CN111375318A - Polylactic acid/cellulose derivative microfiltration membrane and preparation method thereof - Google Patents
Polylactic acid/cellulose derivative microfiltration membrane and preparation method thereof Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/48—Polyesters
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/14—Ultrafiltration; Microfiltration
- B01D61/147—Microfiltration
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- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
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- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0013—Casting processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0016—Coagulation
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/06—Organic material
- B01D71/08—Polysaccharides
- B01D71/12—Cellulose derivatives
- B01D71/14—Esters of organic acids
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- B01D71/06—Organic material
- B01D71/08—Polysaccharides
- B01D71/12—Cellulose derivatives
- B01D71/14—Esters of organic acids
- B01D71/16—Cellulose acetate
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D2323/00—Details relating to membrane preparation
- B01D2323/08—Specific temperatures applied
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The invention provides a polylactic acid/cellulose derivative microfiltration membrane and a preparation method thereof, wherein the polylactic acid/cellulose derivative microfiltration membrane is prepared from polylactic acid and a cellulose derivative, and comprises the following steps: firstly, respectively dissolving polylactic acid and cellulose derivatives in respective organic solvents to form transparent solutions, then mixing the two solutions in a certain proportion to obtain a casting solution, and standing; then uniformly coating the casting solution to form a membrane, and soaking the membrane in a coagulating bath for several hours by using a non-solvent induced phase separation method; finally, drying to obtain the polylactic acid/cellulose derivative microfiltration membrane; the polylactic acid/cellulose derivative microfiltration membrane has the effects of high flux, low cost, environmental friendliness and the like.
Description
Technical Field
The invention relates to the technical field of new materials, in particular to a polylactic acid/cellulose derivative microfiltration membrane and a preparation method thereof.
Background
In recent years, with the rapid development of the industries such as papermaking, printing and dyeing, pharmacy, electroplating and the like in China, the consumption rate of fresh water resources all over the country is increased day by day, and the insufficient fresh water resources become more deficient. In the face of increasingly strict drinking water standards and continuously improved living standards, conventional water treatment processes cannot effectively deal with pollutants with various types and concentrations, and cannot meet the requirements of drinking water safety guarantee. The membrane separation technology not only can efficiently intercept impurities in water, does not produce byproducts, has high chemical safety and biological safety, but also can select corresponding membranes to treat according to different water qualities, and finally achieves ideal water purification effect.
Currently, the most used membrane materials are polymeric materials. The polymer material can be classified into synthetic polymer and natural polymer. Common synthetic polymer materials include: polycaprolactone, polylactic acid, polyvinyl alcohol, and the like. Polylactic acid is an environment-friendly and excellent polymer material, and can be prepared from corn or potatoes by processing into starch and fermenting at a large scale and at a low cost. Common natural polymer materials include starch, cellulose, chitosan, and the like. Cellulose is a natural high molecular compound with the most abundant deposits in the world, and production raw materials are derived from wood, cotton linter, wheat straw, reed, hemp, mulberry bark, bagasse and the like. The cellulose derivative is usually obtained by the reaction of esterification, etherification and the like of cellulose through hydroxyl, and is a powerful choice for preparing environment-friendly functional materials due to wide sources and excellent degradation performance. Therefore, if an environmentally friendly polylactic acid and a wide variety of cellulose derivatives can be used to prepare a water treatment microfiltration membrane, it will be of great practical significance to reduce environmental load.
Disclosure of Invention
The invention aims to provide a polylactic acid/cellulose derivative microfiltration membrane and a preparation method thereof, and solves the technical problems of low water flux, high price and difficult environmental degradation of the microfiltration membrane in the prior art.
The invention provides a polylactic acid/cellulose derivative microfiltration membrane, which is tested under the condition of 0.04MPa to achieve the pure water flux of 70L/m2·h-1。
The preparation method of the polylactic acid/microfiltration membrane provided by the invention comprises the following steps:
1) dissolving polylactic acid in an organic solvent A, dissolving a cellulose derivative in an organic solvent B, mixing and stirring the two solutions in a certain proportion, and standing to prepare a membrane casting solution;
2) uniformly coating the casting solution on a substrate, exposing the substrate in air for 0.5-2 min, and then soaking the substrate in a coagulating bath to form a polylactic acid/cellulose derivative film;
3) and drying the polylactic acid/cellulose derivative film to obtain the polylactic acid/cellulose derivative microfiltration membrane.
Furthermore, the dissolving time of the polylactic acid and the cellulose derivative is 4-12 hours, and the dissolving temperature is 80-150 ℃.
Further, the mixing time of the two different solutions is 1-4 hours after the two different solutions are mixed and dissolved, the mixing temperature is 80-150 ℃, the standing time of the casting solution is 2-4 hours, and the standing temperature is 40-150 ℃.
Further, after the casting solution is coated on the substrate, dipping is carried out for 4-20 h at the temperature of 20-120 ℃ in a coagulating bath, the solvent of the coagulating bath is replaced every 2h, and finally, drying is carried out in a vacuum drying oven or under normal pressure at the temperature of 30-60 ℃.
Further, the cellulose derivative is any one or a group consisting of hydroxyethyl cellulose, ethyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, cellulose monoacetate, cellulose diacetate, and cellulose triacetate.
Further, the organic solvent a is any one or a group consisting of dichloromethane, chloroform, N-dimethylformamide, and N, N-dimethylacetamide.
Further, the organic solvent B is any one or a group consisting of acetone, N-methylpyrrolidone, dimethyl sulfoxide, diethyl sulfoxide and benzyl benzene sulfoxide.
Further, the solvent used in the coagulation bath is any one or a group consisting of methanol, ethanol, ethylene glycol, isopropanol and deionized water.
The invention has the beneficial effects that: 1. the invention provides a preparation method of a polylactic acid/cellulose derivative microfiltration membrane, the prepared microfiltration membrane has higher membrane water flux, and the pure water flux of the microfiltration membrane is tested under the condition of 0.04MPa and basically reaches 70L/m2·h-1；
2. The invention provides a preparation method of a polylactic acid/cellulose derivative microfiltration membrane, and the prepared microfiltration membrane has low cost;
3. the invention provides a preparation method of a polylactic acid/cellulose derivative microfiltration membrane, and the prepared microfiltration membrane is easy to degrade in environment; polylactic acid and cellulose are widely used as membrane-making materials due to good degradation performance, and the microfiltration membrane prepared by combining the polylactic acid and the cellulose is green and environment-friendly and has excellent degradation performance. The degradation rate of the micro-filtration membrane in the alkaline solution is high, and the degradation rate is improved along with the increase of the concentration of the alkaline solution and the increase of the temperature;
4. the invention provides a preparation method of a polylactic acid/cellulose derivative microfiltration membrane, which is characterized in that polylactic acid and a cellulose derivative are respectively dissolved in different solvents, and then the two solutions are mixed and dissolved in order to fully dissolve solutes, the uniform mixing is favorable for molecular weight homogeneous hybridization, so that the prepared membrane has a more stable structure, and the performance of the membrane is greatly improved.
The above and other aspects of the invention will be apparent from and elucidated with reference to the following description of various embodiments of a method for the preparation of a polylactic acid/cellulose derivative microfiltration membrane according to the invention.
Drawings
FIG. 1 is a flow chart of a method for preparing a polylactic acid/cellulose derivative microfiltration membrane provided by the invention.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention.
Referring to fig. 1, the present invention provides a method for preparing a polylactic acid/cellulose derivative microfiltration membrane, comprising the steps of:
1) dissolving polylactic acid in an organic solvent A, dissolving a cellulose derivative in an organic solvent B, mixing and stirring the two solutions in a certain proportion, and standing to prepare a membrane casting solution;
2) uniformly coating the casting solution on a substrate, exposing the substrate in air for 0.5-2 min, and then soaking the substrate in a coagulating bath to form a polylactic acid/cellulose derivative film;
3) and drying the polylactic acid/cellulose derivative film to obtain the polylactic acid/cellulose derivative microfiltration membrane.
Preferably, the dissolving time of the polylactic acid and the dissolving time of the cellulose derivative are respectively 4-12 h, the dissolving temperature is 80-150 ℃, the preferred dissolving time is 6-8 h, and the dissolving temperature is 90-110 ℃.
Preferably, the mixing time of the two different solutions is 1-4 h after the two different solutions are mixed and dissolved, the mixing temperature is 80-150 ℃, the standing time of the casting solution is 2-4 h, and the standing temperature is 40-150 ℃; preferably, the stirring time is 2-3 h, the stirring temperature is 90-110 ℃, the standing time of the casting solution is 2-3 h, and the standing temperature is 80-100 ℃.
Preferably, after the substrate is coated with the casting solution, dipping the substrate in a coagulation bath at a temperature of 20-120 ℃ for 4-20 hours, preferably at a temperature of 40-60 ℃ for 8-12 hours, and changing the solvent of the coagulation bath every 2 hours, and finally drying the substrate in a vacuum drying oven or under normal pressure at a temperature of 30-60 ℃, preferably at a temperature of 30-50 ℃.
Examples
Materials and equipment used in the following examples are commercially available.
Example 1
(1) Dissolving polylactic acid in dichloromethane, dissolving ethyl cellulose in acetone, respectively stirring at 80 ℃ for 4h, and mixing the two solutions in a ratio of 1:1, stirring the mixture for 2 hours at the temperature of 80 ℃, and standing for 3 hours at the temperature of 40 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, soaking the substrate in deionized water at 20 ℃ after the substrate is exposed in the air for 1min, soaking for 4h, and replacing the deionized water every 2h to form a polylactic acid/ethyl cellulose membrane;
(3) and drying the polylactic acid/ethyl cellulose membrane at the temperature of 30 ℃ under normal pressure to obtain the polylactic acid/ethyl cellulose microfiltration membrane.
The pure water flux of the polylactic acid/ethyl cellulose micro-filtration membrane under the condition of 0.04MPa is measured and reaches 68L/m2·h-1。
Example 2
(1) Dissolving polylactic acid in dichloromethane, dissolving cellulose propionate in dimethyl sulfoxide, stirring at 150 ℃ for 12h respectively, and mixing the two solutions in a ratio of 1:2, stirring the mixture for 4 hours at the temperature of 150 ℃, and standing for 2 hours at the temperature of 150 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, exposing the substrate in air for 1min, soaking the substrate in 70 ℃ deionized water for 12h, and replacing the deionized water every 2h to form a polylactic acid/propionic acid cellulose membrane;
(3) and drying the polylactic acid/cellulose propionate film at 30 ℃ under normal pressure to obtain the polylactic acid/cellulose propionate microfiltration membrane.
The pure water flux of the polylactic acid/cellulose propionate micro-filtration membrane under the condition of 0.04MPa is measured and reaches 65L/m2·h-1。
Example 3
(1) Dissolving polylactic acid in dichloromethane, dissolving hydroxyethyl cellulose in N-methyl pyrrolidone, stirring at 120 ℃ for 8h respectively, and mixing the two solutions in a ratio of 2:1, stirring for 4 hours at the temperature of 120 ℃, and standing for 3 hours at the temperature of 100 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, soaking the substrate in 30 ℃ ethanol after the substrate is exposed in the air for 1min, soaking for 20h, and replacing deionized water every 2h to form a polylactic acid/hydroxyethyl cellulose membrane;
(3) and carrying out vacuum drying on the polylactic acid/hydroxyethyl cellulose membrane at 45 ℃ to obtain the polylactic acid/hydroxyethyl cellulose microfiltration membrane.
The pure water flux of the polylactic acid/hydroxyethyl cellulose micro-filtration membrane under the condition of 0.04MPa is measured and reaches 70L/m2·h-1。
Example 4
(1) Dissolving polylactic acid in dichloromethane, dissolving hydroxyethyl cellulose in dimethyl sulfoxide, stirring at 80 ℃ for 4h, and mixing the two solutions in a ratio of 1:1, stirring the mixture for 2 hours at the temperature of 80 ℃, and standing for 4 hours at the temperature of 100 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, soaking the substrate in 20 ℃ ethanol after the substrate is exposed in the air for 1min, soaking for 12h, and replacing deionized water every 2h to form a polylactic acid/hydroxyethyl cellulose membrane;
(3) and carrying out vacuum drying on the polylactic acid/hydroxyethyl cellulose membrane at 45 ℃ to obtain the polylactic acid/hydroxyethyl cellulose microfiltration membrane.
The pure water flux of the polylactic acid/hydroxyethyl cellulose micro-filtration membrane under the condition of 0.04MPa is measured and reaches 69L/m2·h-1。
Example 5
(1) Dissolving polylactic acid in dichloromethane, dissolving cellulose triacetate in N-methyl pyrrolidone, stirring at 150 ℃ for 8h respectively, and mixing the two solutions in a ratio of 2:1, stirring for 4 hours at the temperature of 150 ℃, and standing for 2 hours at the temperature of 100 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, soaking the substrate in 70 ℃ deionized water after the substrate is exposed in the air for 1min, soaking for 4h, and replacing the deionized water every 2h to form a polylactic acid/cellulose triacetate film;
(3) and drying the polylactic acid/cellulose triacetate film at the temperature of 30 ℃ under normal pressure to obtain the polylactic acid/cellulose triacetate microfiltration film.
Measuring the milk aggregationThe pure water flux of the acid/cellulose triacetate micro-filtration membrane under the condition of 0.04MPa reaches 63L/m2·h-1。
Example 6
(1) Dissolving polylactic acid in chloroform, dissolving cellulose triacetate in dimethyl sulfoxide, respectively stirring at 150 ℃ for 12h, and mixing the two solutions in a proportion of 1:2, stirring the mixture for 2 hours at the temperature of 80 ℃, and standing for 3 hours at the temperature of 40 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, soaking the substrate in 20 ℃ ethanol after the substrate is exposed in the air for 1min, soaking for 12h, and replacing deionized water every 2h to form a polylactic acid/cellulose triacetate film;
(3) and drying the polylactic acid/cellulose triacetate film at the temperature of 30 ℃ under normal pressure to obtain the polylactic acid/cellulose triacetate microfiltration film.
The pure water flux of the polylactic acid/cellulose triacetate micro-filtration membrane under the condition of 0.04MPa is measured and reaches 63L/m2·h-1。
Example 7
(1) Dissolving polylactic acid in chloroform, dissolving cellulose acetate propionate in dimethyl sulfoxide, stirring at 150 ℃ for 12h respectively, and mixing the two solutions in a ratio of 1:2, stirring the mixture for 1h at the temperature of 150 ℃, and standing for 2h at the temperature of 100 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, exposing the substrate in air for 1min, soaking the substrate in deionized water at 20 ℃, soaking for 12h, and replacing the deionized water every 2h to form a polylactic acid/cellulose acetate membrane;
(3) and drying the polylactic acid/cellulose acetate propionate film at the temperature of 30 ℃ under normal pressure to obtain the polylactic acid/cellulose acetate propionate microfiltration film.
The pure water flux of the polylactic acid/cellulose acetate propionate micro-filtration membrane under the condition of 0.04MPa is measured and reaches 68L/m2·h-1。
Example 8
(1) Dissolving polylactic acid in trichloromethane, dissolving hydroxyethyl cellulose in N-methyl pyrrolidone, stirring at 120 ℃ for 8h respectively, and mixing the two solutions in a proportion of 2:1, stirring for 4 hours at the temperature of 120 ℃, and standing for 3 hours at the temperature of 100 ℃ to prepare a membrane casting solution;
(2) uniformly coating the casting solution on a substrate, soaking the substrate in 20 ℃ ethanol after the substrate is exposed in the air for 1min, soaking for 20h, and replacing deionized water every 2h to form a polylactic acid/hydroxyethyl cellulose membrane;
(3) and carrying out vacuum drying on the polylactic acid/hydroxyethyl cellulose membrane at 45 ℃ to obtain the polylactic acid/hydroxyethyl cellulose microfiltration membrane.
The pure water flux of the polylactic acid/hydroxyethyl cellulose micro-filtration membrane under the condition of 0.04MPa is measured and reaches 70L/m2·h-1。
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A polylactic acid/cellulose derivative microfiltration membrane characterized by: the pure water flux of the biological microfiltration membrane is tested under the condition of 0.04MPa and reaches 70L/m2·h-1。
2. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 1, wherein: the preparation method comprises the following steps:
dissolving polylactic acid in an organic solvent A, dissolving a cellulose derivative in an organic solvent B, mixing and stirring the two solutions in a ratio of 1:1, 1:2 or 2:1, and standing to obtain a casting solution;
step two, uniformly coating the casting solution prepared in the step one on a substrate, exposing the substrate in air for 0.5-2 min, and then soaking the substrate in a coagulating bath to form a polylactic acid/cellulose derivative film;
and step three, drying the polylactic acid/cellulose derivative membrane obtained in the step two to obtain the polylactic acid/cellulose derivative microfiltration membrane.
3. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: the cellulose derivative in the first step is any one or any combination of hydroxyethyl cellulose, ethyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, cellulose monoacetate, cellulose diacetate and cellulose triacetate.
4. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: the organic solvent A in the first step is any one or any combination of dichloromethane, chloroform, N, N-dimethylformamide and N, N-dimethylacetamide.
5. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: the organic solvent B in the first step is any one or any combination of acetone, N-methyl pyrrolidone, dimethyl sulfoxide, diethyl sulfoxide and benzyl benzene sulfoxide.
6. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: in the first step, the dissolving time of the polylactic acid in the organic solvent A and the dissolving time of the cellulose derivative in the organic solvent B are both 4-12 hours, and the dissolving temperature is both 80-150 ℃.
7. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: and in the first step, the two solutions are mixed and dissolved, then the stirring time is 1-4 h, the stirring temperature is 80-150 ℃, the standing time of the casting solution is 2-4 h, and the standing temperature is 40-150 ℃.
8. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: and in the second step, the solvent used by the coagulating bath is any one or a group consisting of methanol, ethanol, ethylene glycol, isopropanol and deionized water.
9. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: and in the second step, the temperature of the dipping coagulation bath is 20-120 ℃, the dipping time is 4-20 h, and the coagulation bath solvent is replaced every 2 h.
10. The method for preparing a polylactic acid/cellulose derivative microfiltration membrane according to claim 2, wherein: the drying in the third step is as follows: and drying in a vacuum drying oven or under normal pressure at the temperature of 30-60 ℃.
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Application publication date: 20200707 |