CN102698620A - Method for preparing reverse osmosis composite membrane by taking hyperbranched polymer as monomer - Google Patents

Abstract

The invention discloses a method for preparing a reverse osmosis composite membrane using a hyperbranched polymer as a monomer. excess water phase solution on the membrane surface; (2) place the obtained porous support membrane in the air to dry in the shade, and then soak in the oil phase solution to carry out interfacial reaction to obtain the nascent eco-film; (3) after the nascent eco-film is heat-treated, dry it in the shade at room temperature, A reverse osmosis composite membrane is obtained; the aqueous phase solution is an aqueous solution of a water-soluble hyperbranched polymer containing a catalyst 4-aminopyridine derivative whose end is an amino group or a hydroxyl group; the reaction monomer in the oil phase solution is a multi-acid chloride or One or more mixtures of polyisocyanates. The invention discloses a method for preparing a reverse osmosis composite membrane using a hyperbranched polymer as a monomer, which can rapidly prepare a reverse osmosis composite membrane with excellent performance, is simple to operate, and has high salt rejection while realizing high membrane flux. It can be used in water treatment fields such as seawater desalination.

Description

A kind of method that takes hyperbranched polymer as monomer to prepare reverse osmosis composite membrane

technical field

The invention relates to the field of reverse osmosis membranes in membrane science and technology, in particular to a method for preparing reverse osmosis composite membranes by using hyperbranched polymers as monomers through interfacial polymerization.

Background technique

The intensification of the water resource crisis has prompted the rapid development of membrane water treatment technology. Among them, the application of reverse osmosis membrane in the field of water treatment has attracted more and more attention, especially the high-flux reverse osmosis membrane, which can greatly improve the water treatment capacity. Reduce water treatment costs.

At present, the most commonly used reverse osmosis membrane preparation method is the composite method, that is, a layer of nano-pore ultra-thin film with separation performance is composited on the microporous base membrane (porous support membrane) to obtain a composite membrane. The interfacial polymerization method is due to the operation Simple, rapid reaction, can be used to prepare ultra-thin films, and after film formation, the membrane flux is large and the hydrophilicity is good, so it is widely used.

The invention with application number 200580033707.1 discloses a method for manufacturing composite reverse osmosis membranes in an industrially stable and continuous manner. , including: step A, which moves the porous support while applying an aqueous solution A containing a compound having two or more active amine groups on the porous support to form an aqueous solution coating layer; step B, which moves the porous support Keep the aqueous solution coating layer on the support body for 0.2 to 15 seconds, so that the aqueous solution A penetrates into the micropores of the porous support body; step C, while maintaining the aqueous solution A in the micropores of the porous support body Inside, while removing the aqueous solution coating layer; and step D, after step C, apply an organic solution B containing a polyfunctional acid halide on the surface of the porous support, and bring the organic solution B into contact with the aqueous solution A Interfacial polymerization is carried out to form a polyamide-based skin layer, and a composite reverse osmosis membrane is continuously manufactured.

The invention whose application number is 88106576.5 discloses an improved composite polyamide membrane and its manufacturing method. The improved membrane is prepared by interfacial polymerization of a cationic polymeric wetting agent with an acid halide in an aqueous solution containing a polyfunctional amine reactant to form a layer on a microporous support. Thin film polyamide inhibitory layer; alternatively, the wetting agent is applied directly to the substrate and interfacial polymerization can take place on the treated substrate.

The membrane performance test of the reverse osmosis membrane is that under the pressure required for separation provided by the high-pressure valve, the raw salt solution enters the membrane module in a cross-flow full circulation mode, and the permeate is obtained after membrane treatment. By recording the amount of liquid that passes through the reverse osmosis membrane within a certain period of time during stable operation, the membrane flux is obtained, and the membrane rejection rate is obtained by comparing the ion concentration of the permeate and the raw material. Membrane flux can also be obtained by recording the time required to pass a certain amount of liquid during stable operation.

In response to the growing shortage of water resources, it is necessary to prepare reverse osmosis composite membranes with higher membrane flux and salt rejection rate, which can be applied to seawater desalination treatment, which can greatly alleviate the current water resource shortage in many countries and regions.

In order to obtain a reverse osmosis composite membrane with better membrane separation performance, new monomers can be found on the basis of existing reverse osmosis composite membranes prepared from polyacyl chlorides and polyamines.

Contents of the invention

The invention provides a method for preparing a reverse osmosis composite membrane using a hyperbranched polymer as a monomer. The operation is simple, the preparation time is short, and the prepared membrane has excellent performance. While maintaining a high membrane flux, a higher Salt rejection.

A kind of method that takes hyperbranched polymer as monomer to prepare reverse osmosis composite membrane is characterized in that, comprises the steps:

(1) After soaking the porous support membrane in the aqueous phase solution for a period of time, remove the excess aqueous phase solution on the surface of the porous support membrane;

(2) Place the obtained porous support membrane in the air to dry in the shade, then soak in the oil phase solution, carry out interfacial reaction, and obtain the nascent eco-membrane;

(3) After heat treatment of the nascent membrane, dry in the shade at room temperature to obtain a reverse osmosis composite membrane;

The aqueous phase solution is an aqueous solution of a water-soluble hyperbranched polymer containing a catalyst 4-aminopyridine derivative whose end is an amino group or a hydroxyl group;

The reactive monomer in the oil phase solution is one or more of polyacyl chloride or polyisocyanate.

The porous support membrane must have a certain support strength and a suitable pore size, and not participate in interfacial reactions, such as polysulfone membrane, polyethersulfone membrane, polyacrylonitrile, polyvinylidene fluoride and the like.

The 4-aminopyridine derivative in the water phase solution is used as a catalyst, and the water-soluble hyperbranched polymer with an amino group or hydroxyl group at the end is used as a water phase monomer.

Since polyacyl chlorides and polyisocyanates can be dissolved in non-water-miscible organic solvents such as n-hexane and cyclohexane, polyacyl chlorides contain multiple acid chloride groups, and polyisocyanate contains multiple isocyanate groups. The acid chloride groups and isocyanate The group can undergo polycondensation reaction with amine group or hydroxyl group to form a polymer. Therefore, the polyacyl chloride or polyisocyanate in the oil phase solution can be water-soluble with the amino group or hydroxyl group in the water phase solution at the interface between the oil phase and the water phase Hyperbranched polymers react to form polymer ultrathin films.

The polyacyl chlorides include trimesoyl chloride, isophthaloyl chloride, etc., the polyisocyanates include toluene diisocyanate, etc., and the reaction monomer in the oil phase can be a mixture of several polyacyl chlorides, or several The mixture of polyisocyanates can also be a mixture of at least one polyacyl chloride and at least one polyisocyanate.

The porous support membrane is the carrier of the interfacial polymerization reaction, and is also a component of the synthetic reverse osmosis composite membrane, which can improve the strength of the reverse osmosis composite membrane. The porous support membrane is immersed in the aqueous phase solution to make the aqueous phase solution Fully diffuse into the micropores of the porous support membrane, then take out the porous support membrane, remove the excess water phase solution and air bubbles on the surface, and place the porous support membrane in the air to dry in the shade until a thin layer of water phase is evenly distributed on the surface solution, and then the porous support membrane is placed in the oil phase solution, and the hyperbranched water-soluble polymer whose terminal is an amine or hydroxyl group in the water phase solution and the reactive monomer in the oil phase solution react rapidly after the two-phase interface contacts After a period of time, a uniform and dense ultra-thin nascent membrane with nano-scale pores is formed.

The composite film obtained by interfacial polymerization is placed under the condition of 50-60° C., heat-treated for 10-30 minutes, and then immersed in pure water for storage until use.

In order to overcome the high molecular weight of the water-soluble hyperbranched polymer whose terminal is an amine group or a hydroxyl group, when it is polymerized with polyacyl chloride or polyisocyanate at the interface of the water phase and the oil phase, there is a large reaction steric hindrance and transmission resistance. Adding 4-aminopyridine derivatives into the aqueous phase solution can be used as a phase transfer catalyst and an acylation reaction catalyst at the same time, so as to improve the activity of the amine group or hydroxyl group, thereby promoting the reaction of the amine group or hydroxyl group.

Preferably, the hyperbranched polymer is water-soluble hyperbranched aromatic polyamide ester, hyperbranched polyethyleneimine, hyperbranched polyurethane.

The end of the hyperbranched polymer is substituted by amino group or hydroxyl group, and can be dissolved in pure water to form an aqueous phase solution.

Preferably, the mass fraction of the water-soluble hyperbranched polymer whose terminal is an amino group or a hydroxyl group in the aqueous phase solution is 0.5% to 3%.

For different reaction systems, the mass fraction of water-soluble hyperbranched polymers (i.e., water phase monomers) with amino or hydroxyl groups at the end in the aqueous phase solution is slightly different, and the mass fraction of the aqueous phase monomers is too large, which is not conducive to water The diffusion of phase solution in the porous support membrane, the mass fraction of the water phase monomer is too small, the water phase monomer participating in the interface reaction is too little, which is not conducive to the progress of the reaction, and then affects the membrane performance of the obtained reverse osmosis composite membrane .

Preferably, the mass fraction of the water-soluble hyperbranched polymer whose terminal is an amino group or a hydroxyl group in the aqueous phase solution is 2%.

When the mass fraction of the water-soluble hyperbranched polymer whose terminal is amine or hydroxyl group in the aqueous phase solution is 2%, the membrane performance of the prepared reverse osmosis composite membrane is the best.

Preferably, the mass ratio of the catalyst 4-aminopyridine derivative to the water-soluble hyperbranched polymer whose terminal is an amino or hydroxyl group in the aqueous phase solution is 1-16:100.

The amount of catalyst 4-aminopyridine derivatives is too small, can not play a good catalytic effect, too much, resulting in waste, when the catalyst 4-aminopyridine derivatives and the end of the hyperbranched water-soluble polymerization When the mass ratio of the catalyst is 1-16:100, both the catalytic effect and the catalytic efficiency can be taken into account.

Preferably, the catalyst 4-aminopyridine derivative is one of 4-dimethylaminopyridine or 4-pyrrolidinylpyridine.

4-dimethylaminopyridine or 4-pyrrolidinylpyridine can obtain higher catalytic efficiency and obtain a reverse osmosis composite membrane with excellent performance.

Preferably, the organic solvent used in the oil phase solution is one or a mixture of n-hexane, cyclohexane or ethyl acetate.

The organic solvent should be a good solvent for the reaction monomer in the oil phase solution, has stable properties, does not participate in the reaction, and is incompatible with water. Normal hexane, cyclohexane or ethyl acetate are commonly used solvents and meet the requirements. They can be used as solvents for reactive monomers in the oil phase solution to obtain reverse osmosis composite membranes with good membrane performance.

Preferably, the mass fraction of the reactive monomer in the oil phase solution is 0.1%-2.0%.

The mass fraction of the reaction monomer in the oil phase solution depends on the mass fraction of the water phase monomer in the water phase solution, and the mass fraction of the water phase monomer in the water phase solution is 0.5 to 3%, which can be determined according to the stoichiometric number and reaction Conditions, calculate the mass fraction of the appropriate oil phase monomer in the oil phase solution.

Preferably, the soaking time in the aqueous phase solution in the step (1) is 10-30 minutes.

The immersion time in the aqueous phase solution should ensure that the aqueous phase solution can fully diffuse into the micropores of the porous support membrane, so that when the porous support membrane is immersed in the oil phase solution, the water phase monomer and oil in the aqueous phase solution The reactive monomers in the phase solution react rapidly at the water-oil interface.

Preferably, the interfacial reaction time in the step (2) is at least 4 minutes.

The interfacial reaction is carried out until the oil phase solvent is completely volatilized, which should be at least 4 minutes.

The invention discloses a method for preparing a reverse osmosis composite membrane using a hyperbranched polymer as a monomer, which can rapidly prepare a reverse osmosis composite membrane with excellent performance, is simple to operate, and has high salt rejection while realizing high membrane flux. It can be used in water treatment fields such as seawater desalination.

Description of drawings

Fig. 1 is the scanning electron micrograph of the reverse osmosis composite membrane that embodiment 1 prepares;

Fig. 2 is the scanning electron micrograph of the reverse osmosis composite membrane that embodiment 2 prepares;

Fig. 3 is the scanning electron micrograph of the reverse osmosis composite membrane that embodiment 16 prepares;

Fig. 4 is a scanning electron micrograph of the reverse osmosis composite membrane prepared in Example 15.

Detailed ways

Example 1

(1) The polysulfone base film is soaked in 2%wt/v octahydroxyl hyperbranched aromatic polyamide ester PS-1200 (Netherlands DSM Company) aqueous solution containing 4-dimethylaminopyridine (DMAP) for 20min, 4- The mass ratio of dimethylaminopyridine to octahydroxy hyperbranched aromatic polyamide ester PS-1200 is 2:100 to remove excess solution and air bubbles on the surface of the polysulfone bottom film;

(2) Place the gained nascent eco-film in the air to dry in the shade until a layer of thin water phase solution is evenly distributed on the surface of the polysulfone base film, then soak in 1% wt/v trimesoyl chloride-n-hexane solution, and carry out interfacial reaction until The n-hexane is completely volatilized to obtain the nascent eco-film;

(3) Treat the nascent membrane at 60°C for 20 minutes, dry it in the shade at room temperature to obtain a reverse osmosis composite membrane, and immerse it in pure water for preservation;

Add the salt solution to be treated into the raw material tank, put the prepared reverse osmosis composite membrane into the membrane module, turn on the raw material pump, the raw material liquid passes through the rotameter and the valve, and adjust the valve so that the raw material liquid flows at a rate of 3.0L/min at a different rate. The flow enters the membrane module in the way of full circulation, and adjust the high pressure at the same time, so that the pressure difference rises slowly to 0.6MPa within half an hour. After one hour of stable operation, record the time required to collect 10mL of permeate at the outlet of the module to obtain the membrane flux. And use a conductivity meter to measure the permeation conductivity to obtain its ion concentration, and obtain the rejection rate by comparing the ion concentration of the permeate and the raw material solution.

The raw material solution is 2000ppm NaCl aqueous solution, and the membrane properties of the obtained reverse osmosis composite membrane are shown in Table 1.

Embodiment 2～7

Only change the mass ratio of 4-dimethylaminopyridine and octahydroxyl hyperbranched aromatic polyamide ester PS-1200 (see Table 1), all the other experimental operations and experimental conditions are the same as in Example 1, the prepared reverse osmosis composite membrane The membrane properties are listed in Table 1.

Table 1

Embodiment 8-14

The mass ratio of 4-dimethylaminopyridine to octahydroxyl hyperbranched aromatic polyamide ester PS-1200 is 8:100, and the mass concentration of octahydroxyl hyperbranched aromatic polyamide ester PS-1200 is shown in Table 2. The remaining experimental operations And the experimental conditions are the same as in Example 1, and the membrane properties of the prepared reverse osmosis composite membrane are shown in Table 2.

Table 2

Examples 15-20

Replace trimesoyl chloride with toluene diisocyanate (TDI), the mass ratio of 4-dimethylaminopyridine to octahydroxy hyperbranched aromatic polyamide ester PS-1200 is 8:100, octahydroxy hyperbranched aromatic polyamide ester The mass concentration of PS-1200 was 2.0%, and the rest of the experimental operation and experimental conditions were the same as in Example 1. The membrane properties of the prepared reverse osmosis composite membrane are shown in Table 3.

table 3

Example 21

The polysulfone ultrafiltration bottom membrane was replaced with polyethersulfone ultrafiltration bottom membrane (PES), the mass ratio of 4-dimethylaminopyridine to octahydroxy hyperbranched aromatic polyamide ester PS-1200 was 8:100, and octahydroxy hyperbranched The mass concentration of aromatic polyamide ester PS-1200 is 2.0%. The rest of the experimental operation and experimental conditions are the same as in Example 1. The membrane flux of the prepared reverse osmosis composite membrane is 58.3L·m ^-2 ·h ^-1 . The rejection rate was 91.8%.

Examples 22-28

Replace octahydroxy hyperbranched aromatic polyamide ester PS-1200 with hyperbranched polyethyleneimine (PEI) with a weight average molecular weight of 20,000, and replace 4-dimethylaminopyridine with 4-pyrrolidinylpyridine (4-PPY) , the mass concentration of hyperbranched polyethyleneimine is 1% (wt/v) (the mass ratio of 4-pyrrolidinopyridine and hyperbranched polyethyleneimine is shown in Table 3), except that the operating pressure becomes 1.6MPa, the other The experimental operation and experimental conditions are the same as in Example 1, and the membrane properties of the prepared reverse osmosis composite membrane are shown in Table 3.

table 3

Examples 29-32

Replace octahydroxy hyperbranched aromatic polyamide ester PS-1200 with hyperbranched polyethyleneimine (PEI) with a weight average molecular weight of 20,000, and replace 4-dimethylaminopyridine with 4-pyrrolidinylpyridine (4-PPY) , (the mass concentration of hyperbranched polyethyleneimine in the aqueous phase solution is shown in Table 4), the mass ratio of 4-pyrrolidinopyridine and hyperbranched polyethyleneimine is 4: 100, except that the operating pressure is 1.6MPa, the other The experimental operation and experimental conditions are the same as in Example 1, and the membrane properties of the prepared reverse osmosis composite membrane are shown in Table 4.

Table 4

Example 29 30 31 32 The mass concentration of PEI in the aqueous phase solution 0.5% 1.0% 1.5% 2.0% Membrane flux (L·m ^-2 ·h ^-1 ) 35 32 31 30 Salt rejection rate (%) 77.5 82.5 85 88

Claims (10)

1. one kind is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, comprises the steps:

(1) porous support membrane was soaked in the aqueous phase solution after a period of time, removes the unnecessary aqueous phase solution in porous support membrane surface;

(2) place air to dry in the shade the gained porous support membrane, be soaked in oil-phase solution again, carry out interfacial reaction, obtain the nascent state film;

(3) after the heat treatment of nascent state film, dry in the shade under the room temperature, obtain reverse osmosis composite membrane;

Said aqueous phase solution is that the end that contains catalyst 4-amido pyridine derivate is the water-soluble ultrabranching aqueous solutions of polymers of amido or hydroxyl;

Reaction monomers is one or more the mixture in polynary acyl chlorides or the polynary isocyanide ester in the said oil-phase solution.

2. as claimed in claim 1 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, described dissaving polymer is water-soluble ultrabranching aromatic polyamide ester, hyperbranched polyethyleneimine, super branched polyurethane.

3. as claimed in claim 2 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, end is 0.5%～3% for the mass fraction of the water-soluble ultrabranching polymer of amido or hydroxyl in the said aqueous phase solution.

4. as claimed in claim 3 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, end is 2% for the mass fraction of the water-soluble ultrabranching polymer of amido or hydroxyl in the said aqueous phase solution.

5. as claimed in claim 1 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer; It is characterized in that catalyst 4-amido pyridine derivate and end are 1～16: 100 for the mass ratio of the hyperbranched water-soluble polymer of amido or hydroxyl in the said aqueous phase solution.

As claim 1 or 5 described be the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that said catalyst 4-amido pyridine derivatives is a kind of in 4-dimethylamino pyridine or the 4-pyrrolidinyl pyridine.

7. as claimed in claim 1 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, used organic solvent is one or more the mixture in n-hexane, cyclohexane or the ethyl acetate in the said oil-phase solution.

8. as claimed in claim 1 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, the mass fraction of reaction monomers is 0.1%～2.0% in the said oil-phase solution.

9. as claimed in claim 1 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, the soak time in the said step (1) in aqueous phase solution is 10～30min.

10. as claimed in claim 1 is the method that monomer prepares reverse osmosis composite membrane with the dissaving polymer, it is characterized in that, said step (2) the median surface reaction time is at least 4min.

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