CN111686594B - High-flux high-rejection composite membrane and preparation method thereof - Google Patents
High-flux high-rejection composite membrane and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a high-flux and high-retention composite membrane, which comprises a porous polymer-based membrane and a separation layer, and is characterized in that: the surface aperture of the basement membrane is an ultrafiltration membrane with the aperture of about 10-100 nanometers, the separation layer is a crosslinked polyamide layer containing amino polymer particles, the thickness of the separation layer is 50-300 nanometers, and the diameter of the amino polymer particles contained in the separation layer is 20-80 nanometers. The pure water flux of the composite membrane obtained under the transmembrane pressure difference of 0.5MPa can reach 220 liters per square meter for hours, and the sodium sulfate interception reaches more than 99.0 percent. The invention also relates to a preparation method of the high-flux and high-rejection composite membrane. The composite membrane can be used for nanofiltration and reverse osmosis processes, such as drinking water treatment, seawater desalination, industrial wastewater treatment, biological medicine separation and other fields.
Description
Technical Field
The invention belongs to the field of membrane manufacturing, relates to a high-flux and high-interception composite membrane and a preparation method thereof, and further relates to application of the composite membrane in the fields of environmental protection, water treatment and the like.
Background
The nanofiltration membrane is a novel separation membrane developed in the 70 s of the 20 th century, the surface of the membrane is charged, the membrane has a charge effect, the molecular weight cut-off is between reverse osmosis and ultrafiltration, and the nanofiltration membrane is widely applied to the aspects of sea salt water desalination, urban and industrial sewage treatment, biological medicine separation, purification and the like.
The most common nanofiltration membrane preparation method at present is an interfacial polymerization method. The method is characterized in that a porous support body is used as a base membrane, two water phase monomers and organic phase monomers with high reaction activity are coated on the surface of the base membrane in sequence, and the two monomers are subjected to polymerization reaction at an interface of two solvents which are not mutually soluble, so that a thin functional separation layer is formed on the surface of the porous support body, and the nanofiltration membrane is prepared. However, the reaction monomer has high activity in the reaction, the reaction speed is very fast (usually can be completed within 100 seconds), and the separation performance of the membrane is difficult to regulate, so that the liquid flux of the obtained nanofiltration membrane is not high (generally 10-20L/sq m hour bar), the retention rate is not ideal, and the like.
Science (2018, 360 (6388): 518-521) reports that a certain amount of PVA is added into an interfacial polymerization aqueous phase solution, the PVA is combined with an aqueous phase monomer through hydrogen bonds, the viscosity of the aqueous phase solution is improved, the diffusion rate of the aqueous phase monomer is reduced, and a Tuoling structure is generated under the condition of unstable diffusion driving to prepare a high-flux nanofiltration membrane.
In recent years, in order to improve the separation performance of the nanofiltration membrane and further improve the liquid flux and rejection rate, various metal and metal oxide nanoparticles, carbon-based nanomaterials, metal-organic framework materials, aquaporins and organic micro/nanoparticles are widely applied to the preparation process of the functional separation layer of the nanofiltration membrane in the interfacial polymerization process. For example, CN108515751A prepares a high-throughput composite nanofiltration membrane by introducing mesoporous silica into a polyamide separation layer by interfacial polymerization. CN108889139A discloses a method for efficiently preparing high-flux Covalent Organic Frameworks (COFs) nanofiltration membranes based on interfacial polymerization. On one hand, due to the material difference between the nano particles and the separating layer, micro pores are formed around the nano particles to form a new water channel, so that the liquid flux of the nanofiltration membrane is improved; on the other hand, the addition of the nano particles improves the effective separation layer area on the unit membrane area by improving the surface roughness of the nano-filtration membrane, thereby improving the liquid flux. However, the structure of the separation layer is not fundamentally changed by adding the nano particles, so that the regulation and control of the structure of the membrane are limited by adding the nano particles, and the performance of the obtained nanofiltration membrane is not obviously improved.
In view of the problems of the prior art, the present invention provides a high flux-high rejection composite membrane, comprising a porous polymer-based membrane and a separation layer, which has excellent separation performance and certain antibacterial and bactericidal functions. According to the difference of organic amine used in the interfacial polymerization process, two composite membranes of a composite nanofiltration membrane and a composite reverse osmosis membrane can be prepared. The nanofiltration membrane can be effectively used for separating monovalent and divalent metal ions, separating and concentrating organic micromolecular substances and the like, and can be used in the fields of reducing water hardness in water works, household water purification filtration, seawater desalination, industrial wastewater treatment and the like.
Disclosure of Invention
The invention provides a high-flux and high-retention composite membrane, which comprises a porous polymer-based membrane and a separation layer, and is characterized in that: the surface pore size of the basement membrane is an ultrafiltration membrane of about 10-100 nanometers, the separation layer is a crosslinked polyamide layer containing amino polymer particles, the thickness of the separation layer is 50-300 nanometers, and the diameters of the amino polymer particles contained in the separation layer are 20-80 nanometers.
The material of the polymer base membrane is selected from one or more of polysulfone, polyethersulfone, polyacrylonitrile, polyvinyl chloride, sulfonated polysulfone and sulfonated polyethersulfone.
The amino polymer is a polymer containing amino on a main chain and/or a side chain, is selected from one of chitosan, polyethyleneimine, polyvinylamine, polyacrylamide, alpha or epsilon polylysine and polyarginine, and has a molecular weight of 5-20 ten thousand daltons.
The amino polymer particles are generated in situ by the ionic crosslinking of an amino polymer, micromolecular polyamine and a crosslinking agent in an aqueous solution, and the mass ratio of the amino polymer to the crosslinking agent is 1.0-5.0. The cross-linking agent may be one or more of polyphosphoric acid, polyphosphate, phytic acid or phytate. The small-molecule polyamine compound is preferably one or more of piperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, polyethyleneimine, 1,3, 5-triaminobenzene, 1,2, 4-triaminobenzene, 3, 5-diaminobenzoic acid, 2, 4-diaminotoluene, 2, 4-diaminoanisole, xylylenediamine, 1, 2-diaminocyclohexane, 1, 4-diaminocyclohexane, 1, 3-bispiperidylpropane, and 4-aminomethylpiperazine.
The composite membrane has pure water flux of over 220L/sq m hr (0.5 MPa transmembrane pressure difference) and sodium sulfate trapping rate of over 99.0%.
The present invention further provides a process for preparing a high flux-high rejection composite membrane according to the present invention, comprising the steps of:
1) Preparing a polyamine aqueous phase solution containing the amino polymer particles: dissolving an amino polymer in water to prepare a solution, dissolving a small molecular polyamine compound in the amino polymer solution, mixing the small molecular polyamine compound with a cross-linking agent solution, and carrying out in-situ cross-linking reaction to form particles so as to obtain an aqueous phase solution containing amino polymer particles, free amino polymer and the small molecular polyamine compound; wherein the free amine-based polymer is the excess amine-based polymer remaining from the amine-based polymer reacted with the crosslinking agent.
2) Preparing a composite membrane with a separation layer containing amine-based polymer particles: coating the water phase solution prepared in the step 1) on the surface of a porous polymer base membrane, after 2-10 minutes, purging residual water solution on the surface of the membrane by using nitrogen, then coating an organic phase solution containing polyacyl chloride for interfacial polymerization to prepare a separation layer, and after 10-120 seconds, placing the whole membrane in deionized water for storage to prepare the composite membrane of which the separation layer contains amino polymer particles.
In the step 1), the amino polymer refers to a polymer containing amino on a main chain and/or a side chain, preferably one of chitosan, polyethyleneimine, polyvinylamine, polyacrylamide, alpha or epsilon polylysine and polyarginine, and has a molecular weight of 5-20 ten thousand daltons.
Wherein the cross-linking agent is selected from one or more of polyphosphoric acid, polyphosphate, phytic acid or phytate.
The small-molecule polyamine compound is preferably one or more of piperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, polyethyleneimine, 1,3, 5-triaminobenzene, 1,2, 4-triaminobenzene, 3, 5-diaminobenzoic acid, 2, 4-diaminotoluene, 2, 4-diaminoanisole, xylylenediamine, 1, 2-diaminocyclohexane, 1, 4-diaminocyclohexane, 1, 3-bispiperidylpropane, and 4-aminomethylpiperazine.
In the step 1), the amino polymer accounts for 0.1-1 part by mass; 0.5-3.5 parts of micromolecule polyamine, 0.1-5 parts of cross-linking agent and 90.5-99.2 parts of water.
The amino polymer particles are formed by ionic crosslinking of amino polymer, micromolecular polyamine and a crosslinking agent, and the diameter of the obtained amino polymer particles is 20-80 nanometers when observed by a scanning electron microscope.
The polybasic acyl chloride used in the step 2) is one or more of terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, biphenyldicarbonyl chloride, benzenedisulfonyl chloride, trimesoyl chloride, butanetriacyl chloride, butanedioyl chloride, pentatriacyl chloride, glutaryl chloride, hexanetriyl chloride, adipoyl chloride, sebacoyl chloride and sebacoyl chloride.
The organic solvent used for preparing the organic phase solution of the polyacyl chloride is one or more of n-hexane, cyclohexane, n-heptane and n-octane, the mass of the polyacyl chloride in the organic phase solution accounts for 0.1-3.5 parts, and the mass of the organic solvent accounts for 96.5-99.9 parts.
The porous polymer-based membrane in the step 2) can be prepared by adopting a traditional non-solvent phase inversion method and is prepared by blending one or more materials of polysulfone, polyethersulfone, polyacrylonitrile, polyvinyl chloride, sulfonated polysulfone and sulfonated polyethersulfone. The polymer-based film may also be purchased as a finished polymer film, as desired.
And 2) carrying out vacuum freeze drying on the composite membrane obtained in the step 2 for 24 hours, then preparing a sample, and measuring the thickness of a separation layer of the composite membrane by using a scanning electron microscope to be 50-300 nanometers.
According to the method, two composite membranes, namely a composite nanofiltration membrane and a composite reverse osmosis membrane, can be prepared respectively according to different small molecular polyamines, for example, piperazine serving as an aqueous phase monomer reacts with polyacyl chloride to prepare the composite nanofiltration membrane, and m-phenylenediamine serving as an aqueous phase monomer reacts with polyacyl chloride to prepare the composite reverse osmosis membrane.
Compared with the prior art, the invention has the advantages that:
(1) Compared with other composite membranes in which the separation layer in the prior art contains nano particles (such as graphene oxide, carbon nano tubes, aquaporin and the like), the composite membrane has the advantages of strong permeability-selectivity, easily adjustable structure and simple preparation method. (2) The surface of the amino polymer particles contained in the separation layer of the composite membrane contains a certain number of hydroxyl and amino, has good hydrophilicity, can react with polyacyl chloride, and enables the amino polymer particles to be combined with the separation layer more firmly. (3) The separation performance of the composite membrane of the invention is significantly higher than that of the composite membranes of the prior art.
The method of the invention uses the aqueous monomer solution to replace the aqueous monomer solution (generally piperazine aqueous solution) used in the conventional interfacial polymerization, and has the following advantages:
1. due to the existence of free amine polymers and nanoparticles in the aqueous monomer solution, the viscosity of the aqueous monomer solution is increased, so that the migration resistance of polyamine small molecules in the solution in the interfacial polymerization process is improved, and the interfacial polymerization speed is further reduced;
2. because a certain amount of polyamine small molecules can be wrapped in the process of forming the nano particles, in the process of interfacial polymerization, the partially wrapped polyamine small molecules can participate in interfacial polymerization only in a slow migration (slow release) mode, and the interfacial polymerization speed is also reduced;
3. the nano-particles used in the method are generated in situ in the water phase, so the nano-particles have good dispersibility in the water phase monomer solution, the adverse phenomenon of nano-particle agglomeration in the conventional particle doping process is avoided, uniform doping to the functional separation layer of the nanofiltration membrane is facilitated, and the purposes of improving a water channel and the surface area of the functional separation layer are better achieved.
Therefore, the method solves the problem of reducing the interfacial polymerization speed to a certain extent, improves the uniformity and compactness of the separation layer of the composite membrane obtained by interfacial polymerization, simultaneously reduces the thickness of the separation layer of the membrane, improves the effective surface area of the separation layer, and greatly improves the liquid flux and the retention rate of the membrane.
Detailed description of the drawings
FIG. 1 is a schematic structural view of a composite membrane according to the present invention in which a separation layer contains amine-based polymer particles.
Detailed Description
The invention is further illustrated by the following specific examples. These examples are intended to illustrate the invention only and are not intended to be limiting. In practice, the invention will be understood to cover all modifications and variations of this invention provided they come within the scope of the appended claims.
Reagents and raw materials used in the examples of the present invention are commercially available.
Example 1
Preparation of porous polymer-based membrane: weighing 20g of polyacrylonitrile, dissolving in 80g of N, N-dimethylformamide, mechanically stirring for 8h at 70 ℃, standing for 8h, and defoaming to obtain the casting solution with a stable system. And (3) quickly immersing the scraped 200-micron membrane into deionized water for phase inversion, taking out the base membrane after 5 minutes, and storing the base membrane in the deionized water.
Preparation of polyamine aqueous phase solution containing amine-based polymer particles: weighing 0.2g of polyvinylamine, adding the polyvinylamine into 99.8g of deionized water, stirring and dissolving to obtain 0.2% of polyvinylamine solution, adding 0.5g of piperazine, stirring and dissolving to obtain piperazine/polyvinylamine blended solution, slowly adding 20mL of 10mg/mL sodium polyphosphate solution at the rotation speed of 1000r/min for ionic crosslinking, wherein the mass ratio of the polyvinylamine to the sodium polyphosphate is 5.0, uniformly stirring, standing and aging for 2h to obtain polyamine solution containing amino polymer particles, and the polyamine solution is called as aqueous phase solution.
Preparing an organic phase solution containing polyacyl chloride: 0.1g of trimesoyl chloride is weighed and dissolved in 99.9g of normal hexane by mass percent to obtain 0.1 percent of polyacyl chloride solution which is called as organic phase solution.
Preparing a composite membrane: fixing the base film by adopting an acrylic mould, coating the water-phase solution on the upper surface of the base film, pouring the water-phase solution out after 10min, and immediately blowing the redundant water solution on the surface of the film by using nitrogen. And coating 120s of organic phase solution, immediately placing the composite membrane in deionized water for storage after the interfacial polymerization is finished, and obtaining the composite membrane of which the separation layer contains amino polymer particles. Pure water flux and Na2SO4 (1000 ppm) rejection were measured at 0.5MPa, the procedure is shown in example 5, and the results are shown in Table 1.
Example 2
Preparation of porous polymer-based membrane: weighing 16.0g of polyether sulfone and 4.0g of sulfonated polysulfone, dissolving in 80g of N, N-dimethylacetamide, mechanically stirring for 8h at 70 ℃, standing for 8h, and defoaming to obtain the casting solution with a stable system. And (3) quickly immersing the scraped film of 200 micrometers into deionized water for phase inversion, taking out the base film after 5 minutes, and storing the base film in the deionized water.
Preparation of polyamine aqueous phase solution containing amine-based polymer particles: weighing 100g of 0.5% chitosan solution, adding 3.5g of piperazine, stirring and dissolving to obtain a chitosan/piperazine blending solution, slowly adding 20mL of 10mg/mL sodium polyphosphate solution at the rotating speed of 1000r/min for ionic crosslinking, wherein the mass ratio of chitosan to sodium polyphosphate is 2.5, uniformly stirring, standing and aging for 8h to obtain a polyamine solution containing amino polymer particles, and the polyamine solution is called an aqueous solution.
Preparing an organic phase solution containing polyacyl chloride: weighing 3.5g of trimesoyl chloride in percentage by mass, dissolving in 96.5g of n-hexane, and obtaining a polybasic acyl chloride solution with the concentration of 3.5 percent, namely an organic phase solution.
Preparing a composite membrane: fixing the base film by adopting an acrylic mould, coating the water phase solution on the upper surface of the base film, pouring the water phase solution after 2min, and immediately blowing the redundant water solution on the surface of the film by using nitrogen. And coating the organic phase solution for 10 seconds, immediately placing the composite membrane in deionized water for storage after the interfacial polymerization is finished, and obtaining the composite membrane of which the separation layer contains amino polymer particles. Pure water flux and Na were measured at 0.5MPa 2 SO 4 (1000 ppm) retention, the procedure is shown in example 5 and the results are shown in Table 1.
Example 3
Preparation of porous polymer-based membrane: weighing 20g of polyacrylonitrile, dissolving in 80g of N, N-dimethylformamide, mechanically stirring for 8h at 70 ℃, standing for 8h, and defoaming to obtain the casting solution with a stable system. And (3) quickly immersing the scraped 200-micron membrane into deionized water for phase inversion, taking out the base membrane after 5 minutes, and storing the base membrane in the deionized water.
Preparation of polyamine aqueous phase solution containing amine-based polymer particles: weighing 100g of 0.2% chitosan solution, adding 1g of piperazine, stirring and dissolving to obtain a chitosan/piperazine blending solution, slowly adding 20mL of 10mg/mL sodium polyphosphate solution at the rotation speed of 1000r/min for ionic crosslinking, wherein the mass ratio of chitosan to sodium polyphosphate is 1.0, stirring uniformly, standing and aging for 12h to obtain a polyamine solution containing amino polymer particles, namely an aqueous phase solution.
Preparing an organic phase solution containing polyacyl chloride: 0.5g of trimesoyl chloride is weighed and dissolved in 99.5g of normal hexane by mass percent to obtain 0.5 percent polyacyl chloride solution which is called as organic phase solution.
Preparing a composite membrane: fixing the base film by adopting an acrylic mould, coating the water phase solution on the upper surface of the base film, pouring the water phase solution after 5min, and immediately blowing the redundant water solution on the surface of the film by using nitrogen. And coating the composite membrane with an organic phase solution for 30 seconds, immediately placing the composite membrane in deionized water for storage after the interfacial polymerization is finished, and obtaining the composite membrane of which the separation layer contains amino polymer particles. Pure water flux and Na were measured at 0.5MPa 2 SO 4 (1000 ppm) retention, the procedure is shown in example 5 and the results are shown in Table 1.
Example 4
Preparation of porous polymer-based membranes: weighing 20g of polyacrylonitrile, dissolving in 80g of N, N-dimethylformamide, mechanically stirring at 70 ℃ for 8h, standing for 8h, and defoaming to obtain a casting solution with a stable system. And (3) quickly immersing the scraped film of 200 micrometers into deionized water for phase inversion, taking out the base film after 5 minutes, and storing the base film in the deionized water.
Preparing a polyamine aqueous phase solution containing amine-based polymer particles: weighing 0.2g of polyvinylamine, adding the polyvinylamine into 99.8g of deionized water, stirring and dissolving to obtain 0.2% of polyvinylamine solution, adding 0.8g of m-phenylenediamine, stirring and dissolving to obtain polyvinylamine/m-phenylenediamine blended solution, slowly adding 20mL (containing 0.2g of sodium phytate) of 10mg/mL of sodium phytate solution at the rotating speed of 800r/min for ionic crosslinking, stirring uniformly, standing and aging for 12h to obtain polyamine solution containing amino polymer particles, and obtaining the aqueous phase solution.
Preparing an organic phase solution containing polyacyl chloride: 0.5g of trimesoyl chloride is weighed and dissolved in 99.5g of normal hexane by mass percent to obtain 0.5 percent polyacyl chloride solution which is called as organic phase solution.
Preparing a composite membrane: fixing the base film by an acrylic mould, and coating the upper surface of the base filmAqueous solution, 5min later the aqueous solution was poured out and immediately the excess aqueous solution on the membrane surface was purged with nitrogen. Coating organic phase solution for 30s, immediately placing the composite membrane in deionized water for storage after interfacial polymerization is completed to obtain a composite membrane with a separating layer containing amino polymer particles, wherein the composite membrane has reverse osmosis membrane property, specifically, the rejection rate of NaCl (1000 ppm) reaches 99.2% under 1.5MPa, and the pure water flux is 30.2 L.m -2 ·h -1 The test results are shown in Table 1.
Example 5
And (3) testing the separation performance of the composite membrane: the membrane separation performance test is carried out through the cross-flow filtering device, firstly, a membrane is arranged in a membrane pool, pure water is used for pre-pressurizing for 30min under 0.6MPa, the pressure is slowly regulated to 0.5MPa, the stability is carried out for 10min, and 20min penetrating fluid is collected for pure water flux calculation. Then, the flow-off test was carried out with NaCl (concentration 1000 ppm) under a pressure of 0.5MPa, and the measurement was repeated three times or more, and the average value was recorded.
The water Flux (Flux, F) test formula is as follows:
F＝V/(At) (1)
wherein F is the water flux of the composite membrane and the unit is L.m -2 ·h -1 (ii) a V is the volume of water permeating the membrane in t time, and the unit is L; a is the effective membrane area in m 2 (ii) a t is the transmission time in h.
The salt Rejection rate (Rejection, R) is measured as follows:
R＝(1-C p /C f )*100％ (2)
in the formula, R is the desalination rate of the composite membrane in unit%; c p The conductivity of the permeate in units of μ S/cm; c f To test the conductivity of the stock solution, units μ S/cm are used.
Comparative example 1
Preparation of porous polymer-based membrane: weighing 20g of polyether sulfone, dissolving in 80g of N, N-dimethylacetamide, mechanically stirring for 8h at 70 ℃, standing for 8h, and defoaming to obtain the casting solution with a stable system. And (3) quickly immersing the scraped film of 200 micrometers into deionized water for phase inversion, taking out the base film after 5 minutes, and storing the base film in the deionized water.
Preparation of aqueous polyamine solution containing no amine-based polymer particles: weighing 99g of deionized water according to mass percent, adding 0.5g of piperazine, stirring for dissolving, and adding 0.5g of triethylamine as an acid acceptor to obtain a piperazine aqueous solution with the piperazine concentration of 0.5%, namely a polyamine aqueous phase solution without amino polymer particles, which is called an aqueous phase solution.
Preparing an organic phase solution containing polyacyl chloride: 0.1g of trimesoyl chloride is weighed and dissolved in 99.9g of normal hexane by mass percent to obtain 0.1 percent polybasic acyl chloride solution which is called as organic phase solution.
Preparing a composite membrane: fixing the base film by adopting an acrylic mould, coating the water phase solution on the upper surface of the base film, pouring the water phase solution after 10min, and immediately blowing the redundant water solution on the surface of the film by using nitrogen. And coating the organic phase solution for 120 seconds, immediately placing the composite membrane in deionized water for storage after the interfacial polymerization is finished, and obtaining the composite membrane of which the separation layer does not contain amino polymer particles. Pure water flux and Na were measured at 0.5MPa 2 SO 4 (1000 ppm) retention, the procedure is shown in example 5 and the results are shown in Table 1.
Comparative example 2
Preparation of porous polymer-based membranes: weighing 16.0g of polyether sulfone and 4.0g of sulfonated polysulfone, dissolving in 80g of N, N-dimethylacetamide, mechanically stirring for 8h at 70 ℃, standing for 8h, and defoaming to obtain the casting solution with a stable system. And (3) quickly immersing the scraped 200-micron membrane into deionized water for phase inversion, taking out the base membrane after 5 minutes, and storing the base membrane in the deionized water.
Preparation of aqueous polyamine solution containing no amine-based polymer particles: weighing 96g of deionized water according to mass percent, adding 3.5g of piperazine, stirring for dissolving, and adding 0.5g of triethylamine as an acid acceptor to obtain a piperazine aqueous solution with the piperazine concentration of 3.5%, namely a polyamine aqueous phase solution without amino polymer particles, which is called an aqueous phase solution.
Preparing an organic phase solution containing polyacyl chloride: weighing 3.5g of trimesoyl chloride in percentage by mass, dissolving in 96.5g of n-hexane, and obtaining a polybasic acyl chloride solution with the concentration of 3.5 percent, namely an organic phase solution.
Preparing a composite membrane: adopts acrylicFixing the base membrane by using a mold, coating the water phase solution on the upper surface of the base membrane, pouring the water phase solution after 2min, and immediately blowing the redundant water solution on the surface of the membrane by using nitrogen. And coating the organic phase solution for 10 seconds, immediately placing the composite membrane in deionized water for storage after the interfacial polymerization is finished, and obtaining the composite membrane of which the separation layer does not contain amino polymer particles. Pure water flux and Na were measured at 0.5MPa 2 SO 4 (1000 ppm) retention, the procedure is shown in example 5 and the results are shown in Table 1.
Comparative example 3
Preparation of porous polymer-based membranes: weighing 20g of polyacrylonitrile, dissolving in 80g of N, N-dimethylformamide, mechanically stirring for 8h at 70 ℃, standing for 8h, and defoaming to obtain the casting solution with a stable system. And (3) quickly immersing the scraped 200-micron membrane into deionized water for phase inversion, taking out the base membrane after 5 minutes, and storing the base membrane in the deionized water.
Preparation of polyamine aqueous phase solution containing no amine-based polymer particles: weighing 98.5g of deionized water according to mass percent, adding 1.0g of piperazine, stirring for dissolving, and adding 0.5g of triethylamine as an acid acceptor to obtain a piperazine aqueous solution with the piperazine concentration of 3.5%, namely a polyamine aqueous phase solution without amino polymer particles, which is called an aqueous phase solution.
Preparing an organic phase solution containing polyacyl chloride: 0.5g of trimesoyl chloride is weighed and dissolved in 99.5g of normal hexane by mass percent to obtain 0.5 percent polyacyl chloride solution which is called as organic phase solution.
Preparing a composite membrane: fixing the base film by adopting an acrylic mold, coating the water-phase solution on the upper surface of the base film, pouring the water-phase solution after 5min, and immediately blowing the redundant water solution on the surface of the film by using nitrogen. And coating the composite membrane with an organic phase solution for 30 seconds, immediately placing the composite membrane in deionized water for storage after the interfacial polymerization is finished, and obtaining the composite membrane of which the separation layer does not contain amino polymer particles. Pure water flux and Na were measured at 0.5MPa 2 SO 4 (1000 ppm) retention, the procedure is shown in example 5 and the results are shown in Table 1.
In light of the above teachings, those skilled in the art will readily appreciate that the materials and their equivalents, the processes and their equivalents, as listed or exemplified herein, are capable of performing the invention in any of its several forms, and that the upper and lower limits of the parameters of the materials and processes, and the ranges of values between these limits are not specifically enumerated herein.
TABLE 1
Claims (8)
1. A high flux-high retention composite membrane comprises a porous polymer base membrane and a separation layer, wherein the pore diameter of the surface of the base membrane is an ultrafiltration membrane with the diameter of 10-100 nanometers, the separation layer is a crosslinked polyamide layer containing amino polymer particles, the thickness of the separation layer is 50-300 nanometers, and the diameter of the amino polymer particles contained in the separation layer is 20-80 nanometers; the amino polymer particles are generated in situ by amino polymer, micromolecular polyamine compound and cross-linking agent through ionic cross-linking in aqueous phase solution; the amino polymer is selected from one of chitosan, alpha or epsilon polylysine and polyarginine.
2. The composite membrane of claim 1, wherein the polymer-based membrane is selected from one or more of polysulfone, polyethersulfone, polyacrylonitrile, polyvinyl chloride, sulfonated polysulfone, and sulfonated polyethersulfone.
3. The composite film of claim 1, wherein the small molecule polyamine compound is one or more of piperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, polyethyleneimine, 1,3, 5-triaminobenzene, 1,2, 4-triaminobenzene, 3, 5-diaminobenzoic acid, 2, 4-diaminotoluene, 2, 4-diaminoanisole, xylylenediamine, 1, 2-diaminocyclohexane, 1, 4-diaminocyclohexane, 1, 3-bispiperidylpropane, 4-aminomethylpiperazine.
4. A method of making a composite membrane according to any preceding claim, comprising the steps of:
1) Preparing a small molecular polyamine compound aqueous phase solution containing amino polymer particles:
dissolving an amino polymer in a proper solvent to prepare a solution, then dissolving a small molecular polyamine compound in the amino polymer solution, mixing the solution with a cross-linking agent solution, and carrying out in-situ cross-linking reaction to form particles so as to obtain an aqueous phase solution containing amino polymer particles, free amino polymer and the small molecular polyamine compound;
2) Preparing a composite membrane with a separation layer containing amine-based polymer particles:
coating the water phase solution prepared in the step 1) on the surface of a porous polymer base membrane, after 2-10 minutes, purging residual water solution on the surface of the membrane by using nitrogen, then coating an organic phase solution containing polyacyl chloride for interfacial polymerization to prepare a separation layer, and after 10-120 seconds, placing the whole membrane in deionized water for storage to prepare the composite membrane of which the separation layer contains amino polymer particles.
5. The method of claim 4, wherein: in step 1), the cross-linking agent is one or more of polyphosphoric acid, polyphosphate, phytic acid or phytate.
6. The method according to claim 4, wherein in step 1), the amine-based polymer is present in an amount of 0.1 to 1 part; 0.5-3.5 parts of micromolecule polyamine compound, 0.1-5 parts of cross-linking agent and 90.5-99.2 parts of water.
7. The preparation method according to claim 4, wherein in the step 2), the mass of the polyacyl chloride in the polyacyl chloride organic phase solution accounts for 0.1-3.5 parts, and the mass of the organic solvent accounts for 96.5-99.9 parts.
8. Use of a composite membrane according to any one of the preceding claims 1-3 or a composite membrane prepared by a method according to any one of claims 4-7 in the field of nanofiltration and reverse osmosis.
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