CN103752174A - Antibacterial hydrophilic hollow fiber assembly for water treatment - Google Patents

Abstract

The invention relates to an antibacterial hydrophilic hollow fiber membrane module for water treatment, which belongs to the field of water treatment and membrane separation science and technology. An antibacterial hydrophilic hollow fiber membrane module for water treatment, comprising a hollow fiber membrane, a hydrophilic polymer layer with antibacterial function; a kind of antibacterial hydrophilic hollow fiber membrane module for water treatment of the present invention can prevent Microorganisms adhere and grow on the membrane-water interface, avoiding the biological contamination of the membrane by microorganisms, avoiding or reducing the number of sterilization cleaning and disinfection dosage of the membrane module during use, and improving the water flux of the membrane module. Improve the separation effect of ultrafiltration, microfiltration and nanofiltration membranes, delay the decline of water flux, prolong the service life of membrane modules, and have good economic and social benefits.

Description

An antibacterial hydrophilic hollow fiber membrane module for water treatment

technical field

The invention relates to an antibacterial hydrophilic hollow fiber membrane module for water treatment, which belongs to the field of water treatment and membrane separation science and technology.

Background technique

The so-called membrane module is a unit assembled by the membrane, the supporting material for fixing the membrane, the spacer or the shell, etc. In simple terms, it is a tool for separating the components in the system. The main types are hollow fiber type, roll type, plate type, etc. Frame type, tube type, etc.

Membrane technology, known as the water treatment technology of the 21st century, has developed rapidly in the past 40 years. Compared with traditional water treatment technology, membrane technology has the advantages of energy saving, less investment, easy operation and high treatment efficiency, and its application has brought huge environmental and economic benefits to human beings. Membrane technology has a wide range of applications in water treatment, both for drinking water treatment and wastewater treatment, and also involved in water treatment in some special industries.

Membrane fouling is the biggest problem in the application of membrane technology. With the prolongation of use time, microorganisms adsorb on the surface of the membrane and form a layer of biofilm through accumulation, growth and reproduction, resulting in biofilm pollution. This kind of biofilm pollution often causes the deterioration of membrane separation performance and the shortening of membrane life, which is an important factor affecting the safety of drinking water quality and has become one of the bottlenecks in the membrane water treatment process.

In order to avoid the growth of bacteria and other microorganisms on the surface of the membrane and further cause membrane fouling, regular sterilization is generally used. The operation cycle of sterilization depends on the water quality of the supplied raw water, but in any case, the working time of the ultrafiltration membrane module is shortened. . For ordinary tap water in cities, the sterilization cycle is 7-10 days in summer, 30-40 days in winter, and 20-30 days in spring and autumn. When surface water is used as the water supply source, the sterilization cycle is shorter. Sterilization drugs can be circulated or soaked in 300mg/L sodium hypochlorite solution or 1% hydrogen peroxide aqueous solution for about half an hour. However, these small molecule disinfectants will cause secondary pollution in water and cause harm to human health. In terms of bactericidal effect, the persistence of the bactericidal effect of these small molecule bactericides is relatively poor, which limits their application to a certain extent. limits.

In addition to the use of sterilizing chemicals, ultraviolet light or ozone can also be used for sterilization. Utility model patent 201320203353.2 provides a direct drinking water preparation device based on ultrafiltration, using municipal tap water as raw water, passing through two-stage ultrafiltration membranes, activated carbon adsorption, ultraviolet sterilization, and safe and stable water production. Utility model patent 201320342111.1 discloses a sewage treatment device in which an ultraviolet light sterilizer is installed under the biofilm module. The source water can also be pretreated. For example, invention patent 201210264844.8 discloses a quality-separated water supply ultrafiltration machine with bromine resin sterilization treatment. By installing a pre-bromine resin filter element, the source water entering the ultrafiltration membrane module is sterilized and disinfected. , can effectively prolong the service life of the filter membrane and reduce the growth of bacteria in the ultrafiltration machine. Due to the additional use of ultraviolet rays, ozone equipment or pretreatment components in the above methods, the cost of the equipment will be increased, the volume will be increased, and the floor area will be increased.

The preparation of separation membranes with antibacterial function is a hot research direction, and there are a large number of documents and patents. Generally, inorganic small molecules or organic polymer antibacterial agents are combined with the basement membrane with separation function through bulk blending, surface deposition or grafting, layer-by-layer self-assembly or cross-linking, so as to realize the antibacterial improvement of the basement membrane. sex. For example, invention patents 200610165240.2 and 200610165242.1 synthesized antibacterial quaternary ammonium salt monomer methacryloyloxyethyl-benzyl-dimethylammonium chloride (DMAE-BC), and through chemical grafting, radiation grafting and photografting The DMAE-BC is connected to the cellulose fiber and the dense polyethylene film respectively, and the polymer covalently combined with the antibacterial monomer has obvious inhibitory and killing effects on Escherichia coli E.coli. Invention patent 201010256453.2 In-situ generation of silver nanoparticles on the surface of the separation membrane and formation of a quaternized cross-linked layer to prepare a composite antibacterial separation membrane. However, the above methods can only be used for small-scale modification of single membranes or membrane filaments, but cannot be used for overall modification of commercial membrane modules.

On the other hand, due to the commonly used membrane materials for water treatment, such as polyolefins, mainly polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc., are non-polar It is a non-reactive material with low surface energy, inertness and hydrophobicity. The membrane prepared by it has obvious disadvantages such as poor water absorption, low flux and poor pollution resistance. It is difficult to fully exert the membrane performance in practical applications and is greatly limited.

Contents of the invention

The purpose of the present invention is to provide an antibacterial hydrophilic hollow fiber membrane module for water treatment in order to solve the problem of low flux caused by the lack of antibacterial function and poor hydrophilicity of the existing commercial water treatment membrane modules.

The purpose of the present invention is achieved through the following technical solutions.

An antibacterial hydrophilic hollow fiber membrane module for water treatment, comprising a hollow fiber membrane and a hydrophilic polymer layer with antibacterial function;

The hollow fiber membrane can be an ultrafiltration membrane, a microfiltration membrane, or a nanofiltration membrane.

The hollow fiber membrane material can be an olefin polymer, including polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), or polysulfone (PSf) , Polyethersulfone (PES).

The preparation method of the membrane module adopts the remote plasma device and method disclosed in the invention patent 201210249376.7 to carry out integral chemical grafting of the membrane module; however, an initiator is added to the active monomer solution in step 3, so that the initiator and The active monomer solution is transported into the membrane module together, and undergoes dynamic circulation to induce graft polymerization, and then forms a polymer antibacterial layer on the surface of the membrane.

The polymer antibacterial layer is formed by free radical polymerization of monomers with antibacterial function under the action of an initiator.

The monomer with antibacterial function is a polymerizable quaternary ammonium salt monomer, characterized by a polymerizable double bond and a quaternary ammonium salt group with antibacterial function, such as methacryloyloxyethyl-benzyl -Dimethylammonium chloride (DMAE-BC), methacryloyloxyethyl-butyl-dimethylammonium bromide (MBDAB) and methacryloyloxyethyl-ethyl-dimethylammonium bromide Ammonium (MEDAB).

The initiator is a thermal initiator, mainly persulfates, such as ammonium persulfate and potassium persulfate, and the dosage is 0.01wt.%-5wt.%.

The membrane modules can be used alone or in parallel; the operation mode of dead-end filtration can be adopted, and the operation mode of cross-flow filtration can also be adopted. During dead-end filtration, the water to be treated enters the hollow fiber membrane module from the inlet of the shell side. After the water to be treated is filled with the membrane module, the outlet of the shell side is closed. Under the pressure of 0.01-0.3MPa, the water passes through the hollow fiber membrane and enters the inside of the membrane. (that is, the tube pass), and then come out from the first tube pass outlet or the second tube pass outlet; the first tube pass outlet and the second tube pass outlet can be selected according to the water outlet needs, or they can be used at the same time. During cross-flow filtration, the water to be treated enters the hollow fiber membrane module from the inlet of the shell side, and the concentrated water comes out from the outlet of the shell side; under the pressure of 0.01-0.3MPa, the water passes through the hollow fiber membrane and enters the interior of the membrane (ie, the tube side) , and then come out from the outlet of the first tube pass or the outlet of the second tube pass; the outlet of the first tube pass and the outlet of the second tube pass can be selected according to the needs of water outlet, or can be used at the same time.

Beneficial effect

Compared with the prior art, the present invention has the following advantages:

(1) An antibacterial hydrophilic hollow fiber membrane module for water treatment of the present invention can prevent microorganisms from adhering and growing on the membrane-water interface, avoiding the biological contamination of the membrane by microorganisms, and can avoid or reduce the The number of times of sterilization and cleaning and the amount of disinfectant used during the use of the module can improve the water flux of the membrane module, improve the separation effect of ultrafiltration, microfiltration and nanofiltration membranes, delay the decline of water flux, and prolong the service life of the membrane module. Better economic and social benefits.

(2) An antibacterial hydrophilic hollow fiber membrane module for water treatment of the present invention, the polymer with antibacterial function is connected to the polymer membrane material by grafting, and disinfection is realized while filtering, so that the traditional In the water treatment operation, the two links of sterilization and filtration, which are independent of each other, are combined into one, which not only avoids the secondary pollution of water and the environment by small molecule disinfectants, but also avoids the use of ultraviolet light, ozone and other sterilization equipment, reducing costs. It also makes the water treatment equipment more compact and concise. Membrane modules can be used for both drinking water purification and membrane bioreactors for wastewater treatment.

(3) An antibacterial hydrophilic hollow fiber membrane module for water treatment of the present invention, because the traditional chemical grafting, radiation grafting and photografting methods are not suitable for the membrane treatment of the overall scale of the membrane module, therefore, In the prior art, the membrane filaments are usually modified and then assembled into membrane modules, and the treatment time is long and the efficiency is low. However, the present invention can directly process the commercial membrane modules for water treatment, with short treatment time and high efficiency. It is suitable for large-scale treatment, and only a small amount of initiator and a low-concentration antibacterial monomer aqueous solution are involved in the treatment process, which has the characteristics of an environmentally friendly process.

(4) An antibacterial hydrophilic hollow fiber membrane module for water treatment of the present invention, after the membrane module is modified, the combined polymer with antibacterial function can also improve the hydrophilicity of the membrane, improve the flux and Anti-fouling performance, so as to improve the water treatment capacity per unit time and improve the membrane fouling problem.

Description of drawings

Fig. 1 is a kind of antibacterial hydrophilic hollow fiber membrane module for water treatment;

Figure 2 is a scanning electron micrograph of the membrane in the membrane module after the membrane module has been continuously operated for 48 hours in Example 1 (a) the original membrane module; (b) the antibacterial membrane module;

Fig. 3 is a scanning electron micrograph of the membrane in the membrane module in Example 4 after 6 days of operation (a) the original membrane module; (b) the antibacterial membrane module.

Among them, 1-hollow fiber membrane module; 2-hollow fiber membrane filament; 3-shell side inlet; 4-shell side outlet; mouth.

Detailed ways

The content of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

PE hollow fiber microfiltration membrane module, the average pore size is 0.1-0.2μm, the length is 25cm, and the number of filled membrane filaments is 10. Put the module into the overall modification device of the remote plasma membrane module. When the Ar gas flow rate is 0.5sccm, the pressure is 40Pa, and the discharge power is 100W, the Ar plasma flow is introduced into the membrane module through a vacuum pump to realize the inner surface of the membrane module. Activation pretreatment of the outer surface of all membrane filaments, stopped after 280 seconds. The components were removed and exposed to air for 10 minutes at room temperature to form peroxy radicals on the surface. Put the module into the solution circulation module grafting device, introduce the aqueous solution of DMAE-BC and ammonium persulfate into the hollow fiber membrane module through the peristaltic pump, and carry out the circulation grafting reaction. The inflow method is external pressure type, DMAE-BC and ammonium persulfate The concentrations are 6.0% and 0.4%, respectively, the polymerization temperature is 50°C, and the cycle polymerization time is 120 minutes; after the grafting is completed, the hollow fiber membrane module with the required performance is obtained by washing with water circulation for 30 minutes.

The static antibacterial performance of the membrane module was investigated by measuring the number of surviving colonies of E. coli suspension (10 ⁵ cells/mL) in the membrane module with the contact time. After 180 minutes of contact, the number of surviving colonies in the suspension was reduced by about 90%. . Under 0.1MPa, the E. coli suspension (10 ⁵ cells/mL) was dynamically circulated and filtered for 48 hours. The outer surface of the original membrane adsorbed a large number of E. coli that could continue to multiply; while the outer surface of the antibacterial modified membrane was clean, Only a few colonies were found at the end positions of the modules. See attached picture 2. This further demonstrates that the grafted antibacterial layer has the ability to kill and/or inhibit bacteria.

Both the original membrane module and the antibacterially modified membrane module had a 100% retention rate for E. coli, that is, no E. coli was detected in the filtered permeate water.

The hydrophilicity of the membrane was characterized by the contact angle. After graft modification, the average water contact angle on the outer surface of the membrane decreased from 120° of the original PE membrane to 45°. It shows that the hydrophilicity of the membrane module is greatly enhanced after modification.

With the operation method of dead-end filtration, as shown in Figure 1, the water to be treated enters the hollow fiber membrane module 1 from the inlet 3 of the shell side, and after the water to be treated is filled with the hollow fiber membrane module 1, the outlet 4 of the shell side is closed, and at a pressure of 0.1 MPa Next, water penetrates the hollow fiber membrane filament 2 into the interior of the membrane filament (i.e., the tube pass), and then comes out from the first tube pass outlet 5 or the second tube pass outlet 6; the first tube pass outlet 5 and the second tube pass outlet 6 One of them can be selected according to the needs of effluent, and they can also be used at the same time. The pure water fluxes of the original membrane and the antibacterially modified membrane module at steady state were about 35 and 85L·m ^-2 ·h ^-1 , the latter being 2.4 times that of the former. With the operation method of cross-flow filtration, as shown in Figure 1, Escherichia coli suspension (10 ⁵ cells/mL) is selected as the simulated wastewater system, the water to be treated enters the hollow fiber membrane module 1 from the shell side inlet 3, and the concentrated water flows from the Outlet 4 of the first tube pass; under the pressure of 0.1MPa, water penetrates the hollow fiber membrane 2 into the interior of the membrane (i.e., the tube pass), and then comes out from the first tube pass outlet 5 or the second tube pass outlet 6; the first tube pass Outlet 5 and outlet 6 of the second tube side can be selected according to the needs of water outlet, or they can be used at the same time; after 48 hours of continuous operation, the flux of the original membrane and the membrane module after antibacterial modification in steady state is 4L· m ^-2 ·h ^-1 and 19L·m ^-2 ·h ^-1 , the latter is 4.8 times that of the former. It shows that the water flux of the membrane module is greatly enhanced after modification.

Example 2

PE hollow fiber microfiltration membrane module, the average pore size is 0.1-0.2μm, the length is 85cm, and the number of filled membrane filaments is 50. Put the module into the overall modification device of the remote plasma membrane module. When the Ar gas flow rate is 1sccm, the pressure is 50Pa, and the discharge power is 40W, the Ar plasma flow is introduced into the membrane module through a vacuum pump to realize all Activation pretreatment of the outer surface of the membrane filament, stopped after 280 seconds. The components were removed and exposed to air for 15 minutes at room temperature to form peroxy radicals on the surface. Put the module into the grafting device of the solution circulation module, introduce the aqueous solution of MEDAB and potassium persulfate into the hollow fiber membrane module through the peristaltic pump, and carry out the circulation grafting reaction. The inflow method is the external pressure type, and the concentrations of MEDAB and potassium persulfate are respectively 2.0% and 1%, the polymerization temperature is 55°C, and the cycle polymerization time is 120 minutes; after the grafting is completed, it is washed with water for 30 minutes to obtain the hollow fiber membrane module with the required performance.

The results of the static antibacterial performance test showed that the number of surviving colonies in the suspension was reduced by about 92% after contact for 180 minutes. The Escherichia coli suspension (10 ⁵ cells/mL) was dynamically circulated and filtered for 48 hours, and the outer surface of the original membrane adsorbed a large number of Escherichia coli that could continue to multiply; while the outer surface of the antibacterial modified membrane was clean.

Both the original membrane module and the antibacterially modified membrane module had a 100% retention rate for E. coli, that is, no E. coli was detected in the filtered permeate water.

Example 3

PP hollow fiber microfiltration membrane module, the average pore size is 0.1-0.2μm, the length is 45cm, and the number of filled membrane filaments is 20. Put the module into the overall modification device of the remote plasma membrane module. When the Ar gas flow rate is 2sccm, the pressure is 15Pa, and the discharge power is 70W, the Ar plasma flow is introduced into the membrane module through a vacuum pump, so that all Activation pretreatment of the outer surface of the membrane filament, stopped after 240 seconds. The components were removed and exposed to air at room temperature for 20 minutes to form peroxyl radicals on the surface. Put the module into the solution circulation module grafting device, introduce the aqueous solution of MBDAB and ammonium persulfate into the hollow fiber membrane module through the peristaltic pump, and carry out the circulation grafting reaction. The inflow method is external pressure type, and the concentrations of MBDAB and ammonium persulfate are respectively 3.0% and 0.8%, the polymerization temperature is 60°C, and the cycle polymerization time is 120 minutes; after the grafting is completed, the water cycle is washed for 30 minutes; the hollow fiber membrane module with the required performance is obtained.

The static antibacterial performance of the membrane module was investigated by measuring the number of surviving colonies of the E. coli suspension (10 ⁵ cells/mL) in the membrane module with the contact time. After 180 minutes of contact, the number of surviving colonies in the suspension was reduced by about 95%. . The Escherichia coli suspension (10 ⁵ cells/mL) was dynamically circulated and filtered for 48 hours, and the outer surface of the original membrane adsorbed a large number of Escherichia coli that could continue to multiply; while the outer surface of the antibacterial modified membrane was clean.

Both the original membrane module and the antibacterially modified membrane module had a 100% retention rate for E. coli, that is, no E. coli was detected in the filtered permeate water.

Example 4

The PVC hollow fiber ultrafiltration membrane module has a molecular weight cut-off of 70KDa, a length of 50cm, and the number of filled membrane filaments is 30. Put the module into the overall modification device of the remote plasma membrane module. When the Ar gas flow rate is 3sccm, the pressure is 12Pa, and the discharge power is 80W, the Ar plasma flow is introduced into the membrane module through a vacuum pump to realize all Activation pretreatment of the outer surface of the membrane filament, stopped after 240 seconds. The components were removed and exposed to air at room temperature for 20 minutes to form peroxyl radicals on the surface. Put the module into the solution circulation module grafting device, introduce the aqueous solution of DMAE-BC and potassium persulfate into the hollow fiber membrane module through the peristaltic pump, and carry out the circulation grafting reaction. The inflow method is external pressure type, DMAE-BC and potassium persulfate The concentrations are 5.0% and 0.5%, respectively, the polymerization temperature is 65°C, and the cycle polymerization time is 120 minutes; after the grafting is completed, the hollow fiber membrane module with the required performance is obtained by washing with water circulation for 30 minutes.

The static antibacterial performance of the membrane module was investigated by measuring the number of surviving colonies of the Escherichia coli suspension (10 ⁵ cells/mL) in the membrane module with the contact time. After 80 minutes of contact, the bactericidal rate reached 100%. After 6 days of dynamic circulation filtration of the E. coli suspension (10 ⁵ cells/mL), for the original membrane module, the membrane surface was covered with a large number of pollutants, and many individual cells with complete forms were found, indicating that E. coli did not lose its biological activity and could still continue to Reproduction and growth; while the surface of the antibacterial membrane module was clean, no complete individual bacteria were found (see Figure 3), which proved that the grafted membrane has the ability to resist adhesion and inhibit the formation of biofilm.

Both the original membrane module and the antibacterially modified membrane module had a 100% retention rate for E. coli, that is, no E. coli was detected in the filtered permeate water.

The hydrophilicity of the membrane was characterized by the contact angle. After graft modification, the average water contact angle on the outer surface of the membrane decreased from 90° of the original membrane to 45°. It shows that the hydrophilicity of the membrane module is greatly enhanced after modification.

With the operation mode of dead-end filtration, at 0.1MPa, the pure water fluxes of the original membrane and the antibacterial modified membrane module at steady state are about 8 and 32L·m ^-2 ·h ^-1 respectively, the latter is 4 times of the former. In the operation mode of cross-flow filtration, Escherichia coli suspension (10 ⁵ cells/mL) was selected as the simulated wastewater system, and the flux of the antibacterial membrane module was 4 times that of the original membrane module. After 6 days of operation, the flux of the original membrane module is 54% of its initial flux, while the flux of the antibacterial membrane module is 64% of its initial flux.

Claims (5)

1. for an antibacterial hydrophilic hollow fiber film assembly for water treatment, it is characterized in that: comprise hollow-fibre membrane, there is the hydrophilic polymer layer of antibacterial functions;

Described hollow-fibre membrane is milipore filter, micro-filtration membrane or NF membrane;

Described polymer antibiotic layer be by the monomer with antibacterial functions under the initiation of initator, through radical polymerization, form;

The described monomer with antibacterial functions is polymerizable quaternary ammonium salt monomer, feature is the quaternary ammonium salt group with a polymerizable double bond and with antibacterial functions, as methylacryoyloxyethyl-benzyl-alkyl dimethyl ammonium chloride, methylacryoyloxyethyl-butyl-dimethyl ammonium bromide and methylacryoyloxyethyl-ethyl-dimethyl ammonium bromide.

2. a kind of antibacterial hydrophilic hollow fiber film assembly for water treatment as claimed in claim 1, it is characterized in that: described doughnut membrane material is olefin polymer, comprising polyethylene, polypropylene, Kynoar, polyvinyl chloride, can be also polysulfones, polyether sulfone.

3. a kind of antibacterial hydrophilic hollow fiber film assembly for water treatment as claimed in claim 1, is characterized in that: the preparation method of described hollow fiber film assembly adopts the apparatus and method that in patent of invention 201210249376.7, disclosed remote plasma carries out overall chemical grafting to membrane module; But in the activated monomer solution in step 3, add initator, initator is transported in membrane module together with activated monomer solution, carry out dynamic circulation induced grafting polymerisation, and then form polymer antibiotic layer on film surface.

4. a kind of antibacterial hydrophilic hollow fiber film assembly for water treatment as described in claim 1 or 3, is characterized in that: described initator is thermal initiator, is mainly persulfuric acid salt, and as ammonium persulfate and potassium peroxydisulfate, consumption is 0.01wt.%～5wt.%.

5. a kind of antibacterial hydrophilic hollow fiber film assembly for water treatment as claimed in claim 1, is characterized in that: described membrane module can be used separately, also can multiple parallel connections use; Can adopt the mode of operation of dead-end filtration, also can adopt the mode of operation of cross-flow filtration; During dead-end filtration, pending water enters hollow fiber film assembly from shell side import, and pending water is full of after membrane module, close shell side outlet, under 0.01～0.3MPa pressure, water sees through hollow fiber film thread and enters film silk inside, then from the first tube side outlet or the second tube side, exports out; The first tube side outlet and the outlet of the second tube side can, according to water outlet needs, be selected one of them, also can use simultaneously; During cross-flow filtration, pending water enters hollow fiber film assembly from shell side import, and condensed water exports out from shell side; Under 0.01～0.3MPa pressure, water sees through hollow fiber film thread and enters film silk inside, then from the first tube side outlet or the second tube side, exports out; The first tube side outlet and the outlet of the second tube side can, according to water outlet needs, be selected one of them, also can use simultaneously.

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