Method for improving anti-pollution performance of anion exchange membrane in electrodialysis membrane assembly and electrodialysis membrane assembly

Abstract

The invention provides a method for improving the anti-pollution performance of an anion exchange membrane in an electrodialysis membrane assembly and the electrodialysis membrane assembly. The method comprises the following steps: S1, circulating a water-phase solution containing polyphenol monomers in a desalination chamber to enable the water-phase solution to be in contact with an anion exchange membrane, and meanwhile, applying a direct-current electric field with constant current density to enable the polyphenol monomers to be directionally attached to one side, facing the desalination chamber, of the anion exchange membrane; after contacting for a certain time, discharging the water phase solution; s2, enabling the organic phase solution containing the acyl chloride monomer to be in contact with the anion exchange membrane in a desalination chamber so as to generate an interfacial polymerization modification layer on the surface of the anion exchange membrane; and after contacting for a certain time, discharging the organic phase solution. The method realizes in-situ construction of the interfacial polymerization modification layer with ideal and stable anti-pollution performance on the surface of the anion exchange membrane on the premise of not dismounting the membrane stack.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane surface modification, and particularly relates to a method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module and an electrodialysis membrane module. Background Art

[0002] Electrodialysis has attracted much attention in the field of high-salt wastewater resource utilization due to its advantages such as high concentration multiple of concentrated water (the salt content of concentrated water is as high as 15% - 20%), high integration, high water reuse rate, and low energy consumption. However, during the operation of an electrodialysis device, membrane fouling will occur due to the adsorption and blockage of organic substances and impurity components on the membrane surface or in the membrane pores, resulting in an increase in the membrane stack resistance and the flow resistance of the compartments, thereby affecting the desalination rate and energy consumption. Among them, the organic fouling of the anion exchange membrane is particularly serious, which has become a bottleneck problem restricting the wide application of electrodialysis technology. Therefore, it is of great significance to develop an anion exchange membrane with anti-fouling performance for promoting the popularization and application of this technology in the field of high-salt wastewater resource utilization.

[0003] At the same time, in practical applications, an electrodialysis membrane stack usually consists of hundreds of stacked ion exchange membranes. If the anti-fouling modification process requires disassembling the membrane module for the independent construction of each membrane, it will face high operating costs and feasibility challenges. Therefore, exploring a method for in-situ constructing an anti-fouling modification layer in an electrodialysis membrane module has important practical value for solving the membrane fouling problem. There have been reports (CN117943133A; CN107998900A; CN108905658A) on in-situ constructing a modification layer by electro-depositing a negatively charged modifier on the surface of an ion exchange membrane in an electrodialysis membrane module. However, these anti-fouling modification layers are mainly attached to the anion exchange membrane through electrostatic interaction, resulting in insufficient stability. CN116443997A discloses a method for in-situ constructing a multi-component modification layer on the surface of an anion exchange membrane by introducing dopamine in a layer-by-layer self-assembly (polyelectrolyte) of an electro-deposited layer, which improves the anti-fouling performance and enhances the stability of the modification layer. However, the above methods require more operation time and steps, increasing the cost and process difficulty of constructing the modification layer. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method for improving the anti-organic fouling performance of an anion exchange membrane in an electrodialysis membrane module, which simultaneously realizes the in-situ construction of an interfacial polymerization modification layer by an interfacial polymerization method.

[0005] Correspondingly, the present invention also provides an electrodialysis membrane module obtained by the above method.

[0006] The present invention adopts the following technical solutions:

[0007] A method for improving the anti-pollution performance of an anion exchange membrane in an electrodialysis membrane module, the method comprising the following steps:

[0008] S1: Circulate an aqueous solution containing polyphenol monomers in the desalination chamber to bring the aqueous solution into contact with the anion exchange membrane. At the same time, apply a direct current electric field with a constant current density to direct the attachment of the polyphenol monomers to one side of the anion exchange membrane facing the desalination chamber. After contacting for a certain time, discharge the aqueous solution;

[0009] S2: Bring an organic phase solution containing acyl chloride monomers into contact with the anion exchange membrane in the desalination chamber, thereby forming an interfacial polymerization modification layer on the surface of the anion exchange membrane. After contacting for a certain time, discharge the organic phase solution.

[0010] Wherein, the mass concentration ratio of the polyphenol monomers in the aqueous solution to the acyl chloride monomers in the organic phase solution is 1:10 - 2:1.

[0011] Wherein, the mass concentration of the polyphenol monomers in the aqueous solution is 0.01 wt% - 1 wt%, and the mass concentration of the acyl chloride monomers in the organic phase solution is 0.01 wt% - 1 wt%.

[0012] Wherein, after discharging the aqueous solution in step S1, it further includes a step of drying the surface of the ion exchange membrane, the diaphragm, and the pipeline;

[0013] After discharging the organic phase solution in step S2, it further includes a step of drying the surface of the ion exchange membrane, the diaphragm, and the pipeline.

[0014] Wherein, the contact time in step S1 is 120 - 1800 s; the contact time in step S2 is 30 - 600 s.

[0015] Wherein, the current density of the direct current electric field applied in step S1 is 1 - 20 mA / cm 2 .

[0016] Wherein, in steps S1 and S2, a peristaltic pump is used to drive the circulation of the aqueous solution in the desalination chamber, and the flow rate of the peristaltic pump is 30 - 1000 mL / min.

[0017] Wherein, the aqueous solution in step S1 is obtained by dissolving polyphenol monomers in a phosphate buffer solution, and the pH of the phosphate buffer solution is 6 - 8. The polyphenol monomers can be one or several of tannic acid, gallic acid, ellagic acid, catechol, hydroquinone, or resorcinol.

[0018] The organic phase solution is obtained by dissolving acyl chloride monomers in an organic solvent. The acyl chloride monomers can be one or several of trimesoyl chloride, terephthaloyl chloride, or isophthaloyl chloride, and the organic solvent can be n-hexane, cyclohexane, or toluene.

[0019] Among them, the drying is achieved by blowing hot air, where the hot air purge flow rate is 0.1 - 1.0 L / min, the time is 60 - 600 s, and the temperature is 30 - 80 °C.

[0020] An electrodialysis membrane module includes a cation exchange membrane and an anion exchange membrane. The electrodialysis module further includes an interfacial polymerization modification layer constructed on the surface of the anion exchange membrane, and the interfacial polymerization modification layer is constructed by the method for improving the anti-fouling performance of the anion exchange membrane in the electrodialysis membrane module as described above.

[0021] The method of the present invention enables polyphenol monomers to be directionally attached to the surface of the anion exchange membrane assisted by a direct current electric field, and then an oil phase solution containing acyl chloride monomers is introduced to react with them to polymerize, so that an interfacial polymerization functional layer can be in-situ constructed on the membrane surface without disassembling the membrane stack; by changing the concentration of the aqueous phase / oil phase monomers, the esterification degree of the functional layer can be regulated, the hydrophilicity and negative charge density of the membrane surface can be optimized, the anti-organic fouling performance of the anion exchange membrane can be improved, and thus the wide application of electrodialysis technology in the field of industrial wastewater resource utilization can be promoted.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) The method of the present invention can realize the in-situ construction of the interfacial polymerization modification layer in the existing electrodialysis membrane stack only by changing the feed liquid, with simple operation, short operation time, and low cost.

[0024] (2) The method of the present invention has good treatment effect, and can significantly increase the anti-fouling performance of the anion exchange membrane after treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the principle of a method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module of the present invention.

[0026] Figure 2 It is a characterization diagram of the physical and chemical properties of the ion exchange membranes obtained in Examples 1 - 3, Comparative Example 1, and Comparative Example 2 of the present invention. Among them, a is the membrane surface resistance diagram, b is the ion exchange capacity diagram, c is the Zeta potential diagram, and d is the contact angle diagram.

[0027] Figure 3 It is a graph showing the change of the conductivity of the feed liquid in the desalination chamber of the membrane stack over time obtained in Examples 1 - 3, Comparative Example 1, and Comparative Example 2 of the present invention.

[0028] Figure 4 This is a graph showing the change in transmembrane voltage of the anion exchange membranes obtained in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention over time.

[0029] Figure 5 This is a comparative graph of the Zeta potential of the ion exchange membranes obtained in Example 1 of the present invention and Comparative Example 3. Detailed implementation manners

[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The present invention constructs an interfacial polymerization modification layer by the interfacial polymerization method. The interfacial polymerization modification layer prepared by interfacial polymerization is stably connected by pure chemical bonds and is sufficiently stable. Moreover, the residual acyl chloride groups on the surface form carboxylic acid groups through hydrolysis, so that its surface is usually negatively charged. Furthermore, by regulating key process parameters such as the electric field strength, monomer concentration, and reaction time, the physicochemical properties such as the esterification degree, surface hydrophilicity and hydrophobicity, and negative charge density of the modified layer are optimized, thereby significantly improving the anti-organic pollution ability of the anion exchange membrane.

[0032] A method for improving the anti-pollution performance of an anion exchange membrane in an electrodialysis membrane module, the method comprising the following steps:

[0033] S1: Circulate an aqueous solution containing a polyphenol monomer in the desalination chamber to bring the aqueous solution into contact with the anion exchange membrane. At the same time, apply a direct current electric field with a constant current density to make the polyphenol monomer attach directionally to the side of the anion exchange membrane facing the desalination chamber; after contacting for a certain time, drain the aqueous solution;

[0034] S2: Bring an organic phase solution containing an acyl chloride monomer into contact with the anion exchange membrane in the desalination chamber, thereby generating an interfacial polymerization modification layer on the surface of the anion exchange membrane; after contacting for a certain time, drain the organic phase solution.

[0035] Specifically, use a Na2SO4 solution as the feed liquid in the electrode chamber, and circulate it through compartments 1 and 4 (electrode chambers) driven by a peristaltic pump; use a NaCl solution as the feed liquid in the concentration chamber, and circulate it through compartment 2 (concentration chamber) driven by a peristaltic pump to ensure that an electric current path can be formed in the electrodialysis membrane stack. Dissolve the polyphenol monomer in a phosphate buffer solution as the aqueous phase solution, and circulate it through compartment 3 (dilution chamber); under the condition of a constant current density, the polyphenol monomer will be directionally attached to the side of the anion exchange membrane facing the dilution chamber under the action of a direct current electric field and the adhesion effect, and try to avoid attaching to the surface of the cation exchange membrane. After completion, quickly drain the feed liquid in each compartment, and fully dry the membrane surface, compartments, and pipelines by blowing air to avoid polymerization reactions between the residual aqueous phase monomers and organic monomers in the separators and pipelines.

[0036] Next, fill compartment 3 with an oil phase solution containing an acyl chloride monomer, and use the interfacial polymerization reaction between the polyphenol monomer and the acyl chloride monomer to form a stable interfacial polymerization anti-fouling modification layer ( Figure 1 as shown), and the oil phase solution is prepared by dissolving acyl chloride monomers with different concentrations in an organic solution. During this process, it is also necessary to fill compartments 1 and 4 with a Na2SO4 solution and fill compartment 2 with a NaCl solution to ensure the stability of the volume of each compartment. After completion, quickly drain the feed liquid in each compartment, fully dry the membrane surface, compartments, and pipelines by blowing hot air, and fill the membrane stack with ultrapure water to protect the membrane stack for standby.

[0037] In step S1, the contact time between the aqueous phase and the membrane is preferably 120 - 1800 s, and the flow rate of the peristaltic pump is preferably 30 - 1000 mL / min.

[0038] In step S1, the current density is preferably 1 - 20 mA / cm 2 .

[0039] In step S1, the pH of the phosphate buffer solution is preferably between 6 and 8.

[0040] In step S1, the air blowing flow rate is preferably 0.1 - 1.0 L / min; the time for blowing air to purge the membrane stack is preferably 60 - 600 s.

[0041] In step S1, the concentration of the polyphenol monomer is preferably 0.01 wt% - 1 wt%, in step S2, the concentration of the acyl chloride monomer is preferably 0.01 wt% - 1 wt%, and the concentration ratio of the polyphenol monomer to the acyl chloride monomer is 1:10 - 2:1.

[0042] In step S2, the organic solvent in the organic phase solution is preferably n-hexane, cyclohexane, or toluene, and the reaction time (contact time) of the interfacial polymerization is preferably 30 - 600 s.

[0043] The air purge flow rate in the step (3) is preferably 0.1 - 1.0 L / min; the time for blowing air to purge the membrane stack is preferably 60 - 600 s, and the temperature is preferably 30 - 80 °C.

[0044] There is 1 pair of membranes in the above electrodialysis device, but in actual applications, the number of membrane pairs can be increased to 2 pairs, 3 pairs, 4 pairs, 5 pairs, 6 pairs, 7 pairs... according to requirements to achieve the in-situ construction of a stable interfacial polymerization anti-pollution modification layer on the surfaces of multiple anion exchange membranes simultaneously.

[0045] Example 1

[0046] This example is carried out in a laboratory-scale electrodialysis device, and the membrane stack is composed of one anion exchange membrane and two cation exchange membranes. As Figure 1 shown, A is the anion exchange membrane, C is the cation exchange membrane, and the cation exchange membrane and the anion exchange membrane divide the electrodialysis device into four compartments, namely compartment 1, compartment 2, compartment 3, and compartment 4, where compartment 1 and compartment 4 are electrode compartments, compartment 3 is the desalination compartment, and compartment 2 is the concentration compartment.

[0047] A method for improving the anti-organic pollution performance of anion exchange membranes in an electrodialysis membrane module, comprising the following steps:

[0048] S0: Form a current path: Specifically, use a Na2SO4 solution as the feed liquid in the electrode compartments and circulate it through compartment 1 and compartment 4 under the drive of a peristaltic pump; use a NaCl solution as the feed liquid in the concentration compartment and circulate it through compartment 2 under the drive of a peristaltic pump to ensure that the electrodialysis membrane stack can form a current path;

[0049] S1: Dissolve 0.1 wt% tannic acid in 0.10 M phosphate buffer (pH = 7) as the aqueous solution and circulate it through the desalination compartment under the drive of a peristaltic pump. Operate for 600 s under the condition of a constant current density of 5 mA / cm 2 . At this time, polyphenol monomers will be directionally attached to the side of the anion exchange membrane facing the desalination compartment under the action of a direct current electric field and the adhesion effect. After completion, quickly drain the feed liquid in each compartment, and fully dry the membrane surface, compartments, and pipelines by blowing air (the hot air purge flow rate is 0.5 L / min, the time is 120 s, and the temperature is 60 °C). The flow rate of the peristaltic pump is 30 mL / min.

[0050] S2: Fill the electrode chamber with 0.1 M Na2SO4 solution, fill the concentration chamber with 0.1 M NaCl solution, and fill the desalination chamber with a 0.05 wt% oil-phase solution. React for 180 s to in-situ form an interfacial polymerization modification layer. The oil-phase solution is prepared by dissolving trimesoyl chloride in n-hexane, where the mass percentage concentration of trimesoyl chloride is 0.05 wt%. After completion, quickly drain the feed liquid in each compartment, and fully dry the membrane surface, compartments, and pipelines by blowing hot air. The flow rate of the peristaltic pump in this step is 30 mL / min.

[0051] The membrane stack obtained in Example 1 is named TA@TMC0.05wt%-M.

[0052] Example 2

[0053] The treatment process of Example 2 is the same as that of Example 1, except that the concentration of the oil-phase solution is 0.1 wt%. The membrane stack obtained in Example 2 is named TA@TMC0.1wt%-M.

[0054] Example 3

[0055] The treatment process of Example 3 is the same as that of Example 1, except that the concentration of the oil-phase solution is 0.15 wt%. The membrane stack obtained in Example 3 is named TA@TMC0.15wt%-M.

[0056] Comparative Example 1

[0057] Comparative Example 1 is the original membrane stack without any treatment. The membrane stack obtained in Comparative Example 1 is named PM.

[0058] Comparative Example 2

[0059] Comparative Example 2 is the membrane stack without modification by the oil-phase solution, that is, the method does not include step S2. The membrane stack obtained in Comparative Example 2 is named eTA-M.

[0060] Comparative Example 3

[0061] The treatment process of Comparative Example 3 is the same as that of Example 1, except that the current density in step S1 is 0 mA / cm 2 (i.e., no electric field is applied).

[0062] Example 4

[0063] A method for improving the anti-organic fouling performance of an anion exchange membrane in an electrodialysis membrane module, comprising the following steps:

[0064] S0: Forming an electric current path: Specifically, use a Na2SO4 solution as the feed liquid in the electrode chamber and circulate it through compartments 1 and 4 under the drive of a peristaltic pump; use a NaCl solution as the feed liquid in the concentrated water chamber and circulate it through compartment 2 under the drive of a peristaltic pump to ensure that an electric current path can be formed in the electrodialysis membrane stack;

[0065] S1: Dissolve 0.1 wt% of gallic acid in a phosphate buffer solution with a pH of about 6 as the aqueous phase solution and circulate it through the fresh water chamber under the drive of a peristaltic pump (the flow rate of the peristaltic pump is 300 mL / min). Operate for 120 s under the condition of a constant current density of 1 mA / cm 2 After completion, quickly drain the feed liquid in each compartment and fully dry the membrane surface, compartments and pipelines by blowing air. Among them, the hot air blowing flow rate is 0.1 L / min, the time is 60 s, and the temperature is 80 °C;

[0066] S2: Fill the electrode chamber with 0.1 M Na2SO4 solution, fill the concentrated water chamber with 0.1 M NaCl solution, and fill the fresh water chamber with an oil phase solution (the flow rate of the peristaltic pump is 300 mL / min), and react for 300 s to in-situ form an interfacial polymerization modification layer. The oil phase solution is prepared by dissolving terephthaloyl chloride in cyclohexane, and the mass percentage concentration of the acyl chloride monomer is 1 wt%. After completion, quickly drain the feed liquid in each compartment and fully dry the membrane surface, compartments and pipelines by blowing hot air. Among them, the hot air blowing flow rate is 1.0 L / min, the time is 200 s, and the temperature is 40 °C.

[0067] Example 5

[0068] A method for improving the anti-organic fouling performance of an anion exchange membrane in an electrodialysis membrane module, comprising the following steps:

[0069] S0: Forming an electric current path: Specifically, use a Na2SO4 solution as the feed liquid in the electrode chamber and circulate it through compartments 1 and 4 under the drive of a peristaltic pump; use a NaCl solution as the feed liquid in the concentrated water chamber and circulate it through compartment 2 under the drive of a peristaltic pump to ensure that an electric current path can be formed in the electrodialysis membrane stack;

[0070] S1: Dissolve 0.01 wt% of catechol in a phosphate buffer solution with a pH of about 8 as the aqueous phase solution and circulate it through the fresh water chamber under the drive of a peristaltic pump (the flow rate of the peristaltic pump is 1000 mL / min). Operate for 1800 s under the condition of a constant current density of 20 mA / cm 2 After completion, quickly drain the feed liquid in each compartment and fully dry the membrane surface, compartments and pipelines by blowing air. Among them, the hot air blowing flow rate is 1.0 L / min, the time is 600 s, and the temperature is 30 °C;

[0071] S2: Fill the electrode chamber with 0.1 M Na2SO4 solution, fill the concentrated water chamber with 0.1 M NaCl solution, and fill the fresh water chamber with an oil-phase solution. React for 30 s to in-situ form an interfacial polymerization functional layer. The oil-phase solution is prepared by dissolving terephthaloyl chloride in cyclohexane, and the mass percentage concentration of the acyl chloride monomer is 0.01 wt%. After completion, quickly drain the feed liquid in each compartment, and fully dry the membrane surface, compartments, and pipelines by blowing hot air. The hot air blowing flow rate is 0.8 L / min, the time is 60 s, and the temperature is 80 °C.

[0072] Example 6

[0073] A method for improving the anti-organic fouling performance of an anion exchange membrane in an electrodialysis membrane module, comprising the following steps:

[0074] S0: Form a current path: Specifically, use Na2SO4 solution as the feed liquid in the electrode chamber and circulate it through compartments 1 and 4 under the drive of a peristaltic pump; use NaCl solution as the feed liquid in the concentrated water chamber and circulate it through compartment 2 under the drive of a peristaltic pump to ensure that the electrodialysis membrane stack can form a current path;

[0075] S1: Dissolve 1 wt% of catechol in a phosphate buffer solution with a pH of about 7 as the aqueous-phase solution and circulate it through the fresh water chamber under the drive of a peristaltic pump (the flow rate of the peristaltic pump is 500 mL / min). Operate for 600 s under the condition of a constant current density of 15 mA / cm 2 After completion, quickly drain the feed liquid in each compartment, and fully dry the membrane surface, compartments, and pipelines by blowing air. The hot air blowing flow rate is 1.0 L / min, the time is 600 s, and the temperature is 50 °C;

[0076] S2: Fill the electrode chamber with 0.1 M Na2SO4 solution, fill the concentrated water chamber with 0.1 M NaCl solution, and fill the fresh water chamber with an oil-phase solution. React for 600 s to in-situ form an interfacial polymerization modification layer. The oil-phase solution is prepared by dissolving terephthaloyl chloride in cyclohexane, and the mass percentage concentration of the acyl chloride monomer is 1 wt%. After completion, quickly drain the feed liquid in each compartment, and fully dry the membrane surface, compartments, and pipelines by blowing hot air. The hot air blowing flow rate is 0.8 L / min, the time is 600 s, and the temperature is 30 °C.

[0077] The physical and chemical properties of the ion exchange membranes in the electrodialysis membrane stacks obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are characterized as Figure 2 shown, where AEM is an anion exchange membrane and CEM is a cation exchange membrane. From Figure 2It can be found that the membrane surface resistance and ion exchange capacity of the ion exchange membranes in different modified membrane stacks are close to those of the ion exchange membranes in the original membrane stack, that is, the negative impact of different modification methods on the membrane surface resistance can be ignored.

[0078] In contrast, as Figure 2 shown in c and d, the Zeta potential of all modified anion exchange membranes changes from positive to negative, and the contact angle also decreases significantly, indicating that the hydrophilicity and negative charge density of the membrane surface have been effectively improved, thus having the potential to inhibit organic pollution. When tannic acid containing a large number of phenolic hydroxyl groups is deposited on the membrane surface through a DC electric field, the negative charge density and hydrophilicity of the eTA-M surface are significantly improved. On this basis, after introducing an oil-phase solution containing trimesoyl chloride to form an in-situ interfacial polymerization modification layer, the contact angle of the membrane surface increases and increases with the increase of the concentration, that is, the interfacial polymerization reaction will lead to a decrease in the hydrophilicity of the membrane surface. In addition, when an oil-phase solution with a concentration of 0.05 wt% is introduced, the Zeta potential of its surface is similar to that of eTA-M. When the concentration increases to 0.10 wt%, the Zeta potential of the TA@TMC0.10 wt%-M surface drops to -31.25 mV, that is, the negative charge density on its surface is enhanced. However, when the concentration of trimesoyl chloride continues to increase to 0.15 wt%, the negative charge density of TA@TMC0.15 wt%-M shows a decreasing trend because when the monomer concentration is too high, the interfacial polymerization reaction tends to generate polyester substances with small molecular weights during the process, affecting the stability of the modification layer.

[0079] Test Example 1

[0080] This test example examines the desalination performance of the electrodialysis membrane stacks obtained in Examples 1 to 3 and Comparative Examples 1 and 2 in the electrodialysis fouling experiment. There is a linear relationship between the ion concentration and conductivity of the salt solution, so the desalination rate can be represented by the decrease rate of conductivity.

[0081] The electrodialysis fouling experiment was carried out on a laboratory-scale electrodialysis device. The membrane stack consists of one anion exchange membrane and two cation exchange membranes. A 0.10 M sodium sulfate and 0.10 M sodium chloride solution were driven by a peristaltic pump and flowed through the electrode chamber and the concentration chamber of the electrodialysis membrane stack respectively. A 0.10 M sodium chloride and 200 mg / L sodium dodecyl sulfate (SDS) mixed solution was driven by a peristaltic pump and flowed through the desalination chamber of the electrodialysis membrane stack. The solution flow rate was 100 mL / min. Under the condition of a constant voltage of 3.5 V, the desalination performance and anti-fouling performance of different membrane stacks were evaluated by online recording the change trend of the conductivity of the feed liquid in the desalination chamber over time. The results are as Figure 3As shown. In the pollution test with 200 mg / L SDS, the desalination rate of the original membrane stack (PM) only decreased from 11.21 mS / cm to 10.17 mS / cm after running for 120 min, that is, the desalination rate was only 9.28%. The results showed that the presence of SDS caused the pollution of the anion exchange membrane, resulting in an increase in the membrane stack resistance and seriously affecting the desalination performance of electrodialysis. In contrast, the desalination rate of eTA-M was 32.19% after running for 150 min, but it was still lower than the desalination rate without SDS, indicating that this modification method could enhance the anti-pollution performance of the membrane stack, but it was still polluted. The desalination rates of the membrane stacks modified by in-situ interfacial polymerization prepared in Examples 1 to 3 were 38.06% (TA@TMC0.05 wt%-M), 41.42% (TA@TMC0.10 wt%-M), and 38.08% (TA@TMC0.15 wt%-M), respectively, which were significantly higher than that of eTA and close to the desalination rate of the original membrane stack when there was no organic pollutant (PM(NaCl)).

[0082] Test Example 2

[0083] This test example investigated the desalination performance, anti-pollution performance, and stability of the electrodialysis membrane stacks obtained in Examples 1 to 3 and Comparative Examples 1 and 2 in the electrodialysis pollution experiment.

[0084] The electrodialysis pollution experiment was carried out in a laboratory-scale electrodialysis device. The membrane stack was composed of an anion exchange membrane and two cation exchange membranes. The electrode chambers were filled with 0.10 M sodium sulfate solution, which was driven by a peristaltic pump and flowed through the electrode chambers of the electrodialysis membrane stack respectively. The feed solutions in the dilution chamber and the concentration chamber were a mixed solution of 0.1 M sodium chloride and 200 mg / L SDS from the same feed solution tank. Under the condition of a constant current of 3 mA / cm 2 , the change trend of the potential difference (transmembrane voltage, ΔE) on both sides of the anion exchange membrane with time was monitored online to evaluate the anti-pollution performance and stability of the anion exchange membrane. The results were as follows Figure 4As shown, the ΔE of the original membrane stack (PM) increased rapidly and reached 2.20 V after 30 min of operation, indicating that the original anion exchange membrane had little ability to inhibit SDS pollution. The ΔE of eTA-M also increased from the beginning and reached 0.88 V after 180 min of operation. This result shows that the anti-pollution ability of this modification method is limited and unstable, and it is difficult to completely inhibit SDS pollution. The growth rate of ΔE of TA@TMC0.05 wt%-M during operation was significantly slower than that of eTA, and it reached 0.60 V only after 540 min of operation, indicating that the participation of interfacial polymerization reaction can significantly enhance the anti-pollution performance and stability of anion exchange membranes. With the continuous increase of the oil-phase monomer concentration in the in-situ IP modification process, the changes in ΔE of TA@TMC0.10 wt%-M and TA@TMC0.15 wt%-M decreased significantly and remained relatively stable during 1200 min of operation, indicating that both the anti-pollution performance and stability of the anion exchange membrane have been improved.

[0085] As Figure 5 shown, compared with the case without an electric field, the Zeta potential on the surface of the AEM is lower with a DC electric field, that is, the surface negative charge density is better, and its ability to inhibit organic pollution is stronger. In addition, when there is no electric field (current density is 0 mA / cm 2 ), the negative charge density on the surface of the CEM is significantly lower than that of the CEM when an electric field is applied; under the action of a DC electric field, the negative charge density on the surface of the CEM in the modified membrane stack is closer to that of the PM-CEM, indicating that the DC electric field is the key to ensuring the directional migration of the modified components to the surface of the AEM to in-situ construct an interfacial polymerization modification layer, which can minimize the negative impact on the CEM.

[0086] The inventors found that organic pollution is particularly serious in the electrodialysis membrane pollution. The organic substances causing organic pollution mainly carry negative charges, so it is easier to cause pollution of the anion exchange membrane (the ion exchange groups are mainly quaternary ammonium groups carrying positive charges). Therefore, the focus of this invention is to improve the anti-pollution performance of the anion exchange membrane; further, during the operation of the electrodialysis device, under the action of an electric field, organic pollution mainly occurs on the side of the anion exchange membrane facing the desalination chamber. Since the polyphenol-based modified components mainly contain negatively charged groups, they will migrate directionally to the side of the anion membrane facing the fresh water chamber under the action of an electric field; on both sides of the desalination chamber of the electrodialysis, there is an anion exchange membrane on one side and a cation exchange membrane on the other side. Therefore, a DC electric field is required to directionally drive the negatively charged polyphenol aqueous monomers to adhere to the surface of the anion exchange membrane. In this invention, an interfacial polymerization modification layer is only constructed on the side of the cation exchange membrane close to the desalination chamber, rather than on the surface of the cation exchange membrane, because forming a modification layer on the surface of the cation exchange membrane will affect its surface properties, such as reducing its surface negative charge density and increasing its mass transfer resistance.

[0087] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

[0088] The parts not elaborated in detail in the specification of the present invention belong to the well-known technologies in the art. The above embodiments are provided only for the purpose of describing the present invention, rather than to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent replacements and modifications made without departing from the spirit and principles of the present invention shall be covered within the scope of the present invention.

Claims

1. A method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module, characterized in that, The method comprises the following steps: S1: Circulate the aqueous solution containing polyphenol monomers in the desalination chamber to bring the aqueous solution into contact with the anion exchange membrane. At the same time, apply a direct current electric field with a constant current density to direct the attachment of polyphenol monomers to the side of the anion exchange membrane facing the desalination chamber. After contacting for a certain time, discharge the aqueous solution. S2: Bring the organic phase solution containing acyl chloride monomers into contact with the anion exchange membrane in the desalination chamber, thereby generating an interfacial polymerization modification layer on the surface of the anion exchange membrane. After contacting for a certain time, discharge the organic phase solution.

2. The method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module according to claim 1, wherein The mass concentration ratio of polyphenol monomers in the aqueous solution to acyl chloride monomers in the organic phase solution is 1:10 to 2:

1.

3. The method for improving the anti-fouling performance of the anion exchange membrane in the electrodialysis membrane module according to claim 2, characterized in that The mass concentration of polyphenol monomers in the aqueous solution is 0.01 wt% - 1 wt%, and the mass concentration of acyl chloride monomers in the organic phase solution is 0.01 wt% - 1 wt%.

4. The method for improving the anti-pollution performance of an anion exchange membrane in an electrodialysis membrane module according to claim 1, wherein After discharging the aqueous solution in step S1, it further includes a step of drying the surface of the ion exchange membrane, the separator, and the pipeline. After discharging the organic phase solution in step S2, it further includes a step of drying the surface of the ion exchange membrane, the separator, and the pipeline.

5. The method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module according to any one of claims 1 to 4, characterized in that, The contact time in step S1 is 120 - 1800 s; the contact time in step S2 is 30 - 600 s.

6. The method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module according to any one of claims 1 to 4, characterized in that, The current density of the DC electric field applied in step S1 is 1 to 20 mA / cm 2 .

7. The method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module according to any one of claims 1 to 4, characterized in that In steps S1 and S2, a peristaltic pump is used to drive the circulation of the aqueous solution in the desalination chamber, and the flow rate of the peristaltic pump is 30 - 1000 mL / min.

8. The method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module according to any one of claims 1 to 4, characterized in that, The aqueous solution in step S1 is obtained by dissolving polyphenol monomers in a phosphate buffer solution, where the pH of the phosphate buffer solution is 6 - 8.

9. The method for improving the anti-fouling performance of an anion exchange membrane in an electrodialysis membrane module according to claim 4, wherein, The drying is achieved by blowing hot air, where the hot air purging flow rate is 0.1 - 1.0 L / min, the time is 60 - 600 s, and the temperature is 30 - 80°C.

10. An electrodialysis membrane module, comprising a cation exchange membrane and an anion exchange membrane, characterized in that, The electrodialysis module further includes an interfacial polymerization modification layer constructed on the surface of the anion exchange membrane, and the interfacial polymerization modification layer is constructed by the method for improving the anti-fouling performance of the anion exchange membrane in the electrodialysis membrane module according to any one of claims 1 to 9.

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