A method for preparing material for selective adsorption of iodine-131 nuclide

Abstract

The present invention provides a method for preparing a material for selective adsorption of iodine-131 nuclide, belonging to the technical field of purification and treatment of radioactive wastewater in nuclear medicine. The steps include: synthesizing graphene oxide in a membrane-uniform microreactor using graphite powder, concentrated sulfuric acid, phosphoric acid, potassium permanganate, and hydrogen peroxide as raw materials; synthesizing nanoporous graphene in a membrane-uniform microreactor using a graphene suspension and Zn(NO3)·6H2O as raw materials; and sequentially filtering the solution of graphene oxide, the solution of nanoporous graphene, and the solution of graphene oxide through a substrate membrane to obtain a graphene oxide / nanoporous graphene / graphene oxide two-dimensional separation membrane. The method for preparing a material for selective adsorption of iodine-131 nuclide provided by the present invention yields a material for selective adsorption of iodine-131 nuclide with good selectivity, high adsorption capacity, and strong stability.

Description

Technical Field

[0001] The present invention relates to the technical field of purification treatment of radioactive wastewater in nuclear medicine, and particularly relates to a method for preparing a material for selectively adsorbing iodine-131 nuclide. Background Art

[0002] Since the discovery of radioactivity by humans 108 years ago, nuclear scientists and medical scientists have tried to apply radionuclides to medicine shortly after that. However, the real combination of nuclear technology and medicine occurred in the late 1950s. In China, radionuclides began to be used for diagnosing and treating diseases in 1958. After a long period of research and development, the nuclear medicine department has emerged and developed rapidly. In recent years, with the rapid development of medical science and technology in China, the application of radioactive isotopes in nuclear medicine has received great attention and development. The unique advantages in its diagnosis and treatment have made nuclear medicine increasingly become an important branch discipline of modern medicine. Medical radioactive elements (mostly short-lived nuclides) are mainly applied to: equipment and instruments for diagnosing diseases, such as 68 Ge for the calibration of computerized tomography (PET-CT) devices, etc.; drugs for diagnosing diseases, such as ECT imaging drugs 99m Tc, radioactive isotopes used in PET / CT diagnosis 18 F, etc.; drugs for treating diseases, such as 131 I for treating hyperthyroidism, 125 I seeds for treating tumor diseases, etc.

[0003] With the rapid development of nuclear energy technology, nuclear safety issues have attracted increasing attention. The sewage wastewater in hospitals has complex components. If it is directly discharged into natural water bodies without treatment, it will cause very serious pollution to the soil and surrounding waters, and become an important way for the spread of diseases, greatly endangering people's daily lives. Hospital sewage mainly comes from the drainage of different departments such as operating rooms, X-ray film developing, wards, isotope therapy diagnosis, laboratories, and consulting rooms. According to the different components and water volumes of the sewage discharged from each department, it is mainly divided into heavy metal wastewater, oily wastewater, film developing wastewater, radioactive wastewater, etc. Among them, the radioactive sewage (wastewater) generated during the nuclear medicine practice mainly comes from the excreta (including vomit) of patients and examinees, the residual liquid of radionuclide agents, induced radioactive cooling water, the vessels for storing radionuclide agents, and the washing drainage of the staff in the nuclear medicine department. If radioactive sewage is discharged or treated improperly, it will cause environmental pollution and endanger public safety and health. Among them, unstable radioactive nuclides spontaneously emit α, β, and γ rays through their own decay. These rays have specific energies and have different penetration and ionization abilities for tissues such as cells, skin, bones, and internal organs in the human body, thus inducing different degrees of physical, chemical, or biochemical changes in the human body. When exposed to a relatively large radiation dose, it will act on the human body, directly destroying the molecular structure of substances in the human body, breaking the protein molecular bonds and ribonucleic acid bonds, and causing the enzymes of great significance to the human body to lose their corresponding biological activities and unable to work properly, resulting in a series of major diseases such as hair loss, skin erythema, reduction of white blood cells or platelets, cataracts, and liver and kidney failure. Under a large dose of irradiation, it can cause direct death to people.

[0004] The treatment technologies for radioactive sewage (wastewater) mainly include: natural decay method, chemical precipitation method, ion exchange method, adsorption method, evaporation concentration, membrane separation technology, biological treatment method, magnetic-molecular method, inert solidification method, etc. According to the usage characteristics of medical radioactive nuclides (mainly 131 I, 99m Tc, etc.), the half-life of the nuclides is short, the types of nuclides are not many, and the total activity of the nuclides is small. Therefore, the methods for treating radioactive medical wastewater generally adopt the decay method, dilution method, and adsorption ion exchange. Among them, for the natural decay method and dilution method, according to the long or short half-life of radioactive sewage, the radioactive sewage with a longer half-life is stored in a container, and the radioactive sewage with a shorter half-life is discharged into a decay pool for treatment. If the radioactive sewage still does not meet the standards after being treated in the decay pool, the dilution method can be adopted - mixing it with other medical sewage in the hospital area to further reduce the concentration.

[0005] Traditional sewage treatment methods such as chemical precipitation, ion exchange, and evaporation have their own advantages and disadvantages, and can all treat radioactive wastewater to a certain extent. Usually, methods such as chemical precipitation and ion exchange / adsorption can be used as effective pretreatment means in the treatment of radioactive wastewater. As a relatively new sewage treatment method, membrane separation technology has a wide application range, simple operation, low energy consumption, and good effluent quality, and is an efficient separation means. In modern sewage treatment technologies, membrane separation technology is often combined with traditional processes to obtain a higher decontamination factor (DF) and concentration factor (CF). The biological method has low cost, high concentration factor, and no secondary pollution, but it also has great limitations. It is necessary to find organisms suitable for different radionuclides and also consider their living environment, so its practicality is relatively low. Through comprehensive analysis, each method has certain limitations, and combined processes can be used to make up for them. The currently widely used combined process is the combination of membrane separation and adsorption method or chemical precipitation method.

[0006] Currently, the relatively mature treatment method for iodine-131 nuclide in radioactive waste liquid is to use materials such as activated carbon for adsorption. Although there are some iodine-131 adsorption materials on the market, they usually have problems such as poor selectivity, low adsorption capacity, and insufficient stability. For example, traditional adsorption materials may have weak adsorption ability for iodine-131 and are easily interfered by other ions, resulting in poor effects in practical applications. In addition, some adsorption materials are prone to losing their adsorption performance in a radiation environment, limiting their application at the nuclear accident site.

[0007] Therefore, there is an urgent need for a method for preparing a material with good selectivity, high adsorption capacity, and strong stability for the selective adsorption of iodine-131 nuclide. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing a material with good selectivity, high adsorption capacity, and strong stability for the selective adsorption of iodine-131 nuclide.

[0009] To solve the above technical problem, the present invention provides a method for preparing a material for the selective adsorption of iodine-131 nuclide, comprising the following steps:

[0010] Using graphite powder, concentrated sulfuric acid, phosphoric acid, potassium permanganate, and hydrogen peroxide as raw materials to synthesize graphene oxide in a membrane-uniform microreactor;

[0011] Using graphene suspension and Zn(NO 3 )·6H 2 O as raw materials to synthesize nanoporous graphene in a membrane-uniform microreactor;

[0012] The solution of graphene oxide, the solution of nanoporous graphene, and the solution of graphene oxide are sequentially filtered through a substrate membrane to obtain a graphene oxide / nanoporous graphene / graphene oxide two-dimensional separation membrane.

[0013] Furthermore, the membrane-distributed microreactor includes a tubular membrane and a reaction vessel. The tubular membrane is disposed in the middle of the reaction vessel, and a magnetic stirring rotor is provided at the bottom of the reaction vessel;

[0014] The tubular membrane is coiled into a spiral shape with 3 - 6 turns, and the diameter is 4 - 6 mm. The diameter of the dispersion holes on the tubular membrane is 0.1 - 0.5 μm;

[0015] The rotational speed of the magnetic stirring rotor at the bottom of the reaction vessel is 50 - 200 rpm.

[0016] Furthermore, when the membrane-distributed microreactor is used, it includes the following steps:

[0017] Place the continuous phase in the reaction vessel and stir it with a magnetic stirring rotor,

[0018] Block one end of the tubular membrane, and inject the dispersed phase into the other end of the tubular membrane at a flow rate of 0.1 - 1 mL / min through a metering pump;

[0019] The dispersed phase in the form of droplets oozes out from the dispersion holes of the tubular membrane and contacts and reacts with the continuous phase.

[0020] Furthermore, the synthesis of graphene oxide includes the following steps:

[0021] Add 0.5 - 2 g of graphite powder and 10 - 20 ml of concentrated sulfuric acid to the membrane-distributed microreactor and stir and mix them with a magnetic stirring rotor to obtain a mixture;

[0022] Add the mixed solution formed by mixing 0.5 - 2.5 mL of phosphoric acid and 3 - 10 g of potassium permanganate to the mixture in multiple portions, and stir at 0 - 10 °C for 0.5 - 2 h to obtain a pre-reaction solution;

[0023] Heat the pre-reaction solution to 40 - 90 °C and continuously stir and react for 10 - 15 h to obtain a post-reaction solution;

[0024] Cool the post-reaction solution to room temperature and pour it into ice water. Add 0.5 - 5 mL of hydrogen peroxide to continue the reaction while stirring through the spiral tubular membrane of the membrane-distributed microreactor;

[0025] After the solution reaction turns golden yellow, filter to obtain a reaction product;

[0026] Wash the reaction product with distilled water and 2 - 10 vol% hydrochloric acid respectively until the pH is 6 - 8;

[0027] The washed product is dispersed in water and sonicated for 5 - 10 h, followed by vacuum freeze - drying to obtain graphene oxide powder.

[0028] Further, the graphite powder is flaky graphite powder with a particle size of 100 - 1000 mesh, and the phosphoric acid is AR - grade phosphoric acid.

[0029] Further, the membrane - distributed micro - reactor used for synthesizing graphene oxide is a spiral formed by winding a tubular membrane 4 turns, with a diameter of 5 mm, a dispersed pore diameter of 0.1 - 0.5 μm, an external magnetic stirring speed of 100 - 200 rpm, and the flow rate of the phosphoric acid into the tubular membrane is 0.1 - 1 mL / min.

[0030] Further, the synthesis of the nanoporous graphene includes the following steps:

[0031] The synthesized graphene oxide is added with water to prepare a graphene suspension with a concentration of 0.5 - 5 g / L.

[0032] The 0.5 - 5 g / L graphene suspension and 400 - 800 g / L Zn(NO3)·6H 2 O are mixed and reacted in a membrane - distributed micro - reactor at a volume ratio of 1:1 - 1:3 to obtain a mixed turbid liquid.

[0033] The mixed turbid liquid is vacuum - filtered to obtain a filter cake.

[0034] The filter cake and the filter paper are dried at 50 - 70 °C and then burned, and the combustion residue is washed with HCl and deionized water to obtain nanoporous graphene.

[0035] Further, the membrane - distributed micro - reactor used for synthesizing nanoporous graphene is a spiral formed by winding a tubular membrane 6 turns, with a diameter of 4 mm, a dispersed pore diameter of 0.1 - 0.5 μm, an external magnetic stirring speed of 100 - 200 rpm, and the flow rates of the graphene suspension and Zn(NO3)·6H 2 O into the tubular membrane are 0.2 - 0.5 mL / min.

[0036] Further, the synthesis of the graphene oxide / nanoporous graphene / graphene oxide two - dimensional separation membrane includes the following steps:

[0037] The prepared nanoporous graphene and graphene oxide are respectively formulated into a nanoporous graphene turbid liquid with a concentration of 1 - 5 g / L and a graphene oxide turbid liquid with a concentration of 0.1 - 0.8 g / L.

[0038] Using a polyethersulfone ultrafiltration membrane as the substrate membrane, 1 - 5 mL of graphene oxide, 1 - 5 mL of nanoporous graphene turbid liquid, and 1 - 5 mL of graphene oxide turbid liquid are sequentially filtered through the substrate membrane by negative pressure filtration to obtain a loaded substrate membrane.

[0039] The loaded substrate membrane is vacuum-dried to obtain a two-dimensional separation membrane of graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane.

[0040] Further, the vacuum drying of the loaded substrate membrane is to place the loaded substrate membrane in a vacuum drying oven and dry it at room temperature for 20 - 30 h.

[0041] A method for preparing a material for selective adsorption of iodine-131 nuclide provided by the present invention adopts a membrane-distributed microreactor during the preparation process, and controls the internal structure and specific surface area of the prepared adsorption material by regulating relevant parameters such as the diameter of the membrane channels, the size of the distributed small holes in the membrane channels, the number of winding turns and the diameter of the membrane channels of the membrane-distributed microreactor, which can greatly reduce the magnification effect and non-uniformity during the preparation process, make the internal particles and the size and morphology distribution of the pores of the prepared adsorption material more uniform, the average size of the internal particles and pores of the prepared adsorption material can be reduced by 20 - 30%, increase the specific surface area of the material, greatly increase the active adsorption sites, thereby greatly improving the adsorption effect of the adsorption material. Compared with the traditional adsorption material, the selective adsorption ability of the adsorption material prepared by the present invention for iodine-131 nuclide is increased by 10 - 40%, and the purification coefficient is increased to 40 - 50, which is 4 - 5 times higher than that of the traditional adsorption material.

[0042] Therefore, a method for preparing a material for selective adsorption of iodine-131 nuclide provided by the present invention, the prepared adsorption material is used to treat iodine-131 nuclide in radioactive sewage (waste) water, has higher selectivity and stronger adsorption ability, makes the treated radioactive sewage (waste) water safer and more environmentally friendly, and truly achieves the principle of "radioactive waste minimization". Description of the Drawings

[0043] Figure 1 It is a flow chart of the method for preparing a material for selective adsorption of iodine-131 nuclide provided by an embodiment of the present invention;

[0044] Figure 2 It is a schematic structural diagram of a membrane-distributed microreactor in the method for preparing a material for selective adsorption of iodine-131 nuclide provided by an embodiment of the present invention.

[0045] Description of the Reference Numerals:

[0046] 1 - tubular membrane, 2 - reaction vessel, 3 - magnetic stirring rotor. Detailed Embodiments

[0047] See Figure 1 , a method for preparing a material for selective adsorption of iodine-131 nuclide provided by an embodiment of the present invention includes the following steps:

[0048] Step 1) Graphene oxide is synthesized in a membrane-uniform microreactor using graphite powder, concentrated sulfuric acid, phosphoric acid, potassium permanganate, and hydrogen peroxide as raw materials.

[0049] Among them, referring to Figure 2 , the membrane-uniform microreactor includes a tubular membrane 1 and a reaction vessel 2. The tubular membrane 1 is arranged in the middle of the reaction vessel 2, and a magnetic stirring rotor 3 is arranged at the bottom of the reaction vessel 2. Among them, the tubular membrane 1 is coiled into a spiral shape of 3-6 turns, with a diameter of 4-6 mm, and uniformly dispersed with dispersion holes with a diameter of 0.1-0.5 μm on the tubular membrane 1. The rotational speed of the magnetic stirring rotor 3 at the bottom of the reaction vessel 2 is 50-200 rpm.

[0050] When using the membrane-uniform microreactor, the continuous phase is placed in the reaction vessel 2 and stirred with the magnetic stirring rotor 3. Then, one end of the tubular membrane 1 is blocked, and the dispersed phase is injected into the other end of the tubular membrane 1 at a flow rate of 0.1-1 mL / min through a metering pump. Then, the dispersed phase entering the tubular membrane 1 will ooze out from each dispersion hole of the tubular membrane 1 in the form of liquid droplets to contact the continuous phase, and the oozed dispersed phase is fully mixed with the continuous phase under the stirring action of the magnetic stirring rotor 3 to react.

[0051] Among them, the synthesis of graphene oxide is prepared based on the improved Hummers method, and specifically includes the following steps:

[0052] 1. 0.5-2 g of graphite powder and 10-20 ml of concentrated sulfuric acid are added in advance as the continuous phase to the reaction vessel 2 of the membrane-uniform microreactor. The magnetic stirring rotor 3 at the bottom of the reaction vessel 2 is started, and the mixture of graphite powder and concentrated sulfuric acid is stirred at a rotational speed of 100-200 rpm.

[0053] 2. One end of the tubular membrane 1 is blocked, and a mixed solution of 0.5-2.5 mL of phosphoric acid and 3-10 g of potassium permanganate is injected into the tubular membrane 1 in multiple times at a flow rate of 0.1-1 mL / min from the other end of the tubular membrane 1 through a metering pump.

[0054] As a specific embodiment of the present invention, 0.5-2.5 mL of phosphoric acid and 3-10 g of potassium permanganate are mixed and added to the tubular membrane 1 in 2-5 times, so that the graphite powder can be oxidized to graphene oxide by potassium permanganate in an acidic environment.

[0055] 3. The mixed solution of phosphoric acid and potassium permanganate oozes out from each dispersion hole of the tubular membrane 1 and enters the mixture of graphite powder and concentrated sulfuric acid in the form of liquid droplets, and is stirred at a temperature of 0-10 °C for 0.5-2 h, so that sulfuric acid and potassium permanganate are inserted between the graphite layers and pre-oxidized, thus obtaining a pre-reaction solution.

[0056] By carrying out the reaction in a membrane-uniform microreactor, high-viscosity phosphoric acid can stably and in small amounts react with reactants through a spiral membrane pipeline to improve the Hummers reaction, enhance the mixing effect, and make the particle distribution on the material surface finer and more uniform.

[0057] 4. Continue to heat the pre-reaction solution to raise the temperature to 40 - 90 °C, and continuously stir and react for 10 - 15 h to dissociate and remove the sulfur-containing groups generated during the oxidation process, obtaining the post-reaction solution.

[0058] 5. After cooling the post-reaction solution to room temperature, pour it into ice water, and add 0.5 - 5 mL of hydrogen peroxide through the tubular membrane 1 of the membrane-uniform microreactor under stirring to continue the reaction and remove the excess potassium permanganate in the post-reaction solution.

[0059] 6. After the solution reaction turns golden yellow, filter to obtain the reaction product.

[0060] 7. Wash the reaction product with distilled water and 2 - 10 vol% hydrochloric acid respectively until the pH is 6 - 8.

[0061] 8. Disperse the washed product in water and ultrasonicate for 5 - 10 h, and then vacuum freeze-dry it to avoid the decomposition and reduction of graphene oxide at high temperatures while maintaining its own fluffy structure, thereby obtaining graphene oxide powder.

[0062] Among them, the graphite powder is flaky graphite powder with a particle size of 100 - 1000 mesh, and the phosphoric acid is AR pure phosphoric acid.

[0063] As a specific embodiment of the present invention, the membrane-uniform microreactor used for synthesizing graphene oxide is a spiral shape formed by winding the tubular membrane 1 for 4 turns, with a diameter of 5 mm. The diameter of the dispersion holes on the tubular membrane 1 is 0.1 - 0.5 μm, and the external magnetic stirring speed is 100 - 200 rpm. And the flow rate of phosphoric acid introduced into the tubular membrane 1 is 0.1 - 1 mL / min.

[0064] Step 2) Use the graphene suspension and Zn(NO 3 )·6H 2 O solution as raw materials to synthesize nanoporous graphene in a membrane-uniform microreactor.

[0065] Among them, the synthesis of nanoporous graphene includes the following steps:

[0066] 1. Add the synthesized graphene oxide and water as the continuous phase into the reaction vessel 2 of the membrane-uniform microreactor in advance, start the magnetic stirring rotor 3 at the bottom of the reaction vessel 2, and stir the mixture of the synthesized graphene oxide and water at a speed of 100 - 200 rpm to prepare a graphene suspension with a concentration of 0.5 - 5 g / L.

[0067] 2. Block one end of the tubular membrane 1, and use a metering pump to inject a 400 - 800 g / L Zn(NO₃)·6H₂O solution, whose volume ratio to the 0.5 - 5 g / L graphene suspension is 1:1 - 1:3, into the tubular membrane 1 from the other end at a flow rate of 0.2 - 0.5 mL / min. The Zn(NO₃)·6H₂O solution seeps out from each dispersion pore of the tubular membrane 1 and enters the graphene suspension in the form of droplets. Under the continuous stirring of the magnetic stirring rotor 3, the two are mixed and reacted for 0.5 - 3 h to obtain a mixed turbid liquid. 2 O solution as the dispersed phase is injected into the tubular membrane 1 from the other end of the tubular membrane 1 at a flow rate of 0.2 - 0.5 mL / min. The Zn(NO₃)·6H₂O solution seeps out from each dispersion pore of the tubular membrane 1 and enters the graphene suspension in the form of droplets. Under the continuous stirring of the magnetic stirring rotor 3, the two are mixed and reacted for 0.5 - 3 h to obtain a mixed turbid liquid. 2 O solution seeps out from each dispersion pore of the tubular membrane 1 and enters the graphene suspension in the form of droplets. Under the continuous stirring of the magnetic stirring rotor 3, the two are mixed and reacted for 0.5 - 3 h to obtain a mixed turbid liquid.

[0068] 3. Vacuum filter the mixed turbid liquid to obtain a filter cake, and insert Zn(NO₃)·6H₂O between the graphene layers. 2 O is inserted between the graphene layers.

[0069] 4. Place the filter cake and filter paper together in an oven at 50 - 70 °C for 2 h to remove the residual moisture in the filter cake. Then ignite the dried filter cake with an alcohol lamp. After a 5 - 10 s intense combustion process, the combustion consumes and removes the oxygen-containing groups on the graphene surface. Finally, wash with HCl and deionized water to remove the combustion residues on the graphene surface, and then nanoporous graphene can be obtained.

[0070] Among them, the membrane-distributed microreactor used in synthesizing nanoporous graphene is a spiral shape formed by winding the tubular membrane 6 times, with a diameter of 4 mm, a dispersion pore diameter of 0.1 - 0.5 μm, an external magnetic stirring speed of 100 - 200 rpm, and the flow rate of the graphene suspension and Zn(NO₃)·6H₂O into the tubular membrane is 0.2 - 0.5 mL / min. 2 O is introduced into the tubular membrane at a flow rate of 0.2 - 0.5 mL / min.

[0071] Step 3) Filter the graphene oxide solution, the nanoporous graphene solution, and the graphene oxide solution in sequence on the substrate membrane to obtain a graphene oxide / nanoporous graphene / graphene oxide two-dimensional separation membrane. Specifically, it includes the following steps:

[0072] 1. Prepare the obtained nanoporous graphene and graphene oxide into a 1 - 5 g / L nanoporous graphene turbid liquid and a 0.1 - 0.8 g / L graphene oxide turbid liquid respectively by adding water.

[0073] 2. Using a polyethersulfone ultrafiltration membrane as the substrate membrane, first filter 1 - 5 mL of the graphene oxide turbid liquid through the substrate membrane by negative pressure filtration, then filter 1 - 5 mL of the nanoporous graphene turbid liquid on the substrate membrane in the same way, and then filter 1 - 5 mL of the graphene oxide turbid liquid on the substrate membrane to obtain a loaded substrate membrane.

[0074] 3. Place the supported substrate membrane in a vacuum drying oven and dry it at room temperature for 20 - 30 h to obtain a two-dimensional separation membrane of graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane.

[0075] The present invention provides a method for preparing a material for selective adsorption of iodine-131 nuclide. During the preparation process, a membrane-distributed microreactor is adopted, and by adjusting relevant parameters such as the diameter of the membrane pipeline, the size of the distributed small holes in the membrane pipeline, the number of winding turns and the diameter of the membrane pipeline of the membrane-distributed microreactor, the internal structure and specific surface area of the prepared adsorption material can be controlled, which can greatly reduce the amplification effect and non-uniformity during the preparation process, make the internal particles and the size and morphology distribution of the pores of the prepared adsorption material more uniform, the average size of the internal particles and pores of the prepared adsorption material can be reduced by 20 - 30%, increase the specific surface area of the material, and greatly increase the active adsorption sites, thereby greatly improving the adsorption effect of the adsorption material. Compared with traditional adsorption materials, the selective adsorption ability of the adsorption material prepared by the present invention for iodine-131 nuclide is increased by 10 - 40%, and the purification coefficient is increased to 40 - 50, which is 4 - 5 times higher than that of traditional adsorption materials. In this way, using the prepared adsorption material to treat iodine-131 nuclide in radioactive sewage (waste) water has higher selectivity and stronger adsorption ability, making the treated radioactive sewage (waste) water safer and more environmentally friendly, and truly achieving the principle of "radioactive waste minimization".

[0076] The following specifically illustrates a method for preparing a material for selective adsorption of iodine-131 nuclide provided by the present invention through examples.

[0077] Example 1

[0078] S1: Add 0.5 g of flaky graphite powder with a particle size of 100 mesh and 10 ml of AR pure concentrated sulfuric acid as the continuous phase in advance to the reaction vessel 2 of a membrane-distributed microreactor with a tubular membrane 1 wound in a spiral shape for 4 turns, a diameter of 5 mm, and a dispersion hole diameter of 0.1 μm. Start the magnetic stirring rotor 3 at the bottom of the reaction vessel 2 and stir the mixture of graphite powder and concentrated sulfuric acid at a speed of 100 rpm.

[0079] S2: Block one end of the tubular membrane 1, and inject a mixture of 0.5 mL of phosphoric acid and 3 g of potassium permanganate as the dispersed phase into the tubular membrane 1 from the other end of the tubular membrane 1 in 2 times at a flow rate of 0.1 mL / min through a metering pump. The mixture of phosphoric acid and potassium permanganate oozes out from each dispersion hole of the tubular membrane 1 and enters the mixture of graphite powder and concentrated sulfuric acid in the form of liquid droplets. Through the feeding and reaction of the membrane-distributed microreactor, the highly viscous phosphoric acid can stably and microscopically react with the reactants through the spiral membrane pipeline to carry out the improved Hummers reaction, which can strengthen the mixing effect and make the surface particle distribution of the prepared material finer and more uniform.

[0080] The reactants are first stirred and reacted at a temperature of 0 °C for 0.5 h to insert sulfuric acid and potassium permanganate between the graphite layers and carry out pre-oxidation to obtain a pre-reaction solution.

[0081] S3: The pre-reaction solution is continuously heated to raise the temperature to 40 °C, and the reaction is continuously stirred for 10 h to dissociate and remove the sulfur-containing groups generated during the oxidation process to obtain a post-reaction solution.

[0082] S4: The post-reaction solution is cooled to room temperature and then poured into ice water. Under stirring, 0.5 mL of hydrogen peroxide is added through the tubular membrane 1 of the membrane-distributed microreactor to continue the reaction to remove the excess potassium permanganate in the post-reaction solution until the post-reaction solution turns golden yellow, and then it is filtered to obtain a reaction product.

[0083] S5: The reaction product is washed with distilled water and 2 vol% hydrochloric acid respectively until the pH is 6, and then the washed product is dispersed in water and ultrasonically treated for 5 h. Finally, the ultrasonically treated product is vacuum freeze-dried to avoid the decomposition and reduction of graphene oxide at high temperatures while maintaining its own fluffy structure, thereby obtaining graphene oxide powder.

[0084] S6: The graphene oxide synthesized in S5 and water are added in advance as a continuous phase to the reaction vessel 2 of the membrane-distributed microreactor with its tubular membrane 1 wound into a 6-turn helix, a diameter of 4 mm, and a dispersed pore diameter of 0.1 μm. The magnetic stirring rotor 3 at the bottom of the reaction vessel 2 is started, and the mixture of the synthesized graphene oxide and water is stirred at a speed of 100 rpm to prepare a graphene suspension with a concentration of 0.5 g / L.

[0085] S7: One end of the tubular membrane 1 is blocked, and a 400 g / L Zn(NO3)·6H 2 O solution with a volume ratio of 1:1 to the 0.5 g / L graphene suspension is injected into the tubular membrane 1 from the other end of the tubular membrane 1 through a metering pump at a flow rate of 0.2 mL / min. The Zn(NO3)·6H 2 O solution oozes out from each dispersed pore of the tubular membrane 1 and enters the graphene suspension in the form of droplets. Under the continuous stirring of the magnetic stirring rotor 3, the two are mixed and reacted for 0.5 h to obtain a mixed turbid liquid.

[0086] S8: The mixed turbid liquid is vacuum filtered to obtain a filter cake, and Zn(NO3)·6H 2 O is inserted between the graphene layers.

[0087] S9: Place the filter cake together with the filter paper in an oven at 50 °C for drying for 2 h to remove the residual moisture in the filter cake. Then ignite the dried filter cake with an alcohol lamp. After a 5-s intense combustion process, the combustion consumes and removes the oxygen-containing groups on the surface of the graphene. Finally, wash and remove the combustion residues on the surface of the graphene with HCl and deionized water to obtain nanoporous graphene.

[0088] S10: Prepare a 1 g / L nanoporous graphene suspension and a 0.1 g / L graphene oxide suspension by adding water to the nanoporous graphene obtained in S9 and the graphene oxide obtained in S5, respectively.

[0089] S11: Using a polyethersulfone ultrafiltration membrane as the substrate membrane, first filter 1 mL of the graphene oxide suspension through the substrate membrane by means of negative pressure filtration. Then filter 1 mL of the nanoporous graphene suspension on the substrate membrane in the same way. Next, filter 1 mL of the graphene oxide suspension on the substrate membrane to obtain the loaded substrate membrane.

[0090] S12: Place the loaded substrate membrane in a vacuum drying oven and dry it at room temperature for 20 h to obtain a graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane.

[0091] For the graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane prepared in the embodiment of the present invention, the internal particles and pore sizes of the material can reach 160 - 300 nm. Compared with traditional adsorption materials, the average internal particle and pore sizes of the material are reduced by 20 - 30%, which greatly increases the specific surface area of the material and significantly increases the active adsorption sites of the material, resulting in better adsorption effect. When the graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane prepared in the embodiment of the present invention is used to adsorb iodine-131 nuclide in radioactive waste liquid, the selective adsorption capacity for iodine-131 in a radioactive environment can reach 250 - 350 mg / g. Compared with traditional adsorption materials, the selective adsorption capacity for iodine-131 is increased by 10 - 40%, and its purification coefficient can be increased to 40 - 50. Compared with traditional adsorption materials, its purification coefficient is increased by 4 - 5 times.

[0092] Example 2

[0093] S1: Add 2 g of flaky graphite powder with a particle size of 1000 mesh and 20 ml of AR pure concentrated sulfuric acid as the continuous phase in advance to the reaction vessel 2 of the membrane-distributed microreactor with the tubular membrane 1 wound into 4 turns of a helix, a diameter of 5 mm, and a dispersed pore diameter of 0.5 μm. Start the magnetic stirring rotor 3 at the bottom of the reaction vessel 2 and stir the mixture of graphite powder and concentrated sulfuric acid at a speed of 200 rpm.

[0094] S2: Block one end of the tubular membrane 1. Using a metering pump, inject a mixture of 2.5 mL of phosphoric acid and 10 g of potassium permanganate as the dispersed phase into the tubular membrane 1 from the other end at a flow rate of 1 mL / min in 5 portions. The mixture of phosphoric acid and potassium permanganate seeps out from each dispersion pore of the tubular membrane 1 and enters the mixture of graphite powder and concentrated sulfuric acid in the form of droplets. Through the membrane-distributed microreactor for feeding and reaction, the highly viscous phosphoric acid can stably and in small amounts react with the reactants through the spiral membrane pipeline in the improved Hummers reaction, which can enhance the mixing effect and make the surface particle distribution of the prepared material finer and more uniform.

[0095] The reactants are first stirred and reacted at a temperature of 10 °C for 2 h to insert sulfuric acid and potassium permanganate between the graphite layers and carry out pre-oxidation to obtain a pre-reaction solution.

[0096] S3: Continue to heat the pre-reaction solution to raise the temperature to 90 °C and continuously stir and react for 15 h to dissociate and remove the sulfur-containing groups generated during the oxidation process to obtain a post-reaction solution.

[0097] S4: Cool the post-reaction solution to room temperature and then pour it into ice water. While stirring, add 5 mL of hydrogen peroxide through the tubular membrane 1 of the membrane-distributed microreactor to continue the reaction to remove the excess potassium permanganate in the post-reaction solution. Filter the solution until it turns golden yellow to obtain the reaction product.

[0098] S5: Wash the reaction product with distilled water and 10 vol% hydrochloric acid respectively until the pH is 8. Then disperse the washed product in water and perform ultrasonic treatment for 10 h. Finally, vacuum freeze-dry the ultrasonically treated product to avoid the decomposition and reduction of graphene oxide at high temperatures while maintaining its fluffy structure, thereby obtaining graphene oxide powder.

[0099] S6: Add the graphene oxide synthesized in S5 and water as the continuous phase in advance to the reaction vessel 2 of the membrane-distributed microreactor with its tubular membrane 1 wound into a 6-turn spiral shape, a diameter of 4 mm, and a dispersion pore diameter of 0.1 - 0.5 μm. Start the magnetic stirring rotor 3 at the bottom of the reaction vessel 2 and stir the mixture of synthesized graphene oxide and water at a speed of 200 rpm to prepare a 5 g / L graphene suspension.

[0100] S7: Block one end of the tubular membrane 1. Using a metering pump, inject a 400 - 800 g / L Zn(NO3)·6H 2 O solution with a volume ratio of 1:3 to the 5 g / L graphene suspension as the dispersed phase into the tubular membrane 1 from the other end at a flow rate of 0.5 mL / min. Zn(NO3)·6H 2The O solution seeps out from each dispersion pore of the tubular membrane 1 and enters the graphene suspension in the form of droplets. Under the continuous stirring of the magnetic stirring rotor 3, the two are mixed and reacted for 3 h to obtain a mixed turbid solution.

[0101] S8: The mixed turbid solution is vacuum filtered to obtain a filter cake, and Zn(NO3)·6H 2 O is inserted between the graphene layers.

[0102] S9: The filter cake and the filter paper are placed in an oven at 70 °C and dried for 2 h to remove the residual moisture in the filter cake. Then, the dried filter cake is ignited with an alcohol lamp. After a 10-s intense combustion process, the combustion consumes and removes the oxygen-containing groups on the graphene surface. Finally, the combustion residues on the graphene surface are removed by washing with HCl and deionized water, and nanoporous graphene can be obtained.

[0103] S10: The nanoporous graphene prepared in S9 and the graphene oxide prepared in S5 are respectively added with water to prepare a nanoporous graphene turbid solution with a concentration of 5 g / L and a graphene oxide turbid solution with a concentration of 0.8 g / L.

[0104] S11: Using a polyethersulfone ultrafiltration membrane as the substrate membrane, first, 5 mL of the graphene oxide turbid solution is filtered through the substrate membrane by means of negative pressure filtration. Then, 5 mL of the nanoporous graphene turbid solution is filtered on the substrate membrane in the same way, and then 5 mL of the graphene oxide turbid solution is filtered on the substrate membrane to obtain a loaded substrate membrane.

[0105] S12: The loaded substrate membrane is placed in a vacuum drying oven and dried at room temperature for 30 h to obtain a graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane.

[0106] For the graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane prepared in the embodiment of the present invention, the internal particles and pore sizes of the material can reach 40-100 nm. Compared with traditional adsorption materials, the internal particles and pore sizes of the material are on average reduced by 20-30%, which greatly increases the specific surface area of the material and significantly increases the active adsorption sites of the material, resulting in better adsorption effect. When the graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane prepared in the embodiment of the present invention is used to adsorb iodine-131 nuclide in radioactive waste liquid, the selective adsorption capacity for iodine-131 in a radioactive environment can reach 350-550 mg / g. Compared with traditional adsorption materials, the selective adsorption capacity for iodine-131 is increased by 10-40%, and its purification coefficient can be increased to 40-50. Compared with traditional adsorption materials, its purification coefficient is increased by 4-5 times.

[0107] Example 3

[0108] S1: Add 1.5 g of flaky graphite powder with a particle size of 500 mesh and 15 ml of AR pure concentrated sulfuric acid as the continuous phase into the reaction vessel 2 of the membrane-distributed microreactor with a tubular membrane 1 wound into a 4-turn helix, a diameter of 5 mm, and a dispersion pore diameter of 0.3 μm. Start the magnetic stirring rotor 3 at the bottom of the reaction vessel 2 and stir the mixture of graphite powder and concentrated sulfuric acid at a speed of 150 rpm.

[0109] S2: Block one end of the tubular membrane 1, and use a metering pump to inject a mixture of 1.5 mL of phosphoric acid and 6 g of potassium permanganate as the dispersed phase into the tubular membrane 1 from the other end in 4 portions at a flow rate of 0.5 mL / min. The mixture of phosphoric acid and potassium permanganate oozes out from each dispersion pore of the tubular membrane 1 and enters the mixture of graphite powder and concentrated sulfuric acid in the form of droplets. Through the feeding and reaction of the membrane-distributed microreactor, the highly viscous phosphoric acid can stably and in small amounts react with the reactants through the spiral membrane pipeline in the improved Hummers reaction, which can enhance the mixing effect and make the surface particle distribution of the prepared material finer and more uniform.

[0110] The reactants are first stirred and reacted at a temperature of 5 °C for 1.5 h to insert sulfuric acid and potassium permanganate between the graphite layers and carry out pre-oxidation to obtain a pre-reaction solution.

[0111] S3: Continue to heat the pre-reaction solution to raise the temperature to 70 °C and continuously stir and react for 13 h to dissociate and remove the sulfur-containing groups generated during the oxidation process to obtain a post-reaction solution.

[0112] S4: Cool the post-reaction solution to room temperature and then pour it into ice water. While stirring, add 3 mL of hydrogen peroxide through the tubular membrane 1 of the membrane-distributed microreactor to continue the reaction to remove the excess potassium permanganate in the post-reaction solution until the post-reaction solution turns golden yellow and then filter to obtain the reaction product.

[0113] S5: Wash the reaction product with distilled water and 6 vol% hydrochloric acid respectively until the pH is 7, then disperse the washed product in water and perform ultrasonic treatment for 7 h. Finally, vacuum freeze-dry the ultrasonically treated product to avoid the decomposition and reduction of graphene oxide at high temperatures while maintaining its fluffy structure, thereby obtaining graphene oxide powder.

[0114] S6: Add the graphene oxide synthesized in S5 and water as the continuous phase into the reaction vessel 2 of the membrane-distributed microreactor with a tubular membrane 1 wound into a 6-turn helix, a diameter of 4 mm, and a dispersion pore diameter of 0.3 μm in advance. Start the magnetic stirring rotor 3 at the bottom of the reaction vessel 2 and stir the mixture of the synthesized graphene oxide and water at a speed of 150 rpm to prepare a graphene suspension with a concentration of 2.5 g / L.

[0115] S7: Block one end of the tubular membrane 1, and use a metering pump to inject a 600 g / L Zn(NO3)·6H 2 O solution, which is the dispersed phase with a volume ratio of 1:2 to the 2.5 g / L graphene suspension, into the tubular membrane 1 from the other end of the tubular membrane 1 at a flow rate of 0.25 mL / min. The Zn(NO3)·6H 2 O solution seeps out from each dispersion hole of the tubular membrane 1 and enters the graphene suspension in the form of droplets. Under the continuous stirring of the magnetic stirring rotor 3, the two are mixed and reacted for 1.5 h to obtain a mixed turbid liquid.

[0116] S8: Vacuum filter the mixed turbid liquid to obtain a filter cake, and insert Zn(NO3)·6H 2 O between the graphene layers.

[0117] S9: Place the filter cake and filter paper in an oven at 50 - 70 °C and dry for 2 h to remove the residual moisture in the filter cake. Then ignite the dried filter cake with an alcohol lamp. After a 7-s intense combustion process, the combustion consumes and removes the oxygen-containing groups on the graphene surface. Finally, wash with HCl and deionized water to remove the combustion residues on the graphene surface, and then nanoporous graphene can be obtained.

[0118] S10: Prepare a 2.5 g / L nanoporous graphene suspension and a 0.5 g / L graphene oxide suspension by adding water to the nanoporous graphene obtained in S9 and the graphene oxide obtained in S5 respectively.

[0119] S11: Use a polyethersulfone ultrafiltration membrane as the substrate membrane. First, filter 2.5 mL of the graphene oxide suspension through the substrate membrane by negative pressure filtration. Then filter 2.5 mL of the nanoporous graphene suspension on the substrate membrane in the same way. Then filter 2.5 mL of the graphene oxide suspension on the substrate membrane to obtain a loaded substrate membrane.

[0120] S12: Place the loaded substrate membrane in a vacuum drying oven and dry at room temperature for 25 h to obtain a two-dimensional separation membrane of graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane.

[0121] The two-dimensional separation membrane of graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane prepared in the embodiments of the present invention has internal particles and pore sizes in the material that can reach 80 - 200 nm. Compared with traditional adsorption materials, the average size of internal particles and pores in the material is reduced by 20 - 30%. This greatly increases the specific surface area of the material, significantly increases the active adsorption sites of the material, and has a better adsorption effect. The two-dimensional separation membrane of graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane prepared in the embodiments of the present invention is used to adsorb iodine-131 nuclide in radioactive waste liquid. The selective adsorption capacity for iodine-131 in a radioactive environment can reach 300 - 450 mg / g. Compared with traditional adsorption materials, the selective adsorption capacity for iodine-131 is increased by 10 - 40%, and its purification coefficient can be increased to 40 - 50. Compared with traditional adsorption materials, its purification coefficient is increased by 4 - 5 times.

[0122] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing a material for selective adsorption of iodine-131 nuclides, characterized in that: The steps include: Graphene oxide was synthesized in a membrane-distributed microreactor using graphite powder, concentrated sulfuric acid, phosphoric acid, potassium permanganate and hydrogen peroxide as raw materials. Nanoporous graphene was synthesized in a uniformly distributed membrane microreactor using graphene suspension and Zn(NO3)2·6H2O as raw materials. The graphene oxide solution, the nanoporous graphene solution and the graphene oxide solution are filtered sequentially on the substrate membrane to obtain a graphene oxide / nanoporous graphene / graphene oxide two-dimensional separation membrane; The uniformly distributed membrane microreactor comprises a tubular membrane and a reaction container, wherein the tubular membrane is arranged in the middle of the reaction container, a magnetic stirring rotor is arranged at the bottom of the reaction container, and dispersed holes with a diameter of 0.1-0.5 μm are arranged on the tubular membrane; when using the uniformly distributed membrane microreactor, one end of the tubular membrane needs to be blocked; Wherein, the synthesis of graphene oxide comprises the following steps: Adding 0.5-2 g of graphite powder and 10-20 ml of concentrated sulfuric acid as a continuous phase into the reaction container and stirring and mixing with the magnetic stirring rotor to obtain a mixture; A mixed solution formed by mixing 0.5-2.5 mL of phosphoric acid and 3-10 g of potassium permanganate is added into the mixture through the tubular membrane in multiple times as a dispersed phase, and stirred at 0-10° C. for 0.5-2 h to obtain a pre-reaction solution; Heat the pre-reaction solution to 40-90° C., and continue stirring the reaction for 10-15 hours to obtain a post-reaction solution; The reaction solution was cooled to room temperature and poured into ice water, and 0.5-5 mL of hydrogen peroxide was added through the tubular membrane under stirring to continue the reaction; After the solution turns golden yellow, the reaction product is obtained by filtration; The reaction product was washed with distilled water and 2-10 vol% hydrochloric acid to a pH of 6-8; The washed product is dispersed in water and ultrasonicated for 5-10 hours, and then vacuum freeze-dried to obtain graphene oxide powder; Wherein, the synthesis of the nanoporous graphene comprises the following steps: Add the synthesized graphene oxide powder and water as a continuous phase into the reaction container, stir and mix to form a graphene suspension of 0.5-5 g / L; Adding 400-800 g / L Zn(NO3)2·6H2O solution having a volume ratio of 1:1-1:3 to the graphene suspension as a dispersed phase from the tubular membrane to the graphene suspension for mixed reaction to obtain a mixed turbid solution; The mixed turbid liquid is vacuum filtered to obtain a filter cake; The filter cake and the filter paper are dried at 50-70° C. and then burned. The combustion residue is washed with HCl and deionized water to obtain nanoporous graphene.

2. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 1, characterized in that: The tubular membrane is coiled into a spiral shape with 3 to 6 turns and a diameter of 4 to 6 mm; The rotation speed of the magnetic stirring rotor at the bottom of the reaction container is 50-200 rpm.

3. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 2, characterized in that: The membrane uniformly distributed microreactor comprises the following steps when used: The continuous phase is placed in the reaction vessel and stirred with a magnetic stirring rotor. One end of the tubular membrane is blocked, and the dispersed phase is injected from the other end of the tubular membrane at a flow rate of 0.1-1 mL / min through a metering pump; The dispersed phase in the form of droplets seeps out from the dispersed pores of the tubular membrane and contacts and reacts with the continuous phase.

4. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 3, characterized in that: The graphite powder is flaky graphite powder with a particle size of 100-1000 meshes, and the phosphoric acid is AR pure phosphoric acid.

5. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 4, characterized in that: The membrane uniformly distributed microreactor used for graphene oxide synthesis is a tubular membrane wound into a spiral shape with 4 turns, with a diameter of 5mm, a dispersion hole diameter of 0.1-0.5μm, an external magnetic stirring speed of 100-200rpm, and a flow rate of 0.1-1mL / min for the phosphoric acid to pass into the tubular membrane.

6. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 5, characterized in that: The membrane uniformly distributed microreactor used for the nanoporous graphene synthesis is a tubular membrane wound into a spiral shape with 6 turns, with a diameter of 4mm, a dispersed pore diameter of 0.1-0.5μm, an external magnetic stirring speed of 100-200rpm, and the flow rate of the graphene suspension and Zn(NO3)2·6H2O passing into the tubular membrane is 0.2-0.5mL / min.

7. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 1, characterized in that: The synthesis of the graphene oxide / nanoporous graphene / graphene oxide two-dimensional separation membrane comprises the following steps: The prepared nanoporous graphene and graphene oxide are respectively prepared into 1-5 g / L nanoporous graphene turbid solution and 0.1-0.8 g / L graphene oxide turbid solution; Using a polyethersulfone ultrafiltration membrane as a basement membrane, 1-5 mL of graphene oxide, 1-5 mL of nanoporous graphene turbid solution, and 1-5 mL of graphene oxide turbid solution are filtered through the basement membrane in a negative pressure filtration manner to obtain a loaded basement membrane; The supported substrate membrane is vacuum dried to obtain a graphene oxide membrane / nanoporous graphene membrane / graphene oxide membrane two-dimensional separation membrane.

8. The method for preparing a material for selective adsorption of iodine-131 nuclides according to claim 7, characterized in that: The vacuum drying of the loaded substrate membrane is to place the loaded substrate membrane in a vacuum drying oven and dry it at room temperature for 20-30 hours.

Images