Carrier composite membrane for low-concentration F- / Cl-separation as well as preparation method and application of carrier composite membrane

Abstract

The invention discloses a carrier composite membrane for low-concentration F- / Cl-separation and a preparation method and application thereof, and belongs to the technical field of separation membranes, the preparation method of the carrier composite membrane comprises the following steps: S1, dissolving a polymer substrate in an organic solvent to obtain a solution A; s2, adding a carrier and a plasticizer into the solution A, and mixing and stirring to obtain a solution B; s3, the solution B is poured into a membrane casting plate, the organic solvent is volatilized, and the carrier composite membrane is obtained. The carrier composite membrane is integrated into a flowing electrode electro-adsorption system, preferential removal of a low-concentration mixed solution containing fluorine ions (fluorine ions) and chloride ions (chlorine ions) is achieved, the selective permeability is remarkably improved (the separation coefficient is increased to 3.2), and the technology has the advantages of being low in energy consumption, free of secondary pollution, suitable for low-concentration treatment and the like and has a wide application prospect. The method is especially suitable for green treatment of fluorine-containing underground water and application requirements of small and medium-sized enterprises.

Description

Technical Field

[0001] This invention relates to the field of separation membrane technology, and in particular to a membrane for low concentrations. / Separated carrier composite membranes, their preparation methods, and applications. Background Technology

[0002] Fluoride ions ( Fluoride is widely present in groundwater and industrial wastewater. Excessive intake can lead to health problems such as dental fluorosis and skeletal fluorosis. Therefore, there is an urgent need for an efficient and safe fluoride removal technology. Existing fluoride removal methods mainly include precipitation, ion exchange, and adsorption, but all of them have obvious technical bottlenecks: (1) Precipitation relies on chemical reactions to generate precipitates such as calcium fluoride, which easily produces a large amount of sludge. The treatment process is cumbersome and there is a risk of secondary pollution; (2) Ion exchange has poor selectivity in multi-ion systems and is easily affected by ion exchange. The competitive interference of coexisting anions, and the need for frequent regeneration of the exchange resin, resulting in high operating costs; (3) the metal oxides or activated carbon adsorbents commonly used in adsorption methods have limited adsorption capacity and are difficult to regenerate; (4) although electro-driven membrane methods (such as electrodialysis) have continuous operation capabilities, they are limited in treating low concentrations. / Coexistence systems exhibit insufficient selectivity and high energy consumption. Especially in... and In coexisting groundwater systems, because both have the same charge and similar hydration radii, conventional separation methods are insufficient to achieve separation. Selective removal. Therefore, development of methods targeting low concentrations. / High selectivity, high stability, and low energy consumption in defluorination technology have become key directions for current research and engineering applications. Summary of the Invention

[0003] The purpose of this invention is to provide a method for low concentration / Separated carrier composite membranes, their preparation methods, and applications, to address the aforementioned issues. and In coexisting groundwater systems, it is difficult to achieve [the goal of controlling / distributing] water. The problem of selective removal. To address the above problem, this invention prepares a method for selective removal. A carrier-based composite anion exchange membrane with preferential transport capability replaces traditional anion exchange membranes. Combining electric field-driven and membrane interface selective migration mechanisms, it effectively shields... and promote This allows for efficient and precise selective separation through penetration. Furthermore, the system can operate under low salinity conditions, consumes significantly less energy than electrodialysis, and requires no chemical precipitants or adsorbents, making it environmentally friendly and possessing significant engineering application potential.

[0004] To achieve the above object, the first aspect of the present application provides a carrier composite membrane for low-concentration / The preparation method of the separated carrier composite membrane comprises the following steps:

[0005] S1: dissolving a polymer substrate in an organic solvent to obtain solution A;

[0006] S2: adding a carrier and a plasticizer into solution A and mixing to obtain solution B;

[0007] S3: pouring solution B into a casting plate and volatilizing the organic solvent to obtain a carrier composite membrane.

[0008] Preferably, the polymer substrate is cellulose triacetate, the carrier is methyltrioctylammonium chloride, the plasticizer is tributyl phosphate, and the organic solvent is chloroform.

[0009] Preferably, the mass ratio of the polymer substrate, the carrier and the plasticizer is (2-4):(4-6):(1-3).

[0010] Preferably, the mass-volume ratio of the polymer substrate and the organic solvent is (2-4) g:(20-40) mL.

[0011] The composite membrane prepared by the present application is special for low-concentration / The separation of fluoride ions and chloride ions in the mixed solution is more difficult than the separation of metal ions and organic small molecules in the prior art, mainly because the physical and chemical properties of metal ions and organic small molecules are quite different, and the separation is relatively simple, while the charge of fluoride ions and chloride ions in the present application is the same and the hydration radius is similar, which brings many difficulties to the separation. In addition, the separation of metal ions and organic small molecules in the prior art essentially involves dimensional differences in charge quantity, polarity, complexing behavior, etc., while the separation of fluoride ions and chloride ions in the present application must rely on highly selective interface mechanism or transport channel difference.

[0012] The composite membrane prepared by the present application is integrated in a flow electrode electrosorption system to replace a conventional polymer-based anion exchange membrane, and an electrosorption+carrier composite membrane coupling technology is adopted, which emphasizes the "barrier effect" of the membrane on and the "enhanced permeation selectivity" of the membrane on , i.e. constructing a charge barrier and a solubility-diffusion selective interface in the membrane material. The design of the present application focuses on forming a charge structure and a hydrophobic interaction network in the membrane, which is more easily penetrated by and is repelled by .

[0013] The second aspect of the present application provides a carrier composite membrane for low-concentration / The isolated carrier composite membrane is prepared by the preparation method.

[0014] Preferably, the thickness of the carrier composite membrane is 45-55 μm. The membrane thickness needs to be controlled within a certain range. The thicker the membrane, the larger the overall energy consumption, and the membrane flux (water production per unit area per unit time) is inversely proportional to the membrane thickness. Thinner membrane, shorter solute diffusion path, more easily through the membrane hole, may lead to the decrease of selectivity.

[0015] The third aspect of the present application provides a flow electrode electrosorption system, which comprises the carrier composite membrane.

[0016] Preferably, the flow electrode electrosorption system further comprises a cathode plate, a cation exchange membrane, a mesh gasket and an anode plate, and the cathode plate and the anode plate are provided with groove flow channels for the flow electrode liquid.

[0017] The flow electrode electrosorption system is composed of a cathode plate, a cation exchange membrane, a mesh gasket, an anion exchange membrane and an anode plate in sequence, wherein the anion exchange membrane uses the carrier composite membrane. The cathode plate and the anode plate have groove flow channels for the flow of the electrode liquid, and the cation exchange membrane and the anion exchange membrane are used to separate the electrode chamber and the feed chamber and inhibit the occurrence of the common ion effect.

[0018] The electrode liquid channel: the anode plate and the cathode plate are provided with groove flow channels for guiding the circulation of the flow electrode (flowing carbon slurry), which is pumped into the anode cavity and the cathode cavity by peristaltic pumps, respectively.

[0019] Ion exchange membrane: located between the electrode liquid and the feed liquid, which plays a role in isolating the electrode liquid and the feed liquid, preventing the leakage of the electrode liquid while allowing the target ions to migrate. The cation exchange membrane allows the passage of cations and blocks anions; the carrier composite membrane is a key innovative component, which has high selective permeation capacity for and strong blocking capacity for .

[0020] Feed liquid channel: located between the cation exchange membrane and the carrier composite membrane, with a mesh gasket (used for supporting structure and maintaining fluid flow) in between, which ensures smooth water flow, reduces pressure drop, and at the same time forms an effective ion migration space.

[0021] The fourth aspect of the present application provides a method for separating / and from a mixed solution, wherein the flow electrode electrosorption system is used in the separation process.

[0022] Preferably, the separation process comprises the following steps:​

[0023] (1) Pretreatment

[0024] The groundwater containing F- and Cl- is filtered to remove large-particle impurities to obtain a feed liquid; and

[0025] (2) Liquid injection

[0026] The feed liquid and the flow electrode liquid are transported into the feed chamber and the electrode chamber of the flow electrode electrosorption system;

[0027] (3) Applying an electric field

[0028] A constant current of 0.33-2.67 mA / cm 2 is applied to the flow electrode electrosorption system to form a directional electric field;

[0029] (4) Ion migration and separation

[0030] Under the action of the electric field and the carrier composite membrane, F- preferentially migrates to the flow electrode liquid through the carrier composite membrane, Cl- is blocked at the interface of the carrier composite membrane, and at this time, F- and Cl- are separated;

[0031] (5) Collection and recycling

[0032] The separated feed liquid flows out from the water outlet, and the flow electrode liquid is recycled and regenerated.

[0033] The concentrations of F- and Cl- in different groundwater are different, and the specific concentration of F- has obvious regional differences. The concentration of F- in the groundwater in the plain is about 0.2-5 mg / L, and the concentration of F- in the high-fluorine area may reach 10 or 20 mg / L. The concentration of Cl- is about 30-500 mg / L, and the concentration of Cl- in some areas may reach 1500 mg / L.

[0034] Therefore, the application adopts the above-mentioned carrier composite membrane for separating low-concentration / F- and Cl-, and has the following beneficial effects:

[0035] (1) Compared with the existing defluorination technologies (such as the precipitation method, the adsorption method, and the electrodialysis), the application can accurately separate / two kinds of monovalent anions, and the separation coefficient reaches 3.2, thereby solving the problem of difficulty in selectively removing F- and Cl- when they coexist.

[0036] ​(2) The carrier composite membrane of the application as an anion exchange membrane of the flow electrode electrosorption system has a functionalized membrane structure and a hydrophobic interaction design, which can limit the migration of , while promoting the directional penetration of , thereby realizing effective separation of fluoride ions and chloride ions.

[0037] (3) Compared with traditional electrically driven separation methods such as electrodialysis, the application can work efficiently under low-voltage and low-concentration solution conditions, thereby reducing energy consumption and equipment burden.

[0038] (4) The application does not rely on precipitants or adsorbents during the separation process of low-concentration / mixed solutions, does not require subsequent regeneration treatment, and will not produce secondary pollution (such as sludge or concentrated liquid), and is suitable for environmentally sensitive scenarios such as groundwater treatment.

[0039] (5) The flow electrode electrosorption system of the application is simple to operate, suitable for small and medium-sized enterprises or remote areas for groundwater defluorination treatment, and has good industrialization and popularization potential.

[0040] The technical solutions of the application will be further described below with reference to the drawings and examples. DETAILED DESCRIPTION

[0041] Figure 1 is a structural schematic diagram of the flow electrode electrosorption system. CONCRETE EMBODIMENT

[0042] The application will be further described below. It should be noted that the present embodiment is based on the technical solutions, and detailed implementation methods and specific operation processes are given, but the application is not limited to the present embodiment.

[0043] Example 1

[0044] A preparation method of a carrier composite membrane for low-concentration / separation, characterized by comprising the following steps:

[0045] S1: Dissolve 0.33 g of cellulose triacetate in 30 mL of chloroform, and continuously stir under room temperature to obtain solution A;

[0046] S2: Add 0.55 g of methyltrioctylammonium chloride and 0.22 g of tributyl phosphate to solution A, and mix and stir again for 1 h under room temperature to obtain solution B;

[0047] S3: Pour solution B into a flat-bottomed tetrafluoroethylene casting plate with a diameter of 13 cm, and let the organic solvent trichloromethane volatilize at room temperature for 24 h or more to obtain a carrier composite membrane. The thickness of the membrane is 51 ± 1 μm.

[0048] Example 2

[0049] As shown in Figure 1 , the composition of the flow electrode electrosorption system is as follows:

[0050] The flow electrode electrosorption system is composed of a cathode plate, a cation exchange membrane, a mesh gasket, an anion exchange membrane, and an anode plate, which are arranged in order, wherein the anion exchange membrane uses the carrier composite membrane prepared in Example 1. The cathode plate and the anode plate have grooved flow channels for the flow of electrode liquid therein, and the cation exchange membrane and the anion exchange membrane are used to separate the electrode chamber and the feed chamber, and to inhibit the occurrence of the common ion effect.

[0051] Example 3

[0052] The flow electrode electrosorption system of Example 2 is used to separate low-concentration / mixed solutions of and , and the specific process is as follows:

[0053] (1) Pretreatment

[0054] The groundwater containing and is filtered to remove large-particle impurities to obtain a feed liquid;

[0055] The low-concentration groundwater used in the experiment has a concentration of : 5 mg / L, : 600 mg / L;

[0056] (2) Liquid injection

[0057] The feed liquid and the flow electrode liquid are fed into the feed chamber and the electrode chamber of the flow electrode electrosorption system;

[0058] (3) Application of electric field

[0059] A constant current of 1.50 mA / cm 2 is applied to the flow electrode electrosorption system to form a directional electric field;

[0060] (4) Ion migration and separation

[0061] Under the action of the electric field and the carrier composite membrane, preferentially migrates through the carrier composite membrane to the flow electrode liquid, is hindered at the interface of the carrier composite membrane, at which time and separation occurs;

[0062] (5) collecting and recycling

[0063] The separated feed liquid flows out from the water outlet and the electrode liquid is recycled and regenerated.

[0064] The concentration of fluoride ions in the separated feed liquid is less than 1.5 mg / L, and the concentration of chloride ions is less than 420 mg / L.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 3 is that the anion exchange membrane in the flow electrode electrosorption system is different. The anion exchange membrane in this comparative example is a conventional polymer-based anion exchange membrane (AMX anion membrane produced by Japan Astom). The conventional polymer anion membrane cannot achieve the separation of and .

[0067] The treatment results of groundwater containing and in Example 3 and Comparative Example 1 were tested and calculated, and the calculation process of the separation coefficient is as follows:

[0068] ① The rate constants of and are calculated according to the first-order kinetic formula:

[0069] ;

[0070] Wherein C0 is the initial concentration of ions (mg·L –1 ), C t is the ion concentration after operation (mg·L –1 ), t is the operation time (s), (s –1 ) is the rate constant.

[0071] ② The separation coefficient θ is calculated according to the following formula:

[0072] ;

[0073] Wherein is the rate constant of , is the rate constant of .

[0074] After calculation, the separation coefficient in Example 3 is 3.2, and the separation coefficient in Comparative Example 1 is 0.5. Compared with the carrier composite membrane prepared in the application, the separation coefficient of the conventional polymer-based anion exchange membrane is <1, which indicates that the carrier composite membrane prepared in the application can achieve the separation of low-concentration The separation of fluoride ions from chloride ions in the mixed solution demonstrates the excellent selectivity of the membrane material to the target ions.

[0075] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or equivalently replaced, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.​

Claims

1. A method for low concentration A method for producing a separated carrier composite film, characterized by: The preparation method comprises the following steps: ​ S1: dissolving a polymer base in an organic solvent to obtain solution A; S2: adding a carrier and a plasticizer to solution A and mixing to obtain solution B; S3: pouring solution B into a casting plate and allowing the organic solvent to volatilize to obtain a carrier composite film.

2. A method according to claim 1 for low concentration / Method for the production of a separated carrier composite film, characterized in that The polymer base is cellulose triacetate, the carrier is methyltrioctylammonium chloride, the plasticizer is tributyl phosphate, and the organic solvent is chloroform.

3. A method for low concentration F - / Cl - The method for producing a separated carrier composite film is characterized by comprising: The mass ratio of the polymer base, the carrier, and the plasticizer is (2-4):(4-6):(1-3).

4. A method for low concentration F - / Cl - The method for producing a separated carrier composite film is characterized by comprising: The mass-volume ratio of the polymer base and the organic solvent is (2-4) g:(20-40) mL.

5. A method for low concentration F - / Cl - A separated carrier composite film, characterized by: The carrier composite film is prepared by the preparation method of any one of claims 1-4.

6. A method according to claim 5, wherein the low concentration F - / Cl - The isolated carrier composite film is characterized in that: The thickness of the carrier composite film is 45-55 μm.

7. A flow electrode electrosorption system, comprising: The flow electrode electrosorption system comprises the carrier composite film of any one of claims 5-6.

8. The flow-by electrode electrosorption system of claim 7, wherein: The flow electrode electrosorption system further comprises a cathode plate, a cation exchange membrane, a mesh gasket, and an anode plate, and the cathode plate and the anode plate are provided with groove flow channels for the flow electrode solution.

9. A low concentration / method for separating F - and characterized by: The flow electrode electrosorption system of any one of claims 7-8 is used in the separation process.

10. A low concentration of a compound according to claim 9. / Separation of F - and by mixing solutions, characterized in that: The separation process comprises the following steps: (1) pretreatment The groundwater containing F - and is filtered to remove large-particle impurities to obtain a feed liquid; (2) liquid injection The feed liquid and the flow electrode solution are fed into the feed chamber and the electrode chamber of the flow electrode electrosorption system; (3) applying an electric field A constant current of 0.33-2.67 mA / cm is applied to the flow electrode electric adsorption system 2 , forming a directional electric field; (4) ion migration and separation Under the action of electric field and carrier complex membrane, Migrate to the flowing electrode liquid through the carrier complex membrane preferentially, Blocked by the carrier complex membrane interface, at this time And Separation occurs; (5) collection and recycling The separated feed liquid flows out from the water outlet, and the flow electrode solution is recycled and regenerated.

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