Preparation method of aramid nanofiber reinforced cross-linked hyperbranched polyamide-amine composite adsorption ball

Abstract

The invention relates to a sewage adsorbent, and discloses a preparation method of an aramid nanofiber reinforced cross-linked hyperbranched polyamide-amine composite adsorption ball, which comprises the following steps: 1) mixing aramid nanofiber, KOH, ultrapure water and DMSO, stirring at a constant temperature, adding deionized water, filtering, adding a filtered substance into deionized water, and carrying out ultrasonic dispersion to prepare an aramid nanofiber suspension; and 2) adding hyperbranched polyamide-amine into the aramid nanofiber suspension, adding a cross-linking agent, uniformly stirring, adding a dispersing agent into an organic medium, carrying out water bath heat preservation, dropwise adding the mixed solution, carrying out a cross-linking reaction, filtering, washing, and carrying out vacuum drying to obtain the hyperbranched polyamide-amine / aramid nanofiber composite material. According to the method, hyperbranched polyamide-amine is subjected to in-situ cross-linking in an aramid nanofiber suspension to prepare the aramid nanofiber reinforced cross-linked hyperbranched polyamide-amine composite adsorption ball, so that agglomeration of aramid nanofibers in a matrix is avoided, and the reinforcing effect of the aramid nanofibers can be played.

Description

Technical Field

[0001] The present invention relates to a sewage adsorbent, and particularly to a preparation method of an aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere. Background Art

[0002] Water pollution includes domestic wastewater and industrial wastewater. The composition of industrial wastewater is complex, including heavy metal wastewater, organic dye wastewater, pesticide wastewater, radioactive wastewater, and organophosphorus wastewater, etc. Therefore, various water treatment technologies such as chemical precipitation, adsorption method, and biological filtration have been proposed to solve the water pollution problem. At present, due to the advantages of high removal efficiency and simple operation, the adsorption method has become one of the most commonly used technologies for removing pollutants in the water environment.

[0003] Hyperbranched polyamide-amine is a water-soluble high-capacity chelating nanomaterial with a dendritic structure containing primary amine and tertiary amine groups. It is easy to synthesize and suitable for large-scale industrial applications, especially in environmental remediation. Since it is easily soluble in water, to prevent the risk of secondary pollution, it is crosslinked when used as an adsorbent. However, in addition to poor mechanical properties, the high swelling rate caused by excellent hydrophilicity of traditional polymer gels often causes structural damage under the action of high water load during adsorption, limiting the practical application of the material. Summary of the Invention

[0004] To solve the above problems, the present invention provides a preparation method of an aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere, including the following steps:

[0005] 1) Mix aramid nanofibers, KOH, ultrapure water, and DMSO, and stir at a constant temperature to obtain an aramid nanofiber solution. Then continue to add deionized water, fully stir and filter. Add the filtrate to deionized water and disperse it by ultrasonic waves to obtain an aramid nanofiber suspension;

[0006] 2) Add hyperbranched polyamide-amine to the obtained aramid nanofiber suspension, add a crosslinking agent and stir evenly to obtain a mixed solution. Add a dispersant to the organic medium and keep it warm in a water bath. Drop the mixed solution drop by drop for crosslinking reaction. After the reaction is completed, filter, wash the filtrate with hot ethanol and pure water, and dry it under vacuum to obtain the product.

[0007] The aramid nanofibers used in the present invention are terephthaloyl terephthalamide, and the concentration of aramid nanofibers in the suspension is 2 - 10 g / L.

[0008] Hyperbranched polyamide-amine is a water-soluble high-capacity chelating nanomaterial with a dendritic structure containing primary amine and tertiary amine groups. It is easy to synthesize and suitable for large-scale industrial applications, especially in environmental remediation. Due to its high solubility in water, to prevent the risk of secondary pollution, we crosslink it when used as an adsorbent. However, in addition to poor mechanical properties, the high swelling rate caused by excellent hydrophilicity of traditional polymer gels often causes structural damage under the high water load during adsorption, limiting the practical application of the materials. High-performance aramid nanofibers have excellent mechanical strength and modulus and have made outstanding contributions to the reinforcement of composite materials. Dispersing aramid nanofibers in crosslinked hyperbranched polyamide-amine to form a rigid "skeleton" restricts the excessive swelling of crosslinked hyperbranched polyamide-amine, thereby achieving the purpose of improving mechanical strength. Therefore, the selection of aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine is of great significance for practical application and recycling. The present invention enriches the design ideas and methods of adsorption materials by developing an easily prepared, high-capacity, and economical aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere. The hyperbranched polyamide-amine used in the present invention has a molecular structure as shown in Figure 1 shown.

[0009] The present invention prepares an aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere by in-situ crosslinking of hyperbranched polyamide-amine in an aramid nanofiber suspension through a suspension polymerization process. The addition of aramid nanofibers greatly enhances the mechanical properties of crosslinked hyperbranched polyamide-amine, which is attributed to the excellent dispersion of aramid nanofibers in crosslinked hyperbranched polyamide-amine and the strong interfacial interaction between aramid nanofibers and crosslinked hyperbranched polyamide-amine. In addition, a large number of amino functional groups provide a large number of adsorption sites for pollutants. Therefore, the composite adsorption sphere has a high adsorption capacity and excellent mechanical properties and can be applied to large-scale industrial sewage treatment.

[0010] Specifically, the crosslinking agent is one of diglycidyl ether, ethylene glycol diglycidyl ether, or diethylene glycol diglycidyl ether; the organic medium is one of n-pentane, n-hexane, n-heptane, n-octane, gasoline, cyclohexane, toluene, xylene, benzene, liquid paraffin, or carbon tetrachloride; the dispersant is a nonionic surfactant of Span and Tween series.

[0011] Compared with the prior art, the present invention has the following advantages: The present invention adopts a method of preparing aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres by in-situ crosslinking of hyperbranched polyamide-amine in an aramid nanofiber suspension, which avoids the agglomeration of aramid nanofibers in the matrix and is conducive to exerting the reinforcing effect of aramid nanofibers; The method of inverse suspension polymerization is used to prepare spherical adsorbents, which has the advantages of smaller bulk density, larger specific surface area, small flow resistance, safer and more stable compared with other shapes; The reaction of the present invention is a one-pot synthesis, which has the advantages of simple preparation process and low cost. Description of the Drawings

[0012] Figure 1 It is the molecular structure diagram of the hyperbranched polyamide-amine adopted by the present invention.

[0013] Figure 2 They are the scanning electron microscope images of Comparative Example 1 (a), Example 1 (b), and Example 2 (c).

[0014] Figure 3 They are the compressive stress-strain curves of Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5.

[0015] Figure 4 They are the compressive stress-strain curves of Example 1, Example 6, Example 7, Example 8, and Example 9.

[0016] Figure 5 They are the adsorption amounts of methylene blue, new carmine, and acid orange by Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5. Detailed Embodiments

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] Example 1

[0019] A preparation method of aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres, comprising the following steps: (1) Dissolve 2.5 g of aramid fiber, 7.5 g of KOH, 20 mL of ultrapure water and 480 mL of DMSO in a 35 °C water bath with stirring for 12 h to obtain a 5 g / L aramid nanofiber solution for standby; (2) Add 40 mL of the aramid nanofiber solution in step (1) to deionized water and stir for protonation, filter and wash away the excess KOH and DMSO, redisperse it in deionized water to make the total volume 100 mL, and ultrasonically crush it at 600 W for 20 min to prepare a 100 mL aramid nanofiber suspension with a concentration of 2 g / L for standby; (3) Add 100 mL of the dispersion medium liquid paraffin into a flask, drop in 1 wt% of the dispersant Span80 in liquid paraffin, and mechanically stir at 450 rmp; (4) Weigh 4 g of hyperbranched polyamide - amine and add it to dissolve in 20 mL of the aramid nanofiber suspension in step (2), add 2.991 mL of the crosslinking agent diethylene glycol diglycidyl ether (DEGDGE), stir evenly, and drop it into the flask in step (3) with a water bath heating at 60 °C for crosslinking for 3 h, then filter to obtain aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres; (5) Wash the aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres in step (4) with hot ethanol and pure water, and vacuum dry at 60 °C (vacuum degree is - 0.8 MPa) for 10 h to obtain pure aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres (ANFs2 / HP - DEGDGE3).

[0020] Example 2

[0021] The difference from Example 1 is only that in step (2), the volume of the aramid nanofiber solution is 60 mL, the concentration of the aramid nanofiber suspension is 3 g / L, and aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres (ANFs3 / HP - DEGDGE3) are prepared.

[0022] Example 3

[0023] The difference from Example 1 is only that in step (2), the volume of the aramid nanofiber solution is 80 mL, the concentration of the aramid nanofiber suspension is 4 g / L, and aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres (ANFs4 / HP - DEGDGE3) are prepared.

[0024] Example 4

[0025] The difference from Example 1 is only that in step (2), the volume of the aramid nanofiber solution is 100 mL, the concentration of the aramid nanofiber suspension is 5 g / L, and aramid nanofiber reinforced crosslinked hyperbranched polyamide - amine composite adsorption spheres (ANFs5 / HP - DEGDGE3) are prepared.

[0026] Example 5

[0027] The difference from Example 1 is only that in step (2), the volume of the aramid nanofiber solution is 120 mL, and the concentration of the aramid nanofiber suspension is 6 g / L, to obtain aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres (ANFs6 / HP-DEGDGE3).

[0028] Example 6

[0029] A preparation method of aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres includes the following steps: (1) Dissolve 2.5 g of aramid fiber, 7.5 g of KOH, 20 mL of ultrapure water and 480 mL of DMSO in a water bath at 35 °C with stirring for 12 h to obtain a 5 g / L aramid nanofiber solution for standby; (2) Add 60 mL of the aramid nanofiber solution in step (1) to deionized water and stir for protonation, filter and wash away the excess KOH and DMSO, redisperse it in deionized water to make the total volume 100 mL, and ultrasonically crush it at 600 W for 20 min to obtain a 100 mL aramid nanofiber suspension with a concentration of 3 g / L for standby; (3) Add 100 mL of the dispersion medium liquid paraffin to a flask, drop in 1 wt% of the dispersant Span80 of liquid paraffin and stir mechanically, with the stirring speed of 450 rmp; (4) Weigh 4 g of hyperbranched polyamide-amine and add it to the 20 mL of the aramid nanofiber suspension in step (2) to dissolve, add 3.988 mL of the crosslinking agent diethylene glycol diglycidyl ether (DEGDGE), stir evenly, and drop it into the flask in step (3) with a water bath heating at 60 °C for crosslinking for 3 h, and filter to obtain aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres; (5) Wash the aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres in step (4) with hot ethanol and pure water, and vacuum dry them at 60 °C (vacuum degree is -0.8 MPa) for 10 h to obtain pure aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres (ANFs3 / HP-DEGDGE4).

[0030] Example 7

[0031] The difference from Example 6 is only that in step (4), the volume of DEGDGE is 4.985 mL, to obtain aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres (ANFs3 / HP-DEGDGE5).

[0032] Example 8

[0033] The difference from Example 6 is only that in step (4), the volume of DEGDGE is 5.982 mL, to obtain aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres (ANFs3 / HP-DEGDGE6).

[0034] Example 9

[0035] The difference from Example 6 is only that the volume of DEGDGE in step (4) is 6.979 mL, and the aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere (ANFs3 / HP-DEGDGE7) is prepared.

[0036] Example 10

[0037] A preparation method of an aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere includes the following steps: (1) Dissolve 2.5 g of aramid fiber, 7.5 g of KOH, 20 mL of ultrapure water and 480 mL of DMSO in a water bath at 35 °C for 12 h to obtain a 5 g / L aramid nanofiber solution for standby; (2) Add 60 mL of the aramid nanofiber solution in step (1) to deionized water and stir for protonation, filter and wash the excess KOH and DMSO, redisperse it in deionized water to make the total volume 100 mL, and ultrasonically crush it at 600 W for 20 min to obtain 100 mL of an aramid nanofiber suspension with a concentration of 3 g / L for standby; (3) Add 100 mL of the dispersion medium liquid paraffin to a flask, drop in 1 wt% of the dispersant Span80 of liquid paraffin, and mechanically stir at a stirring speed of 450 rmp; (4) Weigh 4 g of hyperbranched polyamide-amine and add it to 20 mL of the aramid nanofiber suspension in step (2) to dissolve, add 2.388 mL of the crosslinking agent ethylene glycol diglycidyl ether (EGDE), stir evenly, and drop it into the flask in step (3) with a water bath heating at 50 °C for crosslinking for 4 h, and filter to obtain the aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere; (5) Wash the aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere in step (4) with hot ethanol and pure water, and vacuum dry it at 60 °C (vacuum degree -0.8 MPa) for 10 h to obtain a pure aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption sphere (ANFs3 / HP-EGDE3).

[0038] Example 11

[0039] A preparation method of aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres, comprising the following steps: (1) Dissolve 2.5 g of aramid fiber, 7.5 g of KOH, 20 mL of ultrapure water and 480 mL of DMSO in a water bath at 35 °C with stirring for 12 h to obtain a 5 g / L aramid nanofiber solution for standby; (2) Add 60 mL of the aramid nanofiber solution in step (1) to deionized water and stir for protonation, filter and wash away the excess KOH and DMSO, redisperse it in deionized water to make the total volume 100 mL, and ultrasonically crush it at 600 W for 20 min to obtain a 100 mL aramid nanofiber suspension with a concentration of 3 g / L for standby; (3) Add 100 mL of the dispersion medium cyclopentane to a flask, drop in 0.8 wt% of the dispersant Span80 of liquid paraffin, and stir mechanically at a stirring speed of 360 rmp; (4) Weigh 4 g of hyperbranched polyamide-amine and add it to 20 mL of the aramid nanofiber suspension in step (2) to dissolve, add 2.991 mL of the crosslinking agent diethylene glycol diglycidyl ether (DEGDGE), stir evenly, and drop it into the flask in step (3) with a water bath heating at 60 °C for crosslinking for 4 h, and filter to obtain aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres; (5) Wash the aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres in step (4) with hot ethanol and pure water, and dry them in vacuum at 60 °C (vacuum degree is -0.8 MPa) for 10 h to obtain pure aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres (ANFs3 / HP-DEGDGE3).

[0040] Comparative Example 1

[0041] A preparation method of crosslinked hyperbranched polyamide-amine spheres without aramid nanofibers, comprising the following steps: (1) Add 100 mL of the dispersion medium liquid paraffin to a flask, drop in 1 wt% of the dispersant Span80 of liquid paraffin, and stir mechanically at a stirring speed of 450 rmp; (2) Weigh 4 g of hyperbranched polyamide-amine and add it to 20 mL of pure water to dissolve, add 2.991 mL of the crosslinking agent diethylene glycol diglycidyl ether (DEGDGE), stir evenly, and drop it into the flask in step (1) with a water bath heating at 60 °C for crosslinking for 3 h, and filter to obtain aramid nanofiber reinforced crosslinked hyperbranched polyamide-amine composite adsorption spheres; (3) Wash the crosslinked hyperbranched polyamide-amine composite adsorption spheres in step (2) with hot ethanol and pure water, and dry them in vacuum at 60 °C (vacuum degree is -0.8 MPa) for 10 h to obtain pure crosslinked hyperbranched polyamide-amine adsorption spheres (HP-DEGDGE3).

[0042] Test 1: Use a scanning electron microscope to observe the surface morphologies of HP-DEGDGE3 in Comparative Example 1, the ANFs2 / HP-DEGDGE3 adsorption spheres in Example 1, and the ANFs3 / HP-DEGDGE3 adsorption spheres in Example 2, asFigure 2 As shown, the surface of the HP-DEGDGE3 adsorption sphere without aramid nanofibers added is smooth with some damage on the surface. The surface of the ANFs2 / HP-DEGDGE3 adsorption sphere is smooth and no obvious damage is seen. The surface of the ANFs3 / HP-DEGDGE3 adsorption sphere is rough and has pores, and the surface is relatively intact. This shows that the addition of aramid nanofibers reduces the possibility of adhesion in the system and has a certain impact on the material surface, increasing the specific surface area of the material, which will provide more adsorption sites for pollutants.

[0043] Test 2: Use a universal testing machine to conduct mechanical property tests on the aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine wet gel. The test results of the compressive stress-strain curve are as Figure 3 shown. The compressive stress-strain curves of Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5 show that as the addition amount of aramid nanofibers increases, the compressive strength of the material increases. This benefits from the good dispersion of aramid nanofibers in the crosslinked hyperbranched polyamide-amine and the strong interfacial interaction.

[0044] Test 3: Use a universal testing machine to conduct mechanical property tests on the aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine wet gel. The test results of the compressive stress-strain curve are as Figure 4 shown. The compressive stress-strain curves of Example 1, Example 6, Example 7, Example 8, and Example 9 show that as the crosslinking agent dosage increases, the compressive strength of the material increases. This benefits from the dense polymer network caused by the high crosslinking degree, which greatly improves the mechanical properties of the material. However, the reduction of functional groups will be unfavorable for the adsorption performance.

[0045] Test 4: Use an ultraviolet-visible spectrophotometer to detect the dye concentration before and after the adsorption of the aramid nanofiber-reinforced crosslinked hyperbranched polyamide-amine adsorption sphere. The adsorption amounts of the adsorption spheres of Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5 for methylene blue (MB), congo red (NC), and acid orange (OA) are as Figure 5 shown. It can be seen from the figure that the adsorption capacities of the adsorption spheres for the three dyes are all large, and the addition of aramid nanofibers improves the adsorption capacity of the material. This benefits from the fact that aramid nanofibers make the surface of the adsorption sphere rough and form surface pores, which is conducive to creating more adsorption sites for pollutants.

[0046] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing aramid nanofiber reinforced cross-linked hyperbranched polyamide-amine composite adsorption spheres, characterized in that: The following steps are involved: 1) Aramid nanofibers, KOH, ultrapure water and DMSO are mixed and stirred at a constant temperature to obtain an aramid nanofiber solution, deionized water is added, the mixture is fully stirred and filtered, and the filtrate is added to deionized water and ultrasonically dispersed to obtain an aramid nanofiber suspension; 2) adding the hyperbranched polyamide-amine to the obtained aramid nanofiber suspension, adding the cross-linking agent and stirring evenly to obtain a mixed solution, adding the dispersant to the organic medium and keeping it warm in a water bath, dripping the mixed solution drop by drop to perform a cross-linking reaction, filtering after the reaction is completed, washing the filtrate with hot ethanol and pure water, and vacuum drying to obtain the obtained solution.

2. The preparation method according to claim 1, characterized in that: In step 1), the aramid nanofiber material is p-phenylene terephthalamide.

3. The preparation method according to claim 1, characterized in that: In step 1), the concentration of aramid nanofibers in the obtained aramid nanofiber suspension is 2-10 g / L.

4. The preparation method according to claim 1, characterized in that: In step 2), the cross-linking agent is one of diglycidyl ether, ethylene glycol diglycidyl ether or diethylene glycol diglycidyl ether.

5. The preparation method according to claim 1, characterized in that: In step 2), the organic medium is one of n-pentane, n-hexane, n-heptane, n-octane, gasoline, cyclohexane, toluene, xylene, benzene, liquid paraffin or carbon tetrachloride.

6. The preparation method according to claim 1, characterized in that: In step 2), the dispersant is a non-ionic surfactant of the Span or Tween series.

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