Preparation method of polydopamine modified wood aerogel for efficient seawater evaporation

Abstract

The invention relates to a preparation method of polydopamine modified wood aerogel for efficient seawater evaporation, which comprises the following specific steps: preparing wood aerogel by removing hemicellulose and lignin in wood, and modifying the obtained wood aerogel by using a buffer solution containing dopamine hydrochloride, and finally, carrying out copper crosslinking to obtain the wood aerogel for seawater evaporation. The polydopamine modified wood aerogel is adopted, operation is easy, the experimental environment is not complex, controllability in the reaction process is good, and the modified aerogel has high seawater evaporation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of seawater evaporation materials technology, and specifically relates to a method for preparing polydopamine-modified wood aerogel for efficient seawater evaporation. Background Technology

[0002] In recent years, the increasing scarcity of global freshwater resources has spurred widespread research into water purification technologies. Extracting clean / potable water from seawater / wastewater sources through solar water purification is considered one of the most feasible solutions to alleviate water shortages, making seawater desalination a crucial approach to addressing the water crisis. Traditional seawater evaporation technologies rely on fossil fuels for heat, resulting in high energy consumption, severe equipment corrosion, and high operating costs. Solar-driven interfacial evaporation technology has attracted widespread attention due to its green and low-energy characteristics. Its core lies in utilizing photothermal materials to efficiently convert solar energy into heat, achieving localized heating and rapid evaporation. However, traditional photothermal materials (such as carbon-based materials and metal nanoparticles) are susceptible to salt crystallization and accumulation during long-term use, leading to decreased evaporation efficiency or even failure. Furthermore, conventional evaporators suffer from significant heat loss, and the efficiency of solar energy utilization still needs improvement.

[0003] Aerogel materials, with their unique structure characterized by ultra-lightweight properties, high porosity, and extremely low thermal conductivity, demonstrate remarkable application potential in solar-driven seawater evaporation. Compared to traditional evaporation materials, aerogels offer several significant advantages: their three-dimensional porous network structure not only efficiently loads photothermal materials for excellent solar energy absorption and localized heating but also significantly enhances light energy utilization through multiple light scattering effects; their ultra-low thermal conductivity effectively suppresses heat loss, concentrating energy at the evaporation interface and significantly improving evaporation efficiency; their high porosity (over 90%) and interconnected pore structure ensure rapid water transport and maintain a stable evaporation rate; surface modification or structural design can impart excellent salt resistance, effectively solving the problem of salt crystallization blockage; furthermore, biomass-based aerogel raw materials are widely available, environmentally friendly, and cost-effective, showcasing promising prospects for large-scale application. However, existing technologies, such as CN 115448401 A, which use freeze-drying to produce Ulva prolifera aerogel and then carbonizing the surface of the aerogel to obtain an integrated Ulva prolifera structure, only achieve a maximum seawater evaporation rate of 1.87 kg / m³. 2 The method has problems such as low photothermal conversion efficiency and complex preparation process. Summary of the Invention

[0004] The purpose of this invention is to address the problem of poor seawater evaporation efficiency in existing seawater evaporation materials by providing a method for preparing polydopamine-modified wood aerogel for high-efficiency seawater evaporation. This method improves the Cu loading of the aerogel by encapsulating it with a polydopamine layer, thereby enhancing the seawater evaporation efficiency.

[0005] The technical solution of this invention is: a method for preparing polydopamine-modified wood aerogel for efficient seawater evaporation, the specific steps of which are as follows:

[0006] (1) Preparation of wood aerogel

[0007] The wood is cleaned and dried, then soaked in a sodium salt solution, and the pH of the sodium salt solution is adjusted with an acidic solution. The wood is then heated in a water bath to remove lignin. The wood after lignin removal is transferred to an alkaline solution and heated in a water bath to remove hemicellulose. After the process is complete, the wood is cleaned and freeze-dried to obtain wood aerogel.

[0008] (2) Polydopamine PDA modified wood aerogel

[0009] Wood aerogels were immersed in a buffer solution containing dopamine hydrochloride (DA) and stirred. The dopamine hydrochloride (DA) underwent spontaneous oxidation and self-polymerization to form a polydopamine (PDA) layer. The above steps were repeated with fresh solution instead of the mother liquor to obtain PDA-modified wood aerogels.

[0010] (3) Copper crosslinked modified aerogel

[0011] Weigh out copper salt and dissolve it in alcohol solution to prepare copper salt alcohol solution. Then, put the modified wood aerogel obtained in step (2) into copper salt alcohol solution for copper crosslinking. Prepare a mixed solution of sulfur salt and alkali. Then, put the copper crosslinked wood aerogel into a hydrothermal reactor, pour it into the prepared mixed solution, heat and react, freeze dry, and obtain copper ion crosslinked modified wood aerogel.

[0012] The preferred wood in step (1) is one of balsa wood, poplar, or pine; the sodium salt is one of sodium chlorite or sodium sulfite; the concentration of the sodium salt solution is 0.10-0.20 mol / L; the acidic solution in step (1) is one of glacial acetic acid, phosphoric acid, or citric acid; and the pH of the sodium salt solution is adjusted to 4.6-5.4.

[0013] The preferred step (1) is to use a water bath heating temperature of 80-90°C and a heating time of 8-10 hours to remove lignin.

[0014] The preferred alkaline solution in step (1) is one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution or ammonia solution, and the concentration of the alkaline solution is 1-2 mol / L; the water bath heating temperature during the removal of hemifiber is 85-95℃ and the heating time is 8-10h.

[0015] The preferred buffer in step (2) is one of tris(hydroxymethyl)aminomethane buffer, phosphate buffer or borate buffer; the pH of the buffer is adjusted to 8-9 with acid; the molar ratio of buffer to dopamine hydrochloride is 1:(1-3).

[0016] The preferred stirring speed in step (2) is 150-200 rpm, and the stirring time is 6-8 hours; the mother liquor is replaced and repeated 3-4 times.

[0017] The preferred copper salt in step (3) is one of copper nitrate, copper sulfate, or copper chloride; the alcohol solution is one of anhydrous ethanol, methanol, or ethylene glycol; and the concentration of copper salt in the copper salt alcohol solution is 40 mmol / L to 60 mmol / L.

[0018] The preferred temperature for copper crosslinking in step (3) is -12 to 25°C, and the copper crosslinking time is 12 to 24 hours.

[0019] The preferred step (3) is to use either thiourea or Na2S as the sulfur salt; the preferred step is to use either sodium hydroxide or ammonia water as the alkali; and the molar ratio of sulfur salt to alkali is 1:(1-3).

[0020] The preferred step (3) is to raise the temperature of the reaction to 120-150°C and the reaction time to 6-8 hours.

[0021] The advantages of this invention compared to the prior art are as follows:

[0022] (1) A method for preparing polydopamine-modified wood aerogel for efficient seawater evaporation, which is simple to operate, has a simple experimental environment, and is highly controllable during the reaction process. The coating of polydopamine layer can increase the amount of Cu adhesion.

[0023] (2) The modified wood aerogel has a higher evaporation efficiency than seawater, 2.27 kg / m³. 2 / h. Attached Figure Description

[0024] Figure 1 This is a SEM image of the modified wood aerogel prepared in Example 1. Detailed Implementation

[0025] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0026] Example 1

[0027] Prepare 1 L of 0.10 mol / L sodium chlorite solution in a beaker, and add washed and dried balsa wood. Adjust the pH of the sodium chlorite solution to 4.6 with glacial acetic acid. Place the beaker in a water bath and heat to 90°C for 8 hours. After removing the lignin, wash the wood with deionized water, add 1 L of 1 mol / L sodium hydroxide solution, and heat in a water bath to 95°C for 8 hours. Remove the wood after the reaction, gently wash with deionized water, and freeze-dry to obtain wood aerogel. Prepare 1 L of a tris(hydroxymethyl)aminomethane buffer solution containing 10 mM dopamine hydrochloride (10 mM tris(hydroxymethyl)aminomethane, pH adjusted to 8.0 with hydrochloric acid). Immerse the wood aerogel in the buffer solution, and stir at 150 rpm for 8 hours. After replacing the mother liquor 4 times, polydopamine-coated wood aerogel is obtained. The modified wood aerogel was placed in a 40 mmol / L copper nitrate ethanol solution and crosslinked with copper at -25°C for 12 h. After crosslinking, the wood aerogel was removed and transferred to a hydrothermal reactor, where a 1:1 molar ratio mixture of thiourea and sodium hydroxide was added and the temperature was raised to 120°C for 8 h. The wood aerogel was then removed from the hydrothermal reactor and freeze-dried. The structure of the dried wood aerogel is shown below. Figure 1 As shown, a xenon lamp was used as a simulated solar light source. The light intensity was controlled by adjusting the distance between the xenon lamp and the sample, and the light intensity was measured using a power meter. The prepared sample was irradiated under one solar intensity, and tests showed that the seawater evaporation rate of the polydopamine-modified wood aerogel reached 2.1 kg / m³. 2 / h.

[0028] Example 2

[0029] Prepare 1 L of 0.20 mol / L sodium chlorite solution in a beaker, and add washed and dried balsa wood. Adjust the pH of the sodium chlorite solution to 5.4 with glacial acetic acid. Place the beaker in a water bath and heat to 80°C, reacting for 10 h. After removing lignin, wash the wood with deionized water, then add 1 L of 2 mol / L ammonia solution, and heat in a water bath to 85°C for 10 h. Remove the wood after the reaction, gently wash with deionized water, and freeze-dry to obtain wood aerogel. Prepare 1 L of phosphate buffer containing 30 mmol dopamine hydrochloride (10 mmol phosphate, pH adjusted to 9.0 with hydrochloric acid), immerse the wood aerogel in the buffer, and stir at 200 rpm for 6 h. After replacing the mother liquor three times, polydopamine-coated wood aerogel is obtained. The modified wood aerogel was placed in a 60 mmol / L copper nitrate ethanol solution and crosslinked with copper at -12°C for 24 h. After crosslinking, the wood aerogel was transferred to a hydrothermal reactor, and a 1:3 molar ratio of thiourea and sodium hydroxide was added. The temperature was raised to 150°C and reacted for 6 h. The wood aerogel was then removed from the hydrothermal reactor and freeze-dried. A xenon lamp was used as a simulated solar light source. The light intensity was controlled by adjusting the distance between the xenon lamp and the sample, and the light intensity was measured using a power meter. The prepared sample was irradiated under one solar intensity. Tests showed that the seawater evaporation rate of the polydopamine-modified wood aerogel reached 2.17 kg / m³. 2 / h.

[0030] Example 3

[0031] Prepare 1 L of 0.12 mol / L sodium chlorite solution in a beaker, and add washed and dried balsa wood. Adjust the pH of the sodium chlorite solution to 4.6 with glacial acetic acid. Place the beaker in a water bath and heat to 80°C, reacting for 8 hours. After removing lignin, wash the wood with deionized water, then add 1 L of 1.04 mol / L sodium hydroxide solution, heat in a water bath to 85°C, and react for 8 hours. Remove the wood after the reaction, gently wash with deionized water, and freeze-dry to obtain wood aerogel. Prepare 1 L of a tris(hydroxymethyl)aminomethane buffer solution containing 11 mmol dopamine hydrochloride (10 mmol tris(hydroxymethyl)aminomethane, pH adjusted to 8.5 with hydrochloric acid). Immerse the wood aerogel in the buffer solution, and stir at 150 rpm for 8 hours. After replacing the mother liquor 4 times, polydopamine-coated wood aerogel is obtained. The modified wood aerogel was placed in a 42 mmol / L copper nitrate ethanol solution and crosslinked with copper at -20°C for 20 h. After crosslinking, the wood aerogel was transferred to a hydrothermal reactor, and a 1:2 molar ratio of thiourea and sodium hydroxide was added. The temperature was raised to 120°C, and the reaction was carried out for 6 h. The wood aerogel was then removed from the hydrothermal reactor and freeze-dried. A xenon lamp was used as a simulated solar light source. The light intensity was controlled by adjusting the distance between the xenon lamp and the sample, and the light intensity was measured using a power meter. The prepared sample was irradiated under one solar intensity. The test showed that the seawater evaporation rate of the polydopamine-modified wood aerogel reached 2.27 kg / m³. 2 / h.

[0032] Example 4

[0033] Prepare 1 L of 0.11 mol / L sodium sulfite solution in a beaker, and add washed and dried poplar wood. Adjust the pH of the sodium sulfite solution to 4.6 with citric acid, and react for 8.5 h. Place the beaker in a water bath and heat to 90℃ for 8 h. After removing lignin, wash the wood with deionized water, add 1 L of 1.5 mol / L potassium hydroxide solution, and heat in a water bath to 90℃ for 8 h. Remove the wood after the reaction, gently wash with deionized water, and freeze-dry to obtain wood aerogel. Prepare 1 L of a tris(hydroxymethyl)aminomethane buffer solution containing 20 mmol dopamine hydrochloride (10 mmol tris(hydroxymethyl)aminomethane, pH adjusted to 8.5 with hydrochloric acid). Immerse the wood aerogel in the buffer solution, and stir at 170 rpm for 7 h. After replacing the mother liquor 4 times, polydopamine-coated wood aerogel is obtained. The modified wood aerogel was placed in a 50 mmol / L copper nitrate ethylene glycol solution and crosslinked with copper at -20°C for 12 h. After crosslinking, the wood aerogel was transferred to a hydrothermal reactor, and a 1:2 molar ratio of Na₂S and sodium hydroxide was added. The temperature was raised to 140°C, and the reaction was carried out for 7.5 h. The wood aerogel was then removed from the hydrothermal reactor and freeze-dried. A xenon lamp was used as a simulated solar light source. The light intensity was controlled by adjusting the distance between the xenon lamp and the sample, and the light intensity was measured using a power meter. The prepared sample was irradiated under one solar intensity. The seawater evaporation rate of the polydopamine-modified wood aerogel was found to be 2.09 kg / m³. 2 / h.

[0034] Example 5

[0035] Prepare 1 L of 0.12 mol / L sodium sulfite solution in a beaker, and add washed and dried pine wood. Adjust the pH of the sodium sulfite solution to 5 with phosphoric acid. Place the beaker in a water bath and heat to 85°C for 9 hours. After removing the lignin, wash the wood with deionized water, add 1 L of 1.5 mol / L sodium hydroxide solution, and heat in a water bath to 85°C for 8 hours. Remove the wood after the reaction, gently wash with deionized water, and freeze-dry to obtain wood aerogel. Prepare 1 L of borate buffer containing 20 mmol dopamine hydrochloride (10 mmol borate, pH adjusted to 8.5 with hydrochloric acid). Immerse the wood aerogel in the buffer solution, and stir at 150 rpm for 8 hours. After replacing the mother liquor three times, polydopamine-coated wood aerogel is obtained. The modified wood aerogel was placed in a 50 mmol / L copper chloride ethanol solution and crosslinked with copper at -22°C for 15 h. After crosslinking, the wood aerogel was transferred to a hydrothermal reactor, and a Na₂S and sodium hydroxide mixture (molar ratio 1:2.5) was added. The temperature was raised to 120°C, and the reaction was carried out for 6 h. The wood aerogel was then removed from the hydrothermal reactor and freeze-dried. A xenon lamp was used as a simulated solar light source. The light intensity was controlled by adjusting the distance between the xenon lamp and the sample, and the light intensity was measured using a power meter. The prepared sample was irradiated under one solar intensity. Tests showed that the seawater evaporation rate of the polydopamine-modified wood aerogel reached 1.96 kg / m³. 2 / h.

[0036] Example 6

[0037] Prepare 1 L of 0.115 mol / L sodium chlorite solution in a beaker, and add washed and dried balsa wood. Adjust the pH of the sodium chlorite solution to 5.2 with citric acid. Place the beaker in a water bath and heat to 80°C, reacting for 8 hours. After removing lignin, wash the wood with deionized water, then add 1 L of 1.04 mol / L sodium hydroxide solution, heat in a water bath to 85°C, and react for 8 hours. Remove the wood after the reaction, gently wash with deionized water, and freeze-dry to obtain wood aerogel. Prepare 1 L of a tris(hydroxymethyl)aminomethane buffer solution containing 11 mM dopamine hydrochloride (10 mmol of tris(hydroxymethyl)aminomethane, pH adjusted to 8.5 with hydrochloric acid). Immerse the wood aerogel in the buffer solution, and stir at 150 rpm for 8 hours. After replacing the mother liquor 4 times, polydopamine-coated wood aerogel is obtained. The modified wood aerogel was placed in a 42 mmol / L copper sulfate ethanol solution and crosslinked with copper at -22°C for 20 h. After crosslinking, the wood aerogel was transferred to a hydrothermal reactor, and a 1:2 molar ratio of Na₂S and ammonia solution was added. The temperature was raised to 140°C and reacted for 6 h. The wood aerogel was then removed from the hydrothermal reactor and freeze-dried. A xenon lamp was used as a simulated solar light source. The light intensity was controlled by adjusting the distance between the xenon lamp and the sample, and the light intensity was measured using a power meter. The prepared sample was irradiated under one solar intensity. Tests showed that the seawater evaporation rate of the polydopamine-modified wood aerogel reached 2.23 kg / m³. 2 / h.

Claims

1. A method for preparing polydopamine-modified wood aerogel for efficient seawater evaporation, the specific steps of which are as follows: (1) Preparation of wood aerogel The wood is cleaned and dried, then soaked in a sodium salt solution, and the pH of the sodium salt solution is adjusted with an acidic solution. The wood is then heated in a water bath to remove lignin. The wood after lignin removal is transferred to an alkaline solution and heated in a water bath to remove hemicellulose. After the process is complete, the wood is cleaned and freeze-dried to obtain wood aerogel. (2) Polydopamine PDA modified wood aerogel Wood aerogels were immersed in a buffer solution containing dopamine hydrochloride (DA) and stirred. The dopamine hydrochloride (DA) underwent spontaneous oxidation and self-polymerization to form a polydopamine (PDA) layer. The above steps were repeated with fresh solution instead of the mother liquor to obtain PDA-modified wood aerogels. (3) Copper crosslinked modified aerogel Weigh out copper salt and dissolve it in alcohol solution to prepare copper salt alcohol solution. Then, put the modified wood aerogel obtained in step (2) into copper salt alcohol solution for copper crosslinking. Prepare a mixed solution of sulfur salt and alkali. Then, put the copper crosslinked wood aerogel into a hydrothermal reactor, pour it into the prepared mixed solution, heat and react, freeze dry, and obtain copper ion crosslinked modified wood aerogel.

2. The preparation method according to claim 1, characterized in that... The wood mentioned in step (1) is one of balsa wood, poplar or pine; the sodium salt is one of sodium chlorite or sodium sulfite; the concentration of the sodium salt solution is 0.10-0.20 mol / L; the acidic solution mentioned in step (1) is one of glacial acetic acid, phosphoric acid or citric acid; the pH of the sodium salt solution is adjusted to 4.6-5.

4.

3. The preparation method according to claim 1, characterized in that... In step (1), the water bath heating temperature during the lignin removal process is 80-90℃ and the heating time is 8-10h.

4. The preparation method according to claim 1, characterized in that... The alkaline solution mentioned in step (1) is one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution or ammonia solution, and the concentration of the alkaline solution is 1-2 mol / L; the water bath heating temperature during the removal of hemifiber is 85-95℃ and the heating time is 8-10h.

5. The preparation method according to claim 1, characterized in that... The buffer solution mentioned in step (2) is one of tris(hydroxymethyl)aminomethane buffer, phosphate buffer or borate buffer; the pH value of the buffer solution is adjusted to 8-9 with acid; the molar ratio of buffer solution to dopamine hydrochloride is 1:(1-3).

6. The preparation method according to claim 1, characterized in that... The stirring speed in step (2) is 150-200 rpm, and the stirring time is 6-8 hours; the mother liquor is replaced and repeated 3-4 times.

7. The preparation method according to claim 1, characterized in that... The copper salt mentioned in step (3) is one of copper nitrate, copper sulfate or copper chloride; the alcohol solution is one of anhydrous ethanol, methanol or ethylene glycol; the concentration of copper salt in the copper salt alcohol solution is 40 mmol / L to 60 mmol / L.

8. The preparation method according to claim 1, characterized in that... The temperature for copper crosslinking in step (3) is -12 to 25°C, and the time for copper crosslinking is 12 to 24 hours.

9. The preparation method according to claim 1, characterized in that... The sulfur salt mentioned in step (3) is either thiourea or Na2S; the alkali is either sodium hydroxide or ammonia water; the molar ratio of sulfur salt to alkali is 1:(1-3).

10. The preparation method according to claim 1, characterized in that... The temperature for the heating reaction in step (3) is 120-150°C and the reaction time is 6-8 hours.

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