Preparation method of polysaccharide functionalized nanocomposite membrane and obtained polysaccharide functionalized nanocomposite membrane and application thereof

Abstract

The present invention discloses a method for preparing a polysaccharide-functionalized nanocomposite membrane, the obtained nanocomposite membrane, and its application. The method comprises: (1) obtaining a chitosan-functionalized iron nanomaterial; (2) mixing the chitosan-functionalized iron nanomaterial with an organic solvent, a polymer matrix, and optionally polyvinyl pyrrolidone to form a casting solution; (3) scraping the casting solution, then placing the solution in water and allowing it to stand, and then taking it out to obtain a nano-matrix membrane; and (4) coating a sodium alginate aqueous solution on one surface of the nano-matrix membrane to obtain the polysaccharide-functionalized nanocomposite membrane. The polysaccharide-functionalized nanocomposite membrane of the present invention is an asymmetric composite membrane, which is divided into an upper dense alginate active layer and a lower nano-material-containing support layer. The dense layer is mainly responsible for intercepting antimony, while the support layer is responsible for adsorption.

Description

Technical Field

[0001] The present invention belongs to the field of membrane materials, in particular to membrane materials for removing heavy metal ions, and specifically to a preparation method of a polysaccharide functionalized nanocomposite membrane and the obtained polysaccharide functionalized nanocomposite membrane and its application. Background Art

[0002] Industrial wastewater often releases toxic pollutants into the environment, including heavy metals, organic and oily pollutants, and inorganic salts. Among the heavy metal pollutants, antimony (Sb) typically exists in the form of Sb(III) and Sb(V), both of which are considered non-biodegradable and carcinogenic. The reversible dissolution / adsorption of antimony in aquifers and ores leads to serious water pollution. Many countries and regions have set a permissible limit of 5 μg / L for antimony in drinking water. Therefore, there is a great need to develop effective technologies for removing Sb.

[0003] Currently, the main methods for removing heavy metals from water include precipitation, coagulation-flocculation, ion exchange, adsorption and membrane separation. Among them, adsorption has attracted widespread attention due to its advantages such as simplicity, high efficiency and easy operation.

[0004] Nanoparticles are widely used to remove heavy metals from water due to their large specific surface area and high chemical activity caused by the size quantization effect. However, due to van der Waals interactions, nanoparticles easily agglomerate, thereby reducing the removal efficiency of heavy metals. The subsequent collection and treatment of nanoparticles is also a major problem. Therefore, immobilizing nanoparticles in porous hosts such as zeolites, clays, activated carbon and polymer membranes is the key to solving the problem. Considering factors such as cost, operational flexibility and simplicity, polymer matrix membranes are one of the most widely used choices as porous hosts.

[0005] Chitosan functionalized iron nanomaterials have good selective adsorption for the removal of antimony. Choosing it as the nano-adsorption filler of the nano-matrix membrane can achieve a good adsorption and removal effect for antimony.

[0006] Polymer membranes are primarily prepared by non-solvent-induced phase separation and thermally induced phase separation. Non-solvent-induced phase separation is the most common method. While nanomatrix membranes offer significant advantages in static adsorption removal, they are less effective in dynamic filtration removal, primarily due to the lack of a dense active layer, resulting in suboptimal retention. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the present invention provides a method for preparing a polysaccharide-functionalized nanocomposite membrane with a simple process and green environmental protection. The method is a one-step method with simple preparation, low cost and suitable for large-scale production. At the same time, the prepared polysaccharide-functionalized nanocomposite membrane will form a negatively charged dense active layer on the surface of the nanomatrix membrane, which can intercept trivalent antimony and pentavalent antimony based on steric hindrance and electrostatic repulsion effects. The nanomatrix membrane serves as a support membrane, and the nanoparticles inside it provide adsorption sites for the removal of trivalent antimony and pentavalent antimony.

[0008] One of the purposes of the present invention is to provide a method for preparing a polysaccharide functionalized nanocomposite membrane, comprising:

[0009] (1) Obtaining chitosan functionalized iron nanomaterials;

[0010] (2) mixing the chitosan-functionalized iron nanomaterial with an organic solvent, a polymer matrix, and optionally polyvinyl pyrrolidone to form a casting solution;

[0011] (3) scraping the film using the casting solution, then placing it in water and letting it stand for phase inversion treatment, and then taking it out to obtain a nano matrix film;

[0012] (4) coating a sodium alginate aqueous solution on one surface of the nano-matrix membrane (preferably the denser or darker side) to obtain the polysaccharide functionalized nanocomposite membrane.

[0013] In the present invention, the alginate polysaccharide active layer and the chitosan in the nanomaterial have opposite charges and can be tightly attached to the support membrane containing the nanomaterial through electrostatic interaction, thereby forming a thin, negatively charged, dense layer on the support membrane.

[0014] In a preferred embodiment, in step (1), the chitosan functionalized iron nanomaterial is obtained as follows:

[0015] (1.1) dissolving chitosan with acid to obtain a chitosan aqueous solution;

[0016] (1.2) introducing an inert gas into the chitosan aqueous solution, then adding a solution containing ferrous ions thereto, and stirring;

[0017] (1.3) Add a reducing agent to the system to reduce the ferrous ions to produce a black precipitate;

[0018] (1.4) stirring, washing with water, and then drying to obtain the chitosan functionalized iron nanomaterial.

[0019] In a preferred embodiment, in step (1.1), the acid is selected from acetic acid and / or hydrochloric acid.

[0020] In a preferred embodiment, in step (1.1), the molecular weight of the chitosan is 150,000 Da to 800,000 Da, preferably 500,000 Da to 800,000 Da.

[0021] In a preferred embodiment, in step (1.1), the weight ratio of acetic acid to chitosan is (0.5-4):1, preferably (0.5-2):1.

[0022] In a preferred embodiment, in step (1.2), the solution containing ferrous ions is an aqueous solution containing ferrous compounds.

[0023] In a further preferred embodiment, the ferrous compound is selected from at least one of ferrous sulfate and ferrous chloride.

[0024] In a further preferred embodiment, in the aqueous solution containing the ferrous compound, the weight concentration of the ferrous compound is 1 to 20 wt %, preferably 5 to 10 wt %.

[0025] In a preferred embodiment, the volume ratio of the aqueous solution containing the ferrous compound to the chitosan solution is (1-10):1, preferably (1-4):1.

[0026] In a preferred embodiment, in step (1.3), the reducing agent is selected from NaBH4 and / or KBH4.

[0027] In a further preferred embodiment, the weight ratio of the reducing agent to the ferrous compound is (0.1-2):1, preferably (0.1-0.5):1.

[0028] In the present invention, the chitosan functionalized iron nanomaterial is used to give the composite membrane good adsorption capacity to adsorb heavy metals.

[0029] In a preferred embodiment, in step (2), the organic solvent is selected from at least one of N,N-dimethylacetamide and N,N-dimethylformamide.

[0030] In a further preferred embodiment, in step (2), the organic solvent is N,N-dimethylacetamide.

[0031] In a preferred embodiment, in step (2), the polymer matrix is ​​selected from at least one of polysulfone, polyethersulfone, and polyvinylidene fluoride.

[0032] In a further preferred embodiment, in step (2), the polymer matrix is ​​selected from polysulfone.

[0033] Among them, the role of the polymer matrix is ​​to serve as a carrier of chitosan functionalized nanomaterials.

[0034] In a preferred embodiment, in step (2), based on 100 wt% of the polymer matrix, the amount of the chitosan functionalized iron nanomaterial is 0 to 70 wt%, preferably 5 wt% to 25 wt%.

[0035] In a preferred embodiment, in step (2), the mass ratio of polyvinyl pyrrolidone, polymer matrix, and organic solvent is (0-2):(3-15):(20-80).

[0036] In a further preferred embodiment, in step (2), the mass ratio of polyvinyl pyrrolidone, polymer matrix, and organic solvent is (0-1):(7-10):(35-50).

[0037] Among them, polyvinyl pyrrolidone is optionally added. During the phase inversion membrane-making process, it is soluble in water and increases the porosity of the membrane.

[0038] In a preferred embodiment, step (2) includes the following sub-steps:

[0039] (2.1) adding chitosan-functionalized iron nanomaterials into a solvent and subjecting the mixture to ultrasonic treatment to obtain a dispersion;

[0040] (2.2) Adding the polymer matrix to the dispersion, stirring, and then ultrasonically degassing to obtain the casting solution.

[0041] In a preferred embodiment, in step (2.1), the ultrasonic treatment is performed for 10 min to 2 h, preferably 20 min to 50 min.

[0042] The purpose of ultrasonic treatment is to make the mixed liquid highly dispersed and prevent agglomeration.

[0043] In a preferred embodiment, in step (2.2), stirring is performed for 10 h to 36 h, and then ultrasonic degassing is performed for 5 min to 40 min.

[0044] In a further preferred embodiment, in step (2.2), stirring is performed for 10 h to 24 h, and then ultrasonic degassing is performed for 20 min to 50 min.

[0045] In a preferred embodiment, in step (3), the scraping film has a thickness of 100 to 400 μm, preferably 150 to 250 μm.

[0046] In a preferred embodiment, in step (4), the concentration of the sodium alginate aqueous solution is 0-1%, preferably 0.1-0.5%; after the coating, the aqueous solution is maintained for 3-10 minutes, and then the excess aqueous solution is removed to obtain the polysaccharide functionalized nanocomposite membrane.

[0047] In the phase inversion membrane formation described in step (3), water enters the liquid membrane, increasing the polymer concentration on the liquid membrane surface. The macromolecules on the membrane surface aggregate with each other, and the membrane and water interface diffuse with each other. The solvent diffuses into the water bath, and the water diffuses into the membrane. After a period of time, the exchange between the solvent and water reaches a certain level, at which point the solution becomes thermodynamically unstable and the polymer solution undergoes liquid-liquid phase separation. If the outward diffusion rate of the solvent is greater than the inward diffusion rate of water, the polymer concentration at the membrane interface increases, forming a surface cortex. The formation of the surface cortex reduces the outward diffusion rate of the solvent, resulting in a decrease in the polymer concentration in the membrane, forming a porous layer. As the solvent and water continue to exchange, the membrane after liquid-liquid phase separation enters the glass transition zone, forming a loose and porous asymmetric membrane.

[0048] In the present invention, the structure of the nano matrix film obtained in step (3) is as follows Figure 1 As shown by Figure 1 It can be seen that

[0049] In a preferred embodiment, in step (4), the coating is maintained for 3 to 10 minutes, and then the excess aqueous solution is removed to obtain the polysaccharide functionalized nanocomposite membrane.

[0050] In the present invention, the alginate polysaccharide active layer and the chitosan in the nanomaterial have opposite charges and can be tightly attached to the support membrane containing the nanomaterial through electrostatic interaction, thereby forming a thin, negatively charged, dense layer on the support membrane.

[0051] The second object of the present invention is to provide a polysaccharide functionalized nanocomposite membrane obtained by the preparation method described in the first object of the present invention.

[0052] The third object of the present invention is to provide the use of the polysaccharide functionalized nanocomposite membrane obtained by the preparation method described in the first object of the present invention or the polysaccharide functionalized nanocomposite membrane described in the second object of the present invention in treating sewage, especially in treating sewage containing heavy metals.

[0053] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) The preparation method of the present invention is simple, and the raw materials used are natural, green and degradable sodium alginate polysaccharide and chitosan functionalized iron nanomaterial composite materials, which are non-toxic and harmless and will not cause harm to the environment during the wastewater treatment process;

[0056] (2) The polysaccharide functionalized nanocomposite membrane of the present invention is an asymmetric composite membrane, which is divided into an upper dense alginate active layer and a lower support layer. The dense layer is mainly responsible for intercepting antimony, while the support layer containing iron nanomaterials is mainly responsible for adsorption;

[0057] (3) The method of the present invention forms a negatively charged dense layer of alginate on the surface of the support layer containing the chitosan-functionalized iron nanomaterial. This dense layer can intercept trivalent antimony and pentavalent antimony through steric hindrance. The chitosan-functionalized iron nanomaterial inside the polymer provides adsorption sites for the removal of trivalent antimony and pentavalent antimony. In addition, the electrostatic repulsion between the negatively charged functionalized dense layer and the negatively charged pentavalent antimony also promotes the interception of pentavalent antimony. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Electron microscope photographs of the nano-matrix films (support films) prepared in Comparative Examples 1 to 6 are shown (mainly showing the cross-section of the nano-matrix film, magnification: 5000 times);

[0059] Figure 2 The water flux images of the membranes prepared in Comparative Examples 1 to 6 are shown (the filtration pressure is 1 bar);

[0060] Figure 3 The water flux images of the nano-matrix membrane prepared in Comparative Example 5 and the chitosan functionalized nano-composite membrane prepared in Example 1 are shown (the filtration pressure is 1 bar);

[0061] Figure 4 The graph shows the dynamic adsorption performance test of trivalent antimony by the nano matrix film prepared in Comparative Example 5 and the chitosan functionalized nano composite film prepared in Example 1;

[0062] Figure 5 The figure shows the dynamic adsorption performance test of pentavalent antimony by the chitosan functionalized nanocomposite membrane prepared in Example 1. DETAILED DESCRIPTION

[0063] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0064] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0065] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the scope of protection of the present invention.

[0066] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0067] In Comparative Examples 1 to 7 and Examples 1 to 3, the chitosan functionalized iron nanomaterials were obtained as follows:

[0068] 1. Weigh 0.5 g of chitosan (molecular weight 700,000-800,000 Da) and disperse it in ultrapure water. Then, add 0.85 g of glacial acetic acid to dissolve the chitosan to prepare a chitosan aqueous solution I with a mass concentration of 0.5%;

[0069] 2. Weigh 5.56g FeSO4 and dissolve it in 100mL ultrapure water to prepare 0.2M Fe2 + Aqueous solution II;

[0070] 3. Weigh 1.52 g of NaBH4 and dissolve it in 100 mL of ultrapure water to prepare a 0.4 M NaBH4 aqueous solution III.

[0071] 4. Weigh a certain volume of aqueous solution I, introduce nitrogen into it, and then add the same volume of aqueous solution II dropwise under magnetic stirring. After reacting for 20 minutes, add the same volume of solution III dropwise and continue stirring for 20 minutes. Then, centrifuge, wash, and dry to obtain chitosan-functionalized iron nanomaterials.

[0072] [Comparative Example]

[0073] [Comparative Example 1] Preparation of nano-matrix film

[0074] According to the mass ratio of polyvinyl pyrrolidone, polysulfone and N,N-dimethylacetamide of 1:8:41, 16g of polysulfone and 2g of polyvinyl pyrrolidone were weighed and added to 82g of N,N-dimethylacetamide organic solvent. The mixture was magnetically stirred for 24h, then ultrasonicated for 30min, scraped, washed and soaked in ultrapure water. The obtained membrane was freeze-dried and its cross-section was examined by electron microscopy. It was found that the membrane was divided into a dense skin layer and a finger-like layer structure, such as Figure 1 (a). At the same time, the prepared membrane was tested for pure water flux, such as Figure 2 shown.

[0075] [Comparative Example 2] Preparation of nano-matrix film

[0076] Weigh 5% of the mass ratio of chitosan functionalized iron nanomaterials to polysulfone and ultrasonically disperse them in 82g of N,N-dimethylacetamide organic solution (ultrasonic time is 30min). Then, polysulfone and polyvinyl pyrrolidone are weighed according to the mass ratio of polyvinyl pyrrolidone, polysulfone and N,N-dimethylacetamide of 1:8:41 and added to the dispersion. The mixture is magnetically stirred for 24h, ultrasonicated for 30min, and then the membrane is scraped, washed and soaked in ultrapure water. After freeze-drying, the cross section of the obtained membrane is examined by electron microscopy. It is found that the chitosan functionalized iron nanomaterials in the membrane matrix do not block the membrane pores. Figure 1 (b).

[0077] EDS spectrum analysis revealed that the polysaccharide functionalized iron nanomaterials were evenly dispersed in the membrane matrix, but the amount of dispersion was small. At the same time, the prepared membrane was tested for pure water flux, and the water flux of the membrane prepared in Comparative Example 1 was not much different (e.g. Figure 2 This further verifies that the nanoparticles are evenly dispersed without causing membrane pore blockage.

[0078] [Comparative Example 3] Preparation of nano-matrix film

[0079] The process of Comparative Example 2 was repeated, except that 10% of the mass ratio of the polysulfone to the chitosan functionalized iron nanomaterial was weighed. The obtained membrane was freeze-dried and then its cross section was examined by electron microscopy. Figure 1 (c) It was found that chitosan-functionalized iron nanomaterials did not block the membrane pores in the membrane matrix.

[0080] EDS energy spectrum analysis showed that the polysaccharide functionalized iron nanomaterials were evenly dispersed in the membrane matrix, and the dispersion amount was increased compared with that of Comparative Example 2. At the same time, the pure water flux of the prepared membrane was tested, and the water flux of the membrane prepared in Comparative Examples 1 and 2 was not much different. Figure 2shown.

[0081] [Comparative Example 4] Preparation of nano-matrix film

[0082] The process of Comparative Example 2 was repeated, except that 15% of the mass ratio of the chitosan-functionalized iron nanomaterial to the polysulfone was added. The resulting membrane was freeze-dried and then subjected to electron microscopy. It was found that the chitosan-functionalized iron nanomaterial did not block the membrane pores in the membrane matrix. Figure 1 (d).

[0083] EDS spectrum analysis showed that the polysaccharide functionalized iron nanomaterials were evenly dispersed in the membrane matrix, and the dispersion amount was further increased compared with that of Comparative Example 3. At the same time, the pure water flux of the prepared membrane was tested, and the water flux of the membranes prepared in Comparative Examples 1 to 3 was not much different. Figure 2 shown.

[0084] [Comparative Example 5] Preparation of nano-matrix film

[0085] The process of Comparative Example 2 was repeated, except that 20% of the mass ratio of the chitosan-functionalized iron nanomaterial to the polysulfone was weighed. The cross-section of the obtained membrane was freeze-dried and examined by electron microscopy. The cross-section of the obtained membrane was freeze-dried and examined by electron microscopy. It was found that the chitosan-functionalized iron nanomaterial did not block the membrane pores in the membrane matrix. Figure 1 (e).

[0086] EDS spectrum analysis showed that the polysaccharide functionalized iron nanomaterials were evenly dispersed in the membrane matrix, and the dispersion amount was further increased compared with that of Comparative Example 4. At the same time, the pure water flux of the prepared membrane was tested, and the water flux of the membranes prepared in Comparative Examples 1 to 4 was not much different. Figure 2 shown.

[0087] [Comparative Example 6] Preparation of nano-matrix film

[0088] The process of Example 2 was repeated, except that 25% of the mass ratio of chitosan functionalized iron nanomaterial to polysulfone was added. The obtained membrane was freeze-dried and its cross section was examined by electron microscopy. The dense side showed agglomeration and clogging of the membrane pores, such as Figure 1 (f).

[0089] EDS spectrum analysis revealed that the chitosan functionalized iron nanomaterials were unevenly dispersed in the membrane matrix. The pure water flux test of the prepared membrane was also conducted. The water flux of the membranes prepared in Comparative Examples 1 to 4 was very different, and the water flux decreased by more than 1 times. Figure 2 shown.

[0090] [Comparative Example 7] Preparation of nano-matrix film

[0091] The process of Example 2 was repeated, except that 62.5% of the weight of the polysulfone was used as chitosan-functionalized iron nanomaterial. The resulting membrane exhibited severe nanoparticle agglomeration, and SEM observations revealed severe pore blockage.

[0092] [Example]

[0093] [Example 1] Preparation of polysaccharide functionalized nanocomposite membrane

[0094] The process of Comparative Example 5 was repeated, except that: the darker dense surface of the nano-matrix membrane prepared in Comparative Example 5 was coated with a sodium alginate aqueous solution with a mass concentration of 0.2% for 5 minutes, and then the sodium alginate that had not been cross-linked was washed away, and the membrane was stored in ultrapure water for use.

[0095] The results showed that the water flux of the sodium alginate functionalized nanocomposite membrane was significantly reduced compared to the nano-matrix membrane as the support membrane. The pure water flux test showed that the water flux of the membrane decreased by nearly one-third compared to the membrane without SA coating in comparative example 5. Figure 3 This indicates that sodium alginate self-assembles on the support membrane containing chitosan functionalized iron nanomaterials through electrostatic interaction, forming a dense active layer on the surface of the nano-matrix membrane.

[0096] [Example 2] Preparation of polysaccharide functionalized nanocomposite membrane

[0097] The process of Example 1 was repeated, except that the mass concentration of the sodium alginate aqueous solution was 0.1%. Pure water flux testing revealed that the water flux of the membrane was reduced by approximately half compared to the membrane of Comparative Example 5 without SA coating, but was greater than that of the membrane prepared in Example 1.

[0098] [Example 3] Preparation of polysaccharide functionalized nanocomposite membrane

[0099] The process of Example 1 was repeated, except that the sodium alginate aqueous solution concentration was 0.5%. Pure water flux testing revealed that the membrane's water flux was similar to that of Example 1. This indicates that at a sodium alginate aqueous solution concentration of 0.2%, the electrostatic self-assembly between the alginic acid and the nanomaterial-containing support membrane reaches equilibrium, and the thickness of the formed active layer no longer increases with increasing alginate concentration.

[0100] [Example 4]

[0101] Chitosan functionalized iron nanomaterials were obtained as follows:

[0102] 1. Weigh 0.5 g of chitosan (molecular weight 700,000-800,000 Da) and disperse it in ultrapure water. Then, add 0.5 g of glacial acetic acid to dissolve the chitosan to prepare a chitosan aqueous solution I with a mass concentration of 0.5%;

[0103] 2. Weigh 5.56g FeSO4 and dissolve it in ultrapure water to prepare 0.2M Fe 2+ Aqueous solution II;

[0104] 3. Weigh 1.52 g of KBH4 and dissolve it in ultrapure water to prepare a 0.4 M NaBH4 aqueous solution III;

[0105] A certain volume of aqueous solution I was weighed, nitrogen was introduced into it, and then twice the volume of aqueous solution II was added dropwise under magnetic stirring. After reacting for 20 minutes, twice the volume of solution III was added dropwise, and stirring was continued for 20 minutes. Then, the chitosan-functionalized iron nanomaterial was obtained after centrifugation, washing, and drying.

[0106] The nanomatrix film was prepared as follows:

[0107] Chitosan functionalized iron nanomaterials accounting for 30% of the mass ratio of polyvinylidene fluoride were weighed and ultrasonically dispersed in N,N-dimethylacetamide organic solution (ultrasonic time was 30 min), and then polyvinylidene fluoride and polyvinyl pyrrolidone were weighed according to the mass ratio of polyvinylidene fluoride, polyvinylidene fluoride and N,N-dimethylacetamide of 1:5:50 and added to the dispersion. The mixture was magnetically stirred for 24 h, and then ultrasonicated for 30 min, and then the film was scraped, washed, and soaked in ultrapure water for use.

[0108] Applying sodium alginate layer:

[0109] The darker dense surface of the obtained nano-matrix membrane was coated with a sodium alginate aqueous solution with a mass concentration of 0.7% for 10 minutes, and then the sodium alginate that had not undergone cross-linking reaction was washed away, and the membrane was stored in ultrapure water for future use.

[0110] The membrane prepared in Example 4 also has excellent removal rates for Sb(III) and Sb(V).

[0111] [Example 5]

[0112] Chitosan functionalized iron nanomaterials were obtained as follows:

[0113] 4. Weigh 0.5 g of chitosan (molecular weight 700,000-800,000 Da) and disperse it in ultrapure water. Then, add 1 g of glacial acetic acid to dissolve the chitosan to prepare a chitosan aqueous solution I with a mass concentration of 0.5%;

[0114] 5. Weigh 5.56g FeSO4 and dissolve it in ultrapure water to prepare 0.2M Fe 2+ Aqueous solution II;

[0115] 6. Weigh 1.52 g of NaBH4 and dissolve it in ultrapure water to prepare a 0.4 M NaBH4 aqueous solution III.

[0116] A certain volume of aqueous solution I was weighed, nitrogen was introduced into it, and three times the volume of aqueous solution II was added dropwise under magnetic stirring. After reacting for 20 minutes, three times the volume of solution III was added dropwise, and stirring was continued for 20 minutes. Then, the chitosan-functionalized iron nanomaterial was obtained after centrifugation, washing, and drying.

[0117] The nanomatrix film was prepared as follows:

[0118] Chitosan functionalized iron nanomaterials accounting for 40% of the mass ratio of polyethersulfone were weighed and ultrasonically dispersed in N,N-dimethylacetamide organic solution (ultrasonic time was 30 min). Then, polyethersulfone and polyvinylpyrrolidone were weighed according to the mass ratio of polyvinylpyrrolidone, polyethersulfone and N,N-dimethylacetamide of 1:7:35 and added to the dispersion. The mixture was magnetically stirred for 24 h, ultrasonicated for 30 min, and then scraped, washed, and soaked in ultrapure water for use.

[0119] Applying sodium alginate layer:

[0120] The darker dense surface of the obtained nano-matrix membrane was coated with a sodium alginate aqueous solution with a mass concentration of 0.05% for 3 minutes, and then the sodium alginate that had not undergone cross-linking reaction was washed away. The membrane was stored in ultrapure water for later use.

[0121] The membrane prepared in Example 5 also has excellent removal rates for Sb(III) and Sb(V).

[0122]

Experimental Example

[0123] The membranes obtained in Comparative Example 5 and Example 1 were tested for dynamic adsorption performance.

[0124] (1) A fixed area of ​​each of the nano-matrix membrane obtained in Comparative Example 5 and the polysaccharide functionalized nanocomposite membrane obtained in Example 1 was cut and placed in a filtration device at a filtration pressure of 1 bar. 100 mL of trivalent antimony with different concentrations (0.2, 2, 5, and 8 mg / L) was subjected to dynamic adsorption. Figure 4 As shown in Figure 2, it was found that the retention performance of the nano-matrix membrane functionalized with sodium alginate for antimony was greatly improved at low concentrations. However, as the concentration increased further, the retention performance was no longer significant, which may be due to the adsorption equilibrium being reached.

[0125] (2) A fixed area of ​​each of the nano-matrix membrane obtained in Comparative Example 5 and the polysaccharide functionalized nanocomposite membrane obtained in Example 1 was cut and placed in a filtration device at a filtration pressure of 1 bar. 100 mL of pentavalent antimony with different concentrations (0.2, 2, 5, and 8 mg / L) was subjected to dynamic adsorption. The results are shown in Figure 2. Figure 5As shown (only Example 1 is shown), it was found that the sodium alginate functionalized nanocomposite membrane had a significantly improved antimony retention performance at low concentrations. However, as the concentration increased further, the retention performance was no longer significant, which may be due to the adsorption equilibrium being reached.

[0126] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a polysaccharide functionalized nanocomposite membrane, comprising: (1) Obtain chitosan functionalized iron nanomaterials; (2) mixing the chitosan functionalized iron nanomaterial with an organic solvent, a polymer matrix and polyvinylpyrrolidone to form a casting solution; the polymer matrix is ​​selected from at least one of polysulfone, polyethersulfone and polyvinylidene fluoride; (3) scraping the film using the casting solution, then placing it in water and letting it stand, and then taking it out to obtain a nano-matrix film, which is divided into a dense skin layer and a finger-like layer structure; (4) coating a sodium alginate aqueous solution on the dense side of the nano-matrix membrane surface to obtain the polysaccharide functionalized nanocomposite membrane.

2. The preparation method according to claim 1, characterized in that In step (1), the chitosan functionalized iron nanomaterial is obtained as follows: (1.1) Dissolving chitosan with acid to obtain a chitosan aqueous solution; (1.2) introducing an inert gas into the chitosan aqueous solution, then adding a solution containing a ferrous compound thereto, and stirring; (1.3) Add a reducing agent to the system to produce a black precipitate; (1.4) stirring, washing with water, centrifuging, and then drying to obtain the chitosan functionalized iron nanomaterial.

3. The preparation method according to claim 2, wherein In step (1.1), the acid is selected from acetic acid and / or hydrochloric acid; and / or In step (1.1), the molecular weight of the chitosan is 150,000 Da to 800,000 Da; and / or In step (1.1), the weight ratio of acetic acid to chitosan is (0.5-4):1; and / or In step (1.2), the solution containing ferrous compounds is an aqueous solution containing ferrous compounds; and / or In step (1.3), the reducing agent is selected from NaBH4 and / or KBH4.

4. The preparation method according to claim 2, wherein In step (1.1), the molecular weight of the chitosan is 500,000 Da to 800,000 Da; and / or In step (1.1), the weight ratio of acetic acid to chitosan is (0.5-2):1; and / or In step (1.2), the ferrous compound is selected from at least one of ferrous sulfate and ferrous chloride; and / or In step (1.3), the reducing agent is selected from NaBH4 and / or KBH4.

5. The preparation method according to claim 2, characterized in that In the aqueous solution containing the ferrous compound, the weight concentration of the ferrous compound is 1-20 wt %.

6. The preparation method according to claim 2, characterized in that In the aqueous solution containing the ferrous compound, the weight concentration of the ferrous compound is 5-10 wt %.

7. The preparation method according to claim 3, wherein The volume ratio of the solution containing the ferrous compound to the chitosan solution is (1-10):1; and / or The weight ratio of the reducing agent to the ferrous compound is (0.1-2):

1.

8. The preparation method according to claim 3, wherein The volume ratio of the solution containing the ferrous compound to the chitosan solution is (1-4):1; and / or The weight ratio of the reducing agent to the ferrous compound is (0.1-0.5):

1.

9. The preparation method according to claim 1, wherein In step (2), The organic solvent is selected from at least one of N,N-dimethylacetamide and N,N-dimethylformamide; and / or The polymer matrix is ​​selected from polysulfone.

10. The preparation method according to claim 1, wherein In step (2), Based on 100 wt% of the polymer matrix, the amount of the chitosan-functionalized iron nanomaterial is 0-70 wt%; and / or The mass ratio of polyvinyl pyrrolidone, polymer matrix and organic solvent is (0-2):(3-15):(20-80).

11. The preparation method according to claim 1, wherein In step (2), Based on 100 wt% of the polymer matrix, the amount of the chitosan functionalized iron nanomaterial is 5 wt% to 25 wt%; and / or The mass ratio of polyvinyl pyrrolidone, polymer matrix and organic solvent is (0~1):(7-10):(35-50).

12. The preparation method according to claim 1, characterized in that Step (2) includes the following sub-steps: (2.1) Adding chitosan-functionalized iron nanomaterials to a solvent and ultrasonically treating the mixture to obtain a dispersion; (2.2) Adding the polymer matrix to the dispersion, stirring, and then ultrasonically degassing to obtain the casting solution.

13. The preparation method according to claim 12, wherein In step (2.1), ultrasonic treatment for 10 min to 2 h; and / or In step (2.2), stirring is performed for 10 h to 36 h, and then ultrasonic degassing is performed for 5 min to 40 min.

14. The preparation method according to claim 12, characterized in that In step (2.1), ultrasonic treatment was performed for 20 min to 50 min.

15. The preparation method according to any one of claims 1 to 14, characterized in that In step (3), the scraping film thickness is 100~400µm; and / or In step (4), the mass concentration of the sodium alginate aqueous solution is 0-1%; after the coating, the aqueous solution is maintained for 3 minutes to 10 minutes, and then the excess aqueous solution is removed and washed to obtain the polysaccharide functionalized nanocomposite membrane.

16. The preparation method according to any one of claims 1 to 14, characterized in that In step (3), the scraping film thickness is 150-250µm; and / or In step (4), the mass concentration of the sodium alginate aqueous solution is 0.1-0.5%.

17. A polysaccharide-functionalized nanocomposite membrane obtained by the preparation method according to any one of claims 1 to 8, wherein the polysaccharide-functionalized nanocomposite membrane is an asymmetric composite membrane comprising an upper dense alginate active layer and a lower support layer, wherein the lower support layer comprises a dense skin layer and a finger-like layer structure.

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