High-flux high-chemical-resistance composite nanofiltration membrane, and preparation method and application thereof

Abstract

The application provides a high-flux high-chemical-resistance composite nanofiltration membrane and a preparation method and application thereof. The nanofiltration membrane comprises a polyether sulfone porous support layer, an intermediate layer formed by reaction of a macrocyclic polyamine and an epoxy-modified silicone resin emulsion, and a polyamide separation layer formed on the intermediate layer. The intermediate layer is formed by loading the macrocyclic polyamine and the epoxy-modified silicone resin emulsion on the polyether sulfone porous support layer and then performing heat treatment and reaction curing reaction, and the separation layer is formed by interfacial polymerization of an aqueous phase containing a polyamine and an organic phase containing a polyacyl chloride. The intermediate layer provides reaction sites, regulates the structure of the polyamide separation layer, constructs effective water channels, effectively improves the membrane flux, and the active sites of the intermediate layer can avoid direct chemical attack on the polyamide, thereby improving the chemical resistance of the membrane.

Description

Technical Field

[0001] This invention belongs to the field of water treatment membrane technology, specifically relating to a high-flux, high-chemical-resistant composite nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] In recent years, membrane technology has played an increasingly important role in gas separation, aqueous solution separation, and the separation and purification of chemical and biochemical products. It has been widely applied in food and beverage processing, industrial wastewater treatment, large-scale gas separation, and hydrometallurgical technology. Nanofiltration membranes are an important branch of membrane technology, with molecular weight cutoffs ranging from 200 to 2000 and often carrying surface charges. Through the combined effects of multiple mechanisms, including pore size sieving and the Donnan effect, nanofiltration membranes selectively separate monovalent and polyvalent salt ions and exhibit different retention effects for organic compounds of varying molecular weights. They have been widely used in chlor-alkali denitrification, lithium extraction from salt lakes, municipal water treatment, concentration and purification of pharmaceutical active substances, and seawater desalination pretreatment.

[0003] Introducing an interlayer between the nanofiltration membrane base and the polyamide retention layer can optimize the water transport pathway of the nanofiltration membrane, thereby improving the overall water permeability of the membrane. Furthermore, the abundant active sites on the interlayer can regulate the interfacial polymerization process, thus affecting the properties of the polyamide retention layer. However, the introduction of many interlayers can affect the stability of the polyamide layer or cause other performance losses.

[0004] Based on current research on nanofiltration membrane interlayers, it is necessary to propose a new method for regulating membrane performance using an interlayer on composite nanofiltration membranes prepared by traditional interfacial polymerization, so as to improve the flux and chemical resistance of composite nanofiltration membranes while ensuring the separation characteristics of nanofiltration membranes. Summary of the Invention

[0005] One of the objectives of this invention is to provide a high-flux, highly chemical-resistant nanofiltration membrane. By regulating the polyamide layer structure through an intermediate layer, the water flux of the membrane is increased, and the intermediate layer provides attack sites for chemical attacks, avoiding direct attack of the amide bonds by the polyamide, thereby improving the membrane's chemical resistance.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a high-flux, high-chemical-resistant composite nanofiltration membrane, the nanofiltration membrane comprising a polyethersulfone porous support layer, an intermediate layer formed by the emulsion reaction of a macrocyclic polyamine and an epoxy-modified silicone resin, and a polyamide separation layer formed on the intermediate layer.

[0008] A second aspect of the present invention provides a method for preparing a high-flux, highly chemical-resistant composite nanofiltration membrane.

[0009] A method for preparing the above-mentioned high-flux, high-chemical-resistance composite nanofiltration membrane, the method comprising the following steps:

[0010] (1) A macrocyclic polyamine and epoxy-modified silicone resin emulsion are loaded onto a polyethersulfone porous support layer to form an intermediate layer.

[0011] (2) An aqueous phase containing polyamines and an organic phase containing polyacryl chlorides form a separation layer on the intermediate layer through interfacial polymerization.

[0012] In one embodiment of the present invention, step (1) specifically involves: immersing the polyethersulfone porous support layer sequentially in a macrocyclic polyamine solution and an epoxy-modified silicone resin emulsion, draining it, and removing excess liquid from the surface.

[0013] Preferably, the macrocyclic polyamine is selected from one or more of 1,5,9,13-tetraazacyclohexadecane, 1,5,8,11,14-pentazacyclohexadecane, 1,4,8,11-tetraazacyclotetradecane, 1,4,7,10-tetraazacyclododecane, and 1,5,9-triazacyclododecane; the solvent for the macrocyclic polyamine solution can be water or an organic solvent (such as methanol), and is not limited thereto. The concentration of the macrocyclic polyamine solution is 2–10 wt%, such as 3 wt%, 5 wt%, 6 wt%, or 8 wt%.

[0014] Preferably, the epoxy value of the epoxy-modified silicone resin emulsion is 0.1-0.3, and the solid content is preferably 40-60%.

[0015] Preferably, the polyethersulfone porous support layer is impregnated in the macrocyclic polyamine solution for 2–10 min; and impregnated in the epoxy-modified silicone resin emulsion for 10–60 min.

[0016] In one embodiment of the present invention, the polyamine in step (2) is an aliphatic polyamine and the polyacrylamide chloride is an aromatic polyacrylamide chloride; step (2) specifically involves: mixing the aliphatic polyamine with water to obtain an aqueous solution, mixing the aromatic polyacrylamide chloride with an organic solvent to obtain an oil solution, contacting the polyethersulfone porous support layer of the loaded intermediate layer with the aqueous solution, removing excess solution from the surface, contacting it with the oil solution, heating and curing the intermediate layer, and further polymerizing the separation layer to obtain the nanofiltration membrane.

[0017] In one embodiment of the present invention, the aliphatic polyamine is selected from one or more of piperazine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, and aminoethylpiperazine; preferably, the concentration of the aqueous solution of the aliphatic polyamine is 1 to 2.5 wt%.

[0018] In one embodiment of the present invention, the aromatic polyacryl chloride is selected from one or more of pyromellitic chloroformyl chloride, phthaloyl chloride and isophthaloyl chloride.

[0019] In one embodiment of the present invention, the organic solvent in the oil phase solution is selected from one or more isoalkanes selected from n-hexane, n-heptane, n-decane, Isopar L, and Isopar G; preferably, the concentration of the oil phase solution is 0.1 to 0.25 wt%.

[0020] In one embodiment of the present invention, the polyethersulfone porous support layer of the load intermediate layer is in contact with the aqueous solution for 2 to 10 minutes and with the oil solution for 1 to 3 minutes.

[0021] In one embodiment of the present invention, after contacting the oil phase solution and removing the surface solution, the product is heated and cured at a temperature of 100–180°C for 2–20 minutes.

[0022] A third aspect of the present invention provides the use of a composite nanofiltration membrane.

[0023] An application of a composite nanofiltration membrane, wherein the nanofiltration membrane is the nanofiltration membrane described above or prepared by the above method, and the nanofiltration membrane is used as a high-flux, high-chemical-resistant nanofiltration membrane, preferably used in water treatment and material separation components.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] In the preparation method of this invention, macrocyclic polyamine and epoxy-modified silicone resin emulsion are firmly loaded onto a porous polyethersulfone support layer through the reaction of amino groups and epoxy resin and subsequent heat treatment, forming an intermediate layer to regulate the morphology of the poly-nanofiltration membrane, increase the surface undulation of the polyamide separation layer, and at the same time provide reaction sites. The unreacted amino groups of the macrocyclic polyamine react with acyl chloride, and the epoxy groups of the epoxy silicone resin can react with the carboxyl groups after hydrolysis of acyl chloride, which can directly affect the polyamide network structure, construct water channels, increase the water flux of the membrane, and improve the bonding stability of the support layer and the intermediate separation layer. At the same time, it can reduce the direct attack of chemicals such as oxidants and sodium hydroxide on the surface of the nanofiltration membrane to a certain extent, and improve its chemical resistance. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] The separation performance of the prepared nanofiltration membrane is mainly evaluated by two characteristic parameters: the water flux and the rejection rate of the membrane.

[0028] Water flux (LMH) is defined as the volume of water passing through the effective membrane area per unit time under a certain operating pressure.

[0029] Retention rate calculation formula: R = (1 – TOC)p / TOC f )×100%, where R represents the rejection rate, TOC p and TOC f The concentrations (ppm) of total organic carbon (TOC) in the permeate and feed liquid are respectively.

[0030] Total organic carbon (TOC) was determined using a Jena multi N / C 2100TOC Total Organic Carbon / Total Nitrogen Analyzer (Germany).

[0031] The separation performance of the membrane was determined by cross-flow test using the Huzhou Yuequan nanofiltration membrane test bench.

[0032] The test conditions for the separation performance of the membrane of the present invention are as follows: the feed liquid is a 100 ppm sucrose solution, the feed liquid temperature is 25°C, and the operating pressure is 0.69 MPa (gauge pressure).

[0033] To better understand this testing method, the steps are briefly described below.

[0034] (1) Solution preparation: Prepare a 100 ppm sucrose aqueous solution as the initial performance test stock solution.

[0035] (2) Initial performance test: The membrane that has undergone the initial performance test is subjected to cross-flow test at 0.69MPa, and the TOC of the test raw material liquid and the permeate liquid is tested.

[0036] (3) Chlorine resistance test: The static immersion method was adopted. The membrane that had completed the separation performance test was placed in a sodium hypochlorite aqueous solution with pH=7.0 and containing 1000ppm active chlorine and immersed at a constant temperature of 25.0±0.5℃ for 24h. The product of active chlorine concentration and immersion time (ppm·h) was used as the chlorination intensity index. Then, the chlorinated membrane was repeatedly rinsed with deionized water to completely remove the active chlorine remaining in the membrane. Finally, the change in the membrane's sucrose retention performance was tested under the aforementioned test conditions to examine the membrane's chlorine resistance.

[0037] (4) Alkali resistance test: The static immersion method was used. The membrane that had completed the separation performance test was placed in a sodium hydroxide aqueous solution with pH=13.0 and immersed at a constant temperature of 35.0±0.5℃ for 24h. Then, the membrane treated with alkali solution was repeatedly rinsed with deionized water. Finally, the change in the membrane’s sucrose retention performance was tested under the aforementioned test conditions to examine the membrane’s alkali resistance.

[0038] The main raw materials used in the specific embodiments of the present invention are shown in Table 1.

[0039] Table 1 Main Raw Materials

[0040] Raw material name Parameter Indicators Manufacturer Polyethersulfone-based film 50nm aperture Wanhua Chemical Anhydrous piperazine Purity ≥ 99% Aladdin Reagents Trimethylbenzene chloride Purity ≥ 99% Sanlibenno n-Decane Purity ≥ 98% Aladdin Reagents Macrocyclic polyamines Purity ≥ 99% Merck Epoxy modified silicone resin emulsion Epoxy value 0.1-0.3, solid content 50%. Shenzhen Jipeng Silicon Fluorine Materials sucrose Purity ≥ 99% Aladdin Reagents

[0041] Example 1

[0042] A polyethersulfone-based membrane was immersed in a methanol solution of 1,4,8,11-tetraazacyclotetradecane (2 wt%) for 2 min, then vertically drained to remove surface liquid. The membrane was then immersed in an epoxy-modified silicone resin emulsion (epoxy value 0.1) for 10 min, and vertically drained to remove surface liquid. It was then immersed in an aqueous solution containing 1.5 wt% piperazine for 2 min, and vertically drained to remove surface liquid. Finally, it was immersed in an oil solution of n-decane containing 0.15 wt% trimesoyl chloride for 1 min, vertically drained to remove surface liquid, and then placed in a 150°C oven for 10 min. Afterward, it was removed and soaked in deionized water to obtain a nanofiltration membrane.

[0043] Example 2

[0044] A polyethersulfone-based membrane was immersed in an 8 wt% aqueous solution of 1,4,7,10-tetraazacyclododecane for 10 min, then vertically drained to remove the liquid from the membrane surface. The membrane was then immersed in an epoxy-modified silicone resin emulsion with an epoxy value of 0.3 for 60 min, and vertically drained to remove the liquid from the membrane surface. It was then immersed in an aqueous solution containing 2.5 wt% triethylenetetramine for 10 min, and vertically drained to remove the liquid from the membrane surface. Finally, it was immersed in an oil solution containing 0.20 wt% trimesoyl chloride in n-decane for 2 min, and vertically drained to remove the liquid from the membrane surface. The membrane was then placed in an oven at 180°C for 20 min and then soaked in deionized water to obtain a nanofiltration membrane.

[0045] Example 3

[0046] The polyethersulfone-based membrane was immersed in an aqueous solution of 1,5,9-triazacyclododecane (5 wt%) for 5 min, then vertically drained to remove the liquid from the membrane surface. The membrane was then immersed in an epoxy-modified silicone resin emulsion with an epoxy value of 0.2 for 30 min, and vertically drained to remove the liquid from the membrane surface. It was then immersed in an aqueous solution containing 1.5 wt% piperazine for 2 min, and vertically drained to remove the liquid from the membrane surface. Finally, it was immersed in an oil solution containing 0.15 wt% isophthaloyl chloride in n-decane for 2 min, vertically drained to remove the liquid from the membrane surface, and then placed in a 150°C oven for 10 min. Afterward, it was removed and soaked in deionized water to obtain the nanofiltration membrane.

[0047] Comparative Example 1

[0048] The polyethersulfone-based membrane was immersed in an aqueous solution containing 1.5 wt% piperazine for 2 min, then vertically drained to remove the liquid from the membrane surface, and then immersed in an oil solution containing 0.15 wt% trimesoyl chloride in n-decane for 2 min. After vertically draining to remove the liquid from the membrane surface, it was placed in a 150°C oven for 10 min to react, and then removed and soaked in deionized water to obtain a nanofiltration membrane.

[0049] Comparative Example 2

[0050] The polyethersulfone-based membrane was immersed in an aqueous solution of 1,5,9-triazacyclododecane (5 wt%) for 5 min, then vertically drained to remove the liquid from the membrane surface. It was then immersed in an aqueous solution containing 1.5 wt% piperazine for 2 min, then vertically drained to remove the liquid from the membrane surface. Next, it was immersed in an oil solution of n-decane containing 0.15 wt% trimesoyl chloride for 2 min, vertically drained to remove the liquid from the membrane surface, and then placed in a 150°C oven for 10 min. Finally, it was removed and soaked in deionized water to obtain the nanofiltration membrane.

[0051] Comparative Example 3

[0052] The polyethersulfone-based membrane was immersed in an epoxy-modified silicone resin emulsion with an epoxy value of 0.2 for 30 minutes, then vertically drained to remove the liquid from the membrane surface. It was then immersed in a mixed aqueous solution containing 1.5 wt% piperazine for 2 minutes, then vertically drained to remove the liquid from the membrane surface. Next, it was immersed in a n-decane oil solution containing 0.15 wt% trimesoyl chloride for 2 minutes, and vertically drained to remove the liquid from the membrane surface. Finally, it was placed in a 150°C oven for 10 minutes to react. After that, it was taken out and soaked in deionized water to obtain a nanofiltration membrane.

[0053] Comparative Example 4

[0054] A polyethersulfone-based membrane was immersed in an epoxy-modified silicone resin emulsion with an epoxy value of 0.2 for 30 minutes, then vertically drained to remove the liquid from the membrane surface. It was then immersed in a mixed aqueous solution containing 1.5 wt% piperazine and 5.0 wt% 1,5,9-triazacyclododecane for 2 minutes, then vertically drained to remove the liquid from the membrane surface. Next, it was immersed in a n-decane oil solution containing 0.15 wt% trimesoyl chloride for 2 minutes, vertically drained to remove the liquid from the membrane surface, and then placed in a 150°C oven for 10 minutes. Finally, it was removed and soaked in deionized water to obtain a nanofiltration membrane.

[0055] Table 2. Nanofiltration membrane performance tests of Examples 1-3 and Comparative Examples 1-4

[0056]

[0057] The test results in Table 2 show that when the intermediate layer is prepared using macrocyclic polyamine and epoxy-modified silicone resin emulsion, the flux of the nanofiltration membrane at 0.69 MPa is significantly improved compared with comparative examples 1 to 4, and the rejection rate is greater than 90%. Moreover, the rejection rate is stable after chlorine and alkali resistance tests, and the chemical resistance of the membrane is greatly improved.

[0058] In Comparative Examples 1–4, the lack of an intermediate layer with the synergistic effect of macrocyclic polyamine and epoxy-modified silicone resin made it impossible to simultaneously guarantee high initial flux and rejection rate of the nanofiltration membrane. Furthermore, the rejection rate decreased significantly after chlorine-resistant or alkali-resistant treatment.

Claims

1. A high-flux, high-chemical-resistance composite nanofiltration membrane, characterized in that, The nanofiltration membrane comprises a polyethersulfone porous support layer, an intermediate layer formed by the emulsion reaction of macrocyclic polyamine and epoxy-modified silicone resin, and a polyamide separation layer formed on the intermediate layer.

2. A method for preparing a high-flux, highly chemically resistant composite nanofiltration membrane, characterized in that, Includes the following steps: (1) Macrocyclic polyamine and epoxy-modified silicone resin emulsion are loaded onto a porous polyethersulfone support layer to form an intermediate layer; (2) An aqueous phase containing polyamines and an organic phase containing polyacryl chlorides are polymerized at the interface to form a polyamide separation layer on the intermediate layer.

3. The method according to claim 2, characterized in that, Step (1) specifically involves immersing the polyethersulfone porous support layer sequentially in a macrocyclic polyamine solution and an epoxy-modified silicone resin emulsion, draining it, and removing excess solution from the surface.

4. The method according to claim 3, characterized in that, The macrocyclic polyamine is selected from one or more of the following: 1,5,9,13-tetraazacyclohexadecane, 1,5,8,11,14-pentazacyclohexadecane, 1,4,8,11-tetraazacyclotetradecane, 1,4,7,10-tetraazacyclododecane, and 1,5,9-triazacyclododecane. And / or, the concentration of the macrocyclic polyamine solution is 2–10 wt%.

5. The method according to claim 3 or 4, characterized in that, The impregnation time of the polyethersulfone porous support layer in the macrocyclic polyamine solution is 2 to 10 minutes; And / or, the impregnation time of the polyethersulfone porous support layer in the epoxy-modified silicone resin emulsion is 10 to 60 minutes.

6. The method according to claim 3, characterized in that, The epoxy value of epoxy-modified silicone resin emulsion is 0.1-0.

3.

7. The method according to claim 2, characterized in that, The polyamine mentioned in step (2) is an aliphatic polyamine, and the polyacryl chloride is an aromatic polyacryl chloride.

8. The method according to claim 2, characterized in that, Step (2) specifically involves: mixing an aliphatic polyamine with water to obtain an aqueous solution, mixing an aromatic polyacrylamide chloride with an organic solvent to obtain an oil solution, contacting the polyethersulfone porous support layer of the loaded intermediate layer with the aqueous solution, removing excess solution from the surface, contacting it with the oil solution, heating and curing to obtain the nanofiltration membrane.

9. The method according to claim 8, characterized in that, The aliphatic polyamine is selected from one or more of piperazine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, and aminoethylpiperazine.

10. The method according to claim 9, characterized in that, The concentration of the aqueous solution is 1–2.5 wt%.

11. The method according to claim 8, characterized in that, Aromatic polyacryl chlorides are selected from one or more of pyromellitic chloride, phthaloyl chloride, and isophthaloyl chloride.

12. The method according to claim 11, characterized in that, The organic solvent is selected from one or more isoalkanes, including n-hexane, n-heptane, n-decane, Isopar L, and Isopar G.

13. The method according to claim 12, characterized in that, The concentration of the oil phase solution is 0.1–0.25 wt%.

14. The method according to claim 8, characterized in that, The contact time between the polyethersulfone porous support layer of the load intermediate layer and the aqueous solution is 2 to 10 minutes. And / or, the contact time between the polyethersulfone porous support layer of the load intermediate layer and the oil phase solution is 1 to 3 minutes.

15. The method according to claim 8, characterized in that, The curing temperature is 100-180℃, and the time is 2-20 minutes.

16. The use of a composite nanofiltration membrane as described in claim 1 or a composite nanofiltration membrane prepared by any one of claims 2-15, characterized in that, The nanofiltration membrane is used as a water treatment or material separation component.

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