Preparation method and application of palm fiber nanocellulose / aramid nanofiber composite aerogel

Abstract

The application discloses a preparation method and application of palm fiber nanocellulose / aramid nanofiber composite aerogel, and the preparation method comprises the following steps: dissolving palm fiber nanocellulose and aramid nanofiber in an organic solvent containing a dissolving promoter to obtain a uniform solution; placing the solution in a crosslinking agent solution after freezing and replacement to perform a crosslinking reaction, so as to obtain a wet gel; and performing replacement and freezing molding. The composite aerogel prepared by the application has high porosity, uniform and stable adsorption sites, good adsorption effect and high structural strength, and the adsorption efficiency of the composite aerogel on cationic dyes reaches more than 92 %.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of filter materials, in particular to a preparation method of palm fiber nanocellulose / aramid nanofiber composite aerogel and application thereof in cationic dye adsorption in textile dyes. BACKGROUND

[0002] Printing and dyeing wastewater and papermaking wastewater have the characteristics of large water quantity, high concentration, large colority and complex composition. The diversity of dyes and the large use of chemical pulp make the wastewater contain a large amount of organic matter that is difficult to biodegrade. Long-term accumulation of the wastewater leads to extremely deep color and serious environmental damage, which is one of the major environmental problems that need to be treated at present.

[0003] Cellulose is a renewable and abundant resource, but the utilization rate of substances containing a large amount of cellulose such as straw and fallen leaves is low at present. Most of them are treated by incineration. If they can be reasonably developed and reused, it is expected to solve the problem of resource shortage, realize waste-to-resource and improve economic benefits.

[0004] Chinese patent CN 108727639 B discloses a preparation method and application of bacterial cellulose / aramid nanofiber composite aerogel. The preparation method is as follows: bacterial cellulose is put into distilled water, and a bacterial cellulose suspension is obtained by crushing with a beater; aramid and potassium hydroxide are put into dimethyl sulfoxide and stirred to obtain an aramid nanofiber solution; the bacterial cellulose suspension and the aramid nanofiber solution are mixed and stirred to obtain a gel; the bacterial cellulose / aramid nanofiber composite gel is obtained by vacuum filtration; and the bacterial cellulose / aramid nanofiber composite aerogel is obtained by freeze-drying.

[0005] The present inventors found that the above-mentioned composite aerogel at least has the following disadvantages when implementing the technical solutions of the present application:

[0006] 1. The bacterial cellulose and the aramid nanofiber in the prepared composite aerogel cannot be uniformly mixed, the adsorption sites of the aerogels in the same batch are greatly different, and the adsorption effect of the aerogel is unstable and the adsorption quality is poor during the use of dyes;

[0007] 2. The specific surface area of the aerogel is small, the adsorption efficiency is low, and the treatment efficiency of cationic dye mist water is low;

[0008] 3. The composite aerogel is prone to disintegration during use. SUMMARY

[0009] The present application provides a preparation method and application of palm fiber nanocellulose / aramid nanofiber composite aerogel, which solves the above-mentioned problems of the composite aerogel in the adsorption treatment of printing and dyeing wastewater in the prior art.

[0010] To solve the above technical problems, the application provides a preparation method of palm fiber nanocellulose / aramid nanofiber composite aerogel, which comprises the following steps:

[0011] (1) preparing a mixed solution: dissolving palm fiber nanocellulose and aramid nanofiber in an organic solvent containing a dissolving promoter to obtain a uniform solution;

[0012] (2) freezing and replacement: freezing the uniform solution obtained in step (1) into a block, and then placing the block in distilled water for replacement to obtain a block-shaped material

[0013] (3) crosslinking reaction: placing the block-shaped material after the replacement in step (2) in a crosslinking agent solution for crosslinking reaction to obtain a wet gel;

[0014] (4) replacement and freeze forming: transferring the wet gel obtained in step (3) to an organic alcohol solvent for solution replacement, and then freeze drying to obtain the palm fiber nanocellulose / aramid nanofiber composite aerogel.

[0015] In a preferred embodiment of the application, in step (1), the mass ratio of the palm fiber nanocellulose and the aramid nanofiber is 1:0.1-9.

[0016] In a preferred embodiment of the application, in step (1), the dissolving promoter is tetrabutylammonium fluoride.

[0017] In a preferred embodiment of the application, in step (2), the replacement time is 3-6 h.

[0018] In a preferred embodiment of the application, in step (3), the process conditions of the crosslinking reaction are as follows: the temperature is 80-110 ℃, and the time is 2-4 h.

[0019] In a preferred embodiment of the application, in step (3), before the crosslinking reaction, the frozen block is placed in the crosslinking agent solution for 1-2 h.

[0020] In a preferred embodiment of the application, the crosslinking agent is at least one of glutaraldehyde, glyoxal or epichlorohydrin.

[0021] In a preferred embodiment of the application, in step (4), the process conditions of the freeze drying are as follows: the temperature is -60 ℃ to -90 ℃, and the time is 36 h to 72 h.

[0022] To solve the above technical problems, the application further provides an application of the palm fiber nanocellulose / aramid nanofiber composite aerogel, and the palm fiber nanocellulose / aramid nanofiber composite aerogel is used for adsorbing cationic dyes.

[0023] The palm fiber nanocellulose / aramid nanofiber composite aerogel prepared by the method has the following beneficial effects:

[0024] 1. By dissolving the palm fiber nanocellulose and aramid nanofiber to prepare a uniform solution, the palm fiber nanocellulose and aramid nanofiber can be uniformly distributed when forming a gel, and the stability of the sample is ensured.

[0025] 2. In the preparation process of the palm fiber nanocellulose / aramid nanofiber composite aerogel, the wet gel is formed by the method of freezing, distilled water replacement, crosslinking and alcohol solvent replacement, the porosity and adsorption sites are effectively improved under the premise of ensuring the product quality, and the adsorption effect is improved.

[0026] 3. In the preparation process of the palm fiber nanocellulose / aramid nanofiber composite aerogel, the crosslinking agent is used to connect the hydroxyl groups on the surface of the palm fiber nanocellulose and the amine groups on the surface of the aramid nanofiber, so that a stable structure is formed between the palm fiber nanocellulose and the aramid nanofiber, and the product strength is improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a micro-morphology diagram of palm fiber nanocellulose;

[0028] Figure 2 is a micro-morphology diagram of aramid nanofiber;

[0029] Figure 3 is a micro-morphology diagram of the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 1 of the present application;

[0030] Figure 4 is a digital photo of the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 1 of the present application;

[0031] Figure 5 is a contrast digital photo diagram of the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 1 of the present application before and after adsorbing a low-concentration methylene blue solution (0.04 mmol / L) for 13 hours;

[0032] Figure 6 is an ultraviolet absorption spectrum diagram of the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 1 of the present application before and after adsorbing a low-concentration methylene blue solution (0.04 mmol / L) for 13 hours;

[0033] Figure 7is a contrast digital photo of palm fiber nanocellulose / aramid nanofiber composite aerogel prepared by the present application embodiment 2 before and after adsorbing low concentration Congo red solution (0.04mmol / L) for 13h;

[0034] Figure 8 is a UV absorption spectrum of palm fiber nanocellulose / aramid nanofiber composite aerogel prepared by the present application embodiment 2 before and after adsorbing low concentration Congo red solution (0.04mmol / L) for 13h;

[0035] Figure 9 is a contrast digital photo of palm fiber nanocellulose / aramid nanofiber composite aerogel prepared by the present application embodiment 3 before and after adsorbing low concentration cationic green solution (0.04mmol / L) for 13h;

[0036] Figure 10 is a contrast digital photo of palm fiber nanocellulose / aramid nanofiber composite aerogel prepared by the present application embodiment 4 before and after adsorbing low concentration disperse blue solution (0.04mmol / L) for 13h;

[0037] Figure 11 is a digital photo of the composite aerogel prepared by the present application comparative example 1 and example 1, wherein the left side is the composite aerogel prepared by the comparative example 1, and the right side is the composite aerogel prepared by the example 1. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present application are described in detail below with reference to the accompanying drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the protection scope of the present application can be more clearly defined.

[0039] The present application discloses a preparation method of palm fiber nanocellulose / aramid nanofiber composite aerogel, comprising the following steps:

[0040] (1) preparing a uniform solution:

[0041] The palm fiber nanocellulose and aramid nanofiber are added into the reaction bottle containing the dimethyl sulfoxide containing the solubilizing agent tetrabutylammonium fluoride according to the mass ratio of 1:0.1-9, then the reaction bottle is heated to 80-90℃, and stirred at the temperature for 2-4h, so that the palm fiber nanocellulose and aramid nanofiber are dissolved in the dimethyl sulfoxide, and a uniform solution is formed. In the uniform solution, the palm fiber nanocellulose and aramid nanofiber can be uniformly distributed when gelling, so as to ensure that the adsorption sites in the prepared composite aerogel are uniform and stable, and ensure the adsorption effect and quality;

[0042] (2) Freezing, replacement: pour the uniform solution obtained in step (1) into a mold, freeze at -20℃ for 1h to obtain a frozen block; then put the obtained frozen block into distilled water for replacement for 2-3h each time, remove the organic solvent by replacement with distilled water, and make the aramid nanofiber and palm fiber nanocellulose uniformly distributed in the frozen block contact with the distilled water, so as to realize gelation;

[0043] (3) Crosslinking reaction: place the frozen block after replacement in step (2) in a crosslinking agent solution with a mass concentration of 30-60% for 1h-2h, then heat the crosslinking agent solution to 80-110℃, and perform crosslinking reaction under this condition for 2h-4h to obtain a wet gel; the crosslinking agent is at least one of glutaraldehyde, glyoxal or epichlorohydrin.

[0044] Through the standing before the crosslinking reaction, the crosslinking agent is uniformly distributed in the frozen block, so that the surface and the interior of the obtained wet gel are crosslinked, improving the uniformity of crosslinking and improving the finishing firmness.

[0045] And through crosslinking, the hydroxyl group on the surface of the palm fiber nanocellulose is connected with the amine group on the surface of the aramid nanofiber, so that the prepared composite aerogel forms a stable structure, which is conducive to improving the product strength and preventing the aerogel from disintegrating.

[0046] (4) Replacement, freezing molding: transfer the wet gel obtained in step (3) to an organic alcohol solvent for solution replacement, each replacement time is 6-12h, and the number of repetitions is 3-6 times, so as to replace the distilled water in the wet gel, and then place it in a freeze dryer for freeze drying at -60℃ to -90℃ for 36h-72h to obtain the palm fiber nanocellulose / aramid nanofiber composite aerogel.

[0047] The palm fiber nanocellulose / aramid nanofiber composite aerogel prepared by the above method can be used for adsorbing cationic dyes.

[0048] Example 1

[0049] 10 parts by mass of palm fiber nanocellulose and 10 parts by mass of aramid nanofiber were added to 3666 parts by mass of dimethyl sulfoxide, and then 333 parts by mass of tetrabutylammonium fluoride was added to obtain a mixture. Then the reaction bottle containing the mixture was heated to 80℃ and kept at a constant temperature for continuous stirring for 3h to obtain a uniform orange solution.

[0050] Pour the above uniform orange solution into a mold and freeze at -20℃ for 1h to obtain a frozen block.

[0051] The obtained frozen block is placed in distilled water for replacement for 3h, repeated for 2 times, then transferred to a glutaraldehyde solution with a mass concentration of 50% for standing for 2h, heated to 110℃ for reaction for 4h, to obtain a wet gel.

[0052] The crosslinked wet gel is transferred to a tert-butyl alcohol solution for replacement for 6h, repeated for 6 times, to remove the distilled water in the wet gel, then placed in a freeze dryer at-83℃ for freeze drying for 72h, to remove the tert-butyl alcohol, to obtain the palm fiber nanocellulose / aramid nanofiber composite aerogel, with a density of 0.00834g / cm 3 .

[0053] Performance test:

[0054] The palm fiber nanocellulose / aramid nanofiber composite aerogel prepared above is subjected to microscopic morphology test, and the results are shown in Figure 3 and Figure 4 .

[0055] As shown in Figure 3 and Figure 4 , the composite aerogel prepared in the application has extremely high porosity, many combination sites when applied to adsorption, has obvious crosslinking phenomenon, and can effectively improve the strength of the aerogel. And the material is recycled for 5 times, and no obvious disintegration phenomenon occurs.

[0056] A certain amount of palm fiber nanocellulose / aramid nanofiber composite aerogel is put into a methylene blue solution with a concentration of 0.04mmol / L for adsorption test. The adsorption photo is shown in Figure 5 , and the adsorption test results are shown in Table 1.

[0057] Table 1

[0058] Methylene blue solution First time Second time Third time Average value Adsorption rate 91.97％ 92.02％ 92.05％ 92.01％

[0059] As shown in the results in Table 1, the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 1 has very obvious adsorption effect on methylene blue, and the adsorption rate can reach 92%.

[0060] Example 2

[0061] 2 parts of palm fiber nanocellulose and 18 parts of aramid nanofiber are added into 3666 parts of dimethyl sulfoxide, then 333 parts of tetrabutylammonium fluoride is added to obtain a mixture, then the reaction bottle containing the mixture is heated to 80℃ and kept constant temperature for continuous stirring for 3h, to obtain a uniform orange solution.

[0062] The above uniform orange solution is poured into a mold, and frozen for 1h under the condition of-20℃, to obtain a frozen block.

[0063] The obtained frozen block is placed in distilled water for replacement for 3 h, repeated for 2 times, then transferred to a glutaraldehyde solution with a mass concentration of 50% for standing for 2 h, heated to 110 °C for reaction for 4 h, to obtain a wet gel.

[0064] The crosslinked wet gel is transferred to a tert-butyl alcohol solution for replacement for 8 h, repeated for 5 times, to remove the distilled water in the wet gel, then placed in a freeze dryer at -83 °C for freeze drying for 72 h, to remove the tert-butyl alcohol, to obtain the palm fiber nanocellulose / aramid nanofiber composite aerogel.

[0065] Performance test:

[0066] A certain amount of palm fiber nanocellulose / aramid nanofiber composite aerogel is put into a Congo red solution with a concentration of 0.04 mmol / L for adsorption test, and the adsorption test results are shown in Table 2.

[0067] Table 2

[0068] Congo red solution First time Second time Third time Average value Adsorption rate 94.92％ 94.73％ 94.85％ 94.83％

[0069] As can be seen from the results in Table 2, the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 2 has a very obvious adsorption effect on Congo red, and the adsorption rate can reach 94.83%.

[0070] Example 3

[0071] The present embodiment provides a preparation method of a palm fiber nanocellulose / aramid nanofiber composite aerogel, comprising the following steps:

[0072] 6 parts by mass of palm fiber nanocellulose and 14 parts by mass of aramid nanofiber are added into 3666 parts by mass of dimethyl sulfoxide, then 333 parts by mass of tetrabutylammonium fluoride is added to obtain a mixture, then the reaction bottle containing the mixture is heated to 80 °C and kept constant temperature for continuous stirring for 3 h, to obtain a uniform orange solution.

[0073] The above uniform orange solution is poured into a mold, frozen at -20 °C for 1 h to obtain a frozen block.

[0074] The obtained frozen block is placed in distilled water for replacement for 3 h, repeated for 2 times, then transferred to a glutaraldehyde solution with a mass concentration of 50% for standing for 2 h, heated to 110 °C for reaction for 4 h, to obtain a wet gel.

[0075] The crosslinked wet gel is transferred to a tert-butyl alcohol solution for replacement for 10 h, repeated for 4 times, to remove the distilled water in the wet gel, then placed in a freeze dryer at -83 °C for freeze drying for 72 h, to remove the tert-butyl alcohol, to obtain the palm fiber nanocellulose / aramid nanofiber composite aerogel.

[0076] Performance test:

[0077] A certain amount of palm fiber nanocellulose / aramid nanofiber composite aerogel was put into a cationic green solution with a concentration of 0.04 mmol / L for adsorption test, and the adsorption test results are shown in Table 3.

[0078] Table 3

[0079] Cation green solution First time Second time Third time Average value Adsorption rate 92.28％ 93.16％ 94.59％ 93.34％

[0080] As can be seen from the results in Table 3, the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 3 has a very obvious adsorption effect on cationic green, and the adsorption rate can reach 93.34%.

[0081] Example 4

[0082] The present embodiment provides a preparation method of a palm fiber nanocellulose / aramid nanofiber composite aerogel, comprising the following steps:

[0083] 8 parts by mass of palm fiber nanocellulose and 12 parts by mass of aramid nanofiber were added to 3666 parts by mass of dimethyl sulfoxide, and then 333 parts by mass of tetrabutylammonium fluoride was added to obtain a mixture. Then the reaction bottle containing the mixture was heated to 80°C and kept constant temperature for continuous stirring for 3h to obtain a uniform orange solution.

[0084] The above uniform orange solution was poured into a mold and frozen at -20°C for 1h to obtain a frozen block.

[0085] The obtained frozen block was placed in distilled water for 3h, repeated for 2 times, and then transferred to a glutaraldehyde solution with a mass concentration of 50% for 2h, and then heated to 110°C for 4h to obtain a wet gel.

[0086] The crosslinked wet gel was transferred to a tert-butyl alcohol solution for 12 hours, repeated for 4 times, and then placed in a freeze dryer at -83°C for 72h to remove the tert-butyl alcohol, to obtain a palm fiber nanocellulose / aramid nanofiber composite aerogel.

[0087] Performance test:

[0088] A certain amount of palm fiber nanocellulose / aramid nanofiber composite aerogel was put into a cationic green solution with a concentration of 0.04 mmol / L for adsorption test, and the adsorption test results are shown in Table 3.

[0089] Table 4

[0090] Disperse blue solution First time Second time Third time Average value Adsorption rate 95.56％ 94.33％ 95.72％ 95.20％

[0091] From the results of Table 4, it can be seen that the palm fiber nanocellulose / aramid nanofiber composite aerogel prepared in Example 4 has a very obvious adsorption effect on disperse blue, and the adsorption rate can reach 95.20%.

[0092] Comparative Example 1

[0093] Compared with Example 1, the difference is that the obtained frozen block is placed in distilled water for replacement for 3 h, and after repeating 2 times, it is then transferred to a glutaraldehyde solution with a mass concentration of 50%, and directly heated to 110 DEG C for reaction for 4 h to obtain a wet gel.

[0094] Results:

[0095] Crosslinking with glutaraldehyde occurs on the surface of the gel, while the interior of the gel is not crosslinked. After drying, due to the decrease in the supporting property of the internal skeleton, the interior strongly shrinks, resulting in a decrease in the volume of the aerogel, a decrease in the pore density, and a decrease in the adsorption performance.

[0096] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent flow transformation using the content of the specification and drawings of the present application, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a palm fiber nanocellulose / aramid nanofiber composite aerogel, characterized by, The method comprises the following steps: (1) preparing a uniform solution: dissolving palm fiber nanocellulose and aramid nanofiber in an organic solvent containing a dissolving agent to obtain a uniform solution; (2) freezing and replacement: freezing the uniform solution obtained in step (1) into a block, and then placing it in distilled water for replacement to obtain a block; (3) crosslinking reaction: placing the block after replacement in step (2) in a crosslinking agent solution, heating and performing crosslinking reaction to obtain a wet gel; (4) replacement and freeze forming: transferring the wet gel obtained in step (3) to an organic alcohol solvent for solution replacement, and then freeze drying to obtain the palm fiber nanocellulose / aramid nanofiber composite aerogel. In step (3), the block is placed in the crosslinking agent solution for 1h-2h before the crosslinking reaction.

2. The preparation method of palm fiber nanocellulose / aramid nanofiber composite aerogel according to claim 1, characterized in that, In step (1), the mass ratio of the palm fiber nanocellulose and the aramid nanofiber is 1:0.1-9.

3. The method for preparing a palm fiber nanocellulose / aramid nanofiber composite aerogel according to claim 1, characterized in that, In step (1), the dissolving agent is tetrabutylammonium fluoride.

4. The method for preparing a palm fiber nanocellulose / aramid nanofiber composite aerogel according to claim 1, characterized in that, In step (2), the replacement time is 3-6h.

5. The method for preparing a palm fiber nanocellulose / aramid nanofiber composite aerogel according to claim 1, characterized in that, In step (3), the process conditions of the crosslinking reaction are: temperature 80℃-110℃, time 2h-4h.

6. The preparation method of palm fiber nanocellulose / aramid nanofiber composite aerogel according to claim 1, 4 or 5, characterized in that, The crosslinking agent is at least one of glutaraldehyde, glyoxal or epichlorohydrin.

7. The method for preparing a palm fiber nanocellulose / aramid nanofiber composite aerogel according to claim 4, characterized in that, In step (4), the process conditions of the freeze drying are: temperature -60℃--90℃, time 36h-72h.

8. The use of palm fiber nanocellulose / aramid nanofiber composite aerogels prepared as claimed in claim 1, characterized by, The palm fiber nanocellulose / aramid nanofiber composite aerogel is used for adsorbing cationic dyes.

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