Preparation method of double-layer hydrogel for seawater desalination

Abstract

The invention discloses hydrogel capable of being used for seawater desalination and a preparation method of the hydrogel, and belongs to the technical field of water treatment. The preparation method comprises the following steps: uniformly mixing a monomer, a cross-linking agent, an initiator and a catalyst to obtain a mixed material, then transferring the mixed material into a mold, polymerizing for 5-10 minutes under an ultraviolet lamp, and then freezing and drying in a freeze dryer to obtain the hydrogel for seawater desalination. The method disclosed by the invention is convenient and rapid, so that the method has the advantage of being used under special conditions such as seawater desalination and sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and in particular relates to a method for preparing a double-layer hydrogel for seawater desalination. Background Art

[0002] With the rapid growth of the world's population, the continuous intensification of human activities and the resulting climate change and environmental pollution, the earth's freshwater resources that can be directly drunk are becoming increasingly scarce. The water crisis has become one of the most serious challenges facing mankind around the world. Vigorously developing seawater desalination technology will become one of the important ways to alleviate the shortage of freshwater resources.

[0003] In order to solve this problem, various seawater desalination technologies have emerged. Such as reverse osmosis (RO), multi-effect desalination (MED), thermal vapor compression (TVC), humidification and dehumidification (HDH), hybrid system and multi-stage flash memory (MSF). However, these technologies are difficult to be widely promoted and applied due to their high operating costs. Solar energy is an almost inexhaustible renewable resource in nature. Solar-driven desalination technology is superior to other technologies with its low cost and high photothermal conversion efficiency, and has become one of the effective ways to alleviate water shortages.

[0004] Hydrogel is a three-dimensional network structure formed by the accumulation of long polymer chains or colloidal particles with water as the medium, which can hold a large amount of water without dissolving. Due to its highly adjustable physical and chemical properties, it has received extensive attention and application development in the fields of inclusive artificial tissues, sanitary products, contact lenses, drug delivery and agricultural fertilizers. As one of the most important materials in the process of water evaporation and desalination, hydrogel has a high water evaporation rate and efficiency, which is attributed to the heat localization at the air-water interface; the weak interaction between water molecules and polymer chains can form intermediate water, thereby reducing the energy requirement for water vaporization.

[0005] Therefore, developing a new desalination membrane material with high photothermal conversion efficiency and seawater utilization rate is of great significance to improving the efficiency of seawater desalination. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and provide a method for preparing a double-layer hydrogel for seawater desalination. The present invention uses carbon nanotubes as a basis, and through in-situ energy conversion of carbon nanotubes, obtains a higher photothermal conversion efficiency and can achieve a higher water evaporation rate under the condition of one sun.

[0007] The technical principle of the present invention is as follows: The present invention uses an in-situ polymerization method to combine an acrylamide hydrogel body with carbon nanotubes to design a functional double-layer hydrogel. The evaporator consists of a top light absorption layer and a bottom water transmission layer to effectively generate solar steam. The upper layer is an acrylamide hydrogel modified by carbon nanotubes. The carbon nanotubes and the acrylamide hydrogel skeleton lead to strong light absorption, which greatly improves the photothermal conversion efficiency. The bottom layer is composed of acrylamide hydrogel. The three-dimensional porous structure of the gel skeleton improves the water transmission efficiency through capillary action, realizing its efficient desalination in the seawater desalination process.

[0008] Technical solution: According to the preparation method of the double-layer hydrogel for seawater desalination according to the embodiment of the present invention, the method comprises the following steps: step 1: mixing acrylamide and deionized water, stirring for 5-10 minutes, and obtaining an acrylamide solution; step 2: mixing the acrylamide solution obtained in step 1, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate, adding the deionized water, stirring for 1-5 minutes, transferring to a polytetrafluoroethylene template, and irradiating under ultraviolet light for 5-10 minutes to obtain a poly(acrylamide) hydrogel; step 3: mixing carbon nanotubes and the deionized water, and ultrasonically crushing for 5-10 minutes to obtain a carbon nanotube solution; step 4: mixing the acrylamide, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and ammonium persulfate, adding the deionized water, and irradiating under ultraviolet light for 5-10 minutes to obtain a poly(acrylamide) hydrogel. methylenebisacrylamide, the ammonium persulfate and the carbon nanotube solution obtained in step 3 are mixed, the deionized water is added, and the mixture is stirred for 5-10 minutes, and then transferred to the poly(acrylamide) hydrogel obtained in step 2, and illuminated under the ultraviolet lamp for 5-10 minutes to obtain a poly(acrylamide-carbon nanotube) hydrogel; step 5: soaking the poly(acrylamide-carbon nanotube) hydrogel obtained in step 4 in a beaker containing the deionized water for 3-8 hours; step 6: carefully taking out the poly(acrylamide-carbon nanotube) hydrogel from the beaker, placing it in a freeze dryer for 24-72 hours, and then placing it in a vacuum drying oven for 6-24 hours to obtain a poly(acrylamide-carbon nanotube) aerogel.

[0009] According to the method for preparing the double-layer hydrogel for seawater desalination of the embodiment of the present invention, the poly(acrylamide-carbon nanotube) double-layer hydrogel is prepared by in-situ polymerization. Therefore, compared with the traditional technology for seawater desalination, the preparation process is simple, the production cost is low, the raw materials are green, pollution-free and low-priced, and the evaporation efficiency of seawater is improved.

[0010] Furthermore, the mass volume ratio of the acrylamide and the deionized water in the step 1 is (100-500): 1 mg / mL.

[0011] Furthermore, in the step 2, the mass ratio of the acrylamide solution, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate is (5000-10000): (1-10): (1-10): (1-10), and the mass volume ratio of the total mass of the acrylamide solution, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate to the deionized water is (1-10): 1 g / mL.

[0012] Furthermore, the mass volume ratio of the carbon nanotubes and the deionized water in step 3 is (1-5): 1 mg / mL.

[0013] Furthermore, in the step 4, the mass ratio of the carbon nanotube solution, the acrylamide, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate is (5000-10000): (500-2000): (1-10): (1-10): (1-10), and the mass volume ratio of the total mass of the acrylamide solution, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate to the deionized water is (1-10): 1 g / mL.

[0014] Furthermore, the mass volume ratio of the poly(acrylamide-carbon nanotube) hydrogel to the deionized water in step 5 is (1-10): 1 g / mL.

[0015] Beneficial effects: 1. The present invention utilizes the inherent characteristics of acrylamide materials, which have good hydrophilicity and low thermal conductivity; 2. By combining carbon nanotubes and acrylamide, adjusting their concentration ratio and adjusting the thickness of the hydrogel, and preparing a double-layer hydrogel by in-situ polymerization, the water vapor flux can be effectively increased, and the evaporation rate can reach up to 2.11 kg·m -2 ·h -1 ; 3. The preparation process of the present invention is simple, the raw materials are green, pollution-free and low-priced, and are conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 3 is a curve showing the influence of different carbon nanotube contents on the evaporation rate of the double-layer hydrogel according to an embodiment of the present invention.

[0018] Figure 2 1 is an evaporation rate curve of a double-layer hydrogel according to an embodiment of the present invention under different simulated seawater salinities. DETAILED DESCRIPTION

[0019] The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] The present invention aims to provide a method for preparing a double-layer hydrogel for seawater desalination.

[0021] According to the preparation method of the double-layer hydrogel for seawater desalination according to the embodiment of the present invention, the steps are as follows: Step 1: Mix acrylamide and deionized water, stir for 5-10 minutes, and obtain an acrylamide solution. Step 2: Mix the acrylamide solution obtained in step 1, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate, add deionized water, stir for 1-5 minutes, transfer to a polytetrafluoroethylene template, and illuminate under ultraviolet light for 5-10 minutes to obtain a poly(acrylamide) hydrogel. Step 3: Mix carbon nanotubes and deionized water, ultrasonically crush for 5-10 minutes, and obtain a carbon nanotube solution. Step 4: Mix acrylamide, tetramethylethylenediamine, N,N-methylenebisacrylamide, ammonium persulfate and the carbon nanotube solution obtained in step 3, add deionized water, stir for 5-10 minutes, and transfer to the poly(acrylamide) hydrogel obtained in step 2, and illuminate under ultraviolet light for 5-10 minutes to obtain a poly(acrylamide-carbon nanotube) hydrogel. Step 5: Soak the poly(acrylamide-carbon nanotube) hydrogel obtained in step 4 in a beaker containing the deionized water for 3-8 hours. Step 6: Carefully take out the poly(acrylamide-carbon nanotube) hydrogel from the beaker, place it in a freeze dryer for 24-72 hours, and then place it in a vacuum drying oven for 6-24 hours to obtain a poly(acrylamide-carbon nanotube) aerogel.

[0022] Preparation of poly(acrylamide-carbon nanotube) hydrogel: 1.2 g acrylamide was dissolved in 8 mL of water, stirred, and 2 mL of a mixed solution containing 4 μl tetramethylethylenediamine, 0.0072 g N,N-methylenebisacrylamide, and 0.0060 g ammonium persulfate was prepared. The mixed solution was added to acrylamide and quickly shaken. After shaking, the mixed solution was poured into the template and placed under ultraviolet light for 10 minutes. The solution became acrylamide gel; 17.5 mg carbon nanotubes were dissolved in 8 mL of water, ultrasonically crushed, and 2 mL of a mixed solution containing 1.2 g acrylamide, 4 μL tetramethylethylenediamine, 0.0072 g N,N-methylenebisacrylamide, and 0.0060 g ammonium persulfate was prepared. The mixed solution was added to the carbon nanotube solution and quickly shaken. After shaking, the mixed solution was poured into the template with acrylamide gel as the bottom and placed under ultraviolet light for 10 minutes. The solution became poly(acrylamide-carbon nanotube) hydrogel.

[0023] Preparation of poly(acrylamide-carbon nanotube) aerogel: The poly(acrylamide-carbon nanotube) hydrogel obtained in step 4 is soaked in deionized water for 6 hours, then freeze-dried for 48 hours, and vacuum-dried for 12 hours. A double-layer hydrogel with excellent performance in seawater desalination can be obtained.

[0024] Acrylamide has good hydrophilicity and low thermal conductivity. By combining carbon nanotubes and acrylamide, adjusting their concentration ratio and adjusting the thickness of the hydrogel, a double-layer hydrogel was prepared by in-situ polymerization, which can effectively increase the flux of water vapor and achieve an evaporation rate of up to 2.11 kg·m -2 h -1 .

[0025] The present invention uses an in-situ polymerization method to combine an acrylamide hydrogel main body with carbon nanotubes to design a functional double-layer hydrogel. The evaporator consists of a top light absorption layer and a bottom water transmission layer to effectively generate solar steam. The upper layer is an acrylamide hydrogel modified by carbon nanotubes. The carbon nanotubes and the acrylamide hydrogel skeleton lead to strong light absorption, which greatly improves the photothermal conversion efficiency. The bottom layer is composed of acrylamide hydrogel. The three-dimensional porous structure of the gel skeleton improves the water transmission efficiency through capillary action, realizing its efficient desalination in the seawater desalination process.

[0026] In this way, the obtained double-layer hydrogel reduces the evaporation enthalpy of seawater, so that seawater evaporates with lower energy, thereby achieving the desalination of seawater. The preparation process of the invention is simple, the raw materials are green, pollution-free and low-priced, and the evaporation efficiency of seawater is improved.

[0027] According to the method for preparing the double-layer hydrogel for seawater desalination of the embodiment of the present invention, the poly(acrylamide-carbon nanotube) double-layer hydrogel is prepared by in-situ polymerization. Therefore, compared with the traditional technology for seawater desalination, the preparation process is simple, the production cost is low, the raw materials are green, pollution-free and low-priced, and the evaporation efficiency of seawater is improved.

[0028] Furthermore, the mass volume ratio of acrylamide and deionized water in step 1 is (100-500): 1 mg / mL. A mixed solution is obtained by mixing acrylamide and deionized water in a mass volume ratio of (100-500): 1 mg / mL to facilitate the subsequent preparation of poly(acrylamide) hydrogel.

[0029] Further, the mass ratio of acrylamide solution, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate in step 2 is (5000-10000): (1-10): (1-10): (1-10), and the mass volume ratio of the total mass of acrylamide solution, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate to deionized water is (1-10): 1g / mL. Take 1.2 g of acrylamide and dissolve it in 8 mL of water, stir it, and prepare 2 ml of a mixed solution containing 4 μL of tetramethylethylenediamine, 0.0072 g of N,N-methylenebisacrylamide and 0.0060 g of ammonium persulfate. Add the mixed solution to acrylamide and shake it quickly. After shaking, pour the mixed solution into the template and irradiate it under ultraviolet light for 10 minutes. The solution becomes acrylamide gel.

[0030] In this way, a poly(acrylamide) gel is obtained, which is convenient for preparing the subsequent poly(acrylamide-carbon nanotube) hydrogel.

[0031] Furthermore, the mass volume ratio of carbon nanotubes to deionized water in step 3 is (1-5): 1 mg / mL. The mass ratio of carbon nanotube solution, acrylamide, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate in step 4 is (5000-10000): (500-2000): (1-10): (1-10): (1-10), and the mass volume ratio of the total mass of acrylamide solution, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate to deionized water is (1-10): 1 g / mL. The mass volume ratio of poly(acrylamide-carbon nanotube) hydrogel to deionized water in step 5 is (1-10); 1 g / mL.

[0032] Take 17.5 mg of carbon nanotubes and dissolve them in 8 mL of water. Ultrasonic crush them and prepare 2 ml of a mixed solution containing 1.2 g of acrylamide, 4 μl of tetramethylethylenediamine, 0.0072 g of N,N-methylenebisacrylamide and 0.0060 g of ammonium persulfate. Add the mixed solution to the carbon nanotube solution and shake it quickly. After shaking, pour the mixed solution into a template with acrylamide gel as the bottom and irradiate it under ultraviolet light for 10 minutes. The solution becomes poly(acrylamide-carbon nanotube) hydrogel.

[0033] The poly(acrylamide-carbon nanotube) hydrogel obtained in this way can effectively improve the flux of water vapor, and the evaporation rate can reach up to 2.11 kg·m -2 h -1 .

[0034] Although embodiments of the present invention have been shown and described above, it should be understood that these embodiments are exemplary and are not to be construed as limitations of the present invention, and that they may be changed, modified, substituted or altered within the scope of the present invention by a person skilled in the art without departing from the principles and purposes of the present invention.

Claims

1. A method for preparing a double-layer hydrogel for seawater desalination, characterized in that: The steps of preparing the hydrogel are as follows: Step 1: Mix acrylamide and deionized water, and stir for 5-10 minutes to obtain an acrylamide solution; Step 2: Mix the acrylamide solution, tetramethylethylenediamine, N,N-methylenebisacrylamide and ammonium persulfate obtained in step 1, add the deionized water, stir for 1-5 minutes, transfer to a polytetrafluoroethylene template, and illuminate under ultraviolet light for 5-10 minutes to obtain a poly(acrylamide) hydrogel; Step 3: mixing the carbon nanotubes and the deionized water, and ultrasonically crushing for 5-10 minutes to obtain a carbon nanotube solution; Step 4: mixing the acrylamide, the tetramethylethylenediamine, the N,N-methylenebisacrylamide, the ammonium persulfate and the carbon nanotube solution obtained in step 3, adding the deionized water, stirring for 5-10 minutes, and then transferring to the poly(acrylamide) hydrogel obtained in step 2, and irradiating under the ultraviolet lamp for 5-10 minutes to obtain a poly(acrylamide-carbon nanotube) hydrogel; Step 5: Soaking the poly(acrylamide-carbon nanotube) hydrogel obtained in step 4 in a beaker containing deionized water for 3-8 hours; Step 6: Carefully take out the poly(acrylamide-carbon nanotube) hydrogel from the beaker, place it in a freeze dryer for 24-72 hours, and then place it in a vacuum drying oven for 6-24 hours to obtain a poly(acrylamide-carbon nanotube) aerogel;.

2. The method for preparing a double-layer hydrogel for seawater desalination according to claim 1, characterized in that: The mass volume ratio of the acrylamide and the deionized water in the step 1 (100-500) is: 1 mg / mL.

3. The method for preparing a double-layer hydrogel for seawater desalination according to claim 1, characterized in that: The mass ratio of the acrylamide solution, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate in the step 2 is (5000-10000): (1-10): (1-10): (1-10), and the mass volume ratio of the total mass of the acrylamide solution, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate to the deionized water is (1-10): 1 g / mL.

4. The method for preparing a double-layer hydrogel for seawater desalination according to claim 1, characterized in that: The mass volume ratio of the carbon nanotubes and the deionized water in step 3 (1-5) is: 1 mg / mL.

5. The method for preparing a double-layer hydrogel for seawater desalination according to claim 1, characterized in that: The mass ratio of the carbon nanotube solution, the acrylamide, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate in the step 4 is (5000-10000): (500-2000): (1-10): (1-10): (1-10), and the mass volume ratio of the total mass of the acrylamide solution, the tetramethylethylenediamine, the N,N-methylenebisacrylamide and the ammonium persulfate to the deionized water is (1-10): 1 g / mL.

6. The method for preparing a double-layer hydrogel for seawater desalination according to claim 1, characterized in that: The mass volume ratio of the poly(acrylamide-carbon nanotube) hydrogel to the deionized water in step 5 is (1-10): 1 g / mL.

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