A high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization and a preparation method thereof

Abstract

The application discloses a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization and a preparation method thereof, and comprises the following steps: (1) fixing a polysulfone ultrafiltration membrane on an organic glass frame to remove liquid drops on the membrane surface; (2) pouring an aqueous solution containing m-phenylenediamine, camphor sulfonic acid, triethylamine and pectin on the surface of the polysulfone ultrafiltration membrane, and then removing residual aqueous solution after standing for a period of time; (3) pouring an organic solution containing trimesoyl chloride on the surface of the membrane obtained in the step (2), and then removing excess organic solution after standing for a period of time; and (4) obtaining the high-pressure reverse osmosis membrane by sequentially subjecting the membrane obtained in the step (3) to standing, heat treatment and pure water rinsing. The natural high polymer pectin is used as an adjusting agent in the application, the thickness and pore size distribution of the polyamide separation layer are reduced, the hydrophilicity and the chargeability of the membrane are improved, and the effect that the permeation flux and the rejection rate of the reverse osmosis membrane are simultaneously improved is achieved.

Description

Technical Field

[0001] This invention relates to the field of high-pressure reverse osmosis membrane preparation technology, and in particular to a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization and its preparation method. Background Technology

[0002] Aromatic polyamide (PA) thin-layer composite (TFC) membranes are the most advanced commercially available reverse osmosis membranes. The PA separation layer, which enables desalination, is formed by rapid cross-linking of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) as reactive monomers on the surface of a polysulfone (PSF) supported membrane via interfacial polymerization (IP). High-pressure reverse osmosis (HPRO) membranes, as a special type of reverse osmosis membrane, are suitable for extremely high pressure (5.52 MPa) and salinity (32,000 mg / L NaCl) conditions, and possess better water permeability and permeability selectivity. However, because the aromatic polyamide separation layer of HPRO membranes typically has irregular and discontinuous sub-nanometer transport channels, a "trade-off" effect occurs, where water permeability and separation selectivity are mutually exclusive. Therefore, the preparation of HPRO membranes faces the significant challenge of simultaneously achieving high permeability and high selectivity.

[0003] By precisely controlling the thickness, pore size distribution, hydrophilicity, and charge of the aromatic polyamide separation layer, the desalination rate and water permeation flux of high-pressure reverse osmosis membranes can be adjusted. However, due to the rapid diffusion rate of the reactants and the intense interfacial polymerization reaction, the aromatic polyamide separation layer has an extremely dense but non-uniform multi-scale structure, with a thickness typically exceeding 250 nm, which is difficult to precisely control, thus limiting the improvement of water permeability. On the other hand, due to the interaction forces between the reactants, uniform dispersion is difficult, resulting in a highly disordered polyamide polymer chain structure, leading to a large free volume (pore size) in the polyamide separation layer (typically...). The relatively wide pore size distribution makes it difficult to further improve the desalination rate. In summary, how to overcome the "trade-off" effect between water permeability and separation selectivity has become a bottleneck problem restricting the performance improvement of reverse osmosis membranes, especially high-pressure reverse osmosis membranes.

[0004] By regulating the distribution and diffusion of reactive monomers, the interfacial polymerization rate can be controlled, improving the orderliness of the interfacial polymerization reaction. This allows for narrowing the pore size distribution while reducing film thickness, becoming an effective strategy and approach to overcome the "trade-off" effect. Pectin, a natural polymer, is a typical anionic heteropolysaccharide widely found in the peels of citrus fruits such as oranges, lemons, and grapefruits. Due to its rich hydroxyl and carboxyl groups in its molecular structure, pectin possesses excellent hydrophilicity. Furthermore, as a commonly used food thickener, pectin can significantly increase the viscosity of liquids. Summary of the Invention

[0005] This invention addresses the "trade-off" effect between permeation flux and rejection rate in high-pressure reverse osmosis (HSO) membranes by providing a Pectin-assisted interfacial polymerization (PA)-based HSO membrane and its preparation method. Pectin is used as an additive in the aqueous solution of the interfacial polymerization reaction. By increasing the viscosity of the aqueous solution, the diffusion rate of poly(MPD) into the organic phase is slowed, reducing the depth of the miscible zone in the interfacial polymerization reaction and thus decreasing the thickness of the polyamide separation layer. Simultaneously, by weakening the interactions between MPD monomers in the aqueous solution, the uniformity of MPD dispersion is improved, enhancing the orderliness of the interfacial polymerization reaction and the regularity of the polyamide polymer chain entanglement. This results in increased polyamide packing density, narrower pore size distribution, and optimized pore structure. Furthermore, the abundant functional groups in the pectin molecular structure endow the polyamide separation layer with higher hydrophilicity and charge, contributing to further improving the permeation selectivity of the HSO membrane.

[0006] This invention is achieved by a method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization, comprising the following steps:

[0007] (1) Fix the polysulfone ultrafiltration membrane on the plexiglass frame and drain the water droplets on the surface of the polysulfone ultrafiltration membrane;

[0008] (2) Pour an aqueous solution containing m-phenylenediamine, camphor sulfonic acid, triethylamine and an interfacial polymerization reaction modifier onto the surface of a polysulfone ultrafiltration membrane, let it stand for a period of time, and then remove the residual aqueous phase solution on the surface; wherein, the interfacial polymerization reaction modifier is pectin, with a mass percentage of 0.05 to 0.3 wt%.

[0009] (3) Pour the organic solution containing pyromellitic chloride onto the surface of the membrane obtained in step (2), let it stand for a period of time, and then remove the residual organic phase solution on the surface.

[0010] (4) Let the membrane obtained in step (3) stand until the excess solution on the surface evaporates naturally, then put it into a forced-air drying oven and heat-treat it at a certain temperature for a period of time. Rinse the membrane surface with deionized water to remove the residue on the membrane surface and obtain a high-pressure reverse osmosis membrane.

[0011] Preferably, in step (1), the polysulfone ultrafiltration membrane has a pure water permeation flux of 400–500 L·m at 0.1 MPa. -2 ·h -1 The bovine serum albumin retention rate was 90.1%–90.3%.

[0012] Preferably, in the aqueous solution of step (2), the mass percentage of m-phenylenediamine is 1.5-4 wt%, the mass percentage of camphor sulfonic acid is 2-3.5 wt%, the mass percentage of triethylamine is 0.8-2 wt%, the mass percentage of pectin is 0.05-0.3 wt%, and the solvent of the aqueous solution is deionized water.

[0013] More preferably, in the aqueous solution of step (2), the mass percentage of m-phenylenediamine is 2.8 wt%, the mass percentage of camphor sulfonic acid is 2.8 wt%, the mass percentage of triethylamine is 1.3 wt%, and the mass percentage of pectin is 0.05-0.3 wt%.

[0014] Preferably, in step (2), the settling time is 30 to 50 seconds.

[0015] Preferably, in the organic solution of step (3), the mass percentage of pyromellitic chloroform is 0.1 to 0.25 wt%, and the solvent of the organic solution is one or more of n-hexane, isoparaffin G, isoparaffin H, isoparaffin L, and isoparaffin M.

[0016] More preferably, in the organic solution of step (3), the mass percentage of pyromellitic acid chloride is 0.17 wt%, and the solvent of the organic solution is n-hexane.

[0017] Preferably, in step (3), the settling time is 30 to 50 seconds.

[0018] Preferably, in step (4), the temperature of the forced-air drying oven is 80-120℃ and the heat treatment time is 100-300s.

[0019] Further preferably, the temperature of the forced-air drying oven is 95℃, and the heat treatment time is 190s.

[0020] A high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization was prepared using the above-described method.

[0021] High-pressure reverse osmosis membranes can achieve a rejection rate of 99.57% for 32000 mg / L NaCl at 5.52 MPa, with a permeation flux of up to 80.15 L·m⁻². -2 ·h -1 .

[0022] The advantages and positive effects of this invention are:

[0023] In this invention, pectin is used as an auxiliary interfacial polymerizing agent to improve the permeation flux and permeation selectivity of the high-pressure reverse osmosis membrane. Its advantages are as follows:

[0024] 1. In this invention, pectin is used as an additive in the aqueous solution of the interfacial polymerization reaction. By increasing the viscosity of the aqueous solution, the diffusion rate of MPD into the organic phase is slowed down, the depth of the miscible zone of the interfacial polymerization reaction is reduced, thereby reducing the thickness of the PA separation layer.

[0025] 2. This invention improves the uniformity of MPD dispersion, enhances the orderliness of interfacial polymerization reactions and the regularity of polyamide polymer chain entanglement by weakening the interaction between MPD reactive monomers in aqueous solution, thereby increasing the polyamide packing density, narrowing the pore size distribution, and optimizing the pore structure.

[0026] 3. The abundant functional groups in the pectin molecular structure can endow the polyamide separation layer with higher hydrophilicity and charge, which helps to further improve the permeation selectivity of the high-pressure reverse osmosis membrane.

[0027] 4. Pectin is a typical anionic heteropolysaccharide that is widely found in the peels of citrus fruits, lemons, and grapefruits. It is inexpensive, green, natural, and pollution-free, which meets current environmental protection requirements and the concept of sustainable development.

[0028] 5. The preparation method of this invention is simple and easy to industrialize. Pectin, as an interface-assisted polymerization agent, can improve the separation performance of reverse osmosis membranes without participating in the polymerization reaction itself when added to aqueous solution. Compared with other chemical modification methods, it is simple to operate and does not require additional production processes and equipment.

[0029] 6. Although the mass percentage of pectin added in the preparation method of this invention is less than 0.3 wt%, the performance of the reverse osmosis membrane is significantly improved. Attached Figure Description

[0030] Figure 1 The infrared spectra of the high-pressure reverse osmosis membranes obtained in Examples 2 and 5 and Comparative Examples 1 and 2 of this invention are shown below.

[0031] Figure 2 The above are the positron annihilation lifetime spectra of the high-pressure reverse osmosis membranes obtained in Examples 2 and 5 and Comparative Examples 1 and 2 of this invention.

[0032] Figure 3 This is a scanning electron microscope image of the surface of the high-pressure reverse osmosis membrane obtained in Example 2 of the present invention;

[0033] Figure 4 This is a scanning electron microscope image of the surface of the high-pressure reverse osmosis membrane obtained in Example 5 of the present invention;

[0034] Figure 5 This is a cross-sectional scanning electron microscope image of the high-pressure reverse osmosis membrane obtained in Example 2 of the present invention;

[0035] Figure 6 This is a cross-sectional scanning electron microscope image of the high-pressure reverse osmosis membrane obtained in Example 5 of the present invention;

[0036] Figure 7 This is a scanning electron microscope image of the surface of the high-pressure reverse osmosis membrane obtained in Comparative Example 1 of the present invention;

[0037] Figure 8 This is a scanning electron microscope image of the surface of the high-pressure reverse osmosis membrane obtained in Comparative Example 2 of the present invention;

[0038] Figure 9 This is a cross-sectional scanning electron microscope image of the high-pressure reverse osmosis membrane obtained in Comparative Example 1 of the present invention;

[0039] Figure 10 This is a cross-sectional scanning electron microscope image of the high-pressure reverse osmosis membrane obtained in Comparative Example 2 of the present invention. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following embodiments are only preferred embodiments of the present invention, and the scope of protection claimed by the present invention is not limited thereto.

[0041] This invention provides a method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization, comprising the following steps:

[0042] (1) Fix the polysulfone ultrafiltration membrane on the plexiglass frame and drain the water droplets on the surface of the polysulfone ultrafiltration membrane;

[0043] Among them, the polysulfone ultrafiltration membrane has a pure water permeation flux of 400–500 L·m at 0.1 MPa. -2 ·h -1 The bovine serum albumin retention rate was 90.1%–90.3%.

[0044] (2) Pour an aqueous solution containing m-phenylenediamine, camphor sulfonic acid, triethylamine and an interfacial polymerization reaction modifier onto the surface of a polysulfone ultrafiltration membrane, let it stand for a period of time, and then remove the residual aqueous phase solution on the surface; wherein, the interfacial polymerization reaction modifier is pectin, with a mass percentage of 0.05 to 0.3 wt%.

[0045] In this aqueous solution, the mass percentages of m-phenylenediamine are 1.5–4 wt%, camphor sulfonic acid is 2–3.5 wt%, triethylamine is 0.8–2 wt%, and pectin is 0.05–0.3 wt%. The solvent for the aqueous solution is deionized water. In this preferred embodiment, the mass percentages of m-phenylenediamine, camphor sulfonic acid, triethylamine, and pectin in the aqueous solution are 2.8 wt%, 2.8 wt%, 1.3 wt%, and 0.05–0.3 wt%.

[0046] The settling time is 30-50 seconds. In this embodiment, the settling time is preferably 40 seconds.

[0047] (3) Pour the organic solution containing pyromellitic chloride onto the surface of the membrane obtained in step (2), let it stand for a period of time, and then remove the residual organic phase solution on the surface.

[0048] In this embodiment, the organic solution contains 0.1–0.25 wt% trimesoyl chloride by mass, and the solvent is one or more of n-hexane, isoalkanes G, H, L, and M. Preferably, in this embodiment, the organic solution contains 0.17 wt% trimesoyl chloride by mass, and the solvent is n-hexane.

[0049] The settling time is 30-50 seconds. In this embodiment, the settling time is preferably 40 seconds.

[0050] (4) Let the membrane obtained in step (3) stand until the excess solution on the surface evaporates naturally, then put it into a forced-air drying oven and heat-treat it at a certain temperature for a period of time. Rinse the membrane surface with deionized water to remove the residue on the membrane surface and obtain a high-pressure reverse osmosis membrane.

[0051] The temperature of the forced-air drying oven is 80-120℃, and the heat treatment time is 100-300s. In this embodiment, the temperature of the forced-air drying oven is preferably 95℃, and the heat treatment time is 190s.

[0052] To better understand the above embodiments of the present invention, further explanation is provided below with reference to specific examples.

[0053] In the following embodiments and comparative examples:

[0054] m-Phenylenediamine, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of 99 wt%;

[0055] Camphor sulfonic acid, purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd., with a purity >98wt%;

[0056] Triethylamine, purchased from Tianjin Kemeo Chemical Reagent Co., Ltd., analytical grade;

[0057] Pectin, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with galacturonic acid (dry basis) ≥74.0%;

[0058] Polysulfone ultrafiltration membrane, pure water permeation flux at 0.1 MPa is 400–500 L·m⁻¹ -2 ·h -1 The bovine serum albumin retention rate was 90.1%–90.3%.

[0059] Tristyroyl chloride, purchased from Alfa Aesar, purity >98 wt.%;

[0060] n-Hexane, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., analytical grade.

[0061] Example 1:

[0062] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization includes the following steps:

[0063] (1) Fix the polysulfone ultrafiltration membrane on the plexiglass frame and drain the water droplets on the surface of the polysulfone ultrafiltration membrane;

[0064] (2) Pour an aqueous solution containing m-phenylenediamine, camphor sulfonic acid, triethylamine and pectin onto the surface of the polysulfone ultrafiltration membrane, let it stand for 40 seconds, and then remove the residual aqueous solution on the surface; wherein, the mass percentage of m-phenylenediamine is 2.8 wt%, the mass percentage of camphor sulfonic acid is 2.8 wt%, the mass percentage of triethylamine is 1.3 wt%, and the mass percentage of pectin is 0.05 wt%.

[0065] (3) Pour the hexane solution containing trimesoyl chloride onto the surface of the membrane obtained in step (2), let it stand for 40 seconds, and then remove the residual organic phase solution on the surface; wherein the mass percentage of trimesoyl chloride is 0.17 wt%.

[0066] (4) Let the membrane obtained in step (3) stand until the excess solution on the surface evaporates naturally, then put it into a forced-air drying oven and heat-treat it at 95°C for 190s. Rinse the membrane surface with deionized water to remove the residue on the membrane surface and obtain a high-pressure reverse osmosis membrane.

[0067] Example 2:

[0068] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that: in step (2), the mass percentage of pectin is 0.1 wt%, and the other conditions remain unchanged.

[0069] Example 3:

[0070] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that: in step (2), the mass percentage of pectin is 0.15 wt%, and the other conditions remain unchanged.

[0071] Example 4:

[0072] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that: in step (2), the mass percentage of pectin is 0.2 wt%, and the other conditions remain unchanged.

[0073] Example 5:

[0074] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that: in step (2), the mass percentage of pectin is 0.3 wt%, and the other conditions remain unchanged.

[0075] Comparative Example 1:

[0076] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that pectin is not added in step (2), while the other conditions remain unchanged.

[0077] Comparative Example 2:

[0078] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that: in step (2), the mass percentage of pectin is 0.5 wt%, and the other conditions remain unchanged.

[0079] Comparative Example 3:

[0080] A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization differs from Example 1 in that: in step (2), the mass percentage of pectin is 1 wt%, and the other conditions remain unchanged.

[0081] Performance testing

[0082] In this invention, a cross-flow filtration evaluation system was used to test the performance of the high-pressure reverse osmosis membranes prepared in Examples 1-5 and Comparative Examples 1-3.

[0083] The obtained membrane sample was placed in three parallel filtration units, with an effective membrane pool area of ​​28.46 cm². 2 A 32000 mg / L NaCl aqueous solution was used as the feed solution, and the pH of the feed solution was adjusted to 7.0 ± 0.5. First, the high-pressure reverse osmosis membrane was pre-pressurized for 30 min at 5.52 MPa and 25 ± 1 °C, and then filtered at a pressure of 5.52 MPa and a flow rate of 6 L / min. -1 Permeate was collected at a cross-flow rate.

[0084] Water permeation flux is calculated using formula (1):

[0085]

[0086] In the formula, J w Water permeation flux, in L·m -2 ·h -1 S represents the effective membrane area, in m². 2Δt is the infiltration time, in hours (h); Δv is the amount of infiltrated water collected within a certain time Δt, in liters (L).

[0087] The NaCl rejection rate R is calculated using formula (2):

[0088]

[0089] In the formula, C P The concentration of NaCl in the permeate is expressed in mg / L; C f The concentration of NaCl in the feed solution is expressed in mg / L.

[0090] The water permeability coefficient A and the salt permeability coefficient B can be calculated using formulas (3) and (4), respectively:

[0091]

[0092] In the formula, A is the water permeability coefficient, with units of L·m. -2 ·h -1 ·bar -1 B is the salt permeability coefficient, with units of L·m. -2 ·h -1 ΔP and π represent the transmembrane pressure difference and the osmotic pressure of the feed solution, respectively, both in bar.

[0093] The test results are shown in Table 1.

[0094] Table 1 Characterization results and separation performance of high-pressure reverse osmosis membrane

[0095]

[0096] As shown in Table 1, when the pectin content does not exceed 0.3 wt% (Examples 1-5), the electronegativity of the high-pressure reverse osmosis membrane gradually increases, and the NaCl rejection rate is greater than 99.4%; in addition, the water contact angle gradually decreases, the hydrophilicity increases, and the water permeation flux is significantly increased, reaching a maximum of 80.15 L·m -2 ·h -1 In particular, when the pectin content is 0.3 wt%, the NaCl rejection rate is as high as 99.57%, and the water permeability flux is as high as 80.15 L·m⁻¹. -2 ·h -1 Compared with high-pressure reverse osmosis membranes without added pectin (Comparative Example 1), the permeation flux increased by 24.34%. Therefore, it achieved the effect of simultaneously improving water permeability, desalination rate and permeation selectivity, breaking through the "trade-off" effect between permeation flux and rejection rate.

[0097] The polyamide separation layer of the high-pressure reverse osmosis membranes obtained in Examples 2 and 5 and Comparative Examples 1 and 2 was characterized by infrared spectroscopy. Figure 1 As shown, the characteristic absorption peak of pectin is at 3300 cm⁻¹. -1 and 1047cm -1 At this location, 3300cm -1 It is caused by the stretching vibration of the OH group, 1047 cm⁻¹ -1 This is caused by the stretching vibration between carbon and oxygen atoms in the α-1,4-glycosidic bond COC. As the pectin concentration in the aqueous solution gradually increases, the two characteristic peaks mentioned above in Comparative Example 1, Example 2, Example 5, and Comparative Example 2 all gradually increase, indicating that pectin is incorporated into the polyamide layer. Due to the good hydrophilicity and abundant carboxyl functional groups of pectin, the hydrophilicity and electronegativity of the high-pressure reverse osmosis membranes obtained in Examples 1-5 gradually improve.

[0098] The surface and cross-sectional morphology of the high-pressure reverse osmosis membranes obtained in Examples 2 and 5 and Comparative Examples 1 and 2 were analyzed, and the scanning electron microscope images are shown below. Figures 3-10 As shown. Figure 3 , 4 As shown in Figures 7 and 8, the surfaces of the high-pressure reverse osmosis membranes all exhibit typical polyamide leaf-like structures, with no significant changes in surface morphology. Figure 5 , 6 As shown in Figures 9 and 10, the cross-sectional morphology of high-pressure reverse osmosis membranes is similar. Figure 9 As shown, the polyamide separation layer thickness of the high-pressure reverse osmosis membrane obtained in Comparative Example 1 is approximately 260.49 nm; Figure 5 , 6 As shown in Figures 1 and 10, the thickness of the polyamide separation layer in the high-pressure reverse osmosis membranes obtained in Examples 2, 5, and Comparative Example 2 gradually decreased, reaching approximately 251.87 nm, 234.98 nm, and 207.37 nm, respectively. Due to the introduction of pectin, the viscosity of the aqueous solution gradually increased, the diffusion rate slowed down, and the thickness of the polyamide separation layer gradually decreased, thus promoting an increase in water permeation flux. The introduction of pectin into the aqueous phase did not significantly alter the morphology of the membrane surface, but it thinned the polyamide layer, greatly improving the water permeation flux.

[0099] In addition, the interaction energies between MPD molecules and between pectin molecules and MPD molecules were calculated under different pectin addition conditions. The calculation formulas are as follows:

[0100] E int =E A+B -(E A +E B (5)

[0101] Among them, E int E represents the interaction energy between MPD molecules and pectin molecules. A+B E represents the total energy of the MPD-pectin complex. AE represents the energy of the MPD molecule in the complex. B The values ​​represent the energy of pectin molecules in the complex, all expressed in kcal / mol.

[0102] The test results are shown in Table 2.

[0103] Table 2. Interaction energy between MPD molecules and MPD molecules under different pectin addition levels.

[0104]

[0105] The results of molecular simulation calculations are shown in Table 2. The interaction energy between pectin and MPD is negative, indicating that there is an attraction between them. With the increase of pectin content, the viscosity of the aqueous solution gradually increases, hindering the interaction between pectin and MPD. The attraction between pectin and MPD weakens, decreasing from 28.34 kcal / mol to 23.56 kcal / mol. Simultaneously, the π-π interaction force between MPD molecules also gradually weakens due to the increase in aqueous solution viscosity, decreasing from 8.63 kcal / mol to 3.99 kcal / mol. This means that the dispersion uniformity of MPD molecules in the aqueous solution is improved.

[0106] The polyamide separation layer of the high-pressure reverse osmosis membranes obtained in Examples 2 and 5 and Comparative Examples 1 and 2 was characterized by positron annihilation lifetime spectroscopy, and the results are as follows: Figure 2 As shown. Due to the weaker intermolecular interactions of MPD, the high-pressure reverse osmosis membranes obtained in Examples 2 and 5 have a narrower pore size distribution compared to the high-pressure reverse osmosis membrane without pectin (Comparative Example 1), and the free volume radius gradually decreases with increasing pectin concentration. However, because pectin molecules contain a large number of carboxyl groups, when the amount added is large, the amino groups in the MPD molecules undergo protonation. This protonation generates mutual repulsion between MPD molecules (2.07 kcal / mol), leading to an increase in the free volume radius of the membrane in Comparative Example 2. Therefore, when the pectin content reaches or exceeds 0.5 wt% (Comparative Examples 2 and 3), both the permeate flux and NaCl rejection rate decrease significantly. In summary, when the amount of pectin added is low, the viscosity of the aqueous solution increases with the introduction of pectin, the intermolecular interactions of MPD weaken, the dispersibility of MPD is improved, the pore size distribution of the PA layer narrows, the free volume radius decreases, and the salt rejection rate is improved. This invention utilizes natural high-molecular-weight pectin as an additive. When its concentration is no higher than 0.3 wt%, it can significantly increase the permeation flux of the high-pressure reverse osmosis membrane while ensuring the NaCl rejection rate. The high-pressure reverse osmosis membrane prepared by this invention can be used in processes such as seawater desalination and high-salinity industrial wastewater treatment.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization, characterized in that, Includes the following steps: (1) Fix the polysulfone ultrafiltration membrane on the plexiglass frame and drain the water droplets on the surface of the polysulfone ultrafiltration membrane; (2) Pour an aqueous solution containing m-phenylenediamine, camphor sulfonic acid, triethylamine and an interfacial polymerization reaction modifier onto the surface of the polysulfone ultrafiltration membrane, let it stand for a period of time, and then remove the residual aqueous phase solution on the surface; wherein, the interfacial polymerization reaction modifier is pectin, with a mass percentage of 0.05~0.3 wt%; (3) Pour the organic solution containing pyromellitic chloride onto the surface of the membrane obtained in step (2), let it stand for a period of time, and then remove the residual organic phase solution on the surface. (4) Let the membrane obtained in step (3) stand until the excess solution on the surface evaporates naturally, then put it into a forced-air drying oven and heat-treat it at a certain temperature for a period of time. Rinse the membrane surface with deionized water to remove the residue on the membrane surface and obtain a high-pressure reverse osmosis membrane.

2. The method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 1, characterized in that, In step (1), the pure water permeation flux of the polysulfone ultrafiltration membrane is 400~500 L·m at 0.1 MPa. -2 ·h -1 The bovine serum albumin retention rate was 90.1%–90.3%.

3. The method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 1, characterized in that, In the aqueous solution of step (2), the mass percentage of m-phenylenediamine is 1.5~4 wt%, the mass percentage of camphor sulfonic acid is 2~3.5 wt%, the mass percentage of triethylamine is 0.8~2 wt%, the mass percentage of pectin is 0.05~0.3 wt%, and the solvent of the aqueous solution is deionized water.

4. The method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 1, characterized in that, In step (2), the settling time is 30~50s.

5. The method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 1, characterized in that, In the organic solution of step (3), the mass percentage of pyromellitic chloroform is 0.1~0.25 wt%, and the solvent of the organic solution is one or more of n-hexane, isoalkanes G, H, L, and M.

6. The method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 1, characterized in that, In step (3), the settling time is 30~50s.

7. The method for preparing a high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 1, characterized in that, In step (4), the temperature of the forced-air drying oven is 80-120℃, and the heat treatment time is 100-300 s.

8. A high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization, characterized in that, The high-pressure reverse osmosis membrane is prepared by the method of any one of claims 1 to 7 based on pectin-assisted interfacial polymerization.

9. The high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 8, characterized in that, The high-pressure reverse osmosis membrane at 5.52 MPa exhibited a 99.57% rejection rate for 32000 mg / L NaCl and a permeation flux of 80.15 L·m⁻². -2 ·h -1 .

10. An application of the high-pressure reverse osmosis membrane based on pectin-assisted interfacial polymerization according to claim 8, characterized in that, The high-pressure reverse osmosis membrane is used in seawater desalination and high-salt industrial wastewater treatment processes.

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