CN112569806B

CN112569806B - Polyvinylidene fluoride mixed matrix membrane with white spirit catalytic filtration performance and preparation and application thereof

Info

Publication number: CN112569806B
Application number: CN202011299841.9A
Authority: CN
Inventors: 陈桂娥; 陈镇; 谢焕银; 李怡静; 万佳俊; 刘连静; 汪洋; 许振良
Original assignee: Shanghai Institute of Technology
Current assignee: Shanghai Institute of Technology
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2023-02-10
Anticipated expiration: 2040-11-19
Also published as: CN112569806A

Abstract

The invention relates to a polyvinylidene fluoride mixed matrix membrane with white spirit catalytic filtration performance and preparation and application thereof, wherein the polyvinylidene fluoride mixed matrix membrane comprises the following steps: s1: preparing a casting solution by polyvinylidene fluoride, and scraping the casting solution on a substrate; s2: and (3) placing the substrate with the membrane casting solution in a gel bath dispersed with N435 immobilized lipase, and realizing the adhesion of the N435 immobilized lipase on the surface of the matrix membrane by delaying the phase conversion process to obtain the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance. Compared with the prior art, the method utilizes the viscosity of the polyvinylidene fluoride casting solution, and introduces N435 immobilized lipase and a delayed phase conversion method into the coagulating bath to modify the PVDF membrane, so that a large number of active particles are adhered to the surface of the composite membrane, the hydrophilicity is greatly enhanced, and the composite membrane has better catalytic activity and interception performance; the produced white spirit has good taste and rich fragrance, and does not have the phenomena of crystalline precipitation, white flocculent precipitation and light loss.

Description

Polyvinylidene fluoride mixed matrix membrane with white spirit catalytic filtration performance and preparation and application thereof

Technical Field

The invention relates to the technical field of membrane separation, in particular to a polyvinylidene fluoride mixed matrix membrane with white spirit catalytic filtration performance, and preparation and application thereof.

Background

The white spirit is a unique traditional product in China, has been for thousands of years, and the quality standard established by the nation for the white spirit firstly requires color and appearance in the aspect of sensory requirements, namely colorless or slightly yellow, clear and transparent, and no suspended matter or sediment. The physical and chemical indexes of the white spirit require that the solid content is less than or equal to 0.4g/L (such as strong aromatic white spirit). The impurities in the wine must be removed by a filtering process and filtering equipment, and with the development of filtering technology, the produced filtering forms and filtering materials are various, and the filtering forms and the filtering materials are firstly silk filtering, paper filtering, sand rod filtering, bag filtering, then plate type filter pressing, activated carbon adsorption, diatomite filtering, then the commonly used molecular sieve medium filtering, folding membranes, ceramic sieve plates, temperature changing treatment and the like.

Although the adopted process and the used materials are more and more advanced, the processes have advantages and disadvantages, and a plurality of problems exist in the using process, such as the common activated carbon adsorption method, easy saturation, black pollution and precipitation, and large loss of aroma components; traditional candle formula diatomaceous earth filter easily leaks earth, leaks charcoal, weeping, and the power failure during filtration, diatomaceous earth will drop, fall the sediment, causes phenomenon such as filtration failure, and these have seriously influenced white spirit filtration quality and quality.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, provides a polyvinylidene fluoride mixed matrix membrane with white spirit catalytic filtration performance, and preparation and application thereof, and is used for solving the problems of white spirit turbidity and light loss, long aging time of raw stock wine and the like.

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

the invention idea of the technical scheme is that the lipase is proved to be capable of synthesizing a series of aromatic esters, so the technical scheme utilizes the property to convert acid and alcohol fragrant substances in the white spirit into esters during membrane filtration to obtain base liquor rich in fragrant substances, thereby not only solving the problems of turbidity, less fragrant substances and the like of the original wine, but also greatly improving the quality of the base liquor.

In addition, due to the extremely strong viscosity of polyvinylidene fluoride (PVDF) materials in an organic solvent NMP, a phase transition speed can be slowed down by adopting a delayed phase transition method, so that N435 immobilized lipase particles have enough time to adhere to the surface of a PVDF membrane, and the possibility is provided for industrial production.

According to the technical scheme, synthesis of aromatic ester is accelerated and catalyzed by using lipase, a lipase catalysis technology is combined with a membrane filtration technology to form the composite white spirit catalytic separation modified membrane, and the ester catalytic capability, the hydrophilic performance and the interception characteristic of the membrane can be effectively improved.

The polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance comprises the following steps:

s1: preparing a casting solution by polyvinylidene fluoride, and scraping the casting solution on a substrate;

s2: and (3) placing the substrate with the membrane casting solution in a gel bath dispersed with the N435 immobilized lipase, and realizing the adhesion of the N435 immobilized lipase on the surface of the matrix membrane by delaying the phase conversion process to obtain the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance.

Further, the preparation method of the casting solution in S1 comprises the following steps:

and adding polyvinylidene fluoride and a pore-foaming agent into N-methyl pyrrolidone, uniformly stirring, standing and defoaming to obtain the membrane casting solution.

Further, the pore-foaming agent is polyvinylpyrrolidone.

Further, the delay phase conversion process in S2 is:

and (3) carrying out delayed phase separation on the substrate with the membrane casting solution in a gel bath in which the N435 immobilized lipase is dispersed, so that the N435 immobilized lipase is fixedly embedded in the concave surface of the membrane surface.

Further, the addition amount of the N435 immobilized lipase in the gel bath is 0.1-1.0 g/L;

the gel bath is a mixed solution consisting of ethanol and water in a volume ratio of (2.4-3.5) to (1.8-2.8), and the temperature of the gel bath is 14-30 ℃.

Further, the pore-foaming agent is polyvinylpyrrolidone;

the mass ratio of the pore-foaming agent to the polyvinylidene fluoride is (0.5-3.5) to (14-20);

in the stirring process, the stirring temperature is 30-80 ℃, and the stirring time is 8-18 h;

and in the standing and defoaming process, the standing time is 5-12 h.

Further, the thickness of the scraping film is 100-260 mu m.

The polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance is also protected in the invention.

The invention also protects the application of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance in the white spirit refining turbidity removal and catalytic ester increase.

Furthermore, the mixed matrix membrane can make the higher alcohol, higher fatty acid ethyl ester, inorganic salts and other substances in the white spirit blocked on the surface layer of the filter disc through the comprehensive effects of surface blocking, depth effect and electrostatic adsorption in the filtration.

Furthermore, the lipase molecules adhered to the surface of the mixed matrix membrane enable alcohol, ester and acid in the white spirit to quickly reach an equilibrium state, so that the storage time of the white spirit is shortened.

The PVDF ultrafiltration membrane adhered with the N435 immobilized lipase can be used for a catalytic membrane reactor device, and can realize one-step liquor refining catalysis, so that liquor is clear and transparent, and the flavor is rich. The method for realizing white spirit refining catalysis by using the PVDF ultrafiltration membrane adhered with the N435 immobilized lipase comprises the following steps:

constructing a catalytic membrane reactor device, fixing a PVDF ultrafiltration membrane adhered with N435 immobilized lipase on a membrane component, applying the PVDF ultrafiltration membrane adhered with the N435 immobilized lipase to a white spirit flux experiment, and realizing one-step white spirit refining catalysis through white spirit primary pulp.

Compared with the prior art, the invention has the following technical advantages:

1) The PVDF ultrafiltration membrane adhered with the N435 immobilized lipase prepared by the method has small resistance during filtration and thorough separation.

2) The PVDF ultrafiltration membrane adhered with the N435 immobilized lipase prepared by the method is filtered by adopting a surface compact layer for interception, a channel below the surface compact layer is deeply detained, and impurities are rubbed with pores to be subjected to super-strong electrostatic adsorption.

3) The PVDF ultrafiltration membrane adhered with the N435 immobilized lipase prepared by the method has strong pressure resistance, the maximum working pressure is 0.5MPa, and the backwashing pressure is less than or equal to 0.6MPa. The working temperature is strong in adaptability, and the device can be used at the temperature of-20-150 ℃.

4) The method for preparing the PVDF ultrafiltration membrane adhered with the N435 immobilized lipase is simple and easy to operate, the used equipment is conventional instruments in the field, the process period is short, the requirement on the process environment is low, the cost is low, and the method can be widely applied to preparation of enzyme modified PVDF membranes;

5) The method for preparing the PVDF ultrafiltration membrane with the N435 immobilized lipase adhered is a self-adhesion modification method, the enzyme catalyst N435 on the surface of the modified membrane is not easy to dissolve out along with wine in the using process, the pollution to the wine body is avoided, and the durability and the stability of the membrane structure are ensured.

Drawings

FIG. 1 is a scanning electron micrograph of the surface of a polyvinylidene fluoride film prepared in example 1;

FIG. 2 is a graph comparing the alcohol flux and the rejection (ethyl palmitate, ethyl oleate, ethyl linoleate) of the PVDF membranes (M1-M5) to which the N435-immobilized lipases are adhered prepared in examples 1-5 with the PVDF original membrane M0.

FIG. 3 shows the change in the contents of ethyl acetate and ethyl hexanoate in 50% vol% of white spirit after and before filtration of the PVDF membranes (M1 to M5) to which N435-immobilized lipase prepared in examples 1 to 5 was adhered and the PVDF original membrane M0.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The preparation method of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance by the self-adhesion method comprises the following steps:

1) Preparing a casting solution: adding pore-forming agents polyvinyl pyrrolidone (PVP) and polyvinylidene fluoride (PVDF) into N-methyl pyrrolidone (NMP), stirring at 30-80 ℃ for 8-18 h, and standing and defoaming to obtain a membrane casting solution;

wherein the mass ratio of the pore-foaming agent to the polyvinylidene fluoride is (0.5-3.5) to (14-20);

2) Preparing a polyvinylidene fluoride mixed matrix membrane by a delayed phase conversion method: and (3) coating the casting solution on a glass plate in a scraping manner, wherein the thickness of the scraping film is 100-260 mu m, and placing the glass plate in a 14-30 ℃ gel bath consisting of ethanol and water in a volume ratio of (2.4-3.5) to (1.8-2.8) for phase separation, wherein the addition amount of the N435 immobilized lipase in the gel bath is 0.1-1.0 g/L, so that the polyvinylidene fluoride mixed matrix film is obtained.

The following are more detailed embodiments, and the technical solutions and the technical effects obtained by the present invention will be further described by the following embodiments.

The PVDF ultrafiltration membrane adhered with the N435 immobilized lipase adopts the principle of a molecular sieve, and three functions (surface blocking, depth effect and electrostatic adsorption) are generated during the filtration by utilizing the permeability of a membrane material, so that a comprehensive effect is achieved during the filtration, substances such as higher alcohols, higher fatty acid ethyl esters, inorganic salts and the like in the white spirit are blocked on the surface layer of a filter disc, the triple effects of clarification, turbidity removal and purification are achieved, visible substances and turbid substances in the liquid can be thoroughly intercepted, and the filtrate is completely clear and transparent and has mellow mouthfeel. Meanwhile, the lipase molecules adhered to the surface of the membrane can enable alcohol, ester and acid in the white spirit to quickly reach a balanced state, and the white spirit storage time is shortened.

When the polyvinylidene fluoride mixed matrix membrane is used for treating the liquor primary pulp, the membrane shows excellent catalytic activity, and the rejection rate is obviously improved. This is because the lipase molecule is effectively immobilized by the adhesive surface of the PVDF membrane, and thus is prevented from inactivation and exhibits high activity. Meanwhile, the modified membrane is smaller than the pore diameter of the higher fatty acid ester, so that turbid higher fatty acid ester floccule precipitates can be effectively intercepted, and a higher retention rate is shown.

The preparation method of the invention comprises the steps of preparing a casting solution from polyvinylidene fluoride, scraping the casting solution into a film, and then pasting the film with N435 immobilized lipase dispersed in a coagulating bath by a delayed phase conversion method to prepare the polyvinylidene fluoride mixed matrix film, which not only greatly improves the hydrophilicity, but also endows the composite film with enzyme catalysis performance, and self-adhesion is the simplest and most common film modification method. Compared with other methods, the self-adhesion modification has the following advantages: the self-adhesion and the film formation are carried out synchronously, the process is simple, and complicated post-treatment steps are not needed; the additive can cover the membrane surface without causing damage to the membrane structure.

Example 1

The preparation method of the polyvinylidene fluoride mixed matrix film is as follows:

1) Dissolving PVP and PVDF in NMP according to the mass ratio of 2.0;

2) Coating the casting solution on a glass plate in a scraping way, wherein the thickness of the scraped film is 250 mu m;

3) Immersing the glass plate with the membrane liquid into a mixture of ethanol and deionized water at 15 ℃ in a volume ratio of 2.8 to 2.3 for phase separation, wherein the addition amount of the N435 immobilized lipase in a gel bath is 0.5 g/L;

4) And transferring the membrane after phase splitting into deionized water for soaking to remove redundant solvent, and then putting into clean deionized water for storage to obtain a polyvinylidene fluoride mixed matrix membrane, which is marked as an M1 ultrafiltration membrane.

The obtained M1 ultrafiltration membrane was characterized by surface scanning electron microscopy, and the results are shown in fig. 1. As can be seen from the figure, N435 immobilized lipase nanoparticles were successfully adhered to the membrane surface.

Example 2

1) Dissolving PVP and PVDF in NMP according to a mass ratio of 2.5;

2) Coating the casting solution on a glass plate in a scraping way, wherein the thickness of the scraped film is 150 mu m;

3) Immersing the glass plate with the membrane liquid into a mixture of ethanol and deionized water at the temperature of 20 ℃ and the volume ratio of 3.2 to 2.5 for phase separation, wherein the addition amount of the N435 immobilized lipase in a gel bath is 0.7 g/L;

4) And transferring the membrane after phase splitting into deionized water for soaking to remove redundant solvent, and then putting into clean deionized water for storage to obtain a polyvinylidene fluoride mixed matrix membrane, which is marked as an M2 ultrafiltration membrane.

Example 3

1) Dissolving PVP and PVDF in NMP according to a mass ratio of 1.5;

2) Coating the casting solution on a glass plate in a scraping way, wherein the thickness of the scraped film is 130 mu m;

3) Immersing the glass plate with the membrane liquid into a mixture of ethanol and deionized water at 25 ℃ in a volume ratio of 2.5 to 2.0 for phase separation, wherein the addition amount of the N435 immobilized lipase in a gel bath is 0.3 g/L;

4) And transferring the membrane after phase separation into deionized water to be soaked so as to remove redundant solvent, and then putting the membrane into clean deionized water for storage to obtain a polyvinylidene fluoride mixed matrix membrane, which is marked as an M3 ultrafiltration membrane.

Example 4

1) Dissolving PVP and PVDF in NMP according to a mass ratio of 0.5;

2) Coating the casting solution on a glass plate in a scraping way, wherein the thickness of the scraped film is 100 mu m;

3) Immersing the glass plate with the membrane liquid into a mixture of ethanol and deionized water at 14 ℃ in a volume ratio of 2.4 to 1.8 for phase separation, wherein the addition amount of the N435 immobilized lipase in a gel bath is 0.1 g/L;

4) And transferring the membrane after phase separation into deionized water to be soaked so as to remove redundant solvent, and then putting the membrane into clean deionized water for storage to obtain a polyvinylidene fluoride mixed matrix membrane, which is marked as an M4 ultrafiltration membrane.

Example 5

1) Dissolving PVP and PVDF in NMP according to the mass ratio of 3.5;

2) Coating the casting solution on a glass plate in a scraping way, wherein the thickness of the scraped film is 260 mu m;

3) Immersing a glass plate with the membrane liquid into a mixture of ethanol and deionized water at the temperature of 30 ℃ and the volume ratio of 3.5 to 2.8 for phase separation, wherein the addition amount of the N435 immobilized lipase in a gel bath is 1.0 g/L;

4) And transferring the membrane after phase separation into deionized water to be soaked so as to remove redundant solvent, and then putting the membrane into clean deionized water for storage to obtain a polyvinylidene fluoride mixed matrix membrane, which is marked as an M5 ultrafiltration membrane.

Comparative example 1

In this comparative example, a polyvinylidene fluoride flat membrane without N435 immobilized lipase was prepared by a delayed phase conversion method, and the specific preparation method was as follows:

1) Dissolving PVP and PVDF in NMP according to the mass ratio of 2.0;

3) Immersing the glass plate with the membrane liquid into a mixture of ethanol and deionized water at 15 ℃ in a volume ratio of 2.8;

4) And transferring the membrane after phase splitting into deionized water for soaking to remove redundant solvent, and then putting into clean deionized water for storage to obtain an unmodified polyvinylidene fluoride flat membrane, which is marked as an M0 ultrafiltration membrane.

The ultrafiltration membranes of examples 1 to 5 and comparative example were subjected to the test for the alcohol flux and the higher fatty acid ester rejection, wherein the test methods for the alcohol flux and the higher fatty acid ester rejection are described in the following references: y, wang, gui-E Chen, hai-Ling Wu, contamination of GO-Ag/PVDF/F127 modified membrane IPA conjugation base for catalytic reduction of 4-nitrophenol, sep. purify. Technol. 235 (2020) 116143. The contents of ethyl acetate and ethyl caproate in the wine are quantitatively detected by using a gas chromatograph-mass spectrometer.

The test results are shown in fig. 2 and fig. 3, respectively, and it can be seen from the figures that each membrane with N435 enzyme adhered on the surface shows superior permeability and better separation performance compared with the original PVDF membrane, and the content of aromatic ester in the white spirit is also significantly increased.

The increase in permeability may be due to the following factors: the addition of the nanoparticles will impart hydrophilicity to the membrane, thereby increasing the rate of wine passage through the membrane.

The improvement in separation performance can be illustrated by three reasons:

1) The pore diameter of the membrane (30-50 nm) is smaller than the size of the higher fatty acid ester flocculent precipitate (200-280 nm).

2) The flocculent precipitate can be effectively intercepted by the complex structure of the sponge hole formed by delayed phase separation.

3) The theory of increased hydrophilicity with an interfacial hydration layer is used to reduce the contact between the floc and the membrane surface, thereby preventing the floc from penetrating the modified membrane. The improvement of the content of aromatic ester in the white spirit is mainly attributed to the catalytic esterification of the lipase molecules on the surface of the membrane, which shows that the lipase molecules immobilized by the membrane have enhanced ester catalytic activity.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The application of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance in white spirit refining turbidity removal and catalytic ester increase is characterized in that the polyvinylidene fluoride mixed matrix membrane is assembled in a catalytic membrane reactor, and white spirit raw stock passes through the catalytic membrane reactor to realize the refining turbidity removal and catalytic ester increase of white spirit;

the preparation method of the polyvinylidene fluoride mixed matrix film comprises the following steps:

s2: placing the substrate with the membrane casting solution in a gel bath dispersed with N435 immobilized lipase, and realizing the adhesion of the N435 immobilized lipase on the surface of a matrix membrane by delaying the phase conversion process to obtain a polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance;

the delayed phase conversion process in the S2 comprises the following steps:

carrying out delayed phase separation on the substrate with the membrane casting solution in a gel bath in which N435 immobilized lipase is dispersed, so that the N435 immobilized lipase is fixedly embedded in the concave surface of the membrane surface;

the addition amount of the N435 immobilized lipase in the gel bath is 0.1-1.0 g/L;

the gel bath is a mixed solution consisting of ethanol and water in a volume ratio of (2.4-3.5) to (1.8-2.8), and the temperature of the gel bath is 14-30 ℃;

the preparation method of the casting solution in S1 comprises the following steps:

2. The application of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance in white spirit refining turbidity removal and catalytic ester increase according to claim 1, wherein the pore-forming agent is polyvinylpyrrolidone.

3. The application of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance in white spirit refining turbidity removal and catalytic ester increase according to claim 2 is characterized in that the mass ratio of the pore-forming agent to the polyvinylidene fluoride is (0.5-3.5) to (14-20);

and in the standing and defoaming process, the standing time is 5-12 h.

4. The application of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance in white spirit refining turbidity removal and catalytic ester increase is characterized in that the mixed matrix membrane enables substances such as higher alcohols, higher fatty acid ethyl esters and inorganic salts in the white spirit to be blocked on the surface layer of the filter disc through comprehensive effects of surface blocking, depth effect and electrostatic adsorption in filtration.

5. The application of the polyvinylidene fluoride mixed matrix membrane with the white spirit catalytic filtration performance in white spirit refining turbidity removal and catalytic ester increase according to claim 1 is characterized in that lipase molecules adhered to the surface of the mixed matrix membrane enable alcohol, ester and acid in the white spirit to quickly reach a balanced state, so that the white spirit storage time is shortened.