Compact ultrafiltration membrane for efficient dye / salt separation as well as preparation method and application of compact ultrafiltration membrane
The dense ultrafiltration membrane prepared by interfacial polymerization of covalent organic framework materials with tannic acid and trimesoyl chloride solves the problems of biotoxicity of traditional aqueous monomers and dispersibility of nanofillers, and achieves efficient dye/salt separation with high rejection rate and high water flux.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-09
- Publication Date
- 2026-03-17
AI Technical Summary
In traditional interfacial polymerization processes, the aqueous monomers are biotoxic, and the hydrophobic and disordered structure of the resulting polyamide separation layer leads to mutual constraints on permeability and selectivity. The introduction of nanofillers also brings about dispersibility and compatibility issues, making it difficult to achieve green and environmentally friendly high-efficiency dye/salt separation.
A dense ultrafiltration membrane, TA-COF-TMC, was prepared by interfacial polymerization of covalent organic framework materials with tannic acid and trimesoyl chloride. Through the synergistic effect of COF nanomaterials and tannic acid, more water molecule transport channels were constructed, thereby improving permeability and retention rate.
It achieves high dye rejection rate and high water flux, has good antifouling performance and long-term stability, and can effectively separate dyes/salts, especially with a near 100% rejection rate for negatively charged dyes and selective permeation of salts.
Smart Images
Figure CN121669002A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane separation technology, specifically relating to a dense ultrafiltration membrane for efficient dye / salt separation, its preparation method, and its application. Background Technology
[0002] Membrane separation technology, especially thin-layer composite membranes based on interfacial polymerization, plays an increasingly crucial role in many important fields such as resource recovery, seawater desalination, and wastewater treatment due to its advantages of low energy consumption, small footprint, and environmental friendliness. However, the aqueous monomers used in traditional interfacial polymerization processes (such as piperazine PIP and m-phenylenediamine MPD) not only have certain biotoxicity, but the polyamide separation layer formed by them is limited by its inherent hydrophobicity and disordered structure, facing a bottleneck of trade-off between permeability and selectivity. To solve these problems, existing technologies often introduce nanomaterials to regulate the structure and performance of the separation layer. However, the introduction of nanofillers also brings new challenges, such as their dispersibility and interfacial compatibility in the polymer matrix, while still failing to solve the fundamental shortcomings of traditional aqueous monomers in terms of green environmental protection. Therefore, developing a new strategy that can achieve greening from the source and synergistically enhance membrane performance with nanofillers has become an important development direction in this field. Summary of the Invention
[0003] The purpose of this invention is to provide a dense ultrafiltration membrane for efficient dye / salt separation, its preparation method, and its application. The dense ultrafiltration membrane prepared by this invention has both a high rejection rate and a high water flux.
[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a dense ultrafiltration membrane for high-efficiency dye / salt separation, comprising the following steps: (1) Dissolve tannic acid in a buffer solution to obtain a first aqueous solution; uniformly disperse covalent organic framework material in deionized water to obtain a second aqueous solution; dissolve pyromellitic acid chloride in an organic solvent to obtain an organic solution; (2) The first aqueous solution, the second aqueous solution and the organic solution obtained in step (1) are sequentially coated on the surface of the support membrane, and then subjected to heat treatment after interfacial polymerization reaction to obtain a TA-COF-TMC dense ultrafiltration membrane.
[0005] Preferably, the buffer solution in step (1) includes a phosphate buffer solution or a Tris buffer solution; the pH value of the buffer solution is 7 to 8.5.
[0006] Preferably, the concentration of tannic acid in the first aqueous phase solution in step (1) is 0.01~3.0 g / L.
[0007] Preferably, the concentration of the covalent organic framework material in the second aqueous solution of step (1) is 0.001~0.03 g / L.
[0008] Preferably, the concentration of pyromellitic chlorobenzene chloride in the organic phase solution in step (1) is 0.1~3.0 g / L.
[0009] Preferably, in step (2), the volume ratio of the first aqueous phase solution, the second aqueous phase solution, and the organic phase solution is 1:(0.8~1.2):(0.8~1.2).
[0010] Preferably, the temperature of the interfacial polymerization reaction in step (2) is 20~30℃ and the time of the interfacial polymerization reaction is 20~120s.
[0011] Preferably, the heat treatment temperature in step (2) is 50~100℃ and the heat treatment time is 30s~30min.
[0012] The present invention also provides a TA-COF-TMC dense ultrafiltration membrane prepared by the preparation method described in the above technical solution.
[0013] The present invention also provides the application of the TA-COF-TMC dense ultrafiltration membrane described in the above technical solution in the treatment of dye wastewater.
[0014] This invention provides a method for preparing a dense ultrafiltration membrane for efficient dye / salt separation, comprising the following steps: (1) dissolving tannic acid in a buffer solution to obtain a first aqueous solution; uniformly dispersing a covalent organic framework material in deionized water to obtain a second aqueous solution; dissolving trimesoyl chloride in an organic solvent to obtain an organic solution; (2) sequentially coating the first aqueous solution, the second aqueous solution, and the organic solution obtained in step (1) onto the surface of a supporting membrane, followed by interfacial polymerization and heat treatment to obtain a TA-COF-TMC dense ultrafiltration membrane. This invention uses covalent organic framework (COF) material as a filler, combined with the tannic acid (TA)-tristoyl chloride (TMC) interfacial polymerization process to prepare a COF-modified dense ultrafiltration membrane. Due to the synergistic effect of COF nanomaterials and TA, more water molecule transport channels are constructed, improving the permeation performance. The prepared dense ultrafiltration membrane has a high dye rejection rate and a high water flux in dye separation, effectively separating dyes / salts and exhibiting good antifouling performance and long-term stability. The results of the examples show that the dense ultrafiltration membrane prepared in this invention has a nearly 100% rejection rate for negatively charged direct red dye (1373.07 Da) and a rejection rate of only 2.8% for sodium chloride in the separation process of a mixed solution of dye and salt. Attached Figure Description
[0015] Figure 1The images show scanning electron microscope (SEM) images of the surface and cross-sectional morphology of the two films in Example 2 and Comparative Example 1. Figure 2 The following are the FTIR spectra of the two films in Example 2 and Comparative Example 1; Figure 3 The Zeta potential diagrams are for the two membranes in Example 2 and Comparative Example 1. Figure 4 The graph shows the molecular weight cutoff (MWCO) of the two membranes in Example 2 and Comparative Example 1. Figure 5 The pore size distribution diagrams are shown for the two membranes in Example 2 and Comparative Example 1. Figure 6 The graph shows the selectivity of the two membranes in Example 2 and Comparative Example 1 for different dyes at high concentrations (200 mg / L) and low concentrations (20 mg / L); Figure 7 The graphs show the permeability and salt selectivity of the two membranes in Example 2 and Comparative Example 1 for four representative single salts (sodium sulfate, magnesium sulfate, magnesium chloride, and sodium chloride). Figure 8 The graphs show the dye / salt separation performance of the two membranes in Example 2 and Comparative Example 1 for DR80+LY / NaCl. Figure 9 The graphs show the long-term stability test results of the two membranes in Example 2 and Comparative Example 1. Detailed Implementation
[0016] This invention provides a method for preparing a dense ultrafiltration membrane for high-efficiency dye / salt separation, comprising the following steps: (1) Dissolve tannic acid in a buffer solution to obtain a first aqueous solution; uniformly disperse covalent organic framework material in deionized water to obtain a second aqueous solution; dissolve pyromellitic acid chloride in an organic solvent to obtain an organic solution; (2) The first aqueous solution, the second aqueous solution and the organic solution obtained in step (1) are sequentially coated on the surface of the support membrane, and then subjected to heat treatment after interfacial polymerization reaction to obtain a TA-COF-TMC dense ultrafiltration membrane.
[0017] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and products prepared by commercially available products well known to those skilled in the art or by conventional preparation methods are acceptable.
[0018] In this invention, tannic acid is dissolved in a buffer solution to obtain a first aqueous solution.
[0019] In this invention, the buffer solution preferably comprises a phosphate buffer solution or a Tris buffer solution; the pH value of the buffer solution is preferably 7-8.5, more preferably 8. By controlling the pH value of the buffer solution within the above range, this invention can improve the solubility of tannic acid, maintain excellent reactivity, and is also more conducive to the subsequent interfacial polymerization reaction.
[0020] In this invention, the concentration of tannic acid in the first aqueous solution is preferably 0.01~3.0 g / L. As one embodiment, the concentration of tannic acid in the first aqueous solution can specifically be 0.01 g / L, 0.05 g / L, 0.1 g / L, 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, or 3.0 g / L.
[0021] This invention involves uniformly dispersing a covalent organic framework material in deionized water to obtain a second aqueous solution.
[0022] This invention does not specifically limit the type of covalent organic framework material; any covalent organic framework material well-known to those skilled in the art for use in the field of water treatment can be used. As one embodiment, the covalent organic framework material may specifically be COF-LZU1.
[0023] As one embodiment, the preparation method of COF-LZU1 is as follows: 50-300 mg of 1,3,5-benzyltriformaldehyde is dissolved in 5-30 mL of 1,4-dioxane and sonicated to dissolve it. Then, 50-300 mg of p-phenylenediamine is added to the above mixed solution and sonicated to disperse and dissolve it. 0.2-1.2 mL of acetic acid aqueous solution (1-4 mol / L) is added to the mixed solution as a catalyst. After standing at room temperature for three days, the mixture is centrifuged and washed three times with 1,4-dioxane and ethanol. Finally, it is vacuum dried at 50-70°C for 10-20 h.
[0024] In this invention, the particle size of the covalent organic framework material is preferably 0.05~2.0 μm.
[0025] In this invention, the concentration of the covalent organic framework material in the second aqueous solution is preferably 0.001~0.03 g / L. As one embodiment, the concentration of the covalent organic framework material in the second aqueous solution can specifically be 0.001 g / L, 0.002 g / L, 0.004 g / L, 0.005 g / L, 0.006 g / L, 0.008 g / L, 0.01 g / L, 0.02 g / L, or 0.03 g / L.
[0026] In this invention, pyromellitic methyl chloride is dissolved in an organic solvent to obtain an organic phase solution.
[0027] In this invention, the organic solvent preferably includes one of n-hexane, cyclohexane, n-heptane, and Isopar G.
[0028] In this invention, the concentration of trimesoyl chloride in the organic phase solution is preferably 0.1~3.0 g / L. As one embodiment, the concentration of trimesoyl chloride in the organic phase solution can specifically be 0.1 g / L, 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, or 3.0 g / L.
[0029] After obtaining the first aqueous solution, the second aqueous solution, and the organic solution, the present invention sequentially coats the first aqueous solution, the second aqueous solution, and the organic solution onto the surface of the support membrane, and performs heat treatment after interfacial polymerization reaction to obtain a TA-COF-TMC dense ultrafiltration membrane.
[0030] The present invention does not have any special limitation on the type of support membrane, and any support membrane for ultrafiltration that is well known to those skilled in the art can be used.
[0031] In one embodiment, the support film may specifically be a polyethersulfone support film.
[0032] As one embodiment, the preparation method of the polyethersulfone (PES) supported membrane can be specifically as follows: N-methylpyrrolidone, sodium dodecyl sulfate, polyethylene glycol, and PES are mixed in a mass ratio of 82:1:1:16 to prepare a casting solution. After being stirred and heated to dissolve evenly, the solution is placed in a 60°C oven for degassing. After cooling to room temperature, the solution is evenly coated onto a nonwoven fabric using a doctor blade and immediately immersed in deionized water for phase inversion, thus obtaining the PES ultrafiltration supported membrane. This membrane is then immersed in deionized water for subsequent use. As one embodiment, the thickness of the supported membrane can be specifically 100~250 μm. The present invention does not impose any special limitations on the size of the supported membrane; it can be selected according to actual needs.
[0033] In this invention, the support membrane is preferably soaked in deionized water for 10-15 hours before use.
[0034] In this invention, the volume ratio of the first aqueous solution, the second aqueous solution, and the organic solution is preferably 1:(0.8~1.2):(0.8~1.2), and more preferably 1:1:1.
[0035] The present invention does not impose any particular limitation on the coating operation; any technique well-known to those skilled in the art can be used to form a film of uniform thickness. As one embodiment, the coating is performed by pouring.
[0036] After the first aqueous solution is coated, the present invention preferably allows the coated substrate to stand for 5 to 25 minutes, then uses filter paper to gently absorb the residual solvent on the membrane surface, and then coats the second aqueous solution.
[0037] After the second aqueous solution coating is completed, the coated substrate is preferably allowed to stand for 1-30 minutes, then the residual solvent on the membrane surface is gently blotted dry with filter paper before coating with the organic phase solution. In this invention, during the standing process, tannic acid and COF material undergo covalent interaction, achieving membrane surface modification.
[0038] In this invention, the preferred temperature for the interfacial polymerization reaction is 20-30°C; the preferred time for the interfacial polymerization reaction is 20-120 seconds; and the preferred humidity for the interfacial polymerization reaction is 55-65%. In this invention, the interfacial polymerization reaction occurs when the organic phase solution comes into contact with the aqueous phase monomer.
[0039] In this invention, the heat treatment temperature is preferably 50~100℃; the heat treatment time is preferably 30s~30min. As one embodiment, the heat treatment temperature can specifically be 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃; the heat treatment time can specifically be 30s, 1min, 5min, 10min, 15min, 20min, 25min or 30min.
[0040] This invention controls the concentration, temperature, and time of each solution within the above-mentioned range, which can further improve the performance of the dense ultrafiltration membrane.
[0041] In this invention, the obtained TA-COF-TMC dense ultrafiltration membrane is preferably immersed in deionized water for later use.
[0042] This invention generates a polyester film through the interfacial polymerization reaction of aqueous monomer tannic acid and organic monomer trimesoyl chloride. By adjusting the reaction time and concentration of COF nanomaterials, the membrane performance is optimized, and the prepared dense ultrafiltration membrane achieves efficient dye retention and selective salt ion permeation while significantly improving water flux, thus realizing dye / salt separation.
[0043] This invention uses COF nanomaterials as membrane modifiers to introduce them into the membrane, thereby regulating the interfacial polymerization process of tannic acid and trimesoyl chloride. This results in a modified dense ultrafiltration membrane with higher water flux and better rejection rate. The introduction of COF nanomaterials in this invention enhances the surface roughness and electronegativity of the membrane, exhibiting excellent dye / salt selective permeation, and effectively treating dye wastewater.
[0044] The present invention also provides a TA-COF-TMC dense ultrafiltration membrane prepared by the preparation method described in the above technical solution.
[0045] The present invention also provides the application of the TA-COF-TMC dense ultrafiltration membrane described in the above technical solution in the treatment of dye wastewater.
[0046] The dense ultrafiltration membrane prepared by this invention significantly improves water flux while achieving efficient dye retention and selective salt ion permeation, enabling dye / salt separation. Therefore, it can be used for dye wastewater treatment.
[0047] The present invention does not impose any special limitations on the operation of the application, and any technical solution known to those skilled in the art can be used.
[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0049] The preparation method of the polyethersulfone support membrane in the embodiments and comparative examples of the present invention is as follows: N-methylpyrrolidone, sodium dodecyl sulfate, polyethylene glycol, and polyethersulfone are mixed in a mass ratio of 82:1:1:16 to prepare a casting solution. After being stirred and heated to dissolve evenly, the solution is placed in a 60°C oven for degassing treatment. After cooling to room temperature, the solution is evenly coated onto a nonwoven fabric using a doctor blade and immediately immersed in deionized water for phase inversion, thus obtaining the polyethersulfone ultrafiltration support membrane. The membrane is then immersed in deionized water for subsequent use, with a thickness of 200 μm.
[0050] The preparation method of COF-LZU1 in the embodiments and comparative examples of this invention is as follows: 150 mg of 1,3,5-benzyltriformaldehyde is dissolved in 15 mL of 1,4-dioxane, and the solution is sonicated to dissolve it. Then, 150 mg of p-phenylenediamine is added to the above mixed solution and sonicated to disperse and dissolve it. 0.6 mL of 1.0 mol / L acetic acid aqueous solution is added to the mixed solution as a catalyst. After standing at room temperature for three days, the solution is centrifuged and washed three times with 1,4-dioxane and ethanol. The solution is then vacuum dried at 60 °C for 12 h to obtain COF-LZU1 with a particle size of 0.5~1.2 μm.
[0051] Example 1 A method for preparing a dense ultrafiltration membrane for high-efficiency dye / salt separation is as follows: (1) Dissolve tannic acid in 30 mL of phosphate buffer solution to obtain the first aqueous phase solution, wherein the pH value of the phosphate buffer solution is 8 and the concentration of tannic acid in the first aqueous phase solution is 0.05 g / L; COF nanomaterials (COF-LZU1) were uniformly dispersed in 30 mL of deionized water to obtain a second aqueous solution, wherein the concentration of COF nanomaterials was 0.001 g / L. Tristyrene chloride was dissolved in 30 mL of n-hexane solution to obtain an organic phase solution, wherein the concentration of tristyrene chloride was 3.0 g / L; (2) Under room temperature (25℃, 60% humidity) conditions, the polyethersulfone supported membrane was soaked in deionized water for 12h, and then fixed in the membrane reaction device. The first aqueous phase solution obtained in step (1) was poured onto the surface of the polyethersulfone supported membrane. After standing for 25min, the residual solvent on the membrane surface was gently blotted with filter paper. Then the second aqueous phase solution was poured. After standing for 3min, the residual solvent on the membrane surface was gently blotted with filter paper. Then the organic phase solution was poured. After the interfacial polymerization reaction was carried out for 20s, it was placed in an oven for heat treatment. The heat treatment temperature was 60℃ and the time was 30s. After the heat treatment was completed, the membrane was taken out from the membrane reaction device and soaked in deionized water for later use. The TA-COF-TMC dense ultrafiltration membrane was obtained and denoted as TA-COF-TMC. 0.001 .
[0052] Example 2 The mass concentration of COF nanomaterials in the second aqueous solution of Example 1 was replaced with 0.005 g / L, while all other aspects remained the same as in Example 1, resulting in a dense TA-COF-TMC ultrafiltration membrane, denoted as TA-COF-TMC. 0.005 .
[0053] Example 3 The mass concentration of COF nanomaterials in the second aqueous solution of Example 1 was replaced with 0.01 g / L, while all other parameters remained the same as in Example 1, resulting in a dense TA-COF-TMC ultrafiltration membrane, denoted as TA-COF-TMC. 0.01 .
[0054] Example 4 The mass concentration of COF nanomaterials in the second aqueous solution of Example 1 was replaced with 0.02 g / L, while all other parameters remained the same as in Example 1, resulting in a dense TA-COF-TMC ultrafiltration membrane, denoted as TA-COF-TMC. 0.02 .
[0055] Comparative Example 1 The second aqueous phase solution in Example 1 is omitted and referred to as TA-TMC membrane.
[0056] A cross-flow apparatus was used to test the permeate flux of the membrane to dye and the rejection rate of direct red dye (the concentration of the direct red dye solution was 20 mg / L). The apparatus consisted of a pump, membrane cells, pipelines, pressure regulating valves, reflux valves, and flow detectors. The cross-flow apparatus had three membrane cells, each with a diameter of 7.068 cm³. 2 The effective filtration area. Before the formal test, the prepared membrane was pre-pressurized at 0.15 MPa for 20 min until the water permeability reached a stable state. In the formal experiment, the pressure was changed to 0.1 MPa, the pure water flux of the membrane was tested, and the ambient temperature was room temperature. The water flux (J) was calculated using formula (1).
[0057] Equation (1), In equation (1), J (Lm) -2 h -1 bar -1 ), ΔV (L) A (m) 2 )and Δt (h) represents membrane flux, permeate volume, effective membrane area, and permeate time, respectively.
[0058] The retention rates (%) of dyes and salts are calculated using formula (2).
[0059] Equation (2), In equation (2), Cp It is the concentration of the permeate (g / L). C f This is the concentration of the stock solution (g / L).
[0060] The performance test results of the dense ultrafiltration membranes in Comparative Example 1 and Examples 1-4 are shown in Table 1.
[0061] Table 1. Performance test results of the dense ultrafiltration membranes in Comparative Example 1 and Examples 1-4
[0062] Scanning electron microscope (SEM) images of the surface and cross-sectional morphology of the two films in Example 2 and Comparative Example 1 are shown below. Figure 1 As shown. From Figure 1 As can be seen, the two membranes have similar surface morphologies, being flat and smooth, but their cross-sections are significantly different. The TA-TMC membrane has a relatively flat cross-section, while after modification with nanomaterials, the cross-section shows obvious protrusions and the membrane thickness increases, indicating that COF was successfully introduced into the membrane.
[0063] The Fourier Transform Infrared (FTIR) spectra of the two films in Example 2 and Comparative Example 1 are as follows: Figure 2 As shown. From Figure 2 As can be seen from the data, the two membranes are effective at depths of 3200~3600 cm⁻¹. -1 A broad peak exists at 1710 cm⁻¹, which is the NH / OH stretching vibration peak. This may indicate the presence of unreacted amino groups or that the peak is entirely due to the -OH stretching vibration of TA, suggesting successful introduction of the TA molecule. All peaks are located at 1710 cm⁻¹. -1 The characteristic stretching vibration peak of the ester group at 1620 cm⁻¹ indicates that TA successfully replaced traditional amine monomers and participated in the construction of the separation layer. Furthermore, the TA-COF-TMC membrane exhibits a peak at 1620 cm⁻¹. -1A distinct strong absorption peak appeared at [value missing], which is the stretching vibration of the imine bond (C=N), due to the reversible condensation reaction of the aldehyde and amino groups in COF-LZU1. Combined with the characteristic signal of the imine bond in FTIR, it can be seen that the COF nanomaterial has been successfully introduced into the film.
[0064] The Zeta potential diagrams of the two membranes in Example 2 and Comparative Example 1 are shown below. Figure 3 As shown. From Figure 3 As can be seen, compared with TA-TMC membrane, COF nanomaterials change the surface properties of the membrane. The electronegativity of the nanomaterials enhances the surface electronegativity of the membrane, thereby improving the electrostatic repulsion effect on the membrane surface and further improving the membrane's retention of negatively charged dyes.
[0065] The molecular weight cutoff (MWCO) of the two membranes in Example 2 and Comparative Example 1 are shown in the figure below. Figure 4 As shown, the aperture distribution diagram is as follows: Figure 5 As shown. From Figure 4 As can be seen, the MWCO of the TA-TMC membrane is 3547 Da. After introducing a certain concentration of COF nanomaterials, the modified membrane prepared has a molecular weight cutoff of 9894 Da. Figure 5 As can be seen, the introduction of COF nanomaterials increases the membrane pore size from 0.3 nm to 2.7 nm, and the increased pore size will significantly improve the membrane water flux.
[0066] The selectivity of the two membranes in Example 2 and Comparative Example 1 for different dyes at high concentrations (200 mg / L) and low concentrations (20 mg / L) is as follows: Figure 6 As shown. From Figure 6 As can be seen, the TA-COF-TMC membrane has a nearly 100% rejection rate for the negatively charged dyes Direct Red (DR80) and Methyl Blue (MB). Based on the size sieving effect, the molecular weight of DR80 (1373.07 Da) is greater than that of MB (799.8 Da), making its rejection performance better than MB. Due to the influence of the size sieving effect and the Donnan effect, the molecular weights of the two dyes are relatively small and the membrane is negatively charged. Therefore, the rejection rates for the neutral dye Tartrazine (LY, 534.36 Da) and the positively charged dye Rhodamine B (RhB, 479.01 Da) are only 67.028% and 21.96%, respectively. This membrane exhibits good rejection rates for negatively charged macromolecular dyes.
[0067] The permeability and salt selectivity of the two membranes in Example 2 and Comparative Example 1 to four representative single salts (sodium sulfate, magnesium sulfate, magnesium chloride, and sodium chloride, each with a concentration of 2.0 g / L) are as follows: Figure 7 As shown. From Figure 7 As can be seen, the membrane with added COF nanomaterials exhibits good selective permeability for the retention of four single salts.
[0068] The permeation and separation performance of the two membranes in Example 2 and Comparative Example 1 for DR80+LY / NaCl dye / salt (DR80, LY and NaCl concentrations of 20 mg / L, 20 mg / L and 2 g / L, respectively) are as follows: Figure 8 As shown. From Figure 8 As can be seen, the TA-COF-TMC membrane still maintains good retention performance for DR80 dye and achieves selective salt permeation. The TA-COF-TMC membrane will effectively separate dye / salt.
[0069] The long-term stability tests of the two membranes in Example 2 and Comparative Example 1 are as follows: Figure 9 As shown, DR80 at a concentration of 20 mg / L was used as the feed solution, and continuous testing was conducted for 48 hours. From Figure 9 As can be seen, both membranes maintained a high dye rejection rate during the 48-hour operation.
[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a compact ultrafiltration membrane with high dye / salt separation efficiency, comprising the following steps: (1) dissolving tannic acid in a buffer solution to obtain a first aqueous solution; uniformly dispersing a covalent organic framework material in deionized water to obtain a second aqueous solution; and dissolving trimesoyl chloride in an organic solvent to obtain an organic solution; (2) sequentially coating the first aqueous solution, the second aqueous solution and the organic solution obtained in step (1) on a support membrane, and then performing interfacial polymerization and heat treatment to obtain a TA-COF-TMC compact ultrafiltration membrane.
2. The production method according to claim 1, characterized by, The buffer solution in step (1) comprises a phosphate buffer solution or a Tris buffer solution, and the pH value of the buffer solution is 7-8.
5.
3. The preparation method according to claim 1, characterized in that, The concentration of tannic acid in the first aqueous solution in step (1) is 0.01-3.0 g / L.
4. The method of claim 1, wherein, The concentration of the covalent organic framework material in the second aqueous solution in step (1) is 0.001-0.03 g / L.
5. The preparation method according to claim 1, characterized in that, The concentration of trimesoyl chloride in the organic solution in step (1) is 0.1-3.0 g / L.
6. The method of claim 1, wherein, The volume ratio of the first aqueous solution, the second aqueous solution and the organic solution in step (2) is 1: (0.8-1.2): (0.8-1.2).
7. The preparation method according to claim 1, characterized in that, The temperature of the interfacial polymerization in step (2) is 20-30℃, and the time of the interfacial polymerization is 20-120 s.
8. The method of claim 1, wherein, The temperature of the heat treatment in step (2) is 50-100℃, and the time of the heat treatment is 30 s-30 min. 9.The TA-COF-TMC compact ultrafiltration membrane prepared by the method of any one of claims 1-8. 10.The application of the TA-COF-TMC compact ultrafiltration membrane of claim 9 in dye wastewater treatment.