CN105617882B - A kind of compound forward osmosis membrane of chitosan-modified stannic oxide/graphene nano and preparation method thereof - Google Patents

Abstract

The invention discloses a chitosan-modified graphene oxide nanocomposite forward osmosis membrane and a preparation method thereof. The forward osmosis membrane is made by coating a membrane-making liquid on an ultrafiltration support base membrane. The percentage meter is made of the following components: chitosan modified graphene oxide 0.1%-1.0%; chitosan 2%-5%; hydrophilic additive 0.1-0.3%; dilute acetic acid solution 91%-97%; Dialdehyde solution 0.1-3%. The method of the present invention is simple to operate, and at the same time, chitosan, as a natural polymer, has good hydrophilicity and salt-cutting property, and at the same time, the preparation cost of the composite forward osmosis membrane is low, and while improving the hydrophilicity of the surface of the composite membrane, , the unique sheet-like structure of graphene oxide can achieve better salt interception effect.

Description

A chitosan modified graphene oxide nanocomposite forward osmosis membrane and preparation method thereof

technical field

The invention belongs to the technical field of membrane separation, and relates to a preparation method and a product of a chitosan-modified graphene oxide nanocomposite forward osmosis membrane.

Background technique

Water is the source of life. In today's world of energy shortages and increasingly serious water and environmental pollution, seawater desalination, brackish water desalination, and industrial wastewater treatment have become the main means of obtaining freshwater resources.

Membrane technology is a new type of separation technology, which has the advantages of high efficiency, energy saving, and environmental protection. It has attracted great attention from all over the world in seawater desalination, desalination, food processing, and medicine. Research reports have shown that membrane desalination technology accounts for 44% of the world's water desalination equipment capacity.

Forward osmosis (FO) is a new type of membrane separation technology. It uses the osmotic pressure difference of the solution on both sides of the membrane as the driving force, without external pressure, so as to achieve the purpose of separation and concentration. It has the advantages of simple operation, low energy consumption, and low cost. Mainly used in seawater desalination, wastewater treatment, food processing, power generation, etc. Compared with desalination technologies such as nanofiltration and reverse osmosis, forward osmosis technology has gradually become an alternative desalination technology due to its advantages of low energy consumption and zero discharge of industrial sewage.

According to the existing research results, the selection of forward osmosis membrane material is the core of forward osmosis technology. An ideal forward osmosis membrane should have the following characteristics: a thinner dense skin layer to ensure high membrane retention and reduce concentration polarization; a loose support layer with a macroporous structure to ensure higher water flux. The materials used for forward osmosis membrane research are mainly: cellulose triacetate (CTA), polybenzimidazole (PBI), polysulfone (PSf), polyethersulfone (PES) and so on. At present, the preparation of forward osmosis FO mainly includes blending method and interfacial polymerization method. The blending method is mainly to blend film-forming materials such as cellulose acetate and polyvinylidene fluoride with hydrophilic nanoparticles to prepare FO membranes; interfacial polymerization The method mainly uses hydrophilic substances such as graphene oxide to modify the ultrafiltration bottom membrane, and then performs interfacial polymerization on the surface of the ultrafiltration bottom membrane to prepare a forward osmosis membrane with an ultra-thin desalination skin layer. These two methods are currently available. received widespread attention.

In recent years, due to the good water solubility and surface activity of graphene oxide (GO), many scholars at home and abroad have used graphene oxide for blending and modification of membrane materials, and achieved good research results. Graphene oxide can effectively improve the hydrophilicity, mechanical properties and salt rejection of ultrafiltration membranes. In their research, Ganesh et al. found that adding GO to the polysulfone casting solution can improve the hydrophilic performance of the membrane, and at the same time increase the rejection rate of the salt Na ₂ SO ₄ to 74% (BMGanesh, Arun M.Isloor, AFIsmail.Enhanced Hydrophilicity and salt rejection study of graphene oxide-polysulfone mixed matrix membrane. Desalination, 313(2013) 199-207). Xu et al. blended organosilane-functionalized GO with polyvinylidene fluoride (PVDF) to form a membrane. The mechanical strength and flux of the prepared ultrafiltration membrane were greatly improved, and the surface roughness and The anti-fouling properties have been significantly improved (ZWXu, JG Zhang, MJ Shan, et al, Organosilane-functionalized graphene oxide for enhanced anti-fouling and mechanical properties of polyvinylidene fluoride ultrafiltration membranes, Journal of Membrane Science, 458(2014) 1-13).

Graphene oxide has also received extensive attention in the construction of forward osmosis membranes. Xu Tongwen from the University of Science and Technology of China (Y.Q.Wang, R.W.Ou, H.T.Wang, et al, Graphene oxide modified graphitic carbonnitride as a modifier for thin film composite forward osmosis membrane, Journal of Membrane Science, 475(2015) 281-289) oxidized Graphene is used for the modification of forward osmosis (FO) membrane, and carbon nitride (CN) is used to modify graphene oxide to prepare a functional CN/rGO membrane modifier. The water flux of the modified forward osmosis membrane has been greatly improved. Since the concentration polarization in the membrane will affect the water flux and separation of the forward osmosis membrane, CN/rGO can effectively improve the structure and hydrophilicity of the porous support layer, thereby reducing the influence of the concentration polarization in the membrane. Wang Liguo et al. disclosed in their patents (Wang Liguo; Shi Xinlian; Li Yuan, etc., a high-performance flat cellulose acetate/graphene blended forward osmosis membrane; publication number CN104474919A; publication date: 2015-04-01). A kind of high-performance flat type cellulose acetate/graphene blending forward osmosis membrane, its preparation method is that cellulose acetate, additive, graphene and dimethyl formamide or dimethyl acetamide or N-methylpyrrolidone and acetone The mixed solvent was prepared as a forward osmosis membrane casting solution, and a high-performance flat cellulose acetate/graphene blended forward osmosis membrane was prepared on a support material by a phase inversion method. Li Fang of Donghua University, etc. proposed a method for preparing an amino-modified graphene oxide composite forward osmosis membrane in their invention patent (Li Fang; Zhao Yongjun; Li Jiafeng, et al., an amino-modified graphene oxide composite forward osmosis membrane The preparation method of film; publication number CN103861472A; publication date: 2014-06-18), its preparation method is to mix graphene oxide, dimethylformamide, organic amine and dicyclohexyl carboximide, ultrasonic, and then React at 100-150°C for 40-50 hours, add absolute ethanol, stand still, filter, and the obtained precipitate is washed and dried to obtain amino-modified graphene oxide; mix amino-modified graphene oxide with a solvent, Ultrasound, then add additives and film-forming polymers to the above mixed solution to prepare a casting solution, after degassing, use the phase inversion method to make a base film, soak in pure water for later use, and then use the interfacial polymerization method to prepare a desalination skin layer FO membrane. The invention has high mechanical strength, good chemical stability, large permeation flux of pure water and high salt retention rate.

The above reports show that GO has obvious advantages in improving polymer porous base membranes, etc., and can greatly improve the hydrophilicity and anti-fouling properties of membranes, providing technical support for the research of GO in improving porous support membranes of forward osmosis. However, in the above research, the ultrafiltration membrane material is first prepared by blending graphene oxide with PES through the phase inversion method, and then the ultra-thin desalination skin layer is prepared by interfacial polymerization. The membrane making process is complicated, and the water flux of the membrane is not easy to control, etc. question. In addition, if graphene oxide is directly used for membrane modification, there is still the problem that graphene oxide is easy to lose. If graphene oxide can be modified with macromolecules, graphene oxide can be fixed through the action of macromolecules, and at the same time Functional modification of graphene is also a good means of membrane modification.

Among many polymers, chitosan (CS) is a biodegradable, non-toxic, bio- and blood-compatible, and reusable natural polymer polysaccharide, which is widely distributed in nature and has abundant sources. It has good application value in the fields of environment, medicine, food, chemical industry, membrane separation and so on. As a natural polymer membrane material, it has been widely used in the preparation of ultrafiltration, nanofiltration, reverse osmosis membranes and intelligent responsive membranes. At present, the research on chitosan membrane is mainly to improve the water resistance, permeability, chargeability and mechanical properties of chitosan membrane. Ma et al. (B.M.Ma, A.W.Qin, X.Li, et al, Structure and properties of chitin whisker reinforced chitosan membranes, International Journal of Biological Macromolecules, 64(2014) 341-346) used chitin whiskers as an additive to modify chitosan membrane, after modification, the tensile strength of the chitosan composite membrane is 2.8 times that of the pure chitosan membrane. Lei Siyu et al. published a patent document (Lei Siyu, Lin Dawei; a preparation method of organosilicon-modified chitosan film; publication number: CN105037768A; publication date: 2015-11-11) The preparation method of organosilicon modified chitosan film, through the reaction of epoxy polysiloxane and chitosan in acetic acid solution, the film is made by casting method, and the obtained modified chitosan film has excellent water resistance , high temperature and low temperature resistance and air permeability, the elongation at break of the film is increased by more than 30%, and the flexibility is significantly improved. At the same time, chitosan-modified graphene oxide nanocomposites are often used for adsorption and desorption regeneration of heavy metal ions and organic dyes in water due to their good adsorption properties. Therefore, at present, CS-GO is mainly used as an adsorbent for the adsorption and removal of organic pollutants and heavy metal ions in aqueous solution, and the research in the field of forward osmosis membrane has not been reported yet.

Contents of the invention

The invention provides a chitosan-modified graphene oxide nanocomposite forward osmosis membrane and a preparation method thereof. The method is simple to operate, and at the same time, chitosan, as a natural polymer, has good hydrophilicity and salt-cutting properties At the same time, the preparation cost of the composite forward osmosis membrane is low. While improving the hydrophilicity of the composite membrane surface, the unique sheet-like structure of graphene oxide can achieve a better salt interception effect.

A chitosan-modified graphene oxide nanocomposite forward osmosis membrane is made by coating the membrane-making solution on the ultrafiltration support base membrane,

The film-making solution is made of the following components in mass percent:

Chitosan itself is a film-forming material with good hydrophilicity and chargeability, and it has good compatibility with CS-GO, which can ensure that graphene oxide will not detach from the film during the application process of the film. At the same time, CS-GO has positive significance for improving the mechanical properties, permeability and desalination performance of chitosan composite membranes.

Preferably, the chitosan-modified graphene oxide is prepared by the following method:

(1) Ultrasonic disperse graphene oxide (GO) in deionized water, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N-hydroxy Succinimide (NHS), continue to stir for 0.5 ~ 1.5h;

(2) After the reaction in step (1), slowly add chitosan (CS) solution, react at 50-70°C for 0.5-1.5h; cool to room temperature and perform post-treatment; graphene oxide, 1-ethyl- The mass ratio of (3-dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxysuccinimide and chitosan is 1:(0.5～2.5):(0.5～1.5):(2.5～ 3.5).

The dropping rate of the chitosan solution described in the above step (2) is controlled at 0.1 to 0.2 mL/min; most preferably 0.15 mL/min. If the dropping speed is too fast, it will affect the reaction degree of chitosan and graphene oxide. The solvent of the chitosan solution is a dilute acetic acid solution with a volume fraction of 1%. If the concentration of the acetic acid solution is too high, the dissolution of the chitosan will be reduced. The molecular weight of the chitosan is 50KDa-200KDa.

The ultrasonic dispersion time of graphene oxide in deionized water in the above step (1) is 1.5-2.5 hours. More preferably 2h.

The reaction time in the above step (2) is further preferably 2h.

The post-treatment step in the above step (2) is: wash with 1% (W/V) NaOH aqueous solution and deionized water for several times until the pH is about 7.0, and vacuum-dry at 40° C. to obtain it.

The mass ratio of graphene oxide, 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxysuccinimide and chitosan (GO/EDC·HCl/NHS/ CS) is most preferably 1:2:1:3.

The graphene oxide (GO) is a commercial product.

Preferably, the molecular weight of chitosan is 100KDa-500KDa, the degree of deacetylation is 80-95%, and the mass fraction of the acetic acid solution is 1.5-2.5%.

Preferably, the ultrafiltration support bottom membrane is polyvinylidene fluoride membrane, polyethersulfone membrane, sulfonated polyethersulfone membrane, polysulfone membrane or polypropylene ultrafiltration membrane. The base film should be soaked and dried before use.

The hydrophilic additive is glycerin or Tween 80.

The mass concentration of the glutaraldehyde solution is 45%-55%, preferably 50%.

In the present invention, amino groups in chitosan react with epoxy groups in graphene oxide and are blended and cross-linked with chitosan body on the surface of a commercial membrane to obtain a nanocomposite forward osmosis membrane. Before the graphene oxide is mixed with the chitosan, the chitosan with a molecular weight of 50KDa-200KDa is modified to improve its compatibility with the chitosan with a molecular weight of 100KDa-500KDa in step (2). In the present invention, chitosan-graphene oxide (GO-CS) nanomaterials can effectively improve the permeability and salt interception rate of the composite layer, while chitosan itself can effectively improve the hydrophilicity and chargeability of the composite layer , in order to improve the overall permeability and salt rejection rate of forward osmosis composite membrane.

Compared with the existing forward osmosis membrane, the water flux of the forward osmosis membrane of the present invention is greater than 12L/m ² ·h, and the salt interception performance is also greatly improved.

Membrane-making liquid of the present invention, a kind of more selected technical scheme, is made up of following component by mass percent:

Under this preferred combination, the water flux of the forward osmosis membrane is greater than 15 L/m ² ·h, and the reverse salt flux is below 4.5 g/m ² ·h.

Membrane-making solution of the present invention, most preferably, is made up of following components in mass percent:

Under this preferred combination, the water flux of the forward osmosis membrane is greater than 20 L/m ² ·h, and the reverse salt flux is below 4.0 g/m ² ·h.

The invention provides a chitosan-modified graphene oxide nanocomposite forward osmosis membrane, comprising the steps of:

(1) Dissolve chitosan and hydrophilic additives in dilute acetic acid solution according to the proportion, stir at 50-70°C (preferably 60°C) until the chitosan is completely dissolved, then remove the insoluble impurities by suction filtration, and then add according to the proportion by ultrasonic dispersion The treated chitosan-modified graphene oxide dispersion is stirred at 50 to 70°C (preferably 60°C) until uniformly dispersed to obtain a mixed liquid;

The ratio of raw materials in terms of mass percentage is:

(2) Add dilute glutaraldehyde solution to the obtained mixed solution after vacuum defoaming, mix evenly and scrape it on the bottom membrane of the filter support, place it horizontally at room temperature for 2-6 hours, and then dry it at 40-60°C, in terms of mass percentage, Dilute glutaraldehyde dialdehyde solution accounts for 0.1-3% of raw materials;

(3) Immerse the dried film in a mixed solution of sodium hydroxide and ethanol for 0.5 to 1.5 hours, wash it with water, and dry it in the air;

The volume ratio of sodium hydroxide solution to ethanol in the mixed solution of sodium hydroxide and ethanol is 2:1, wherein the mass concentration of sodium hydroxide solution is 3%, and the purity of ethanol is 50%.

Preferably, the thickness of the scraped liquid film on the supporting base film in step (2) is 5-30 μm.

A variety of defoaming treatment methods can be selected for the defoaming treatment. The preferred defoaming treatment method is: vacuumize the CS/GO-CS solution, let it stand for 30 minutes, and after all the bubbles run out, put the CS/GO-CS solution -CS solution is taken out, and the standing time should not be too long. If the standing time is too long, acetic acid is volatile, which will affect the dissolution of chitosan. In addition, graphene oxide will produce partial deposition, which will eventually affect the performance of the composite forward osmosis membrane.

The invention has simple process, low preparation cost and meets the requirement of green production.

Description of drawings

Figure 1 is the surface infrared spectrum of pure CS membrane and CS/CS-GO composite FO membrane (the -N-H base peak is the characteristic peak of CS-GO)

Detailed ways

The characterization methods used in the following embodiments mainly include:

Chemical composition and structure of the film surface: measured by total reflection infrared spectrometer (VERTEX 70, Germany).

Membrane permeation flux measurement: The water flux and reverse salt flux of the forward osmosis membrane are measured by the laboratory-specific forward osmosis membrane test device, and 0.5mol/L Na ₂ SO ₄ aqueous solution is used as the driving solution. The water flux of the forward osmosis membrane can be calculated according to the formula (1) per unit time and the water flux passing through the effective area of the membrane.

In the formula: J _w is the forward osmosis water flux, L/m ² h; Δm is the added value of the drawn liquid mass, kg; ρ is the density of pure water, kg/m ³ ; S is the effective area of forward osmosis, m ² ; t is time, h.

The reverse salt flux in the membrane permeation process can be calculated according to the formula (2) per unit time, and the reverse salt flux passing through the effective area of the membrane.

In the formula, J _s is the reverse-phase salt flux, g/m ² h; C is the salt concentration in the draw solution, which can be calculated from the conductivity, mol/L, and V is the volume of the draw solution after running for t time; M _NaCl is the chlorine Relative molecular mass of sodium chloride; s is the effective area of forward osmosis, m ² ; t is time, h.

The present invention will be described in more detail below in conjunction with the following examples, but the examples do not constitute a limitation to the present invention.

The graphene oxide preparation method of chitosan modification is as follows:

Commercially available graphene oxide (GO) was added to deionized water, ultrasonically dispersed for 2 h, and then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N -Hydroxysuccinimide (NHS), continuously stirred for 1h, then chitosan (CS, 50KDa-200KDa, deacetylation degree 80-95%, solvent is 1% dilute acetic acid solution by volume fraction) solution in 0.15mL Slowly added to the GO dispersion at 60°C for 1 hour, cooled to room temperature and then centrifuged, the mass ratio between the reaction substances GO/EDC·HCl/NHS/CS=1:(0.5～2.5):(0.5 ~1.5): (2.5~3.5) (1:2:1:3 is preferred). Then wash several times with 1% (W/V) NaOH aqueous solution and deionized water until the pH is about 7.0, and vacuum-dry at 40°C to obtain the graphene oxide modifier (CS-GO) modified by chitosan macromolecules .

The mass concentration of dilute acetic acid used in the following examples is 2%; The mass concentration of dilute glutaraldehyde solution is 50%

Example 1

Chitosan-modified graphene oxide (CS-GO) was added to deionized water, and ultrasonically dispersed for 2 hours to obtain a uniform CS-GO dispersion; chitosan and hydrophilic additive (glycerin) were dissolved in dilute In acetic acid, stir continuously at 60°C for 6 hours, and filter with suction to remove insoluble impurities. Then the CS-GO dispersion was added to the chitosan solution and continued to stir continuously at 60 °C for 2 h.

After defoaming the above CS/CS-GO solution, add the formulated amount of dilute glutaraldehyde solution, stir evenly, scrape a thin layer of liquid film with a thickness of 30 μm on the polysulfone ultrafiltration bottom membrane, and place it horizontally at room temperature Leave it for 2 hours, then dry it in an oven at 50°C. The dried composite film was immersed in a mixed solution of sodium hydroxide and ethanol (mixing volume ratio 2:1, the mass concentration of sodium hydroxide solution was 3%, and the purity of ethanol was 50%) to continue treatment for 1h, and then used The composite membrane is washed repeatedly with ion water, and finally the membrane is dried to obtain a forward osmosis composite membrane.

The raw material formula and the permeation flux and salt interception performance of the obtained forward osmosis membrane are shown in Table 1.

Example 2

Chitosan-modified graphene oxide (CS-GO) was added to deionized water, and ultrasonically dispersed for 2 hours to obtain a uniform CS-GO dispersion; chitosan and hydrophilic additive (Tween 80) were dissolved according to the formula In dilute acetic acid, stir continuously at 60°C for 8 hours, and filter with suction to remove insoluble impurities. Then the CS-GO dispersion was added to the chitosan solution and continued to stir continuously at 60 °C for 4 h.

After defoaming the above CS/CS-GO solution, add the formula amount of dilute glutaraldehyde solution, stir evenly, scrape a thin layer of liquid film with a thickness of 20 μm on the polyethersulfone ultrafiltration bottom membrane, and place it at room temperature Place it horizontally for 4 hours, and then dry it in an oven at 50°C. The dried composite membrane is soaked in a mixed solution of sodium hydroxide and ethanol to continue treatment for 1 hour, then the composite membrane is repeatedly washed with deionized water, and finally the membrane is dried to obtain a forward osmosis composite membrane.

The raw material formula and the permeation flux and salt interception performance of the obtained forward osmosis membrane are shown in Table 1.

Example 3

Chitosan-modified graphene oxide (CS-GO) was added to deionized water, and ultrasonically dispersed for 2 hours to obtain a uniform CS-GO dispersion; chitosan and hydrophilic additive (glycerin) were dissolved in dilute In acetic acid, stir continuously at 60°C for 10 hours, and filter with suction to remove insoluble impurities. Then the CS-GO dispersion was added into the chitosan solution and continued to stir continuously at 60 °C for 6 h.

After defoaming the above CS/CS-GO solution, add the formulated amount of dilute glutaraldehyde solution, stir evenly, scrape a thin layer of liquid film with a thickness of 10 μm on the polyethersulfone ultrafiltration bottom membrane, and place it at room temperature Place it horizontally for 6 hours, and then put it into an oven at 50°C for drying. The dried composite membrane is soaked in a mixed solution of sodium hydroxide and ethanol to continue treatment for 1 hour, then the composite membrane is repeatedly washed with deionized water, and finally the membrane is dried to obtain a forward osmosis composite membrane.

The raw material formula and the permeation flux and salt interception performance of the obtained forward osmosis membrane are shown in Table 1.

The infrared spectrum of the obtained forward osmosis membrane and pure chitosan is shown in Figure 1.

Example 4

Chitosan-modified graphene oxide (CS-GO) was added to deionized water, and ultrasonically dispersed for 2 hours to obtain a uniform CS-GO dispersion; chitosan and hydrophilic additive (Tween 80) were dissolved according to the formula In dilute acetic acid, stir continuously at 60°C for 12 hours, and filter with suction to remove insoluble impurities. Then the CS-GO dispersion was added to the chitosan solution and continued to stir continuously at 60 °C for 2 h.

After defoaming the above CS/CS-GO solution, add the formula amount of dilute glutaraldehyde solution, stir evenly, scrape a thin layer of liquid film with a thickness of 5 μm on the sulfonated polyethersulfone ultrafiltration bottom membrane, and place it on the Place it horizontally at room temperature for 4 hours, and then dry it in an oven at 50°C. The dried composite membrane is soaked in a mixed solution of sodium hydroxide and ethanol to continue treatment for 1 hour, then the composite membrane is repeatedly washed with deionized water, and finally the membrane is dried to obtain a forward osmosis composite membrane.

The raw material formula and the permeation flux and salt interception performance of the obtained forward osmosis membrane are shown in Table 1.

Example 5

Chitosan-modified graphene oxide (CS-GO) was added to deionized water, and ultrasonically dispersed for 2 hours to obtain a uniform CS-GO dispersion; chitosan and hydrophilic additive (glycerin) were dissolved in dilute In acetic acid, stir continuously at 60°C for 6 hours, and filter with suction to remove insoluble impurities. Then the CS-GO dispersion was added to the chitosan solution and continued to stir continuously at 60 °C for 4 h.

After defoaming the above CS/CS-GO solution, add the formula amount of dilute glutaraldehyde solution, stir evenly, scrape a thin layer of liquid film with a thickness of 5 μm on the sulfonated polyethersulfone ultrafiltration bottom membrane, and place it on the Place it horizontally at room temperature for 2 hours, and then dry it in an oven at 50°C. The dried composite membrane is soaked in a mixed solution of sodium hydroxide and ethanol to continue treatment for 1 hour, then the composite membrane is repeatedly washed with deionized water, and finally the membrane is dried to obtain a forward osmosis composite membrane.

The raw material formula and the permeation flux and salt interception performance of the obtained forward osmosis membrane are shown in Table 1.

Example 6

Chitosan-modified graphene oxide (CS-GO) was added to deionized water, and ultrasonically dispersed for 2 hours to obtain a uniform CS-GO dispersion; chitosan and hydrophilic additive (Tween 80) were dissolved according to the formula In dilute acetic acid, stir continuously at 60°C for 6 hours, and filter with suction to remove insoluble impurities. Then the CS-GO dispersion was added to the chitosan solution and continued to stir continuously at 60 °C for 4 h.

After defoaming the above CS/CS-GO solution, add the formula amount of dilute glutaraldehyde solution, stir evenly, scrape a thin layer of liquid film with a thickness of 10 μm on the polyvinylidene fluoride ultrafiltration bottom membrane, and place it at room temperature Place it horizontally for 2 hours, and then dry it in an oven at 50°C. The dried composite membrane is soaked in a mixed solution of sodium hydroxide and ethanol to continue treatment for 1 hour, then the composite membrane is repeatedly washed with deionized water, and finally the membrane is dried to obtain a forward osmosis composite membrane.

The raw material formula and the permeation flux and salt interception performance of the obtained forward osmosis membrane are shown in Table 1.

Forward osmosis membrane membrane-making liquid composition and membrane performance in the embodiment of table 1

From the results in Table 1, it can be seen that the water flux of the forward osmosis membrane of the present invention can basically reach more than 12L/m ² ·h, and can reach about 20L/m ² ·h by optimizing the formula of the membrane-making liquid; The amount is within 6g/m ² ·h, and can be around 4g/m ² ·h by optimizing the formulation of the film-forming solution.

The above is only a specific implementation case of the patent of the present invention, but the technical features of the patent of the present invention are not limited thereto, and any changes or modifications made by those skilled in the relevant field within the field of the patent of the present invention are covered by the present invention within the scope of the patent.

Claims (9)

1. a preparation method of chitosan modified graphene oxide nanocomposite forward osmosis membrane, is characterized in that, comprises the steps: (1) Dissolve chitosan and hydrophilic additives in dilute acetic acid solution according to the proportion, stir at 50-70°C until the chitosan is completely dissolved, then filter to remove insoluble impurities, and then add chitosan treated by ultrasonic dispersion according to the proportion Modified graphene oxide dispersion, stirred at 50-70°C until uniformly dispersed to obtain a mixed solution; The ratio of raw materials in terms of mass percentage is: (2) Add dilute glutaraldehyde solution to the obtained mixed solution after vacuum defoaming, mix evenly, scrape it on the ultrafiltration support bottom membrane, place it horizontally at room temperature for 2-6 hours, then dry it at 40-60°C, calculated by mass percentage , the dilute glutaraldehyde solution accounts for 0.1-3% of the raw material; (3) Immerse the dried film in a mixed solution of sodium hydroxide and ethanol for 0.5 to 1.5 hours, wash it with water, and dry it in the air. 2. according to the described preparation method of claim 1, it is characterized in that, the volume ratio of sodium hydroxide solution and ethanol in sodium hydroxide and ethanol mixed solution is 2:1, wherein the mass concentration of sodium hydroxide solution is 3%, ethanol The volume concentration is 50%. 3. The preparation method according to claim 1, characterized in that the thickness of the scraped liquid film on the supporting bottom film is 530 μm. 4. The preparation method according to claim 1, characterized in that the molecular weight of chitosan is 100KDa-500KDa, the degree of deacetylation is 80-95%; the mass fraction of dilute acetic acid solution is 1.5-2.5%. 5. according to the described preparation method of claim 1, it is characterized in that, described chitosan modified graphene oxide is prepared by following method: (1) Ultrasonic disperse graphene oxide in deionized water, then add 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, continue to stir for 0.5 ~1.5h; (2) After the reaction in step (1), slowly add chitosan solution, and react at 50-70°C for 0.5-1.5h; after cooling to room temperature, carry out post-treatment; graphene oxide, 1-ethyl-(3- The mass ratio of dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxysuccinimide and chitosan is 1:(0.5-2.5):(0.5-1.5):(2.5-3.5). 6. according to the described preparation method of claim 5, it is characterized in that, the dropping rate of chitosan solution described in the step (2) of chitosan modified graphene oxide preparation method is 0.1～0.2mL/min, chitosan The sugar molecular weight is 50KDa-200KDa, and the degree of deacetylation is 80-95%. 7. The preparation method according to claim 1, wherein the hydrophilic additive is glycerol or Tween 80. 8. The preparation method according to claim 1, characterized in that the mass concentration of the dilute glutaraldehyde solution is 45-55%. 9. The preparation method according to claim 1, characterized in that, the ultrafiltration support bottom membrane is a polyvinylidene fluoride membrane, a polyethersulfone membrane, a sulfonated polyethersulfone membrane, a polysulfone membrane or a polypropylene ultrafiltration membrane , the supporting base film is cleaned by soaking in ethanol before use.