AU2021104808A4

AU2021104808A4 - Ultrafiltration membrane having hydrophilic and antibacterial properties and preparation method thereof

Info

Publication number: AU2021104808A4
Application number: AU2021104808A
Authority: AU
Inventors: Yanjun Chen; Zhenbo Peng; Jiahao ZHOU
Original assignee: Ningbo Polytechnic
Current assignee: Ningbo Polytechnic
Priority date: 2021-02-01
Filing date: 2021-08-02
Publication date: 2021-09-30
Anticipated expiration: 2029-08-02
Also published as: CN112933977A; CN112933977B

Abstract

OF THE DISCLOSURE The present disclosure relates to a high-flux ultrafiltration membrane having hydrophilic and antibacterial properties and a preparation method thereof, and belongs to the technical field of polymeric membrane materials. The ultrafiltration membrane is prepared by dissolving a membrane-forming polymer and a pore-forming agent into an organic solvent to obtain a casting solution, forming a membrane with a phase transformation method and storing the membrane in a wet state; and the casting solution is composed of the following components by mass percent: 16-20% of the polymer, 1-8% of povidone iodine (PVPI) and 72-83% of the organic solvent. The present disclosure uses the PVPI as the pore-forming agent and the antibacterial agent. During membrane formation, the PVPI is dissolved in the non-organic solvent to form a great number of pores in the membrane. And meanwhile, owing to the complexiation between the PVPI and the polymer, a part of the PVPI is migrated to the surface of the membrane during the phase transformation, such that the membrane achieves the antibacterial property. As a part of the PVPI is lost during membrane filtration, the membrane may be immersed into the PVPI aqueous solution for a certain time to restore the PVPI content on the surface of the membrane. The method is simple and practicable, and can be industrially applied to protein concentration or wastewater biotreatment. ABSTRACT DRAWING - FIG 3 10 17931816_1 (GHMatters) P116903.AU - 1/2 FIG 1 SPI 4% FWI l Number of waves (cm-) FIG 2 17931803_1 (GHMatters) P116903.AU

Description

- 1/2

FIG 1

SPI

4% FWIl

Number of waves (cm-)

FIG 2

17931803_1 (GHMatters) P116903.AU

ULTRAFILTRATION MEMBRANE HAVING HYDROPHILIC AND ANTIBACTERIAL PROPERTIES AND PREPARATION METHOD THEREOF TECHNICAL FIELD

[01] The present disclosure relates to a high-flux ultrafiltration membrane having hydrophilic and antibacterial properties and a preparation method thereof, and belongs to the technical field of polymeric membrane materials.

BACKGROUNDART

[02] Polyethersulfone (PES), polyvinylidene fluoride (PVDF) and polysulfone (PSF) are typically used as preferred materials of ultrafiltration membranes because of such excellent properties as the high temperature resistance, acid and alkali resistance and high mechanical strength. However, due to the inherent hydrophobicity of these materials, the prepared ultrafiltration membranes are easily polluted by the proteins, humic acids, bacteria and so on, thereby reducing the separating property and increasing the operation cost. Accordingly, at present, the ultrafiltration membranes are often hydrophilically modified by blending, coating, photo-grafting and other manners.

[03] In order to improve the porosity of the separation membrane, water-soluble small organic molecules are necessarily added to a casting solution to serve as a pore-foaming agent. The common pore-foaming agents include polyethylene glycol (PEG)-400, PEG-600 and polyvinylpyrrolidone (PVP)-K30, all of which are dissolved into a non-organic solvent during phase transformation to form pores of a certain size in the membrane. A patent for invention with the application No. CN202010411513.7 discloses a PVDF flat sheet ultrafiltration membrane and a preparation method thereof, where a casting solution includes 80-90 parts of a PVDF membrane substrate, 10-20 parts of a modifier formed by a polyethylene glycol polymer (PEG) and N-vinylpyrrolidone (PVP), 5-10 parts of N,N-methylenebisacrylamide and 1-5 parts of ceric ions. The casting process uses the PEG and the PVP together to serve as the pore-forming agent, with the content up to 10-20%, such that the obtained ultrafiltration membrane achieves the desirable permeability and pollution resistance; and moreover, since the ultrafiltration membrane is modified with a photo-grafting technology during preparation, the illumination time is very demanding and any deviation will reduce the flux of the ultrafiltration membrane obviously. A patent for invention with the application No. CN202010521728.4 provides a biological nano-silver antibacterial ultrafiltration membrane and a preparation method thereof. The method prepares the biological nano-silver antibacterial ultrafiltration membrane with a phase transformation method by adding bio-silver to the casting solution, stirring the bio-silver to completely disperse, and carrying out

17931816_1 (GHMatters) P116903.AU standing and defoaming. The prepared ultrafiltration membrane has the good antibacterial ability, the silver particles are highly stable, the whole preparation process is simple, the materials are environment-friendly and non-toxic, and the service life of the product is long. However, due to the dispersibility, the bio-silver is aggregated easily in the interior and on the surface of the membrane to reduce the separating property of the membrane; and the nanoparticles are not cost-effective. Therefore, there is an urgent need to develop an ultrafiltration membrane having a high flux, a high retention rate, and hydrophilic and antibacterial properties, etc.

SUMMARY

[04] In view of the above problems in the prior art, an objective of the present disclosure is to provide an ultrafiltration membrane having a high flux, a high retention rate, and hydrophilic and antibacterial properties and a preparation method thereof. The ultrafiltration membrane has the excellent protein adsorption resistance and antibacterial ability.

[05] The objective of the present disclosure can be achieved by the following technical solutions.

[06] An ultrafiltration membrane having hydrophilic and antibacterial properties is prepared by dissolving a membrane-forming polymer and a pore-forming agent into an organic solvent to obtain a casting solution, forming a membrane with a phase transformation method and storing the membrane in a wet state; and the casting solution is composed of the following components by mass percent: 16-20% of the polymer, 1-8% of povidone iodine (PVPI) and 72-83% of the organic solvent.

[07] The PVPI serves as a broad-spectrum disinfectant, and its main disinfection principle is to oxidize the damage. It can release free iodine slowly in water. The free iodine can be binded to amino acids of bacterial proteins for modification, and can further oxidize such active groups as SH-, OH- and NH- and the double bond of unsaturated fatty acids in the bacterial protein, thereby inactivating the microbes, killing the microbes, inhibiting the microbial reproduction and releasing toxins. The PVP-I is water-soluble as a complex of PVP and iodine. The iodide ions are binded to the PVP firmly through complexation and are released continuously, such that the antibacterial effect can be kept for a long time. Additionally, the present disclosure has a PVPI content of 1-8%. With the increase of the PVPI content, the membrane properties are improved. However, when the PVPI content increases to a certain amount (8% in the present disclosure), the membrane properties are reduced with the increase of the PVPI content. This is mainly because when the PVPI content increases to a certain degree, the viscosity of the casting solution increases greatly to become adverse to the membrane formation, and the sublayers on sectional structures of the prepared membrane have a lot of pores to sharply decrease the mechanical strength of the membrane and 2 17931816_1 (GHMatters) P116903.AU reduce the separating property and the protein adsorption resistance.

[08] Preferably, the polymer may be selected from one or more of the group consisting of PSF, PES and PVDF.

[09] Preferably, the polymer may be18-20% by mass percent.

[10] Preferably, the organic solvent may be one or more of the group consisting of N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF) and N-methylpyrrolidinone (NMP).

[11] A second objective of the present disclosure is to provide a method for preparing the ultrafiltration membrane, including the following steps:

[12] 1) adding, according to the above mass percent, the PVPI to the organic solvent to be fully dissolved, adding the polymer for dissolving to form a polymer/solvent/pore-forming agent ternary casting solution, and carrying out sealing, standing and defoaming, thereby obtaining the casting solution; and

[13] 2) filtering the completely defoamed casting solution, coating a resulting casting solution on a glass plate, putting the glass plate coated with the casting solution into pure water, forming the membrane with the phase transformation method and storing the prepared membrane in the wet state.

[14] Preferably, the polymer may be stirred for 30-60 min when dissolved.

[15] Preferably, a temperature of the ternary casting solution may be kept at 60-80°C during the sealing, standing and defoaming, and the time for the sealing, standing and defoaming may last for 12-24 h.

[16] Preferably, the casting solution may have a coated thickness of 0.15-0.25 mm on the glass plate. With control of the thickness within this range, it is ensured that the prepared membrane has the basic mechanical strength, and the flux of the membrane is within the reasonable range. If the casting solution is too thin, the mechanical strength of the prepared membrane is not enough; and if the coated casting solution is too thick, the prepared membrane has the small flux.

[17] Preferably, a membrane preparation chamber may be controlled at a relative humidity of -55% and a temperature of 25°C in the process of forming the membrane with the phase transformation method. When the ultrafiltration membrane is prepared by the phase transformation, the humidity in the membrane preparation chamber must be controlled. The high humidity will result in the coagulation of the pristine membrane in the air to affect the separating property of the membrane, while the low humidity will result in the high energy consumption.

[18] Compared with the prior art, the present disclosure has the following beneficial technical effects:

[19] (1) The present disclosure uses the PVPI as the pore-forming agent and the antibacterial 3 17931816_1 (GHMatters) P116903.AU agent. During membrane formation, the PVPI is dissolved in the non-organic solvent to form a great number of pores in the membrane; and meanwhile, owing to the complexiation between the PVPI and the polymer, a part of the PVPI is migrated to the surface of the membrane during the phase transformation, such that the membrane achieves the antibacterial property.

[20] (2) As a part of the PVPI is lost during membrane filtration, the membrane may be immersed into the PVPI aqueous solution for a certain time to restore the PVPI content on the surface of the membrane. The method is simple and practicable, and can be industrially applied to protein concentration or wastewater biotreatment.

BRIEF DESCRIPTION OF THE DRAWINGS

[21] FIG. 1 shows pictures of membranes prepared in Examples 1-4 and Comparative Example 1.

[22] FIG. 2 shows Fourier Transform Infrared Spectroscopy (FTIR) pictures of membranes prepared in Examples 1-4 and Comparative Example 1.

[23] FIG. 3 shows an antibacterial effect picture of a membrane prepared in Example 1 for escherichia coli.

[24] FIG. 4 shows an antibacterial effect picture of a membrane prepared in Comparative Example 1 for escherichia coli.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[25] The technical solutions of the present disclosure are further described below with reference to the specific examples, but the present disclosure is not limited thereto. Unless otherwise specifically stated, parts used in the examples of the present disclosure are all common parts in the art, and methods used in the examples are all common methods in the art.

[26] Example 1

[27] Based on the mass percent, the composite membrane was prepared with 18% of PS as a membrane material, 74% of DMF as an organic solvent, and 8% of PVPI as a pore-forming agent and an antibacterial agent.

[28] According to the above mass percent, the PVPI was dissolved in the DMF, the PS was added and stirred for 40 min at a room temperature for dissolving, and the resulting solution was allowed to seal, stand and defoam for 18h at 70°C; a certain amount of casting solution was spread onto a glass plate with a scraping knife; the completely defoamed casting solution was filtered, and coated on the glass plate by an automatic membrane scraping machine, with a thickness of 0.20 mm; and then, the glass plate coated with the casting solution was put into pure water and formed into the membrane with the phase transformation method, the membrane preparation chamber being 4 17931816_1 (GHMatters) P116903.AU controlled at a relative humidity of 50% and a temperature of 25°C.

[29] The prepared membrane was put into running water for 24 h or more to completely remove the organic solvent in the membrane, and the newly-prepared antibacterial film was used to test its antibacterial property for escherichia coli. The results reveal that the membrane has an antibacterial rate of up to 99% for the escherichia coli. Under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 186 L/m 2h, and a retention rate of 99% for 1 g/ lipid-bound sialic acid (LBSA).

[30] Example 2

[31] Based on the mass percent, the composite membrane was prepared with 17% of PVDF as a membrane material, 72-83% of DMF as an organic solvent, and 4% of PVPI as a pore-forming agent and an antibacterial agent.

[32] According to the above mass percent, the PVPI was dissolved in the DMF, the PVDF was added and stirred for 50 min at a room temperature for dissolving, and the resulting solution was allowed to seal, stand and defoam for 14 h at 65°C; a certain amount of casting solution was spread onto a glass plate with a scraping knife; the completely defoamed casting solution was filtered, and coated on the glass plate by an automatic membrane scraping machine, with a thickness of 0.22 mm; and then, the glass plate coated with the casting solution was put into pure water and formed into the membrane with the phase transformation method, the membrane preparation chamber being controlled at a relative humidity of 52% and a temperature of 25°C.

[33] The prepared membrane was put into running water for 24 h or more to completely remove the organic solvent in the membrane, and the newly-prepared antibacterial film was used to test its antibacterial property for pseudomonas aeruginosa. The results reveal that the membrane has an antibacterial rate of up to 99% for the pseudomonas aeruginosa. Under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 151 L/m 2 h, and a retention rate of 98% for 1 g/LBSA.

[34] Example 3

[35] Based on the mass percent, the composite membrane was prepared with 16% of PES as a membrane material, 82% of NMP as an organic solvent, and 2% of PVPI as a pore-forming agent and an antibacterial agent.

[36] According to the above mass percent, the PVPI was dissolved in the NMP, the PES was added and stirred for 60 min at a room temperature for dissolving, and the resulting solution was allowed to seal, stand and defoam for 24 h at 80°C; a certain amount of casting solution was spread onto a glass plate with a scraping knife; the completely defoamed casting solution was filtered, and coated on the glass plate by an automatic membrane scraping machine, with a thickness of 0.15 mm; and then, the glass plate coated with the casting solution was put into pure water and formed into 5 17931816_1 (GHMatters) P116903.AU the membrane with the phase transformation method, the membrane preparation chamber being controlled at a relative humidity of 55% and a temperature of 25°C.

[37] The prepared membrane was put into running water for 24 h or more to completely remove the organic solvent in the membrane, and the newly-prepared antibacterial film was used to test its antibacterial property for escherichia coli and pseudomonas aeruginosa. The results reveal that the membrane has an antibacterial rate of up to 99% for the escherichia coli and the pseudomonas aeruginosa. Under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 134 L/m 2 h, and a retention rate of 97.5% for 1 g/LBSA.

[38] Example 4

[39] Based on the mass percent, the composite membrane was prepared with 20% of PVDF as a membrane material, 79% of DMAC as an organic solvent, and 1% of PVPI as a pore-forming agent and an antibacterial agent.

[40] According to the above mass percent, the PVPI was dissolved in the DMAC, the PVDF was added and stirred for 30 min at a room temperature for dissolving, and the resulting solution was allowed to seal, stand and defoam for 12 h at 60°C; a certain amount of casting solution was spread onto a glass plate with a scraping knife; the completely defoamed casting solution was filtered, and coated on the glass plate by an automatic membrane scraping machine, with a thickness of 0.25 mm; and then, the glass plate coated with the casting solution was put into pure water and formed into the membrane with the phase transformation method, the membrane preparation chamber being controlled at a relative humidity of 45% and a temperature of 25°C.

[41] The prepared membrane was put into running water for 24 h or more to completely remove the organic solvent in the membrane, and the newly-prepared antibacterial film was used to test its antibacterial property for escherichia coli. The results reveal that the membrane has an antibacterial rate of up to 99% for the escherichia coli. Under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 121 L/m2h, and a retention rate of 98% for 1 g/LBSA.

[42] Comparative Example 1

[43] The difference from Example 1 merely lies in: The casting solution does not contain the PVPI, but other components and formulas of the casting solution and the membrane-forming method are the same as Example 1. Under the operating pressure of 0.2 MPa, the prepared ultrafiltration membrane shows a pure water flux of 56 L/m 2 h, a retention rate of 79% for 1 g/LBSA, and no antibacterial property for the escherichia coli.

[44] Comparative Example 2

[45] The difference from Example 1 merely lies in: The casting solution has a coated thickness of 0.35 mm on the glass plate. By testing the antibacterial property of the newly-prepared antibacterial film for the escherichia coli, results reveal that the membrane has an antibacterial rate 6 17931816_1 (GHMatters) P116903.AU of 97% for the escherichia coli; and under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 104 L/m 2 h, and a retention rate of 92% for 1 g/LBSA.

[46] Comparative Example 3

[47] The difference from Example 1 merely lies in: The membrane preparation chamber has a relative humidity of 60% when the membrane is formed with the phase transformation method. By testing the antibacterial property of the newly-prepared antibacterial film for the escherichia coli, results reveal that the membrane has an antibacterial rate of 93% for the escherichia coli; and under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 118 L/m 2h, and a retention rate of 93% for 1 g/LBSA.

[48] Comparative Example 4

[49] The difference from Example 1 merely lies in: The addition amount of the PVPI in the casting solution is 10%. By testing the antibacterial property of the newly-prepared antibacterial film for the escherichia coli, results reveal that the membrane has an antibacterial rate of 98% for the escherichia coli; and under the operating pressure of 0.2 MPa, the membrane shows a pure water flux of 109 L/m 2 h, and a retention rate of 91% for 1 g/LBSA.

[50] Any non-exhaustive descriptions on values of the example within the technical scope of the present disclosure and new technical solutions formed by making an equivalent replacement for one or more technical features in the technical solutions of the example also fall within the scope of protection of the present disclosure; and unless otherwise specifically stated, all parameters involved in the solutions of the present disclosure do not form an irreplaceable unique combination to each other.

[51] Although the present disclosure has been described in detail and some specific examples are cited, it is apparent to those skilled in the art that various changes or modifications may be made without departing from the spirit and scope of the present disclosure.

[52] It is to be understood that, if any prior art publication is referred to herein, such reference

does not constitute an admission that the publication forms a part of the common general

knowledge in the art, in Australia or any other country.

[531 In the claims which follow and in the preceding description of the invention, except where

the context requires otherwise due to express language or necessary implication, the word

"comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to

specify the presence of the stated features but not to preclude the presence or addition of further

features in various embodiments of the invention.

7 17931816_1 (GHMatters) P116903.AU

Claims

WHAT IS CLAIMED IS:

S1. An ultrafiltration membrane having hydrophilic and antibacterial properties, wherein the ultrafiltration membrane is prepared by dissolving a membrane-forming polymer and a pore-forming agent into an organic solvent to obtain a casting solution, forming a membrane with a phase transformation method and storing the membrane in a wet state; wherein the casting solution is composed of the following components by mass percent: 1 6 - 2 0 % of the polymer, 1- 8 % of povidone iodine (PVPI) and 72-83% of the organic solvent.
2. The ultrafiltration membrane according to claim 1, wherein the polymer is selected from one or more of the group consisting of polysulfone (PSF), polyethersulfone (PES) and polyvinylidene fluoride (PVDF).
3. The ultrafiltration membrane according to claim 1, wherein the polymer is 18-20% by mass percent.
4. The ultrafiltration membrane according to claim 1, wherein the organic solvent is one or more of the group consisting of N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF) and N-methylpyrrolidinone (NMP).
5. A method for preparing the ultrafiltration membrane according to claim 1, wherein the preparation method comprises the following steps: 1) adding, according to the above mass percent, the PVPI to the organic solvent to be fully dissolved, adding the polymer for dissolving to form a polymer/solvent/pore-forming agent ternary casting solution, and carrying out sealing, standing and defoaming, thereby obtaining the casting solution; and 2) filtering the completely defoamed casting solution, coating a resulting casting solution on a glass plate, putting the glass plate coated with the casting solution into pure water, forming the membrane with the phase transformation method and storing the prepared membrane in the wet state; wherein the polymer is stirred for 30-60 min when dissolved; wherein a temperature of the ternary casting solution is kept at 60-80°C during the sealing, standing and defoaming, and the time for the sealing, standing and defoaming lasts for 12-24 h; wherein the casting solution has a coated thickness of 0.15-0.25 mm on the glass plate; wherein a membrane preparation chamber is controlled at a relative humidity of 45-55% and a 8 17931816_1 (GHMatters) P116903.AU temperature of 25°C in the process of forming the membrane with the phase transformation method.

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FIG. 1

FIG. 2

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FIG. 3

FIG. 4

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