A composite material for absorbing PFOA pollutants in water and preparation method thereof

Abstract

The present invention discloses a composite material for absorbing PFOA pollutants in water and a preparation method thereof, wherein the composite material is composited by hydrothermal reaction of a Cu-based MOFs material and a nanocellulose membrane, wherein the Cu-based MOFs material is NH2-CuBTC, and the nanocellulose membrane is an alkali-modified nanocellulose membrane prepared from asparagus stems as raw materials. The preparation steps include extracting alkali-modified cellulose from asparagus stems by ball milling alkali hydrolysis, preparing hydroxyl- and amino-co-modified alkaline nanocellulose membrane OH / NH2-CM by microwave reaction, and hydrothermal preparation of Cu-based MOFs-nanocellulose membrane composite material NH2-CuBTC@OH / NH2-CM. The application method of the composite material is as follows: the composite material is coated on a floating ball in a river, aquaculture waters or the sea, and the floating ball adsorbs PFOA pollutants in the water while giving a warning; it can also be coated on the surface of a waterscape prosthesis to treat PFOA pollution while decorating water parks and scenic water bodies.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution control, and specifically relates to a composite material for adsorbing PFAS pollutants in water and a preparation method thereof. Background Art

[0002] Water is an irreplaceable necessity for human survival and development, and plays an important role in our lives, but it is also easily polluted by human interference. Water pollution is generally divided into six categories: physical pollution, inorganic pollution, organic pollution, nutrient pollution and eutrophication of water bodies, biological pollution and radioactive pollution. Water pollution will destroy the virtuous cycle of water resources, destroy the ecosystem and biodiversity, threaten human survival and health, restrict agriculture, fisheries, industry and ecological environment, and cause serious economic losses.

[0003] In recent years, with the continuous development of new materials and technologies, some new pollutants have gradually appeared in the water environment. With the continuous detection of new pollutants in the water environment, their potential hazards cannot be ignored. New pollutants refer to chemical substances with environmental persistence, bioaccumulation and biotoxicity. These new pollutants may cause varying degrees of harm to human health and the environment.

[0004] PFAS, per- and polyfluoroalkyl substances, are a class of chemicals used to make coatings and products with heat-resistant, oil-repellent, and stain-resistant properties, such as clothing, adhesives, food packaging, and heat-resistant non-stick cooking utensils. They affect the body's metabolism and immune system and are even carcinogenic. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are still produced and used in many countries, leading to their release into the environment and causing pollution of water sources such as drinking water. The protection and control of new pollutants in water sources such as drinking water and aquaculture water are imminent. The research and development of materials with good adsorption properties for new pollutants in various water sources is of great environmental significance. Summary of the invention

[0005] In view of the incompleteness of the prior art, the present invention provides a composite material for adsorbing PFOA pollutants in water and a preparation method thereof, so as to solve the urgent problem of treating the new pollutant PFOA in water sources such as drinking water and aquaculture water, improve the adsorption amount and selectivity of the adsorbent for PFOA, and provide appropriate application methods for different water bodies.

[0006] In order to solve the existing problems, the technical solution adopted by the present invention is:

[0007] A composite material for adsorbing PFOA pollutants in water, which is composed of a Cu-based MOFs material and an alkaline nanocellulose membrane, and is denoted as NH2-CuBTC@OH / NH2-CMx, wherein the Cu-based MOFs material is denoted as NH2-CuBTC, and the alkaline nanocellulose membrane is denoted as OH / NH2-CM; wherein x refers to the mass ratio of OH / NH2-CM to the entire composite material, and x=0.05-0.2.

[0008] The specific surface area of ​​the composite material is 1500-1537m 2 / g, total pore volume is 0.8-0.88m 3 / g, micropore volume is 0.29-0.33m 3 / g.

[0009] A method for adsorbing a composite material of PFOA pollutants in water comprises the following steps:

[0010] Step 1, using dried asparagus stems as raw materials, chopping them into pieces and processing them with a high-speed wall-breaking machine to obtain asparagus stem powder, weighing the asparagus stem powder and adding it into a container, then adding anhydrous ethanol, ammonia water and sodium hydroxide, and ultrasonically treating until the sodium hydroxide is completely dissolved to obtain a mixed phase A;

[0011] Step 2, transferring the beaker containing the mixed phase A to a water bath, stirring it with magnetic force at a constant temperature, and then transferring it to a ball mill for ball milling to obtain a mixed phase B;

[0012] Step 3, adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand to obtain mixed phase C;

[0013] Step 4, transferring the mixed phase C to a microwave reactor, and then subjecting the mixed phase C to microwave reaction for 10 minutes. After the reaction, a transparent membrane material is obtained, which is washed with anhydrous ethanol and centrifuged for 1-3 times, and dried at 60° C. to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which is recorded as OH / NH2-CM.

[0014] Step 5, Cu(NO3)2·3H2O, trimesic acid, 2-aminoterephthalic acid and OH / NH2-CM are dispersed in a mixture of N,N-dimethylformamide, ethanol and water, stirred and mixed, and then transferred to a reactor, hydrothermally reacted at 85°C for 24 hours, cooled to room temperature, washed with DMF and ethanol and centrifuged 1-3 times respectively, and then vacuum dried at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CMx.

[0015] Furthermore, in step 1, the mass ratio of reed stem powder to sodium hydroxide is 5:6.

[0016] Furthermore, in some embodiments, the concentration of the ammonia water added in step 1 is 25%, the volume is 20 mL, the volume of the anhydrous ethanol added is 160 mL, and the mass of the added sodium hydroxide is 6 g.

[0017] Furthermore, in step 2, the water bath temperature is set to 60° C., and the water bath time is 8 hours; the ball mill speed is set to 1000 r / h, and the ball milling time is 30 min.

[0018] Furthermore, the concentration of the sodium hypochlorite solution added in step 3 is 2 wt %, and the volume ratio of the mixed phase B to the sodium hypochlorite solution is 3:1.

[0019] Furthermore, the power of the microwave reaction in step 4 was 500 W and the temperature was 50°C;

[0020] Furthermore, in step 5, the volume ratio of DMF, ethanol and deionized water in the mixed solution is 1:1:1; the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) is 4:1:1:(0.3-1.2);

[0021] When used, the composite material is coated on floating balls in rivers, aquaculture waters or the sea. The floating balls not only give warnings but also absorb PFOA pollutants in the water. The composite material can also be coated on the surface of water landscape prostheses to control PFOA pollution while decorating water parks and scenic spots. Beneficial Effects

[0022] Compared with the prior art, the composite material of the present invention is composited by hydrothermal reaction of aminated aminated Cu-based MOFs material and alkaline nanocellulose membrane, wherein the Cu-based MOFs material is NH2-CuBTC, which not only has a huge surface area to provide physical adsorption sites, but also has NH2- and Cu 2+ Two chemical adsorption sites; alkaline nanocellulose membrane is prepared by ball milling alkaline hydrolysis and microwave reaction, using hydroxyl and amino co-modified alkaline nanocellulose membrane, and then in the hydrothermal reaction, the groups on the cellulose membrane molecular chain will react with Cu 2+ Cross-linking forms Cu-O bonds, which firmly embed the cellulose membrane into NH2-CuBTC and form a more developed pore structure and high specific surface area. More physical adsorption sites and chemical adsorption sites jointly improve the adsorption performance of the composite material for new environmental pollutants such as PFOA. In addition, coating the composite material on the surface of floating balls or water landscape prostheses provides a feasible application method for the composite material in pollution control in various water bodies and situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1The PFOA adsorption performance of the products prepared in different embodiments and comparative examples;

[0024] Figure 2 The effect of pH value on the PFOA adsorption performance of the product prepared in Example 3;

[0025] Figure 3 SEM morphology of products prepared in different embodiments and comparative examples: (a) NH2-CuBTC, (b) NH2-CuBTC@OH / NH2-CM 0.15 , (c) CuBTC@OH / NH2-CM 0.15 , (d) NH2-CuBTC@OH-CM 0.15 . DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Example 1

[0027] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol, 20 mL of 25% ammonia water and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0028] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0029] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0030] (4) The mixed phase C was transferred to a microwave reactor, and then subjected to microwave reaction at a power of 500 W and 50°C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times, and dried at 60°C to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which was recorded as OH / NH2-CM.

[0031] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:1:1:0.3. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuum at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CM. 0.05 . Example 2

[0032] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol, 20 mL of 25% ammonia water and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0033] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0034] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0035] (4) The mixed phase C was transferred to a microwave reactor, and then subjected to microwave reaction at a power of 500 W and 50°C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times, and dried at 60°C to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which was recorded as OH / NH2-CM.

[0036] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:1:1:0.6. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuo at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CM. 0.10 . Example 3

[0037] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol, 20 mL of 25% ammonia water and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0038] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0039] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0040] (4) The mixed phase C was transferred to a microwave reactor, and then subjected to microwave reaction at a power of 500 W and 50°C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times, and dried at 60°C to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which was recorded as OH / NH2-CM.

[0041] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:1:1:0.9. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuum at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CM. 0.15 . Example 4

[0042] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol, 20 mL of 25% ammonia water and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0043] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0044] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0045] (4) The mixed phase C was transferred to a microwave reactor, and then subjected to microwave reaction at a power of 500 W and 50°C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times, and dried at 60°C to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which was recorded as OH / NH2-CM.

[0046] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:1:1:1. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuum at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CM. 0.20 . Comparative Example 1

[0047] Cu(NO3)2·3H2O, trimesic acid (H3BTC) and 2-aminoterephthalic acid (AAPD) are dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water is 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC) and 2-aminoterephthalic acid (AAPD) is 4:1:1; after stirring and mixing, the mixture is transferred to a reactor, subjected to hydrothermal reaction at 85°C for 24h, cooled to room temperature, washed and centrifuged 3 times with DMF and ethanol respectively, and then vacuum dried at 85°C to obtain NH2-CuBTC. Comparative Example 2

[0048] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol, 20 mL of 25% ammonia water and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0049] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0050] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0051] (4) The mixed phase C was transferred to a microwave reactor, and then subjected to microwave reaction at a power of 500 W and 50°C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times, and dried at 60°C to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which was recorded as OH / NH2-CM.

[0052] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC) and alkaline nanocellulose membrane (OH / NH2-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:2:0.9. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuum at 85°C to obtain a composite material CuBTC@OH / NH2-CM. 0.15 . Comparative Example 3

[0053] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0054] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0055] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0056] (4) The mixed phase C was transferred to a microwave reactor and then subjected to microwave reaction at a power of 500 W and 50 °C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times and dried at 60 °C to obtain a hydroxyl-modified alkaline nanocellulose membrane, which was recorded as OH-CM.

[0057] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water. The volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC), 2-aminoterephthalic acid (AAPD) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:1:1:0.9. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuum at 85°C to obtain the composite material NH2-CuBTC@OH-CM. 0.15 . Comparative Example 4

[0058] (1) Using dried asparagus stems as raw materials, chop them into pieces and process them with a high-speed wall breaking machine for 1 min to obtain asparagus stem powder. Weigh 5 g of asparagus stem powder and add it into a 300 mL beaker. Then add 160 mL of anhydrous ethanol and 6 g of sodium hydroxide. Ultrasonic treatment is performed until the sodium hydroxide is completely dissolved to obtain a mixed phase A.

[0059] (2) The beaker containing the mixed phase A was transferred to a water bath, and magnetically stirred at a constant temperature of 60°C for 8 h. Then, the mixture was transferred to a ball mill and ball milled at a speed of 1000 r / h for 30 min to obtain a mixed phase B.

[0060] (3) adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand for 2 hours to obtain mixed phase C; the mass concentration of the added sodium hypochlorite solution is 2%, and the volume ratio of mixed phase B to sodium hypochlorite solution is 3:1;

[0061] (4) The mixed phase C was transferred to a microwave reactor and then subjected to microwave reaction at a power of 500 W and 50 °C for 10 min. After the reaction, a transparent membrane material was obtained, which was washed with anhydrous ethanol and centrifuged three times and dried at 60 °C to obtain a hydroxyl-modified alkaline nanocellulose membrane, which was recorded as OH-CM.

[0062] (5) Cu(NO3)2·3H2O, trimesic acid (H3BTC) and alkaline nanocellulose membrane (OH-CM) were dispersed in a mixture of N,N-dimethylformamide (DMF), ethanol and water, wherein the volume ratio of DMF, ethanol and deionized water was 1:1:1, and the mass ratio of Cu(NO3)2·3H2O, trimesic acid (H3BTC) and alkaline nanocellulose membrane (OH / NH2-CM) was 4:2:0.9. After stirring and mixing, the mixture was transferred to a reactor and subjected to hydrothermal reaction at 85°C for 24 h. The mixture was cooled to room temperature, washed with DMF and ethanol and centrifuged three times, respectively, and then dried in vacuum at 85°C to obtain the composite material CuBTC@OH-CM. 0.15 .

[0063] Take 0.5g of different composite materials and disperse them in conical flasks, pour in 300mL of 100mg / L PFOA solution, shake and adsorb at 25℃ for 24h, then take samples to test the PFOA concentration. Figure 1 shown.

[0064] The PFOA adsorption capacity of NH2-CuBTC is 117 mg / g, and the PFOA adsorption capacity of NH2-CuBTC@OH / NH2-CM x The PFOA adsorption of the series of samples increased first and then decreased with the increase of OH / NH2-CM content of cellulose membrane. 0.15 The optimal PFOA adsorption capacity is 206 mg / g, so the optimal doping amount of cellulose membrane in the composite material is 15%; NH2-CuBTC@OH / NH2-CM 0.15 Based on the above, NH2-CuBTC was replaced by CuBTC, and OH / NH2-CM 0.15 Replaced by OH-CM 0.15 , and the two are replaced simultaneously to obtain CuBTC@OH / NH2-CM 0.15 、NH2-CuBTC@OH-CM 0.15 and CuBTC@OH-CM 0.15 The PFOA adsorption of the three was 141 mg / g, 183 mg / g and 128 mg / g, respectively, which were higher than 117 mg / g (PFOA adsorption of NH2-CuBTC) and lower than 206 mg / g (PFOA adsorption of NH2-CuBTC@OH / NH2-CM 0.15 PFOA adsorption), it can be seen that NH2-CuBTC and OH / NH2-CM 0.15Both can increase the adsorption of PFOA by the composite material. The former accounts for a higher proportion in the composite material (85%), so it contributes more to improving the adsorption of PFOA. Although the latter accounts for a lower proportion (15%), it also plays an important role in improving the adsorption of PFOA.

[0065] NH2-CuBTC@OH / NH2-CM has the best PFOA adsorption capacity 0.15 Take the pH value as an example to investigate the effect of the sample adsorption performance. The results are as follows Figure 2 As shown in the figure, the PFOA adsorption of the sample decreases with the increase of pH value. In the pH range of 2-5, the PFOA adsorption decreases significantly; in the pH range of 5-8, the decrease trend of PFOA adsorption slows down significantly. When pH=2, the PFOA adsorption of the sample is the largest, which is 264 mg / g, and when pH=8, the PFOA adsorption of the sample is the smallest, which is 185 mg / g.

[0066] The specific surface area, total pore volume and micropore volume of the samples were tested by low-temperature nitrogen physical adsorption. The results are listed in Table 1. The specific surface area of ​​NH2-CuBTC is 1442 m 2 / g, and the total pore volume is 0.71 m 3 / g, and the micropore volume is 0.23 m 3 / g. After doping with 15% OH / NH2-CM, the specific surface area increased to 1537 m 2 / g, and the total pore volume increased to 0.88 m 3 / g, the micropore volume increased to 0.33 m 3 / g; NH2-CuBTC@OH / NH2-CM 0.15 Based on the above, NH2-CuBTC was replaced by CuBTC, and OH / NH2-CM 0.15 Replaced by OH-CM 0.15 , and the two were replaced at the same time, the specific surface area increased to 1506m 2 / g, 1522m 2 / g and 1529m 2 / g, and the total pore volume increased to 0.85 m 3 / g, 0.82 m 3 / g and 0.84 m 3 / g, and the micropore volume increased to 0.32 m 3 / g, 0.29 m 3 / g and 0.31 m 3 / g; Compared with NH2-CuBTC, the specific surface area, total pore volume and micropore volume of other samples are improved. 0.15It has the largest specific surface area, total pore volume and micropore volume, corresponding to the best PFOA adsorption capacity. The developed pore structure and huge specific surface area provide more physical adsorption sites for the composite material to adsorb PFOA. In addition, the amino and hydroxyl groups in the composite material also provide chemical adsorption sites.

[0067] Table 1 Specific surface area, total pore volume and micropore volume of samples obtained in some examples and comparative examples

[0068] Adsorbent <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (m 3 / g)]]> <![CDATA[Micropore volume (m 3 / g)]]> <![CDATA[Cu-BTC-NH2]]> 1442 0.71 0.23 <![CDATA[NH2-CuBTC@OH / NH2-CM 0.15 ]]> 1537 0.88 0.33 <![CDATA[CuBTC@OH / NH2-CM 0.15 ]]> 1506 0.85 0.32 <![CDATA[NH2-CuBTC@OH-CM 0.15 ]]> 1522 0.82 0.29 <![CDATA[CuBTC@OH-CM 0.15 ]]> 1529 0.84 0.31

[0069] The morphology of the samples was observed using a scanning electron microscope. Figure 3 As shown. Figure 3 As shown in (a), the shape of NH2-CuBTC is octahedral, with a relatively smooth surface and some small particles attached to it, with a size of about 15-20 μm. Figure 3 (b), (c) and (d) are NH2-CuBTC@OH / NH2-CM 0.15 、CuBTC@OH / NH2-CM 0.15 and NH2-CuBTC@OH-CM 0.15 Compared with NH2-CuBTC, the three still retain the octahedral shape and the size does not change significantly, but the surface becomes rough, which is the surface morphology change caused by the cellulose membrane embedded in the MOFs material.

Claims

1. A composite material for absorbing PFOA pollutants in water, characterized in that: The composite material is composed of a Cu-based MOFs material and an alkaline nanocellulose membrane, and is denoted as NH2-CuBTC@OH / NH2-CMx, wherein the Cu-based MOFs material is denoted as NH2-CuBTC, and the alkaline nanocellulose membrane is denoted as OH / NH2-CM; wherein x refers to the mass ratio of OH / NH2-CM to the entire composite material, and x=0.05-0.

2. The specific surface area of ​​the composite material is 1500-1537m 2 / g, total pore volume is 0.8-0.88m 3 / g, micropore volume is 0.29-0.33m 3 / g, the composite material is prepared according to the following method steps: Step 1, using dried asparagus stems as raw materials, chopping them into pieces and processing them with a high-speed wall-breaking machine to obtain asparagus stem powder, weighing the asparagus stem powder and adding it into a container, then adding anhydrous ethanol, ammonia water and sodium hydroxide, and ultrasonically treating until the sodium hydroxide is completely dissolved to obtain a mixed phase A; Step 2, transferring the beaker containing the mixed phase A to a water bath, stirring it with magnetic force at a constant temperature, and then transferring it to a ball mill for ball milling to obtain a mixed phase B; Step 3, adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand to obtain mixed phase C; Step 4, transferring the mixed phase C to a microwave reactor, and then subjecting the mixed phase C to microwave reaction for 10 minutes. After the reaction, a transparent membrane material is obtained, which is washed with anhydrous ethanol and centrifuged for 1-3 times, and dried at 60° C. to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which is recorded as OH / NH2-CM. Step 5, Cu(NO3)2·3H2O, trimesic acid, 2-aminoterephthalic acid and OH / NH2-CM are dispersed in a mixture of N,N-dimethylformamide, ethanol and water, stirred and mixed, and then transferred to a reactor, hydrothermally reacted at 85°C for 24 hours, cooled to room temperature, washed with DMF and ethanol and centrifuged 1-3 times respectively, and then vacuum dried at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CMx.

2. A method for preparing the composite material for absorbing PFOA pollutants in water as claimed in claim 1, characterized in that: The following steps are involved: Step 1, using dried asparagus stems as raw materials, chopping them into pieces and processing them with a high-speed wall-breaking machine to obtain asparagus stem powder, weighing the asparagus stem powder and adding it into a container, then adding anhydrous ethanol, ammonia water and sodium hydroxide, and ultrasonically treating until the sodium hydroxide is completely dissolved to obtain a mixed phase A; Step 2, transferring the beaker containing the mixed phase A to a water bath, stirring it with magnetic force at a constant temperature, and then transferring it to a ball mill for ball milling to obtain a mixed phase B; Step 3, adding sodium hypochlorite solution to mixed phase B, stirring and mixing, and letting stand to obtain mixed phase C; Step 4, transferring the mixed phase C to a microwave reactor, and then subjecting the mixed phase C to microwave reaction for 10 minutes. After the reaction, a transparent membrane material is obtained, which is washed with anhydrous ethanol and centrifuged for 1-3 times, and dried at 60° C. to obtain an alkaline nanocellulose membrane co-modified with hydroxyl and amino groups, which is recorded as OH / NH2-CM. Step 5, Cu(NO3)2·3H2O, trimesic acid, 2-aminoterephthalic acid and OH / NH2-CM are dispersed in a mixture of N,N-dimethylformamide, ethanol and water, stirred and mixed, and then transferred to a reactor, hydrothermally reacted at 85°C for 24 hours, cooled to room temperature, washed with DMF and ethanol and centrifuged 1-3 times respectively, and then vacuum dried at 85°C to obtain a composite material NH2-CuBTC@OH / NH2-CMx.

3. The method for preparing a composite material for adsorbing PFOA pollutants in water according to claim 2, characterized in that: In step 1, the mass ratio of reed stem powder to sodium hydroxide is 5:

6.

4. The method for preparing a composite material for adsorbing PFOA pollutants in water according to claim 2, characterized in that: In step 2, the water bath temperature is set to 60° C., and the water bath time is 8 hours; the ball mill speed is set to 1000 r / h, and the ball milling time is 30 min.

5. The method for preparing a composite material for adsorbing PFOA pollutants in water according to claim 2, characterized in that: The concentration of the sodium hypochlorite solution added in step 3 is 2 wt %, and the volume ratio of the mixed phase B to the sodium hypochlorite solution is 3:

1.

6. The method for preparing a composite material for adsorbing PFOA pollutants in water according to claim 2, characterized in that: The power of the microwave reaction in step 4 was 500 W and the temperature was 50°C.

7. The method for preparing a composite material for adsorbing PFOA pollutants in water according to claim 2, characterized in that: In step 5, the volume ratio of DMF, ethanol and water in the mixed solution is 1:1:1; the mass ratio of Cu(NO3)2·3H2O, trimesic acid, 2-aminoterephthalic acid and OH / NH2-CM is 4:1:1:(0.3-1.2).

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