Preparation method of titanium-based adsorption membrane material and application thereof

Abstract

The application relates to a preparation method of a titanium-based adsorption membrane material and application of the titanium-based adsorption membrane material in electrochemical separation of cesium ions. The preparation method comprises the following steps: taking a titanium-based porous membrane as a base membrane, firstly, pretreating the base membrane to remove impurities on the surface of the base membrane; placing the titanium-based porous membrane in a sodium hydroxide solution to perform a hydrothermal reaction, then performing hydrogen chloride acidification and a sintering process, and in-situ growing titanium dioxide nanowires; and through a chemical immersion method, in-situ growing titanium ferrocyanide on the membrane loaded with the titanium dioxide nanowires to prepare the titanium-based adsorption membrane material. By utilizing the conductivity of the membrane material, the membrane filtration technology and the electrochemical adsorption and desorption technology can be coupled by directly applying an electric field, and the coupled technology can be used for efficient separation of cesium ions in water.

Description

Technical Field

[0001] This invention belongs to the field of water treatment applications, specifically relating to membrane separation and electrochemical adsorption technology, and particularly to a method for preparing a titanium-based adsorption membrane material and its application in the electrochemical separation of cesium ions. Background Technology

[0002] Nuclear energy, characterized by its high efficiency and environmental friendliness, has been widely used as one of the most important future energy sources. However, improper handling of nuclear energy can cause enormous harm, with radioactive elements spreading widely and causing environmental pollution, which is extremely harmful to organisms. Currently, nuclear pollution has evolved into a serious global environmental problem. The radioactive cesium produced is one of the most dangerous radionuclides due to its long half-life, easy migration, and high radioactivity. Various methods, including chemical precipitation, biological methods, and adsorption methods, are used to remove cesium ions from water bodies, among which adsorption methods using transition metal ferricyanide (MHCF) as a specific adsorbent are the most widely used.

[0003] However, traditional adsorption technologies face the risks of complex desorption processes and potential secondary pollution. Electrochemical adsorption technology can effectively control the adsorption and desorption of cesium ions by regulating the redox reaction of MHCF 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, traditional intermittent treatment modes have drawbacks such as long cesium ion diffusion distances and the inability to operate continuously. Membrane filtration can effectively enhance the mass transfer efficiency of the cesium ion adsorption process and achieve continuous, real-time separation of the purified water. However, the cesium ion adsorption membrane materials currently used are mainly non-conductive organic membranes, which cannot possess electrochemical adsorption and desorption capabilities.

[0004] If electrochemical adsorption and membrane adsorption technologies can be coupled to achieve complementary advantages of the two technologies, it is expected to become a new technology for the efficient removal of cesium ions. However, how to achieve the organic coupling of the two is a key challenge that needs to be solved. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing a high-performance conductive titanium-based adsorption membrane material and its application. Titanium dioxide nanowires are grown in situ on a conductive titanium-based porous membrane, followed by impregnation to grow titanium ferrocyanide, thus preparing a titanium-based adsorption membrane material. Utilizing its excellent conductivity, an electrochemical adsorption-desorption function is introduced by applying a DC electric field, achieving an integrated coupling of membrane filtration and electrochemical adsorption-desorption technologies for the efficient separation and removal of cesium ions in water.

[0006] A method for preparing a titanium-based adsorption membrane material includes the following steps:

[0007] (1) Using titanium-based porous membrane as the base membrane, pre-treatment is carried out: First, the titanium-based porous membrane is polished with sandpaper and ultrasonically cleaned in acetone to remove the residue on the membrane; then, it is successively immersed in hot sodium hydroxide solution and oxalic acid solution for treatment; finally, it is washed with deionized water and dried for use.

[0008] (2) The titanium-based porous membrane pretreated in step (1) was placed in sodium hydroxide solution for hydrothermal reaction. After the reaction, it was cooled to room temperature and then washed with deionized water, acidified with hydrogen chloride solution, washed with deionized water, dried and placed in a muffle furnace for annealing to prepare a titanium-based porous membrane with in-situ grown titanium dioxide nanowires.

[0009] (3) The titanium-based porous membrane obtained in step (2) is immersed in a mixed aqueous solution of hydrogen chloride and potassium ferrocyanide to react. Titanium ferrocyanide is grown in situ on the membrane loaded with titanium dioxide nanowires by chemical impregnation. Then it is taken out, washed with deionized water and dried to obtain titanium-based adsorption membrane material.

[0010] Furthermore, in step (1), the porous titanium membrane configuration includes plate type, tubular type or hollow fiber membrane.

[0011] Furthermore, in step (1), the average pore size of the porous titanium film material is 0.1 to 10 μm, preferably 1.0 to 4.0 μm; the porosity is 20% to 60%, preferably 30% to 50%.

[0012] Furthermore, in step (1), the sandpaper is 200-600 grit sandpaper.

[0013] Furthermore, in step (1), the ultrasound time is 10 to 300 min, preferably 15 to 100 min.

[0014] Furthermore, in step (1), the concentration of the sodium hydroxide solution is 0.5–3.5 mol / L, preferably 0.5–2.5 mol / L, and more preferably 1–2.5 mol / L; the corresponding treatment temperature is 60–100°C, preferably 80–100°C; and the corresponding treatment time is 20–120 min, preferably 60–100 min, and more preferably 60–70 min.

[0015] Furthermore, in step (1), the concentration of the oxalic acid solution is 0.01–2.5 mol / L, preferably 0.1–1.5 mol / L; the corresponding treatment temperature is 60–150°C, preferably 80–100°C; and the corresponding treatment time is 10–150 min, preferably 10–100 min.

[0016] Furthermore, in step (2), the concentration of the sodium hydroxide solution used in the hydrothermal reaction is 5-15 mol / L, preferably 10-14 mol / L; the reaction temperature is 80-240℃, preferably 140-180℃; and the reaction time is 2-48 h, preferably 6-24 h.

[0017] Furthermore, in step (2), the concentration of hydrogen chloride used for acidification is 0.1–3.5 mol / L, preferably 0.4–0.8 mol / L; the acidification time is 5–25 h, preferably 10–14 h; and the acidification temperature is 25–70 °C, preferably 30–55 °C.

[0018] Furthermore, in step (2), the annealing conditions are as follows: the calcination temperature is 200-800℃, preferably 250-650℃; the calcination time is 0.5-10h, preferably 2-5h.

[0019] Furthermore, in step (3), the concentration of hydrogen chloride in the mixed aqueous solution of hydrogen chloride and potassium ferrocyanide is 0.1 to 3.5 mol / L, preferably 1.5 to 2.0 mol / L.

[0020] Furthermore, in step (3), the concentration of potassium ferrocyanide in the mixed aqueous solution of hydrogen chloride and potassium ferrocyanide is 0.1 to 2.5 mol / L, preferably 0.1 to 0.2 mol / L.

[0021] Furthermore, in step (3), the growth is carried out in situ at room temperature for a period of 0.5 to 48 hours, preferably 5 to 24 hours, and more preferably 12 to 24 hours.

[0022] Furthermore, the preparation method of the titanium-based adsorption membrane material is specifically as follows:

[0023] (1) Using titanium-based porous membranes with an average pore size of 0.1–10 μm and a porosity of 20%–60% as the base membrane, pretreatment was performed as follows: First, the base membrane was polished with 200–600 grit sandpaper and then ultrasonically cleaned in acetone for 10–300 min to remove residues. Then, it was immersed in a hot sodium hydroxide solution with a concentration of 0.5–3.5 mol / L at a treatment temperature of 60–100℃ for 20–120 min. After that, it was immersed in an oxalic acid solution with a concentration of 0.01–2.5 mol / L at a treatment temperature of 60–150℃ for 10–150 min. Finally, it was rinsed with deionized water and dried for later use.

[0024] (2) The titanium-based porous membrane pretreated in step (1) is placed in a polytetrafluoroethylene liner containing a sodium hydroxide solution with a concentration of 5-15 mol / L and subjected to hydrothermal reaction in a stainless steel high-pressure reactor. The reaction time is 2-48 h at a reaction temperature of 80-240 °C. After the reaction, the membrane is cooled to room temperature. The product is washed with deionized water, acidified with a hydrogen chloride solution with a concentration of 0.1-3.5 mol / L at 25-70 °C for 5-25 h, washed with deionized water, dried, and then placed in a muffle furnace with a temperature set at 200-800 °C for annealing treatment. The calcination time is 0.5-10 h to prepare a titanium-based porous membrane with in-situ grown titanium dioxide nanowires.

[0025] (3) The titanium-based porous membrane obtained in step (2) is immersed in a mixed aqueous solution of hydrogen chloride with a concentration of 0.1-3.5 mol / L and potassium ferrocyanide with a concentration of 0.1-2.5 mol / L and reacted. Titanium ferrocyanide is obtained by in-situ growth at room temperature for 0.5-48 h. Then it is taken out, washed with deionized water and dried.

[0026] The titanium-based adsorption membrane material prepared by the above method.

[0027] The above-mentioned titanium-based adsorption membrane material is used in the electrochemical removal of cesium ions.

[0028] Furthermore, the application of the titanium-based adsorption membrane material in the electrochemical removal of cesium ions includes the following steps:

[0029] The membrane module is placed in polluted water containing cesium ions, and the membrane module contains the above-mentioned titanium-based adsorption membrane material;

[0030] Adsorption stage: By applying an electric field coupled to the electrochemical adsorption function on the titanium-based adsorption membrane material, the cesium-containing water body is made to pass through the adsorption membrane under the action of a pump. The cesium ions in the water are adsorbed on the membrane material, and the purified permeate is obtained from the other side of the membrane.

[0031] Desorption stage: When the titanium-based adsorption membrane material reaches adsorption saturation, the direction of the electric field is changed, and backwashing liquid is introduced from the original permeation side to desorb the cesium ions adsorbed on the adsorption membrane into the backwashing liquid, thereby realizing the desorption and regeneration of the adsorption membrane.

[0032] Furthermore, the concentration of cesium ions in the polluted water containing cesium ions is 0.01 ppm to 25 ppm.

[0033] Furthermore, during the adsorption stage, the voltage used is -1 to -4V, preferably -2 to -3V; the residence time is 1 to 20 minutes, preferably 5 to 10 minutes.

[0034] Furthermore, during the desorption stage, the voltage used is 1 to 4V, preferably 2 to 4V; the residence time is 1 to 45 minutes, preferably 0.5 to 10 minutes, and more preferably 2 to 5 minutes.

[0035] Furthermore, the backwash solution is a sodium sulfate solution with a concentration of 0.1–10 mol / L, preferably 1–5 mol / L.

[0036] Compared with existing technologies, the present invention has the following advantages and outstanding effects:

[0037] (1) By utilizing the conductivity of titanium-based porous membranes, an integrated coupling of electrochemical adsorption-desorption and membrane filtration technology is achieved by directly applying an electric field. This technology is used for the efficient separation of cesium ions in water and has advantages such as high adsorption efficiency, simple desorption process, high mass transfer efficiency, and real-time separation of purified water.

[0038] (2) The titanium ferrocyanide synthesized based on in-situ grown titanium dioxide nanowires has high bonding stability with the base film, large specific surface area, and many exposed active adsorption sites, which ensures the high stability and high adsorption capacity of the adsorption membrane material.

[0039] This invention is expected to provide a new approach for the development of novel membrane materials, and has broad application prospects in water treatment, especially in the field of nuclear wastewater treatment. Detailed Implementation

[0040] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0041] Example 1

[0042] (1) A plate-type titanium-based porous membrane with a length of 6 cm, a width of 6 cm, and a thickness of 1 cm was used as the base membrane. The average pore size of the base membrane was 2.5 μm and the porosity was 40%. The base membrane was pretreated as follows: First, the base membrane was polished with 350-grit sandpaper and then ultrasonically cleaned in acetone for 20 min to remove residues. Then, it was immersed in a 2.5 mol / L sodium hydroxide solution at a treatment temperature of 90℃ for 60 min. After being taken out and cleaned with deionized water, it was immersed in a 1.2 mol / L oxalic acid solution at a treatment temperature of 90℃ for 90 min. Finally, it was cleaned with deionized water and dried for later use.

[0043] (2) The titanium-based porous membrane pretreated in step (1) was placed in a polytetrafluoroethylene liner containing a sodium hydroxide solution of 13 mol / L and subjected to hydrothermal reaction at 160°C in a stainless steel high-pressure reactor for 24 h. After the reaction, it was cooled to room temperature and washed with deionized water, acidified with 0.5 mol / L hydrogen chloride solution at 50°C for 10 h, washed with deionized water again, dried and placed in a muffle furnace at 600°C for annealing for 2 h to obtain a titanium-based porous membrane with in-situ grown titanium dioxide nanowires.

[0044] (3) The titanium-based porous membrane obtained in step (2) is immersed in a mixed aqueous solution of 1.5 mol / L hydrogen chloride and 0.2 mol / L potassium ferrocyanide and reacted. It is grown in situ at room temperature for 20 h to obtain titanium ferrocyanide. Then it is taken out, washed with deionized water and dried to obtain titanium-based adsorption membrane material.

[0045] Adsorption treatment stage: The membrane module is immersed in simulated nuclear wastewater containing 0.1 mg / L cesium ions. Electrochemical adsorption is achieved by applying an electric field coupled to the titanium-based adsorption membrane material. Under the action of a pump, the cesium-containing water passes through the adsorption membrane, and the cesium ions in the water are adsorbed onto the membrane material. Purified permeate is obtained from the other side of the membrane. The voltage used in this process is -2V, and the residence time is 5 minutes. Desorption stage: When the titanium-based adsorption membrane material reaches adsorption saturation, the direction of the electric field is changed, and simultaneously, a 0.5 mol / L sodium sulfate solution is introduced from the original permeate side as a backwash solution. The cesium ions adsorbed on the adsorption membrane are desorbed into the backwash solution, achieving desorption and regeneration of the adsorption membrane. The voltage used in this process is 2V, and the residence time is 2 minutes.

[0046] Example 2

[0047] (1) A titanium-based porous tubular membrane with an inner diameter of 2 cm, a length of 10 cm, and a wall thickness of 0.5 cm was used as the base membrane. The average pore size of the base membrane was 1.5 μm and the porosity was 45%. The base membrane was pretreated as follows: First, the base membrane was polished with 600-grit sandpaper and then ultrasonically cleaned in acetone for 20 min to remove residues. Then, it was immersed in a 1 mol / L sodium hydroxide solution at a treatment temperature of 100℃ for 70 min. After being taken out and cleaned with deionized water, it was immersed in a 1.0 mol / L oxalic acid solution for 60 min. Finally, it was cleaned with deionized water and dried for later use.

[0048] (2) At a reaction temperature of 150℃, the titanium-based porous membrane pretreated in step (1) was placed in a polytetrafluoroethylene liner containing a sodium hydroxide solution of 14 mol / L and placed in a stainless steel high-pressure reactor for hydrothermal reaction for 24 h. After the reaction, the membrane was cooled to room temperature. The product was washed with deionized water, acidified with a hydrogen chloride solution of 0.5 mol / L at 30℃ for 14 h, washed with deionized water, dried, and then placed in a muffle furnace at a temperature of 700℃ for annealing treatment for 2 h. The titanium-based porous membrane with in-situ grown titanium dioxide nanowires was thus prepared.

[0049] (3) The titanium-based porous membrane obtained in step (2) is immersed in a mixed aqueous solution of 1.8 mol / L hydrogen chloride and 0.15 mol / L potassium ferrocyanide and reacted. It is grown in situ for 24 h to obtain titanium ferrocyanide. Then it is taken out, washed with deionized water and dried to obtain titanium-based adsorption membrane material.

[0050] Adsorption treatment stage: The membrane module is immersed in simulated seawater containing 0.5 mg / L cesium ions. Electrochemical adsorption is achieved by applying an electric field coupled to the titanium-based adsorption membrane material. Under the action of a pump, the cesium-containing water passes through the adsorption membrane, and the cesium ions in the water are adsorbed onto the membrane material. The purified permeate is obtained from the other side of the membrane. The voltage used in this process is -2.5 V, and the residence time is 6 min. Desorption stage: When the titanium-based adsorption membrane material reaches adsorption saturation, the direction of the electric field is changed, and simultaneously, a 0.5 mol / L sodium sulfate solution is introduced from the original permeate side as a backwash solution. The cesium ions adsorbed on the adsorption membrane are desorbed into the backwash solution, achieving desorption and regeneration of the adsorption membrane. The voltage used in this process is 2.5 V, and the residence time is 3 min.

[0051] Example 3

[0052] (1) A 6cm long titanium-based porous hollow fiber membrane was used as the base membrane, with an average pore size of 1.0μm and a porosity of 50%. Pretreatment was performed as follows: First, the base membrane was polished with 350-grit sandpaper and then ultrasonically cleaned in acetone for 30 minutes to remove residues. Next, it was immersed in a 1.3mol / L sodium hydroxide solution at 95℃ for 60 minutes, and then immersed in a 0.1mol / L oxalic acid solution for 10 minutes. Finally, it was rinsed with deionized water and dried for later use.

[0053] (2) At a reaction temperature of 170℃, the titanium-based porous membrane pretreated in step (1) was placed in a polytetrafluoroethylene liner containing a sodium hydroxide solution of 12 mol / L and placed in a stainless steel high-pressure reactor for hydrothermal reaction for 20 h. After the reaction, the membrane was cooled to room temperature. The product was washed with deionized water, acidified with a hydrogen chloride solution of 0.6 mol / L at 35℃ for 12 h, washed with deionized water, dried, and then placed in a muffle furnace at a temperature of 500℃ for annealing treatment for 2 h. The titanium-based porous membrane with in-situ grown titanium dioxide nanowires was thus prepared.

[0054] (3) The titanium-based porous membrane obtained in step (2) is immersed in a mixed aqueous solution of 2 mol / L hydrogen chloride and 0.1 mol / L potassium ferrocyanide and reacted. It is grown in situ for 12 h to obtain titanium ferrocyanide. Then it is taken out, washed with deionized water and dried to obtain titanium-based adsorption membrane material.

[0055] Adsorption treatment stage: The membrane module is immersed in simulated salt lake water containing 1 mg / L cesium ions. Electrochemical adsorption is achieved by applying an electric field coupled to the titanium-based adsorption membrane material. Under the action of a pump, the cesium-containing water passes through the adsorption membrane, and the cesium ions in the water are adsorbed onto the membrane material. Purified permeate is obtained from the other side of the membrane. The voltage used in this process is -3V, and the residence time is 5 minutes. Desorption stage: When the titanium-based adsorption membrane material reaches adsorption saturation, the direction of the electric field is changed, and simultaneously, a 1.5 mol / L sodium sulfate solution is introduced from the original permeate side as a backwash solution. The cesium ions adsorbed on the adsorption membrane are desorbed into the backwash solution, achieving desorption and regeneration of the adsorption membrane. The voltage used in this process is 3V, and the residence time is 3 minutes.

[0056] The water treatment performance of the titanium-based adsorption membrane materials prepared in Examples 1-3 is shown in the table below:

[0057]

Claims

1. A method for preparing a titanium-based adsorption membrane material, characterized in that, Includes the following steps: (1) Using titanium-based porous membrane as the base membrane, pretreatment is carried out: First, the titanium-based porous membrane is polished with sandpaper and ultrasonically cleaned in acetone to remove the residue on the membrane; then, it is successively immersed in hot sodium hydroxide solution and oxalic acid solution for treatment; finally, it is washed with deionized water and dried for later use. (2) The titanium-based porous membrane pretreated in step (1) was placed in sodium hydroxide solution for hydrothermal reaction. After the reaction, it was cooled to room temperature and then washed with deionized water, acidified with hydrogen chloride solution, washed with deionized water, dried and placed in a muffle furnace for annealing to prepare a titanium-based porous membrane with in-situ grown titanium dioxide nanowires. (3) The titanium-based porous membrane obtained in step (2) is immersed in a mixed aqueous solution of hydrogen chloride and potassium ferrocyanide to react and grow titanium ferrocyanide in situ. Then it is taken out, washed with deionized water and dried to obtain titanium-based adsorption membrane material.

2. The method for preparing the titanium-based adsorption membrane material according to claim 1, characterized in that: In step (1), the porous titanium membrane has the following configurations: a flat titanium membrane, a tubular titanium membrane, or a hollow fiber titanium membrane, with an average pore size of 0.1~10μm and a porosity of 20%~60%; the sandpaper is 200~600 mesh sandpaper; the ultrasonic time is 10~300 min; the concentration of the sodium hydroxide solution is 0.5~3.5 mol / L, the corresponding treatment temperature is 60~100 ℃, and the treatment time is 20~120 min; the concentration of the oxalic acid solution is 0.01~2.5 mol / L, the corresponding treatment temperature is 60~150 ℃, and the treatment time is 10~150 min.

3. The method for preparing the titanium-based adsorption membrane material according to claim 1, characterized in that, In step (2), the concentration of the sodium hydroxide solution used in the hydrothermal reaction is 5~15 mol / L, the reaction temperature is 80~240 ℃, and the reaction time is 2~48 h; The concentration of hydrogen chloride used for acidification is 0.1~3.5 mol / L, the acidification time is 5~25h, and the acidification temperature is 25~70℃; The annealing process is carried out at a temperature of 200~800℃ for a time of 0.5~10h.

4. The method for preparing the titanium-based adsorption membrane material according to claim 1, characterized in that, In step (3), the hydrogen chloride solution in the mixed aqueous solution of hydrogen chloride and potassium ferrocyanide is 0.1~3.5 mol / L, the potassium ferrocyanide concentration is 0.1~2.5 mol / L, and the in-situ growth time at room temperature is 0.5~48 h.

5. The titanium-based adsorption membrane material prepared by the preparation method according to any one of claims 1-4.

6. The application of the titanium-based adsorption membrane material according to claim 5 in the electrochemical separation of cesium ions.

7. The application according to claim 6, characterized in that, Includes the following steps: The membrane module is placed in wastewater containing cesium ions, and the membrane module contains the titanium-based adsorption membrane material as described in claim 5; Adsorption stage: By applying an electric field coupled to the electrochemical adsorption function on the titanium-based adsorption membrane material, the cesium-containing water body is made to pass through the adsorption membrane under the action of a pump. The cesium ions in the water are adsorbed on the membrane material, and the purified permeate is obtained from the other side of the membrane. Desorption stage: When the titanium-based adsorption membrane material reaches adsorption saturation, the direction of the electric field is changed, and backwash liquid is introduced from the original permeation side to desorb the cesium ions adsorbed on the adsorption membrane into the backwash liquid, thereby realizing the desorption and regeneration of the adsorption membrane. The voltage used in this process is 1~4 V, and the residence time is 1~45 min.

8. The application according to claim 7, characterized in that, During the adsorption stage, the voltage used is -1 to -4 V, and the residence time is 1 to 20 min; during the desorption stage, the voltage used is 1 to 4 V, and the residence time is 1 to 10 min.

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