Preparation method of loose nanofiltration membrane based on reactive polyarylene ether nitrile oxime

Abstract

The invention discloses a preparation method of a loose nanofiltration membrane based on reactive polyarylene ether nitrile oxime, and belongs to the technical field of high polymer materials. Starting from a side chain nitrile group of polyarylene ether nitrile (PEN), the nitrile group is converted into an amidoxime group and a carboxyl group with reactivity, so that the originally relatively inert polyarylene ether nitrile has chemical reaction activity. The nanofiltration membrane which is high in flux, high in interception effect and excellent in acid and alkali resistance is prepared by utilizing an active group on a side chain of the modified reactive poly (arylene ether nitrile) (PEA) through a phase inversion method. The nitrile group conversion provides more cross-linking sites in the nanofiltration membrane preparation process, further improves the cross-linking density, can significantly improve the compatibility with other resins, and provides a brand new thought for the development and utilization of the high-molecular side chain nitrile group and the preparation of the nanofiltration membrane.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a synthesis method of reactive polyarylether oxime and its application in loose nanofiltration membranes. Background Art

[0002] With the continuous development of industrial technology, the problem of water pollution has become increasingly serious. For general insoluble substances (such as sediment), they can be relatively simply removed by methods such as precipitation and coagulation. However, for soluble pollutants with relatively small molecular weights (such as dyes, heavy metal ions, organic substances, etc.), traditional industrial technologies often require complex processes to effectively remove them. Such processes not only have high energy consumption and belong to energy-intensive industries, but may also cause secondary pollution to the environment. Membrane separation technology can efficiently separate pollutants only by pressure driving, with simple processes and energy consumption reduced by about 90% compared to traditional processes, which well meets the requirements of the current circular economy. Generally speaking, while ensuring excellent separation effects, membrane separation technology also has advantages such as economy, simplicity of operation, and environmental friendliness, thus showing broad application prospects in fields such as printing and dyeing wastewater treatment, battery waste liquid purification, lithium extraction from seawater, and seawater desalination. In addition, liquid membrane separation technology can achieve separation without phase transformation, which not only reduces energy consumption but also maximally maintains the original physical and chemical properties of the separated liquid. This is particularly important in the separation process of organic substances that require the protection of molecular structure and biological activity (such as proteins, polypeptides, and microorganisms), and has wide applications in fields such as organic synthesis, extraction of active substances, and dialysis.

[0003] There are various preparation methods for polymer nanofiltration membranes, mainly including: phase inversion method, interfacial polymerization method, layer-by-layer assembly method, surface grafting method, surface coating method, etc. Among them, the phase inversion method and the interfacial polymerization method are the most widely used in industrial production. The formation of a membrane by the phase inversion method can be simply summarized as a process of transforming a liquid polymer into a solid state in a certain way (non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS)). The key to this method lies in precisely controlling the membrane formation process to balance the flux and rejection rate of the membrane. The main factors affecting the performance of nanofiltration membranes include polymer ratio, coagulation bath composition, membrane thickness, solvent type, and operating temperature, etc. The interfacial polymerization method is a reaction at the interface between the organic phase and the aqueous phase, forming a dense membrane layer at the interface. The core of this method lies in the precise control of the concentrations of the two-phase reactants, temperature, and reaction time. Compared with the two methods, the phase inversion method has the advantages of simple operation, low raw material cost, and relatively low difficulty in industrial implementation. At the same time, the obtained membrane shows higher mechanical strength and more excellent durability without considering the substrate, but the separation flux is generally lower than that of the interfacial polymerization method.

[0004] At present, the commonly used raw materials for preparing nanofiltration membranes include polysulfone, polyimide, polyetheretherketone and polyacrylonitrile. However, from the perspective of comprehensive performance, economy and industrialization, new materials still need to be further developed. After years of research, polyarylethernitrile (PEN) has achieved industrial production and has a lower production cost than polyetheretherketone. Compared with polysulfone, the introduction of nitrile groups significantly improves the hydrophilicity and cross-linking reaction activity of the material, making it have better chemical stability under harsh environments. Therefore, polyarylethernitrile is a high-quality raw material for preparing nanofiltration membranes. However, the large number of nitrile groups on the side chains of polyarylethernitrile have not been fully paid attention to and utilized. If the potential of these nitrile groups can be effectively developed, the performance and application range of polyarylethernitrile will be further improved. Summary of the invention

[0005] The purpose of the present invention is to propose a method for preparing a loose nanofiltration membrane based on reactive polyarylethernitrileoxime in view of the problems existing in the background technology. The present invention converts the side chain nitrile group of polyarylethernitrile (PEN) into reactive amidoxime group and carboxyl group, and uses the converted reactive polyarylethernitrile (PEA) as raw material to prepare a nanofiltration membrane with high flux and excellent acid and alkali resistance by a phase inversion method. In the present invention, the conversion of the nitrile group not only provides more cross-linking sites in the preparation process of the nanofiltration membrane, thereby increasing the cross-linking density, but also significantly improves its compatibility with other resins.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A reactive polyarylether nitrile oxime is a random copolymer formed by randomly distributing three structural units A, B and C in a polymer long chain. The molar ratio of the three structural units A, B and C is A:B:C=(0.5-1):(4-6):(3-4). The structural formulas of the three structural units A, B and C are as follows:

[0008]

[0009] A method for preparing a reactive polyarylether nitrile oxime comprises the following steps:

[0010] Step 1. Add 10 parts by mass of poly(arylene ether nitrile) into 50 to 100 parts by mass of a solvent, and stir at 80 to 100° C. to obtain a homogeneous solution;

[0011] Step 2. Add 1 part by mass of a base, 1 to 2 parts by mass of sodium bicarbonate and 6 to 12 parts by mass of hydroxylamine hydrochloride to the homogeneous solution obtained in step 1, and stir the reaction at 60 to 120° C. for 12 to 48 hours;

[0012] Step 3. Soak the material after the reaction in step 2 in anhydrous ethanol for 12 to 24 hours;

[0013] Step 4. Crush the material processed in Step 3 into granular form, and wash it with boiling water until the supernatant is clear;

[0014] Step 5. Filter and dry to obtain reactive polyarylether nitrile oxime (PEA pellets).

[0015] Further, the solvent described in Step 1 is N-N'-dimethylformamide (DMF), N-N'-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), etc.

[0016] Further, the base described in Step 2 is sodium hydroxide, potassium hydroxide, etc.

[0017] Further, the chemical structural formula of the polyarylether nitrile (PEN) described in Step 1 is

[0018]

[0019] Further, by controlling the addition amount of the base, the molecular weight of the polyarylether nitrile (PEN), and the addition amount of hydroxylamine hydrochloride, the ratio of the oxime group to the carboxyl group in the reactive polyarylether nitrile oxime is adjusted. Specifically, when the molecular weight of the polyarylether nitrile (PEN) is less than 60,000, 1 part by mass of the base, 1 - 1.5 parts by mass of sodium bicarbonate, and 10 - 12 parts by mass of hydroxylamine hydrochloride are added in Step 2, the oxime group is the main group in the obtained reactive polyarylether nitrile oxime, that is, the number of oxime groups is greater than that of carboxyl groups; when the molecular weight of the polyarylether nitrile (PEN) is greater than 60,000, 1 part by mass of the base, 1 - 2 parts by mass of sodium bicarbonate, and 10 - 12 parts by mass of hydroxylamine hydrochloride are added in Step 2, and the reaction time is controlled within 12 - 24 h, the oxime group is the main group in the obtained reactive polyarylether nitrile oxime.

[0020] A preparation method of a loose nanofiltration membrane based on reactive polyarylether nitrile oxime, comprising the following steps:

[0021] Step 1. Sequentially add the reactive polyarylether nitrile oxime (PEA pellets) obtained by the above method and 0.1 - 10 wt% of ferric chloride (FeCl3) equivalent to the mass of the reactive polyarylether nitrile oxime into a reaction vessel, then add a solvent, and stir and mix evenly to obtain a casting solution with a solid content of 10 - 20 wt%;

[0022] Step 2. Magnetically stir the casting solution prepared in Step 1 at 25 - 40 °C for 12 - 24 h;

[0023] Step 3. Perform ultrasonic defoaming treatment on the solution obtained after stirring in Step 2, set the ultrasonic water bath at 30 - 40 °C, keep it for 25 - 60 min, and after the ultrasonic treatment, let it stand in the water bath for 10 - 20 min to obtain a casting solution;

[0024] Step 4. Pour the casting solution obtained in Step 3 evenly onto a glass plate, scrape it evenly using a four-sided spreader, place it in a coagulation bath to complete phase inversion, and then soak it in deionized water for 24 - 48 hours;

[0025] Step 5. After the soaking is completed, take out the membrane sheet and air-dry it at room temperature;

[0026] Step 6. Place the air-dried membrane sheet in a forced-air oven and treat it at 80 - 200 °C for 2 hours to obtain a nanofiltration membrane.

[0027] Further, the solvent described in Step 1 is N-N'-dimethylformamide (DMF), N-N'-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), etc.

[0028] Further, in Step 4, the coagulation bath is deionized water, hydrochloric acid aqueous solution, ethanol aqueous solution, etc.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The present invention converts relatively inert polyarylether nitrile (PEN) into reactive polyarylether nitrile (PEA), converts a large number of nitrile groups on the side chain into reactive amidoxime groups and carboxyl groups, increasing the active sites of polyarylether nitrile. It solves the compatibility problem when blending or copolymerizing with some resins (such as thermoplastic and thermosetting resins like epoxy resin, phthalonitrile resin, polyetheretherketone, etc.), and provides a new idea for the application of nitrile groups of other polymers containing a large number of side-chain nitrile groups.

[0031] 2. The present invention prepares a high-flux acid- and alkali-resistant loose nanofiltration membrane based on reactive polyarylether nitrile (PEA), which has the following advantages: First, the nanofiltration membrane is prepared using reactive polyarylether nitrile (PEA) as the raw material, and its performance is more stable under extreme conditions compared with materials such as polysulfone, and it has a price advantage compared with materials such as polyetheretherketone, with high comprehensive cost performance; Second, the nanofiltration membrane is formed by phase inversion, and the preparation process is simpler than interfacial polymerization; In addition, when preparing the nanofiltration membrane, a method of low-temperature thermal crosslinking is proposed, which eliminates crack-like defects while increasing the surface crosslinking density, and breaks through the constraint effect of separation flux and rejection rate by controlling high and low molecular weights, providing a new solution for the preparation of loose nanofiltration (LNF) membranes. Description of the Drawings

[0032] Figure 1 FTIR comparison chart of the reactive polyarylether nitrile oxime (PEA) and polyarylether nitrile (PEN) raw materials prepared in Example 1;

[0033] Figure 2DSC curve comparison diagram of the reactive polyarylether nitrile oxime (PEA) and polyarylether nitrile (PEN) raw materials prepared in Example 1, Example 2, and Example 3;

[0034] Figure 3 Results of the rejection rate and permeability of the nanofiltration membrane prepared in Example 4 for neutral rhodamine B dye;

[0035] Figure 4 Results of the rejection rate and permeability of the nanofiltration membrane prepared in Example 5 for neutral rhodamine B dye;

[0036] Figure 5 Results of the cyclic test of the nanofiltration membranes prepared in Example 4 and Example 5 for neutral rhodamine B dye;

[0037] Figure 6 Results of the rejection rate and permeability of the nanofiltration membranes prepared in Example 4 and Example 5 for rhodamine B dye under different pH conditions. Detailed implementation manners

[0038] The present invention will be further described below through the description of specific implementation manners. However, this is not a limitation to the present invention. Those skilled in the art can make various variations or modifications according to the basic idea of the present invention. As long as they do not depart from the basic idea of the present invention, they are all within the scope of the present invention.

[0039] The present invention provides a method for preparing a loose nanofiltration membrane based on reactive polyarylether nitrile oxime. The core of the preparation of the nanofiltration membrane lies in how to balance the flux and the rejection rate, that is, to control the density of the membrane surface within a reasonable range. Excessive density will lead to a decrease in flux and make the membrane brittle; too low density will affect the rejection performance. The present invention uses carboxyl groups to quickly react with iron ions during the phase inversion process to ensure the content of iron ions in the system; subsequently, heat treatment is used to regulate the coordination of the slower-reacting amidoxime groups with iron ions to eliminate crack defects and precisely control the membrane pore size.

[0040] Example 1

[0041] A method for preparing a reactive polyarylether nitrile oxime (PEA), comprising the following steps:

[0042] Step 1. Add 350 g of polyarylether nitrile to 4000 g of NMP, and stir at 85 °C to obtain a homogeneous solution;

[0043] Step 2. Add 35 g of sodium hydroxide, 35 g of sodium bicarbonate, and 420 g of hydroxylamine hydrochloride to the homogeneous solution obtained in Step 1, and stir and react at 80 °C for 24 h;

[0044] Step 3. Immerse the material after the reaction in Step 2 in 5000 g of absolute ethanol for 24 h;

[0045] Step 4. Crush the material processed in Step 3 into granular form, and wash it with boiling water until the supernatant is clear;

[0046] Step 5. Filter and dry to obtain reactive polyarylether nitrile oxime (PEA pellets).

[0047] The reactive polyarylether nitrile oxime (PEA pellets) prepared in Example 1 was subjected to FTIR testing, and the results are as Figure 1 shown. From the Fourier transform infrared spectroscopy curve, it can be seen that the absorption peak of the nitrile group is significantly weakened, and a carbon-oxygen double bond (-C=O-) absorption peak attributed to the carboxyl group appears at 1720 cm -1 The primary amine absorption peak of the amidoxime group appears at 3486 cm -1 and 3374 cm -1 (-NH2), the carbon-nitrogen double bond at 1658 cm -1 (-C=N-), and the nitrogen-oxygen bond at 928 cm -1 (-N-O-). The reactive polyarylether nitrile oxime (PEA pellets) prepared in Example 1 was subjected to DSC testing, and the results are as Figure 2 shown. It was found that an obvious exothermic reaction peak appears at 210 °C, and the enthalpy is 8.23 J / g, indicating that PEN was successfully converted to PEA.

[0048] Example 2

[0049] A preparation method of reactive polyarylether nitrile oxime (PEA) includes the following steps:

[0050] Step 1. Add 10 g of polyarylether nitrile to 100 g of NMP, and stir at 85 °C to obtain a homogeneous solution;

[0051] Step 2. Add 1 g of sodium hydroxide, 2 g of sodium bicarbonate, and 12 g of hydroxylamine hydrochloride to the homogeneous solution obtained in Step 1, and stir and react at 80 °C for 24 h;

[0052] Step 3. Immerse the material after the reaction in Step 2 in 100 g of absolute ethanol for 24 h;

[0053] Step 4. Crush the material processed in Step 3 into granular form, and wash it with boiling water until the supernatant is clear;

[0054] Step 5. Filter and dry to obtain reactive polyarylether nitrile oxime (PEA pellets).

[0055] The reactive polyarylether nitrile oxime (PEA pellets) prepared in Example 2 was subjected to DSC testing, and the results are as Figure 2 shown. It was found that an obvious exothermic reaction peak appears at 201 °C, and the enthalpy is 35.49 J / g.

[0056] Example 3

[0057] A preparation method of reactive polyarylether nitrile oxime (PEA) comprises the following steps:

[0058] Step 1. Add 10 g of polyarylether nitrile into 100 g of NMP, and stir at 80 °C to obtain a homogeneous solution;

[0059] Step 2. Add 2 g of sodium hydroxide, 4 g of sodium bicarbonate and 24 g of hydroxylamine hydrochloride into the homogeneous solution obtained in Step 1, and stir and react at 80 °C for 24 h;

[0060] Step 3. Immerse the material after the reaction in Step 2 in 100 g of absolute ethanol for 24 h;

[0061] Step 4. Crush the material treated in Step 3 into granular form, and wash with boiling water until the supernatant is clear;

[0062] Step 5. Filter and dry to obtain reactive polyarylether nitrile oxime (PEA pellets).

[0063] Perform DSC test on the reactive polyarylether nitrile oxime (PEA pellets) prepared in Example 2, and the results are as Figure 2 shown. It is found that an obvious exothermic reaction peak appears at 201 °C, and the enthalpy is 80.49 J / g.

[0064] Example 4

[0065] A preparation method of a loose nanofiltration membrane based on reactive polyarylether nitrile oxime comprises the following steps:

[0066] Step 1. Add 0.7 g of the reactive polyarylether nitrile oxime (PEA granular material) obtained in Example 1 and 4.98 g of N,N'-dimethylformamide (DMF) solvent into a reaction vessel, stir and mix evenly to obtain a casting solution with a solid content of 15 wt%;

[0067] Step 2. Magnetically stir the casting solution prepared in Step 1 at 25 °C for 24 h;

[0068] Step 3. Perform ultrasonic defoaming treatment on the solution obtained after stirring in Step 2. Set the ultrasonic water bath at 35 °C, keep it for 25 min, and let it stand in the water bath for 10 min after ultrasonic treatment to obtain a casting solution;

[0069] Step 4. Pour 2 mL of the casting solution obtained in Step 3 evenly onto a glass plate, scrape and coat it evenly with a four-sided spreader, put it into a deionized water coagulation bath to complete phase inversion, and soak it in deionized water for 24 hours (change the water after 12 h of soaking);

[0070] Step 5. After soaking, take out the membrane sheet and air-dry it at room temperature for 24 h;

[0071] Step 6. The air-dried membrane sheets are placed in a forced-air oven and treated at 100 °C, 130 °C, and 160 °C for 2 hours respectively to obtain nanofiltration membranes.

[0072] The retention rate and permeation rate of the nanofiltration membrane sheets prepared in Example 4 are tested in a neutral aqueous solution of rhodamine B with a concentration of 50 mg / L, and the results are as Figure 3 shown. It can be Figure 3 seen that the retention rate of the membrane sheets after heat treatment at 100 °C is 87.44%, and the permeation rate is 179.03 L·(m 2 ·h·bar) -1 ; the retention rate of the membrane sheets after heat treatment at 130 °C is 91.73%, and the permeation rate is 127.87 L·(m 2 ·h·bar) -1 ; the retention rate of the membrane sheets after heat treatment at 160 °C is 92.11%, and the permeation rate is 36.34 L·(m 2 ·h·bar) -1 .

[0073] The membrane sheets after heat treatment at 130 °C are selected for the cyclic performance test, and the results are as Figure 5 shown. It can be seen that the retention rate is already lower than 95% at the second cycle, lower than 90% after the fifth cycle, and lower than 80% after the tenth cycle. The membrane sheets are damaged at the twentieth cycle and basically do not have the retention ability.

[0074] Rhodamine B solutions with different pH values and a concentration of 50 mg / L are prepared using hydrochloric acid and sodium hydroxide aqueous solutions. The membrane sheets after heat treatment at 130 °C are selected for the acid and alkali resistance test, and the results are as Figure 6 shown. It can be seen that for the rhodamine B solution prepared with 10% hydrochloric acid solution, the retention rate is 63.28%, and the permeation rate is 6.95 L·(m 2 ·h·bar) -1 ; for the rhodamine B solution prepared with 5% hydrochloric acid solution, the retention rate is 85.97%, and the permeation rate is 32.75 L·(m 2 ·h·bar) -1 ; for the rhodamine B solution prepared with 2.5% hydrochloric acid solution, the retention rate is 89.34%, and the permeation rate is 59.28 L·(m 2 ·h·bar) -1 ; for the rhodamine B solution prepared with 1% hydrochloric acid solution, the retention rate is 96.13%, and the permeation rate is 80.65 L·(m 2 ·h·bar) -1 ; for the rhodamine B solution prepared with 10% sodium hydroxide solution, the retention rate is 95.78%, and the permeation rate is 16.98 L·(m 2 ·h·bar)-1 .

[0075] Example 5

[0076] A preparation method of a loose nanofiltration membrane based on reactive polyarylether nitrile oxime, comprising the following steps:

[0077] Step 1. Add 0.7 g of the reactive polyarylether nitrile oxime (PEA pellet) obtained in Example 1, 0.014 g of ferric chloride and 4.98 g of N-N'-dimethylformamide (DMF) solvent into a reaction vessel in sequence, stir and mix evenly to obtain a casting solution with a solid content of 15 wt%;

[0078] Step 2. Magnetically stir the casting solution prepared in Step 1 at 25 °C for 24 h;

[0079] Step 3. Perform ultrasonic defoaming treatment on the solution obtained after stirring in Step 2, set the ultrasonic water bath at 35 °C, keep it for 25 min, and let it stand in the water bath for 10 min after ultrasonic treatment to obtain a casting solution;

[0080] Step 4. Pour 2 mL of the casting solution obtained in Step 3 evenly onto a glass plate, scrape and coat it evenly with a four-sided spreader, and put it into a deionized water coagulation bath to complete phase inversion, and then soak it in deionized water for 24 hours (change the water after soaking for 12 h);

[0081] Step 5. After soaking, take out the membrane sheet and air-dry it at room temperature for 24 h;

[0082] Step 6. Place the air-dried membrane sheet in a forced-air oven and treat it at 100 °C, 130 °C and 160 °C for 2 hours respectively to obtain a nanofiltration membrane.

[0083] The retention rate and permeability of the nanofiltration membrane sheet prepared in Example 5 were tested in a neutral aqueous solution of rhodamine B with a concentration of 50 mg / L, and the results are as Figure 4 shown. It can be seen from Figure 4 that the retention rate of the membrane sheet after heat treatment at 100 °C is 90.80%, and the permeability is 85.09 L·(m 2 ·h·bar) -1 ; the retention rate of the membrane sheet after heat treatment at 130 °C is 97.39%, and the permeability is 81.36 L·(m 2 ·h·bar) -1 ; the retention rate of the membrane sheet after heat treatment at 160 °C is 97.53%, and the permeability is 11.93 L·(m 2 ·h·bar) -1 .

[0084] Select the membrane sheet after heat treatment at 130 °C for cyclic performance test, and the results are as Figure 5As shown, it can be seen that the rejection rate remains above 95% after 6 cycles, still above 90% after 17 cycles, and above 85% after 20 cycles.

[0085] Rhodamine B solutions with a concentration of 50 mg / L at different pH values were prepared using hydrochloric acid and sodium hydroxide aqueous solutions. Membrane samples heat-treated at 130 °C were selected for acid and alkali resistance tests. The results are as Figure 6 shown. It can be seen that for the Rhodamine B solution prepared with 10% hydrochloric acid solution, the rejection rate is 75.94% and the permeation rate is 21.83 L·(m 2 ·h·bar) -1 ; for the Rhodamine B solution prepared with 5% hydrochloric acid solution, the rejection rate is 93.75% and the permeation rate is 35.24 L·(m 2 ·h·bar) -1 ; for the Rhodamine B solution prepared with 2.5% hydrochloric acid solution, the rejection rate is 97.39% and the permeation rate is 74.59 L·(m 2 ·h·bar) -1 ; for the Rhodamine B solution prepared with 1% hydrochloric acid solution, the rejection rate is 97.42% and the permeation rate is 81.36 L·(m 2 ·h·bar) -1 ; for the Rhodamine B solution prepared with 10% sodium hydroxide solution, the rejection rate is 97.02% and the permeation rate is 23.75 L·(m 2 ·h·bar) -1 .

Claims

1. A reactive polyarylether nitrile oxime, characterized in that: The reactive polyarylether nitrile oxime is a random copolymer formed by randomly distributing three structural units A, B and C in a polymer long chain, wherein the molar ratio of the three structural units A, B and C is A:B:C=(0.5-1):(4-6):(3-4), and the structural formulas of the three structural units A, B and C are as follows:

2. A method for preparing a reactive polyarylether nitrile oxime, characterized in that: The following steps are involved: Step 1. adding 10 parts by weight of poly(arylene ether nitrile) to 50 to 100 parts by weight of a solvent, stirring at 80 to 100° C. to obtain a homogeneous solution; Step 2. Add 1 part by mass of a base, 1 to 2 parts by mass of sodium bicarbonate and 6 to 12 parts by mass of hydroxylamine hydrochloride to the homogeneous solution obtained in step 1, and stir the reaction at 60 to 120° C. for 12 to 48 hours; Step 3. Soak the material after the reaction in step 2 in anhydrous ethanol for 12 to 24 hours; Step 4. crush the material processed in step 3 into particles and wash until the supernatant is clear; Step 5. Filter and dry to obtain reactive polyarylether nitrile oxime.

3. The method for preparing the reactive polyarylether nitrile oxime according to claim 2, characterized in that: The solvent in step 1 is N-N'dimethylformamide, N-N'dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

4. The method for preparing the reactive polyarylether nitrile oxime according to claim 2, characterized in that: The alkali in step 2 is sodium hydroxide or potassium hydroxide.

5. The method for preparing reactive polyarylether nitrile oxime according to claim 2, characterized in that: The chemical structural formula of the poly(arylene ether nitrile) in step 1 is:

6. The method for preparing reactive polyarylether nitrile oxime according to claim 2, characterized in that: The ratio of oxime group to carboxyl group in the reactive polyarylethernitrile oxime is adjusted by controlling the amount of base added, the molecular weight of the polyarylethernitrile and the amount of hydroxylamine hydrochloride added.

7. The method for preparing reactive polyarylether nitrile oxime according to claim 6, characterized in that: When the molecular weight of the polyarylether nitrile is less than 60,000, 1 part by mass of a base, 1 to 1.5 parts by mass of sodium bicarbonate and 10 to 12 parts by mass of hydroxylamine hydrochloride are added in step 2, and the oxime group in the obtained reactive polyarylether nitrile oxime is the main group; when the molecular weight of the polyarylether nitrile is greater than 60,000, 1 part by mass of a base, 1 to 2 parts by mass of sodium bicarbonate and 10 to 12 parts by mass of hydroxylamine hydrochloride are added in step 2, and the reaction time is controlled at 12 to 24 hours, the oxime group in the obtained reactive polyarylether nitrile oxime is the main group.

8. A method for preparing a loose nanofiltration membrane based on reactive polyarylether nitrile oxime, characterized in that: The following steps are involved: Step 1. In a reaction vessel, the reactive polyarylether nitrile oxime obtained by the method according to any one of claims 2 to 7 and 0.1 to 10 wt % of ferric chloride equivalent to the mass of the reactive polyarylether nitrile oxime are sequentially added, and then a solvent is added, and the mixture is stirred and mixed to obtain a casting solution having a solid content of 10 to 20 wt %; Step 2. The casting solution prepared in step 1 is magnetically stirred at 25-40° C. for 12-24 hours; Step 3. Perform ultrasonic defoaming treatment on the solution obtained after stirring in step 2, set an ultrasonic water bath at 30-40°C, maintain for 25-60 minutes, and let it stand in the water bath after the ultrasonic treatment to obtain a casting solution; Step 4. Pour the casting solution obtained in step 3 evenly onto a glass plate, apply it evenly by scraping, put it into a coagulation bath to complete phase inversion, and then soak it in deionized water for 24 to 48 hours; Step 5. After soaking, take out the membrane and dry it in the shade at room temperature; Step 6. The membrane piece after air drying is dried at 80-200° C. for 2 hours to obtain a nanofiltration membrane.

9. The method for preparing a loose nanofiltration membrane based on reactive polyarylether nitrile oxime according to claim 8, characterized in that: The solvent in step 1 is N-N'dimethylformamide, N-N'dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

10. The method for preparing a loose nanofiltration membrane based on reactive polyarylether nitrile oxime according to claim 8, characterized in that: In step 4, the coagulation bath is deionized water, hydrochloric acid aqueous solution or ethanol aqueous solution.

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