La-MOF-COOH / AO-PAN composite membrane material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of membrane material preparation and water treatment, and discloses a La-MOF-COOH / AO-PAN composite membrane material and a preparation method and application thereof, and the preparation method of the membrane comprises the following steps: preparing a PAN membrane; preparing an AO-PAN membrane; the preparation method comprises the following steps: preparing La-MOF-COOH; and the preparation of the La-MOF-COOH / AO-PAN film is carried out. The composite membrane material is composed of modified polyacrylonitrile fibers, metal lanthanum and an organic ligand. Amino groups and hydroxyl groups in amidoximated PAN participate in hydrogen bonds and covalent interaction, so that the interfacial compatibility and stability of La-MOF-COOH and AO-PAN are improved, agglomeration of La-MOF-COOH filler is avoided, the structural uniformity, stability and functionality of the La-MOF-COOH / AO-PAN composite membrane are improved, and the composite membrane has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane material preparation and water treatment, in particular to a La-MOF-COOH / AO-PAN composite membrane material and a preparation method and application thereof. Background Art

[0002] Phosphorus pollution is one of the main sources of surface water pollution and poses a serious threat to aquatic ecosystems. Phosphorus is one of the key limiting elements for the growth of aquatic plants and algae. Excessive phosphorus content in water bodies can lead to abnormal reproduction of algae and phytoplankton, forming algal blooms or red tides, and destroying the ecological balance of water bodies. Excessive phosphorus mainly comes from agricultural fertilization, domestic wastewater and industrial wastewater. Ecological degradation caused by phosphorus pollution may damage related industries such as fisheries, tourism and agriculture, and increase the operating costs of water treatment facilities.

[0003] Metal-Organic Frameworks (MOFs) are porous materials assembled from metal ions or organic clusters. They have adjustable pore size structures, and a variety of metal nodes and organic ligands that are adjustable. MOFs have attracted much attention in water treatment and phosphorus removal due to their excellent structural characteristics and functionalization potential. Most MOF materials exist in the form of powders, which have limitations such as inconvenient recycling and are difficult to use on a large scale in water treatment. The advantages of polyacrylonitrile membranes (PAN) in water treatment include excellent chemical and mechanical stability, low cost, and easy functional modification. These characteristics make PAN a high-quality substrate material for the deposition of MOF materials.

[0004] Chinese patent publication CN 118179449A discloses a method for preparing and using a porous lanthanum-based metal organic framework La MOF-XC adsorbent and filter membrane, wherein the MOF mixed dispersion is vacuum filtered to a glass fiber filter membrane to obtain a LaMOF-XC filter membrane, thereby avoiding secondary pollution caused by powder materials in actual water applications. However, in the preparation of the membrane material, the MOF filler and the glass fiber filter membrane lack interaction, which may cause the MOF to fall off during long-term use, limiting its practical application.

[0005] Chinese patent publication CN 108310985A discloses a MOF-199@PVDF matrix blended membrane with high anti-pollution performance and a preparation method. The membrane material is prepared by blending PVDF, metal organic framework material MOF-199 and porogen through a phase inversion method. The pure water flux of the blended membrane is greatly improved. However, due to the poor interface compatibility between filler and polymer in direct blending, filler aggregation reduces the stability of MOF on the membrane.

[0006] Specifically, the prior art still has the following deficiencies:

[0007] Insufficient interfacial bonding force causes MOF particles to fall off. This is because there is no interaction force between the MOF filler and the membrane matrix, and it only relies on physical coating or weak van der Waals forces. It lacks chemical bonding or strong anchoring mechanisms, making it difficult to form a continuous interfacial bonding network, so the interface is prone to slippage or breakage. This weakly bonded interface is prone to slippage under dynamic water flow or mechanical stress, causing MOF particles to gradually detach from the membrane surface. MOF particles are only fixed by physical contact on the surface, and particles at the edge of the pores are more susceptible to falling off due to hydraulic shear. In long-term use, the shedding rate may increase significantly with the accumulation of interface fatigue.

[0008] Poor interfacial compatibility between fillers and polymers, which is caused by filler agglomeration, sedimentation and weak interactions, will impair adsorption performance. If the filler is not evenly dispersed, it will lead to a reduction in effective adsorption sites, affecting the overall performance. The interfacial compatibility between inorganic particles and polymers is critical to ensure the high performance of composite materials. Due to the poor interfacial compatibility between MOFs and polymers, performance improvements are often not achieved, which leads to interfacial defects. The filler surface only relies on physical interactions such as van der Waals forces or hydrogen bonds to bind to the polymer, and is prone to debonding under thermal / mechanical stress.

[0009] Long-term stability defects can cause the risk of secondary pollution. pH fluctuations, temperature changes or the presence of organic solvents in the water treatment environment will weaken the interface between MOF and the membrane. The composite membrane will be loosened in the interface under temperature fluctuations, humidity changes or mechanical stress. The long-term stability of MOF membrane materials in the water environment is insufficient, reducing adsorption performance. The detached MOF particles may diffuse through the water body, causing secondary pollution.

[0010] Therefore, due to the poor interfacial compatibility between the filler and the polymer, the filler is difficult to disperse in the polymer film and forms no force or weak force between the filler and the polymer film, which seriously destroys the stability of the composite film and reduces the practical feasibility of the composite film. Summary of the invention

[0011] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a La-MOF-COOH / AO-PAN composite membrane material and a preparation method and application thereof.

[0012] The technical solution adopted by the present invention to solve its technical problem is:

[0013] A method for preparing a La-MOF-COOH / AO-PAN composite membrane material comprises the following steps:

[0014] (1) Preparation of PAN membrane: polyacrylonitrile PAN powder and porogen are added to an organic solvent, heated and stirred in a water bath, then allowed to stand for degassing, poured onto a glass plate and scraped, and phase-transformed into a PAN membrane in a coagulation bath;

[0015] (2) Preparation of AO-PAN membrane: dissolving hydroxylamine hydrochloride in water and methanol solvent, adjusting the pH with an alkaline reagent, placing the membrane in step (1) in the solution and heating it for reaction, and then rinsing it with deionized water to obtain an AO-PAN membrane;

[0016] (3) Preparation of La-MOF-COOH: Weigh metal salt and organic ligand and add them to an organic solvent, transfer the mixed solution to a high-pressure reactor, place it in an oven for hydrothermal reaction, cool and discard the supernatant, collect the precipitate by centrifugation, wash, dry, and collect La-MOF-COOH powder;

[0017] (4) Preparation of La-MOF-COOH / AO-PAN membrane

[0018] 1) Preparation of La-MOF-COOH dispersion

[0019] Weigh the La-MOF-COOH powder obtained in step (3) into the dispersion liquid, place the mixture in a magnetic stirrer, and stir at room temperature for preliminary dispersion; then place the mixture in a probe ultrasound machine for ultrasonic treatment at 500 W, and cool in an ice bath to prevent overheating, thereby obtaining a La-MOF-COOH dispersion liquid;

[0020] 2) Stabilization

[0021] Weigh a surfactant and add it to the dispersion in step 1), stir and disperse evenly to avoid secondary agglomeration, to obtain a mixed solution;

[0022] 3) Vacuum filtration load

[0023] The AO-PAN membrane of step (2) was laid flat on the surface of the filter membrane and soaked in deionized water for 5 minutes for pre-wetting; then the mixed solution of step 2) was slowly poured in, the flow rate was controlled at 1 mL / min, and the loading was repeated three times, and each time the membrane was drained after 5 minutes; after loading, the residual droplets on the membrane surface were removed with filter paper to obtain a composite membrane;

[0024] 4) Post-processing and interface strengthening

[0025] The activator is prepared and put into a buffer solution, and the pH of the buffer solution is adjusted. The composite membrane of step 3) is immersed in the above buffer solution to activate the carboxyl group and the amino group; and then rinsed with deionized water to obtain a La-MOF-COOH / AO-PAN composite membrane material.

[0026] Furthermore, in step (1), the porogen is one of polyvinyl pyrrolidone, polyethylene glycol or silicon dioxide;

[0027] Alternatively, in step (1), the ratio of PAN powder, porogen, and organic solvent g:g:mL is 15-18:5-15:100;

[0028] Alternatively, the organic solvent in step (1) is one or a mixed solvent of two or more selected from N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide;

[0029] Alternatively, in step (1), the heating temperature in the water bath is 50°C to 70°C, and the heating time is 6h to 10h;

[0030] Alternatively, the coagulation bath condition for the phase inversion in step (1) is one of water or ethanol solvent.

[0031] Furthermore, in step (2), the ratio of hydroxylamine hydrochloride, water, and methanol solvent is 2-8:30-75:30-75 in g:mL:mL;

[0032] Alternatively, the alkaline reagent in step (2) is one of sodium carbonate, sodium hydroxide or sodium bicarbonate;

[0033] Alternatively, in step (2), the pH is adjusted to 7-8 using an alkaline reagent;

[0034] Alternatively, in step (2), the heating temperature is 30° C. to 80° C., and the heating time is 2 h to 6 h.

[0035] Furthermore, in step (3), the ratio of metal salt, organic ligand and organic solvent g:g:mL is 2-4:2-3:100.

[0036] Furthermore, in step (3), the metal salt is one of lanthanum chloride heptahydrate or lanthanum nitrate hexahydrate;

[0037] Alternatively, the organic ligand in step (3) is one of terephthalic acid or pyromellitic acid;

[0038] Alternatively, the hydrothermal conditions in step (3) are a heating temperature of 80 to 150° C. and a reaction time of 8 to 24 h;

[0039] Alternatively, the drying conditions in step (3) are a temperature of 30 to 80° C. and a heating time of 8 to 24 hours.

[0040] Further, in step (4), the dispersion liquid in 1) is one of water or ethanol;

[0041] Alternatively, the surfactant in step (4) is one of sodium dodecylbenzene sulfonate or sodium dodecyl diphenyl ether disulfonate;

[0042] Alternatively, 0.01-0.2 g of a surfactant is added to every 50-200 mL of the dispersion in step 1);

[0043] Alternatively, the stirring and dispersing time in step (4) is 10-60 min.

[0044] Furthermore, in step (4), the activating agent is one or two of EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride), NHS (N-hydroxysuccinimide), and DCC (dicyclohexylcarbodiimide);

[0045] Alternatively, the concentration of the activator in step (4) is 0.5-5 mM;

[0046] Alternatively, the buffer in step (4) is PBS, i.e., one of phosphate buffer or borate buffer;

[0047] Alternatively, adjust the buffer pH to 5-8;

[0048] Alternatively, the soaking time in step (4) is 0.5-3h.

[0049] Furthermore, in step (4), the ratio of the dispersion in 1) to the La-MOF-COOH powder is 100-200:0.3.

[0050] The La-MOF-COOH / AO-PAN composite membrane material was prepared by the preparation method described above.

[0051] Application of the La-MOF-COOH / AO-PAN composite membrane material as described above in phosphate adsorption and / or removal.

[0052] The advantages and positive effects achieved by the present invention are:

[0053] 1. Improvement of interface compatibility and structural uniformity

[0054] In the present invention, La-MOF-COOH forms a covalent bond with the amino group in AO-PAN, and the amino group and hydroxyl group in AO-PAN participate in hydrogen bonding, thereby enhancing the interface bonding between the filler and the matrix. This prevents the agglomeration of the La-MOF-COOH filler and ensures the structural uniformity of the membrane. The structural uniformity improves the mechanical strength and durability of the membrane and ensures the uniform distribution of functional groups (such as adsorption sites). The consistency and reliability of the membrane in practical applications are ensured. Traditional methods mostly rely on a single effect (such as physical dispersion or surface modification), while the present invention significantly reduces the risk of filler phase separation through the synergistic effect of covalent bonds and hydrogen bonds.

[0055] 2. Enhanced stability and durability

[0056] The strong combination of covalent bonds and hydrogen bonds in the present invention improves the chemical and physical stability of the membrane, especially in complex environments (such as acid-base solutions, high temperatures or high humidity). The service life of the membrane is extended, the maintenance cost is reduced, and it is suitable for industrial continuous operation. The stability ensures that the performance of the membrane is maintained in long-term use, which is particularly suitable for the field of water treatment. The dynamic reversibility of hydrogen bonds implies self-repair potential. When the local structure is damaged, the hydrogen bond network may be reformed to maintain the overall performance of the membrane.

[0057] 3. Improvement of adsorption performance

[0058] In the present invention, in addition to forming an inner sphere complex with phosphate, the carboxyl group and phosphate are bonded through hydrogen bonds, which enhances the adsorption site and improves the adsorption selectivity for phosphate. In addition, the electrostatic interaction between the amino group and the phosphate further stabilizes the hydrogen bond network, improving the adsorption selectivity and capacity. The membrane is more efficient in adsorbing target substances (such as phosphates). This multiple interaction mechanism can be applied to the adsorption of trace pollutants (such as low-concentration phosphates in surface water), providing new solutions for difficult fields such as surface water remediation and treatment. The adsorption performance not only relies on traditional coordination chemistry, but also combines the "dual drive" mode of electrostatic interaction and hydrogen bonding.

[0059] 4. Simple operation and mild preparation conditions, environmental friendliness and economy

[0060] The preparation process of the present invention emphasizes simple operation, mild conditions, and no extreme conditions. The energy consumption and technical threshold in the production process are reduced. At the same time, the impact on the environment is reduced, which is in line with the development trend of green chemistry. Mild preparation conditions and versatility imply the environmental friendliness and cost-effectiveness of the membrane in production and use. The use of high-energy consumption processes and toxic solvents is reduced, and production costs are reduced. The efficient adsorption performance reduces the subsequent processing steps and improves the economy. The membrane may achieve a circular economy by recycling and reusing La-MOF-COOH filler. For example, after adsorption saturation, the filler is desorbed and regenerated by simple chemical treatment for the next round of membrane preparation.

[0061] 5. Multifunctionality and expansion of application prospects

[0062] The membrane of the present invention integrates structural uniformity, stability and excellent adsorption performance, and has multifunctional characteristics. The functional groups can be adjusted according to needs to meet the customized needs of different scenarios such as water treatment, gas separation, and catalytic carriers. The application range is expanded. The prepared La-MOF-COOH / AO-PAN membrane has excellent comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a Fourier transform infrared spectrum of the AO-PAN film prepared in Example 1 of the present invention;

[0064] Figure 2 is a Fourier transform infrared spectrum of the La-MOF-COOH / AO-PAN film prepared in Example 1 of the present invention;

[0065] Figure 3 This is an electronic scanning image of the La-MOF-COOH / AO-PAN composite film prepared in Example 1 of the present invention before ultrasound;

[0066] Figure 4 This is an electronic scanning image of the La-MOF-COOH / AO-PAN composite film obtained in Example 1 of the present invention after ultrasound treatment;

[0067] Figure 5 This is an electronic scanning image of the La-MOF / PAN composite film prepared in Comparative Example 1 of the present invention before ultrasound;

[0068] Figure 6 This is an electronic scanning image of the La-MOF / PAN composite film obtained in Comparative Example 1 of the present invention after ultrasound treatment;

[0069] Figure 7 This is an electronic scanning image of the La-MOF-COOH / PAN composite film prepared in Comparative Example 2 of the present invention before ultrasound;

[0070] Figure 8 This is an electronic scanning image of the La-MOF-COOH / PAN composite film prepared in Comparative Example 2 of the present invention after ultrasound treatment;

[0071] Fig. 9 is a Fourier transform infrared spectrum of the AO-PAN composite film prepared in Comparative Example 3 of the present invention;

[0072] Fig.10 This is an electronic scanning image of the La-MOF / AO-PAN composite film prepared in Comparative Example 3 of the present invention before ultrasound treatment;

[0073] Fig.11 This is an electron scanning image of the La-MOF / AO-PAN composite membrane prepared in Comparative Example 3 of the present invention after ultrasound treatment. DETAILED DESCRIPTION

[0074] The present invention will be further described below in conjunction with the embodiments. The following embodiments are descriptive rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0075] The various experimental operations involved in the specific embodiments are all routine techniques in the art. For parts not specially annotated in this document, ordinary technicians in the art can implement them by referring to various commonly used reference books, scientific and technological literature or related instructions, manuals, etc. before the filing date of this invention.

[0076] A method for preparing a La-MOF-COOH / AO-PAN composite membrane material comprises the following steps:

[0077] (1) Preparation of PAN membrane: polyacrylonitrile PAN powder and porogen are added to an organic solvent, heated and stirred in a water bath, then allowed to stand for degassing, poured onto a glass plate and scraped, and phase-transformed into a PAN membrane in a coagulation bath;

[0078] (2) Preparation of AO-PAN membrane: dissolving hydroxylamine hydrochloride in water and methanol solvent, adjusting the pH with an alkaline reagent, placing the membrane in step (1) in the solution and heating it for reaction, and then rinsing it with deionized water to obtain an AO-PAN membrane;

[0079] (3) Preparation of La-MOF-COOH: Weigh metal salt and organic ligand and add them to an organic solvent, transfer the mixed solution to a high-pressure reactor, place it in an oven for hydrothermal reaction, cool and discard the supernatant, collect the precipitate by centrifugation, wash, dry, and collect La-MOF-COOH powder;

[0080] (4) Preparation of La-MOF-COOH / AO-PAN membrane

[0081] 1) Preparation of La-MOF-COOH dispersion

[0082] Weigh the La-MOF-COOH powder obtained in step (3) into the dispersion liquid, place the obtained mixture in a magnetic stirrer, and stir at room temperature for preliminary dispersion; then place the mixture in a probe ultrasound machine and perform ultrasound treatment at 500 W, and cool in an ice bath to prevent overheating, thereby obtaining a La-MOF-COOH dispersion liquid;

[0083] 2) Stabilization

[0084] Weigh a surfactant and add it to the dispersion in step 1), stir and disperse evenly to avoid secondary agglomeration, to obtain a mixed solution;

[0085] 3) Vacuum filtration load

[0086] The AO-PAN membrane of step (2) was laid flat on the surface of the filter membrane and soaked in deionized water for 5 minutes for pre-wetting; then the mixed solution of step 2) was slowly poured in, the flow rate was controlled at 1 mL / min, and the loading was repeated three times, and each time the membrane was drained after 5 minutes; after loading, the residual droplets on the membrane surface were removed with filter paper to obtain a composite membrane;

[0087] 4) Post-processing and interface strengthening

[0088] The activator is prepared and placed in a buffer solution, and the pH of the buffer solution is adjusted. The composite membrane of step 3) is immersed in the buffer solution with adjusted pH to activate the carboxyl and amino groups; and then rinsed with deionized water to obtain a La-MOF-COOH / AO-PAN composite membrane material.

[0089] Preferably, the porogen in step (1) is one of polyvinyl pyrrolidone, polyethylene glycol or silicon dioxide;

[0090] Alternatively, in step (1), the ratio of PAN powder, porogen, and organic solvent g:g:mL is 15-18:5-15:100;

[0091] Alternatively, the organic solvent in step (1) is one or a mixed solvent of two or more selected from N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide;

[0092] Alternatively, in step (1), the heating temperature in the water bath is 50°C to 70°C, and the heating time is 6h to 10h;

[0093] Alternatively, the coagulation bath condition for the phase inversion in step (1) is one of water or ethanol solvent.

[0094] Preferably, in step (2), the ratio of hydroxylamine hydrochloride, water, and methanol solvent is 2-8:30-75:30-75 in g:mL:mL;

[0095] Alternatively, the alkaline reagent in step (2) is one of sodium carbonate, sodium hydroxide or sodium bicarbonate;

[0096] Alternatively, in step (2), the pH is adjusted to 7-8 using an alkaline reagent;

[0097] Alternatively, in step (2), the heating temperature is 30° C. to 80° C., and the heating time is 2 h to 6 h.

[0098] Preferably, in step (3), the ratio of metal salt, organic ligand, and organic solvent (g:g:mL) is 2-4:2-3:100.

[0099] Preferably, the metal salt in step (3) is one of lanthanum chloride heptahydrate or lanthanum nitrate hexahydrate;

[0100] Alternatively, the organic ligand in step (3) is one of terephthalic acid or pyromellitic acid;

[0101] Alternatively, the hydrothermal conditions in step (3) are a heating temperature of 80 to 150° C. and a reaction time of 8 to 24 h;

[0102] Alternatively, the drying conditions in step (3) are a temperature of 30 to 80° C. and a heating time of 8 to 24 hours.

[0103] Preferably, the dispersion in step (4) 1) is one of water or ethanol;

[0104] Alternatively, the surfactant in step (4) is one of sodium dodecylbenzene sulfonate or sodium dodecyl diphenyl ether disulfonate;

[0105] Alternatively, 0.01-0.2 g of a surfactant is added to every 50-200 mL of the dispersion in step 1);

[0106] Alternatively, the stirring and dispersing time in step (4) is 10-60 min.

[0107] Preferably, the activating agent in step (4) is one or two of EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride), NHS (N-hydroxysuccinimide), and DCC (dicyclohexylcarbodiimide);

[0108] Alternatively, the concentration of the activator in step (4) is 0.5-5 mM;

[0109] Alternatively, the buffer in step (4) is PBS, i.e., one of phosphate buffer or borate buffer;

[0110] Alternatively, adjust the buffer pH to 5-8;

[0111] Alternatively, the soaking time in step (4) is 0.5-3h.

[0112] Preferably, in step (4), the ratio of the dispersion in 1) to the La-MOF-COOH powder is 100-200:0.3 in mL:g.

[0113] The La-MOF-COOH / AO-PAN composite membrane material was prepared by the preparation method described above.

[0114] Application of the La-MOF-COOH / AO-PAN composite membrane material as described above in phosphate adsorption and / or removal.

[0115] Specifically, the relevant preparation and detection are as follows:

[0116] Example 1

[0117] A La-MOF-COOH / AO-PAN composite membrane material, the synthesis preparation steps of which are as follows:

[0118] 1. Preparation of PAN (polyacrylonitrile) membrane: Dissolve 15g PAN (polyacrylonitrile) powder and 15g polyvinyl pyrrolidone in 100mL N,N-dimethylformamide, heat and stir at 60℃ in a water bath for 8h, let it stand to degas, pour it onto a glass plate and scrape it, and transform it into PAN membrane in a water coagulation bath.

[0119] 2. Preparation of AO-PAN membrane: Dissolve 5 g of hydroxylamine hydrochloride in 50 mL of water and 50 mL of methanol solvent, adjust the pH to 8 with sodium hydroxide reagent, put the membrane prepared in step 1 into the solution and heat it at 60°C for 4 h, rinse with deionized water to obtain AO-PAN membrane.

[0120] 3. Preparation of La-MOF-COOH: Weigh 3.73 g of lanthanum chloride heptahydrate and 2.54 g of pyromellitic acid and add them to 100 mL of N,N-dimethylformamide solvent. Transfer the mixed solution to a reactor and place it in an oven at 120°C for 12 h. Centrifuge and wash, collect the precipitate and dry it at 80°C for 12 h to obtain La-MOF-COOH powder.

[0121] 4. Preparation of La-MOF-COOH / AO-PAN membrane

[0122] (1) Preparation of La-MOF-COOH dispersion

[0123] Accurately weigh 20 mg of the powder from step 3 and dissolve it in 100 mL of ethanol solvent. Place the mixture in a magnetic stirrer and rotate at 300 rpm for 30 min at room temperature for preliminary dispersion. Then place it in a probe ultrasound machine and perform ultrasound treatment at 500 W for 30 min. Cool it in an ice bath every 5 min to prevent overheating, and obtain a La-MOF-COOH dispersion.

[0124] (2) Stabilization

[0125] Weigh 0.1 g of sodium dodecylbenzene sulfonate and put it into 100 mL of the dispersion prepared in step (1). Stir for 10 min to disperse the mixture evenly and avoid secondary agglomeration.

[0126] (3) Vacuum filtration load

[0127] The membrane from step 2 was laid flat on the surface of the filter membrane and pre-wetted with deionized water for 5 minutes. Then the dispersion prepared in step (2) was slowly poured in, the flow rate was controlled to be 1 mL / min, and the loading was repeated three times, with each time interval of 5 minutes to drain. After loading, the membrane surface was gently pressed with filter paper to remove residual droplets, and a composite membrane was obtained.

[0128] (4) Post-processing and interface strengthening

[0129] Prepare a PBS buffer containing 5 mM EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride) and 2 mM NHS (N-hydroxysuccinimide), adjust the pH of the buffer to 7, and soak the composite membrane in step (3) for 2 h to activate the carboxyl and amino groups. Then rinse with deionized water to obtain the La-MOF-COOH / AO-PAN composite membrane material.

[0130] The Fourier transform infrared spectrum of the AO-PAN film prepared in this example is as follows: Figure 1 As shown by Figure 1 It can be seen that for the Fourier transform infrared spectrum of PAN, the peak intensity of the -CN group is significantly reduced, which means that the conversion of the -CN bond into the amidoxime group is feasible. -1 The peaks are significantly broadened and enhanced in the wavelength range, which is mainly due to the amidoxime reaction of PAN with -OH and -NH 2 The amount of AO-PAN increased. This further proves the existence of amidoxime groups. This example successfully prepared AO-PAN membrane.

[0131] The Fourier transform infrared spectrum of the La-MOF-COOH / AO-PAN film prepared in this example is shown in Figure 2 As shown in the Fourier transform infrared spectrum, the 3000-3500 cm -1 The band between -OH and -NH 2 The peaks of La-MOF-COOH / AO-PAN film are broader than those of La-MOF-COOH and AO-PAN, which promotes the formation of hydrogen bond network or covalent network on the surface, thus improving the interface descriptive properties.

[0132] The bonding stability between La-MOF-COOH and AO-PAN film was determined by electron scanning image characterization. The SEM image of the La-MOF-COOH / AO-PAN film prepared in this example is shown in FIG. Figure 3 As shown in FIG. 1 , the thickness of the composite film is 4.14±0.5 μm. The La-MOF-COOH / AO-PAN film was placed in a 70W water bath ultrasound treatment for 10 min. The SEM image of the composite film after ultrasound treatment is shown in FIG. Figure 4 As shown in Figure 3, the thickness of the composite film after ultrasound was 3.29 ± 0.5 μm. The results indicate that ultrasound removes the loosely adsorbed La-MOF-COOH layer and retains the chemically bonded / deeply embedded La-MOF-COOH.

[0133] The synergistic effect of hydrogen bonds and covalent bonds is the core force. The covalent bonds activated by EDC / NHS provide the main binding force, while hydrogen bonds as a secondary effect help disperse stress and enhance interfacial compatibility. The synergistic force between La-MOF-COOH and AO-PAN membrane improves interfacial stability. The covalent bonds formed by EDC / NHS activation synergize with the hydrogen bond network to anchor MOF particles in the polymer matrix. SEM shows that MOF is evenly distributed after ultrasound, with only slight fluctuations in thickness, verifying the strong binding properties of the interface. The results shown indicate that the sample La-MOF-COOH of Example 1 is fixed on the surface of the AO-PAN membrane. This process proves that the binding between La-MOF-COOH and the AO-PAN membrane is stable.

[0134] The La-MOF-COOH / AO-PAN membrane after ultrasound was placed in a phosphate solution for performance testing. The test conditions were: phosphate concentration of 2 mg / L, pH = 7. The phosphate removal rate of the La-MOF-COOH / AO-PAN membrane was measured to be 99.09%. The high phosphorus removal rate of the La-MOF-COOH / AO-PAN membrane proves that the La-MOF-COOH is stably bound to the AO-PAN membrane. MOF in the modified membrane is evenly dispersed to form continuous channels, providing a fast diffusion path for phosphate. This strong interface bonding keeps MOF particles stable in a dynamic environment, avoids the shedding of adsorption active sites, and ensures a 99.09% phosphate removal rate. The phosphorus removal performance of the La-MOF-COOH / PAN composite membrane directly depends on the interface stability and MOF retention rate. The strong binding dominated by covalent bonds and the dynamic repair assisted by hydrogen bonds are the key to inhibiting MOF shedding.

[0135] The organic ligand pyromellitic acid has good stability and modifiable carboxyl functional groups, which can form an interaction force with the modified PAN, help La-MOF-COOH to be evenly loaded on AO-PAN, and improve the interfacial compatibility between La-MOF-COOH and AO-PAN. Pyromellitic acid forms a covalent and hydrogen-bonded synergistic interface with the amino / hydroxyl groups of AO-PAN through the dual characteristics of multidentate coordination and modifiable carboxyl groups, solving the problem of MOF dispersion and stability in polymers. This molecular-level design strategy provides a theoretical basis for the development of high-performance composite membranes.

[0136] Comparative Example 1

[0137] A La-MOF / PAN composite membrane material, the material is a La-MOF / PAN composite membrane, and the synthesis preparation steps are as follows:

[0138] 1. Preparation of PAN (polyacrylonitrile) membrane: Dissolve 15g PAN (polyacrylonitrile) powder and 15g polyvinyl pyrrolidone in 100mL N,N-dimethylformamide, heat at 60℃ in a water bath and stir for 8h. After standing to degas, pour it onto a glass plate and scrape it. The water coagulation bath phase is transformed into PAN membrane.

[0139] 2. Preparation of La-MOF: Weigh 3.73 g of lanthanum chloride heptahydrate and 1.66 g of terephthalic acid and add them to 100 mL of N,N-dimethylformamide solvent. Transfer the mixed solution to a reactor and place it in an oven at 120°C for 12 h. Centrifuge and wash. Collect the precipitate and dry it at 80°C for 12 h to obtain La-MOF powder.

[0140] 3. Preparation of La-MOF / PAN membrane

[0141] (1) Preparation of La-MOF dispersion

[0142] Accurately weigh 20 mg of the powder from step 2 into 100 mL of ethanol solvent. Place the mixture in a magnetic stirrer and rotate at 300 rpm for 30 min at room temperature for preliminary dispersion. Then place it in a probe ultrasound machine and perform ultrasound treatment at 500 W for 30 min. Cool it in an ice bath every 5 min to prevent overheating, and obtain a La-MOF dispersion.

[0143] (2) Stabilization

[0144] Weigh 0.1 g of sodium dodecylbenzene sulfonate and put it into 100 mL of the dispersion prepared in step (1). Stir for 10 min to disperse the mixture evenly and avoid secondary agglomeration.

[0145] (3) Vacuum filtration load

[0146] The membrane of step 1 was laid flat on the surface of the filter membrane and pre-wetted with deionized water for 5 minutes. Then the dispersion of step (2) was slowly poured in, the flow rate was controlled at 1 mL / min, and the loading was repeated three times, with an interval of 5 minutes between each time. After loading, the residual droplets were gently pressed on the membrane surface with filter paper to remove them. The La-MOF / PAN membrane was obtained.

[0147] (4) Post-processing and interface strengthening

[0148] Prepare a PBS buffer containing 5 mM EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride) and 2 mM NHS (N-hydroxysuccinimide), adjust the pH of the buffer to 7, and soak the composite membrane in step (3) for 2 h to activate the carboxyl and amino groups. Then rinse with deionized water to obtain the La-MOF / PAN composite membrane material.

[0149] The bonding stability of La-MOF and PAN film was determined by electron scanning image characterization. The SEM image of the La-MOF / PAN film prepared in this comparative example 1 is as follows: Figure 5 As shown in FIG. 1 , the thickness of the composite film is 4.10±0.5 μm. The La-MOF / PAN film was placed in a 70W water bath ultrasound treatment for 10 min. The SEM image of the composite film after ultrasound treatment is shown in FIG. Figure 6 As shown, the thickness of the composite film after ultrasound is 351.0±0.5 nm. La-MOF falls off from the surface of the PAN membrane, and the overall thickness of the membrane will decrease accordingly. A large number of La-MOF particles are shaken off by ultrasound, and the film thickness is significantly lower than the initial 4.10±0.5μm range. The mechanical vibration and cavitation effect generated by water bath ultrasound will destroy the interaction force between La-MOF and the PAN membrane. The two are mainly combined through physical adsorption. Ultrasonic energy causes La-MOF particles to fall off the surface of the PAN membrane, and the binding stability decreases. It was observed that the distribution of La-MOF on the surface of the PAN membrane became sparse, and some areas that were originally covered with La-MOF but are now exposed appeared. The results show that the La-MOF of the comparative example 1 sample is unstable on the surface of the PAN membrane.

[0150] The La-MOF / PAN composite membrane after ultrasound was placed in a phosphate solution for performance testing. The test conditions were: phosphate concentration of 2 mg / L, pH = 7. The performance removal rate of the La-MOF / PAN composite membrane was measured to be 26.22%. The removal rate of phosphate by the composite membrane after ultrasound decreased. MOF shedding resulted in a reduction in the effective adsorption surface area and loss of adsorption active sites. The exposed PAN matrix (without MOF modification) had a low affinity for phosphate. At the same time, the interface defects hindered the mass transfer of the solution to the MOF pores, and the kinetic adsorption capacity decreased.

[0151] Comparative Example 2

[0152] A La-MOF-COOH / PAN composite membrane material, wherein the material is a La-MOF-COOH / PAN composite membrane, and the synthesis preparation steps are as follows:

[0153] 1. Preparation of PAN (polyacrylonitrile) membrane: Dissolve 15g PAN (polyacrylonitrile) powder and 15g polyvinyl pyrrolidone in 100mL N,N-dimethylformamide, heat at 60℃ in a water bath and stir for 8h. After standing to degas, pour it onto a glass plate and scrape it. The water coagulation bath phase is transformed into PAN membrane.

[0154] 2. Preparation of La-MOF-COOH: Weigh 3.73 g of lanthanum chloride heptahydrate and 2.54 g of pyromellitic acid and add them to 100 mL of N,N-dimethylformamide solvent. Transfer the mixed solution to a reactor and place it in an oven at 120°C for 12 h. Centrifuge and wash, collect the precipitate and dry it at 80°C for 12 h to obtain La-MOF-COOH powder.

[0155] 3. Preparation of La-MOF-COOH / PAN membrane

[0156] (1) Preparation of La-MOF-COOH dispersion

[0157] Accurately weigh 20 mg of the powder from step 2 and dissolve it in 100 mL of ethanol solvent. Place the mixture in a magnetic stirrer and rotate it at 300 rpm for 30 min at room temperature for preliminary dispersion. Then place it in a probe ultrasound machine and perform ultrasound treatment at 500 W for 30 min. Cool it in an ice bath every 5 min to prevent overheating, and obtain a La-MOF-COOH dispersion.

[0158] (2) Stabilization

[0159] Weigh 0.1 g of sodium dodecylbenzene sulfonate and put it into 100 mL of the dispersion prepared in step (1). Stir for 10 min to disperse the mixture evenly and avoid secondary agglomeration.

[0160] (3) Vacuum filtration load

[0161] The membrane of step 1 was laid flat on the surface of the filter membrane and pre-wetted with deionized water for 5 minutes. Then the dispersion of step (2) was slowly poured in, the flow rate was controlled at 1 mL / min, and the loading was repeated three times, with an interval of 5 minutes between each time. After loading, the residual droplets were gently pressed on the membrane surface with filter paper to remove them. The La-MOF-COOH / PAN membrane was obtained.

[0162] (4) Post-processing and interface strengthening

[0163] Prepare a PBS buffer containing 5 mM EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride) and 2 mM NHS (N-hydroxysuccinimide), adjust the pH of the buffer to 7, and soak the composite membrane in step (3) for 2 h to activate the carboxyl and amino groups. Then rinse with deionized water to obtain the La-MOF-COOH / PAN composite membrane material.

[0164] The bonding stability between La-MOF-COOH and PAN film was determined by electron scanning image characterization. The SEM image of the La-MOF-COOH / PAN film prepared in this comparative example 2 is as follows: Figure 7As shown, the thickness of the composite film is 4.08±0.5 μm. The La-MOF-COOH / PAN film was placed in a 70W water bath ultrasound treatment for 10 min. The SEM image of the composite film after ultrasound is shown in Figure 8 As shown, the thickness of the composite film after ultrasound is 1.68±0.5 μm. Ultrasonic action affects the bonding force between La-MOF-COOH particles and the PAN matrix. The bonding force is weakened by ultrasound, and separation is observed between the La-MOF-COOH particles and the PAN matrix. There are signs that particles fall off the surface of the matrix, which is manifested in the image as obvious gaps around the particles. Ultrasound causes the originally uniformly distributed La-MOF-COOH particles to agglomerate. In the SEM image, the particles can be seen to aggregate together to form larger agglomerates. The results shown show that La-MOF-COOH is peeled off from the surface of the PAN membrane after ultrasound in the comparative example 2 sample. This process proves that the bonding between La-MOF-COOH and the PAN membrane is unstable.

[0165] The La-MOF-COOH / PAN composite membrane after ultrasound was placed in a phosphate solution for performance testing. The test conditions were: phosphate concentration of 2 mg / L, pH = 7. The performance removal rate of the La-MOF-COOH / PAN composite membrane was measured to be 29.75%. Phosphate was captured by MOF through coordination (La-OP) and other mechanisms, and the detachment of La-MOF-COOH directly weakened these effects. The shedding of MOF directly affected the ability to capture phosphate. MOF shedding directly led to the effective La 3+ The number of active sites is reduced, and the exposed PAN substrate has no affinity for phosphate.

[0166] Comparative Example 3

[0167] A La-MOF / AO-PAN composite membrane material and a preparation method and application thereof. The material is a La-MOF / AO-PAN composite membrane. The synthesis preparation steps are as follows:

[0168] 1. Preparation of PAN (polyacrylonitrile) membrane: Dissolve 15g PAN (polyacrylonitrile) powder and 15g polyvinyl pyrrolidone in 100mL N,N-dimethylformamide, heat at 60℃ in a water bath and stir for 8h. After standing to degas, pour it onto a glass plate and scrape it. The water coagulation bath phase is transformed into PAN membrane.

[0169] 2. Preparation of AO-PAN membrane: Dissolve 5 g of hydroxylamine hydrochloride in 50 mL of water and 50 mL of methanol solvent, adjust the pH to 8 with sodium hydroxide reagent, put the membrane prepared in step 1 into the solution and heat it at 60°C for 4 h, rinse with deionized water to obtain AO-PAN membrane.

[0170] 3. Preparation of La-MOF: Weigh 3.73 g of lanthanum chloride heptahydrate and 1.66 g of terephthalic acid and add them to 100 mL of N,N-dimethylformamide solvent. Transfer the mixed solution to a reactor and place it in an oven at 120°C for 12 h. Centrifuge and wash, collect the precipitate and dry it at 80°C for 12 h to obtain La-MOF powder.

[0171] 4. Preparation of La-MOF / AO-PAN membrane

[0172] (1) Preparation of La-MOF dispersion

[0173] Accurately weigh 20 mg of the powder from step 3 and dissolve it in 100 mL of ethanol solvent. Place the mixture in a magnetic stirrer and rotate it at 300 rpm for 30 min at room temperature for preliminary dispersion. Then place it in a probe ultrasound machine and perform ultrasound treatment at 500 W for 30 min. Cool it in an ice bath every 5 min to prevent overheating, and obtain a La-MOF dispersion.

[0174] (2) Stabilization

[0175] Weigh 0.1 g of sodium dodecylbenzene sulfonate and put it into 100 mL of the dispersion prepared in step (1). Stir for 10 min to disperse the mixture evenly and avoid secondary agglomeration.

[0176] (3) Vacuum filtration load

[0177] The membrane from step 2 was laid flat on the surface of the filter membrane and pre-wetted with deionized water for 5 minutes. Then the dispersion from step (2) was slowly poured in, the flow rate was controlled at 1 mL / min, and the loading was repeated three times, with each time interval of 5 minutes to drain. After loading, the membrane surface was gently pressed with filter paper to remove residual droplets. The La-MOF / AO-PAN composite membrane was obtained.

[0178] (4) Post-processing and interface strengthening

[0179] Prepare a PBS buffer containing 5 mM EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride) and 2 mM NHS (N-hydroxysuccinimide), adjust the pH of the buffer to 7, and soak the composite membrane in step (3) for 2 h to activate the carboxyl and amino groups. Then rinse with deionized water to obtain the La-MOF / AO-PAN composite membrane material.

[0180] The Fourier transform infrared spectrum of the AO-PAN film prepared in Comparative Example 3 is shown in FIG. Fig. 9 As shown by Fig. 9 It can be seen that the Fourier transform infrared spectrum proves the existence of amidoxime groups. This comparative example 3 successfully prepared the AO-PAN film.

[0181] The bonding stability of La-MOF and AO-PAN membrane was determined by electron scanning image characterization. The SEM image of the La-MOF / AO-PAN membrane prepared in this comparative example 3 is as follows: Fig.10 As shown in FIG. 1 , the thickness of the composite film is 3.77±0.5 μm. The La-MOF / AO-PAN film was placed in a 70W water bath ultrasound treatment for 10 min. The SEM image of the composite film after ultrasound treatment is shown in FIG. Fig.11 As shown, the thickness of the composite film after ultrasound is 2.09±0.5 μm. Ultrasonic treatment causes the MOF particles to fall off, and the lack of covalent bonds cannot provide sufficient binding force, and the binding fails only by physical action. Ultrasonic treatment causes the thickness of the La-MOF / AO-PAN composite film to decrease, indicating that MOF particles are peeled off from the substrate surface in large quantities. SEM comparison shows that the unmodified MOF is only bound to the membrane through physical adsorption, lacking chemical bonding and anchoring. The interface between the unmodified MOF and the polymer is prone to slippage and shedding under dynamic stress. The results shown show that the ultrasonic La-MOF of the comparative example 3 sample is unstable on the AO-PAN membrane surface.

[0182] The La-MOF / AO-PAN composite membrane after ultrasound was placed in a phosphate solution for performance testing. The test conditions were: phosphate concentration of 2 mg / L, pH = 7. The performance removal rate of the La-MOF / modified PAN composite membrane was measured to be 31.16%. The thickness of the La-MOF / AO-PAN membrane decreased after ultrasound, and SEM showed that the MOF particles fell off, resulting in a decrease in adsorption performance. The weak binding characteristics dominated by physical adsorption caused the MOF particles to fall off. When the material interface only relies on van der Waals forces or physical coating, the dynamic water flow shear force will destroy the binding. The MOF particles are only fixed by surface contact, and the particles at the edge of the pores fall off preferentially under hydraulic scouring. Insufficient interfacial bonding leads to physical shedding, affecting mass transfer efficiency and structural stability.

[0183] At the same time, by comparing Example 1 and Comparative Examples 1-3, it can be seen that in the method of the present invention, there is a synergistic effect between pyromellitic acid and the AO-PAN membrane, which can synergistically improve the relevant properties of the prepared La-MOF-COOH / AO-PAN composite membrane material.

[0184] Relevant comparison between the present invention and the prior art:

[0185] 1. Comparison of interface action mechanism upgrade: The present invention is a stable adsorption dominated by chemical bonding (breaking through the limitation of physical adsorption). The patented technology of traditional MOF composite membrane (such as Chinese patent CN118179449A, a porous lanthanum-based metal organic framework La MOF-XC adsorbent and filter membrane preparation method and application) only relies on physical load (vacuum filtration) and ignores the synergistic effect between particles and polymer carriers. The present invention creatively combines La-MOF-COOH with AO-PAN to achieve simultaneous improvement of adsorption capacity and interface stability. The film-forming technology uses chemical action (hydrogen bonding and covalent action to assist vacuum filtration).

[0186] 2. Comparison of the relationship between dosage and phosphorus removal efficiency: The present invention makes a breakthrough in optimizing the relationship between dosage and phosphorus removal efficiency, and reduces the critical dosage threshold. The patented technology (Chinese patent CN114870823A, a lanthanum-based metal organic framework phosphorus removal composite material and its preparation method and application) requires 2g / L dosage to achieve a 95% phosphorus removal rate (taking 480 minutes), while the present invention stabilizes the La-MOF-COOH with high phosphorus removal performance on the AO-PAN carrier, retains a large number of adsorption sites, and uses La 3+ With the La-OP coordination bond of phosphate, the dosage was reduced to 0.01-0.04 g / L and the removal rate reached 99.09% (it took 60 minutes).

[0187] 3. Comparison of the simplification degree of reaction steps: In the patented technology (Chinese patent CN113262651A, a modified polyacrylonitrile ultrafiltration membrane for removing phosphates in water and its preparation method), silane coupling agent is used to modify iron oxide to obtain amino iron oxide, then grafted with propylene, and then copolymerized with acrylonitrile, and finally formed into a film to improve dispersibility and interfacial compatibility. The whole process involves multi-step chemical reactions, requiring different reaction conditions and equipment and multiple purification steps. The steps are many and complicated. After the present invention prepares La-MOF-COOH and AO-PAN, EDC / NHS activates the carboxyl group and the amino group to directly form a covalent bond, eliminating the intermediate grafting and copolymerization steps. Only simple solution treatment and conventional equipment are required, which greatly simplifies the process. At the same time, it significantly reduces equipment investment and energy consumption.

[0188] In summary, the present invention has significant advantages over the prior art.

[0189] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing La-MOF-COOH / AO-PAN composite membrane material, Features: The steps include: (1) Preparation of PAN membrane: polyacrylonitrile PAN powder and porogen are added to an organic solvent, heated and stirred in a water bath, then allowed to stand for degassing, poured onto a glass plate and scraped, and phase-transformed into a PAN membrane in a coagulation bath; (2) Preparation of AO-PAN membrane: dissolving hydroxylamine hydrochloride in water and methanol solvent, adjusting the pH with an alkaline reagent, placing the membrane in step (1) in the solution and heating it for reaction, and then rinsing it with deionized water to obtain an AO-PAN membrane; (3) Preparation of La-MOF-COOH: Weigh metal salt and organic ligand and add them to an organic solvent. Transfer the mixed solution to a high-pressure reactor and place it in an oven for hydrothermal reaction. After cooling, discard the upper clear layer, collect the precipitate by centrifugation, wash, and dry to obtain La-MOF-COOH powder. (4) Preparation of La-MOF-COOH / AO-PAN membrane 1) Preparation of La-MOF-COOH dispersion Weigh the La-MOF-COOH powder obtained in step (3) into the dispersion liquid, place the obtained mixture in a magnetic stirrer, and stir at room temperature for preliminary dispersion; then place the mixture in a probe ultrasound machine and perform ultrasound treatment at 500 W, and cool in an ice bath to prevent overheating, thereby obtaining a La-MOF-COOH dispersion liquid; 2) Stabilization Weigh a surfactant and add it to the dispersion in step 1), stir and disperse evenly to avoid secondary agglomeration, to obtain a mixed solution; 3) Vacuum filtration load The AO-PAN membrane of step (2) was laid flat on the surface of the filter membrane and soaked in deionized water for 5 minutes for pre-wetting; then the mixed solution of step 2) was slowly poured in, the flow rate was controlled at 1 mL / min, and the loading was repeated three times, and each time the membrane was drained after 5 minutes; after loading, the residual droplets on the membrane surface were removed with filter paper to obtain a composite membrane; 4) Post-processing and interface strengthening The activator is prepared and placed in a buffer solution, and the pH of the buffer solution is adjusted. The composite membrane of step 3) is immersed in the buffer solution with adjusted pH to activate the carboxyl and amino groups; and then rinsed with deionized water to obtain a La-MOF-COOH / AO-PAN composite membrane material.

2. The preparation method according to claim 1, Features: In step (1), the porogen is one of polyvinyl pyrrolidone, polyethylene glycol or silicon dioxide; Alternatively, in step (1), the ratio of PAN powder, porogen, and organic solvent g:g:mL is 15-18:5-15:100; Alternatively, the organic solvent in step (1) is one or a mixed solvent of two or more selected from N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide; Alternatively, in step (1), the heating temperature in the water bath is 50°C to 70°C, and the heating time is 6h to 10h; Alternatively, the coagulation bath condition for the phase inversion in step (1) is one of water or ethanol solvent.

3. The preparation method according to claim 1, Features: In step (2), the ratio of hydroxylamine hydrochloride, water and methanol solvent is 2-8:30-75:30-75. Alternatively, the alkaline reagent in step (2) is one of sodium carbonate, sodium hydroxide or sodium bicarbonate; Alternatively, in step (2), the pH is adjusted to 7-8 using an alkaline reagent; Alternatively, in step (2), the heating temperature is 30° C. to 80° C., and the heating time is 2 h to 6 h.

4. The preparation method according to claim 1, Features: In step (3), the ratio of metal salt, organic ligand and organic solvent is 2-4:2-3:100 (g:g:mL).

5. The preparation method according to claim 1, Features: In step (3), the metal salt is one of lanthanum chloride heptahydrate or lanthanum nitrate hexahydrate; Alternatively, the organic ligand in step (3) is one of terephthalic acid or pyromellitic acid; Alternatively, the hydrothermal conditions in step (3) are a heating temperature of 80 to 150° C. and a reaction time of 8 to 24 h; Alternatively, the drying conditions in step (3) are a temperature of 30 to 80° C. and a heating time of 8 to 24 hours.

6. The preparation method according to claim 1, Features: In step (4), the dispersion liquid in 1) is one of water or ethanol; Alternatively, the surfactant in step (4) is one of sodium dodecylbenzene sulfonate or sodium dodecyl diphenyl ether disulfonate; Alternatively, 0.01-0.2 g of a surfactant is added to every 50-200 mL of the dispersion in step 1); Alternatively, the stirring and dispersing time in step (4) is 10-60 min.

7. The preparation method according to any one of claims 1 to 6, Features: In step (4), the activating agent is one or two of EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride), NHS (N-hydroxysuccinimide), and DCC (dicyclohexylcarbodiimide); Alternatively, the concentration of the activator in step (4) is 0.5-5 mM; Alternatively, the buffer in step (4) is PBS, i.e., one of phosphate buffer or borate buffer; Alternatively, adjust the buffer pH to 5-8; Alternatively, the soaking time in step (4) is 0.5-3h.

8. The preparation method according to claim 7, Features: In step (4), the ratio of the dispersion in 1) to the La-MOF-COOH powder is 100-200:0.

3.

9. The La-MOF-COOH / AO-PAN composite membrane material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the La-MOF-COOH / AO-PAN composite membrane material according to claim 9 in phosphate adsorption and / or removal.

Images