KR0171507B1 - Method for manufacturing chitosan-based composite pervaporation membrane - Google Patents

Abstract

The present invention provides a high permeability to water contained in the organic liquid mixture while forming an active layer by forming a active layer by forming a film using α-chitosan or β-chitosan obtained in nature and crosslinking with aldehyde or acid. The present invention relates to a method for producing a chitosan-based pervaporation composite membrane for separating an organic aqueous solution which can be separated at a high purity by showing a low transmittance.

Description

Method for producing chitosan permeation composite membrane

The present invention relates to a method for producing a chitosan-based pervaporation-composite membrane, and more specifically to forming an active layer by forming a active layer by forming a active layer by forming a film using α-chitosan or β-chitosan obtained in nature and crosslinking it with an aldehyde or an acid. The present invention relates to a method for preparing a chitosan-based pervaporation composite membrane for separating an organic water solution having high permeability for water contained in the mixture and low permeability for an organic layer to separate organic solvents with high purity.

In general, when the organic solvent is used in a chemical process, a high purity organic solvent is required. Therefore, it is necessary to separate the organic liquid solvent in order to suppress the water contained in the organic solvent as much as possible. Evaporation is one of the useful methods for separating organic liquid solvents. In particular, the energy consumption is very high because of the high boiling point of the mixed materials in the organic liquid mixture, and a simple distillation process when separating a mixture or a heat sensitive mixture of a material that is limited to separation due to an azeotropic mixing point, a compound having a similar boiling point By separating the organic solvent using a more pervaporation membrane, the operating cost is not only inexpensively consumed, but there is an advantage that the separation process can be efficiently performed at a low temperature by a simple operation.

Therefore, many studies have been carried out to develop a permeation evaporation membrane for separating organic liquid mixtures when a simple distillation process is not applicable, and for the first time, a permeation evaporation membrane was developed using polyethylene membranes from America Oil Company, USA. Although it had excellent selectivity, it was not practically used due to the low permeation rate, and since then, it was not effective due to the lack of membrane material.

Recently, however, the cutting of membranes to be used for a specific separation process has been possible, and new attention has been focused on the separation of organic solvent solutions using synthetic resin membranes due to the emergence of hollow fibers or composite membranes. We developed a permeable evaporation membrane containing) as the main raw material, and succeeded in dehydrating the organic solvent and its mixture on a commercial scale.

The PVA permeation membrane has been mainly used for dehydration of organic solvents (mixtures of organic solvents and water) due to its high permeability to water and low permeability to organic solvents, but the concentration of organic solvents in the feed liquid is 80% or less. In this case, since the selectivity is sharply lowered, there is a disadvantage in that the practical use is impossible when the concentration of the feed liquid is 80% or less.

In addition, Korean Patent Publication No. 92-10859 discloses a permeation evaporation membrane formed only with chitosan, an organic acid such as alkali, chlorosulfonic acid, chloroacetic acid such as sodium hydroxide and carboxylic acid after forming with chitosan, an acidic group, a basic group or the like. Although a pervaporation membrane treated with a compound such as a vinyl monomer having a functional group (eg, acrylonitrile, acrylic acid, allylamine) has been described, the selectivity is not satisfactory, and the mechanical strength is low, so durability is reduced and α-chitosan There was a problem that there is a restriction on the raw material by using only.

Therefore, the present inventors cast the α-chitosan or β-chitosan deacetylated α-chitin or β-chitin on a polysulfone support to form a film, crosslinking with an aldehyde or an acid, and then poly The present invention was completed by discovering that chitosan-based pervaporation composite membranes capable of separating organic solvents with high purity due to excellent water selectivity and excellent permeate flow rate and mechanical strength by adhering an ester nonwoven fabric were completed. .

Chitosan is a substance deacetylated chitin, composed of a non-molecular chain of β- (1 → 4) -2-acetamide-2-deoxy-D-glucose residue, and has a structure similar to cellulose and is a fungus. Yeast, invertebrate marine animals, crustaceans are found in the exoskeleton. In general, chitin obtained from crustaceans is α-chitin, and chitin obtained from invertebrate marine animals is β-chitin. Chitin is insoluble in water and other solvents, while chitosan is soluble in various acidic solvents, such as formic acid or acetic acid, so it is more industrially applied than chitin. In the present invention, since chitosan has a structure similar to cellulose, mechanical strength is excellent, and affinity with water is improved by using chitosan as it is or by chemical treatment to improve affinity with water, but insoluble in water. Phosphorus material was prepared and used for separation of the organic solvent.

That is, an object of the present invention is to separate the organic solvent and water in the organic liquid mixture, not only has excellent selectivity for water, but also excellent permeate flow rate and mechanical strength, which can separate the organic solvent with high purity. It is to provide a method for producing an evaporation composite film.

The present invention is described in more detail as follows.

In the chitosan permeation evaporation composite membrane of the present invention, α-chitosan or β-chitosan having a deacetylation degree of 50 to 99% is dissolved in 2% by weight aqueous acetic acid so as to be 0.5 to 2.5% by weight, and the solution has a fraction molecular weight of 5,000. It is prepared by forming a film on a polysulfone membrane for ultrafiltration of ˜500,000, desolventizing it, crosslinking with an aldehyde or an acid, heat treatment, and bonding a polyester nonwoven fabric to the back surface of the polysulfone membrane.

In the chitosan composite membrane of the present invention, a dense active layer made of chitosan is present in the upper layer, and a support layer made of polysulfone including continuous pores and a polyester nonwoven fabric for maintaining mechanical strength is present in the lower layer. The chitosan active layer has excellent performance in selectively separating the organic liquid mixture, and in general, as the thickness of the chitosan membrane becomes thinner, the permeability can be increased, so that the supporting layer is maintained to maintain the mechanical strength while reducing the thickness of the active layer. To prepare a composite membrane.

The chitosan used in the present invention preferably has a deacetylation degree of 50 to 99%, and when the deacetylation degree is less than 50%, the degree of dissolution in an aqueous acetic acid solution is weak, which makes it difficult to form a film. If it exceeds, it is impossible to identify chitosan with the naked eye, which leads to difficulty in film production.

In addition, it is preferable to dissolve the chitosan so as to be 0.5 to 2.5% by weight when dissolved in an acetic acid aqueous solution, when the concentration is less than 0.5%, there is a problem that the film thickness is not formed to the desired degree, when it exceeds 2.5% by weight The viscosity rises, making uniform film formation impossible.

If the fractional molecular weight of the polysulfone membrane used as the support is less than 5,000, the durability of the composite membrane produced is lowered, and if it exceeds 500,000, there is a problem in that the transmittance of the organic solvent is poor.

In the case of the aldehyde treatment, glutalaldehyde, glyoxal, terephthalaldehyde and the like are dissolved in alcohol or water such as ethanol and methanol at 0.001-0.1% by weight, and the chitosan-based composite membrane is dissolved in this solution for several hundred minutes, preferably Crosslink by immersion for 5 to 300 minutes. In the case of crosslinking the aldehyde, a Schiff base is formed in the amino period of the chitosan to increase the selectivity of water of the chitosan-based composite membrane, which is advantageous for the concentration of the organic mixture.

In the case of treating with acid, hydrochloric acid, sulfuric acid, phosphoric acid, and the like are dissolved in alcohol or water such as ethanol and methanol at 0.001-0.1% by weight, and the chitosan crab composite membrane is contained in this solution for several minutes to several hundred minutes. Crosslink by immersion for 300 minutes. In the case of crosslinking with an acid as described above, crosslinking is ionically performed in the amino period of chitosan to increase the selectivity of water in the chitosan-based composite membrane, which is advantageous for the concentration of the organic mixture.

As the solvent used in the present invention, a solvent capable of dissolving chitosan in addition to acetic acid, for example, formic acid, sulfuric acid, or a mixed solvent thereof may be used, and the thickness of the membrane need not be limited, but in the case of the chitosan active layer, -30㎛, in the case of polysulfone support it is good to maintain 20-200㎛.

The heat treatment is inversely related to the treatment temperature and time, and it is preferable to perform the heat treatment for 5 to 300 minutes at a temperature of 100 to 200 ° C in view of the overall physical properties of the composite film to be produced.

Chitosan, which is used as a main component of the synthetic resin film in the present invention, is known to be excellent in biosynthesis, and is used in surgical sutures, medical materials, and cosmetic additives in the form of fibers or films, and in the present invention, such chitosan is used. When the membrane was made and the organic solvent and water were separated by pervaporation, a membrane having excellent selectivity and flow rate was prepared.

The pervaporation composite membrane prepared in the present invention can be applied to pervaporation separation of various kinds of liquid mixtures, and typical examples thereof may be applied to liquid mixtures containing water-soluble organic substances such as alcohols, ethers, ketones, esters, and the like. Can be. From an industrial point of view, it is very important to separate and recover ethanol economically. Ethanol is a kind of oxygen-containing fuel (methanol, ethanol, methyl tertiary butyl ether, ethyl tertiary butyl ether), which is an oxygen-containing fuel added to improve the fuel quality of gasoline. Alcohol in the state is called fuel alcohol. Alcohol for fuel is a low concentration of ethanol obtained through the fermentation of grains by using a distillation method to concentrate it again above the azeotropic point, the pervaporation method is useful.

When the aqueous solution of ethanol is separated using the composite membrane prepared by the method of the present invention, the aqueous solution of ethanol is filled on one side of the membrane and the pressure on the other side is reduced with a vacuum pump. The pressure in the feed liquid can vary from 1-100 atm, but for industrial applications, the closer to 1 atm, the better. In addition, the lower the pressure in the permeate, the better, and the industrial pressure range is 0.1-100mmHg.

As shown in the following examples, the chitosan composite membrane has an excellent pervaporation performance, particularly for separation of aqueous ethanol solution.

Here, the separation coefficient α can be obtained from the following equation (1).

Where Y is the concentration of the permeate side component and X is the concentration of the liquid feed liquid.

Permeate flow rate J is obtained from the following equation (2).

Where Q is the transmission rate (g / hr) and A is the membrane area (m 2).

The following examples illustrate the invention in more detail, but do not limit the scope of the invention.

Example 1

Chitosan powder (Japan Nippon Chemical Co., Ltd., viscosity 500cps) is dissolved in 2% by weight of acetic acid solution at 1% by weight and filtered through a glass filter to remove insoluble matters.

The solution was deposited on a polysulfone support to a thickness of 1.5 mm using an automatic casting device, and then the solvent was evaporated for about 1 minute and then dried in an oven at 65 ° C. for a composite membrane having a thickness of 15 μm of the chitosan active layer.

This membrane was used to immerse in a methanol solution containing glutaraldehyde, glyoxal or terephthalaldehyde in 0.01% by weight to crosslink the reaction, and then dried at room temperature for 2 days to be used for pervaporation experiments.

This membrane was used to separate ethanol and water using a pervaporation method in which the ethanol concentration in the feed liquid was 95% by weight, the feed liquid temperature was 75 ° C., and the pressure in the permeate was 3 mmHg. Are listed in Table 1.

Example 2

In the membrane prepared in Example 1, a glutaraldehyde-crosslinked membrane was used, and as shown in Table 2, the ethanol concentration in the feed solution was 95% by weight, the operating temperature of the feed solution was 35 ° C-75 ° C, and the pressure in the permeate was 3 mmHg. The separation of atanol and water was carried out using a permeation evaporation method, and the results of the separation characteristics and permeate flow rate of the membrane are shown in Table 2.

Example 3

Among the membranes prepared in Example 1, the membranes were prepared by varying the heat treatment time of the glutalatehydrocrosslinked membranes in an oven at 120 ° C.

Using these membranes, ethanol and water were separated by pervaporation using a ethanol concentration of 95% by weight, a feed temperature of 75 ° C, and a pressure of permeate of 3 mmHg. Are listed in Table 3.

Example 4

Chitosan powder (Nippon Nippon Chemical Co., Ltd., viscosity 500 CPS) is dissolved in 2% by weight aqueous acetic acid solution at 1% by weight, and filtered through a glass filter to remove insoluble matters.

The solution was formed on the polysulfone support with a thickness of 1.5 mm by an automatic casting device, and then the solvent was evaporated for about 1 minute and then dried in an oven at 65 ° C. for a composite membrane having a thickness of 15 μm of the chitosan active layer.

The membrane was immersed in a methanol solution containing 0.01% by weight of sulfuric acid, hydrochloric acid or phosphoric acid to prepare an ion-crosslinked chitosan composite membrane.

Using these membranes, ethanol and water were separated by pervaporation using a ethanol concentration of 95% by weight, a feed temperature of 75 ° C, and a pressure of permeate of 3 mmHg. Are listed in Table 4.

Example 5

In Example 4, ethanol and water were separated using a permeation evaporation method in which the ethanol concentration in the feed liquid was 95% by weight, the feed liquid temperature was 75 ° C, and the pressure in the permeate liquid was 3 mmHg. Table 5 shows the separation characteristics and the permeate flow rate of the membrane.

Claims (11)

A method for producing a chitosan permeation evaporation composite membrane comprising dissolving α-chitosan or β-chitosan in an organic solvent to form a film on a support, and treating and reacting an aldehyde or an acid to activate it. The chitosan permeation evaporation composite membrane according to claim 1, wherein the chitosan has a deacetylation degree of 50 to 99%. The method of claim 1, wherein the organic solvent is an aqueous acetic acid solution. The method of claim 1, wherein the support is a polysulfone membrane. The method of claim 4, wherein the polysulfone membrane is an ultrafiltration membrane having a molecular weight of 5,000 to 500,000. The method of claim 1, wherein the aldehyde is glyoxal, glutaraldehyde or terephthalaldehyde. The method of claim 1, wherein the acid is sulfuric acid, hydrochloric acid, or phosphoric acid. The method for producing a chitosan-based pervaporation composite membrane according to claim 1, wherein the aldehyde or acid treatment is immersed in a solution in which aldehyde or acid is dissolved in alcohol at a concentration of 0.001 to 0.1% by weight for 5 to 300 minutes. The method of claim 1, wherein the membrane is heat-treated at a temperature of 100 to 200 ° C. for 5 to 300 minutes. The method for producing a chitosan-based pervaporation composite film according to claim 1, wherein a polyester nonwoven fabric is bonded to the back surface of the support. Separation of the liquid mixture, characterized in that the organic solvent is concentrated using a chitosan permeation evaporation composite membrane activated by dissolving α-chitosan or β-chitosan in an organic solvent to form a film on a support, and treating and reacting an aldehyde or an acid. Way.