Loose nanofiltration membrane and preparation method thereof

Abstract

The invention discloses a loose nanofiltration membrane and a preparation method thereof, and belongs to the technical field of membrane separation, and the preparation method comprises the following steps: S1, preparing a water-phase monomer solution; s2, preparing an oil-phase monomer solution; s3, a polysulfone ultrafiltration membrane is sequentially soaked in the water-phase monomer solution and the oil-phase monomer solution, and the loose nanofiltration membrane is prepared. According to the loose nanofiltration membrane and the preparation method thereof, the retention rate of inorganic salt and dye of the loose nanofiltration membrane can be regulated and controlled by regulating the relative content of glycerol triglycidyl ether in the oil-phase monomer solution, so that the requirements of separation, concentration, desalination and the like of materials are met.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, in particular to a loose nanofiltration membrane and a preparation method thereof. Background Art

[0002] Nanofiltration technology is a low-energy membrane separation technology. Its membrane pore size and operating pressure are between those of ultrafiltration membrane and reverse osmosis membrane. It intercepts substances with a molecular weight of about 200-2000 Daltons through the synergistic effect of pore screening and electrostatic repulsion. Nanofiltration membranes are generally prepared by interfacial polymerization of water-phase monomer piperazine and oil-phase monomer trimesoyl chloride. Introducing polymers such as nanomaterials and polyvinyl alcohol into the aqueous solution, or performing acid-base treatment after membrane formation, can regulate the pore size of the nanofiltration membrane and further regulate the retention capacity of inorganic salts.

[0003] The separation functional layer structure of loose nanofiltration membrane is relatively loose, the membrane pore size is relatively large, and the retention rate of inorganic salts is low. Therefore, it can be used in the fields of material separation, concentration, desalination, etc. In the pharmaceutical industry, loose nanofiltration membranes are used for desalination and concentration of antibiotic resin analytical solutions and vitamin concentration; in the dye industry, it can complete the desalination and concentration of dyes, thereby replacing the traditional salting out and acid precipitation processes; in the food field, it can achieve the separation and purification of oligosaccharides and starch sugars, fruit juice concentration and plant extraction, etc. With the continuous development of membrane separation technology, the application field of loose nanofiltration membranes will continue to expand, and new application scenarios will be found in more industries.

[0004] Epoxy resin is a widely used polymer material. Its synthesis mainly depends on the ring-opening reaction of epoxy groups and the addition reaction of amino groups, which can build a stable three-dimensional cross-linked network structure. In addition, the chemical bonds generated by the reaction of epoxy groups and amino groups have certain acid-base stability and oxidation resistance. Taking commercial propylene glycol triglycidyl ether as an example, it contains three epoxy groups, which can participate in chemical cross-linking reactions to form dense chain and network structures, so that the generated epoxy resin has good mechanical properties such as tensile strength, flexural strength, compressive strength and impact strength.

[0005] Based on the characteristics of the addition reaction between epoxy groups and amino groups in the synthesis of epoxy resin, it is possible to consider introducing epoxy groups into the separation functional layer of the nanofiltration membrane, and by adjusting the reaction conditions (such as monomer ratio, reaction time, etc.), appropriately reducing the cross-linking density, thereby increasing the pore size of the nanofiltration membrane and forming a loose separation functional layer structure. Combining the chemical synthesis strategy of epoxy resin with the interfacial polymerization technology of nanofiltration membrane may open up a new research direction for the development of high-performance loose nanofiltration membranes. Summary of the invention

[0006] The purpose of the present invention is to provide a loose nanofiltration membrane and a preparation method thereof. By adjusting the relative content of propylene glycol triglycidyl ether in an oil phase monomer solution, the inorganic salt and dye retention rates of the loose nanofiltration membrane can be regulated to meet the needs of separation, concentration, desalination, etc. of materials.

[0007] To achieve the above object, the present invention provides a method for preparing a loose nanofiltration membrane, comprising the following steps:

[0008] S1, preparing an aqueous monomer solution;

[0009] S2, preparing an oil phase monomer solution;

[0010] S3, soaking the polysulfone ultrafiltration membrane in the aqueous monomer solution and the oily monomer solution in sequence to prepare a loose nanofiltration membrane.

[0011] Preferably, in S1, the aqueous phase monomer is a polyvalent organic amine with a mass fraction concentration of 0.5-5.0%, and the polyvalent organic amine is one of piperazine, polyethylene polyamine, polyethyleneimine, and m-phenylenediamine.

[0012] Preferably, the specific steps of S2 are: dissolving the oil phase monomer in the oil phase solvent, and then adding the oil phase monomer regulator.

[0013] Preferably, in S2, the oil phase monomer is trimesoyl chloride, and the mass fraction concentration is 0.01-1.0%.

[0014] Preferably, in S2, the oil phase solvent is one of n-hexane, n-heptane and isoparaffin.

[0015] Preferably, in S2, the oil phase monomer regulator is propylene glycol triglycidyl ether;

[0016] The mass ratio of the oil phase monomer to the oil phase monomer regulator is 1:0.1-1:1.

[0017] Preferably, the specific steps of S3 are: immersing the polysulfone ultrafiltration membrane in an aqueous monomer solution, drying it, and then immersing it in an oily monomer solution to cause an interfacial polymerization reaction, and then performing a heat treatment to obtain a loose nanofiltration membrane.

[0018] Preferably, in S3, the soaking time is 1-10 min.

[0019] Preferably, in S3, the heat treatment temperature is 50-90° C., and the heat treatment time is 1-10 min.

[0020] The present invention provides a loose nanofiltration membrane, which is prepared by adopting the above-mentioned method for preparing a loose nanofiltration membrane.

[0021] Therefore, the present invention adopts the above-mentioned loose nanofiltration membrane and its preparation method, which has the following beneficial effects:

[0022] (1) In the polyamide separation functional layer of the nanofiltration membrane, glycerol triglycidyl ether groups are introduced. The three epoxy groups of glycerol triglycidyl ether react with organic amines to undergo chemical cross-linking reactions and participate in interfacial polymerization reactions, which correspondingly increase the pore size of the nanofiltration membrane and form a loose nanofiltration membrane.

[0023] (2) Increasing the relative content of glycerol triglycidyl ether in the oil phase solution can control the magnesium sulfate retention rate of the loose nanofiltration membrane from 95% to 20%, which is suitable for the separation, concentration, desalination and other needs of materials.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a photo of a loose nanofiltration membrane according to an embodiment of the present invention and a preparation method thereof. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0027] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0028] A loose nanofiltration membrane, the preparation method of which comprises the following steps:

[0029] S1. Prepare an aqueous monomer solution with a mass fraction of 0.5-5.0% of a polyvalent organic amine; the polyvalent organic amine is one of piperazine, polyethylene polyamine, polyethyleneimine, and m-phenylenediamine.

[0030] S2. Dissolving trimesoyl chloride in an oil phase solvent, and then adding glycerol triglycidyl ether to prepare an oil phase monomer solution; wherein the oil phase solvent is one of n-hexane, n-heptane, and isoparaffin, the mass fraction of trimesoyl chloride is 0.01-1.0%, and the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.1-1:1.

[0031] S3. Soak the polysulfone ultrafiltration membrane in an aqueous monomer solution for 1-10 minutes, blow dry it, and then soak it in an oily monomer solution for 1-10 minutes. The epoxy groups of propylene triglycidyl ether and the polyorganic amine undergo a chemical cross-linking reaction to form a network or chain structure, which participates in the interfacial polymerization reaction with trimesoyl chloride. The membrane is then heat treated in an oven at 50-90°C for 1-10 minutes to obtain a loose nanofiltration membrane.

[0032] Example 1

[0033] A loose nanofiltration membrane, the preparation method of which comprises the following steps:

[0034] S1, preparing an aqueous monomer solution with a piperazine mass fraction of 2.0%;

[0035] S2. Dissolving trimesoyl chloride in isoparaffin, and then adding glycerol triglycidyl ether to prepare an oil phase monomer solution; wherein the mass fraction of trimesoyl chloride is 0.1%, and the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.1.

[0036] S3. Soak the polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 minutes, blow dry it, and then soak it in the oily monomer solution for 1 minute. Heat-treat it in an oven at 60° C. for 10 minutes to obtain a loose nanofiltration membrane.

[0037] Example 2

[0038] The difference between Example 2 and Example 1 is that the relative content of trimesoyl chloride and propylene glycol triglycidyl ether is 1:0.2.

[0039] Example 3

[0040] The difference between Example 3 and Example 1 is that the relative content of trimesoyl chloride and propylene glycol triglycidyl ether is 1:0.4.

[0041] Example 4

[0042] The difference between Example 4 and Example 1 is that the relative content of trimesoyl chloride and propylene glycol triglycidyl ether is 1:0.6.

[0043] Example 5

[0044] The difference between Example 5 and Example 1 is that the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.7.

[0045] Example 6

[0046] The difference between Example 6 and Example 1 is that the relative content of trimesoyl chloride and propylene glycol triglycidyl ether is 1:0.8.

[0047] Example 7

[0048] The difference between Example 7 and Example 1 is that the relative content of trimesoyl chloride and propylene glycol triglycidyl ether is 1:1.

[0049] Example 8

[0050] A loose nanofiltration membrane, the preparation method of which comprises the following steps:

[0051] S1, preparing an aqueous monomer solution with a piperazine mass fraction of 1.5%;

[0052] S2. Dissolve trimesoyl chloride in n-heptane, and then add glycerol triglycidyl ether to prepare an oil phase monomer solution; wherein the mass fraction of trimesoyl chloride is 0.15%, and the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.4.

[0053] S3. Soak the polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 minutes, blow dry it, and then soak it in the oily monomer solution for 1 minute. Heat-treat it in an oven at 50° C. for 5 minutes to obtain a loose nanofiltration membrane.

[0054] Example 9

[0055] The difference between Example 9 and Example 8 is that the mass fraction of piperazine is 2.5%, the immersion time of the polysulfone ultrafiltration membrane in the aqueous monomer solution and the oily monomer solution is 5 min and 2 min respectively, and the temperature and time of the heat treatment are 90° C. and 10 min respectively.

[0056] Example 10

[0057] The difference between Example 10 and Example 8 is that the mass fraction of piperazine is 2.0%, the immersion time of the polysulfone ultrafiltration membrane in the aqueous monomer solution is 5 minutes, and the temperature and time of the heat treatment are 80° C. and 10 minutes, respectively.

[0058] Embodiment 11

[0059] A loose nanofiltration membrane, the preparation method of which comprises the following steps:

[0060] S1, preparing an aqueous monomer solution with a piperazine mass fraction of 4.0%;

[0061] S2. Dissolving trimesoyl chloride in isoparaffin, and then adding glycerol triglycidyl ether to prepare an oil phase monomer solution; wherein the mass fraction of trimesoyl chloride is 0.3%, and the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.5.

[0062] S3. Soak the polysulfone ultrafiltration membrane in the aqueous monomer solution for 5 minutes, blow dry it, and then soak it in the oily monomer solution for 2 minutes. Heat-treat it in an oven at 70° C. for 3 minutes to obtain a loose nanofiltration membrane.

[0063] Example 12

[0064] The difference between Example 12 and Example 11 is that the mass fraction of piperazine is 2.0%, the relative content of trimesoyl chloride and propylene triglycidyl ether is 1:0.6, the immersion time of the polysulfone ultrafiltration membrane in the oil phase monomer solution is 5 minutes, and the temperature and time of the heat treatment are 60°C and 10 minutes, respectively.

[0065] Example 13

[0066] A loose nanofiltration membrane, the preparation method of which comprises the following steps:

[0067] S1, preparing an aqueous monomer solution with a mass fraction of 2.0% of triethylenetetramine;

[0068] S2. Dissolving trimesoyl chloride in isoparaffin, and then adding glycerol triglycidyl ether to prepare an oil phase monomer solution; wherein the mass fraction of trimesoyl chloride is 0.3%, and the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.4.

[0069] S3. Soak the polysulfone ultrafiltration membrane in the aqueous monomer solution for 5 minutes, blow dry it, and then soak it in the oily monomer solution for 2 minutes. Heat-treat it in an oven at 60° C. for 10 minutes to obtain a loose nanofiltration membrane.

[0070] Embodiment 14

[0071] A loose nanofiltration membrane, the preparation method of which comprises the following steps:

[0072] S1, preparing an aqueous monomer solution with a mass fraction of 2.0% polyethyleneimine;

[0073] S2. Dissolve trimesoyl chloride in n-heptane, and then add glycerol triglycidyl ether to prepare an oil phase monomer solution; wherein the mass fraction of trimesoyl chloride is 0.3%, and the relative content of trimesoyl chloride and glycerol triglycidyl ether is 1:0.3.

[0074] S3. Soak the polysulfone ultrafiltration membrane in the aqueous monomer solution for 5 minutes, blow dry it, and then soak it in the oily monomer solution for 2 minutes. Heat-treat it in an oven at 80° C. for 10 minutes to obtain a loose nanofiltration membrane.

[0075] Performance Testing:

[0076] Water flux:

[0077] Using a cross-flow membrane pool, the water flux of a loose nanofiltration membrane is calculated by the following formula:

[0078]

[0079] Where: J is water flux, L / (m 2 h bar); V is the permeate volume, L; A is the membrane surface area, m 2 ; Δt is the membrane filtration running time, h; P is the operating pressure, bar.

[0080] Inorganic salt or dye retention rate:

[0081] The separation performance of the loose nanofiltration membrane was characterized by the retention rate of inorganic salt magnesium sulfate and Congo red dye (molecular weight 696.68) using a cross-flow membrane pool. The inorganic salt concentration was measured by a conductivity meter, and the dye concentration was measured by a spectrophotometer. The inorganic salt or dye retention rate of the loose nanofiltration membrane was calculated by the following formula:

[0082]

[0083] Where: R is the inorganic salt or dye interception rate, %; C p is the turbidity of the filtrate; C f is the turbidity of the raw material solution.

[0084] The water flux of the loose nanofiltration membrane prepared in Examples 1-14 is shown in Table 1, and the retention rates of a magnesium sulfate solution with a mass fraction of 0.1% and a Congo red dye solution with a mass fraction of 0.01% are shown in Tables 2 and 3, respectively.

[0085] Table 1 Water flux of loose nanofiltration membrane

[0086] Example <![CDATA[Water flux L / (m 2 hbar)]]> Example <![CDATA[Water flux L / (m 2 hbar)]]> 1 6.9 8 8.4 2 7.8 9 9.9 3 5.7 10 9.9 4 9.2 11 6.8 5 10.2 12 6.7 6 7.8 13 5.3 7 10.2 14 5.4

[0087] Table 2 Magnesium sulfate retention rate of loose nanofiltration membrane

[0088] Example Retention rate % Example Retention rate % 1 95.0 8 73.6 2 90.6 9 83.6 3 85.3 10 63.6 4 76.4 11 68.6 5 65.3 12 65.2 6 38.4 13 34.2 7 20.4 14 45.3

[0089] Table 3 Congo red dye retention rate of loose nanofiltration membrane

[0090] Example Retention rate % Example Retention rate % 1 96.5 8 55.3 2 90.4 9 43.5 3 76.9 10 34.5 4 54.2 11 46.5 5 50.2 12 38.6 6 24.2 13 18.6 7 8.2 14 21.8

[0091] As can be seen from Table 2 and Table 3, in Examples 1-7, as the content of glycerol triglycidyl ether in the oil phase monomer solution increases, the retention rate of the loose nanofiltration membrane for magnesium sulfate inorganic salt and Congo red dye gradually decreases, from 95% and 96.5% to 20.4 and 8.2%, respectively. It can be seen that by adjusting the relative content of glycerol triglycidyl ether and the oil phase monomer, the retention rate of magnesium sulfate and Congo red dye of the loose nanofiltration membrane can be controlled, so the loose nanofiltration membrane can be applied to the separation, concentration, desalination and other needs of materials.

[0092] Therefore, the present invention adopts the above-mentioned loose nanofiltration membrane and its preparation method, and by adjusting the relative content of propylene glycol triglycidyl ether in the oil phase monomer solution, the inorganic salt and dye retention rate of the loose nanofiltration membrane can be regulated, thereby meeting the needs of material separation, concentration, desalination, etc.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a loose nanofiltration membrane, characterized in that: The following steps are involved: S1, preparing an aqueous monomer solution; S2, preparing an oil phase monomer solution; S3, soaking the polysulfone ultrafiltration membrane in the aqueous monomer solution and the oily monomer solution in sequence to prepare a loose nanofiltration membrane.

2. The preparation method according to claim 1, characterized in that: In S1, the aqueous phase monomer is a polyvalent organic amine with a mass fraction concentration of 0.5-5.0%, and the polyvalent organic amine is one of piperazine, polyethylene polyamine, polyethylene imine, and meta-phenylenediamine.

3. The preparation method according to claim 1, characterized in that: The specific steps of S2 are: dissolving the oil phase monomer in the oil phase solvent, and then adding the oil phase monomer regulator.

4. The preparation method according to claim 3, characterized in that: In S2, the oil phase monomer is trimesoyl chloride, and the mass fraction concentration is 0.01-1.0%.

5. The preparation method according to claim 3, characterized in that: In S2, the oil phase solvent is one of n-hexane, n-heptane, and isoparaffin.

6. The preparation method according to claim 4, characterized in that: In S2, the oil phase monomer regulator is propylene glycol triglycidyl ether; The mass ratio of the oil phase monomer to the oil phase monomer regulator is 1:0.1-1:

1.

7. The preparation method according to claim 1, characterized in that: The specific steps of S3 are: immersing the polysulfone ultrafiltration membrane in an aqueous monomer solution, drying it, and then immersing it in an oily monomer solution to cause an interfacial polymerization reaction, and then performing a heat treatment to obtain a loose nanofiltration membrane.

8. The preparation method according to claim 7, characterized in that: In S3, the soaking time is 1-10 minutes.

9. The preparation method according to claim 7, characterized in that: In S3, the heat treatment temperature is 50-90°C and the heat treatment time is 1-10 min.

10. A loose nanofiltration membrane, characterized in that: The nanofiltration membrane is prepared by the method for preparing a loose nanofiltration membrane according to any one of claims 1 to 9.

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