Preparation method and application of organic-inorganic hybrid nanofiltration membrane

Abstract

The present invention belongs to the technical field of the preparation of organic-inorganic hybrid membrane materials, and specifically relates to a preparation method and application of an organic-inorganic hybrid nanofiltration membrane. A high-concentration SiO2-ZrO2 sol and a low-concentration SiO2-ZrO2 sol are respectively prepared. The high-concentration SiO2-ZrO2 sol is coated on a carrier and calcined to obtain a SiO2-ZrO2 layer. After UiO-66-NH2 is mixed into the low-concentration SiO2-ZrO2 sol, it is coated on the SiO2-ZrO2 layer and calcined. The obtained composite membrane can be used as a nanofiltration membrane to separate organic or inorganic substances from water, and is suitable for intercepting and separating an aqueous solution of DCF. The organic-inorganic hybrid ceramic nanofiltration membrane of the present invention has the advantages of excellent separation performance, high hydrothermal stability, good renewable property, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of organic-inorganic hybrid membrane materials, and specifically relates to a preparation method and application of an organic-inorganic hybrid nanofiltration membrane. Background Art

[0002] Nanofiltration (NF) is a membrane separation technology between ultrafiltration and reverse osmosis. Compared with reverse osmosis technology, it has the advantages of higher membrane flux, low monovalent ion rejection and high multivalent ion rejection rate. Therefore, nanofiltration membrane is also called "loose reverse osmosis membrane". Nanofiltration is usually used in seawater desalination and industrial separation and purification due to its high separation efficiency, low operating pressure and low pollution. In terms of water softening, nanofiltration membrane can also remove synthetic detergents, magnesium ion hardness components and soluble organic matter in aqueous solutions.

[0003] Nanofiltration membranes used in commerce are generally polyamide nanofiltration membranes, which are generally composed of a porous support layer and a polyamide selective layer (PA). The porous substrate usually serves as a mechanical support, while the polyamide layer determines the water flux and selectivity of the membrane. Although polyamide nanofiltration membranes have been commercialized and widely used in the water treatment industry, in actual applications, there is a "trade-off" effect between water flux and retention rate, as well as insufficient anti-pollution properties, which leads to problems such as reduced service life of the nanofiltration membrane, thereby increasing operating costs. In addition, the membrane thickness of the nanofiltration membrane has a great influence on the flux. The thicker the membrane layer, the lower the flux, but the thinner the membrane layer, the more likely it is that the nanofiltration membrane will have leaks.

[0004] Therefore, how to obtain a nanofiltration membrane with high rejection rate, ideal water flux, and good membrane integrity remains the consistent goal in this field. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing an organic-inorganic hybrid nanofiltration membrane.

[0006] (1) Prepare high concentration SiO2-ZrO2 sol and low concentration SiO2-ZrO2 sol respectively,

[0007] Specifically, after the silicon source is hydrolyzed for a period of time, zirconium salt is added thereto and the temperature is raised to continue the hydrolysis reaction to obtain SiO2-ZrO2 sol.

[0008] The molar ratio of silicon to zirconium is 1:1, and the temperature is raised to 100-120°C for hydrolysis reaction for 12-18 hours.

[0009] The mass concentration of high-concentration SiO2-ZrO2 sol is 2.0-5.0%, and the mass concentration of low-concentration SiO2-ZrO2 sol is 0.5-1.0%.

[0010] (2) coating the high concentration SiO2-ZrO2 sol obtained in step (1) onto a carrier and calcining to obtain a SiO2-ZrO2 layer,

[0011] Repeat the process of coating and calcining the high concentration SiO2-ZrO2 sol in step (2) for 2 to 6 times.

[0012] (3) mixing UiO-66-NH2 into the low concentration SiO2-ZrO2 sol obtained in step (1), coating the mixture on the SiO2-ZrO2 layer obtained in step (2) after sufficient mixing, and calcining to obtain a UiO-66-NH2 / SiO2-ZrO2 hybrid layer,

[0013] The preparation method of UiO-66-NH2 is as follows: zirconium chloride and 2-amino-1,4-phthalic acid are dispersed in N,N-dimethylformamide, and acetic acid is added to carry out solvent thermal reaction, and the product is filtered out after the reaction and washed and dried to obtain UiO-66-NH2 crystals.

[0014] The temperature of the solvent thermal reaction is 130-160°C, and the reaction time is 24-40h.

[0015] UiO-66-NH2 is mixed into low concentration SiO2-ZrO2 sol at a mass concentration of 0.05-0.6%.

[0016] The operation of coating and calcining the mixed sol in step (3) is repeated 2 to 6 times.

[0017] The present invention also provides an application of the organic-inorganic hybrid nanofiltration membrane prepared above to separate organic or inorganic matter from water. Furthermore, the organic-inorganic hybrid nanofiltration membrane is used to intercept and separate an aqueous solution of DCF.

[0018] Beneficial effects of the present invention:

[0019] The present invention adjusts the membrane pore size after calcination and membrane formation by controlling the concentration of the coating sol, and through the interlayer synergistic effect of sols of different concentrations after membrane formation, a nanoscale pore size is stably formed on the surface of the microfiltration carrier with a relatively large original pore size, and is successfully used for nanofiltration separation; adding hydrophilic and porous UiO-66-NH2 to the nanofiltration layer promotes the water flux of the nanofiltration membrane, and UiO-66-NH2 itself is a rigid particle, which is easy to cause membrane defects when used as a membrane-forming component, and in this scheme, UiO-66-NH2 is mixed with SiO2-ZrO2 sol to form a membrane, and Zr and the uncoordinated carboxyl groups on UiO-66-NH2 produce a mutually attractive complexing effect, thereby greatly promoting the integrity of the membrane layer after calcination and membrane formation. In summary, the organic-inorganic hybrid ceramic nanofiltration membrane of the present invention has the advantages of excellent separation performance, high hydrothermal stability, good reproducibility, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a comparison diagram of the particle size distribution of sols of different concentrations prepared in Example 1,

[0021] Figure 2 This is a SEM image of the surface of the UiO-66-NH2 / SiO2-ZrO2 hybrid layer prepared in step (4) of Example 1.

[0022] Figure 3 This is a cross-sectional SEM image of the composite membrane finally prepared in Example 1.

[0023] Figure 4 This is a SEM image of the surface of the SiO2-ZrO2 separation layer prepared in step (3) of Comparative Example 1.

[0024] Figure 5 This is a SEM image of the surface of the SiO2 separation layer prepared in step (3) of Comparative Example 3.

[0025] Figure 6 This is the SEM image of the surface of the UiO-66-NH2 / SiO2 hybrid layer prepared in step (4) of Comparative Example 4. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0027] Example 1

[0028] (1) 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid (mass concentration 35%, the same below) were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added. Finally, 215 g of deionized water was added and heated to 100° C. and stirred for 12 hours to obtain a high-concentration SiO2-ZrO2 sol with a mass fraction of 2.0%.

[0029] 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added, and finally 455 g of deionized water was added and heated to 100 ° C and stirred for 12 hours to obtain a low-concentration SiO2-ZrO2 sol with a mass fraction of 1.0%.

[0030] The effect of the above sol concentration on particle size is shown in the attached Figure 1 ;

[0031] (2) Using a hollow flat ceramic membrane as a carrier (pore size 500 nm), the high-concentration SiO2-ZrO2 sol in step (1) is uniformly coated on the carrier, and placed in a muffle furnace for calcination at 550°C for 20 min. This process is repeated 4 times to obtain a SiO2-ZrO2 layer;

[0032] (3) 0.88 g zirconium chloride (ZrCl4) and 0.68 g 2-amino-1,4-phthalic acid (H2BDC-NH2) were dissolved in 42 ml N,N-dimethylformamide (DMF) respectively. The two solutions were mixed and ultrasonicated for 10 min. Then, 10 ml acetic acid (mass concentration 10%, the same below) was added and placed in a hydrothermal reactor. The reaction was carried out at 150 ° C for 20 h. The product was taken out and centrifuged and washed. Finally, it was dried at 60 ° C to obtain UiO-66-NH2 crystals.

[0033] The UiO-66-NH2 crystals are mixed into the low-concentration SiO2-ZrO2 sol in step (1) at a mass concentration of 0.6% to obtain a mixed sol;

[0034] (4) The mixed sol in step (3) is uniformly coated on the SiO2-ZrO2 layer obtained in step (2), and is placed in a muffle furnace and calcined for 20 min at 550°C. This process is repeated twice to obtain a UiO-66-NH2 / SiO2-ZrO2 hybrid layer.

[0035] Figure 2 It can be seen that the surface of the UiO-66-NH2 / SiO2-ZrO2 hybrid layer is continuous, defect-free, and has good integrity.

[0036] Figure 3 It can be seen that the film thickness of Example 1 on the carrier is about 200 nm, which is relatively small and is beneficial to the water flux of the nanofiltration membrane.

[0037] The composite membrane finally prepared in Example 1 was subjected to nanofiltration test using polyvinyl alcohol (PEG) with molecular weights of 200 / 400 / 600 / 800 / 1000, and the membrane pore size was found to be 1.0 nm, which is within the range of nanofiltration membrane.

[0038] The composite membrane finally prepared in Example 1 was used for 0.05 g·L -1 Separation of diclofenac sodium (DCF) aqueous solution, operating pressure 0.6MPa, operating temperature 70℃, test time 50h,

[0039] Nanofiltration performance of DCF aqueous solution: flux is 14.25L·m -2 ·h -1 The DCF retention rate is above 98.1%, and the hydrothermal stability is excellent.

[0040] Example 2

[0041] (1) 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added. Finally, 215 g of deionized water was added and heated to 100° C. and stirred for 12 hours to obtain a high-concentration SiO2-ZrO2 sol with a mass fraction of 2.0%.

[0042] 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added, and finally 455 g of deionized water was added and heated to 100° C. and stirred for reaction for 12 hours to obtain a low-concentration SiO2-ZrO2 sol with a mass fraction of 1.0%;

[0043] (2) Using a hollow flat ceramic membrane as a carrier (pore size 500 nm), the high-concentration SiO2-ZrO2 sol in step (1) is uniformly coated on the carrier, and placed in a muffle furnace for calcination at 550°C for 20 min. This process is repeated 4 times to obtain a SiO2-ZrO2 layer;

[0044] (3) 0.88 g zirconium chloride (ZrCl4) and 0.68 g 2-amino-1,4-phthalic acid (H2BDC-NH2) were dissolved in 42 ml N,N-dimethylformamide (DMF) respectively. The two solutions were mixed and ultrasonicated for 10 min. Then, 10 ml acetic acid was added and placed in a hydrothermal reactor. The reaction was carried out at 150 °C for 20 h. The product was taken out and centrifuged for washing. Finally, it was dried at 60 °C to obtain UiO-66-NH2 crystals.

[0045] The UiO-66-NH2 crystals are mixed into the low-concentration SiO2-ZrO2 sol in step (1) at a mass concentration of 0.5% to obtain a mixed sol;

[0046] (4) The mixed sol in step (3) is uniformly coated on the SiO2-ZrO2 layer obtained in step (2), and is placed in a muffle furnace and calcined for 20 min at 550°C. This process is repeated twice to obtain a UiO-66-NH2 / SiO2-ZrO2 hybrid layer.

[0047] The total thickness of the film formed on the support is about 200 nm.

[0048] The composite membrane finally prepared in Example 2 was subjected to nanofiltration test using polyvinyl alcohol (PEG) with molecular weights of 200 / 400 / 600 / 800 / 1000, and the membrane pore size was found to be 1.1 nm, which is within the range of nanofiltration membrane.

[0049] The composite membrane finally prepared in Example 2 was used for 0.05 g·L -1 Separation of diclofenac sodium (DCF) aqueous solution, operating pressure 0.6MPa, operating temperature 70℃, test time 50h,

[0050] Nanofiltration performance of DCF aqueous solution: flux is 12.61L·m -2 ·h -1 The DCF retention rate is above 98.7%, and the hydrothermal stability is excellent.

[0051] Comparative Example 1

[0052] UiO-66-NH2 was not introduced, and the remaining operations were the same as in Example 1:

[0053] (1) 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added. Finally, 215 g of deionized water was added and heated to 100° C. and stirred for 12 hours to obtain a high-concentration SiO2-ZrO2 sol with a mass fraction of 2.0%.

[0054] 1.6 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 6.08 g of zirconium n-butoxide (ZrBT) was added, and finally 455 g of deionized water was added and heated to 100° C. and stirred for reaction for 12 hours to obtain a low-concentration SiO2-ZrO2 sol with a mass fraction of 1.6%;

[0055] (2) Using a hollow flat ceramic membrane as a carrier (pore size 500 nm), the high-concentration SiO2-ZrO2 sol in step (1) is uniformly coated on the carrier, and placed in a muffle furnace for calcination at 550°C for 20 min. This process is repeated 4 times to obtain a SiO2-ZrO2 layer;

[0056] (3) The low concentration SiO2-ZrO2 sol in step (1) is uniformly coated on the SiO2-ZrO2 layer obtained in step (2), and the mixture is placed in a muffle furnace at 550°C and calcined for 20 min. This process is repeated twice to obtain a SiO2-ZrO2 separation layer.

[0057] The total thickness of the film formed on the carrier is about 200nm. Figure 4 It can be seen that the surface of the SiO2-ZrO2 separation layer is smooth, continuous, defect-free and has good integrity.

[0058] The composite membrane finally prepared in Comparative Example 1 was subjected to nanofiltration test using polyvinyl alcohol (PEG) with molecular weights of 200 / 400 / 600 / 800 / 1000, and the membrane pore size was found to be 1.2 nm, which is within the range of nanofiltration membrane.

[0059] The composite membrane finally prepared in Comparative Example 1 was used for 0.05 g·L -1 Separation of diclofenac sodium (DCF) aqueous solution, operating pressure 0.6MPa, operating temperature 70℃, test time 50h,

[0060] Nanofiltration performance of DCF aqueous solution: flux is 8.25L·m -2 ·h -1 , the DCF retention rate is 92%.

[0061] Comparative Example 2

[0062] Low concentration SiO2-ZrO2 sol and UiO-66-NH2 were not introduced, and the remaining operations were the same as in Example 1:

[0063] (1) 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added, and finally 215 g of deionized water was added and heated to 100° C. and stirred for 12 hours to prepare a high-concentration SiO2-ZrO2 sol with a mass fraction of 2.0%;

[0064] (2) Using a hollow flat ceramic membrane as a carrier (pore size 500 nm), the high concentration SiO2-ZrO2 sol in step (1) is evenly coated on the carrier and placed in a muffle furnace at 550°C for calcination for 20 min. This process is repeated 6 times to obtain a SiO2-ZrO2 separation layer.

[0065] The composite membrane finally prepared in Comparative Example 2 was tested by polyvinyl alcohol (PEG) with molecular weights of 200 / 400 / 600 / 800 / 1000, and the membrane pore size was found to be 2 nm.

[0066] The composite membrane finally prepared in Comparative Example 2 was used for 0.05 g·L -1 Separation of diclofenac sodium (DCF) aqueous solution, operating pressure 0.6MPa, operating temperature 70℃, test time 50h,

[0067] Nanofiltration performance of DCF aqueous solution: flux is 9.0L·m -2 ·h -1 , the DCF retention rate is less than 50%.

[0068] Comparative Example 3

[0069] No zirconium source and UiO-66-NH2 were introduced into the low-concentration film-forming sol, and the remaining operations were the same as those in Example 1:

[0070] (1) 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added. Finally, 215 g of deionized water was added and heated to 100° C. and stirred for 12 hours to obtain a high-concentration SiO2-ZrO2 sol with a mass fraction of 2.0%.

[0071] 1.6 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.30 g of tetraethyl orthosilicate (TEOS) was added, and finally 455 g of deionized water was added and heated to 100° C. and stirred for reaction for 12 hours to obtain a low-concentration SiO2 sol with a mass fraction of 1.6%;

[0072] (2) Using a hollow flat ceramic membrane as a carrier (pore size 500 nm), the high-concentration SiO2-ZrO2 sol in step (1) is uniformly coated on the carrier, and placed in a muffle furnace for calcination at 550°C for 20 min. This process is repeated 4 times to obtain a SiO2-ZrO2 layer;

[0073] (3) The low-concentration SiO2 sol in step (1) is uniformly coated on the SiO2-ZrO2 layer obtained in step (2), and the mixture is placed in a muffle furnace at 550°C and calcined for 20 min. This process is repeated twice to obtain a SiO2 separation layer.

[0074] Figure 5 It can be seen that the surface of the SiO2 separation layer is smooth, continuous, defect-free and has good integrity.

[0075] Comparative Example 4

[0076] When no zirconium source is introduced into the low-concentration film-forming sol, UiO-66-NH2 is added, and the rest of the operations are the same as those in Example 1:

[0077] (1) 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 3.80 g of zirconium n-butoxide (ZrBT) was added. Finally, 215 g of deionized water was added and heated to 100° C. and stirred for 12 hours to obtain a high-concentration SiO2-ZrO2 sol with a mass fraction of 2.0%.

[0078] 1.0 g of tetraethyl orthosilicate (TEOS) was dissolved in 19.8 g of ethanol (ETOH), and then 0.28 g of water and 0.06 g of hydrochloric acid were added and stirred for 60 minutes, and then 2.06 g of tetraethyl orthosilicate (TEOS) was added, and finally 455 g of deionized water was added and heated to 100° C. and stirred for reaction for 12 hours to obtain a low-concentration SiO2 sol with a mass fraction of 1.0%;

[0079] (2) Using a hollow flat ceramic membrane as a carrier (pore size 500 nm), the high-concentration SiO2-ZrO2 sol in step (1) is uniformly coated on the carrier, and placed in a muffle furnace for calcination at 550°C for 20 min. This process is repeated 4 times to obtain a SiO2-ZrO2 layer;

[0080] (3) 0.88 g zirconium chloride (ZrCl4) and 0.68 g 2-amino-1,4-benzenedicarboxylic acid (H2BDC-NH2) were dissolved in 42 ml N,N-dimethylformamide (DMF) respectively. The two solutions were mixed and ultrasonicated for 10 min. Then, 10 ml acetic acid was added and placed in a hydrothermal reactor. The reaction was carried out at 150 °C for 20 h. The product was taken out and centrifuged for washing. Finally, it was dried at 60 °C to obtain UiO-66-NH2 crystals.

[0081] The UiO-66-NH2 crystals are mixed into the low-concentration SiO2 sol in step (1) at a mass concentration of 0.6% to obtain a mixed sol;

[0082] (4) The mixed sol in step (3) is uniformly coated on the SiO2-ZrO2 layer obtained in step (2), and is placed in a muffle furnace and calcined for 20 min at 550°C. This process is repeated twice to obtain a UiO-66-NH2 / SiO2 hybrid layer.

[0083] Figure 6 It can be seen that compared with Comparative Example 3, after the introduction of UiO-66-NH2 into the SiO2 layer, obvious cracks appeared during film formation and the film could not be used as a filter membrane.

Claims

1. A method for preparing an organic-inorganic hybrid nanofiltration membrane, comprising the following steps: (1) preparing high concentration SiO2-ZrO2 sol and low concentration SiO2-ZrO2 sol respectively, wherein: The preparation method of the SiO2-ZrO2 sol is as follows: after a period of hydrolysis reaction of a silicon source, a zirconium salt is added thereto and the temperature is raised and the hydrolysis reaction is continued to obtain the SiO2-ZrO2 sol, wherein the mass concentration of the high-concentration SiO2-ZrO2 sol is 2.0-5.0%, and the mass concentration of the low-concentration SiO2-ZrO2 sol is 0.5-1.0%. (2) coating the high-concentration SiO2-ZrO2 sol obtained in step (1) onto a carrier and calcining the mixture, repeating the process 2 to 6 times to obtain a SiO2-ZrO2 layer. (3) UiO-66-NH2 is mixed into the low concentration SiO2-ZrO2 sol obtained in step (1), and after sufficient mixing, the mixture is coated on the SiO2-ZrO2 layer obtained in step (2), and calcined. The mixture is repeated 2 to 6 times to obtain a UiO-66-NH2 / SiO2-ZrO2 hybrid layer.

2. The method for preparing an organic-inorganic hybrid nanofiltration membrane according to claim 1, characterized in that: In step (1), the molar ratio of silicon to zirconium is 1:1, and the temperature is raised to 100-120° C. for hydrolysis reaction for 12-18 hours.

3. The method for preparing the organic-inorganic hybrid nanofiltration membrane according to claim 1, characterized in that: In step (3), the preparation method of UiO-66-NH2 is to disperse zirconium chloride and 2-amino-1,4-phthalic acid in N,N-dimethylformamide, add acetic acid and carry out solvent thermal reaction, filter out the product after the reaction and wash and dry it to obtain UiO-66-NH2 crystals.

4. The method for preparing the organic-inorganic hybrid nanofiltration membrane according to claim 1, characterized in that: In step (3), UiO-66-NH2 is mixed into the low concentration SiO2-ZrO2 sol at a mass concentration of 0.05-0.6%.

5. Use of the organic-inorganic hybrid nanofiltration membrane obtained by the preparation method according to any one of claims 1 to 4 for separating organic or inorganic substances from water.

6. The use of the organic-inorganic hybrid nanofiltration membrane according to claim 5, characterized in that: The organic-inorganic hybrid nanofiltration membrane was used to intercept and separate the DCF aqueous solution.

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