Loose nanofiltration membrane with slow-release sterilization function and preparation method thereof

Abstract

The invention discloses a loose nanofiltration membrane with a slow-release sterilization function and a preparation method of the loose nanofiltration membrane. The nanofiltration membrane can realize slow release and long-acting antibiosis of silver ions. The preparation method of the membrane comprises the following steps: synthesizing UiO-66-NH2 nano particles by a hydrothermal method, mixing the UiO-66-NH2 nano particles with an AgNO3 solution, and reducing by using NaBH4 to prepare Ag-coated UiO-66-NH2 nano particles; the preparation method comprises the following steps: blending Ag-coated UiO-66-NH2 and polybenzimidazole, preparing a PBI-based mixed matrix membrane by using a non-solvent induced phase inversion method, and then crosslinking the PBI-based mixed matrix membrane by using trimesoyl chloride to obtain the biological pollution resistant loose nanofiltration membrane. Test results show that the loose nanofiltration membrane prepared by the method has excellent dye desalination performance and antibacterial performance. The salt retention rate is less than 1% while the crystal violet dye retention rate is kept to be 99% or above. An antibacterial experiment shows that after the membrane is co-cultured for 36 hours, the antibacterial rates of the membrane on escherichia coli and staphylococcus aureus respectively reach 97.4% and 96.3%. Slow-release experiments show that the prepared loose nanofiltration membrane can stably maintain the release amount at 0.1 [mu] g.L <-1 >. Day <-1 >, and can realize long-term effective sterilization.

Description

Technical Field

[0001] The invention relates to the field of printing and dyeing wastewater treatment and membrane separation technology, and in particular to a loose nanofiltration membrane with slow-release bactericidal effect and a preparation method thereof, and studies the application of the loose nanofiltration membrane in dye desalination and anti-biological pollution. Background Art

[0002] Dyes are widely used in colored products in many industries. Taking the textile industry as an example, the printing and dyeing wastewater it produces has become a pollution problem of national concern. In order to better solve this serious problem, developing more efficient, energy-saving and environmentally friendly technologies to treat textile industrial wastewater, and effectively recovering and recycling high value-added materials (i.e. dyes and salts) from wastewater are the top priorities for promoting industry progress. Traditional nanofiltration membranes are difficult to effectively separate dyes and salts. In contrast, loose nanofiltration membranes can effectively intercept dye molecules and permeate inorganic salts. At the same time, they have the advantages of low operating energy consumption and high dye removal rate. They can achieve green separation at the molecular level and have great potential in treating printing and dyeing wastewater. However, there are some problems with loose nanofiltration membranes in the actual operation process. The more typical ones are the membrane's permeability selectivity and biological contamination problems. These problems restrict the further development and application of loose nanofiltration membranes. The traditional solution to the anti-pollution problem is to introduce bactericides into the membrane, but because the bactericides have a short durability in the test environment, it is difficult to achieve long-term and stable antibacterial purposes. Therefore, the immobilization of silver through the intermediate medium can not only achieve the enrichment of silver, but also achieve the slow release of silver nanoparticles and achieve effective anti-biological pollution performance.

[0003] UiO-66-NH2 is a new type of porous metal skeleton material with the advantages of large specific surface area and high adsorption capacity. It can overcome the difficulty of enrichment of Ag NPs and is often used to deliver therapeutic agents and release metal ions. At present, many studies have been devoted to the preparation of inorganic-organic hybrid nanofiltration membranes by blending MOF with organic polymer materials. This nanofiltration membrane is a promising material for dye desalination and concentration process, and provides a design idea for the preparation of loose nanofiltration membranes without selective macropore defects. The emergence of MOF / polymer mixed matrix membranes provides a simple and economical universal material field for the development of membrane technology. The application of MOF as a nanofiller in the field of selective separation of substances has significant advantages. The mixed matrix membrane maintains a relatively stable separation performance while obtaining higher permeability. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention first provides a MOF material and then provides a polybenzimidazole (PBI) material. After the two materials are blended, a MOF@PBI loose nanofiltration membrane is prepared by a non-solvent phase inversion method, wherein the MOF material is Ag@UiO-66-NH2, which can realize the loose nanofiltration membrane for Ag + The slow release effect improves the membrane's anti-biological fouling performance.

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a loose nanofiltration membrane with a slow-release bactericidal function.

[0006] The second object of the present invention is to provide a method for preparing a loose nanofiltration membrane with a slow-release bactericidal function.

[0007] The technical solution of the above-mentioned loose nanofiltration membrane with slow-release bactericidal function is summarized as follows:

[0008] A method for preparing a loose nanofiltration membrane with a slow-release bactericidal function comprises the following steps:

[0009] (1) UiO-66-NH2 was synthesized by a hydrothermal method, mixed with 1 mol / L silver nitrate solution, and reduced with 0.5 mol / L sodium borohydride solution to prepare Ag@UiO-66-NH2 nanoparticles;

[0010] (2) Mixing the Ag@UiO-66-NH2 nanoparticles prepared in step (1) with a solvent, ultrasonically dispersing, and then vigorously mechanically stirring

[0011] (3) The nanoparticles and solvent dispersed system in step (2) and the 0.1 wt % MOF nanoparticles in step (1) are mixed and stirred vigorously to prepare a membrane by a non-solvent induced phase inversion method.

[0012] (4) The mixed matrix membrane obtained in step (3) is cross-linked and fixed with 0.1 mol / L trimesoyl chloride to prepare a loose nanofiltration membrane with sustained-release bactericidal function.

[0013] In a preferred embodiment of the present invention, the solvents used in the non-solvent induced phase inversion method are all deionized water.

[0014] In a preferred embodiment of the present invention, the solvent for MOF and polybenzimidazole is N-methylpyrrolidone.

[0015] The loose nanofiltration membrane with slow-release bactericidal function prepared by the above method.

[0016] The advantages of the present invention are: a MOF@PBI loose nanofiltration membrane with excellent dye / salt permeation selectivity is prepared by simple blending. At the same time, the present invention realizes the immobilization and controllable release of nanosilver by the loose nanofiltration membrane, so that the membrane has good bactericidal properties, thereby obtaining a loose nanofiltration membrane with excellent anti-biological contamination performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The Ag in the loose nanofiltration membrane with slow-release bactericidal function prepared in Example 4 + release rate. DETAILED DESCRIPTION

[0018] The present invention is further described below by specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1

[0020] Preparation of MOF

[0025] (1) Weigh 0.19 g of 2-aminoterephthalic acid and 0.24 g of zirconium tetrachloride into a reactor, add 60 mL of N,N-dimethylformamide and mix well, then add 3.6 mL of acetic acid, and place the reactor in a 120°C drying oven for 24 h. After the mixture is taken out and cooled to room temperature, it is washed three times with N,N-dimethylformamide and methanol respectively, and the precipitate is collected by centrifugation and dried in a 65°C drying oven for 24 h to obtain UiO-66-NH2 nanoparticles.

[0026] (2) Weigh 100 mg of UiO-66-NH2 in a beaker, add 30 mL of deionized water and 1.7 mL of 1 g / mL silver nitrate solution, stir for 3 h, then add 1 mL of 0.5 mol / L sodium borohydride solution to reduce silver ions, stir magnetically for 1 h at room temperature, and collect the precipitate by centrifugation. Wash the precipitate with deionized water and methanol three times respectively, collect the MOF particle precipitate by centrifugation, and dry it in a drying oven at 80 ° C for 24 h.

[0023] Example 2

[0024] MOF is evenly dispersed in solvent

[0025] (1) Weigh 0.015 g of Ag@UiO-66-NH2 into a three-necked flask, add 12.75 g of N-methylpyrrolidone and disperse evenly by ultrasonication, then stir vigorously for 12 h in a mechanical stirrer to obtain a system in which MOF nanoparticles and solvent are evenly dispersed.

[0026] Example 3

[0027] A loose nanofiltration membrane with slow-release bactericidal function and preparation method thereof

[0028] (1) 2.25 g of polybenzimidazole powder was slowly added to the homogeneous system obtained in Example 2 in three steps, and the mixture was mechanically stirred at 80° C. for 24 h and allowed to stand overnight for degassing to obtain a 0.1 wt % MOF@PBI casting solution.

[0029] (2) The casting solution was scraped onto a clean polyester non-woven fabric supported by a glass plate using a 250 μm scraper, and then quickly placed in pure water for phase transformation into a membrane. The membrane was taken out 12 hours after the phase transformation and stored in deionized water to obtain a 0.1 wt% MOF@PBI loose nanofiltration membrane.

[0030] Example 4

[0031] Crosslinking of MOF and PBI

[0032] The loose nanofiltration membrane obtained in Example 3 was placed in acetonitrile to displace the water in the membrane pores, and then transferred to a 0.1 mol / L acetonitrile solution of trimesoyl chloride for cross-linking for 6 hours to complete the cross-linking.

[0033] Comparative Example 1

[0034] Preparation of polybenzimidazole loose nanofiltration membrane

[0035] (1) Weigh 12.75 g of N-methylpyrrolidone into a single-necked flask, then add 2.25 g of polybenzimidazole powder, and mechanically stir at 80° C. for 24 h to obtain a polybenzimidazole casting solution.

[0036] (2) Using a 250 μm scraper, the casting solution was scraped onto a clean polyester non-woven fabric supported by a glass plate, and then quickly placed in water for phase conversion into a membrane. After 12 hours, the membrane was taken out and stored in deionized water to obtain a polybenzimidazole loose nanofiltration membrane.

[0037] Comparative Example 2

[0038] Preparation of UIO-66-NH2@PBI loose nanofiltration membrane

[0039] (1) Weigh 0.015 g of UiO-66-NH2 into a three-necked flask, add 12.75 g of N-methylpyrrolidone and disperse evenly by ultrasonication, then stir vigorously for 12 h in a mechanical stirrer to obtain a system in which MOF nanoparticles and solvent are evenly dispersed.

[0040] (2) 2.25 g of polybenzimidazole powder was slowly added to the homogeneous system obtained in (1) of Comparative Example 2 in three steps, mechanically stirred at 80° C. for 24 h, and allowed to stand overnight for degassing to obtain a 0.1 wt % UIO-66-NH2@PBI casting solution.

[0041] (3) The casting solution was scraped onto a clean polyester non-woven fabric supported by a glass plate using a 250 μm scraper, and then quickly placed in pure water for phase transformation into a membrane. The membrane was taken out 12 hours after the phase transformation and stored in deionized water to obtain a 0.1 wt% UIO-66-NH2@PBI loose nanofiltration membrane.

[0042] The loose nanofiltration membrane obtained in Example 3 was placed in acetonitrile to displace the water in the membrane pores, and then transferred to a 0.1 mol / L acetonitrile solution of trimesoyl chloride for cross-linking for 6 hours to complete the cross-linking.

[0043] Membrane performance test

[0044] 1. Penetration selection performance test

[0045] Flux and retention are two important parameters for evaluating the permeability selectivity of loose nanofiltration membranes. The separation performance of loose nanofiltration membranes was evaluated using a laboratory-made nanofiltration cross-flow filtration test device.

[0046] The performance test conditions of the loose nanofiltration membrane with slow-release bactericidal function of the present invention are as follows: the test area is 7 cm 2 The concentration of crystal violet dye feed solution was 1000ppm, the concentration of sodium chloride and sodium sulfate feed solution was 1000ppm, the operating pressure was 0.1MPa, the pressure was stabilized for 30min before the test, the test temperature was 25℃, and the flux and retention rate of the loose nanofiltration membrane were tested.

[0047] Flux (J) refers to the volume of permeate passing through a unit membrane area per unit time, and the calculation formula is: J = V / (A×t);

[0048] Where J is the permeation flux of the loose nanofiltration membrane (L m -2 h -1 ), A is the effective membrane area tested in the nanofiltration test device (m 2 ), V is the volume of permeate passing through the loose nanofiltration membrane during the test time (L), and t is the test time (h).

[0049] Retention rate (R) refers to the ability of loose nanofiltration membrane to separate a certain component in the feed liquid. The calculation formula is R = (C f -C p ) / C f ×100%.

[0050] Where, R is the retention rate of the test component in the solution (%), C f is the absorbance or conductivity of the feed solution, C p is the absorbance or conductivity of the permeate.

[0051] 2. Anti-biological contamination performance test

[0052] The anti-biological contamination performance of a loose nanofiltration membrane with slow-release bactericidal function prepared in each embodiment and control example was tested by co-culture oscillation method, plate counting method and silver ion release experiment. Each sample was cut into pieces, 0.3 g was taken and placed in a 100 mL conical flask, 2 mL of bacterial solution and 28 mL of PBS buffer (pH = 7.4-7.6) were added respectively, and the conical flask was placed in a constant temperature shaking shaker, and oscillated at 120 r / min at 37 ° C for 24 hours. Take 300 μL of the cultured bacterial solution, dilute it with sterile deionized water for 10-10 minutes, and then add 100 μL of the cultured bacterial solution to the flask. 7 times and dilute 10-10 7 Take 100 μL of each of the 200 μL bacterial suspensions, spread them evenly on the solid culture medium with a spreader, and culture them in a constant temperature incubator at 37°C for 24-36 hours. After the culture is completed, record the number of colonies and calculate the inhibition rate.

[0053] The calculation formula of antibacterial rate is: N = Z × R; K = (1-N m / N0)×100%

[0054] Where R is the dilution factor; N (CFU / mL) is the concentration of bacteria in each conical flask; Z (CFU / mL) is the average number of colonies in the solid culture medium corresponding to each film sample, and K (%) is the inhibition rate; N m (CFU / mL) is the bacterial concentration corresponding to the membrane sample; N0 (CFU / mL) is the bacterial concentration in the blank control group.

[0055] in conclusion

[0056] (1) After testing, Table 1 lists the selective permeability performance data of a loose nanofiltration membrane with slow-release bactericidal function prepared in Example 4. From the results, it can be seen that Example 4 has excellent dye desalination performance. While maintaining a 100% crystal violet dye interception rate, the salt permeability reaches more than 99%.

[0057] (2) After testing, the antibacterial test data of a loose nanofiltration membrane with a sustained-release bactericidal function prepared by Example 4 and Comparative Examples 1-2 are listed in Table 2. From the results, it can be seen that Example 4 of the present invention has a strong bactericidal ability against Gram-negative bacteria represented by Escherichia coli and Gram-positive bacteria represented by Staphylococcus aureus, reaching an inhibition rate of 97.4% and 96.3% respectively.

[0058] (3) The loose nanofiltration membrane with slow-release bactericidal function prepared in Example 4 was tested for Ag + The release of Figure 1 As shown. + The release rate was kept stable at 0.1 μg / L -1 day -1This indicates that the silver nanoparticles in the loose nanofiltration membrane of the present invention are stably immobilized in the MOF and are slowly released stably for a long time, thereby achieving long-term stable sterilization performance.

[0059] Table 1:

[0060] Table 2:

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a loose nanofiltration membrane resistant to biological contamination, comprising the following steps: (1) UiO-66-NH2 was synthesized by a hydrothermal method, mixed with a silver nitrate solution and stirred for 1 to 12 h, and reduced with a sodium borohydride solution to prepare Ag@UiO-66-NH2 nanoparticles; (2) The polybenzimidazole is uniformly blended with a certain amount of MOF obtained in step (1), and a loose nanofiltration membrane with a sustained-release bactericidal function is prepared by a non-solvent-induced phase transformation method. (3) The loose nanofiltration membrane obtained in step (2) is placed in acetonitrile to displace the water in the membrane pores, and then transferred to an acetonitrile solution of trimesoyl chloride of appropriate concentration for cross-linking for 1-12 hours to obtain a cross-linked MOF@PBI membrane.

2. The method according to claim 1, characterized in that The solvent is DMAC.

3. The method according to claim 1, characterized in that The solvent and non-solvent are both deionized water.

4. The method according to claim 3, characterized in that The polybenzimidazole solvent is N-methylpyrrolidone.

5. A loose nanofiltration membrane with sustained-release bactericidal function prepared by the method of claims 1-4.

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