Preparation method of polyvinyl composite forward osmosis membrane, obtained composite forward osmosis membrane and application of composite forward osmosis membrane

Abstract

The invention provides a preparation method of a polyvinyl composite forward osmosis membrane, which comprises the following steps: carrying out interfacial polymerization reaction on a 10-50 mu m polyvinyl membrane, a water phase solution and an oil phase solution, drying, modifying twice, and drying to obtain the forward osmosis membrane. The invention also provides application of the forward osmosis membrane prepared by the preparation method in preparation of emergency water purification equipment. The polyvinyl composite forward osmosis membrane is good and stable in performance and high in water flux, and the water permeation time can be obviously shortened. Besides, the forward osmosis membrane water bag has the advantages of being small in size, low in manufacturing cost, small in mass, easy to carry and capable of being repeatedly used, escherichia coli can be intercepted, harmful substances such as viruses and heavy metal can be efficiently intercepted, and the forward osmosis membrane water bag is suitable for various use scenes.

Description

Technical Field

[0001] The invention relates to the technical field of forward osmosis membranes, in particular to a method for preparing a polyethylene-based composite forward osmosis membrane based on an interfacial polymerization reaction, and also relates to a forward osmosis membrane obtained by the preparation method, and an emergency water bag prepared using the forward osmosis membrane. Background Art

[0002] Forward osmosis (FO) is a pollution-resistant, low-energy separation technology that is carried out spontaneously without the need for additional energy. It has broad application prospects in the fields of seawater (brackish water) desalination, sewage treatment, and portable drinking water generation equipment.

[0003] The emergency water bag developed based on forward osmosis technology uses only the osmotic pressure difference between the original solution and the drawn liquid as the driving force to diffuse the water in the original solution through the forward osmosis membrane to the drawn liquid side, thereby removing bacteria, viruses, suspended matter, metal ions, toxic and harmful substances in the original solution.

[0004] (1) Chinese utility model patent CN 201811374872.9 discloses a forward osmosis water bag, the interior of which is composed of a partition net and a forward osmosis membrane that are closely connected to each other, vertically dividing the water bag into two parts: an extraction liquid chamber and a treatment liquid chamber; the extraction liquid chamber is filled with a high-concentration sugar extraction liquid; when in use, first pour the unclean water to be treated into the treatment water chamber from the water inlet, and then pour the prepared extraction liquid into the extraction liquid chamber from the drinking water outlet. After standing, the water molecules in the water to be treated penetrate into the extraction liquid chamber through the forward osmosis membrane, thereby obtaining a low-concentration extraction liquid for drinking. However, the forward osmosis membrane of the water bag is made of a non-woven fabric support layer, which has a high cost; on the other hand, its permeation rate is low, and the time it takes to obtain drinking water by forward osmosis is too long (2 to 8 hours), which cannot be quickly drunk to meet emergency needs; in addition, most of these water bags are disposable equipment and cannot be reused multiple times. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and firstly propose a forward osmosis membrane that is more economical, has good performance and higher water flux, which can be applied to emergency water production equipment.

[0006] Based on this, the present invention provides a method for preparing a polyethylene-based composite forward osmosis membrane, the method comprising the following steps:

[0007] (1) Basement membrane pretreatment

[0008] Take a polyethylene film with a thickness of 10 to 50 μm, place it in solution A to fully wet it, then use a roller to scrape off excess solvent on the surface of the film, and then rinse it with pure water for later use;

[0009] (2) Preparation of solution required for interfacial polymerization

[0010] Prepare an aqueous solution: weigh m-phenylenediamine and sodium dodecyl sulfate, with the remainder being distilled water, and mix them evenly to obtain an aqueous solution with a mass concentration of 1% to 5% m-phenylenediamine and 0.01% to 0.20% sodium dodecyl sulfate;

[0011] Prepare the oil phase solution: weigh 0.1% to 0.5% of trimesoyl chloride and the solvent ParG by mass ratio, mix them evenly to obtain a trimesoyl chloride oil phase solution with a mass concentration of 0.1% to 0.5%;

[0012] (3) Interfacial Polymerization Reaction

[0013] The base film obtained in step (1) is placed in an aqueous solution, and soaked for 0.5 to 4.5 minutes at a temperature of 20°C to 50°C. After taking out the film, the excess solution on the surface of the film is scraped off with an air knife, and then placed in an oil phase solution for interfacial polymerization reaction, the reaction temperature is 20°C to 50°C, and the reaction time is 0.5 to 1.5 minutes. After the reaction is completed, the excess solution on the surface of the film is removed, and then the film is placed in an oven at a temperature of 50°C to 100°C for drying for 0.5 to 5 minutes to obtain a film after interfacial polymerization reaction;

[0014] (4) Modification

[0015] The membrane obtained in step (3) is placed in solution B for 3 to 10 minutes, taken out and washed with an alkaline solution to remove excess interfacial polymerization reaction by-products on the surface of the membrane, and then washed with pure water or citric acid aqueous solution. The washed membrane is placed in a sodium nitrite solution for 0.5 to 1 minute for modification, and then immersed in a second modification solution for 0.5 to 1 minute, wherein the second modification solution is an aqueous solution containing 0.1% to 10% PVA, 0.1% to 10% glycerol and 0 to 1% sodium bisulfite in a mass ratio, and taken out and dried to obtain a forward osmosis membrane.

[0016] In the present invention, the base film wetting solution A in step (1) is selected from a mixture of one or more solvents selected from 15-40% isopropyl alcohol and 5-10% sodium dodecyl sulfate (SDS).

[0017] As a conventional technical means in the art, the sufficient wetting of step (1) is achieved by placing the base film in a solvent for 0.1 to 10 hours. The scraping of step (1) is achieved by using a pressure roller to squeeze the film surface at a pressure of 0.1 to 1 MPa.

[0018] Usually, the concentration of the aqueous solution in step (2) is 0.5-5%.

[0019] Preferably, the alkaline solution in step (4) is an aqueous solution of sodium carbonate, sodium bicarbonate or sodium hydroxide, with a pH of 7.0 to 11.0.

[0020] The citric acid aqueous solution of step (4) has a pH of 2.0 to 6.0

[0021] The concentration of the sodium nitrite solution in step (4) is 10-20%, and the sodium nitrite solution is used to nitrate and modify the membrane.

[0022] The polyethylene-based composite forward osmosis membrane of the present invention is a polyamide composite membrane that uses a polyethylene diaphragm instead of a traditional non-woven fabric plus polysulfone as a base membrane, cross-integrates the lithium battery industry technology with the water treatment technology, and completes a revolutionary innovation in membrane materials.

[0023] On the other hand, the polyethylene fibers in the polyethylene-based membrane have a higher degree of bonding with the desalination layer, which can form a thinner polyamide desalination layer, ensuring that the forward osmosis membrane has a high retention rate and better anti-pollution performance.

[0024] With respect to the forward osmosis membrane in the prior art, the thickness of the polyethylene-based composite forward osmosis membrane of the present invention is only 20 μm, which is significantly lower than the thickness of the existing forward osmosis membrane materials while ensuring a good retention rate; secondly, since PET and PS are not used in the preparation method of the present invention, the desalination layer is firmly combined with the substrate and has excellent alkali resistance, organic solvent resistance, and good back pressure resistance. The uniform and dense vesicle structure of the desalination layer enables the composite forward osmosis membrane to have better water permeability and higher water flux; in addition, in the preparation method of the present invention, the amount of organic solvent used is small and recyclable, which is in line with the advanced concepts of sustainable development and carbon neutrality.

[0025] Based on this, the present invention also provides the use of the forward osmosis membrane prepared by the above preparation method in the preparation of emergency water purification equipment.

[0026] Specifically, the present invention also provides a forward osmosis membrane emergency water bag, which includes an outer water bag 1 and an inner water bag 2 placed in the outer water bag 1, and the inner water bag is also composed of a forward osmosis membrane prepared by the preparation method according to any one of claims 1 to 4, and at least part of the edge of the inner water bag 2 is fixed together with the hard mesh cloth and fixed on the inner side of the outer water bag 1; the inner side of the inner water bag 2 is an extraction liquid cavity 7, and the cavity between the outer water bag 1 and the inner water bag 2 is a raw solution cavity 8; a closable raw liquid inlet is provided on the outer water bag 1, and the raw liquid inlet is connected to the raw solution cavity 8; a closable extraction liquid inlet 4 is installed on the emergency water bag, and the extraction liquid inlet 4 passes through the outer water bag 1 and the inner water bag 2 and is connected to the extraction liquid cavity 7.

[0027] According to a preferred embodiment, the hard mesh cloth is a PET, PP or PE mesh cloth.

[0028] As a preferred embodiment, the drawn liquid inlet 4 includes a drinking water connector 41 with a hollow flow channel, a nut 43 matching the external thread of the drinking water connector 41, and a bolt 42 matching the internal thread of the drinking water connector 41. The drinking water connector 41 includes a tubular body and an extension 411 located at the rear of the tubular body. The extension 411 is placed in the drawn liquid cavity 7, and the nut 43 outside the outer water bag 1 is tightened to fix the drawn liquid inlet 4 on the emergency water bag.

[0029] The drinking water connector 41 further includes a sealing ring 44 disposed between the extension portion 411 and the inner wall of the inner water bag 2 .

[0030] In order to realize multiple utilization of the emergency water bag, the emergency water bag further comprises a push-type dropper bottle having a dropper bottle mouth, and the diameter of the dropper bottle mouth matches the drinking water connector 41 .

[0031] In the present invention, the self-developed polyolefin forward osmosis membrane has good and stable performance, and the water flux can be as high as 25 to 60LMH, so the water permeation time can be significantly shortened, and the water can be quickly drunk in 1 to 60 minutes. In addition, the present invention is small in size, low in cost, and the water bag is small in weight. The handle design is easy to carry, and the upper sealing port is opened to enter the original solution, which is convenient and fast. The drawn liquid is stored in a push-type transparent pointed dropper bottle in the form of a concentrated liquid, which is small in size, easy to carry, and can be reused many times.

[0032] The filtration accuracy of the forward osmosis membrane of the present invention is as high as 0.1nm, which can intercept 100% of Escherichia coli and achieve high efficiency interception of harmful substances such as viruses and heavy metals to protect human health; the interception rate of the membrane for Fe, Cu, Al and Zn can reach more than 98%.

[0033] The water flux of the forward osmosis membrane of the present invention can be as high as 25 to 80 LMH, so the water permeation time can be significantly shortened, and the water can be quickly drunk within 1 to 60 minutes.

[0034] The emergency water bag provided by the present invention adopts a portable design, is convenient to carry, and occupies little space; it has a simple structure and low cost, and can be adapted to a variety of usage scenarios, such as: outdoor activities, military use, coal mine emergencies, water pollution emergencies, sea voyages, etc.

[0035] The emergency water bag of the present invention can be reused due to structural improvement and is environmentally friendly and durable. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The changes of membrane flux and reverse solute flux with operation time under different draw concentrations;

[0037] Figure 2 This is a schematic diagram of the structure of a forward osmosis emergency water bag;

[0038] Figure 3 This is a partial structural diagram of a forward osmosis emergency water bag;

[0039] Figure 4 It is a schematic diagram of the structure of a pointed-mouth dropper bottle for containing the drawn liquid;

[0040] Figure 5 It is the amount of water that the forward osmosis emergency water bag can absorb under different test liquid conditions. DETAILED DESCRIPTION

[0041] The following examples are used to explain the technical solutions of the present invention in a non-limiting manner.

[0042] In the present invention, unless otherwise specified, "%" used to explain concentrations refers to mass percentage, and ":" refers to mass ratio.

[0043] Example 1 Preparation of forward osmosis membrane

[0044] Take a 50 μm polyethylene base film, place it in isopropanol / SDS to fully wet it, then use a pressure roller to scrape off excess solvent on the surface of the film at a pressure of 0.5 MPa, and rinse with pure water to obtain a clean base film.

[0045] Prepare aqueous phase solution: weigh 2% m-phenylenediamine and 0.10% sodium dodecyl sulfate, the balance is distilled water, mix well to obtain aqueous phase solution;

[0046] Prepare the oil phase solution: weigh 0.2% of trimesoyl chloride and the balance of ParG (solvent), mix well to obtain the oil phase solution.

[0047] Place the clean base membrane in the aqueous solution and soak it at room temperature for 1.0 min. After taking out the membrane, use a wind knife to scrape off the excess solution on the surface of the membrane, and then place it in the oil phase solution for interfacial polymerization reaction. The reaction time is 0.5 min. After the reaction is completed, remove the excess solution on the surface of the membrane, and then place the membrane in an 80°C oven to dry to obtain a membrane that has undergone interfacial polymerization reaction.

[0048] The obtained membrane is placed in 30%:8% isopropanol / SDS for 3.0 minutes, taken out and washed with an alkaline solution to remove excess interfacial polymerization reaction byproducts on the membrane surface, and then washed with pure water or citric acid aqueous solution. After washing, the membrane is placed in a sodium nitrite solution for 40 seconds for modification, and then immersed in an aqueous solution containing 5% PVA, 5% glycerol and 1% sodium bisulfite for modification, and taken out and dried to obtain a forward osmosis membrane.

[0049] A conventional forward osmosis membrane testing device is constructed according to the teachings of the prior art. The testing device includes a forward osmosis membrane fixing device arranged in an acrylic shell, a water inlet for the drawn liquid and raw water is arranged at one end of the acrylic shell, and a water outlet for the drawn liquid and raw water is arranged at the other end, and the inlet and outlet of the drawn liquid and raw water are on the same acrylic plate.

[0050] The obtained forward osmosis membrane was fixed in the test equipment, and the membrane flux and reverse solute flux were tested at a flow rate of 5 cm / s according to the working principle of the forward osmosis membrane. The draw solution was composed of sodium chloride with a mass concentration of 2.5%, 5%, 10%, 15% and 20%, respectively, and the raw water was pure water. The results are as follows Figure 1 shown.

[0051] Figure 1 The results show the changes of membrane flux and reverse solute flux with running time when NaCl aqueous solution with different extraction concentrations is used as the test solution and the original solution is pure water.

[0052] Example 2 Preparation of forward osmosis emergency water bag

[0053] The forward osmosis membrane obtained in Example 1 is cut into a suitable size (length * width = 10 ~ 1000mm * 10 ~ 1000mm) and folded in half, with the forward osmosis membrane separation layer located inside. An opening the size of the drinking water connector 41 is opened on one side of the folded membrane sheet, and a sealing ring is put on the opening for installing the drinking water connector 41. Then, the prepared polyurethane glue is used to seal the two sides of the internal separation layer and 10mm ± 5mm on the upper side. The membrane is placed in an oven at 30℃ ~ 80℃ for more than 3 hours, and then left to air at room temperature for more than 3 hours. After the polyurethane glue is solidified and the seal is complete, the membrane bag is completed.

[0054] The forward osmosis membrane bag divides the interior of the shell into two independent spaces, which are the drawing liquid chamber and the original solution chamber from the inside. The original solution inlet is set outside the original solution chamber, and the drawing liquid chamber is connected to the drawing liquid inlet. Similarly, an opening the size of the drinking water connector 41 is opened at the membrane shell position, and a nut 43 is tightened and sealed along the thread of the drinking water connector 41. The drawing liquid inlet (drinking water outlet) 4 is installed and equipped with a drinking water straw for drinking water, and the required emergency water bag is obtained.

[0055] In the present invention, the shell is made of waterproof material, and the main components are rubber, latex, polyethylene or PVC polyester fiber, etc., which are non-toxic, tasteless, aging-resistant, water-free, and non-reactive with solutions.

[0056] In the present invention, the raw solution is mainly water resources available outdoors, at sea, in mining, in areas where natural disasters and sudden pollution incidents occur, namely rainwater, river water, lake water, mine water and seawater.

[0057] In the present invention, the extraction liquid is placed in a push-type transparent pointed-mouth dropper bottle, and is composed of high-energy concentrated solutions such as salts and sugars that are easily soluble and can produce high osmotic pressure, that is, a concentrated solution of one or more of sodium chloride, chitosan oligosaccharides, glucose, fructose, lactose, sucrose, galacto-oligosaccharides, pantothenic acid, edible flavorings, folic acid, phospholipids, bifidobacteria, biotin, arachidonic acid, nucleotides, taurine, lutein, carotene, docosahexaenoic acid, pyridoxine hydrochloride, palmitate, vitamin B1, vitamin B2, vitamin C, vitamin B6, vitamin 12, vitamin E, vitamin K, vitamin D3, inositol, and nicotinamide configured in a certain proportion.

[0058] When in use, immerse the water bag in the original solution, and the original solution enters the original solution cavity 8 from the original solution inlet (sealed portion) 2, open the cap 9 of the pointed-mouth dropper bottle filled with the drawn liquid, align the extrusion outlet with the drawn liquid inlet (drinking water outlet) 4 and squeeze the bottle body 12, so that the drawn liquid in the pointed-mouth dropper bottle can be added to the drawn liquid cavity 7 through the drawn liquid inlet 4; ensure that each inlet is in a closed state, shake the water bag evenly and place it horizontally, and with the help of the solution osmotic pressure difference on both sides of the forward osmosis membrane, the original solution in the original solution cavity 8 diffuses to one side of the drawn liquid cavity 7 without external power, and the diluted drawn liquid can be directly drunk by connecting the drinking water straw 5 through the drawn liquid inlet (drinking water outlet) 4.

[0059] Figure 5 Shows the amount of water that the forward osmosis emergency water bag can absorb when the original solution is pure water, using a single solute aqueous solution or a multi-solute aqueous solution of different concentrations as the test solution.

Claims

1. A method for preparing a polyethylene-based composite forward osmosis membrane, the method comprising the following steps: (1) Basement membrane pretreatment Take a polyethylene film with a thickness of 10 to 50 μm, place it in solution A to fully wet it, then use a roller to scrape off excess solvent on the surface of the film, and then rinse it with pure water for later use; (2) Preparation of solution required for interfacial polymerization Prepare an aqueous solution: weigh m-phenylenediamine and sodium dodecyl sulfate, with the remainder being distilled water, and mix them evenly to obtain an aqueous solution with a mass concentration of 1% to 5% m-phenylenediamine and 0.01% to 0.20% sodium dodecyl sulfate; Prepare the oil phase solution: weigh trimesoyl chloride and solvent ParG according to the mass ratio, mix them evenly to obtain a trimesoyl chloride oil phase solution with a mass concentration of 0.1% to 0.5%; (3) Interfacial Polymerization Reaction The base film obtained in step (1) is placed in an aqueous solution, and soaked at a temperature of 20°C to 50°C for 0.5 to 4.5 minutes. After taking out the film, the excess solution on the surface of the film is scraped off with an air knife, and then placed in an oil phase solution for interfacial polymerization reaction, the reaction temperature is 20°C to 50°C, and the reaction time is 0.5 to 1.5 minutes. After the reaction is completed, the excess solution on the surface of the film is removed, and then the film is placed in an oven at a temperature of 50°C to 100°C for drying for 0.5 to 5 minutes to obtain a film after interfacial polymerization reaction; (4) Modification The membrane obtained in step (3) is placed in solution B for 3 to 10 minutes, taken out and washed with an alkaline solution to remove excess interfacial polymerization reaction by-products on the surface of the membrane, and then washed with pure water or citric acid aqueous solution. The washed membrane is placed in a sodium nitrite solution for 0.5 to 1 minute for modification, and then immersed in a second modification solution for 0.5 to 1 minute, wherein the second modification solution is an aqueous solution containing 0.1% to 10% PVA, 0.1% to 10% glycerol and 0 to 1% sodium bisulfite in a mass ratio, and taken out and dried to obtain a forward osmosis membrane.

2. The preparation method according to claim 1, characterized in that The solution A in step (1) is selected from one of 15-40% isopropanol and 5-10% sodium dodecyl sulfate (SDS), or a mixture of the two solvents.

3. The preparation method according to claim 1, characterized in that The alkaline solution in step (4) is an aqueous solution of sodium carbonate, sodium bicarbonate or sodium hydroxide, pH = 7.0 to 11.0; an aqueous solution of citric acid, pH = 2.0 to 6.

0.

4. The preparation method according to claim 1, characterized in that The concentration of the sodium nitrite solution in step (4) is 10-20%.

5. The preparation method according to claim 1, characterized in that The solvent B in step (4) is 15-40%:5-10% isopropanol / SDS.

6. Use of the forward osmosis membrane prepared by the preparation method according to any one of claims 1 to 4 in the preparation of emergency water purification equipment.

7. A forward osmosis membrane emergency water bag, the emergency water bag comprising an outer water bag (1) and an inner water bag (2) placed inside the outer water bag (1), the inner water bag being composed of a forward osmosis membrane prepared according to the preparation method described in any one of claims 1 to 4, at least part of the edge of the inner water bag (2) being fixed to a hard mesh cloth and being fixed to the inner side of the outer water bag (1); the inner side of the inner water bag (2) being an extraction liquid cavity (7), the cavity between the outer water bag (1) and the inner water bag (2) being an original solution cavity (8); a closable original solution inlet being provided on the outer water bag (1), the original solution inlet being connected to the original solution cavity (8); a closable extraction liquid inlet (4) being installed on the emergency water bag, the extraction liquid inlet (4) passing through the outer water bag (1) and the inner water bag (2) being connected to the extraction liquid cavity (7).

8. The emergency water bag according to claim 7, characterized in that The hard mesh is PET, PP or PE mesh.

9. The emergency water bag according to claim 7, characterized in that The drawn liquid inlet (4) comprises a drinking water connector (41) having a hollow flow channel, a nut (43) matched with the external thread of the drinking water connector (41), and a bolt (42) matched with the internal thread of the drinking water connector (41); the drinking water connector (41) comprises a tubular body and an extension (411) located at the rear of the tubular body; the extension (411) is placed in the drawn liquid cavity (7); the nut (43) outside the outer water bag (1) is tightened, and the drawn liquid inlet (4) is fixed to the emergency water bag.

10. The emergency water bag according to claim 7, characterized in that The emergency water bag also includes a push-type dropper bottle, which has a dropper bottle mouth, and the diameter of the dropper bottle mouth matches the drinking water connector (41).

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