Preservation solution for separation membranes and packaging container for water treatment separation membranes containing the same.

Abstract

The present invention relates to a preservation solution for separation membranes and a water treatment separation membrane packaging container containing the same. The present invention relates to a preservation solution for water treatment separation membranes and a water treatment separation membrane packaging container containing the same, wherein the salt removal rate of the water treatment separation membrane stored in the preservation solution does not decrease significantly even when stored in the preservation solution, the water treatment equipment does not deform when the water treatment separation membrane stored in the preservation solution is used in the water treatment equipment, and bacteria do not proliferate even during the time the water treatment separation membrane is stored in the preservation solution.

Description

Technical Field

[0001] The present invention relates to a storage solution for a separation membrane and a separation membrane packaging container for water treatment containing the same. The separation membrane for water treatment stored in the storage solution for the separation membrane of the present invention has a salt rejection rate that does not significantly decrease even when stored in the storage solution for the separation membrane, and there is no deformation of the water treatment equipment even when the separation membrane for water treatment stored in the storage solution for the separation membrane is used in the water treatment equipment. The present invention also relates to a storage solution for a water treatment separation membrane in which bacteria do not propagate even during the time when the water treatment separation membrane is stored in the storage solution for the separation membrane, and a water treatment separation membrane packaging container containing the same.

Background Art

[0002] Separation membranes are classified into microfiltration membranes (MF), ultrafiltration membranes (UF), nanofiltration membranes (NF), or reverse osmosis membranes (RO) according to the pore size. Among them, an ultrafiltration membrane is usually defined as a membrane having the ability to separate colloidal substances and polymer solutions with a molecular weight of 1,000 to 300,000.

[0003] Specifically, in the past, cellulose membranes were used for ultrafiltration membranes, but in recent years, due to the development of synthetic polymer chemistry, membranes with excellent permeability using hydrophilic polymers such as polyvinyl alcohol have been developed. Ultrafiltration membranes are often used to obtain concentrated water rather than permeated water, contrary to reverse osmosis membranes, and are used in food wastewater treatment, pharmaceutical purification, electrical equipment painting, etc. Korean Registered Patent No. 0815276 discloses a pharmaceutical composition containing a high ratio of panaxadiol series saponin fractions separated from red ginseng by ultrafiltration, and ultrafiltration is also utilized in the concentration and purification of foods.

[0004] The aforementioned nanoseparation membrane is typically defined as a membrane capable of separating compounds with a molecular weight of less than 1,000. Specifically, it is a membrane with selective separation capability for nanometer-scale solutes, exhibiting a high salt removal rate for divalent ions and a relatively wide salt removal rate of over 40% for monovalent ions, and having a water permeability 5 to 10 times greater than that of reverse osmosis membranes using polyfunctional aromatic amines. In particular, nanoseparation membranes have the advantage of being able to remove substances such as geosmin, a typical off-flavor substance, and produce water from which pollutants generated during water treatment, such as nitrate nitrogen and trihalomethane, have been removed.

[0005] The aforementioned reverse osmosis membrane is a separation membrane capable of removing monovalent ions, salts, etc., that cannot be removed by microfiltration (MF) or ultrafiltration (UF), and is effectively used in desalination processes for water obtained from seawater or brine for drinking, agricultural, or other purposes. For a reverse osmosis membrane to have properties suitable for its intended use, it must have a high salt rejection rate and a high flow rate (Flux). In other words, a reverse osmosis membrane can only be commercially applicable to desalination processes if it can allow a large amount of water to pass through the membrane under relatively low pressure.

[0006] As described above, the membranes are generally stored and distributed with a preservative solution to prevent deterioration of their performance after manufacturing, storage, distribution, and use, or, in particular, to prevent the growth of microorganisms and molds when the membranes are used for food and beverages.

[0007] Conventionally, the aforementioned preservation solution was used with the addition of sodium bisulfite to prevent the growth of microorganisms and molds. However, preservation solutions with added sodium bisulfite have the problem of causing damage to polyacetal components in devices to which separation membranes or modules containing it are attached, such as water purifier components, and causing discoloration and deformation in the case of silicone components.

[0008] Furthermore, when using conventional preservation solutions that utilize chitosan or chito-oligosaccharides, the high cost, the complex process of dissolving them in the solution, and the resulting increase in production time and unit cost were problematic. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention was devised to solve the above-mentioned problems, and aims to provide a water treatment separation membrane preservation solution and a water treatment separation membrane packaging container containing the same, in which the salt removal rate of the water treatment separation membrane stored in the separation membrane preservation solution does not decrease significantly even when stored in the separation membrane preservation solution, the water treatment equipment does not deform when the water treatment separation membrane stored in the separation membrane preservation solution is used in the water treatment equipment, and bacteria do not proliferate even during the time the water treatment separation membrane is stored in the separation membrane preservation solution. [Means for solving the problem]

[0010] To solve the above-mentioned problems, the preservation solution for separation membranes of the present invention may contain an aqueous solution of citric acid. In one preferred embodiment of the present invention, the preservation solution for the separation membrane may be composed of an aqueous citric acid solution.

[0011] In a preferred embodiment of the present invention, the aqueous citric acid solution may contain 0.3 to 1.5% by weight of citric acid based on the total weight. In a preferred embodiment of the present invention, the aqueous citric acid solution may contain 0.3 to 0.8% by weight of citric acid based on the total weight.

[0012] In a preferred embodiment of the present invention, the citric acid aqueous solution may have a pH of 2.0 to 4.0. On the other hand, the water treatment separation membrane packaging container of the present invention is a water treatment separation membrane packaging container having a storage section inside which contents can be stored, wherein the storage section contains a water treatment separation membrane and the separation membrane preservation solution of the present invention, and the water treatment separation membrane may be immersed in the separation membrane preservation solution.

[0013] In one preferred embodiment of the present invention, the water treatment separation membrane may contain one or more polymeric substances selected from the group consisting of polysulfone polymers, polyamide polymers, polyimide polymers, polyester polymers, olefin polymers, fluorine polymers, polybenzimidazole polymers, and polyacrylonitrile.

[0014] In one preferred embodiment of the present invention, the separation membrane for water treatment may be a flat membrane or a hollow fiber membrane. In one preferred embodiment of the present invention, the water treatment separation membrane may be a cylindrical water treatment separation membrane module. [Effects of the Invention]

[0015] The separation membrane preservation solution and the water treatment separation membrane packaging container containing it of the present invention provide the following advantages: the salt removal rate of the water treatment separation membrane stored in the separation membrane preservation solution does not decrease significantly even when stored in the separation membrane preservation solution; the water treatment equipment does not deform when the water treatment separation membrane stored in the separation membrane preservation solution is used in the water treatment equipment; and bacteria do not proliferate even during the time the water treatment separation membrane is stored in the separation membrane preservation solution. [Brief explanation of the drawing]

[0016] [Figure 1] This is a photograph of a cylindrical water treatment separation membrane module, manufactured in Preparation Example 1, sealed in packaging material and vacuum-packed. [Figure 2] This photograph shows that when a water treatment separation membrane module, stored in the separation membrane preservation solution produced in Comparative Example 2, was placed into equipment for evaluating the performance of the treatment separation membrane module, the equipment was damaged during operation. [Figure 3] This is a photograph showing how bacteria proliferate in a preservation solution used for separation membranes. [Figure 4] This is a photograph showing that no bacteria have grown in the preservation solution for the separation membrane. [Modes for carrying out the invention]

[0017] Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. The present invention can be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts not related to the description are omitted in order to clearly explain the present invention, and the same reference numerals are added to the same or similar components throughout the specification.

[0018] The preservation solution for the separation membrane of the present invention can contain an aqueous solution of citric acid. Specifically, the preservation solution for the separation membrane of the present invention may be composed of an aqueous solution of citric acid. If other components are included in addition to the aqueous solution of citric acid as the preservation solution for the separation membrane of the present invention, there may be a problem of deterioration of physical properties.

[0019] Also, the aqueous solution of citric acid can contain citric acid at 0.3 to 1.5% by weight, preferably 0.3 to 1.2% by weight, more preferably 0.3 to 0.8% by weight, based on the total weight%. If the content of citric acid is less than 0.3% by weight, there may be a problem of microbial growth, and if it exceeds 1.5% by weight, there may be a problem of precipitation during storage at a high temperature of 40 °C or higher.

[0020] Moreover, the aqueous solution of citric acid may have a pH of 2.0 to 4.0, preferably 2.3 to 3.5, more preferably 2.5 to 3.0. If the pH is less than 2.0, there may be a problem of deformation of the member during long-term storage, and if the pH exceeds 4.0, there may be a problem of microbial growth. <​​​​​When the shape of the separation membrane is that of a normal separation membrane, there is no limitation, and as a preferable example, it may be a flat membrane or a hollow fiber membrane. The separation membrane can be used regardless of its application, that is, a microfiltration membrane, an ultrafiltration membrane, a nano-separation membrane, or a reverse osmosis membrane depending on the pore size, and can be used as a separation membrane by the osmosis method such as a reverse osmosis membrane, a pressure retarded osmosis membrane, or a forward osmosis membrane. However, most preferably, the separation membrane of the present invention may be a cylindrical separation membrane module for water treatment.

[0023] The material of the separation membrane can include substances used in normal separation membranes, and preferably, it can include any one or more polymer substances selected from the group consisting of polysulfone-based polymers, polyamide-based polymers, polyimide-based polymers, polyester-based polymers, olefin-based polymers, fluorinated polymers, polybenzimidazole polymers, and polyacrylonitrile.

[0024] In the case of a fluorinated polymer, specifically, it may be any one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE)-based, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA)-based, tetrafluoroethylene-hexafluoropropylene copolymer (FEP)-based, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)-based, tetrafluoroethylene-ethylene copolymer (ETFE)-based, polychlorotrifluoroethylene (PCTFE)-based, and chlorotrifluoroethylene-ethylene copolymer (ECTFE)-based.

[0025] The present invention has been described above, primarily focusing on embodiments. However, these are merely illustrative examples and do not limit the embodiments of the present invention. Anyone with ordinary skill in the art to which the embodiments of the present invention belong will understand that various modifications and applications not exemplified above are possible, as long as they do not deviate from the essential characteristics of the present invention. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. Such differences related to modifications and applications should be interpreted as being included within the scope of the present invention as defined in the appended claims.

[0026] <Preparation Example 1: Manufacturing of cylindrical water treatment separation membrane modules> (1) A porous support layer forming solution was prepared by dissolving Udel P-3500, a polysulfone polymer resin sold by Solvay, in dimethylformamide (DMF), a polar aprotic organic solvent. The porous support layer forming solution was prepared by mixing 17.5% by weight of Udel P-3500 and 82.5% by weight of dimethylformamide, based on the total weight.

[0027] (2) A nonwoven fabric (polyester synthetic fiber, thickness: 90 μm) was prepared as a base material. The porous support layer forming solution prepared was cast onto one side of the prepared nonwoven fabric to an average thickness of 120 μm. After immersion in distilled water at 25°C to induce a phase transition, the solvent of the porous support layer forming solution was replaced with distilled water by washing with water, thereby forming a porous support layer on one side of the base material. After that, it was stored in pure water at room temperature (25°C).

[0028] (3) A substrate with a porous support layer formed on one surface was immersed in an aqueous solution containing 1.5% by weight of metaphenylenediamine for 1 minute, and after removing the surface water by pressing, it was immersed in an organic solution containing 0.1% by weight of trimesoyl chloride for 1 minute to induce interfacial polymerization. Thereafter, it was air-dried at room temperature (25°C) for 1 minute and 30 seconds to form a polyamide active layer composed of a polyamide polymer compound with an average thickness of 0.2 μm on one surface of the porous support layer, thereby producing a separation membrane for water treatment.

[0029] (4) A large number of the manufactured water treatment separation membranes were prepared, and a large number of cylindrical water treatment separation membrane modules having a diameter of 45.5 mm and a length of 183.5 mm were manufactured by rolling the large number of water treatment separation membranes.

[0030] <Example 1: Production of preservation solution for separation membranes> A preservation solution for separation membranes with a pH of 2.88 was prepared by dissolving citric acid in distilled water. This preservation solution was prepared by mixing 0.4% by weight of citric acid and 99.6% by weight of distilled water, relative to the total weight.

[0031] <Example 2: Production of preservation solution for separation membranes> A preservation solution for separation membranes with a pH of 2.5 was prepared by dissolving citric acid in distilled water. This preservation solution was prepared by mixing 1.2% by weight of citric acid and 98.8% by weight of distilled water, relative to the total weight.

[0032] <Example 3: Production of preservation solution for separation membranes> A preservation solution for separation membranes with a pH of 3.6 was prepared by dissolving citric acid in distilled water. This preservation solution was prepared by mixing 0.2% by weight of citric acid and 99.8% by weight of distilled water, relative to the total weight.

[0033] <Example 4: Production of preservation solution for separation membranes> A separation membrane preservation solution with a pH of 4.86 was prepared by dissolving citric acid and sodium benzoate in distilled water. This preservation solution was prepared by mixing 0.2% by weight of citric acid, 0.2% by weight of sodium benzoate, and 99.6% by weight of distilled water, based on the total weight.

[0034] <Example 5: Production of preservation solution for separation membranes> A separation membrane preservation solution with a pH of 4.55 was prepared by dissolving citric acid and sodium benzoate in distilled water. This preservation solution was prepared by mixing 0.4% by weight of citric acid, 0.2% by weight of sodium benzoate, and 99.4% by weight of distilled water, based on the total weight percentage.

[0035] <Comparative Example 1: Production of Preservation Solution for Separation Membranes> A separation membrane preservation solution with a pH of 3.8 was prepared by dissolving sodium metabisulfite in distilled water. This preservation solution was prepared by mixing 1.0% by weight of sodium metabisulfite and 99.0% by weight of distilled water, relative to the total weight.

[0036] <Comparative Example 2: Production of Preservation Solution for Separation Membranes> A separation membrane preservation solution with a pH of 3.57 was prepared by dissolving sodium metabisulfite in distilled water. This preservation solution was prepared by mixing 1.5% by weight of sodium metabisulfite and 98.5% by weight of distilled water, relative to the total weight.

[0037] <Comparative Example 3: Production of Preservation Solution for Separation Membranes> A preservation solution for separation membranes with a pH of 4.5 was prepared by dissolving benzoic acid in distilled water. This preservation solution was prepared by mixing 0.1% by weight of benzoic acid and 99.9% by weight of distilled water, relative to the total weight.

[0038] <Comparative Example 4: Production of Preservation Solution for Separation Membranes> A preservation solution for separation membranes with a pH of 3.28 was prepared by dissolving benzoic acid in distilled water. This preservation solution was prepared by mixing 0.2% by weight of benzoic acid and 99.8% by weight of distilled water, relative to the total weight.

[0039] <Comparative Example 5: Production of Preservation Solution for Separation Membranes> A separation membrane preservation solution with a pH of 3.7 was prepared by dissolving benzoic acid and sodium benzoate in distilled water. The separation membrane preservation solution was prepared by mixing 0.1% by weight of benzoic acid, 0.2% by weight of sodium benzoate, and 99.7% by weight of distilled water, based on the total weight.

[0040] <Comparative Example 6: Production of Preservation Solution for Separation Membranes> A separation membrane preservation solution with a pH of 3.4 was prepared by dissolving benzoic acid and sodium benzoate in distilled water. The separation membrane preservation solution was prepared by mixing 0.2% by weight of benzoic acid, 0.2% by weight of sodium benzoate, and 99.6% by weight of distilled water, based on the total weight.

[0041] <Experimental Example 1: Performance measurement of a cylindrical water treatment separation membrane module before and after storage in a separation membrane preservation solution> To stabilize the equipment used to evaluate the performance of the water treatment separation membrane modules, a 15-minute preliminary run was performed using reverse osmotic distilled water. Subsequently, multiple cylindrical water treatment separation membrane modules manufactured in Preparation Example 1 were operated for 10 minutes in cross-flow mode at 25°C and 20 psi pressure conditions using a 200 ppm sodium chloride aqueous solution to confirm stabilization. After that, the initial permeate flow rate and initial salt removal rate were measured and are shown in Table 1 below.

[0042] Subsequently, each of the cylindrical water treatment separation membrane modules manufactured in Preparation Example 1 was immersed for 10 minutes in the separation membrane preservation solution manufactured in Examples 1-5 and Comparative Examples 1-6, and then placed inside a PE (Polyethylene) packaging material. Then, as shown in Figure 1, a pressure of -400 mbar was applied to the PE packaging material containing the cylindrical water treatment separation membrane modules manufactured in Preparation Example 1 for 2 seconds, after which it was sealed and vacuum-packed, and stored for 2 weeks. After confirming that the cylindrical water treatment separation membrane modules manufactured in Preparation Example 1, which had been stored in the PE packaging material for 2 weeks, were stabilized by operating them in a cross-flow mode for 10 minutes at 25°C and a pressure of 20 psi using a 200 ppm sodium chloride aqueous solution, the permeate flow rate, salt removal rate, and pH of the separation membrane preservation solution after storage were measured and are shown in Table 1 below.

[0043] Furthermore, during operation of the equipment used to evaluate the performance of the water treatment separation membrane module, we checked for any damage to the equipment valves, as shown in Table 1 below. Furthermore, we confirmed whether or not bacteria proliferated when the water treatment separation membrane module was stored in the separation membrane preservation solution, and the results are shown in Table 1 below.

[0044] [Table 1]

[0045] As can be seen from Table 1 above, the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 1 did not experience a significant decrease in salt removal rate even when stored in the separation membrane preservation solution. Furthermore, when the water treatment separation membrane module stored in the separation membrane preservation solution was used in the water treatment equipment, there was no deformation of the water treatment equipment. It was also confirmed that bacteria did not proliferate even during the time the water treatment separation membrane module was stored in the separation membrane preservation solution.

[0046] On the other hand, compared to the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 1, it was confirmed that the amount of change in salt removal rate increased for the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 2.

[0047] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 1, it was confirmed that the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 3 not only showed an increased change in salt removal rate, but also allowed bacteria to proliferate.

[0048] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 1, it was confirmed that the amount of change in salt removal rate increased for the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 4.

[0049] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 1, it was confirmed that the amount of change in salt removal rate increased for the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 5.

[0050] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 1, it was confirmed that bacteria proliferated in the water treatment separation membrane module stored in the separation membrane preservation solution produced in Comparative Example 1.

[0051] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 1, it was confirmed that the water treatment separation membrane module stored in the separation membrane preservation solution produced in Comparative Example 2 suffered damage to the water treatment equipment and underwent deformation, as shown in Figure 2.

[0052] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 1, the water treatment separation membrane module stored in the separation membrane preservation solution produced in Comparative Example 3 not only showed a significant increase in the change in salt removal rate, but it was also confirmed that bacteria proliferated.

[0053] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 1, it was confirmed that the amount of change in salt removal rate increased significantly in the water treatment separation membrane module stored in the separation membrane storage solution produced in Comparative Example 4.

[0054] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane preservation solution produced in Example 1, the water treatment separation membrane module stored in the separation membrane preservation solution produced in Comparative Example 5 not only showed a significant increase in the change in salt removal rate, but it was also confirmed that bacteria proliferated.

[0055] Furthermore, compared to the water treatment separation membrane module stored in the separation membrane storage solution produced in Example 1, it was confirmed that the amount of change in salt removal rate increased significantly in the water treatment separation membrane module stored in the separation membrane storage solution produced in Comparative Example 6.

[0056] Furthermore, as shown in Figure 3, bacteria proliferated in the separation membrane preservation solutions prepared in Example 3, Comparative Example 1, Comparative Example 3, and Comparative Example 5, while bacteria did not proliferate in the separation membrane preservation solutions prepared in Examples 1-2, Examples 4-5, Comparative Example 2, Comparative Example 4, and Comparative Example 6, as shown in Figure 4.

[0057] Simple modifications and alterations of the present invention can be readily carried out by a person with ordinary skill in the art, and all such modifications and alterations are considered to fall within the scope of the present invention.

Claims

1. A preservation solution for separation membranes, characterized by containing an aqueous solution of citric acid.

2. The separation membrane preservation solution according to claim 1, characterized in that the preservation solution for the separation membrane is composed of the citric acid aqueous solution.

3. The separation membrane preservation solution according to claim 1, characterized in that the citric acid aqueous solution contains 0.3 to 1.5% by weight of citric acid based on the total weight.

4. The separation membrane preservation solution according to claim 3, characterized in that the citric acid aqueous solution contains 0.3 to 0.8% by weight of citric acid based on the total weight.

5. The separation membrane preservation solution according to claim 1, characterized in that the citric acid aqueous solution has a pH of 2.0 to 4.

0.

6. A water treatment separation membrane packaging container having a storage compartment that can hold contents inside, A water treatment separation membrane packaging container, characterized in that the containment section contains a water treatment separation membrane and the separation membrane preservation solution described in claim 1, and the water treatment separation membrane is immersed in the separation membrane preservation solution.

7. The water treatment separation membrane packaging container according to claim 6, characterized in that the water treatment separation membrane contains one or more polymeric substances selected from the group consisting of polysulfone polymers, polyamide polymers, polyimide polymers, polyester polymers, olefin polymers, fluorine polymers, polybenzimidazole polymers, and polyacrylonitrile.

8. The water treatment separation membrane packaging container according to claim 6, characterized in that the water treatment separation membrane is a flat membrane or a hollow fiber membrane.

9. The water treatment separation membrane packaging container according to claim 6, characterized in that the water treatment separation membrane is a cylindrical water treatment separation membrane module.

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