A pumpless household nanofiltration membrane and a preparation method thereof

Abstract

The application belongs to the technical field of new material household water purification separation membrane, and particularly relates to a pump-free household nanofiltration membrane and a preparation method thereof. A blended casting solution of polyether sulfone and polysulfone is embedded into the reverse layer of non-woven fabric to form a rough base membrane layer, and then the base membrane layer is shaped through an oven with a temperature of 50 DEG C, and then is subjected to three-phase (water phase, amphiphilic phase and oil phase) interfacial polymerization, and finally is subjected to post-treatment and shaping again, so that a membrane with a screening function capable of selectively separating monovalent ions and divalent ions is obtained, and the household nanofiltration membrane with satisfactory water output under the condition of no pump is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of new material household water purification separation membranes, and particularly relates to a pump-free household nanofiltration membrane and a preparation method thereof. Background Art

[0002] As household drinking water treatment becomes increasingly common, water purifiers have become widely used in the household water purification industry. The membrane materials used in household water purifiers primarily rely on reverse osmosis filtration and ultrafiltration. These two membrane filtration methods exist alongside each other for drinking water treatment.

[0003] The advantage of using reverse osmosis membranes is that the effluent is entirely composed of water molecules, pure and ion-free. This has been shown to be effective in removing contaminants from water in areas with high mineral content and salinity. However, the use of reverse osmosis membranes also has significant disadvantages. The absence of minerals in the effluent reduces the mineral intake required by the population, hindering the natural properties of municipal water supplies. Furthermore, the dense structure of reverse osmosis membranes necessitates the use of high-pressure pumps as driving force in water purifiers. This necessitates a dependency on electricity, and the connection of pressure tanks to the purifiers at the end of the process often serves as a water storage tank. This takes up considerable space in home kitchens, limiting the use of reverse osmosis water purifiers.

[0004] Ultrafiltration membrane filtration, another type of end-of-line filtration, has the advantage of intercepting pathogens, bacteria, colloids, blue-green algae, and sewage particles in the water, ensuring hygienic and safe water quality at the end, making it suitable for drinking directly. Furthermore, because the ultrafiltration membrane uses a fully mechanized microporous filtration method, driven by the municipal water pressure, no separate power connection is required. This is an energy-saving, hygienic, and safe instant online water production method, and is very popular in the market. However, the microporous nature of the ultrafiltration membrane means that ultrafiltration does not intercept mineral ions in the water, and therefore cannot solve the problem of softening high-hardness water.

[0005] Based on the current status of the water treatment methods of the above two filter membranes, the end-of-line water purification treatment in the water purification industry currently requires a new household water treatment membrane filtration method. Summary of the Invention

[0006] In response to the confusion in the existing terminal water treatment of household water purification, the present invention provides a pump-free household nanofiltration membrane and a preparation method thereof, which fills the shortcomings of the existing ultrafiltration membrane and reverse osmosis membrane.

[0007] The pump-free household nanofiltration membrane of the present invention is prepared by embedding a blended casting liquid of polyethersulfone and polysulfone into the reverse layer of a non-woven fabric to form a rough base membrane layer, which is then shaped in a drying tunnel at a temperature of 50°C, and then polymerized at the interface of an aqueous phase solution, an amphiphilic phase solution, and an oil phase solution, and finally cleaned and dried to be shaped again to obtain a nanofiltration membrane with screening function.

[0008] The specific preparation method of the pumpless household nanofiltration membrane is as follows:

[0009] (1) placing an organic solvent, polysulfone, and polyethersulfone into a dissolving tank and stirring to mix uniformly, then adding polyvinyl pyrrolidone until completely dissolved to obtain a casting solution;

[0010] The composition of the casting solution in parts by mass is: 20-25 parts of polysulfone and polyethersulfone blending material, 7-10 parts of polyvinylpyrrolidone K90, and 65-85 parts of organic solvent.

[0011] The mass ratio of polysulfone to polyethersulfone is 3-5:5-8.

[0012] The organic solvent is one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

[0013] (2) At room temperature, in a scraping machine, the casting solution prepared in step (1) is applied to the reverse side of the non-woven fabric using a scraper, and then the film is formed in a drying oven at 50° C. to prepare a nanofiltration base membrane;

[0014] (3) At room temperature, the base film is immersed in an aqueous solution tank containing piperazine for 8 to 15 minutes; the composition of the aqueous solution containing piperazine is as follows in terms of mass percentage: 1.0-1.5% piperazine, 1.0-1.5% sodium carbonate, 0.6-1.0% polyvinyl alcohol, and the rest water.

[0015] (4) At room temperature, the base film of step (3) is immersed in a bath of an amphiphilic phase solution containing polyethylene glycol for 8 to 15 minutes; the amphiphilic phase polyethylene glycol solution is composed of the following mass percentages: 30-50% polyethylene glycol, 30-50% polyethylene glycol methyl ether, 10% water, and 10% n-hexane.

[0016] (5) The membrane treated in step (4) is transferred into an oil phase solution tank containing trimesoyl chloride and soaked for 3 to 5 minutes, and then washed and dried to obtain a pump-free household nanofiltration membrane;

[0017] The oil phase solution containing trimesoyl chloride is a normal hexane solution of trimesoyl chloride with a mass concentration of 0.4-0.6%.

[0018] The drying temperature is: 40-60°C, and the drying time is 5-8 minutes.

[0019] Beneficial effects:

[0020] (1) The casting liquid prepared by the blend of polyethersulfone and polysulfone is embedded in the rough back layer of the non-woven fabric to form a water-permeable layer that is both tightly bonded and loose in structure. The base membrane layer is then fully polymerized through the three phases of hydrophilic phase, amphiphilic phase, and lipophilic phase. This forms a pump-free ultra-low pressure household nanofiltration membrane that has good water permeability and can fully screen monovalent and divalent ions in water.

[0021] (2) The nanofiltration membrane of the present invention is more hydrophilic after being soaked in a biphilic phase solution, and has better bonding with the polymer, so that the prepared nanofiltration membrane can achieve separation without pressurization.

[0022] (3) The product features of the present invention are: first, it is driven by tap water pressure without a pump, eliminating the need for a power source. Second, the product has a high removal rate of mineral ions that cause buildup in water, while retaining more ions beneficial to the human body. Third, the water flow rate is large without a pump, providing a better water experience for household use. Fourth, the filtration is done online, and there is no need for a pressure tank, which saves kitchen space and is more suitable for household use. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an electron microscope image of the plate nanofiltration membrane prepared in the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the embodiments:

[0025] Example 1

[0026] (1) 70 g of N,N-dimethylformamide, 10 g of polysulfone, and 15 g of polyethersulfone were placed in a dissolving tank and stirred to mix evenly, and then 8 g of polyvinylpyrrolidone was added until completely dissolved to obtain a casting solution;

[0027] (2) At room temperature, in a scraping machine, the casting solution prepared in step (1) is applied to the reverse side of the non-woven fabric using a scraper, and then the film is formed in a drying oven at 50° C. to prepare a nanofiltration base membrane;

[0028] (3) Soak the basement membrane in an aqueous solution containing piperazine for 10 minutes at room temperature;

[0029] The composition of the piperazine-containing aqueous solution is as follows: 1.2% piperazine, 1.2% sodium carbonate, 0.8% polyvinyl alcohol, and the remainder water.

[0030] (4) Soaking the basement membrane from step (3) in a bath of amphiphilic phase solution containing polyvinyl alcohol for 10 minutes at room temperature;

[0031] The composition of the amphiphilic phase polyethylene glycol solution is: 40% polyethylene glycol, 40% polyethylene glycol methyl ether, 10% water and 10% n-hexane.

[0032] (5) The membrane treated in step (4) was transferred into an oil phase solution tank containing trimesoyl chloride and soaked for 5 minutes, and then subjected to post-treatment, cleaning, and drying to obtain a pump-free household nanofiltration membrane;

[0033] The oil phase solution containing trimesoyl chloride is a n-hexane solution of trimesoyl chloride with a mass concentration of 0.5%.

[0034] Example 2

[0035] Compared with Example 1, step (1) was changed to: 70g N,N-dimethylformamide, 7.2g polysulfone and 16.8g polyethersulfone were put into a dissolution tank and stirred to mix evenly, and then 8g polyvinylpyrrolidone was added until completely dissolved to obtain a casting solution.

[0036] The remaining steps are the same as in Example 1.

[0037] Example 3

[0038] Compared with Example 1, step (1) was changed to: 70g N,N-dimethylformamide, 12.5g polysulfone and 12.5g polyethersulfone were put into a dissolving tank and stirred to mix evenly, and then 8g polyvinylpyrrolidone was added until completely dissolved to obtain a casting solution.

[0039] The remaining steps are the same as in Example 1.

[0040] Example 4

[0041] Compared with Example 1, the composition of the aqueous phase solution containing piperazine in step (3) was changed to: 1.0% piperazine, 1.0% sodium carbonate, 0.6% polyvinyl alcohol, and the rest water.

[0042] The remaining steps are the same as in Example 1.

[0043] Example 5

[0044] Compared with Example 1, the composition of the aqueous phase solution containing piperazine in step (3) was changed to: 1.5% piperazine, 1.5% sodium carbonate, 1.0% polyvinyl alcohol, and the rest water.

[0045] The remaining steps are the same as in Example 1.

[0046] Example 6

[0047] Compared with Example 1, the composition of the amphiphilic phase solution containing polyvinyl alcohol in step (4) was changed to: 30% polyethylene glycol, 50% polyethylene glycol methyl ether, 10% water, and 10% n-hexane.

[0048] The remaining steps are the same as in Example 1.

[0049] Example 7

[0050] Compared with Example 1, the composition of the amphiphilic phase solution containing polyvinyl alcohol in step (4) was changed to: 50% polyethylene glycol, 30% polyethylene glycol methyl ether, 10% water, and 10% n-hexane.

[0051] The remaining steps are the same as in Example 1.

[0052] Example 8

[0053] Compared with Example 1, the concentration of the oil phase solution in step (5) was changed to 0.4%.

[0054] The remaining steps are the same as in Example 1.

[0055] Comparative Example 1

[0056] Steps (1)-(3) are the same as in Example 1.

[0057] (4) The membrane treated in step (3) was transferred into an oil phase solution tank containing trimesoyl chloride and soaked for 5 minutes, and then subjected to post-treatment, cleaning and drying to obtain a pump-free household nanofiltration membrane;

[0058] The oil phase solution containing trimesoyl chloride is a n-hexane solution of trimesoyl chloride with a mass concentration of 0.5%.

[0059] Comparative Example 2

[0060] Steps (1)-(2) are the same as in Example 1.

[0061] (3) Soak the basement membrane in a solution containing piperazine for 10 minutes at room temperature;

[0062] The composition of the piperazine-containing aqueous solution is as follows: 1.2% piperazine, 1.2% sodium carbonate, 0.8% polyvinyl alcohol, 40% polyethylene glycol, and the remainder water.

[0063] (4) The membrane treated in step (3) was transferred into an oil phase solution tank containing trimesoyl chloride and soaked for 5 minutes, and then subjected to post-treatment, cleaning and drying to obtain a pump-free household nanofiltration membrane;

[0064] The oil phase solution containing trimesoyl chloride comprises trimesoyl chloride with a mass concentration of 0.5%, polyethylene glycol methyl ether 40%, and the rest being n-hexane solution.

[0065] Test method:

[0066] Connect the nanofiltration membrane assembly to the test device, connect it to pure water, adjust the water pressure to 0.3 MPa and run for 30 minutes. Then collect the filtrate, time it for 10 minutes, and calculate the flow rate.

[0067] Divalent desalination rate: Analyze pure MgSO4, prepare the stock solution and add the standard to 1000-2000us / cm, filter at 0.3MPa, take the filtrate to measure the conductivity and calculate the desalination rate.

[0068] Monovalent desalination rate: Prepare the stock solution of analytical pure NaCl, add the spiked solution to 1000-2000 μs / cm, filter at 0.3 MPa, and measure the conductivity of the filtrate to calculate the desalination rate.

[0069] Test conditions

[0070] Unless otherwise specified, the test should be carried out under the following conditions. See Table 1 for specific conditions.

[0071] Table 1

[0072]

[0073] Test raw water configuration

[0074] Prepare a test solution of a specified concentration using pure water (with a conductivity less than 10 μS / cm) and analytically pure reagents according to the test conditions. Adjust the pH using NaOH or HCl. Store the prepared test solution in a sealed container away from light and use it immediately after preparation.

[0075] test

[0076] a) Install the nanofiltration membrane assembly to be tested into the membrane housing and flush it with pure water with a conductivity of less than 10 μS / cm according to the pressure and recovery rate in the test conditions for 30 minutes.

[0077] b) Connect the flushed nanofiltration membrane assembly to the test device according to B.2 in Appendix B of GB / T 30306-2013 and introduce a conductivity (standard solution) solution under test conditions. After the system has been running stably for 10 minutes, collect a certain amount of the conductivity (standard solution) test solution raw water and the nanofiltration membrane assembly outlet water in a beaker and test the conductivity using the conductivity measurement method. While testing the conductivity, the total hardness of the raw and produced water samples can be measured simultaneously to calculate the removal rate. The total hardness test method is based on GB / T5750.4-2006.

[0078] c) Connect the MgSO4 test solution. After the system has been running stably for 10 minutes, use beakers to collect a certain amount of MgSO4 test solution raw water and water from the nanofiltration membrane module outlet, and test the conductivity using the conductivity measurement method.

[0079] d) Connect the NaCl test solution. After the system has been running stably for 10 minutes, use beakers to collect a certain amount of NaCl test solution raw water and water from the nanofiltration membrane module outlet, and test the conductivity using the conductivity measurement method.

[0080] e) Select a newly opened nanofiltration membrane element to test the PEG200 removal rate, referring to the method in GB / T 34242-2017.

[0081] The performance test results of the embodiments of the present invention and the comparative embodiments are shown in Table 2.

[0082] Table 2

[0083]

Claims

1. A pump-free household nanofiltration membrane, characterized in that: The nanofiltration membrane is prepared by embedding a blended casting solution of polyethersulfone and polysulfone into the reverse layer of a non-woven fabric to form a rough base membrane layer, which is then shaped in a drying tunnel at a temperature of 50°C, and then polymerized at the interface of an aqueous solution, an amphiphilic phase solution, and an oil phase solution, and finally washed and dried to be shaped again to obtain a nanofiltration membrane with screening function. The amphiphilic phase solution comprises the following components in terms of mass percentage: 30-50% polyethylene glycol, 30-50% polyethylene glycol methyl ether, 10% water and 10% n-hexane.

2. The pump-free household nanofiltration membrane according to claim 1, characterized in that: The blended casting solution is composed of 20-25 parts of polysulfone and polyethersulfone blending material, 7-10 parts of polyvinylpyrrolidone K90, and 65-85 parts of organic solvent in parts by mass.

3. The pump-free household nanofiltration membrane according to claim 2, wherein: The mass ratio of polysulfone to polyethersulfone in the blended material is 3-5:5-8.

4. The pump-free household nanofiltration membrane according to claim 2, wherein: The organic solvent is one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

5. The pump-free household nanofiltration membrane according to claim 1, wherein: The aqueous phase solution is composed of the following components in terms of mass percentage: 1.0-1.5% piperazine, 1.0-1.5% sodium carbonate, 0.6-1.0% polyvinyl alcohol, and the remainder water.

6. The pump-free household nanofiltration membrane according to claim 1, characterized in that: The oil phase solution is a n-hexane solution of trimesoyl chloride with a mass concentration of 0.4-0.6%.

7. A method for preparing a pump-free household nanofiltration membrane according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Put the organic solvent, polysulfone and polyethersulfone into a dissolving tank and stir them thoroughly to mix them evenly, then add polyvinyl pyrrolidone until it is completely dissolved to obtain a casting solution; (2) At room temperature, in a scraping machine, use a scraper to apply the casting solution prepared in step (1) to the back layer of the non-woven fabric, and then pass it through a drying oven at 50°C to form a film to prepare a nanofiltration base membrane; (3) Soak the basement membrane in an aqueous solution containing piperazine for 8 to 15 minutes at room temperature; (4) At room temperature, the base film of step (3) is immersed in a bath containing a biphilic phase solution of polyethylene glycol and polyethylene glycol methyl ether for 8 to 15 minutes; (5) The membrane treated in step (4) is transferred into an oil phase solution tank containing trimesoyl chloride and soaked for 3 to 5 minutes, and then washed and dried to obtain a pump-free household nanofiltration membrane.

8. The method for preparing a pump-free household nanofiltration membrane according to claim 7, wherein: The drying temperature is 40-60° C., and the drying time is 5-8 minutes.

Images