Preparation method and application of macromolecular polysaccharide membrane loaded metal nanoparticle composite material

Abstract

The invention discloses a preparation method of a high-molecular polysaccharide membrane loaded metal nanoparticle composite material, which is characterized by comprising the following steps: adding a periodate solution or a metaperiodate solution into a high-molecular polysaccharide solution, and carrying out sealed reaction to prepare high-molecular polysaccharide sol; placing the high-molecular polysaccharide sol in a mold for molding, cooling, and refrigerating and freezing to obtain high-molecular polysaccharide gel; air-drying the high-molecular polysaccharide gel at 2-10 DEG C by using circulating air to obtain a high-molecular polysaccharide cold-dried material; placing the macromolecular polysaccharide cold dry material in a metal salt solution for oscillation, adding a reducing agent for reduction, and cleaning to prepare a macromolecular polysaccharide membrane loaded metal nanoparticle composite material; the composite material disclosed by the invention is large in loading capacity, has adsorption and reduction capacities on pollutants, and does not generate secondary pollution when being used for water pollution treatment; and the composite material can be recycled, is easy to recover, can be biodegraded, can also be swelled and hydrolyzed, meets the green production requirement in the field of water pollution treatment, and shows remarkable environmental value and economic value.

Description

Technical Field

[0001] The present invention relates to a method for preparing a composite material of a polymer polysaccharide film loaded with metal nanoparticles and the use of the polymer polysaccharide film composite material loaded with metal nanoparticles in removing heavy metals, antibiotics, and dyes in water bodies. Background Art

[0002] Common water-soluble pollutants include dyes, antibiotics, heavy metal ions, etc. Dye wastewater is characterized by large water volume, complex composition, deep color, high toxicity, etc. Antibiotics, such as tetracycline, are widely used in the livestock industry and are difficult to remove after entering the water and soil environment. Cr(VI) is also a typical water-soluble environmental pollutant. Cr(VI) generated in industrial processes is highly toxic and carcinogenic, and will seriously damage the biological system. For such highly toxic water-soluble pollutants, conventional treatment methods such as coagulation, precipitation, biological methods, membrane filtration, etc. are relatively ineffective, and adsorption and photocatalytic degradation are considered to be one of the most effective methods for eliminating water-soluble organic pollutants. Metal nanoparticles and their composite materials represented by nano zero-valent iron can be used as adsorbents to remove pollutants and also as photocatalytic materials to degrade pollutants. However, metal particles such as nano iron are easily oxidized and agglomerated, which makes them unable to play a 100% role in removing pollutants. Even, it may be inhibited due to a large dosage, and at the same time, it causes waste of materials. In addition, it is also a problem that must be solved that it is difficult to recycle after being used to remove pollutants. Otherwise, the materials used to remove pollutants will instead become pollutants and harm the environment. All of the above reasons limit its application to a certain extent.

[0003] Polymer materials have many excellent properties, are suitable for modern production, have significant economic benefits, and are not restricted by region and climate. Therefore, polymer materials have made rapid development. The synthetic polymer industry has greatly promoted the development of modern society. However, environmental pollution problems caused by the difficult biodegradability of synthetic polymer materials have made people more and more interested in the research and development of biodegradable and environmentally friendly renewable resource polymers. As a renewable resource, the modification and utilization of natural polymers can, on the one hand, save a large amount of non-renewable resources, and on the other hand, alleviate the serious environmental pollution caused by a large number of non-degradable synthetic polymer material wastes. Using natural polymer materials to prepare membrane carriers loaded with metal particles such as nano iron can effectively solve the defects of easy agglomeration and difficult recovery. The biodegradability of natural polymer membrane carriers also effectively solves the environmental pollution problem caused by difficult degradation after material recovery, making it more widely used in the removal of pollutants in water bodies. Summary of the Invention

[0004] Aiming at the problems that metal nanoparticles such as nano-iron are prone to agglomeration and difficult to recover, the carrier material has the potential risk of secondary pollution, and the mechanical properties of the polymer polysaccharide film are insufficient, the present invention provides a preparation method of a polymer polysaccharide film loaded with metal nanoparticles composite material, and the use of the polymer polysaccharide film loaded with metal nanoparticles composite material in treating pollutants such as heavy metals, antibiotics, and dyes in water bodies.

[0005] The preparation method of the polymer polysaccharide film loaded with metal nanoparticles composite material of the present invention is as follows: 1. Add a periodate solution or a metaperiodate solution to the polymer polysaccharide solution, seal it, and stir and mix evenly at 25~100 °C to obtain a polymer polysaccharide sol; The polymer polysaccharide is selected from chitosan, starch, cellulose and its derivatives, chitin, lignin, konjac glucomannan, xanthan gum, gelatin, guar gum, locust bean gum; the periodate is selected from potassium periodate, sodium periodate, barium periodate; the metaperiodate is selected from potassium metaperiodate, sodium metaperiodate, and the addition amount of the periodate or metaperiodate is 10%~30% of the mass of the polymer polysaccharide; 2. Place the polymer polysaccharide sol in a mold to form, after cooling, refrigerate at 2~10 °C for 6~12 h, and then freeze at -18~-50 °C for 6~12 h to obtain a polymer polysaccharide gel; 3. The polymer polysaccharide gel is air-dried with circulating air at 2~10 °C to obtain a polymer polysaccharide cold-dried material; 4. Place the polymer polysaccharide cold-dried material in a metal salt solution, oscillate it, then add a reducing agent for reduction, and after reduction, wash the film with ultrapure water to obtain a polymer polysaccharide film loaded with metal nanoparticles composite material; The metal salt is one or more of iron salt, cobalt salt, nickel salt, copper salt, zinc salt, silver salt, aluminum salt, and the concentration of the metal salt solution is 0.1~0.5 mol / L; when there are two metal salts, the molar ratio of the two metals is 1:10~10:1; The reducing agent is an alkali metal borohydride, tea polyphenols, anthocyanins, vitamin C, vitamin E, or an extract of one or more of green tea, yellow tea, dark tea, white tea, oolong tea, black tea, black goji berry, blackberry, black rice, purple sweet potato, purple corn, grape, eggplant, purple cauliflower, purple radish, kale, betel leaf, betel nut, eucalyptus leaf, mulberry leaf, loquat leaf, cherry leaf, grapevine leaf, olive leaf, red-flowered cinnamon leaf, bodhi leaf, longan leaf, ginkgo leaf, pomegranate leaf, loquat leaf, plane tree, cotton rose hibiscus, Korla fragrant pear, rose, thyme, nettle, pomegranate peel, papaya peel, ginseng peel. The extract is obtained by washing the raw materials with deionized water, air-drying at room temperature, placing the air-dried material in boiling water at 80 °C for 1 h, and then vacuum filtering.

[0006] After obtaining the cold-dried polymer polysaccharide material in step 3 above, the method of the present invention can also soak the cold-dried polymer polysaccharide material in ultrapure water for 1-3 hours first, and then soak it in an organic solvent for 1-3 hours. After taking it out and air-drying it, a modified dry film is obtained; the modified dry material is then placed in a metal salt solution and oscillated to load metal particles; The organic solvent is selected from anhydrous methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-hexanol, and benzyl alcohol.

[0007] Another object of the present invention is to apply the composite material of the polymer polysaccharide film loaded with metal nanoparticles prepared by the above method to the removal of pollutants in water bodies, and the pollutants are heavy metals, antibiotics, dyes, etc.

[0008] Compared with the prior art, the advantages of the present invention are as follows: 1. The raw material polymer polysaccharide of the method of the present invention is all green and natural substances, without biological toxicity, and is safe and reliable; 2. The composite material prepared by the method of the present invention has good water resistance and acid and alkali corrosion resistance for a long time, and can withstand strong acid or alkali corrosion with pH≤10; 3. Modification with an organic solvent can improve the mechanical properties of the film. The composite film has good flexibility and toughness, can be stretched, extruded and folded, and at the same time has strong resistance to fracture; 4. By using the method of circulating air drying at 2-10°C, the composite material of the polymer polysaccharide film loaded with metal nanoparticles can be given a unique dendritic structure. Compared with the conventional method, a film with a larger specific surface area can be obtained. Through scanning electron microscopy, it can be found that this dendritic pattern is an orderly arranged skeleton structure, providing more positions for the loading of metal particles; 5. The composite material of the present invention has biodegradability and swelling hydrolysis properties. By controlling the swelling time of the composite film in the solution, the specific surface area can be increased. If the swelling is not controlled all the time, the film can be hydrolyzed after 16 days. After hydrolysis, the metal particles on the film can be recovered to avoid secondary pollution of the waste film; 6. The composite film of the present invention has the ability to adsorb and reduce pollutants, and does not produce secondary pollution after use, and has both environmental and economic benefits in water pollution treatment. Description of the Drawings

[0009] Figure 1 It is the scanning electron microscope image of the film prepared in Example 1, where Figure a is the scanning electron microscope image of the cold-dried film of konjac glucomannan and guar gum blend; Figure b is the scanning electron microscope image of the composite material of ethanol-modified konjac glucomannan and guar gum blend cold-dried film loaded with nano-zero-valent iron; Figure c is the scanning electron microscope image of the air-dried film of konjac glucomannan and guar gum blend; Figure 2Schematic diagram of the water resistance experiment results of konjac glucomannan film; Figure 3 Schematic diagram of the water resistance experiment results of guar gum film; Figure 4 Schematic diagram of the water resistance experiment and hydrolysis experiment results of the blend cold-dried film of konjac glucomannan and guar gum. Specific implementation manners

[0010] The present invention will be further described in detail below through embodiments, but the protection scope of the present invention is not limited to the content described; Example 1: Preparation of a composite material of ethanol-modified konjac glucomannan and guar gum blend cold-dried film loaded with nano-zero valent iron and its removal of hexavalent chromium 1. Mix konjac glucomannan and guar gum powders in a mass ratio of 3:2. Weigh 1.25 g of the mixture and dissolve it in 50 mL of ultrapure water, and stir to disperse it; dissolve 0.250 g of sodium periodate in ultrapure water and add it to the polysaccharide solution. Seal the mixture in a constant temperature magnetic stirrer at 85 °C and stir for 2 h, and finally let it stand for 30 min to eliminate bubbles to obtain a blend sol; 2. Use a 10 mL syringe to inject 3 mL of the blend polysaccharide sol into a 6-well mold. After cooling to room temperature, place it in a refrigerator at 2 °C and refrigerate for 6 h. After taking it out, place it at -18 °C and freeze for 6 h to obtain a blend gel; 3. Place the blend gel on a culture plate and put it in a 2 °C refrigerator. Use a circulating fan to simulate natural wind to air-dry it to obtain a blend cold-dried film of konjac glucomannan and guar gum. The scanning electron micrograph of this film is shown in Figure 1 a. It can be seen from the figure that the blend cold-dried film has an orderly arranged skeleton structure, and there are a large number of spaces in the middle of the skeleton; use a fully automatic specific surface area and porosity analyzer to detect the specific surface area of the cold-dried film. In the dry state, its specific surface area reaches 54.635 m 2 / g; 4. Immerse the blend cold-dried film of konjac glucomannan and guar gum in ultrapure water for 1 h, then immerse it in absolute ethanol for 1 h, take it out and air-dry it to obtain an ethanol-modified blend (KGM-GG) cold-dried film of konjac glucomannan and guar gum. Use an electronic universal testing machine to detect its mechanical properties. Its tensile stress is 28.53 MPa and its elastic modulus is 599.01 MPa.

[0011] 5. Immerse the ethanol-modified blend cold-dried film of konjac glucomannan and guar gum in 25 mL of a 0.4 mol / L ferrous sulfate solution and oscillate for 3 h; dissolve 0.28 g of tea polyphenols in 50 mL of ultrapure water to prepare a tea polyphenol solution. The loaded Fe 2+The ethanol-modified konjac glucomannan and guar gum blend cold-dried film is placed in a tea polyphenol solution for reduction for more than 30 minutes until the ethanol-modified konjac glucomannan and guar gum blend cold-dried film changes from transparent to purple-black, indicating that Fe 2+ is successfully loaded on the film and reduced to nano-zero-valent iron; the ethanol-modified konjac glucomannan and guar gum blend cold-dried film loaded with nano-zero-valent iron is placed in ultrapure water to wash the residual tea polyphenol solution, and the ethanol-modified konjac glucomannan and guar gum blend cold-dried film loaded with nano-zero-valent iron is prepared; its SEM image is shown in Figure 1 Figure b. It can be seen from the figure that the interior of the composite material presents a three-dimensional network structure, and at the same time, a large number of spherical particles appear on the skeleton of the three-dimensional network, indicating that nano-zero-valent iron has been successfully loaded onto the ethanol-modified konjac glucomannan and guar gum blend cold-dried film, and is evenly distributed without large-area agglomeration. The dendritic skeleton structure formed on the surface of the ethanol-modified konjac glucomannan and guar gum blend cold-dried film provides more loading sites for nano-zero-valent iron, and at the same time provides more contact reaction space between nano-zero-valent iron and pollutants; 6. Place 0.09 g of the composite material prepared in step 4 into 50 mL of a 30 mg / L potassium dichromate solution and oscillate for reaction for 60 minutes. Take 1 mL of the solution and place it in a 50 mL colorimetric tube, dilute it with water to the calibration line, and use a UV-visible spectrophotometer to measure the remaining hexavalent chromium concentration in the solution by the diphenylcarbazide spectrophotometric method. Calculate the hexavalent chromium removal efficiency of the ethanol-modified konjac glucomannan and guar gum blend cold-dried film loaded with nano-zero-valent iron to be 99.34%; Comparative Example 1: The ethanol-modified konjac glucomannan and guar gum blend cold-dried film prepared in steps 1-4 of Example 1 is used as a control; place 0.09 g of the blend cold-dried film into 50 mL of a 30 mg / L potassium dichromate solution and oscillate for reaction for 60 minutes. Take 1 mL of the solution and place it in a 50 mL colorimetric tube, dilute it with water to the calibration line, and use a UV-visible spectrophotometer to measure the remaining hexavalent chromium concentration in the solution by the diphenylcarbazide spectrophotometric method. Calculate the hexavalent chromium removal efficiency of the ethanol-modified konjac glucomannan and guar gum blend cold-dried film to be 11.67%.

[0012] Comparative Example 2: Weigh 1.25 g of konjac glucomannan and guar gum powder respectively and dissolve them in 50 mL of ultrapure water. After stirring to disperse them evenly, pour the solution into a molding mold and dry it in an oven at 25 °C to prepare konjac glucomannan (KGM) film or guar gum (GG) film. The mechanical properties of the two were detected using an electronic universal testing machine. The tensile stress of the KGM film is 1.40 MPa, and the elastic modulus is 6.25 MPa; the tensile stress of the GG film is 1.01 MPa, and the elastic modulus is 6.61 MPa; Comparative Example 3: The preparation process was the same as that of Example 1, except that in Step 3, the co-gel was naturally air-dried at room temperature (25 °C) for 48 h to obtain a konjac glucomannan and guar gum blend air-dried film (see the scanning electron microscopy results in Figure 1 c). The specific surface area of the film was measured using a fully automatic specific surface area and porosity analyzer. In the dry state, its specific surface area was 29.873 m 2 / g. The remaining steps were the same as those in Example 1. The removal efficiency of hexavalent chromium by the ethanol-modified konjac glucomannan and guar gum blend air-dried film loaded with nano-zero-valent iron prepared in this comparative example was 71.24%.

[0013] Example 2: Preparation of a Composite Material of Konjac Glucomannan and Guar Gum Blend Cold-Dried Film Loaded with Nano-Zero-Valent Iron and Its Removal of Hexavalent Chromium 1. Mix konjac glucomannan and guar gum powders in a mass ratio of 1:1. Weigh 1.5 g of the mixture and dissolve it in 50 mL of ultrapure water, and stir to disperse it. Dissolve 0.33 g of potassium periodate in ultrapure water and add it to the polysaccharide solution. Seal the mixture in a 90 °C constant temperature water bath magnetic stirrer and stir for 3 h. Finally, let it stand for 30 min to remove bubbles to obtain a co-blended sol. 2. Use a 10 mL syringe to inject 3 mL of the co-blended polysaccharide sol into a 6-well mold. After cooling to room temperature, place it in a refrigerator at 4 °C for 8 h. Take it out and then freeze it at -25 °C for 8 h to obtain a co-gel. 3. Place the co-gel on a culture plate and put it in a 6 °C refrigerator. Use a circulating fan to simulate natural air drying to obtain a konjac glucomannan and guar gum blend (KGM-GG) cold-dried film. The mechanical properties of the KGM-GG film were tested using an electronic universal testing machine. The tensile stress of the KGM-GG film was 17.72 MPa, and the elastic modulus was 256.80 MPa. 4. Place the konjac glucomannan and guar gum blend cold-dried film in 25 mL of a 0.3 mol / L iron chloride solution and shake for 3 h. Place the konjac glucomannan and guar gum blend cold-dried film loaded with Fe 3+ in a vitamin E solution (prepared by dissolving 0.2 g of vitamin E in 50 mL of ultrapure water) and reduce it for more than 30 min until the konjac glucomannan and guar gum blend cold-dried film changes from transparent to purple-black. After washing with ultrapure water, a composite material of konjac glucomannan and guar gum blend cold-dried film loaded with nano-zero-valent iron was prepared. 5. Refer to the method in Example 1 to detect the removal efficiency of hexavalent chromium by the composite material prepared in this example. The removal efficiency was 95.62% in 60 min. Comparative Example 4: The preparation process was the same as that of Example 2, except that in step 3, the co-gel was naturally air-dried at room temperature (25 °C) for 48 h to obtain a konjac glucomannan and guar gum blend air-dried film, and the remaining steps were the same as those of Example 2; the removal efficiency of hexavalent chromium by the konjac glucomannan and guar gum blend air-dried film loaded with nano-zero-valent iron prepared in this comparative example was 68.55%; 6. The konjac glucomannan and guar gum blend freeze-dried film loaded with nano-zero-valent iron composite material prepared in step 4 was respectively placed in 50 mL of 30 mg / L potassium dichromate solution with pH values of 0.5, 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, and oscillated for 60 min. After 60 min, the composite film in the potassium dichromate solution with pH 12.0 was broken and disintegrated, and the composite films after reaction under other pH conditions were intact and unbroken. Referring to the method of Example 1, the removal efficiencies of the composite materials for hexavalent chromium were 99.34%, 99.34%, 36.6%, 24.8%, 12.2%, 10.8%, and 8.9% respectively.

[0014] 7. The konjac glucomannan film, guar gum film of Comparative Example 2, and the konjac glucomannan and guar gum blend freeze-dried film prepared in step 3 of this example were respectively placed in a beaker containing 100 mL of tap water. The beaker was placed in an oscillator and oscillated for 3 h and then taken out and left to stand. Observe the morphology and dissolution state of the film in water at regular intervals; Figure 2 、 3 It can be seen that the konjac glucomannan film and the guar gum film were broken and dissolved after oscillating for 3 h, and continued to dissolve within the 3 h of standing, causing the size of the film to continuously decrease; Figure 4 It can be seen that the konjac glucomannan and guar gum blend freeze-dried film remained intact after oscillating for 3 h and still maintained the integrity of the film itself within 7 days of standing, indicating that the konjac glucomannan and guar gum blend freeze-dried film prepared by the present invention has good mechanical properties and water resistance; within 7 days, the konjac glucomannan and guar gum blend freeze-dried film continuously swelled, and the thickness and size continued to increase, and it was broken and disintegrated on the 9th day and dissolved into one body with water on the 16th day.

[0015] Example 3: Preparation of gelatin and guar gum blend freeze-dried film loaded with nano-zero-valent iron / nickel composite material and removal of hexavalent chromium 1. Gelatin and guar gum powders were mixed in a mass ratio of 5:1, and 6 g of the mixture was dissolved in 50 mL of ultrapure water and stirred to disperse it; ultrapure water was taken to dissolve 0.9 g of potassium periodate and added to the polysaccharide solution. The mixture was sealed in an 80 °C constant temperature water bath magnetic stirrer and stirred for 3 h, and finally left to stand for 30 min to remove bubbles, obtaining a co-blended sol; 2. Use a 10 mL syringe to inject 2 mL of the blended polysaccharide sol into a 6-well mold. After cooling to room temperature, place it in a refrigerator at 6 °C for 10 h. After taking it out, place it in a freezer at -30 °C for 7 h to obtain the co-gel. 3. Place the polysaccharide gel on a culture plate and put it in a refrigerator at 7 °C. Use a circulating fan to simulate natural wind for air drying to obtain the blend cold-dried film of gelatin and guar gum. 4. Add ferrous sulfate and nickel sulfate to 100 mL of ultrapure water. The molar ratio of ferrous sulfate to nickel sulfate is 8:1 to prepare a bimetallic solution. Place the blend cold-dried film of gelatin and guar gum in the bimetallic solution and shake for 5 h, then put it into the green tea extract for reduction for more than 80 min. After washing with ultrapure water, obtain the blend cold-dried film of gelatin and guar gum loaded with nano-zero-valent iron / nickel composite material. Among them, thoroughly wash the green tea leaves with deionized water, place them at room temperature for four days, then crush 15 g of green tea leaves and add 200 mL of ultrapure water, stir and extract at 80 °C for 3 h, and then vacuum filter. The liquid is the green tea extract. 5. Refer to the method of Example 1 to detect the removal efficiency of hexavalent chromium by the composite material prepared in this example. The removal efficiency is 93.4% in 60 min.

[0016] Example 4: Preparation of the blend cold-dried film of konjac glucomannan and guar gum loaded with nano-zero-valent iron composite material and its removal of methyl blue 1. Mix konjac glucomannan and guar gum powders in a mass ratio of 7:3. Weigh 1.4 g of the mixture and dissolve it in 50 mL of ultrapure water, and stir to disperse it. Dissolve 0.35 g of sodium periodate in ultrapure water and add it to the polysaccharide solution. Seal the mixture in a 90 °C constant temperature water bath magnetic stirrer and stir for 2.5 h. Finally, let it stand for 30 min to eliminate bubbles to obtain the blended sol. 2. Use a 10 mL syringe to inject 3 mL of the blended sol into a 6-well mold. After cooling to room temperature, place it in a refrigerator at 10 °C for 12 h. After taking it out, place it in a freezer at -20 °C for 12 h to obtain the co-gel. 3. Place the co-gel on a culture plate and put it in a refrigerator at 10 °C. Use a circulating fan to simulate natural wind for air drying to obtain the blend cold-dried film of konjac glucomannan and guar gum. 4. Place the blend cold-dried film of konjac glucomannan and guar gum in 25 mL of a 0.4 mol / L ferrous sulfate solution and shake for 6 h. Place the blend cold-dried film of konjac glucomannan and guar gum loaded with Fe 2+ in the black tea extract (prepared in the same way as in Example 3) for reduction for more than 60 min. After washing with ultrapure water, obtain the blend cold-dried film of konjac glucomannan and guar gum loaded with nano-zero-valent iron composite material. 5. After placing 0.09 g of the composite material in 50 mL of a 30 mg / L methylene blue solution and ultrasonically treating it for 30 min, the remaining methylene blue concentration in the solution was measured using an ultraviolet-visible spectrophotometer, and the removal efficiency of the composite material for methylene blue was calculated to be 97.81%. Comparative Example 5: The preparation process was the same as that of Example 4, except that in Step 3, the co-coagulated gel was naturally air-dried at room temperature (25°C) for 48 h to obtain a konjac glucomannan and guar gum blend air-dried film, and the remaining steps were the same as those of Example 4; the removal efficiency of the konjac glucomannan and guar gum blend air-dried film loaded with nano-zero-valent iron prepared in this comparative example for methylene blue was 80.56%.

[0017] Example 5: Preparation of a chitosan freeze-dried film loaded with nano-zero-valent iron composite material and its removal of tetracycline 1. Weigh 1.5 g of chitosan and dissolve it in 50 mL of ultrapure water, and stir to disperse it; dissolve 0.39 g of potassium periodate in ultrapure water and add it to the polysaccharide solution, seal the mixture in a 25°C constant temperature water bath magnetic stirrer and stir for 2 h, and finally let it stand for 30 min to eliminate bubbles to obtain a chitosan sol. 2. Use a 10 mL syringe to inject 2.5 mL of the chitosan sol into a 6-well mold, place it in a refrigerator at 9°C for 6.5 h, take it out and then place it in a freezer at -20°C for 8 h to obtain a chitosan gel. 3. Place the chitosan gel on a culture plate and put it in a 9°C refrigerator, and use a circulating fan to simulate natural wind to air-dry it to obtain a chitosan freeze-dried film. 4. Place the chitosan freeze-dried film in 25 mL of a 0.2 mol / L ferrous sulfate solution and oscillate for 6 h; place the chitosan freeze-dried film loaded with Fe 2+ in black tea extract for reduction for more than 60 min, wash it with ultrapure water, and obtain a chitosan freeze-dried film loaded with nano-zero-valent iron composite material. 5. After placing 0.10 g of the composite material in 50 mL of a 30 mg / L tetracycline solution and oscillating for 60 min, the remaining tetracycline concentration in the solution was measured using an ultraviolet-visible spectrophotometer, and the removal efficiency of the composite material for tetracycline was calculated to be 96.11%.

[0018] Example 6: Preparation of a cellulose freeze-dried film loaded with nano-zero-valent iron / silver composite material and its photocatalytic degradation of methyl orange 1. Weigh 5 g of cellulose and dissolve it in 35 mL of an aqueous solution containing 80% by mass of N-methylmorpholine-N-oxide (NMMO), and stir to disperse it; dissolve 0.5 g of metaperiodate in ultrapure water and add it to the polysaccharide solution, seal the mixture in an 80°C constant temperature water bath magnetic stirrer and stir for 1.5 h, and finally let it stand for 30 min to eliminate bubbles to obtain a cellulose sol. 2. Use a 10 mL syringe to inject 3.5 mL of cellulose sol into a 6-well mold. After cooling to room temperature, place it in a refrigerator at 5 °C and refrigerate for 4.5 h. After taking it out, place it at -20 °C and freeze for 6 h to obtain a cellulose gel. 3. Place the chitosan gel on a culture plate and put it in a refrigerator at 5 °C. Use a circulating fan to imitate natural wind to air-dry it to obtain a cellulose cold-dried film. 4. Add ferrous sulfate and silver nitrate to 100 mL of ultrapure water. The molar ratio of ferrous sulfate to silver nitrate is 5:1 to prepare a bimetallic solution. Place the cellulose cold-dried film in the bimetallic solution and oscillate for 4 h, then put it into a sodium borohydride solution for reduction for more than 30 min. After washing with ultrapure water, a cellulose cold-dried film loaded with nano-zero-valent iron / silver composite material is prepared. 5. Place 0.22 g of the composite material in 50 mL of a 20 m / L methyl orange solution and oscillate for 60 min. Then use a UV-visible spectrophotometer to measure the remaining methyl orange concentration in the solution, and calculate that the removal efficiency of the composite material for tetracycline is 98.38%.

[0019] Example 7: Preparation of a chitin cold-dried film loaded with nano-zero-valent iron composite material and its removal of metronidazole 1. Weigh 1 g of chitin and disperse it in 50 g of an aqueous solution containing 11.4% NaOH and 4% urea by mass. Stir evenly, then freeze at 50 °C for 3 h, and then thaw at 5 °C. Repeat the freezing / thawing process 3 times to obtain a chitin solution. Dissolve 0.21 g of sodium periodate in ultrapure water and add it to the chitin solution. Seal the mixture in a 25 °C constant temperature water bath magnetic stirrer and stir for 1 h to prepare a chitosan sol. 2. Use a 10 mL syringe to inject 4 mL of chitosan sol into a 6-well mold. After cooling to room temperature, place it in a refrigerator at 5 °C and refrigerate for 3 h. After taking it out, place it at -20 °C and freeze for 12 h to obtain a chitin gel. 3. Place the chitin gel on a culture plate and put it in a refrigerator at 5 °C. Use a circulating fan to imitate natural wind to air-dry it to obtain a chitin cold-dried film. 4. Place the chitin cold-dried film in 25 mL of a 0.35 mol / L ferrous sulfate solution and oscillate for 5 h; place the chitin cold-dried film loaded with Fe 2+ in potassium borohydride for reduction for more than 30 min. After washing with ultrapure water, a chitin cold-dried film loaded with nano-zero-valent iron composite material is prepared. 5. Place 0.08 g of the composite material in 50 mL of a 10 mg / L metronidazole solution and oscillate for 60 min. Then use a UV-visible spectrophotometer to measure the remaining metronidazole concentration in the solution, and calculate that the removal efficiency of the composite material for tetracycline is 97.86%.

Claims

1. A method for preparing a composite material of a polymer polysaccharide film loaded with metal nanoparticles, characterized in that: Adding a periodate solution or a metaperiodate solution to a polymer polysaccharide solution, sealing the solution, and stirring and mixing the solution at 25-100°C to obtain a polymer polysaccharide sol; placing the polymer polysaccharide sol in a mold to form the solution, cooling the solution, refrigerating the solution at 2-10°C for 6-12 hours, and then freezing the solution at -18--50°C for 6-12 hours to obtain a polymer polysaccharide gel; air-drying the polymer polysaccharide gel at 2-10°C with circulating air to obtain a polymer polysaccharide cold-dried material; placing the polymer polysaccharide cold-dried material in a metal salt solution for oscillation, adding a reducing agent for reduction, and washing the reduced film with ultrapure water to obtain a polymer polysaccharide film-loaded metal nanoparticle composite material.

2. The method for preparing a composite material of polymer polysaccharide film loaded with metal nanoparticles according to claim 1, characterized in that: The polymer polysaccharide freeze-dried material is first soaked in ultrapure water for 1 to 3 hours, then soaked in an organic solvent for 1 to 3 hours, taken out and air-dried, and then the dried film is placed in a metal salt solution to oscillate and load metal nanoparticles.

3. The method for preparing the polymer polysaccharide film-loaded metal nanoparticle composite material according to claim 1, characterized in that: The high molecular weight polysaccharide is selected from chitosan, starch, cellulose and its derivatives, chitin, lignin, konjac glucomannan, xanthan gum, gelatin, guar gum and locust bean gum.

4. The method for preparing a composite material of polymer polysaccharide film loaded with metal nanoparticles according to claim 1, characterized in that: The periodate is selected from potassium periodate, sodium periodate, and barium periodate; the metaperiodate is selected from potassium metaperiodate and sodium metaperiodate, and the addition amount of the periodate or metaperiodate is 10% to 30% of the mass of the high molecular weight polysaccharide.

5. The method for preparing a composite material of polymer polysaccharide film loaded with metal nanoparticles according to claim 2, characterized in that: The organic solvent is selected from anhydrous methanol, anhydrous ethanol, anhydrous ethylene glycol, anhydrous propanol, anhydrous isopropanol, anhydrous glycerol, anhydrous n-butanol, anhydrous isobutanol, anhydrous sec-butanol, anhydrous tert-butanol, anhydrous n-hexyl alcohol, and anhydrous benzyl alcohol.

6. The method for preparing a composite material of polymer polysaccharide film loaded with metal nanoparticles according to claim 1, characterized in that: The metal salt is one or more of iron salt, cobalt salt, nickel salt, copper salt, zinc salt, silver salt and aluminum salt, and the concentration of the metal salt solution is 0.1-0.5 mol / L; when there are two metal salts, the molar ratio of the two metals is 1:10-10:

1.

7. The method for preparing a composite material of polymer polysaccharide film loaded with metal nanoparticles according to claim 1, characterized in that: The reducing agent is an alkali metal borohydride, tea polyphenols, anthocyanins, vitamin C, vitamin E or an extract of one or more of green tea, yellow tea, black tea, white tea, oolong tea, black tea, black wolfberry, blackberry, black rice, purple sweet potato, purple corn, grape, eggplant, purple cauliflower, purple radish, kale, betel nut leaves, betel nut nuts, eucalyptus leaves, mulberry leaves, loquat leaves, cherry leaves, grapevine leaves, olive leaves, red-backed laurel leaves, bodhi leaves, longan leaves, ginkgo leaves, pomegranate leaves, loquat leaves, sycamore, hibiscus, Korla pear, rose, thyme, nettle, pomegranate peel, papaya peel, and human fruit peel.

8. Use of the composite material of polymer polysaccharide membrane-supported metal nanoparticles prepared by the method for preparing the composite material of polymer polysaccharide membrane-supported metal nanoparticles according to any one of claims 1 to 7 in removing water pollutants.

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