CN113457459B - Continuous preparation method and device of polyamide functional composite membrane - Google Patents
Continuous preparation method and device of polyamide functional composite membrane Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0006—Organic membrane manufacture by chemical reactions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/10—Supported membranes; Membrane supports
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/56—Polyamides, e.g. polyester-amides
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention discloses a continuous preparation method and a device of a polyamide functional composite membrane, which comprises the following steps: (1) Uniformly coating the polyamine solution on the surface of the conveying mechanism through a scraper to form a polyamine liquid film; (2) Spraying a polyacyl chloride solution onto a polyamine liquid film through a spraying mechanism, and carrying out interfacial polymerization reaction on polyamine and polyacyl chloride to generate a polyamide self-supporting film; (3) The conveying mechanism attached with the polyamide self-supporting film is immersed in water in a rinsing bath, and the polyamide self-supporting film is separated from the conveying mechanism and enters a drying mechanism for drying and heat treatment; (4) And compounding the dried and heat-treated polyamide self-supporting membrane with a porous supporting material to obtain the polyamide functional composite membrane. The preparation method disclosed by the invention is simple and convenient to operate, mild in reaction conditions, less in monomer consumption, green and environment-friendly, and capable of continuously preparing the polyamide functional composite membrane with uniform structure and stable performance in a large area.
Description
Technical Field
The invention relates to the technical field of membrane separation, in particular to a continuous preparation method and a continuous preparation device of a polyamide functional composite membrane.
Background
The polyamide functional composite membrane is widely applied to the processes of nanofiltration, reverse osmosis and the like due to simple and convenient preparation process, mild operation conditions and excellent separation performance, and plays a vital role in the fields of seawater and brackish water desalination, domestic water softening, industrial wastewater treatment, purification, concentration, separation and the like related to food, medicine and chemistry. And the like. Currently, the most commonly used polyamide functional composite films in industry are aromatic polyamide composite films prepared by an interfacial polymerization process. The membrane consists of a porous supporting layer and a compact aromatic polyamide film. The separation is mainly performed by a polyamide film, and the structure of the polyamide film is crucial to the performance of the composite membrane. The aromatic polyamide film is obtained by the interfacial polymerization reaction of aromatic polyamine and aromatic polyacyl chloride, so that the control of the interfacial polymerization process is the key for preparing the high-performance polyamide functional composite film.
For example, chinese patent publication No. CN109499395a discloses a method for preparing a high-performance reverse osmosis seawater membrane, which comprises coating the back surface of a polysulfone basement membrane with a pre-coating aqueous solution, drying in the shade, coating the front surface of the basement membrane with a water-phase solution containing polyamine, drying in the shade twice, coating an oil-phase solution of polyacyl chloride, and performing an interfacial polymerization reaction to prepare the high-performance reverse osmosis seawater membrane. The method improves the uniformity of the distribution of the aqueous monomer solution on the surface of the substrate to a certain extent, but cannot avoid the influence of the rough structure of the surface of the substrate on the uniformity of the interfacial polymerization reaction.
Chinese patent document CN108392992A discloses a method for preparing a reverse osmosis membrane, wherein a temporary intermediate layer with high porosity is coated on the surface of a polysulfone ultrafiltration membrane for improving the influence of large roughness and uneven pore size distribution of a base membrane on the uniformity of interfacial polymerization, and a prepared polyamide desalting layer has uniform structure and flux distribution. Chinese patent publication No. CN111214965a discloses a reverse osmosis membrane, and a preparation method and application thereof, wherein a carbon nanotube membrane intermediate layer with uniform pore size distribution and high porosity is loaded on the surface of a porous filter membrane, so as to realize uniform distribution of amine monomer solution and controllable release of monomers, thereby preparing an ultrathin high-quality polyamide reverse osmosis membrane. The method for improving the distribution uniformity of the amine monomer solution on the surface of the substrate by adopting the middle layer can enhance the uniformity degree of interfacial polymerization reaction and improve the uniformity of the performance of the polyamide reverse osmosis membrane, but the introduction of the middle layer leads the preparation process of the reverse osmosis membrane to be complicated, has high cost and is not beneficial to large-scale preparation.
Chinese patent publication No. CN111888943A discloses a method for preparing a buffer layer-containing free interfacial polymerization reverse osmosis membrane, wherein after a buffer layer is added on the surface of an aqueous phase monomer solution, an organic phase monomer solution is added on the surface of the buffer layer to perform a free interfacial polymerization reaction, and a synthesized polyamide self-supporting film is combined with a substrate to prepare a reverse osmosis membrane with excellent desalting performance and excellent stability. The method adopts free interface polymerization reaction, and avoids the influence of a substrate on the reaction uniformity; a buffer layer is introduced between the two-phase solution, so that the rate of interfacial polymerization reaction is slowed down, the uniformity of the reaction is improved, and the generated polyamide film is uniform and compact. However, in this method, the control of the interfacial polymerization reaction requires the addition of an additional buffer layer, and the reaction is carried out in a static container, which is disadvantageous for the large-area continuous production of a polyamide self-supporting film.
Glycerin is a colorless, odorless, nontoxic, and environmentally friendly water-soluble polyol compound, and is often used as a sweetener, a humectant, a lubricant, and the like in the fields of food, cosmetics, and medicine. Glycerol is also widely used in membrane-making processes, and is often used as a pore-forming agent, a shape-retaining agent, a wetting agent, and the like. The glycerol has high viscosity and can be mutually dissolved with water, and can be used for adjusting the viscosity of amine monomer solution and reducing the diffusion rate of amine monomers, thereby improving the stability and uniformity of interfacial polymerization reaction; meanwhile, the high-viscosity amine monomer solution is beneficial to forming a stable liquid film on a conveying belt, provides a reaction interface with a controllable area, and solves the problem of preparing the polyamide self-supporting reverse osmosis membrane or nanofiltration membrane in a large area.
Disclosure of Invention
The invention provides a continuous preparation method and a device of a polyamide functional composite membrane, the method is simple and convenient to operate, mild in reaction conditions, less in monomer consumption, green and environment-friendly, and capable of continuously preparing a polyamide self-supporting membrane with uniform structure and stable performance in a large area, and the obtained polyamide self-supporting membrane can be compounded with different kinds of porous supporting materials to prepare various reverse osmosis membranes or nanofiltration membranes.
The technical scheme of the invention is as follows:
a continuous preparation device of a self-supporting film comprises a conveying mechanism, a feeding mechanism, a spraying mechanism, a rinsing bath, a drying mechanism and a winding mechanism;
the feeding mechanism is arranged above the conveying mechanism and used for blade-coating the first reaction monomer solution on the surface of the conveying mechanism to form a first reaction monomer liquid film;
the spraying mechanism is arranged at the downstream of the feeding mechanism and at the upstream of the rinsing bath and is used for spraying the second reaction monomer solution onto the first reaction monomer liquid film, and the first reaction monomer and the second reaction monomer generate interfacial polymerization reaction to generate a self-supporting film;
the washing tank is arranged below the conveying mechanism, at least one part of the conveying mechanism is immersed in the washing liquid in the washing tank, and the self-supporting film is separated from the conveying mechanism after being washed;
and the cleaned self-supporting film enters a drying mechanism for drying and heat treatment, and is wound by a winding mechanism.
Preferably, the conveying mechanism is a roller or a conveying belt.
Preferably, the material of the conveying mechanism is aluminum, steel, glass, silicon, nylon, polyester film, polyurethane or polytetrafluoroethylene; the width of the conveying mechanism is 0.05-10 m. The surface of the conveying mechanism is flat, smooth and compact, and a stable and flat liquid film is formed on the conveying mechanism by the reaction monomer solution.
Preferably, the conveying mechanism is driven by a motor.
Preferably, the feeding mechanism comprises a feeding funnel and a scraper, and the distance between the scraper and the conveying mechanism is adjustable.
The invention also provides a method for continuously preparing the polyamide functional composite membrane by adopting the continuous preparation device, which comprises the following steps:
(1) Uniformly coating the polyamine solution on the surface of the conveying mechanism through a scraper to form a polyamine liquid film;
(2) Spraying a polyacyl chloride solution onto a polyamine liquid film through a spraying mechanism, and carrying out interfacial polymerization reaction on polyamine and polyacyl chloride to generate a polyamide self-supporting film;
(3) The conveying mechanism attached with the polyamide self-supporting film is immersed in water in a rinsing bath, and the polyamide self-supporting film is separated from the conveying mechanism and enters a drying mechanism for drying and heat treatment;
(4) And compounding the dried and heat-treated polyamide self-supporting membrane with a porous supporting material to obtain the polyamide functional composite membrane.
In the step (1):
preferably, the polyamine solution is glycerol aqueous solution of polyamine.
In the step (1), a layer of film of polyamine solution with uniform thickness and stable existence is coated on the surface of the conveying mechanism through a scraper, so that a uniform and stable reaction interface is provided for the subsequent interfacial polymerization reaction. And (3) spraying the polyacyl chloride solution on the surface of the polyamine solution by a spraying device in the step (2) to initiate free interface polymerization. The reaction is carried out at a uniform and stable free interface, so that the influence of a substrate on the reaction is avoided, and the polyamide self-supporting film with a uniform structure is favorably generated. In the step (3), the conveying mechanism is immersed in a water tank to wash off the redundant solution between the polyamide self-supporting film and the conveying belt, the polyamide self-supporting film automatically floats on the water surface, the redundant solution in the polyamide self-supporting film is removed through drying in an oven and heat treatment, the polyamide self-supporting film is further crosslinked, and the continuously prepared polyamide self-supporting film is obtained after winding. The obtained polyamide self-supporting film can be compounded with different kinds of porous supporting materials to obtain various types of reverse osmosis membranes or nanofiltration membranes. The conveying mechanism moves circularly to realize the continuous preparation of the self-supporting film.
More preferably, the polyamine solution has a viscosity of 1 to 500 mPas.
The polyamine solution with the viscosity range can be uniformly coated on a conveyor belt to form a stable and flat aromatic polyamine solution film. Although the stability and the smoothness of the polyamine solution film are enhanced along with the increase of the solution viscosity, the solution viscosity is too high, on one hand, the degree of interfacial polymerization reaction is excessively inhibited, so that the crosslinking degree of the polyamide film is reduced, and the interception performance is influenced; on the other hand, the difficulty of eluting the synthesized polyamide self-supporting film from the surface of the high-viscosity solution is increased.
More preferably, the polyamine solution has a viscosity of 1 to 200 mPas.
The thickness of the polyamine liquid film can be controlled by adjusting the distance between the scraper and the conveying mechanism.
Preferably, the thickness of the polyamine liquid film is 10 to 500 μm.
When the polyamine liquid film is too thin, the liquid film cannot provide enough amine monomers to participate in interfacial polymerization reaction, and the generated polyamide film has low crosslinking degree. When the polyamine liquid film is too thick, the monomer is not saved, and the smoothness and the stability of the liquid level in the operation process of the conveying mechanism are difficult to ensure, so that the uniformity of subsequent interface polymerization is influenced.
More preferably, the thickness of the polyamine liquid film is 50 to 200 μm.
Preferably, the polyamine is at least one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, piperazine, 1,3-cyclohexyldimethylamine and diethylenetriamine; the concentration of the polyamine solution is 0.1-50 g/L.
The concentration of the polyamine solution has an important influence on the thickness and the degree of crosslinking of the polyamide film. When the concentration of the polyamine solution is higher, the synthesized polyamide film has high crosslinking degree and good interception performance, but also has thicker film thickness and low permeation flux; when the concentration of the aromatic polyamine solution is low, the synthesized polyamide film is thin and high in permeation flux, but the film is low in crosslinking degree and poor in retention performance.
More preferably, the concentration of the polyamine solution is 1 to 30g/L.
In the step (2):
the polybasic acyl chloride is at least one of phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride and trimesoyl chloride; the solvent of the polybasic acyl chloride solution is at least one of trifluorotrichloroethane, normal hexane, cyclohexane, heptane and isoparaffin; the concentration of the polybasic acyl chloride solution is 0.1-5 g/L.
The concentration of the polyacyl chloride solution has a great influence on the degree of crosslinking of the synthesized polyamide self-supporting film. The excessive concentration of the acyl chloride solution can cause excessive acyl chloride monomers during the interfacial polymerization reaction, which is not beneficial to forming a polyamide cross-linked structure; too low a concentration of the acid chloride solution may result in insufficient monomer to participate in the reaction during interfacial polymerization, resulting in a decrease in the degree of crosslinking of the polyamide film.
Preferably, the time of the interfacial polymerization reaction is 5 to 600 seconds.
Too short a reaction time does not allow the formation of a polyamide film having a high degree of crosslinking, while too long a reaction time results in a thicker film and a lower permeation flux.
More preferably, the interfacial polymerization reaction time is 15 to 90 seconds.
In the step (3):
the temperature of drying and heat treatment is 60-100 ℃; the time is 5-30 min.
The thickness of the polyamide self-supporting film has a large influence on the structural integrity when it is wound and the stability of the properties when it is separated. The film thickness is too thin, so that defects are easily introduced when the self-supporting film is wound, and the stability of the film structure is reduced when the reverse osmosis membrane runs for a long time; the membrane thickness is too thick, which leads to a decrease in permeation flux.
Preferably, the dried and heat-treated polyamide free-standing film has a thickness of 10 to 200nm.
The width of the polyamide self-supporting film can be adjusted by the width of the conveying mechanism. Preferably, the width of the polyamide self-supporting film is 0.05 to 10m.
The polyamide self-supporting membrane can be compounded with different kinds of porous supporting materials to obtain various types of reverse osmosis membranes or nanofiltration membranes. Preferably, the porous support material is at least one of an ultrafiltration membrane or a microfiltration membrane of polysulfone, polyethersulfone, cellulose acetate, polyethylene, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polypropylene and polyacrylonitrile.
When the polyamine is at least one of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine and the polybasic acyl chloride is at least one of phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride and trimesoyl chloride, the prepared polyamide functional composite membrane is a reverse osmosis membrane.
The polyamine is at least one of piperazine, p-phenylenediamine, 1,3-cyclohexyldimethylamine and diethylenetriamine, and when the polyacyl chloride is trimesoyl chloride, the prepared polyamide functional composite membrane is a nanofiltration membrane. Compared with the prior art, the invention has the beneficial effects that:
(1) The preparation method can continuously prepare the polyamide functional composite membrane in a large area, and has simple and convenient operation and strong controllability.
(2) The polyamine solution with high viscosity slows down the intensity of interfacial polymerization reaction, improves the stability of a reaction interface, enhances the uniformity of the interfacial polymerization reaction, and effectively improves the structural uniformity and the performance stability of the polyamide functional composite membrane.
(3) The influence of the material and the pore size distribution of the porous supporting substrate on the structure of the polyamide film is avoided by adopting free interface polymerization.
(4) Compared with hydrophilic porous supporting materials mainly used in industrial production, the polyamide self-supporting film prepared by the preparation method can be compounded with hydrophobic porous supporting materials, and the application range of the reverse osmosis membrane or the nanofiltration membrane is widened.
(5) The polyacyl chloride solution is coated by adopting a spraying mode, so that the use amount of polyacyl chloride and an organic solvent is greatly reduced, the cost is reduced, and the environment is protected.
Drawings
FIG. 1 is a schematic configuration diagram of a preferred embodiment of a continuous production apparatus;
FIG. 2 is a schematic configuration diagram of another preferred embodiment of the continuous production apparatus;
FIG. 3 is a scanning electron microscope photograph of the surface of a self-supporting reverse osmosis membrane of polyamide prepared in example 1.
Detailed Description
The preparation method can adopt a self-supporting film continuous preparation device for preparation.
One structure of the self-supporting film continuous preparation device is shown in figure 1, and comprises a roller 11, a feeding mechanism, a spraying mechanism 3, a rinsing bath 41, a drying mechanism 5 and a winding mechanism 6;
the feeding mechanism is arranged above the roller 11 and comprises a feeding funnel 21 and a scraper 22, and the distance between the scraper 22 and the roller 11 is adjustable; the feeding mechanism is used for blade-coating the first reaction monomer solution on the surface of the roller 11;
the spraying mechanism 3 is arranged at the downstream of the feeding mechanism and at the upstream of the rinsing tank 41 and is used for spraying the second reaction monomer solution onto the liquid film of the first reaction monomer solution on the surface of the roller 11, and the first reaction monomer and the second reaction monomer generate interfacial polymerization reaction to generate a self-supporting film;
a rinsing bath 41 is arranged below the roller 11, and the self-supporting film is immersed in water and separated from the roller 11;
the cleaned self-supporting film enters a drying mechanism 5 to be dried and then is wound by a winding mechanism 6.
One structure of another self-supporting film continuous preparation device is shown in fig. 2, and comprises a conveyor belt 12, a feeding mechanism, a spraying mechanism 3, a rinsing bath 41, a drying mechanism 5 and a winding mechanism 6;
the feeding mechanism is arranged above the conveyor belt 12 and comprises a feeding hopper 21 and a scraper 22, and the distance between the scraper 22 and the conveyor belt 12 is adjustable; the feeding mechanism is used for blade-coating the first reaction monomer solution on the surface of the conveyor belt 12;
the spraying mechanism 3 is arranged at the downstream of the feeding mechanism and at the upstream of the rinsing bath 41 and is used for spraying the second reaction monomer solution onto a liquid film of the first reaction monomer solution on the surface of the conveyor belt 12, and the first reaction monomer and the second reaction monomer generate an interfacial polymerization reaction to generate a self-supporting film;
the washing tank 41 is arranged below the conveyor belt 12, the conveyor belt 12 passes through the guide roller and then is immersed in water in the washing tank 41, and the self-supporting film is immersed in the water and separated from the conveyor belt 12;
the cleaned self-supporting film enters a drying mechanism 5 to be dried and then is wound by a winding mechanism 6.
In the above-mentioned continuous self-supporting film-producing apparatus, the transfer speeds of the roll 11 and the conveyor belt 12 are adjustable, and the washing tank 41 has a water valve 42 for adjusting the water level in the washing tank 41.
When the self-supporting film continuous preparation device is used for preparing the polyamide self-supporting reverse osmosis membrane or nanofiltration membrane, the conveyer belt or the rotary drum firstly passes through a container containing polyamine solution, a layer of uniform polyamine solution film is coated on the surface of the conveyer belt or the rotary drum through a scraper, and then polyacyl chloride solution is sprayed on the surface of the polyamine solution film through a spraying device to carry out interfacial polymerization reaction, so that the polyamide self-supporting film is obtained. After the polyamide self-supporting film is generated, the conveyer belt or the rotary drum is immersed into a water tank for washing, and the solution between the conveyer belt or the rotary drum and the polyamide self-supporting film is washed away. Drying, heat treating and winding the polyamide self-supporting film which automatically falls off and floats on the water surface, and then compounding the polyamide self-supporting film with a porous supporting material to obtain the polyamide reverse osmosis membrane or the nanofiltration membrane.
The prepared polyamide reverse osmosis membrane or nanofiltration membrane is used for desalination, and the desalination rate and the water flux are two important parameters for evaluating the reverse osmosis membrane or the nanofiltration membrane. Wherein the salt rejection is defined as:
wherein, C f Indicating the concentration of salt ions in the feed liquid before treatment; c p The concentration of salt ions in the filtrate after the treatment is shown.
The water flux is defined as: the volume of water per membrane area per unit time at a given operating pressure is expressed in L/m 2 H, the formula is:
wherein V represents the volume of the filtrate which permeates through the reverse osmosis membrane or the nanofiltration membrane, and the unit is L; a represents the effective membrane area in m 2 (ii) a t represents time in units of h.
The present invention is described in more detail by the following examples, which are not intended to limit the present invention.
Example 1
M-phenylenediamine is selected as a polyamine monomer, and is dissolved in a glycerol aqueous solution, wherein the concentration of the m-phenylenediamine is 30g/L, and the viscosity of the solution is 100-200 mPas. Trimesoyl chloride is selected as a polybasic acyl chloride monomer, and is dissolved in isoalkane, and the concentration of the trimesoyl chloride is 1.5g/L.
A conveyor belt with a width of 2m and a smooth surface runs through a container filled with the m-phenylenediamine solution, and a layer of m-phenylenediamine solution film with the thickness of 100 mu m is coated on the surface of the conveyor belt through a scraper. And then entering a spraying device, spraying a trimesoyl chloride solution on the surface of the m-phenylenediamine solution, after the interfacial polymerization reaction is carried out for 60s, immersing a conveyer belt into a water tank, drying the automatically-falling polyamide film at 80 ℃, carrying out heat treatment for 10min, and winding to obtain the polyamide self-supporting film. And compounding the polyamide self-supporting film with a polyether sulfone microporous supporting material to obtain the reverse osmosis membrane. The results of the desalting test are shown in Table 1. The scanning electron microscope picture of the surface of the prepared polyamide self-supporting reverse osmosis membrane is shown in figure 3.
Examples 2 to 6
The viscosity ranges of the polyamine solutions were adjusted to 5 to 10 mPas, 10 to 100 mPas, 200 to 300 mPas, 300 to 400 mPas, and 400 to 500 mPas, respectively, and the other conditions were the same as in example 1.
Test example 1
The polyamide self-supporting reverse osmosis membranes prepared in examples 1 to 6 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 1.
TABLE 1 salt rejection and Water flux of the Polyamide self-supporting reverse osmosis membranes prepared in examples 1 to 6
As is clear from the data in Table 1, the water flux of the polyamide self-supporting reverse osmosis membrane of the present invention gradually increased with the increase in the viscosity of the polyamine solution, and the salt rejection rate increased and then decreased. On one hand, the viscosity of the polyamine solution is improved, the diffusion of amine monomers is inhibited, the interfacial polymerization reaction rate is reduced, and the generated polyamide self-supporting film is thinner, so that the flux is higher. On the other hand, the higher viscosity of the polyamine solution ensures the stability of the polyamine solution film on the surface of the conveyer belt and the stability of the interfacial polymerization reaction interface, effectively improves the uniformity of the interfacial polymerization reaction, and is beneficial to obtaining the polyamide self-supporting reverse osmosis membrane with uniform structure and high desalination rate. However, the polyamine solution has too high viscosity, the diffusion of the amine monomer to the reaction interface is excessively inhibited, and the produced polyamide film has low degree of crosslinking and poor retention performance.
Examples 7 to 11
The thicknesses of the polyamine solution films uniformly coated on the conveyer belt were adjusted to 10 μm, 50 μm, 200 μm, 300 μm and 500 μm, respectively, and the other conditions were the same as in example 1.
Test example 2
The polyamide self-supporting reverse osmosis membranes prepared in examples 7 to 11 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 2.
TABLE 2 salt rejection and Water flux of Polyamide self-supporting reverse osmosis membranes prepared in examples 7 to 11
As can be seen from the data in Table 2, as the film thickness of the polyamine solution uniformly coated on the belt increases, the salt rejection of the self-supporting reverse osmosis polyamide membrane of the present invention increases and then decreases, and the flux decreases and then increases. When the polyamine solution film is thin, the solution can not provide enough amine monomers to participate in interfacial polymerization reaction, and the generated polyamide film has low crosslinking degree, so that the film has poor retention performance. When the polyamine solution film is thick, the smoothness and stability of the liquid surface in the operation process of the conveyer belt are difficult to ensure, the uniformity of subsequent interfacial polymerization is influenced, and the polyamide film with high interception performance cannot be synthesized.
Examples 12 to 15
The materials of the adjusting conveyer belt are respectively nylon, polytetrafluoroethylene, polyurethane and polyester film, and the rest conditions are the same as those of the embodiment 1.
Test example 3
The polyamide self-supporting reverse osmosis membranes prepared in examples 12 to 15 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 3.
TABLE 3 salt rejection and Water flux of the Polyamide self-supporting reverse osmosis membranes prepared in examples 12 to 15
As can be seen from the data in Table 3, the use of different materials as the conveyor belt material did not significantly affect the separation performance of the polyamide self-supporting reverse osmosis membrane prepared in accordance with the present invention. The invention adopts a free interface polymerization method, avoids the influence of the material of the conveyer belt on the interface polymerization reaction, and widens the selection range of the material of the conveyer belt.
Examples 16 to 20
The widths of the conveyer belts were adjusted to 0.05m, 0.5m, 1m, 5m, and 10m, respectively, and the other conditions were the same as in example 1.
Test example 4
The polyamide self-supporting reverse osmosis membranes prepared in examples 16 to 20 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 4.
TABLE 4 salt rejection and Water flux of the Polyamide self-supporting reverse osmosis membranes prepared in examples 16 to 20
As can be seen from the data in Table 4, the width of the conveyer belt has no significant influence on the separation performance of the polyamide self-supporting reverse osmosis membrane prepared by the invention, which shows that the preparation method of the invention can realize the large-area preparation of the high-performance polyamide self-supporting reverse osmosis membrane.
Examples 21 to 24
The concentrations of m-phenylenediamine solution were adjusted to 2g/L, 5g/L, 10g/L and 50g/L, and the concentrations of trimesoyl chloride solution were adjusted to 0.1g/L, 0.25g/L, 0.5g/L and 2.5g/L, respectively, and the other conditions were the same as in example 1.
Test example 5
The polyamide self-supporting reverse osmosis membranes prepared in examples 21 to 24 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 5.
TABLE 5 salt rejection and Water flux of Polyamide self-supporting reverse osmosis membranes prepared in examples 21 to 24
As can be seen from the data in Table 5, the salt rejection rate of the polyamide self-supporting reverse osmosis membrane prepared by the invention gradually increases and the water flux continuously decreases with the increase of the concentrations of the amine monomer and the acyl chloride monomer. The concentration of the reaction monomer is increased, the crosslinking degree and the thickness of the polyamide film generated by interfacial polymerization are both increased, so that the interception performance of the polyamide self-supporting reverse osmosis membrane is increased, and the permeability is reduced.
Examples 25 to 28
The interfacial polymerization reaction times were adjusted to 5s, 15s, 30s, and 120s, respectively, and the other conditions were the same as in example 1.
Test example 6
The polyamide self-supporting reverse osmosis membranes prepared in examples 25 to 28 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 6.
TABLE 6 salt rejection and Water flux of Polyamide self-supporting reverse osmosis membranes prepared in examples 25 to 28
As can be seen from the data in Table 6, the salt rejection rate of the polyamide self-supporting reverse osmosis membrane prepared by the invention gradually increases and becomes stable with the increase of the interfacial polymerization reaction time, and the water flux continuously decreases. The interfacial polymerization reaction time is too short, and the generated polyamide film has low crosslinking degree, lower interception performance and higher permeability. The interfacial polymerization reaction time exceeds 30s, the degree of crosslinking of the polyamide film reaches a high degree, the increase along with the reaction time is not obvious, the interception performance tends to be stable, but the thickness of the film is gradually thickened along with the reaction time, and the permeability is continuously reduced.
Examples 29 to 36
The heat treatment temperature was adjusted to 60 ℃, 70 ℃, 90 ℃, 100 ℃ and the heat treatment time was 5min, 15min, 20min, 30min, and the other conditions were the same as in example 1.
Test example 7
The polyamide self-supporting reverse osmosis membranes prepared in examples 29 to 36 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 7.
TABLE 7 salt rejection and Water flux of Polyamide self-supporting reverse osmosis membranes prepared in examples 29 to 36
As can be seen from the data in Table 7, the salt rejection of the polyamide self-supporting reverse osmosis membrane prepared by the invention gradually increases and the water flux gradually decreases as the heat treatment temperature increases from 60 ℃ to 80 ℃, and the performance of the reverse osmosis membrane does not change obviously when the heat treatment temperature is above 80 ℃. The higher heat treatment temperature is beneficial to accelerating the volatilization of the residual solution on the surface of the polyamide self-supporting reverse osmosis membrane and improving the crosslinking degree of the polyamide, so that the interception performance of the reverse osmosis membrane is improved, and the permeability is reduced. With the increase of the heat treatment time to 10min, the salt rejection of the reverse osmosis membrane is increased, the water flux is slightly reduced, and the performance change of the reverse osmosis membrane is not obvious when the heat treatment time is more than 10min. The heat treatment time of 10min is enough to obtain the completely dried polyamide self-supporting reverse osmosis membrane with high crosslinking degree. From the viewpoint of improving the production efficiency and saving energy, the heat treatment temperature and time are preferably 80 ℃ and 10min, respectively.
Examples 37 to 42
The porous support materials are adjusted to be polysulfone, cellulose acetate, polyethylene, polyvinylidene fluoride, polytetrafluoroethylene and polypropylene respectively, and the rest conditions are the same as those in example 1.
Test example 8
The polyamide self-supporting reverse osmosis membranes prepared in examples 37 to 42 were tested for salt rejection and water flux. The test method comprises the following steps: the prepared reverse osmosis membrane is placed in a standard reverse osmosis testing device, and the desalination rate and the water flux of the reverse osmosis membrane to 2000ppm NaCl solution are tested under the conditions of 25 ℃ and 1.5 MPa. The results are shown in Table 8.
TABLE 8 salt rejection and Water flux of Polyamide self-supporting reverse osmosis membranes prepared in examples 37 to 42
As can be seen from the data in Table 8, the porous support material had no significant effect on the separation performance of the polyamide self-supporting reverse osmosis membrane prepared in accordance with the present invention. The polyamide self-supporting film prepared by the method can be well compounded with different porous supporting materials, so that the reverse osmosis membrane with excellent performance is obtained.
Reverse osmosis membranes were prepared in examples 1-42.
Example 43
(1) Piperazine is selected as a polyamine monomer. Piperazine was dissolved in water, and the viscosity of the solution was adjusted using glycerol to obtain a piperazine solution having a viscosity of 50mPa · s of 5g/L. The conveyor belt material used was stainless steel with a width of 0.15m. The piperazine solution was coated on the surface of the belt with a doctor blade to obtain a liquid film having a thickness of 100 μm.
(2) Trimesoyl chloride is selected as a polybasic acyl chloride monomer. Trimesoyl chloride was dissolved in isoparaffin ISOPAR H to give a polybasic acid chloride solution with a concentration of 1.5g/L. And (3) spraying the polyacyl chloride solution on the liquid film in the step (1), wherein the liquid inlet amount of the spraying operation is 1mL/min, and the spraying time is 1min.
(3) The conveyer belt is introduced into a water tank at 30 ℃ for rinsing, and the polyamide formed by reaction floats on the water surface in a self-supporting Bao Mopiao. Collecting the polyamide film on the water surface by using another conveyer belt, heating and drying, and winding to obtain the self-supporting polyamide film.
(4) The polyamide film and the polyether sulfone base film are compounded by using the conveying belt, and the acting force of the skin layer and the base film is enhanced through a post-treatment step, so that the thin-layer composite nanofiltration membrane is prepared.
The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The water flux of the prepared polyamide nanofiltration membrane is 60.1L/m 2 H, the salt rejection was 95.2%.
Examples 44 to 47
The liquid film thickness by blade coating was changed to 50 μm, 200 μm, 300 μm, and 400 μm, respectively, and the other conditions were the same as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 9.
TABLE 9 Experimental results of nanofiltration membrane preparation with different liquid film thicknesses
Examples 48 to 51
The piperazine concentration was changed to 1g/L, 3g/L, 7g/L, and 10g/L, and then the experiment was performed under the same conditions as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 10.
TABLE 10 Experimental results for nanofiltration membrane preparation with different piperazine concentrations
Examples 52 to 56
The viscosity of the polyamine solution was adjusted to 5 mPas, 10 mPas, 25 mPas, 100 mPas and 200 mPas, respectively, under the same conditions as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 11.
TABLE 11 Experimental results for nanofiltration membrane preparation with different aqueous phase solution viscosities
Examples 57 to 59
The polyamine monomers were replaced with p-phenylenediamine, 1,3-cyclohexyldimethylamine and diethylenetriamine, respectively, and the other conditions were the same as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 12.
TABLE 12 Experimental results of nanofiltration membranes prepared from different amine monomers
Examples 60 to 63
The trimesoyl chloride concentrations were changed to 0.5g/L, 1g/L, 3g/L, and 5g/L, respectively, and the other conditions were the same as in example 43. The test method comprises the following steps: placing the nanofiltration membrane in a standard nanofiltration test device at 25 deg.C and 0.4MTesting the nanofiltration membrane to 2000ppm Na under the Pa condition 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 13.
TABLE 13 Experimental results for nanofiltration membrane preparation with different trimesoyl chloride concentrations
Examples 64 to 66
The solvent of the polyacyl chloride solution was replaced with n-hexane, cyclohexane, and n-heptane, respectively, and the other conditions were the same as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 14.
TABLE 14 experimental results of nanofiltration membrane preparation using different oil phase solvents
Examples 67 to 70
The feed amount was changed to 0.5mL/min, 2mL/min, 5mL/min, 10mL/min, respectively, and the other conditions were the same as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 15.
TABLE 15 experimental results of nanofiltration membrane preparation by using different oil phase solution feed liquor quantities
Examples 71 to 74
The spraying time was changed to 0.5min, 2min, 5min, 8min, respectively, and the other conditions were the same as in example 43. The test method comprises the following steps: the prepared nanofiltration membranePlacing in a standard nanofiltration test device, testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 16.
TABLE 16 Experimental results of nanofiltration membrane preparation at different spraying times
Examples 75 to 78
The conditions of example 43 were the same except that the water temperature for rinsing the polyamide film was changed to 20 ℃, 40 ℃, 50 ℃ and 60 ℃. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 17.
TABLE 17 Experimental results of nanofiltration membrane preparation at different rinsing water temperatures
Examples 79 to 83
The kind of the polymer porous base film was replaced with polyethylene, polypropylene, polysulfone, polyvinyl chloride, polyacrylonitrile, and the other conditions were the same as in example 43. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 18.
TABLE 18 experimental results of nanofiltration membrane preparation using different polymer-based membranes
Examples 84 to 87
The material of the conveyor belt was replaced with aluminum, polyurethane, nylon, polytetrafluoroethylene, respectively, and the other conditions were the same as in example 43. The results of the experiment are shown in Table 19.
TABLE 19 Experimental results of nanofiltration membranes prepared from different conveyor belt materials
Examples 88 to 91
The same conditions as in example 43 were applied except that the belt widths were changed to 0.05m, 0.5m, 1m and 5m, respectively. The test method comprises the following steps: placing the prepared nanofiltration membrane in a standard nanofiltration testing device, and testing the nanofiltration membrane to 2000ppm Na under the conditions of 25 ℃ and 0.4MPa 2 SO 4 Salt rejection and water flux of the solution. The results of the experiment are shown in Table 20.
TABLE 20 Experimental results for preparing nanofiltration membranes at different widths of conveyor belts
Nanofiltration membranes were prepared according to examples 43 to 91.
The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (3)
1. A continuous preparation method of a polyamide functional composite membrane is characterized in that the adopted device comprises a conveying mechanism, a feeding mechanism, a spraying mechanism, a rinsing bath, a drying mechanism and a winding mechanism;
the conveying mechanism is a roller or a conveying belt;
the feeding mechanism is arranged above the conveying mechanism and used for blade-coating the first reaction monomer solution on the surface of the conveying mechanism to form a first reaction monomer liquid film; the feeding mechanism comprises a feeding funnel and a scraper, and the distance between the scraper and the conveying mechanism is adjustable;
the spraying mechanism is arranged at the downstream of the feeding mechanism and the upstream of the rinsing bath and is used for spraying the second reaction monomer solution onto the first reaction monomer liquid film, and the first reaction monomer and the second reaction monomer generate interfacial polymerization reaction to generate a self-supporting film;
the washing tank is arranged below the conveying mechanism, at least one part of the conveying mechanism is immersed in the washing liquid in the washing tank, and the self-supporting film is separated from the conveying mechanism after being washed;
the cleaned self-supporting film enters a drying mechanism for drying and heat treatment, and is wound by a winding mechanism;
the continuous preparation method comprises the following steps:
(1) Uniformly coating a polyamine solution on the surface of a conveying mechanism through a scraper to form a polyamine liquid film, wherein the thickness of the polyamine liquid film is 10-500 mu m; the polyamine solution is a glycerol aqueous solution of polyamine; the viscosity of the polyamine solution is 1-500 mPa & s; the polyamine is at least one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, piperazine, 1,3-cyclohexyldimethylamine and diethylenetriamine; the concentration of the polyamine solution is 0.1-50 g/L;
(2) Spraying a polyacyl chloride solution onto a polyamine liquid film through a spraying mechanism, and carrying out interfacial polymerization reaction on polyamine and polyacyl chloride to generate a polyamide self-supporting film; the polybasic acyl chloride is at least one of phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride and trimesoyl chloride; the solvent of the polybasic acyl chloride solution is at least one of trifluorotrichloroethane, normal hexane, cyclohexane, heptane and isoparaffin; the concentration of the polybasic acyl chloride solution is 0.1-5 g/L;
(3) The conveying mechanism attached with the polyamide self-supporting film is immersed in water in a rinsing bath, and the polyamide self-supporting film is separated from the conveying mechanism and enters a drying mechanism for drying and heat treatment;
(4) And compounding the dried and heat-treated polyamide self-supporting membrane with a porous supporting material to obtain the polyamide functional composite membrane.
2. The continuous preparation method of the polyamide functional composite membrane according to claim 1, wherein the time of the interfacial polymerization reaction is 5 to 600s.
3. The continuous preparation method of the polyamide functional composite membrane according to claim 1, wherein the temperature of the drying and heat treatment is 60 to 100 ℃; the time is 5-30 min.
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