A method for anti-biofouling modification of polyamide composite membranes using hydrated electrons

Abstract

The present invention discloses a method for modifying a polyamide composite membrane to resist biofouling using hydrated electrons. The method comprises the following steps: S1. affixing a polyamide (PATFC) membrane to a membrane cell, adding a coupling solution and then sulfite to the cell, and discarding the solution after a predetermined reaction time; S2. adding an SBMA solution to the cell, followed by the addition of sulfite and bismuth oxyiodide. Irradiating the membrane with a UV lamp for a predetermined period of time, the reaction vessel is opened and the solution is exposed to air, thereby obtaining a modified PATFC membrane grafted with SBMA. This method utilizes UV light to generate hydrated electrons. The membrane surface modified with the coupling solution is then grafted with SBMA via an ARGETATRP reaction mediated by the hydrated electrons, thereby preparing a modified PATFC membrane to resist biofouling. This modification method utilizes hydrated electrons to react with alkyl halides to generate alkyl radicals. The reaction conditions are mild, the reaction time is short, and the reaction process is highly controllable. This method effectively reduces membrane fouling while avoiding the problem of generating hazardous metal ion-containing wastewater due to the use of metal catalysts in the ARGETATRP reaction.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation water treatment, and in particular to a method for modifying a polyamide composite membrane to resist biological fouling by utilizing hydrated electrons. Background Art

[0002] Polyamide composite membrane (PATFC) has become the most widely used reverse osmosis (RO) and nanofiltration membrane material due to its high water flux, salt rejection rate, and chemical stability. Membrane fouling, especially membrane biofouling, is one of the bottlenecks restricting the promotion and application of PATFC membranes. The research and development of anti-fouling membrane materials is the key to controlling membrane fouling, and the preparation and modification of membrane materials based on biological methods are at the forefront of membrane material research. Currently, the main methods for controlling membrane biofouling include pretreatment of raw water, optimization of operating conditions, physical or chemical cleaning, optimization of PATFC membrane preparation conditions, or modification of its surface.

[0003] Atom transfer radical polymerization (ATRP) is often used to modify membrane surface grafted polymers due to its strong controllability, mild reaction conditions, and powerful functions. Atom transfer radical polymerization with electron transfer activation and regeneration catalyst (ARGETATRP) is proposed based on the traditional ATRP reaction. Compared with the traditional ATRP reaction, ARGETATRP reaction reduces the amount of catalyst used and has relatively low requirements for the oxygen-free reaction environment, thereby reducing the difficulty and cost of the reaction. However, the ARGETATRP reaction still has the following problems: (1) Transition metal ions are often used as catalysts. Low-valent transition metal ions can capture the halogen atoms of halogenated hydrocarbons to form free radicals, thereby initiating monomer polymerization; (2) Using metal ions as catalysts may produce harmful wastewater containing metal ions; (3) There are requirements for the reaction environment and the stability of the metal catalyst, and the reaction is relatively difficult. Therefore, it is necessary to improve the ARGETATRP membrane modification method. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for modifying polyamide composite membranes to resist biofouling using hydrated electrons. The method uses hydrated electrons and alkyl halides to generate alkyl free radicals. The reaction conditions are mild, the reaction time is short, and the reaction process is highly controllable. While effectively reducing membrane fouling, the problem of generating harmful wastewater containing metal ions due to the use of metal catalysts is avoided.

[0005] To achieve the above object, the present invention provides a method for modifying a polyamide composite membrane to resist biofouling by utilizing hydrated electrons, comprising the following steps:

[0006] S1. Fix the PATFC membrane into the membrane pool, add coupling solution into the membrane pool, then add sulfite, and after a certain reaction time, pour out the solution in the membrane pool;

[0007] S2. Add the SBMA solution to the membrane pool, then add sulfite and bismuth iodide in sequence, turn on the ultraviolet light for a certain period of time, and then open the reaction container to allow the solution to come into contact with air to obtain a modified PATFC membrane grafted with SBMA.

[0008] Preferably, the method comprises the following steps:

[0009] S1. Fix the PATFC membrane into the membrane pool, add 40 mL of coupling solution into the membrane pool, then add 12 μmol of sulfite, and after a certain reaction time, pour out the solution in the membrane pool;

[0010] S2. Add 100 mL of SBMA solution to the membrane pool, then add 1-1.5 mmol of sulfite and 8-16 μmol of bismuth iodide oxide in sequence, turn on the ultraviolet light for a certain period of time, and then open the reaction container to allow the solution to come into contact with air to obtain a modified PATFC membrane grafted with SBMA.

[0011] Preferably, the PATFC membrane in step S1 is a commercial reverse osmosis membrane, which is soaked in 25% isopropyl alcohol for 30 minutes before use, and then soaked in deionized water for 48 hours, with the water being changed every 12 hours.

[0012] Preferably, the coupling solution in step S1 is a DA-BIBB coupling solution prepared from DA and BIBB.

[0013] Preferably, the DA-BIBB coupling solution is adjusted to pH ≈ 9.0 with a Tris-HCl buffer solution, and the contact time between the DA-BIBB coupling solution and the PATFC membrane is 8-10 min.

[0014] Preferably, the membrane pool in step S1 is a 10 cm×10 cm polytetrafluoroethylene sealed shallow pool with a quartz top cover. During the reaction, the headspace volume above the membrane pool solution is kept as small as possible to reduce reoxygenation caused by air.

[0015] Preferably, the sulfite is one of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite, potassium metabisulfite, sodium metabisulfite, and potassium metabisulfite.

[0016] Preferably, the UV lamp in step S2 is a medium-pressure UV lamp, and the radiated light is filtered through a 220nm UV narrow-band filter to retain ultraviolet light near 220nm. 220nm is the main absorption wavelength of iodide ions. This operation can retain ultraviolet light that can effectively excite iodine ions on the one hand, and on the other hand, it can shield short-wavelength ultraviolet light below 220nm, thereby reducing the aging effect on the membrane surface; the UV intensity on the surface of the reaction solution is 0.05-0.10mJ·cm -2If the UV intensity is too high, it will damage the membrane surface; if it is too low, it will not be conducive to the excitation of iodine ions to produce hydrated electrons; the UV lamp irradiation time is 15-20 minutes. Too long time will cause the solution temperature to rise and the side reactions to increase. Too short time will lead to poor grafting modification effect.

[0017] Preferably, the SBMA in step S2 is of industrial grade purity. Before use, the SBMA is dispersed in a mixed solution of isopropyl alcohol and water in a ratio of 1:1 to ensure uniform addition of the SBMA.

[0018] Preferably, the bismuth iodide in step S2 is commercial bismuth iodide. The slow-release iodide ion property of bismuth iodide enables the solution to maintain a certain iodide ion solubility, and the bismuth iodide particles can scatter ultraviolet light to protect the surface of the film; the bismuth iodide is pretreated by soaking in a sodium chloride solution before addition, and part of the iodide ions in the bismuth iodide structure are replaced with chloride ions to adjust the release rate of iodide ions after the bismuth iodide is added to the reaction solution, thereby adjusting the yield of hydrated electrons; the soaking pretreatment time in the sodium chloride solution is 20 minutes, at which time the iodide ion release rate is about 1 μM·min -1 .

[0019] Therefore, compared with the existing technology, the method of the present invention for modifying polyamide composite membranes to resist biofouling by using hydrated electrons has the following specific beneficial effects:

[0020] (1) The reaction conditions are mild, the reaction time is short, the reagents required are simple, and the main reagent, bismuth iodide (BiOI), can be recycled and regenerated;

[0021] (2) Effectively reducing membrane pollution while avoiding the problem of harmful wastewater containing metal ions caused by the use of metal catalysts;

[0022] (3) The generation of free radicals can be precisely regulated, and the controllability is better. Under the same SBMA concentration conditions, the grafting efficiency is higher.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an XPS (X-ray photoelectron spectroscopy) elemental analysis spectrum of the original PATFC membrane surface in a method for modifying polyamide composite membranes against biofouling using hydrated electrons of the present invention;

[0025] Figure 2 The invention discloses an XPS element analysis spectrum of the surface of a modified PATFC membrane grafted with SBMA, according to a method for modifying a polyamide composite membrane for anti-biological fouling by utilizing hydrated electrons. DETAILED DESCRIPTION

[0026] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for modifying a polyamide composite membrane to resist biofouling by utilizing hydrated electrons comprises the following steps:

[0029] S1. Take a PATFC commercial reverse osmosis membrane as the original membrane. Before use, soak it in 25% isopropanol for 30 minutes, then soak it in deionized water for 48 hours, changing the water every 12 hours. Fix the original membrane in a 10 cm × 10 cm polytetrafluoroethylene sealed shallow membrane pool with a quartz top cover, add 40 mL of DA-BIBB coupling solution (dopamine hydrochloride (DA) coupled with α-bromoisobutyryl bromide (BIBB)) adjusted to pH ≈ 9.0 with Tris-HCl buffer solution, and then quickly add 12 μmol of sodium sulfite to obtain a sodium sulfite solution with a molar concentration of 0.3 mM. Let it stand for 10 minutes, and pour out the solution in the membrane pool.

[0030] S2. Add 100 mL of 8 mg / L industrial-grade sulfobetaine methyl acrylate (SBMA) dispersion solution to the membrane pool. Before use, disperse SBMA in a 1:1 mixed solution of isopropanol and water. Then, add 1.0 mmol of sodium sulfite and 8 μmol of BiOI (iodide ion release rate 1 μM min) to the membrane pool. -1 ), then open the preheated UV lamp baffle, and filter the radiated light through a 220nm UV narrowband filter to retain only the ultraviolet light near 220nm. The UV intensity on the surface of the reaction solution is 0.10mJ·cm -2 The reaction solution was irradiated through the membrane pool for 10 minutes. After the irradiation was completed, the UV lamp baffle was closed to terminate the reaction, thereby obtaining a modified PATFC membrane grafted with SBMA.

[0031] test:

[0032] The original PATFC membrane and the modified PATFC membrane grafted with SBMA were respectively characterized by X-ray photoelectron spectroscopy (XPS) technology. The relevant data are as follows: Figure 1 and Figure 2 As shown in FIG, by comparing the changes in element ratios, it can be seen that the surface grafting rate of the SBMA modified membrane (calculated as the S element ratio) is 1.38%.

[0033] Take the original PATFC membrane and the modified PATFC membrane grafted with SBMA, respectively, and use 106 CFU·mL -1 coli and 0.1% LB culture medium solution were used to conduct a 7-day dynamic filtration experiment on the membrane to test the membrane's anti-biofouling performance. The membrane biofouling situation was characterized by laser confocal observation technology. The surface biological observation data of the original membrane and the modified membrane after the 7-day biofouling test are shown in Table 1 and Table 2, respectively.

[0034] Table 1

[0035]

[0036] Table 2

[0037]

[0038] By comparing the data in the two tables, it can be found that the biofilm on the original membrane surface is mainly composed of live bacteria, while the biofilm on the modified membrane surface has a large proportion of dead bacteria, and the thickness of the biofilm has decreased significantly, which proves that the modification method of the present invention can effectively reduce membrane biofouling.

[0039] Example 2

[0040] Unlike Example 1, the amount of sodium sulfite added to S2 was 1.25 mmol. All other steps and parameters were the same as in Example 1. Surface biofilm observation data for the modified membrane after the 7-day biofouling test are shown in Table 3. Compared to the original membrane (Table 1), both the average biofilm thickness and the viable bacterial biovolume showed significant decreases.

[0041] Table 3

[0042]

[0043] Example 3

[0044] Unlike Example 1, the amount of sodium sulfite added to S2 was 1.5 mmol. All other steps and parameters were the same as in Example 1. Surface biofilm observation data for the modified membrane after the 7-day biofouling test are shown in Table 4. Compared to the original membrane (Table 1), both the average biofilm thickness and the viable bacterial biovolume showed significant decreases.

[0045] Table 4

[0046]

[0047] Example 4

[0048] Unlike Example 1, the amount of bismuth iodide added to S2 was 12 μmol. All other steps and parameters were the same as in Example 1. Surface biofilm observation data for the modified membrane after the 7-day biofouling test are shown in Table 5. Compared to the original membrane (Table 1), both the average biofilm thickness and the viable bacterial biovolume showed significant decreases.

[0049] Table 5

[0050]

[0051] Example 5

[0052] Unlike Example 1, the amount of bismuth iodide added to S2 was 16 μmol. All other steps and parameters were the same as in Example 1. Surface biofilm observation data for the modified membrane after the 7-day biofouling test are shown in Table 6. Compared to the original membrane (Table 1), both the average biofilm thickness and the viable bacterial biovolume showed significant decreases.

[0053] Table 6

[0054]

[0055] Therefore, the present invention provides a method for modifying polyamide composite membranes to resist biological fouling using hydrated electrons. This method uses hydrated electrons and alkyl halides to generate alkyl free radicals. The reaction conditions are mild, the reaction time is short, and the reaction process is highly controllable. It can effectively reduce membrane fouling and avoid the problem of generating harmful wastewater containing metal ions due to the use of metal catalysts.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for modifying polyamide composite membranes to resist biofouling by utilizing hydrated electrons, characterized in that: The following steps are involved: S1. Fix the polyamide composite membrane into the membrane pool, add 40 mL of coupling solution into the membrane pool, then add 12 μmol of sulfite, and after a certain reaction time, pour out the solution in the membrane pool; The coupling solution is a dopamine hydrochloride-α-bromoisobutyryl bromide coupling solution prepared from dopamine hydrochloride and α-bromoisobutyryl bromide, and the dopamine hydrochloride-α-bromoisobutyryl bromide coupling solution is adjusted to pH ≈ 9.0 with a Tris-HCl buffer solution; S2. Add 100 mL of sulfobetaine methyl acrylate solution to the membrane pool, then add 1-1.5 mmol of sulfite and 8-16 μmol of bismuth iodide oxide in sequence, turn on the ultraviolet light for a certain period of time to generate hydrated electrons, and then open the reaction container to allow the solution to come into contact with air to obtain a modified polyamide composite membrane grafted with sulfobetaine methyl acrylate.

2. The method for modifying a polyamide composite membrane to resist biofouling by utilizing hydrated electrons according to claim 1, characterized in that: The polyamide composite membrane in step S1 is a commercial reverse osmosis membrane, which is soaked in 25% isopropyl alcohol for 30 minutes before use, and then soaked in deionized water for 48 hours, with the water being changed every 12 hours.

3. The method for modifying polyamide composite membranes to resist biofouling by utilizing hydrated electrons according to claim 1, characterized in that: The contact time between the dopamine hydrochloride-α-bromoisobutyryl bromide coupling solution and the polyamide composite membrane is 8-10 minutes.

4. The method of claim 1 for resisting biological contamination of polyamide composite membranes by utilizing hydrated electrons. The modification method is characterized by: In step S1, the membrane pool is a 10 cm×10 cm polytetrafluoroethylene sealed shallow pool with a quartz top cover.

5. The method for modifying polyamide composite membranes to resist biofouling by utilizing hydrated electrons according to claim 1, characterized in that: The sulfite is one of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, sodium pyrosulfite, potassium pyrosulfite, sodium pyrobisulfite, and potassium pyrobisulfite.

6. The method for modifying polyamide composite membranes to resist biofouling by utilizing hydrated electrons according to claim 1, characterized in that: The UV lamp in step S2 is a medium-pressure UV lamp, and the radiated light is filtered through a 220nm UV narrow-band filter to retain ultraviolet light near 220nm. The UV intensity on the surface of the reaction solution is 0.05-0.10mJ·cm -2 , the UV lamp irradiation time is 15-20min.

7. The method for modifying polyamide composite membranes to resist biofouling by utilizing hydrated electrons according to claim 1, characterized in that: The sulfobetaine methyl acrylate in step S2 is of industrial grade purity. Before use, the sulfobetaine methyl acrylate is first dispersed in a mixed solution of isopropyl alcohol and water in a ratio of 1:

1.

8. The method for modifying polyamide composite membranes to resist biofouling by utilizing hydrated electrons according to claim 1, characterized in that: The bismuth iodide oxide in step S2 is commercial bismuth iodide oxide, and the bismuth iodide oxide is pretreated by soaking in a sodium chloride solution for 20 minutes before use.

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