A zif-8-nh2 doped bridged silicone reverse osmosis membrane and a preparation method thereof

Abstract

The application discloses a ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane and a preparation method thereof. The membrane is prepared by doping ZIF-8-NH2 metal organic framework material into polymeric organic silicon sol, and forming a ZIF-8-NH2 / organic silicon hybrid membrane on the surface of a prefabricated ceramic support by a rubbing coating method. The ZIF-8-NH2 / bridge organic silicon membrane prepared by the application has high water permeability and high salt retention rate (NaCl retention rate is greater than 99.2%) in reverse osmosis desalination application, and the membrane structure is stable in the process of treating high-salt wastewater with TDS greater than 7 wt%.

Description

Technical Field

[0001] This invention belongs to the field of composite membrane technology, specifically relating to a ZIF-8-NH2-doped bridged organosilicon reverse osmosis membrane and its preparation method. Background Technology

[0002] Saltwater desalination is considered a major source of clean freshwater from various sources. Desalination refers to the process of removing salts and minerals (contaminants) from seawater or brackish water to obtain clean water suitable for human consumption, industrial use, and domestic use. Currently, membrane-based brine separation technologies include reverse osmosis (RO), nanofiltration (NF), and membrane distillation (MD). Compared to RO, NF membranes have larger pore sizes and cannot completely remove all ions and dissolved solids, resulting in a lower desalination rate. Furthermore, NF membranes may have some permeability to some small-molecule organic pollutants and microorganisms, requiring auxiliary processes and subsequent treatments for further removal. RO, on the other hand, has a high removal capacity for various ions and organic substances and a high desalination rate. Therefore, RO is one of the most widely used membrane desalination technologies currently.

[0003] Currently, the membrane materials used for RO desalination mainly include aromatic polyamide (PA), polysulfone (PS), and cellulose acetate (CA). However, these organic polymer membranes are prone to fouling and have poor membrane structure stability during the reverse osmosis desalination process of high-salt wastewater.

[0004] Metal-organic frameworks (MOFs) are promising brine separation membrane materials due to their inherent physical and chemical properties. Compared with other MOF materials, ZIF-8 exhibits superior hydrothermal stability, chemical stability, and a large specific surface area. Theoretically, ZIF-8 can provide faster flow channels for water molecules, achieving high salt repulsion and better compatibility with polymers. The pore size of ZIF-8 is [not specified in the original text]. Between typical salt ions and the size of water molecules This makes it an ideal water molecule sieve. However, ZIF-8 material has low hydrophilicity, resulting in poor desalination performance in practical applications. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the present application aims at overcoming the deficiencies in the prior art and providing a preparation method of ZIF-8-NH2 doped bridge-structured organosilicon reverse osmosis membrane.

[0008] To solve the above technical problems, the present application provides a preparation method of ZIF-8-NH2 doped bridge-structured organosilicon reverse osmosis membrane, comprising,

[0009] The silicon source precursor and the hydrochloric acid catalyst are subjected to hydrolysis polymerization reaction with water in an ethanol solution to obtain a bridge-structured organosilicon polymeric sol;

[0010] The ZIF-8-NH2 crystals are added to the bridge-structured organosilicon polymeric sol, and ultrasonic treatment is performed to obtain a uniformly mixed and dispersed ZIF-8-NH2 / bridge-structured organosilicon mixed sol;

[0011] The ZIF-8-NH2 / bridge-structured organosilicon mixed sol is coated on a ceramic support of a silica-zirconia nanometer transition layer by an immersion-drawing method, and calcination is performed in air to obtain a ZIF-8-NH2 / organosilicon reverse osmosis membrane.

[0012] As a preferred scheme of the preparation method, the silicon source precursor is bis(triethoxysilyl) ethylene.

[0013] As a preferred scheme of the preparation method, the molar ratio of the silicon source precursor, water and hydrochloric acid is 1:30-240:0.1-0.3, the hydrolysis polymerization reaction temperature is 25-60 DEG C, and the hydrolysis polymerization reaction time is 1-4 h.

[0014] As a preferred scheme of the preparation method, the ZIF-8-NH2 crystals are prepared by,

[0015] The zinc nitrate hexahydrate and the imidazole ligand are dissolved in methanol, and stirring reaction is performed at room temperature, and then centrifugation is performed after removal;

[0016] The obtained ZIF-8-NH2 is washed with anhydrous methanol for 2-3 times, vacuum dried and baked to obtain ZIF-8-NH2 crystals.

[0017] The imidazole ligand is a mixture of 2-methyl imidazole and 2-amino benzimidazole, and the molar ratio of 2-methyl imidazole and 2-amino benzimidazole is 95:5.

[0018] As a preferred scheme of the preparation method, the mass ratio of ZIF-8-NH2 to the bridge-structured organosilicon polymeric sol in the ZIF-8-NH2 / bridge-structured organosilicon mixed sol is 0.1-1:1.

[0019] As a preferred solution of the preparation method, the ultrasonic time is 10-30 min.

[0020] As a preferred solution of the preparation method, the ceramic support is an alpha-Al2O3, ZrO2 or SiO2 ceramic membrane.

[0021] As a preferred solution of the preparation method, the preparation method of the silica-zirconia transition layer comprises,

[0022] The silica-zirconia sol is first diluted to 0.1-1 wt% with deionized water, the ceramic support is then preheated to 150 DEG C, the silica-zirconia sol is then quickly coated on the surface of the membrane by using the deionized water to dip the cotton, and then the membrane is placed in a tube furnace and calcined at 550 DEG C in an air atmosphere for 15-30 min, and the process is repeated 6-10 times to form the transition layer.

[0023] As a preferred solution of the preparation method, the calcination temperature is 200-300 DEG C, the calcination time is 15-30 min, and the process is repeated 1-3 times.

[0024] Still another object of the present application is to provide a preparation method of a ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane to overcome the defects in the prior art.

[0025] The present application has the following advantages:

[0026] (1) The ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane prepared by the present application can maintain a high rejection rate, and the desalination rate is always maintained above 99% in the continuous reverse osmosis desalination process of high-concentration brine, and has excellent stability.

[0027] (2) The method of the present application dopes ZIF-8-NH2 into organic silicon to modify the network structure of the bridge organic silicon membrane to improve the hydrophilicity of the membrane surface and the pore; the preparation method of the present application is simple, and the ammonia functionalized ZIF-8 (ZIF-8-NH2) MOFs are selected as the nanometer membrane, because the introduced amino groups can be used as hydrophilic sites for subsequent water adsorption, thereby enhancing the transport of water molecules through the hybrid membrane, the introduction of ZIF-8-NH2 strengthens the affinity of the organic silicon hybrid network for water molecules, and the regular pores of ZIF-8-NH2 can also provide a transmission channel for water molecules; in a high-salinity water environment, the introduction of ZIF-8-NH2 into organic silicon can effectively inhibit the hydrolysis rearrangement of the organic silicon network, thereby enhancing the stability of the membrane; the addition of ZIF-8-NH2 adjusts the pore size distribution of the organic silicon hybrid network, so that the pore size of the membrane surface is dense and can pass water molecules but not hydrated salt ions, which makes the reverse osmosis membrane always have a high desalination rate. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0029] Figure 1 The graph shows the water flux and NaCl rejection rate of BTESEthy membrane and ZIF-8-NH2 / BTESEthy composite membranes with different ratios in 7wt% NaCl solution at 70℃.

[0030] Figure 2 Nitrogen adsorption isotherms for BTESEthy, ZIF-8, ZIF-8-NH2, and ZNB-0.5 membranes;

[0031] Figure 3 Water contact angle diagrams of BTESEthy membranes and ZIF-8-NH2 / BTESEthy composite membranes with different ratios;

[0032] Figure 4 SEM images of the surface (a) and cross-section (b) of the ZIF-8-NH2 / BTESEthy composite membrane;

[0033] Figure 5 Thermogravimetric diagrams of BTESEthy, ZIF-8-NH2, ZNB-0.5, and ZIF-8 dry gels. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0037] The separation performance of the reverse osmosis membrane prepared in the application is generally evaluated by water flux and NaCl rejection rate, and the water flux and NaCl rejection rate of the membrane can be obtained by corresponding calculation.

[0038] The calculation formula of water flux (the water output within a certain time under 25-70℃ and 1.0-1.5MPa) is as follows:

[0039] F=Q / (A·t)

[0040] In the formula, Q is the permeation volume (L), A is the effective area of the membrane (m 2 ), and t is the permeation time (h).

[0041] The calculation formula of NaCl rejection rate (the rejection rate of 1wt%-13wt% NaCl solution under 25-70℃ and 1.0-1.5MPa) is as follows:

[0042]

[0043] In the formula, C f and C p are the conductivities of the solution before and after filtration respectively.

[0044] Example 1

[0045] This example provides a preparation method of ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane, and the main steps are as follows:

[0046] (1) Hydrolytic polymerization reaction of bis(triethoxysilyl) ethylene (BTESEthy) as a silicon source precursor and water is carried out in an ethanol solution (the ethanol solution is a solvent to keep the mass fraction of BTESEthy at 5%) with hydrochloric acid as a catalyst; wherein the molar ratio of BTESEthy, water and hydrochloric acid is 1:60:0.2, and the solution is stirred at 40℃ for 2h to obtain a bridge BTESEthy polymeric sol.

[0047] (2) ZIF-8-NH2 crystals are synthesized by using a room temperature rapid synthesis method:

[0048] Zinc nitrate hexahydrate and 2-methyl imidazole, 2-amino benzimidazole (the molar ratio of zinc nitrate hexahydrate:2-methyl imidazole:2-amino benzimidazole is 12.5:95:5) are dissolved in methanol, and after stirring at room temperature for 1.5h, the obtained ZIF-8-NH2 product is centrifuged, washed with anhydrous methanol for 3 times, and then vacuum dried at 100℃ for 24h to obtain ZIF-8-NH2 crystals.

[0049] (3) ZIF-8-NH2crystals were added into the bridge BTESEthy sol and ultrasonically mixed for 30 min to prepare a ZIF-8-NH2 / bridge BTESEthy mixed sol;

[0050] The ZIF-8-NH2 / bridge BTESEthy samples with different compositions were designated as ZNB-n, (n = 0.5) indicating the mass ratio of ZIF-8-NH2to BTESEthy in the solution.

[0051] (4) The ZIF-8-NH2 / bridge BTESEthy mixed sol was coated onto the α-Al2O3 ceramic support containing a silica-zirconia nano-transition layer by the rubbing method, wherein the silica-zirconia transition layer was prepared by first diluting the silica-zirconia sol to 0.5 wt% with deionized water, then preheating the ceramic support to 150°C, then quickly rubbing the film surface with the silica-zirconia sol using a cotton swab, and then transferring it to a tube furnace for calcination at 550°C in air for 30 min. This step was repeated 6-10 times to form the intermediate layer.

[0052] After coating, the sample was calcined at 250°C in air for 20 min to obtain the ZIF-8-NH2 / bridge BTESEthy film (ZNB-0.5).

[0053] Example 2

[0054] The present embodiment provides a preparation method of a ZIF-8-NH2doped bridge organic silicon reverse osmosis membrane, and the main steps are as follows:

[0055] (1) Bis(triethoxysilyl)ethylene (BTESEthy) was used as a silicon source precursor and hydrochloric acid was used as a catalyst for hydrolysis and polymerization reaction with water in an ethanol solution (the ethanol solution was a solvent to maintain the mass fraction of BTESEthy at 5%); wherein the molar ratio of BTESEthy, water and hydrochloric acid was 1:60:0.2, and the solution was stirred at 40°C for 2h to obtain a bridge BTESEthy polymer sol.

[0056] (2) ZIF-8-NH2crystals were synthesized using a room temperature rapid synthesis method:

[0057] Zinc nitrate hexahydrate and 2-methylimidazole, 2-aminobenzimidazole (the molar ratio of zinc nitrate hexahydrate:2-methylimidazole:2-aminobenzimidazole was 12.5:95:5) were dissolved in methanol, stirred at room temperature for 1.5h, then centrifuged, the obtained ZIF-8-NH2product was washed with anhydrous methanol for 3 times, and then vacuum dried at 100°C for 24h to obtain ZIF-8-NH2crystals.

[0058] (3) ZIF-8-NH2crystals were added into the bridge BTESEthy sol and ultrasonically mixed for 30 min to prepare a ZIF-8-NH2 / bridge BTESEthy mixed sol;

[0059] The ZIF-8-NH2 / bridge BTESEthy samples with different compositions were designated as ZNB-n (n = 0.2) to represent the mass ratio of ZIF-8-NH2 to BTESEthy in the solution.

[0060] (4) The ZIF-8-NH2 / bridge BTESEthy mixed sol was coated onto the α-Al2O3 ceramic support containing a silica-zirconia nano-transition layer by the rubbing method, wherein the silica-zirconia transition layer was prepared by first diluting the silica-zirconia sol to 0.5 wt% with deionized water, then preheating the ceramic support to 150°C, then quickly rubbing the surface of the film with the silica-zirconia sol using a cotton swab, and then transferring it to a tube furnace for calcination at 550°C in air for 30 min. This step was repeated 6-10 times to form the intermediate layer.

[0061] After coating, the sample was calcined at 250°C in air for 20 min to obtain the ZIF-8-NH2 / bridge BTESEthy film (ZNB-0.2).

[0062] Example 3

[0063] The present embodiment provides a preparation method of a ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane, and the main steps are as follows:

[0064] (1) A hydrolysis and polymerization reaction was carried out in an ethanol solution (the ethanol solution was used as a solvent to maintain the mass fraction of BTESEthy at 5%) using bis(triethoxysilyl) ethylene (BTESEthy) as a silicon source precursor and hydrochloric acid as a catalyst; wherein the molar ratio of BTESEthy, water and hydrochloric acid was 1:60:0.2, and the solution was stirred at 40°C for 2 h to obtain a bridge BTESEthy polymer sol.

[0065] (2) ZIF-8-NH2crystals were synthesized using a room temperature rapid synthesis method:

[0066] Zinc nitrate hexahydrate and 2-methylimidazole, 2-aminobenzimidazole (the molar ratio of zinc nitrate hexahydrate:2-methylimidazole:2-aminobenzimidazole was 12.5:95:5) were dissolved in methanol, and after stirring at room temperature for 1.5 h, the obtained ZIF-8-NH2product was centrifuged, washed with anhydrous methanol for 3 times, and then vacuum dried at 100°C for 24 h to obtain ZIF-8-NH2crystals.

[0067] (3) ZIF-8-NH2crystals were added into the bridge BTESEthy sol and ultrasonically mixed for 30 min to prepare a ZIF-8-NH2 / bridge BTESEthy mixed sol;

[0068] The ZIF-8-NH2 / bridge BTESEthy samples with different compositions were designated as ZNB-n (n = 0.8) to represent the mass ratio of ZIF-8-NH2 to BTESEthy in the solution.

[0069] (4) The ZIF-8-NH2 / bridge BTESEthy mixed sol was coated onto the α-Al2O3 ceramic support containing a silica-zirconia nano-transition layer by the rubbing method, wherein the silica-zirconia transition layer was prepared by first diluting the silica-zirconia sol to 0.5 wt% with deionized water, then preheating the ceramic support to 150°C, then quickly rubbing the film surface with the silica-zirconia sol using a cotton swab, and then transferring it to a tube furnace for calcination at 550°C in air for 30 min. This step was repeated 6-10 times to form the intermediate layer.

[0070] After coating, the sample was calcined at 250°C in air for 20 min to obtain the ZIF-8-NH2 / bridge BTESEthy film (ZNB-0.8).

[0071] Example 4

[0072] The present embodiment provides a method for preparing a ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane, and the main steps are as follows:

[0073] (1) A hydrolysis and polymerization reaction was carried out in an ethanol solution (the ethanol solution was used as a solvent to maintain the mass fraction of BTESEthy at 5%) using bis(triethoxysilyl) ethylene (BTESEthy) as a silicon source precursor and hydrochloric acid as a catalyst; wherein the molar ratio of BTESEthy, water and hydrochloric acid was 1:60:0.2, and the solution was stirred at 40°C for 2 h to obtain a bridge BTESEthy polymer sol.

[0074] (2) ZIF-8-NH2crystals were synthesized using a room temperature rapid synthesis method:

[0075] Zinc nitrate hexahydrate and 2-methylimidazole, 2-aminobenzimidazole (the molar ratio of zinc nitrate hexahydrate:2-methylimidazole:2-aminobenzimidazole was 12.5:95:5) were dissolved in methanol, and after stirring at room temperature for 1.5 h, the obtained ZIF-8-NH2product was centrifuged, washed with anhydrous methanol for 3 times, and then vacuum dried at 100°C for 24 h to obtain ZIF-8-NH2crystals.

[0076] (3) ZIF-8-NH2crystals were added into the bridge BTESEthy sol and ultrasonically mixed for 30 min to prepare a ZIF-8-NH2 / bridge BTESEthy mixed sol;

[0077] The ZIF-8-NH2 / bridge BTESEthy samples with different compositions were designated as ZNB-n (n = 1) to represent the mass ratio of ZIF-8-NH2to BTESEthy in the solution.

[0078] (4) The ZIF-8-NH2 / bridge BTESEthy mixed sol was coated onto the α-Al2O3 ceramic support containing a silica-zirconia nano transition layer by the rubbing method, wherein the silica-zirconia transition layer was prepared by first diluting the silica-zirconia sol with deionized water to 0.5 wt%, then preheating the ceramic support to 150°C, then quickly rubbing the silica-zirconia sol on the surface of the film with absorbent cotton, and then transferring it to a tube furnace and calcining at 550°C in air for 30 min, and this step was repeated 6-10 times to form an intermediate layer.

[0079] After coating, calcination was performed at 250°C in air for 20 min to obtain a ZIF-8-NH2 / bridge BTESEthy film (ZNB-1).

[0080] Comparative Example 1

[0081] (1) Bis(triethoxysilyl)ethylene (BTESEthy) was used as a silicon source precursor and hydrochloric acid was used as a catalyst for hydrolysis and polymerization reaction with water in an ethanol solution (the ethanol solution was a solvent to maintain the mass fraction of BTESEthy at 5%).

[0082] The molar ratio of BTESEthy, water, and hydrochloric acid was 1:60:0.2, and the solution was stirred at 40°C for 2 h to obtain a bridge BTESEthy polymer sol.

[0083] (2) The bridge BTESEthy sol was coated onto the α-Al2O3 ceramic support containing a silica-zirconia nano transition layer by the rubbing method, wherein the silica-zirconia transition layer was prepared by first diluting the silica-zirconia sol with deionized water to 0.5 wt%, then preheating the ceramic support to 150°C, then quickly rubbing the silica-zirconia sol on the surface of the film with absorbent cotton, and then transferring it to a tube furnace and calcining at 550°C in air for 30 min, and this step was repeated 6-10 times to form an intermediate layer;

[0084] After coating, calcination was performed at 250°C in air for 20 min to obtain a bridge BTESEthy film.

[0085] Comparative Example 2

[0086] (1) Bis(triethoxysilyl) ethylene (BTESEthy) as a silicon source precursor, hydrochloric acid as a catalyst, hydrolysis and polymerization reaction with water in ethanol solution (ethanol solution is a solvent to keep the mass fraction of BTESEthy at 5%); wherein the molar ratio of BTESEthy, water, and hydrochloric acid is 1:60:0.2, the solution is stirred at 40°C for 2h, and a bridging BTESEthy polymeric sol is obtained.

[0087] (2) ZIF-8 crystals are synthesized by using a room temperature rapid synthesis method:

[0088] Zinc nitrate hexahydrate and 2-methylimidazole (the molar ratio of zinc nitrate hexahydrate:2-methylimidazole is 1:8) are dissolved in methanol, stirred at room temperature for 1.5h, then centrifuged, the obtained ZIF-8 product is washed with anhydrous methanol for 3 times, and then dried at 100°C under vacuum for 24h to obtain ZIF-8 crystals.

[0089] (3) ZIF-8 crystals are added to the bridging BTESEthy sol to prepare a ZIF-8 / bridging BTESEthy mixed sol by ultrasonic mixing for 30min; wherein the mass ratio of ZIF-8 to BTESEthy is 0.5.

[0090] (4) The ZIF-8 / bridging BTESEthy mixed sol is coated on an α-Al2O3 ceramic support containing a silica-zirconia nano transition layer by a rubbing coating method, wherein the silica-zirconia transition layer is first diluted to 0.5wt% by using deionized water to dilute the silica-zirconia sol, then the ceramic support is preheated to 150°C, then the silica-zirconia sol is dipped with absorbent cotton and quickly rubbed on the film surface, and then transferred to a tube furnace, calcined at 550°C in air for 30min, and this step is repeated for 6-10 times to form an intermediate layer.

[0091] After coating, the ZB-0.5 ZIF-8 / bridging BTESEthy film is obtained by calcining at 250°C in air for 20min.

[0092] The water flux and NaCl rejection rate of the BTESEthy film and the ZIF-8-NH2 / BTESEthy composite film with different proportions in a 7wt% NaCl solution at 70°C are shown in Figure 1 It can be seen that the water flux and salt rejection rate are different under the condition of 70°C, 1.5MPa, and 7wt% NaCl solution, and the water flux and salt rejection rate increase with the increase of the addition amount of ZIF-8-NH2, and the water flux and rejection rate reach the highest when the addition amount is 0.5.

[0093] N2 adsorption curves of ZIF-8, ZIF-8-NH2, BTESEthy and ZNB-0.5 materials are shown in Figure 1. Figure 2 As can be seen, all the samples show type I adsorption curves, which is a typical feature of microporous materials.

[0094] Water contact angle diagrams of BTESEthy film and ZIF-8-NH2 / BTESEthy composite films with different proportions are shown in Figure 2. Figure 3 , Figure 3 Water contact angle diagrams of ZIF-8-NH2 / BTESEthy composite films with different proportions are shown in Figure 3, which are obtained by coating the sol on a glass sheet by spin coating, drying, and then testing the data by a water contact angle instrument. As can be seen, the water contact angle of the ZNB-0.5 film is 57°, which is significantly lower than the water contact angle of the ZB-0.5 film of 65°, indicating that the amino-functionalized ZIF-8-NH2 / BTESEthy composite film has higher surface hydrophilicity.

[0095] Surface and cross-sectional morphological diagrams of the ZNB-0.5 composite film taken by a scanning electron microscope are shown in Figure 4. Figure 4 Thermogravimetric curves of ZIF-8, ZIF-8-NH2, BTESEthy and ZNB-0.5 xerogels in air atmosphere are shown in Figure 5. Figure 5 As can be seen, the thermogravimetric curves of ZIF-8 and ZIF-8-NH2 are basically coincident, and the obvious weight loss above 400℃ is due to the decomposition of the organic ligand; ZIF-8-NH2 shows good thermal stability, indicating that the addition of 2-aminobenzimidazole in the mixed ligand has no obvious effect on the thermal stability of ZIF-8; due to the incorporation of ZIF-8-NH2, the thermal stability of the BTESEthy network is significantly improved.

[0096] Comparative Example 3

[0097] The preparation method of the embodiment is implemented by including the following steps:

[0098] (1) Hydrolytic polymerization reaction of BTESE (bis-triethoxysilyl) ethane) as a silicon source precursor and water in an ethanol solution (the ethanol solution is a solvent to keep the mass fraction of BTESE at 5%) with hydrochloric acid as a catalyst;

[0099] The molar ratio of BTESE, water and hydrochloric acid is 1:60:0.2, and the solution is stirred at 40℃ for 2h to obtain a bridged BTESE polymer sol.

[0100] (2) Synthesis of ZIF-8-NH2 crystals using a room temperature rapid synthesis method:

[0101] Zinc nitrate hexahydrate and 2-methylimidazole, 2-aminobenzimidazole (molar ratio of zinc nitrate hexahydrate:2-methylimidazole:2-aminobenzimidazole is 12.5:95:5) were dissolved in methanol, and the reaction was stirred at room temperature for 1.5 h, then centrifuged, and the obtained ZIF-8-NH2 product was washed with anhydrous methanol for 3 times, and then dried at 100℃ under vacuum for 24 h to obtain ZIF-8-NH2 crystals.

[0102] (3) The ZIF-8-NH2 crystals were added to the bridge BTESE sol, and ultrasonic treatment was performed for 30 min to prepare a ZIF-8-NH2 / bridge BTESE mixed sol; wherein the mass ratio of ZIF-8-NH2 to BTESE was 0.5.

[0103] (4) The ZIF-8-NH2 / bridge BTESE mixed sol was coated on the α-Al2O3 ceramic support containing a silica-zirconia nano transition layer by the rubbing coating method, wherein the silica-zirconia transition layer was prepared by first diluting the silica-zirconia sol to 0.5wt% with deionized water, then preheating the ceramic support to 150℃, then quickly rubbing the surface of the film with the silica-zirconia sol using a cotton swab, and then transferring it to a tube furnace, and calcining at 550℃ in air for 30 min, and repeating the above steps 6-10 times to form an intermediate layer.

[0104] After coating, the sample was calcined at 250℃ in air for 20 min to obtain a ZIF-8-NH2 / bridge BTESE film.

[0105] Comparative Example 4

[0106] (1) Bis(triethoxysilyl)ethane (BTESE) was used as a silicon source precursor, and hydrochloric acid was used as a catalyst to perform hydrolysis and polymerization reaction with water in an ethanol solution (the ethanol solution is a solvent to maintain the mass fraction of BTESE at 5%);

[0107] The molar ratio of BTESE, water, and hydrochloric acid was 1:60:0.2, and the solution was stirred at 40℃ for 2 h to obtain a bridge BTESE polymer sol.

[0108] (2) ZIF-8 crystals were synthesized using a room temperature rapid synthesis method:

[0109] Zinc nitrate hexahydrate and 2-methylimidazole (molar ratio of zinc nitrate hexahydrate:2-methylimidazole is 1:8) were dissolved in methanol, and the reaction was stirred at room temperature for 1.5 h, then centrifuged, and the obtained ZIF-8 product was washed with anhydrous methanol for 3 times, and then dried at 100℃ under vacuum for 24 h to obtain ZIF-8 crystals.

[0110] (3) ZIF-8 crystals are added into the bridge BTESE polymeric sol, and ultrasonic treatment is performed for 30 min to uniformly mix and disperse to prepare a ZIF-8 / bridge BTESE mixed sol; wherein the mass ratio of ZIF-8 to BTESE is 0.5.

[0111] (4) The ZIF-8 / bridge BTESE mixed sol is coated onto the α-Al2O3 ceramic support containing the silica-zirconia nano transition layer by the rubbing coating method, wherein the silica-zirconia transition layer is prepared by first diluting the silica-zirconia sol to 0.5 wt% with deionized water, then preheating the ceramic support to 150℃, then quickly rubbing the film surface with the silica-zirconia sol absorbed by the absorbent cotton, and then transferring to a tube furnace for calcination at 550℃ in air for 30 min, and repeating the step 6-10 times to form the intermediate layer.

[0112] After coating, calcination is performed at 250℃ in air for 20 min to obtain a ZIF-8 / bridge BTESE film.

[0113] The separation performance of the above Example 1 and Comparative Examples 3 and 4 is generally evaluated by water flux and NaCl rejection rate, and by corresponding calculation (at 70℃, 1.5 MPa, 7 wt% NaCl solution), the water flux and NaCl rejection rate of the membrane can be obtained, and the experimental results are shown in Table 1.

[0114] Table 1

[0115] Membrane Flux (L / m 2 • h) Retention (%) Example 1 9.9 99.1 Comparative Example 3 9.2 95.8 Comparative Example 4 8.5 85.1

[0116] In summary, the ZIF-8-NH2 doped bridge organic silicon reverse osmosis membrane prepared by the present application can maintain a high rejection rate, and in the continuous reverse osmosis desalination process of high-concentration brine, the desalination rate is always maintained above 99%, and has excellent stability.

[0117] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the present application.

Claims

1. A method for preparing a ZIF-8-NH2-doped bridged organosilicon reverse osmosis membrane, characterized in that: include, A silicon source precursor and a hydrochloric acid catalyst were hydrolyzed and polymerized with water in an ethanol solution to obtain a bridged organosilicon polymer sol, wherein the silicon source precursor was bis(triethoxysilyl)ethylene. ZIF-8-NH2 crystals were added to the bridge-type silicone polymer sol, and ultrasonication was used to obtain a uniformly dispersed ZIF-8-NH2 / bridge-type silicone mixed sol. The mass ratio of ZIF-8-NH2 to bridge-type silicone polymer sol in the ZIF-8-NH2 / bridge-type silicone mixed sol was 0.5:

1. ZIF-8-NH2 / bridge silicone mixed sol was coated onto a ceramic support of silica-zirconia nano-transition layer by dip-coating and calcination in air to obtain ZIF-8-NH2 / silicon reverse osmosis membrane.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the silicon source precursor, water, and hydrochloric acid is 1:30~240:0.1~0.3, the hydrolysis polymerization reaction temperature is 25~60℃, and the hydrolysis polymerization reaction time is 1~4h.

3. The preparation method according to claim 1, characterized in that: The ZIF-8-NH2 crystal is prepared by including, Zinc nitrate hexahydrate and imidazole ligand were dissolved in methanol, stirred at room temperature, and then centrifuged. The obtained ZIF-8-NH2 was washed 2-3 times with anhydrous methanol, then vacuum dried and oven-dried to obtain ZIF-8-NH2 crystals. The imidazole ligand is a mixture of 2-methylimidazole and 2-aminobenzimidazole, with a molar ratio of 95:

5.

4. The preparation method according to claim 1, characterized in that: The ultrasound time is 10-30 minutes.

5. The preparation method according to claim 4, characterized in that: The ceramic support is an α-Al2O3, ZrO2, or SiO2 ceramic film.

6. The preparation method according to claim 5, characterized in that: The method for preparing the silica-zirconia nanotransition layer includes, First, dilute the silicon zirconium sol to 0.1~1wt% with deionized water. Then, preheat the ceramic support to 150℃. Next, use degreased cotton to quickly apply the silicon zirconium sol to the film surface. Then, place it in a tube furnace and calcine it in an air atmosphere at 550℃ for 15~30 minutes. Repeat this process 6~10 times to form a transition layer.

7. The preparation method according to claim 6, characterized in that: The calcination temperature is 200~300℃, the calcination time is 15~30min, and it is repeated 1~3 times.

8. The ZIF-8-NH2-doped bridged organosilicon reverse osmosis membrane prepared by any of the preparation methods described in claims 1 to 7.

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