阅读说明：本技术 一种纤维素醚反渗透膜及其制备方法 (Cellulose ether reverse osmosis membrane and preparation method thereof ) 是由 瞿睿 徐强强 李爱祥 卢舒晴 于 2021-10-14 设计创作，主要内容包括：一种纤维素醚反渗透膜及其制备方法。提供了一种具有优良的耐酸碱性的一种纤维素醚反渗透膜及其制备方法。本发明中使用改进的溶媒法制备氰乙基纤维素,氰乙基基团在纤维素单元上均匀取代,使产物具有优良的耐酸碱性能；所制备的反渗透膜能够在酸碱环境下正常运作,有较长的使用寿命,避免了极性废水处理时频繁更换膜产品所带来的成本增加、出水水质不稳定带来的风险增加。(A cellulose ether reverse osmosis membrane and a preparation method thereof. A cellulose ether reverse osmosis membrane having excellent acid and alkali resistance and a method for preparing the same are provided. In the invention, the cyanoethyl cellulose is prepared by using an improved solvent method, and cyanoethyl groups are uniformly substituted on a cellulose unit, so that the product has excellent acid and alkali resistance; the prepared reverse osmosis membrane can normally operate in an acid-base environment, has longer service life, and avoids the increase of cost and the increase of risk caused by unstable water quality of effluent water due to frequent membrane replacement in polar wastewater treatment.)

1. A cellulose ether reverse osmosis membrane and a preparation method thereof are characterized by comprising the following steps:

s1: preparing cyanoethyl cellulose:

s1.1 alkalization one: mixing and stirring 600ml of isopropanol and a NaOH solution with the pH =12 in a ratio of 1:1, observing the state of the solution, slowing down the stirring speed, adding 100g of cellulose, accelerating the stirring speed to ensure uniform alkalization, keeping the mixture at room temperature for 1 hour, and performing suction filtration to complete primary alkalization;

s1.2 alkalization II: mixing and stirring 500ml of isopropanol and benzene 7:3, adding the first alkalized product, keeping the mixture at room temperature for 1.5 hours, performing suction filtration and squeezing, and completing second alkalization to obtain alkali cellulose;

s1.3, placing the alkali cellulose in a three-neck flask, slowly dripping 1000ml of acrylonitrile from the upper part of a constant-pressure separating funnel, heating to 50 ℃, refluxing for 2 hours, neutralizing with acetic acid to terminate the reaction, washing a product, and drying to obtain a final product, namely cyanoethyl cellulose;

s2: preparing a casting solution:

mixing cellulose ether, solvent and additive to prepare a casting solution, and stirring the solution uniformly at 65 ℃ to form a clear and transparent solution;

s3: preparing a base film by a phase inversion method:

blade-coating the casting solution prepared in the step S2 on the surface of a support, and finishing the liquid-solid phase conversion process in a 5% ethanol solution to obtain a basement membrane taking cyanoethyl cellulose as a matrix;

s4: preparing a reverse osmosis membrane by an interfacial polymerization method:

sequentially soaking and drying the base membrane by using an aqueous phase solution and an oil phase solution prepared from m-phenylenediamine and isophthaloyl dichloride to obtain the cellulose ether reverse osmosis membrane.

2. The reverse osmosis membrane of cellulose ether and the preparation method thereof according to claim 1, wherein the cellulose ether is one or a mixture of cyanoethyl cellulose and ethyl cyanoethyl cellulose.

3. The reverse osmosis membrane of cellulose ethers and the process for preparing the same according to claim 1, wherein the solvent comprises one or a mixture of dimethylformamide and dimethylsulfoxide.

4. The cellulose ether reverse osmosis membrane and the preparation method thereof according to claim 1, wherein the additive is one or a mixture of polyethylene glycol, acetone, lithium chloride and nano TiO 2.

5. The cellulose ether reverse osmosis membrane and the preparation method thereof according to claim 1, wherein the aqueous solution is dried after staying on the surface of the supporting layer for 10-30S after being coated in step S4.

6. The cellulose ether reverse osmosis membrane and the preparation method thereof according to claim 1, wherein the oil phase solution is coated in step S4, and then the coated oil phase solution is kept on the surface of the supporting layer for 20-60S and then dried in vacuum at 50-65 ℃ for 5 min.

7. The reverse osmosis membrane made of cellulose ether and the preparation method thereof according to claim 1, wherein the weight ratio of the cellulose ether to the solvent to the additive is (11-15): (80-89): 0-5).

8. The cellulose ether reverse osmosis membrane and the preparation method thereof according to claim 1, wherein in step S4, m-phenylenediamine is prepared in a molar ratio of: an aqueous phase solution and an oil phase solution of isophthaloyl dichloride (= (1-2): (2-4.5)).

9. A cellulose ether reverse osmosis membrane is characterized by comprising a non-woven fabric support body, a cellulose ether-based membrane layer and an interface polymerization layer which are sequentially connected.

10. The cellulose ether reverse osmosis membrane of claim 9, wherein the cellulose ether-based membrane layer has a thickness of from 30 to 60 microns.

Technical Field

The invention relates to a reverse osmosis membrane preparation technology, in particular to a cellulose ether reverse osmosis membrane and a preparation method thereof.

Background

The reverse osmosis membrane technology takes the pressure difference between two sides of the membrane as a driving force, so that a solvent (usually water) selectively permeates the membrane to realize the separation process of the solvent and the solute, has the advantages of no relation to phase change, low energy consumption, small occupied area, simple operation, strong adaptability, less environmental pollution and the like, and has good prospects in the fields of high-industrial wastewater treatment, reclaimed water reuse, seawater desalination and the like. Cellulose acetate as a reverse osmosis membrane material has the advantages of good chlorine resistance, high breaking strength, pollution resistance and the like, and is widely applied to the field of commercial membranes.

At present, industrial waste water has extremely acid, extremely alkaline, the characteristic of high pollution according to the source difference, and these waste water all need carry out the preliminary treatment before getting into membrane system, and the membrane that uses must have fine acid and alkali-resistance and anti pollution characteristic, otherwise needs often to change or maintain, increases use cost.

The currently commonly used reverse osmosis membrane materials with acid-base resistance and pollution resistance are mainly inorganic materials, such as ceramics, metals, titanium dioxide and the like, but the inorganic materials are brittle and easy to break, the membrane product is difficult to process, the raw material cost is high, and the separation performance is not ideal; some researchers put forward that the hybrid membrane is prepared by using inorganic and organic materials in proportion, but most of the hybrid membrane stays in a theoretical stage, and the stability of the hybrid membrane product is greatly reduced due to the compatibility problem of the organic and inorganic materials in the actual production, so that the hybrid membrane is not suitable for large-scale production and commercial use.

Disclosure of Invention

The invention provides a cellulose ether reverse osmosis membrane with excellent acid and alkali resistance and a preparation method thereof.

The technical scheme of the invention is as follows: a cellulose ether reverse osmosis membrane and a preparation method thereof comprise the following steps:

s1: preparing cyanoethyl cellulose:

s1.1 alkalization one: mixing and stirring 600ml of isopropanol and a NaOH solution with the pH =12 in a ratio of 1:1, observing the state of the solution, slowing down the stirring speed, adding 100g of cellulose, accelerating the stirring speed to ensure uniform alkalization, keeping the mixture at room temperature for 1 hour, and performing suction filtration to complete primary alkalization;

s1.2 alkalization II: mixing and stirring 500ml of isopropanol and benzene 7:3, adding the first alkalized product, keeping the mixture at room temperature for 1.5 hours, performing suction filtration and squeezing, and completing second alkalization to obtain alkali cellulose;

s1.3, placing the alkali cellulose in a three-neck flask, slowly dripping 1000ml of acrylonitrile from the upper part of a constant-pressure separating funnel, heating to 50 ℃, refluxing for 2 hours, neutralizing with acetic acid to terminate the reaction, washing a product, and drying to obtain a final product, namely cyanoethyl cellulose;

s2: preparing a casting solution:

mixing cellulose ether, solvent and additive to prepare a casting solution, and stirring the solution uniformly at 65 ℃ to form a clear and transparent solution;

s3: preparing a base film by a phase inversion method:

blade-coating the casting solution prepared in the step S2 on the surface of a support, and finishing the liquid-solid phase conversion process in a 5% ethanol solution to obtain a basement membrane taking cyanoethyl cellulose as a matrix;

s4: preparing a reverse osmosis membrane by an interfacial polymerization method:

sequentially soaking and drying the base membrane by using an aqueous phase solution and an oil phase solution prepared from m-phenylenediamine and isophthaloyl dichloride to obtain the cellulose ether reverse osmosis membrane.

The cellulose ether is one or a mixture of cyanoethyl cellulose and ethyl-cyanoethyl cellulose.

The solvent comprises one or two mixtures of dimethylformamide and dimethyl sulfoxide.

The additive is one or a mixture of polyethylene glycol, acetone, lithium chloride and nano TiO 2.

And in the step S4, the water phase solution is dried after staying on the surface of the supporting layer for 10-30S after being coated.

And step S4, after the oil phase solution is coated, the oil phase solution is required to stay on the surface of the supporting layer for 20-60S and then is dried in vacuum at 50-65 ℃ for 5 min.

The weight ratio of the cellulose ether, the solvent and the additive is (11-15): (80-89): 0-5).

In step S4, m-phenylenediamine is prepared in a molar ratio: an aqueous phase solution and an oil phase solution of isophthaloyl dichloride (= (1-2): (2-4.5)).

A cellulose ether reverse osmosis membrane comprises a non-woven fabric support body, a cellulose ether-based membrane layer and an interfacial polymerization layer which are sequentially connected.

The thickness of the cellulose ether base film layer is 30-60 micrometers.

In the invention, the cyanoethyl cellulose is prepared by using an improved solvent method, and cyanoethyl groups are uniformly substituted on a cellulose unit, so that the product has excellent acid and alkali resistance; the prepared reverse osmosis membrane can normally operate in an acid-base environment, has longer service life, and avoids the increase of cost and the increase of risk caused by unstable water quality of effluent water due to frequent membrane replacement in polar wastewater treatment.

Drawings

FIG. 1 is a schematic cross-sectional view of a cellulose ether;

in the figure, 1 is an interfacial polymerization layer, 2 is a cellulose ether-based film layer, and 3 is a nonwoven fabric support.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

A cellulose ether reverse osmosis membrane and a preparation method thereof comprise the following steps:

s1: preparing cyanoethyl cellulose (CEC) by adopting a solvent method:

s1.1 alkalization one: mixing and stirring 600ml of isopropanol and a NaOH solution with the pH =12 in a ratio of 1:1, observing the state of the solution, slowing down the stirring speed, adding 100g of cellulose, accelerating the stirring speed to ensure uniform alkalization, keeping the mixture at room temperature (20-25 ℃) for 1 hour, and performing suction filtration to complete primary alkalization;

s1.2 alkalization II: mixing and stirring 500ml of isopropanol and benzene 7:3, adding the first alkalized product, keeping the mixture at room temperature for 1.5 hours, performing suction filtration and squeezing, and completing second alkalization to obtain alkali cellulose;

s1.3, placing the alkali cellulose in a three-neck flask, slowly dripping 1000ml of acrylonitrile from the upper part of a constant-pressure separating funnel, heating to 50 ℃, refluxing for 2 hours, neutralizing with acetic acid to terminate the reaction, washing a product, and drying to obtain a final product, namely cyanoethyl cellulose;

s2: preparing a casting solution:

mixing cellulose ether, solvent and additive to prepare a casting solution, and stirring the solution uniformly at 65 ℃ to form a clear and transparent solution;

s3: preparing a base film by a phase inversion method:

coating the casting solution prepared in the step S2 on the surface of a support body at a speed of 3m/min, and finishing a liquid-solid phase conversion process in a 5% ethanol solution to obtain a basement membrane taking cyanoethyl cellulose as a matrix;

s4: preparing a reverse osmosis membrane by an interfacial polymerization method:

sequentially soaking and drying the base membrane by using an aqueous phase solution and an oil phase solution prepared from m-phenylenediamine and isophthaloyl dichloride to obtain the cellulose ether reverse osmosis membrane.

The cellulose ether is one or a mixture of cyanoethyl cellulose and ethyl-cyanoethyl cellulose.

The solvent comprises one or two mixtures of dimethylformamide and dimethyl sulfoxide.

The additive is polyethylene glycol (molecular weight 400-10000), acetone, lithium chloride and nano TiO₂One or a mixture of several of them.

And in the step S4, the water phase solution is dried after staying on the surface of the supporting layer for 10-30S after being coated.

And step S4, after the oil phase solution is coated, the oil phase solution is required to stay on the surface of the supporting layer for 20-60S and then is dried in vacuum at 50-65 ℃ for 5 min.

The weight ratio of the cellulose ether, the solvent and the additive is (11-15): (80-89): 0-5).

Further optimizing, wherein the weight ratio of the cellulose ether to the solvent to the additive is 11:89: 0;

further optimizing, wherein the weight ratio of the cellulose ether to the solvent to the additive is 15:80: 5;

in step S4, m-phenylenediamine is prepared in a molar ratio: an aqueous phase solution and an oil phase solution of isophthaloyl dichloride (= (1-2): (2-4.5)). The solute of the aqueous phase solution is m-phenylenediamine, and the solute of the oil phase solution is isophthaloyl dichloride.

Further optimizing, when the solute of the aqueous phase solution is m-phenylenediamine, the ratio of m-phenylenediamine: the isophthaloyl dichloride is 1: 2.5;

further optimizing, when the solute of the oil phase solution is isophthaloyl dichloride, the ratio of m-phenylenediamine to m-phenylenediamine is as follows: isophthaloyl dichloride is 1.5: 4.

A cellulose ether reverse osmosis membrane comprises a non-woven fabric support body 3, a cellulose ether-based membrane layer 2 and an interfacial polymerization layer 1 which are sequentially connected.

The thickness of the cellulose ether base film layer is 30-60 micrometers.

Each glucose ring of natural cellulose molecule has three hydroxyls respectively located on the 2 nd, 3 rd and 6 th carbon atoms, and the reaction capacities are different from each other for oxidation, esterification, etherification, graft copolymerization and the like, and the reacted cellulose derivative has correspondingly different characteristics, for example, cellulose sulfonate has adhesiveness, hydroxyethyl cellulose has good ionic compatibility, and cyanoethyl cellulose has good acid-base resistance and dielectric property. Due to c₂When the hydroxyl is etherified, the reaction capacity is highest and is about 2 times faster than other hydroxyl, so that the types and positions of functional groups can be set, and the substitution degree and the substitution distribution of the functional groups are controlled, so that the chemical structure of etherified cellulose is designed on a base ring, the acid and alkali resistance of the cyanoethyl cellulose is improved, and the cyanoethyl cellulose is used for a membrane separation material.

The solvent method takes an organic solvent as a medium, two alkalization processes are carried out to inhibit the side reaction to the maximum extent, the heat transfer and mass transfer in the reaction process are uniform, the utilization rate of an etherifying agent is improved compared with the traditional aqueous medium method, and the substitution degree and uniformity of the product are greatly improved.

Example one

S1: preparing cyanoethyl cellulose (CEC) by adopting a solvent method:

alkalization: mixing and stirring 600ml of isopropanol and a NaOH solution with the pH =12 in a ratio of 1:1, observing the state of the solution, slowing down the stirring speed, adding 100g of cellulose, accelerating the stirring speed to ensure uniform alkalization, keeping the mixture at room temperature (20-25 ℃) for 1 hour, and performing suction filtration to complete primary alkalization;

mixing and stirring 500ml of isopropanol and benzene 7:3, adding the first alkalized product, keeping the mixture at room temperature for 1.5 hours, performing suction filtration and squeezing, and completing second alkalization to obtain alkali cellulose;

cyanoethylation (etherification): placing the alkali cellulose in a three-neck flask, slowly dropwise adding 1000ml of acrylonitrile from the upper part of a constant-pressure separating funnel, heating to 50 ℃, refluxing for 2 hours, neutralizing with acetic acid to terminate the reaction, washing a product, and drying to obtain a final product, namely cyanoethyl cellulose.

S2: preparing a casting solution:

cyanoethyl cellulose, dimethylformamide and polyethylene glycol (400) are mixed according to the weight ratio of 12:84:4 to prepare a casting solution, and the casting solution is uniformly stirred at 65 ℃ to be in a color-clear and transparent state.

S3: preparing a base film by a phase inversion method:

and (3) blade-coating the casting solution on the surface of the support body at the speed of 3m/min, and finishing the liquid-solid phase conversion process in a 5% ethanol solution to obtain the basement membrane taking cyanoethyl cellulose as a matrix.

S4: preparing a reverse osmosis membrane by an interfacial polymerization method:

preparing m-phenylenediamine in a molar ratio: and (3) sequentially soaking and drying the base membrane in an oil-water phase solution of isophthaloyl dichloride = (1: 2.5) to obtain the reverse osmosis membrane described by the invention.

Comparative example

Preparation of conventional Cellulose Acetate (CA) film

(1) Mixing cellulose acetate: dimethylformamide: polyethylene glycol (400) is mixed according to the weight ratio of 12:84:4 to prepare a casting solution, and the casting solution is uniformly stirred at 65 ℃ to be in a color-clear and transparent state.

(2) Preparing a base film by a phase inversion method:

and (3) blade-coating the casting solution on the surface of the support body at the speed of 3m/min, and finishing the liquid-solid phase conversion process in deionized water to obtain the base film taking cellulose acetate as a matrix.

(3) Preparing a reverse osmosis membrane by an interfacial polymerization method:

preparing m-phenylenediamine in a molar ratio: and (3) sequentially soaking and drying the base membrane in an oil-water phase solution of isophthaloyl dichloride = (1: 2.5) to obtain the reverse osmosis membrane described by the invention.

Acid and alkali resistance test of film

The membrane was immersed in a 0.5mol/L hydrochloric acid solution and a sodium hydroxide solution having a pH of 12 to 14 at room temperature for several days, respectively, and compared with a conventional Cellulose Acetate (CA) membrane and a polyamide membrane of comparative examples.

Table 1: the cyanoethyl cellulose membrane prepared by the embodiment of the invention

Table 2: conventional Cellulose Acetate (CA) membranes

As can be seen from the data in the table, the reverse osmosis membrane prepared by the embodiment of the invention is soaked in the strong acid solution for 7 days, the membrane surface is unchanged, and the salt rejection rate is slightly reduced; when the membrane is soaked in the alkaline solution for 5 days, the membrane surface is unchanged, the membrane surface slightly swells after about 7 days, and the salt rejection rate is reduced in the period.

The conventional CA membrane prepared by the comparative example swells after being soaked in an acid/alkali solution for 3 days, and the surface of the conventional CA membrane decays after 7 days, which shows that CA is easy to hydrolyze, and cyanoethyl groups have good acid-base hydrolysis resistance.

The above embodiments are only embodiments disclosed in the present disclosure, but the scope of the disclosure is not limited thereto, and the scope of the disclosure should be determined by the scope of the claims.