CN113877426A

CN113877426A - Super-hydrophobic polypropylene modified ultrafiltration membrane and preparation method and application thereof

Info

Publication number: CN113877426A
Application number: CN202111186835.7A
Authority: CN
Inventors: 陈桂娥; 韩晓杨; 李怡静; 谢焕银; 陈镇; 马文霄; 张浩然; 范志宇; 梁计晨; 许振良
Original assignee: Shanghai Institute of Technology
Current assignee: Shanghai Institute of Technology
Priority date: 2021-10-12
Filing date: 2021-10-12
Publication date: 2022-01-04

Abstract

The invention relates to a super-hydrophobic polypropylene modified ultrafiltration membrane, a preparation method and application thereof, wherein the method comprises the following steps: dissolving zirconium tetrachloride, dopamine hydrochloride and tris (hydroxymethyl) aminomethane in a solvent to prepare a first solution for later use; dissolving zirconium tetrachloride and 2-amino terephthalic acid in a solvent to prepare a second solution for later use; immersing the PP ultrafiltration membrane into the first solution, and immersing to obtain a treated membrane; and immersing the treated membrane into the second solution, and reacting to prepare a super-hydrophobic polypropylene modified ultrafiltration membrane, namely the TF-DUT-52/PP membrane, wherein the modified ultrafiltration membrane is applied to cyclohexane degradation. Compared with the prior art, the method has the advantages of higher separation rate of the water-oil emulsion, higher cyclohexane photocatalytic degradation capability and the like.

Description

Super-hydrophobic polypropylene modified ultrafiltration membrane and preparation method and application thereof

Technical Field

The invention relates to the technical field of membrane separation, in particular to a super-hydrophobic polypropylene modified ultrafiltration membrane and a preparation method and application thereof.

Background

The application of membrane separation to oil-water separation is a relatively new method. The membrane separation technology is to separate substances needing to be intercepted by utilizing the selective permeability and the selective permeation of a membrane. Common membrane separation processes are microfiltration, ultrafiltration, reverse osmosis, and the like. The separation method is determined according to the particle size of oil drops in water. The membrane separation process has the advantages of no phase change, less energy consumption in the separation process, good separation effect and the like.

Chinese patent (publication No. CN 111777782A) discloses a hydrophobic self-cleaning polyvinyl chloride film and a preparation method thereof, wherein nano polyvinyl chloride and nano silicon dioxide are combined with a base film to form a film with a micro-rough surface with micro-pits, and nano particles are distributed on the micro-rough surface; however, the method has a complex preparation process, active components are concentrated on the surface of the nanoparticles, and the oil-water separation performance is limited.

Chinese patent (publication No. CN 107243260A) discloses a novel super-hydrophobic polyvinylidene fluoride oil-water separation membrane and a preparation method thereof. The method has the advantages of simple preparation process, low material price, no toxic reagent involved in the experimental process, suitability for industrial production, high strength and high flux of the obtained super-hydrophobic polyvinylidene fluoride flat membrane, stable flux in the oil-water separation process, excellent separation performance and wide industrial application value in oil-water separation, sewage treatment and marine oil leakage. However, it is only possible to separate oil from water, and it is impossible to decompose organic substances, and therefore, it is necessary to perform post-treatment operations such as concentration, purification, and separation of organic substances, which results in high use cost.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a super-hydrophobic polypropylene modified ultrafiltration membrane with higher water-oil emulsion separation rate and cyclohexane photocatalytic degradation capability, and a preparation method and application thereof.

The purpose of the invention can be realized by the following technical scheme:

the inventor knows that metal organic framework Materials (MOFs) are microporous crystal materials formed by coordination of metal ions and organic ligands, have the performance of both inorganic materials and organic materials, and have wide application space. The optical transition, photoelectrochemical and photochemical activities of MOFs indicate that they have semiconductor behavior. With TiO₂MOFs have excellent optical tunability compared to typical semiconductor materials such as CdS and ZnO. Tunable SBUs or functionalized organic ligands in MOFs can act as "antennas" to capture and absorb light, thereby generating photo-generated electron-hole pairs. The photocatalytic performance of individual MOFs is often poor, and the photocatalytic activity of the MOFs can be improved by methods such as modifying a ligand of the MOFs, adding a metal molecular catalyst, synthesizing the MOFs composite material (the MOFs is respectively combined with metal, a semiconductor material and other active substances), and the like, so that the following specific scheme is proposed:

a preparation method of a super-hydrophobic polypropylene modified ultrafiltration membrane comprises the following steps:

dissolving zirconium tetrachloride, dopamine hydrochloride and tris (hydroxymethyl) aminomethane in a solvent to prepare a first solution for later use;

dissolving zirconium tetrachloride and 2-amino terephthalic acid in a solvent to prepare a second solution for later use;

immersing the PP ultrafiltration membrane into the first solution, and immersing to obtain a treated membrane;

and immersing the treated membrane into a second solution, and reacting to prepare the super-hydrophobic polypropylene modified ultrafiltration membrane, namely the TF-DUT-52/PP membrane.

The method specifically comprises the following steps:

and adopting an in-situ crosslinking polymerization method to synthesize the TF-DUT-52/PP film.

(1) Zirconium tetrachloride (ZrCl)₄) Dissolving dopamine hydrochloride and tris (hydroxymethyl) aminomethane in a solvent to prepare a solution;

(2) immersing a PP ultrafiltration membrane into the solution prepared in the step (1), and immersing to obtain a treated membrane;

(3) zirconium tetrachloride (ZrCl)₄) And 2-aminoterephthalic acid (H)₂NDC-NHCOCF) is dissolved in a solvent to prepare a solution;

(4) and (3) immersing the membrane treated in the step (2) into the solution prepared in the step (3), and reacting to prepare the TF-DUT-52/PP membrane.

Furthermore, the molar ratio of the zirconium tetrachloride to the dopamine hydrochloride is 1 (2-5), preferably 1 (3.2-3.8).

Further, the solvent comprises one or more of water, ethanol or DMF.

Further, the soaking time is 0.1-24 h; the reaction temperature is 90-160 ℃, preferably 100-140 ℃, and the reaction time is 1-96 hours, preferably 12-48 hours.

Further, the pH of the first solution is 7 to 10, preferably 8 to 8.5.

Further, the PP ultrafiltration membrane is prepared by the following steps:

(1) fully dissolving polyvinylpyrrolidone as an additive and polypropylene in DMF (dimethyl formamide) to prepare a PP casting solution;

(2) scraping the casting solution on a glass plate to form a film;

(3) and (3) taking deionized water as a gel bath, putting the membrane and the glass plate into the gel bath together for phase separation to obtain the PP ultrafiltration membrane.

Further, the thickness of the PP ultrafiltration membrane is 100-200 μm, preferably 120-180 μm.

Furthermore, the mass ratio of the polyvinylpyrrolidone to the polypropylene is 1 (5-12), preferably 1 (6-10).

A super-hydrophobic polypropylene modified ultrafiltration membrane prepared by the method.

The application of the super-hydrophobic polypropylene modified ultrafiltration membrane is applied to cyclohexane degradation.

The invention adopts an in-situ cross-linking polymerization method to synthesize the TF-DUT-52/PP membrane, and fixes a large amount of TF-DUT-52 on the surface of the PP membrane, thereby obtaining the super-hydrophobic polypropylene modified ultrafiltration membrane with cyclohexane degradation performance. The membrane prepared by the method has stronger hydrophobicity, can effectively separate oil-water emulsion, and has higher photocatalytic degradation effect on cyclohexane under visible light.

In the invention, the hydrophobicity of the TF-DUT-52 is improved due to the existence of the trifluoroacetamide group, but the preparation method of the invention can lead the TF-DUT-52 to be uniformly and densely loaded on the surface of the membrane, thus leading the membrane to have excellent oil-water separation capability, and simultaneously leading the TF-DUT-52 to carry out aerobic oxidation on cyclohexane under mild conditions.

The invention adopts two-step impregnation, so that the TF-DUT-52 can be more densely loaded, the hydrophobicity of the membrane can be improved due to the increase of the loading amount, and the effective contact area with pollutants can be increased.

In the present invention, DUT-52 is a zirconium (Zr) metal organic framework with a face centered cubic topology of DUT-52(DUT stands for Dresden University of Technology) structure, and TF-DUT-52 is formed by substituting H for TF-DUT-52₂NDC-NH₂Conversion to rigid 1- (2,2, 2-trifluoroacetylamino) naphthalene-3, 7-dicarboxylic acid (H)₂NDC-NHCOCF₃) Ligand, TF is an abbreviation for english.

Compared with the prior art, the preparation method of the ultrafiltration membrane has the beneficial effects that: the TF-DUT-52/PP membrane is synthesized by adopting an in-situ cross-linking polymerization method, a large number of TF-DUT-52 are fixed on the surface of the PP membrane, and because the TF-DUT-52 has high hydrophobicity and strong cyclohexane degradation capability, the ultrafiltration membrane prepared by the method has strong oil-water emulsion separation capability, can efficiently remove cyclohexane in sewage while oil-water separation, and does not need to increase a post-treatment process.

Drawings

FIG. 1 is a graph showing the oil-water emulsion separation test of TF-DUT-52/PP membrane in examples 1 to 3;

FIG. 2 is a graph showing the effect of TF-DUT-52/PP film prepared in example 1 on the catalytic degradation rate of cyclohexane;

FIG. 3 is a sectional electron micrograph of the TF-DUT-52/PP film of examples 1 to 3.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

Through a great deal of research, the applicant provides a preparation method of a super-hydrophobic polypropylene modified ultrafiltration membrane with cyclohexane degradation performance.

The TF-DUT-52/PP hydrophobic membrane synthesized by the invention has higher water-oil emulsion separation rate and the capability of degrading cyclohexane by photocatalysis, and the invention is completed on the basis.

One aspect of the invention provides a preparation method of a super-hydrophobic polypropylene modified ultrafiltration membrane.

Adopting an in-situ crosslinking polymerization method to synthesize the TF-DUT-52/PP membrane, comprising the following steps:

dissolving zirconium tetrachloride, dopamine hydrochloride and tris (hydroxymethyl) aminomethane in a solvent to prepare a first solution for later use; the molar ratio of zirconium tetrachloride to dopamine hydrochloride is 1 (2-5), preferably 1 (2.8-4), more preferably 1 (3.2-3.8). The solvent is zirconium tetrachloride (ZrCl)₄) 1-10 times, 1-2 times, 2-4 times, 4-6 times, 6-8 times, or 8-10 times, preferably 2-6 times, the mass of dopamine hydrochloride and tris (hydroxymethyl) aminomethane. The solvent can be one or more of water, ethanol and DMF; the pH of the first solution was 7-10,the pH is preferably 8 to 8.5.

Dissolving zirconium tetrachloride and 2-amino terephthalic acid in a solvent to prepare a second solution for later use; the solvent can be one or combination of ethanol and DMF; the solvent B is zirconium tetrachloride (ZrCl)₄) And 2-aminoterephthalic acid (H)₂NDC-NHCOCF) of 1 to 10 times, 1 to 2 times, 2 to 4 times, 4 to 6 times, 6 to 8 times, or 8 to 10 times, preferably 2 to 6 times.

Immersing the PP ultrafiltration membrane into the first solution, and immersing to obtain a treated membrane; the soaking time is 0.1-24h, preferably 0.5-12h, preferably 0.5-6h, preferably 1-12h, more preferably 6-12 h; the reaction temperature is 90-160 ℃, preferably 100-160 ℃, more preferably 100-140 ℃, such as 110 ℃, 120 ℃ and 130 ℃, and the time is 1-96h, preferably 12-48h, more preferably 12-24 h.

The PP ultrafiltration membrane is prepared by the following steps:

(1) fully dissolving polyvinylpyrrolidone as an additive and polypropylene in DMF (dimethyl formamide) to prepare a PP casting solution; magnetically stirring the casting solution at normal temperature until the casting solution is completely dissolved, and transferring the casting solution to an oven for defoaming at 60 ℃ for 12-48 h; the mass ratio of the polyvinylpyrrolidone to the polypropylene is 1 (5-12), preferably 1 (6-10).

(2) Scraping the casting solution on a glass plate to form a film;

(3) and (3) taking deionized water as a gel bath, putting the membrane and the glass plate into the gel bath together for phase separation to obtain the PP ultrafiltration membrane. The thickness of the PP ultrafiltration membrane is 100-200 μm, preferably 120-180 μm, more preferably 120-150 μm, such as 130 μm, 140 μm, etc.

And immersing the treated membrane into the second solution, and reacting to prepare a super-hydrophobic polypropylene modified ultrafiltration membrane, namely the TF-DUT-52/PP membrane, wherein the modified ultrafiltration membrane is applied to cyclohexane degradation.

Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.

Example 1

(1-1) fully dissolving 2g of PVP and 18g of PP in DMF to prepare a casting solution of PP, stirring for 20h, standing for defoaming or transferring to an oven for defoaming at 60 ℃ for 24 h;

(1-2) scraping the casting solution obtained in the step (1-1) on a glass plate to form a membrane with the thickness of 150 microns, and putting the glass plate into a gel bath by taking deionized water as the gel bath for phase separation to obtain a polypropylene ultrafiltration membrane;

(1-3) reacting zirconium tetrachloride (ZrCl)₄) And dopamine hydrochloride according to 1: 3.5 adding into a trihydroxymethyl aminomethane aqueous solution with the pH value of 8.5 and immersing the PP film into the solution;

(1-4) placing the treated film in a container containing 2-aminoterephthalic acid (H)₂NDC-NHCOCF) and ZrCl₄And placing the obtained product in a reaction kettle of N, N-Dimethylformamide (DMF) solution at the temperature of 120 ℃ to react for 24 hours to obtain the TF-DUT-52/PP membrane.

Example 2

The difference from example 1 is that the film thickness is 120. mu.m.

Example 3

The difference from example 1 is that the film thickness is 180. mu.m.

Example 4

(2-1) scraping the casting solution obtained in the step (1-1) in the example 1 on a glass flat plate to form a membrane with the thickness of 120 microns, and putting the glass plate into a gel bath by taking deionized water as the gel bath for phase separation to obtain a polypropylene ultrafiltration membrane;

(2-2) reacting zirconium tetrachloride (ZrCl)₄) And dopamine hydrochloride according to 1: 3.2 adding the solution into a trihydroxymethyl aminomethane aqueous solution with the pH value of 8.5 and immersing a PP film into the solution;

(2-3) placing the treated film in a container containing 2-aminoterephthalic acid (H)₂NDC-NHCOCF) and ZrCl₄The obtained product is placed in an oven with the temperature of 100 ℃ for reaction for 12 hours to obtain the TF-DUT-52/PP membrane.

Example 5

(3-1) scraping the casting solution obtained in the step (1-1) in the example 1 on a glass flat plate to form a membrane with the thickness of 180 microns, and putting the glass plate into a gel bath by taking deionized water as the gel bath for phase separation to obtain a polypropylene ultrafiltration membrane;

(3-2) reacting zirconium tetrachloride (ZrCl)₄) And dopamine hydrochloride according to 1: 3.8 adding into a tris aqueous solution with a pH value of 8.5 and immersing the PP film therein;

(3-3) placing the treated film in a container containing 2-aminoterephthalic acid (H)₂NDC-NHCOCF) and ZrCl₄In a reaction kettle, and placing the reaction kettle in an oven at the temperature of 140 ℃ for reaction for 48 hours to obtain the TF-DUT-52/PP membrane.

As shown in FIG. 3, sectional electron micrographs of TF-DUT-52/PP films prepared in example 2, example 1 and example 3 from top to bottom respectively show that TF-DUT-52 was successfully loaded on PP films.

Oil-water emulsion separation test

The oil-water emulsion is obtained by mixing 99% of petroleum ether, 1% of deionized water and 1.5g/L of Span-80 and then stirring for 3 hours, and the separation efficiency data of the oil-water emulsion is collected by a cross-flow filtering device self-made by a laboratory under 0.1 MPa. Data were collected after each film was pre-stressed for 30min by DI to ensure accuracy, data being stable values obtained for more than three measurements per film. The test results are shown in figure 1.

The results of the attached figure 1 show that the TF-DUT-52/PP membranes prepared in the examples 1, 2 and 3 have oil-water separation performance, the TF-DUT-52/PP membrane prepared in the example 1 has intermediate film thickness and optimal oil-water emulsion separation performance, and the water removal rate is as high as 99.8%; this is because the hydrophobic property of TF-DUT-52 improves the oil-water separation performance of the membrane, but as the thickness of the membrane increases, the thickness of the membrane surface layer gradually increases, and the too thick membrane surface layer decreases the load factor of TF-DUT-52, resulting in a decrease in the oil-water separation performance of the membrane.

Test for catalytic Performance

The photocatalytic reduction of cyclohexane is carried out by using cyclohexane water solution at normal temperature, the initial volume of the solution is 50.0mL, and the initial concentration is C₀Is 10.0mg L^-1. Three pieces of 9cm²A TF-DUT-52/PP film of the size was immersed in the above solution, left to stand in the dark for 30min, and then irradiated under visible light supplied from an LED with 50mW of optical power for 120 min. The residual cyclohexane concentration can be measured by uv-vis spectrophotometry, Ct being the cyclohexane concentration in the permeate at time t. The test results are shown in FIG. 2.

As can be seen from FIG. 2, the catalytic degradation rate of cyclohexane in example 1 was 89.8% at a test time of 120 minutes.

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a super-hydrophobic polypropylene modified ultrafiltration membrane is characterized by comprising the following steps:

2. The preparation method of the superhydrophobic polypropylene modified ultrafiltration membrane according to claim 1, wherein the molar ratio of the zirconium tetrachloride to the dopamine hydrochloride is 1 (2-5).

3. The method for preparing the superhydrophobic polypropylene modified ultrafiltration membrane according to claim 1, wherein the solvent comprises one or more of water, ethanol or DMF.

4. The preparation method of the super-hydrophobic polypropylene modified ultrafiltration membrane according to claim 1, wherein the soaking time is 0.1-24 h; the reaction temperature is 90-160 ℃ and the reaction time is 1-96 h.

5. The method for preparing the superhydrophobic polypropylene modified ultrafiltration membrane according to claim 1, wherein the pH of the first solution is 7-10.

6. The preparation method of the ultra-hydrophobic polypropylene modified ultrafiltration membrane according to claim 1, wherein the PP ultrafiltration membrane is prepared by the following steps:

(2) scraping the casting solution on a glass plate to form a film;

7. The method for preparing the super-hydrophobic polypropylene modified ultrafiltration membrane according to claim 1 or 6, wherein the thickness of the PP ultrafiltration membrane is 100-200 μm.

8. The preparation method of the superhydrophobic polypropylene modified ultrafiltration membrane according to claim 6, wherein the mass ratio of the polyvinylpyrrolidone to the polypropylene is 1 (5-12).

9. A superhydrophobic polypropylene modified ultrafiltration membrane prepared according to the method of any one of claims 1-8.

10. Use of the ultrahydrophobic polypropylene modified ultrafiltration membrane of claim 9 in cyclohexane degradation.