CN110882632A - Reverse osmosis membrane and preparation method thereof - Google Patents

Abstract

The invention discloses a reverse osmosis membrane and a preparation method thereof, and relates to the technical field of filtration membranes, so as to solve the problem of low water production of the reverse osmosis membrane in the water treatment process. The reverse osmosis membrane includes: a support layer, which includes a flat ultrafiltration membrane; a functional layer formed on the support layer, and the functional layer includes stacked and overlapped graphene oxide sheets. The preparation method of the reverse osmosis membrane comprises: compounding the graphene oxide dispersion on the surface of the support layer to form a compound membrane; and strengthening the compound membrane with coordination ions to obtain the required reverse osmosis membrane. The reverse osmosis membrane of the present invention can effectively increase the water production in the water treatment process.

Description

A kind of reverse osmosis membrane and preparation method thereof

technical field

The invention relates to the technical field of filtration membranes, in particular to a reverse osmosis membrane and a preparation method thereof.

Background technique

Water shortage is one of the biggest challenges facing the world today. 70% of the earth is covered by seawater, and freshwater resources also have serious water pollution problems. Therefore, desalination and sewage treatment are increasingly attracting people's attention. Reverse osmosis technology refers to a separation method that separates the solute and solvent in a solution by means of the selective permeability of the reverse osmosis membrane under a certain pressure. Reverse osmosis membrane technology has received extensive attention and application in the field of seawater desalination and water treatment due to its advantages of low energy consumption, stable structure, and excellent separation performance.

At present, the functional layer materials of reverse osmosis membranes mainly include cellulose acetate, linear polyamide and aromatic polyamide. The reverse osmosis membrane made of these three types of materials has a water yield (the amount of water filtered by the reverse osmosis membrane) during water treatment. output) is low.

SUMMARY OF THE INVENTION

In view of the above problems in the prior art, the embodiments of the present invention provide a reverse osmosis membrane and a preparation method thereof, so as to solve the problem of low water production of the reverse osmosis membrane in the water treatment process.

In order to achieve the above object, the embodiments of the present invention adopt the following technical solutions:

In a first aspect, an embodiment of the present invention provides a reverse osmosis membrane, comprising: a support layer, the support layer comprising a flat ultrafiltration membrane; a functional layer formed on the support layer, the functional layer comprising a stack overlap of graphene oxide sheets.

In the reverse osmosis membrane provided by the embodiment of the present invention, graphene oxide has good hydrophilicity and ion recognition functions, and the functional layer adopts stacked and overlapped graphene oxide, so that a selective layer of graphene oxide can be formed between the graphene oxide sheets. Two-dimensional nanochannels provide high-speed transport channels for water molecules, thereby achieving efficient water treatment and increasing water production during water treatment. At the same time, the two-dimensional nanochannels formed by stacking and overlapping graphene oxide sheets can prevent the passage of solute macromolecules, and the support layer with a flat ultrafiltration membrane can also separate solute molecules with small pore sizes in water. Under the joint action of , the separation performance of the reverse osmosis membrane is greatly improved.

Preferably, the sheet diameter of the graphene oxide sheet is 8-20 μm, and the number of layers is 2-10.

Preferably, the thickness of the functional layer is 0.1-0.5 μm.

Preferably, the surface pore size of the flat ultrafiltration membrane is 0.1-1 μm.

Preferably, the functional layer and the support layer are bonded by an adhesive, and the adhesive includes any one or more of polyethylene glycol, polyvinylpyrrolidone and polyvinyl alcohol.

In a second aspect, embodiments of the present invention also provide a method for preparing a reverse osmosis membrane, which is used to prepare the reverse osmosis membrane according to the first aspect, the preparation method comprising: compounding a graphene oxide dispersion into a A composite membrane is formed on the surface of the support layer; the composite membrane is strengthened by coordination ions to obtain the desired reverse osmosis membrane. The support layer includes a flat ultrafiltration membrane.

In the preparation method of the reverse osmosis membrane provided by the embodiment of the present invention, the composite membrane is strengthened by coordination ions, and the functional layer is further strengthened by chemical cross-linking, so that the prepared reverse osmosis membrane has higher stability and firmness. . The beneficial effects of the reverse osmosis membrane prepared by the method for preparing the reverse osmosis membrane provided by the embodiment of the present invention are the same as those that can be achieved by the reverse osmosis membrane provided in the first aspect, and are not repeated here.

Preferably, the step of compounding the graphene oxide dispersion on the surface of the support layer to form a composite film includes: spraying the graphene oxide dispersion on the surface of the support layer; wherein the spraying pressure is 0.1～0.5MPa, spraying time is 1～10s.

Preferably, the step of performing coordination ion strengthening on the composite membrane to obtain the desired reverse osmosis membrane includes: placing the composite membrane in a reaction solution for a coordination ion strengthening reaction; the reaction solution includes A coordinating ion aqueous solution and an equal volume of ethanol with the coordinating ion aqueous solution; rinsing the composite membrane with ethanol, and then allowing the composite membrane to stand for a certain period of time to obtain the desired reverse osmosis membrane.

Preferably, the complex ion aqueous solution includes any one or more of calcium chloride solution, magnesium chloride solution and aluminum chloride solution, and the mass percentage of the solute in the complex ion aqueous solution is 3-10%.

Preferably, the time for the coordination ion-enhanced reaction is 1 to 4 hours.

Preferably, before the step of compounding the graphene oxide dispersion on the surface of the support layer to form a composite film, it also includes the step of making the graphene oxide dispersion, and the step includes: dispersing the graphene oxide In the dispersant, and adding a layer-stretching stabilizer to form a dispersion liquid precursor; adding an alkaline solution to the dispersion liquid precursor, so that the PH value of the dispersion liquid precursor reaches 7 to 9 to obtain the desired oxidation Graphene dispersion.

Preferably, the mass concentration of graphene oxide in the dispersion of graphene oxide is

0.1～5mg/ml.

Preferably, the dispersing agent includes any one of ultrapure water, ethanol and N-methylpyrrolidone.

Preferably, the layer expansion stabilizer includes any one of sodium deoxycholate, sodium dodecylbenzenesulfonate and sodium polystyrene sulfonate, and the layer expansion stabilizer in the graphene oxide dispersion The mass percentage is 0.1 to 5%.

Preferably, before the step of compounding the graphene oxide dispersion on the surface of the support layer to form a compound membrane, it also includes the step of processing the flat ultrafiltration membrane of the support layer, and the step includes: The flat ultrafiltration membrane is put into an aqueous solution of a binder, soaked and then air-dried; wherein, in the aqueous solution of the binder, the mass percentage of the binder is 1-10%.

Preferably, after the step of compounding the graphene oxide dispersion on the surface of the support layer to form a compound membrane, and after the coordination ion strengthening of the compound membrane, the desired reverse osmosis membrane is obtained It also includes the step of thermal reduction treatment on the composite film before the step of the method, and the step includes: heating the composite film in a vacuum at 60-80° C. for 30-45 min, and then placing it to room temperature.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

Fig. 1 is the schematic diagram of the reverse osmosis membrane in the embodiment of the present invention;

Fig. 2 is the surface electron microscope image of the functional layer of the reverse osmosis membrane in the embodiment of the present invention;

Fig. 3 is the cross-sectional electron microscope view of the reverse osmosis membrane in the embodiment of the present invention;

FIG. 4 is a flow chart of a method for preparing a reverse osmosis membrane in an embodiment of the present invention.

Reference number:

1-functional layer, 2-support layer.

Detailed ways

As mentioned in the background art, reverse osmosis membranes made of materials such as cellulose acetate, linear polyamide and aromatic polyamide have the problem of low water production during water treatment, and the material solvation effect is poor during the preparation process, which cannot be Preparation by solution method requires interfacial polymerization, complex reaction and high defect rate; due to the high operating pressure in the reverse osmosis process, the material is easily compacted, resulting in multiple problems such as low water production and membrane blockage, so it is necessary to explore new functional layers. Material.

Graphene oxide (Graphene Oxide, GO) is a derivative of graphene, usually prepared by the modified Hummers method. , epoxy group and carbonyl group, etc.), the structure is similar to that of aquaporins, with good hydrophilicity and ion recognition functions, both high specific surface area and high reactivity, so graphene oxide is an ideal separation membrane material.

Based on the above situation, the embodiments of the present invention propose a reverse osmosis membrane and a preparation method thereof, so as to solve the problem of low water production in the water treatment process. Please refer to FIG. 1 and FIG. 3 , the reverse osmosis membrane includes: a support layer 2, which includes a flat ultrafiltration membrane; a functional layer 1 formed on the support layer 2, and the functional layer 1 includes stacked and overlapped graphene oxide sheets . In the cross-sectional electron microscope picture of the reverse osmosis membrane in Fig. 3, the upper right part is the section of the support layer 2, the part inclined from the upper left to the lower right in the middle part along the diagonal of the picture is the section of the functional layer 1, and the lower left part is the surface of the functional layer 1.

In the reverse osmosis membrane provided by the embodiment of the present invention, graphene oxide has good hydrophilicity and ion recognition functions, and the functional layer 1 adopts stacked and overlapped graphene oxide to form a layered film, so that the graphene oxide sheets are formed between the graphene oxide sheets. Selective two-dimensional nanochannels can be formed, providing high-speed transport channels for water molecules, thereby achieving efficient water treatment and increasing water production during water treatment. At the same time, the two-dimensional nanochannels formed by stacking and overlapping graphene oxide can prevent the passage of macromolecules, and the support layer 2 with the flat ultrafiltration membrane can also separate the solute molecules with small pore size in water. Under the joint action of 2, the separation performance of the reverse osmosis membrane is greatly improved. In addition, due to the strong hydrogen bonds between the graphene oxide sheets, it has good mechanical properties and high mechanical strength, can run continuously under high operating pressure, and also has good cleaning resistance.

The structure of the functional layer 1 is composed of graphene oxide in a sheet-like structure stacked and overlapped, so the flatness of the stack and the tightness of the overlap have a great influence on the separation performance of the functional layer 1, and the main factors that determine the flatness and tightness. It is the basic sheet size and processing method of graphene oxide. Among them, the size of the graphene oxide sheet has a great influence on the stability of the functional layer 1 after stacking. , the graphene oxide in the dispersion is prone to agglomeration and precipitation. Therefore, the selection of graphene oxide sheets of suitable size is very important for the formation of reverse osmosis membranes with good performance. Exemplarily, the sheet diameter of the graphene oxide sheet may be 8-20 μm, or the sheet diameter of the graphene oxide sheet may also be 8-10 μm, 8-15 μm, 10-15 μm, 12-17 μm, 15-20 μm, etc. The number of layers of the graphene sheet can be 2-10, and a graphene oxide sheet with the number of layers of 2-5, 5-10, 2-8, 8-10, 4-7 or 6-9 can also be selected.

The thickness of the functional layer 1 formed by stacking and overlapping the graphene oxide sheets can be in the range of 0.1-0.5 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, and the like.

In some embodiments, the surface pore size of the selected flat ultrafiltration membrane may be 0.1-1 μm.

In some embodiments, the functional layer 1 and the support layer 2 may be bonded by an adhesive, and the adhesive may include any one or more of polyethylene glycol, polyvinylpyrrolidone and polyvinyl alcohol, that is, , one of the above-mentioned adhesives can be selected, or a mixture of two or more of the above-mentioned adhesives can be selected as the adhesives.

Referring to FIG. 4 , an embodiment of the present invention also provides a method for preparing a reverse osmosis membrane for preparing the above-mentioned reverse osmosis membrane, the preparation method comprising: compounding a graphene oxide dispersion to the support layer 2 The surface of the composite membrane is formed, wherein the support layer includes a flat ultrafiltration membrane; the composite membrane is strengthened by coordination ions to obtain the required reverse osmosis membrane.

After graphene oxide is stacked to form a film, its membrane structure in the aqueous phase is less stable, and the laminated structure is prone to disintegration and re-dispersion in the solvent, resulting in the loss of its separation performance. In the preparation method of the reverse osmosis membrane provided by the embodiment of the present invention, the composite membrane is strengthened by coordination ions, and the functional layer 1 is further strengthened by chemical cross-linking, so that the prepared reverse osmosis membrane has higher stability and firmness. sex. The beneficial effects of the reverse osmosis membrane prepared by the method for preparing the reverse osmosis membrane provided in the embodiment of the present invention are the same as those that can be achieved by the reverse osmosis membrane provided above, and will not be repeated here.

Please refer to FIG. 4, in some embodiments, before the step of compounding the dispersion of graphene oxide on the surface of the support layer 2 to form the compound film, it also includes the step of making the dispersion of graphene oxide, and the step includes: S11, dispersing graphene oxide in a dispersant, and adding a layer expansion stabilizer to form a dispersion liquid precursor; S12, adding an alkaline solution, such as ammonia water, strong sodium oxide solution, etc., to the dispersion liquid precursor to make the dispersion liquid The pH value of the body reaches 7 to 9, and the desired dispersion of graphene oxide is obtained.

In some embodiments, the mass concentration of graphene oxide in the prepared graphene oxide dispersion is 0.1-5 mg/ml, for example, 0.1 mg/ml, 5 mg/ml, 2.5 mg/ml, 1 mg/ml, 2 mg /ml, 3mg/ml, 4mg/ml, etc.

Graphene oxide can be dispersed in a variety of reagents, but the dispersion state of graphene oxide sheets in the reagent will directly affect the performance of functional layer 1, so it is necessary to select a suitable dispersant to improve the dispersion effect of graphene oxide. Exemplarily, any one of water, ethanol, and N-methylpyrrolidone can be selected as the dispersant to improve the dispersion effect of graphene oxide. In the actual operation process, the dispersion effect of graphene oxide can also be improved by stirring and ultrasonically treating the solution.

Since graphene oxide is prone to agglomeration, resulting in a decrease in the retention rate, in some embodiments, a small amount of layer-expanding stabilizer may be added to the graphene oxide dispersion to facilitate the smooth lap joint of graphene oxide, thereby increasing the The water flux is also more conducive to the stability of the dispersion and reduces the difficulty of preparation and processing. The layer expansion stabilizer can be selected from any one of sodium deoxycholate, sodium dodecylbenzenesulfonate and sodium polystyrene sulfonate, and the mass percentage of the layer expansion stabilizer in the graphene oxide dispersion can be 0.1～ 5%.

Referring to FIG. 4, in some embodiments, before the step of compounding the dispersion of graphene oxide on the surface of the support layer 2 to form the compound membrane, it also includes the step of processing the flat ultrafiltration membrane of the support layer 2, The step includes: S2, placing the flat ultrafiltration membrane in the aqueous solution of the adhesive, soaking it and then drying it. Wherein, in the aqueous solution of the adhesive, the mass percentage of the adhesive is 1-10%, for example, 1%, 3%, 5%, 6%, 8%, or 10%. The above-mentioned adhesive can be selected from any one or more of polyethylene glycol, polyvinylpyrrolidone and polyvinyl alcohol.

In some embodiments, the flat ultrafiltration membrane of the support layer 2 may be a polysulfone or polyethersulfone material. Due to the difference in surface tension between the graphene oxide dispersion and the flat ultrafiltration membrane (polysulfone/polyethersulfone membrane) of the support layer 2, if the graphene oxide dispersion is directly compounded on the support layer 2, there may be When the dispersion liquid is in the form of mist droplets on the surface of the support layer 2 and cannot form a film, the support layer 2 needs to be treated, and amphiphilic substances such as polyethylene glycol, polyvinylpyrrolidone and polyvinyl alcohol are used as adhesives to the support layer. 2. Surface modification is performed to improve the surface roughness of the support layer 2, so that the surface tension of the support layer 2 is closer to the surface tension of the graphene oxide dispersion. The group can be combined with the graphene oxide that is subsequently compounded to the surface of the support layer 2, so that the support layer 2 and the functional layer 1 are firmly "stick" together. Therefore, pre-processing the support layer 2 is beneficial to the spreading of graphene oxide on the surface of the support layer 2, and is also conducive to the firm adhesion of the two.

Referring to FIG. 4, in some embodiments, the step of compounding the dispersion of graphene oxide on the surface of the support layer 2 to form a composite film includes: S3, spraying the dispersion of graphene oxide onto the surface of the support layer 2 . In actual operation, the composite film of graphene oxide can be prepared by spraying method, using a spray gun as a spraying tool, and relying on the spraying pressure to achieve continuous film formation of graphene oxide sheets stacked, the pressure of the spraying tool and the surface tension of the support layer 2 are both effective for the composite film. The structure of the film has an influence. Exemplarily, the spraying pressure is 0.1-0.5MPa, and the spraying effect is better. The spraying pressure can also be 0.1MPa, 0.5MPa, MPa, 0.25MPa, 0.3MPa, etc. The spraying time can be 1-10s, for example, spraying is 1s, 10s, 5s, 2s, 3s, 6s, 7s or 8s. The longer the spraying time and the higher the dispersion concentration of graphene oxide, the thicker the thickness of the formed functional layer.

Referring to FIG. 4 , in some embodiments, after the step of compounding the graphene oxide dispersion on the surface of the support layer 2 to form a compound film, and after performing coordination ion strengthening on the compound film, the desired Before the step of the reverse osmosis membrane, it also includes the step of thermal reduction treatment on the composite membrane, and the step includes: S4 , heating the composite membrane in a vacuum at 60-80° C. for 30-45 minutes, and then placing it to room temperature. Because graphene oxide has hydrophilic groups, the functional layer 1 formed by it is applied in an aqueous environment, and graphene oxide floats and separates easily. After the thermal reduction step, the stability of graphene oxide can be increased and the function of reinforcement can be achieved. The role of layer 1.

Although the graphene oxide composite membrane prepared initially has a separation function, because graphene oxide contains a large number of hydrophilic groups and operates in a water environment for a long time, the graphene oxide sheet is easily lost with water and causes the structure of functional layer 1 to collapse. It is also easy to cause the functional layer 1 to peel off due to the loss of amphiphilic substances such as adhesives with water, so that the formed composite film can be further reinforced. Referring to FIG. 4 , in some embodiments, the steps of performing coordination ion strengthening on the composite membrane to obtain a desired reverse osmosis membrane include: S51 , placing the composite membrane in a reaction solution to perform a coordination ion strengthening reaction; reaction The solution includes an aqueous solution of complex ions and an equal volume of ethanol with the aqueous solution of complex ions; S52, the composite membrane is rinsed with ethanol, and then the composite membrane is allowed to stand for a certain period of time to obtain the desired reverse osmosis membrane.

In some embodiments, the complex ion aqueous solution may include any one or more of calcium chloride solution, magnesium chloride solution and aluminum chloride solution, that is to say, one of the above-mentioned complex ion aqueous solutions may be selected, or A mixed solution containing two or more of the above solutions can be selected as the complex ion aqueous solution. The mass percentage of the solute in the complex ion aqueous solution is 3 to 10%, for example, the mass percentage of the solute may be 3%, 10%, 6%, 7%, or 5%.

In actual operation, the coordination ion-enhanced reaction can be carried out at room temperature, and the reaction time can be 1 to 4 hours. After the reaction time is reached, the composite membrane can be taken out, and the composite membrane can be rinsed with ethanol to rinse off excess reactive ions, thereby terminating the reaction.

In graphene oxide, a large number of oxygen-containing groups, including hydroxyl and epoxy groups, are introduced on the sheet-like base, while carboxyl and carbonyl groups are distributed at the edge of the graphene oxide sheet. Through the coordination ion strengthening reaction, divalent metal ions (such as calcium, magnesium, aluminum ions) can be used to bond the edges of two graphene oxide sheets to achieve the effect of chemical cross-linking strengthening. At the same time, for the hydroxyl groups of the graphene oxide sheet-like base surface and the hydroxyl groups of the amphiphilic substances such as the adhesive on the surface of the support layer 2, the effect of chemical crosslinking can also be strengthened, thereby realizing the volume crosslinking of the functional layer 1 and increasing its firmness. As shown in Figure 2, the "wrinkle" in the figure indicates that the graphene oxide has been successfully attached to the surface of the support layer 2 to form a stable and firm functional layer 1.

Several examples of applying the method of the present invention to prepare a reverse osmosis membrane are given below, so that those skilled in the art can better understand the content of the present invention.

Example 1

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 8 to 10 μm and a number of layers of 2 to 5 are dispersed in ultrapure water, and the mass concentration of graphene oxide is 1 mg/ml. Magnetic stirring was performed for 5 minutes, ultrasonic dispersion was carried out for 30 minutes, and 1 ml of an aqueous solution of sodium deoxycholate with a mass fraction of 1% was added, and the mixture was uniformly mixed to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, and 25% ammonia water was added to adjust the pH value of the dispersion liquid precursor to make the pH value reach 8.5, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of processing the support layer 2, a polysulfone flat ultrafiltration membrane with a pore size of 0.1 μm was selected as the support layer 2, and the flat ultrafiltration membrane was soaked in a polyvinyl alcohol aqueous solution with a mass concentration of 5% for two hours, and then taken out. Leave to dry for 24h.

The graphene oxide dispersion is sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spraying pressure is 0.2 MPa and the spraying time is 5s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 80° C. for 30 min, and then brought to room temperature.

In the process of coordinating ion strengthening of the composite membrane, a calcium chloride aqueous solution with a mass concentration of 5% is prepared, and an equal volume of ethanol is added to the calcium chloride aqueous solution, and the composite membrane after thermal reduction is immersed in the solution. In the mixed solution of ethanol and calcium chloride solution, after reacting for 1 hour, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane function The thickness of layer 1 is 0.2 μm.

Example 2

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 15 to 20 μm and a number of layers of 5 to 8 are dispersed in N-methylpyrrolidone, and the mass concentration of graphene oxide is 1 mg/ml, The solution was magnetically stirred for 5 minutes, ultrasonically dispersed for 30 minutes, and 2 ml of an aqueous solution of sodium deoxycholate with a mass fraction of 1% was added, and the mixture was uniformly mixed to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, and 25% ammonia water was added to adjust the pH value of the dispersion liquid precursor to make the pH value reach 8.5, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of processing the support layer 2, a polysulfone flat ultrafiltration membrane with a pore size of 0.1 μm was selected as the support layer 2, and the flat ultrafiltration membrane was soaked in a polyvinyl alcohol aqueous solution with a mass concentration of 5% for two hours, and then taken out. Leave to dry for 24h.

The graphene oxide dispersion was sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spraying pressure was 0.4 MPa and the spraying time was 8s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 80° C. for 45 min, and then placed at room temperature.

In the process of coordinating ion strengthening of the composite membrane, a calcium chloride aqueous solution with a mass concentration of 5% is prepared, and an equal volume of ethanol is added to the calcium chloride aqueous solution, and the composite membrane after thermal reduction is immersed in the solution. In the mixed solution of ethanol and calcium chloride solution, after reacting for 1 hour, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane function The thickness of layer 1 is 0.25 μm.

Example 3

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 15 to 20 μm and a number of layers of 8 to 10 are dispersed in ethanol, and the mass concentration of graphene oxide is 5 mg/ml, and the solution is subjected to a magnetic force. Stir for 5 minutes, ultrasonically disperse for 20 minutes, add 2 ml of a 3% sodium deoxycholate aqueous solution by mass, and mix uniformly to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, and 25% ammonia water was added to adjust the pH value of the dispersion liquid precursor to make the pH value reach 8.5, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of processing the support layer 2, a polyethersulfone flat ultrafiltration membrane with a pore size of 0.1 μm was selected as the support layer 2, and the flat ultrafiltration membrane was soaked in a polyvinyl alcohol aqueous solution with a mass concentration of 5% for two hours. Take it out and let it dry for 24 hours.

The graphene oxide dispersion was sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spraying pressure was 0.2 MPa and the spraying time was 3s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 80° C. for 45 min, and then placed at room temperature.

During the coordination ion strengthening process of the composite membrane, a magnesium chloride aqueous solution with a mass concentration of 10% was prepared, and an equal volume of ethanol was added to the calcium chloride aqueous solution, and the composite membrane after thermal reduction was immersed in ethanol and ethanol. In the mixed solution of calcium chloride solution, after reacting for 1 hour, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane functional layer 1 The thickness is 0.5 μm.

Example 4

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 8 to 10 μm and a number of layers of 4 to 6 are dispersed in ultrapure water, and the mass concentration of graphene oxide is 3 mg/ml. Magnetic stirring was performed for 5 minutes, ultrasonic dispersion was carried out for 30 minutes, and 1 ml of an aqueous solution of sodium deoxycholate with a mass fraction of 1% was added, and the mixture was uniformly mixed to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, 25% ammonia water was added to adjust the pH value of the dispersion liquid precursor to make the pH value reach 7, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of processing the support layer 2, a polysulfone flat ultrafiltration membrane with a pore size of 0.1 μm was selected as the support layer 2, and the flat ultrafiltration membrane was soaked in a polyethylene glycol aqueous solution with a mass concentration of 5% for two hours. Take it out and let it dry for 24 hours.

The graphene oxide dispersion is sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spraying pressure is 0.2 MPa, and the spraying time is 2s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 80° C. for 30 min, and then brought to room temperature.

In the process of coordinating ion strengthening of the composite membrane, a calcium chloride aqueous solution with a mass concentration of 5% is prepared, and an equal volume of ethanol is added to the calcium chloride aqueous solution, and the composite membrane after thermal reduction is immersed in the solution. In the mixed solution of ethanol and calcium chloride solution, after reacting for 1 hour, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane function The thickness of layer 1 is 0.3 μm.

Example 5

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 8 to 10 μm and a number of layers of 5 to 10 are dispersed in ultrapure water, and the mass concentration of graphene oxide is 3 mg/ml. Magnetic stirring was performed for 5 minutes, ultrasonic dispersion was performed for 30 minutes, and 2 ml of an aqueous solution of sodium dodecylbenzenesulfonate with a mass fraction of 1% was added, and the mixture was uniformly mixed to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, and the pH value of the dispersion liquid precursor was adjusted by adding ammonia water with a concentration of 25% to make the pH value reach 9, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of processing the support layer 2, a polysulfone flat ultrafiltration membrane with a pore size of 0.1 μm was selected as the support layer 2, and the flat ultrafiltration membrane was soaked in a polyvinyl alcohol aqueous solution with a mass concentration of 5% for two hours, and then taken out. Leave to dry for 24h.

The graphene oxide dispersion was sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spraying pressure was 0.3 MPa and the spraying time was 9s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 80° C. for 30 min, and then brought to room temperature.

In the process of coordinating ion strengthening of the composite membrane, a calcium chloride aqueous solution with a mass concentration of 5% is prepared, and an equal volume of ethanol is added to the calcium chloride aqueous solution, and the composite membrane after thermal reduction is immersed in the solution. In the mixed solution of ethanol and calcium chloride solution, after reacting for 1 hour, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane function The thickness of layer 1 is 0.5 μm.

Example 6

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 10 to 15 μm and a number of layers of 2 to 10 are dispersed in ultrapure water, and the mass concentration of graphene oxide is 0.1 mg/ml. The solution was magnetically stirred for 5 minutes, ultrasonically dispersed for 30 minutes, and 3 ml of an aqueous solution of sodium polystyrene sulfonate with a mass fraction of 0.1% was added, and the mixture was uniformly mixed to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, and the pH value of the dispersion liquid precursor was adjusted by adding ammonia water with a concentration of 25%, so that the pH value reached 8, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of processing the support layer 2, a polyethersulfone flat ultrafiltration membrane with a pore size of 0.5 μm was selected as the support layer 2, and the flat ultrafiltration membrane was immersed in a polyvinylpyrrolidone aqueous solution with a mass concentration of 1% for two hours. Take it out and let it dry for 24h.

The graphene oxide dispersion was sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spraying pressure was 0.1 MPa and the spraying time was 10s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 60° C. for 40 min, and then brought to room temperature.

In the process of coordinating ion strengthening of the composite membrane, an aqueous solution of aluminum chloride with a mass concentration of 3% is prepared, and an equal volume of ethanol is added to the aqueous calcium chloride solution, and the composite membrane after thermal reduction is immersed in the solution. In the mixed solution of ethanol and calcium chloride solution, after reacting for 4 hours, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane function The thickness of layer 1 is 0.2 μm.

Example 7

In the process of preparing the dispersion liquid of graphene oxide, graphene oxide sheets with a sheet diameter of 10 to 15 μm and a number of layers of 3 to 7 are dispersed in ethanol, and the mass concentration of graphene oxide is 2.5 mg/ml. Magnetic stirring for 5 minutes, ultrasonic dispersion for 30 minutes, and adding 1 ml of an aqueous solution of sodium deoxycholate with a mass fraction of 5%, and mixing uniformly to form a dispersion liquid precursor. The dispersion liquid precursor was allowed to stand for 1 hour, and the pH value of the dispersion liquid precursor was adjusted by adding ammonia water with a concentration of 25%, so that the pH value reached 8, and the solution was stabilized for 30 minutes to obtain the required graphene oxide dispersion liquid.

In the process of treating the support layer 2, a polyethersulfone flat ultrafiltration membrane with a pore size of 1 μm was selected as the support layer 2, and the flat ultrafiltration membrane was soaked in an aqueous solution of polyvinylpyrrolidone with a mass concentration of 10% for two hours, and then taken out. Leave to dry for 24h.

The graphene oxide dispersion is sprayed onto the surface of the support layer 2 by a spray gun to form a composite film, wherein the spray pressure is 0.5 MPa, and the spray time is 1 s.

In the process of thermal reduction post-treatment of the composite film, the composite film after spraying was put into a vacuum oven for heat treatment at 70° C. for 35 min, and then placed at room temperature.

In the process of coordinating ion strengthening of the composite membrane, an aqueous solution of aluminum chloride with a mass concentration of 7% is prepared, and an equal volume of ethanol is added to the aqueous calcium chloride solution, and the composite membrane after thermal reduction is immersed in the solution. In the mixed solution of ethanol and calcium chloride solution, after reacting for 2.5 hours, the composite membrane was taken out and rinsed repeatedly with ethanol. After rinsing, the composite membrane was placed for 24 hours to obtain the required reverse osmosis membrane. Among them, the reverse osmosis membrane The thickness of the functional layer 1 was 0.2 μm.

The performance test of the reverse osmosis membrane prepared in the above example is carried out. The test equipment is a universal dead-end cup reverse osmosis membrane evaluation equipment. Sampling was carried out after the reverse osmosis membrane ran stably for 30 min. For the specific testing process, refer to the prior art, which will not be repeated here. The test results are shown in Table 1.

Table 1

example number Desalination rate (%) Water flux (L/M²/H) 1 95 165 2 97 157 3 99 104 4 97.8 125 5 97.5 115 6 95 170 7 97 145

At present, the dead-end test performance of commercially available reverse osmosis membranes is about 95-97% of the salt rejection, and the water flux is 35-50 L/M ² /H. Compared with the test results data in the examples of the present invention, the method of the present invention is adopted. The advantage of the prepared reverse osmosis membrane to improve water flux is very obvious.

For the above example, a variable pressure test experiment was also carried out, and the experimental conditions were similar to those of the reverse osmosis membrane performance test. The results show that the reverse osmosis membrane of the embodiment of the present invention has good pressure resistance performance. Since the test results of each example have the same trend, only the test results of the reverse osmosis membrane prepared in Example 3 are listed below as a reference, see Table 2 for details.

Table 2

Test pressure (MPa) Desalination rate (%) Water flux (L/M²/H) 1.5 97 97 2 99 104 3 99 120 5 99 119

As can be seen from Table 2, with the gradual increase of the test pressure, the salt rejection and water flux of the reverse osmosis membrane of the embodiment of the present invention both increase, and the reverse osmosis membrane does not have the phenomenon of high pressure-induced functional layer densification. There is no phenomenon of reduced water production, failure of functional layer or sharp decline of salt rejection, indicating that the reverse osmosis membrane of the embodiment of the present invention can withstand high operating pressure and has good pressure resistance performance.

The reverse osmosis membrane produced by the preparation method provided in the embodiment of the present invention has good desalination rate and high water flux, can operate continuously under high operating pressure, has good cleaning resistance, and has a simple preparation method, The membrane has a long life cycle, which is conducive to large-scale production and wide application, and is suitable for ultrapure water preparation, seawater desalination and other fields.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (16)

1. A reverse osmosis membrane, comprising:

a support layer comprising a flat ultrafiltration membrane;

a functional layer formed on the support layer, the functional layer comprising stacked overlapping graphene oxide sheets.

2. The reverse osmosis membrane according to claim 1, wherein the graphene oxide sheets have a sheet diameter of 8 to 20 μm and a number of layers of 2 to 10.

3. The reverse osmosis membrane according to claim 1, wherein the functional layer has a thickness of 0.1 to 0.5 μm.

4. The reverse osmosis membrane according to claim 1, wherein the surface pore size of the flat ultrafiltration membrane is 0.1-1 μm.

5. The reverse osmosis membrane of claim 1, wherein the functional layer is bonded to the support layer by an adhesive comprising any one or more of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol.

6. A method for producing a reverse osmosis membrane, which is used for producing the reverse osmosis membrane according to any one of claims 1 to 5, comprising:

compounding the dispersion liquid of the graphene oxide on the surface of the supporting layer to form a composite film; the support layer comprises a flat ultrafiltration membrane;

and (3) performing coordination ion reinforcement on the composite membrane to obtain the required reverse osmosis membrane.

7. The method for preparing a reverse osmosis membrane according to claim 6, wherein the step of forming a composite membrane by compositing the dispersion of graphene oxide on the surface of the support layer comprises: spraying the dispersion of graphene oxide onto the surface of the support layer;

wherein the spraying pressure is 0.1-0.5 MPa, and the spraying time is 1-10 s.

8. The method of preparing a reverse osmosis membrane according to claim 6, wherein the step of subjecting the composite membrane to complex ion strengthening to obtain the desired reverse osmosis membrane comprises:

putting the composite membrane into a reaction solution to carry out a coordination ion strengthening reaction; the reaction solution comprises a coordination ion aqueous solution and ethanol with the same volume as the coordination ion aqueous solution;

and (3) showering the composite membrane by using ethanol, and standing the composite membrane for a certain time to obtain the required reverse osmosis membrane.

9. The preparation method of a reverse osmosis membrane according to claim 8, characterized in that the complex ion aqueous solution comprises one or more of a calcium chloride solution, a magnesium chloride solution and an aluminum chloride solution, and the mass percentage of solute in the complex ion aqueous solution is 3-10%.

10. The method for producing a reverse osmosis membrane according to claim 8, wherein the time for the complex ion strengthening reaction is 1 to 4 hours.

11. The method for preparing a reverse osmosis membrane according to claim 6, further comprising a step of preparing the dispersion liquid of graphene oxide before the step of forming the composite membrane by compositing the dispersion liquid of graphene oxide on the surface of the support layer, wherein the step of preparing the dispersion liquid of graphene oxide comprises:

dispersing graphene oxide in a dispersing agent, and adding a layer expanding stabilizer to form a dispersion liquid precursor;

and adding an alkali solution into the dispersion liquid precursor to enable the pH value of the dispersion liquid precursor to reach 7-9, so as to obtain the required dispersion liquid of the graphene oxide.

12. The method for preparing a reverse osmosis membrane according to claim 11, wherein the mass concentration of graphene oxide in the graphene oxide dispersion liquid is 0.1-5 mg/ml.

13. A method of manufacturing a reverse osmosis membrane according to claim 11, wherein the dispersant comprises any one of ultrapure water, ethanol, and N-methylpyrrolidone.

14. The preparation method of a reverse osmosis membrane according to claim 11, wherein the layer-expanding stabilizer comprises any one of sodium deoxycholate, sodium dodecylbenzenesulfonate and sodium polystyrene sulfonate, and the mass percentage of the layer-expanding stabilizer in the graphene oxide dispersion is 0.1-5%.

15. The method for preparing a reverse osmosis membrane according to claim 6, further comprising a step of treating the flat ultrafiltration membrane of the support layer before the step of forming the composite membrane by compositing the dispersion of graphene oxide on the surface of the support layer, wherein the step comprises: putting the flat ultrafiltration membrane into an aqueous solution of an adhesive, soaking and then airing; wherein in the aqueous solution of the adhesive, the mass percent of the adhesive is 1-10%.

16. The method for preparing a reverse osmosis membrane according to claim 6, further comprising a step of performing thermal reduction treatment on the composite membrane after the step of forming the composite membrane by compositing the dispersion of graphene oxide on the surface of the support layer and before the step of performing coordinated ion strengthening on the composite membrane to obtain the desired reverse osmosis membrane, wherein the step of performing thermal reduction treatment on the composite membrane comprises: and (3) heating the composite film at the temperature of 60-80 ℃ in vacuum for 30-45 min, and then cooling to room temperature.

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