CN103084081B - Preparation method of large-flux amphiprotic nano-filtration membrane - Google Patents

Abstract

The invention relates to a preparation method of a large flux amphoteric nanofiltration membrane. Traditional nanofiltration membrane preparation methods are mainly divided into phase inversion method and composite method, but it is difficult to obtain a membrane with a large flux. The method is that the ultrafiltration membrane is washed with ethanol and deionized water, then soaked in an olefinic cationic monomer solution, and irradiated under a 100-600W ultraviolet lamp for 3-120 minutes to obtain a cationic nanofiltration membrane; Washing with ionized water, soaking in amphoteric olefin monomer solution, and irradiating with 100-600W ultraviolet lamp for 2-40 minutes to obtain amphoteric nanofiltration membrane; finally, amphoteric nanofiltration membrane is washed with deionized water. The amphoteric nanofiltration membrane prepared by the method of the present invention has a water flux of 55 to 200 L/m ² h at 0.5 MPa, and a rejection rate of 40 to 85%, 80 to 97%, and 60 to 40% for sodium chloride, MgCl ₂ and MgSO ₄ , respectively. 93%. The preparation process of the method of the invention is simple and reliable, and is suitable for industrialization.

Description

A kind of preparation method of large flux amphoteric nanofiltration membrane

technical field

The invention belongs to the technical field of membrane separation, and relates to a preparation method of a large-flux amphoteric nanofiltration membrane.

Background technique

Nanofiltration membrane is a pressure-driven membrane with properties between ultrafiltration and reverse osmosis. The nanofiltration membrane has the following characteristics: the molecular weight cut-off is between 200 and 1000Da, which is suitable for removing dissolved components of about 1nm; the operating pressure is lower than that required by reverse osmosis, so it is also called "low pressure reverse osmosis". "Membrane"; with ion selectivity, a major feature of nanofiltration membranes is that the membrane body is charged, and through electrostatic interaction, divalent and multivalent ions in aqueous solution can be removed, and the interception of divalent and multivalent ions The rejection rate of monovalent ions is less than 80%, so the separation of ions of different valence states can be realized. Due to the above characteristics, nanofiltration membranes have been widely used in various industries such as environmental protection, water resources, food, medicine, and chemical industry.

The preparation methods of nanofiltration membranes can be divided into phase inversion method and composite method. The preparation of nanofiltration membranes by phase inversion method is simple and easy to operate, but it is very important to select suitable membrane materials. It is difficult to directly produce membranes with small pore diameters from traditional polymer membrane materials. The preparation of nanofiltration membrane by composite method mainly includes two steps: the first step is the preparation of microporous base membrane; the second step is the preparation of ultra-thin surface layer, the main methods are coating method, interfacial polymerization method, heat, light, radiation crosslinking Curing method, plasma polymerization method, etc. Among them, the key of the coating method is to select the composite solution that matches the basement membrane, but the composite solution and the basement membrane are physically adsorbed, and the composite solution will be lost during cleaning, losing the function of nanofiltration. The interfacial polymerization method is to use two highly reactive monomers to polymerize at two mutually incompatible interfaces, thereby forming a thin layer on the porous support. Using this Chinese patent (CN102423643A) to prepare a high-flux anion composite nanofiltration membrane by interfacial polycondensation method between sericin aqueous solution and organic solution containing aromatic polyacyl chloride; Chinese patent (CN1636626A) A new type of nanofiltration membrane was prepared by interfacial polymerization of amide and polyphthaloyl chloride organic solution. The water flux of the membrane was between 38.3 and 56.8 L/m ² h at 0.6 MPa, and the rejection rate of 1000 mg/L sodium chloride was 41.8 ~53.8%; however, this method has strict requirements on the selection and preparation of the base film, the regulation of the distribution coefficient and diffusion rate of the two types of reactants, the optimization of the interface conditions, and the rationalization of the looseness of the surface. Chinese patent (CN101766962A) uses the combination of complex coating and thermal cross ^- linking curing method to prepare a positively charged nanofiltration membrane. The rejection rate is generally 75 to 95%, and the rejection rate for monovalent cations is lower than 65%. Compared with the preparation methods of the above various nanofiltration membranes, the ultraviolet grafting method has the characteristics of simple preparation process and controllable reaction, and can only change the surface properties of the membrane without changing the properties of the base membrane. The hydrophilic nanofiltration membrane still has good stability in water. Among them, the Chinese patent (CN102247771A) prepared a negatively charged nanofiltration membrane by step-by-step grafting of sulfonic acid group-containing vinyl monomers and hydroxyl or carboxyl-containing vinyl monomers. The flux of the membrane at 0.4MPa is 28.3-36.6L/m ² h, the rejection rate of sodium sulfate is 94.8-97.9%, and the rejection rate of sodium chloride is 60.2-65.3%, but the salt solution of high-valent cations The rejection rate is low; the Chinese patent (CN101934204A) uses ultraviolet irradiation step-by-step grafting method to _prepare amphoteric nanofiltration membrane with polyether ether ketone ultrafiltration membrane as the base membrane. The anion (Na ₂ SO ₄ ) salt solution has a high rejection rate above 90%, but the flux of the membrane is relatively low, and the flux is only 3.2-9.6L/m ² h at 0.4MPa.

Through the analysis of the above preparation methods of various nanofiltration membranes, it is found that the preparation of nanofiltration membranes by ultraviolet irradiation grafting has become a membrane technology with potential application value. Flux polysulfone ultrafiltration membrane as the base membrane to prepare high-flux nanofiltration membrane is not reported.

Contents of the invention

The object of the present invention aims at the deficiencies of the prior art, and provides a method for preparing a large-flux amphoteric nanofiltration membrane.

In the invention, the ultrafiltration membrane is used as the base membrane, and the large-flux amphoteric nanofiltration membrane is prepared by an ultraviolet irradiation grafting method.

The concrete steps of the inventive method are:

Step (1). Wash the ultrafiltration membrane with ethanol for 1 to 10 times, and then wash it with deionized water for 5 to 20 times to remove impurities on the surface of the membrane;

The material of the ultrafiltration membrane is one or more of polysulfone (PSF), polyetherketone (PEK) and polyethersulfone (PES);

As preferably, the ultrafiltration membrane is washed 4 to 7 times with ethanol;

As preferably, the ultrafiltration membrane is washed 10 to 15 times with deionized water;

Step (2). Soak the washed ultrafiltration membrane in the olefinic cationic monomer solution, the distance between the upper surface of the ultrafiltration membrane and the liquid surface of the olefinic cationic monomer solution is 1-5mm, 100-600W ultraviolet lamp Under irradiation for 3 to 120 minutes, the distance between the upper surface of the ultrafiltration membrane and the ultraviolet lamp is 5 to 40 cm, and a cationic nanofiltration membrane is obtained;

The olefinic cationic monomer solution is an aqueous solution or a methanol solution or an ethanol solution with a mass fraction of 1 to 65% of the olefinic cationic monomer;

The olefinic cationic monomer is an olefin containing a quaternary ammonium salt or a tertiary amino group;

The ultraviolet lamp is a high-pressure mercury lamp with a wavelength of 290-400nm, and reacts in the air at 10-30°C;

Preferably, the mass content of the olefin cationic monomer in the olefin cationic monomer solution is 5-50%;

Preferably, the power of the ultraviolet lamp is 300-500W, the ultraviolet irradiation time is 5-30min, and the distance between the upper surface of the ultrafiltration membrane and the ultraviolet lamp is 10-30cm;

Step (3). Wash the cationic nanofiltration membrane obtained after ultraviolet radiation with deionized water for 5 to 10 times to remove residual olefin cationic monomers on the surface of the membrane, and then soak the washed cationic nanofiltration membrane in amphoteric olefins In the monomer solution, the distance between the upper surface of the cationic nanofiltration membrane and the liquid surface of the amphoteric olefin monomer solution is 1 to 5 mm, and the upper surface of the cationic nanofiltration membrane and the liquid surface of the amphoteric olefin monomer solution are irradiated for 2 to 40 minutes under a 100-600W ultraviolet lamp. The distance of the ultraviolet lamp is 5-40cm, and the amphoteric nanofiltration membrane is obtained;

The amphoteric olefin monomer solution is an aqueous solution or methanol solution or ethanol solution with a mass fraction of 1 to 30% amphoteric olefin monomer;

The amphoteric olefin monomers are olefins containing amphoteric groups; the negative groups in the amphoteric olefin monomers are one or both of sulfonic acid groups and carboxyl groups, and the positive groups are quaternary ammonium salts and tertiary amino groups. one or two;

Preferably, the mass content of the amphoteric olefinic monomer in the amphoteric olefinic monomer solution is 5-20%;

Preferably, the power of the ultraviolet lamp is 300-500W, the ultraviolet irradiation time is 10-30min, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 10-30cm;

Step (4). Washing the obtained amphoteric nanofiltration membrane with deionized water for 10 to 20 times to remove residual amphoteric olefin monomers on the surface of the membrane.

The distance from the upper surface of the film to the ultraviolet lamp and the power of the ultraviolet lamp are used to control the radiation intensity.

The performance of the amphoteric nanofiltration membrane prepared by the invention is controlled by changing the irradiation time, monomer concentration and radiation intensity. By changing the type of grafted monomer to control the type of charge on the surface of the nanofiltration membrane, the properties of the amphoteric nanofiltration membrane can be changed in a large range, and the amphoteric charge with a high rejection rate for high-valent cations and high-valent anions can be obtained. Nanofiltration.

The amphoteric nanofiltration membrane prepared by the method of the present invention has a water flux of 55-200 L/m ^h at 0.5 MPa, a rejection rate of 40-85% to sodium chloride, and a rejection rate of 80-97% to _MgCl , the rejection rate of MgSO ₄ is 60-93%.

The preparation process of the method of the invention is simple and reliable, and is suitable for industrial production.

Detailed ways

The present invention is further analyzed below in conjunction with embodiment.

Example 1.

Step (1). The polysulfone ultrafiltration membrane is washed once with ethanol, and then washed eight times with deionized water to remove impurities on the surface of the membrane;

Step (2). The polysulfone ultrafiltration membrane after washing is soaked in the aqueous solution that mass fraction is 1% 4-vinylpyridine, and the membrane upper surface of polysulfone ultrafiltration membrane and mass fraction are 1% 4-vinylpyridine The distance between the liquid surface of the aqueous solution is 1 mm, irradiated for 120 minutes under a 100W ultraviolet lamp, and the distance between the film upper surface of the polysulfone ultrafiltration membrane and the ultraviolet lamp is 5 cm, and a cationic nanofiltration membrane is obtained;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 5 times with deionized water to remove residual 4-vinylpyridine on the surface of the membrane, and then the washed cationic nanofiltration membrane is soaked in a 1% mass fraction In the aqueous solution of 2-vinylpyridinepropylsulfonate, the distance between the upper surface of the cationic nanofiltration membrane and the liquid surface of the aqueous solution with a mass fraction of 1% 2-vinylpyridinepropylsulfonate is 1mm, under a 100W ultraviolet lamp Irradiate for 40min, the distance between the membrane upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 5cm, and obtain the amphoteric nanofiltration membrane;

Step (4). The obtained amphoteric nanofiltration membrane was washed 10 times with deionized water to remove residual 2-vinylpyridinepropylsulfonate on the surface of the membrane.

The water flux of the amphoteric nanofiltration membrane prepared in embodiment ₁ is 200L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 40%, the rejection rate to MgCl is 80%, and the rejection rate to _MgSO is 60%.

Example 2.

Step (1). Wash the polyetherketone ultrafiltration membrane twice with ethanol, and then wash it 10 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polyetherketone ultrafiltration membrane after washing in the aqueous solution of 5% 3-methacrylamidopropyltrimethylammonium in mass fraction, the film upper surface of polyetherketone ultrafiltration membrane and The distance between the liquid surface of the aqueous solution with a mass fraction of 5% 3-methacrylamidopropyltrimethylammonium is 1.5mm, and the 150W ultraviolet lamp is irradiated for 110 minutes. The distance is 8cm, and the cationic nanofiltration membrane is obtained;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 6 times with deionized water to remove residual 3-methacrylamidopropyltrimethylammonium on the membrane surface, and then the washed cationic nanofiltration The membrane is soaked in an aqueous solution with a mass fraction of 5% m-vinyl-o-picoline propyl sulfonate, the upper surface of the cationic nanofiltration membrane and the mass fraction of 5% m-vinyl-o-methyl The distance between the liquid surface of the aqueous solution of pyridine propyl sulfonate is 1.5 mm, irradiated under a 150W ultraviolet lamp for 38 minutes, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 8 cm, and an amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 11 times with deionized water to remove residual m-vinyl-o-picoline propylsulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration _membrane prepared in embodiment ² is 180L/m h at 0.5MPa, the rejection rate to sodium chloride is 48.7%, the rejection rate to MgCl is 82.1%, and the rejection rate to _MgSO It is 63.2%.

Example 3.

Step (1). The polyethersulfone ultrafiltration membrane is washed 3 times with ethanol, and then washed 9 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polyethersulfone ultrafiltration membrane after washing in the aqueous solution of 30% diallyl dimethyl ammonium chloride in mass fraction, the film upper surface and mass fraction of polyethersulfone ultrafiltration membrane are The distance between the liquid surface of the aqueous solution of 30% diallyl dimethyl ammonium chloride is 2 mm, and it is irradiated under a 180W ultraviolet lamp for 90 minutes. The distance between the upper surface of the polyethersulfone ultrafiltration membrane and the ultraviolet lamp is 10 cm, and the cationic nano membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 7 times with deionized water to remove residual diallyl dimethyl ammonium chloride on the membrane surface, and then the cationic nanofiltration membrane after washing is soaked in In an aqueous solution with a mass fraction of 10% acrylamido ethyl dimethyl ammonium propyl sulfonate, the membrane upper surface of the cationic nanofiltration membrane and a mass fraction of 10% acrylamido ethyl dimethyl ammonium propyl sulfonic acid The distance between the liquid surface of the aqueous salt solution is 2 mm, irradiated under a 180W ultraviolet lamp for 35 minutes, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 10 cm, and an amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 12 times with deionized water to remove residual acrylamido ethyl dimethyl ammonium propyl sulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration membrane prepared in embodiment 3 is 100L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 65.3%, the rejection rate to _MgCl is 85.9%, and the rejection rate to _MgSO It is 72.7%.

Example 4.

Step (1). The polysulfone/polyetherketone ultrafiltration membrane is washed 4 times with ethanol, and then washed 5 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the washed polysulfone/polyetherketone ultrafiltration membrane in an aqueous solution with a mass fraction of 50% methacryloyloxyethyltrimethylammonium chloride, polysulfone/polyetherketone ultrafiltration The distance between the upper surface of the membrane and the liquid surface of an aqueous solution with a mass fraction of 50% methacryloyloxyethyltrimethylammonium chloride is 2.5mm, irradiated by a 200W ultraviolet lamp for 80 minutes, polysulfone/polyetherketone ultrafiltration The distance between the membrane upper surface of the membrane and the ultraviolet lamp is 12cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 8 times with deionized water to remove residual methacryloyloxyethyltrimethylammonium chloride on the membrane surface, and then the washed cationic nanofiltration In an aqueous solution where the membrane is soaked with a mass fraction of 20% 2-methacrylamide ethyl diethylammonium propyl sulfonate, the membrane upper surface of the cationic nanofiltration membrane and the mass fraction of 20% 2-methacrylamide ethyl The distance between the liquid surface of the aqueous solution of diethylammonium propyl sulfonate is 2mm, irradiated under a 200W ultraviolet lamp for 32min, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 12cm, and an amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 13 times with deionized water to remove residual 2-methacrylamide ethyl diethyl ammonium propyl sulfonate on the membrane surface.

The water _flux of the amphoteric nanofiltration membrane prepared in embodiment 4 is 72L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 78.3%, the rejection rate to _MgCl is 89.5%, and the rejection rate to MgSO It is 82.3%.

Example 5.

Step (1). The polysulfone/polyethersulfone ultrafiltration membrane is washed 5 times with ethanol, and then 6 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the washed polysulfone/polyethersulfone ultrafiltration membrane in an aqueous solution with a mass fraction of 65% 3-acrylamido-3-methylbutyltrimethylammonium, polysulfone/polyether The distance between the upper surface of the membrane of the sulfone ultrafiltration membrane and the liquid surface of an aqueous solution with a mass fraction of 65% 3-acrylamido-3-methylbutyltrimethylammonium is 3 mm, and the polysulfone/ The distance between the upper surface of the polyethersulfone ultrafiltration membrane and the ultraviolet lamp is 15 cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 9 times with deionized water to remove residual 3-acrylamide-3-methylbutyltrimethylammonium on the surface of the membrane, and then the washed The cationic nanofiltration membrane is immersed in an aqueous solution with a mass fraction of 30% 2-methacryloyloxyethyl dimethyl ammonium propyl sulfonate, and the upper surface of the cationic nanofiltration membrane and the mass fraction are 30% 2-form The distance between the liquid surface of the aqueous solution of acryloyloxyethyl dimethyl ammonium propyl sulfonate is 3mm, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 15cm under the irradiation of 250W ultraviolet lamp for 28min, and the amphoteric nanofiltration membrane is obtained membrane;

Step (4). The obtained amphoteric nanofiltration membrane was washed 14 times with deionized water to remove residual 2-methacryloyloxyethyldimethylammonium propylsulfonate on the surface of the membrane.

The water flux of the amphoteric nanofiltration membrane prepared in embodiment 5 is 65L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 80.3%, the rejection rate to _MgCl is _91.4 %, and the rejection rate to MgSO It is 87.2%.

Example 6.

Step (1). The polyetherketone/polyethersulfone ultrafiltration membrane is washed 6 times with ethanol, and then washed 7 times with deionized water to remove impurities on the surface of the membrane;

Step (2). Soak the washed polyetherketone/polyethersulfone ultrafiltration membrane in a methanol solution with a mass fraction of 1% 4-vinylpyridine, and the membrane upper surface of the polyetherketone/polyethersulfone ultrafiltration membrane The distance from the liquid surface of the methanol solution with a mass fraction of 1% 4-vinylpyridine is 3.5mm, irradiated under a 280W ultraviolet lamp for 65 minutes, and the distance between the upper surface of the ultrafiltration membrane and the ultraviolet lamp is 20cm, and a cationic nanofiltration membrane is obtained. ;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 10 times with deionized water to remove residual 4-vinylpyridine on the surface of the membrane, and then the washed cationic nanofiltration membrane is soaked in a 1% mass fraction In the methanol solution of 2-methacryloyloxyethyldiethylammonium propylsulfonate, the membrane upper surface and mass fraction of the cationic nanofiltration membrane are 1% 2-methacryloyloxyethyldiethylammonium The distance between the liquid surface of the methanol solution of propylsulfonate is 3.5mm, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 20cm, and the amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 15 times with deionized water to remove residual 2-methacryloyloxyethyldiethylammonium propylsulfonate on the surface of the membrane.

The water flux of the amphoteric nanofiltration membrane prepared in embodiment 6 is 195L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 40.3%, the rejection rate to _MgCl is _80.9 %, and the rejection rate to MgSO It is 61.2%.

Example 7.

Step (1). The polysulfone/polyetherketone/polyethersulfone ultrafiltration membrane is washed 7 times with ethanol, and then washed 11 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the washed polysulfone/polyether ketone/polyethersulfone ultrafiltration membrane in the methanol solution of 5% 3-methacrylamidopropyltrimethylammonium in mass fraction, polysulfone/polyether ketone The distance between the upper surface of the polyetherketone/polyethersulfone ultrafiltration membrane and the liquid surface of the methanol solution with a mass fraction of 5% 3-methacrylamidopropyltrimethylammonium is 4mm, and it is irradiated under a 300W ultraviolet lamp for 60 minutes , the distance between the upper surface of the polysulfone/polyetherketone/polyethersulfone ultrafiltration membrane and the ultraviolet lamp is 18cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 5 times with deionized water to remove residual 3-methacrylamidopropyltrimethylammonium on the membrane surface, and then the washed cationic nanofiltration The membrane is immersed in a methanol solution with a mass fraction of 5% 2-vinylpyridine propyl sulfonate. The liquid surface distance is 4.5mm, irradiated under a 300W ultraviolet lamp for 25min, and the distance between the membrane upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 18cm, and an amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 16 times with deionized water to remove residual 2-vinylpyridinepropylsulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration membrane prepared in embodiment 7 is 140L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 50.4%, the rejection rate to _MgCl is _83.2 %, and the rejection rate to MgSO It is 65.3%.

Example 8.

Step (1). The polysulfone ultrafiltration membrane is washed 8 times with ethanol, and then washed 12 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polysulfone ultrafiltration membrane after washing in the methanol solution of 20% diallyl dimethyl ammonium chloride in mass fraction, the film upper surface and mass fraction of polysulfone ultrafiltration membrane are 20% ﹪Diallyldimethylammonium chloride methanol solution liquid surface distance is 5mm, irradiated under 350W ultraviolet lamp for 50 minutes, the distance between the membrane upper surface of the polysulfone ultrafiltration membrane and the ultraviolet lamp is 22cm, to obtain cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 6 times with deionized water to remove residual diallyl dimethyl ammonium chloride on the membrane surface, and then the cationic nanofiltration membrane after washing is soaked in In the methanol solution with a mass fraction of 8% m-vinyl-o-picoline propyl sulfonate, the membrane upper surface of the cationic nanofiltration membrane and the mass fraction of 8% m-vinyl-o-picoline propyl The methanol solution liquid surface distance of base sulfonate is 5mm, 22min is irradiated under the 350W ultraviolet lamp, the film upper surface of cationic nanofiltration membrane and the distance of ultraviolet lamp are 22cm, obtain amphoteric nanofiltration membrane;

Step (4). The obtained amphoteric nanofiltration membrane was washed 17 times with deionized water to remove residual m-vinyl-o-picoline propylsulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration membrane prepared in Example 8 is 85L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 67.3%, the rejection rate to _MgCl is _86.4 %, and the rejection rate to MgSO It is 74.5%.

Example 9.

Step (1). The polyetherketone ultrafiltration membrane is washed 9 times with ethanol, and then washed 14 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polyetherketone ultrafiltration membrane after washing in the methanol solution of 50% methacryloyloxyethyltrimethylammonium chloride by mass fraction, the membrane upper surface of the polyetherketone ultrafiltration membrane The distance from the liquid surface of the methanol solution with a mass fraction of 50% methacryloyloxyethyltrimethylammonium chloride is 2.5mm, and irradiated under a 380W ultraviolet lamp for 40 minutes, the upper surface of the polyetherketone ultrafiltration membrane and the ultraviolet The distance between the lamps is 25cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 7 times with deionized water to remove residual methacryloyloxyethyltrimethylammonium chloride on the membrane surface, and then the washed cationic nanofiltration The membrane is immersed in a methanol solution with a mass fraction of 20% acrylamido ethyl dimethyl ammonium propyl sulfonate. The distance between the liquid surface of the methanol solution of propylsulfonate is 2.5mm, and the irradiated under a 380W ultraviolet lamp for 20min, the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 25cm, and an amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 18 times with deionized water to remove residual acrylamido ethyl dimethyl ammonium propyl sulfonate on the membrane surface.

The water flux of _the amphoteric nanofiltration membrane prepared in Implementation 9 is 62L/m ² h at 0.5MPa, the rejection rate to sodium chloride is 81.2%, the rejection rate to MgCl is 92.5%, and the rejection rate to _MgSO is 89.4%.

Example 10.

Step (1). The polyethersulfone ultrafiltration membrane is washed 10 times with ethanol, and then washed 15 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polyethersulfone ultrafiltration membrane after washing in the methanol solution of 65% 3-acrylamido-3-methylbutyltrimethylammonium in mass fraction, the polyethersulfone ultrafiltration membrane The distance between the upper surface of the membrane and the liquid surface of methanol solution with a mass fraction of 65% of 3-acrylamido-3-methylbutyltrimethylammonium is 3.5mm, irradiated under 400W ultraviolet lamp for 30 minutes, polyethersulfone ultrafiltration membrane The distance between the upper surface of the membrane and the ultraviolet lamp is 30cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 8 times with deionized water to remove residual 3-acrylamido-3-methylbutyltrimethylammonium on the surface of the membrane, and then the washed The cationic nanofiltration membrane is soaked in a methanol solution with a mass fraction of 30% 2-methacrylamide ethyl diethylammonium propyl sulfonate, the upper surface of the cationic nanofiltration membrane and the mass fraction of 30% 2-form The distance between the liquid surface of the methanol solution of methacrylamide ethyl diethylammonium propyl sulfonate is 3.5 mm, irradiated under a 400W ultraviolet lamp for 18 minutes, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 30 cm, and the amphoteric Nanofiltration;

Step (4). The obtained amphoteric nanofiltration membrane was washed 19 times with deionized water to remove residual 2-methacrylamide ethyl diethyl ammonium propyl sulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration membrane prepared in Example 10 is 55L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 85%, the rejection rate to _MgCl is 97%, and the rejection rate to _MgSO is 93%.

Example 11.

Step (1). The polysulfone/polyetherketone ultrafiltration membrane is washed 5 times with ethanol, and then washed 16 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polysulfone/polyetherketone ultrafiltration membrane after washing in the ethanol solution of 1% 4-vinylpyridine with a mass fraction, the membrane upper surface and mass of the polysulfone/polyetherketone ultrafiltration membrane The distance between the liquid surface of the ethanol solution with a fraction of 1% of 4-vinylpyridine is 4.5mm, irradiated under a 450W ultraviolet lamp for 100 minutes, and the distance between the upper surface of the polysulfone/polyetherketone ultrafiltration membrane and the ultraviolet lamp is 32cm, and the obtained Cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 5 to 10 times with deionized water to remove residual 4-vinylpyridine on the surface of the membrane, and then the washed cationic nanofiltration membrane is soaked in a mass fraction of In the ethanol solution of 1% 2-methacryloyloxyethyl dimethyl ammonium propyl sulfonate, the membrane upper surface and mass fraction of the cationic nanofiltration membrane are 1% 2-methacryloyloxyethyl dimethyl The liquid surface distance of the ethanol solution of ammonium propyl sulfonate is 4.5mm, irradiated under 450W ultraviolet lamp for 10min, and the distance between the membrane upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 32cm, and the amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 20 times with deionized water to remove residual 2-methacryloyloxyethyldimethylammonium propylsulfonate on the surface of the membrane.

The water flux of the amphoteric nanofiltration membrane prepared in Example 11 is 193 L/m ^h at 0.5 MPa, the rejection rate to sodium chloride is 41.3%, the rejection rate to _MgCl is _81.7 %, and the rejection rate to MgSO It is 61.5%.

Example 12.

Step (1). The polysulfone/polyethersulfone ultrafiltration membrane is washed 7 times with ethanol, and then washed 18 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the washed polysulfone/polyethersulfone ultrafiltration membrane in an ethanol solution with a mass fraction of 5% 3-methacrylamidopropyltrimethylammonium, polysulfone/polyethersulfone ultrafiltration The distance between the upper surface of the filter membrane and the liquid surface of the ethanol solution with a mass fraction of 5% 3-methacrylamidopropyltrimethylammonium is 4mm, and the polysulfone/polyethersulfone ultra- The distance between the membrane upper surface of the filter membrane and the ultraviolet lamp is 35cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 9 times with deionized water to remove residual 3-methacrylamidopropyltrimethylammonium on the membrane surface, and then the washed cationic nanofiltration The membrane is immersed in an ethanol solution with a mass fraction of 5% 2-methacryloyloxyethyldiethylammonium propyl sulfonate, and the upper surface of the cationic nanofiltration membrane and the mass fraction of 2-methacrylic acid The distance between the liquid surface of the ethanol solution of acyloxyethyl diethylammonium propyl sulfonate is 4mm, irradiated under a 500W ultraviolet lamp for 15min, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 35cm, and the amphoteric nanofiltration is obtained. membrane;

Step (4). The obtained amphoteric nanofiltration membrane was washed 20 times with deionized water to remove residual 2-methacryloyloxyethyldiethylammonium propylsulfonate on the surface of the membrane.

The water flux of _the amphoteric nanofiltration membrane prepared in Example 12 is 120L/m ^h at 0.5MPa, the rejection rate to sodium chloride is 55.3%, the rejection rate to MgCl is _84.5 %, and the rejection rate to MgSO It is 67.2%.

Example 13.

Step (1). The polyetherketone/polyethersulfone ultrafiltration membrane is washed 9 times with ethanol, and then washed 20 times with deionized water to remove impurities on the surface of the membrane;

Step (2). Soak the ultrafiltration membrane after washing in the ethanol solution of 40% diallyl dimethyl ammonium chloride in mass fraction, the film upper surface and mass fraction of ultrafiltration membrane are 40% diallyl The ethanol solution liquid surface distance of dimethyl ammonium chloride is 5mm, irradiates 3 minutes under the 550W ultraviolet lamp, and the film upper surface of ultrafiltration membrane and the distance of ultraviolet lamp are 38cm, obtain cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 10 times with deionized water to remove residual diallyl dimethyl ammonium chloride on the membrane surface, and then the cationic nanofiltration membrane after washing is soaked in In an ethanol solution with a mass fraction of 15% of 2-vinylpyridine propyl sulfonate, the distance between the upper surface of the cationic nanofiltration membrane and the liquid surface of an ethanol solution with a mass fraction of 15% of 2-vinyl pyridine propyl sulfonate 5mm, irradiated for 5min under a 550W ultraviolet lamp, and the distance between the membrane upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 38cm to obtain an amphoteric nanofiltration membrane;

Step (4). The obtained amphoteric nanofiltration membrane was washed 15 times with deionized water to remove residual 2-vinylpyridinepropylsulfonate on the surface of the membrane.

The water flux of the amphoteric nanofiltration membrane prepared in Example 13 is 77L/ ^m2h at 0.5MPa, the rejection rate to sodium chloride is 72.5%, the rejection rate to _MgCl is 88.3%, and the rejection rate to _MgSO It is 80.1%.

Example 14.

Step (1). The polysulfone/polyetherketone/polyethersulfone ultrafiltration membrane is washed 8 times with ethanol, and then washed 19 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the washed polysulfone/polyether ketone/polyether sulfone ultrafiltration membrane in a 50% ethanol solution of methacryloyloxyethyltrimethylammonium chloride, on the membrane of the ultrafiltration membrane The distance between the surface and the ethanol solution of 50% methacryloyloxyethyltrimethylammonium chloride is 3.5mm, irradiated under 600W ultraviolet lamp for 3 minutes, the ultrafiltration membrane of polysulfone/polyetherketone/polyethersulfone The distance between the upper surface of the membrane and the ultraviolet lamp is 40cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 8 times with deionized water to remove residual methacryloyloxyethyltrimethylammonium chloride on the membrane surface, and then the washed cationic nanofiltration The membrane is soaked in an ethanol solution with a mass fraction of 20% m-vinyl-o-picoline propyl sulfonate. The ethanol solution liquid surface distance of pyridyl propyl group sulfonate is 2mm, irradiates 2min under the 600W ultraviolet lamp, and the film upper surface of cationic nanofiltration membrane and the distance of ultraviolet lamp are 40cm, obtain amphoteric nanofiltration membrane;

Step (4). The obtained amphoteric nanofiltration membrane was washed 18 times with deionized water to remove residual m-vinyl-o-picoline propylsulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration membrane prepared in Example 14 is 68 L/m ^h at 0.5 MPa, the rejection rate to sodium chloride is 80.1%, the rejection rate to _MgCl is 90.8%, and the rejection rate to _MgSO It is 85.7%.

Example 15.

Step (1). The polysulfone ultrafiltration membrane is washed 6 times with ethanol, and then washed 17 times with deionized water to remove impurities on the membrane surface;

Step (2). Soak the polysulfone ultrafiltration membrane after washing in the ethanol solution of 65% 3-acrylamido-3-methylbutyltrimethylammonium in mass fraction, on the membrane of polysulfone ultrafiltration membrane The distance between the surface and the liquid surface of the ethanol solution with a mass fraction of 65% of 3-acrylamido-3-methylbutyltrimethylammonium is 5 mm, and the upper surface of the polysulfone ultrafiltration membrane is irradiated for 5 minutes under a 600W ultraviolet lamp. The distance from the ultraviolet lamp is 30cm to obtain a cationic nanofiltration membrane;

Step (3). The cationic nanofiltration membrane obtained after ultraviolet radiation is washed 8 times with deionized water to remove residual 3-acrylamido-3-methylbutyltrimethylammonium on the surface of the membrane, and then the washed The cationic nanofiltration membrane is soaked in an ethanol solution with a mass fraction of 30% acrylamido ethyl dimethyl ammonium propyl sulfonate, the upper surface of the cationic nanofiltration membrane and the mass fraction of 30% acrylamido ethyl di The liquid surface distance of the ethanol solution of methylammonium propyl sulfonate is 5 mm, irradiated under a 600W ultraviolet lamp for 30 minutes, and the distance between the upper surface of the cationic nanofiltration membrane and the ultraviolet lamp is 30 cm, and an amphoteric nanofiltration membrane is obtained;

Step (4). The obtained amphoteric nanofiltration membrane was washed 15 times with deionized water to remove residual acrylamido ethyl dimethyl ammonium propyl sulfonate on the membrane surface.

The water flux of the amphoteric nanofiltration membrane prepared in Example 15 is 57 L/m ^h at 0.5 MPa, the rejection rate to sodium chloride is 83.2%, the rejection rate to _MgCl is 94.3%, and the rejection rate to _MgSO It is 91.7%.

The wavelength of the used ultraviolet lamp of above-mentioned embodiment 1～15 is the high-pressure mercury lamp of 290～400nm, reacts at 10～30 ℃, carries out in the air; radiation intensity.

The filtration performance of the amphoteric nanofiltration membrane prepared in the present invention is evaluated in a membrane evaluation instrument. The test temperature is normal temperature and the pressure is 0.5MPa. The filtration performance of _the amphoteric nanofiltration membrane is represented by _the water flux (unit: L/m ² h) permeability under the conditions; The rejection rate is used to represent its selectivity.

Claims (8)

1. a preparation method of large flux amphoteric nanofiltration membrane, is characterized in that the method may further comprise the steps: Step (1). Wash the ultrafiltration membrane with ethanol for 1 to 10 times, and then wash it with deionized water for 5 to 20 times to remove impurities on the surface of the membrane; Step (2). Soak the washed ultrafiltration membrane in the olefinic cationic monomer solution, the distance between the upper surface of the ultrafiltration membrane and the liquid surface of the olefinic cationic monomer solution is 1-5mm, 100-600W ultraviolet lamp Under irradiation for 3 to 120 minutes, the distance between the upper surface of the ultrafiltration membrane and the ultraviolet lamp is 5 to 40 cm, and a cationic nanofiltration membrane is obtained; The olefinic cationic monomer solution is an aqueous solution or a methanol solution or an ethanol solution with a mass fraction of 1 to 65% of the olefinic cationic monomer; The olefinic cationic monomer is an olefin containing a tertiary amino group; Step (3). Wash the cationic nanofiltration membrane obtained after ultraviolet radiation with deionized water for 5 to 10 times to remove residual olefin cationic monomers on the surface of the membrane, and then soak the washed cationic nanofiltration membrane in amphoteric olefins In the monomer solution, the distance between the upper surface of the cationic nanofiltration membrane and the liquid surface of the amphoteric olefin monomer solution is 1 to 5 mm, and the upper surface of the cationic nanofiltration membrane and the liquid surface of the amphoteric olefin monomer solution are irradiated for 2 to 40 minutes under a 100-600W ultraviolet lamp. The distance of the ultraviolet lamp is 5-40cm, and the amphoteric nanofiltration membrane is obtained; The amphoteric olefin monomer solution is an aqueous solution or methanol solution or ethanol solution with a mass fraction of 1 to 30% amphoteric olefin monomer; The amphoteric olefinic monomer is acrylamido ethyl dimethyl ammonium propyl sulfonate or 2-methacrylamide ethyl diethyl ammonium propyl sulfonate; Step (4). Washing the obtained amphoteric nanofiltration membrane with deionized water for 10 to 20 times to remove residual amphoteric olefin ionic monomers on the surface of the membrane. 2. the preparation method of a kind of large flux amphoteric nanofiltration membrane as claimed in claim 1 is characterized in that the material of the ultrafiltration membrane described in step (1) is polysulfone, polyetherketone, polyethersulfone one or more. 3. the preparation method of a kind of large-flux amphoteric nanofiltration membrane as claimed in claim 1 is characterized in that the ultraviolet lamp described in step (2) is the high-pressure mercury lamp that wavelength is 290～400nm, at 10～30 The reaction was carried out in air at ℃. 4. the preparation method of a kind of large-flux amphoteric nanofiltration membrane as claimed in claim 1 is characterized in that in step (1), ultrafiltration membrane is washed 4～7 times with ethanol, then washes 10～15 with deionized water. Second-rate. 5. the preparation method of a kind of large-flux amphoteric nanofiltration membrane as claimed in claim 1 is characterized in that the power of ultraviolet lamp is 300～500W in the step (2), and the ultraviolet irradiation time is 5～30min, ultrafiltration The distance between the upper surface of the film and the ultraviolet lamp is 10-30 cm. 6. the preparation method of a kind of large-flux amphoteric nanofiltration membrane as claimed in claim 1 is characterized in that the power of the ultraviolet lamp is 300～500W in the step (3), and the ultraviolet irradiation time is 10～30min, and cationic nanofiltration The distance between the upper surface of the filter membrane and the ultraviolet lamp is 10-30 cm. 7. The preparation method of a large-flux amphoteric nanofiltration membrane as claimed in claim 3, characterized in that the mass content of the olefin cationic monomer in the solution of the olefin cationic monomer is 5-50%. 8 . The method for preparing a large-flux amphoteric nanofiltration membrane according to claim 5 , wherein the mass content of the amphoteric olefinic monomer in the amphoteric olefinic monomer solution is 5-20%.