CN110665377B - High-flux anti-pollution reverse osmosis membrane and preparation method thereof - Google Patents
High-flux anti-pollution reverse osmosis membrane and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of reverse osmosis membranes, and particularly relates to a high-flux anti-pollution reverse osmosis membrane and a preparation method thereof. The reverse osmosis membrane comprises a polysulfone-based membrane layer, a polyamide desalting layer and a polyvinyl alcohol protective layer from bottom to top in sequence; the polyvinyl alcohol protective layer comprises the following components in parts by mass: 1 part of polyvinyl alcohol, 0.02-0.1 part of nano titanium dioxide modified clay mineral and 0.2 part of 3-aminopropylsilanetriol. The invention also provides a preparation method of the high-flux anti-pollution reverse osmosis membrane. The method solves the problem of water flux reduction after coating the polyvinyl alcohol protective layer, and simultaneously improves the anti-pollution performance of the reverse osmosis membrane, so that the reverse osmosis membrane can still maintain excellent water flux and desalination rate after long-term scouring pollution of surface water.
Description
Technical Field
The invention belongs to the technical field of reverse osmosis membranes, and particularly relates to a high-flux anti-pollution reverse osmosis membrane and a preparation method thereof.
Background
With the increase of global industrialization, the water pollution problem is becoming more and more serious due to the rise of industries such as printing and dyeing, electronics, chemical engineering and the like. How to effectively recycle, purify and reuse water resources becomes one of the major problems facing human society. Compared with the traditional treatment method, the membrane separation method has the advantages of low energy consumption, good water quality, high recovery rate, large water yield and the like, and gradually becomes a mainstream technology in the field of water treatment. At present, the separation membrane is widely applied to the fields of brackish water desalination, seawater desalination, urban sewage recycling, household water purification and the like.
The membrane surface has an obvious peak valley-shaped bulge structure and is easily oxidized and polluted by inlet water in long-term use, so that the desalting performance of the membrane is reduced, and the water production is reduced. Meanwhile, the reverse osmosis membrane can be applied to a water treatment system only by being rolled into a reverse osmosis membrane element with a corresponding size by matching with membrane components such as a dense net, a light net and a central pipe before use, and a desalting layer on the surface of the membrane is extremely easy to scratch and damage in the rolling process. In order to reduce the oxidation pollution of the desalting layer of the membrane and reduce the physical damage of the membrane in the rolling process, a compact polyvinyl alcohol protective layer is generally required to be coated on the surface of the membrane. Avoiding direct contact between the contaminants and the membrane separation layer to contaminate the membrane. However, in practical application, the polyvinyl alcohol protective layer coated on the surface of the membrane is easy to block the pore canal of the separation layer of the membrane, so that the water flux of the membrane is greatly reduced. Meanwhile, the adhesion degree between the coated polyvinyl alcohol protective layer and the film surface is poor, the surface protective layer is easy to fall off in use, and the effect of protecting the film surface for a long time cannot be achieved. In view of the above-mentioned contradiction, it is necessary to develop a protection layer of polyvinyl alcohol which can simultaneously improve the anti-pollution performance and water flux performance of the membrane.
Chinese patent CN107638805 discloses a preparation method of a graphene oxide/polyvinyl alcohol coating modified reverse osmosis membrane, which takes graphene oxide as a modifier and utilizes a multilayer nano-stack structure of graphene to improve the water flux of the polyvinyl alcohol coating. However, the method still has the following defects: 1. graphene is a layered two-dimensional carbon nanomaterial, has small interlayer spacing, and is difficult to form an effective interlayer channel without column support or mechanical stripping. 2. The graphene is flaky and is easily covered by polyvinyl alcohol, and the flow guide effect is lost. 3. Graphene is expensive and not suitable for large-scale industrial production.
In view of this, the invention is particularly proposed.
Disclosure of Invention
Aiming at the defects of low water flux, poor pollution resistance, weak combination of a protective layer and a membrane surface and the like of a reverse osmosis membrane coated with a polyvinyl alcohol protective layer on the surface in the prior art. The invention aims to provide a high-water-flux anti-pollution reverse osmosis membrane and a preparation method thereof, which are used for solving the problem of water flux reduction after a polyvinyl alcohol protective layer is coated, and simultaneously, the anti-pollution performance of the reverse osmosis membrane is synchronously improved, so that the reverse osmosis membrane can still keep excellent water flux and desalination rate after surface water is washed and polluted for a long time.
The invention is realized by the following technical scheme:
a high flux antipollution reverse osmosis membrane comprises a polysulfone-based membrane layer, a polyamide desalting layer and a polyvinyl alcohol protective layer from bottom to top in sequence;
the polyvinyl alcohol protective layer comprises the following components in parts by mass: 1 part of polyvinyl alcohol, 0.02-0.1 part of nano titanium dioxide modified clay mineral and 0.2 part of 3-aminopropylsilanetriol.
Further, the preparation method of the nano titanium dioxide modified clay mineral comprises the following steps:
(1) adjusting the titanium dioxide precursor solution to be neutral by using a sodium hydroxide solution;
(2) dispersing clay mineral in deionized water, taking the upper suspension, uniformly mixing the upper suspension with the neutralized titanium dioxide precursor solution obtained in the step (1), crystallizing at the temperature of 80 ℃ for 2 hours, then performing suction filtration, washing, drying at the temperature of 80 ℃, and grinding to obtain the nano titanium dioxide modified clay mineral.
Preferably, the clay mineral in the step (2) is one or more of attapulgite, sepiolite, erlotine nanotubes and carbon nanotubes; the concentration of the titanium dioxide precursor solution is 2-2.5mol/L, wherein the titanium dioxide precursor is TiCl4One or more of tetrabutyl titanate and titanium tetraisopropoxide; the mass ratio of the titanium dioxide precursor to the clay mineral is 0.3.
Preferably, the polyvinyl alcohol protective layer further comprises an acidic curing agent, and the acidic curing agent is one or more of citric acid, boric acid, borax, maleic anhydride and oxalic acid.
Preferably, the molecular weight of the polyvinyl alcohol is between 11000 and 20000, and the solid content is 0.5-1%. The polyvinyl alcohol has too large molecular weight, and the harder the protective layer formed on the surface of the membrane, the easier the polyvinyl alcohol is to crack during rolling, so that the desalting layer on the surface of the base membrane is damaged; and the molecular weight of the polyvinyl alcohol is too small, the formed protective layer can not effectively coat the raised structure of the desalting layer on the surface of the reverse osmosis membrane, and the protective effect can not be achieved.
Preferably, the thickness of the polyvinyl alcohol protective layer is 200-500 nm.
The invention also provides a preparation method of the high-flux anti-pollution reverse osmosis membrane, which is characterized by comprising the following steps:
(1) soaking the polysulfone basal membrane in an aqueous phase solution containing m-phenylenediamine and sodium hydroxide for 0.5-1min, removing the redundant aqueous phase solution on the surface, soaking the polysulfone basal membrane in an oil phase solution containing trimesoyl chloride for interfacial polymerization for 0.5-1.5min, removing the redundant oil phase solution on the surface, and drying to obtain a nascent state reverse osmosis membrane with a polyamide desalting layer on the surface;
(2) dissolving 10g of polyvinyl alcohol in deionized water, dissolving at 80 ℃ to obtain a clear solution to obtain a polyvinyl alcohol protective solution, then adding the nano titanium dioxide modified clay mineral and 3-aminopropylsilanetriol, uniformly stirring, adding an acid solution to adjust the pH value to 5-6 to obtain a modified polyvinyl alcohol protective solution;
(3) and (3) soaking the nascent reverse osmosis membrane obtained in the step (1) in the modified polyvinyl alcohol protective solution obtained in the step (2) for 4-7s, and then quickly taking out and drying to obtain the high-flux anti-pollution reverse osmosis membrane.
Preferably, the mass concentration of the m-phenylenediamine in the aqueous phase solution in the step (1) is 1-3%, and the mass concentration of the sodium hydroxide is 3-5%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.1-0.2%.
Preferably, the mass concentration of the polyvinyl alcohol in the polyvinyl alcohol protective solution in the step (2) is 1%; the mass concentration of the acidic curing agent in the acidic curing agent solution is 5-8%.
Preferably, the drying temperature in the step (2) is 80 ℃, and the drying time is 5-8 min.
The invention has the beneficial effects that:
(1) the natural environment-friendly clay mineral attapulgite (a silicate mineral rich in Mg and Al), sepiolite, halloysite nanotubes and carbon nanotubes adopted in the reverse osmosis membrane have rich nanopores on the surface, can be used for adsorbing and removing pollutants such as Cr, methylene blue, colloidal substances, methyl orange and the like in water, have excellent adsorption performance, can effectively protect the surface of a polyvinyl alcohol protective layer, and reduce the adsorption of the pollutants on the surface; meanwhile, the clay minerals are distributed in a cluster shape, a three-dimensional nano stacking morphology can be formed in the polyvinyl alcohol protective layer, so that the thickness of the polyvinyl alcohol protective layer is reduced, water flow channels are increased, a nano flow guide channel can be formed on the surface of the polyvinyl alcohol protective layer among the clusters, the water flux of the reverse osmosis membrane is improved, and the flux reduction of the reverse osmosis membrane after the polyvinyl alcohol protective layer is coated is reduced.
(2) In order to avoid the pollutants from directly polluting the surface of the membrane through a nanometer diversion channel formed by clay minerals, the invention loads nanometer titanium dioxide particles with high anti-pollution performance on the surface of the clay minerals through a low-temperature crystallization method, so that the adhesion of planktonic microorganisms and nanometer colloidal pollutants in water on the surface of the membrane can be effectively resisted, the nanometer titanium dioxide modified clay minerals can synchronously reduce the pollution on the surface of the reverse osmosis membrane while increasing the water flux, and the service cycle of the reverse osmosis membrane is prolonged. Meanwhile, hydroxyl and carboxyl functional groups on the surface of the clay mineral can be effectively reserved by a low-temperature crystallization method, and the functional groups can be combined with hydroxyl on the surface of polyvinyl alcohol to firmly graft the nano titanium dioxide modified clay mineral in a polyvinyl alcohol protective layer.
(3) The surface of the 3-aminopropyl silanetriol component introduced into the polyvinyl alcohol protective layer contains abundant hydroxyl and amino functional groups, the amino at one end of the 3-aminopropyl silanetriol can react with residual acyl chloride groups on the surface of the reverse osmosis membrane, and meanwhile, the residual hydroxyl functional groups at the other end can be combined with carboxyl in the acid curing agent and hydroxyl in polyvinyl alcohol, so that firm functional group connection can be formed between the polyvinyl alcohol protective layer and the polyamide desalting layer, and the scouring resistance of the protective layer is improved.
Drawings
FIG. 1 shows a schematic view of aFor the attapulgite (a) and TiO in example 12TEM image of modified attapulgite (b);
FIG. 2 shows Attapulgite (ATP) and TiO in example 12-XRD pattern of ATP;
FIG. 3 is an SEM photograph of the nascent reverse osmosis membrane (a) and the reverse osmosis membrane (b) coated with a protective layer of polyvinyl alcohol in example 1.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments, but is not limited thereto.
Preparation of high-flux anti-pollution reverse osmosis membrane
Example 1
A high flux antipollution reverse osmosis membrane comprises a polysulfone-based membrane layer, a polyamide desalting layer and a polyvinyl alcohol protective layer from bottom to top in sequence;
the polyvinyl alcohol protective layer comprises the following components in parts by mass: 1 part of polyvinyl alcohol, 0.5 part of nano titanium dioxide modified clay mineral, 0.2 part of 3-aminopropyl silanetriol and an acidic curing agent;
the nano titanium dioxide modified clay mineral is nano titanium dioxide modified attapulgite, the acidic curing agent is citric acid, and the dosage of the citric acid is based on the condition that the pH value of the modified polyvinyl alcohol protective solution is 5-6.
The preparation method of the high-flux anti-pollution reverse osmosis membrane comprises the following steps:
(1) 10mL of 2.5mol/L TiCl are initially taken4The solution is put into a three-neck flask, and the pH value of the solution is adjusted to be neutral by using 1.5mol/L NaOH solution under the condition of stirring. Then weighing 10g of natural attapulgite, placing in 100mL of deionized water, ultrasonically dispersing for 20min, placing the upper suspension in the three-neck flask, heating to 80 deg.C, crystallizing for 2h, suction filtering after reaction, washing to neutrality, oven drying at 80 deg.C for 7min, and grinding to obtain attapulgite (TiO) modified by rod-shaped nanometer titanium dioxide2-ATP) for use.
(2) Soaking a polysulfone base membrane in a water phase solution containing m-phenylenediamine and sodium hydroxide for 1min, removing redundant water phase solution on the surface, soaking the polysulfone base membrane in an oil phase solution containing trimesoyl chloride to perform interfacial polymerization for 1min, removing redundant oil phase solution, placing the obtained solution in an oven, and drying to obtain a nascent state reverse osmosis membrane containing a polyamide desalting layer on the surface for later use;
the mass concentration of m-phenylenediamine in the aqueous phase solution is 2%, and the mass concentration of sodium hydroxide is 4%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.18%.
(3) Dissolving 10g of polyvinyl alcohol solid powder in deionized water, dissolving at 80 ℃ to obtain a clear solution to obtain a polyvinyl alcohol protective solution, and then weighing 0.2g of TiO in the step (1)2Adding ATP into the polyvinyl alcohol protective solution, simultaneously adding 2g of 3-aminopropylsilanetriol, diluting the protective solution to 1000g by using deionized water, adding a citric acid solution with the mass concentration of 7% after completely stirring to adjust the pH to 5, and thus obtaining the modified polyvinyl alcohol protective solution (TiO in the protective solution)2-mass ratio of ATP to polyvinyl alcohol 0.02: 1).
(4) And (3) soaking the nascent reverse osmosis membrane prepared in the step (2) in the modified polyvinyl alcohol protective solution prepared in the step (3) for 5s, then quickly taking out the nascent reverse osmosis membrane, and drying the nascent reverse osmosis membrane in an oven at the temperature of 80 ℃ for 8min to obtain the high-flux anti-pollution reverse osmosis membrane.
FIG. 1 shows attapulgite (a) and TiO in this example2TEM image of modified attapulgite (b); as can be seen from FIG. 1(a), the supported TiO2The attapulgite in front of the nano material is in bundle-shaped penetration distribution, the diameter of a single bundle is 30-50 nm, the length is 0.5-2 mu m, and the bundle-shaped appearance is combined on the surface of polyvinyl alcohol to form a nano flow guide channel, so that the flux reduction caused by coating a polyvinyl alcohol protective layer is reduced; as can be seen from FIG. 1(b), the polymer is passing through TiO2After the load modification, a layer of TiO with nano-size distribution is adsorbed on the surface of the attapulgite2And (3) granules.
FIG. 2 shows attapulgite (a) and TiO in this example2The XRD pattern of the modified attapulgite (b); it can be seen that the attapulgite is passing through TiO2After the load modification, nano titanium dioxide belonging to anatase crystal form appears at 2 theta (25.2 degrees)The diffraction peak, combined with FIG. 1(b), can show that the nanometer titanium dioxide is successfully loaded on the surface of the attapulgite, i.e. the nanometer titanium dioxide modified attapulgite (TiO) is successfully prepared2-ATP)。
FIG. 3 is an SEM photograph of the nascent reverse osmosis membrane (a) and the reverse osmosis membrane (b) coated with a protective layer of polyvinyl alcohol in this example. As can be seen from FIG. 1(a), in the nascent state reverse osmosis membrane containing polyamide desalination layer obtained by interfacial polymerization, the membrane surface thereof presents obvious peak-valley shape, and this structure can ensure that the reverse osmosis membrane has excellent water flux and desalination rate, but the peak-valley shape of the surface is very easy to be covered and blocked by pollutants in the test, which causes the performance of the reverse osmosis membrane to be reduced. As can be seen from FIG. 1(b), after the polyvinyl alcohol protective layer is coated, the peak-valley shape of the surface of the reverse osmosis membrane is completely covered, which shows that the polyvinyl alcohol protective layer of the invention can effectively protect the surface of the reverse osmosis membrane and prevent pollutants from directly contacting with the polyamide desalting layer, thereby prolonging the service life of the reverse osmosis membrane.
Examples 2 to 5
A high flux antipollution reverse osmosis membrane comprises a polysulfone-based membrane layer, a polyamide desalting layer and a polyvinyl alcohol protective layer from bottom to top in sequence;
the polyvinyl alcohol protective layer comprises the following components in parts by mass: 1 part of polyvinyl alcohol, 0.5 part of nano titanium dioxide modified clay mineral, 0.2 part of 3-aminopropyl silanetriol and an acidic curing agent;
the nano titanium dioxide modified clay mineral is nano titanium dioxide modified attapulgite, the acidic curing agent is citric acid, and the dosage of the citric acid is based on the condition that the pH value of the modified polyvinyl alcohol protective solution is 5-6;
in examples 2-5, the mass ratios of the nano titanium dioxide to the attapulgite in the nano titanium dioxide modified attapulgite are different, as shown in table 1.
The preparation method of the high flux anti-pollution reverse osmosis membrane is the same as that of the example 1, except that TiO is added in the step (3)2The mass of ATP was different, as shown in table 1:
TABLE 1
Comparative example 1
The reverse osmosis membrane prepared in this example differs from that of example 1 in that: the preparation method does not comprise a polyvinyl alcohol protective layer and comprises the following steps:
(2) soaking a polysulfone base membrane in a water phase solution containing m-phenylenediamine and sodium hydroxide for 1min, removing redundant water phase solution on the surface, soaking the polysulfone base membrane in an oil phase solution containing trimesoyl chloride to perform interfacial polymerization for 1min, removing redundant oil phase solution, placing the obtained solution in an oven, and drying to obtain a nascent reverse osmosis membrane with a polyamide desalting layer on the surface;
the mass concentration of m-phenylenediamine in the aqueous phase solution is 2%, and the mass concentration of sodium hydroxide is 4%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.18%.
Comparative example 2
The reverse osmosis membrane prepared in this example differs from that of example 1 in that: omitting TiO in polyvinyl alcohol protective layer2ATP, prepared as follows:
(1) soaking a polysulfone base membrane in a water phase solution containing m-phenylenediamine and sodium hydroxide for 1min, removing redundant water phase solution on the surface, soaking the polysulfone base membrane in an oil phase solution containing trimesoyl chloride to perform interfacial polymerization for 1min, removing redundant oil phase solution, placing the obtained solution in an oven, and drying to obtain a nascent state reverse osmosis membrane containing a polyamide desalting layer on the surface for later use;
the mass concentration of m-phenylenediamine in the aqueous phase solution is 2%, and the mass concentration of sodium hydroxide is 4%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.18%.
(2) Dissolving 10g of polyvinyl alcohol solid powder in deionized water, dissolving at 80 ℃ to obtain a clear solution to obtain a polyvinyl alcohol protective solution, then adding 2g of 3-aminopropylsilanetriol, diluting the protective solution to 1000g with deionized water, and waiting until the protective solution is dissolved in the deionized waterAdding citric acid solution with mass concentration of 7% after stirring completely to adjust pH to 5 to obtain the product containing no TiO2-a polyvinyl alcohol protective solution of ATP.
(3) And (3) soaking the nascent reverse osmosis membrane prepared in the step (1) in the polyvinyl alcohol protection solution prepared in the step (2) for 5s, then quickly taking out and placing in an oven to dry for 8min at the temperature of 80 ℃ to obtain the high-flux anti-pollution reverse osmosis membrane.
Comparative example 3
The reverse osmosis membrane prepared in this example differs from that of example 1 in that: the preparation method of omitting 3-aminopropyl silanetriol in the polyvinyl alcohol protective layer comprises the following specific steps:
(1) soaking a polysulfone base membrane in a water phase solution containing m-phenylenediamine and sodium hydroxide for 1min, removing redundant water phase solution on the surface, soaking the polysulfone base membrane in an oil phase solution containing trimesoyl chloride to perform interfacial polymerization for 1min, removing redundant oil phase solution, placing the obtained solution in an oven, and drying to obtain a nascent state reverse osmosis membrane containing a polyamide desalting layer on the surface for later use;
the mass concentration of m-phenylenediamine in the aqueous phase solution is 2%, and the mass concentration of sodium hydroxide is 4%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.18%.
(2) Dissolving 10g of polyvinyl alcohol solid powder in deionized water, dissolving at 80 ℃ to obtain a clear solution to obtain a polyvinyl alcohol protective solution, and then weighing 0.2g of TiO prepared in example 12Adding ATP into the polyvinyl alcohol protective solution, adding 2g of 3-aminopropyl silanetriol, diluting the protective solution to 1000g by using deionized water, adding a citric acid solution with the mass concentration of 7% after completely stirring, and adjusting the pH to 5 to obtain the modified polyvinyl alcohol protective solution.
(3) And (3) soaking the nascent reverse osmosis membrane prepared in the step (1) in the modified polyvinyl alcohol protective solution prepared in the step (2) for 5s, then quickly taking out the nascent reverse osmosis membrane, and drying the nascent reverse osmosis membrane in an oven at the temperature of 80 ℃ for 8min to obtain the high-flux anti-pollution reverse osmosis membrane.
Comparative example 4
The reverse osmosis membrane prepared in this example differs from that of example 1 in that: the attapulgite in the polyvinyl alcohol protective layer is not modified by the nano titanium dioxide, and the specific preparation method comprises the following steps:
(1) weighing 10g of natural attapulgite, placing in 100mL of deionized water, ultrasonically dispersing for 20min, taking the upper suspension, filtering, washing, drying at 80 ℃, and grinding for later use, wherein the obtained product is recorded as ATP.
(2) Soaking a polysulfone base membrane in a water phase solution containing m-phenylenediamine and sodium hydroxide for 1min, removing redundant water phase solution on the surface, soaking the polysulfone base membrane in an oil phase solution containing trimesoyl chloride to perform interfacial polymerization for 1min, removing redundant oil phase solution, placing the obtained solution in an oven, and drying to obtain a nascent state reverse osmosis membrane containing a polyamide desalting layer on the surface for later use;
the mass concentration of m-phenylenediamine in the aqueous phase solution is 2%, and the mass concentration of sodium hydroxide is 4%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.18%.
(3) Dissolving 10g of polyvinyl alcohol solid powder in deionized water, dissolving at 80 ℃ to obtain a clear solution to obtain a polyvinyl alcohol protective solution, then weighing 0.2g of ATP prepared in the step (1), adding the ATP into the polyvinyl alcohol protective solution, simultaneously adding 2g of 3-aminopropylsilanetriol, diluting the protective solution to 1000g by using deionized water, adding a citric acid solution with the mass concentration of 7% after completely stirring, and adjusting the pH to 5 to obtain the modified polyvinyl alcohol protective solution.
(4) And (2) soaking the nascent reverse osmosis membrane prepared in the step (1) in the modified polyvinyl alcohol protective solution prepared in the step (3) for 5s, then quickly taking out the nascent reverse osmosis membrane, and drying the nascent reverse osmosis membrane in an oven at the temperature of 80 ℃ for 8min to obtain the high-flux anti-pollution reverse osmosis membrane.
Second, performance test of reverse osmosis membrane
1. Reverse osmosis membrane desalination solution testing
The water flux and the desalination rate of the reverse osmosis membranes prepared in the embodiments 1-5 and the comparative examples 1-4 are tested on a membrane test table, the test method refers to a GB/T32373-2015 reverse osmosis membrane test method, the test solution is a NaCl aqueous solution with the conductivity of 4000 mu S, the pH value of the test solution is adjusted to 7.5 +/-0.5 by using hydrochloric acid or sodium hydroxide, the reverse osmosis membrane to be tested is firstly placed in deionized water for soaking for about 30min before testing, then the reverse osmosis membrane to be tested is cut to a corresponding size and placed in a test membrane pool, the test pressure is adjusted to 250psi, the test temperature is 25 ℃, the reverse osmosis membrane to be tested is stably operated for 30min at constant temperature and constant pressure, a permeate water sample in a certain time after stable operation is collected, the conductivity and the volume of the test solution are calculated according to a formula, and the desalination rate and the water flux of the reverse osmosis membrane to be tested are calculated, and the measurement results are shown in Table 2.
The reverse osmosis membrane desalination rate formula is as follows:
in the formula:
r-salt rejection rate;
kp-permeant conductivity in microsiemens per centimeter (μ S/cm);
kf-measuring the conductivity of the fluid in microsiemens per centimeter (. mu.S/cm).
The formula of the water flux of the reverse osmosis membrane is as follows:
in the formula:
f-water flux in liters per square meter hour [ L/(m)2 h)]；
The volume of permeate collected over time V-t, in liters (L);
a-effective membrane area in square meters (m)2)；
t-the time taken to collect V volumes of permeate in hours (h).
The reverse osmosis membrane test results are shown in table 2:
TABLE 2
| Examples | Water flux (GFD) | Salt rejection (%) |
| Example 1 | 36.13 | 99.73 |
| Example 2 | 36.37 | 99.70 |
| Example 3 | 36.81 | 99.71 |
| Example 4 | 37.41 | 99.79 |
| Example 5 | 36.77 | 99.78 |
| Comparative example 1 | 37.43 | 99.61 |
| Comparative example 2 | 32.48 | 99.76 |
| Comparative example 3 | 36.15 | 99.71 |
| Comparative example 4 | 36.33 | 99.69 |
2. Reverse osmosis membrane surface water performance test
Taking the reverse osmosis membranes prepared in the examples 1-5 and the comparative examples 1-4, taking surface river water as a test solution (total organic carbon, TOC is 3.5mg/L), continuously running and testing for 72 hours under the pressure of 225psi, then washing the surface of the reverse osmosis membrane clean by deionized water, continuously testing the water flux and the salt rejection rate of the membrane by taking a NaCl aqueous solution with the conductivity of 4000 mu S as the test solution, prepressing for 30 minutes under the conditions that the test pressure is 225psi, the test solution temperature is 25 ℃ and the test solution pH is 7.0 +/-0.5, collecting produced water, and calculating the water flux and the salt rejection rate of the reverse osmosis membrane.
The reverse osmosis membrane surface water test results are shown in table 3:
TABLE 3
| Examples | Water flux (GFD) | Salt rejection (%) |
| Example 1 | 35.13 | 99.61 |
| Example 2 | 35.27 | 99.58 |
| Example 3 | 35.35 | 99.64 |
| Example 4 | 36.81 | 99.71 |
| Example 5 | 35.37 | 99.68 |
| Comparative example 1 | 29.39 | 98.77 |
| Comparative example 2 | 29.88 | 99.56 |
| Comparative example 3 | 31.68 | 99.19 |
| Comparative example 4 | 33.52 | 99.41 |
As can be seen from the test results in Table 2, compared with the nascent state reverse osmosis membrane (comparative example 1), the flux of the membrane is reduced by about 5GFD after the polyvinyl alcohol protective layer is coated on the surface of the nascent state reverse osmosis membrane (comparative example 2), and the flux of the membrane is gradually increased along with the increase of the added amount after the nano titanium oxide modified attapulgite clay is introduced into the polyvinyl alcohol protective solutionWhen being TiO 22Optimum water flux and desalination rate were obtained at an ATP to polyvinyl alcohol mass ratio of 0.08:1 (example 4), while continuing to upgrade TiO2No further improvement in the performance at the addition of ATP (example 5) is noted, mainly because too much addition easily leads to TiO2Agglomeration of ATP on the surface of polyvinyl alcohol, affecting TiO2Further enhancement of the diversion of ATP and anti-pollution effects.
As shown in the test results in Table 3, the test data of the comparative example 3 and the examples 1-5 show that when the 3-aminopropyl silanetriol component is absent in the polyvinyl alcohol protective layer, the water flux of the membrane is reduced to 31.68GFD after a flushing pollution test for 72 hours, and the salt rejection rate is also reduced sharply. The main reason is that the polyvinyl alcohol protective layer on the surface of the membrane is connected with the polyamide desalting layer by lacking functional groups, so that the polyvinyl alcohol protective layer has poor washing resistance and cannot resist long-time washing tests, and the membrane is seriously polluted. After the 3-aminopropyl silanetriol is introduced, functional group combination can be formed on the surfaces of the polyvinyl alcohol protective layer and the polyamide desalting layer, the polyvinyl alcohol protective layer can be firmly attached to the surface of the membrane, and the anti-scouring performance of the membrane is improved.
As can be seen from the comparative example 4, when the surface of the attapulgite is not loaded with the nano titanium dioxide, the flux and the salt rejection rate of the reverse osmosis membrane are obviously reduced after the surface water is tested for a long time, which is mainly due to the excellent pollution resistance of the nano titanium dioxide, and the adsorption pollution of the suspended pollutants in the surface water can be effectively reduced due to the rich carboxyl functional groups on the surface of the nano titanium oxide, so that the reverse osmosis membrane can keep excellent performance in the long-time test process.
In conclusion, TiO is synchronously introduced into the polyvinyl alcohol protective layer2-ATP and 3-aminopropylsilanetriol component, TiO2The ATP component can effectively improve the water flux and the anti-pollution capacity of the polyvinyl alcohol protective layer, the 3-aminopropylsilanetriol component can form functional group connection on the protective layer and the surface of the polyamide desalting layer to increase the service cycle of the protective layer, and the combination of the protective layer and the 3-aminopropylsilanetriol component can ensure that the reverse osmosis membrane can be used for a long timeMaintaining excellent performance.
The invention has the characteristics of simple preparation process, environmental protection and low price, and can be widely applied to the actual industrial production process.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A high flux antipollution reverse osmosis membrane is characterized by comprising a polysulfone-based membrane layer, a polyamide desalting layer and a polyvinyl alcohol protective layer from bottom to top in sequence;
the polyvinyl alcohol protective layer comprises the following components in parts by mass: 1 part of polyvinyl alcohol, 0.02-0.1 part of nano titanium dioxide modified clay mineral and 0.2 part of 3-aminopropylsilanetriol;
the preparation method of the nanometer titanium dioxide modified clay mineral comprises the following steps:
(1) adjusting the titanium dioxide precursor solution to be neutral by using a sodium hydroxide solution;
(2) dispersing clay mineral in deionized water, taking the upper suspension, uniformly mixing the upper suspension with the neutral titanium dioxide precursor solution obtained in the step (1), crystallizing for 2 hours at the temperature of 80 ℃, then performing suction filtration, washing, drying at the temperature of 80 ℃, and grinding to obtain the nano titanium dioxide modified clay mineral.
2. The high flux anti-fouling reverse osmosis membrane of claim 1, wherein in step (2) the clay mineral is one or more of attapulgite, sepiolite, halloysite nanotubes, carbon nanotubes; the concentration of the titanium dioxide precursor solution is 2-2.5mol/L, wherein the titanium dioxide precursor is TiCl4One or more of tetrabutyl titanate and titanium tetraisopropoxide; the mass ratio of the titanium dioxide precursor to the clay mineral is 0.3.
3. The high flux anti-fouling reverse osmosis membrane of claim 1, wherein the polyvinyl alcohol protective layer further comprises an acidic curing agent selected from one or more of citric acid, boric acid, borax, maleic anhydride, and oxalic acid.
4. The high flux anti-fouling reverse osmosis membrane of claim 1, wherein the polyvinyl alcohol has a molecular weight of 11000-20000 and a solid content of 0.5-1%.
5. The high flux anti-fouling reverse osmosis membrane of claim 1, wherein the protective layer of polyvinyl alcohol has a thickness of 200 nm and 500 nm.
6. A method of preparing a high flux anti-fouling reverse osmosis membrane according to any one of claims 1-5, comprising the steps of:
(1) soaking the polysulfone basal membrane in an aqueous phase solution containing m-phenylenediamine and sodium hydroxide for 0.5-1min, removing the redundant aqueous phase solution on the surface, soaking the polysulfone basal membrane in an oil phase solution containing trimesoyl chloride for interfacial polymerization for 0.5-1.5min, removing the redundant oil phase solution on the surface, and drying to obtain a nascent state reverse osmosis membrane with a polyamide desalting layer on the surface;
(2) dissolving 10g of polyvinyl alcohol in deionized water, dissolving at 80 ℃ to obtain a clear solution to obtain a polyvinyl alcohol protective solution, then adding the nano titanium dioxide modified clay mineral and 3-aminopropylsilanetriol, uniformly stirring, adding an acidic curing agent solution, and adjusting the pH to 5-6 to obtain a modified polyvinyl alcohol protective solution;
(3) and (3) soaking the nascent reverse osmosis membrane obtained in the step (1) in the modified polyvinyl alcohol protective solution obtained in the step (2) for 4-7s, and then quickly taking out and drying to obtain the high-flux anti-pollution reverse osmosis membrane.
7. The method for preparing the high-flux anti-pollution reverse osmosis membrane according to claim 6, wherein in the step (1), the mass concentration of the m-phenylenediamine in the aqueous phase solution is 1-3%, and the mass concentration of the sodium hydroxide is 3-5%; the mass concentration of trimesoyl chloride in the oil phase solution is 0.1-0.2%.
8. The method for preparing the high-flux anti-pollution reverse osmosis membrane according to claim 6, wherein the mass concentration of the polyvinyl alcohol in the polyvinyl alcohol protective solution in the step (2) is 1%; the mass concentration of the acidic curing agent in the acidic curing agent solution is 5-8%.
9. The method for preparing a high flux anti-pollution reverse osmosis membrane according to claim 6, wherein the drying temperature in the step (2) is 80 ℃, and the drying time is 5-8 min.
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| CN112044271B (en) * | 2020-09-07 | 2022-04-22 | 安徽千一智能设备股份有限公司 | Preparation method of multilayer reverse osmosis composite membrane |
| CN112354366B (en) * | 2020-11-17 | 2021-08-27 | 江苏泷膜环境科技有限公司 | High-flux composite reverse osmosis membrane and preparation method thereof |
| CN113842793A (en) * | 2021-09-22 | 2021-12-28 | 重庆海通环保科技有限公司 | Reverse osmosis membrane for sea water desalination |
| CN116143234A (en) * | 2021-11-22 | 2023-05-23 | 沃顿科技股份有限公司 | Preparation method of sea water desalination reverse osmosis membrane and reverse osmosis membrane prepared by same |
| CN114082307B (en) * | 2021-12-08 | 2024-04-26 | 湖南澳维科技股份有限公司 | Antioxidant reverse osmosis membrane and preparation method thereof |
| CN114247298B (en) * | 2022-03-01 | 2022-07-12 | 湖南沁森高科新材料有限公司 | Post-treatment method for improving stability of reverse osmosis membrane and reverse osmosis membrane product |
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