Polymer filter membrane hydrophilicity modification process for water purification treatment

Abstract

The invention discloses a hydrophilic modification process of a polymer filter membrane for water purification treatment, which comprises the following steps: immersing a cleaned hydrophobic polymer filter membrane into a modification solution prepared from a weakly alkaline buffer solution, and carrying out oscillation reaction at 25-40 DEG C; the modification liquid comprises dopamine (or hydrochloride thereof), tannic acid and metal salt; after the reaction is completed, taking out the membrane, washing and drying; the process disclosed by the invention is efficient and rapid, and compared with pure dopamine coating, the reaction time is greatly shortened, and the modification efficiency is improved; the surface water contact angle of the modified membrane can be reduced to be less than 20 degrees and even reach 0 degree (super-hydrophilic); due to the existence of metal coordinate bonds, the modified layer is very stable, resistant to water flow scouring and acid-base environments and long in hydrophilicity retention time.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of water treatment membranes, in particular to a hydrophilic modification process for a high-molecular filter membrane used for water purification treatment. BACKGROUND

[0002] Background High-molecular filter membranes (such as ultrafiltration and microfiltration membranes) are widely used in water purification treatment. However, commonly used membrane materials (such as PVDF and PSF) are hydrophobic in nature, which easily leads to problems such as membrane pollution, flux decline, frequent cleaning and shortened service life. Therefore, hydrophilic modification of the filter membrane is the key to improving its performance.

[0003] Existing modification methods include surface coating, chemical grafting, plasma treatment and the like. However, these methods often have some shortcomings, such as:

[0004] 1. Chemical grafting: the reaction conditions are severe (strong acid, strong base or oxidizing agent needs to be used), which may damage the membrane structure, and the process is complex.

[0005] 2. Plasma treatment: the equipment is expensive, the modification effect is unstable (easily aged), and it is difficult to realize large-scale continuous production.

[0006] 3. Traditional surface coating: the coating has weak adhesion with the membrane surface and is easy to fall off during use, and has poor durability.

[0007] Therefore, in order to correct the above-mentioned defects, the application provides a hydrophilic modification process for a high-molecular filter membrane used for water purification treatment. SUMMARY

[0008] The application aims to overcome the shortcomings of the prior art and provide a hydrophilic modification process for a high-molecular filter membrane, which is simple to operate, has mild conditions and a stable and firm modification layer.

[0009] To achieve the above-mentioned purpose, the application provides the following technical scheme: a hydrophilic modification process for a high-molecular filter membrane used for water purification treatment, comprising the following steps:

[0010] Membrane pretreatment: immerse the hydrophobic high-molecular filter membrane to be modified in deionized water or an ethanol aqueous solution, ultrasonically clean for 5-30 minutes to remove surface impurities, and then take out and dry or dry with nitrogen.

[0011] Preparation of a modification solution: prepare a Tris-HCl buffer solution (concentration of 10-50 mM, pH value of 8.0-8.5), and then add dopamine hydrochloride, tannic acid and metal salt in sequence in the buffer solution, stir to fully dissolve, and obtain a modification solution;

[0012] The concentration of dopamine hydrochloride is 0.5-2.0g / L, the concentration of tannic acid is 0.5-2.0g / L, and the concentration of metal salt is 0.5-5.0mM.

[0013] The metal salt is trivalent iron salt (such as FeCl3) or divalent copper salt (such as CuSO4).

[0014] Co-deposition modification: the filter membrane treated in step (1) is completely immersed in the modification solution prepared in step (2), and oscillation reaction is carried out in an air atmosphere at a temperature of 25-40℃ for 0.5-4 hours.

[0015] Post-treatment: after the reaction is completed, the membrane is taken out, rinsed with deionized water to remove the physically adsorbed loose particles, and then vacuum dried at 40-60℃ for 2-6 hours to obtain a hydrophilic permanently modified polymer filter membrane.

[0016] The mechanism of the application: dopamine will undergo oxidative self-polymerization to form a polydopamine (PDA) coating under weak alkaline conditions, but the process is slow.

[0017] Tannic acid (TA) is a polyphenol compound, which has similar adhesion properties as dopamine.

[0018] After introducing metal ions (such as Fe 3+ or Cu 2+ ), the metal ions can form a stable TA-M +n -DA ternary complex network structure through high-efficiency coordination with the ortho-diphenol groups in dopamine and tannic acid molecules. This co-deposition process:

[0019] · significantly accelerates the deposition rate and shortens the reaction time.

[0020] · enhances the stability of the coating, and the metal coordination bond is more stable than pure physical adsorption or hydrogen bond.

[0021] · introduces a large number of hydrophilic phenolic hydroxyl groups, greatly improving the hydrophilic properties of the membrane surface. Compared with the prior art, the application has the following beneficial effects:

[0022] 1. High efficiency and speed: compared with pure dopamine coating, the reaction time is greatly shortened, and the modification efficiency is improved.

[0023] 2. Super hydrophilicity and durability: the water contact angle of the modified membrane surface can be reduced to below 20°, and even to 0° (super hydrophilic); the existence of metal coordination bond makes the modified layer very stable, resistant to water flow scouring and acid and alkali environment, and the hydrophilicity is maintained for a long time.

[0024] 3. Excellent anti-fouling performance: strong hydrophilic surface can effectively prevent the adsorption of hydrophobic pollutants such as proteins and oil stains on the membrane surface, significantly reduce membrane fouling, prolong membrane life and reduce cleaning frequency.

[0025] 4. Mild conditions and universality: the entire process is carried out at room temperature and pressure, near neutral pH conditions, without the need for expensive equipment or harsh chemical reactions, without damage to the membrane structure, and is suitable for a variety of hydrophobic polymer filter membranes.

[0026] 5. Environmentally friendly: the reagents used are less toxic and have a small amount, in line with the principles of green chemistry. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a process flow diagram in the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0029] The present application provides a technical solution:

[0030] Please refer to Figure 1 A hydrophilic modification process for a polymer filter membrane for water purification treatment, comprising the following steps:

[0031] Membrane pretreatment: immerse the hydrophobic polymer filter membrane to be modified in deionized water or an ethanol aqueous solution, ultrasonic cleaning for 5-30 minutes, remove surface impurities, then take out and dry or nitrogen blow dry.

[0032] Preparation of modification solution: prepare a Tris-HCl buffer solution (concentration of 10-50 mM, pH value of 8.0-8.5), and then add dopamine hydrochloride, tannic acid and metal salt in sequence in the buffer solution, stir to dissolve thoroughly, to obtain the modification solution;

[0033] The concentration of dopamine hydrochloride is 0.5-2.0 g / L, the concentration of tannic acid is 0.5-2.0 g / L, and the concentration of metal salt is 0.5-5.0 mM.

[0034] The metal salt is a trivalent iron salt (such as FeCl3) or a divalent copper salt (such as CuSO4).

[0035] Co-deposition modification: The clean filter membrane in step (1) is completely immersed in the modification solution prepared in step (2), and is oscillated at a temperature of 25-40°C in an air atmosphere for 0.5-4 hours.

[0036] Post-treatment: After the reaction is completed, the membrane is taken out, rinsed with deionized water to remove the physically adsorbed loose particles, and then vacuum dried at 40-60°C for 2-6 hours to obtain the hydrophilic permanently modified polymer filter membrane.

[0037] Example 1:

[0038] 1. Take a piece of commercial PVDF ultrafiltration membrane, immerse it in an ethanol aqueous solution (volume ratio 1:1) for ultrasonic cleaning for 15 minutes, then rinse with deionized water and dry with nitrogen.

[0039] 2. Prepare 40mM Tris-HCl buffer solution (pH=8.2) 500mL. Add 0.75g dopamine hydrochloride, 0.75g tannic acid and 0.406g FeCl3·6H2O (final concentration 3mM) to it, and magnetically stir for 30 minutes to completely dissolve.

[0040] 3. Immerse the cleaned PVDF membrane in the above modification solution and place it in a constant temperature oscillator at 35°C, with a speed of 120rpm for 2 hours.

[0041] 4. After the reaction is completed, the membrane is taken out, rinsed with a large amount of deionized water until the rinsing liquid is colorless, and then placed in a vacuum oven at 50°C for drying for 4 hours.

[0042] 5. Test the performance of the modified membrane: the water contact angle is reduced from 78° before modification to 8°; after filtering BSA solution, the flux recovery rate (FRR) is increased from 65% of the unmodified membrane to 92%.

[0043] Example 2:

[0044] 1. Take a piece of commercial PES microfiltration membrane, clean and dry as in Example 1.

[0045] 2. Prepare 30mM Tris-HCl buffer solution (pH=8.3) 500mL. Add 1.0g dopamine hydrochloride, 0.5g tannic acid and 0.125g CuSO4 (final concentration 1.6mM) to it, and stir to dissolve.

[0046] 3. Immerse the PES membrane in the modification solution and oscillate at 30°C for 1.5 hours.

[0047] 4. Post-treatment as in Example 1.

[0048] 5. Test results: water contact angle is reduced from 82° to 15°; FRR is increased from 60% to 89%.

[0049] Comparative Example (simple dopamine modification): the steps are the same as in Example 1, but the modification solution does not add tannic acid and FeCl3, only 2.0 g / L dopamine hydrochloride is added, and the reaction time needs to be more than 6 hours to form a uniform coating. The contact angle of the obtained film is about 35°, the FRR is 80%, and part of the coating falls off under the scouring of high-speed water flow.

[0050] The above experiments show that the dopamine / tannic acid-metal ion co-deposition process provided by the present application is significantly superior to the traditional dopamine modification method in terms of modification efficiency, improvement range of hydrophilicity, coating stability and anti-pollution performance

[0051] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for modifying the hydrophilicity of a polymer filter membrane for water purification treatment, characterized by, The method comprises the following steps: S1, membrane pretreatment: immerse the hydrophobic polymer filter membrane to be modified in deionized water or an ethanol aqueous solution, ultrasonic cleaning for 5-30 minutes, remove surface impurities, then take out and air dry or nitrogen dry; S2, completely immerse the filter membrane treated in step (1) in a modification liquid, oscillate the reaction in an air atmosphere at a temperature of 25-40℃ for 0.5-4 hours; The modification liquid comprises dopamine, tannic acid and a metal salt; S3, after the reaction is completed, take out the membrane, rinse with deionized water to remove physically adsorbed loose particles, then vacuum dry at 40-60℃ for 2-6 hours, to obtain a hydrophilic permanently modified polymer filter membrane.

2. The process for hydrophilic modification of a polymer filter membrane for water purification treatment according to claim 1, characterized in that: The modification liquid is prepared: prepare a Tris-HCl buffer solution, then sequentially add dopamine hydrochloride, tannic acid and a metal salt into the buffer solution, stir to fully dissolve, to obtain the modification liquid.

3. The process for hydrophilic modification of polymer membrane for water purification treatment according to claim 2, characterized in that: The concentration of the Tris-HCl buffer solution is 10-50mM, the pH value is 8.0-8.5, the concentration of dopamine hydrochloride is 0.5-2.0g / L, the concentration of tannic acid is 0.5-2.0g / L, and the concentration of the metal salt is 0.5-5.0mM.

4. The process for hydrophilic modification of polymer membrane for water purification treatment according to claim 2, characterized in that: The metal salt is a trivalent iron salt or a divalent copper salt.

5. The process for hydrophilic modification of polymer membrane for water purification treatment according to claim 4, characterized in that: The trivalent iron salt is FeCl3, and the divalent copper salt is CuSO4.

6. The process for hydrophilic modification of polymer membrane for water purification treatment according to claim 1, characterized in that: The hydrophobic polymer filter membrane is one of polyvinylidene fluoride, polysulfone and polyethersulfone.

7. A high hydrophilic and anti-pollution polymer filter membrane prepared by the method for hydrophilic modification of a polymer filter membrane for water purification treatment according to any one of claims 1-6.

8. Application of the high hydrophilic and anti-pollution polymer filter membrane according to claim 7 in water purification treatment.

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