in two ways: a) The introduction of functional groups may "fill" or "modify" the cracks in the layers, making the pore distribution more uniform; b) During layer assembly, the presence of functional groups (especially charged groups such as carboxylic acid, sulfonic acid) can affect the electrostatic repulsion or attraction between layers, affect the way layers slip / overlap, and thus adjust the interlayer distance.

[0018] Interlayer distance: The hydrogen bonding or electrostatic interaction between functional groups can exert a "pulling force" or "stabilizing force" on the interlayer distance, causing the interlayer distance to expand less in the wet state, thereby maintaining a smaller and stable channel size. In this way, the size ratio of the channel to the material to be separated (tritium nuclides or tritium-carrying ion / water molecule complexes, etc.) is better controlled.

[0019] In the present application, the carboxyl group and the sulfonic acid group have a complementary effect: the carboxyl group can interact with water molecules through its strong polarity to regulate the channel structure of water molecules in the membrane, thereby effectively regulating the water flux; at the same time, the presence of the carboxyl group can also stabilize the interlayer spacing to avoid excessive swelling caused by the insertion of water molecules. The sulfonic acid group has strong ionization ability, and the modification of the sulfonic acid group can provide more favorable tritium adsorption sites and greater H-T isotope exchange tendency than other oxygen-containing groups, thereby significantly improving the separation efficiency. More importantly, the synergistic effect of the carboxyl group and the sulfonic acid group enhances the overall hydrophilicity of the membrane, making it easier for water molecules to transport on the membrane surface and in the channel, which is conducive to balancing high flux and high selectivity. In addition, this coupled structure can effectively resist swelling while maintaining the stability of the interlayer spacing, ensuring that the membrane maintains stable performance when in contact with tritium-containing wastewater for a long time, thereby achieving efficient and stable tritium separation.

[0020] As a preferred embodiment, the process for preparing the graphene oxide powder is as follows: Graphene oxide powder is prepared using graphite powder, concentrated sulfuric acid, phosphoric acid, and potassium permanganate as raw materials.

[0021] In the present application, loose graphene oxide powder is obtained by improved Hummers method, which plays an important role in subsequent obtaining functionalized graphene with a layer spacing of 7.5Å~8.7Å and a hole in the layer structure.

[0022] As a preferred embodiment, the particle size of the graphite powder is 3μm~6μm. If the particle size of the graphite powder used is too small, it may result in a small layer of functionalized graphene, and the water flux of the prepared membrane is small. If the particle size is too large, it may result in insufficient functionalization of the graphite powder.

[0023] As a preferred embodiment, the process for sulfonating the graphene oxide powder is as follows: The crude product is obtained by adding the p-aminobenzenesulfonic acid diazonium salt solution dropwise into the graphene oxide solution, and then dispersing the product after reacting with hydrazine and vacuum freeze-drying to obtain loose and porous sulfonated graphene aerogel. The graphene oxide solution is prepared from the obtained graphene oxide powder.

[0024] In the present application, p-aminobenzenesulfonic acid diazonium salt is selected because its diazonium group (-N2 + ) can covalently bond with the graphene skeleton, with high grafting stability and efficiency, which is a unique advantage that other ordinary amino sulfonates (such as amino sulfonic acid and taurine) do not have, and it is also safe and low in cost. For other aromatic diazonium sulfonates (such as 2-aminobenzenesulfonic acid diazonium salt): due to its molecular structure (such as ortho substitution), steric hindrance is generated, which reduces the reaction efficiency and grafting rate, so it is not the most preferred.

[0025] Meanwhile, the sulfonated graphene aerogel obtained in the application is easier to be uniformly dispersed when being re-dispersed, and the agglomeration problem that is prone to occur when wet or dispersed state is directly mixed can be avoided; meanwhile, the aerogel has a large specific surface area and a stable three-dimensional porous structure, and can effectively maintain the distribution state of the sulfonic acid group on the sheet layer, thereby improving the mixing uniformity of the carboxylated graphene oxide. Based on the above factors, the aerogel state is conducive to improving the controllability of the film preparation process and the stability of the film performance.

[0026] As a preferred scheme, the concentration of the p-aminobenzenesulfonic acid diazonium salt solution is 8 g / L to 80 g / L, and the dropping speed is 0.25 mL / s to 0.35 mL / s.

[0027] If the amount of the p-aminobenzenesulfonic acid diazonium salt solution is too small, the sulfonation will not be complete, and if the amount is too large, the purity of the functionalized graphene will be low.

[0028] As a preferred scheme, the process of carboxylation of the graphene oxide powder is as follows: Sodium hydroxide and monochloroacetic acid are added to the graphene oxide colloidal solution, and after ultrasonic filtration and vacuum freeze-drying, carboxylated graphene is obtained; The graphene oxide colloidal solution is prepared by ultrasonic dispersion of the obtained graphene oxide powder; The amount of sodium hydroxide is 0.5 to 160 times the mass of the graphene oxide powder, and the amount of monochloroacetic acid is 0.5 to 160 times the mass of the graphene oxide powder.

[0029] If the amount of sodium hydroxide and monochloroacetic acid is too small, the carboxylation will not be complete, and if the amount is too large, impurities will be produced.

[0030] As a preferred scheme, the mass ratio of the sulfonated graphene aerogel to the carboxylated graphene is 1:0.7 to 1:2.1; The sulfonated graphene aerogel and the carboxylated graphene are stirred with water and then ultrasonically dispersed to obtain a functionalized graphene solution, and the functionalized graphene solution is vacuum freeze-dried to obtain functionalized graphene.

[0031] The third object of the application is to provide a functionalized graphene film for removing tritium from radioactive waste liquid, which is prepared by the method of using any one of the above functionalized graphene to form a film by suction filtration.

[0032] As a preferred scheme, the graphene film of the application has a layered stacking structure of 400 nm to 750 nm, and the micro interlayer spacing of the graphene film is 7.5 Å to 8.7 Å.

[0033] The fourth object of the present application is to provide an application of the functionalized graphene membrane for removing tritium from radioactive waste liquid, which is used for removing tritium from radioactive waste liquid, and the concentration of radioactivity in the tritium-containing radioactive waste liquid is in the order of MBq / L.

[0034] Compared with the prior art, the present application has the following advantages and beneficial effects: 1. In the present application, the difference in kinetics and diffusion rate of H2O molecules and HTO molecules in the membrane, as well as the adsorption and isotope exchange of tritium and functional groups in graphene oxide membrane, are utilized to separate tritium in tritium-containing liquid by functionalized graphene oxide. When the interlayer spacing is between 7.5 Å and 8.7 Å, the transmembrane rate of H2O molecules is higher than that of HTO, and a part of HTO molecules are intercepted on the graphene membrane in the form of adsorption and isotope exchange, so as to achieve effective separation of tritium in tritium-containing liquid.

[0035] 2. In the present application, carboxyl and sulfonic acid groups are introduced as functional groups through molecular structure design, and the two have a complementary effect: the carboxyl group can regulate the channel structure of water molecules in the membrane through its strong polarity and interaction with water molecules, thereby effectively adjusting the water flux; the modification of the sulfonic acid group can provide more favorable tritium adsorption sites and greater H-T isotope exchange tendency, thereby significantly improving the separation efficiency. The synergistic effect of carboxyl and sulfonic acid groups enhances the overall hydrophilicity of the membrane, making water molecules more easily transported on the membrane surface and in the channel, which is conducive to balancing high flux and high selectivity.

[0036] 3. In the present application, the special membrane structure design of carboxyl and sulfonic acid coupling not only maintains the stability of the interlayer spacing, but also effectively resists swelling, ensuring that the membrane remains stable in performance when in contact with tritium-containing wastewater for a long time, thereby realizing efficient and stable tritium separation.

[0037] 4. The membrane method for removing tritium based on the functionalized graphene membrane of the present application has the advantages of mild reaction conditions (room temperature and normal pressure), low material preparation cost, low energy consumption in the treatment process, and easy scale-up production of membrane materials compared with traditional tritium removal methods. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0039] Figure 1 The appearance of the functionalized graphene obtained in the embodiments of the present application is shown in the figure. Figure 2The scanning electron microscope and transmission electron microscope photos of the functionalized graphene nanosheet obtained in the embodiment of the present application are as follows: Figure 2 (1) is a SEM photo, and (2) is a TEM photo; Figure 3 The AFM photo of the functionalized graphene sheet obtained in the embodiment of the present application is as follows: (a) is an AFM photo of the functionalized graphene sheet, and (b) is the thickness data of the functionalized graphene sheet; Figure 4 The surface SEM photo of the functionalized graphene film obtained in the embodiment of the present application is as follows: Figure 5 The element distribution map of the functionalized graphene film obtained in the embodiment of the present application is as follows: Figure 6 The cross-section SEM photo of the functionalized graphene film obtained in the embodiment of the present application is as follows: Figure 7 is a magnified view of Figure 6 ; Figure 8 The Fourier transform infrared spectrum of the functionalized graphene film obtained in the embodiment of the present application before and after separation of the tritium-containing stock solution is as follows. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be given to the present application in combination with embodiments, and the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0041] The range disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit limit the boundary of a particular range. The range limited in this way can include or not include the end value, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0042] If not particularly stated, all the embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0043] If not particularly stated, all the technical features and optional technical features of the present application can be combined to form new technical solutions.

[0044] If not particularly stated, the "including" and "containing" mentioned in the present application means open type, and can also be closed type. For example, the "including" and "containing" can mean that other substances not listed can also be included or contained, or only the listed substances can be included or contained.

[0045] If not otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method mentioned above can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0046] The present application utilizes transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize the micro-morphology of the obtained material; Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) are used to characterize the group and bonding properties of the material; energy dispersive X-ray spectroscopy (EDX) is used to analyze the element types in the material; and X-ray diffraction (XRD) is used to characterize the micro interlayer spacing of the functionalized graphene film. Each of the above characterization processes is a conventional means and will not be described in detail here. Embodiment

[0047] The functionalized graphene of the present application is prepared by the following steps: (I) Preparation of graphene oxide: The graphene oxide is prepared by improved Hummers method, which mainly includes the following 4 steps: (1) 1 g of high-purity graphite powder (flaky, purity 99.99%, 400 mesh, particle size 3 μm ~ 6 μm), 18 mL of concentrated sulfuric acid (H2SO4), 2 mL of phosphoric acid (H3PO4) are added to a three-necked flask, and 6 g of potassium permanganate is added in several times, and stirred in an ice water bath for 1 h; (2) The temperature is raised to 50 degrees Celsius, and the reaction is kept for 12 h; (3) The obtained product is poured into 1500 mL of ice water, 25 mL of hydrogen peroxide is added while stirring, until the solution color turns to golden yellow, then filtered, and the product is washed with distilled water and 5% hydrochloric acid until the pH value approaches 7; (4) The obtained graphene oxide is dispersed in water, ultrasonic for 8 h, and finally vacuum freeze-dried to obtain loose graphene oxide powder.

[0048] (II) Preparation of sulfonated graphene: The preparation method of sulfonated graphene mainly includes the following 3 steps: (1) Synthesis of p-aminobenzenesulfonic acid diazonium salt: In a 100 mL flask, 15 mL of sodium hydroxide solution (5% by mass fraction) and 1 g of p-aminobenzenesulfonic acid were added, and the p-aminobenzenesulfonic acid was fully dissolved under water bath heating. 5 g of sodium nitrite was added to the above solution at 55°C, and after it was fully dissolved, 10 mL of ice water and 1 mL of concentrated hydrochloric acid were added to the flask and stirred constantly. At this time, the temperature of the flask was controlled at 0°C and kept for 6 h, at which time a light pink p-aminobenzenesulfonic acid diazonium salt was formed.

[0049] (2) Synthesis of sulfonated graphene: A 8 g / L p-aminobenzenesulfonic acid diazonium salt solution was added dropwise to a flask containing 50 mL of graphene oxide solution (50 mg / mL by mass concentration, obtained by adding graphene oxide powder obtained above to water) at a rate of 0.35 mL / s, and the mixed solution was continuously stirred in an ice bath for 8 h. The product was centrifuged and washed several times to obtain a crude product of sulfonated graphene; (3) The above crude product was mixed with hydrazine and heated to 100°C and kept for 6 h to remove part of the groups. The sulfonated graphene obtained by the reaction was dispersed in methanol, ultrasonically dispersed for 1 h, and then vacuum freeze-dried to prepare a very loose and porous sulfonated graphene aerogel for subsequent use.

[0050] (Three) Preparation of carboxylated graphene: The preparation method of carboxylated graphene mainly includes the following three steps: (1) 100 mg of graphene oxide powder prepared was weighed and dispersed in 100 mL of deionized water to form a uniform yellow transparent colloidal solution by ultrasonic dispersion; (2) 15 g of sodium hydroxide and 3 g of monochloroacetic acid were added to the above solution and ultrasonically dispersed for 30 min to convert the hydroxyl and epoxy groups on the graphene oxide into carboxyl groups; (3) The solution was filtered while hot to remove impurity ions, and the excess water was evaporated, and vacuum freeze-drying was performed to obtain carboxylated graphene.

[0051] (Four) Preparation of functionalized graphene: 100 mg of carboxylated graphene and sulfonated graphene aerogel obtained above were weighed into a beaker, 100 mL of deionized water was added, and then stirred at room temperature for 3 h, followed by ultrasonic dispersion for 1 h to obtain a uniformly dispersed functionalized graphene solution. Finally, the solution was vacuum freeze-dried to prepare a very loose functionalized graphene powder. As shown in FIG. 1, the graphene powder obtained after vacuum freeze-drying is fluffy. Figure 1 Example

[0052] A functionalized graphene of the present application is prepared by the following steps: ​(I) Preparation of graphene oxide: Graphene oxide was prepared by a modified Hummers method, which mainly includes the following four steps: (1) 1 g of high-purity graphite powder (flaky, 99.99% pure, 400 mesh, particle size 3-6 μm), 18 mL of concentrated sulfuric acid (H2SO4), and 2 mL of phosphoric acid (H3PO4) were added to a three-necked flask, and 6 g of potassium permanganate was added in several portions, and stirred in an ice water bath for 1 h; (2) The temperature was raised to 50°C and the reaction was maintained for 12 h; (3) The resulting product was poured into 750 mL of ice water, 15 mL of hydrogen peroxide was added while stirring, until the solution color changed to golden yellow, then filtered, and the product was washed with distilled water and 5% hydrochloric acid until the pH value was close to 7; (4) The obtained graphene oxide was dispersed in water, ultrasonic for 8 h, and finally vacuum freeze-dried to obtain loose graphene oxide powder.

[0053] (II) Preparation of sulfonated graphene: The preparation method of sulfonated graphene mainly includes the following three steps: (1) Synthesis of p-aminobenzenesulfonic acid diazonium salt: In a 100 mL flask, 15 mL of sodium hydroxide solution (5% by mass fraction) and 1 g of p-aminobenzenesulfonic acid were added, and the p-aminobenzenesulfonic acid was fully dissolved under water bath heating conditions. 5 g of sodium nitrite was added to the above solution at 55°C, and after it was completely dissolved, 10 mL of ice water and 1 mL of concentrated hydrochloric acid were added to the flask and continuously stirred. At this time, the temperature of the flask was controlled at 0°C and maintained for 6 h, at which time a light pink p-aminobenzenesulfonic acid diazonium salt was formed.

[0054] (2) Synthesis of sulfonated graphene: The p-aminobenzenesulfonic acid diazonium salt solution with a concentration of 80 g / L was added dropwise to a flask containing 50 mL of graphene oxide solution (mass concentration of 50 mg / mL, the graphene oxide powder prepared by the above method was dissolved in ultrapure water to obtain), the dropwise adding speed was 0.25 mL / s, and the mixed solution was continuously stirred in an ice bath for 8 h. The product was centrifuged and washed several times to obtain the crude product of sulfonated graphene; (3) The above crude product was mixed with hydrazine and heated to 100°C and maintained for 6 h to remove part of the groups. The sulfonated graphene obtained by reaction was dispersed in methanol, ultrasonic dispersed for 1 h, and then vacuum freeze-dried to prepare very loose and porous sulfonated graphene aerogel for subsequent use.

[0055] (III) Preparation of carboxylated graphene: The preparation method of carboxylated graphene mainly includes the following three steps: (1) Weigh 100 mg of the prepared graphene oxide powder, disperse it in 100 mL of deionized water, and ultrasonically disperse it into a uniform yellow transparent colloidal solution. (2) Add 10g sodium hydroxide and 8.5g monochloroacetic acid to the above solution and sonicate for 30min to convert the hydroxyl and epoxy groups on the graphene oxide into carboxyl groups; (3) Filter the solution while it is hot to remove impurity ions, evaporate excess water, and freeze dry under vacuum to obtain carboxylated graphene.

[0056] (iv) Preparation of functionalized graphene: 100 mg of the carboxylated graphene and sulfonic acid graphene aerogel obtained above were weighed into beakers, and 100 mL of deionized water was added. The mixture was stirred at room temperature for 3 hours, followed by sonication for 1 hour to obtain a uniformly dispersed functionalized graphene solution. Finally, this solution was freeze-dried under vacuum to prepare an extremely loose functionalized graphene powder. The obtained graphene powder was fluffy.

[0057] The obtained functionalized graphene was subjected to SEM and TEM tests, and the results are as follows: Figure 2 As shown in the diagram, the obtained functionalized graphene has a sheet-like structure, consisting of nanosheets at the nanoscale. And as... Figure 3 (a) shows an AFM image of a functionalized graphene sheet, from Figure 3 As can be seen from (b), the thickness of the functionalized graphene oxide nanosheets is about 2.43 nm. Combined with the thickness data of the functionalized graphene film, the multilayer stacked structure of the graphene film is verified from the side. Example

[0058] This embodiment provides a method for preparing functionalized graphene membranes, which are prepared by negative pressure filtration.

[0059] This device mainly consists of a vacuum circulating water pump, a triangular receiving bottle, a sand core filter head, and a filter cup; depending on the size of the filter cup used, the diameter of the graphene membrane prepared in the experiment is 38 mm; the negative pressure during vacuum filtration is 0.65 MPa to 0.8 MPa.

[0060] The preparation method of graphene film mainly consists of the following three steps: (1) Connect the sand core filter head to the triangular receiving bottle and use a vacuum circulating water pump to create a negative pressure environment; (2) Place the base membrane flat in the center of the sand core filter head, and connect and fix the sand core filter head and the filter cup with the clamp; add an appropriate amount of deionized water to the filter cup to wet the base membrane, and check the sealing of the device; (3) After the base membrane is completely dry, quickly and evenly add a certain volume and concentration of graphene oxide-based solution into the filter cup; (4) After the solution is completely filtered, the rubber tube connected between the vacuum circulating water pump and the triangular receiving bottle is quickly pulled out, and the vacuum pump is closed. Finally, the triangular receiving bottle is separated from the other parts of the filtering device, and after completely naturally drying, the graphene oxide membrane fixed between the sand core filter head and the filter cup is obtained.

[0061] The whole preparation process is simple, easy to operate, and the device is a conventional filtering system in the laboratory.

[0062] The inventors carried out SEM characterization, element distribution characterization and cross-section SEM characterization on the obtained graphene membrane. The SEM characterization of the surface of the graphene membrane is shown in Figure 4 From Figure 4 , it can be observed that the membrane surface presents a morphology of stacked wrinkles, which is beneficial to maintaining the long-term stability of the channel structure and promoting the high selectivity and high flux separation of tritium.

[0063] The element distribution map of the graphene membrane is shown in Figure 5 , from Figure 5 , it can be seen that the signals of carbon, oxygen and sulfur elements are uniformly distributed on the surface of the graphene membrane, which shows that: 1) The uniform distribution of carbon and oxygen elements shows that the graphene membrane has good structural consistency and does not appear serious phase separation or composition segregation. 2) The uniform distribution of sulfur elements shows that the sulfonation reaction does not occur only in the local graphene-based material, but is successfully and uniformly grafted into the three-dimensional network structure of the carbon material, forming uniform and high-density sulfonic acid functional sites. 3) The distribution of the signals of the three elements is highly coincident, which shows that the sulfonic acid group and the graphene substrate form a composite material with uniform chemical properties and continuous functional site distribution. The highly dispersed sulfonic acid group selectively captures tritium through the isotope ion exchange mechanism, and the good hydrophilicity and low hydrogen bond network mass transfer resistance given by the uniform element distribution ensure that this capture process can be carried out efficiently, quickly and fully.

[0064] The morphology of the cross-section of the graphene membrane is shown in Figure 6 , it can be clearly known that the functionalized graphene membrane of the application is in a layered and stacked state. From the enlarged view of Figure 7 , it can be clearly seen that the multilayer structure is in a stacked state, and the spacing between the layers is 7.5 Å~8.7 Å.

[0065] Taking the functionalized graphene obtained in Example 2 as an example, functionalized graphene solutions with different volumes were prepared, and the solution concentration was 0.1 g / L, and the volume was 5.0 mL, 7.5 mL and 10.0 mL respectively. And the corresponding membranes were prepared, which were named as membranes MIX-1, MIX-2 and MIX-3 respectively. It was determined that the membrane layer spacing of membranes MIX-1, MIX-2 and MIX-3 was 7.60 Å, 8.91 Å and 8.70 Å respectively.

[0066] Using the three kinds of membranes, and adopting the following method, 10 mL of tritium-containing wastewater was subjected to three-stage separation filtration. The specific operation method of three-stage filtration is as follows: (1) The prepared graphene oxide membrane was retained in the middle of the sand core filter head and the filter cup, and after drying, it was connected with the washed and dried triangular receiving bottle. A vacuum circulating water pump was used to create a negative pressure environment, providing the necessary experimental conditions for the filtration process of tritium water.

[0067] (2) 10 mL of tritium-containing wastewater was slowly added to the filter cup, and it was ensured that the tritium water passed through the sand core filter head and was filtered into the triangular receiving bottle. This step ensured that the tritium water was separated by the functionalized graphene-based membrane.

[0068] (3) The tritium water in the triangular receiving bottle in (2) was collected and slowly added to the unused separation device obtained in (1) for the second stage of separation, and it was ensured that the tritium water passed through the sand core filter head and was filtered into the triangular receiving bottle. This step ensured that the tritium water was separated by the functionalized graphene-based membrane.

[0069] (4) The tritium water in the triangular receiving bottle in (3) was collected and slowly added to the unused separation device obtained in (1) for the third stage of separation, and it was ensured that the tritium water passed through the sand core filter head and was filtered into the triangular receiving bottle. This step ensured that the tritium water was separated by the functionalized graphene-based membrane.

[0070] (5) The tritium water in the triangular receiving bottle in (4) was collected and used for testing and recording the separation efficiency data of the three-stage membrane.

[0071] The data are shown in Table 1 below: Table 1

[0072] The results show that the tritium removal rate of the graphene membrane for three-stage filtration of tritium-containing wastewater can reach 53.07%. When the membrane layer spacing is greater than 8.7 Å, such as membrane MIX-2, the tritium removal rate is greatly reduced.

[0073] Figure 8 The Fourier transform infrared spectra of the functionalized graphene before and after separating the tritium-containing raw solution are given in Table 1. Curves 1-5 correspond to the materials: (1) graphene oxide powder in Example 2, (2) sulfonated graphene powder, (3) carboxylated graphene powder, (4) functionalized graphene powder, and functionalized graphene powder on the membrane after separating tritium water. As can be seen from the figure, each sample has a peak corresponding to the C=O stretching vibration of the carbonyl group in the graphene oxide structure at 1599-1626 cm -1 -1 ​The characteristic peak appeared at 1164 cm -1 The characteristic peak appeared at 1164 cm -1 The characteristic peak appeared at 1164 cm -1 , 1623 cm -1 and 1164 cm -1 , which respectively represented the -SO3H structure, the C=O bond stretching vibration and the S-O bond stretching vibration. This indicated that after the functionalized graphene membrane separated the tritium-containing sample, the functional groups did not change greatly, and the main composition of the membrane remained stable. It was expected that the functionalized graphene membrane had the potential for reuse. However, the characteristic peak corresponding to the C-T bond or the O-T bond was not observed by Fourier transform infrared spectroscopy, which might be caused by the low concentration of the tritium-containing sample.

[0074] In the present application, carboxyl and sulfonic acid groups were introduced into graphene oxide as functional groups by molecular structure design, and the micro interlayer spacing of graphene sheets was considered. The functionalized graphene membrane which can effectively separate tritium and water was obtained. The functionalized graphene structure is stable, has good tritium removal performance, low energy consumption in the treatment process, and the membrane material is easy to scale up, which fills the technical blank of using functionalized graphene to effectively separate tritium in radioactive wastewater.

[0075] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A functionalized graphene for deuterium removal from radioactive liquid waste, characterized in that, The functionalized graphene is a flaky substance formed by stacking of sheet layer structures, and the spacing between the stacked flaky structures is 7.5 Å~8.7 Å.

2. The functionalized graphene for deuterium removal from radioactive waste liquid according to claim 1, characterized in that, The lateral dimension of the sheet layer structure ranges from 1 μm to 5 μm, and the thickness is 1 nm~2.5 nm; The particle size of the flaky substance formed by stacking of sheet layer structures is 40 μm~75 μm; And / or, the flaky structure is twisted and has wrinkles.

3. A method for preparing functionalized graphene for detritonation of radioactive waste liquid according to any one of claims 1 to 2, characterized in that, The method comprises the following steps: Preparation of graphene oxide powder; Sulfonated graphene aerogel is obtained by sulfonating the graphene oxide powder; Carboxylated graphene is obtained by carboxylating the graphene oxide powder; The functionalized graphene is obtained by mixing, stirring, ultrasonic dispersion and vacuum freeze-drying of the sulfonated graphene aerogel and the carboxylated graphene.

4. The method for preparing functionalized graphene for detritonation of radioactive waste liquid according to claim 3, characterized in that, The process for preparing the graphene oxide powder is as follows: Graphene oxide powder is prepared by using graphite powder, concentrated sulfuric acid, phosphoric acid and potassium permanganate as raw materials.

5. The method for preparing functionalized graphene for detritium removal from radioactive waste liquid according to claim 4, characterized in that, The particle size of the graphite powder is 3 μm~6 μm.

6. The method for preparing functionalized graphene for detritium removal from radioactive waste liquid according to claim 3, characterized in that, The process for sulfonating the graphene oxide powder is as follows: The sulfonated graphene aerogel is obtained by adding the p-aminobenzenesulfonic acid diazonium salt solution dropwise into the graphene oxide solution to obtain a crude product, and then dispersing and vacuum freeze-drying the product after reacting the crude product with hydrazine; The graphene oxide solution is prepared from the obtained graphene oxide powder.

7. The method for preparing functionalized graphene for detritium removal from radioactive waste liquid according to claim 6, characterized in that, The concentration of the p-aminobenzenesulfonic acid diazonium salt solution is 8 g / L~80 g / L, and the dropping speed is 0.25 mL / s~0.35 mL / s.

8. The method for preparing functionalized graphene for detritium removal from radioactive waste liquid according to claim 3, characterized in that, The process for carboxylating the graphene oxide powder is as follows: Carboxylated graphene is obtained by adding sodium hydroxide and monochloroacetic acid into the graphene oxide colloidal solution, ultrasonic filtration and vacuum freeze-drying; The graphene oxide colloidal solution is prepared by ultrasonic dispersion of the obtained graphene oxide powder; The amount of sodium hydroxide is 0.5~160 times the mass of the graphene oxide powder, and the amount of monochloroacetic acid is 0.5~160 times the mass of the graphene oxide powder.

9. The method for preparing functionalized graphene for detritium removal from radioactive waste liquid according to claim 3, characterized in that, The mass ratio of the sulfonated graphene aerogel to the carboxylated graphene is 1:0.7~1:2.1; The functionalized graphene solution is obtained by stirring the sulfonated graphene aerogel and the carboxylated graphene in water and then ultrasonic dispersion.

10. A functionalized graphene membrane for deuterium removal from radioactive liquid waste, characterized in that, The functionalized graphene is prepared by the method of membrane formation by suction filtration.

11. The functionalized graphene membrane for deuterium removal from radioactive waste liquid according to claim 10, characterized in that, The graphene membrane is a layered stack structure with a thickness of 400 nm~750 nm, and the micro interlayer spacing of the graphene membrane is 7.5 Å~8.7 Å.

12. Use of a functionalized graphene film according to any one of claims 10-11, characterized in that, The functionalized graphene is used for removing tritium from radioactive waste liquid, and the concentration of the radioactivity in the tritium-containing radioactive waste liquid is in the order of MBq / L.

Images