CN112999891A

CN112999891A - Graphite alkyne composite filtering membrane and preparation method and application thereof

Info

Publication number: CN112999891A
Application number: CN202110267729.5A
Authority: CN
Inventors: 曾高峰; 杨京京; 孙予罕
Original assignee: Shanghai Advanced Research Institute of CAS
Current assignee: Shanghai Advanced Research Institute of CAS
Priority date: 2021-03-11
Filing date: 2021-03-11
Publication date: 2021-06-22
Anticipated expiration: 2041-03-11
Also published as: CN112999891B

Abstract

The invention belongs to the technical field of material preparation, and particularly relates to a graphite alkyne composite filtering membrane as well as a preparation method and application thereof. A preparation method of a graphite alkyne composite filtering membrane comprises the step of carrying out coupling reaction on a polyacetylene compound and a porous material with copper on the surface in a solvent to obtain the graphite alkyne composite filtering membrane. The graphite alkyne composite filtering membrane obtained by the invention can selectively filter water molecules, potassium ions, sodium ions, magnesium ions, calcium ions, chloride ions and sulfate ions in seawater, namely, water molecules are allowed to pass through, but potassium ions, sodium ions, magnesium ions, calcium ions, chloride ions and sulfate ions are not allowed to pass through. The method for preparing the graphite alkyne composite filtering membrane is simple to operate and low in energy consumption, and a hydrophobic graphite alkyne layer can be directly grown on the surface of a porous material with copper on the surface, so that seawater desalination is realized.

Description

Graphite alkyne composite filtering membrane and preparation method and application thereof

Technical Field

The invention belongs to the technical field of material preparation, and particularly relates to a graphite alkyne composite filtering membrane as well as a preparation method and application thereof.

Background

The shortage of fresh water resources in the world draws more and more attention. As a means of fresh water supply, seawater desalination becomes an important solution to the water source crisis. Common seawater desalination technologies are mainly classified into two types: distillation and membrane separation. The distillation method requires high energy consumption, and the membrane separation has low energy consumption and low investment, and requires high desalting rate and high fresh water flux. Most desalination processes have also attracted considerable attention in recent years due to the potential of combining reverse osmosis, membrane distillation and forward osmosis with renewable energy. In all membrane separations, increasing the fresh water flux is a significant challenge in membrane separation in desalination of sea water, ensuring high salt rejection.

Polymer membranes used in reverse osmosis and forward osmosis desalination processes act through a solution-diffusion mechanism, and thus the polymer membranes are relatively dense; while used for membrane distillation are microporous membranes which transport water vapor and prevent the passage of liquids by knudsen diffusion. But the permeation flux is low due to the dense structure of the polymer membrane, and the water vapor transmission density is limited. Recent studies have shown that water can be transported at high speed through aquaporins (j.am. chem. soc, 2012, 134, 18631-. A large number of simulation studies show that salt ions can be effectively retained by a molecular sieving mechanism if the pipe diameter is less than 1.1 nm. However, effective control of tube diameter and sealing of the gaps between tubes remains a challenge for membrane preparation. The common method of sealing the gap between the tubes is to mix the matrix film, but suffers from a number of limitations such as poor dispensability, low loading rates, defects due to misalignment, and the like. The graphene and graphene oxide membrane has great potential in gas and liquid separation, and particularly when the epoxy resin is used for wrapping the swelling effect of the graphene oxide membrane, the salt ion rejection rate reaches 97% (nat. nanotech, 2017, 12, 546-551).

The graphoyne is composed of sp²And sp hybridization to conjugate benzene ring with alkyne bondThe connection forms a two-dimensional plane network structure, and the Liyuliang subject group of the chemical research institute of the Chinese academy of sciences in 2010 reports that large-area synthesis of graphite diyne is carried out on the surface of the copper foil for the first time, and opens up a precedent for artificial chemical synthesis of carbon allotropes. The graphdine has a plane layer with single atom thickness, plane height conjugation, nanometer-scale holes (0.25nm) and an interlayer distance of about 0.365nm, and is attracted more and more attention and researches.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a graphite alkyne composite filter membrane, a method for preparing the same, and a use thereof, which are used to solve the problems of the prior art.

To achieve the above objects and other related objects, the present invention is achieved by the following technical solutions.

One of the purposes of the invention is to provide a preparation method of a graphite alkyne composite filtering membrane, which comprises the following steps:

and carrying out coupling reaction on a polyacetylene compound and a porous material with copper on the surface in a solvent to obtain the graphite alkyne composite filtering membrane.

Preferably, the porous material with the surface containing copper is porous copper or porous ceramic with the surface covered by a copper layer.

More preferably, the pore diameter of the porous copper is 1 μm to 10 μm.

More preferably, the pore diameter of the porous copper is 1 μm to 5 μm.

More preferably, the pore diameter of the porous ceramic is 2nm to 10 nm.

Further preferably, the pore diameter of the porous ceramic is 2nm to 6 nm.

More preferably, the material of the porous ceramic is zirconia.

Still more preferably, the preparation method of the porous ceramic with the copper layer covered on the surface comprises the following steps: and plating copper on the surface of the porous ceramic by an ion sputtering method.

Specifically, the sputtering time is 5min to 30 min.

Preferably, the porous material with the copper-containing surface further comprises a cleaning step, and the cleaning step is sequentially performed by water, ethanol and acetone.

Preferably, the polyacetylene compound comprises one of hexaethynylbenzene and triethynylbenzene.

Preferably, the mass ratio of the polyacetylene compound to copper is 1: (20 to 50).

Preferably, the solvent is one or both of acetone and pyridine.

More preferably, the solvent is a mixed solution of acetone and pyridine, and the volume ratio of the acetone to the pyridine is 1: (5-50).

Still more preferably, the volume ratio of acetone to pyridine is 1: (20-40).

Preferably, the coupling reaction temperature is 50 ℃ to 100 ℃.

More preferably, the reaction temperature can be 50-70 ℃, also can be 60-80 ℃, also can be 70-100 ℃.

Preferably, the coupling reaction time is 12h to 72 h.

More preferably, the reaction time may be 12 to 30 hours, 25 to 50 hours, 35 to 65 hours, or 45 to 72 hours.

Preferably, the coupling reaction is carried out under a protective atmosphere and protected from light.

More preferably, the shielding gas is argon.

Preferably, the polyacetylene compound is dissolved in a solvent and then is dropwise added to the porous material with copper on the surface.

More preferably, the solvent is acetone or pyridine.

More preferably, the mass-volume ratio of the polyacetylene compound to the solvent is 1mg (30-70) mL.

Preferably, the graphite alkyne composite filter membrane further comprises cleaning, and the cleaning is sequentially washed by acetone, dimethylformamide and water.

Preferably, the graphite alkyne composite filtering membrane further comprises drying, wherein the drying atmosphere is argon or vacuum, and the drying temperature is 25-100 ℃.

The second purpose of the invention is to provide the graphite alkyne composite filtering membrane prepared by the preparation method.

Preferably, the graphite alkyne composite filter membrane is formed by wrapping a graphite alkyne layer outside a porous material with copper on the surface, and the thickness of the graphite alkyne layer is 5-20 μm. The thickness of the graphite alkyne layer can not be too thick or too thin, and when the graphite alkyne layer is too thick, seawater desalination treatment is carried out, so that the permeation flux of seawater can be reduced; when the graphite alkyne layer is too thin, the porous material with copper on the surface cannot be covered, the seawater desalination treatment is carried out, the seawater desalination effect is poor, and the seawater desalination effect cannot be achieved.

The invention also aims to provide the application of the graphite alkyne composite filtering membrane in seawater desalination.

In the application, the simulated seawater desalination treatment is carried out by adopting a pervaporation technology, and the graphite alkyne composite filtering membrane is used as a separation membrane. When the simulated seawater is desalinated, the graphite alkyne composite filtering membrane is placed in a salt solution of the simulated seawater, one end of the graphite alkyne composite filtering membrane is sealed by epoxy resin, and the other end of the graphite alkyne composite filtering membrane is used as a permeation side.

Preferably, the pervaporation temperature is 25-90 ℃, the pressure of the permeation side is 0-10 kPa, and the feed flow of the salt solution is 20-200 mL/min.

Preferably, the salt solution simulating seawater is selected from the group consisting of Na-containing salt solutions⁺、K⁺、Mg²⁺、Ca²⁺、Cl^-And SO₄ ^2-One or more of them.

Preferably, the concentration of the salt solution of the simulated seawater is 0.1 mol/L-0.6 mol/L.

At present, the surface of porous copper or porous ceramic has pores, water can pass through the pores, but the pore size ratio is large, the desalting effect is not realized, and the porous copper or porous ceramic cannot be used for desalting seawater. According to the method, a porous material with a copper-containing surface is used as a carrier, hexaethynylbenzene or triethynylbenzene is dissolved in a solvent and is dripped on the carrier, and a coupling reaction is carried out in pyridine or/and acetone, so that the graphite alkyne composite filtering membrane is obtained. The graphite alkyne composite filtering membrane is formed by wrapping a graphite alkyne layer outside a porous material with copper on the surface, wherein the graphite alkyne layer can cover holes of the porous material and form a hydrophobic protective layer on the surface of the porous material, so that water molecules and potassium ions, sodium ions, magnesium ions, calcium ions, chloride ions and sulfate ions can be selectively filtered, namely the water molecules are allowed to pass but the potassium ions, the sodium ions, the magnesium ions, the calcium ions, the chloride ions and the sulfate ions are not allowed to pass, and the graphite alkyne composite filtering membrane is particularly suitable for seawater desalination.

Compared with the prior art, the invention has the following beneficial effects:

1) the hydrophobic graphite alkyne film grows in situ on the surface of the porous material with copper on the surface to obtain the graphite alkyne composite filtering film, the filtering film can selectively filter water molecules, potassium ions, sodium ions, magnesium ions, calcium ions, chloride ions and sulfate ions, and the graphite alkyne composite filtering film can be used as a separation film for desalting salt solutions and lays a foundation for the application in seawater desalination.

2) The method for preparing the graphite alkyne composite filtering membrane is simple to operate and low in energy consumption.

Drawings

FIG. 1 shows an SEM image of the surface topography of a graphite alkyne composite filter membrane in example 1 of the present application.

FIG. 2 shows an SEM image of the surface topography of a graphite alkyne composite filter membrane in example 2 of the present application.

FIG. 3 is an SEM image of the surface topography of the graphite alkyne composite filter membrane of example 3 in the present application.

FIG. 4 shows an SEM image of the surface topography of a graphite alkyne composite filter membrane in example 4 of the present application.

FIG. 5 is an SEM image of the cross section of the graphite alkyne composite filter membrane in example 4 of the present application.

FIG. 6 shows a surface topography SEM image of a comparative example in this application.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Before the present embodiments are further described, it is to be understood that the scope of the invention is not limited to the particular embodiments described below; it is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. The test methods in the following examples, in which specific conditions are not specified, are generally carried out according to conventional conditions or according to conditions recommended by the respective manufacturers.

When numerical ranges are given in the examples, it is understood that both endpoints of each of the numerical ranges and any value therebetween can be selected unless the invention otherwise indicated. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition to the specific methods, devices, and materials used in the examples, any methods, devices, and materials similar or equivalent to those described in the examples herein can be used in the practice of the invention in accordance with the teachings of the present invention as determined by one of ordinary skill in the art.

In the embodiment of the application, the simulated seawater desalination treatment is carried out by adopting a pervaporation technology, and the graphite alkyne composite filtering membrane is used as a separation membrane. Since the hydrophobic graphite alkyne layer is formed on the surface of the porous material through the coupling reaction in the application, when the seawater desalination treatment is carried out, only water molecules can pass through the graphite alkyne layer and escape from a water channel formed by the porous material, and ions in the seawater such as potassium ions, sodium ions, magnesium ions, calcium ions, chloride ions and sulfate ions cannot pass through the graphite alkyne layer.

In order to facilitate the simulation of the pervaporation process of the graphite alkyne composite filtering membrane or enable the graphite alkyne composite filtering membrane to form a pervaporation membrane separation assembly, the porous copper adopted in the embodiment of the application is a porous copper tube, the length of the porous copper tube is 3-5 cm, the weight of the copper tube with the length of 3-5 cm is 300-500mg, and the aperture of the porous copper is 1.5-2 μm.

When the simulated seawater is desalinated, the graphite alkyne composite filtering membrane is placed in a salt solution of the simulated seawater, one end of the graphite alkyne composite filtering membrane is sealed by epoxy resin, and the other end of the graphite alkyne composite filtering membrane is used as a permeation side.

The content of metal ions in the salt solution and the permeate was analyzed by a desalting test using a conductivity meter, thereby calculating the ion rejection. Wherein the permeation flux F (kg m)^-2h^-1) And the calculation formula of the ion rejection rate R (%) is as follows:

wherein t represents the permeation time in h; w represents the mass of liquid water collected in the permeate side in kg; a represents the surface area of the graphite alkyne composite filter membrane for separation, and the unit m²；C_0iDenotes the ion concentration, C, in the salt solution of initially simulated seawater_iDenotes the ion concentration in the permeate obtained after the permeation time t, in mol L^-1。

Example 1

In this embodiment, preparing the graphite alkyne composite filter membrane and performing seawater desalination treatment includes the following steps:

1) sequentially carrying out ultrasonic cleaning on porous copper with the length of 5cm in water, ethanol and acetone, and storing the treated copper in acetone for later use; porous copper was mixed with a solvent in a three-necked flask, which was a mixture of 100mL acetone and 5mL pyridine, and heated to 50 ℃ under argon.

2) Hexaethynylbenzene 10mg was dissolved in 50mL of acetone to obtain an acetone solution of hexaethynylbenzene.

3) Slowly contacting the acetone solution of the hexaethynylbenzene in the step 2) with the mixture of the porous copper and the solvent in the step 1) within 2h, and then carrying out coupling reaction for 1 day at 50 ℃ under the conditions of argon and light shielding to prepare the graphite alkyne composite filtering membrane.

4) And (3) washing the graphite alkyne composite filter membrane in the step 3) with acetone, dimethylformamide and water in sequence, and drying for 12 hours in vacuum at 50 ℃.

The graphite alkyne composite filter membrane prepared in the embodiment simulates seawater desalination by adopting a pervaporation technology, the simulated seawater in the embodiment is 0.1mol/L NaCl aqueous solution, the permeation pressure is 300Pa, the pervaporation temperature is 70 ℃, the feeding flow is 100mL/min, and the separation test result is shown in Table 1. As can be seen from Table 1, the graphite alkyne composite filtering membrane obtained in the example has a desalination rate of 20% and a permeation flux of 3961kg m in simulated seawater desalination^-2h^-1。

Fig. 1 is an SEM image of the porous graphite alkyne composite filtration membrane prepared in example 1, and it can be seen from fig. 1 that the membrane cannot completely cover the surface of the porous copper, and the pores on the surface of the porous copper are directly exposed.

Example 2

In this example, step 3), the reaction time of the polyacetylene compound and the porous copper in the solvent was 3 days, and the rest of the steps were the same as those in example 1.

The results of the separation test of this example 2 are shown in table 1.

Fig. 2 is an SEM image of the graphite-acetylene composite filtration membrane prepared in example 2, and it can be seen from fig. 1 that the surface of porous copper is not completely covered with the membrane and the pores on the surface of porous copper are directly exposed.

Example 3

In this example, step 3), the reaction time of the polyacetylene compound and the porous copper in the solvent was 5 days, and the rest of the steps were the same as in example 1. The thickness of the graphoyne layer in this example was 20 μm.

The results of the separation test of this example 3 are shown in table 1.

Fig. 3 is an SEM image of the graphyne composite filtration membrane prepared in example 3, and it can be seen from fig. 1 that the graphyne layer completely covers the surface of the porous copper and the graphyne layer is relatively loose.

TABLE 1

Example 4

1) sequentially carrying out ultrasonic cleaning on porous copper with the length of 5cm in water, ethanol and acetone, and storing the treated copper in acetone for later use; porous copper was mixed with a solvent in a three-necked flask, heated to 50 ℃ under argon, and the solvent was 100mL pyridine.

2) Hexaethynylbenzene 10mg was dissolved in 50mL of pyridine to obtain a pyridine solution of hexaethynylbenzene.

3) Slowly contacting the pyridine solution of the hexaethynylbenzene in the step 2) with the mixture of the porous copper and the solvent in the step 1) within 2h, and then reacting for 3 days at 50 ℃ under the conditions of argon and dark to prepare the graphite alkyne composite filtering membrane.

4) Washing the graphite alkyne composite filter membrane in the step 3) with acetone, dimethylformamide and water in sequence, and drying for 12 hours in vacuum at 50 ℃.

Fig. 4 is an SEM image of the surface morphology of the graphite alkyne composite filtering membrane prepared in this example 4, and fig. 5 is an SEM image of the cross-sectional morphology of the graphite alkyne composite filtering membrane prepared in this example 4, and it can be seen from fig. 4 and fig. 5 that the graphite alkyne layer can completely cover the surface of the porous copper within 3 days in this example and the graphite alkyne layer is relatively loose compared to example 2, and the thickness of the graphite alkyne layer is about 6 μm as seen from the cross-sectional morphology.

In the embodiment, seawater desalination is simulated by adopting an pervaporation technology, wherein the pervaporation temperature is 70 ℃, the osmotic pressure is 100Pa, the feeding flow is 50mL/min, and the salt solutions are 0.1mol/L NaCl aqueous solution, 0.1mol/L KCl aqueous solution and 0.1mol/L MgCl₂Aqueous solution, 0.1mol/L CaCl₂Aqueous solution, 0.1mol/L of Na₂SO₄Aqueous solution, 0.1mol/L MgSO₄Aqueous solutions, and 0.1, 0.2, 0.4, and 0.6mol/L aqueous NaCl solutions, the separation test results are shown in tables 2 and 3.

TABLE 2

TABLE 3

Compared with the examples 1-3, in the example 4, pyridine is used as a solvent, copper and pyridine are easier to form a Cu-N ligand catalytic coupling reaction, so that the graphite alkyne membrane is easier to grow, and when the graphite alkyne membrane obtained in the example 4 is subjected to seawater desalination treatment, the graphite alkyne composite filtering membrane has proper water flux and can effectively intercept ions in a salt solution, wherein the desalination rate is more than 99.6 percent, and the permeation flux is 51.60kg m^-2h^-1The above.

Comparative example

Porous copper with the length of 5cm is directly used as a filtering membrane to simulate seawater desalination treatment.

The seawater desalination is carried out by adopting the pervaporation technology, the simulated seawater in the comparative example is 0.1mol/L NaCl aqueous solution, the osmotic pressure is 100Pa, the pervaporation temperature is 70 ℃, the feeding flow is 100mL/min, when the seawater desalination treatment is simulated by adopting porous copper, the desalination rate is 18.5 percent, and the permeation flux is 6363kg m^-2h^-1。

Fig. 6 is an SEM image of the surface morphology of the porous copper tube of the comparative example.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. The preparation method of the graphite alkyne composite filtering membrane is characterized by comprising the following steps:

2. The production method according to claim 1, wherein the porous material having a surface containing copper is porous copper or a porous ceramic having a surface covered with a copper layer.

3. The production method according to claim 2, wherein the pore diameter of the porous copper is 1 μm to 10 μm;

and/or the pore diameter of the porous ceramic is 2 nm-10 nm.

4. The method according to claim 3, wherein the porous ceramic is made of zirconia.

5. The method according to claim 1, wherein the polyacetylene-based compound comprises one of hexaethynylbenzene and triethynylbenzene;

and/or, based on copper, the mass ratio of the polyacetylene compound to the copper is 1: (20 to 50).

6. The method according to claim 1, wherein the solvent is one or both of acetone and pyridine.

7. The method according to claim 1, wherein the reaction temperature is 50 ℃ to 100 ℃;

and/or the reaction time is 12-72 h.

8. The graphite alkyne composite filtering membrane prepared by the preparation method according to any one of claims 1 to 7.

9. The graphite alkyne composite filter membrane according to claim 8, wherein the graphite alkyne composite filter membrane is formed by wrapping a graphite alkyne layer outside a porous material with copper on the surface, and the thickness of the graphite alkyne layer is 5-20 μm.

10. Use of the graphite alkyne composite filter membrane according to claim 8 or 9 in seawater desalination.