CN115738765A - Polyamide composite film containing anthracene-based monomer - Google Patents

Abstract

The invention provides a polyamide composite membrane which has high flux and high salt rejection rate, and simultaneously has high blocking performance to boron which is non-dissociative in a neutral area. The preparation method of the polyamide composite membrane comprises the following steps: (1) Applying a polyfunctional amine monomer, an acyl halide reactive monomer and a polyfunctional acyl halide monomer on the surface of a porous carrier for interfacial polymerization to form a polyamide composite membrane; (2) Irradiating the obtained polyamide film for a certain time by using an ultraviolet surface light source with a specific wavelength to cause the monomer to generate light with the wavelength of [4+4]]And performing crosslinking reaction to obtain the processed polyamide composite membrane. The acyl halide reactive monomer has the following structure

Description

Polyamide composite film containing anthracene-based monomer

Technical Field

The invention belongs to the technical field of membranes, and relates to a preparation method and application of a polyamide composite membrane capable of realizing high flux and high salt rejection rate and having good retention capacity on boron which is not dissociated in a neutral zone.

Background

There are various techniques for removing substances (e.g., salts) dissolved in a solvent (e.g., water). Composite membranes of porous supports coated with "thin film" polyamide layers are currently the most common type of separation membranes, wherein the polyamide thin film is mainly obtained by interfacial polymerization of a polar solution containing polyfunctional amines (generally containing m-phenylenediamine, trimesamine, piperazine, aliphatic amines, polyether amines, etc.) and a non-polar solution containing polyfunctional acyl halides (generally containing trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride, etc.). Reverse osmosis membranes (see in particular the process for the preparation of reverse osmosis membranes disclosed in US4277344 to Cadotte et al) obtained by sequentially coating immiscible solutions comprising the corresponding monomers on the surface of a support (polyester + polysulfone) are widely used, for example, in the case of obtaining drinking water from seawater, alkaline water, water containing harmful substances, etc., or in the production of industrial ultrapure water, wastewater treatment, recovery of valuable substances, etc.

Boron is toxic to human bodies, animals and plants, and causes symptoms of nerve damage, growth inhibition, and the like, so that the demand of the world health organization for the content of boron in water is more strict, but since seawater contains a large amount of boron, boron removal in seawater desalination is important, and the level of the demand for the performance of removing trace amount of boron contained in seawater is more strict. Therefore, various methods for improving the boron removal performance of the composite semipermeable membrane have been proposed:

for example, patent document 1 (CN 102781560) reports a method for improving the performance by increasing the interfacial polymerization temperature and heat-treating the resulting polyamide composite membrane. Document 2 (ZHAI X, MENG J, LI R, et al. Hyperchlorine treatment on film composite RO membrane to active boron removal performance [ J ]. Desalination,2011,274 (1-3): 136-143.) also discloses a method of contacting a composite semipermeable membrane prepared by interfacial polymerization with an aqueous solution containing free chlorine. Document 3 (CHONG C Y, LAU W J, YUSOF N, et al. Students on the properties of RO membranes for salt and boron removal: fluorescence of thermal treatment methods and heating treatment [ J ]. Desalination,2018, 428) reports a method for improving the boron removal of polyamide composite membranes after interfacial polymerization by changing the kind of organic solvent;

when seawater having a pH of 8, a boron concentration of 5ppm and a TDS concentration of 3.5 wt% is permeated at 25 ℃ under an operation pressure of 5.5MPa using the membrane described in patent document 1 or patent document 2, the membrane permeation flux is 36LMH or less, the boron removal rate is not more than about 95% at most, and development of a composite semipermeable membrane having higher boron rejection performance and higher flux is desired. The composite semipermeable membrane produced according to document 3 is capable of improving boron removal performance while maintaining flux, but is far from achieving the intended purpose.

Disclosure of Invention

The invention aims to provide a polyamide composite membrane and a preparation method thereof aiming at the defects in the prior art. The polyamide composite membrane provided by the invention can realize high flux and high salt rejection rate, and has good rejection capability on boron which is not dissociated in a neutral area.

In order to achieve the above object, the present invention provides a method for preparing an anthracene-based monomer-containing polyamide composite film, comprising the steps of:

(1) Applying a mixed solution containing an acid halide reactive monomer and a polyfunctional amine monomer to the surface of a porous support, and then applying a polyfunctional acid halide monomer to form a polyamide composite membrane by interfacial polymerization;

(2) And irradiating the prepared polyamide composite film under a purple light area light source with a specific wavelength.

In step (1) of the present invention, the acyl halide reactive monomer is represented by formula (1):

wherein, R1 and R2 are independently selected from: hydrogen, amino, hydroxyl, methoxyl, carboxyl, ether group, sulfate group and sulfonic group, and at least one of R1 and R2 is amino;

r3 and R4 are independently selected from: hydrogen, hydroxyl, methoxy, carboxyl, ether group, sulfonic group and sulfuric acid group, wherein at least one of R3 and R4 is preferably hydrogen, and more preferably R3 is hydrogen;

r5, R6, R7, R8 are independently selected from: hydrogen, hydroxyl, amino, methoxy, carboxyl, sulfonic acid group, sulfuric acid group and ether group, at least one of R5, R6, R7 and R8 is amino, preferably R5, R6 or R8 is amino;

more preferably, the acid halide reactive monomer is 2, 6-diaminoanthracene, 1, 8-diaminoanthracene, 1, 5-diaminoanthracene, or the like.

In step (1) of the present invention, the polyfunctional amine monomer is preferably m-phenylenediamine and/or p-phenylenediamine, more preferably m-phenylenediamine;

the molar ratio of the acyl halide-reactive monomer to the polyfunctional amine monomer is 1:20-1:5;

in one embodiment, the mixed solution of the acid halide-containing reactive monomer and the polyfunctional amine monomer is prepared by: the polyfunctional amine monomer is preferably dissolved in a polar solvent a such as methanol, water, etc., more preferably water from the viewpoint of cost and safety; the acid halide reactive monomer is preferably dissolved in solvent B, which is N, N-Dimethylformamide (DMF), N-Dimethylacetamide (DMA), or N-methylpyrrolidone (NMP), with N-methylpyrrolidone (NMP) being more preferred; the two solutions were then mixed. Wherein the mass ratio of the solvent B to the polar solvent A is preferably 1:4-1:200, more preferably 1:20-1:100.

The porous carrier can be polysulfone-based membrane, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyphenylene oxide, polyphenylene sulfide sulfone, polyamide, polyimide, polyester, vinyl polymer, cellulose-based polymer and the like formed on non-woven fabric, wherein the vinyl polymer is selected from polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like, and the cellulose-based polymer is selected from cellulose acetate, cellulose nitrate and the like and can be a blend of one or more of the polymers. The application method on the surface of the porous carrier can be coating, soaking, spraying and the like.

The polyfunctional acyl halide monomer is not particularly limited, and aromatic or alicyclic polyfunctional acyl halide monomers and combinations thereof may be used. Non-limiting examples of aromatic polyfunctional acyl halides include trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyldicarboxylic acid chloride and naphthalenedicarboxylic acid chloride. Non-limiting examples of cycloaliphatic polyfunctional self-acid halides include cyclopropane tri-carboxylic acid chloride, cyclobutane tetra-carboxylic acid chloride, cyclopentane tri-carboxylic acid chloride, cyclopentane tetra-carboxylic acid chloride, cyclohexane tri-carboxylic acid chloride, cyclopentane dicarboxylic acid chloride, cyclobutane dicarboxylic acid chloride, cyclohexane dicarboxylic acid chloride, and tetrahydrofuran dicarboxylic acid chloride. One preferred polyfunctional acyl halide monomer is trimesoyl chloride (TMC);

the polyfunctional acyl halide monomer is dissolved in a non-polar solvent, preferably a hydrocarbon solvent (oil phase), non-limiting examples of suitable hydrocarbon solvents include: paraffin (any one or a combination of at least two of n-hexane, octane, nonane, decane, etc.), isoparaffin (any one or a combination of at least two of Isopar E, isopar G, isopar L, etc.) and aromatic hydrocarbon (any one or a combination of at least two of mesitylene, m-xylene, toluene, etc.), more preferably n-decane and Isopar G;

the concentration of the polyfunctional acyl halide monomer in the above hydrocarbon solvent is about 0.01 to 5% by weight, preferably 0.05 to 0.5% by weight.

The mass concentration ratio of the sum of the polyfunctional amine monomer and the acyl halide-reactive monomer in the mixed solution to the polyfunctional acyl halide monomer in the hydrocarbon solvent is preferably 4.

Upon contacting the polar solution and the oil phase solution with each other, the polyfunctional amine monomer and the acyl halide reactive monomer and the polyfunctional acyl halide monomer undergo interfacial polymerization at an oil-water interface to form a polyamide membrane, the interfacial polymerization temperature being 10 to 50 deg.C, more preferably 20 to 30 deg.C, and the interfacial polymerization time being less than one second, but the oil-water contact time being about 0.5 to 5 minutes, more preferably 0.5 to 2 minutes. The excess liquid can then be removed by any means of air knife, drying, hanging drop, oven drying, and the like.

In order to promote the interfacial polymerization reaction, control the reaction rate and the performance of the composite film, the temperature of the water phase or the oil phase participating in the reaction can be adjusted, and a phase transfer catalyst (such as dodecyl trimethyl ammonium chloride), an acid scavenger (such as sodium hydroxide, camphorsulfonic acid and triethylamine salt), a solubilizer (such as toluene), a complexing agent (such as phosphate compounds), a humectant (such as glycerol) and the like can be added.

In step (2) of the present invention, the polyamide composite film prepared in step (1) is irradiated with an ultraviolet surface light source. The ultraviolet light wavelength is 250-400nm, preferably 300-365nm. The irradiation time is from 0.2 to 10 minutes, preferably from 2 to 4 minutes.

In step (2), when the acyl halide reactive monomer in the polymer network is exposed to ultraviolet light, the adjacent monomer can undergo [4+4] photopolymerization to form a new covalent bond, thereby increasing the degree of crosslinking of the polymer, as shown in formula (2):

formula (2):

to further illustrate the structural change of the polyamide composite film in step (1) before and after ultraviolet irradiation, the polyamide part of the example 1, 5-diaminoanthracene is shown as formula (3):

after the polyamide composite membrane is irradiated by ultraviolet, intramolecular and intermolecular [4+4] crosslinking reaction or partial crosslinking can be simultaneously carried out, the crosslinking degree of the polyamide composite membrane is further improved, and the retention capacity of a composite membrane sheet, particularly the retention capacity of boron with non-dissociative property in a neutral area is improved.

The polyamide composite membrane prepared according to the present invention may optionally contain a hygroscopic polymer on at least a part of the surface of its polyamide layer. Polymers include polymeric surfactants, polyacrylic acids, polyvinyl acetates, polyalkylene oxide compounds, poly (oxazoline) compounds, polyacrylamides, and related reaction products, such as those generally described in US 7815987, US7918349, US 7905361, and US 201/0220569. In some embodiments, these polymers may be blended and/or reacted, and may be coated or otherwise applied to the polyamide layer surface from the same solution, or applied sequentially.

The invention has the beneficial effects that:

an anthracene group-containing acyl halide reactive monomer which has large steric hindrance and can generate [4+4] photopolymerization is introduced into a water phase, so that the desalting capability of the membrane can be greatly improved on the premise of slightly reducing the flux of the polyamide membrane, and the boron with non-dissociative property in a neutral region has high stopping performance.

Detailed Description

In order to better understand the technical solution of the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

1. The main reagent sources and designations in the examples and comparative examples are:

polysulfone available from BASF, germany, ultrason S6010.

Non-woven fabrics, available from chekiang billows science and technology ltd, R80.

Polysulfone-based membranes, preparation method: dissolving polysulfone in N, N-dimethylformamide to prepare a solution with a solid content of 18%, coating the polysulfone solution on the surface of a non-woven fabric by using a wet film preparation device with a thickness of 250 micrometers, standing in the air for 4-5 seconds, soaking the non-woven fabric in pure water at room temperature for 5 minutes to complete phase inversion, soaking the polysulfone base film subjected to phase inversion in the pure water at room temperature, replacing water every 2 hours, fully cleaning the residual solvent, and cutting for later use.

The other reagents are purchased from Shanghai Aladdin Biotechnology, inc. and are reagent grade raw materials unless otherwise specified.

2. Test methods for polyamide films in examples and comparative examples:

regarding various properties of the polyamide composite membranes in the comparative examples and examples, the polyamide composite membranes were subjected to membrane operation treatment for 24 hours by supplying seawater (salt concentration: about 3.5%) having an operating pressure of 5.5MPa and a pH adjusted to 25 ℃ and a pH of 7.0, and the membrane properties were determined by measuring the quality of permeate water and supply water before and after the membrane:

salt rejection calculation method:

salt rejection (%) =100 × {1- (salinity of permeate water/salinity of feed water) };

the calculation method of the flux comprises the following steps:

the amount of membrane permeation water of feed water (seawater) was converted into the amount of water permeation per 1 square meter of membrane area per 1 hour (cubic decimeter), and the membrane permeation flux (L/m) ² H) represents;

the boron removal rate calculation method comprises the following steps:

the boron concentrations in the feed water and the permeated water were analyzed by an ICP emission analyzer (P-4010 manufactured by hitachi), and the percentage of shed light was obtained by the following equation:

the boron removal rate (%) =100 × {1- (boron concentration in permeated water/boron concentration in supplied water) }.

The ultraviolet spectrum characterization method of the polyamide membrane material comprises the following steps: an ultraviolet spectrum adopts a UV-3600 instrument manufactured by Shimadzu to test the ultraviolet absorption spectrum of the polyamide film at different irradiation time periods, and the absorption intensity in the range of 350 +/-5 nm is measured;

x = Abs (end)/Abs (initial)

And Abs (end) is the ultraviolet absorption intensity measured at 350 +/-5 nm after the irradiation of the ultraviolet surface light source is finished, and Abs (initial) is the ultraviolet absorption intensity measured at 350 +/-5 nm when the ultraviolet surface light source is not irradiated.

Example 1:

sticking the cut polysulfone base membrane on a plate frame at 25 ℃, wherein the size of the plate frame is a rectangle with the side length of 16 x 12cm;

dissolving 1, 5-diaminoanthracene in N-methylpyrrolidone, and mixing with an aqueous solution containing m-phenylenediamine, camphorsulfonic acid, and triethylamine to obtain an aqueous solution containing 0.5wt% of 1, 5-diaminoanthracene, 5wt% of N-methylpyrrolidone, 4wt% of m-phenylenediamine, 6wt% of camphorsulfonic acid, and 3wt% of triethylamine;

immersing a plate frame into the aqueous phase solution for 1 minute, extruding by a rubber stick to remove redundant aqueous phase, pouring an organic phase of n-decane containing 0.165wt% of trimesoyl chloride onto the surface of a polysulfone base membrane, reacting for 1 minute, controlling the temperature of the membrane surface to be 25 ℃, removing redundant solution on the membrane surface by using an air knife, removing residual organic phase by spray washing through 1wt% of sodium carbonate solution and pure water, cleaning for 2 minutes in hot water at 90 ℃ to obtain a target polyamide composite membrane, and irradiating the polyamide composite membrane for 25 seconds by placing the polyamide composite membrane under an ultraviolet surface light source (with the wavelength of 365 +/-10 nm) to obtain a polyamide composite membrane which is immersed in the pure water for later use. The prepared polyamide composite membrane was then treated with a 0.3 wt% sodium nitrite aqueous solution adjusted to pH 2.2 with sulfuric acid at room temperature (25 ℃) for 1 minute, the polyamide composite membrane was taken out of the sodium nitrite aqueous solution, the solution was drained, the polyamide composite membrane was immersed in a 1wt% sodium sulfite aqueous solution for 0.5 minute, the polyamide composite membrane was taken out of the sodium sulfite and then treated in 90 ℃ water for 2 minutes, and the obtained polyamide composite membrane was tested and showed the membrane flux, salt rejection and boron removal performance as shown in table 2.

Examples 2 to 6:

the polyamide composite films used for the treatment, the interfacial polymerization temperature, the monomer concentration and the irradiation time of the ultraviolet surface light source were changed as shown in table 1, the other operations were conducted in the same manner as in example 1, and the X value of the polyamide composite film for each example is shown in table 2. The prepared membrane was immersed in pure water for use, and the flux, salt rejection and boron removal performance of the prepared polyamide composite membrane are shown in table 2.

Comparative example 1

The cut polysulfone based membrane is attached to a plate frame at 25 ℃, the plate frame is a rectangle with the size of 16 x 12cm on one side, the plate frame is immersed in an aqueous phase solution containing 4.5wt% of m-phenylenediamine, 6wt% of camphorsulfonic acid and 3wt% of triethylamine and soaked for 1 minute, a rubber stick is used for removing redundant aqueous phase solution on the surface, then an organic phase containing 0.165wt% of trimesoyl chloride and n-decane is poured on the surface of the polysulfone based membrane and reacts for 1 minute, the temperature of the membrane surface is controlled to be 25 ℃, then redundant solution on the membrane surface is removed by an air knife, then the residual organic phase on the membrane surface is removed by spraying and washing with 1wt% of sodium carbonate solution and pure water, then the membrane is washed in hot water at 90 ℃ for 2 minutes, the polyamide composite membrane is obtained and soaked in the pure water for standby, and the subsequent processing mode is the same as that of the embodiment 1.

Comparative example 2

The polyamide composite membrane used for the treatment was changed as shown in table 1, and the other operations were performed in the same manner as in example 1, and the prepared membrane was immersed in pure water for use, and the flux, salt rejection and boron removal performance for preparing the polyamide composite membrane are shown in table 2.

TABLE 1

TABLE 2

	Value of X	Rate of salt removal/%)	flux/LMH	Boron removal rate/%)
					Comparative example 1	0	99.71	40.2	88.6
Comparative example 2	0	99.72	38	89.5
					Example 1	0.55	99.76	37	92
Example 2	0.7	99.72	38.2	90.8
					Example 3	0.22	99.85	36	96.8
Example 4	0.55	99.8	37.4	93.2
					Example 5	0.45	99.75	39.5	91.5
Example 6	0.38	99.8	38	94

Claims (8)

1. A polyamide composite membrane characterized in that a compound represented by the formula (1) is contained in a monomer for preparation:

wherein R1 and R2 are independently selected from: hydrogen, amino, hydroxyl, methoxy, carboxyl, sulfonic group, sulfuric acid group and ether group, and at least one of R1 and R2 is amino;

r3 and R4 are independently selected from: hydrogen, hydroxyl, methoxy, carboxyl, ether group, sulfonic group and sulfuric acid group, preferably at least one of R3 and R4 is hydrogen;

r5, R6, R7, R8 are independently selected from: hydrogen, hydroxyl, amino, methoxy, carboxyl, sulfonic acid group, sulfuric acid group and ether group, at least one of R5, R6, R7 and R8 is amino, preferably R5, R6 or R8 is amino;

more preferably, the formula (1) is 2, 6-diaminoanthracene, 1, 8-diaminoanthracene or 1, 5-diaminoanthracene.

2. A preparation method of a polyamide composite membrane comprises the following steps:

(1) Applying a solution containing an acyl halide reactive monomer, a polyfunctional amine monomer and a solution containing a polyfunctional acyl halide monomer to the surface of a porous support, and forming a polyamide composite membrane through interfacial polymerization;

(2) Irradiating the prepared polyamide composite film under an ultraviolet surface light source with a specific wavelength;

wherein the acyl halide reactive monomer is represented by formula (1):

wherein, R1 and R2 are independently selected from: hydrogen, amino, hydroxyl, methoxyl, carboxyl, ether group, sulfate group and sulfonic group, and at least one of R1 and R2 is amino;

r3, R4 are independently selected from: hydrogen, hydroxyl, methoxyl, carboxyl, ether group, sulfonic group, sulfate group, preferably at least one of R3 and R4 is hydrogen;

r5, R6, R7, R8 are independently selected from: hydrogen, hydroxyl, amino, methoxy, carboxyl, sulfonic acid, sulfuric acid and ether groups, and at least one of R5, R6, R7, R8 is an amino group, preferably R5, R6 or R8 is an amino group;

more preferably, the acid halide reactive monomer is 2, 6-diaminoanthracene, 1, 8-diaminoanthracene, or 1, 5-diaminoanthracene.

3. The method according to claim 2, wherein the polyfunctional amine monomer is selected from m-phenylenediamine and p-phenylenediamine.

4. A process according to claim 2 or 3, wherein the molar ratio of acyl halide-reactive monomer to polyfunctional amine monomer is 1:20-1:5.

5. the production method according to any one of claims 2 to 4, wherein the polyfunctional acyl halide monomer is an aromatic or alicyclic polyfunctional acyl halide monomer, preferably trimesoyl chloride.

6. The production process according to any one of claims 2 to 5, wherein the interfacial polymerization temperature is 10 to 50 ℃, preferably 20 to 30 ℃ and the interfacial polymerization time is 0.5 to 5 minutes, preferably 0.5 to 2 minutes.

7. The method of any one of claims 2-6, wherein the ultraviolet light has a wavelength of 250-400nm, preferably 300-365nm.

8. The production method according to any one of claims 2 to 7, wherein the irradiation time period in the step (2) is 0.2 to 10 minutes.