High-flux nanofiltration membrane prepared by modifying surfactant and method thereof

Abstract

The invention relates to the technical field of nanofiltration membrane materials, in particular to a high-flux nanofiltration membrane prepared through surfactant modification and a method thereof.The method comprises the steps that a surfactant and a novel diamine monomer are mixed to serve as a water phase, an ultrafiltration bottom membrane is immersed into a water-phase solution, a rubber roller is used for removing the surface solution, then the ultrafiltration bottom membrane is immersed into an organic-phase solution for interfacial polymerization reaction, and the high-flux nanofiltration membrane is obtained. The preparation method comprises the following steps: adding a water-phase monomer and an oil-phase monomer into a reaction kettle, fully contacting the water-phase monomer and the oil-phase monomer, carrying out polymerization reaction at a two-phase interface to form a separation layer, drying and curing, and regulating the interfacial polymerization process by adopting a surfactant on the basis of a novel diamine monomer to obtain the high-flux nanofiltration membrane. The preparation method disclosed by the invention is simple to operate, mild in condition and easy to realize industrial production, and the prepared high-flux nanofiltration membrane has a wide application prospect in the fields of water treatment, chemical separation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiltration membrane materials, and specifically to a surfactant-modified method for preparing a high-flux nanofiltration membrane and the method thereof. Background Art

[0002] As an efficient water treatment technology, the nanofiltration membrane separation technology has been widely used in many fields such as drinking water purification, industrial wastewater treatment, food and beverage processing, and biomedicine due to its advantages in removing organic matters, divalent ions, and some monovalent ions in water. However, in practical applications, due to the existence of the "Trade-off" effect, it is difficult to achieve both high flux and high rejection rate simultaneously, which has become a bottleneck restricting the further development of nanofiltration membrane technology. Therefore, how to prepare a nanofiltration membrane with both high flux and high selectivity has become an urgent problem to be solved in this field.

[0003] In order to improve the high-flux and high-selectivity separation performance of the nanofiltration membrane, it is an effective strategy to use a novel diamine monomer to regulate the interfacial polymerization reaction activity; in addition, the hydrophilic and hydrophobic groups contained in the surfactant can effectively regulate the permeation flux and selectivity of the nanofiltration membrane by reducing the interfacial tension between the aqueous phase and the oil phase and regulating the diffusion rate of the monomer.

[0004] Based on this, the present invention proposes a preparation method for a surfactant-modified high-flux nanofiltration membrane, aiming to solve the existing technical problems and promote the development and application of nanofiltration membrane technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a surfactant-modified method for preparing a high-flux nanofiltration membrane and the method thereof, which is used to solve the problem of a nanofiltration membrane with both high permeation flux and high selectivity.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method for a surfactant-modified high-flux nanofiltration membrane, comprising the following steps:

[0008] Pretreat the ultrafiltration substrate membrane to obtain a pretreated nanofiltration base membrane;

[0009] Mix a novel diamine monomer, a surfactant, and deionized water to obtain an aqueous solution;

[0010] Mix 1,3,5-benzenetricarbonyl chloride and n-hexane to obtain an organic solution;

[0011] Immerse the pretreated ultrafiltration bottom membrane into the aqueous solution. After taking it out, remove the surface solution of the bottom membrane with a rubber roller, then immerse it into the organic phase solution for interfacial polymerization reaction, and then perform drying and curing to obtain a high-flux nanofiltration membrane.

[0012] Perform drying and curing on the base membrane after the interfacial polymerization reaction in sequence to obtain a nanofiltration membrane.

[0013] As a further technical solution, the material of the ultrafiltration membrane is one of polyethersulfone, polyacrylonitrile, and polyvinylidene fluoride.

[0014] As a further technical solution, the novel diamine monomer in the aqueous solution is one of 2-methylpiperazine and trans-2,5-dimethylpiperazine, and the concentration is 0.05 wt% - 0.20 wt%.

[0015] As a further technical solution, the surfactant in the aqueous solution is one of alkyltrimethylammonium bromides with different carbon chain lengths, and the carbon chain length is 4 - 12.

[0016] As a further technical solution, the surfactant in the aqueous solution is one of alkyltrimethylammonium bromides with different carbon chain lengths, and the concentration is 0.2 - 2 CMC.

[0017] As a further technical solution, the concentration of 1,3,5-benzenetricarbonyl chloride in the organic phase solution is 0.01 wt% - 0.5 wt%.

[0018] As a further technical solution, the immersion time of the ultrafiltration bottom membrane into the aqueous solution is 1 min - 10 min, and the time of the interfacial polymerization reaction is 10 s - 180 s.

[0019] As a further technical solution, perform drying and curing on the base membrane after the interfacial polymerization reaction in sequence. The curing time is 0.3 min - 5 min, and the curing temperature is 10°C - 90°C.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The preparation method of the surfactant-modified high-flux nanofiltration membrane provided by the present invention has relatively obvious advantages compared with the existing nanofiltration membranes. First, in terms of raw material selection, the ultrafiltration bottom membrane uses high-quality materials such as polyethersulfone, polyacrylonitrile, and polyvinylidene fluoride, combined with a specific concentration of novel diamine monomer, alkyltrimethylammonium bromide surfactants with different carbon chain lengths and concentrations, and a reasonable concentration of 1,3,5-benzenetricarbonyl chloride, laying a foundation for the preparation of high-performance nanofiltration membranes.

[0022] After pre-treating the ultrafiltration bottom membrane, the interfacial polymerization reaction is carried out by allowing the aqueous and organic phase solutions to come into full contact, and parameters such as the immersion time, reaction time, curing time, and temperature are controlled to enable the nanofiltration membrane to have a higher flux. The addition of surfactants can effectively regulate the microstructure and surface properties of the membrane surface, reduce the mass transfer resistance, and significantly increase the water flux while ensuring a high rejection rate.

[0023] In addition, the preparation method of the present invention is simple to operate, has mild conditions, is easy to realize industrial production, and the prepared high-flux nanofiltration membrane has broad application prospects in the field of water treatment. Specific Embodiments

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0026] Example 1

[0027] (1) A polyethersulfone ultrafiltration membrane with a size of 8 cm × 8 cm (its molecular weight cut-off is 100 KDa) is immersed in deionized water for pretreatment. The immersion time is 48 h, and the deionized water needs to be replaced every 24 h.

[0028] (2) Prepare an aqueous solution with a concentration of 0.1 wt% of trans-2,5-dimethylpiperazine, and mix 0.016 mol / L of octyltrimethylammonium bromide surfactant as the aqueous solution.

[0029] (3) Prepare an organic phase solution with an oil phase concentration of 0.2 wt%.

[0030] (4) Immerse the bottom membrane obtained in step (1) into the aqueous solution obtained in step (2) for 5 min, then take out the immersed base membrane, remove the surface solution with a rubber roller, and then immerse it into the organic phase solution for an interfacial polymerization reaction for 30 s.

[0031] (5) Put the membrane after the interfacial polymerization reaction obtained in step (4) into a constant temperature drying oven and cure it at 40 °C for 2 min to obtain a nanofiltration membrane.

[0032] Example 2

[0033] (1) A polyethersulfone ultrafiltration membrane with a size of 8 cm × 8 cm (its molecular weight cut-off is 100 KDa) is immersed in deionized water for pretreatment. The immersion time is 48 h, and the deionized water needs to be replaced every 24 h.

[0034] (2) Prepare an aqueous solution with a concentration of 0.15 wt% of trans-2,5-dimethylpiperazine, and mix it with 0.02 mol / L of dodecyltrimethylammonium bromide surfactant as the aqueous solution.

[0035] (3) Prepare an organic phase solution with an oil phase concentration of 0.2 wt%.

[0036] (4) Immerse the bottom film obtained in step (1) into the aqueous solution obtained in step (2) for 3 min. Then, take out the immersed base film, remove the surface solution with a rubber roller, and then immerse it into the organic phase solution for interfacial polymerization reaction for 60 s.

[0037] (5) Put the film after the interfacial polymerization reaction obtained in step (4) into a constant temperature drying oven and cure it at 50 °C for 2 min to obtain a nanofiltration membrane.

[0038] Example 3

[0039] (1) Immerse a polyacrylonitrile ultrafiltration membrane with a size of 8 cm × 8 cm (its molecular weight cut-off is 100 KDa) in deionized water for pretreatment. The immersion time is 48 h, and the deionized water needs to be replaced every 24 h.

[0040] (2) Prepare an aqueous solution with a concentration of 0.15 wt% of 2-methylpiperazine, and mix it with 0.1 mol / L of dodecyltrimethylammonium bromide surfactant as the aqueous solution.

[0041] (3) Prepare an organic phase solution with an oil phase concentration of 0.3 wt%.

[0042] (4) Immerse the bottom film obtained in step (1) into the aqueous solution obtained in step (2) for 5 min. Then, take out the immersed base film, remove the surface solution with a rubber roller, and then immerse it into the organic phase solution for interfacial polymerization reaction for 60 s.

[0043] (5) Put the film after the interfacial polymerization reaction obtained in step (4) into a constant temperature drying oven and cure it at 50 °C for 2 min to obtain a nanofiltration membrane.

[0044] Example 4

[0045] (1) Immerse a polyacrylonitrile ultrafiltration membrane with a size of 8 cm × 8 cm (its molecular weight cut-off is 100 KDa) in deionized water for pretreatment. The immersion time is 48 h, and the deionized water needs to be replaced every 24 h.

[0046] (2) Prepare an aqueous solution with a concentration of 0.2 wt% of trans-2,5-dimethylpiperazine, and mix it with 2.0 mol / L of tetraalkyltrimethylammonium bromide surfactant as the aqueous solution.

[0047] (3) Prepare an organic phase solution with an oil phase concentration of 0.25 wt%.

[0048] (4) Immerse the bottom film obtained in step (1) into the aqueous phase solution obtained in step (2) for 5 min. Then, take out the immersed substrate film, remove the surface solution with a rubber roller, and then immerse it into the organic phase solution for interfacial polymerization reaction for 60 s.

[0049] (5) Put the film after the interfacial polymerization reaction obtained in step (4) into a constant temperature drying oven and cure it at 60 °C for 1 min to obtain a nanofiltration membrane.

[0050] Comparative Example 1

[0051] (1) Immerse a polyethersulfone ultrafiltration membrane with a size of 8 cm × 8 cm (its molecular weight cut-off is 100 KDa) in deionized water for pretreatment. The immersion time is 48 h, and the deionized water needs to be replaced every 24 h.

[0052] (2) Prepare an aqueous phase solution with a concentration of 0.1 wt% of trans-2,5-dimethylpiperazine.

[0053] (3) Prepare an organic phase solution with an oil phase concentration of 0.2 wt%.

[0054] (4) Immerse the bottom film obtained in step (1) into the aqueous phase solution obtained in step (2) for 5 min. Then, take out the immersed substrate film, remove the surface solution with a rubber roller, and then immerse it into the organic phase solution for interfacial polymerization reaction for 30 s.

[0055] (5) Put the film after the interfacial polymerization reaction obtained in step (4) into a constant temperature drying oven and cure it at 40 °C for 2 min to obtain a nanofiltration membrane.

[0056] Comparative Example 2

[0057] (1) Immerse a polyethersulfone ultrafiltration membrane with a size of 8 cm × 8 cm (its molecular weight cut-off is 100 KDa) in deionized water for pretreatment. The immersion time is 48 h, and the deionized water needs to be replaced every 24 h.

[0058] (2) Prepare an aqueous phase solution with a concentration of 0.1 wt% of trans-2,5-dimethylpiperazine and mix 0.016 mol / L of sodium dodecylbenzenesulfonate surfactant as the aqueous phase solution.

[0059] (3) Prepare an organic phase solution with an oil phase concentration of 0.2 wt%.

[0060] (4) Immerse the bottom film obtained in step (1) into the aqueous phase solution obtained in step (2) for 5 min. Then, take out the immersed substrate film, remove the surface solution with a rubber roller, and then immerse it into the organic phase solution for interfacial polymerization reaction for 30 s.

[0061] (5) Put the membrane after interfacial polymerization obtained in step (4) into a constant temperature drying oven and cure it at 40 °C for 2 min to obtain a nanofiltration membrane.

[0062] Experiment

[0063] Under a pressure of 0.2 MPa, test the performance of the nanofiltration membrane of the example with 2000 ppm of Na2SO4. The results are as follows:

[0064] Table 1

[0065] <![CDATA[Pure water permeation flux L·m -2 ·h-1·bar -1 > <![CDATA[Retention rate of Na2SO4 aqueous solution %]]> Example 1 38.62 98.12 Example 2 40.08 98.24 Example 3 42.27 98.16 Example 4 44.36 98.13 Comparative Example 1 27.74 93.28 Comparative Example 2 31.18 95.73

[0066] As can be seen from Table 1, the nanofiltration membrane prepared by the present invention has a high water permeation flux and Na2SO4 aqueous solution rejection rate. Adding no surfactant or using other surfactants will reduce the pure water permeation flux and Na2SO4 aqueous solution rejection rate of the nanofiltration membrane.

[0067] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification.

Claims

1. A preparation method for preparing a high-flux nanofiltration membrane by surfactant modification, comprising the following steps: Pre-treat the ultrafiltration substrate membrane to obtain a pre-treated nanofiltration substrate membrane; Mix a novel diamine monomer, a surfactant and deionized water to obtain an aqueous solution; Mix 1,3,5-benzenetricarbonyl chloride and n-hexane to obtain an organic solution; Immerse the pre-treated ultrafiltration substrate membrane into the aqueous solution, take it out and remove the surface solution of the substrate membrane with a rubber roller, then immerse it into the organic solution for interfacial polymerization reaction, and then perform drying and curing to obtain a high-flux nanofiltration membrane.

2. The preparation method according to claim 1, wherein The material of the ultrafiltration substrate membrane is one of polyethersulfone, polyacrylonitrile, and polyvinylidene fluoride.

3. The preparation method according to claim 1, characterized in that, The novel diamine monomer in the aqueous solution is one of 2-methylpiperazine and trans-2,5-dimethylpiperazine, and the concentration is 0.05 wt% - 0.20 wt%.

4. The preparation method according to claim 1, characterized in that The surfactant in the aqueous solution is one of alkyltrimethylammonium bromides with different carbon chain lengths, and the carbon chain length is 4 - 12.

5. The preparation method according to claim 1, characterized in that, The surfactant in the aqueous solution is one of alkyltrimethylammonium bromides with different carbon chain lengths, and the concentration is 0.2 - 2 CMC.

6. The preparation method according to claim 1, characterized in that, The concentration of 1,3,5-benzenetricarbonyl chloride in the organic solution is 0.01 wt% - 0.5 wt%.

7. The preparation method according to claim 1, characterized in that, The immersion time of the ultrafiltration substrate membrane into the aqueous solution is from 1 min to 10 min, and the time of the interfacial polymerization reaction is from 10 s to 180 s.

8. The preparation method according to claim 1, characterized in that, The substrate membrane after the interfacial polymerization reaction is successively dried and cured, the curing time is 0.3 min - 5 min, and the curing temperature is 10 °C - 90 °C.

9. A nanofiltration membrane prepared by the preparation method according to any one of claims 1 - 8.