CN115920673A - High-flux aromatic polyamide reverse osmosis membrane and preparation method thereof - Google Patents
High-flux aromatic polyamide reverse osmosis membrane and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-flux aromatic polyamide reverse osmosis membrane and a preparation method thereof. The reverse osmosis membrane comprises a non-woven fabric, a polysulfone porous supporting layer and a polyamide desalting layer, wherein the polyamide desalting layer is formed by performing interfacial polycondensation on a water phase solution of m-phenylenediamine and an oil phase solution of trimesoyl chloride. The reverse osmosis membrane provided by the invention has high flux,The desalination rate of the reverse osmosis membrane is more than 98.0 percent and the permeation flux is 60.0L/(m) under the operation pressure of 0.41MPaG by taking sodium chloride with the concentration of 250mg/L as raw water at the temperature of 25 ℃, and the operating pressure of the reverse osmosis membrane is 2 H) above, the magnitude of the permeate flux decay is less than 15% after 90 hours of continuous operation. The membrane provided by the invention can be used in the fields of household water purifiers, pure water manufacturing, industrial wastewater treatment and the like.
Description
Technical Field
The invention belongs to the field of reverse osmosis membranes, and particularly relates to a high-flux aromatic polyamide reverse osmosis membrane and a preparation method thereof.
Background
In recent years, with the improvement of living standard of people and the frequent occurrence of water pollution events, the attention on the water quality safety of drinking water is higher and higher. The reverse osmosis membrane technology is the most effective desalination method, is not only widely applied to the fields of seawater desalination, ultrapure water manufacture, industrial wastewater treatment and recycling and the like, but also can be applied to household and commercial water purifiers so as to reduce the content of calcium, magnesium and other ions in tap water, remove harmful heavy metals and organic matters and ensure the health of drinking water of people. In order to reduce the water production waiting time of the water purifier and reduce the ratio of wastewater/pure water, it is necessary to provide a reverse osmosis membrane having high flux and high salt rejection rate at a relatively low pressure.
The method for obtaining the commercial aromatic polyamide reverse osmosis membrane by performing interfacial polymerization on the surface of a polysulfone basal membrane by using m-phenylenediamine and trimesoyl chloride comprises the following steps of: adding alcohol solvents (CN 1104939C, CN 1170627A) such as isopropanol and the like, additives such as phosphate complexing agents (CN 1210093C, CN1441693, CN210093C, CN 104470627A), carboxylic acid or carboxylic ester (CN 1328483A) and the like into a water phase or an oil phase to regulate and control an interfacial polycondensation process, and optimizing a polyamide layer structure; dissolving oligomers in the polyamide layer by using polar pure solvents such as isopropanol, ethanol, benzyl alcohol and the like, and simultaneously piling and winding the polyamide in a continuous manner again (CN 111545065A); chemical reagents such as sodium hypochlorite (US 5876602, CN 1103625C) or nitrous acid (CN 105377406A, CN105848765B, CN105873666A, CN106170333B, CN106257977B, CN108348869A, CN102665881A, CN103025412A, CN 105026022A) are adopted for treatment to change the species and the proportion of the groups in the polyamide layer. These measures have limited flux increase range for reverse osmosis membrane on one hand, and even mostly trade off the salt rejection rate of the membrane by reducing the degree of crosslinking of polyamide on the other hand. The loose desalted layer is extremely unstable, and although the initial flux is high, the flux is seriously attenuated in the use process, so that the requirement of a household water purifier cannot be met.
As described above, although various means are disclosed to increase the flux of the reverse osmosis membrane, there are problems that the flux increase width is insufficient, the salt rejection rate is low, and the flux attenuation is severe for long-term operation.
Disclosure of Invention
The invention aims to provide an aromatic polyamide reverse osmosis membrane which has high flux, high desalination rate and reduced flux attenuation in long-term operation, and can overcome the problems of insufficient flux increase amplitude, low desalination rate and serious flux attenuation in long-term operation.
In order to achieve the purpose, the invention adopts the following technical scheme:
a high-flux aromatic polyamide reverse osmosis membrane comprises a non-woven fabric, a polysulfone porous supporting layer and a polyamide desalting layer, wherein the polyamide desalting layer is formed by an interfacial polycondensation reaction of an aqueous phase solution of m-phenylenediamine and an oil phase solution of trimesoyl chloride; wherein the oil phase solution contains carboxylic acid compounds of indole and organic tin auxiliary agents.
The carboxylic acid compound of indole is a compound containing indole structure and carboxylic acid group in molecule, and the indoleacetic acid which is a representative compound is an important plant growth hormone. The inventor has surprisingly found that the carboxylic acid compound of indole is introduced into the polyamide desalting layer, and phosphate in the water phase and methyl benzene and organic tin containing auxiliary agent in the oil phase are mixed, so that the permeation flux of the reverse osmosis membrane can be greatly improved while the high desalting rate is maintained. The possible principle of the synergistic action of the organotin auxiliaries and the indole derivatives is: (1) The organic tin compound is a metal organic compound directly connected with tin and carbon atoms and mainly used as a catalyst auxiliary agent and a stabilizer, so that the polycondensation reaction is slowed down, the molecular weight distribution of the formed polyamide is more uniform, and the water permeable channel is increased; (2) The indole structure contains secondary amine groups, the secondary amine groups can react with acyl chloride groups in an oil phase to participate in the process of forming a polyamide desalting layer by interfacial polymerization, and carboxylic acid groups in molecules can adjust the content of carboxylic acid groups in the polyamide desalting layer, so that more hydrophilic permeation channels are provided, and the permeation flux of the reverse osmosis membrane is improved.
In the invention, hydrogen on nitrogen atom of indole ring in the molecular structure of the carboxylic acid compound of the indole is not substituted, the indole ring has only one substituent, and the substituent is alkyl acid substituent containing 1-5 carbon atoms; preferably, the carboxylic acid compound of indole is selected from one or more of indole-2-carboxylic acid, indole-3-carboxylic acid, indole-4-carboxylic acid, indole-5-carboxylic acid, indole-6-carboxylic acid, indole-7-carboxylic acid, 3-indolebutyric acid.
In the invention, at least 2 alkyl groups or phenyl groups in the molecular structure of the organotin auxiliary agent are directly connected with tin atoms; preferably, the organic tin auxiliary agent is selected from one or more of dimethyltin dichloride, hexa-n-butylditin and tetraphenyltinum.
In the present invention, the aqueous solution contains a phosphate ester, preferably triethyl phosphate.
In the present invention, the oil phase solution contains methylbenzene, preferably 1,3, 5-trimethylbenzene.
The base membrane of the polyamide reverse osmosis membrane is generally used as a physical support layer of a thinner polyamide desalting layer, so that the whole reverse osmosis membrane is endowed with mechanical strength and does not have the retention performance on small molecular organic matters, salt ions and the like. The base film is composed of a non-woven fabric base material and a porous supporting layer. The following parameters relating to the base film, including the nonwoven substrate and the porous support layer, are selected as parameters commonly employed in the art.
In one embodiment, the nonwoven fabric substrate serves as a physical support material for the porous support layer, and serves to provide mechanical strength and, based thereon, to form a porous support layer having a uniform thickness and surface pore size.
In one embodiment, the nonwoven fabric substrate is preferably made of polyethylene, polypropylene, or polyethylene terephthalate (PET for short), and more preferably polyethylene terephthalate in view of hydrophilicity, mechanical stability, thermal stability, and the like.
In one embodiment, the thickness of the nonwoven fabric substrate is preferably in the range of 20 to 100. Mu.m, more preferably 80 to 90 μm. When the thickness of the nonwoven fabric is 60 μm or less, the strength of the nonwoven fabric itself is insufficient as a physical support of the porous support layer, and the base film or reverse osmosis membrane formed therefrom has a risk of breaking in the transverse direction or longitudinal direction, and is not satisfactory. When the thickness of the non-woven fabric is more than 100 μm, although the strength of the non-woven fabric serving as a physical support is sufficient, the thickness of the finally obtained reverse osmosis membrane is too thick, so that the membrane filling area of a membrane element or a module manufactured by the non-woven fabric is too low, the water yield of a single membrane element or module is influenced, and on the other hand, the amount of unreacted substances (mainly aromatic polybasic amine) remained in the non-woven fabric substrate in the membrane preparation process is increased, the cleaning is difficult, the membrane permeation flux is reduced, and the acid-base cleaning performance is also reduced. From the viewpoint of physical support strength, membrane area to be loaded with membrane elements or modules, and membrane performance, the thickness of the nonwoven fabric substrate is more preferably in the range of 80 to 90 μm. The range of variation in thickness of the nonwoven fabric substrate is preferably. + -. 5 μm or less, more preferably. + -. 3 μm or less. When the thickness deviation of the nonwoven fabric substrate is too large, it is difficult to apply the casting solution for the porous support layer on the surface thereof by using a doctor blade or slit die, and the problem of uneven thickness of the polysulfone porous support layer may be caused.
In one embodiment, the air permeability of the nonwoven fabric substrate is preferably 1.0 to 5.0cc/cm 2 In the range of/sec, more preferably 1.5 to 3.0cc/cm 2 In the range of/sec, more preferably 1.5 to 2.5cc/cm 2 In the/sec range. When the air permeability is less than 1.0cc/cm 2 In the case of sec, the penetration depth of the casting solution for forming the porous support layer into the nonwoven fabric substrate is shallow, and the bonding strength between the porous support layer and the nonwoven fabric substrate is weakened, and the porous support layer is likely to be peeled off from the nonwoven fabric substrate. When the air permeability is more than 5.0, the casting solution for forming the porous support layer may penetrate into the nonwoven fabric substrate too much, and may penetrate into the back surface (non-coated surface) of the nonwoven fabric substrate to cause coating defects such as pinholes. When the air permeability is within the preferred range, on the one hand, the bonding strength between the porous support layer and the nonwoven fabric substrate is high, and on the other hand, when the casting solution coated to form the porous support layer is immersed in the coagulation bath to cause phase inversion, the diffusion rate of the non-solvent in the coagulation bath from the back surface (non-coated surface) to the coating of the casting solution is appropriate, and an asymmetric porous support layer structure is more easily formed, which also has a beneficial effect on the retention amount and diffusion rate of the polyamine during the subsequent interfacial polycondensation reaction.
In one embodiment, the material of the porous support layer may be selected from: polysulfones, polyether sulfones, sulfonated polyether sulfones, linear aromatic polyamides, polyethylene terephthalates, polyether ether ketones, polyphenylene sulfones, polyphenylene oxides, polyethylene, polypropylene, polyacrylonitrile, polyvinyl chloride, and the like. Among them, polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, and the like are more preferable. Polysulfone is more preferable from the viewpoint of surface tension, chemical stability, rigidity, thermal stability, solubility, and the like. Specifically, the polysulfone material having the following structural formula is particularly preferred because it can be easily dissolved in a polar solvent to form a porous support layer, which has the advantages of good pressure resistance and easy control of the surface pore size.
In one embodiment, as a solvent for dissolving the polysulfone material, one or a mixture of: n, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, and the like. The solvent used is specifically chosen so long as it dissolves polysulfone well and is miscible with the coagulating bath (e.g., water). From the viewpoints of cost, the type of pores forming the porous support layer, ease of handling, and safety, N-dimethylformamide or N, N-dimethylacetamide is preferable.
In one embodiment, the thickness of the porous support layer is preferably in the range of 10 to 60 μm, more preferably in the range of 30 to 50 μm.
It should be noted that the thicknesses of the nonwoven fabric substrate and the porous support layer can be obtained by continuously measuring 15 samples by a digital thickness measuring instrument and taking an average value. The thickness of the porous support layer is obtained by subtracting the thickness of the nonwoven fabric substrate from the thickness of the base film.
In one embodiment, the surface pore size of the porous support layer is preferably in the range of 1 to 100nm, more preferably 5 to 50nm, and still more preferably 7 to 20nm. The surface aperture is measured by using a field emission scanning electron microscope (FE-SEM), a base film is adhered to a sample table by using conductive adhesive, and after the sample is subjected to metal spraying treatment, an electron microscope picture under 10 ten thousand times is taken. And (4) calculating and measuring the pore size of the surface of the basement membrane according to a matched software ruler of the FE-SEM.
In one embodiment, the aromatic polyamide desalination layer is the functional layer in the reverse osmosis membrane that performs the actual separation. Specifically, the polyamide desalting layer is three-dimensional network crosslinked polyamide formed by the interfacial polycondensation reaction of an aqueous phase solution of polybasic aromatic amine and an oil phase solution of aromatic polybasic acyl chloride on the surface of a base film. The polyamide desalting layer is formed by performing interfacial polycondensation reaction on a water phase solution of m-phenylenediamine and an oil phase solution of trimesoyl chloride, wherein the water phase solution contains phosphate, and the oil phase solution contains a carboxylic acid compound containing indole and methylbenzene.
In one embodiment, the polyvalent aromatic amine refers to a compound having a benzene ring structure and 2 or more amino groups in a molecule, and is not particularly limited, and may be one or more selected from m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 3, 5-diaminobenzoic acid, 2, 4-diaminobenzenesulfonic acid, 1,3, 5-triaminobenzene, N-dimethyl-m-phenylenediamine, N-diethyl-m-phenylenediamine, 3-aminobenzylamine, and 4-aminobenzylamine, alone or in combination. M-phenylenediamine is preferable from the viewpoint of easy availability and salt rejection rate, permeation flux of the resulting membrane.
In one embodiment, the aromatic polybasic acid chloride refers to a compound having a benzene ring structure and 2 or more acid chloride groups in the molecule, and may be one or more selected from trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride, and azodicarbonyl chloride, alone or in combination, without limitation. Trimesoyl chloride is preferred in view of easy availability and salt rejection rate and permeation flux of the resulting membrane.
In one embodiment, the oil phase solvent in which the poly-aromatic acid chloride is dissolved is not particularly limited as long as it is immiscible with water, forms an oil-water interface, and does not dissolve the porous support layer material and the nonwoven fabric substrate, and may be, for example, benzene, halogenated hydrocarbon, and alkane solvents. Examples of the benzene-based solvent include benzene and toluene. Examples of the halogenated hydrocarbon solvent include trichlorotrifluoroethane. Examples of the alkane solvent include straight-chain alkanes such as n-hexane, n-heptane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane and n-heptadecane, cycloalkanes such as cyclooctane and ethylcyclohexane, and isoparaffins such as isopar E, isopar G, isopar L and isopar M, which are available from Exxon Mobil corporation.
In one embodiment, in addition to the aromatic amine and the aromatic acid chloride, additives such as co-solvent, complexing agent, acid-binding agent, acylation catalyst, phase transfer agent, organic tin promoter, etc. may be added to the aqueous phase or the oil phase solution to adjust molecular diffusion, acylation catalysis, etc. as long as the interfacial polycondensation reaction is not hindered. As co-solvent, it may be chosen from: n-methylpyrrolidone, acetone, ethanol, isopropanol, benzene, toluene, m-xylene, 1,3, 5-trimethylbenzene, etc.; as complexing agents, it is possible to select from: phosphate, tributyl phosphate, 1-methylimidazole, 4-methylpyridine, etc.; the acid-binding agent may be selected from: triethylamine, N-diisopropylethylamine, sodium hydroxide, sodium carbonate, sodium phosphate, and the like; as regards the antioxidant, it may be chosen from: sodium sulfite, sodium metabisulfite, ascorbic acid, and the like; examples of the acylation catalyst include caprolactam, N-dimethylformamide, 4-dimethylaminopyridine and the like; as phase transfer catalyst, it may be selected from: hexamethylphosphoric triamide, tetrabutylammonium bromide, tetramethylammonium bromide, dodecylammonium bromide, and the like.
In one embodiment, optionally, a dry reverse osmosis membrane can be optionally manufactured for ease of subsequent membrane element fabrication. In order to prevent the membrane from collapsing due to the porous support layer during the drying process, so that the permeation flux of the membrane is reduced, the membrane needs to be moisturized by using a moisturizing agent. The humectant used in the reverse osmosis membrane of the present invention is not particularly limited, and any humectant may be used as long as it can absorb moisture without damaging the reverse osmosis membrane material, and examples thereof include glycerin, citric acid, sodium acetate, and glucose.
Another object of the present invention is to provide a method for preparing a high flux aromatic polyamide reverse osmosis membrane.
A method for preparing the above high-flux aromatic polyamide reverse osmosis membrane, comprising the steps of:
s1: interfacial polycondensation: dissolving m-phenylenediamine and phosphate in water to prepare a water phase solution, and dissolving trimesoyl chloride, indole carboxylic acid compound, organic tin auxiliary agent and methylbenzene in a solvent to prepare an oil phase solution; forming a membrane containing an aromatic polyamide desalting layer on the surface of a polysulfone base membrane containing non-woven fabrics and a polysulfone porous supporting layer by an interfacial polycondensation reaction through the water phase solution and the oil phase solution;
s2: primary cleaning: dipping and cleaning the membrane;
s3: chemical treatment: immersing the membrane in an aqueous hypochlorite solution, and then immersing the membrane in an aqueous solution containing a reducing alkali metal salt and an inorganic strong base;
s4: secondary cleaning: dipping and cleaning the membrane;
s5: moisture preservation and drying: soaking the membrane in glycerol water solution, taking out and drying.
In the invention, the mass ratio of m-phenylenediamine to trimesoyl chloride in S1 is (15-25): 1, in the above range.
In the invention, the mass percent of the phosphate in the S1 is 0.1-1%, the mass percent of the methylbenzene is 5-15%, the mass percent of the carboxylic acid compound of the indole is 0.05-0.1%, and the mass percent of the organic tin auxiliary agent is 0.05-0.1%, based on the total mass of the oil phase solution.
In the present invention, S1 is performed at normal temperature.
In the invention, S2 is firstly soaked in 50-95 ℃ aqueous solution containing citric acid and glycerin for cleaning, and then is soaked in 50-95 ℃ water for cleaning.
In the invention, the temperature range of the aqueous solution containing citric acid and glycerin in S2 is 50-95 ℃.
In the invention, the mass percent of hypochlorite in the S3 hypochlorite aqueous solution is 0.01-0.05%.
In the invention, the pH value of the S3 hypochlorite aqueous solution is 7-12, and acid is adopted to adjust the pH value of the hypochlorite aqueous solution.
In the present invention, the membrane is washed by immersing in pure water at S4.
It is still another object of the present invention to provide a use of a high flux aromatic polyamide reverse osmosis membrane.
The application of the high-flux aromatic polyamide reverse osmosis membrane is disclosed, wherein the reverse osmosis membrane is the high-flux aromatic polyamide reverse osmosis membrane or the reverse osmosis membrane prepared by the preparation method, and the reverse osmosis membrane is used in the fields of household water purifiers, pure water manufacturing and industrial wastewater treatment.
When the reverse osmosis membrane is used in the field, the salt rejection rate of the reverse osmosis membrane is more than 98.0% and the permeation flux is 60.0L/(m) under the operation pressure of 0.41MPaG by taking sodium chloride with the concentration of 250mg/L as raw water at the temperature of 25 DEG C 2 H) above, the magnitude of the permeate flux decay is less than 15% after 90 hours of continuous operation.
Compared with the prior art, the invention has the beneficial effects that:
(1) The high-flux polyamide reverse osmosis membrane provided by the invention keeps high desalination rate, has less flux attenuation after long-time operation, takes sodium chloride with the concentration of 250mg/L at 25 ℃ as raw water, and has the desalination rate of more than 98.0 percent and the permeation flux of 60.0L/(m) under the operation pressure of 0.41MPaG 2 H) above, the magnitude of the permeate flux decay is less than 15% after 90 hours of continuous operation.
(2) The invention has no great change from the traditional production line in the realization process and is easy to realize industrialization.
Detailed Description
In order to better understand the concrete content of the present invention, the following examples are further provided to illustrate the content of the present invention, but the content of the present invention is not limited to the following examples.
The starting materials used in the following examples or comparative examples, unless otherwise specified, are all commercially available conventional starting materials, and the information on the main raw materials is given in the following table:
in addition, the indole-2-carboxylic acid, indole-3-carboxylic acid, indole-4-carboxylic acid, indole-5-carboxylic acid, indole-6-carboxylic acid, indole-7-carboxylic acid, 3-indolebutyric acid and other indole carboxylic acid compounds and organotin aids such as dimethyltin dichloride, hexa-n-butylditin, tetraphenyltinum used in this example were of analytical grade, and all manufacturers were Shanghai Arlatin Biotech Co., ltd.
The following examples of the invention or comparative examples illustrate possible methods of use:
evaluation of salt rejection and permeation flux and long-term operation flux attenuation performance:
salt rejection and permeate flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. According to the content in GB/T32373-2005 reverse osmosis membrane test method, the separation performance of the reverse osmosis membrane is evaluated.
The salt rejection (R) is defined as: under certain operating conditions, the salt concentration (C) of the reverse osmosis membrane feed solution f ) With the permeate salt concentration (C) p ) The difference is divided by the salt concentration (C) of the feed solution f ) As described by the following equation.
The permeate flux is defined as: the volume of water per membrane area per unit time is L/(m) under certain operating conditions 2 ·h)。
The reverse osmosis membrane performance test conditions in the invention are as follows: the feed solution was 250mg/L aqueous solution at 25 + -0.5 deg.C, pH 7.5 + -0.5, and operating pressure 0.41MPaG. The membrane flux salt rejection at 30 minutes of continuous operation was taken as the initial performance, and the membrane flux and salt rejection at 90 hours of continuous operation were taken as the performance after long-time operation decay. The percentage of flux reduction at 90 hours compared to 30 minutes was calculated as the long run flux decay rate.
Example 1
A pilot plant production line is adopted to prepare the reverse osmosis membrane, and the method comprises the following steps:
polysulfone based films were prepared roll-to-roll: uniformly coating a DMF (dimethyl formamide) solution with the mass percent of polysulfone being 16.5% on a polyester non-woven fabric substrate at the temperature of 25 ℃, wherein the thickness of a wet coating is 150 mu m, soaking the wet coating in deionized water for 1 minute after the wet coating stays in the air for 1.5 seconds, and then soaking the wet coating in the deionized water at the temperature of 70 ℃ for 2 minutes to obtain a coiled base membrane with the width of 400mm and containing the non-woven fabric substrate and a polysulfone porous supporting layer.
Reverse osmosis membranes were prepared in a "roll-to-roll" manner: unreeling the coiled base film with the width of 400mm, soaking the coiled base film in an aqueous phase solution with the mass percent of m-phenylenediamine of 2.4% and the mass percent of triethyl phosphate of 0.6% for 30 seconds, lifting the base film in the vertical direction, pulling out the base film from an aqueous phase solution tank, removing the redundant aqueous phase solution on the surface by using a rubber extrusion roller, uniformly coating an n-decane oil phase solution with the mass percent of trimesoyl chloride of 0.12%, mesitylene of 10%, indole-2-carboxylic acid of 0.08% and dimethyltin dichloride of 0.08% on the surface of the base film, standing for 30 seconds, and removing the redundant oil phase solution on the surface by using an oil displacement rubber roller and an air knife. In the process, the mass ratio of the m-phenylenediamine to the trimesoyl chloride is 20:1.
then, the obtained film was immersed in an aqueous solution containing 6% by mass of citric acid and 3% by mass of glycerin at 80 ℃ for 1 minute (1 st water tank), and then immersed in deionized water at 90 ℃ for 2 minutes to clean (2 nd water tank). Then, the membrane was sequentially immersed in a sodium hypochlorite aqueous solution at room temperature of 0.03% by mass and having a pH of 7 (3 rd water tank), in a sodium sulfite aqueous solution at room temperature of 1% by mass and 1% by mass of sodium hydroxide (4 th water tank), in hot water at 90 ℃ for 2 minutes (5 th water tank), in a glycerol aqueous solution at room temperature of 5% by mass for 1 minute, taken out, and dried to obtain a polyamide composite reverse osmosis membrane. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in table 1.
Example 2
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid was replaced with indole-3-carboxylic acid in example 1, the temperature of the 1 st tank was 50 ℃, and a 0.01% by mass aqueous solution of sodium hypochlorite was used. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 3
A reverse osmosis membrane was produced in the same manner as in example 1, except that indole-2-carboxylic acid was replaced with indole-4-carboxylic acid in example 1, the temperature of the 1 st water tank was 95 ℃, and a 0.04% by mass aqueous solution of sodium hypochlorite was used. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 4
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid was replaced with indole-5-carboxylic acid and dimethyltin dichloride was replaced with tetraphenyltin in example 1. The desalination rate and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 5
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid was replaced with indole-6-carboxylic acid and dimethyltin dichloride was replaced with tetraphenyltin in example 1. The desalination rate and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 6
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid was replaced with indole-7-carboxylic acid and dimethyltin dichloride was replaced with tetraphenyltin in example 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 7
A reverse osmosis membrane was produced in the same manner as in example 1 except that in example 1, indole-2-carboxylic acid was replaced with 3-indolebutyric acid, dimethyltin dichloride was replaced with tetraphenyltin, mesitylene was replaced with xylene, and triethyl phosphate was replaced with diethyl phosphate. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 8
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that in example 1, indole-2-carboxylic acid was replaced with indole-4-carboxylic acid, dimethyltin dichloride was replaced with hexa-n-butylditin, and the mass percentage of indole-4-carboxylic acid and organotin auxiliary hexa-n-butylditin was replaced with 0.05%. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 9
A reverse osmosis membrane was produced in the same manner as in example 8, except that in example 8, the mass percentage of indole-4-carboxylic acid and organotin auxiliary hexa-n-butylditin was changed from 0.05% to 0.1%. The desalination rate and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 10
A reverse osmosis membrane was fabricated in the same manner as in example 8, except that in example 8, the mass percentage of mesitylene was changed from 10% to 5%. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 11
A reverse osmosis membrane was produced in the same manner as in example 8, except that the mass percentage of mesitylene in example 8 was changed from 10% to 15%. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 12
A reverse osmosis membrane was produced in the same manner as in example 8, except that the mass percentage of triethyl phosphate in example 8 was changed from 0.6% to 0.1%. The desalination rate and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 13
A reverse osmosis membrane was produced in the same manner as in example 8, except that the mass percentage of triethyl phosphate in example 8 was changed from 0.6% to 1.0%. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 14
A reverse osmosis membrane was produced in the same manner as in example 8, except that the pH of sodium hypochlorite in the 3 rd water tank in example 8 was adjusted from 7 to 9. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 15
A reverse osmosis membrane was produced in the same manner as in example 8 except that the pH of sodium hypochlorite in the 3 rd water tank in example 8 was adjusted from 7 to 12, and the sodium hypochlorite aqueous solution was replaced with a 0.05% by mass sodium hypochlorite aqueous solution. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 16
A reverse osmosis membrane was produced in the same manner as in example 1, except that triethyl phosphate in example 1 was replaced with diethyl phosphate. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 17
A reverse osmosis membrane was produced in the same manner as in example 1, except that 1,3, 5-trimethylbenzene was replaced with m-xylene in example 1. The desalination rate and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 18
Except that 1,3, 5-trimethylbenzene in example 1 was replaced with m-xylene and the mass ratio of m-phenylenediamine to trimesoyl chloride was changed from 20:1 is changed into 15: a reverse osmosis membrane was produced in the same manner as in example 1 except for 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Example 19
Except that 1,3, 5-trimethylbenzene in example 1 was replaced with m-xylene and the mass ratio of m-phenylenediamine to trimesoyl chloride was changed from 20:1 is changed to 25: a reverse osmosis membrane was produced in the same manner as in example 1 except for 1. The desalination rate and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Comparative example 1
A reverse osmosis membrane was produced in the same manner as in example 1, except that triethyl phosphate was not added to the m-phenylenediamine aqueous phase solution and indole-2-carboxylic acid, mesitylene and dimethyltin dichloride were not added to the trimesoyl chloride oil phase solution, as compared with example 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Comparative example 2
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid, mesitylene and dimethyltin dichloride were not added to the trimesoyl chloride oil phase solution, as compared to example 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Comparative example 3
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid and dimethyltin dichloride were not added to the trimesoyl chloride oil phase solution, as compared to example 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Comparative example 4
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that dimethyltin dichloride was not added to the trimesoyl chloride oil phase solution as in example 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
Comparative example 5
A reverse osmosis membrane was fabricated in the same manner as in example 1, except that indole-2-carboxylic acid was not added to the trimesoyl chloride oil phase solution as in example 1. The salt rejection and the permeation flux of the obtained reverse osmosis membrane and the performance of the membrane after continuous operation for 90 hours are tested, and the results are shown in tables 1 and 2.
TABLE 1 reaction materials Table
TABLE 2 reverse osmosis membrane Performance
As can be seen from comparative examples 1 to 3, the addition of phosphate to the aqueous phase solution and the addition of methylbenzene-containing to the oil phase solution increased the flux of the membrane, but the flux declined more during long-term use of the membrane.
As can be seen from comparative examples 4 to 5, the addition of the organotin auxiliary agent alone or the carboxylic acid compound of indole to the oil phase solution further increased the flux decay rate of the membrane during long-term use, although the membrane flux was further improved.
It can be seen from examples 1 to 19 and comparative examples 4 to 5 that the organic tin auxiliary agent and the carboxylic acid compound of indole are simultaneously added into the oil phase solution, and the phosphate is added into the water phase, so that the high flux of the reverse osmosis membrane is realized, and the flux attenuation rate of the reverse osmosis membrane in long-term use is obviously reduced.
It will be appreciated by those skilled in the art that modifications and adaptations of the invention are possible in light of the teachings of this specification and are intended to be within the scope of the appended claims.
The embodiment of the invention only needs to reduce the flux attenuation amplitude of the reverse osmosis membrane after long-time operation by adding the additive on the premise of keeping high permeation flux and high salt rejection rate under the premise of keeping the process of the existing production line unchanged, and has better industrial applicability.
Claims (9)
1. A high-flux aromatic polyamide reverse osmosis membrane comprises a non-woven fabric, a polysulfone porous supporting layer and a polyamide desalting layer, and is characterized in that the polyamide desalting layer is formed by an interfacial polycondensation reaction of a water phase solution of m-phenylenediamine and an oil phase solution of trimesoyl chloride;
wherein the oil phase solution contains carboxylic acid compounds of indole and organic tin auxiliary agents.
2. A reverse osmosis membrane according to claim 1 wherein the carboxylic acid compound of the indole is one in which the hydrogen on the nitrogen atom of the indole ring is unsubstituted, the indole ring has only one substituent, and the substituent is an alkyl acid substituent having from 1 to 5 carbon atoms; preferably, the carboxylic acid compound of indole is selected from one or more of indole-2-carboxylic acid, indole-3-carboxylic acid, indole-4-carboxylic acid, indole-5-carboxylic acid, indole-6-carboxylic acid, indole-7-carboxylic acid, 3-indolebutyric acid.
3. A reverse osmosis membrane according to claim 1 or 2 wherein at least 2 alkyl or phenyl groups in the molecular structure of the organotin promoter are directly attached to the tin atom; preferably, the organic tin auxiliary agent is selected from one or more of dimethyltin dichloride, hexa-n-butylditin and tetraphenyltinum.
4. A reverse osmosis membrane according to any one of claims 1 to 3 wherein the aqueous solution contains a phosphate ester, preferably triethyl phosphate;
and/or the oil phase solution contains methylbenzene, preferably 1,3, 5-trimethylbenzene.
5. A method of making the high flux aromatic polyamide reverse osmosis membrane of any one of claims 1-4, comprising the steps of:
s1: interfacial polycondensation: dissolving m-phenylenediamine and phosphate in water to prepare a water phase solution, and dissolving trimesoyl chloride, carboxylic acid compounds of indole, organic tin auxiliaries and methyl benzene in a solvent to prepare an oil phase solution; forming a membrane containing an aromatic polyamide desalting layer on the surface of a polysulfone base membrane containing non-woven fabrics and a polysulfone porous supporting layer by an interfacial polycondensation reaction through the water phase solution and the oil phase solution;
s2: primary cleaning: dipping and cleaning the membrane;
s3: chemical treatment: immersing the membrane in an aqueous hypochlorite solution, and then immersing the membrane in an aqueous solution containing a reducing alkali metal salt and an inorganic strong base;
s4: secondary cleaning: dipping and cleaning the membrane;
s5: moisture preservation and drying: soaking the membrane in glycerol water solution, taking out and drying.
6. The preparation method according to claim 5, wherein the mass ratio of m-phenylenediamine to trimesoyl chloride in S1 is 15-25: 1 in the range of;
and/or 0.1-1% of phosphate ester, 5-15% of methylbenzene, 0.05-0.1% of carboxylic acid compound of indole and 0.05-0.1% of organic tin auxiliary agent in the S1 by mass percent, based on the total mass of the oil phase solution.
7. The production method according to claim 6, wherein S1 is carried out at normal temperature;
and/or the S2 membrane is firstly soaked in 50-95 ℃ aqueous solution containing citric acid and glycerin for cleaning, and then is soaked in 50-95 ℃ water for cleaning;
and/or the mass percent of hypochlorite in the S3 hypochlorite aqueous solution is 0.01-0.05%;
and/or, the pH value of the S3 hypochlorite aqueous solution is 7-12, and the pH value of the hypochlorite aqueous solution is adjusted by acid;
and/or, the S4 is used for soaking the membrane in pure water for cleaning.
8. Use of a high flux aromatic polyamide reverse osmosis membrane according to any one of claims 1 to 4 or produced by the production process according to any one of claims 5 to 7 in the fields of household water purifiers, pure water production and industrial wastewater treatment.
9. The use according to claim 8, wherein the reverse osmosis membrane is used in the above-mentioned fields, and has a rejection of more than 98.0% and a permeate flux of 60.0L/(m) at an operating pressure of 0.41MPaG in the presence of sodium chloride at 25 ℃ and a concentration of 250mg/L as raw water 2 H) above, the magnitude of the permeate flux decay is less than 15% after 90 hours of continuous operation.
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