Polyamide composite nanofiltration membrane prepared based on cross-polyolefin-based membrane different-side anti-diffusion interfacial polymerization and preparation method of polyamide composite nanofiltration membrane

Abstract

The preparation method comprises the following steps: firstly, soaking a supporting bottom membrane in an organic phase solution containing a trimesoyl chloride monomer, and overturning the supporting bottom membrane soaked with an organic phase, so as to obtain a polyamide composite nanofiltration membrane; a water phase solution containing piperazine and diaminobenzene sulfonic acid monomers is subjected to cross-base-membrane anti-diffusion interfacial polymerization, and the polyamide composite nanofiltration membrane is obtained. The preparation method has the technical advantages that the process is simple, the operation is simple, and the synthesis method and preparation conditions are easy; diaminobenzene sulfonic acid is added into the water phase, so that the hydrophilicity and retention rate of the membrane are improved; the nanofiltration membrane formed by different-side cross-base-membrane back-diffusion interface polymerization is beneficial to obtaining excellent separation performance and pure water flux at the same time.

Description

Technical Field

[0001] The invention relates to a polyamide composite nanofiltration membrane and a preparation method thereof, and in particular to a polyamide composite nanofiltration membrane prepared based on reverse diffusion interface polymerization across a polyolefin base membrane on opposite sides and a preparation method thereof. Background Art

[0002] Nanofiltration membrane separation technology is a new separation technology with the advantages of simple operation, low energy consumption, high efficiency and environmental friendliness. It has become one of the most important means in today's separation science. It uses a selectively permeable membrane as a barrier to achieve the separation, concentration, purification and refinement of materials under the driving force of pressure difference, temperature difference or concentration difference on both sides of the membrane. The core of the membrane process is the membrane material. The ideal nanofiltration membrane material should have both high permeability and high selectivity.

[0003] The separation performance of mainstream membrane products on the market often has the problem of mutual restriction of permeability and selectivity, that is, the trade-off effect. Traditional polysulfone base membranes are costly, the preparation process is complicated and not environmentally friendly. Polyethylene lithium-ion battery separator (PE) is a thermoplastic resin made by ethylene polymerization. PE has the advantages of low cost, excellent mechanical properties and low mass transport resistance. Therefore, it is necessary to develop a low-cost, high-flux, high-selectivity and high-stability polyamide composite nanofiltration membrane material based on polyethylene. Summary of the invention

[0004] In order to solve the shortcomings of the above-mentioned technology, the present invention provides a polyamide composite nanofiltration membrane prepared based on reverse diffusion interfacial polymerization across a polyolefin base membrane and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a preparation method of a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin base membrane, firstly, the supporting base membrane is soaked with an organic phase solution containing trimesoyl chloride monomer, the supporting base membrane after soaking in the organic phase is turned over, and an aqueous phase solution containing piperazine and diaminobenzenesulfonic acid monomers is subjected to reverse diffusion interfacial polymerization across the base membrane to obtain a polyamide composite nanofiltration membrane.

[0006] Preferably, the method specifically comprises the following steps:

[0007] Step 1: dissolving trimesoyl chloride in an organic phase solution to obtain an organic phase solution;

[0008] Step 2: dissolving piperazine and diaminobenzenesulfonic acid monomers in water to obtain an aqueous solution;

[0009] Step 3: soaking the supporting base membrane with the organic phase solution prepared in step 1 to obtain a supporting base membrane infiltrated with organic phase monomers;

[0010] Step 4: Turn over the support base membrane obtained in step 3, and immerse the other side thereof in the aqueous solution prepared in step 2 to perform an interfacial polymerization reaction to obtain a polyamide composite nanofiltration membrane;

[0011] Step 5: heat-treating the polyamide composite nanofiltration membrane obtained in step 4 to obtain a nanofiltration membrane with high separation performance.

[0012] Preferably, the supporting base film is composed of one or more of polyethylene, polypropylene, polyvinylidene fluoride, and polytetrafluoroethylene.

[0013] Preferably, in step 1, the concentration of trimesoyl chloride monomer is 0.025-0.2 w / v%. The organic phase solution may be n-hexane, but is not limited to n-hexane solution.

[0014] Preferably, in step 2, the diaminobenzenesulfonic acid monomer is a mixture of one or more of 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, 3,4-diaminobenzenesulfonic acid or their derivatives.

[0015] Preferably, in step 2, the concentration of piperazine is 0.02-0.2 wt %, and the concentration of diaminobenzenesulfonic acid monomer is 0.01-0.1 wt %.

[0016] Preferably, in step three, the immersion time is 1 to 15 minutes; and in step four, the reaction time of the interfacial polymerization reaction is 5 to 20 minutes.

[0017] Preferably, in step five, the heat treatment temperature is 60° C. and the time is 10 to 60 minutes.

[0018] A polyamide composite nanofiltration membrane prepared based on reverse diffusion interface polymerization on opposite sides of a polyolefin base membrane is prepared by the above-mentioned preparation method.

[0019] After adding diaminobenzenesulfonic acid, the addition of sulfonic acid groups improves the hydrophilicity of the membrane surface; piperazine and diaminobenzenesulfonic acid are mixed as the aqueous phase, reacting with trimesoyl chloride (TMC) to form a polyamide layer, which improves the retention rate of sodium sulfate. Therefore, while maintaining high retention of sodium sulfate and low retention of sodium chloride, the flux is greatly improved, and it can be applied to the system of separating monovalent and divalent ions.

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

[0021] 1) The preparation process is simple, the operability is strong, and the synthesis method and preparation conditions are easy;

[0022] 2) Due to the trade-off effect, generally speaking, the flux is increased while the retention is reduced, and the retention is increased while the flux is reduced. The present application overcomes the trade-off effect by adding diaminobenzenesulfonic acid (2,4-DABSA, 2,5-DABSA, 3,4-DABSA) to the aqueous phase, thereby improving the flux and retention rate of the membrane at the same time;

[0023] 3) The NF membrane formed by reverse diffusion interfacial polymerization across the substrate membrane on the opposite side is conducive to obtaining excellent separation performance and pure water flux at the same time, and also has the characteristics of low cost, high performance, high selectivity and high stability.

[0024] The invention discloses a method for preparing a piperazine / diaminobenzenesulfonic acid polyamide nanofiltration membrane by reverse diffusion interfacial polymerization across a substrate. By using a polyolefin porous membrane as a supporting substrate, the thickness of the supporting layer and the preparation cost can be greatly reduced. By using this method, piperazine (PIP) and diaminobenzenesulfonic acid (2,4-DABSA, 2,5-DABSA, 3,4-DABSA) are used as aqueous phases, and trimesoyl chloride (TMC) is used as an organic phase, and reverse diffusion interfacial polymerization across a substrate is performed on a polyolefin substrate. The prepared nanofiltration membrane has the characteristics of high water flux and interception, excellent stability, high separation ratio, simple process, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the preparation process of the present invention.

[0026] Figure 2 This is a plane scanning electron microscope image of Example 1 of the present invention.

[0027] Figure 3 This is a plane scanning electron microscope image of Example 2 of the present invention.

[0028] Figure 4 This is a plane scanning electron microscope image of Example 3 of the present invention.

[0029] Figure 5 This is a plane scanning electron microscope image of comparative example 1 of the present invention.

[0030] Figure 6 These are water contact angle diagrams of Comparative Example 1, Example 1, Example 2, and Example 3 of the present invention.

[0031] Figure 7 It is the infrared spectra of Comparative Example 1, Example 1, Example 2 and Example 3 of the present invention.

[0032] Figure 8 It is a schematic diagram of the membrane structure of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0034] Materials used in the present invention: There is no particular limitation on the sources of all raw materials in the present invention and the following examples, and any raw materials may be commercially available.

[0035] Figure 1 This is the preparation flow chart of the present invention. Polyolefin is used as the base membrane. An organic phase is first added to one side of the base membrane for a period of time. The base membrane is turned over and an aqueous phase is added to the other side. Interfacial polymerization reaction is carried out for a period of time, and then heat treatment is performed to obtain the prepared nanofiltration membrane.

[0036] The membrane flux test method of the prepared NF membrane is as follows: the membrane permeation selectivity performance test system is used to test the water permeation flux and salt retention rate of the membrane. The test system includes a pump, a membrane tank, a pipeline, a regulating valve, and a pressure and flow detector. The effective membrane area tested is 19.64 cm 2 , the test pressure is 6 bar, the test temperature is 25±0.5℃. The salt concentration of the test salt retention rate is 1000ppm.

[0037] Figure 8 The structure of the membrane is shown in Figure 1, where a polyamide layer is formed at the polyolefin base membrane. As can be seen from the figure, the nanofiltration membrane is very sensitive to divalent ions (SO4 2- ) has a higher retention rate than monovalent ions.

[0038] Embodiment 1:

[0039] A n-hexane solution containing 0.1% trimesoyl chloride was prepared as an organic phase solution, and a mixed solution containing 0.08% piperazine and 0.02% 2,4-diaminobenzenesulfonic acid was prepared as an aqueous phase solution.

[0040] First, the organic phase solution is placed on the surface of the polyolefin support membrane and kept for 5 minutes, and the excess solution is removed. Then, the polyolefin membrane is turned over, and the aqueous phase mixed solution is placed on the other side of the support membrane. The reaction is carried out for 10 minutes, and the excess solution is removed. Then, the obtained nanofiltration membrane is placed in a 60°C forced air drying oven and dried for 15 minutes to obtain the prepared polyamide composite nanofiltration membrane.

[0041] like Figure 2 The figure shows a planar scanning electron microscope image of the nanofiltration membrane obtained in Example 1. It can be seen from the figure that the surface of the nanofiltration membrane has no obvious pore structure and has become denser.

[0042] Embodiment 2:

[0043] The monomers in the aqueous mixed liquid of this embodiment are 0.08% piperazine and 0.02% 2,5-diaminobenzenesulfonic acid, and the rest are the same as in Embodiment 1.

[0044] like Figure 3The figure shows a planar scanning electron microscope image of the nanofiltration membrane obtained in Example 2. It can be seen from the figure that there is no obvious pore structure on the surface of the nanofiltration membrane, and it has become more dense.

[0045] Embodiment 3:

[0046] The monomers in the aqueous mixed liquid of this embodiment are 0.08% piperazine and 0.02% 3,4-diaminobenzenesulfonic acid, and the rest are the same as in Embodiment 1.

[0047] like Figure 4 The figure shows a planar scanning electron microscope image of the nanofiltration membrane obtained in Example 3. It can be seen from the figure that the surface of the nanofiltration membrane has no obvious pore structure and has become denser.

[0048] Comparative Example 1:

[0049] Prepare a n-hexane solution containing 0.1% trimesoyl chloride as an organic phase solution. Prepare a solution containing 0.08% piperazine as an aqueous phase mixture. First, place the organic phase mixture on the surface of the polyolefin support base membrane, keep it for 5 minutes, remove the excess solution, then turn the polyolefin base membrane over, place the aqueous phase mixture on the other side of the base membrane, react for 10 minutes, remove the excess solution, and then place the membrane in a 60°C forced air drying oven for 15 minutes to obtain the prepared nanofiltration membrane.

[0050] like Figure 5 The figure shows a planar scanning electron microscope image of the nanofiltration membrane obtained in Comparative Example 1. It can be seen from the figure that the surface of the nanofiltration membrane has a porous structure; compared with Comparative Example 1, the surface of the nanofiltration membrane obtained in Examples 1-3 is denser.

[0051] Test analysis:

[0052] The nanofiltration membranes prepared in Example 1, Example 2, Example 3 and Comparative Example 1 were tested by a cross-flow filtration device at room temperature and a pressure of 6 bar, and the test results are shown in Table 1. R (Na2SO4) and R (NaCl) in the table are the retention rates of sodium sulfate and sodium chloride, respectively, and PWP is the pure water flux.

[0053]

[0054]

[0055] As can be seen from Table 1, the pure water flux of Comparative Example 1 is 130.22 L / m 2 ·h, after adding diaminobenzenesulfonic acid, the pure water flux of Examples 1, 2, and 3 was 150.66 / m 2 h, 134.39 / m 2 h, 144.57L / m 2·h, the pure water flux has been improved to varying degrees. The sodium sulfate retention rate of comparative example 1 is 93.6%. After adding diaminobenzenesulfonic acid, the sodium sulfate retention rates of Examples 1, 2, and 3 are 96.5%, 96.7%, and 95.9%, respectively, and the sodium sulfate retention rates have been improved. The sodium chloride retention rate of comparative example 1 is 15.6%. After adding diaminobenzenesulfonic acid, the sodium chloride retention rates of Examples 1, 2, and 3 are 11.2%, 24.7%, and 22.5%, respectively, and the sodium chloride retention rate is kept low.

[0056] In summary, compared with the case without adding diaminobenzenesulfonic acid, the flux is greatly improved while maintaining high retention of sodium sulfate and low retention of sodium chloride. The performance is excellent and can be applied to the system of separation of monovalent and divalent ions.

[0057] Figure 6 The water contact angle comparison diagram of the nanofiltration membrane obtained in Example 1, Example 2, Example 3, and Comparative Example 1 is shown. As can be seen from the figure, the water contact angle of Comparative Example 1 is 58.3°, and the water contact angles of Examples 1, 2, and 3 are 44.8°, 51.6°, and 41.2°, respectively. After adding diaminobenzenesulfonic acid, the water contact angle is reduced to varying degrees, thereby improving the hydrophilicity of the membrane.

[0058] Figure 7 The infrared spectra of the nanofiltration membranes obtained in Example 1, Example 2, Example 3, and Comparative Example 1 are shown. As can be seen from the figure, compared with Comparative Example 1, Examples 1, 2, and 3 have a higher infrared spectrum at 1300-1000 cm -1 There is obvious -SO3 2- characteristic infrared peaks.

[0059] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane, characterized in that: First, the supporting base membrane is soaked with an organic phase solution containing trimesoyl chloride monomer, the supporting base membrane after soaking in the organic phase is turned over, and an aqueous phase solution containing piperazine and diaminobenzenesulfonic acid monomers is subjected to cross-base membrane reverse diffusion interface polymerization to obtain a polyamide composite nanofiltration membrane.

2. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane according to claim 1, characterized in that: The method specifically comprises the following steps: Step 1: dissolving trimesoyl chloride in an organic phase solution to obtain an organic phase solution; Step 2: dissolving piperazine and diaminobenzenesulfonic acid monomers in water to obtain an aqueous solution; Step 3: soaking the supporting base membrane with the organic phase solution prepared in step 1 to obtain a supporting base membrane infiltrated with organic phase monomers; Step 4: Turn over the support base membrane obtained in step 3, and immerse the other side thereof in the aqueous solution prepared in step 2 to perform an interfacial polymerization reaction to obtain a polyamide composite nanofiltration membrane; Step 5: heat-treating the polyamide composite nanofiltration membrane obtained in step 4 to obtain a nanofiltration membrane with high separation performance.

3. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane according to claim 2, characterized in that: The supporting base film is composed of one or more of polyethylene, polypropylene, polyvinylidene fluoride and polytetrafluoroethylene.

4. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane according to claim 3, characterized in that: In step 1, the concentration of trimesoyl chloride monomer is 0.025-0.2 w / v%.

5. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane according to claim 3, characterized in that: In step 2, the diaminobenzenesulfonic acid monomer is a mixture of one or more of 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, 3,4-diaminobenzenesulfonic acid or their derivatives.

6. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane according to claim 5, characterized in that: In step 2, the concentration of piperazine is 0.02-0.2 wt %, and the concentration of diaminobenzenesulfonic acid monomer is 0.01-0.1 wt %.

7. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin-based membrane according to claim 2, characterized in that: In step three, the immersion time is 1 to 15 minutes; in step four, the reaction time of the interfacial polymerization reaction is 5 to 20 minutes.

8. The method for preparing a polyamide composite nanofiltration membrane based on reverse diffusion interfacial polymerization across a polyolefin base membrane according to claim 3, characterized in that: In step 5, the heat treatment temperature is 60° C. and the time is 10 to 60 minutes.

9. A polyamide composite nanofiltration membrane prepared by reverse diffusion interfacial polymerization across a polyolefin-based membrane, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

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