Forward osmosis membranes, methods of making and using the same

Abstract

The application relates to a membrane separation technology and discloses a forward osmosis membrane and a preparation method and application thereof. The forward osmosis membrane comprises a support layer formed by modified nanocellulose and an active layer connected with the support layer, the active layer is located on one side of the support layer, and the modified nanocellulose is at least one selected from C6 modified carboxymethyl cellulose, dialdehyde carboxymethyl cellulose, amino acid-C6 modified carboxymethyl cellulose and amino acid-dialdehyde carboxymethyl cellulose. The forward osmosis membrane adopts the modified nanocellulose as the support layer, can guarantee high water flux and retention rate, has good heavy metal adsorption effect, and has good mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to membrane separation technology, in particular to a forward osmosis membrane and a preparation method and application thereof. BACKGROUND

[0002] In recent years, with the continuous increase of world population and the rapid advancement of industrialization, water resources, as the source of life, are increasingly scarce, and China is also facing serious water shortages, serious pollution and low reuse rates. To cope with water resource pressure, various water treatment technologies have been developed, including renewable water reuse and seawater desalination technologies.

[0003] Forward osmosis (FO) membrane separation technology is a new type of membrane separation technology that has developed rapidly in recent years, and its applications in seawater desalination, heavy metal concentration and recovery, drinking water preparation, seawater desalination, wastewater treatment and food processing are increasing. Compared with other traditional technologies, FO technology does not require external pressure, and water molecules spontaneously flow from the raw material liquid (low osmotic pressure) to the draw liquid (high osmotic pressure) through the forward osmosis membrane under high osmotic pressure difference, thereby removing pollutants. Therefore, FO technology has the advantages of high rejection rate, relatively low energy consumption, low membrane fouling and high water recovery rate.

[0004] However, as one of the key FO technologies, forward osmosis membranes have many problems that are difficult to solve, such as low water flux, low desalination rate and difficulty in removing heavy metals in water. At the same time, with the development of FO technology, higher requirements are placed on the functionality of the membrane, so the development of functional forward osmosis membranes has far-reaching significance. SUMMARY

[0005] The purpose of the present application is to overcome the problems existing in the prior art, provide a forward osmosis membrane and a preparation method and application thereof, which uses modified nanocellulose as a support layer, can ensure high water flux and rejection rate, has good heavy metal adsorption effect, and has good mechanical strength.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides a forward osmosis membrane, which comprises a support layer formed by modified nanocellulose and an active layer connected with the support layer, and the active layer is located on one side of the support layer; the modified nanocellulose is selected from at least one of C6 modified carboxylated cellulose, dialdehyde carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde carboxylated cellulose.

[0007] Preferably, the modified nanocellulose is amino acid-C6 modified carboxylated cellulose and / or amino acid-dialdehyde carboxylated cellulose.

[0008] Preferably, the thickness of the forward osmosis membrane is 140-180 μm, and the thickness of the active layer is 150-180 nm.

[0009] Preferably, the preparation method of the C6-modified carboxylated cellulose comprises the following steps: mixing nanocellulose with 2,2,6,6-tetramethylpiperidine oxide, a bromide salt and a hypochlorite salt in a reaction solvent I, and then adjusting the pH to a constant value by using a lye.

[0010] Preferably, the weight ratio of the nanocellulose, the 2,2,6,6-tetramethylpiperidine oxide, the bromide salt and the hypochlorite salt is 1:0.01-0.2:0.02-0.2:0.2-19; and the condition of adjusting the pH to a constant value comprises: the pH is 10-11, and the rotation speed is 300-500 rpm.

[0011] Preferably, the preparation method of the dialdehyde group carboxylated cellulose comprises the following steps: mixing the C6-modified carboxylated cellulose with a periodate salt in a reaction solvent II to perform a mixing reaction I.

[0012] Preferably, the weight ratio of the nanocellulose and the periodate salt is 1:0.5-8; and the condition of the mixing reaction I comprises: avoiding light, the temperature is 30-50℃, the rotation speed is 700-900 rpm, the time is 2.5-5h, and the pH is 3.5-4.5.

[0013] Preferably, the preparation method of the amino acid-C6-modified carboxylated cellulose comprises the following steps: mixing the C6-modified carboxylated cellulose with an amino acid in the presence of a reaction solvent III and a stabilizer I to perform a mixing reaction II, and then adding a reducing agent I for reduction.

[0014] Preferably, the weight ratio of the nanocellulose and the amino acid is 1:0.9-4; and the condition of the mixing reaction II comprises: the temperature is 30-50℃, and the time is 5-8h.

[0015] Preferably, the preparation method of the amino acid-dialdehyde group carboxylated cellulose comprises the following steps: mixing the dialdehyde group carboxylated cellulose with the amino acid in the presence of a reaction solvent IV and a stabilizer II to perform a mixing reaction III, and then adding a reducing agent II for reduction.

[0016] Preferably, the weight ratio of the nanocellulose and the amino acid is 1:0.9-4; and the condition of the mixing reaction III comprises: the temperature is 30-50℃, and the time is 5-8h.

[0017] Preferably, the stabilizer I and the stabilizer II are dimethyl sulfoxide; and the reducing agent I and the reducing agent II are sodium borohydride.

[0018] Preferably, the amino acid is at least one selected from the group consisting of lysine, glycine, proline, glutamic acid and tyrosine, more preferably lysine.

[0019] Preferably, the active layer is a polyamide active layer.

[0020] Preferably, the polyamide active layer is prepared by interfacial polymerization of a polyamine and a polyacyl chloride; the mass concentration ratio of the polyamine to the polyacyl chloride is 0.2-5:1.

[0021] Preferably, the polyamine is at least one selected from the group consisting of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine and m-phenylene triamine; the polyacyl chloride is at least one selected from the group consisting of m-phenylene tricarbonyl chloride, m-phenylene dicarbonyl chloride and p-phenylene dicarbonyl chloride.

[0022] The second aspect of the present application provides a preparation method of the forward osmosis membrane of the first aspect, comprising the following steps:

[0023] (1) dissolving modified nanocellulose in water to obtain a spinning solution, and performing electrospinning treatment on the spinning solution to obtain a support layer formed by the modified nanocellulose;

[0024] (2) connecting the support layer formed by the modified nanocellulose with an active layer to obtain a forward osmosis membrane;

[0025] Preferably, the active layer is located on one side of the support layer; the modified nanocellulose is at least one selected from the group consisting of C6 modified carboxylated cellulose, dialdehyde carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde carboxylated cellulose.

[0026] Preferably, in step (1), the concentration of the modified nanocellulose in the spinning solution is 2-10 wt%.

[0027] Preferably, the electrospinning treatment is performed under the following conditions: the spinning voltage is 13-17 kV, the distance between the spinneret and the receiving roller is 5-10 cm, and the time is 0.5-2 h.

[0028] Preferably, in step (2), the preparation method of the active layer comprises the following steps: contacting the support layer with a solution containing a polyamine and a solution containing a polyacyl chloride, and then performing heat treatment.

[0029] Preferably, the contacting is performed under the following conditions: the temperature is 10-40℃, and the time is 10-60 s.

[0030] Preferably, the heat treatment is performed under the following conditions: the temperature is 50-120℃, and the time is 1-10 min.

[0031] The third aspect of the present application provides application of the forward osmosis membrane of the first aspect or the forward osmosis membrane prepared by the preparation method of the second aspect in heavy metal ion adsorption.

[0032] Preferably, the heavy metal ions are arsenic and / or lead.

[0033] Through the technical solution, the present application has the beneficial effects that the forward osmosis membrane provided by the present application includes a support layer formed by modified nanocellulose and an active layer connected with the support layer, the active layer is located on one side of the support layer, at least one of C6 modified carboxylated cellulose, dialdehyde-based carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde-based carboxylated cellulose obtained by modification is formed into the support layer, the internal concentration polarization phenomenon of the support layer can be slowed down, the prepared forward osmosis membrane has good heavy metal ion adsorption effect while ensuring high water flux and retention rate, and has good mechanical strength. DETAILED DESCRIPTION

[0034] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values of the endpoints of the ranges and the separate numerical values are not to be construed as being critical to the application. Any numerical value, however, can be expressed or represented as being approximate, by

[0035] The first aspect of the present application provides a forward osmosis membrane, the forward osmosis membrane includes a support layer formed by modified nanocellulose and an active layer connected with the support layer, the active layer is located on one side of the support layer; the modified nanocellulose is at least one selected from C6 modified carboxylated cellulose, dialdehyde-based carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde-based carboxylated cellulose.

[0036] The inventor of the present application found in the research process that by modifying nanocellulose, at least one of C6 modified carboxylated cellulose, dialdehyde-based carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde-based carboxylated cellulose obtained by modification is formed into the support layer, the prepared forward osmosis membrane has good heavy metal adsorption effect while ensuring high water flux and retention rate, and has good mechanical strength.

[0037] In the present application, the modified nanocellulose can be C6 modified carboxylated cellulose alone, or dialdehyde group carboxylated cellulose alone, or amino acid-C6 modified carboxylated cellulose alone, or amino acid-dialdehyde group carboxylated cellulose alone; or a mixture of C6 modified carboxylated cellulose and dialdehyde group carboxylated cellulose, or a mixture of C6 modified carboxylated cellulose and amino acid-C6 modified carboxylated cellulose, or a mixture of C6 modified carboxylated cellulose and amino acid-C6 modified carboxylated cellulose, or a mixture of dialdehyde group carboxylated cellulose and amino acid-C6 modified carboxylated cellulose, or a mixture of dialdehyde group carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose, or a mixture of amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose; or a mixture of C6 modified carboxylated cellulose, dialdehyde group carboxylated cellulose and amino acid-C6 modified carboxylated cellulose, or a mixture of C6 modified carboxylated cellulose, dialdehyde group carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose, or a mixture of C6 modified carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose, or a mixture of dialdehyde group carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose; or a mixture of C6 modified carboxylated cellulose, dialdehyde group carboxylated cellulose, amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose. When the modified nanocellulose is a mixture, the weight ratio between the components can be selected within a wide range.

[0038] According to the present application, preferably, the modified nanocellulose is amino acid-C6 modified carboxylated cellulose and / or amino acid-dialdehyde group carboxylated cellulose. The inventors have found that in this preferred specific embodiment, amino groups are introduced into the support layer, which can bind with metal ions to form colored complexes, thereby improving the adsorption capacity of the support layer for heavy metal ions, and further improving the adsorption effect of the forward osmosis membrane for heavy metal ions.

[0039] According to the present application, in order to further improve the adsorption capacity of the support layer for heavy metal ions, when the modified nanocellulose is a mixture of amino acid-C6 modified carboxylated cellulose and amino acid-dialdehyde group carboxylated cellulose, the weight ratio of amino acid-C6 modified carboxylated cellulose to amino acid-dialdehyde group carboxylated cellulose in the modified nanocellulose is preferably 1:1-5, and can be 1:1, 1:2, 1:3, 1:4, 1:5, or any value between the above two values.

[0040] According to the application, in order to further improve the water flux and rejection rate of the forward osmosis membrane, preferably, the thickness of the forward osmosis membrane is 140-180 μm, specifically can be 140 μm, 160 μm, 180 μm, or any value between the above two values; the thickness of the active layer is 150-180 nm, specifically can be 150 nm, 160 nm, 170 nm, 180 nm, or any value between the above two values.

[0041] According to the application, preferably, the preparation method of the C6 modified carboxylated cellulose comprises the following steps: mixing nanocellulose with 2,2,6,6-tetramethylpiperidine oxide, bromide salt and hypochlorite salt in reaction solvent I, and then adjusting the pH to a constant value by using lye. The inventors found that under this preferred embodiment, the surface of the nanocellulose is selectively oxidized, so that the surface of the nanocellulose contains carboxyl groups, which can improve the adsorption capacity of the support layer for heavy metal ions, and further improve the adsorption effect of the forward osmosis membrane for heavy metal ions.

[0042] According to the application, nanocellulose is a nanometer-sized cellulose derivative product derived from natural plant cellulose, has a fine nanostructure, contains a large number of oxygen-containing functional groups on the surface, is easy to modify to improve reactivity, and can be commercially available.

[0043] According to the application, in order to further improve the adsorption capacity of the support layer formed by the C6 modified carboxylated cellulose for heavy metal ions, preferably, the weight ratio of the nanocellulose, the 2,2,6,6-tetramethylpiperidine oxide, the bromide salt and the hypochlorite salt is 1:0.01-0.2:0.02-0.2:0.2-19. The conditions for adjusting the pH to a constant value include: the pH is 10-11, specifically can be 10, 10.5, 11, or any value between the above two values; the rotation speed is 300-500 rpm, specifically can be 300 rpm, 400 rpm, 500 rpm, or any value between the above two values.

[0044] According to the application, the types of bromide salt and hypochlorite salt are not limited, specifically, the bromide salt is sodium bromide, and the hypochlorite salt is sodium hypochlorite.

[0045] According to the application, the type of lye is not limited, specifically, the lye is sodium hydroxide solution.

[0046] In the present application, under alkaline conditions, when 2,2,6,6-tetramethylpiperidine oxide coexists with sodium bromide and sodium hypochlorite, the primary alcohol hydroxyl group at the C6 position on the surface of nanocellulose can be selectively converted into a carboxyl group. The large number of uniformly distributed carboxyl groups on the surface are beneficial to increasing the solubility and absorbability of nanocellulose in water, forming fiber welding between fibers, being conducive to the stability of the support layer structure, and at the same time, can improve the mechanical strength.

[0047] According to the present application, preferably, the preparation method of the dialdehyde group carboxylated cellulose comprises the following steps: mixing the C6 modified carboxylated cellulose with a periodate salt in a reaction solvent II to perform a mixing reaction I. The inventors found that in this preferred specific embodiment, the C2 and C3 position hydroxyl groups on the C6 modified carboxylated cellulose can be selectively ring-opening oxidized, introducing aldehyde groups with reducing properties, giving more chemical functional groups, increasing the cross-linking effect and hydrogen bond connection between fibers, improving the mechanical strength of the forward osmosis membrane, and through the synergistic adsorption effect of carboxyl and aldehyde groups, improving the adsorption capacity of dialdehyde group carboxylated cellulose for heavy metal ions, and further improving the adsorption effect of the forward osmosis membrane for heavy metal ions.

[0048] According to the present application, in order to further improve the adsorption capacity of the support layer formed by the dialdehyde group carboxylated cellulose for heavy metal ions, preferably, the weight ratio of the nanocellulose to the periodate salt is 1:0.5-8, specifically can be 1:0.5, 1:2, 1:4, 1:6, 1:8, or any value between the above two values; the conditions of the mixing reaction I include: avoiding light, temperature is 30-50℃, specifically can be 30℃, 40℃, 50℃, or any value between the above two values; rotation speed is 700-900rpm, specifically can be 700rpm, 800rpm, 900rpm, or any value between the above two values; time is 2.5-5h, specifically can be 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, or any value between the above two values; pH is 3.5-4.5, specifically can be 3.5, 4, 4.5, or any value between the above two values.

[0049] According to the present application, the type of periodate salt is not limited, specifically, the periodate salt is sodium periodate.

[0050] According to the present application, preferably, the preparation method of the amino acid-C6 modified carboxylated cellulose comprises the following steps: after the mixing reaction II of the C6 modified carboxylated cellulose and the amino acid in the presence of the reaction solvent III and the stabilizer I, a reducing agent I is added for reduction. The inventors have found that in this preferred specific embodiment, the amino acid group is connected to the C6 modified carboxylated cellulose through Schiff base reaction, which strengthens the cross-linking effect and hydrogen bond connection between fibers, and improves the adsorption capacity of the support layer to heavy metal ions and the mechanical strength of the forward osmosis membrane.

[0051] According to the present application, in order to further improve the adsorption capacity of the support layer formed by the amino acid-C6 modified carboxylated cellulose to heavy metal ions, preferably, the weight ratio of the nanocellulose to the amino acid is 1:0.9-4, which can be specifically 1:0.9, 1:1, 1:2, 1:3, 1:4, or any value between the above two values. The conditions of the mixing reaction II include: the temperature is 30-50℃, which can be specifically 30℃, 40℃, 50℃, or any value between the above two values; the time is 5-8h, which can be specifically 5h, 6h, 7h, 8h, or any value between the above two values.

[0052] According to the present application, preferably, the preparation method of the amino acid-dialdehyde group carboxylated cellulose comprises the following steps: after the mixing reaction III of the dialdehyde group carboxylated cellulose and the amino acid in the presence of the reaction solvent IV and the stabilizer II, a reducing agent II is added for reduction. The inventors have found that in this preferred specific embodiment, the amino acid group is connected to the dialdehyde group carboxylated cellulose through Schiff base reaction, which strengthens the cross-linking effect and hydrogen bond connection between fibers, and improves the adsorption capacity of the support layer to heavy metal ions and the mechanical strength of the forward osmosis membrane.

[0053] According to the present application, in order to further improve the adsorption capacity of the support layer formed by the amino acid-dialdehyde group carboxylated cellulose to heavy metal ions, preferably, the weight ratio of the nanocellulose to the amino acid is 1:0.9-4, which can be specifically 1:0.9, 1:1, 1:2, 1:3, 1:4, or any value between the above two values. The conditions of the mixing reaction III include: the temperature is 30-50℃, which can be specifically 30℃, 40℃, 50℃, or any value between the above two values; the time is 5-8h, which can be specifically 5h, 6h, 7h, 8h, or any value between the above two values.

[0054] According to the present application, preferably, the reaction solvent I, the reaction solvent II, the reaction solvent III and the reaction solvent IV are all water, the inventors find that, in this preferred embodiment, the nanocellulose and the modified nanocellulose can be better dispersed in the reaction solvent, the modification effect of the nanocellulose is improved, and the yield of the modified nanocellulose is further improved.

[0055] According to the present application, preferably, the stabilizer I and the stabilizer II are dimethyl sulfoxide; and the reducing agent I and the reducing agent II are sodium borohydride. The inventors find that, in this preferred embodiment, the dimethyl sulfoxide can stabilize the structure of the nanocellulose, and the sodium borohydride can reduce the excess carboxyl groups in the reaction system into hydroxyl groups.

[0056] In the present application, the obtained C6-modified carboxylated cellulose dispersion, dialdehyde carboxylated cellulose dispersion, amino acid-C6-modified carboxylated cellulose dispersion and amino acid-dialdehyde carboxylated cellulose dispersion can also be purified. The method of purification is not limited, and can be a conventional selection in the art, and exemplarily, the dialysis method is selected for purification.

[0057] According to the present application, the specific method of dialysis is not limited, and can be a conventional selection in the art, for example, the modified nanocellulose is loaded into a dialysis bag, and then the dialysis bag is placed in pure water. Preferably, the dialysis purification conditions include: temperature of 20-30℃, and time of 2-3 days. In this preferred embodiment, the modified nanocellulose with higher purity can be prepared.

[0058] According to the present application, in order to extract the modified nanocellulose, the method of the present application further comprises: after dialysis, the solvent of the dispersion in the dialysis bag is removed, for example, evaporation is performed by using a rotary evaporator or freeze-drying is performed.

[0059] In the present application, freeze-drying is vacuum freeze-drying, and the conditions of freeze-drying are not limited, and can be a conventional selection in the art.

[0060] According to the present application, preferably, the amino acid is selected from at least one of lysine, glycine, proline, glutamic acid and tyrosine, and more preferably, the amino acid is lysine.

[0061] According to the present application, preferably, the active layer is a polyamide active layer. The inventors find that, in this preferred embodiment, the polyamide active layer can improve the adsorption capacity of the forward osmosis membrane to the heavy metal ions.

[0062] According to the present application, in order to further improve the adsorption capacity of the forward osmosis membrane to heavy metal ions, preferably, the polyamide active layer is formed by interfacial polymerization of a polyamine and a polyacyl chloride; the mass concentration ratio of the polyamine to the polyacyl chloride is 0.2-5:1, and specifically can be 0.2:1, 1:1, 2:1, 3:1, 4:1, 5:1, or any value between the above two values.

[0063] In the present application, the term "interfacial polymerization" refers to a polymerization reaction performed at the interface of two mutually immiscible solutions each of which dissolves two monomers (or at the side of the interfacial organic phase).

[0064] According to the present application, the type of the polyamine is not particularly limited and can be an amine compound generally used in the art for preparing a polyamide. Preferably, the polyamine is selected from at least one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine, and m-phenylene triamine. In addition, when performing the interfacial polymerization, the polyamine is preferably used in the form of a solution, and as a solvent for dissolving the polyamine, a solvent immiscible with the solvent for dissolving the polyacyl chloride described later and inert to the polyamine can be used. As such a solvent, at least one of water, methanol, and acetonitrile can be used, and water is preferred.

[0065] In addition, the concentration of the polyamine in the polyamine solution is not particularly limited and can be a conventional selection in the art. Preferably, the concentration of the polyamine in the polyamine solution is 1-5% by weight, and specifically can be 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, or any value between the above two values.

[0066] According to the present application, the type of the polyacyl chloride is not particularly limited and can be an acyl chloride compound generally used in the art for preparing a polyamide. Preferably, the polyacyl chloride is selected from at least one of m-phenylene tricarbonyl chloride, m-phenylene dicarbonyl chloride, and p-phenylene dicarbonyl chloride. In addition, when performing the interfacial polymerization, the polyacyl chloride is preferably used in the form of a solution, and as a solvent for dissolving the polyacyl chloride, a solvent immiscible with the solvent for dissolving the polyamine described above and inert to the polyacyl chloride can be used. As such a solvent, for example, an organic solvent can be used, and as the organic solvent, at least one of n-hexane, dodecane, and n-heptane is preferred, and n-hexane is more preferred.

[0067] In addition, the concentration of the polyamine in the polyamine solution is not particularly limited and can be a conventional selection in the art. Preferably, the concentration of the polyamine in the polyamine solution is 1-5% by weight, and specifically can be 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, or any value between the above two values.

[0068] The second aspect of the present application provides a method for preparing a forward osmosis membrane, comprising the following steps:

[0069] (1) dissolving modified nanocellulose in water to obtain a spinning solution, and performing electrospinning treatment on the spinning solution to obtain a support layer formed by the modified nanocellulose;

[0070] (2) connecting the support layer formed by the modified nanocellulose with an active layer to obtain a forward osmosis membrane;

[0071] wherein the active layer is located on one side of the support layer; and the modified nanocellulose is at least one selected from C6-modified carboxylated cellulose, dialdehyde carboxylated cellulose, amino acid-C6-modified carboxylated cellulose, and amino acid-dialdehyde carboxylated cellulose.

[0072] According to the present application, in order to further improve the water flux, retention rate and adsorption effect of the forward osmosis membrane, preferably, in step (1), the concentration of the modified nanocellulose in the spinning solution is 2-10 wt%, specifically, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, or any value between the above two values.

[0073] According to the present application, preferably, the conditions of the electrospinning treatment include: the spinning voltage is 13-17 kV, specifically, 13 kV, 14 kV, 15 kV, 16 kV, 17 kV, or any value between the above two values; the distance between the spinneret and the receiving roller is 5-10 cm, specifically, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or any value between the above two values; and the time is 0.5-2 h, specifically, 0.5 h, 1 h, 1.5 h, 2 h, or any value between the above two values.

[0074] According to the present application, in step (2), as a method for forming a polyamide active layer on one surface of the support layer, it can be obtained by interfacial polymerization of a polyamine and a polyacyl chloride. The way of interfacial polymerization of a polyamine and a polyacyl chloride to obtain a polyamide active layer is not particularly limited, and can be various conventional contact methods used in the art for interfacial polymerization of a polyamine and a polyacyl chloride. Preferably, in step (2), the preparation method of the active layer comprises the following steps: contacting the active layer with a solution containing a polyamine and a solution containing a polyacyl chloride, and then performing heat treatment.

[0075] In the present application, the conditions of the contacting are not limited and can be selected conventionally in the art. Preferably, the conditions of the contacting include: the temperature is 10-40℃, specifically can be 10℃, 20℃, 30℃, 40℃, or any value between the above two values; the time is 10-60s, specifically can be 10s, 20s, 30s, 40s, 50s, 60s, or any value between the above two values. Exemplarily, the single side of the support layer is immersed in the aqueous solution containing the polyamine to make it fully contact, drained, then subjected to interfacial polymerization reaction with the organic solution containing the polyacyl chloride, and finally subjected to heat treatment to prepare.

[0076] In the present application, the conditions of the heat treatment are not limited and can be selected conventionally in the art. Preferably, the conditions of the heat treatment include: the temperature is 50-120℃, specifically can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, or any value between the above two values; the time is 1-10min, specifically can be 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, or any value between the above two values.

[0077] The third aspect of the present application provides the use of the forward osmosis membrane of the first aspect or prepared by the method of the second aspect in adsorption of heavy metal ions.

[0078] According to the present application, preferably, the heavy metal ions are arsenic and / or lead.

[0079] According to a particularly preferred embodiment of the present application, a method for preparing a forward osmosis membrane is provided, comprising the following steps:

[0080] (1) dissolving the modified nanocellulose in water to obtain a spinning solution, and subjecting the spinning solution to electrospinning treatment under the conditions of a spinning voltage of 13-17kV and a distance between the spinning head and the receiving roller of 5-10cm for 0.5-2h to obtain a support layer formed by the modified nanocellulose;

[0081] (2) contacting the support layer formed by the modified nanocellulose with a solution containing a polyamine and a solution containing a polyacyl chloride under the conditions of a temperature of 10-40℃ for 10-60s, removing the excess solution by purging, and then heat treating under the conditions of a temperature of 50-120℃ for 1-10min to obtain the forward osmosis membrane;

[0082] wherein the active layer is located on one side of the support layer; the modified nanocellulose is lysine-C6 modified carboxylated cellulose and / or lysine-dialdehyde carboxylated cellulose;

[0083] The preparation method of the C6 modified carboxylated cellulose comprises the following steps: mixing nanocellulose, 2,2,6,6-tetramethylpiperidine oxide, bromide salt, hypochlorite salt and water, and then adjusting the pH to 10-11 by using lye under the condition of 300-500 rpm; the weight ratio of nanocellulose, 2,2,6,6-tetramethylpiperidine oxide, bromide salt and hypochlorite salt is 1:0.01-0.2:0.02-0.2:0.2-19;

[0084] The preparation method of the dialdehyde group carboxylated cellulose comprises the following steps: mixing the C6 modified carboxylated cellulose, periodate salt and water, and then mixing and reacting under the condition of 30-50℃, 700-900 rpm, pH 3.5-4.5 and light shielding for 2.5-5h; the weight ratio of nanocellulose and periodate salt is 1:0.5-8;

[0085] The preparation method of the lysine-C6 modified carboxylated cellulose comprises the following steps: mixing the C6 modified carboxylated cellulose and lysine in the presence of dimethyl sulfoxide and water at 30-50℃ for 5-8h, and then adding sodium borohydride for reduction; the weight ratio of nanocellulose and lysine is 1:0.9-4;

[0086] The preparation method of the lysine-dialdehyde group carboxylated cellulose comprises the following steps: mixing the dialdehyde group carboxylated cellulose and lysine in the presence of dimethyl sulfoxide and water at 30-50℃ for 5-8h, and then adding sodium borohydride for reduction; the weight ratio of nanocellulose and lysine is 1:0.9-4;

[0087] The polyamine is at least one selected from m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine and m-phenylenediamine; the polyacyl chloride is at least one selected from m-phenylenediamine, p-phenylenediamine and p-phenylenediamine; the mass concentration ratio of the polyamine and the polyacyl chloride is 0.2-5:1.

[0088] In the above particularly preferred embodiment, the preparation method of the forward osmosis membrane is simple, the process stability is good, and the operation is simple.

[0089] The application will be described in detail below through examples.

[0090] In the following examples and comparative examples, the nanocellulose is purchased from Zhejiang Jinggaohao Green Nanomaterials Co., Ltd., and the model number is CNF-H1; the lysine is purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., and the model number is L823654; in the absence of special instructions, the remaining raw materials are also from commercial purchase.

[0091] Example 1

[0092] (1) Accurately weigh 0.068 g of 2,2,6,6-tetramethylpiperidine oxide into 1116 mL of ionized water, stir until uniform, disperse 4 g of nanocellulose in the water, accurately weigh 0.132 g of sodium bromide, and add to the nanocellulose dispersion. Add 44.64 g of sodium hypochlorite to the nanocellulose dispersion, stir until uniform using a glass rod, measure the pH, and if it is less than 10, adjust the pH to above 10 using 0.4 mol / L sodium hydroxide solution. Stir the dispersion using a magnetic stirrer at a speed of 400 rpm until the pH no longer decreases, and if it does decrease, adjust the pH to above 10 using 0.4 mol / L sodium hydroxide solution and continue stirring until the reaction is complete. Neutralize using 0.5 mol / L hydrochloric acid and purify by dialysis to obtain a C6 modified carboxylated cellulose dispersion. Concentrate the C6 modified carboxylated cellulose dispersion by rotary evaporation to a volume of 100 mL. Accurately weigh 16 g of sodium periodate, dissolve, and transfer to a 200 mL volumetric flask, and make up to volume. Take 167 mL of the sodium periodate solution and add to the C6 modified carboxylated cellulose dispersion, avoid light during the process, and ensure that the pH is maintained at about 4. Stir using a magnetic stirrer at a speed of 800 rpm and a temperature of 40°C for 3 h. After stirring is complete, wash away the excess sodium periodate solution using 6 mL of ethylene glycol, adjust the pH to 8, and stir at a speed of 800 rpm for 30 min. Purify by dialysis to obtain a dialdehyde carboxylated cellulose dispersion.

[0093] (2) Concentrate the dialdehyde carboxylated cellulose dispersion by rotary evaporation to a volume of 100 mL, accurately weigh 12 g of lysine, and add to the dispersion. Stir until uniform using a glass rod, add 3 mL of dimethyl sulfoxide, and stir using a magnetic stirrer at a speed of 400 rpm and a temperature of 40°C for 6 h. After stirring is complete, add 3 g of sodium borohydride, and react until no gas bubbles are produced. Purify by dialysis and lyophilize to obtain lysine-dialdehyde carboxylated cellulose.

[0094] (3) Dissolve the lysine-dialdehyde carboxylated cellulose in water to obtain a spinning solution containing 5% by weight of lysine-dialdehyde carboxylated cellulose. Perform electrospinning under the following conditions: a spinning voltage of 15 kV, a distance between the spinneret and the receiving roller of 7 cm, and a spinning time of 1 h to obtain a lysine modified nanocellulose membrane, which is the support layer.

[0095] (4) Fix the support layer with a glass and contact it with a 2.5% by weight m-phenylenediamine aqueous solution. After 20 s of contact at 25°C, remove the excess solution by blowing on one side of the support layer. Then contact the support layer with a 3% by weight tris- (4-formylphenyl) methane chloroform solution in n-hexane. After 20 s of contact at 25°C, remove the excess solution by blowing on the same side of the support layer, and place the membrane in an oven and heat at 70°C for 3 min to obtain a forward osmosis membrane.

[0096] Example 2

[0097] (1) Accurately weigh 0.04 g of 2,2,6,6-tetramethylpiperidine oxide into 1116 mL of ionized water, stir until uniform, disperse 4 g of nanocellulose in the water, and accurately weigh 0.4 g of sodium bromide into the nanocellulose dispersion. Add 4 g of sodium hypochlorite to the nanocellulose dispersion, stir until uniform using a glass rod, and measure the pH. If the pH is less than 10, adjust the pH to 10 or more using 0.4 mol / L sodium hydroxide solution. Stir the dispersion using a magnetic stirrer at 500 rpm until the pH no longer decreases. If the pH decreases, adjust the pH to 10 or more using 0.4 mol / L sodium hydroxide solution and continue stirring until the reaction is complete. Neutralize using 0.5 mol / L hydrochloric acid and purify by dialysis to obtain a C6-modified carboxylated cellulose dispersion. Concentrate the C6-modified carboxylated cellulose dispersion by rotary evaporation to a volume of 100 mL, and divide the C6-modified carboxylated cellulose dispersion into two equal portions, each of 50 mL. Accurately weigh 8.56 g of sodium periodate into a 200 mL volumetric flask, dissolve, and make up to volume. Take 50 mL of the sodium periodate solution and add to one of the 50 mL portions of the C6-modified carboxylated cellulose dispersion, keeping it away from light and maintaining the pH at about 4. Stir using a magnetic stirrer at 900 rpm and 30°C for 2.5 h. Wash the excess sodium periodate solution with 6 mL of ethylene glycol, adjust the pH to 8, and stir at 900 rpm for 30 min. Purify by dialysis to obtain a dialdehyde carboxylated cellulose dispersion.

[0098] (2) Concentrate the dialdehyde carboxylated cellulose dispersion by rotary evaporation to a volume of 50 mL, accurately weigh 8 g of lysine into the dispersion, stir until uniform using a glass rod, add 1 mL of dimethyl sulfoxide, and stir using a magnetic stirrer at 400 rpm and 30°C for 8 h. After stirring is complete, add 1.5 g of sodium borohydride, and react until no gas bubbles are produced. Purify by dialysis and lyophilize to obtain lysine-dialdehyde carboxylated cellulose. In the other 50 mL portion of the C6-modified carboxylated cellulose dispersion obtained in step (1), add 8 g of lysine, stir until uniform using a glass rod, add 1 mL of dimethyl sulfoxide, and stir using a magnetic stirrer at 400 rpm and 30°C for 8 h. After stirring is complete, add 1.5 g of sodium borohydride, and react until no gas bubbles are produced. Purify by dialysis and lyophilize to obtain lysine-C6-modified carboxylated cellulose.

[0099] (3) Dissolve the lysine-dialdehyde carboxylated cellulose and the lysine-C6-modified carboxylated cellulose in water to obtain a spinning solution containing 2% by weight of lysine-dialdehyde carboxylated cellulose and 2% by weight of lysine-C6-modified carboxylated cellulose. Perform electrospinning at a spinning voltage of 13 kV and a distance of 5 cm between the spinneret and the receiving roller for 0.5 h to obtain a lysine-modified nanocellulose membrane, which is the support layer.

[0100] (4) The support layer is clamped with a glass and contacted with a 1 wt% m-phenylenediamine aqueous solution, after 60 s of contact at 40 °C, the excess solution is removed by blowing on one side of the support layer; then the support layer is contacted again with a 5 wt% mesitylene chloride in n-hexane solution, after 60 s of contact at 40 °C, the excess solution is removed by blowing on the same side of the support layer, the membrane is put into an oven and heated at 50 °C for 10 min to obtain a forward osmosis membrane.

[0101] Example 3

[0102] (1) 0.8 g of 2,2,6,6-tetramethylpiperidine oxide was accurately weighed and dissolved in 1116 mL of ionized water, 4 g of nanocellulose was dispersed in water, 0.8 g of sodium bromide was accurately weighed and added to the nanocellulose dispersion. 74.4 g of sodium hypochlorite was added dropwise to the nanocellulose dispersion, and a glass rod was used to stir until uniform, the pH was measured, if less than 10, 0.4 mol / L sodium hydroxide solution was used to adjust the pH to above 10. The dispersion was stirred at a speed of 300 rpm using a magnetic stirrer until the pH no longer decreased, if it decreased, 0.4 mol / L sodium hydroxide solution was used to adjust the pH to above 10 and continue to stir until the reaction was complete. Neutralization was performed using 0.5 mol / L hydrochloric acid, and dialysis purification was performed to obtain a C6 modified carboxylated cellulose dispersion.

[0103] (2) The C6 modified carboxylated cellulose dispersion was rotary evaporated to 100 mL, 3.9 g of lysine was accurately weighed and added to the dispersion, after stirring uniformly with a glass rod, 3 mL of dimethyl sulfoxide was added, and stirring was performed at a speed of 400 rpm and a temperature of 50 °C for 5 h using a magnetic stirrer. After stirring was completed, 3 g of sodium borohydride was added, and the reaction was continued until no gas bubbles were generated, dialysis purification was performed, and freeze-drying was performed to obtain lysine-C6 modified carboxylated cellulose.

[0104] (3) The lysine-C6 modified carboxylated cellulose was dissolved in water to obtain a spinning solution containing 10 wt% lysine-C6 modified carboxylated cellulose, electrospinning was performed under the following conditions: a spinning voltage of 17 kV, a distance between the spinneret and the receiving roller of 10 cm, and a processing time of 2 h to obtain a lysine modified nanocellulose membrane, which is the support layer.

[0105] (4) The support layer was clamped with a glass and contacted with a 5 wt% m-phenylenediamine aqueous solution, after 10 s of contact at 10 °C, the excess solution was removed by blowing on one side of the support layer; then the support layer was contacted again with a 1 wt% mesitylene chloride in n-hexane solution, after 10 s of contact at 10 °C, the excess solution was removed by blowing on the same side of the support layer, the membrane was put into an oven and heated at 120 °C for 1 min to obtain a forward osmosis membrane.

[0106] Example 4

[0107] A forward osmosis membrane was prepared according to the method of Example 1, except that in step (1), the preparation of the dialdehyde carboxylated cellulose was replaced by: 40 g of sodium periodate was accurately weighed, dissolved, transferred into a 200 mL volumetric flask, made up to volume, and 150 mL of the sodium periodate solution was added to the C6 modified carboxylated cellulose dispersion, avoiding light during the process and ensuring that the pH was maintained at about 4. A magnetic stirrer was used to stir at a speed of 700 rpm and a temperature of 50°C for 5 h. After stirring, 6 mL of ethylene glycol was used to wash away the excess sodium periodate solution, the pH was adjusted to 8, and stirring was performed at a speed of 700 rpm for 30 min. Dialysis purification was performed to obtain a dialdehyde carboxylated cellulose dispersion.

[0108] Example 5

[0109] A forward osmosis membrane was prepared according to the method of Example 1, except that steps (2) and (3) were replaced by:

[0110] (2) Rotary evaporation and freeze-drying of the dialdehyde carboxylated cellulose dispersion to obtain dialdehyde carboxylated cellulose.

[0111] (3) Dissolving the dialdehyde carboxylated cellulose in water to obtain a spinning solution containing 5% by weight of dialdehyde carboxylated cellulose, and performing electrospinning treatment for 1 h under the conditions of a spinning voltage of 15 kV and a distance between the spinneret and the receiving roller of 7 cm to obtain a modified nanocellulose membrane, which is the support layer.

[0112] Example 6

[0113] A forward osmosis membrane was prepared according to the method of Example 3, except that steps (2) and (3) were replaced by:

[0114] (2) Rotary evaporation and freeze-drying of the C6 modified carboxylated cellulose dispersion to obtain C6 modified carboxylated cellulose.

[0115] (3) Dissolving the C6 modified carboxylated cellulose in water to obtain a spinning solution containing 5% by weight of C6 modified carboxylated cellulose, and performing electrospinning treatment for 1 h under the conditions of a spinning voltage of 15 kV and a distance between the spinneret and the receiving roller of 7 cm to obtain a lysine-modified nanocellulose membrane, which is the support layer.

[0116] Example 7

[0117] A forward osmosis membrane was prepared according to the method of Example 2, except that steps (2) and (3) were replaced by:

[0118] (2) Dialysis and freeze-drying of dialdehyde carboxylated cellulose dispersion solution to obtain dialdehyde carboxylated cellulose. 4g lysine was accurately weighed and added to another 25mL dialdehyde carboxylated cellulose dispersion solution, and a glass rod was stirred uniformly. Then 1mL dimethyl sulfoxide was added, and the magnetic stirrer was stirred at a speed of 400rpm and a temperature of 40℃ for 8h. After the stirring was completed, 1.5g sodium borohydride was added, and the reaction was continued until no bubbles were generated. Dialysis purification and freeze-drying were performed to obtain lysine-dialdehyde carboxylated cellulose. The other 50mL C6 modified carboxylated cellulose dispersion solution obtained in step (1) was dialyzed and freeze-dried to obtain C6 modified carboxylated cellulose.

[0119] (3) Dissolving lysine-C6 modified carboxylated cellulose and dialdehyde carboxylated cellulose in water to obtain a spinning solution containing 1wt% lysine-C6 modified carboxylated cellulose and 4wt% dialdehyde carboxylated cellulose. Electrospinning treatment was performed under the conditions of a spinning voltage of 13kV and a distance between the spinneret and the receiving roller of 5cm for 0.5h to obtain a lysine modified nanocellulose membrane, which was the support layer.

[0120] Example 8

[0121] The forward osmosis membrane was prepared according to the method of Example 2, except that steps (2), (3) were replaced by:

[0122] (2) Dialysis and freeze-drying of dialdehyde carboxylated cellulose dispersion solution to obtain dialdehyde carboxylated cellulose. 4g lysine was accurately weighed and added to another 25mL dialdehyde carboxylated cellulose dispersion solution, and a glass rod was stirred uniformly. Then 1mL dimethyl sulfoxide was added, and the magnetic stirrer was stirred at a speed of 400rpm and a temperature of 40℃ for 8h. After the stirring was completed, 1.5g sodium borohydride was added, and the reaction was continued until no bubbles were generated. Dialysis purification and freeze-drying were performed to obtain lysine-dialdehyde carboxylated cellulose. The other 50mL C6 modified carboxylated cellulose dispersion solution obtained in step (1) was dialyzed and freeze-dried to obtain C6 modified carboxylated cellulose.

[0123] (3) Dissolving dialdehyde carboxylated cellulose, lysine-dialdehyde carboxylated cellulose and C6 modified carboxylated cellulose in water to obtain a spinning solution containing 1wt% dialdehyde carboxylated cellulose, 1wt% lysine-dialdehyde carboxylated cellulose and 1wt% C6 modified carboxylated cellulose. Electrospinning treatment was performed under the conditions of a spinning voltage of 13kV and a distance between the spinneret and the receiving roller of 5cm for 0.5h to obtain a lysine modified nanocellulose membrane, which was the support layer.

[0124] Example 9

[0125] The forward osmosis membrane was prepared according to the method of Example 2, except that steps (2), (3) were replaced by:

[0126] (2) Rotary-evaporate the dialdehyde carboxylated cellulose dispersion liquid to 50 mL, and divide the dialdehyde carboxylated cellulose dispersion liquid evenly into two portions, each of which is 25 mL. Rotary-evaporate and freeze-dry one of the 25 mL dialdehyde carboxylated cellulose dispersion liquid to obtain dialdehyde carboxylated cellulose. Accurately weigh 4 g of lysine and add it to the other 25 mL dialdehyde carboxylated cellulose dispersion liquid, stir it evenly with a glass rod, then add 1 mL of dimethyl sulfoxide, stir it for 8 h at a speed of 400 rpm and a temperature of 40°C using a magnetic stirrer, add 1.5 g of sodium borohydride after the stirring is completed, react until no bubbles are generated, purify by dialysis, and freeze-dry to obtain lysine-dialdehyde carboxylated cellulose. Divide the other 50 mL C6 modified carboxylated cellulose dispersion liquid obtained in step (1) into two portions, each of which is 25 mL, rotary-evaporate and freeze-dry one of the 25 mL C6 modified carboxylated cellulose dispersion liquid to obtain C6 modified carboxylated cellulose, and add 4 g of lysine to the other 25 mL C6 modified carboxylated cellulose dispersion liquid, stir it evenly with a glass rod, then add 1 mL of dimethyl sulfoxide, stir it for 8 h at a speed of 400 rpm and a temperature of 40°C using a magnetic stirrer, add 1.5 g of sodium borohydride after the stirring is completed, react until no bubbles are generated, purify by dialysis, and freeze-dry to obtain lysine-C6 modified carboxylated cellulose.

[0127] (3) Dissolve the dialdehyde carboxylated cellulose, C6 modified carboxylated cellulose, lysine-dialdehyde carboxylated cellulose, and lysine-C6 modified carboxylated cellulose in water to obtain a spinning liquid containing 1% by weight of dialdehyde carboxylated cellulose, 1% by weight of C6 modified carboxylated cellulose, 1% by weight of lysine-dialdehyde carboxylated cellulose, and 1% by weight of lysine-C6 modified carboxylated cellulose, and perform electrospinning treatment for 0.5 h under the conditions of a spinning voltage of 13 kV and a distance between the spinneret and the receiving roller of 5 cm to obtain a lysine-modified nanocellulose membrane, which is the support layer.

[0128] Example 10

[0129] The forward osmosis membrane is prepared according to the method of Example 1, except that in step (2), the amount of lysine is replaced by 0.4 g.

[0130] Example 11

[0131] The forward osmosis membrane is prepared according to the method of Example 1, except that step (3) is replaced by:

[0132] (3) Dissolve the dialdehyde carboxylated cellulose, C6 modified carboxylated cellulose, lysine-dialdehyde carboxylated cellulose, and lysine-C6 modified carboxylated cellulose in water to obtain a spinning liquid containing 1% by weight of dialdehyde carboxylated cellulose, 1% by weight of C6 modified carboxylated cellulose, 1% by weight of lysine-dialdehyde carboxylated cellulose, and 1% by weight of lysine-C6 modified carboxylated cellulose, and perform electrospinning treatment for 0.5 h under the conditions of a spinning voltage of 13 kV and a distance between the spinneret and the receiving roller of 5 cm to obtain a lysine-modified nanocellulose membrane, which is the support layer.

[0133] Comparative Example 1

[0134] (1) 4 g of nanocellulose was dispersed in 1116 mL of deionized water to obtain a nanocellulose dispersion, 12 g of lysine was added to the nanocellulose dispersion, stirred uniformly with a glass rod, and 3 mL of dimethyl sulfoxide was added, and stirring was performed at a rotation speed of 400 rpm and a temperature of 40°C for 6 h using a magnetic stirrer. After completion of stirring, 3 g of sodium borohydride was added to react until no gas bubbles were generated, and dialysis purification and freeze-drying were performed to obtain lysine-nanocellulose. The lysine-nanocellulose was dissolved in water to obtain a spinning solution containing 5% by weight of lysine-nanocellulose, and electrospinning was performed at a spinning voltage of 15 kV and a distance between the spinneret and the receiving roller of 7 cm for 1 h to obtain a lysine-nanocellulose membrane, which was used as a support layer.

[0135] (2) The support layer was clamped with a glass and contacted with a 2.5% by weight aqueous m-phenylenediamine solution, and after 10 s of contact at 25°C, the excess solution was removed by blowing on one side of the support layer. Then the support layer was contacted with a 3% by weight n-hexane solution containing trimesyl chloride, and after 10 s of contact at 25°C, the excess solution was removed by blowing on the same side of the support layer. The membrane was placed in an oven and heated at 70°C for 3 min to obtain a forward osmosis membrane.

[0136] Comparative Example 2

[0137] (1) The nanocellulose was dissolved in water to obtain a spinning solution containing 5% by weight of nanocellulose, and electrospinning was performed at a spinning voltage of 15 kV and a distance between the spinneret and the receiving roller of 7 cm for 1 h to obtain a modified nanocellulose membrane, which was used as a support layer.

[0138] (2) The support layer was clamped with a glass and contacted with a 2.5% by weight aqueous m-phenylenediamine solution, and after 10 s of contact at 25°C, the excess solution was removed by blowing on one side of the support layer. Then the support layer was contacted with a 3% by weight n-hexane solution containing trimesyl chloride, and after 10 s of contact at 25°C, the excess solution was removed by blowing on the same side of the support layer. The membrane was placed in an oven and heated at 70°C for 3 min to obtain a forward osmosis membrane.

[0139] Test Example 1

[0140] The thickness of the forward osmosis membranes prepared in Examples 1-11 and Comparative Examples 1-2 was measured using a scanning electron microscope, and the results are shown in Table 1.

[0141] Test Example 2

[0142] The forward osmosis performance of the forward osmosis membranes prepared in Examples 1-11 and Comparative Examples 1-2 was tested as follows:

[0143] (1) with 200 mL of 1 mol / L sodium chloride solution as the driving liquid, 1 L of deionized water as the feed liquid, the temperature being 25 DEG C, the liquid flow rate being 60 r / min, testing for 1 h, and the average value of the last 50 minutes being taken as the result, the water flux result being shown in Table 1;

[0144] (2) with 200 mL of 1 mol / L sodium chloride solution as the driving liquid, 1 L of 1000 ppm As as the feed liquid, the temperature being 25 DEG C, the liquid flow rate being 60 r / min, testing for 1 h, and the average value of the last 50 minutes being taken as the result, the forward osmosis flux, the reverse diffusion flux of sodium chloride, the retention rate of the membrane to As, the adsorption capacity of the membrane to As, etc. being shown in Table 2;

[0145] (3) with 200 mL of 1 mol / L sodium chloride solution as the driving liquid, 1 L of 1000 ppm Pb as the feed liquid, the temperature being 25 DEG C, the liquid flow rate being 60 r / min, testing for 1 h, and the average value of the last 50 minutes being taken as the result, the forward osmosis flux, the reverse diffusion flux of sodium chloride, the retention rate of the membrane to Pb, the adsorption capacity of the membrane to Pb, etc. being shown in Table 3.

[0146] Table 1

[0147]

[0148]

[0149] Table 2

[0150]

[0151] Table 3

[0152]

[0153] From the results of Table 1, Table 2 and Table 3, it can be seen that the forward osmosis membrane prepared by the embodiments 1-11 of the present application has excellent water flux, higher retention rate, and better adsorption effect on heavy metals compared with the forward osmosis membranes prepared by the comparative examples 1-2, and has great industrial application prospect.

[0154] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, the technical solutions of the present application can be subjected to various simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application, and all fall within the protection scope of the present application.

Claims

1. A forward osmosis membrane, characterized by, The forward osmosis membrane comprises a support layer formed by modified nanocellulose and an active layer connected with the support layer, and the active layer is located on one side of the support layer; The modified nanocellulose is amino acid-C6 modified carboxylated cellulose and / or amino acid-dialdehyde carboxylated cellulose; the thickness of the forward osmosis membrane is 140-180 μm, and the thickness of the active layer is 150-180 nm; the amino acid is lysine; and the active layer is a polyamide active layer. The preparation method of the C6 modified carboxylated cellulose comprises the following steps: mixing nanocellulose, 2,2,6,6-tetramethylpiperidinoxide, a bromide salt and a hypochlorite salt in a reaction solvent I, and then adjusting the pH to a constant value by using lye; the weight ratio of the nanocellulose, the 2,2,6,6-tetramethylpiperidinoxide, the bromide salt and the hypochlorite salt is 1:0.01-0.2:0.02-0.2:0.2-19; The preparation method of the dialdehyde carboxylated cellulose comprises the following steps: mixing the C6 modified carboxylated cellulose and a periodate salt in a reaction solvent II to perform a mixing reaction I; the weight ratio of the nanocellulose and the periodate salt is 1:0.5-8; The preparation method of the amino acid-C6 modified carboxylated cellulose comprises the following steps: mixing the C6 modified carboxylated cellulose and an amino acid in the presence of a reaction solvent III and a stabilizer I to perform a mixing reaction II, and then adding a reducing agent I for reduction; the weight ratio of the nanocellulose and the amino acid is 1:0.9-4; The preparation method of the amino acid-dialdehyde carboxylated cellulose comprises the following steps: mixing the dialdehyde carboxylated cellulose and the amino acid in the presence of a reaction solvent IV and a stabilizer II to perform a mixing reaction III, and then adding a reducing agent II for reduction; the weight ratio of the nanocellulose and the amino acid is 1:0.9-4; The stabilizer I and the stabilizer II are dimethyl sulfoxide; and the reducing agent I and the reducing agent II are sodium borohydride; The preparation method of the forward osmosis membrane comprises the following steps: (1) dissolving modified nanocellulose in water to obtain a spinning solution, and performing electrospinning treatment on the spinning solution under the conditions that the spinning voltage is 13-17 kV and the distance between the spinning head and the receiving roller is 5-10 cm for 0.5-2 h to obtain a support layer formed by the modified nanocellulose; the concentration of the modified nanocellulose in the spinning solution is 2-10% by weight; (2) connecting the support layer formed by the modified nanocellulose with an active layer to obtain a forward osmosis membrane.

2. The forward osmosis membrane of claim 1, wherein, The conditions for adjusting the pH to a constant value include: the pH is 10-11, and the rotation speed is 300-500 rpm; The conditions for the mixing reaction I include: avoiding light, the temperature is 30-50 ℃, the rotation speed is 700-900 rpm, the time is 2.5-5 h, and the pH is 3.5-4.

5.

3. The forward osmosis membrane of claim 2, wherein, The conditions for the mixing reaction II include: the temperature is 30-50 ℃, and the time is 5-8 h. The conditions for the mixing reaction III include: the temperature is 30-50 ℃, and the time is 5-8 h.

4. The forward osmosis membrane of claim 1, wherein, The polyamide active layer is prepared by interfacial polymerization of a polyamine and a polyacyl chloride; the mass concentration ratio of the polyamine to the polyacyl chloride is 0.2-5:1; The polyamine is selected from at least one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine and m-phenyl triamine; and the polyacyl chloride is selected from at least one of m-phenyl triformyl chloride, m-phenylenediformyl chloride and p-phenylenediformyl chloride.

5. The forward osmosis membrane of claim 1, wherein, In step (2), the preparation method of the active layer comprises the following steps: contacting the support layer with a solution containing a polyamine and a solution containing a polyacyl chloride, and then performing heat treatment.

6. The forward osmosis membrane of claim 5, wherein, The contacting condition comprises: temperature of 10-40℃, and time of 10-60s; The heat treatment condition comprises: temperature of 50-120℃, and time of 1-10min.

7. Application of the forward osmosis membrane according to any one of claims 1 to 6 in heavy metal ion adsorption; The heavy metal ion is arsenic and / or lead.

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