Preparation method of nano-SiO2/cellulose composite separating membranes

[0036] Example 1

[0037] Nano SiO of this embodiment 2 The preparation method of /cellulose composite separation membrane includes the following steps:

[0038] (1) Dissolve cellulose in ionic liquid to form casting film: mix fully dried cotton pulp with ionic liquid 1-ethyl-3-methylimidazole acetate, and dissolve at 90°C for 2h to prepare Into a casting liquid with a mass fraction of 4%.

[0039] (2) Preparation of nano-SiO 2 : Mix tetraethylorthosilicate and ethanol thoroughly at a volume ratio of 1:25 to obtain a reaction solution; add 25% ammonia water to the reaction solution, stir at room temperature for 1 min, and then at 60°C for 20 hours Transparent SiO 2 Gel solution; the volume of the reaction solution is 4% of the volume of ammonia; the obtained gel solution is heated and evaporated to obtain a gel, which is dried at 80° C. for 20 hours to obtain white nano SiO 2 powder.

[0040] (3) Use the silane coupling agent γ-(2,3-glycidoxy) propyl trimethoxy silane on the nano SiO 2 Modification: Add 25mL of toluene to each gram of nano-silica, then add the silane coupling agent γ-(2,3-glycidoxy)propyltrimethoxysilane, ultrasonically disperse for 15 minutes and then keep at 90℃ After stirring and reacting for 6 hours, centrifuged at a speed of 4000r/min at room temperature to obtain modified nano-SiO 2 , Dried in a vacuum drying oven at 50℃ for 20h to obtain white powdery modified nano SiO 2 The added amount of the silane coupling agent is 4% of the mass of the casting solution.

[0041] (4) The modified nano SiO 2 Disperse in the casting solution obtained in step (1) to obtain a mixed casting solution; prepare the mixed casting solution into a thin film and dry it to obtain nano SiO 2 /Cellulose composite separation membrane, specifically: the modified nano SiO 2 Dispersed in the film casting solution obtained in step (1) to obtain a mixed film casting solution, wherein the modified nano SiO 2 The mass ratio to the cellulose in the casting solution is 1:10; after stirring and ultrasonic dispersion, pour the mixed casting solution on a clean glass plate, scrape it into a thin film with a doctor blade, and place it at room temperature for 13 minutes Then, wash the deionized liquid with deionized water to obtain translucent nano SiO 2 /Cellulose composite separation membrane, take the membrane out and place it in a vacuum drying oven at 50℃ for drying.

[0042] The contact angle of the membrane can be used to measure the hydrophilicity of the membrane. The smaller the contact angle, the stronger the hydrophilicity of the membrane. The contact angle of the material can be measured with a contact angle meter. Nano SiO prepared in this embodiment 2 The hydrophilicity evaluation of /cellulose composite separation membrane (sample 1) is shown in Table 1, and it is compared with the addition of unmodified nano SiO 2 Nano SiO 2 /Cellulose composite separation membrane (comparative sample) for comparison; adding unmodified nano SiO 2 Nano SiO 2 The preparation steps of the /cellulose composite separation membrane are: Steps (1), (2), (4) of this embodiment are performed, and Step (3) is not performed.

[0043] Table 1 Hydrophilicity evaluation of sample 1 and comparative sample 1

[0044]

[0045] It can be seen from Table 1 that the addition of inorganic nano SiO 2 The particles can obtain a composite membrane with good hydrophilicity. And SiO 2 The modification has little effect on the hydrophilicity of the composite membrane.

[0046] Table 2 lists the tensile strength and elongation at break of sample 1, comparative sample 1, and comparative sample 2 (pure regenerated cellulose film) prepared in this example. It can be seen from Table 2 that: adding modified nano SiO 2 The tensile strength and elongation at break of the composite film after particles have been greatly improved.

[0047] Table 2 The tensile strength and elongation at break of sample 1, comparative sample 1, and comparative sample 2

[0048]

[0049] figure 1 , 2 These are the SEM electron micrographs of the surface and the cross-section of the comparative sample 1 of this embodiment. It can be seen that the surface of the composite cellulose membrane is firm and has no obvious pores, but the unmodified nano SiO is added 2 After the particles, the surface of the composite film is rough, and the composite film shows that there are obvious large agglomerates. It may be due to the unmodified SiO in the casting solution 2 The particle size is small, the specific surface area is large, contains a large number of hydrophilic groups, and the surface activity is high, and agglomeration occurs. In the heating process, the hydrogen bonds between the cellulose molecular chains are broken at high temperature, and the orderly arrangement of the original molecular chains is destroyed, and the hydroxyl groups are exposed. Therefore, the unmodified nano-SiO 2 The particles have surface coating effect, and the unmodified nano SiO 2 The particles are embedded in the cellulose polymer.

[0050] image 3 , 4 These are the SEM electron micrographs of the surface and cross-section of sample 1 of this embodiment. It can be seen that the modified nano SiO 2 After particles, the surface roughness of the composite film is significantly reduced, the surface is relatively smooth and flat, and the internal structure is evenly distributed. This is because the modified SiO 2 The particle surface polarity is reduced, and the dispersibility and compatibility in the organic matrix are enhanced. Add modified SiO 2 The particles are easier to disperse and fill in the pores between the regenerated cellulose molecules. In addition, add an appropriate amount of coupling agent and SiO 2 Dehydration and condensation between surface hydroxyl groups is easy to occur, which is connected to SiO 2 The coupling agent on the surface blocks the agglomeration between the particles, making the nano SiO 2 It has good dispersibility in casting liquid.

[0051] Example 2

[0052] Nano SiO of this embodiment 2 The preparation method of /cellulose composite separation membrane includes the following steps:

[0053] (1) Dissolve cellulose in ionic liquid to form casting film: mix fully dried cotton pulp with ionic liquid 1-ethyl-3-methylimidazole acetate, and dissolve at 80℃ for 2h to prepare Into a casting liquid with a mass fraction of 3%.

[0054] (2) Preparation of nano-SiO 2 : Mix tetraethyl orthosilicate and ethanol at a volume ratio of 1:50 to obtain a reaction solution; add 30% ammonia water to the reaction solution, stir at room temperature for 1 min, and then at 75°C for 25 hours Transparent SiO 2 Gel solution; the volume of the reaction solution is 9.3% of the volume of ammonia; the obtained gel solution is heated and evaporated to obtain a gel, which is dried at 100 ℃ for 25 hours to obtain white nano SiO 2 powder.

[0055] (3) Use the silane coupling agent γ-(2,3-glycidoxy) propyl trimethoxy silane on the nano SiO 2 Modification: Add 25mL of toluene to each gram of nano-silica, and then add the silane coupling agent γ-(2,3-glycidoxy)propyltrimethoxysilane. After ultrasonic dispersion, the temperature is 80~100℃. After the reaction is stirred at a constant temperature for 4-7 hours, centrifuged at a speed of 3000r/min at room temperature to obtain modified nano-SiO 2 , Dried in a vacuum drying oven at 40℃ for 15h to obtain white powdery modified nano SiO 2 The added amount of the silane coupling agent is 3% of the mass of the casting solution.

[0056] (4) The modified nano SiO 2 Disperse in the casting solution obtained in step (1) to obtain a mixed casting solution; prepare the mixed casting solution into a thin film and dry it to obtain nano SiO 2 /Cellulose composite separation membrane, specifically: the modified nano SiO 2 Dispersed in the film casting solution obtained in step (1) to obtain a mixed film casting solution, wherein the modified nano SiO 2 The mass ratio with the cellulose in the casting solution is 1:5; after stirring and ultrasonic dispersion, pour the mixed casting solution on a clean glass plate, scrape it into a thin film with a doctor blade, and place it at room temperature for 1 min Then, wash the deionized liquid with deionized water to obtain translucent nano SiO 2 /Cellulose composite separation membrane, take the membrane out and place it in a 40℃ vacuum drying oven for drying.

[0057] Example 3

[0058] Nano SiO of this embodiment 2 The preparation method of /cellulose composite separation membrane includes the following steps:

[0059] (1) Dissolve cellulose in ionic liquid to form casting film: mix fully dried cotton pulp with ionic liquid 1-ethyl-3-methylimidazole acetate and dissolve it at 100°C for 3 hours to prepare Into a casting liquid with a mass fraction of 5%.

[0060] (2) Preparation of nano-SiO 2 : Mix tetraethyl orthosilicate and ethanol at a volume ratio of 1:40 to obtain a reaction solution; add 25% ammonia water to the reaction solution, stir at room temperature for 3 minutes, and then at 45°C for 15 hours Transparent SiO 2 Gel solution; the volume of the reaction solution is 1.8% of the volume of ammonia; the obtained gel solution is heated and evaporated to obtain a gel, which is dried at 60° C. for 15 hours to obtain white nano SiO 2 powder.

[0061] (3) Use the silane coupling agent γ-(2,3-glycidoxy) propyl trimethoxy silane on the nano SiO 2 Modification: add 100mL toluene to each gram of nano-silica, then add the silane coupling agent γ-(2,3-glycidoxy)propyltrimethoxysilane, and stir at 100℃ after ultrasonic dispersion. After reacting for 7 hours, centrifuge at a speed of 5000r/min at room temperature to obtain modified nano SiO 2 , Dried in a vacuum drying oven at 60℃ for 24h to obtain white powdery modified nano SiO 2 The added amount of the silane coupling agent is 5% of the mass of the casting solution.

[0062] (4) The modified nano SiO 2 Disperse in the casting solution obtained in step (1) to obtain a mixed casting solution; prepare the mixed casting solution into a thin film and dry it to obtain nano SiO 2 /Cellulose composite separation membrane, specifically: the modified nano SiO 2 Dispersed in the film casting solution obtained in step (1) to obtain a mixed film casting solution, wherein the modified nano SiO 2 The mass ratio to the cellulose in the casting solution is 1:20; after stirring and ultrasonic dispersion, pour the mixed casting solution on a clean glass plate, scrape it into a thin film with a doctor blade, and place it at room temperature for 3 minutes Then, wash the deionized liquid with deionized water to obtain translucent nano SiO 2 /Cellulose composite separation membrane, take the membrane out and place it in a 60℃ vacuum drying oven for drying.