A biomass aerogel with both moisture absorption and photothermal desorption and its preparation method

Abstract

The present invention discloses a biomass aerogel with both moisture absorption and photothermal desorption and a preparation method thereof, relating to the technical field of aerogels, aiming to solve the problems in the prior art that the biomass moisture absorption material prepared from lignosulfonate is prone to deliquescence after moisture absorption and difficult to form a self-supporting structure. It includes a cellulose aerogel, the cellulose aerogel has a porous structure, and lignosulfonate is loaded in the porous structure; the cellulose aerogel can provide a self-supporting structure for the lignosulfonate. The biomass aerogel prepared by the present invention using bamboo cellulose aerogel as a carrier and loading lignosulfonate by vacuum impregnation and vacuum drying methods has excellent moisture absorption effect and photothermal desorption ability.

Description

Technical Field

[0001] The present invention relates to a biomass aerogel with both moisture absorption and photothermal desorption and a preparation method thereof, belonging to the technical field of aerogels. Background Art

[0002] With the increasingly serious problem of global freshwater shortage, the development of atmospheric water harvesting materials provides a new solution to alleviate the freshwater shortage problem. As a branch of atmospheric water harvesting materials, moisture-absorbing materials absorb vapor moisture from the air without relying on surface water sources, and then collect fresh water through heating, condensation and other methods, greatly expanding the source of fresh water. At the same time, as the main source of air humidity, excessive air humidity will cause bacteria to grow and mildew on clothes and food, affecting people's quality of life and physical and mental health. Therefore, the development of moisture-absorbing materials has broad development prospects and important practical significance in alleviating freshwater shortage and the field of dehumidification.

[0003] Traditional atmospheric water harvesting materials mainly include calcium chloride and lithium chloride, which have the advantages of high moisture absorption capacity and fast moisture absorption rate. However, after absorbing water, such materials require a large amount of electrical energy and thermal energy to drive water evaporation and desorption to obtain fresh water, and have disadvantages such as non-degradability after abandonment and difficulty in forming a self-supporting structure, which limit their further application.

[0004] Lignosulfonate, as a natural polymer compound, mainly comes from the by-products of the paper industry. During the papermaking process, lignin in wood is processed and partially sulfonated to form lignosulfonate. The sulfonic acid groups in the molecular structure of lignosulfonate have a good affinity with water molecules, can effectively capture water molecules in the air, and have good moisture absorption performance. More importantly, lignosulfonate has a large number of aromatic ring structures, making it have good light absorption performance and photothermal conversion efficiency. Only by irradiating with sunlight can heat be generated to trigger water desorption, greatly reducing energy loss. Therefore, using lignosulfonate to prepare biomass moisture-absorbing materials is very attractive. However, lignosulfonate generally presents a powdery form and still has the disadvantages of being prone to deliquescence after moisture absorption and difficulty in forming a self-supporting structure. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a biomass aerogel with both moisture absorption and photothermal desorption and a preparation method thereof. The biomass aerogel is prepared by using bamboo cellulose aerogel as a carrier and loading lignosulfonate through vacuum impregnation and vacuum drying methods, and has excellent moisture absorption effect and photothermal desorption ability.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions:

[0007] On the one hand, the present invention provides a biomass aerogel with both moisture absorption and photothermal desorption, including a cellulose aerogel, the cellulose aerogel having a porous structure, and lignosulfonate being loaded in the porous structure; the cellulose aerogel can provide a self-supporting structure for the lignosulfonate.

[0008] Further, the lignosulfonate is in powder form and is one or both of sodium lignosulfonate and calcium lignosulfonate.

[0009] Further, the cellulose aerogel is a bamboo cellulose aerogel.

[0010] On the other hand, the present invention also provides a preparation method of the biomass aerogel with both moisture absorption and photothermal desorption as described in any one of the above, including:

[0011] Treat bamboo powder to obtain a bamboo cellulose dispersion;

[0012] Pour the bamboo cellulose dispersion into a mold and freeze-dry to obtain a bamboo cellulose aerogel;

[0013] Prepare a lignosulfonate solution;

[0014] Place the bamboo cellulose aerogel in the lignosulfonate solution for vacuum impregnation, so that the lignosulfonate solution fills the pores of the bamboo cellulose aerogel, and obtain the biomass aerogel with both moisture absorption and photothermal desorption after vacuum drying.

[0015] Further, the treatment of the bamboo powder to obtain the bamboo cellulose dispersion includes:

[0016] a. Put the bamboo powder into deionized water and boil it, and obtain the treated bamboo powder after suction filtration;

[0017] b. Prepare a mixed solution of sodium chlorite and acetic acid, put the treated bamboo powder into the mixed solution of sodium chlorite and acetic acid, heat and stir, and obtain bamboo powder A after suction filtration and washing with water;

[0018] c. Prepare a sodium hydroxide solution, add bamboo powder A to the sodium hydroxide solution, heat and stir, and obtain bamboo powder B after suction filtration and washing with water;

[0019] d. Prepare a hydrogen peroxide solution, heat bamboo powder B in the hydrogen peroxide solution, heat and stir, and cool to room temperature to obtain a suspension of bamboo powder C;

[0020] e. Sequentially add sodium hypochlorite and 2,2,6,6-tetramethylpiperidine-1-oxyl to the suspension of bamboo powder C, adjust the pH of the solution to alkaline with a sodium hydroxide solution, stir and react, then add ethanol and let it stand, suction filter and wash with water, and prepare it into a dispersion with deionized water, and obtain the bamboo cellulose dispersion after ultrasonic treatment.

[0021] Further, in step b, the sodium chlorite and acetic acid mixed solution comprises a 7-10 wt% sodium chlorite solution and a 15-20 wt% acetic acid solution, the heating temperature is 75-95 °C, and the heating time is 3-13 h;

[0022] And / or, in step c, the concentration range of the sodium hydroxide solution is 5-10 wt%, the heating temperature is 70-90 °C, and the heating time is 3-13 h;

[0023] And / or, in step d, the concentration range of the hydrogen peroxide solution is 15-25 wt%, the heating temperature is 75-95 °C, and the heating time is 3-10 h.

[0024] Further, in step e, the addition amount of sodium hypochlorite is 0.2-2% of the total volume of the bamboo powder suspension, the addition amount of tetramethylpiperidine oxide is 0.01-2% of the total mass of the bamboo powder suspension, the addition amount of ethanol is 0.5-3% of the total volume of the bamboo powder suspension, the pH value range is 10-10.5, the reaction temperature is 25-40 °C, the reaction time is 1-2 h, the standing time is 15-24 h, and the ultrasonic time is 0.5-1 h.

[0025] Further, the concentration range of the bamboo cellulose dispersion is 0.5-2.5 wt%.

[0026] Further, the concentration range of the lignosulfonate solution is 5-50 wt%.

[0027] Further, the freeze-drying time is 24-48 h; and / or, the vacuum impregnation time is 0.5-5 h; and / or, the vacuum drying temperature is 60-80 °C, and the vacuum drying time is 10-15 h.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0029] The biomass aerogel of the present invention has both moisture absorption and photothermal desorption functions, is biodegradable, and has a stable self-supporting structure. It can trigger water desorption through photothermal conversion only by light irradiation, greatly reducing the consumption of thermal energy and electric energy;

[0030] The preparation method of the present invention is simple and easy to operate. By combining lignosulfonate with bamboo cellulose aerogel, the defect that lignosulfonate is difficult to form independently is solved, greatly expanding the application range of lignosulfonate, and enabling it to be applied in the fields of atmospheric water collection and dehumidification. Description of the Drawings

[0031] Figure 1 Schematic diagrams of sodium lignosulfonate and sodium lignosulfonate after moisture absorption in Comparative Example 1 of the present invention;

[0032] Figure 2 For the sodium lignosulfonate of Comparative Example 1 of the present invention at 0.35 kW / m 2 Schematic diagram of the change of surface temperature with time under light irradiation;

[0033] Figure 3 Schematic diagram of the bamboo cellulose aerogel of Comparative Example 2 and the bamboo cellulose / sodium lignosulfonate aerogel of Example 1 of the present invention;

[0034] Figure 4 For the bamboo cellulose aerogel of Comparative Example 2 and the bamboo cellulose / sodium lignosulfonate aerogel of Example 1 of the present invention at 1 kW / m 2 Schematic diagram of the change of surface temperature with time under light irradiation;

[0035] Figure 5 Schematic diagram of the change of moisture absorption amount with time of the bamboo cellulose aerogel of Comparative Example 2 and the bamboo cellulose / sodium lignosulfonate aerogel of Example 1 under the condition of 75% humidity;

[0036] Figure 6 For the bamboo cellulose / sodium lignosulfonate aerogel of Example 1 of the present invention after moisture absorption, at 1 kW / m 2 Schematic diagram of the change of the weight of water desorption with time under light irradiation;

[0037] Figure 7 Schematic diagram of the change of the humidity inside the sealed box with time when the bamboo cellulose / sodium lignosulfonate aerogel of Example 1 of the present invention is placed in a sealed box with a volume of 10 cm × 10 cm × 15 cm. Detailed implementation mode

[0038] The present invention will be further described below with reference to the accompanying drawings. The following examples are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0039] Example 1

[0040] The embodiment of the present invention provides a preparation method of a biomass aerogel with both moisture absorption and photothermal desorption, including the following steps:

[0041] First, prepare a bamboo cellulose aerogel, specifically including:

[0042] Boil the bamboo powder in water to remove water-soluble organic substances, and filter it to obtain the treated bamboo powder.

[0043] Mix the sodium chlorite solution and the acetic acid solution to prepare a mixed solution of sodium chlorite and acetic acid solution. In the mixed solution of sodium chlorite and acetic acid solution, sodium chlorite accounts for 7.4 wt% and acetic acid accounts for 18.5 wt%.

[0044] Add the processed bamboo powder into the mixed solution of sodium chlorite and acetic acid solution, heat it to 90 °C, continuously stir for 12 h, filter it, and rinse it with deionized water to obtain bamboo powder A.

[0045] Prepare a 7.4 wt% sodium hydroxide solution, add bamboo powder A into the sodium hydroxide solution, heat it to 80 °C and react for 12 h, filter it, and rinse it with deionized water to obtain bamboo powder B.

[0046] Prepare an 18 wt% hydrogen peroxide solution, add bamboo powder B into the hydrogen peroxide solution, heat it to 90 °C and react for 8 h, and cool it to room temperature to obtain a suspension of bamboo powder C.

[0047] Add 3 mL of sodium hypochlorite and 0.2 g of tetramethylpiperidine oxide into the suspension of bamboo powder C, adjust the pH to 10 with sodium hydroxide solution, stir and react at 30 °C for 1 h, add 10 mL of ethanol, let it stand for 18 h, then filter, wash with water, and prepare a dispersion with deionized water, and use an ultrasonic machine to ultrasonic for 0.5 h to obtain a homogeneous 2.5 wt% bamboo cellulose dispersion.

[0048] Take 3 mL of the bamboo cellulose dispersion and pour it into a 2 cm × 2 cm × 2 cm square silica gel mold, and perform freeze-drying for 48 h to remove ice crystals to obtain a bamboo cellulose aerogel.

[0049] Secondly, select sodium lignosulfonate and prepare it into a 50 wt% sodium lignosulfonate solution.

[0050] Finally, place the bamboo cellulose aerogel in the sodium lignosulfonate solution for vacuum impregnation for 0.5 h, and vacuum dry it at 80 °C for 15 h to obtain a bamboo cellulose / sodium lignosulfonate aerogel.

[0051] Example 2

[0052] First, prepare a bamboo cellulose aerogel, specifically including:

[0053] Boil the bamboo powder in water to remove water-soluble organic substances, and filter it to obtain the processed bamboo powder.

[0054] Mix and prepare the sodium chlorite solution and acetic acid solution to obtain a mixed solution of sodium chlorite and acetic acid solution. In the mixed solution of sodium chlorite and acetic acid solution, sodium chlorite accounts for 7.4 wt% and acetic acid accounts for 18.5 wt%.

[0055] Add the processed bamboo powder into the mixed solution of sodium chlorite and acetic acid solution, heat it to 90 °C, continuously stir for 12 h, filter it, and rinse it with deionized water to obtain bamboo powder A.

[0056] Prepare a 7.4 wt% sodium hydroxide solution, add bamboo powder A to the sodium hydroxide solution, heat to 80 °C and react for 12 h, filter by suction and wash with deionized water to obtain bamboo powder B.

[0057] Prepare an 18 wt% hydrogen peroxide solution, add bamboo powder B to the hydrogen peroxide solution, heat to 90 °C and react for 8 h, and cool to room temperature to obtain a suspension of bamboo powder C.

[0058] Add 3 mL of sodium hypochlorite and 0.2 g of tetramethylpiperidine oxide to the suspension of bamboo powder C, adjust the pH to 10 with sodium hydroxide solution, stir and react at 30 °C for 1 h, add 10 mL of ethanol, let stand for 18 h, then filter by suction and wash with water, and prepare a dispersion with deionized water, and use an ultrasonic machine to ultrasonicate for 0.5 h to obtain a homogeneous 2.5 wt% bamboo cellulose dispersion.

[0059] Take 3 mL of the bamboo cellulose dispersion and pour it into a 2 cm × 2 cm × 2 cm square silica gel mold and perform freeze-drying for 48 h to remove ice crystals to obtain a bamboo cellulose aerogel.

[0060] Secondly, select calcium lignosulfonate and prepare it into a 50 wt% calcium lignosulfonate solution.

[0061] Finally, place the bamboo cellulose aerogel in the calcium lignosulfonate solution and perform vacuum impregnation for 0.5 h, and vacuum dry at 80 °C for 15 h to obtain a bamboo cellulose / calcium lignosulfonate aerogel.

[0062] Comparative Example 1:

[0063] In this comparative example, sodium lignosulfonate is used as the hygroscopic material. As Figure 1 shown, sodium lignosulfonate is in the form of a brown-yellow powder and has certain hygroscopic properties.

[0064] Place sodium lignosulfonate under irradiation of 0.35 kW / m 2 light, and its surface temperature changes with time as Figure 2 shown. Since sodium lignosulfonate has an aromatic ring structure, it has the property of photothermal conversion. After being irradiated with a light source of 0.35 kW / m 2 intensity for 600 s, the surface temperature of sodium lignosulfonate rises to 42.4 °C.

[0065] Comparative Example 2:

[0066] This comparative example provides a bamboo cellulose aerogel, and its preparation method includes:

[0067] Boil the bamboo powder in water to remove water-soluble organic substances, and filter by suction to obtain the treated bamboo powder.

[0068] Mix the sodium chlorite solution and the acetic acid solution to prepare a mixed solution of sodium chlorite and acetic acid solution. In the mixed solution of sodium chlorite and acetic acid solution, sodium chlorite accounts for 7.4 wt% and acetic acid accounts for 18.5 wt%.

[0069] Add the treated bamboo powder into the mixed solution of sodium chlorite and acetic acid solution, heat to 90 °C, continuously stir and maintain for 12 h, filter by suction and then rinse with deionized water to obtain bamboo powder A.

[0070] Prepare a 7.4 wt% sodium hydroxide solution, add bamboo powder A into the sodium hydroxide solution, heat to 80 °C and react for 12 h, filter by suction and then rinse with deionized water to obtain bamboo powder B.

[0071] Prepare an 18 wt% hydrogen peroxide solution, add bamboo powder B into the hydrogen peroxide solution, heat to 90 °C and react for 8 h, and cool to room temperature to obtain a suspension of bamboo powder C.

[0072] Add 3 mL of sodium hypochlorite and 0.2 g of tetramethylpiperidine oxide into the suspension of bamboo powder C, adjust the pH to 10 with sodium hydroxide solution, stir and react at 30 °C for 1 h, add 10 mL of ethanol, let it stand for 18 h, then filter by suction and wash with water, and prepare a dispersion with deionized water. Use an ultrasonic machine to ultrasonic for 0.5 h to obtain a homogeneous 2.5 wt% bamboo cellulose dispersion.

[0073] Take 3 mL of the bamboo cellulose dispersion and pour it into a 2 cm × 2 cm × 2 cm square silica gel mold, and perform freeze-drying for 48 h to remove ice crystals to obtain bamboo cellulose aerogel.

[0074] The bamboo cellulose aerogel of Comparative Example 2 and the bamboo cellulose / lignosulfonate aerogel of Example 1 are as Figure 3 shown. Compared with lignosulfonate powder, the bamboo cellulose aerogel has a stable self-supporting structure. After vacuum impregnation and vacuum drying, the bamboo cellulose / lignosulfonate aerogel presents a dark brown color.

[0075] The change of the surface temperature of the bamboo cellulose aerogel of Comparative Example 2 and the bamboo cellulose / lignosulfonate aerogel of Example 1 with time under 1 kW / m 2 light irradiation is as Figure 4 shown. Due to the excellent photothermal conversion performance of lignosulfonate, after being irradiated by a 1 kW / m 2 intensity light source for 1200 s, the surface temperature of the bamboo cellulose / lignosulfonate aerogel can reach 64.9 °C, which is significantly higher than that of the bamboo cellulose aerogel, indicating that it has good light absorption performance and photothermal conversion efficiency.

[0076] The moisture absorption amounts of the bamboo cellulose aerogel in Comparative Example 2 and the bamboo cellulose / sodium lignosulfonate aerogel in Example 1 over time under the condition of 75% humidity are as follows Figure 5 shown. The moisture absorption amount of the bamboo cellulose aerogel hardly changed. This is because there are sulfonic acid groups in sodium lignosulfonate. The moisture absorption amount of the bamboo cellulose / sodium lignosulfonate aerogel reached 120.79 kg / m 3 , which is much higher than that of the bamboo cellulose aerogel. After placing the moisture-absorbed bamboo cellulose aerogel and bamboo cellulose / sodium lignosulfonate aerogel under the irradiation of a 1 kW / m 2 intensity light source for 3600 s, as Figure 6 shown, the desorption amount of the bamboo cellulose / sodium lignosulfonate aerogel reached 75.38 kg / m 3 , indicating that the bamboo cellulose / sodium lignosulfonate aerogel has excellent photothermal desorption performance.

[0077] To test the dehumidification performance of the bamboo cellulose / sodium lignosulfonate aerogel, it was placed in a sealed transparent box (with a volume of 10 cm × 10 cm × 15 cm). The humidity in the sealed box decreased from the initial 83.2% to 45.6%.

[0078] In summary, the biomass aerogel prepared in the present invention uses bamboo cellulose aerogel as a carrier and loads lignosulfonate by vacuum impregnation and vacuum drying methods, and has excellent moisture absorption effect and photothermal desorption ability, and can be used in the fields of atmospheric water collection and dehumidification.

[0079] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A biomass aerogel having both moisture absorption and photothermal desorption, characterized in that: The invention comprises a cellulose aerogel, wherein the cellulose aerogel has a porous structure, and lignin sulfonate is loaded in the porous structure; the cellulose aerogel can provide a self-supporting structure for the lignin sulfonate, wherein the cellulose aerogel is a bamboo cellulose aerogel; The method for preparing the biomass aerogel having both moisture absorption and photothermal desorption comprises: Treating bamboo powder to obtain bamboo cellulose dispersion; Pour the bamboo cellulose dispersion into a mold and freeze-dry to obtain the bamboo cellulose aerogel; preparing a lignin sulfonate solution; The bamboo cellulose aerogel is placed in a lignin sulfonate solution for vacuum impregnation, so that the lignin sulfonate solution is filled into the pores of the bamboo cellulose aerogel. After vacuum drying, a biomass aerogel with both moisture absorption and photothermal desorption is obtained.

2. The biomass aerogel having both hygroscopic and photothermal desorption properties according to claim 1, characterized in that: The lignin sulfonate is in powder form and is one or both of sodium lignin sulfonate and calcium lignin sulfonate.

3. The biomass aerogel having both hygroscopic and photothermal desorption properties according to claim 1, characterized in that: The method of treating the bamboo powder to obtain a bamboo cellulose dispersion liquid comprises: a. Put bamboo powder into deionized water and boil it, and then filter to obtain the treated bamboo powder; b. Prepare a mixed solution of sodium chlorite and acetic acid, put the treated bamboo powder into the mixed solution of sodium chlorite and acetic acid, heat and stir, and filter and wash with water to obtain bamboo powder A; c. Prepare a sodium hydroxide solution, add bamboo powder A into the sodium hydroxide solution, heat and stir, and filter and wash with water to obtain bamboo powder B; d. Prepare a hydrogen peroxide solution, add bamboo powder B into the hydrogen peroxide solution, heat and stir, and cool to room temperature to obtain a bamboo powder C suspension; e. Sodium hypochlorite and tetramethylpiperidinium oxide were added to the bamboo powder C suspension in sequence, and the pH value of the solution was adjusted to alkaline with sodium hydroxide solution. After stirring for reaction, ethanol was added and allowed to stand, filtered and washed with water, and a dispersion was prepared with deionized water. After ultrasonication, a bamboo cellulose dispersion was obtained.

4. The biomass aerogel having both hygroscopic and photothermal desorption properties according to claim 3, characterized in that: In step b, the sodium chlorite and acetic acid mixed solution includes 7-10wt% sodium chlorite solution and 15-20wt% acetic acid solution, the heating temperature is 75-95° C., and the heating time is 3-13h; And / or, in step c, the concentration range of the sodium hydroxide solution is 5-10wt%, the heating temperature is 70-90°C, and the heating time is 3-13h; And / or, in step d, the concentration range of the hydrogen peroxide solution is 15-25wt%, the heating temperature is 75-95°C, and the heating time is 3-10h.

5. The biomass aerogel having both hygroscopic and photothermal desorption properties according to claim 3, characterized in that: In step e, the amount of sodium hypochlorite added is 0.2-2% of the total volume of the bamboo powder C suspension, the amount of tetramethyl piperidine oxide added is 0.01-2% of the total mass of the bamboo powder C suspension, the amount of ethanol added is 0.5-3% of the total volume of the bamboo powder C suspension, the pH value range is 10-10.5, the reaction temperature is 25-40° C., the reaction time is 1-2 h, the standing time is 15-24 h, and the ultrasonic time is 0.5-1 h.

6. The method for preparing biomass aerogel with both moisture absorption and photothermal desorption according to claim 1, characterized in that: The concentration of the bamboo cellulose dispersion is in the range of 0.5-2.5 wt %.

7. The method for preparing biomass aerogel with both moisture absorption and photothermal desorption according to claim 1, characterized in that: The concentration of the lignin sulfonate solution is in the range of 5-50 wt %.

8. The method for preparing biomass aerogel with both moisture absorption and photothermal desorption according to claim 1, characterized in that: The freeze drying time is 24-48 hours; and / or, the vacuum impregnation time is 0.5-5 hours; and / or, the vacuum drying temperature is 60-80° C., and the vacuum drying time is 10-15 hours.

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