A method for preparing a lignin-modified high-flux polyamide composite membrane

Abstract

The present invention relates to a method for preparing a polyamide composite membrane, and more particularly to a method for preparing a lignin-modified high-flux polyamide composite membrane. The present invention improves the flatness of a support surface by coating and drying the modified support with lignin, significantly improving the flatness of the support surface and thereby enhancing the spreading effect of organic phase monomers on the support surface, resulting in a more uniform and dense structure of the formed polyamide composite membrane, thereby improving its separation performance. Furthermore, through a specific coating sequence and the use of a specific organic phase solvent capable of dissolving lignin, partial dissolution and effective utilization of the lignin are achieved, not only preventing lignin from clogging the macroporous structure of the support, but also allowing the dissolved lignin to become a hydrophilic additive in the interfacial polymerization process, thereby achieving a dual-effect improvement in the water flux performance of the polyamide composite membrane.

Description

Technical Field

[0001] The present invention relates to a method for preparing a polyamide composite membrane, in particular to a method for preparing a lignin-modified high-flux polyamide composite membrane. Background Art

[0002] As a high-performance separation membrane material, polyamide composite membranes have shown broad application prospects in water treatment, gas separation, membrane reactors, and other fields. Their unique separation properties and excellent mechanical strength make them a key component in many industrial processes. To meet the needs of different application scenarios, the preparation technology of polyamide composite membranes has been continuously explored and developed. Among them, interfacial polymerization technology, as an important preparation method, has attracted much attention due to its advantages such as fast reaction speed, good film formation effect, and strong controllability. This technology utilizes two monomers with different properties to undergo polymerization reaction at the interface of the support to form a polyamide film with excellent separation properties. Through interfacial polymerization technology, the thickness, structure, and properties of the polyamide membrane can be precisely controlled, thereby achieving efficient separation of different substances. Therefore, interfacial polymerization technology plays a vital role in the preparation of polyamide composite membranes.

[0003] In the process of preparing polyamide composite membranes by interfacial polymerization, the surface flatness of the support plays a crucial role. A flat and uniform support surface promotes uniform spreading of aqueous or organic monomers, thereby ensuring that the formed polyamide composite membrane has excellent separation performance and mechanical strength. However, polyamide composite membranes require the support to have good water flux to ensure good permeability of the composite membrane as a whole. As a result, the support used to prepare polyamide composite membranes often has poor flatness, requiring modification or improvement.

[0004] In the prior art, in order to improve the flatness of the support surface, the support is often modified by a sacrificial layer. Among them, prior art CN118142363A discloses the use of lignin coated on the surface of the support to form a polyamide composite film as a support, and the composite film is immersed in an alcohol aqueous solution to remove the lignin. However, the applicant found that because lignin is between the support and the formed polyamide film, the removal of lignin will cause the peel strength between the support and the polyamide film to weaken, thereby affecting the stability and service life of the polyamide composite film, thereby affecting the application of the above method in actual production. Moreover, lignin is a good hydrophilic additive, and the removal of lignin leads to a waste of materials to a certain extent. Therefore, how to solve the technical problem of lignin coating the support has become an important issue to be solved in the field of polyamide composite film preparation. Summary of the Invention

[0005] In view of the above problems, the present invention optimizes the modification method of lignin, so that lignin can be turned into treasure as an additive to optimize the water flux of the polyamide composite membrane while ensuring a flat support.

[0006] To this end, the present invention provides a method for preparing a lignin-modified high-flux polyamide composite membrane, which comprises the following steps:

[0007] a) cleaning the support to remove surface impurities and drying to constant weight;

[0008] b) coating a first organic solution containing lignin on the surface of the support and drying the solution to form a lignin-modified support;

[0009] c) applying a second organic solution containing polyacid chloride to the surface of the lignin-modified support and allowing the solution to stand for 10-60 minutes;

[0010] d) immersing the support coated with the polyacyl chloride in an aqueous solution containing a polyamine to form a polyamide composite film on the surface of the support through an interfacial polymerization reaction;

[0011] The second organic solvent in the second organic solution can dissolve lignin.

[0012] The support in step a) is a polysulfone membrane, a polyethersulfone membrane or a polyvinylidene fluoride membrane.

[0013] Preferably, in step b), the first solvent of the first organic solution is one of methanol and ethanol, and the concentration of lignin in the first organic solution is 0.1-10 wt %.

[0014] Preferably, the coating concentration of lignin on the support in step b) is 0.1-1 mg / cm².

[0015] Preferably, the drying treatment in step b) is carried out at a temperature of 50°C to 100°C for a duration of 1-24 hours.

[0016] Preferably, the second organic solvent in the second organic solution in step c) is one of petroleum ether, dichloromethane, chloroform and dimethyl sulfoxide.

[0017] Preferably, the polyacyl chloride in step c) is one of trimesoyl chloride, terephthaloyl chloride and phthaloyl chloride, and the concentration is 1-5 wt %.

[0018] Preferably, the polyamine in step d) is one of m-phenylenediamine, o-phenylenediamine and p-phenylenediamine, and the concentration is 0.5-2.5 wt%.

[0019] Preferably, the immersion time in the aqueous solution containing the polyamine in step d) is 1-3 minutes.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] First, the present invention significantly improves the flatness of the support surface by coating and drying the modified support with lignin, thereby enhancing the spreading effect of the organic phase monomer on the support surface, so that the formed polyamide composite membrane has a more uniform and dense structure, thereby improving its separation performance.

[0022] Secondly, the present invention achieves partial dissolution and effective utilization of lignin through a specific coating sequence and the use of a specific organic phase solvent capable of dissolving lignin. This not only prevents lignin from clogging the macroporous structure of the support, but also allows the dissolved lignin to act as a hydrophilic additive during the interfacial polymerization process, thereby enhancing the water flux performance of the polyamide composite membrane. Furthermore, this solution of the present invention avoids the problem of weakened peel strength caused by dissolving lignin after the polyamide composite membrane is prepared, which is a problem in the prior art. DETAILED DESCRIPTION

[0023] Example 1

[0024] A method for preparing a lignin-modified high-flux polyamide composite membrane comprises the following steps:

[0025] a) washing the polysulfone membrane support with deionized water to remove surface impurities, and drying at 80°C to constant weight for 12 hours;

[0026] b) coating the surface of the support with an ethanol solution containing 5 wt% lignin at a coating concentration of 0.5 mg / cm², and drying the solution at 70°C for 6 hours to form a lignin-modified support;

[0027] c) applying a petroleum ether solution containing 3 wt% trimesoyl chloride to the surface of the lignin-modified support, and then allowing the support to stand at room temperature for 45 minutes;

[0028] d) The support coated with the polyacyl chloride is further immersed in an aqueous solution containing 1.5 wt % m-phenylenediamine for 2 minutes to form a polyamide composite film on the surface of the support through interfacial polymerization.

[0029] Example 2

[0030] A method for preparing a lignin-modified high-flux polyamide composite membrane comprises the following steps:

[0031] a) washing the polysulfone membrane support with deionized water to remove surface impurities, and drying at 80°C to constant weight for 12 hours;

[0032] b) coating the surface of the support with a petroleum ether solution containing 3 wt % trimesoyl chloride, and then allowing it to stand at room temperature for 45 minutes;

[0033] c) The support coated with the polyacyl chloride is further immersed in an aqueous solution containing 1.5 wt % of m-phenylenediamine for 2 minutes to form a polyamide composite film on the surface of the support through interfacial polymerization.

[0034] Example 3

[0035] A method for preparing a lignin-modified high-flux polyamide composite membrane comprises the following steps:

[0036] a) washing the polysulfone membrane support with deionized water to remove surface impurities, and drying at 80°C to constant weight for 12 hours;

[0037] b) coating the surface of the support with an ethanol solution containing 5 wt% lignin at a coating concentration of 0.5 mg / cm², and drying the solution at 70°C for 6 hours to form a lignin-modified support;

[0038] c) applying a petroleum ether solution containing 3 wt% trimesoyl chloride to the surface of the lignin-modified support, and then allowing the solution to stand at room temperature for 2 minutes;

[0039] d) The support coated with the polyacyl chloride is further immersed in an aqueous solution containing 1.5 wt % m-phenylenediamine for 2 minutes to form a polyamide composite film on the surface of the support through interfacial polymerization.

[0040] Example 4

[0041] A method for preparing a lignin-modified high-flux polyamide composite membrane comprises the following steps:

[0042] a) washing the polysulfone membrane support with deionized water to remove surface impurities, and drying at 80°C to constant weight for 12 hours;

[0043] b) coating the surface of the support with an ethanol solution containing 5 wt% lignin at a coating concentration of 0.5 mg / cm², and drying the solution at 70°C for 6 hours to form a lignin-modified support;

[0044] c) coating an aqueous solution containing 1.5 wt% m-phenylenediamine on the surface of the lignin-modified support, and then allowing it to stand at room temperature for 2 minutes;

[0045] d) The support coated with the polyacyl chloride was further immersed in a petroleum ether solution containing 3 wt % trimesoyl chloride for 2 minutes to form a polyamide composite film on the surface of the support through interfacial polymerization.

[0046] Example 5

[0047] A method for preparing a lignin-modified high-flux polyamide composite membrane comprises the following steps:

[0048] a) washing the polysulfone membrane support with deionized water to remove surface impurities, and drying at 80°C to constant weight for 12 hours;

[0049] b) coating the surface of the support with an ethanol solution containing 5 wt% lignin at a coating concentration of 0.5 mg / cm², and drying the solution at 70°C for 6 hours to form a lignin-modified support;

[0050] c) coating the surface of the lignin-modified support with a n-hexane solution containing 3 wt% trimesoyl chloride, and then allowing the solution to stand at room temperature for 45 minutes;

[0051] d) The support coated with the polyacyl chloride is further immersed in an aqueous solution containing 1.5 wt % m-phenylenediamine for 2 minutes to form a polyamide composite film on the surface of the support through interfacial polymerization.

[0052] Example 6

[0053] A method for preparing a lignin-modified high-flux polyamide composite membrane comprises the following steps:

[0054] a) washing the polysulfone membrane support with deionized water to remove surface impurities, and drying at 80°C to constant weight for 12 hours;

[0055] b) coating the surface of the support with an ethanol solution containing 5 wt% lignin at a coating concentration of 0.5 mg / cm², and drying the solution at 70°C for 6 hours to form a lignin-modified support;

[0056] c) coating an aqueous solution containing 1.5 wt% m-phenylenediamine on the surface of the lignin-modified support, and then allowing it to stand at room temperature for 2 minutes;

[0057] d) The support coated with the polyacyl chloride was further immersed in a petroleum ether solution containing 3 wt % trimesoyl chloride for 2 minutes to form a polyamide composite film on the surface of the support through interfacial polymerization.

[0058] e) The polyamide composite film layer was immersed in a 50% by volume ethanol aqueous solution for 1 minute, and then dried.

[0059] The polyamide composite membranes of Examples 1-6 were tested for their initial permeability to 0.2 wt% sodium sulfate at room temperature at 0.5 MPa, and then the membranes were operated at a reverse pressure of 3.8 MPa for 2 h, and then their subsequent permeability was tested again at room temperature at 0.5 MPa. The results are shown in Table 1.

[0060] Table 1

[0061]

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a lignin-modified high-throughput polyamide composite membrane, characterized in that The following steps are involved: a) cleaning the support to remove surface impurities and drying to constant weight; b) coating a first organic solution containing lignin on the surface of the support and drying the solution to form a lignin-modified support, wherein the coating concentration of the lignin on the support is 0.1-1 mg / cm²; c) applying a second organic solution containing a polyacyl chloride to the surface of the lignin-modified support and allowing the solution to stand for 10-60 minutes, wherein the second organic solvent in the second organic solution is one of petroleum ether, dichloromethane, chloroform, and dimethyl sulfoxide, and the concentration of the polyacyl chloride in the second organic solution is 1-5 wt %; d) immersing the support coated with the polyacyl chloride in an aqueous solution containing a polyamine to form a polyamide composite film on the surface of the support through an interfacial polymerization reaction; The second organic solvent in the second organic solution can dissolve lignin.

2. The preparation method according to claim 1, characterized in that The support in step a) is a polysulfone membrane, a polyethersulfone membrane or a polyvinylidene fluoride membrane.

3. The preparation method according to claim 1, characterized in that In step b), the first solvent of the first organic solution is one of methanol and ethanol, and the concentration of lignin in the first organic solution is 0.1-10 wt %.

4. The preparation method according to claim 1 or 2, characterized in that The drying process in step b) is carried out at a temperature of 50°C to 100°C for a duration of 1-24 hours.

5. The preparation method according to claim 1, characterized in that The polyacid chloride in step c) is one of trimesoyl chloride, terephthaloyl chloride and phthaloyl chloride.

6. The preparation method according to claim 1, characterized in that In step d), the polyamine is one of m-phenylenediamine, o-phenylenediamine and p-phenylenediamine, and the concentration is 0.5-2.5 wt %.

7. The preparation method according to claim 1, characterized in that The immersion time in the aqueous solution containing polyamine in step d) is 1-3 minutes.

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