WO2019153946A1

WO2019153946A1 - High-performance forward osmosis membrane, preparation method therefor and application thereof

Info

Publication number: WO2019153946A1
Application number: PCT/CN2018/124701
Authority: WO
Inventors: 刘长坤; 雷晓斌
Original assignee: 深圳大学
Priority date: 2018-02-09
Filing date: 2018-12-28
Publication date: 2019-08-15
Also published as: CN108355497A; CN108355497B

Abstract

A high-performance forward osmosis membrane, a preparation method therefor and an application thereof, wherein the method comprises the steps of: soaking the top surface of a base membrane in a water solution of a mixture of polyamidoamine dendrimers and m-phenylenediamine for 2-5 minutes before removing the base membrane, and absorbing the solution on the surface of the base membrane using filtering paper to dry; continuing to soak the top surface of the base membrane in a sym-trichlorobenzene solution for 1-3 minutes before pouring out the solution to obtain the forward osmosis membrane.

Description

High-performance forward osmosis membrane and preparation method and application thereof

Technical field

The invention relates to the field of permeable membranes, in particular to a high performance forward osmosis membrane and a preparation method and application thereof.

Background technique

In recent years, freshwater resources have been seriously polluted, such as eutrophication of water bodies, pollution of organic matter and heavy metals, and people's health has been seriously threatened. Heavy metal contaminants are not biodegradable and can enter the human body through the food chain, damaging the central nervous system and organs of the human body. Therefore, many techniques have been applied to remove heavy metal ions in water, such as chemical precipitation, flotation, ion exchange, adsorption, membrane filtration, and the like. However, each of the above techniques has certain drawbacks. The cost of chemical precipitation and flotation is usually very high, and the extra sludge generated by these processes requires additional costs. Ion exchange is non-selective and highly sensitive to the pH of the solution and slow to regenerate. The nanofiltration membrane has a higher tendency to be contaminated, thereby reducing production efficiency and increasing operating costs. In addition, the removal rate of heavy metal ions is insufficient during the water treatment, resulting in an increase in the cost of further purification.

Recently, the forward osmosis technology has a bright future in wastewater treatment. Compared with other conventional technologies, the forward osmosis technology does not require external pressure, and the water molecules spontaneously pass through the raw material liquid (low osmotic pressure) under the condition of high osmotic pressure difference. The permeable membrane flows to the pumping liquid (high osmotic pressure) to remove the pollutants. Therefore, positive permeation has the following advantages: (1) high rejection rate, (2) relatively low energy consumption, (3) low membrane fouling tendency, and (4) high water recovery rate. Therefore, forward osmosis technology can play an important role in the treatment of heavy metal wastewater.

The nanofiltration, reverse osmosis and active selective layers of the reverse osmosis membrane of the thin film composite membrane (referred to as "composite membrane") are usually prepared by interfacial polymerization. The aromatic polyamide (PA) selective layer of the conventional composite forward osmosis membrane is prepared by interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). However, the PA selective layer is not hydrophilic, rough microscopic morphology, Factors such as dense structure and negatively charged groups lead to low water flux and membrane fouling. Therefore, the traditional composite forward osmosis membrane has low water flux and poor stain resistance, and it is necessary to modify the PA selective layer. The PA selective layer modification often adopts two strategies: one is to add nanometer in the aqueous phase or the organic phase. Particles, functional monomers and metal-organic frameworks improve the physicochemical properties of the PA selective layer by interfacial polymerization, and improve the desalting, chlorine and antifouling properties of the forward osmosis membrane, such as the addition of zeolite, carbon nanotubes, graphene oxide, Bovine albumin, tris(2-aminoethyl)amine, and metal organic frameworks, however, the selective layer of the forward osmosis membrane combined with the nanomaterial may adversely affect the selectivity of the membrane; the other is performed on the surface of the PA layer. The secondary interfacial polymerization or grafting reaction significantly changes the hydrophilicity, chargeability and surface roughness of the membrane to improve the separation, antifouling and antibacterial properties of the membrane. For example, surface grafted hydrophilic polyethylene glycol, polyethyleneimine, ethylenediamine, polyamide-amine dendrimer and sodium 2-[(2-aminoethyl)amino]ethanesulfonate Wait. However, this modification method increases the thickness of the PA selective layer, resulting in an increase in the resistance of water to the membrane, thereby suppressing an increase in water flux.

Therefore, the prior art has yet to be improved and developed.

Summary of the invention

In view of the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a high-performance forward osmosis membrane, a preparation method thereof and an application thereof, aiming at solving the low water flux and treatment of a conventional forward osmosis membrane using an aromatic polyamide as a skin layer. The problem of low efficiency of heavy metal wastewater.

The technical solution of the present invention is as follows:

A method for preparing a high performance forward osmosis membrane, comprising the steps of:

A, the upper surface of the base film is immersed in an aqueous solution of a polyamide-amine dendrimer mixed with m-phenylenediamine, and after 2-5 min, the base film is taken out and the solution on the surface of the base film is blotted dry with a filter paper;

B. The upper surface of the base film obtained in the step A is further immersed in the triphenyltrichlorochloride solution, and after 1-3 minutes, the solution is poured off to obtain a high performance forward osmosis membrane.

The method for preparing a high performance forward osmosis membrane, wherein the base membrane material is polyvinylidene fluoride or polysulfone.

The method for producing a high performance forward osmosis membrane, wherein the base membrane has an average pore diameter of 200 to 250 μm.

The method for preparing a high performance forward osmosis membrane, wherein a mass concentration of the polyamide-amine dendrimer is 0.1-0.4% in an aqueous solution in which the polyamide-amine dendrimer is mixed with m-phenylenediamine The mass concentration of m-phenylenediamine was 0.2%.

The method for preparing a high performance forward osmosis membrane, wherein the solvent in the trimestriol solution is n-hexane.

The method for preparing a high performance forward osmosis membrane, wherein the mass concentration of the trimestriol solution is 0.2%.

The method for preparing a high performance forward osmosis membrane, wherein the step B further comprises the following steps:

C. The high-performance forward osmosis membrane is placed in a dry box and dried after being dried at 60-80 ° C for 3-6 min.

A high performance forward osmosis membrane prepared by the above preparation method.

A high performance forward osmosis membrane, wherein the high performance forward osmosis membrane produced by the above preparation method is used to remove heavy metal ions in water.

Advantageous Effects: The present invention adopts a polyamide-amine dendrimer (PAMAM) in-situ modification one-step method to prepare a polyamide forward osmosis membrane, and the preparation steps are simple and easy to control. In the high performance forward osmosis membrane prepared by the invention, PAMAM can increase the relative free volume and hydrophilicity of the polyamide layer, thereby increasing the water flux of the forward osmosis membrane; at the same time, the free amine group on the PAMAM in the polyamide layer can adsorb. Heavy metal ions increase the positive charge of the membrane to enhance the repulsion of heavy metal ions in water, and promote the removal of heavy metal ions from water by the positive osmosis membrane.

DRAWINGS

1 is a flow chart of a preferred embodiment of a method for preparing a high performance forward osmosis membrane of the present invention.

2 is a histogram of the water flux and reverse salt flux measured by the forward osmosis membrane prepared in Example 1 - Example 3 as the selected layer is directed toward the draw solution.

Figure 3 is a histogram of water flux and reverse salt flux as measured by the positive osmosis membranes prepared in Examples 1 - Example 3 as the selected layer faces the feedstock.

Figure 4 is a graphical representation of the results of water flux and reverse salt flux measured for M-0 and M-2 forward osmosis membranes at different concentrations of salt solution with the selected layer facing the draw solution.

Figure 5 is a graphical representation of the results of water flux and reverse salt flux measured for M-0 and M-2 forward osmosis membranes at different concentrations of salt solution with the selected layer facing the feedstock.

Figure 6 is a schematic diagram showing the water flux results of the removal of five heavy metal ions Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ by M-0 and M-2 forward osmosis membranes in AL-DS mode.

Figure 7 is a schematic diagram showing the water flux results of the removal of five heavy metal ions Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ by M-0 and M-2 forward osmosis membranes in AL-FS mode.

Figure 8 is a graph showing the results of rejection of five heavy metal ions Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ in M- and M-2 forward osmosis membranes in AL-DS mode.

Figure 9 is a graph showing the results of rejection of five heavy metal ions Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ in M- and M-2 forward osmosis membranes in AL-FS mode.

Detailed ways

The present invention provides a high-performance forward osmosis membrane, a preparation method and application thereof, and the present invention will be further described in detail below in order to make the objects, technical solutions and effects of the present invention more clear and clear. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Please refer to FIG. 1. FIG. 1 is a flow chart of a preferred embodiment of a method for preparing a high performance forward osmosis membrane according to the present invention.

S10, the upper surface of the base film is immersed in an aqueous solution of a polyamide-amine dendrimer mixed with m-phenylenediamine, and after 2-5 min, the base film is taken out and the solution on the surface of the base film is blotted dry with a filter paper;

S20, the upper surface of the base film obtained in step S10 is further immersed in a solution of trimer trichloride, and after 1-3 minutes, the solution is poured off to obtain a high-performance forward osmosis membrane.

In particular, since the polyamide-amine dendrimer has a radially symmetric, hyperbranched structure, a large number of terminal functional groups, and an approximately spherical molecular structure, it can be used to modify the polyamide layer of the film. By chemical modification, the polyamide-amine dendrimer (PAMAM) can be combined with the polyamide layer and can change the roughness, hydrophilicity and permeability of the polyamide layer to improve the water flux.

In this embodiment, a polyamide reverse osmosis membrane is prepared by a PAMAM in-situ modification one-step method, and the preparation steps are simple and easy to control. In the prepared high performance forward osmosis membrane, PAMAM has a large number of terminal amine groups, which can bind to the polyamide layer and increase the hydrophilicity of the polyamide layer; at the same time, because PAMAM has molecular cavity and nano molecular structure, it can increase The relative free volume of the large polyamide layer increases the permeability of the forward osmosis membrane, thereby increasing the water flux of the forward osmosis membrane; at the same time, the free amine group on the PAMAM in the polyamide layer can adsorb heavy metal ions and increase the positive charge of the membrane. Thereby enhancing the repulsion of heavy metal ions in water, and promoting the removal of heavy metal ions in water by the positive osmosis membrane. The forward osmosis membrane has good performance for removing heavy metal ions under different conditions, and the interception rate of the five heavy metal ions, such as Cu ²⁺ , Ni ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ , exceeds 99.5%.

Preferably, in the present embodiment, the base film material is polyvinylidene fluoride or polysulfone, and more preferably, the base film has an average pore diameter of 200 to 250 μm.

In a specific embodiment, a previously prepared polyvinylidene fluoride film having an average pore diameter of 220 μm is fixed on the experimental apparatus with the front side facing upward; then the polyamide-amine dendrimer is mixed with m-phenylenediamine. The aqueous solution was poured into the above apparatus, and after immersion for 2-5 minutes, the solution was poured out, and the solution on the surface of the base film was blotted with a clean filter paper.

Preferably, in the aqueous solution in which the polyamide-amine dendrimer is mixed with m-phenylenediamine, the mass concentration of the polyamide-amine dendrimer is 0.1-0.4%, and the mass concentration of m-phenylenediamine is 0.2%. . For example, the polyamide-amine dendrimer has a mass concentration of 0.1%, 0.2%, 0.3% or 0.4%.

Further, the triphenyltrichlorochloride solution is poured into the surface of the base film soaked with the mixed aqueous solution of the polyamide-amine dendrimer and the m-phenylenediamine, and after 1-3 minutes, the solution is poured off to obtain a new high-performance positive osmosis. membrane.

In the process, the polyamide-amine dendrimer is interfacially polymerized with m-phenylenediamine and trimestriol on the upper surface of the base film to prepare a PAMAM-modified high-performance forward osmosis membrane. The reaction is as follows:

Preferably, the solvent in the trimestriol solution is n-hexane. More preferably, the isophthalic trichloride solution has a mass concentration of 0.2%.

Further, after the step 20, the high performance forward osmosis membrane is placed in a dry box, dried at 60-80 ° C for 3-6 min, and taken out, and used.

Further, the present invention also provides a high performance forward osmosis membrane which is prepared by the above preparation method.

Still further, the present invention also provides an application of a high performance forward osmosis membrane in which a high performance forward osmosis membrane produced by the above preparation method is used to remove heavy metal ions in water.

The preparation method of a forward osmosis membrane of the present invention is further explained below by way of specific examples:

Example 1

A PAMAM modified composite forward osmosis membrane (TFC type FO membrane) was prepared by interfacial polymerization on a polyvinylidene fluoride (TMC) mixed solution of PAMAM and m-phenylenediamine (MPD) on a polyvinylidene fluoride film.

1), preparing a mixed aqueous solution of PAMAM and MPD of four different mass concentrations, the mass concentration of the PAMAM is 0.1%, 0.2%, 0.3% and 0.4%, respectively, and the mass concentration of the MPD is 2%;

2), completely immersing the upper surface of the polyvinylidene fluoride film in the mixed aqueous solution of the above four different mass concentrations of PAMAM and MPD, and after 2 minutes, the solution is poured off, and the solution remaining on the surface of the base film is removed by the filter paper;

3) The upper surface of the base film soaked in the mixed aqueous solution of PAMAM and MPD was immersed in a n-hexane solution having a mass concentration of 0.2 wt% TMC, and the solution was removed after 1 min of reaction. Throughout the process, the basement membrane was fixed in the experimental apparatus to allow only interfacial polymerization of the upper surface of the membrane. The freshly prepared TFC-type FO film was placed in an oven at 80 ° C for 5 minutes. Finally, the prepared conventional TFC-type FO film was stored in DI water; in the prepared forward osmosis membrane, a membrane with 0.1% PAMAM was recorded as M-1, and a membrane with 0.2% PAMAM was recorded as M- 2. The membrane to which 0.3% PAMAM was added was designated as M-3, and the membrane to which 0.4% of PAMAM was added was designated as M-4.

The above-mentioned new high-performance forward osmosis membrane preparation, because PAMAM has a nanometer-sized molecular structure can increase the relative free volume of the polyamide layer, and the primary and tertiary amine groups on PAMAM are regularly arranged along the molecular chain and the macromolecular single Dispersibility, the molecular cavity of PAMAM can act as a water channel, resulting in enhanced water permeability of the membrane. PAMAM has a large number of terminal amine groups, and the unreacted free amine group can adsorb with heavy metal ions in water. After adsorption of heavy metals, it may enhance the positive charge of the selective layer and enhance the rejection of cations in water.

Example 2

A PAMAM-modified TFC-type FO film was prepared by interfacial polymerization on a polyvinylidene fluoride film with a mass concentration of 1.0% PAMAM aqueous solution (without MPD) and trimesochloride (TMC) on a polyvinylidene fluoride film, denoted as M-5. The preparation steps were similar to those of Example 1.

Example 3

A TFC-type FO film was prepared by interfacial polymerization on a polyvinylidene fluoride film by using an aqueous solution of MPD having a mass concentration of 0.2% and trimer trichloride (TMC), which was designated as M-0, and the preparation procedure was similar to that of Example 1.

Further, the high-performance forward osmosis membranes prepared in the above Examples 1, 2, and 3 were tested for water flux, reverse salt flux, and retention of heavy metal particles. The test methods are as follows:

DI (deionized) water was used as a raw material solution, and 0.5, 1.0, 1.5, 2.0 M MgCl ₂ solution was used as a draw solution to obtain different osmotic pressures. A laboratory-made FO filter device tests the J _w and J _{s of the} TFC-type FO film. The increase in the volume of the draw liquid is monitored by changes in the level of the liquid level, and changes in the salt concentration in the feed liquid can be detected in real time using a conductivity meter. The pure water flux J _w (Lm ^-2 h ^-1 , denoted as LMH) and the reverse salt flux J _s (gm ^-2 h ^-1 , expressed as gMH) are calculated according to the formula:

Where J _w (LMH) is the pure water flux, ΔV (L) is the permeate volume of pure water, Δt(h) is the test time, and A _m (m ² ) is the effective area of the membrane (9 cm ² ). J _s is the pure water flux gMH, V _f,t , V _f,i (L) respectively represent the volume of the raw material liquid changing with time in the FO process, C _f,t , C _f,i (mol L ^-1 ) The concentration of the substance before and after the change in the salt concentration (MgCl ₂ ) in the raw material liquid is shown.

Studying the properties of TFC-type FO membrane for removal of heavy metal ions, preparing raw material liquids containing five heavy metal ions, Cu ²⁺ , Ni ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ , five heavy metal ions in each raw material liquid The concentrations were 1.0 g/L, 2.0 g/L and 5.0 g/L, respectively. The pH of the heavy metal ion wastewater was simulated at room temperature. The heavy metal ion rejection R _h (%) is defined as the percentage of heavy metal ions trapped in the raw material liquid by the TFC type FO membrane. The rejection R _h (%) is calculated as:

Where C _d (g/L) is the concentration of heavy metal ions in the drawdown after the test, V _d (L) is the volume after the draw test, V _p (L) is the total volume of the permeate, C _f ( g/L) is the concentration of heavy metals in the raw material liquid. C _d (g/L) and C _f (g/L) were tested by inductively coupled plasma optical emission spectrometry.

The results measured by the above method are as follows:

As shown in Fig. 2 and Fig. 3, the water flux of the TFC-type FO film increases first and then decreases with the increase of the PAMAM addition amount. The PAMAM has an approximately spherical nano-molecular structure, which can increase the relative free volume of the PA selective layer. Excessive addition causes the relative free volume of the PA selective layer to be too large to increase the reverse salt flux, so that the osmotic pressure difference decreases and the water flux shows a decreasing trend. In the AL-DS (cortex toward the draw solution) and AL-FS (cortex toward the feed solution) mode, when the draw solution concentration is 2M, the water flux of the M-2 membrane is 1.7 and 1.6 times that of the M-0 membrane, respectively. The reverse salt flux of the M-2 membrane was similar to that of the M-0 membrane. The M-5 film shows that the water flux is significantly reduced, and the reverse salt flux is significantly increased. Due to the large molecular size of the PAMAM, the denseness of the PA selective layer is low, and the selectivity of the membrane is lowered.

It can be seen from Fig. 4 and Fig. 5 that both the water flux and the reverse salt flux of the M-0 and M-2 membranes increase as the concentration of the extract increases. In the AL-DS and AL-FS modes, when the concentration of the pumping solution is 2M MgCl ₂ , the water flux of the M-2 membrane is 38.5 and 21.3 LMH, respectively, and the water flux of the M-0 membrane is 21.3 and 13.5 LMH, respectively. The reverse salt flux is basically the same. The AL-DS has a higher water flux than the AL-FS mode, and the internal concentration polarization (ICP) phenomenon in the AL-FS mode is severe. The results show that the M-2 film has good FO properties.

As can be seen from Figures 6 and 7, in the AL-DS and AL-FS modes, the water flux of the M-2 membrane is approximately 35.2 and 18.5 LMH, respectively, while the water flux of the M-0 membrane is approximately 20.0 and 11.8, respectively. LMH. For example, when the concentration of the extract is 2M, the water flux of the five heavy metal ions Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ in the M-2 membrane in the AL-FS mode is 18.6, 19.0, 18.2, 18.3 and 18.5 LMH. In the AL-DS and AL-FS modes, the water flux of the M-2 membrane was increased by 50.0% and 54.2%, respectively, compared to the water flux of the M-0 membrane. Since the PAMAM approximately spherical nanostructures increase the relative free volume, hydrophilicity, and water molecular channels of the PA selective layer, the separation performance of the M-2 film is significantly improved.

It can be seen from Fig. 8 and Fig. 9 that the M-2 and M-0 films have similar rejection rates for the five heavy metal ions. In the AL-DS and AL-FS modes, the heavy metal ion rejection rates of the two films are about 98.1% and 99.5%. When the concentration of the extract is 2M, the interception rate of the five heavy metal ions Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , Zn ²⁺ and Cd ²⁺ in the AL-FS mode is 99.8%, respectively. 99.5%, 99.5%, 99.7% and 99.6%. The results show that PAMAM can significantly improve the water flux and selectivity of the TFC-type FO membrane. Since the PAMAM molecule has a large nano-size and a large number of terminal amino groups, it can increase the relative free volume and hydrophilicity of the PA layer and reduce the passage of water molecules. The resistance of the membrane increases the water flux, and the complexation of the free terminal amino group of PAMAM with the heavy metal ion in the PA selective layer promotes the retention of heavy metal ions.

Example 4

A PAMAM-modified composite forward osmosis membrane (TFC-type FO membrane) was prepared by interfacial polymerization of PAMAM and m-phenylenediamine (MPD) mixed aqueous solution and trimesotrichloride (TMC) on a polysulfone-based membrane.

1), preparing a mixed aqueous solution of PAMAM and MPD of four different mass concentrations, the mass concentration of the PAMAM is 0.1%, 0.2%, 0.3% and 0.4%, respectively, and the mass concentration of the MPD is 3%;

2) completely immersing the upper surface of the polysulfone-based film in a mixed aqueous solution of PAMAM and MPD of the above four different mass concentrations, and after 2 minutes, pouring the solution, and removing the solution remaining on the surface of the base film with a filter paper;

3) The upper surface of the base film soaked in the mixed aqueous solution of PAMAM and MPD was immersed in a n-hexane solution having a mass concentration of 0.3% TMC, and the solution was removed after 1 minute of reaction. Throughout the process, the basement membrane was fixed in the experimental apparatus to allow only interfacial polymerization of the upper surface of the membrane. The newly prepared TFC-type FO film was dried in an incubator at 80 ° C for 5 minutes to obtain a high-performance forward osmosis membrane.

In summary, the present invention adopts a polyamide-amine dendrimer (PAMAM) in-situ modification one-step method to prepare a polyamide forward osmosis membrane, and the preparation steps are simple and easy to control. In the high performance forward osmosis membrane prepared by the invention, PAMAM can increase the relative free volume and hydrophilicity of the polyamide layer, thereby increasing the water flux of the forward osmosis membrane; at the same time, the free amine group on the PAMAM in the polyamide layer can adsorb. Heavy metal ions increase the positive charge of the membrane to enhance the repulsion of heavy metal ions in water, and promote the removal of heavy metal ions from water by the positive osmosis membrane.

It is to be understood that the application of the present invention is not limited to the above-described examples, and those skilled in the art can make modifications and changes in accordance with the above description, all of which are within the scope of the appended claims.

Claims

A method for preparing a high performance forward osmosis membrane, comprising the steps of:

A, the upper surface of the base film is immersed in an aqueous solution of a polyamide-amine dendrimer mixed with m-phenylenediamine, and after 2-5 min, the base film is taken out and the solution on the surface of the base film is blotted dry with a filter paper;

B. The upper surface of the base film obtained in the step A is further immersed in the triphenyltrichlorochloride solution, and after 1-3 minutes, the solution is poured off to obtain a high performance forward osmosis membrane.
The method for preparing a high performance forward osmosis membrane according to claim 1, wherein the base film material is polyvinylidene fluoride or polysulfone.
The method of producing a high performance forward osmosis membrane according to claim 1, wherein the base film has an average pore diameter of from 200 to 250 μm.
The method for preparing a high performance forward osmosis membrane according to claim 1, wherein the quality of the polyamide-amine dendrimer in the aqueous solution in which the polyamide-amine dendrimer is mixed with m-phenylenediamine The concentration was 0.1-0.4%, and the mass concentration of m-phenylenediamine was 0.2%.
The method for producing a high performance forward osmosis membrane according to claim 1, wherein the solvent in the trimestriol solution is n-hexane.
The method for producing a high performance forward osmosis membrane according to claim 1, wherein the isophthalic trichloride solution has a mass concentration of 0.2%.
The method for preparing a high performance forward osmosis membrane according to claim 1, wherein the step B further comprises the following steps:

C. The high-performance forward osmosis membrane is placed in a dry box and dried after being dried at 60-80 ° C for 3-6 min.
A high performance forward osmosis membrane obtained by the preparation method according to any one of claims 1-7.
A high performance forward osmosis membrane for use in the removal of heavy metal ions from water by the high performance forward osmosis membrane produced by the preparation process of any of claims 1-7.