KR20230088624A - Method of Fabricating Anti-fouling Membranes using Biocidal Surfactants - Google Patents

Abstract

The present invention relates to a method for imparting antibacterial and fouling resistance to water treatment and seawater desalination membranes vulnerable to contamination by using a surfactant having antibacterial properties as an additive.

Description

Method of manufacturing fouling-resistant separators using surfactants with antibacterial properties {Method of Fabricating Anti-fouling Membranes using Biocidal Surfactants}

The present invention relates to a method for manufacturing a fouling-resistant separation membrane using a surfactant having antibacterial properties.

Among various separation technologies that can secure clean water/energy resources through water purification, water treatment membrane technology has the advantage of high integration and high process efficiency because it enables continuous processing.

A thin film composite (TFC) separator used in such a water treatment process is manufactured by synthesizing a selective layer through interfacial polymerization between two organic monomers dissolved in a mutually insoluble solvent on a porous polymer support. Therefore, the TFC separator has a form in which a polymer support responsible for mechanical strength and a selective layer responsible for separation performance are combined. The TFC membrane has the advantage of low manufacturing cost and easy large-area manufacturing, so it is used in various process fields such as water treatment, food and bio product purification, valuable metal recovery, and heavy metal removal.

During the process of such a separation membrane, various substances accumulate on the surface of the membrane and cause contamination. In particular, biofouling by microorganisms such as bacteria causes the most serious contamination. Since such membrane fouling impairs permeability of the separation membrane, process efficiency is reduced and overall water treatment process costs are increased.

In order to solve this problem, attempts have been made to coat or graft a hydrophilic or antibacterial material on the surface of the selective layer (Patent Document 1). However, this method of reforming the separator may reduce the separation performance of the separator, and since a modification process must be added to the existing separator manufacturing process, there is a problem in that the manufacturing cost of the separator is increased.

1. 20150137408

Membrane contamination by microorganisms in the membrane process is a major cause of lowering process efficiency and increasing process cost. In order to reduce membrane fouling, a method of coating or grafting a hydrophilic and antibacterial material on the surface of a separator has been proposed, but there is a problem of reducing the performance of the separator or increasing the manufacturing cost.

In order to solve this problem, an object of the present invention is to manufacture a separator excellent in antibacterial property and fouling resistance through a method of simply adding an antimicrobial surfactant when preparing a selective layer of a thin film composite separator.

The present invention includes the steps of impregnating or applying a first solution containing a first organic monomer, a first solvent and an antimicrobial surfactant on a porous support;

impregnating or applying a second solution containing a second organic monomer and a second solvent; and

Forming a selective layer through interfacial polymerization between a first organic monomer and a second organic monomer dissolved in the first solution and the second solution, respectively;

The antimicrobial surfactant is benzalkonium chloride (BAC), and a method for manufacturing a thin film composite separator is provided.

The TFC separation membrane according to the present invention can exhibit excellent fouling resistance by reducing membrane fouling by microorganisms by expressing antimicrobial properties by the uniformly impregnated antimicrobial surfactant.

The antibacterial surfactant is present at the interface and can be effectively impregnated into the selective layer during interfacial polymerization, so that the separation performance of the membrane is not reduced. In addition, since it is a technology of simply adding the antimicrobial surfactant to the solvent used in the existing process, there is little increase in process cost. Therefore, unlike conventional strategies for manufacturing fouling-resistant separation membranes, fouling-resistant TFC membranes can be manufactured in a simple manner without reducing performance and increasing process costs.

In addition, since the present invention uses a polyacrylonitrile (PAN) ultrafiltration membrane with excellent solvent resistance as a porous support, it can be widely used in wastewater treatment and organic solvent purification processes.

1 shows a schematic diagram of manufacturing an antibacterial surfactant-added TFC separator using interfacial polymerization.
2 shows the surface structure of the TFC separator prepared in Example.
3 shows normalized water permeability results for evaluation of fouling resistance performance and surface confocal laser scanning microscope (CLSM) images of the TFC separator after evaluation.

The inventors of the present invention prepared a thin film composite (TFC) separator by adding an antimicrobial surfactant during the separator manufacturing process in order to solve the problem of membrane contamination without using an additional process and without causing a decrease in membrane performance.

A method for manufacturing a TFC separator according to the present invention includes impregnating or applying a first solution containing a first organic monomer, a first solvent, and an antimicrobial surfactant on a porous support;

impregnating or applying a second solution containing a second organic monomer and a second solvent; and

and forming a selective layer through interfacial polymerization between the first organic monomer and the second organic monomer dissolved in the first solution and the second solution, respectively.

Here, the antimicrobial surfactant may be benzalkonium chloride (BAC).

Hereinafter, the manufacturing method of the TFC separator of the present invention will be described in detail.

The TFC separator of the present invention includes a porous support; and a selection layer formed on the porous support, which can be prepared by forming a selection layer on the porous support.

In the present invention, the porous support supports the selective layer and serves to reinforce the mechanical strength of the TFC separator.

Such a porous support may be used by using a commercially available product or synthesized. The porous support is polyacrylonitrile (PAN), polysulfone, polyethylene, polypropylene, polyacetylene, polyisobutylene, polyvinylchloride ), Teflon (polytetrafluoroethylene), polyphenylene sulfide, polyethersulfone, polystyrene, polydimethylsiloxane, polyvinylfluoride, polyvinylalcohol, Formed from one or more polymers selected from the group consisting of polybenzimidazole, polyvinylpyrrolidone, polyetherimide, polyvinylidenefluoride and polyetheretherketone It can be.

In one embodiment, the thickness of the porous support is not particularly limited, and may be, for example, 1 to 1,000 μm, 5 to 200 μm, 10 to 150 μm, or 20 to 70 μm. In the above thickness range, excellent performance as a TFC separator can be realized. Even with a thickness exceeding 1,000 μm, it has physical properties and performance that can be used as a TFC separator, but it may increase manufacturing cost along with a decrease in water permeability, so it is preferable to adjust the thickness to 1 to 1,000 μm.

In one embodiment, the porous support may have an average pore size of 1 nm to 100 μm, 1 to 200 nm, or 10 to 100 nm. Since the density of the selective layer does not decrease within the average pore size range, a TFC separation membrane having excellent salt rejection and fouling resistance can be manufactured. If the average pore size exceeds 100 μm, pinhole defects may occur in the selective layer, resulting in a decrease in salt removal rate.

In one embodiment, the surface porosity of the porous support may be 10 to 90%, 20 to 70%, 30 to 70%, 40 to 70%, or 50 to 70%. In this range, the permeate flow rate is excellent, and the strength of the support is excellent.

In the present invention, the selective layer is formed on a porous support, and is made of cross-linked or non-cross-linked polyamide, polypiperazine-amide, polyester, polyurethane, or polyvinyl. It may be an alcohol, polyimide, or polyetherimide, and may have a fully aromatic, partially aromatic, or fully aliphatic chemical structure.

In one embodiment, the thickness of the selective layer may be 1 to 10000 nm.

In the present invention, the optional layer may be prepared by interfacial polymerization.

The preparation of the selective layer by interfacial polymerization may include impregnating or applying a first solution containing a first organic monomer, a first solvent, and an antibacterial surfactant on a porous support;

impregnating or applying a second solution containing a second organic monomer and a second solvent; and

and forming a selective layer through interfacial polymerization between the first organic monomer and the second organic monomer dissolved in the first solution and the second solution, respectively.

In one embodiment, the type of the first organic monomer is not particularly limited, for example, m -phenylenediamine ( m -phenylenediamine, MPD), o -phenylenediamine ( o -phenylenediamine), p -phenylene Diamine ( p -phenylenediamine), piperazine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, methanediamine, polyethyleneimine, It may be at least one selected from the group consisting of o -dihydroxybenzene, m -dihydroxybenzene, p - dihydroxybenzene , and polyvinyl alcohol.

In one embodiment, the type of the first solvent is not particularly limited, and for example, water, methanol, ethanol, propanol, butanol, isopropanol, acetone ), tetrahydrofuran, and dimethyl sulfoxide.

In one embodiment, the first organic monomer in the first solution may be included in an amount of 0.1 to 10% by weight or 1 to 5% by weight.

In one embodiment, an antimicrobial surfactant may be included in the first solution as an additive.

Surfactant is an amphoteric substance that has a hydrophilic head and a hydrophobic tail at the same time, and can lower interfacial tension and control the characteristics of interfacial reaction by spontaneously existing at the interface where mutually insoluble solvents face each other. In addition, when the selective layer is formed by interfacial polymerization, the surfactant is impregnated into the selective layer, so that the physicochemical properties of the surfactant can be imparted to the selective layer of the TFC separator.

The antimicrobial surfactant may be benzalkonium chloride (BAC).

Benzalkonium chloride (BAC) is a surfactant having a hydrophilic quaternary ammonium head and a hydrophobic tail of two aliphatic carbon chains and a benzene ring, and exhibits high antibacterial activity against bacteria due to quaternary ammonium. That is, benzalkonium chloride is involved in interfacial polymerization to be introduced into the selective layer and imparted with antibacterial properties, thereby producing a TFC separation membrane with excellent fouling resistance against microorganisms.

In one embodiment, the concentration of the antimicrobial surfactant in the first solution may be 1 to 1000 mM, 5 to 500 mM, or 10 to 300 mM.

In one embodiment, the type of the second organic monomer is not particularly limited, and may be, for example, a molecule having an acyl chloride terminal group, preferably trimesoyl chloride (TMC), terephthaloyl chloride (terephthaloyl chloride), cyclohexane-1,3,5-tricarbonyl chloride, 1-isocyanato-3,5-benzenedicarbonyl chloride (1-isocyanato -3,5-benzenedicarbonyl chloride) and isophthaloyl chloride (isophthaloyl chloride) may be at least one selected from the group consisting of.

In addition, in one embodiment , the type of the second solvent is not particularly limited, and for example, n -hexane, pentane, cyclohexane, heptane, octane ), decane, dodecane, carbon tetrachloride, benzene, toluene and xylene.

In one embodiment, the second organic monomer may be included in 0.01 to 4% by weight or 0.1 to 2% by weight.

In the present invention, the above-described first solution includes an amine monomer, and the second solution includes an acyl chloride monomer, and the polyamide selective layer may be synthesized through interfacial polymerization between the monomers.

In one embodiment, a step of adjusting the content of the first organic monomer on the porous support may be further included. The above step is to remove the excess first solution from the surface of the porous support, and the excess solution can be removed using an air gun or a roller, or by nitrogen washing.

In addition, the manufacturing method according to the present invention may further include a step of washing after forming the selective layer.

In addition, the present invention relates to a TFC separator manufactured by the above-described method for manufacturing a TFC separator.

The TFC membrane according to the present invention has high water permeability and excellent salt rejection. In addition, excellent antibacterial properties and antifouling properties can be imparted through the use of antimicrobial surfactants.

These TFC membranes can be applied to forward osmosis (FO), pressure assisted osmosis, pressure-retarded osmosis, nanofiltration and reverse osmosis (RO) processes. can

In one embodiment, when the thin film composite separator is applied to the RO process, the process pressure may be 15 to 50 bar. In addition, under the conditions of a flow rate of 1 L min ^-1 , pressure of 15.5 bar, and 2,000 ppm of NaCl aqueous solution, the water permeability is 1 to 5 L m ^-2 h ^-1 bar ^-1 or 1.5 to 5 L m ^-2 h ^-1 bar ^{- 1} , and the salt (NaCl) removal rate may be 90% or more, 95% or more, or 98% or more.

Example

[Reference] Material

As a porous support, a porous PAN ultrafiltration membrane having an average pore size of about 20 nm and a thickness of about 50 μm was used.

Water is used as the first solvent of the first solution, m -phenylenediamine (MPD) is used as the first monomer, and n - hexane is used as the second solvent of the second solution . and trimesoyl chloride (TMC) was used as the second monomer.

In addition, a surfactant was used as an additive.

Example 1. Preparation of Separator

As shown in FIG. 1, a uniform high-density selective layer containing BAC was synthesized using interfacial polymerization on a porous support.

1) A first solution was prepared by dissolving 2 w/v% and 10 mM of MPD monomer and BAC monomer in water, respectively, and impregnating the surface of the porous support with the first solution for 10 minutes.

2) After the excess first solution on the surface of the porous support is removed by nitrogen washing, a second solution in which TMC is dissolved in n -hexane solvent at 0.1 w/v% is impregnated to synthesize a polyamide selective layer through interfacial polymerization did

3) Unreacted TMC monomer on the surface of the selective layer was washed with n -hexane solvent, dried at room temperature for 3 minutes, and then crosslinked in an oven at 70 °C for 5 minutes.

Comparative Example 1.

A separator was prepared in the same manner as in Example 1, except that no additives were used.

Comparative Example 2.

A separator was prepared in the same manner as in Example 1, except that sodium dodecyl sulfate (SDS) was used as an additive.

Comparative Example 3.

A separator was prepared in the same manner as in Example 1, except that dodecyltrimethylammonium chloride (DTAB) was used as an additive.

Comparative Example 4.

A separator was prepared in the same manner as in Example 1, except that steartrimonium chloride (CTAB) was used as an additive.

Comparative Example 5.

A separator was prepared in the same manner as in Example 1, except that didodecyldimethylammonium bromide (DDAB) was used as an additive.

Comparative Example 6.

A separator was prepared in the same manner as in Example 1, except that octenidine dihydrochloride (OCT) was used as an additive.

Comparative Example 7.

A commercial reverse osmosis membrane, Hydranautics/Nitto Denko's SWC4+ membrane was used.

Experimental Example 1. Observation of membrane structure

The structures of the separators prepared in Example 1 and Comparative Examples 1 to 7 were analyzed using a scanning electron microscope (SEM).

In the present invention, Figure 2 is an image confirmed through a scanning electron microscope of the surface of the TFC separator prepared in Example 1 and Comparative Examples 1 to 7.

As shown in FIG. 2, it can be confirmed that the polyamide selection layer formed in Example 1 has a rough structure that appears in general high-density polyamide selection layers.

Experimental Example 2. Measurement of membrane performance

A 2,000 ppm sodium chloride (NaCl) aqueous solution was passed through the prepared membrane under process conditions of a pressure of 15.5 bar, a temperature of 25° C., and a flow rate of 1 L/min, and the salt removal rate and water permeability were compared.

In addition, for the evaluation of fouling resistance, the water permeability of each membrane was adjusted to 20 LMH (L m ^-2 h ^-1 ), and then a solution containing bacteria (P. aeruginosa, 10 ³ CFU, LB broth 0.5 g / L concentration) was permeated and the decrease in permeability was measured for 12 hours.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Water permeability (L m ^-2 h ^-2 bar ^-1 ) 1.66 0.40 1.28 1.40 1.49 0.46 0.19 1.56 Salt removal rate (%) 99.6 96.1 99.1 97.7 98.4 97.8 93.3 99.4

Table 1 shows the water permeability and salt rejection of the separator.

As shown in Table 1, it can be seen that the separator prepared in Example 1 has higher water permeability and salt rejection compared to the separators of Comparative Examples. Through this, it can be confirmed that the separation membrane manufactured by the manufacturing method according to the present invention has high water permeability and salt removal rate, and thus can produce a large amount of high purity water.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Water permeability (A, L m ^-2 h ^-2 bar ^-1 ) 1.66 0.40 1.28 1.40 1.49 0.46 0.19 1.56 Water permeability contaminated by bacteria for 12 hours
(B, L m ^-2 h ^-2 bar ^-1 ) 1.38 0.29 0.85 0.99 1.03 0.32 0.13 1.06 Normalized water permeability (B/A) 0.83 0.72 0.66 0.71 0.69 0.69 0.69 0.68

Table 2 shows the fouling performance results in the membrane.

As shown in Table 2, it can be seen that the membrane prepared in Example 1 shows a low decrease in permeability under the bacteria feed condition compared to the membranes of Comparative Examples.

That is, in Example 1, it can be confirmed that the hydrophilicity and antibacterial properties of the selective layer of the separation membrane are increased due to the addition of BAC, resulting in a high fouling resistance performance of 10% or more, specifically 11% to 26% compared to the comparative example. .

In addition, Figure 3 shows the normalized water permeability of the separator for 12 hours and confocal microscopy (CLSM) images of the surface of the separator after 12 hours.

As shown in FIG. 3, it can be seen that the surface of the separator of Example 1 shows a very low surface contamination compared to other comparative examples. Through this, it can be confirmed that the separation membrane manufactured by the manufacturing method according to the present invention exhibits significantly better fouling resistance compared to the comparative examples.

Claims (11)

Impregnating or applying a first solution containing a first organic monomer, a first solvent and an antimicrobial surfactant on a porous support;
impregnating or applying a second solution containing a second organic monomer and a second solvent; and
Forming a selective layer through interfacial polymerization between a first organic monomer and a second organic monomer dissolved in the first solution and the second solution, respectively;
The method of manufacturing a thin film composite separator in which the antimicrobial surfactant is benzalkonium chloride (BAC).
According to claim 1,
The porous support is polyacrylonitrile (PAN), polysulfone, polyethylene, polypropylene, polyacetylene, polyisobutylene, polyvinylchloride , polytetrafluoroethylene, polyphenylene sulfide, polyethersulfone, polystyrene, polydimethylsiloxane, polyvinylfluoride, polyvinylalcohol, Formed from one or more polymers selected from the group consisting of polybenzimidazole, polyvinylpyrrolidone, polyetherimide, polyvinylidenefluoride and polyetheretherketone A method for manufacturing a thin film composite separator.
According to claim 1,
A method for producing a thin film composite separator having a thickness of 1 to 1,000 μm, an average pore size of 1 nm to 100 μm, and a surface porosity of 10 to 90%.
According to claim 1,
The optional layer is a cross-linked or uncross-linked polyamide, polypiperazine-amide, polyester, polyurethane, polyvinyl alcohol, polyimide and polyether. A method for producing a thin film composite separator that may be mead and has a chemical structure of fully aromatic, partially aromatic, or fully aliphatic.
According to claim 1,
The first organic monomer is m -phenylenediamine (MPD), o -phenylenediamine ( o -phenylenediamine), p -phenylenediamine ( p -phenylenediamine ), piperazine (piperazine), diethylenetriamine (diethylenetriamine ), triethylenetetramine, diethylaminopropylamine, methanediamine, polyethyleneimine, o -dihydroxybenzene , m -dihydroxy Benzene ( m -dihydroxybenzene), p -dihydroxybenzene ( p -dihydroxybenzene), and a method for producing at least one thin film composite separator selected from the group consisting of polyvinyl alcohol.
According to claim 1,
The first solvent is water, methanol, ethanol, propanol, butanol, isopropanol, acetone, tetrahydrofuran and dimethyl sulfoxide Method for producing a thin film composite separator of at least one selected from the group consisting of.
According to claim 1,
A method for producing a thin film composite separator in which the concentration of the antimicrobial surfactant is 1 to 1000 mM.
According to claim 1,
The second organic monomer has an acyl chloride terminal group, trimesoyl chloride (TMC), terephthaloyl chloride, cyclohexane-1,3,5-tricarbonyl chloride (cyclohexane-1, 3,5-tricarbonyl chloride), 1-isocyanato-3,5-benzenedicarbonyl chloride (1-isocyanato-3,5-benzenedicarbonyl chloride) and isophthaloyl chloride (isophthaloyl chloride) Method for manufacturing a thin film composite separator.
According to claim 1,
The second solvent is n -hexane, pentane, cyclohexane, heptane, octane , decane, dodecane, carbon tetrachloride , A method for manufacturing a thin film composite separator having at least one selected from the group consisting of benzene, toluene, and xylene.
A thin film composite separator manufactured by the manufacturing method according to claim 1 .
According to claim 10,
Thin film composite membrane applied to forward osmosis (FO), pressure assisted osmosis, pressure-retarded osmosis, nanofiltration and reverse osmosis (RO) processes.

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