JPH0460688B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for separating mixed solutions using a permeable membrane, which may also be referred to as a vaporization permeation method. [Prior Art] Research is progressing on pervaporation as a method for separating a mixed solution of two or more components, such as a mixed solution of organic liquids. The principle of this pervaporation method is shown in Figure 2. A separation tank 5 is partitioned into an upper solution chamber 3 and a lower pressure reduction chamber 1 by a permeable membrane 4, and a mixed solution 2 is introduced into the solution chamber 3. Transparent membrane 4
By reducing the pressure in the vacuum chamber 1 while the mixed solution 2 is in contact with the mixed solution 2, specific components in the mixed solution 2 are preferentially permeated and diffused into the permeable membrane 4, and the components that have permeated through the permeable membrane 4 are It is designed to vaporize from the surface of the permeable membrane 4 on the reduced pressure chamber 1 side, and by collecting the components that have permeated through the permeable membrane 4 in this way, it is possible to separate and collect.
Alternatively, separation and collection can be performed by recovering the residual liquid of the mixed solution 2 after the components that permeate the permeable membrane 4 have been removed in this way. However, in this pervaporation method, the mixed solution 2
is in direct contact with the permeable membrane 4, and the permeable membrane 4, which is generally formed of a polymeric material, is often swollen by the mixed solution. When the permeable membrane 4 is swollen in this manner, the membrane function of the permeable membrane 4 is reduced, and the separation performance of the mixed solution 2 is significantly impaired. Therefore, the inventor of the present invention has developed a method which may be called a vaporization infiltration method, and a method for separating a mixed solution using this vaporization infiltration method has been filed as a patent application as Japanese Patent Application No. 309991/1983. In other words, as the principle of this method is shown in FIG. 3, the vacuum chamber 1 and the solution chamber 3 into which the mixed solution 2 is introduced are separated by a permeable membrane 4 that does not come into contact with the mixed solution 2, and the vacuum chamber 1 is depressurized. The vapor of the mixed solution 2 generated in the solution chamber 3 is allowed to permeate through the permeable membrane 4.
In this method, since the permeable membrane 4 does not come into contact with the mixed solution 2, there is no problem of deterioration of membrane function due to swelling of the permeable membrane 4, and the separation performance of the mixed solution 2 can be improved. [Problems to be Solved by the Invention] As mentioned above, the vaporization permeation method can separate the mixed solution 2 with higher separation performance than the permeation vaporization method, but the separation performance is lower in terms of the performance of the permeable membrane 4 itself. may not be sufficient, and it is desired to further improve the separation performance of the mixed solution 2 in the vaporization infiltration method. [Means for Solving the Problems] According to the present invention, a permeable membrane 4a is provided between the reduced pressure chamber 1 and the solution chamber 3 into which the mixed solution 2 is introduced in a state where the mixed solution 2 is not brought into contact with the solution chamber 3. 1 is reduced in pressure to allow the vapor of the mixed solution 2 generated in the solution chamber 3 to permeate through the permeable membrane 4a, and the permeated vapor is further permeated through another permeable membrane 4b. This relates to a method for separating a mixed solution. The present invention will be explained in detail below. FIG. 1 shows an example of the principle device of the present invention, in which a permeable membrane 4a
The separation tank 5 is divided into an upper decompression chamber 1 and a lower solution chamber 3, and a space is formed between the liquid level of the mixed solution 2 introduced into the solution chamber 3 and the lower surface of the permeable membrane 4a. The mixed solution 2 is prevented from coming into contact with the permeable membrane 4a. Furthermore, a permeable membrane 4b is provided inside the decompression chamber 1 to partition the inside of the decompression chamber 1 into two upper and lower chambers 1a and 1b. By reducing the pressure in the chamber 1b of the decompression chamber 1, the pressure in the chamber 1a becomes reduced through the permeable membrane 4b, and the permeable membrane 4a
Through this, the inside of the solution chamber 3 is also brought into a reduced pressure state, and steam is generated from the mixed solution 2 inside the solution chamber 3 in the reduced pressure state. In this way, when the vapor evaporated from the mixed solution 2 in the solution chamber 3 comes into contact with the permeable membrane 4a, it permeates through the permeable membrane 4a and is diffused. Because it is in a high reduced pressure state, it passes through the permeable membrane 4a and enters the chamber 1.
Reach side a. At this time, the permeable membrane 4a preferentially permeates and diffuses a specific component in the vapor of the mixed solution 2. Therefore, the specific component of the vapor permeates the permeable membrane 4a preferentially and enters the chamber 1a. The steam that has reached this point has an increased concentration of that particular component. When this vapor that has reached the chamber 1a comes into contact with the permeable membrane 4b, it permeates the permeable membrane 4b and is diffused.Since the pressure in the chamber 1b is higher than that in the chamber 1a, it permeates through the permeable membrane 4b and enters the chamber. It reaches the 1b side. At this time as well, the permeable membrane 4b preferentially permeates and diffuses specific components in the vapor in the chamber 1a, and specific components of the vapor preferentially permeate the permeable membrane 4b and reach the interior of the chamber 1b. The ivy vapor has an increased concentration of its specific components. For example, when a water-alcohol solution is used as the mixed solution 2 to separate water and alcohol, the permeable membrane 4a is made of an alcohol-selective material that allows alcohol to pass through preferentially, and the permeable membrane 4b is made of an alcohol-selective material that allows alcohol to pass through preferentially. Use a water-selective material that allows water to pass through preferentially. When chamber 1b of decompression chamber 1 is depressurized, alcohol in the vapor generated from mixed solution 2 preferentially permeates through permeable membrane 4a, so that the vapor that reaches chamber 1a has an increased alcohol concentration. Become. and room 1a
The moisture contained in the vapor with increased alcohol concentration in the chamber preferentially permeates through the permeable membrane 4b and is moved to the chamber 1b.
This means that the alcohol concentration can be further increased by removing moisture from the steam in the chamber 1a. In this way, it is possible to recover the alcohol component from the chamber 1a in a separated state with a high concentration. It is also possible to separate two components independently from the mixed solution 2, such as the alcohol component from the chamber 1a and the water from the chamber 1b. Of course, by increasing the number of permeable membranes 4a, 4b, . . . to three or four, it becomes possible to further separate multiple components, such as three or four components, from the mixed solution. As described above, desired components can be separated and collected from a mixed solution by permeating the permeable membranes 4a and 4b and collecting the components that have permeated into the chambers 1a and 1b of the vacuum chamber 1. It can be done. In this case, the mixed solution 2 can be separated into components by the vapor permeating through the permeable membranes 4a and 4b.
are not brought into direct contact with the permeable membranes 4a, 4b. For vapor, which is a gas compared to liquid, a permeable membrane 4 is used.
There is almost no swelling of the permeable membranes 4a and 4b, and therefore there is no risk that the membrane function of the permeable membranes 4a and 4b will deteriorate and the performance of separating the mixed solution 2 will be impaired. Moreover, in this way, the permeable membrane 4a,
Since it is vapor that permeates through the membranes 4a and 4b, the rate of permeation through the permeable membranes 4a and 4b is faster than in the conventional pervaporation method in which liquid permeates, and for this reason, it is also called the vaporization permeation method of the present invention. The method described above makes it possible to increase the permeation separation efficiency of the mixed solution 2. Here, as the permeable membrane, what is called a non-porous membrane can be used, and those used in conventional pervaporation methods can be used.
For example, alginate membrane, chitosan membrane, crosslinked chitosan membrane, chitosan acetate membrane, quaternized chitosan membrane, polystyrene membrane, polyvinylidene chloride membrane, silicone (polydimethylsiloxane) membrane, polyvinylidene fluoride membrane, cellulose nitrate membrane, cellulose acetate membrane. , a crosslinked polyvinyl alcohol film, a polyamic acid film, a poly(1-trimethylsilyl)-1-propyne film, a styrene-dimethylsiloxane graft copolymer film, and the like. Since the permeable membrane is not brought into direct contact with the mixed solution, it can be used without any particular problem even if it is a material that swells upon contact with the mixed solution, and the materials that can be used are limited by the mixed solution. Various materials can be selected and used to facilitate the removal of desired specific components from the mixed solution. For example, when separating a water-alcohol mixed solution as described above, alginate membranes, chitosan membranes, cross-linked chitosan membranes, polystyrene membranes, cross-linked polyvinyl alcohol membranes, polyamic acid membranes, etc. are used as water-selective membranes, and alcohol-selective membranes are used. As the film, a polydimethylsiloxane film, a poly(1-trimethylsilyl)-1-propyne film, a styrene-dimethylsiloxane graft copolymer film, etc. can be used. Furthermore, since the permeation rate within a permeable membrane is inversely proportional to the membrane thickness, the permeation rate can be increased by making the permeable membrane thinner, and the ability to separate components of a mixed solution depends on the membrane thickness. Since this is irrelevant, membrane performance can be improved by making the permeable membrane thinner. The permeation rate within the permeable membrane is also affected by the degree of reduced pressure in the reduced pressure chamber, and the higher the degree of reduced pressure in the reduced pressure chamber, that is, the higher the vacuum, the higher the permeation rate. In addition, since the permeable membrane is formed thin, it is usually fragile and cannot withstand the reduced pressure state of the decompression chamber. It is preferable that the permeable membrane is supported by a porous support such as a porous ceramic plate, and this support prevents the permeable membrane from being torn under the reduced pressure state of the reduced pressure chamber. In the above example shown in FIG. 1, membranes with different properties (water selectivity and alcohol selectivity) are used as the permeable membranes 4a and 4b, but membranes with the same properties (water selectivity and alcohol selectivity) are used as the permeable membranes 4a and 4b. For example, by using alcohol selectivity, the vapor of the mixed solution 2 can be doubly permeated through the permeable membranes 4a and 4b and recovered in a state where the concentration of the specific component is increased. Of course, in this case as well, the permeable membranes 4a and 4b
By increasing the number of ... to three or four,
Furthermore, it becomes possible to increase the concentration of specific components. The method of the present invention can be used to separate various mixed solutions, and is particularly effective for separating mixed solutions that cannot be separated by ordinary distillation. For example, water-alcohol system, water-aromatic compound system,
Recovery of alcohols, aromatic compounds, and ethers from azeotropic mixtures such as water-ether systems, separation and recovery of organic solvents such as hydrocarbons with close boiling points, o-
Separation and recovery of mixtures of structural isomers such as mixtures of xylene, m- and p-xylene, separation and recovery of mixtures of optical isomers such as dextrorotatory and levorotatory, drugs and biological substances,
Separation of thermally decomposable or heat-alterable mixtures such as fruit juices and polymerizable monomers; separation of products from reaction mixtures to accelerate reactions by shifting the reaction equilibrium; ammonia from wastewater; The present invention can be effectively applied to the separation and removal of volatile organic mixtures such as carbon dioxide, amines, hydrogen sulfide, carbon dioxide, and sulfur dioxide gas. Other areas include separation and concentration of alcohol from biomass, separation and recovery of expensive organic solvents such as dimethylformamide, dimethylacetamide, and dimethylsulfoxide from synthetic fiber spinning baths,
Triclean is used for the separation and recovery of solvents in paint waste liquid generated during paint manufacturing and painting lines, separation and concentration of alcohol mixtures and organic solvent mixtures in chemical factories, separation and recovery of salts in these mixtures, and dry cleaning. collection, concentration of emulsion solutions, concentration of solutions containing radioactive substances, concentration and separation of rare earth ions from solutions, concentration of viruses and bacteriophages, use of sterile water and non-sterile water for pharmaceuticals, hospitals, hemodialysis, etc. production of exothermic water;
The present invention can also be applied to the production of ultrapure water for the electronic industry. [Examples] The present invention will be further explained below with reference to Examples. Example 1 Using the vaporization permeation method shown in FIG. 1, an alcohol-selective polydimethylsiloxane membrane that preferentially transmits alcohol is used as the permeable membrane 4a in FIG. 1, and an alcohol-selective polydimethylsiloxane membrane that preferentially transmits water as the permeable membrane 4b. A water-selective dialdehyde-crosslinked chitosan membrane was used in each case. Here, the size of the dialdehyde crosslinked chitosan membrane was adjusted so that its permeation area was five times that of the polydimethylsiloxane membrane. The polydimethylsiloxane film was prepared by mixing 7 parts by weight of polydimethylsiloxane, 0.25 parts by weight of Catalyst RA (manufactured by Shin-Etsu Chemical Co., Ltd.) as a hardening agent, and 49 parts by weight of benzene. The mixture was cast into a film forming device and left to dry at 25° C. for 6 hours to form a film with a thickness of 100 μm. Further, a dialdehyde crosslinked chitosan membrane was prepared as follows. That is, 1% in 1N acetic acid aqueous solution.
A casting liquid prepared by degassing a solution containing % by weight of chitosan under reduced pressure is cast onto a flat shear tray for film formation, and the solvent is completely removed by leaving it in a constant temperature dryer at 60°C for 6 hours. evaporated to form a film of chitosan acetate. This chitosan acetate film was peeled off from the flat shear and immersed in a 1N aqueous sodium hydroxide solution to obtain a chitosan film. Next, this chitosan membrane was immersed at room temperature for 15 minutes in a solution prepared by adding a 0.5N sulfuric acid aqueous solution as a catalyst to a 0.4% glutaraldehyde aqueous solution to crosslink the chitosan with dialdehyde, and then washed with water and reduced pressure at room temperature. As it dries, the thickness increases.
A 20 μm dialdehyde crosslinked chitosan membrane was obtained. Then, ethanol aqueous solutions of various concentrations were introduced into the solution chamber 3 as the mixed solution 2, and each chamber 1a and 1b of the vacuum chamber 1 was adjusted to an atmosphere of 40°C, and the chamber 1b was adjusted to 1.5×10 ^-2 Torr. I tried to reduce the pressure. At this time, the pressure reduction operation is performed by valve 6 of chamber 1a.
This was carried out by closing the chamber 1b and opening the valve 7 of the chamber 1b, and keeping the chamber 1b in a suction state for one hour. After this operation, the concentration of ethanol in the steam in the chamber 1a of the reduced pressure chamber 1 was measured.
The results are shown in Table 1. Comparative Example 1 The apparatus shown in FIG. 3 was used, a polydimethylsiloxane membrane was used as the permeable membrane 4, and the rest was as in Example 1.
In the same manner as above, the pressure inside the vacuum chamber 1 was reduced for 1 hour.
After this operation, the concentration of ethanol in the vapor in the reduced pressure chamber 1 was measured. The results are shown in Table 1.

[Table] As shown in Table 1, compared to Comparative Example 1, which used only an alcohol-selective permeable membrane, a combination of alcohol-selective and water-selective permeable membranes was used. It is confirmed that in Example 1, the concentration of ethanol can be increased and the ethanol can be separated and recovered. Examples 2 and 3 Using the apparatus shown in Fig. 1, each chamber 1 of the decompression chamber 1
The ambient temperature of a and 1b was 25℃ (Example 2) and 55℃
(Example 3) The concentration of ethanol in the steam in the chamber 1a was measured in the same manner as in Example 1, except that the settings were made as in Example 3. The results are shown in Table 2. Comparative Examples 2 and 3 The apparatus shown in Figure 3 was used, and the atmospheric temperature of the decompression chamber 1 was set at 25°C (Comparative Example 2) and 55°C (Comparative Example 3), respectively. In the same manner, the concentration of ethanol in the vapor in the vacuum chamber 1 was measured. The results are shown in Table 2.

[Table] Table 2 also shows examples in which an alcohol-selective membrane and a water-selective membrane were used in combination, compared to Comparative Examples 2 and 3, which used only an alcohol-selective membrane. It is confirmed that in cases 2 and 3, the concentration of ethanol can be increased and the ethanol can be separated and recovered. Furthermore, from Table 2 and Table 1 above, it is confirmed that the separation efficiency of ethanol can be increased by increasing the ambient temperature. [Effects of the Invention] As described above, in the present invention, a permeable membrane is provided between the vacuum chamber and the solution chamber into which the mixed solution is introduced in a state where the mixed solution does not come into contact with each other, and the pressure in the vacuum chamber is reduced to remove the solution. The vapor of the mixed solution generated indoors is permeated through the permeable membrane, and the permeated vapor is further permeated through another permeable membrane, so that the vapor of the mixed solution is permeated through the permeable membrane and the mixed solution is When separating components, multiple permeable membranes can be applied to vapor, and multiple permeable membranes can improve separation performance, improving the separation performance of mixed solutions by vaporization permeation method. It is something that can be done.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the device used in the present invention, Fig. 2 is a schematic diagram of the device used in the conventional pervaporation method, and Fig. 3 is a schematic diagram of the device used in the conventional pervaporation method.
The figure is a schematic diagram of an apparatus used in the vaporization infiltration method. 1 is a vacuum chamber, 1a and 1b are the vacuum chambers, 2 is a mixed solution, 3 is a solution chamber, and 4a and 4b are permeable membranes.

Claims (1)

[Claims] 1. A permeable membrane is provided between the decompression chamber and the solution chamber into which the mixed solution is introduced, so that the mixed solution does not come into contact with it.
A method for separating a mixed solution, which comprises reducing the pressure in a vacuum chamber to allow vapor of the mixed solution generated in the solution chamber to permeate through the permeable membrane, and further permeating the permeated vapor through another permeable membrane.