Preparation method of a high-efficiency air-water-collecting composite gel with vertical pores

Abstract

The present invention relates to a method for preparing a vertically porous high-efficiency air water-collecting composite gel. The first step: preparation of a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix; the second step: preparation of a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel coated with polydopamine; the third step: preparation of a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel. The vertically porous high-efficiency air water-collecting composite gel prepared by the salt template method of the present invention has a high porosity and super-hydrophilicity. The composite hygroscopic calcium chloride can promote the rapid transport of water molecules into the interior of the hydrogel, and the gel network structure can prevent the leakage of the internal aqueous solution. Polydopamine can improve the solar thermal conversion efficiency and improve the water desorption performance. The composite gel preparation method involved in the present invention can quickly, effectively and economically achieve the air water collection effect.

Description

Technical Field

[0001] The invention relates to a method for preparing a high-efficiency air-water-collecting composite gel with vertical pores. Background Art

[0002] Freshwater shortages are becoming a global threat to human survival. Adsorption-based air-based water harvesting is an emerging, low-cost, environmentally sustainable, and wide-humidity air-based water harvesting technology. Compared to fog water harvesting, which requires high humidity, and cooling dew water harvesting, which requires high energy consumption, it offers broader application prospects. However, conventional water-harvesting materials suffer from complex preparation, low adsorption efficiency, and high desorption energy, limiting their practical application in remote and rural inland areas.

[0003] To address these issues, a super-hydrophilic hydrogel with a high-performance hygroscopic agent, calcium chloride, was engineered to create a composite gel that rapidly transports water molecules into the gel and stores them in a swollen form, improving water adsorption. Hydrophilic polydopamine, with its high absorption capacity for ultraviolet and visible light, creates a vertically porous structure that provides pathways for the transport and escape of water molecules, enabling efficient water collection under sunlight. This preparation process is mild, cost-effective, and offers excellent performance, making it widely applicable in the field of air-water harvesting. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a highly efficient air-water-harvesting composite gel with vertical pores. This method is mild, low-cost, and offers excellent performance, suitable for large-scale practical application. The present invention utilizes a super-hydrophilic sodium carboxymethyl cellulose / polyacrylamide / polydopamine vertical porous gel, prepared using a salt-templated method and photopolymerization technology, as the matrix. The surface is coated with polydopamine to impart photothermal properties. The vertical porous structure promotes the transport of water molecules. The resulting composite gel, combined with the high-performance hygroscopic agent calcium chloride, achieves highly efficient air-water harvesting.

[0005] The present invention can be implemented by the following technical solution, which is characterized by:

[0006] Step 1: Preparation of sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix

[0007] 75-150 parts acrylamide, 4-17 parts sodium carboxymethyl cellulose, 1-3 parts N-Methylenebisacrylamide, 2-5 parts 2,2-diethoxyacetophenone, 700-800 parts anhydrous sodium acetate, and 800-900 parts deionized water were placed in a reactor and stirred continuously at 80°C for 2-4 hours. After the reaction, the mixture was poured into a mold and naturally cooled to 20°C. Then, 7-8 parts sodium acetate trihydrate seed crystals were added to the mixed solution. After a uniformly distributed rod-shaped salt template was formed, the mixture was polymerized under 365 nm mercury lamp light for 20 minutes. Finally, the hydrogel was washed with distilled water 10-20 times to remove the salt template inside, resulting in a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0008] Step 2: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix

[0009] 10-50 parts of tris(hydroxymethylaminomethane) and 4000-8000 parts of deionized water were placed in a reactor, and concentrated HCl was used to adjust the pH to 8.5 to prepare a Tris-HCl buffer solution. The above-mentioned sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix and 4-12 parts of dopamine hydrochloride were placed in the Tris-HCl buffer solution, stirred and reacted for 24 hours under dark conditions. After the reaction was completed, the matrix was taken out and washed with deionized water for 10-20 times to obtain a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0010] Step 3: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide / calcium chloride vertical porous composite gel

[0011] The polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix was placed in 1000-2000 parts of 10-30% (mass concentration) calcium chloride solution and immersed for 12-48 hours. After the reaction, it was washed with deionized water for 5-10 times and freeze-dried for 24 hours to obtain a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel.

[0012] The present invention adopts a salt template method and photopolymerization technology to prepare a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel, which has the following characteristics: (1) The vertical porous structure inside the composite gel promotes the transport of water molecules inside the gel, and the aqueous solution is stored inside the gel in the form of swelling; (2) The composite gel prepared by compounding with the high-performance hygroscopic agent calcium chloride can achieve efficient air water collection under wide humidity conditions (30%RH-90%RH); (3) The preparation method of the air water collection material prepared by the present invention has mild conditions, low cost, excellent performance, and can be used in large-scale practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Described are the cross-sectional and longitudinal structural SEM images of the vertical porous composite gel.

[0014] Figure 2 The diagram shows a comparison of the moisture absorption effects of pure hygroscopic agent CaCl2 and vertical porous composite gel before and after absorption. Implementation Method Example

[0015] Step 1: Preparation of sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix

[0016] 75 parts acrylamide, 13 parts sodium carboxymethyl cellulose, 1 part N-Methylenebisacrylamide, 2 parts 2,2-diethoxyacetophenone, 700 parts anhydrous sodium acetate, and 850 parts deionized water were placed in a reactor and stirred continuously at 80°C for 2 hours. After the reaction, the mixture was poured into a mold and naturally cooled to 20°C. Then, 7 parts sodium acetate trihydrate seed crystals were added to the mixed solution. After a uniformly distributed rod-shaped salt template was formed, it was polymerized under a 365 nm mercury lamp for 20 minutes. Finally, the hydrogel was washed 10 times with distilled water to remove the salt template inside, resulting in a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0017] Step 2: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix

[0018] Prepare a Tris-HCl buffer solution by placing 24 parts of tris(hydroxymethylaminomethane) and 4000 parts of deionized water in a reactor and adjusting the pH to 8.5 with concentrated HCl. Add the aforementioned sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix and 6 parts of dopamine hydrochloride to the Tris-HCl buffer solution and stir in the dark for 24 hours. After the reaction is complete, remove the matrix and wash it 10 times with deionized water to obtain a polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0019] Step 3: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide / calcium chloride vertical porous composite gel

[0020] The polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix was immersed in 1000 parts of 20% (mass fraction) calcium chloride solution for 24 hours. After the reaction, it was washed with deionized water 5 times and freeze-dried for 24 hours to obtain a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel. Example

[0021] Step 1: Preparation of sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix

[0022] 100 parts acrylamide, 5 parts sodium carboxymethyl cellulose, 2 parts N-Methylenebisacrylamide, 4 parts 2,2-diethoxyacetophenone, 750 parts anhydrous sodium acetate, and 800 parts deionized water were placed in a reactor and stirred continuously at 80°C for 3 hours. After the reaction, the mixture was poured into a mold and naturally cooled to 20°C. 8 parts sodium acetate trihydrate seed crystals were added to the mixed solution. After a uniformly distributed rod-shaped salt template was formed, the mixture was polymerized under 365 nm mercury lamp light for 25 minutes. Finally, the hydrogel was washed 15 times with distilled water to remove the salt template inside, resulting in a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix, which was set aside.

[0023] Step 2: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix

[0024] 36 parts of tris(hydroxymethylaminomethane) and 6000 parts of deionized water were placed in a reactor and the pH was adjusted to 8.5 with concentrated HCl to prepare a Tris-HCl buffer solution. The aforementioned sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix and 9 parts of dopamine hydrochloride were placed in the Tris-HCl buffer solution and stirred in the dark for 24 hours. After the reaction was complete, the matrix was removed and washed 20 times with deionized water to obtain a polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0025] Step 3: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide / calcium chloride vertical porous composite gel

[0026] The above-mentioned polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix was placed in 1000 parts of 20% (mass fraction) calcium chloride solution and immersed for 24 hours. After the reaction, it was washed with deionized water 6 times and freeze-dried for 24 hours to obtain the polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel. Example

[0027] Step 1: Preparation of sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix

[0028] 125 parts acrylamide, 9 parts sodium carboxymethyl cellulose, 3 parts N-Methylenebisacrylamide, 4 parts 2,2-diethoxyacetophenone, 800 parts anhydrous sodium acetate, and 900 parts deionized water were placed in a reactor and stirred continuously at 80°C for 3 hours. After the reaction, the mixture was poured into a mold and naturally cooled to 20°C. 7 parts sodium acetate trihydrate seed crystals were added to the mixed solution. After a uniformly distributed rod-shaped salt template was formed, the mixture was polymerized under a 365 nm mercury lamp for 20 minutes. Finally, the hydrogel was washed 20 times with distilled water to remove the salt template inside, resulting in a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0029] Step 2: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix

[0030] Place 49 parts of tris(hydroxymethylaminomethane) and 8000 parts of deionized water in a reactor and adjust the pH to 8.5 with concentrated HCl to prepare a Tris-HCl buffer solution. Place the aforementioned sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix and 6 parts of dopamine hydrochloride in the Tris-HCl buffer solution and stir in the dark for 24 hours. After the reaction is complete, remove the matrix and wash it 20 times with deionized water to obtain a polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0031] Step 3: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide / calcium chloride vertical porous composite gel

[0032] The above-mentioned polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix was placed in 1000 parts of 20% (mass fraction) calcium chloride solution and immersed for 24 hours. After the reaction, it was washed with deionized water 8 times and freeze-dried for 24 hours to obtain the polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel. Example

[0033] Step 1: Preparation of sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix

[0034] 150 parts acrylamide, 17 parts sodium carboxymethyl cellulose, 3 parts N-Methylenebisacrylamide, 5 parts 2,2-diethoxyacetophenone, 700 parts anhydrous sodium acetate, and 900 parts deionized water were placed in a reactor and stirred continuously at 80°C for 4 hours. After the reaction, the mixture was poured into a mold and naturally cooled to 20°C. 8 parts sodium acetate trihydrate seed crystals were then added to the mixed solution. Once a uniformly distributed rod-shaped salt template was formed, it was polymerized under a 365 nm mercury lamp for 20 minutes. Finally, the hydrogel was washed 20 times with distilled water to remove the salt template inside, resulting in a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0035] Step 2: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix

[0036] Place 49 parts of tris(hydroxymethylaminomethane) and 8000 parts of deionized water in a reactor and adjust the pH to 8.5 with concentrated HCl to prepare a Tris-HCl buffer solution. Place the aforementioned sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix and 12 parts of dopamine hydrochloride in the Tris-HCl buffer solution and stir in the dark for 24 hours. After the reaction is complete, remove the matrix and wash it 15 times with deionized water to obtain a polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0037] Step 3: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide / calcium chloride vertical porous composite gel

[0038] The above-mentioned polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix was placed in 1500 parts of 20% (mass fraction) calcium chloride solution and immersed for 24 hours. After the reaction, it was washed with deionized water 10 times and freeze-dried for 24 hours to obtain the polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel. Example

[0039] Step 1: Preparation of sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix

[0040] 75 parts acrylamide, 9 parts sodium carboxymethyl cellulose, 2 parts N-Methylenebisacrylamide, 4 parts 2,2-diethoxyacetophenone, 750 parts anhydrous sodium acetate, and 900 parts deionized water were placed in a reactor and stirred continuously at 85°C for 2 hours. After the reaction, the mixture was poured into a mold and naturally cooled to 20°C. 8 parts sodium acetate trihydrate seed crystals were then added to the mixed solution. Once a uniformly distributed rod-shaped salt template was formed, the mixture was polymerized under a 365 nm mercury lamp for 20 minutes. Finally, the hydrogel was washed 15 times with distilled water to remove the salt template inside, resulting in a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0041] Step 2: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix

[0042] 49 parts of tris(hydroxymethylaminomethane) and 4000 parts of deionized water were placed in a reactor and the pH was adjusted to 8.5 with concentrated HCl to prepare a Tris-HCl buffer solution. The aforementioned sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix and 8 parts of dopamine hydrochloride were placed in the Tris-HCl buffer solution and stirred in the dark for 24 hours. After the reaction was complete, the matrix was removed and washed 20 times with deionized water to obtain a polydopamine-coated sodium carboxymethylcellulose / polyacrylamide vertical porous hydrogel matrix for later use.

[0043] Step 3: Preparation of polydopamine-coated sodium carboxymethylcellulose / polyacrylamide / calcium chloride vertical porous composite gel

[0044] The above-mentioned polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix was placed in 1000 parts of 20% (mass fraction) calcium chloride solution and immersed for 24 hours. After the reaction, it was washed with deionized water 8 times and freeze-dried for 24 hours to obtain the polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel.

Claims

1. A method for preparing a highly efficient air-water-collecting composite gel with vertical pores, characterized in that: The method is produced by the following steps, where the "parts" are parts by weight. The first step is to prepare a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix: 75-150 parts of acrylamide, 4-17 parts of sodium carboxymethyl cellulose, 1-3 parts of N,N-methylenebisacrylamide, 2-5 parts of 2,2-diethoxyacetophenone, 700-800 parts of anhydrous sodium acetate, and 800-900 parts of deionized water are placed in a reaction kettle, and stirred continuously at 80°C for 2-4 hours. After the reaction is completed, the mixture is poured into a mold and naturally cooled to 20°C. Then, 7-8 parts of sodium acetate trihydrate seeds are added to the mixed solution, and after a uniformly distributed rod-shaped salt template is formed, the mixture is placed under a mercury lamp with a wavelength of 365nm for polymerization for 20 minutes. Finally, the salt template inside the hydrogel is removed by washing with distilled water for 10-20 times to obtain a sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for standby use. Step 2: Preparation of polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix: 10-50 parts of tris(hydroxymethyl)aminomethane) and 4000-8000 parts of deionized water are placed in a reaction kettle, and the pH is adjusted to 8.5 with concentrated HCl to prepare a Tirs-HCl buffer solution; the above sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix and 4-12 parts of dopamine hydrochloride are placed in the Tirs-HCl buffer solution, stirred for reaction for 24 hours under dark conditions, taken out after the reaction is completed, and washed with deionized water for 10-20 times to obtain a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix for standby use; Step 3: Preparation of polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel: Take the above-mentioned polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide vertical porous hydrogel matrix and place it in 1000-2000 parts of a calcium chloride solution with a mass concentration of 10-30% and immerse it for 12-48 hours. After the reaction is completed, wash it with deionized water for 5-10 times and freeze-dry it for 24 hours to obtain a polydopamine-coated sodium carboxymethyl cellulose / polyacrylamide / calcium chloride vertical porous composite gel.

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