Preparation method of water treatment membrane with surface silica thorn-like array

Abstract

The present invention discloses a preparation method of a water treatment membrane with a surface silica thorn-like array, belonging to the field of water treatment science and technology. The preparation method is as follows: the membrane substrate is hydrophilically modified to obtain a hydrophilically modified membrane substrate; the silicon source precursor diffuses from the solution phase into the liquid phase and reacts under the action of a membrane surface catalyst to obtain a mixed solution; the membrane substrate is placed in the mixed solution to carry out nucleation and growth of the nano-thorn-like structure, and a water treatment membrane with a surface silica thorn-like array is obtained. The water treatment membrane with a surface silica thorn-like array prepared by the present invention has good water flux and mechanical strength, and has an obvious inhibitory effect on the growth and colonization of bacteria and microorganisms on the base membrane, effectively improving the antibacterial and anti-pollution performance of the base membrane, and having potential application value in the field of water treatment.

Description

Technical Field

[0001] The present invention relates to a preparation method of a water treatment membrane with a surface silica spiky array, belonging to the field of water treatment science and technology. Background Art

[0002] Compared with traditional separation methods (coagulation and flocculation, conventional filtration, and biochemical treatment systems), membrane separation technology is widely used in the field of water treatment due to its advantages such as high separation accuracy, low separation energy consumption, simple operation, and small floor area. However, membrane fouling limits the permeation flux of the membrane, reduces the service life and separation efficiency of the membrane, and severely restricts the application and development of membrane technology. Therefore, preventing and controlling membrane fouling remains the research focus in the process of treating wastewater by membrane methods.

[0003] During the membrane technology separation process, bacteria adhere to each other through the extracellular matrix composed of polysaccharides, proteins, nucleic acids, and lipids, and bind to cell surface receptors to form a complex and highly polar biofilm on the membrane surface. To control membrane fouling, antibacterial treatment of the membrane surface (such as hydrophilic modification of the membrane surface, loading antibacterial agents on the membrane surface, antibacterial modification of the membrane surface) is required to eliminate the bacteria adsorbed on the membrane surface and destroy the formation of the biofilm.

[0004] Controlling the surface morphology of the membrane to form a spiky array on the membrane surface can affect bacterial cells, and cause the death of bacteria and microbial cells through physical stress damage and oxidative stress, thereby achieving an antibacterial effect and reducing membrane fouling. Therefore, there is an urgent need for a preparation method of a separation membrane that can form a spiky array on the membrane surface and can regulate the morphology, so that the membrane has good antibacterial and antifouling properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a water treatment membrane with a surface spiky array having high antibacterial and high antifouling properties and a preparation method thereof.

[0006] To solve the above technical problem, the technical solution provided by the present invention is as follows:

[0007] A preparation method of a water treatment membrane with a surface silica spiky array includes the following steps:

[0008] Step 1): Hydrophilic modification of the membrane substrate to obtain a hydrophilically modified membrane substrate;

[0009] Step 2): The silicon source precursor diffuses from the solution phase into the liquid phase and reacts under the action of a membrane surface catalyst to obtain a mixed solution;

[0010] Step 3): Placing the membrane substrate obtained in Step 1) into the mixed solution obtained in Step 2), and carrying out nucleation and growth of the nano-spiky structure to obtain a water treatment membrane with a surface silica spiky array.

[0011] Preferably, step 1) includes the following steps:

[0012] Step 1.1): Place the membrane substrate to be modified in a plasma generator and evacuate to 5 - 20 Pa.

[0013] Step 1.2): Introduce gas to make the vacuum degree not greater than 50 Pa.

[0014] Step 1.3): Adjust the discharge power to 20 - 100 W and the treatment time to 2 - 20 min.

[0015] Preferably, the membrane substrate is any one or several of PVDF membrane, PES membrane, PAN, PSf, and PA membrane.

[0016] More preferably, the gas introduced in step 1.2) is any one or several of argon, nitrogen, and oxygen.

[0017] Preferably, step 2) includes the following steps:

[0018] Step 2.1): Dissolve 2 - 20 g of surfactant in 100 - 500 mL of organic solution by ultrasonic treatment, and then add 0.02 - 0.1 mol / L of sodium citrate.

[0019] Step 2.2): Under ultrasonic conditions, immerse the hydrophilic - modified membrane substrate prepared in step 1) into the solution obtained in step 2.1), and then add 1 - 10 mL of alkaline catalyst.

[0020] Step 2.3): Under ultrasonic conditions, slowly add 200 - 2000 μL of silicon - source precursor to the solution obtained in step 2.2) and react for 1 - 10 min.

[0021] More preferably, the surfactant in step 2.1) is selected from any one or several of sodium dodecyl sulfate, polyvinylpyrrolidone, cetyltrimethylammonium bromide, and polyacrylic acid.

[0022] More preferably, the organic solution in step 2.1) is selected from any one or several of isopropanol, n - propanol, pentanol, butanol, and N,N - dimethylformamide.

[0023] More preferably, the alkaline catalyst in step 2.2) is selected from any one or several of ethylenediamine, aniline, and ammonia water.

[0024] More preferably, the silicon - source precursor in step 2.3) is selected from tetraethyl orthosilicate or tetramethyl orthosilicate.

[0025] Preferably, step 3) includes the following steps:

[0026] Step 3.1): Place the membrane substrate obtained in Step 1) into the mixed solution obtained in Step 2), and leave it standing in an oven at 40 - 80 °C for 2 - 8 h;

[0027] Step 3.2): Take out the membrane substrate and let it dry at room temperature to obtain a water treatment membrane with a silica thorn-like array on its surface.

[0028] The water treatment membrane with a silica thorn-like array prepared by the present invention has good water flux and mechanical strength, and has an obvious inhibitory effect on the growth and colonization of bacteria and microorganisms on the base membrane, effectively improving the antibacterial and anti-pollution performance of the base membrane, and has potential application value in the field of water treatment.

[0029] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0030] 1. The present invention conducts hydrophilic modification treatment on the membrane substrate, reduces the surface energy of the membrane substrate, and drives the adsorption of catalyst droplets in the hydrophilic matrix. In the prior art, the main formation of rod-like structures on the surface of the base membrane is metal oxides, because metal oxides are relatively easy to form rod-like structures due to the presence of crystal lattices, but silica is a non-metal oxide, and it is difficult to form rod-like structures on the membrane surface; and water treatment membrane materials such as PVDF are relatively soft and cannot withstand high temperature and high pressure, so it is necessary to continuously adjust experimental parameters to obtain the desired effect. The inventor found through a large number of attempts that if the membrane substrate is not subjected to hydrophilic modification, a silica nanostructure with good morphology and rod-like growth cannot be obtained.

[0031] 2. During the growth process of the present invention, the catalyst droplets are mainly composed of a surfactant as the middle phase, an aqueous phase containing citrate and a catalyst as the inner phase, and an organic solvent as the outer phase and adhere to the substrate. The growth of rod-like silica is carried out in a reverse micelle system. The high-concentration surfactant in the reverse micelle aggregates at the core of the droplet. After introducing the silicon source, it immediately hydrolyzes within a few minutes and spontaneously polymerizes on the droplet surface to form silica oligomers. During the reaction process, the silicon source substance diffuses from the organic solvent phase to the membrane immersed in the aqueous solution and finally polymerizes into rod-like silica.

[0032] 3. The present invention combines this method with a water treatment membrane, conducts part of this reaction on the membrane surface, and for the first time realizes the growth of rod-like silica on the membrane surface to improve the anti-pollution performance of the water treatment membrane. The silica thorn-like array can inhibit the growth and adhesion of bacteria and microorganisms, and has an obvious inhibitory and killing effect on microorganisms such as Escherichia coli and Staphylococcus aureus.

[0033] 4. The morphology of the formed silica thorn-like array can be regulated by changing the reaction conditions, including the density and aspect ratio of the silica array, and has different antibacterial effects under different morphologies. Description of the Drawings

[0034] Figure 1 Surface morphology diagrams of membrane sample 1 obtained in Example 1 at different magnifications;

[0035] Figure 2 Cross-sectional SEM diagrams of membrane sample 1 obtained in Example 1 at different magnifications;

[0036] Figure 3 Antibacterial efficiency diagram of membrane sample 2 obtained in Example 2;

[0037] Figure 4 Surface morphology diagrams of membrane sample 3 obtained in Comparative Example 1 at different magnifications;

[0038] Figure 5 Comparison diagram of contact angles of membrane sample 1 obtained in Example 1 after hydrophilic modification (left) and after silica thorn array experiment (right);

[0039] Figure 6 Schematic diagram of membrane contact angles of N-type silica / PVDF and M-type silica / PVDF in Comparative Example 2. Detailed implementation manners

[0040] To make the present invention more obvious and understandable, preferred embodiments are provided below in conjunction with the accompanying drawings for detailed description as follows.

[0041] Example 1

[0042] This example provides a preparation method of a water treatment membrane with a surface silica thorn array, and the specific steps are as follows:

[0043] (1) Perform hydrophilic modification on the membrane substrate, including the following steps:

[0044] S1. Place the PVDF membrane substrate to be modified in a plasma generator and evacuate to 5 Pa;

[0045] S2. Introduce oxygen to maintain the vacuum degree at 50 Pa;

[0046] S3. Adjust the discharge power to 100 W and the treatment time to 20 min.

[0047] (2) The silicon source precursor diffuses from the solution phase to the liquid phase and reacts under the action of a membrane surface catalyst, including the following steps:

[0048] M1. Dissolve 20 g of sodium dodecyl sulfate in 100 mL of n-propanol by ultrasonic treatment, and then add 0.1 mol / L sodium citrate;

[0049] M2. Immerse the hydrophilic modified membrane substrate prepared in step (1) in the above solution under ultrasonic conditions and add 10 mL of ammonia water;

[0050] M3. Slowly add 2 mL of tetraethyl orthosilicate to the solution under ultrasonic conditions and react for 5 min.

[0051] (3) Nucleation and growth of the nano-spiky structure to obtain a membrane with a spiky silica array, including the following steps:

[0052] N1. Leave the mixed solution obtained in step M3 in an oven at 60 °C for 4 hours;

[0053] N2. Take out the membrane substrate from the solution and air-dry it at room temperature to obtain membrane sample 1 with a spiky silica array on the surface.

[0054] The scanning electron microscope of the spiky silica structure grown on the PVDF membrane surface in Example 1 is shown by Figure 1 、 2 As can be seen from the figure, the spiky silica grows perpendicular to the membrane surface.

[0055] Example 2

[0056] This example provides a method for preparing a water treatment membrane with a spiky silica array on the surface, and the specific steps are as follows:

[0057] (1) Hydrophilic modification of the membrane substrate, including the following steps:

[0058] S1. Place the PVDF membrane substrate to be modified in a plasma generator and evacuate to 5 Pa;

[0059] S2. Introduce nitrogen to maintain the vacuum at 20 Pa;

[0060] S3. Adjust the discharge power to 80 W and the treatment time to 15 min.

[0061] (2) Diffusion of the silicon source precursor from the solution phase to the liquid phase and reaction under the action of a catalyst on the membrane surface, including the following steps:

[0062] M1. Dissolve 10 g of sodium dodecyl sulfate in 100 mL of n-propanol by ultrasonic treatment, and then add 0.1 mol / L sodium citrate;

[0063] M2. Immerse the hydrophilic modified membrane substrate prepared in step (1) in the above solution under ultrasonic conditions and add 5 mL of ammonia water;

[0064] M3. Slowly add 1 mL of tetraethyl orthosilicate to the solution under ultrasonic conditions and react for 8 min.

[0065] (3) Nucleation and growth of the nano-spiky structure to obtain a membrane with a spiky silica array, including the following steps:

[0066] N1. Leave the mixed solution obtained in step M3 in an oven at 60 °C for 8 hours;

[0067] N2. Take out the membrane substrate from the solution and air-dry it at room temperature to obtain membrane sample 2 with a membrane having a silica spiky array on its surface.

[0068] The antibacterial effect of the PVDF membrane surface with spiky silica grown in Example 2 (bacterial strain diluted 10 times, diluted 100 times) is as Figure 3 shown. It can be seen from the figure that its antibacterial efficiency is approximately between 50% - 80%, showing a good antibacterial effect.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing a water treatment membrane with a silica spiky array on its surface, and the specific steps are as follows:

[0071] (1) Clean the PVDF membrane for standby;

[0072] (2) The silicon source precursor diffuses from the solution phase into the liquid phase and reacts under the action of the catalyst on the membrane surface in (1), including the following steps:

[0073] M1. Dissolve 20 g of sodium dodecyl sulfate in 100 mL of n-propanol by ultrasonic treatment, and then add 0.1 mol / L sodium citrate;

[0074] M2. Immerse the hydrophilic modified membrane substrate prepared in step (1) into the above solution under ultrasonic conditions, and add 10 mL of ammonia water;

[0075] M3. Slowly add 2 mL of tetraethyl orthosilicate to the solution under ultrasonic conditions.

[0076] (3) Nucleation and growth of the nano-spiky silica structure, including the following steps:

[0077] N1. Leave the mixed solution obtained in step M3 in an oven at 60 °C for a period of time;

[0078] N2. Take out the membrane substrate from the solution and air-dry it at room temperature to obtain membrane sample 1 with a membrane having a silica spiky array on its surface;

[0079] The electron micrograph of the PVDF membrane surface with spiky silica grown without hydrophilic modification in Comparative Example 1 is as Figure 4 shown. By comparing with the hydrophilic modified membrane, it is found that only a small amount of silica grows on its surface, and the density is far less than that of the hydrophilic modified membrane. Moreover, the morphology of its silica is mixed with some spherical shapes, which is quite different from the hydrophilic modified membrane.

[0080] Comparative Example 2

[0081] Since there is currently no technical literature on the growth of rod-shaped silica on the membrane surface, a PVDF membrane doped with silica was used for hydrophilicity comparison (Preparation and Properties of Nano-Inorganic Doped Modified Polyvinylidene Fluoride Ultrafiltration Membrane, Liao ChanJuan, Doctoral Dissertation of Wuhan University, May 2011). Figure 6 For this paper Figure 4-3 Shown are the schematic diagrams of the membrane contact angles of N-type silica / PVDF and M-type silica / PVDF. It can be seen from the figure that they are basically above 85°.

[0082] The membrane contact angle prepared in the present invention is as Figure 5 Shown. The contact angle of the membrane hydrophilically modified in the present invention (left) is about 37°, and the contact angle of the membrane with spiky silica grown (right) is about 54°. Compared with the contact angle of the PVDF membrane doped with silica, it is lower, indicating that the present invention better improves the hydrophilic performance of the membrane.

Claims

1. Application of a PVDF membrane with a surface silica thorn-like array in water treatment antibacterial, characterized in that, The preparation method of the surface silica spiky array PVDF membrane comprises the following steps: Step 1): Hydrophilic modification is carried out on the PVDF membrane substrate to obtain a hydrophilically modified membrane substrate; Step 2): The silicon source precursor diffuses from the solution phase into the liquid phase and reacts under the action of a catalyst on the membrane surface to obtain a mixed solution; Step 3): The membrane substrate obtained in Step 1) is placed in the mixed solution obtained in Step 2) for nucleation and growth of the nano-spiky structure to obtain a water treatment membrane with a surface silica spiky array; The said Step 1) comprises the following steps: Step 1.1): Place the membrane substrate to be modified in a plasma generator and evacuate to 5 - 20 Pa; Step 1.2): Introduce argon or nitrogen to make the vacuum degree not more than 50 Pa; Step 1.3): Adjust the discharge power to 20 - 100 W and the treatment time to 2 - 20 min; The said Step 2) comprises the following steps: Step 2.1): Dissolve 2 - 20 g of the surfactant sodium dodecyl sulfate in 100 - 500 mL of the organic solution n-propanol by ultrasonic treatment, and then add 0.02 - 0.1 mol / L of sodium citrate; Step 2.2): Under ultrasonic conditions, immerse the hydrophilically modified membrane substrate prepared in Step 1) into the solution obtained in Step 2.1), and then add 1 - 10 mL of the alkaline catalyst ammonia water; Step 2.3): Under ultrasonic conditions, slowly add 200 - 2000 μL of the silicon source precursor tetraethyl orthosilicate to the solution obtained in Step 2.2) and react for 1 - 10 min; The said Step 3) comprises the following steps: Step 3.1): Place the membrane substrate obtained in Step 1) in the mixed solution obtained in Step 2) and let it stand in an oven at 40 - 80 °C for 2 - 8 h; Step 3.2): Take out the membrane substrate and air-dry it at room temperature to obtain a water treatment membrane with a surface silica spiky array.

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