CN112999884B

CN112999884B - Pervaporation membrane, preparation method thereof and treatment method of coating wastewater

Info

Publication number: CN112999884B
Application number: CN202110359268.4A
Authority: CN
Inventors: 何龙; 黄思远; 黄磊; 姚迎迎; 张静; 尹竞
Original assignee: Shanghai Electric Group Corp
Current assignee: Shanghai Electric Group Corp
Priority date: 2021-04-02
Filing date: 2021-04-02
Publication date: 2022-07-22
Anticipated expiration: 2041-04-02
Also published as: CN112999884A

Abstract

The application relates to the field of wastewater treatment, and discloses a pervaporation membrane, a preparation method thereof and a treatment method of coating wastewater. The pervaporation membrane comprises the following raw materials in parts by weight: 0.5-5 parts of polyethylene glycol grafted silicon dioxide nano particles, 5-20 parts of polydimethylsiloxane, 0.5-3 parts of cross-linking agent and 0.1-1 part of catalyst. The pervaporation membrane has higher stability, and is easy to realize the preparation of large-area pervaporation membranes. The pervaporation membrane is used for treating alcohol ether-containing coating wastewater, and the treatment effect is better.

Description

Pervaporation membrane, preparation method thereof and treatment method of coating wastewater

Technical Field

The application relates to the field of wastewater treatment, in particular to a pervaporation membrane, a preparation method thereof and a treatment method of coating wastewater.

Background

In industrial manufacturing processes, parts, semi-finished products, products and the like often need to be painted. For example, in the automobile manufacturing process, multiple processes of paint spraying and coating are needed. In the continuous painting process of the automobile by using the robot spray gun, the spray gun needs to be frequently cleaned, and the used cleaning agent is a surfactant solution containing alcohol ether, such as ethylene glycol monobutyl ether solution, which can generate a certain amount of paint spraying and gun washing waste liquid containing paint and alcohol ether surfactants and having the concentration of organic matters as high as 10%, wherein the concentration of the alcohol ether surfactant is about 7%.

The coating waste liquid has the characteristics of high organic matter concentration and difficult biochemical treatment. For such waste liquids, chemical and physical treatment methods such as electrolysis, fenton reaction, ozone oxidation, reverse osmosis, nanofiltration, ultrafiltration, MBR, and evaporation have been developed. However, at present, for the waste liquid of the spray gun washing containing about 7% of alcohol ether surfactant and having an organic matter concentration as high as 10%, the organic matter concentration is too high, and the treatment cost per ton is as high as 5000-6000 yuan. And the conventional water treatment technical scheme can not realize treatment.

The pervaporation technology organic matter removal membrane has a good separation effect on the solvent-water system, the separated concentrated solution has the characteristics of pure solvent-water, the concentration is high, the reduction and recycling effects are achieved, and the treated effluent enters a system to effectively reduce the treatment load of a sewage station. Currently, the most used is polysiloxane composite membrane (PDMS), but the preparation process of the PDMS membrane has the problems of uneven dispersion and unstable membrane performance. The PDMS membrane is modified by adopting a chemical crosslinking and grafting method, so that the problems of complex process, difficult amplification and the like exist.

Disclosure of Invention

The application discloses a pervaporation membrane, a preparation method thereof and a treatment method of coating wastewater, which aim to solve the problems of unstable performance and complex preparation process of the existing PDMS membrane.

In order to achieve the purpose, the application provides the following technical scheme:

in a first aspect, the present application provides a pervaporation membrane comprising the following raw materials in parts by weight: 0.5-5 parts of polyethylene glycol grafted silica nano particles, 5-20 parts of polydimethylsiloxane, 0.5-3 parts of a cross-linking agent and 0.1-1 part of a catalyst.

Further, the thickness of the pervaporation membrane is 50 to 150 μm.

In a second aspect, the present application provides a method of making a pervaporation membrane comprising the steps of:

uniformly mixing polyethylene glycol grafted silica nanoparticles, polydimethylsiloxane, a cross-linking agent and a catalyst, and performing vacuum defoaming treatment to obtain a casting solution;

and coating the casting film liquid on the surface of the base film, and drying to obtain the pervaporation film.

Further, the polyethylene glycol grafted silica nanoparticle is prepared by the following method:

mixing SiO₂Mixing the nano particles, diisocyanate, deionized water and low molecular weight polyethylene glycol to obtain a suspension; wherein the low molecular weight polyethylene glycol has a molecular weight of less than 2000;

heating the suspension to 60-80 ℃ under the water bath condition, stirring and reacting for 1.5-2.5h, then adding a hydrochloric acid solution, continuously stirring and reacting for 2.5-4h, cooling to room temperature, and carrying out solid-liquid separation to obtain the polyethylene glycol grafted silicon dioxide nanoparticles.

Furthermore, the addition amount of the polyethylene glycol grafted silica nanoparticles is 1.0-3.0g, the addition amount of the diisocyanate is 0.1-1.0g, and the addition amount of the low molecular polyethylene glycol is 1.0-10g based on 100ml of the deionized water.

Further, the concentration of the hydrochloric acid is 0.3-0.4 g/ml; the addition amount of the hydrochloric acid is 0.1-0.5ml based on 100ml of the deionized water.

Furthermore, in the process of preparing the casting solution, the addition amount of the polyethylene glycol grafted silicon dioxide nano particles is 0.5-5 parts by weight, the addition amount of the polydimethylsiloxane is 5-20 parts by weight, the addition amount of the cross-linking agent is 0.5-3 parts by weight, and the addition amount of the catalyst is 0.1-1 part by weight.

In a third aspect, the present application provides a pervaporation membrane obtained by the method of manufacturing according to the second aspect of the present application.

In a fourth aspect, the present application provides a method for treating coating wastewater, comprising the steps of:

treating the coating wastewater by using a pervaporation device; wherein, the first and the second end of the pipe are connected with each other,

the pervaporation device comprising a pervaporation membrane according to the third aspect of the present application.

Furthermore, the coating wastewater contains 6.5-7.5 wt% of ethylene glycol monobutyl ether and 9.5-11.5 wt% of total organic matter.

Further, in the pervaporation device, the total area of the pervaporation membrane filled is 13 to 15m²。

By adopting the technical scheme of the application, the beneficial effects are as follows:

the application provides a permeate vaporFilming, grafting SiO with polyglycol₂The nano particle doped PDMS is used in preparing permeating and vaporizing film owing to grafting of polyglycol to SiO₂The surface of the nano particle is grafted with low molecular weight polyethylene glycol which has higher compatibility with PDMS, so that the polyethylene glycol is grafted with SiO₂The nano particles have better dispersibility in PDMS, the prepared pervaporation membrane has higher stability, and the preparation of the large-area pervaporation membrane is easy to realize. The pervaporation membrane is used for treating alcohol ether-containing coating wastewater, and the treatment effect is better.

In addition, compared with the existing methods such as chemical oxidation, reverse osmosis, nanofiltration, evaporation and the like, the pervaporation membrane prepared by the preparation method provided by the application is grafted with SiO through polyethylene glycol₂The nano particles have better dispersibility in PDMS, the prepared pervaporation membrane has higher stability, and the preparation of the pervaporation membrane with large area is easy to realize. The pervaporation method for treating the coating wastewater has the advantages of less equipment investment, low treatment cost, good treatment effect and the like.

Drawings

FIG. 1 is a drawing of a polyether oligomer grafted SiO prepared in the examples of the present application₂TEM images of the nanoparticles;

FIG. 2 is a diagram of polyether oligomer grafted SiO prepared in the examples of the present application₂Graph of thermal weight loss of nanoparticles.

FIG. 3 is a diagram of polyether oligomer grafted SiO prepared according to the examples of the present application₂Photograph of the dispersibility of the nanoparticles in DMAc solution;

FIG. 4 is a surface SEM image of a pervaporation membrane prepared according to various embodiments of the present application;

FIG. 5 is a sectional SEM image of a pervaporation membrane prepared according to various embodiments of the present application;

FIG. 6 is an infrared spectrum of a pervaporation membrane prepared according to various examples of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.

It should be noted that: in the present application, all embodiments and preferred methods mentioned herein can be combined with each other to form new solutions, if not specifically stated. In the present application, all the technical features mentioned herein and preferred features may be combined with each other to form new solutions, if not specifically stated. In the present application, percentages (%) or parts refer to percent by weight or parts by weight relative to the composition, unless otherwise specified. In the present application, the components referred to or the preferred components thereof may be combined with each other to form new embodiments, if not specifically stated. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range of "6 to 22" means that all real numbers between "6 to 22" have been listed herein, and "6 to 22" is only a shorthand representation of the combination of these numerical values. The "ranges" disclosed herein may be in the form of lower limits and upper limits, and may be one or more lower limits and one or more upper limits, respectively. In the present application, unless otherwise indicated, the individual reactions or operational steps may be performed sequentially or in an ordered sequence. Preferably, the reaction processes herein are carried out sequentially.

Unless otherwise defined, technical and scientific terms used herein have the same meaning as is familiar to those skilled in the art. In addition, any methods or materials similar or equivalent to those described herein can also be used in the present application.

Aiming at the water-based waste solvent generated by robot coating, the traditional water treatment technology cannot meet the treatment requirement, and the pervaporation membrane can be used as a pretreatment technology to separate organic matters and water in waste liquid. The key material for treating the coating waste liquid by the pervaporation membrane technology is organic silicon polymer, especially Polydimethylsiloxane (PDMS), which is a kind of permeable alcohol ether organic membrane material which is researched more at present because of good chemical stability and strong hydrophobicity. However, the PDMS film requires cross-linking during the film formation process, which results in poor fluidity, and it is difficult to obtain a uniform, ultra-thin, defect-free separation layer, and the mechanical strength of the PDMS film needs to be improved.

In order to solve the technical problem, the application provides a pervaporation membrane, which comprises the following raw materials in parts by weight: 0.5-5 parts of polyethylene glycol grafted silica nano particles, 5-20 parts of polydimethylsiloxane, 0.5-3 parts of a cross-linking agent and 0.1-1 part of a catalyst.

The pervaporation membrane provided by the application uses polyethylene glycol to graft SiO₂The nano particle doped PDMS is used in preparing permeating and vaporizing film owing to grafting of polyglycol to SiO₂The surface of the nano particle is grafted with low molecular weight polyethylene glycol which has higher compatibility with PDMS, so that the polyethylene glycol is grafted with SiO₂The nano particles have better dispersibility in PDMS, the prepared pervaporation membrane has higher stability, and the preparation of the pervaporation membrane with large area is easy to realize. The pervaporation membrane is used for treating alcohol ether-containing coating wastewater, and the treatment effect is better.

Wherein, in the pervaporation membrane, the weight part of the polyethylene glycol grafted silica nanoparticles can be, for example, 0.5 part, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts; the parts by weight of polydimethylsiloxane may be, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts; the weight fraction of crosslinking agent may be, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts or 3; the weight portion of the catalyst may be, for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1 part.

The crosslinking agent may be, for example, Tetraethylorthosilicate (TEOS), and the catalyst may be, for example, dibutyltin dilaurate (DBTDL).

In one embodiment of the present application, the pervaporation membrane has a thickness of 50 to 150 μm. The selectivity of the pervaporation membrane can be further increased by optimizing the thickness of the pervaporation membrane. The thickness of the pervaporation membrane may be, for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, or 150 μm.

and coating the casting film liquid on the surface of a base film, and drying to obtain the pervaporation membrane.

Compared with the prior methods of chemical oxidation, reverse osmosis, nanofiltration, evaporation and the like, the pervaporation membrane prepared by the preparation method provided by the application is grafted with SiO through polyethylene glycol₂The nano particles have better dispersibility in PDMS, the prepared pervaporation membrane has higher stability, and the preparation of the pervaporation membrane with large area is easy to realize. The pervaporation method for treating the coating wastewater has the advantages of less equipment investment, low treatment cost, good treatment effect and the like.

In one embodiment of the present application, the polyethylene glycol grafted silica nanoparticles are prepared by the following method:

step S1) SiO₂Mixing the nano particles, diisocyanate, deionized water and low molecular weight polyethylene glycol to obtain a suspension; wherein the low molecular weight polyethylene glycol has a molecular weight of less than 2000;

step S2), heating the suspension to 60-80 ℃ under the water bath condition, stirring and reacting for 1.5-2.5h, adding hydrochloric acid solution, continuing stirring and reacting for 2.5-4h, cooling to room temperature, and carrying out solid-liquid separation to obtain the polyethylene glycol grafted silica nanoparticles.

Wherein, in step S1), SiO can be added₂Mixing the nano particles, diisocyanate, deionized water and low molecular weight polyethylene glycol, and stirring in a water bath at 30 ℃ until a stable suspension is formed.

In step S2), in N₂Raising the temperature of the water bath to 70 ℃ under protection, stirring the suspension obtained in step S1) for 2 hours, and thenAdding concentrated hydrochloric acid, continuing stirring and reacting for 3 hours, and cooling to room temperature after the reaction is finished.

In an embodiment of the present application, in step S2), the specific operations of solid-liquid separation are as follows: washing with absolute ethyl alcohol after centrifugal separation, repeating for three times, collecting solid powder, drying in vacuum at 60 ℃ for 24 hours, and grinding to obtain the polyethylene glycol grafted silicon dioxide nano particles.

In one embodiment of the present application, based on 100ml of the deionized water, the addition amount of the polyethylene glycol-grafted silica nanoparticles is 1.0 to 3.0g, the addition amount of the diisocyanate is 0.1 to 1.0g, and the addition amount of the low molecular polyethylene glycol is 1.0 to 10 g.

The dispersibility of the polyethylene glycol grafted silica nanoparticles can be further improved and the uniformity of the dispersion can be improved by optimizing the addition amounts of the polyethylene glycol grafted silica nanoparticles, the diisocyanate and the low-molecular polyethylene glycol.

Wherein, the addition amount of the polyethylene glycol grafted silica nanoparticles can be, for example, 1.0g, 1.2g, 1.4g, 1.6g, 1.8g, 2.0g, 2.2g, 2.4g, 2.6g, 2.8g or 3.0g based on 100ml of deionized water; the amount of diisocyanate added may be, for example, 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, 0.7g, 0.8g, 0.9g or 1.0 g; the amount of the low molecular weight polyethylene glycol added may be, for example, 1.0g, 2g, 3g, 4g, 5g, 6g, 7g, 8g, 9g or 10.0 g.

In one embodiment of the present application, the concentration of the hydrochloric acid is 0.3 to 0.4g/ml, preferably 0.365 g/ml.

Wherein the addition amount of the hydrochloric acid is 0.1-0.5ml based on 100ml of the deionized water.

In one embodiment of the present application, in the process of preparing the casting solution, the addition amount of the polyethylene glycol grafted silica nanoparticles is 0.5 to 5 parts by weight, 5 to 20 parts by weight, 0.5 to 3 parts by weight, and 0.1 to 1 part by weight, based on the parts by weight, of the polydimethylsiloxane, the crosslinking agent, and the catalyst.

Wherein, in the prepared casting solution, the weight portion of the polyethylene glycol grafted silica nanoparticles can be, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5; the parts by weight of polydimethylsiloxane can be, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts; the weight fraction of crosslinking agent may be, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts or 3; the weight portion of the catalyst may be, for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1 part.

In one embodiment of the present application, polyethylene glycol grafts to SiO₂Stirring and mixing the nano particles, Polydimethylsiloxane (PDMS) and cross-linking agent Tetraethoxysilane (TEOS) uniformly at 25 ℃, adding catalyst dibutyltin dilaurate (DBTDL) and continuously stirring, standing for 1hr, and measuring the viscosity of the mixture; and when the viscosity of the mixture system is constant, placing the mixture system into a vacuum oven for defoaming to obtain a casting solution.

In an embodiment of the present application, the casting solution is coated on the surface of a base film, and the pervaporation membrane is obtained after drying, which specifically includes:

uniformly pouring the membrane casting solution onto a Polysulfone (PSF) base membrane (the PSF base membrane is fixed on plate glass), and coating the surface of the base membrane with a certain thickness (wet membrane) by using a scraper; horizontally placing the plate glass coated with the casting film liquid composite film in an oven at 50 ℃ for drying for 12 hours to obtain polyether oligomer grafted SiO with a certain thickness₂Nanoparticles are doped with pervaporation membranes (dry films) of PDMS.

Wherein the wet film has a thickness of about 100 to 300 μm, and the dry film has a thickness of 50 to 150 μm.

In a third aspect, the present application provides a pervaporation membrane obtained by the production method according to the second aspect of the present application.

treating the coating wastewater by using a pervaporation device; wherein the pervaporation device comprises a pervaporation membrane according to the third aspect of the present application.

The coating waste water can be, for example, a cleaning waste liquid for cleaning an automobile coating spray gun, wherein the content of ethylene glycol monobutyl ether in the coating waste water is 6.5-7.5 wt%, and the content of total organic matters is 9.5-11.5 wt%.

As an exemplary illustration, the apparatus for treating painting wastewater of the present application includes: a feed liquid tank, an additional pump, a pervaporation device, a condensation system, a vacuum pump and the like.

Wherein the volume of the feed liquid tank can be 3m³. The pump is added to provide stable flow of the feed liquid side, and the range is 0.05-0.08 m³And/min. The total membrane area of the pervaporation membrane stack which can be filled in the pervaporation device is 13-15m²In between, the monolithic film may be 60cm long and 30cm in degree. The pervaporation device maintains a constant temperature of 50-70 ℃. The condensing system maintains a constant temperature of the permeate collector, ranging from-20 to-10 ℃. The vacuum pump maintains the constant pressure of the feed liquid transmission side within the range of 90-110 Pa. During treatment, the operation mode of intermittent and concentrated solution full circulation is adopted.

The pervaporation membrane of the present application will be further explained with reference to specific examples.

Example 1

(1) Low molecular weight polyethylene glycol grafted SiO₂Nanoparticle preparation

1.5g of silica nanomaterial, 0.3g of diisocyanate and 1.0g of low molecular weight polyethylene glycol (molecular chain 1000) were mixed in 100mL of deionized water and stirred in a water bath at 30 ℃ until a stable suspension was formed. And then introducing nitrogen to remove air, heating the water bath temperature to 70 ℃ under the protection of nitrogen, stirring the suspension for 2 hours, adding 0.3mL of concentrated hydrochloric acid, continuously stirring and reacting for 3 hours, cooling the obtained reaction liquid to room temperature, performing centrifugal separation, washing with absolute ethyl alcohol, repeating for three times, collecting solid powder, performing vacuum drying at 60 ℃ for 24 hours, and grinding to obtain the polyethylene glycol grafted silicon dioxide powder.

(2) Preparation of polyether oligomer grafted silicon dioxide doped polydimethylsiloxane mixed matrix membrane

After 1.5g of polyethylene glycol-grafted silica powder, 15g of Polydimethylsiloxane (PDMS) liquid and 2.0g of ethyl orthosilicate (TEOS) as a crosslinking agent were uniformly mixed by stirring at 25 ℃, 0.5g of dibutyltin dilaurate (DBTDL) as a catalyst was added thereto and the mixture was further stirred and allowed to stand for about 1 hour, and then the viscosity was measured. And when the viscosity of the mixture system is stable, placing the mixture system into a vacuum oven for vacuum defoamation to obtain a casting solution.

The casting solution was uniformly poured onto a Polysulfone (PSU) base film and coated on the surface of the base film with a doctor blade (thickness controlled at 200 μm). The glass plate with the composite film is horizontally placed in an oven and dried for 12 hours at 50 ℃ to obtain the polyether oligomer grafted silicon dioxide doped polydimethylsiloxane mixed matrix film with the thickness of about 150 mu m.

Example 2

(1) Low molecular weight polyethylene glycol grafted SiO₂Preparation of nanoparticles

1.0g of silica nanomaterial, 0.3g of diisocyanate and 2.0g of low molecular weight polyethylene glycol (molecular chain 1000) were mixed in 100mL of deionized water and stirred in a 30 ℃ water bath until a stable suspension was formed. And then introducing nitrogen to remove air, heating the water bath to 70 ℃ under the protection of nitrogen, stirring the suspension for 2 hours, adding 0.3mL of concentrated hydrochloric acid, continuously stirring and reacting for 3 hours, cooling the obtained reaction liquid to room temperature, carrying out centrifugal separation, washing with absolute ethyl alcohol, repeating the steps for three times, collecting solid powder, carrying out vacuum drying at 60 ℃ for 24 hours, and grinding to obtain the polyethylene glycol grafted silicon dioxide powder.

After 1.5g of polyethylene glycol-grafted silica powder, 15g of Polydimethylsiloxane (PDMS) liquid and 2.0g of ethyl orthosilicate (TEOS) as a crosslinking agent were uniformly mixed by stirring at 25 ℃, 0.5g of dibutyltin dilaurate (DBTDL) as a catalyst was added thereto and the mixture was further stirred and allowed to stand for about 1 hour, and then the viscosity was measured. And when the viscosity of the mixture system is stable, placing the mixture system into a vacuum oven for vacuum defoamation to obtain the casting solution. The casting solution was uniformly poured onto a Polysulfone (PSU) base film (the base film was fixed on a glass plate), and coated on the surface of the base film (the thickness was controlled at 200 μm) with a doctor blade. The glass plate with the composite film is horizontally placed in an oven and dried for 12 hours at 50 ℃ to obtain the polyether oligomer grafted silicon dioxide doped polydimethylsiloxane mixed matrix film with the thickness of about 150 mu m.

Example 3

1.5g of silica nanomaterial, 0.3g of diisocyanate and 3.0g of low molecular weight polyethylene glycol (molecular chain 1000) were mixed in 100mL of deionized water and stirred in a water bath at 30 ℃ until a stable suspension was formed. And then introducing nitrogen to remove air, heating the water bath temperature to 70 ℃ under the protection of nitrogen, stirring the suspension for 2 hours, adding 0.3mL of concentrated hydrochloric acid, continuously stirring and reacting for 3 hours, cooling the obtained reaction liquid to room temperature, performing centrifugal separation, washing with absolute ethyl alcohol, repeating for three times, collecting solid powder, performing vacuum drying at 60 ℃ for 24 hours, and grinding to obtain the polyethylene glycol grafted silicon dioxide powder.

(2) Preparation of polyether polymer grafted silicon dioxide doped polydimethylsiloxane mixed matrix membrane

After 1.5g of polyethylene glycol graft-silica powder, 15g of Polydimethylsiloxane (PDMS) liquid and 2.0g of cross-linking agent Tetraethoxysilane (TEOS) were stirred and mixed uniformly at 25 ℃, 0.5g of catalyst dibutyltin dilaurate (DBTDL) was added and the mixture was further stirred, and the viscosity was measured after the mixture was left to stand for about 1 hour. And when the viscosity of the mixture system is stable, placing the mixture system into a vacuum oven for vacuum defoamation to obtain the casting solution. The casting solution was uniformly poured onto a Polysulfone (PSU) base film (the base film was fixed on a glass plate), and coated on the surface of the base film (thickness controlled at 200 μm) with a doctor blade. The glass plate with the composite film is horizontally placed in an oven to be dried for 12 hours at 50 ℃ to obtain the polyether polymer grafted silicon dioxide doped polydimethylsiloxane mixed matrix film with the thickness of about 150 mu m.

Example 4

1.5g of silica nanomaterial, 0.3g of diisocyanate and 5.0 g of low molecular weight polyethylene glycol (molecular chain 1000) were mixed in 100mL of deionized water and stirred in a water bath at 30 ℃ until a stable suspension was formed. And then introducing nitrogen to remove air, heating the water bath to 70 ℃ under the protection of nitrogen, stirring the suspension for 2 hours, adding 0.3mL of concentrated hydrochloric acid, continuously stirring and reacting for 3 hours, cooling the obtained reaction liquid to room temperature, carrying out centrifugal separation, washing with absolute ethyl alcohol, repeating the steps for three times, collecting solid powder, carrying out vacuum drying at 60 ℃ for 24 hours, and grinding to obtain the polyethylene glycol grafted silicon dioxide powder.

After 1.5g of polyethylene glycol-grafted silica powder, 15g of Polydimethylsiloxane (PDMS) liquid and 2.0g of ethyl orthosilicate (TEOS) as a crosslinking agent were uniformly mixed by stirring at 25 ℃, 0.5g of dibutyltin dilaurate (DBTDL) as a catalyst was added thereto and the mixture was further stirred and allowed to stand for about 1 hour, and then the viscosity was measured. And when the viscosity of the mixture system is stable, placing the mixture system into a vacuum oven for vacuum defoamation to obtain the casting solution. The casting solution was uniformly poured onto a Polysulfone (PSU) base film (the base film was fixed on a glass plate), and coated on the surface of the base film (thickness controlled at 200 μm) with a doctor blade. The glass plate with the composite film is horizontally placed in an oven to be dried for 12 hours at 50 ℃ to obtain the polyether polymer grafted silicon dioxide doped polydimethylsiloxane mixed matrix film with the thickness of about 150 mu m.

FIG. 1 is a Transmission Electron Microscope (TEM) photograph of polyethylene glycol-grafted SiO2 nanoparticles prepared in examples 1-4 of the present application. FIG. 2 is a Thermogravimetric (TG) curve of polyethylene glycol grafted SiO2 nanoparticles prepared in examples 1-4 of the present application. FIG. 3 is a schematic diagram of the polyethylene glycol grafted SiO prepared in examples 1-4 of the present application₂Photograph of the dispersion of nanoparticles in DMAC solution.

As can be seen from FIGS. 1-3 above, the polyethylene glycol grafted SiO of each of the examples₂The nano particles have uniform appearance and good dispersibility, can keep good thermal stability, and the grafting of the polyethylene glycol improves SiO₂The affinity of the particle surface for the solvent DMAC, so that it remains good in the solvent DMACDispersion of (2).

FIG. 4 is a Scanning Electron Microscope (SEM) image of the surface of the PEG-grafted silica-doped PDMS mixed matrix film prepared in examples 1-4 of the present application. FIG. 5 is a Scanning Electron Microscope (SEM) cross-section of the PEG-grafted silica-doped PDMS mixed matrix film prepared in examples 1-4 of the present application. FIG. 6 is a graph of infrared spectroscopy (FTIR) of films of polyethylene glycol grafted silica doped polydimethylsiloxane mixed matrices prepared in examples 1-4 of the present application.

As can be seen from fig. 4-6, the silica can be uniformly dispersed in the polydimethylsiloxane membrane after being grafted by the polyethylene glycol, as shown in fig. 4 and 5, wherein the white bright spots are the silica particles after being grafted by the polyethylene glycol. When the added polyethylene glycol is grafted to the carbon dioxide nanoparticles gradually, the dispersibility of the silicon dioxide in the polydimethylsiloxane membrane can be remarkably improved, and white bright spots on the surface of the pervaporation membrane in fig. 4 are obviously more uniform.

Referring to fig. 6, only a spectrum of polydimethylsiloxane appeared in the infrared spectrum of the pervaporation membrane of each example due to the small amount of silica added and uniform dispersion.

Comparative example 1

The pervaporation membrane of this comparative example was prepared as follows:

after 15g of Polydimethylsiloxane (PDMS) liquid and 2.0g of ethyl orthosilicate (TEOS) as a crosslinking agent were mixed uniformly at 25 ℃ with stirring, 0.5g of dibutyltin dilaurate (DBTDL) as a catalyst was added thereto with continued stirring, and the viscosity was measured after leaving to stand for about 1 hour. And when the viscosity of the mixture system is stable, placing the mixture system into a vacuum oven for vacuum defoamation to obtain a casting solution. The casting solution was uniformly poured onto a Polysulfone (PSU) base film (the base film was fixed on a glass plate), and coated on the surface of the base film (thickness controlled at 200 μm) with a doctor blade. The glass plate with the composite film is horizontally placed in an oven to be dried for 12 hours at 50 ℃ to obtain the polyether polymer grafted silicon dioxide doped polydimethylsiloxane mixed matrix film with the thickness of about 150 mu m.

Comparative example 2

The pervaporation membrane of this comparative example was prepared as follows:

1.5g of commercial silicon dioxide powder (Yingchuang group, nanosilicon dioxide, type R972), 15g of Polydimethylsiloxane (PDMS) liquid and 2.0g of cross-linking agent Tetraethoxysilane (TEOS) were stirred and mixed uniformly at 25 ℃, 0.5g of catalyst dibutyltin dilaurate (DBTDL) was added and stirred continuously, and the viscosity was measured after standing for about 1 hour. And when the viscosity of the mixture system is stable, placing the mixture system into a vacuum oven for vacuum defoamation to obtain the casting solution. The casting solution was uniformly poured onto a Polysulfone (PSU) base film (the base film was fixed on a glass plate), and coated on the surface of the base film (the thickness was controlled at 200 μm) with a doctor blade. The glass plate with the composite film is horizontally placed in an oven and dried for 12 hours at 50 ℃ to obtain the polyether polymer grafted silicon dioxide doped polydimethylsiloxane mixed matrix film with the thickness of about 150 mu m.

Test examples

Pervaporation test

The waste water system selected in the test example is provided by a certain automobile group in Shanghai, and is flocculated and filtered to obtain waste liquid with the content of ethylene glycol monobutyl ether of 10 wt% and the content of total organic matters of 12 wt%.

The treatment equipment of pervaporation is carried out by adopting an intermittent and concentrated solution full-circulation operation mode. In the treatment equipment, the volume of the feed liquid tank is 3m³The steady flow rate of the feed liquid side is 0.05m³Min, the total membrane area of the membrane stack of the pervaporation membrane filled in the pervaporation device is 14-15 m²The length of the single pervaporation membrane is 60cm, and the width of the single pervaporation membrane is 30 cm. The pervaporation unit maintained a constant temperature of 70 ℃. The permeate collector in the condensation system was kept at a constant temperature of-10 ℃. The vacuum pump maintains the constant pressure of the feed liquid permeation side, and the range is between 90 and 110 Pa.

The contents of the alcohol ether organics in the feed solution and the permeate solution after 5 hours were respectively analyzed by liquid chromatography, and the change in selectivity of the pervaporation membrane was evaluated by the permeation rate of the alcohol ether organics after 5 hours, wherein the above test was performed using the pervaporation membranes of examples 1 to 4 and comparative examples 1 and 2, respectively, and the permeation rates of the alcohol ether organics after 5 hours of pervaporation process are listed in table 1.

TABLE 1

Serial number	Transmittance of light
		Example 1	55％
Example 2	60％
		Example 3	70％
Example 4	80％
		Comparative example 1	41％
Comparative example 2	47％

As can be seen from the data in table 1, after the polyethylene glycol grafted silica nanoparticles are doped, a large amount of polyether groups can be introduced into the formed pervaporation membrane, and thus, according to the principle of similarity and compatibility, the pervaporation treatment capability can be improved. Meanwhile, with the increase of the doping amount of the polyethylene glycol grafted silicon dioxide nano particles, the permeability of the pervaporation membrane in the process of alcohol ether is obviously increased, and the permeability of the alcohol ether can reach 80% after 5 hours. The permeation rates of the pervaporation membranes corresponding to the comparative examples 1 and 2 are below 50%.

It will be apparent to those skilled in the art that various changes and modifications may be made in the embodiments of the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A preparation method of a pervaporation membrane is characterized by comprising the following steps: uniformly mixing polyethylene glycol grafted silica nanoparticles, polydimethylsiloxane, a cross-linking agent and a catalyst, and performing vacuum defoaming treatment to obtain a casting solution; coating the casting film liquid on the surface of a base film, and drying to obtain the pervaporation film; the weight portions are: 0.5-5 parts of polyethylene glycol grafted silica nanoparticles, 5-20 parts of polydimethylsiloxane, 0.5-3 parts of a cross-linking agent and 0.1-1 part of a catalyst;

the polyethylene glycol grafted silicon dioxide nano particle is prepared by the following method: mixing SiO₂Mixing nano particles, diisocyanate, deionized water and low molecular weight polyethylene glycol to obtain a suspension; wherein the low molecular weight polyethylene glycol has a molecular weight of less than 2000; heating the suspension to 60-80 ℃ under the condition of water bath, stirring and reacting for 1.5-2.5h, then adding a hydrochloric acid solution, continuously stirring and reacting for 2.5-4h, cooling to room temperature, and carrying out solid-liquid separation to obtain the polyethylene glycol grafted silicon dioxide nanoparticles.

2. The production method according to claim 1, wherein the thickness of the pervaporation membrane is 50 to 150 μm.

3. The method of claim 1, wherein in the preparation of the polyethylene glycol-grafted silica nanoparticles, the SiO is present in an amount of 100ml of the deionized water₂The addition amount of the nano particles is 1.0-3.0g, the addition amount of the diisocyanate is 0.1-1.0g, and the addition amount of the low molecular weight polyethylene glycol is 1.0-10 g.

4. The method according to claim 1, wherein in the method for preparing the polyethylene glycol-grafted silica nanoparticles, the concentration of the hydrochloric acid is 0.3-0.4 g/ml;

the addition amount of the hydrochloric acid is 0.1-0.5ml based on 100ml of the deionized water.

5. A pervaporation membrane obtained by the production method according to any one of claims 1 to 4.

6. A treatment method of coating wastewater is characterized by comprising the following steps:

the pervaporation device comprising a pervaporation membrane according to claim 5.

7. The treatment method according to claim 6, wherein the coating wastewater is a waste liquid containing 6.5 to 7.5 wt% of ethylene glycol monobutyl ether and 9.5 to 11.5wt% of total organic matter.