A functionalized SiO 2 Preparation method of aluminum silicate nanofiber composite membrane

Abstract

The present invention discloses a preparation method of a functionalized SiO2 / aluminum silicate nanofiber composite membrane, which comprises the steps of: respectively modifying aluminum silicate nanofibers and SiO2 nanoparticles with an amino silane coupling agent to obtain amino-functionalized aluminum silicate nanofibers and amino-functionalized SiO2 nanoparticles; then grafting succinyl chloride on the surfaces of both to obtain acyl chloride-functionalized aluminum silicate nanofibers and acyl chloride-functionalized SiO2 nanoparticles; modifying ethylenediaminetetraacetic dianhydride with 2-amino-1,3-propanediol to obtain an intermediate, using the intermediate as a crosslinking agent, and taking the acyl chloride group as a polymerization site to carry out a crosslinking polymerization reaction between the acyl chloride-functionalized aluminum silicate nanofibers and the acyl chloride-functionalized SiO2 nanoparticles, and then performing suction filtration to form a membrane, obtaining a functionalized SiO2 / aluminum silicate nanofiber composite membrane with a grammage not greater than 15 g / m 2 . The present invention realizes the efficient adsorption of heavy metals and simultaneously solves the problem that it is difficult to recycle nanometer powder materials.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum silicate composite membranes, and in particular to a method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane. Background Art

[0002] Adsorption is a common method for treating heavy metal pollution, and its adsorption effect mainly depends on the selected adsorbent material. Nanomaterials have attracted much attention in the field of heavy metal adsorption due to their unique properties such as small size effect, quantum effect and large specific surface area. In particular, SiO2 nanoparticles have become an important heavy metal adsorption material due to a series of advantages such as high specific surface area, developed porosity, a variety of organic ligands, excellent chemical stability and environmental friendliness. In addition, hydrated aluminum silicate nanofibers, as an emerging environmentally friendly nano-mineral fiber, have a unique mesoporous tubular structure, a large specific surface area and a strong ion exchange capacity, which also makes them have broad application prospects in the field of sewage heavy metal adsorption treatment. However, these nanopowder materials face two major problems in practical applications. On the one hand, they are difficult to completely separate from the treatment system, and there are risks such as agglomeration and leakage, which not only weakens their adsorption performance, but also may cause secondary pollution to the environment. On the other hand, the adsorption functional groups on the surface of nanomaterials are usually relatively single in type and limited in content, which to a certain extent restricts their efficient adsorption capacity for heavy metal ions. These two problems have seriously affected the practical application of nanomaterials such as SiO2 and hydrated aluminum silicate nanofibers in the field of water treatment. Summary of the invention

[0003] In view of the above-mentioned defects in the prior art, the present invention provides a method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane, which achieves efficient adsorption of heavy metals and solves the problem that nanopowder materials are difficult to recycle.

[0004] The technical solution of the present invention is as follows: A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane comprises the following steps:

[0005] (1) Aluminum silicate nanofibers and SiO2 nanoparticles are modified by aminosilane coupling agent to obtain amino-modified aluminum silicate nanofibers and amino-modified SiO2 nanoparticles, respectively;

[0006] (2) grafting succinyl chloride onto the surfaces of the amino aluminum silicate nanofibers and the amino SiO2 nanoparticles, respectively, to obtain acyl chloride aluminum silicate nanofibers and acyl chloride SiO2 nanoparticles;

[0007] (3) Dissolve ethylenediaminetetraacetic acid dianhydride in ‌N , N-dimethylformamide, then add 2-amino-1,3-propanediol and the first acid binding agent to reflux at 120-135°C for 12-18h, add deionized water and ethyl acetate to extract after the reaction, and dry the obtained organic layer and distill under reduced pressure, and recrystallize the product with ethyl acetate to obtain an intermediate, the reaction formula is as follows:

[0008] ;

[0009] (4) using the intermediate as a crosslinking agent and the acyl chloride group as a polymerization site, a crosslinking polymerization reaction is carried out between the acyl chloride aluminum silicate nanofibers and the acyl chloride SiO2 nanoparticles, and then filtering to form a membrane, and after sufficient washing and drying, a film with a gram weight of no more than 15 g / m 2 Functionalized SiO2 / aluminum silicate nanofiber composite membrane.

[0010] Furthermore, the step (1) specifically comprises ultrasonically dispersing aluminum silicate nanofibers in a mixture of ethanol and water, and then adding an aminosilane coupling agent for stirring reaction, wherein the mass ratio of the aluminum silicate nanofibers to the aminosilane coupling agent is 1:(0.1-0.5); ultrasonically dispersing SiO2 nanoparticles in a mixture of ethanol and water, and then adding an aminosilane coupling agent for stirring reaction, wherein the mass ratio of the SiO2 nanoparticles to the aminosilane coupling agent is 1:(0.1-0.5).

[0011] Furthermore, the stirring reaction in step (1) is carried out at 60-90° C. for 8-12 hours.

[0012] Furthermore, the aminosilane coupling agent is one of 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane.

[0013] Furthermore, the step (2) specifically comprises ultrasonically dispersing the amino aluminum silicate nanofibers in ethyl acetate, then adding a second acid binding agent, and slowly dropping succinyl chloride under nitrogen protection, and then stirring the reaction, wherein the mass ratio of the amino aluminum silicate nanofibers, the second acid binding agent and succinyl chloride is 1: (1-2): (2-4); ultrasonically dispersing the amino SiO2 nanoparticles in ethyl acetate, then adding a third acid binding agent, and slowly dropping succinyl chloride under nitrogen protection, and then stirring the reaction, wherein the mass ratio of the amino SiO2 nanoparticles, the third acid binding agent and succinyl chloride is 1: (1-2): (2-4), and the second acid binding agent and the third acid binding agent are preferably triethylamine.

[0014] Furthermore, the stirring reaction in step (2) is carried out under nitrogen protection at room temperature for 12 to 16 hours.

[0015] Furthermore, in step (3), the mass ratio of ethylenediaminetetraacetic acid dianhydride, 2-amino-1,3-propanediol and the first acid binding agent is 1: (0.8-1.2): (0.5-1), and the first acid binding agent is preferably pyridine. The intermediate contains more N atoms with lone pairs of electrons and is rich in hydroxyl groups.

[0016] Furthermore, the step (4) specifically comprises the following steps: ultrasonically dispersing the aluminum silicate nanofibers and the SiO2 nanoparticles in ethyl acetate, and then adding the prepared intermediate and the fourth acid binding agent to carry out a cross-linking reaction, wherein the mass ratio of the aluminum silicate nanofibers, the SiO2 nanoparticles, the intermediate and the fourth acid binding agent is 1:(0.5-1):(1-3):(1-2), and the fourth acid binding agent is preferably triethylamine.

[0017] Furthermore, the cross-linking reaction in step (4) is carried out at 60-80° C. for 8-12 hours.

[0018] On the one hand, the present invention utilizes an amino coupling agent to carry out amino modification on aluminum silicate nanofibers and SiO2 nanoparticles, and then grafts succinyl chloride on their surfaces, thereby introducing abundant acyl chloride groups on the surface of the nanomaterials; on the other hand, the present invention utilizes the reaction between amino groups and acid anhydrides, and uses 2-amino-1,3-propanediol to modify the crosslinking agent, ethylenediaminetetraacetic acid dianhydride, to obtain a new type of modified crosslinking agent with stronger functionality, which not only contains more N atoms with lone pairs of electrons, but also contains abundant hydroxyl groups, which significantly improves its crosslinking effect and functionality. On this basis, the present invention uses the acyl chloride groups on the surfaces of modified aluminum silicate and SiO2 as polymerization sites, and utilizes the modified crosslinking agent to achieve efficient crosslinking and composite modification between aluminum silicate nanofibers and SiO2 nanoparticles. In this way, a SiO2 / nanofiber composite membrane with excellent structural stability can be prepared by a simple vacuum filtration technology, overcoming the problem that nanopowder materials are not easy to recycle. Moreover, using the modified ethylenediaminetetraacetic acid dianhydride as a cross-linking agent can not only further improve the porosity of the material during the cross-linking process, but also introduce more N atoms, O atoms and ester groups containing lone pair electrons that have excellent adsorption properties for heavy metal ions, thereby significantly improving the material's adsorption properties for heavy metal ions.

[0019] The advantages of the present invention compared with the prior art are:

[0020] The present invention realizes the fusion and synergistic enhancement of the adsorption performance of aluminum silicate nanofibers and SiO2 nanoparticles. The prepared composite membrane not only integrates the excellent adsorption capacity of both, but also introduces a large number of atoms and functional groups with excellent adsorption performance for heavy metal ions during the cross-linking reaction process, further improving the pore structure of the material, thereby further significantly improving the adsorption capacity of the composite membrane for heavy metals.

[0021] In addition, the present invention significantly enhances the structural stability of the nanocomposite film through the dual modification strategy of compounding and cross-linking, overcomes the limitation that the traditional nanomaterial powder form is difficult to effectively recycle and reuse during the application process, and enables the composite film to be easily recycled and reused, greatly improving the practical value and economic benefits of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the infrared spectrum of the intermediate obtained in Example 1.

[0023] Figure 2 The following is the H NMR spectrum of the intermediate obtained in Example 1. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the embodiments, but are not intended to limit the present invention.

[0025] Example 1

[0026] A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane comprises the following steps:

[0027] (1) 1 g of aluminum silicate nanofibers were ultrasonically dispersed in a mixture of 95% ethanol and water, and then 0.1 g of 3-aminopropyltrimethoxysilane was added, the temperature was raised to 60°C, and the mixture was stirred for 12 h. After the reaction, the mixture was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain amino-containing aluminum silicate nanofibers. 1 g of SiO2 nanoparticles were ultrasonically dispersed in a mixture of 95% ethanol and water, and then 0.1 g of 3-aminopropyltrimethoxysilane was added, the temperature was raised to 60°C, and the mixture was stirred for 12 h. After the reaction, the mixture was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain amino-containing SiO2 nanoparticles.

[0028] (2) 1g of amino-modified aluminum silicate nanofibers was ultrasonically dispersed in ethyl acetate, and then 1g of triethylamine was added, and 2g of succinyl chloride was slowly added dropwise at 0°C under nitrogen protection. After the addition was completed, the reaction system was stirred for 12h at room temperature under nitrogen protection. After the reaction, it was filtered, repeatedly washed with ethanol and deionized water, and dried to obtain acyl chloride-rich aluminum silicate nanofibers. 1g of amino-modified SiO2 nanoparticles was ultrasonically dispersed in ethyl acetate, and then 1g of triethylamine was added, and 2g of succinyl chloride was slowly added dropwise at 0°C under nitrogen protection. After the addition was completed, the reaction system was stirred for 12h at room temperature under nitrogen protection. After the reaction, it was filtered, repeatedly washed with ethanol and deionized water, and dried to obtain acyl chloride-rich SiO2 nanoparticles.

[0029] (3) Dissolve 1 g of ethylenediaminetetraacetic acid dianhydride in ‌N ,N -dimethylformamide, then add 0.8g of 2-amino-1,3-propanediol and 0.5g of pyridine, reflux the reaction system at 120°C for 18h, add deionized water and ethyl acetate for extraction after the reaction, add anhydrous sodium sulfate to the organic layer for drying, filter and take the filtrate for vacuum distillation, the product is recrystallized with ethyl acetate to obtain an intermediate containing more N atoms with lone pairs of electrons and rich in hydroxyl groups. The reaction formula is as follows:

[0030] .

[0031] The infrared spectrum of the intermediate is shown in Figure 1 As shown in the figure, 3400cm -1 The strong peaks on the left and right are the vibration peaks of -OH, 2920 cm -1 ~2850 cm -1 The absorption peak at 1640 cm is the characteristic peak of CH in methylene. -1 The absorption peak at 1590cm is the vibration peak of C=O. -1 Nearby is the stretching vibration peak of CN in the imide ring. The H NMR spectrum of the intermediate is shown in Figure 2 shown.

[0032] (4) 1 g of acyl chloride-rich aluminum silicate nanofibers and 0.5 g of acyl chloride-rich SiO2 nanoparticles were ultrasonically dispersed in ethyl acetate, and then 1 g of the intermediate and 1 g of triethylamine were added. The reaction system was heated to 60 ° C and stirred for 12 h. After cooling to room temperature, ethyl acetate was added to the reaction system until it reached 2000 mL. 31.4 mL of the reaction solution was filtered and repeatedly washed with deionized water. After drying, the sample membrane was peeled off from the filter membrane to obtain a sample with a diameter of 10 cm and a gram weight of 5 g / m 2 Functionalized SiO2 / aluminum silicate nanofiber composite membrane.

[0033] The adsorption performance test experiment of the functionalized SiO2 / aluminum silicate nanofiber composite membrane prepared in this Example 1 is as follows:

[0034] Prepare 100 mL of an aqueous solution with a lead ion concentration of 100 mg / L (lead nitrate as a reagent) in a flask, adjust the solution pH to 7 with 0.1 M NaOH, add the prepared functionalized SiO2 / aluminum silicate nanofiber composite membrane, and then adsorb for 3 hours at 200 rpm in a constant temperature oscillator at 30°C. After adsorption, take the upper clear liquid, determine the lead ion concentration in the clear liquid by ICP-OES, and calculate the adsorption amount of lead ions by the adsorbent material by the following formula ( Q , mg / g), and the results are listed in Table 1.

[0035] Q =(C 0 - C t ) V / M

[0036] Q is the adsorption amount (mg / g); C 0 is the initial concentration of heavy metal ions (mg / L); C t is the concentration of heavy metal ions after adsorption (mg / L); V is the volume of the solution (L); M is the mass of the adsorbent (mg).

[0037] Example 2

[0038] A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane comprises the following steps:

[0039] (1) 1 g of aluminum silicate nanofibers were ultrasonically dispersed in a mixture of 95% ethanol and water, and then 0.3 g of 3-aminopropyltrimethoxysilane was added, the temperature was raised to 75°C, and the mixture was stirred for 10 h. After the reaction, the mixture was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain amino-containing aluminum silicate nanofibers. 1 g of SiO2 nanoparticles were ultrasonically dispersed in a mixture of 95% ethanol and water, and then 0.3 g of 3-aminopropyltrimethoxysilane was added, the temperature was raised to 75°C, and the mixture was stirred for 10 h. After the reaction, the mixture was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain amino-containing SiO2 nanoparticles.

[0040] (2) 1g of amino-modified aluminum silicate nanofibers was ultrasonically dispersed in ethyl acetate, and then 1.5g of triethylamine was added, and 3g of succinyl chloride was slowly added dropwise at 0℃ under nitrogen protection. After the addition was completed, the reaction system was stirred for 14h at room temperature under nitrogen protection. After the reaction, it was filtered, repeatedly washed with ethanol and deionized water, and dried to obtain acyl chloride-rich aluminum silicate nanofibers. 1g of amino-modified SiO2 nanoparticles was ultrasonically dispersed in ethyl acetate, and then 1.5g of triethylamine was added, and 3g of succinyl chloride was slowly added dropwise at 0℃ under nitrogen protection. After the addition was completed, the reaction system was stirred for 14h at room temperature under nitrogen protection. After the reaction, it was filtered, repeatedly washed with ethanol and deionized water, and dried to obtain acyl chloride-rich SiO2 nanoparticles.

[0041] (3) Dissolve 1 g of ethylenediaminetetraacetic acid dianhydride in ‌N , N-dimethylformamide, then add 1g of 2-amino-1,3-propanediol and 0.75g of pyridine, and reflux the reaction system at 130°C for 15h. After the reaction, add deionized water and ethyl acetate for extraction, and add anhydrous sodium sulfate to the organic layer for drying. After filtering, take the filtrate and perform vacuum distillation. The product is recrystallized from ethyl acetate to obtain an intermediate containing more N atoms with lone pairs of electrons and rich in hydroxyl groups.

[0042] (4) 1 g of acyl chloride-rich aluminum silicate nanofibers and 0.75 g of acyl chloride-rich SiO2 nanoparticles were ultrasonically dispersed in ethyl acetate, and then 2 g of the intermediate and 1.5 g of triethylamine were added. The reaction system was heated to 70 °C and stirred for 10 h. After cooling to room temperature, ethyl acetate was added to the reaction system until it reached 2000 mL. 41.9 mL of the reaction solution was filtered and repeatedly washed with deionized water. After drying, the sample membrane was peeled off from the filter membrane to obtain a sample with a diameter of 10 cm and a gram weight of 10 g / m 2 The adsorption performance of the functionalized SiO2 / aluminum silicate nanofiber composite membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0043] Example 3

[0044] A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane comprises the following steps:

[0045] (1) 1 g of aluminum silicate nanofibers were ultrasonically dispersed in a mixture of 95% ethanol and water, and then 0.5 g of 3-aminopropyltrimethoxysilane was added, the temperature was raised to 90°C, and the mixture was stirred for reaction for 8 h. After the reaction, the mixture was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain amino-containing aluminum silicate nanofibers. 1 g of SiO2 nanoparticles were ultrasonically dispersed in a mixture of 95% ethanol and water, and then 0.5 g of 3-aminopropyltrimethoxysilane was added, the temperature was raised to 90°C, and the mixture was stirred for reaction for 8 h. After the reaction, the mixture was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain amino-containing SiO2 nanoparticles.

[0046] (2) 1g of amino-modified aluminum silicate nanofibers was ultrasonically dispersed in ethyl acetate, and then 2g of triethylamine was added, and 4g of succinyl chloride was slowly added dropwise at 0°C under nitrogen protection. After the addition was completed, the reaction system was stirred for 16h at room temperature under nitrogen protection. After the reaction, it was filtered, repeatedly washed with ethanol and deionized water, and dried to obtain acyl chloride-rich aluminum silicate nanofibers. 1g of amino-modified SiO2 nanoparticles was ultrasonically dispersed in ethyl acetate, and then 2g of triethylamine was added, and 4g of succinyl chloride was slowly added dropwise at 0°C under nitrogen protection. After the addition was completed, the reaction system was stirred for 16h at room temperature under nitrogen protection. After the reaction, it was filtered, repeatedly washed with ethanol and deionized water, and dried to obtain acyl chloride-rich SiO2 nanoparticles.

[0047] (3) Dissolve 1 g of ethylenediaminetetraacetic acid dianhydride in ‌N , N -dimethylformamide, then add 1.2g of 2-amino-1,3-propanediol and 1g of pyridine, and reflux the reaction system at 130°C for 12h. After the reaction, add deionized water and ethyl acetate for extraction, and add anhydrous sodium sulfate to the organic layer for drying. After filtering, take the filtrate and perform vacuum distillation. The product is recrystallized from ethyl acetate to obtain an intermediate containing more N atoms with lone pairs of electrons and rich in hydroxyl groups.

[0048] (4) 1 g of acyl chloride-rich aluminum silicate nanofibers and 1 g of acyl chloride-rich SiO2 nanoparticles were ultrasonically dispersed in ethyl acetate, and then 3 g of the intermediate and 2 g of triethylamine were added. The reaction system was heated to 80 °C and stirred for 8 h. After cooling to room temperature, ethyl acetate was added to the reaction system until it reached 2000 mL. 47.1 mL of the reaction solution was filtered and repeatedly washed with deionized water. After drying, the sample membrane was peeled off from the filter membrane to obtain a sample with a diameter of 10 cm and a gram weight of 15 g / m 2 The adsorption performance of the functionalized SiO2 / aluminum silicate nanofiber composite membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0049] Example 4

[0050] A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane, wherein steps (1), (2) and (3) are the same as those in Example 1, and step (4) is to ultrasonically disperse 1 g of acyl chloride-rich aluminum silicate nanofibers and 0.5 g of acyl chloride-rich SiO2 nanoparticles in ethyl acetate, then add 1 g of an intermediate and 1 g of triethylamine, heat the reaction system to 60°C, stir the reaction for 12 hours, cool the temperature to room temperature, add ethyl acetate to the reaction system to reach 2000 mL, take 62.8 mL of the reaction solution for suction filtration, repeatedly wash with deionized water, and after drying, peel off the sample membrane from the filter membrane to obtain a membrane with a diameter of 10 cm and a gram weight of 10 g / m 2 The adsorption performance of the functionalized SiO2 / aluminum silicate nanofiber composite membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0051] Example 5

[0052] A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane, wherein steps (1), (2) and (3) are the same as those in Example 1, and step (4) is to ultrasonically disperse 1 g of acyl chloride-rich aluminum silicate nanofibers and 0.5 g of acyl chloride-rich SiO2 nanoparticles in ethyl acetate, then add 1 g of an intermediate and 1 g of triethylamine, heat the reaction system to 60°C, stir the reaction for 12 hours, cool the temperature to room temperature, add ethyl acetate to the reaction system to reach 2000 mL, take 94.2 mL of the reaction solution for suction filtration, repeatedly wash with deionized water, and after drying, peel off the sample membrane from the filter membrane to obtain a membrane having a diameter of 10 cm and a gram weight of 15 g / m 2 The adsorption performance of the functionalized SiO2 / aluminum silicate nanofiber composite membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0053] Comparative Example 1

[0054] A method for preparing an amino-modified aluminum silicate nanofiber membrane comprises the following steps:

[0055] According to step (1) of Example 1, amino-modified aluminum silicate nanofibers were prepared, and then 1 g of amino-modified aluminum silicate nanofibers were dispersed in 2000 ml of ethyl acetate and dispersed evenly by ultrasonication. 78.5 ml of the dispersion was filtered to form a membrane, and the membrane was repeatedly washed with deionized water. After drying, the sample membrane was peeled off from the filter membrane to obtain a sample with a diameter of 10 cm and a gram weight of 5 g / m 2 The adsorption performance of the amino-containing aluminum silicate nanofiber membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0056] Comparative Example 2

[0057] A method for preparing an amination SiO2 / aluminum silicate nanofiber composite membrane comprises the following steps:

[0058] According to step (1) in Example 1, amino-modified aluminum silicate nanofibers and amino-modified SiO2 nanoparticles were prepared, and then 1 g of amino-modified aluminum silicate nanofibers and 0.5 g of amino-modified SiO2 nanoparticles were dispersed in 2000 mL of ethyl acetate and dispersed evenly by ultrasonication. 52.4 ml of the dispersion was filtered to form a membrane, and the membrane was repeatedly washed with deionized water. After drying, the sample membrane was peeled off from the filter membrane to obtain a sample with a diameter of 10 cm and a gram weight of 5 g / m 2 The adsorption performance of the amino SiO2 / aluminum silicate nanofiber composite membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0059] Comparative Example 3

[0060] A method for preparing a cross-linked modified SiO2 / aluminum silicate nanofiber composite membrane comprises the following steps:

[0061] According to step (1) in Example 1, amino aluminum silicate nanofibers and amino SiO2 nanoparticles were prepared, and then 1 g of amino aluminum silicate nanofibers and 0.5 g of amino SiO2 nanoparticles were ultrasonically dispersed in N , N -dimethylformamide, add 1g of ethylenediaminetetraacetic anhydride, and stir at 60℃ for 6 h under nitrogen protection. After the reaction is completed, add N , N -dimethylformamide until the reaction system reaches 2000mL, take 31.4mL of the reaction solution for suction filtration, repeatedly wash with deionized water, and peel off the sample membrane from the filter membrane after drying to obtain a sample with a diameter of 10cm and a gram weight of 5g / m 2 The adsorption performance of the cross-linked modified SiO2 / aluminum silicate nanofiber composite membrane was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0062] Table 1 Adsorption amount of lead ions by the adsorption films prepared in Examples 1-3 and Comparative Examples 1-3

[0063]

[0064] It can be seen from the above results that in the composite membrane prepared in the embodiment of the present invention, an effective interface bond is formed between the aluminum silicate nanofibers and the SiO2 nanoparticles, achieving a strong combination and synergistic effect of the two in adsorption performance. At the same time, a rich atom and functional group with excellent adsorption performance for heavy metal ions are introduced during the crosslinking process, and the crosslinking effect further improves the porosity of the composite membrane. These three advantages give the composite membrane an excellent adsorption capacity for lead ions, and its adsorption amount for lead ions can reach 339mg / g. In contrast, in Comparative Example 1, the aluminum silicate nanofibers simply amino-modified cannot form an effective crosslinking structure, and lack the synergistic adsorption effect of rich functional groups and SiO2; in Comparative Example 2, although the adsorption effect of SiO2 and aluminum silicate nanofibers can be synergistically exerted, the interface bond between the two is weak, resulting in a weak synergistic effect between the two, and the adsorption functional groups contained are single and relatively small in content; in Comparative Example 3, the crosslinking agent ethylenediaminetetraacetic acid dianhydride is not modified, so that fewer adsorption functional groups are introduced during the crosslinking reaction. Therefore, the adsorption materials prepared in these three comparative examples cannot be compared with the functionalized SiO2 / aluminum silicate nanofiber composite membrane prepared in the embodiment in terms of the number of adsorption functional groups, the richness of the pore structure, the strength of the synergistic adsorption effect, etc., which leads to a significant reduction in their adsorption capacity for lead ions.

[0065] Furthermore, by comparing the adsorption results of Examples 1, 4, and 5, although increasing the mass of the membrane (mainly by increasing the thickness of the membrane rather than the diameter) can provide more adsorption sites, the increase in thickness slows down the diffusion rate of ions in the membrane, that is, the permeability decreases, which to a certain extent hinders the effective contact and adsorption of metal ions with the active sites. Therefore, when the thickness of the membrane reaches a certain threshold, the growth of the actual adsorption amount is no longer in line with expectations, and may even show a downward trend.

Claims

1. A method for preparing a functionalized SiO2 / aluminum silicate nanofiber composite membrane, characterized in that: The following steps are involved: (1) Aluminum silicate nanofibers and SiO2 nanoparticles are modified by aminosilane coupling agent to obtain amino-modified aluminum silicate nanofibers and amino-modified SiO2 nanoparticles, respectively; (2) grafting succinyl chloride onto the surfaces of the amino aluminum silicate nanofibers and the amino SiO2 nanoparticles, respectively, to obtain acyl chloride aluminum silicate nanofibers and acyl chloride SiO2 nanoparticles; (3) Dissolve ethylenediaminetetraacetic acid dianhydride in ‌N , N -dimethylformamide, then add 2-amino-1,3-propanediol and the first acid binding agent to reflux at 120-135°C for 12-18h, add deionized water and ethyl acetate to extract after the reaction, and dry the obtained organic layer and distill under reduced pressure, and recrystallize the product with ethyl acetate to obtain an intermediate, the reaction formula is as follows: ; (4) using the intermediate as a crosslinking agent and the acyl chloride group as a polymerization site, a crosslinking polymerization reaction is carried out between the acyl chloride aluminum silicate nanofibers and the acyl chloride SiO2 nanoparticles, and then filtering to form a membrane, and after sufficient washing and drying, a film with a gram weight of no more than 15 g / m 2 Functionalized SiO2 / aluminum silicate nanofiber composite membrane.

2. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 1, characterized in that: The step (1) specifically comprises ultrasonically dispersing aluminum silicate nanofibers in a mixture of ethanol and water, and then adding an aminosilane coupling agent for stirring reaction, wherein the mass ratio of the aluminum silicate nanofibers to the aminosilane coupling agent is 1:(0.1-0.5); ultrasonically dispersing SiO2 nanoparticles in a mixture of ethanol and water, and then adding an aminosilane coupling agent for stirring reaction, wherein the mass ratio of the SiO2 nanoparticles to the aminosilane coupling agent is 1:(0.1-0.5).

3. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 2, characterized in that: The stirring reaction in step (1) is carried out at 60-90° C. for 8-12 hours.

4. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 2, characterized in that: The aminosilane coupling agent is one of 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane.

5. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 1, characterized in that: The step (2) specifically comprises ultrasonically dispersing the amino aluminum silicate nanofibers in ethyl acetate, then adding a second acid binding agent, and slowly dropping succinyl chloride under nitrogen protection, and then stirring the reaction, wherein the mass ratio of the amino aluminum silicate nanofibers, the second acid binding agent and succinyl chloride is 1:(1-2):(2-4); ultrasonically dispersing the amino SiO2 nanoparticles in ethyl acetate, then adding a third acid binding agent, and slowly dropping succinyl chloride under nitrogen protection, and then stirring the reaction, wherein the mass ratio of the amino SiO2 nanoparticles, the third acid binding agent and succinyl chloride is 1:(1-2):(2-4).

6. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 5, characterized in that: The stirring reaction in step (2) is carried out under nitrogen protection at room temperature for 12 to 16 hours.

7. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 1, characterized in that: In the step (3), the mass ratio of ethylenediaminetetraacetic acid dianhydride, 2-amino-1,3-propylene glycol and the first acid binding agent is 1: (0.8-1.2): (0.5-1).

8. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 1, characterized in that: The step (4) specifically comprises the following steps: ultrasonically dispersing the aluminum silicate nanofibers and the SiO2 nanoparticles in ethyl acetate, and then adding the prepared intermediate and the fourth acid binding agent to carry out a cross-linking reaction, wherein the mass ratio of the aluminum silicate nanofibers, the SiO2 nanoparticles, the intermediate and the fourth acid binding agent is 1:(0.5-1):(1-3):(1-2).

9. The method for preparing the functionalized SiO2 / aluminum silicate nanofiber composite membrane according to claim 8, characterized in that: The cross-linking reaction in step (4) is carried out at 60-80° C. for 8-12 hours.

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