Preparation method of ion-regulated ceramic-based polyamide nanofiltration membrane
By introducing alkali metal ions and polyamine catalysts onto the surface of ceramic membranes to regulate the interfacial polymerization reaction, the stability and performance issues of ceramic-based nanofiltration membranes under extreme environments have been resolved. This has enabled the preparation of high-flux and high-retention nanofiltration membranes, which are suitable for applications such as seawater desalination and industrial wastewater treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-03-13
AI Technical Summary
Existing nanofiltration membrane supports are prone to aging under acid, alkali, oxidant or high temperature environments, and the ceramic surface has strong hydrophilicity and a limited number of surface hydroxyl groups, resulting in weak bonding between the polyamide layer and the inorganic matrix, making it difficult to obtain high-flux and high-retention composite membranes.
By employing a strong base activation combined with silane coupling agent grafting method, specific alkali metal or alkaline earth metal ions and polyamine catalysts are introduced onto the surface of the ceramic membrane to regulate the interfacial polymerization reaction rate, forming a thinner and more uniform polyamide separation layer, thereby enhancing the chemical bonding strength between the inorganic ceramic and the organic polyamide layer.
It significantly improves the membrane's permeation flux and the rejection rate of divalent salts, enhances the long-term operational stability of the composite membrane, is suitable for the treatment of highly polluted and highly corrosive wastewater, and has a simple preparation process that is easy to industrialize.
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Figure CN121648754A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing an ion-controlled ceramic-based polyamide nanofiltration membrane. Background Technology
[0002] Nanofiltration is a pressure-driven membrane separation process with an operating pressure between ultrafiltration and reverse osmosis. It has advantages such as low energy consumption, high flux, and the ability to separate monovalent and divalent salts, and is widely used in seawater desalination pretreatment, advanced industrial wastewater treatment, and food and pharmaceutical concentration and separation. Currently, the most commercially successful nanofiltration membrane is a thin-layer composite polyamide membrane prepared by interfacial polymerization. Its typical preparation process is as follows: a porous support is immersed in a solution containing aqueous amine monomers such as piperazine (PIP), and then contacted with an oil phase solution containing trimesoyl chloride (TMC). A polymerization reaction occurs instantaneously at the interface between the two phases to form an ultrathin polyamide separation layer.
[0003] However, due to the extremely high reactivity of amine monomers and acyl chloride monomers, the interfacial polymerization reaction is extremely fast (usually completed in a few seconds to tens of seconds), making it difficult to precisely control the thickness, crosslinking degree, and surface morphology of the polyamide layer. This easily leads to the formation of thick, dense layers or defective structures, resulting in a problem where "flux-retention" cannot be balanced. Meanwhile, traditional composite nanofiltration membranes often use organic polymer ultrafiltration membranes such as polysulfone and polyethersulfone as supports. These supports are prone to hydrolysis and aging under long-term exposure to acids, alkalis, oxidants, or high temperatures, resulting in a short overall lifespan for the composite membrane and making it difficult to meet the stable operation requirements under harsh conditions.
[0004] Inorganic ceramic membranes possess excellent resistance to acids and alkalis, high temperatures, oxidation, and high mechanical strength, making them ideal materials for next-generation nanofiltration membrane supports. However, the strong hydrophilicity and limited number of surface hydroxyl groups on ceramic surfaces lead to weak adhesion between the organic polyamide layer and the inorganic matrix during direct interfacial polymerization, resulting in delamination or defects and making it difficult to obtain composite membranes with both high flux and high retention. While some existing technologies have reported interfacial polymerization after grafting silanes onto the ceramic membrane surface, these methods still suffer from excessively rapid reaction rates and inhomogeneous separation layer structures, limiting the improvement in membrane performance. Summary of the Invention
[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing an ion-controlled ceramic-based polyamide nanofiltration membrane.
[0006] The technical solution of the present invention is as follows:
[0007] A method for preparing an ion-controlled ceramic-based polyamide nanofiltration membrane includes the following steps:
[0008] (1) After ultrasonic cleaning and strong alkali activation, the ceramic membrane is loaded with silane coupling agent to obtain silane-grafted ceramic membrane;
[0009] (2) The silane-grafted ceramic membrane obtained in step (1) is reacted with an aqueous solution containing piperazine, alkali metal or alkaline earth metal ions and polyamine catalyst at room temperature, and then the unreacted aqueous solution is removed.
[0010] (3) After reacting the material obtained in step (2) with a hexane solution of trimesoyl chloride at room temperature, the unreacted hexane solution is removed.
[0011] (4) The material obtained in step (3) is air-dried and heat-treated to obtain the ion-controlled ceramic-based polyamide nanofiltration membrane.
[0012] In a preferred embodiment of the present invention, the ceramic membrane is made of alumina, titanium dioxide, or zirconium oxide.
[0013] In a preferred embodiment of the present invention, the strong base in the strong base solution is sodium hydroxide or potassium hydroxide, with a concentration of 1-10 mol / L and an activation time of 10-24 h.
[0014] In a preferred embodiment of the present invention, the silane coupling agent is 3-aminopropyltriethoxysilane, diethyltrimethoxysilane, or diethyltrimethoxysilane.
[0015] In a preferred embodiment of the present invention, the alkali metal or alkaline earth metal ions are selected from lithium ions, sodium ions, potassium ions and magnesium ions, and their concentration in the aqueous solution in step (2) is 0.01-0.05 wt%.
[0016] More preferably, in the aqueous solution of step (2): the concentration of piperazine is 0.05-0.5 wt%, and the concentration of polyamine catalyst is 0.1-0.3 wt%.
[0017] More preferably, the polyamine catalyst is diethylamine or triethylamine.
[0018] In a preferred embodiment of the present invention, the concentration of trimesoamide in the hexane solution of step (3) is 0.05-0.3 wt%.
[0019] In a preferred embodiment of the present invention, the reaction time in step (2) is 1-10 min, and the reaction time in step (3) is 1-10 min.
[0020] More preferably, the temperature of the heat treatment in step (4) is 50-80 ℃.
[0021] The beneficial effects of this invention are:
[0022] 1. This invention effectively regulates the interfacial polymerization rate by introducing specific alkali metal or alkaline earth metal ions into the aqueous phase and cooperating with a polyamine catalyst, resulting in a thinner and more uniform polyamide separation layer, significantly improving the membrane permeation flux while maintaining an extremely high rejection rate for divalent salts.
[0023] 2. This invention employs a strong alkali activation combined with silane coupling agent grafting, which significantly enhances the chemical bonding strength between the inorganic ceramic surface and the organic polyamide layer, avoids the separation layer peeling phenomenon, and greatly improves the long-term operational stability of the composite membrane.
[0024] 3. This invention uses an acid- and alkali-resistant, high-temperature-resistant inorganic ceramic membrane as a support, giving the composite membrane extremely strong chemical stability. It can operate stably for a long time in extreme pH environments such as strong acids and strong alkalis, and is suitable for the treatment of highly polluted and highly corrosive wastewater.
[0025] 4. The preparation process of this invention is simple, the reaction conditions are mild, the reproducibility is good, and it is easy to scale up production and industrial application.
[0026] 5. The ceramic-based polyamide nanofiltration membrane prepared by this invention maintains an extremely high rejection rate while exhibiting a significantly higher pure water flux than traditional organic-supported polyamide membranes and ceramic-based composite membranes without ion regulation, thus overcoming the technical bottleneck of traditional interfacial polymerization membranes where "flux-rejection" is difficult to balance. Attached Figure Description
[0027] Figure 1 This is an electron microscope image of the ceramic-based polyamide nanofiltration membrane prepared in Comparative Example 2 of the present invention.
[0028] Figure 2 This is an electron microscope image of the ceramic-based polyamide nanofiltration membrane prepared in Example 2 of the present invention. Detailed Implementation
[0029] The technical solution of the present invention will be further explained and described below through specific embodiments.
[0030] Comparative Example 1 (Traditional Organic Support Polyamide Nanofiltration Membrane)
[0031] (1) Immerse the polyethersulfone (PES) ultrafiltration membrane base with a molecular weight cutoff of 10,000 Da in an aqueous solution containing 0.1 wt% piperazine and 0.1 wt% diethylamine, react at room temperature for 10 min, and then remove it and blow off the residual liquid on the surface with an air gun.
[0032] (2) The material obtained in step (1) was immersed in a 0.2 wt% hexane solution of trimesoyl chloride (TMC), reacted at room temperature for 10 min, and then removed, rinsed with hexane and dried with an air gun.
[0033] (3) After the material obtained in step (2) is placed in a cool place to air dry naturally, it is transferred to a 50 ℃ oven for heat treatment for 15 min and cooled with the oven to obtain a polyamide composite nanofiltration membrane.
[0034] Performance test (room temperature, 0.69 MPa): Pure water flux 45 L·m -2 ·h -1 The rejection rate for 2 g / L sodium sulfate solution was 97%.
[0035] Comparative Example 2 (Ceramic-supported polyamide nanofiltration membrane, without ion regulation)
[0036] 1. Ceramic membrane pretreatment
[0037] A tubular titanium dioxide ceramic membrane with an average pore size of 50 nm was cut to a length of approximately 50 cm, ultrasonically cleaned for 2 h, immersed in a 1 mol / L potassium hydroxide solution for 10 h, and dried at 100 ℃ for 24 h. After cooling, it was immersed in an ethanol solution of 0.1 wt% 3-aminopropyltriethoxysilane (KH-550) and reacted at room temperature for 12 h. It was then rinsed with ethanol and deionized water sequentially, dried at 150 ℃ for 12 h, and cooled in the furnace to obtain a silane-grafted ceramic membrane.
[0038] 2. Preparation of composite membranes
[0039] (1) The above silane-grafted ceramic membrane was immersed in an aqueous solution containing 0.1 wt% piperazine and 0.1 wt% diethylamine, reacted at room temperature for 10 min, and then removed and the surface residual liquid was dried with an air gun.
[0040] (2) Immerse the material obtained in step (1) in a 0.2 wt% hexane solution of trimesoyl chloride (TMC), react at room temperature for 10 min, remove it, rinse with hexane and dry with an air gun;
[0041] (3) After the material obtained in step (2) is air-dried at room temperature, it is placed in a 50 ℃ oven for heat treatment for 15 min, and then cooled with the oven to obtain the product shown in the figure. Figure 1 The ceramic-based polyamide nanofiltration membrane shown for comparison has a thickness of 166 nm.
[0042] Performance test (room temperature, 0.69 MPa): Pure water flux 75 L·m -2 ·h -1 The rejection rate for 2 g / L sodium sulfate solution is 95%.
[0043] Example 1
[0044] 1. Ceramic membrane pretreatment
[0045] Following step 1 of Comparative Example 2, a silane-grafted ceramic membrane was obtained.
[0046] 2. Preparation of composite membranes
[0047] (1) Immerse the silane-grafted ceramic membrane in an aqueous solution containing 0.1 wt% piperazine, 0.01 wt% lithium chloride and 0.1 wt% diethylamine, react at room temperature for 10 min, and then remove it and blow dry the residual liquid on the surface with an air gun.
[0048] (2) Immerse the material obtained in step (1) in a 0.2 wt% hexane solution of trimesoyl chloride (TMC), react at room temperature for 10 min, remove it, rinse with hexane and dry with an air gun;
[0049] (3) After the material obtained in step (2) is air-dried at room temperature, it is placed in a 50 ℃ oven for heat treatment for 15 min and cooled with the oven to obtain the ion-controlled ceramic-based polyamide nanofiltration membrane.
[0050] Performance test (room temperature, 0.69 MPa): Pure water flux 115 L·m -2 ·h -1 The rejection rate for 2 g / L sodium sulfate solution was 98%.
[0051] Acid and alkali resistance test: After soaking in nitric acid solution (pH=1) and sodium hydroxide solution (pH=12.5) for 40 days, the pure water flux was 112 L·m⁻¹, respectively. -2 ·h -1 and 116 L·m -2 ·h -1 The retention rates were 96% and 95.6%, respectively.
[0052] Example 2
[0053] 1. Ceramic membrane pretreatment
[0054] Same as Comparative Example 2, Step 1.
[0055] 2. Preparation of composite membranes
[0056] (1) Immerse the silane-grafted ceramic membrane in an aqueous solution containing 0.1 wt% piperazine, 0.02 wt% lithium chloride and 0.1 wt% diethylamine, react at room temperature for 10 min, and then remove it and blow dry the residual liquid on the surface with an air gun.
[0057] (2) Immerse the material obtained in step (1) in a 0.2 wt% hexane solution of trimesoyl chloride (TMC), react at room temperature for 10 min, remove it, rinse with hexane and dry with an air gun;
[0058] (3) After the material obtained in step (2) is air-dried at room temperature, it is placed in a 50 ℃ oven for heat treatment for 15 min, and then cooled with the oven to obtain the product shown in the figure. Figure 2The ion-controlled ceramic-based polyamide nanofiltration membrane shown has a thickness of 71.4 nm. Compared with the membrane layer without added ions, the membrane layer with added ions has a more uniform and smoother surface and a thinner thickness.
[0059] Performance test (room temperature, 0.69 MPa): Pure water flux 130 L·m -2 ·h -1 The rejection rate for 2 g / L sodium sulfate solution is 99%.
[0060] Acid and alkali resistance test: After soaking in nitric acid solution (pH=1) and sodium hydroxide solution (pH=12.5) for 40 days, the pure water flux was 128 L·m⁻¹, respectively. -2 ·h -1 and 125 L·m -2 ·h -1 The retention rates were 98.5% and 98.2%, respectively.
[0061] Example 3
[0062] 1. Ceramic membrane pretreatment
[0063] Same as Comparative Example 2, Step 1.
[0064] 2. Preparation of composite membranes
[0065] (1) Immerse the silane-grafted ceramic membrane in an aqueous solution containing 0.1 wt% piperazine, 0.05 wt% lithium chloride and 0.1 wt% diethylamine, react at room temperature for 10 min, and then remove it and blow it dry with an air gun;
[0066] (2) Immerse the material obtained in step (1) in a 0.2 wt% hexane solution of trimesoyl chloride (TMC), react at room temperature for 10 min, remove it, rinse with hexane and dry with an air gun;
[0067] (3) After the material obtained in step (2) is air-dried at room temperature, it is heat-treated at 50 ℃ for 15 min and cooled with the furnace to obtain the ion-controlled ceramic-based polyamide nanofiltration membrane.
[0068] Performance test (room temperature, 0.69 MPa): Pure water flux 110 L·m -2 ·h -1 The rejection rate for 2 g / L sodium sulfate solution was 98.5%.
[0069] Acid and alkali resistance test: After soaking in nitric acid solution (pH=1) and sodium hydroxide solution (pH=12.5) for 40 days, the pure water flux was 105 L·m⁻¹, respectively. -2 ·h -1 and 107 L·m -2 ·h -1The retention rates were 97% and 96.6%, respectively.
[0070] The following list compares the embodiments with the comparative examples:
[0071] Table 1
[0072] project Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Support material Polyethersulfone (PES) ultrafiltration membrane 50 nm titanium dioxide ceramic film 50 nm titanium dioxide ceramic film 50 nm titanium dioxide ceramic film 50 nm titanium dioxide ceramic film Strong base activation none Soak in 1 mol / L KOH for 10 h Soak in 1 mol / L KOH for 10 h Soak in 1 mol / L KOH for 10 h Soak in 1 mol / L KOH for 10 h Silane grafting none 0.1 wt% KH-550, 12 h 0.1 wt% KH-550, 12 h 0.1 wt% KH-550, 12 h 0.1 wt% KH-550, 12 h Aqueous phase piperazine concentration 0.1 wt% 0.1 wt% 0.1 wt% 0.1 wt% 0.1 wt% Aqueous phase ions none none 0.01 wt% Lithium chloride 0.02 wt% Lithium chloride 0.05 wt% Lithium chloride Aqueous catalyst 0.1 wt% diethylamine 0.1 wt% diethylamine 0.1 wt% diethylamine 0.1 wt% diethylamine 0.1 wt% diethylamine Aqueous phase reaction time 10 min 10 min 10 min 10 min 10 min Oil phase TMC concentration 0.2 wt% (n-hexane) 0.2 wt% (n-hexane) 0.2 wt% (n-hexane) 0.2 wt% (n-hexane) 0.2 wt% (n-hexane) Oil phase reaction time 10 min 10 min 10 min 10 min 10 min Heat treatment conditions 50 ℃ × 15 min 50 ℃ × 15 min 50 ℃ × 15 min 50 ℃ × 15 min 50 ℃ × 15 min <![CDATA[Pure water flux (L·m -2 ·h -1 )]]> 45 75 115 130 110 <![CDATA[Intercepting rate for 2 g / L Na2SO4]]> 97% 95% 98% 99% 98.50% <![CDATA[Acid resistance (after soaking in HNO3 with pH = 1 for 40 days)]]> Untested Untested <![CDATA[Flux 112 L·m -2 ·h -1 , retention 96%]]> <![CDATA[Flux 128 L·m -2 ·h -1 , rejection 98.5%]]> <![CDATA[Flux 105 L·m -2 ·h -1 , with 97% retention]]> Alkali resistance (after soaking in NaOH at pH=12.5 for 40 days) Untested Untested <![CDATA[Flux 116 L·m -2 ·h -1 , with 95.6% retention]]> <![CDATA[Flux 125 L·m -2 ·h -1 , retention 98.2%]]> <![CDATA[Flux 107 L·m -2 ·h -1 , with 96.6% retention]]>
[0073] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.
Claims
1. A method for preparing an ion-controlled ceramic-based polyamide nanofiltration membrane, characterized in that: Includes the following steps: (1) After ultrasonic cleaning and strong alkali activation, the ceramic membrane is loaded with silane coupling agent to obtain silane-grafted ceramic membrane; (2) The silane-grafted ceramic membrane obtained in step (1) is reacted with an aqueous solution containing piperazine, alkali metal or alkaline earth metal ions and polyamine catalyst at room temperature, and then the unreacted aqueous solution is removed. (3) After reacting the material obtained in step (2) with a hexane solution of trimesoyl chloride at room temperature, the unreacted hexane solution is removed. (4) The material obtained in step (3) is air-dried and heat-treated to obtain the ion-controlled ceramic-based polyamide nanofiltration membrane.
2. The preparation method according to claim 1, characterized in that: The ceramic membrane is made of alumina, titanium dioxide, or zirconium oxide.
3. The preparation method according to claim 1, characterized in that: The strong base in the strong alkaline solution is sodium hydroxide or potassium hydroxide, with a concentration of 1-10 mol / L and an activation time of 10-24 h.
4. The preparation method according to claim 1, characterized in that: The silane coupling agent is 3-aminopropyltriethoxysilane, diethyltrimethoxysilane, or diethyltrimethoxysilane.
5. The preparation method according to claim 1, characterized in that: The alkali metal or alkaline earth metal ions are selected from lithium ions, sodium ions, potassium ions and magnesium ions, and their concentration in the aqueous solution in step (2) is 0.01-0.05 wt%.
6. The preparation method according to claim 5, characterized in that: In the aqueous solution of step (2), the concentration of piperazine is 0.05-0.5 wt%, and the concentration of polyamine catalyst is 0.1-0.3 wt%.
7. The preparation method according to claim 6, characterized in that: The polyamine catalyst is diethylamine or triethylamine.
8. The preparation method according to claim 1, characterized in that: The concentration of trimesoamide in the hexane solution in step (3) is 0.05-0.3 wt%.
9. The preparation method according to any one of claims 1 to 8, characterized in that: The reaction time in step (2) is 1-10 min, and the reaction time in step (3) is 1-10 min.
10. The preparation method according to claim 9, characterized in that: The heat treatment temperature in step (4) is 50-80 ℃.