Highly selective ion-sieve electrode material and method for preparing the same

Abstract

The application belongs to the technical field of electrochemical water treatment, and particularly relates to a high-selectivity ion sieving electrode material and a preparation method thereof. The high-selectivity ion sieving electrode material comprises a functionalized modified carbon base material and amorphous carbon deposited on the surface of the carbon base material. The beneficial effects of the application include: the high-selectivity ion sieving electrode material realizes sub-angstrom precise regulation of the pore size of the carbon molecular sieve by depositing amorphous carbon on the surface of the carbon base material, and in combination with surface directional functionalization modification, constructs an electrode material with a double-mechanism synergy of "physical size sieving + electrostatic specific adsorption", realizes high-selectivity, high-capacity and low-energy-consumption adsorption of target ions (especially SO4 2‑ ) in high-salinity wastewater, and at the same time guarantees long-term cyclic stability of the material, adapts to the needs of industrial large-scale application, and fills the gap in the prior art.

Description

Technical Field

[0001] This application belongs to the field of electrochemical water treatment technology, specifically relating to a highly selective ion sieving electrode material and its preparation method. Background Technology

[0002] With the rapid development of industrial production, the discharge of high-salinity wastewater has been increasing year by year. This type of wastewater usually contains Cl. - SO4 2- Na + Ca 2+ Mg 2+ Various ions, including SO42- 2- It can easily lead to scaling and blockage in heat exchange equipment and pipes. - It can cause pitting corrosion and stress corrosion in stainless steel equipment, which seriously affects production safety and equipment lifespan. Therefore, achieving selective removal of these specific ions is the key to high-salt wastewater treatment.

[0003] Electroadsorption (CDI), also known as capacitive deionization, has become one of the mainstream technologies for treating high-salinity wastewater due to its advantages such as low operating pressure, no chemical reagents required, environmental friendliness, and significantly lower energy consumption compared to traditional desalination processes like reverse osmosis and evaporation. Its core principle involves applying a low-voltage DC electric field across the electrodes, causing charged ions in the water to migrate directionally to the electrode surface and accumulate and adsorb within the electric double layer, thus achieving water desalination. After adsorption saturation, electrode regeneration can be completed by short-circuiting or reversing the electrode connection, eliminating the need for acid or alkali regeneration and simplifying operation.

[0004] However, existing electroadsorption technologies and electrode materials suffer from unresolved core industry pain points, severely limiting their application in the separation of specific ions in high-salinity wastewater. Traditional electroadsorption electrodes are mostly made of ordinary porous carbon materials, relying solely on the electrostatic interaction of the electric double layer to adsorb ions, lacking specific recognition and sieving capabilities. In high-salinity wastewater, when interfering ions (such as C...)... l- The concentration is much higher than that of the target ion (such as SO4). 2- When high concentrations of interfering ions occupy the vast majority of adsorption sites, the adsorption capacity and removal rate of the target ions drop sharply, making selective separation impossible and resulting in low desalination efficiency. Although some selective electrode materials have been reported in the existing technology, they mostly achieve selective adsorption by grafting ion exchange groups onto the electrode surface. However, in high-salt environments, high concentrations of ions in the water will produce a strong charge shielding effect, which will cause the electrostatic selectivity of the ion exchange groups to decrease significantly, making it impossible to play a stable role and meet the requirements of long-term industrial operation.

[0005] Furthermore, existing carbon molecular sieve electrode materials are mostly prepared through physical activation, chemical activation, and other methods. They have a wide pore size distribution and the pore size cannot be precisely controlled at the sub-angstrom level. They cannot accurately match the diameter differences of different hydrated ions, making it difficult to form a stable molecular sieve sieving effect and fundamentally solve the problem of poor selectivity. Moreover, the surface modification layer of existing modified electrodes is not firmly bonded to the substrate and is easily detached during the adsorption-desorption cycle, resulting in rapid loss of selectivity. At the same time, due to the lack of targeted selectivity, repeated adsorption-desorption of total salt in wastewater is required, resulting in high ineffective energy consumption, frequent electrode regeneration, short service life, and high operating costs.

[0006] Therefore, developing an ion sieving electrode material that can maintain high selectivity, high adsorption capacity, and excellent cycling stability under high-salt environments, and whose preparation process is simple and easy to scale up industrially, has become a core technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] This application provides a high-selectivity ion sieving electrode material, its preparation method, and its application, aiming to solve the problems of poor ion selectivity, poor cycle stability, insufficient pore size control precision, and high energy consumption of existing high-selectivity ion sieving electrode materials.

[0008] The first aspect of this application provides a highly selective ion sieving electrode material, comprising a functionalized carbon substrate material and amorphous carbon deposited on the surface of the carbon substrate material.

[0009] According to some embodiments of the high-selectivity ion sieving electrode material described in this application, the carbon substrate material includes one or more of activated carbon fiber, coal-based activated carbon, coconut shell activated carbon, carbon fiber cloth, graphene aerogel, and carbon nanotubes.

[0010] According to some embodiments of the high-selectivity ion sieving electrode material described in this application, the carbon substrate material is activated carbon fiber; as a preferred embodiment, the specific surface area of ​​the activated carbon fiber is 1000-2000 m². 2 / g, fiber diameter is 10-20μm, and average pore size is 2-50nm.

[0011] According to some embodiments of the highly selective ion sieving electrode material described in this application, the functionalized modified carbon substrate material includes a carbon substrate material grafted with cation exchange groups or a carbon substrate material grafted with anion exchange groups.

[0012] According to some embodiments of the highly selective ion sieving electrode material described in this application, the anion exchange group includes quaternary ammonium groups and / or tertiary amine groups.

[0013] According to some embodiments of the highly selective ion sieving electrode material described in this application, the cation exchange groups include sulfonic acid groups and / or carboxyl groups.

[0014] According to some embodiments of the high-selectivity ion sieving electrode material described in this application, the pore size of the high-selectivity ion sieving electrode material is 0.36-0.44 nm.

[0015] This application also provides a method for preparing the highly selective ion sieving electrode material described in the first aspect of this application, comprising the following steps:

[0016] (1) Depositing amorphous carbon on the surface of a carbon substrate material; (2) The carbon substrate material obtained in step (1) is subjected to anion-selective functionalization or cationic-selective functionalization. (3) The functionalized carbon substrate material is subjected to thermal stabilization treatment to obtain the high-selectivity ion sieving electrode material.

[0017] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, in step (1), amorphous carbon is deposited on the surface of the carbon substrate material by CVD vapor deposition.

[0018] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the gas introduced during the vapor deposition of amorphous carbon includes a carrier gas and a carbon source, wherein the volume concentration of the carbon source is 0.5%-2%.

[0019] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the carrier gas includes nitrogen, and the carbon source includes one or more of benzene vapor, toluene, methane, and acetylene.

[0020] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, in step (1), the flow rate of the gas introduced during the vapor deposition of amorphous carbon is 100-200 mL / min.

[0021] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the vapor deposition temperature is 600-800℃ and the time is 10-60min.

[0022] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the operation steps of the anion-selective functionalization modification include: mixing and reacting the carbon substrate material obtained in step (1) with a solution containing anion exchange groups, and then washing and drying.

[0023] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the solvent of the solution containing anion exchange groups includes ethanol and / or dimethyl sulfoxide.

[0024] According to some embodiments of the preparation method of the highly selective ion sieving electrode material described in this application, the solute of the solution containing anion exchange groups includes 3-chloro-2-hydroxypropyltrimethylammonium chloride and / or N,N-dimethylethanolamine.

[0025] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the mass concentration of the solution containing anion exchange groups is 3%-5%.

[0026] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the mass-to-volume ratio of the carbon substrate material obtained in step (1) to the solution containing anion exchange groups is 1 g: (20-50 mL).

[0027] According to some embodiments of the preparation method of the highly selective ion sieving electrode material described in this application, the temperature of the mixing reaction is 60-80℃ and the time is 4-8h.

[0028] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the operation steps of the cation selective functionalization modification include: mixing the carbon substrate material obtained in step (1) with a solution containing cation exchange groups and reacting them. After the reaction is completed, solidification and oxidation treatments are performed in sequence.

[0029] According to some embodiments of the preparation method of the highly selective ion sieving electrode material described in this application, the solvent of the solution containing cation exchange groups includes ethanol and / or tetrahydrofuran.

[0030] According to some embodiments of the preparation method of the highly selective ion sieving electrode material described in this application, the solute of the solution containing cation exchange groups includes 3-mercaptopropyltrimethoxysilane and / or acrylic acid.

[0031] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the mass concentration of the solution containing cation exchange groups is 2%-4%.

[0032] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the mass-to-volume ratio of the carbon substrate material obtained in step (1) to the solution containing cation exchange groups is 1 g: (25-60 mL).

[0033] According to some embodiments of the preparation method of the highly selective ion sieving electrode material described in this application, the temperature of the mixing reaction is 20-30°C and the time is 12-24h.

[0034] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the curing temperature is 100-150℃ and the time is 1-3h.

[0035] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, the oxidation treatment includes mixing the cured product with a hydrogen peroxide solution to convert thiol groups into sulfonic acid cation exchange groups; more preferably, the mass concentration of the hydrogen peroxide solution is 25%-35%.

[0036] According to some embodiments of the preparation method of the high-selectivity ion sieving electrode material described in this application, in step (3), the temperature of the thermal stabilization treatment is 300-500℃ and the time is 1-3h.

[0037] The third aspect of this application provides an application of the high-selectivity ion sieving electrode material described in the first aspect of this application or the high-selectivity ion sieving electrode material obtained by the preparation method described in the second aspect of this application in ion selective separation.

[0038] According to some embodiments of the application described in this application, the ion selective separation includes SO4. 2- With Cl - Selective separation.

[0039] The beneficial effects of this application include: the highly selective ion sieving electrode material described in this application achieves sub-angstrom level precise control of the pore size of carbon molecular sieves by depositing amorphous carbon on the surface of a carbon substrate material. Combined with surface-oriented functionalization modification, it constructs an electrode material with a synergistic dual mechanism of "physical size sieving + electrostatic specific adsorption," enabling the targeting of ions (especially SO42-) in high-salt wastewater. 2- It features high selectivity, high capacity, and low energy consumption adsorption, while ensuring the long-term cycle stability of the material, meeting the needs of large-scale industrial applications and filling the gap in existing technologies. Detailed Implementation

[0040] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0041] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0042] This application provides a highly selective ion sieving electrode material, comprising a functionalized carbon substrate material and amorphous carbon deposited on the surface of the carbon substrate material.

[0043] The highly selective ion sieving electrode material described in this application achieves sub-angstrom level precise control of the pore size of carbon molecular sieves by depositing amorphous carbon on the surface of a carbon substrate. Combined with surface-oriented functionalization modification, it constructs an electrode material with a synergistic dual mechanism of "physical size sieving + electrostatic specific adsorption," enabling the targeting of target ions (especially SO42-) in high-salinity wastewater. 2- It features high selectivity, high capacity, and low energy consumption adsorption, while ensuring the long-term cycle stability of the material, meeting the needs of large-scale industrial applications and filling the gap in existing technologies.

[0044] In some embodiments of this application, the carbon substrate material includes one or more of activated carbon fibers, coal-based activated carbon, coconut shell activated carbon, carbon fiber cloth, graphene aerogel, and carbon nanotubes. The carbon substrate material has a gradient pore structure of "internal mesoporous-macroporous mass transfer channels + surface microporous sieve layering," and possesses a tunable pore structure.

[0045] In some embodiments of this application, the carbon substrate material is activated carbon fiber; more preferably, the specific surface area of ​​the activated carbon fiber is 1000-2000 m². 2 The fiber diameter is 10-20 μm (e.g., 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.), with an average pore size of 2-50 nm. Controlling the average pore size within this range ensures sufficient space for subsequent pore structure regulation. The mesoporous-macroporous interconnected structure inside the carbon substrate provides a rapid mass transfer channel for ions, significantly reducing ion diffusion resistance and improving adsorption rate and adsorption capacity. Simultaneously, the micropores on the surface are only distributed on the outer surface of the material, avoiding ion retention within the micropores, improving electrode regeneration efficiency, and reducing desorption energy consumption.

[0046] In some embodiments of this application, the functionalized carbon substrate material includes a carbon substrate material grafted with cation exchange groups or a carbon substrate material grafted with anion exchange groups. In practice, the surface of the carbon substrate material can be functionalized according to the charge properties of the target ion, selectively introducing ion exchange groups to enhance the electrostatic adsorption capacity for the target ion.

[0047] In some embodiments of this application, the anion exchange group includes a quaternary ammonium group and / or a tertiary amine group; the anion exchange group may be targeted at SO4. 2- Anions are electrostatically adsorbed.

[0048] In some embodiments of this application, the cation exchange group includes a sulfonic acid group and / or a carboxyl group. The cation exchange group may target Ca... 2+ Mg 2+ Cations are electrostatically adsorbed.

[0049] In some embodiments of this application, the pore size of the highly selective ion sieving electrode material is 0.36-0.44 nm, such as 0.36 nm, 0.38 nm, 0.40 nm, 0.43 nm, 0.44 nm, etc. The pore size is controlled by depositing amorphous carbon on the surface of the carbon substrate material. The pore size of the highly selective ion sieving electrode material is determined based on the difference in hydration kinetic diameter between the target ion and interfering ions, achieving ion sieving and separation at a physical level and fundamentally avoiding competitive adsorption problems. For example, Cl... - The hydrated diameter is approximately 0.36 nm, SO4 2- With a hydrated diameter of approximately 0.44 nm, the pore size of the high-selectivity ion sieving electrode material is designed to be between 0.36 and 0.44 nm, thus allowing for the absorption of smaller Cl- molecules. - It can freely pass through the orifice into the interior of the material, while larger SO4 particles... 2- Adsorption sites trapped on the surface of the pore.

[0050] This application also provides a method for preparing the highly selective ion sieving electrode material described in the first aspect of this application, comprising the following steps: (1) Depositing amorphous carbon on the surface of a carbon substrate material; (2) The carbon substrate material obtained in step (1) is subjected to anion-selective functionalization or cationic-selective functionalization. (3) The functionalized carbon substrate material is subjected to thermal stabilization treatment to obtain the high-selectivity ion sieving electrode material.

[0051] The high-selectivity ion sieving electrode material described in this application achieves precise sub-angstrom level control of the pore size of carbon molecular sieves by depositing amorphous carbon on the surface of a carbon substrate material. Combined with surface-oriented functionalization modification, it constructs an electrode material with a dual mechanism of "physical size sieving + electrostatic specific adsorption", which achieves high selectivity, high capacity and low energy consumption adsorption of target ions in high-salt wastewater, while ensuring the long-term cycle stability of the material.

[0052] The high-selectivity ion sieving electrode material described in this application does not require complex equipment, the CVD deposition and functionalization modification process parameters are controllable, the batch stability is good, and it can achieve large-scale continuous production, making it suitable for large-scale industrial applications.

[0053] In some embodiments of this application, in step (1), amorphous carbon is deposited on the surface of a carbon substrate material using CVD vapor deposition. Because the amorphous carbon layer deposited by CVD is homogeneously bonded to the carbon matrix, there is no risk of detachment; the grafted groups after high-temperature heat treatment are firmly bonded, and after 50 consecutive adsorption-desorption cycles, the selectivity retention rate of the material can exceed 95%, the adsorption capacity retention rate can exceed 92%, and the long-term operating performance is stable, eliminating the need for frequent electrode replacement and further reducing maintenance costs.

[0054] In some embodiments of this application, the gas introduced during the vapor deposition of amorphous carbon includes a carrier gas and a carbon source, wherein the volume concentration of the carbon source is 0.5%-2%, such as 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 2%, etc. Controlling the volume concentration of the carbon source within this range can achieve gentle, controllable, and uniform deposition of amorphous carbon at the micropore openings of the carbon substrate, accurately complete sub-angstrom pore size control, and ensure the ion sieving performance and stability of the electrode material.

[0055] In some embodiments of this application, the carrier gas includes nitrogen, and the carbon source includes one or more of benzene vapor, toluene, methane, and acetylene.

[0056] In some embodiments of this application, in step (1), the flow rate of the gas introduced during the vapor deposition of amorphous carbon is 100-200 mL / min; for example, 100 mL / min, 120 mL / min, 150 mL / min, 180 mL / min, 200 mL / min, etc.

[0057] In some embodiments of this application, the temperature of the vapor deposition is 600-800℃, such as 600℃, 680℃, 700℃, 720℃, 750℃, 800℃, etc., and the time is 10-60min, such as 10min, 15min, 20min, 28min, 32min, 37min, 43min, 55min, 60min, etc.

[0058] In some embodiments of this application, before depositing amorphous carbon on the surface of the carbon substrate material, the carbon substrate material is first ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15-30 minutes each to thoroughly remove surface oil, impurities, and soluble ash. After cleaning, it is placed in a vacuum drying oven and dried at 105-120°C for 12-24 hours for later use.

[0059] In some embodiments of this application, the specific steps for depositing amorphous carbon include: spreading the carbon substrate material flat in the middle of the quartz tube of the tubular CVD furnace, purging with high-purity nitrogen for 30 minutes to completely remove the air in the furnace and prevent the substrate material from being oxidized at high temperatures, then heating to 600-800°C at a heating rate of 10-15°C / min, and depositing after the temperature in the furnace is uniform. After the deposition is completed, the benzene vapor is stopped, the protective gas (high-purity nitrogen) is kept flowing continuously, and the furnace body is allowed to cool naturally to room temperature to obtain a carbon molecular sieve matrix with precisely controlled pore size.

[0060] In some embodiments of this application, the steps of the anion-selective functionalization modification include: mixing and reacting the carbon substrate material obtained in step (1) with a solution containing anion exchange groups, followed by washing and drying. The anion exchange groups are grafted onto the pores of the carbon substrate surface. After the reaction is complete, the substrate is repeatedly rinsed with anhydrous ethanol and deionized water until no free chloride ions are detected in the washing solution. Then, it is vacuum dried at 80°C for 12 hours to remove residual reagents. The surface functionalization groups selected in this application can be replaced with tertiary amine groups, amino groups, crown ethers, or other groups with specific recognition functions, depending on the type of target ion, to meet the selective separation requirements of different ions.

[0061] Ion-exchange groups grafted onto the surface of carbon-based materials generate specific electrostatic interactions with target ions, such as quaternary ammonium groups on divalent SO4. 2- Its adsorption affinity is much higher than that of monovalent Cl. - This further enhances the selective adsorption of target ions, maintaining stable selectivity even under the charge shielding effect in high-salt environments.

[0062] In some embodiments of this application, the solvent of the solution containing anion exchange groups includes ethanol and / or dimethyl sulfoxide.

[0063] In some embodiments of this application, the solute in the solution containing anion exchange groups includes 3-chloro-2-hydroxypropyltrimethylammonium chloride and / or N,N-dimethylethanolamine.

[0064] In some embodiments of this application, the mass concentration of the solution containing anion exchange groups is 3%-5%; for example, 3%, 4%, 5%, etc.

[0065] In some embodiments of this application, the mass-to-volume ratio of the carbon substrate material obtained in step (1) to the solution containing anion exchange groups is 1 g: (20-50 mL).

[0066] In some embodiments of this application, the temperature of the mixing reaction is 60-80°C, such as 60°C, 68°C, 70°C, 75°C, 80°C, etc., and the time is 4-8h, such as 4h, 5h, 6h, 8h, etc.

[0067] In some embodiments of this application, the steps of the cation-selective functionalization modification include: mixing the carbon substrate material obtained in step (1) with a solution containing cation exchange groups for reaction; after the reaction is complete, performing curing and oxidation treatments sequentially. The method also includes rinsing the oxidized material with deionized water until the rinsing solution is neutral, and then vacuum drying at 80°C for 12 hours.

[0068] In some embodiments of this application, the solvent of the solution containing cation exchange groups includes ethanol and / or tetrahydrofuran.

[0069] In some embodiments of this application, the solute of the solution containing cation exchange groups includes 3-mercaptopropyltrimethoxysilane and / or acrylic acid.

[0070] In some embodiments of this application, the mass concentration of the solution containing cation exchange groups is 2%-4%; for example, 2%, 2.8%, 3%, 3.8%, 4%, etc.

[0071] In some embodiments of this application, the mass-to-volume ratio of the carbon substrate material obtained in step (1) to the solution containing cation exchange groups is 1 g: (25-60 mL).

[0072] In some embodiments of this application, the temperature of the mixing reaction is 20-30°C, such as 20°C, 23°C, 28°C, 30°C, etc., and the time is 12-24h, such as 12h, 15h, 18h, 20h, 24h, etc.

[0073] In some embodiments of this application, the curing temperature is 100-150℃, such as 100℃, 110℃, 125℃, 130℃, 138℃, 150℃, etc., and the time is 1-3h; such as 1h, 2h, 3h, etc.

[0074] In some embodiments of this application, the oxidation treatment includes mixing the cured product with a hydrogen peroxide solution to convert thiol groups into sulfonic acid cation exchange groups; more preferably, the mass concentration of the hydrogen peroxide solution is 25%-35%; for example, 25%, 28%, 30%, 32%, 35%, etc.

[0075] In some embodiments of this application, in step (3), the temperature of the thermal stabilization treatment is 300-500℃, such as 300℃, 350℃, 380℃, 430℃, 500℃, etc., and the time is 1-3h, such as 1h, 2h, 3h, etc. Thermal stabilization treatment can remove residual organic reagents from the material surface, strengthen the bonding force between the grafted groups and the carbon matrix, and simultaneously eliminate the internal stress of the CVD-deposited carbon layer, thereby improving the mechanical strength and electrochemical stability of the material.

[0076] This application also provides an application of the high-selectivity ion sieving electrode material described in the first aspect of this application or the high-selectivity ion sieving electrode material obtained by the preparation method described in the second aspect of this application in ion selective separation. The high-selectivity ion sieving electrode material described in this application is adaptable to various electroadsorption processes such as asymmetric electroadsorption (MCDI) and flow electrode electroadsorption (FCDI); it can be applied to high-salt industrial wastewater treatment scenarios in coal chemical, petrochemical, metallurgical, mining, and printing and dyeing industries, and is also suitable for lithium extraction from salt lakes, pre-desalination of seawater desalination, and resource recovery and utilization of industrial wastewater, possessing extremely strong industrial application value.

[0077] In some embodiments of this application, the ion selective separation includes SO4. 2- With Cl - Selective separation. The highly selective ion sieving electrode material described in this application achieves selective separation in Cl... - With SO4 2- In high-salinity wastewater with a concentration ratio of 20:1, SO4 2- / Cl - With a selectivity ratio ≥2.5, it completely solves the industry pain point of ion competitive adsorption in high-salt environments, achieving SO4… 2- Its precise and selective removal fully meets the requirements for selective separation of specific ions in high-salt wastewater.

[0078] Because the high-selectivity ion sieving electrode material described in this application selectively adsorbs target ions, there is no need to repeatedly adsorb and desorb the total salt content in the wastewater. The electrode regeneration frequency is reduced by more than 60%. Compared with traditional electroadsorption technology, the energy consumption per ton of water treated is reduced by more than 40%, and can be reduced to as low as 2.8 kW•h / t, which greatly reduces the cost of industrial operation.

[0079] The technical solution of this application will be further described below with reference to specific embodiments.

[0080] Example 1 A method for preparing a highly selective ion sieving electrode material includes the following steps: (1) With a specific surface area of ​​1500 m² 2 / g, using commercial activated carbon fiber with a fiber diameter of 15μm and an average pore size of 10nm as the base material, cut into 10cm×10cm sheets, the above base material was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 20min each. After cleaning, it was placed in a vacuum drying oven and dried at 110℃ for 20h to remove moisture and set aside for later use. (2) The pretreated activated carbon fibers were laid flat in the middle of the quartz tube of the tube CVD furnace, and high-purity nitrogen (purity ≥99.999%) was introduced. The gas flow rate was controlled at 150 mL / min. The furnace was purged for 30 min to completely remove the air in the furnace and avoid oxidation of the substrate material at high temperature. Then the furnace body was heated to 750℃ at a heating rate of 10℃ / min and kept constant for 30 min to make the temperature in the furnace uniform. Then nitrogen was used as a carrier gas to carry benzene vapor into the reaction chamber of the quartz tube. The volume concentration of benzene vapor was 1%, and the deposition time was 30 min. Benzene molecules were decomposed into amorphous carbon at high temperature and preferentially deposited at the micropore openings of the activated carbon fibers. After the deposition was completed, the benzene vapor was stopped and nitrogen was continuously introduced. The furnace body was naturally cooled to room temperature to obtain a carbon molecular sieve matrix with a pore size of 0.36-0.44 nm. (3) The above carbon molecular sieve matrix was immersed in a 4% (w / w) 3-chloro-2-hydroxypropyltrimethylammonium chloride ethanol solution (wherein the mass-volume ratio of the carbon molecular sieve matrix to the 3-chloro-2-hydroxypropyltrimethylammonium chloride ethanol solution was 1 g: 30 ml) and stirred in a water bath at 70°C for 6 h. After the reaction was completed, it was repeatedly rinsed with anhydrous ethanol and deionized water until no chloride ions were detected. It was then vacuum dried at 80°C for 12 h to obtain a carbon molecular sieve matrix grafted with quaternary ammonium groups. (4) The material obtained in step (3) is placed in a tube furnace and heated to 400°C at 5°C / min under nitrogen protection. It is then kept at a constant temperature for 2 hours and cooled to obtain the high-selectivity ion sieving electrode material.

[0081] Example 2 The only difference between the preparation method of the high-selectivity ion sieving electrode material in Example 2 and that in Example 1 is that, in the preparation process of the high-selectivity ion sieving electrode material in Example 2, cation exchange groups are used to modify the activated carbon fiber substrate material.

[0082] The specific operating steps include: (3) The above carbon molecular sieve matrix was immersed in an ethanol solution of 3-mercaptopropyltrimethoxysilane with a mass concentration of 4% (wherein the mass-volume ratio of carbon molecular sieve matrix and ethanol solution of 3-mercaptopropyltrimethoxysilane is 1g:40mL), stirred at 25°C for 15h, then solidified at 120°C for 2h, and then oxidized by soaking in a 30% hydrogen peroxide solution for 12h to convert the mercapto group (-SH) into a sulfonic acid group (-SO3H) cation exchange group. After the reaction was completed, it was rinsed with deionized water until neutral, and then vacuum dried at 80°C for 12h to obtain a carbon molecular matrix grafted with sulfonic acid groups. The remaining operation steps were the same as in Example 1.

[0083] Example 3 The only difference between the preparation method of the high-selectivity ion sieving electrode material in Example 3 and that in Example 1 is that the deposition time of amorphous carbon on activated carbon fiber during the preparation process of the high-selectivity ion sieving electrode material in Example 3 is 40 min.

[0084] Example 4 The only difference between the preparation method of the high-selectivity ion sieving electrode material in Example 4 and that in Example 1 is that the time for depositing amorphous carbon on activated carbon fiber during the preparation of the high-selectivity ion sieving electrode material in Example 4 is 50 min.

[0085] Example 5 The only difference between the preparation method of the high-selectivity ion sieving electrode material in Example 5 and that in Example 1 is that the deposition time of amorphous carbon on activated carbon fiber during the preparation process of the high-selectivity ion sieving electrode material in Example 5 is 60 min.

[0086] Example 6 The only difference between the preparation method of the high-selectivity ion sieving electrode material described in Example 6 and Example 1 is that the volume concentration of benzene vapor in the carrier gas and benzene vapor mixture introduced during the deposition of amorphous carbon on activated carbon fiber in the preparation process of the high-selectivity ion sieving electrode material described in Example 6 is 1.2%.

[0087] Example 7 The only difference between the preparation method of the high-selectivity ion sieving electrode material described in Example 7 and Example 1 is that the volume concentration of benzene vapor in the carrier gas and benzene vapor mixture introduced during the deposition of amorphous carbon on activated carbon fiber in the preparation process of the high-selectivity ion sieving electrode material described in Example 7 is 1.5%.

[0088] Example 8 The only difference between the preparation method of the high-selectivity ion sieving electrode material described in Example 8 and Example 1 is that the volume concentration of benzene vapor in the carrier gas and benzene vapor mixture introduced during the deposition of amorphous carbon on activated carbon fiber in the preparation process of the high-selectivity ion sieving electrode material described in Example 8 is 2.0%.

[0089] Performance Study of the High Selectivity Ion Sieving Electrode Materials Described in Examples 1-8 of this Application Research Methods: The high-selectivity ion sieving electrode material described in Examples 1-8 of this application and the activated carbon fiber (the carbon substrate material described in Example 1) were ground to below 200 mesh. The electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) was added and stirred to prepare a uniform slurry. The slurry was uniformly coated on a graphite current collector with a coating thickness of 100 μm. After vacuum drying at 60°C for 24 h, the slurry was pressed into a sheet to obtain an electrode sheet for electroadsorption. The electrode sheet was directly assembled into an electroadsorption module for selective removal testing of specific ions in high-salt wastewater.

[0090] Simulated wastewater preparation: Cl - Concentration 2000 mg / L, SO4 2- Concentration 100 mg / L, Cl - SO4 2- Concentration ratio = 20:1, total dissolved solids (TDS) approximately 3500 mg / L, pH = 7.0 ± 0.2; Electroadsorption testing apparatus: Electrode cathodes prepared in Examples 1 and 3-8 were combined with the electrode anode prepared in Example 2 to form a high-selectivity electroadsorption module. An electrode made of activated carbon fiber material was used as the cathode to prepare a conventional electroadsorption module, labeled as Comparative Example 1. The electrode size was 5cm × 5cm, the electrode spacing was 1mm, a DC voltage of 1.2V was applied, the adsorption time was 120min, and desorption was performed using short-circuit discharge for 30min.

[0091] Ion concentration detection: SO4²⁻ in the water before and after adsorption was detected using an ion chromatograph (ICS-600, Thermo Fisher Scientific). - Concentration, Cl - Concentration, Ca 2+ Concentration, calculated using the following formula for SO4 2- / Cl - Choose the ratio coefficient, Ca 2+ Removal rate.

[0092] SO4 2- / Cl - Selection ratio coefficient = (SO4) 2- Adsorption capacity / initial SO4 2- Concentration) / (Cl)- Adsorption capacity / initial Cl - (Concentration), the results are shown in Table 1.

[0093] Ca 2+ Removal rate = Ca 2+ Adsorption amount / initial Ca 2+ The concentrations and results are shown in Table 1.

[0094] Cyclic stability test: 50 adsorption-desorption cycles were performed continuously according to the above experimental procedure. The selectivity and adsorption capacity were tested after each cycle, and the retention rate was calculated. The results are shown in Table 1.

[0095] The formula for calculating the selective retention rate is: (SO4 after the 50th cycle) 2- / Cl - Choose the ratio coefficient ÷ SO4 of the first cycle 2- / Cl - Choose a ratio factor) × 100%.

[0096] The formula for calculating the adsorption capacity retention rate is: (SO4 after the 50th cycle) 2- Adsorption amount ÷ SO4 in the first cycle 2- (Adsorption capacity) × 100%.

[0097] Table 1

[0098] As can be seen from Table 1, the highly selective ion sieving electrode material described in this application exhibits high selectivity in Cl... - With SO4² - In simulated high-salinity wastewater with a concentration ratio of 20:1, SO4²⁻ - / Cl - The selection ratio can reach 2.3-3.0, significantly higher than 0.8 in Comparative Example 1, for SO4²⁻ - It exhibits excellent selective adsorption capacity for Ca²⁺; + The removal rate was 88.3%-92.1%, significantly higher than the 65.4% of Comparative Example 1, demonstrating outstanding cation separation performance. However, under conditions of deposition time of 30-40 min and carbon source vapor volume concentration of 1%-1.2%, the prepared high-selectivity ion sieving electrode material for the cathode showed limited effectiveness in separating SO4²⁻. - It has better selective adsorption performance.

[0099] After 50 adsorption-desorption cycles, the selectivity retention rate of the electrode material was 92.6%-96.5%, and the adsorption capacity retention rate was 88.5%-93.2%, demonstrating significantly better cycle stability than traditional activated carbon electrodes. In summary, the electrode material of this application combines high selectivity, high adsorption capacity, and excellent cycle stability, meeting the industrial application requirements for selective ion separation in high-salt wastewater.

[0100] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A highly selective ion sieving electrode material, characterized in that, This includes functionalized carbon substrate materials and amorphous carbon deposited on the surface of carbon substrate materials.

2. The high-selectivity ion sieving electrode material according to claim 1, characterized in that, The carbon substrate material includes one or more of the following: activated carbon fiber, coal-based activated carbon, coconut shell activated carbon, carbon fiber cloth, graphene aerogel, and carbon nanotubes. Preferably, the carbon substrate material is activated carbon fiber; more preferably, the specific surface area of ​​the activated carbon fiber is 1000-2000 m². 2 / g, fiber diameter is 10-20μm, and average pore size is 2-50nm.

3. The high-selectivity ion sieving electrode material according to claim 1, characterized in that, The functionalized carbon substrate material includes a carbon substrate material grafted with cation exchange groups or a carbon substrate material grafted with anion exchange groups. Preferably, the anion exchange group comprises a quaternary ammonium group and / or a tertiary amine group; Preferably, the cation exchange group includes a sulfonic acid group and / or a carboxyl group.

4. The high-selectivity ion sieving electrode material according to claim 1, characterized in that, The pore size of the highly selective ion sieving electrode material is 0.36-0.44 nm.

5. The method for preparing the highly selective ion sieving electrode material according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Depositing amorphous carbon on the surface of a carbon substrate material; (2) The carbon substrate material obtained in step (1) is subjected to anion-selective functionalization or cationic-selective functionalization. (3) The functionalized carbon substrate material is subjected to thermal stabilization treatment to obtain the high-selectivity ion sieving electrode material.

6. The method for preparing the highly selective ion sieving electrode material according to claim 5, characterized in that, In step (1), amorphous carbon is deposited on the surface of the carbon substrate material using CVD vapor deposition. Preferably, the gas introduced during the vapor deposition of amorphous carbon includes a carrier gas and a carbon source, wherein the volume concentration of the carbon source is 0.5%-2%; Preferably, the carrier gas includes nitrogen, and the carbon source includes one or more of benzene vapor, toluene, methane, and acetylene.

7. The method for preparing the highly selective ion sieving electrode material according to claim 6, characterized in that, In step (1), the flow rate of the gas introduced during the vapor deposition of amorphous carbon is 100-200 mL / min; And / or, the temperature of the vapor deposition is 600-800℃ and the time is 10-60 min.

8. The method for preparing the highly selective ion sieving electrode material according to claim 5, characterized in that, The steps of the anion-selective functionalization modification include: mixing and reacting the carbon substrate material obtained in step (1) with a solution containing anion exchange groups, followed by washing and drying; Preferably, the solvent of the solution containing anion exchange groups includes ethanol and / or dimethyl sulfoxide; Preferably, the solute in the solution containing anion exchange groups includes 3-chloro-2-hydroxypropyltrimethylammonium chloride and / or N,N-dimethylethanolamine; Preferably, the mass concentration of the solution containing anion exchange groups is 3%-5%; Preferably, the mass-to-volume ratio of the carbon substrate material obtained in step (1) to the solution containing anion exchange groups is 1 g: (20-50 mL). Preferably, the mixing reaction is carried out at a temperature of 60-80°C for 4-8 hours.

9. The method for preparing the highly selective ion sieving electrode material according to claim 5, characterized in that, The steps of the cation-selective functionalization modification include: mixing the carbon substrate material obtained in step (1) with a solution containing cation exchange groups and reacting them; after the reaction is completed, solidification and oxidation treatments are carried out in sequence. Preferably, the solvent of the solution containing cation exchange groups includes ethanol and / or tetrahydrofuran; Preferably, the solute in the solution containing cation exchange groups includes 3-mercaptopropyltrimethoxysilane and / or acrylic acid; Preferably, the mass concentration of the solution containing cation exchange groups is 2%-4%; Preferably, the mass-to-volume ratio of the carbon substrate material obtained in step (1) to the solution containing cation exchange groups is 1 g: (25-60 mL). Preferably, the mixing reaction is carried out at a temperature of 20-30°C for 12-24 hours. Preferably, the curing temperature is 100-150℃ and the time is 1-3 hours; Preferably, the oxidation treatment includes mixing the cured product with a hydrogen peroxide solution to convert thiol groups into sulfonic acid cation exchange groups; more preferably, the mass concentration of the hydrogen peroxide solution is 25%-35%. And / or, in step (3), the temperature of the heat stabilization treatment is 300-500℃ and the time is 1-3h.

10. The application of the high-selectivity ion sieving electrode material according to any one of claims 1-4 or the high-selectivity ion sieving electrode material obtained by the preparation method according to any one of claims 5-9 in ion selective separation; Preferably, the ion selective separation includes SO4. 2- With Cl - Selective separation.

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