Multifunctional nanofiltration membrane with corrugated structure and preparation method thereof

文档序号：1897130 发布日期：2021-11-30 浏览：29次中文

阅读说明：本技术 一种褶皱结构多功能纳滤膜及其制备方法 (Multifunctional nanofiltration membrane with corrugated structure and preparation method thereof ) 是由安晓强兰华春崔雨琦刘烈曲久辉刘会娟于 2021-07-30 设计创作，主要内容包括：本发明提出一种褶皱结构多功能纳滤膜及其制备方法,属于污水膜处理技术领域。所述多功能纳滤膜,包括支撑底膜和位于支撑底膜上的氮化碳改性聚酰胺分离层,其中,所述氮化碳改性聚酰胺分离层由含氮化碳溶胶的多元胺单体的水溶液与含多元酰氯单体的有机溶液通过界面聚合反应而得。本发明提出的褶皱结构多功能纳滤膜,借助氮化碳溶胶分子间氢键作用形成自组装结构,为界面聚合反应提供亲水性表面诱导褶皱结构形成,为提升纳滤膜水通量和降低成本提供了简单易控的方法。并且,氮化碳可光催化降解表面截留污染物,使得纳滤膜具有光催化自清洁性能。(The invention provides a multifunctional nanofiltration membrane with a fold structure and a preparation method thereof, belonging to the technical field of sewage membrane treatment. The multifunctional nanofiltration membrane comprises a supporting base membrane and a carbon nitride modified polyamide separation layer positioned on the supporting base membrane, wherein the carbon nitride modified polyamide separation layer is obtained by the interfacial polymerization reaction of an aqueous solution of a polyamine monomer containing a carbon nitride sol and an organic solution containing a polybasic acyl chloride monomer. The multifunctional nanofiltration membrane with the wrinkled structure provided by the invention forms a self-assembly structure by virtue of hydrogen bond action among carbon nitride sol molecules, provides hydrophilic surface for interfacial polymerization reaction to induce the formation of the wrinkled structure, and provides a simple and easily-controlled method for improving the water flux of the nanofiltration membrane and reducing the cost. And the carbon nitride can be used for photocatalytic degradation of surface trapped pollutants, so that the nanofiltration membrane has photocatalytic self-cleaning performance.)

1. A multifunctional nanofiltration membrane with a wrinkled structure comprises a supporting bottom membrane and a carbon nitride modified polyamide separation layer positioned on the supporting bottom membrane, wherein the carbon nitride modified polyamide separation layer is obtained by the interfacial polymerization reaction of an aqueous solution of polyamine monomer containing carbon nitride sol and an organic solution containing polyacyl chloride monomer.

2. Nanofiltration membrane according to claim 1,

the polyamine monomer comprises at least one of piperazine, polyethyleneimine, 1, 4-diaminocyclohexane and m-phenylenediamine.

3. Nanofiltration membrane according to claim 1,

the polybasic acyl chloride monomer comprises at least one of trimesic acid chloride, trimesic acid, 1, 3-benzene disulfonyl chloride and terephthaloyl chloride.

4. Nanofiltration membrane according to claim 1,

the supporting base membrane comprises a polycarbonate filter membrane, a polytetrafluoroethylene filter membrane, a polyether sulfone filter membrane, a polysulfone filter membrane or a polypropylene filter membrane.

5. Nanofiltration membrane according to claim 1,

the organic solution comprises at least one of n-hexane, cyclohexane, benzene and toluene.

6. The preparation method of the multifunctional nanofiltration membrane with the corrugated structure as claimed in any one of claims 1 to 5, comprising the following steps:

1) adding the hydrophilic carbon nitride sol into an aqueous solution of a polyamine monomer, and performing ultrasonic dispersion to obtain a mixed dispersion liquid;

2) soaking a support base membrane in the mixed dispersion liquid, and carrying out interface self-assembly of carbon nitride molecular sol to obtain a carbon nitride-based hydrophilic membrane modified base membrane;

3) and soaking the carbon nitride-based hydrophilic film modified basement membrane in an organic solution of a polyacyl chloride monomer to enable the polyamine monomer and the polyacyl chloride monomer to generate an interfacial polymerization reaction, thereby obtaining the multifunctional nanofiltration membrane with the corrugated structure.

7. The production method according to claim 1,

in the step 1), the preparation method of the hydrophilic carbon nitride sol comprises the following steps: dispersing carbon nitride material in sodium hydroxide solution, and treating with alkali to obtain hydrophilic carbon nitride sol dispersed in water.

8. The production method according to claim 1,

in the step 1), the concentration of the carbon nitride in the polyamine monomer aqueous solution is 0.1-2.0 mg/mL;

in the step 1), the concentration of the aqueous solution of the polyamine monomer is 1-6 mg/mL.

9. The production method according to claim 1,

in the step 2), the soaking time is 20-180 s.

10. The production method according to claim 1,

in the step 3), the temperature of the interfacial polymerization reaction is 20-30 ℃; the relative humidity of the interfacial polymerization reaction is 40-80%; the time of the interfacial polymerization reaction is 20-120 s;

in the step 3), the concentration of the organic solution of the polybasic acyl chloride monomer is 0.3-3 mg/mL.

Technical Field

The invention belongs to the technical field of sewage membrane treatment, and particularly relates to a multifunctional nanofiltration membrane with a fold structure and a preparation method thereof.

Background

The nanofiltration membrane is a pressure driving membrane with the separation performance between that of the ultrafiltration membrane and that of the reverse osmosis membrane, and has irreplaceable effects in the aspects of industrial wastewater, domestic sewage and medical wastewater treatment.

At present, the preparation method of the nanofiltration membrane mainly adopts an interface polymerization method, and an ultrathin polyamide functional layer is formed by the polymerization reaction of a polyamine monomer in a water phase and a polyacyl chloride monomer in an oil phase at an interface.

However, the technology still has the defects of thicker selection layer, compactness, wider pore size distribution and the like, and the lower permeation flux and the lower single-multivalence selectivity are still key obstacles limiting the application and popularization of the technology. Moreover, in order to reduce membrane fouling, the surface of the membrane is often subjected to hydrophilic modification, which also causes a reduction in the separation performance of membrane filtration.

The selective layer structure of the composite nanofiltration membrane plays an important role in nanofiltration performance, and although reducing the thickness of the selective layer can improve the membrane flux, certain technical challenges remain if the selective layer with the thickness of less than 100 nanometers is obtained.

The selective layer material with high water flux, good single-multivalence selectivity and strong pollution resistance is obtained by regulating and controlling the interfacial polymerization process, and is a main problem in the research of nanofiltration membrane separation and water purification.

Disclosure of Invention

The invention provides a multifunctional nanofiltration membrane with a fold structure and a preparation method thereof, wherein a hydrophilic interface is constructed by utilizing the self-assembly characteristic of carbon nitride molecules, so that the fold structure is induced to form in the preparation process of a polyamide layer, the surface of a hydrophilic material with a stable and controllable structure is obtained, and the purpose of inhibiting membrane pollution by photodegradation pollutants while improving water flux is achieved.

The invention provides a multifunctional nanofiltration membrane with a wrinkled structure, which comprises a supporting bottom membrane and a carbon nitride modified polyamide separation layer positioned on the supporting bottom membrane, wherein the carbon nitride modified polyamide separation layer is obtained by performing interfacial polymerization reaction on an aqueous solution of a polyamine monomer containing a carbon nitride sol and an organic solution containing a polybasic acyl chloride monomer.

Further, the polyamine monomer comprises at least one of piperazine, polyethyleneimine, 1, 4-diaminocyclohexane and m-phenylenediamine.

Further, the polybasic acyl chloride monomer comprises at least one of trimesic acid chloride, trimesic acid, 1, 3-benzene disulfonyl chloride and terephthaloyl chloride.

Further, the supporting base membrane comprises a polycarbonate filter membrane, a polytetrafluoroethylene filter membrane, a polyether sulfone filter membrane, a polysulfone filter membrane or a polypropylene filter membrane.

Further, the organic solution comprises at least one of n-hexane, cyclohexane, benzene and toluene.

The invention also provides a preparation method of any one of the multifunctional nanofiltration membranes with the corrugated structures, which comprises the following steps:

1) adding the hydrophilic carbon nitride sol into an aqueous solution of a polyamine monomer, and performing ultrasonic dispersion to obtain a mixed dispersion liquid;

Further, in the step 1), the preparation method of the hydrophilic carbon nitride sol comprises the following steps: dispersing carbon nitride material in sodium hydroxide solution, and treating with alkali to obtain hydrophilic carbon nitride sol dispersed in water.

Further, in the step 1), the concentration of the carbon nitride in the polyamine monomer aqueous solution is 0.1-2.0 mg/mL;

in the step 1), the concentration of the aqueous solution of the polyamine monomer is 1-6 mg/mL.

Further, in the step 2), the soaking time is 20-180 s.

Further, in the step 3), the temperature of the interfacial polymerization reaction is 20-30 ℃; the relative humidity of the interfacial polymerization reaction is 40-80%; the time of the interfacial polymerization reaction is 20-120 s;

in the step 3), the concentration of the organic solution of the polybasic acyl chloride monomer is 0.3-3 mg/mL.

The invention has the following advantages:

the invention forms a self-assembly structure by means of hydrogen bond action among carbon nitride sol molecules, provides hydrophilic surface induced fold structure formation for interfacial polymerization reaction, and provides a simple and easily-controlled method for improving the water flux of the nanofiltration membrane and reducing the cost. And the carbon nitride can be used for photocatalytic degradation of surface trapped pollutants, so that the nanofiltration membrane has photocatalytic self-cleaning performance.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.

In the drawings:

FIG. 1(a) is a transmission electron micrograph of a carbon nitride sol according to example 1; FIG. 1(b) is a scanning electron microscope image of a carbon nitride hydrophilic modification layer formed by self-assembly on the surface of a supporting base film.

FIG. 2(a) is the contact angle change of the hydrophilic layer after the addition of carbon nitride with different concentrations in example 3, showing that the hydrophilicity is gradually increased with the increase of the carbon nitride content; fig. 2(b) is a scanning electron microscope image of the PA selective layer with the wrinkle shape formed by the carbon nitride hydrophilic layer.

Fig. 3 is a performance evaluation of the nanofiltration membrane obtained by modifying the carbon nitride hydrophilic layer and the conventional method in application example 1 and comparative application example 1 to remove salt ions in water.

FIG. 4(a) is a UV-vis graph of the stock solution and the filtrate before and after the dye solution passes through the nanofiltration membrane modified by the carbon nitride hydrophilic layer in application example 2; and (b) the content of pollutants on the surface of the nanofiltration membrane modified by the carbon nitride hydrophilic layer is changed before and after 3 hours of simulated sunlight illumination.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

Compared with the traditional method, the method has the advantages that hydrophilic molecules are added to control the monomer polymerization reaction to prepare the selective layer, and the rough surface is induced to form on the surface of the hydrophilic material, so that the precise regulation and control of the membrane structure are facilitated.

The surface nano regular coarse structure is constructed through the 'reaction-diffusion' process of modulating the oil-water interface, the filtering area can be effectively increased, and the flux of the nanofiltration membrane is increased.

According to the embodiment of the invention, a self-assembly structure is formed by means of hydrogen bond action among carbon nitride sol molecules, a hydrophilic surface induced fold structure is provided for interfacial polymerization reaction, a simple and easily-controlled method is provided for improving the water flux of the nanofiltration membrane, and the production cost is effectively reduced. Meanwhile, the carbon nitride can be used for photocatalytic degradation of surface trapped pollutants, so that the nanofiltration membrane has photocatalytic self-cleaning performance, the problem of insufficient pollution resistance of the traditional interfacial polymerization nanofiltration membrane is expected to be solved, and the application prospect is good.

In an embodiment of the present invention, the supporting base membrane includes a polycarbonate filter membrane (PC), a polytetrafluoroethylene filter membrane (PTFEE), a polyethersulfone filter membrane (PES), a polysulfone filter membrane (PS), or a polypropylene filter membrane (PP).

In an embodiment of the present invention, the polyamine monomer includes at least one of piperazine (PIP), Polyethyleneimine (PEI), 1, 4-Diaminocyclohexane (DCH), and m-phenylenediamine (MPD).

In an embodiment of the present invention, the poly-acid chloride monomer includes at least one of trimesoyl chloride (TMC), trimesic acid (PMA), 1, 3-benzenedisulfonyl chloride (BDSC), and terephthaloyl chloride (TPC).

In an embodiment of the present invention, the organic solution includes at least one of n-hexane, cyclohexane, benzene, and toluene.

The embodiment of the invention also provides a preparation method of the multifunctional nanofiltration membrane with the corrugated structure, which comprises the following steps:

1) adding the hydrophilic carbon nitride sol into an aqueous solution of a polyamine monomer, and performing ultrasonic dispersion to obtain a mixed dispersion liquid;

3) soaking the carbon nitride-based hydrophilic film modified basement membrane in an organic solution of a polybasic acyl chloride monomer to enable the polybasic amine monomer and the polybasic acyl chloride monomer to generate an interfacial polymerization reaction, thereby obtaining the multifunctional nanofiltration membrane with the corrugated structure.

In an embodiment of the present invention, in step 1), the preparation method of the hydrophilic carbon nitride sol specifically includes: dispersing carbon nitride in sodium hydroxide solution, and performing alkali treatment to obtain hydrophilic carbon nitride sol dispersed in water.

Specifically, the concentration of the sodium hydroxide solution is 1-5 mol/L.

Specifically, the preparation method of the hydrophilic carbon nitride sol further comprises the following steps: after the alkali treatment, dialysis treatment was performed. Preferably, the dialysis bag is subjected to dialysis treatment, and the molecular weight cut-off of the dialysis bag is 3500.

In one embodiment of the present invention, in step 1), the concentration of carbon nitride in the aqueous solution of polyamine monomer is 0.1-2.0 mg/mL. The carbon nitride may be added as a hydrophilic carbon nitride sol dispersed in water. In the step 1), the concentration of the aqueous solution of the polyamine monomer is 1-6 mg/mL.

In an embodiment of the present invention, in the step 2), the soaking time is 20 to 180 seconds.

In an embodiment of the present invention, the step 2) further includes removing the excess aqueous solution on the surface after performing interface self-assembly of the carbon nitride molecular sol.

In one embodiment of the invention, in the step 3), the temperature of the interfacial polymerization reaction is 20-30 ℃; the relative humidity of the interfacial polymerization reaction is 40-80%; the time of the interfacial polymerization reaction is 20-120 s.

In the step 3), the concentration of the organic solution of the polybasic acyl chloride monomer is 0.3-3 mg/mL.

The embodiment of the invention also provides application of the multifunctional nanofiltration membrane with the corrugated structure in the field of water treatment. The pure water flux of the multifunctional nanofiltration membrane with the corrugated structure is 40L h^-1m^-2bar^-1The retention rate of the sodium sulfate solution is more than 98 percent, and the retention molecular weight of the saccharide molecules is 360 Da.

The multifunctional nanofiltration membrane is mixed with the carbon nitride material with intrinsic photocatalytic activity, so that the catalytic degradation of surface pollutants can be realized under the irradiation of visible light, and the multifunctional nanofiltration membrane has important contribution to the reduction of membrane pollution.

The present invention will be described in detail with reference to examples.

Example 1A preparation method of a multifunctional nanofiltration membrane with surface wrinkles comprises the following steps:

step 1: dispersing 0.2g of bulk carbon nitride material prepared by thermal polymerization in 2M sodium hydroxide solution, performing alkali treatment modification on carbon nitride molecules by ultrasound or stirring, and performing dialysis treatment on the obtained solution for 2 days by using a dialysis bag with molecular weight cutoff of 3500 to obtain carbon nitride molecule sol solution highly dispersed in water. FIG. 1(a) is a transmission electron micrograph of a carbon nitride sol.

Step 2: preparing 2mg/mL piperazine (water) solution, adding 0.5mg/mL carbon nitride molecular sol (the concentration of carbon nitride in the piperazine water solution is 0.5mg/mL), and performing ultrasonic treatment to uniformly disperse the carbon nitride molecular sol to obtain a mixed dispersion liquid; and dropwise adding 1ml of mixed dispersion liquid onto the surface of the polyether sulfone support base film to assemble the carbon nitride composite hydrophilic layer, soaking for 60s, and removing residual liquid on the surface to obtain the hydrophilic carbon nitride modified support base film surface. FIG. 1(b) is a scanning electron microscope image of a carbon nitride hydrophilic modification layer formed by self-assembly on the surface of a supporting base film.

And step 3: preparing a 1mg/mL n-hexane solution of trimesoyl chloride, and fully infiltrating the surface of the n-hexane solution by utilizing a base membrane subjected to carbon nitride hydrophilic modification to enable piperazine monomers and trimesoyl chloride to perform interfacial polymerization reaction for 60s at a hydrophilic interface to form a Polyamide (PA) selection layer.

And 4, step 4: and (3) drying the obtained film in a forced air drying oven at 60 ℃ for 10 minutes to obtain the carbon nitride composite modified multifunctional nanofiltration membrane.

Example 2A preparation method of a multifunctional nanofiltration membrane with surface wrinkles comprises the following steps:

step 1: dispersing 0.2g of bulk carbon nitride material prepared by thermal polymerization in 3M sodium hydroxide solution, performing alkali treatment modification on carbon nitride molecules by ultrasound or stirring, and performing dialysis treatment on the obtained solution for 2 days by using a dialysis bag with molecular weight cutoff of 3500 to obtain carbon nitride molecule sol solution highly dispersed in water.

Step 2: preparing 2mg/mL piperazine (water) solution, adding 0.5mg/mL carbon nitride molecular sol solution (the concentration of carbon nitride in the piperazine water solution is 0.5mg/mL), and performing ultrasonic treatment to uniformly disperse the carbon nitride molecular sol solution to obtain mixed dispersion liquid; and dropwise adding 1ml of mixed dispersion liquid onto the surface of the polyether sulfone support base film to assemble the carbon nitride composite hydrophilic layer, soaking for 60s, and removing residual liquid on the surface to obtain the hydrophilic carbon nitride modified support base film surface.

And step 3: preparing a 1mg/mL n-hexane solution of trimesoyl chloride, and fully soaking the surface of the supporting base membrane by using carbon nitride hydrophilic modification to enable piperazine monomers and trimesoyl chloride to generate interfacial polymerization reaction for 60s at a hydrophilic interface to form a Polyamide (PA) selection layer.