Preparation method of ultra-low-pressure high-flux reverse osmosis membrane

Abstract

The invention belongs to the technical field of reverse osmosis membranes, and particularly relates to a preparation method of an ultra-low-pressure high-flux reverse osmosis membrane, which comprises the following steps: introducing a PEG derivative containing a succinimide ester function in the process of preparing a polysulfone base membrane, and preparing the base membrane with reaction activity by an immersion precipitation phase inversion method; then immersing the base membrane with reaction activity into a water-phase solution, reacting N-hydroxysuccinimide ester with a water-phase monomer binary primary amine to produce an amido bond, and then carrying out interfacial polymerization reaction with a polyacyl chloride oil-phase monomer to prepare a polyamide functional layer, so that the polyamide functional layer is connected with the base membrane through a chemical bond, thereby effectively preventing the polyamide layer from falling off; meanwhile, polyethylene glycol is embedded between the base membrane and the functional layer, so that the desalination rate of the reverse osmosis membrane is improved. The method is easy to operate and simple in control condition, and the prepared reverse osmosis membrane is low in operation pressure, high in flux and excellent in desalination rate.

Description

Technical Field

[0001] The invention belongs to the technical field of reverse osmosis membranes, and in particular relates to a method for preparing an ultra-low pressure high-flux reverse osmosis membrane. Background Art

[0002] Reverse osmosis is an efficient water purification method with the advantages of high efficiency, low cost, no phase change, modularization and automation. It is widely used in many fields such as high-purity water preparation in the electronics industry, medical water preparation, seawater desalination, brackish water desalination, sewage recycling, etc. With the global shortage of fresh water resources and the increasing severity of water pollution, reverse osmosis technology plays an increasingly important role in water purification. At present, the market is in urgent need of reverse osmosis membranes with low operating pressure, large water production and high desalination rate. The present invention proposes an ultra-low pressure high-flux reverse osmosis membrane and a preparation method thereof.

[0003] The application number is CN201810378598.6, and the invention name is a patent for a method for preparing a high-flux reverse osmosis membrane, a reverse osmosis membrane, and a reverse osmosis membrane preparation system. A polyamide reverse osmosis membrane is obtained by interfacial polymerization, and then a high-flux reverse osmosis membrane is prepared by oxidation post-treatment. The polyamide layer is oxidized by post-treatment to prepare a high-flux reverse osmosis membrane. The performance of the membrane is not optimized and improved from the structure of the polyamide layer.

[0004] The application number is CN201911159558.3, and the invention name is "Method for preparing porous nano antibacterial particles and composite reverse osmosis membrane, and patent for composite reverse osmosis membrane". By adding porous nanoparticles to the polyamide layer, the performance and antibacterial properties of the membrane are improved, and the interfacial polymerization reaction is not regulated.

[0005] The application number is CN202111279786.1, and the invention name is a patent for a method for preparing a multi-layer polyamide composite reverse osmosis membrane. A dopamine solution is physically pressed into a polysulfone-based membrane, and a polydopamine layer is formed on the surface and inside the membrane pores through the reaction of the dopamine solution to prepare a multi-layer polyamide reverse osmosis membrane. There is no chemical bond between the polysulfone-based membrane and the polydopamine layer, and it is physical adsorption.

[0006] The application number is CN202210287997.8, and the invention name is a patent for a high water flux reverse osmosis membrane, its preparation method and application. The porous support membrane is immersed in a reaction solution containing an amino monomer at a temperature of 90-160°C and a reaction time of 24-72h to complete the amino grafting reaction and carry out interfacial polymerization on its surface. The reactive support membrane can change the structure of the formed polyamide separation layer, thereby improving the water permeability of the polyamide reverse osmosis membrane and maintaining the stability of its ion interception performance, but the process is complicated and the steps are cumbersome.

[0007] The application number is CN200810162611.0, and the invention name is a method for preparing a hydrophilic anti-pollution reverse osmosis membrane. First, a layer of polyamide is compounded on a support layer through an interfacial polymerization reaction, and then a cross-linked layer is generated on the polyamide layer through a surface grafting reaction; the activated ester method using N-hydroxysulfosuccinimide sodium salt or N-hydroxysulfosuccinimide as an intermediate is used to graft -(CH2CH2O) n -polymer hydrophilic chain, and -(CH2CH2O) n -The polyamide membrane of the base is chemically bonded to improve the hydrophilicity of the composite reverse osmosis membrane, increase its water flux, improve its anti-fouling performance, and thus extend the service life of the membrane. However, this method is to first prepare the polyamide layer, then activate it through EDC / NHS, and graft PEG, so its base membrane is still not reactive and hydrophilic.

[0008] In summary, the existing technology generally adopts the following methods for modification: 1. Surface modification: modify the surface of the polyamide layer of the reverse osmosis membrane, and improve the performance of the reverse osmosis membrane by changing the surface charge, end groups, etc. of the polyamide layer. During the surface modification process, only the polyamide layer is post-treated, and the interfacial polymerization reaction cannot be regulated, and the membrane performance cannot be improved from the polyamide layer structure. 2. Blending of inorganic and organic nanoparticles in the polyamide layer: a blended polyamide layer structure is obtained by adding inorganic and organic nanoparticles to the water phase or the oil phase, but the addition of particles can easily cause cracks in the polyamide layer structure. 3. Surface coating: the performance of the reverse osmosis membrane is improved by coating a functional layer on the surface of the support layer, and the interfacial polymerization reaction is not regulated. 4. Support layer modification: amino grafting is performed on the support layer, and then interfacial polymerization reaction is performed to improve the membrane flux and desalination rate, but the steps are cumbersome and the grafting efficiency is low. Summary of the invention

[0009] In view of the deficiencies of the prior art, the present invention provides a method for preparing an ultra-low pressure high flux reverse osmosis membrane.

[0010] This is achieved specifically through the following technical solutions:

[0011] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0012] (1) adding a succinimide lipid functional PEG derivative to a polysulfone casting solution to prepare a reactive base membrane;

[0013] (2) immersing the reactive base film in an aqueous solution of m-phenylenediamine;

[0014] (3) contacting the reactive base film immersed in the m-phenylenediamine aqueous solution with an organic solution of trimesoyl chloride;

[0015] (4) The membrane obtained in step (3) is dried in an oven and washed with pure water to obtain an ultra-low pressure high flux reverse osmosis membrane.

[0016] The succinimide-containing lipid functional PEG derivatives are CH3-PEG4-NHS, CH3-PEG 24 -NHS, CH3-PEG 200 -NHS, CH3-PEG 1000 -NHS, CH3-PEG 2000 -NHS, CH3-PEG 4000 -NHS, NHS-PEG4-NHS, NHS-PEG 24 -NHS, NHS-PEG 200 -NHS, NHS-PEG 1000 -NHS, NHS-PEG 2000 -NHS, NHS-PEG 4000 -NHS, Propylene-PEG4-NHS, Propylene-PEG 24 -NHS, Propylene-PEG 200 -NHS, Propylene-PEG 1000 -NHS, Propylene-PEG 2000 -NHS, Propylene-PEG 4000 -One or any combination of NHS.

[0017] The added amount of the functional PEG derivative is 0.01wt% to 10wt% of the total weight of the polysulfone casting solution.

[0018] In step (2), the immersion time is 3-300s and the temperature is room temperature.

[0019] In step (3), the contact time is 3-300 s and the temperature is room temperature.

[0020] The oven drying conditions are: temperature 60° C., time 3 min.

[0021] Beneficial effects:

[0022] The method of the invention is easy to operate and has simple control conditions. The prepared reverse osmosis membrane has low operating pressure, high flux and excellent desalination rate.

[0023] The present invention introduces a succinimide lipid functional PEG derivative in the process of preparing a polysulfone base membrane, prepares a reactive base membrane by an immersion precipitation phase conversion method, and then immerses the reactive base membrane in an aqueous solution, reacts N-hydroxysuccinimide ester with a diprimary amine as an aqueous monomer to produce an amide bond, and then performs an interfacial polymerization reaction with a polyacyl chloride oil phase monomer to prepare a polyamide functional layer, so that the polyamide functional layer is connected to the base membrane by a chemical bond, effectively preventing the polyamide layer from falling off and avoiding the phenomenon of easy layering when exposed to water, and at the same time, embedding polyethylene glycol between the base membrane and the functional layer, improving the generation of defects in the process of forming the polyamide functional layer, and improving the density and cross-linking degree of the polyamide layer, thereby improving the desalination rate of the reverse osmosis membrane.

[0024] The present invention performs efficient polyethylene glycolization on the base membrane, introduces long chains of hydrophilic molecules, improves the hydrophilicity and surface porosity of the base membrane, and improves the water permeability of the reverse osmosis membrane. In addition, the base membrane is reactive, can prevent the polyamide layer from infiltrating into the pores of the support layer, reduces the actual thickness of the formed polyamide separation layer, reduces the water permeation resistance, and can significantly improve the water permeability of the membrane while ensuring the salt retention rate.

[0025] The present invention strictly controls the addition amount of the succinimide lipid functional PEG derivative. If the addition amount is less than 0.01wt%, the comprehensive performance of the membrane cannot be effectively improved; if the addition amount is higher than 10wt%, the mechanical properties of the polysulfone-based membrane will be poor. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are further described in detail below, but the present invention is not limited to these embodiments, and any improvement or substitution based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0027] Example 1

[0028] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0029] (1) Preparation of polysulfone solution: 180 g polysulfone, 10 g CH3-PEG 1000 -NHS was dissolved in 810g DMF solution, filtered through a filter element, vacuum degassed to remove gas impurities, and the polysulfone liquid was transported to the coating head by a cylinder. The coating head evenly coated the liquid on the 120μm polyester non-woven fabric layer to prepare a polysulfone base membrane with uniform thickness;

[0030] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0031] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0032] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0033] Example 2

[0034] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0035] (1) Preparation of polysulfone solution: 180 g polysulfone, 10 g NHS-PEG 1000 -NHS was dissolved in 810g DMF solution, filtered through a filter element, vacuum degassed to remove gas impurities, and the polysulfone liquid was transported to the coating head by a cylinder. The coating head evenly coated the liquid on the 120μm polyester non-woven fabric layer to prepare a polysulfone base membrane with uniform thickness;

[0036] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0037] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0038] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0039] Example 3

[0040] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0041] (1) Preparation of polysulfone solution: 180 g polysulfone, 10 g propylene-PEG 1000 -NHS was dissolved in 810g DMF solution, filtered through a filter element, vacuum degassed to remove gas impurities, and the polysulfone liquid was transported to the coating head by a cylinder. The coating head evenly coated the liquid on the 120μm polyester non-woven fabric layer to prepare a polysulfone base membrane with uniform thickness;

[0042] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0043] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0044] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0045] Example 4

[0046] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0047] (1) Preparation of polysulfone solution: 180 g polysulfone, 10 g CH3-PEG 1000 -NHS, 10gNHS-PEG 1000 -NHS, dissolved in 810g DMF solution, filtered through a filter element, vacuum degassed to remove gas impurities, and transported the polysulfone liquid to the coating head with a cylinder. The coating head evenly coated the liquid on a 120μm polyester non-woven fabric layer to prepare a polysulfone base membrane with uniform thickness;

[0048] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0049] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0050] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0051] Example 5

[0052] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0053] (1) Preparation of polysulfone solution: 180 g polysulfone, 10 g CH3-PEG 1000 -NHS, 10g propylene-PEG1000-NHS, dissolved in 810g DMF solution, filtered through a filter element, vacuum degassed to remove gas impurities, and the polysulfone liquid was transported to the coating head by a cylinder. The coating head evenly coated the liquid on the 120μm polyester non-woven fabric layer to prepare a polysulfone-based membrane with uniform thickness;

[0054] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0055] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0056] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0057] Example 6

[0058] A method for preparing an ultra-low pressure high flux reverse osmosis membrane comprises the following steps:

[0059] (1) Preparation of polysulfone solution: 180 g polysulfone, 10 g NHS-PEG 1000 -NHS, 10g propylene-PEG 1000 -NHS, dissolved in 810g DMF solution, filtered through a filter element, vacuum degassed to remove gas impurities, and transported the polysulfone liquid to the coating head with a cylinder. The coating head evenly coated the liquid on a 120μm polyester non-woven fabric layer to prepare a polysulfone base membrane with uniform thickness;

[0060] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0061] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0062] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0063] Comparative Example

[0064] A method for preparing a reverse osmosis membrane comprises the following steps:

[0065] (1) preparing a polysulfone slurry: dissolving 180 g of polysulfone in 820 g of DMF solution, filtering through a filter element, vacuum degassing to remove gas impurities, and conveying the polysulfone slurry to a coating head using a cylinder. The coating head evenly coats the slurry on a 120 μm polyester non-woven fabric layer to prepare a polysulfone base membrane with uniform thickness;

[0066] (2) Prepare aqueous solution: dissolve 200 g of m-phenylenediamine in 5 kg of water and stir to dissolve;

[0067] (3) Prepare the oil phase solution: dissolve 7.5 g of trimesoyl chloride in 5 kg of n-hexane and stir to dissolve;

[0068] (4) Interfacial polymerization reaction: The polysulfone-based membrane of step (1) was immersed in an aqueous solution for 10 seconds, and the residual aqueous solution on the surface was drained. Then, the polysulfone-based membrane was immersed in an oil solution for 10 seconds, and the residual organic solution on the surface was drained. The membrane was placed in a 60° C. oven and dried for 3 minutes. The membrane was taken out and stored in pure water.

[0069] The reverse osmosis membranes prepared in the comparative example and examples 1-6 were tested on a membrane test bench at an operating pressure of 150 psi, a temperature of 25° C., and a 1500 ppm NaCl aqueous solution to test the sodium chloride retention rate and water flux. The data are summarized in Table 1.

[0070] Table 1:

[0071] Water flux (GFD) Desalination rate (%) Example 1 39.51 99.53 Example 2 36.73 99.63 Example 3 41.83 99.60 Example 4 37.31 99.71 Example 5 45.74 99.73 Example 6 42.38 99.70 Comparative Example 33.28 99.45

[0072] From the above results, it can be seen that adding functional PEG derivatives to the basement membrane can significantly improve the membrane flux and desalination rate.

[0073] Detailed description: It should be understood that the above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principle and spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an ultra-low pressure high flux reverse osmosis membrane, characterized in that: The steps include: (1) adding a succinimide lipid functional PEG derivative to a polysulfone casting solution to prepare a reactive base membrane; (2) immersing the reactive base film in an aqueous solution of m-phenylenediamine; (3) contacting the reactive base film immersed in the m-phenylenediamine aqueous solution with an organic solution of trimesoyl chloride; (4) The membrane obtained in step (3) is dried in an oven and washed with pure water to obtain an ultra-low pressure high flux reverse osmosis membrane.

2. The method for preparing an ultra-low pressure high flux reverse osmosis membrane according to claim 1, characterized in that: The succinimide-containing lipid functional PEG derivatives are CH3-PEG4-NHS, CH3-PEG 24 -NHS, CH3-PEG 200 -NHS, CH3-PEG 1000 -NHS, CH3-PEG 2000 -NHS, CH3-PEG 4000 -NHS, NHS-PEG4-NHS, NHS-PEG 24 -NHS, NHS-PEG 200 -NHS, NHS-PEG 1000 -NHS, NHS-PEG 2000 -NHS, NHS-PEG 4000 -NHS, Propylene-PEG4-NHS, Propylene-PEG 24 -NHS, Propylene-PEG 200 -NHS, Propylene-PEG 1000 -NHS, Propylene-PEG 2000 -NHS, Propylene-PEG 4000 -One or any combination of NHS.

3. The method for preparing an ultra-low pressure high flux reverse osmosis membrane according to claim 1, characterized in that: The added amount of the functional PEG derivative is 0.01wt% to 10wt% of the total weight of the polysulfone casting solution.

4. The method for preparing an ultra-low pressure high flux reverse osmosis membrane according to claim 1, characterized in that: In step (2), the immersion time is 3-300s and the temperature is room temperature.

5. The method for preparing an ultra-low pressure high flux reverse osmosis membrane according to claim 1, characterized in that: In step (3), the contact time is 3-300 s and the temperature is room temperature.

6. The method for preparing an ultra-low pressure high flux reverse osmosis membrane according to claim 1, characterized in that: The oven drying conditions are: temperature 60° C., time 3 min.