Preparation method of functional carbon membrane and application thereof in cesium ion separation

Abstract

The application discloses a preparation method of a functional carbon membrane and application of the functional carbon membrane in cesium ion separation, and belongs to the technical field of water treatment. The functional carbon membrane material is prepared by taking porous carbon membrane with good conductivity as a base film, loading iron-based oxide on the carbon membrane by using an electrochemical deposition method, and then growing Prussian blue particles in situ. The method can effectively control the loading amount of the Prussian blue particles on the carbon membrane and improve the combination stability between the Prussian blue particles and the carbon membrane. The functional carbon membrane is used for deep treatment of wastewater containing Cs + , and can realize integrated coupling of membrane adsorption and electrochemical adsorption functions. On one hand, the adsorption rate of cesium ions is improved, and the desorption regeneration process of the carbon membrane is simplified. On the other hand, real-time separation of the purified water body can be realized, and the functional carbon membrane has a wide application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing a functional carbon membrane and its application in cesium ion separation, belonging to the field of water treatment technology. Background Technology

[0002] In the face of contemporary energy shortages, nuclear energy is an important renewable energy source to replace fossil fuels and occupies a vital position in modern society. However, if it undergoes fission, it will produce radioactive substances. 137 Cesium, when dissolved in water, can have incalculable impacts on water resources and human health. Therefore, designing and developing a process for separating cesium from radioactive wastewater is of great value.

[0003] Common removal methods include chemical precipitation, extraction, and adsorption. Adsorption is widely used due to its high stability and low operating cost. Among these, adsorbents based on Prussian blue and its analogues exhibit ultra-high adsorption selectivity and capacity for cesium ions, making them the most widely used adsorption materials. However, Prussian blue is mainly in powder form, and its direct application in adsorption inevitably leads to agglomeration and difficulty in recovery. To address this, researchers have developed composite adsorbents by immobilizing it on a support. By loading Prussian blue particles onto a membrane material to construct an adsorption membrane, the problems of powder agglomeration and difficulty in recovery can be solved. Furthermore, in flow mode, the diffusion distance can be effectively reduced, increasing the adsorption rate. However, traditional adsorption processes often face challenges such as complex desorption processes and difficulties in recovering the adsorbent material.

[0004] Electrochemical adsorption technology based on Prussian blue can effectively control the adsorption and desorption of cesium ions by regulating the redox reaction of Prussian blue through electrochemical action. This not only increases the adsorption capacity of cesium ions but also solves the problem of difficult regeneration of adsorption materials in traditional processes. However, electrochemical adsorption technology mainly adopts an intermittent treatment mode, which has drawbacks such as long diffusion distance of cesium ions and inability to operate continuously, limiting its further application. If membrane adsorption and electrochemical adsorption can be coupled into one, it is expected to become a new technology for the efficient removal of cesium ions from water. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing a functional carbon membrane and its application in cesium ion separation. The method uses a porous carbon membrane with excellent conductivity as the base membrane, loads iron-based oxides onto the carbon membrane using electrochemical deposition, and then grows Prussian blue particles in situ to obtain the functional carbon membrane. This functional carbon membrane is then used for the separation of Cs-containing ions. + The wastewater is subjected to advanced treatment. This functional carbon membrane serves as both an adsorption electrode and an adsorption membrane, coupling electrochemical adsorption and membrane adsorption technologies into one. The Cs in the water... +The adsorption and removal of cesium ions not only improves the adsorption efficiency of cesium ions but also simplifies the desorption and regeneration process of the carbon membrane. Furthermore, it enables real-time separation of the purified water, and has broad application prospects in the field of cesium ion separation.

[0006] A method for preparing a functional carbon membrane includes the following steps:

[0007] (1) Select a suitable porous carbon-based membrane material as the substrate, and pretreat the carbon membrane with an acid solution to remove minerals and other impurities on the carbon membrane, so as to obtain a clean and usable substrate carbon membrane.

[0008] (2) Prepare an electrochemical deposition solution, use the carbon film treated in step (1) as the working electrode, construct a three-electrode system, and use the electrochemical deposition method to electrochemically deposit the substrate carbon film with in-situ loaded iron-based oxides under constant potential.

[0009] (3) Prepare an in-situ growth solution, put the carbon film sample obtained by electrochemical deposition in step (2) into the in-situ growth solution, grow Prussian blue particles in situ, and then wash and dry with deionized water to obtain the functional carbon film.

[0010] Preferably, in step (1), the porous carbon-based membrane material is prepared from one or more of activated carbon, graphite, petroleum coke, coal and carbon nanotubes as raw materials;

[0011] Furthermore, the porous carbon-based membrane material has a tubular or plate-like configuration, wherein the tubular carbon membrane is a single-channel or multi-channel tubular carbon membrane, and the plate-like carbon membrane is a non-hollow plate-like carbon membrane or a hollow plate-like carbon membrane; its pore structure is well-developed, with a porosity ranging from 20% to 60%, preferably 45% to 55%; the pore size distribution is adjustable, with an average pore size ranging from 0.1 to 5 μm, preferably 1 to 3 μm; the porous carbon-based membrane material has good electrical conductivity, with a resistivity below 1000 mΩ·cm, preferably below 100 mΩ·cm;

[0012] Preferably, the pretreatment of the porous carbon-based membrane material is as follows: the porous carbon-based membrane material is sequentially immersed in hydrochloric acid and hydrofluoric acid solutions for surface modification treatment, then washed with deionized water and dried; wherein, the concentration of hydrochloric acid is 1-10 mol / L, preferably 3-6 mol / L, the mass fraction of hydrofluoric acid solution is between 5%-40%, preferably 15-30%, and the treatment time is 30-180 min, preferably 60-180 min; the washing is performed by washing with deionized water until neutral, and the drying is performed by placing it in an oven at 60-140℃ for 1-8 h.

[0013] Preferably, the electrochemical deposition solution in step (2) is prepared by dissolving iron-based salts and additives in deionized water;

[0014] Furthermore, the iron-based salt is one or more of the following: ferric or ferrous nitrates, sulfates, and chlorides; the additive is one or more of the following: ethylenediaminetetraacetic acid (EDTA), citric acid, tartaric acid, oxalic acid, glycine, ammonium thiocyanate, potassium thiocyanate, alginic acid and its sodium salt, tripolyphosphate, aminotrimethylenephosphonic acid and its sodium salt, polyacrylic acid, and polystyrene sulfonic acid and its sodium salt.

[0015] Preferably, the molar concentration of the iron-based salt is between 0.01-50 mol / L, and more preferably 0.5-10 mol / L; the molar concentration of the additive is between 0.01-30 mol / L, and more preferably 0.1-10 mol / L, and more preferably 0.1-2 mol / L.

[0016] Furthermore, in step (2), the three-electrode system uses a carbon film as the working electrode, a saturated calomel electrode as the reference electrode, and a titanium sheet or titanium plate as the counter electrode.

[0017] Furthermore, the electrochemical deposition of in-situ loaded iron-based oxides under constant potential has a constant potential electrochemical deposition voltage between -10.0V and 10.0V, with a preferred voltage range between -3.0V and 3.0V; the deposition time is 1 to 120 minutes, with a preferred time of 5 to 60 minutes.

[0018] Preferably, the in-situ growth solution mentioned in step (3) is prepared by dissolving potassium ferrocyanide (K4Fe(CN)6·3H2O) in deionized water and adjusting the pH of the solution with hydrochloric acid;

[0019] Furthermore, the concentration of potassium ferrocyanide in the in-situ growth solution is between 0.01-5 mol / L, with a preferred concentration of 0.1-0.5 mol / L, and the pH value is 2-3.

[0020] Further, the in-situ growth of Prussian blue particles on the carbon film involves immersing the carbon film obtained in step (2) in an in-situ growth solution at 10-40°C for 5 min-48 h, wherein the preferred in-situ growth time is 30 min-12 h; the cleaning and drying process involves first cleaning with deionized water until neutral or soaking in hot water at 60-100°C for 0.5-5 h, and then drying in an oven at 60-120°C for 1-9 h.

[0021] A second objective of this invention is to claim protection for a functional carbon membrane prepared by the above-described preparation method.

[0022] A third objective of this invention is to protect the aforementioned functional carbon membrane for its application in cesium ion separation.

[0023] Furthermore, the application of the functional carbon membrane in cesium ion separation includes the following steps:

[0024] Preferably, functional carbon membranes are effectively applied in the adsorption and desorption processes of electrochemical treatment of cesium-containing wastewater;

[0025] Preferably, in adsorption treatment, the process is as follows: first, the functional carbon membrane is used as the cathode and the titanium plate is used as the anode, connected by a DC power supply, and immersed in the solution to be treated containing cesium ions. Under pressure, the water containing cesium ions penetrates the pores of the functional carbon membrane from one side to the other side, resulting in purified water.

[0026] Furthermore, the electric field strength of the adsorption electrochemical treatment is between -8 and -1V, with the preferred voltage being -5 to -2V, and the residence time is between 10s and 30min, with the preferred residence time being between 30s and 10min.

[0027] Preferably, in desorption treatment, the process is as follows: when the functional carbon membrane reaches adsorption saturation, the functional carbon membrane and the counter electrode are transferred to a sodium sulfate solution, the electrode orientation is reversed, and electrochemical regeneration and backwashing are performed for a certain period of time under an applied electric field to achieve desorption and regeneration of the carbon membrane.

[0028] Furthermore, the concentration of sodium sulfate in the desorption electrochemical treatment is 1 mM to 1 M, with a preferred concentration of 50 mM to 0.5 M; the electric field strength is 2 to 10 V, with a preferred voltage of 3 to 5 V; and the residence time of the backwash solution is 1 s to 60 s, with a preferred residence time of 10 to 50 s.

[0029] Furthermore, in the application of adsorption and desorption of cesium-containing wastewater, the target of application can be any one of the following: radioactive wastewater containing cesium ions, nuclear accident contaminated water, seawater, or cesium-containing salt lake water.

[0030] Compared with existing technologies, this invention provides a method for preparing a functional carbon membrane and its application in the cesium ion separation process, which has the following beneficial effects: The functional carbon membrane can achieve integrated coupling of membrane adsorption and electrochemical adsorption technologies, and has the advantages of high cesium ion adsorption efficiency and simple desorption and regeneration process. The method for preparing the functional carbon membrane can, on the one hand, control the loading and morphology of Prussian blue on the carbon membrane by regulating the electrochemical deposition process of iron oxide and the in-situ growth process conditions, while improving the binding performance (stability) of Prussian blue particles to the carbon membrane surface. Furthermore, the preparation process of the functional carbon membrane is simple, and it can be prepared at room temperature through simple electrochemical deposition and in-situ growth methods. It has good environmental compatibility, a simple preparation method, low material cost, no pollution generation or secondary pollution during the preparation process, low energy consumption, and high efficiency. It has a wide range of applications in water bodies, high treatment efficiency, and no secondary pollutant generation, which is of great significance for the removal of radioactive cesium ions from water bodies. Attached Figure Description

[0031] Figure 1 SEM images of coal-based carbon membrane (a), carbon membrane supported on hydroxyl iron oxide (b), and carbon membrane supported on PB functional material (c);

[0032] Figure 2 A schematic diagram of the electrochemical separation of cesium ions using a functional carbon membrane: (a) adsorption; (b) desorption. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These descriptions are for illustrative purposes only and not for limiting the scope of the invention. It should be noted that, in the description of the present invention, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless the manufacturer is specified, are all commercially available conventional products.

[0034] Example 1

[0035] A tubular coal-based porous carbon membrane with an average pore size of 1 μm, a length of 50 mm, an outer diameter of 10 mm, a resistivity of 15 mΩ·cm, and a porosity of 53% was selected. It was sequentially immersed in 3 mol / L hydrochloric acid and 20% hydrofluoric acid solutions for surface modification treatment, with treatment times of 40 min for each. After washing with water until neutral, it was dried in a 60℃ oven for 4 h to obtain a clean, usable coal-based carbon membrane. The electron microscope image is shown below. Figure 1As shown in (a), the coal-based carbon membrane exhibits a rich porous structure. 2.125 g of NaNO3 and 4.97 g of FeCl2·4H2O were dissolved in a 250 mL beaker and subjected to N2 atmosphere (30 min) to prevent oxidation, yielding an electrochemical deposition solution. 21.115 g of potassium ferrocyanide was dissolved in deionized water, and 2 mL of 6 mol / L hydrochloric acid was added dropwise to prepare an in-situ growth solution of 0.1 mol / L K4Fe(CN)6·3H2O and HCl. Next, using the carbon membrane as the working electrode, a saturated calomel electrode as the reference electrode, and a titanium sheet as the counter electrode, electrochemical deposition was performed under a constant voltage condition of -0.8 V in It mode on an electrochemical workstation for 30 min. After deposition, the coal-based carbon membrane was removed from the electrochemical deposition solution, repeatedly rinsed with deionized water, and air-dried under natural conditions. The resulting electron micrograph is shown below. Figure 1 As shown in (b), turf-like iron hydroxyl oxide was successfully loaded onto the surface of the coal-based carbon film. The electrochemically deposited carbon film sample was immersed in a prepared in-situ growth solution at 25°C for 30 min to grow Prussian blue particles in situ. Then, it was immersed in 90°C hot water for 1 h to remove unstable Prussian blue particles. Finally, it was dried in a 60°C oven for 6 h to obtain the functional carbon film. The electron microscope image is shown below. Figure 1 As shown in (c), Prussian blue particles with a cubic structure are successfully loaded onto the visible surface.

[0036] The obtained functional carbon membrane was used in cesium ion adsorption filtration. During the adsorption process, the functional carbon membrane was connected to the negative terminal of a DC power supply as the cathode, and the titanium plate was connected to the positive terminal of the DC power supply as the anode. The cathode and anode were completely immersed in the treatment solution containing cesium ions at a concentration of 5 mg / L. The electric field strength was -4V, and a peristaltic pump was used to provide pressure. Under pressure, the cesium-containing water penetrated the pores of the functional carbon membrane from one side to the other side, with a residence time of 15 minutes, resulting in purified water (see schematic diagram). Figure 2 a) During desorption, the functional carbon membrane and counter electrode are transferred to a sodium sulfate solution, and the electrode orientation is reversed, i.e., the functional carbon membrane is connected to the positive terminal of the DC power supply as the anode, and the titanium plate is connected to the negative terminal of the DC power supply as the cathode. The electric field strength is 5V, and backwashing is performed in a 0.01mol / L sodium sulfate solution. The residence time of the backwash solution is 30s (see schematic diagram). Figure 2 b). Performance is shown in Table 1.

[0037] Comparative Example 1

[0038] The functional carbon membrane prepared in Example 1 was directly used for adsorption and filtration of cesium-containing water without an external electric field. A peristaltic pump was used to provide pressure, and under this pressure, the cesium-containing water penetrated the pores of the functional carbon membrane from one side to the other, with a residence time of 15 minutes. During desorption, the functional carbon membrane and the counter electrode were transferred to a 0.01 mol / L sodium sulfate solution for backwashing and desorption, with a residence time of 30 seconds. Performance is shown in Table 1.

[0039] Comparative Example 2

[0040] A tubular coal-based porous carbon membrane with an average pore size of 1 μm, a length of 50 mm, an outer diameter of 10 mm, a resistivity of 15 mΩ·cm, and a porosity of 53% was selected. It was sequentially immersed in 3 mol / L hydrochloric acid and 20% hydrofluoric acid solutions for surface modification treatment, with treatment times of 40 min each. After washing with water until neutral, it was dried in a 60℃ oven for 4 h to obtain a clean, usable coal-based carbon membrane. 4.97 g of FeCl2·4H2O was weighed and dissolved in a 250 mL beaker. Under a N2 atmosphere (30 min) to prevent oxidation, the carbon membrane was immersed in this solution for 30 min, then removed, washed, and dried for later use. 21.115 g of potassium ferrocyanide was dissolved in deionized water to prepare a 0.1 mol / L solution. The dried carbon membrane was immersed in this solution for 30 min, then removed and dried in a 100℃ oven for 4 h to obtain the functional carbon membrane.

[0041] The obtained functional carbon membrane was used in cesium ion adsorption filtration. During adsorption, the functional carbon membrane was connected to the negative terminal of a DC power supply as the cathode, and the titanium plate was connected to the positive terminal as the anode. The membrane was completely immersed in a solution with a cesium ion concentration of 5 mg / L. The electric field strength was -4V. Under pressure provided by a peristaltic pump, the cesium-containing water penetrated the pores of the functional carbon membrane from one side to the other, with a residence time of 15 minutes, resulting in purified water. During desorption, the functional carbon membrane and the counter electrode were transferred to a sodium sulfate solution. The electrode orientation was reversed, with the functional carbon membrane connected to the positive terminal of the DC power supply as the anode and the titanium plate connected to the negative terminal as the cathode. The electric field strength was 5V, and backwashing was performed in a 0.01 mol / L sodium sulfate solution with a residence time of 30 seconds. Performance is shown in Table 1.

[0042] Example 2

[0043] A plate-shaped petroleum coke-based porous carbon membrane with an average pore size of 0.6 μm, a length of 40 mm, a width of 40 mm, a resistivity of 18 mΩ·cm, and a porosity of 51% was selected. It was sequentially immersed in 5 mol / L hydrochloric acid and 25% hydrofluoric acid solutions for surface modification treatment, with treatment times of 45 min each. After washing with water until neutral, it was dried in a 100℃ oven for 3 h to obtain a clean, usable petroleum coke-based carbon membrane. 3.432 g of C4H6O6 and 5.08 g of Fe2(SO4)3 were weighed and dissolved in a 150 mL beaker to obtain an electrochemical deposition solution. 33.559 g of potassium ferrocyanide was completely dissolved in deionized water, and 3 mL of 3 mol / L hydrochloric acid was added dropwise to prepare a 0.2 mol / L K4Fe(CN)6·3H2O and HCl in-situ growth solution. Using a carbon film as the working electrode, a saturated calomel electrode as the reference electrode, and a titanium sheet as the counter electrode, deposition was performed for 20 min under a constant voltage of 2V in It mode on an electrochemical workstation. After deposition, the petroleum coke-based carbon film was removed from the electrochemical deposition solution, repeatedly rinsed with deionized water, and air-dried for later use. The carbon film sample obtained by electrochemical deposition was immersed in a prepared in-situ growth solution at 30°C for 180 min to grow Prussian blue particles in situ. Then, it was immersed in 80°C hot water for 3 h to remove unstable Prussian blue particles. Finally, it was dried in a 100°C oven for 4 h to obtain the functional carbon film.

[0044] The obtained functional carbon membrane was used in cesium ion adsorption filtration. During adsorption, the functional carbon membrane was connected to the negative terminal of a DC power supply as the cathode, and the titanium plate was connected to the positive terminal as the anode. The membrane was completely immersed in a solution with a cesium ion concentration of 3 mg / L. Under pressure, the cesium-containing water penetrated the membrane pores from one side of the functional carbon membrane to the other side, with a residence time of 20 minutes, resulting in purified water. During desorption, the functional carbon membrane and the counter electrode were transferred to a sodium sulfate solution. The electrodes were reversed, and the functional carbon membrane was connected to the positive terminal of the DC power supply as the anode, and the titanium plate was connected to the negative terminal as the cathode. Backwashing was performed in a 0.03 mol / L sodium sulfate solution with an electric field strength of 4 V, and the residence time of the backwash solution was 15 seconds. Performance is shown in Table 1.

[0045] Comparative Example 3

[0046] The functional carbon membrane prepared in Example 2 was directly used for adsorption and filtration of cesium-containing water without an external electric field. A peristaltic pump was used to provide pressure, and under this pressure, the cesium-containing water penetrated the pores of the functional carbon membrane from one side to the other, with a residence time of 20 minutes. During desorption, the functional carbon membrane and the counter electrode were transferred to a 0.03 mol / L sodium sulfate solution for backwashing and desorption, with a residence time of 15 seconds. Performance is shown in Table 1.

[0047] Comparative Example 4

[0048] A plate-type petroleum coke-based porous carbon membrane with an average pore size of 0.6 μm, a length of 40 mm, a width of 40 mm, a resistivity of 18 mΩ·cm, and a porosity of 51% was selected. It was sequentially immersed in 5 mol / L hydrochloric acid and 25% hydrofluoric acid solutions for surface modification treatment, with treatment times of 45 min each. After washing with water until neutral, it was placed in a 100℃ oven and dried for 3 h to obtain a clean, usable petroleum coke-based carbon membrane. 5.08 g of Fe2(SO4)3 was dissolved in a 150 mL beaker, and the carbon membrane was immersed in this solution for 20 min. It was then removed, washed, and dried for later use. 33.559 g of potassium ferrocyanide was completely dissolved in deionized water to prepare a 0.2 mol / L solution. The dried carbon membrane was immersed in this solution for 180 min, then removed and dried in a 100℃ oven for 4 h to obtain the functional carbon membrane.

[0049] The obtained functional carbon membrane was used in cesium ion adsorption filtration. During adsorption, the functional carbon membrane was connected to the negative terminal of a DC power supply as the cathode, and the titanium plate was connected to the positive terminal as the anode. The membrane was completely immersed in a solution with a cesium ion concentration of 3 mg / L. Under pressure, the cesium-containing water penetrated the membrane pores from one side of the functional carbon membrane to the other side, with a residence time of 20 minutes, resulting in purified water. During desorption, the functional carbon membrane and the counter electrode were transferred to a sodium sulfate solution, and the electrode orientation was reversed. The functional carbon membrane was then connected to the positive terminal of the DC power supply as the anode, and the titanium plate was connected to the negative terminal as the cathode. Backwashing was performed in a 0.03 mol / L sodium sulfate solution with an electric field strength of 4 V, and the residence time of the backwash solution was 15 seconds. Performance is shown in Table 1.

[0050] Example 3

[0051] Hollow plate-type activated carbon-based porous carbon membranes with an average pore size of 1.5 μm, a length of 50 mm, a width of 20 mm, a resistivity of 40 mΩ·cm, and a porosity of 53% were selected. These membranes were sequentially immersed in 6 mol / L hydrochloric acid and 20% hydrofluoric acid solutions for surface modification treatment, with treatment times of 70 min each. After washing with water until neutral, the membranes were dried in an oven at 110℃ for 5 h to obtain clean, usable activated carbon-based carbon membranes. 5.284 g of C6H5Na3O7 and 3.517 g of Fe(NO3)3 were weighed and dissolved in a 200 mL beaker to obtain an electrochemical deposition solution. 29.481 g of potassium ferrocyanide was completely dissolved in deionized water, and 1 mL of 9 mol / L hydrochloric acid was added dropwise to prepare an in-situ growth solution of 0.5 mol / L K4Fe(CN)6·3H2O and HCl. Using a carbon film as the working electrode, a saturated calomel electrode as the reference electrode, and a titanium sheet as the counter electrode, deposition was performed for 50 min under constant voltage conditions of -2V in It mode on an electrochemical workstation. After deposition, the activated carbon-based carbon film was removed from the electrochemical deposition solution, repeatedly rinsed with deionized water, and air-dried for later use. The carbon film sample obtained by electrochemical deposition was immersed in a prepared in-situ growth solution at 40°C for 60 min to grow Prussian blue particles in situ. Then, it was immersed in hot water at 90°C for 2 h to remove unstable Prussian blue particles. Finally, it was dried in an oven at 120°C for 8 h to obtain the functional carbon film.

[0052] The obtained functional carbon membrane was used in cesium ion adsorption filtration. During adsorption, the functional carbon membrane was connected to the negative terminal of a DC power supply as the cathode, and the titanium plate was connected to the positive terminal as the anode. The membrane was completely immersed in a solution with a cesium ion concentration of 1 mg / L. Under pressure, the cesium-containing water penetrated the membrane pores from one side of the functional carbon membrane to the other side, with a residence time of 11 minutes, resulting in purified water. During desorption, the functional carbon membrane and the counter electrode were transferred to a sodium sulfate solution, and the electrode orientation was reversed. The functional carbon membrane was then connected to the positive terminal of the DC power supply as the anode, and the titanium plate was connected to the negative terminal as the cathode. Backwashing was performed in a 0.1 mol / L sodium sulfate solution with an electric field strength of 3 V, and the residence time of the backwash solution was 15 seconds. Performance is shown in Table 1.

[0053] Comparative Example 5

[0054] The functional carbon membrane prepared in Example 3 was directly used for adsorption and filtration of cesium-containing water without an external electric field. A peristaltic pump was used to provide pressure, and under this pressure, the cesium-containing water penetrated the pores of the functional carbon membrane from one side to the other, with a residence time of 11 minutes. During desorption, the functional carbon membrane and the counter electrode were transferred to a 0.1 mol / L sodium sulfate solution for backwashing and desorption, with a residence time of 15 seconds. Performance is shown in Table 1.

[0055] Comparative Example 6

[0056] A hollow plate-type activated carbon-based porous carbon membrane with an average pore size of 1.5 μm, a length of 50 mm, a width of 20 mm, a resistivity of 40 mΩ·cm, and a porosity of 53% was selected. It was sequentially immersed in 6 mol / L hydrochloric acid and 20% hydrofluoric acid solutions for surface modification treatment, with treatment times of 70 min each. After washing with water until neutral, it was placed in a 110℃ oven and dried for 5 h to obtain a clean, usable activated carbon-based carbon membrane. 3.517 g of Fe(NO3)3 was dissolved in a 200 mL beaker, and the carbon membrane was immersed in this solution for 50 min. It was then removed, washed, and dried for later use. 29.481 g of potassium ferrocyanide was completely dissolved in deionized water to prepare a 0.5 mol / L solution. The dried carbon membrane was immersed in this solution for 30 min, then removed and dried in a 120℃ oven for 8 h to obtain the functional carbon membrane.

[0057] The obtained functional carbon membrane was used in cesium ion adsorption filtration. During adsorption, the functional carbon membrane was connected to the negative terminal of a DC power supply as the cathode, and the titanium plate was connected to the positive terminal as the anode. The membrane was completely immersed in a solution with a cesium ion concentration of 1 mg / L. Under pressure, the cesium-containing water penetrated the membrane pores from one side of the functional carbon membrane to the other side, with a residence time of 11 minutes, resulting in purified water. During desorption, the functional carbon membrane and the counter electrode were transferred to a sodium sulfate solution, and the electrode orientation was reversed. The functional carbon membrane was then connected to the positive terminal of the DC power supply as the anode, and the titanium plate was connected to the negative terminal as the cathode. Backwashing was performed in a 0.1 mol / L sodium sulfate solution with an electric field strength of 3 V, and the residence time of the backwash solution was 15 seconds. Performance is shown in Table 1.

[0058] Table 1. Cesium ion separation performance of functional carbon membranes prepared in the examples and comparative examples.

[0059] Number Cesium adsorption amount (mg / g) Purified water amount (L) Regeneration efficiency Desorption time (min) Example 1 205 30 99.95％ 5 Comparative Example 1 145 21 79.10％ 18 Comparative Example 2 50 7 99.66％ 7 Example 2 214 25 99.90％ 3 Comparative Example 3 103 15 71.95％ 15 Comparative Example 4 36 6 98.53％ 8 Example 3 269 60 99.89％ 6 Comparative Example 5 158 39 68.42％ 20 Comparative Example 6 61 14 99.15％ 9

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0061] This invention discloses a method for preparing a functional carbon membrane and its application in cesium ion separation, belonging to the field of water treatment technology. The invention uses a porous carbon membrane with good conductivity as the base membrane, loads iron-based oxides onto the carbon membrane using electrochemical deposition, and then prepares the functional carbon membrane material by in-situ growth of Prussian blue particles. This method can effectively control the loading amount of Prussian blue particles on the carbon membrane and improve the bonding stability between them and the carbon membrane. This functional carbon membrane is used for the separation of Cs-containing ions. + Advanced treatment of wastewater can achieve integrated coupling of membrane adsorption and electrochemical adsorption functions. On the one hand, it can improve the adsorption rate of cesium ions and simplify the desorption and regeneration process of carbon membranes. On the other hand, it can realize real-time separation of the purified water, showing broad application prospects.

Claims

1. A method for preparing a functional carbon membrane, characterized in that: Includes the following steps: (1) Using porous carbon-based membrane material as a substrate, the carbon membrane is pretreated with acid solution to remove impurities on the carbon membrane; (2) Using the carbon film treated in step (1) as the working electrode, place it in the electrochemical deposition solution, use a saturated calomel electrode as the reference electrode, and a titanium sheet or titanium plate as the counter electrode, connect the electrochemical workstation to form a three-electrode deposition system, perform in-situ loading of iron-based oxides under constant potential, and then wash and dry with deionized water; wherein, the preparation process of the electrochemical deposition solution is as follows: dissolve the iron-based salt and additives in deionized water to obtain the electrochemical deposition solution; (3) Place the carbon film sample obtained by electrochemical deposition in step (2) into the in-situ growth solution to grow Prussian blue particles in situ, and then wash and dry it with deionized water to obtain the functional carbon film; wherein, the preparation process of the in-situ growth solution is as follows: dissolve potassium ferrocyanide in deionized water and adjust the pH of the solution with hydrochloric acid to obtain the in-situ growth solution.

2. The method for preparing the functional carbon membrane according to claim 1, characterized in that: In step (1), the substrate carbon membrane is prepared from one or more of activated carbon, graphite, petroleum coke, coal, and carbon nanotubes as raw materials; the substrate carbon membrane is tubular or plate-shaped, wherein the tubular carbon membrane is a single-channel or multi-channel tubular carbon membrane, and the plate-shaped carbon membrane is a non-hollow plate-shaped carbon membrane or a hollow plate-shaped carbon membrane; the porosity of the substrate carbon membrane is 20%-60%, and the pore size is 0.1-5μm; the resistivity of the substrate carbon membrane is below 1000mΩ·cm; the pretreatment of the substrate carbon membrane is as follows: the carbon membrane is placed in hydrochloric acid and hydrofluoric acid solutions for surface treatment in sequence, then washed with water and dried; wherein the concentration of hydrochloric acid is 1-10mol / L, the mass fraction of hydrofluoric acid solution is 5%-40%, the treatment time is 30-180min respectively, and after washing with water until neutral, it is dried.

3. The method for preparing the functional carbon membrane according to claim 1, characterized in that: In the electrochemical deposition solution of step (2), the iron-based salt is one or more of iron or ferrous nitrates, sulfates, and chlorides, and the molar concentration of the iron-based salt is 0.01-50 mol / L; the additive is one or more of ethylenediaminetetraacetic acid, citric acid, tartaric acid, oxalic acid, glycine, ammonium thiocyanate, potassium thiocyanate, alginic acid or its sodium salt, tripolyphosphate, aminotrimethylenephosphonic acid or its sodium salt, polyacrylic acid, polystyrene sulfonic acid or its sodium salt, and the molar concentration of the additive is 0.01-30 mol / L; in the in-situ growth solution of step (3), the concentration of potassium ferrocyanide is 0.01-5 mol / L, and the pH value is 2-3.

4. The method for preparing the functional carbon membrane according to claim 1, characterized in that: In step (2), the electrodeposition voltage is between -10.0V and 10.0V, and the deposition time is between 1 and 120 minutes.

5. The method for preparing the functional carbon membrane according to claim 1, characterized in that: In step (3), the in-situ growth time is 5 min-48 h, and the in-situ growth temperature is controlled at 10-40℃; the cleaning and drying process is as follows: first, clean with deionized water until neutral or soak in hot water at 60-100℃ for 0.5-5 h, and then put into an oven at 60-120℃ to dry for 1-9 h.

6. The functional carbon membrane obtained by the preparation method according to any one of claims 1-5.

7. The application of the functional carbon membrane according to claim 6 in cesium ion separation.

8. The application in cesium ion separation according to claim 7, characterized in that: The specific method is as follows: (1) Adsorption stage: The functional carbon membrane described in claim 6 is used as the cathode and the titanium plate is used as the anode. They are connected by a DC power supply and immersed in the solution to be treated containing cesium ions. Under pressure, the water containing cesium ions penetrates the carbon membrane pores from one side of the functional carbon membrane and enters the other side to obtain purified water. (2) Desorption stage: When the functional carbon membrane reaches adsorption saturation, the functional carbon membrane and the counter electrode are transferred to sodium sulfate solution, the electrode direction is reversed, and backwashing is performed using sodium sulfate solution.

9. The application according to claim 7 or 8, characterized in that: In step (1), the electric field strength used is -8 to -1V, and the residence time is 10s to 30min; in step (2), the concentration of sodium sulfate is 1mM to 1M, the electric field strength is 2 to 10V, and the residence time of the backwash liquid is 1s to 60s.

10. The application according to claim 7 or 8, characterized in that: The liquid to be treated containing cesium ions can be any one of the following: radioactive wastewater containing cesium ions, nuclear accident contaminated water, seawater, or salt lake water.

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