CN114931863A - Conductive forward osmosis membrane and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of water treatment membranes, and discloses a conductive forward osmosis membrane and a preparation method and application thereof. A tubular coal-based carbon membrane is used as a support layer, and polydopamine nanoparticles are first deposited on the tube by a vacuum filtration method. form the inner surface of the coal-based carbon membrane, and then prepare a continuous polyamide layer on the surface of polydopamine nanoparticles through interfacial polymerization to obtain a conductive forward osmosis membrane; the conductive forward osmosis membrane can be used in water treatment, for example, as a water treatment device or equipment filter membrane in . The conductive forward osmosis membrane prepared by the invention achieves good electrical conductivity and chemical stability, and can solve the problems of poor conductivity or unstable conductivity of the composite conductive forward osmosis membrane; it is applied to the field of sewage treatment, and combined with electrochemical action, it can alleviate the problem of Forward osmosis membrane fouling, thereby improving the performance of the membrane, has great theoretical significance and application value.

Description

A conductive forward osmosis membrane and its preparation method and application

technical field

The invention belongs to the technical field of water treatment membranes, and in particular relates to a conductive forward osmosis membrane and a preparation method and application thereof.

Background technique

Forward osmosis technology has been identified as one of the best strategies to alleviate the water shortage problem due to its advantages of low energy consumption and good effluent quality. At present, forward osmosis technology is widely used in the fields of seawater desalination and wastewater treatment. However, membrane fouling hinders the preservation of the performance of forward osmosis technology in long-term applications. Therefore, alleviating membrane fouling is one of the main ways to improve membrane performance. Electrochemical coupling membrane technology has received more and more attention in the control of membrane fouling due to its good characteristics such as easy process control, stable performance, and environmental friendliness.

The conductive forward osmosis membrane and electrochemical coupling have a significant effect on relieving membrane fouling under the electrostatic action and oxidation. Some researchers have proposed that the performance of the membrane can be improved by introducing conductive materials on the surface of the forward osmosis substrate or polyamide layer, but the conductivity or conductivity stability will affect the improvement of the membrane performance.

SUMMARY OF THE INVENTION

The invention aims to widen the preparation method of the conductive forward osmosis membrane, and provides a conductive forward osmosis membrane and its preparation method and application. The tubular coal-based carbon membrane with electrical conductivity is used as a support layer, and polydopamine nanoparticles are dispersed first. The liquid is suction filtered to the inner surface of the coal-based carbon membrane, and then a polyamide layer is obtained through interfacial polymerization. The prepared conductive forward osmosis membrane has good conductivity and stability, and can be effectively alleviated in the sewage treatment process when combined with electrochemical technology. Organic fouling of forward osmosis membranes.

In order to solve the above-mentioned technical problems, the present invention is realized through the following technical solutions:

According to one aspect of the present invention, a method for preparing a conductive forward osmosis membrane is provided. Using a tubular coal-based carbon membrane as a support layer, polydopamine nanoparticles are first deposited on the tubular coal-based carbon membrane by vacuum filtration. On the inner surface of the carbon membrane, a continuous polyamide layer is prepared on the surface of the polydopamine nanoparticles through interfacial polymerization to obtain a conductive forward osmosis membrane.

Further, include the following steps:

(1) preparing polydopamine nanoparticle dispersion;

(2) Preparation of polydopamine nanoparticle intermediate layer: passing the polydopamine nanoparticle dispersion obtained in step (1) through the tubular coal-based carbon membrane, and vacuum filtration to deposit polydopamine nanoparticles on the The inner surface of the tubular coal-based carbon membrane;

(3) Prepare a continuous polyamide layer on the surface of the polydopamine nanoparticles by interfacial polymerization.

Further, in step (1), the preparation method of the polydopamine nanoparticle dispersion is as follows: mixing dopamine hydrochloride powder and Tris solution to obtain a dopamine hydrochloride solution; shaking the dopamine hydrochloride solution for 0.5-1.5 h, Dopamine hydrochloride is oxidized and self-polymerized to obtain a polydopamine solution; the polydopamine nanoparticle dispersion liquid is obtained by ultrasonically dispersing the polydopamine solution.

Preferably, the dosage of the dopamine hydrochloride powder based on 100 mL of water is 0.1-0.2 g; the concentration of the Tris solution is 0.05-0.2 g/L, and the pH is 8-9.

Further, in step (2), the deposition amount of the polydopamine nanoparticles on the inner surface of the tubular coal-based carbon film is 0.4-1.3 mg/cm ² .

Further, in step (3), the method for preparing a continuous polyamide layer on the surface of the polydopamine nanoparticles by interfacial polymerization is as follows: after the film obtained in step (2) is vertically fixed, at a rate of 1-5 mL/min. The flow rate of 1% to 7% mass fraction of m-phenylenediamine solution passes through the inner surface of the membrane, and the excess solution on the surface is removed after infiltration for 1 to 10 minutes; then at the same flow rate, 0.1% to 0.3% mass fraction of trimesoyl chloride The solution reacted through the inner surface of the membrane for 1-5min; after standing for a certain period of time, the membrane was placed in a hot water bath for cross-linking; the membrane was taken out and immersed in sodium hypochlorite solution and sodium bisulfite solution in sequence; The conductive forward osmosis membrane is obtained by placing it in a hot water bath again.

Preferably, the resting time is 3-5 min; the temperature for cross-linking in the hot water bath is 80-100° C., and the time is 1-3 min.

Preferably, the concentration of the sodium hypochlorite solution is 0.1-0.5g/L, and the soaking time is 1-3min; the concentration of the sodium bisulfite solution is 1-3g/L, and the soaking time is 20-40s; The temperature in the hot water bath is 80 to 100°C, and the time is 5 to 8 minutes.

According to another aspect of the present invention, there is provided a conductive forward osmosis membrane obtained by the above preparation method.

According to another aspect of the present invention, an application of the above conductive forward osmosis membrane in water treatment is provided.

The beneficial effects of the present invention are:

In the conductive forward osmosis membrane prepared by the invention, polydopamine nanoparticles are deposited on the inner surface of the tubular coal-based carbon membrane by vacuum filtration, and the inner surface of the carbon membrane which is rough, hydrophobic and has macropore defects is covered to form a hydrophilic, pore size A uniformly distributed intermediate layer; and a complete and continuous polyamide layer is obtained through interfacial polymerization, and the polyamide layer has good permeability and excellent selectivity; the final prepared conductive forward osmosis membrane achieves good conductivity and chemical stability, which solves the problem of The problem of poor conductivity or unstable conductivity of composite conductive forward osmosis membrane.

In the present invention, the polyamide layer is prepared on the inner surface of the coal-based carbon membrane, and when the conductive forward osmosis membrane is on the polyamide layer to deal with the polluted water in the mode of drawing liquid, under the condition of an external electric field, the membrane acts as an electrode, and the outer surface with a large surface area is The electrical conductivity can reduce the deposition of contaminants on the film surface through electrostatic repulsion and oxidation.

The conductive forward osmosis membrane of the present invention is applied to the field of sewage treatment, and combined with electrochemical action, the pollution of the forward osmosis membrane can be alleviated, thereby improving the performance of the membrane, and has great theoretical significance and application value.

Description of drawings

Fig. 1 is the preparation process schematic diagram of the conductive forward osmosis membrane provided by the present invention;

2 is a schematic diagram of the effect of applied voltage on the flux and flux recovery rate of Rhodamine B solution treated by the conductive forward osmosis membrane prepared in Example 2;

Among them, (a) is the flux decrease curve of Rhodamine B solution treated by conductive carbon-based forward osmosis membrane at different voltages;

Among them, (b) is the flux recovery rate and rejection rate of Rhodamine B solution treated by conductive carbon-based forward osmosis membrane at different voltages;

3 is a schematic diagram of the effect of applied voltage on the flux and flux recovery rate of the conductive forward osmosis membrane prepared in Example 2 to treat the chromium black T solution;

Among them, (a) is the flux drop curve of chrome black T solution treated by conductive carbon-based forward osmosis membrane at different voltages;

Among them, (b) is the flux recovery rate and rejection rate of chrome black T solution treated by conductive carbon-based forward osmosis membrane at different voltages.

Detailed ways

As shown in Figure 1, the present invention provides a method for preparing a conductive forward osmosis membrane, comprising the following steps:

(1) preparing polydopamine nanoparticle dispersion;

As a preferred preparation method: first, mix dopamine hydrochloride powder and Tris solution to obtain a dopamine hydrochloride solution; then shake the dopamine hydrochloride solution for 0.5-1.5 h to make dopamine hydrochloride undergo oxidation and self-polymerization to obtain a polydopamine solution; The dopamine solution is ultrasonically dispersed to obtain a polydopamine nanoparticle dispersion.

Preferably, the dosage of the dopamine hydrochloride powder based on 100 mL of water is 0.1-0.2 g; the concentration of the Tris solution is 0.05-0.2 g/L, and the pH is 8-9.

(2) Preparation of polydopamine nanoparticle intermediate layer: take a certain volume of polydopamine nanoparticle dispersion to pass through the tubular coal-based carbon membrane, and deposit polydopamine nanoparticles on the inner surface of the tubular coal-based carbon membrane by vacuum filtration ; The deposition amount of polydopamine nanoparticles on the inner surface of the tubular coal-based carbon film is preferably 0.4-1.3 mg/cm ² .

(3) Preparation of continuous polyamide layers on the surface of polydopamine nanoparticles by interfacial polymerization.

As a preferred preparation method: after the film obtained in step (2) is vertically fixed, the m-phenylenediamine solution of 1% to 7% mass fraction passes through the inner surface of the film at a flow rate of 1 to 5 mL/min, and soaks 1 After ~10min, remove the excess solution on the surface; then make 0.1% ~ 0.3% mass fraction of trimesic acid chloride solution through the inner surface of the membrane to react for 1 ~ 5min at the same flow rate; after standing for 3 ~ 5min, put the membrane in 80 ~ Crosslink in a hot water bath at 100°C for 1 to 3 minutes; then take out the membrane, soak it in a sodium hypochlorite solution with a concentration of 0.1 to 0.5 g/L for 1 to 3 minutes, and then place it in a hydrogen sulfite solution with a concentration of 1 to 3 g/L Soak in the sodium solution for 20-40 s; then place the membrane in a hot water bath at 80-100° C. for 5-8 minutes to obtain a conductive forward osmosis membrane.

The conductive forward osmosis membrane prepared by the present invention can be used in water treatment, for example, as a filter membrane in a water treatment device or equipment.

In order to better understand the content of the present invention, the content of the present invention will be described in detail below with reference to specific embodiments and corresponding comparative examples, but the specific embodiments described herein are only used to explain the present invention, and are not intended to limit the present invention.

The raw materials used in the examples of the present invention and the comparative examples can be purchased from the market, or can be synthesized by methods known in the art.

Example 1:

Prepare a conductive forward osmosis membrane as follows:

(1) Preparation of polydopamine nanoparticle dispersion: Weigh 0.2 g of dopamine hydrochloride and dissolve it in 100 mL of Tris solution with a pH of 8.5 and a concentration of 50 mM to obtain a dopamine hydrochloride solution; shake the dopamine hydrochloride solution for 1 hour to oxidize dopamine hydrochloride The polydopamine solution is obtained by self-polymerization; the polydopamine nanoparticle dispersion liquid is obtained by ultrasonicating the polydopamine solution.

(2) Preparation of polydopamine nanoparticle intermediate layer: take 5 mL of the polydopamine nanoparticle dispersion obtained in step (1) through a peristaltic pump and pass through the tube of the tubular coal-based carbon membrane at a flow rate of 3 mL/min, at a pressure of 0.2 Mpa Next, polydopamine nanoparticles were deposited on the inner surface of the tubular coal-based carbon membrane by vacuum filtration. Finally, the deposition amount of polydopamine nanoparticles on the inner surface of the tubular coal-based carbon film was 0.4 mg/cm ² .

(3) Preparation of a continuous polyamide layer on the surface of polydopamine nanoparticles by interfacial polymerization: the film obtained in step (2) was vertically fixed, and 3.0 wt% m-phenylenediamine solution was passed through the film at a flow rate of 3 mL/min. The inner surface was soaked for 5 minutes to remove the excess solution on the surface; then the 0.15wt% trimesoyl chloride solution was reacted through the inner surface of the membrane at the same flow rate for 1.5 minutes, and after standing for 3 minutes, the membrane was placed in a 90°C hot water bath After being taken out, the membrane was soaked in 0.2g/L sodium hypochlorite for 2min; then placed in 1g/L sodium bisulfite solution for 0.5min, and then the membrane was placed in 90°C hot water again In the bath for 6 min, the conductive forward osmosis membrane of this embodiment was obtained.

The water flux and salt flux of the conductive forward osmosis membrane are obtained from equations (1) and (2), respectively:

Among them, ΔV—volume change of the drawn liquid, L; A—effective membrane area, m ² ; Δt—interval time, h.

Wherein, V _t —the volume of the drawn solution at the end of the test, L; C _t —the salt concentration of the drawn solution at the end of the test, mol/L; V ₀ — the initial volume of the drawn solution, L; C ₀ — the drawn solution Liquid initial salt concentration, mol/L.

The measured water flux of the conductive forward osmosis membrane obtained in Example 1 was 7.5 L/(m ² ·h), and the reverse salt flux was 10.2 g/(m ² ·h).

Example 2

A conductive forward osmosis membrane was prepared according to the steps of Example 1, except that in step (2), the volume of the polydopamine nanoparticle dispersion was 10 mL, and the final polydopamine nanoparticles in the tubular coal-based carbon membrane The deposition amount on the inner surface was 0.91 mg/cm ² .

According to the measurement method in Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 2 was measured to be 10.75 L/(m ² ·h), and the reverse salt flux was 1.83 g/(m ² ·h).

Example 3

A conductive forward osmosis membrane was prepared according to the steps of Example 1, the only difference being that in step (2), the volume of the polydopamine nanoparticle dispersion was 15 mL, and the final polydopamine nanoparticles in the tubular coal-based carbon membrane The deposition amount on the inner surface was 1.23 mg/cm ² .

According to the measurement method in Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 3 was measured to be 7.17 L/(m ² ·h), and the reverse salt flux was 1.65 g/(m ² ·h).

Example 4

A conductive forward osmosis membrane was prepared according to the steps of Example 2, except that in step (3), the concentration of the m-phenylenediamine solution was 1 wt %.

According to the measurement method in Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 4 was measured to be 15.01 L/(m ² ·h), and the reverse salt flux was 6.1 g/(m ² ·h).

Example 5

A conductive forward osmosis membrane was prepared according to the steps of Example 2, except that in step (3), the concentration of the m-phenylenediamine solution was 5wt%.

According to the measurement method of Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 5 was measured to be 10.37 L/(m ² ·h), and the reverse salt flux was 6.43 g/(m ² ·h).

Example 6

A conductive forward osmosis membrane was prepared according to the steps of Example 2, the only difference being that, in step (3), the concentration of the m-phenylenediamine solution was 7 wt %.

According to the measurement method in Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 6 was measured to be 11.64 L/(m ² ·h), and the reverse salt flux was 106.97 g/(m ² ·h).

Example 7

A conductive forward osmosis membrane was prepared according to the steps of Example 2, except that in step (3), the concentration of the trimesoyl chloride solution was 0.1 wt %.

According to the measurement method in Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 7 was measured to be 16.21 L/(m ² ·h), and the reverse salt flux was 55.28 g/(m ² ·h).

Example 8

A conductive forward osmosis membrane was prepared according to the steps of Example 2, except that in step (3), the concentration of the trimesoyl chloride solution was 0.2 wt %.

According to the measurement method in Example 1, the water flux of the conductive forward osmosis membrane obtained in Example 8 was measured to be 8.39 L/(m ² ·h), and the reverse salt flux was 1.78 g/(m ² ·h).

Example 9

A conductive forward osmosis membrane was prepared according to the steps of Example 2, except that in step (3), the concentration of the trimesoyl chloride solution was 0.3 wt %.

According to the measurement method of Example (1), the water flux of the conductive forward osmosis membrane obtained in Example 9 was measured to be 7.08L/(m ² ·h), and the reverse salt flux was 11.16g/(m ² ·h).

The conductive forward osmosis membrane prepared by the above embodiment is treated with positively charged dyes to alleviate the membrane fouling research as follows:

Using the conductive forward osmosis membrane prepared in Example 2, an anti-pollution experiment was carried out with Rhodamine B solution with a concentration of 100 ppm and a pH of 4 as the target pollutant. Figure 2 shows the effect of applied voltage on the flux and flux recovery rate of this conductive forward osmosis membrane. When a voltage of +1.5V was applied to the membrane, compared with no application, the flux increased by 21.57% and the flux recovery rate increased by 4.5% after 8h of operation compared with no voltage.

The conductive forward osmosis membrane prepared in the above-mentioned embodiment is treated with negatively charged dyes to alleviate the membrane fouling research as follows:

Using the conductive forward osmosis membrane prepared in Example 2, an anti-pollution experiment was carried out with a chromium black T solution with a concentration of 100 ppm and a pH of 6 as the target pollutant. Figure 3 shows the effect of applied voltage on the flux and flux recovery rate of this conductive forward osmosis membrane. When a voltage of -1.5V was applied to the membrane, the flux increased by 14.47% and the flux recovery rate increased by 4.1% after 8 h of operation compared with no voltage.

The above-mentioned research on the treatment of positively and negatively charged dyes with conductive positive osmosis membranes to alleviate membrane fouling shows that the anti-fouling performance of conductive membranes depends on the surface charge of pollutants. When the contaminant and the membrane surface have the same charge, the membrane fouling is reduced; when the contaminant and the membrane surface have opposite charges, the membrane fouling is aggravated.

The conductive carbon-based forward osmosis membranes prepared by preparing the interlayer of polydopamine nanoparticles with a deposition amount of 0.4-1.3 mg/ ^cm2 on the carbon membrane substrate all have good permeability. When the deposition amount of polydopamine nanoparticles was 0.91 mg/cm ² , the carbon membrane substrate was completely covered, forming a hydrophilic intermediate layer with uniform pore size distribution. At this time, the prepared conductive carbon-based forward osmosis membrane had the best permeability.

Based on this, the effects of m-phenylenediamine solution concentration and trimesoyl chloride solution concentration on the forward osmosis performance of the prepared conductive carbon-based forward osmosis membrane were investigated respectively. The concentration range of m-phenylenediamine solution is 1wt%-5wt%, and the concentration range of trimesoyl chloride solution is .0.15wt%-0.3wt%. When the concentration of phenylenediamine solution is 3w% and the concentration of trimesoyl chloride solution is 0.15wt%, the performance of the prepared conductive carbon-based forward osmosis membrane is the best. Excessive m-phenylenediamine (7wt% concentration) or trimesoyl chloride solution (0.3wt% concentration) will cause defects in the polyamide layer by interrupting the formation of the polyamide network and reduce the forward osmosis performance of the polyamide layer.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. Under the inspiration of the present invention, without departing from the scope of the present invention and the protection scope of the claims, personnel can also make many specific transformations, which all fall within the protection scope of the present invention.

Claims (10)

1. The preparation method of the conductive forward osmosis membrane is characterized in that a tubular coal-based carbon membrane is used as a supporting layer, polydopamine nano-particles are deposited on the inner surface of the tubular coal-based carbon membrane by a vacuum filtration method, and then a continuous polyamide layer is prepared on the surfaces of the polydopamine nano-particles through interfacial polymerization to obtain the conductive forward osmosis membrane.

2. The method for preparing a conductive forward osmosis membrane according to claim 1, comprising the steps of:

(1) preparing a polydopamine nanoparticle dispersion liquid;

(2) preparing a middle layer of poly-dopamine nano-particles: enabling the polydopamine nanoparticle dispersion liquid obtained in the step (1) to pass through the tubular coal-based carbon membrane, and depositing polydopamine nanoparticles on the inner surface of the tubular coal-based carbon membrane through vacuum filtration;

(3) and preparing a continuous polyamide layer on the surface of the polydopamine nano-particles through interfacial polymerization.

3. The method for preparing a conductive forward osmosis membrane according to claim 2, wherein in the step (1), the poly-dopamine nanoparticle dispersion liquid is prepared by: mixing dopamine hydrochloride powder with a Tris solution to obtain a dopamine hydrochloride solution; shaking the dopamine hydrochloride solution for 0.5-1.5 h to enable dopamine hydrochloride to undergo oxidative autopolymerization to obtain a polydopamine solution; and ultrasonically dispersing the polydopamine solution to obtain the polydopamine nanoparticle dispersion liquid.

4. The method for preparing a conductive forward osmosis membrane according to claim 3, wherein the dopamine hydrochloride powder is used in an amount of 0.1 to 0.2g based on 100mL of water; the concentration of the Tris solution is 0.05-0.2 g/L, and the pH value is 8-9.

5. The method for preparing a conductive forward osmosis membrane according to claim 2, wherein in step (2), the poly-dopamine nanoparticle is deposited on the inner surface of the tubular coal-based carbon membrane in an amount of 0.4 to 1.3mg/cm ² 。

6. The method for preparing a conductive forward osmosis membrane according to claim 2, wherein in the step (3), the method for preparing the continuous polyamide layer on the surface of the polydopamine nanoparticle by interfacial polymerization comprises the following steps: vertically fixing the film obtained in the step (2), enabling a 1-7% m-phenylenediamine solution to pass through the inner surface of the film at a flow rate of 1-5 mL/min, and soaking for 1-10 min to remove redundant solution on the surface; enabling 0.1-0.3% of trimesoyl chloride solution in mass fraction to pass through the inner surface of the membrane at the same flow rate to react for 1-5 min; after standing for a certain time, placing the membrane in a hot water bath for crosslinking; taking out the film and sequentially soaking the film in a sodium hypochlorite solution and a sodium bisulfite solution; and then placing the film in a hot water bath again to obtain the conductive forward osmosis film.

7. The method for preparing a conductive forward osmosis membrane according to claim 6, wherein the resting time is 3-5 min; the temperature for crosslinking in the hot water bath is 80-100 ℃, and the time is 1-3 min.

8. The method for preparing a conductive forward osmosis membrane according to claim 6, wherein the concentration of the sodium hypochlorite solution is 0.1-0.5 g/L, and the soaking time is 1-3 min; the concentration of the sodium bisulfite solution is 1-3 g/L, and the soaking time is 20-40 s; and placing the film in a hot water bath again at the temperature of 80-100 ℃ for 5-8 min.

9. An electrically conductive forward osmosis membrane, characterized by being obtained by the production method of any one of claims 1 to 8.

10. Use of a conductive forward osmosis membrane according to claim 9 in water treatment.

Images