Preservation solution for reverse osmosis membrane element

Abstract

The present invention relates to a preservation solution for a reverse osmosis membrane element. Based on the total mass of the preservation solution, the preservation solution comprises the following components: 5,900-18,000 ppm of sodium ions, 9,000-30,000 ppm of chloride ions, 1-3,000 ppm of multivalent cations, 2-200 ppm of an ether polymer, 1-20,000 ppm of a non-oxidizing bactericide and a solvent, wherein the solvent comprises water; the multivalent cations comprise divalent and / or trivalent metal ions; and the ether polymer comprises a structural unit derived from ethylene oxide. The preservation solution for a reverse osmosis membrane element in one embodiment of the present invention can be used for preservation of reverse osmosis membrane elements. By using the preservation solution to preserve seawater desalination reverse osmosis membrane elements, the elements can maintain stable water production, salt rejection rate, boron rejection rate and the like even after long-term storage, and the reproduction of microorganisms can be effectively controlled.

Description

A reverse osmosis membrane element preservation solution Technical Field

[0001] This invention relates to the preservation of reverse osmosis membrane elements, and more particularly to a preservation solution for seawater desalination reverse osmosis membrane elements. Background Technology

[0002] Reverse osmosis membrane technology is currently the most commonly used seawater desalination technology. Freshwater filtered through reverse osmosis membrane elements is widely used for municipal water supply and industrial water use. Seawater contains approximately 5 ppm of boron, which can affect human health. The "Standards for Drinking Water Quality" (GB5749-2022) requires a boron content of less than 1 ppm. Therefore, boron removal rate is a crucial indicator for seawater desalination reverse osmosis membranes.

[0003] Seawater has a high salt content. To ensure the quality of the produced water, the seawater desalination reverse osmosis membrane elements are tested with standard test solutions before leaving the factory. After confirming that they are qualified, the wet elements are stored in a 1wt% food-grade sodium metabisulfite standard protective solution to prevent the growth of microorganisms. Then, they are sealed in plastic bags to isolate them from the air.

[0004] However, after storing seawater desalination reverse osmosis membrane elements using the aforementioned packaging method, the boron removal rate of the elements decreases significantly over time. Therefore, ensuring that the wet elements do not breed microorganisms while maintaining their boron removal rate is a pressing issue that needs to be addressed.

[0005] Summary of the Invention

[0006] To overcome at least one of the defects of the prior art, in a first aspect, one embodiment of the present invention provides a reverse osmosis membrane element preservation solution, wherein, based on the total mass of the preservation solution, the preservation solution comprises the following components: 5900-18000 ppm sodium ions, 9000-30000 ppm chloride ions, 1-3000 ppm polyvalent cations, 2-200 ppm ether polymers, 1-20000 ppm non-oxidizing bactericides and solvents;

[0007] The solvent includes water; the multivalent cation includes divalent and / or trivalent metal ions; and the ether polymer includes structural units derived from ethylene oxide.

[0008] Secondly, one embodiment of the present invention provides the application of the above-described preservation solution in the preservation of reverse osmosis membrane elements.

[0009] Thirdly, one embodiment of the present invention provides a method for preserving a reverse osmosis membrane element, comprising immersing the reverse osmosis membrane element in the above-mentioned preservation solution or allowing the preservation solution to wet the reverse osmosis membrane element.

[0010] Fourthly, one embodiment of the present invention provides a reverse osmosis wetted membrane element, including a reverse osmosis membrane element and the aforementioned preservation solution impregnating the reverse osmosis membrane element.

[0011] Fifthly, one embodiment of the present invention provides a reverse osmosis membrane element product, including a reverse osmosis wet membrane element and a packaging bag, wherein the reverse osmosis wet membrane element is located inside the packaging bag, and the reverse osmosis wet membrane element includes a reverse osmosis membrane element and a preservation solution impregnating the reverse osmosis membrane element.

[0012] The reverse osmosis membrane element preservation solution of one embodiment of the present invention can be used for the preservation of reverse osmosis membrane elements. By using this preservation solution to preserve seawater desalination reverse osmosis membrane elements, the elements can maintain stable water production, desalination rate, boron removal rate, etc. after long-term storage, and can effectively control the reproduction of microorganisms. Detailed Implementation

[0013] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the description herein is for illustrative purposes only and not intended to limit the present invention.

[0014] One embodiment of the present invention provides a preservation solution for reverse osmosis membrane elements. Based on the total mass of the preservation solution, the preservation solution includes the following components: 5900-18000 ppm sodium ions, 9000-30000 ppm chloride ions, 1-3000 ppm polyvalent cations, 2-200 ppm ether polymers, 1-20000 ppm non-oxidizing bactericides and solvents.

[0015] The solvent includes water, the polyvalent cations include divalent and / or trivalent metal ions, and the ether polymers include structural units derived from ethylene oxide.

[0016] In one embodiment, the preservation solution for the reverse osmosis membrane element is an aqueous solution.

[0017] In one embodiment, the pH value of the reverse osmosis membrane element preservation solution is 3 to 10, for example, 3, 4, 5, 6, 7, 8, 9 or 10.

[0018] In one embodiment, the mass content of sodium ions in the preservation solution can be, for example, 5930ppm, 5940ppm, 6000ppm, 7000ppm, 8000ppm, 10000ppm, 12000ppm, 12580ppm, 12585ppm, 12590ppm, 13760ppm, 13765ppm, 14940ppm, 14945ppm, 15000ppm, 17000ppm, 17690ppm, or 17700ppm.

[0019] In one embodiment, the chloride ion content in the preservation solution can be 9000–30000 ppm, for example 9160 ppm, 9170 ppm, 9190 ppm, 9200 ppm, 10000 ppm, 12000 ppm, 15000 ppm, 19000 ppm, 19410 ppm, 19420 ppm, 19430 ppm, 20000 ppm, 21530 ppm, 21540 ppm, 23080 ppm, 23090 ppm, 25000 ppm, 27300 ppm, 27310 ppm, 27410 ppm, 27420 ppm, 28000 ppm, 29590 ppm, or 29600 ppm.

[0020] In one embodiment, the mass content of polyvalent cations in the preservation solution can be 1 to 3000 ppm, for example, 1 ppm, 1.5 ppm, 2 ppm, 10 ppm, 20 ppm, 21 ppm, 25 ppm, 30 ppm, 40 ppm, 43 ppm, 44 ppm, 50 ppm, 80 ppm, 100 ppm, 101 ppm, 102 ppm, 150 ppm, 200 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 2940 ppm, 2950 ppm.

[0021] In one embodiment, the mass content of the ether polymer in the preservation solution can be, for example, 1 ppm, 2 ppm, 5 ppm, 10 ppm, 20 ppm, 23 ppm, 25 ppm, 30 ppm, 40 ppm, 44 ppm, 45 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 160 ppm, 180 ppm, 190 ppm, 195 ppm, 198 ppm, or 200 ppm.

[0022] In one embodiment, the mass content of the non-oxidizing bactericide in the preservation solution can be, for example, 1 ppm, 10 ppm, 50 ppm, 100 ppm, 200 ppm, 500 ppm, 800 ppm, 1000 ppm, 5000 ppm, 10000 ppm, 150000 ppm, or 18000 ppm.

[0023] In one embodiment, the polyvalent cation includes one, two, or more of magnesium, calcium, aluminum, zinc, and copper.

[0024] In one embodiment, the ether polymer includes structural units derived from ethylene oxide, the number of which can be 4 to 12,000, for example 5, 9, 10, 20, 50, 80, 100, 120, 150, 180, 200, 220, 250, 300, 500, 1000, 2000, 5000, 8000, 10000.

[0025] In one embodiment, the ether polymer includes polyoxyethylene ether segments, for example, the ether polymer may be one or more of polyethylene glycol, allyl polyethylene glycol ether, methyl allyl polyethylene glycol ether, isopentenyl polyethylene glycol ether, and ethylene glycol monovinyl polyethylene glycol ether.

[0026] In one embodiment, the weight-average molecular weight of the ether polymer is 200 to 500,000, for example 300, 350, 400, 500, 800, 1000, 2000, 5000, 10000, 20000, 50000, 100000, 150000, 200000, 250000, and 500000.

[0027] In one embodiment, the ether polymer can be an existing polycarboxylate superplasticizer, such as a polycarboxylate superplasticizer containing polyoxyethylene ether segments.

[0028] In one embodiment, the ether polymer can be a polycarboxylate superplasticizer containing isopentenyl alcohol polyoxyethylene ether segments, such as the NPC-07 polycarboxylate superplasticizer purchased from Liaoning Kelong Fine Chemical Co., Ltd.

[0029] In one embodiment, the non-oxidizing bactericide includes 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) and / or 2-methyl-4-isothiazolin-3-one (MIT).

[0030] One embodiment of the present invention provides the application of the above-described preservation solution in the preservation of reverse osmosis membrane elements.

[0031] In one embodiment, the reverse osmosis membrane element preserved with the above-mentioned preservation solution is a seawater desalination reverse osmosis membrane element for seawater desalination, such as the SW-8040-400-HR reverse osmosis membrane element produced by Wanhua Chemical Group Co., Ltd.

[0032] In one embodiment, the reverse osmosis membrane element preserved with the above-mentioned preservation solution is a wet element.

[0033] In one embodiment, the reverse osmosis membrane element is a product with a boron removal rate of 85% or greater, and the test method for the boron removal rate is the same as the test method for the boron removal rate used in the examples.

[0034] One embodiment of the present invention provides a method for preserving a reverse osmosis membrane element, comprising placing the reverse osmosis membrane element in (or immersing it in) the above-mentioned preservation solution for preservation, or allowing the preservation solution to wet the reverse osmosis membrane element for preservation.

[0035] One embodiment of the present invention provides a reverse osmosis wetted membrane element, including a reverse osmosis membrane element and the above-described preservation solution that impregnates (or wets) the reverse osmosis membrane element.

[0036] One embodiment of the present invention provides a reverse osmosis membrane element product, including a reverse osmosis wet membrane element and a packaging bag, wherein the reverse osmosis wet membrane element is located inside the packaging bag, and the reverse osmosis wet membrane element includes a reverse osmosis membrane element and a preservation solution that wets the reverse osmosis membrane element.

[0037] In one embodiment, the reverse osmosis membrane element is immersed in a storage solution, removed and drained to obtain a reverse osmosis wet membrane element, which is then sealed in a packaging bag for storage.

[0038] In one embodiment, the absolute pressure inside the packaging bag is less than 30 kPa, allowing the reverse osmosis membrane element (or reverse osmosis wet membrane element) to be stored under vacuum conditions. Furthermore, the absolute pressure inside the packaging bag can be reduced to less than 30 kPa by vacuuming.

[0039] In one embodiment, the absolute pressure inside the packaging bag can be 10 to 29 kPa, for example, 15 kPa, 20 kPa, 24 kPa, or 25 kPa.

[0040] In one embodiment, the packaging bag is a plastic bag, such as a PE composite packaging bag.

[0041] In one embodiment, the packaging bag is a waterproof bag.

[0042] In one embodiment, the oxygen permeation rate of the packaging bag at 23°C can be less than 100 cm⁻¹. 3 / m 2 / day, further for sizes smaller than 30cm 3 / m 2 / day, and even more advanced, it can be used for sizes smaller than 10cm. 3 / m 2 / sky.

[0043] In one embodiment, the oxygen permeation rate of the packaging bag at 23°C can be 10–100 cm⁻¹. 3 / m 2 / day, for example, 20cm 3 / m 2 / day, 30cm 3 / m 2 / day, 50cm 3 / m 2 / day, 60cm 3 / m 2 / day, 80cm 3 / m 2 / sky.

[0044] The reverse osmosis membrane element preservation solution of one embodiment of the present invention can be used for the preservation of reverse osmosis membrane elements. By using this preservation solution to preserve seawater desalination reverse osmosis membrane elements, the elements can maintain stable water production, desalination rate, boron removal rate, etc. after long-term storage, and can effectively control the reproduction of microorganisms.

[0045] The present invention discloses a method for preserving reverse osmosis membrane elements, which is simple to operate and enables seawater desalination reverse osmosis membrane elements to maintain stable water production, desalination rate, and boron removal rate after long-term storage, while also preventing microbial growth, thus showing good prospects for industrialization.

[0046] The following describes, in conjunction with embodiments, a reverse osmosis membrane element preservation solution of the present invention and its use. The raw materials and testing methods involved in each embodiment and comparative example are as follows:

[0047] 1. Raw materials

[0048] The seawater desalination reverse osmosis membrane element is manufactured by Wanhua Chemical Group Co., Ltd., and its model number is SW-8040-400-HR.

[0049] The polycarboxylate superplasticizer containing isopentenyl alcohol polyoxyethylene ether segments was purchased from Liaoning Kelong Fine Chemical Co., Ltd., model number NPC-07.

[0050] PE composite packaging bags, manufactured by Yantai Hesun Packaging & Paper Co., Ltd., include PE-1, PE-2, and PE-3 bags with different oxygen permeability (23℃). The oxygen permeability of the three bags is ≤10cm. 3 / m 2 / day, ≤30cm3 / m 2 / day, ≤100cm 3 / m 2 / sky.

[0051] 5-Chloro-2-methyl-4-isothiazolin-3-one (CIT), purchased from Huayuan Mall, brand AccuStandard, is a 100ppm standard sample aqueous solution.

[0052] Isothiazolinone, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., is composed of an aqueous solution of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) and 2-methyl-4-isothiazolin-3-one (MIT), wherein the content of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) is 1.825-1.925 wt%, the content of 2-methyl-4-isothiazolin-3-one (MIT) is 0.575-0.675 wt%, and the total concentration is 2.5 wt%.

[0053] 2-Methyl-4-isothiazolin-3-one (MIT), purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of 95%.

[0054] All other reagents were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and are reagent-grade raw materials.

[0055] The vacuum packaging machine, model DZ, was purchased from Zhucheng Wankang Vacuum Packaging Machine Equipment Co., Ltd.

[0056] 2. Testing Methods

[0057] Testing of desalination rate, water production rate and boron removal rate

[0058] The desalination rate and permeate flow rate of a single seawater desalination reverse osmosis membrane element were tested according to the test method for desalination rate and permeate flow rate in GB / T 34241-2017 "Wound Polyamide Composite Reverse Osmosis Membrane Elements". The test solution temperature was 25℃, pH was 8.0, the test solution was a 32000ppm sodium chloride aqueous solution, the test pressure was 5.5MPa, and the element recovery rate was 8%. Boric acid was added to ensure the boron content in the test solution was 5ppm. The sodium chloride content was measured using a conductivity meter. The test methods for boron content (Cfb and Cpb) in the test solution and permeate were based on GB / T 5750.6-2006 "Standard Examination Methods for Drinking Water - Metallic Indicators". The boron removal rate was calculated using the formula (1-Cpb / Cfb)*100%.

[0059] Chloride ion content test

[0060] The chloride ion content was determined according to GB / T 15453-2018 Determination of chloride ions in industrial circulating cooling water and boiler water.

[0061] Sodium ion content test

[0062] The sodium ion content was measured according to GB / T 5750.6-2006 "Standard Examination Methods for Drinking Water - Metal Index".

[0063] Multivalent cation content test

[0064] The content of polyvalent cations was determined according to GB / T 5750.6-2006 "Standard Examination Methods for Drinking Water - Metal Index".

[0065] Oxygen permeation rate test of plastic bags

[0066] The oxygen permeation rate was measured according to GB / T 19789 "Test method for oxygen permeability of plastic films and sheets for packaging materials - coulometric method".

[0067] Test for the number of molds in the preservation solution

[0068] According to GB 4789.15-2010 "National Food Safety Standard - Microbiological Examination of Food: Counting of Molds and Yeasts", the packaging is opened at certain time intervals, and the remaining preservation liquid in the packaging bag is collected to test the number of molds in the liquid.

[0069] Example

[0070] Add bactericides and ether polymers (polyethylene glycol, polyethylene oxide, or NPC-07) to water, then add sodium chloride and hydrochloride of polyvalent cations, and adjust the concentration of each component accordingly. Adjust the pH value with hydrochloric acid or sodium hydroxide to prepare a preservation solution.

[0071] Examples 1 to 7 and Comparative Examples 1 to 6 were prepared with different concentrations of preservation solution according to the same or similar procedures. The specific concentrations are shown in Table 1.

[0072] Application examples

[0073] Five pre-rolled seawater desalination reverse osmosis membrane elements (SW-8040-400-HR) were immersed in a preservation solution for 1–3 minutes, drained for 10 minutes, and then vacuum-sealed in PE bags and stored at a constant temperature of 20°C. The membrane elements were then removed at different storage times (7 days, 14 days, 30 days, 90 days, and 180 days) for various performance tests. The results are shown in Tables 2 and 3.

[0074] The preservation solutions of Examples 1 to 7 and Comparative Examples 1 to 6 were preserved and tested according to the above steps. The type of packaging bag and vacuum pressure used are shown in Table 1.

[0075] Table 1. Composition and packaging of the preservation solutions used in each embodiment and comparative example.

[0076] Table 2 shows the test results of boron removal rate for membrane elements in each embodiment and comparative example.

[0077] Table 3. Results of mold count tests in the membrane element preservation solutions of each embodiment and comparative example.

[0078] Table 4. Test results of water production and desalination rate of membrane elements in each embodiment and comparative example.

[0079] As can be seen from Tables 1 to 4, the seawater desalination reverse osmosis membrane elements of Examples 1 to 7 of the present invention still have a high boron removal rate (above 90%) after being stored in a preservation solution containing specific components for 7 days, 14 days, 30 days, 90 days and 180 days, and the number of molds is maintained at a level of less than 1 CFU / mL, while maintaining a stable water production and desalination rate.

[0080] The Na2S2O5 preservation solution used in Comparative Example 1 is an existing preservation solution used to preserve reverse osmosis membrane elements. According to the results in Tables 2 and 3, although the number of molds can be kept below 1 CFU / mL when the membrane element is preserved using the preservation solution of Comparative Example 1, the boron removal rate of the membrane element is significantly reduced after 90 days and 180 days of preservation.

[0081] Although the preservation solutions of Comparative Examples 3 to 5 also contained sodium ions, chloride ions, polyvalent cations, and bactericides, they lacked ether polymers compared to Examples 1 to 5. The results in Table 2 show that while the boron removal rate of the membrane elements preserved in Comparative Examples 3 to 5 was higher than that in Comparative Example 1, it still could not reach over 90%.

[0082] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0083] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A preservation solution for reverse osmosis membrane elements, wherein the preservation solution comprises the following components based on the total mass of the preservation solution: 5900-18000 ppm sodium ions, 9000-30000 ppm chloride ions, 1-3000 ppm polyvalent cations, 2-200 ppm ether polymers, 1-20000 ppm non-oxidizing bactericides and solvents; in, The solvent includes water; the multivalent cation includes divalent and / or trivalent metal ions; and the ether polymer includes structural units derived from ethylene oxide.

2. The preservation solution according to claim 1, wherein, The polyvalent cations include one or more of magnesium, calcium, aluminum, zinc, and copper; and / or, The number of structural units derived from ethylene oxide is 4 to 12,000; and / or, The pH value of the preservation solution is 3 to 10.

3. The preservation solution according to claim 1 or 2, wherein, The weight-average molecular weight of the ether polymer is 200–500,000; and / or, The ether polymers include one or more of polyethylene glycol, allyl polyethylene glycol ether, methyl allyl polyethylene glycol ether, isopentenyl polyethylene glycol ether, and ethylene glycol monovinyl polyethylene glycol ether.

4. The preservation solution according to any one of claims 1 to 3, wherein, The ether polymers include polycarboxylate superplasticizers containing polyoxyethylene ether segments; and / or, The non-oxidizing bactericides include 5-chloro-2-methyl-4-isothiazolin-3-one and / or 2-methyl-4-isothiazolin-3-one.

5. The use of the preservation solution according to any one of claims 1 to 4 in preserving reverse osmosis membrane elements.

6. In the application according to claim 5, the reverse osmosis membrane element is a seawater desalination reverse osmosis membrane element.

7. A method for preserving a reverse osmosis membrane element, comprising immersing the reverse osmosis membrane element in the preservation solution according to any one of claims 1 to 4 or wetting the reverse osmosis membrane element with the preservation solution.

8. A reverse osmosis wetted membrane element, comprising a reverse osmosis membrane element and a preservation solution according to any one of claims 1 to 4, which wets the reverse osmosis membrane element.

9. A reverse osmosis membrane element product, comprising a reverse osmosis wet membrane element and a packaging bag, wherein, The reverse osmosis wet membrane element is located inside the packaging bag, and the reverse osmosis wet membrane element includes a reverse osmosis membrane element and the preservation solution that wets the reverse osmosis membrane element.

10. The product according to claim 9, wherein, The reverse osmosis membrane element is a seawater desalination reverse osmosis membrane element; and / or, The absolute pressure inside the packaging bag is less than 30 kPa; and / or, The packaging bag is a plastic bag; and / or, The oxygen permeability of the packaging bag at 23°C is less than 100 cm⁻¹. 3 / m 2 / day; and / or, The packaging bag is a waterproof bag.

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