WO2019090470A1 - Highly permeable and highly selective pva/ga/cs-m+ pervaporation film for dehydration of organic solutions - Google Patents

Abstract

A highly permeable and highly selective pervaporation film for dehydration of organic solutions and a preparation method therefor, which uses CS (chitosan) chelated with a heavy metal ion (M+) such as Ag+, Cu2+, or Fe3+ as a precursor, blends the chelated CS with PVA (polyvinyl alcohol), and then adds GA (glutaraldehyde) as a crosslinking agent, forming a PVA/GA/CS-M+ pervaporation film with high mechanical strength and thermal stability and exhibiting excellent permeability and selectivity for dehydration of organic solutions.

Description

Highly permeable and highly selective PVA/GA/CS-M+ pervaporation film for dehydration of organic solutions Technical field

The invention relates to a pervaporation film, in particular to a high-permeability and high-selectivity pervaporation film for dehydration of an organic solution and a preparation method thereof.

Background technique

Isopropanol (IPA) can be used to produce acetone, isopropyl ester, isopropylamine and other raw materials. It is also widely used in pharmaceuticals, pesticides, cosmetics, plastics, perfumes, coatings, etc., and as a cleaning agent in oils, oils and gums. Solvents such as waxes and cosmetics. Ethanol (EtOH) can be used to make acetic acid, acetaldehyde, ether, ethyl acetate, ethylamine, etc. It is also a raw material for the production of medicines, cosmetics, dyes, paints, detergents, beverages, flavors, and fuels for vehicles. Acetone can be used in the manufacture of bisphenol A, methyl methacrylate, acetone cyanohydrin, methyl isobutyl ketone, etc., as well as in medicine, cosmetics, building materials, paints, plastics, fibers, gunpowder, Resin, rubber, photographic film, etc. The reuse of organic solvents clearly contributes to economic advantages and environmental protection, and the dehydration of organic solvents is particularly important in the development of thin film technology. The use of a pervaporation membrane to separate the alcohol/water mixture is superior to conventional distillation methods because it overcomes the azeotropy of the alcohol/water. In particular, pervaporation membrane separation is an efficient process for energy saving since it does not require operation at high temperatures.

The dissolution-diffusion model has undoubtedly been accepted to describe the transport phenomena in pervaporation membrane technology. The structure of the film can greatly affect the dissolution-diffusion behavior of the solution, thereby affecting the transmission efficiency.

Lu et al. proposed a hydration of the film during pervaporation as a dynamic process involving adsorption-desorption equilibrium. Since the hydrophilic film can make the water easy to be absorbed-diffused, the transfer efficiency can be improved. Therefore, the water absorption property of the hydrophilic membrane becomes a key factor in the design of the pervaporation separation membrane.

PVA is a highly hydrophilic polymer with good film forming properties and chemical resistance, and has become a preferred material for pervaporation dehydration. However, due to the presence of its hydroxyl group, its swelling phenomenon in aqueous nighttime is difficult to be masked. By introducing a crosslinking agent, the intermolecular structure of the PVA-based film can enhance the formation of strong covalent bonds between the polymer chains, rather than weaker hydrogen bonds, thereby increasing mechanical strength and greatly improving stability. The pervaporation test is used to evaluate the pervaporation separation efficiency of the film, and the physical and chemical properties of the obtained film are measured according to the contact angle, the degree of expansion, the mechanical properties, and the thermal stability. However, although the cross-linking agent can make the structure of the membrane relatively stable, it will consume the hydrophilic group of the polymer chain. It is known that the cross-linking agent can form a relatively stable membrane structure for the PVA matrix, and also penetrates in water. This has a negative impact because the formation of the crosslinker will consume hydroxyl groups in the PVA polymer. Therefore, how to improve the pervaporation film so that it can be used for dehydration of an organic solution, and can effectively promote water transmittance, Without losing its selectivity, it is a problem that needs to be solved now.

Summary of the invention

It is an object of the present invention to provide a highly permeable and highly selective pervaporation film for dehydration of an organic solution and a process for the preparation thereof.

In order to achieve the above object, the present invention provides a method for preparing a highly permeable and highly selective pervaporation film for dehydration of an organic solution, which comprises the following steps:

Preparation of materials: preparation of polyvinyl alcohol (PVA), chitosan (CS), 25 weight percent of glutaraldehyde (GA) and 99 weight percent of isopropanol, ethanol and acetone;

Dissolving a unit weight of the chitosan in nine unit weight of deionized water, stirring at room temperature for 7-10 hours to form a solution;

Adding silver ions or copper ions or iron ions to the solution to form liquid A, and continuing to stir;

Dissolving a unit weight of the polyvinyl alcohol in nine unit weight of deionized water, stirring at 70 ° C for 20 to 24 hours to form a liquid B;

The liquid A and the liquid B are thoroughly mixed and stirred for at least 2 hours to form a mixed solution C;

Stir at 70 ° C for at least 1 hour, place the mixed solution C in a Petri dish made of polyethylene, dry in an oven at a temperature of 25 ° C to 50 ° C for 1 day and add glutaraldehyde to form a usable organic solution. A highly selective permeation evaporation membrane for dehydration.

Further, the organic solution is a 99% by weight aqueous solution of isopropanol, an aqueous solution of ethanol, an aqueous solution of acetone or another aqueous solution of an organic solvent.

Further, wherein the unit weight is 5 g, and the nine unit weight is 45 g.

Further, the stirring time of the chitosan dissolved in the ionized water was 8 hours, and the stirring time of the PVA dissolved in the deionized water was 24 hours.

Further, when a higher concentration of silver ions or copper ions or iron ions is added, a film having a relatively uniform network structure can be obtained, which means that CS chelated silver ions or copper ions or iron ions interact with PVA. Thereby improving the compatibility of CS and PVA.

Further, wherein the concentration of the glutaraldehyde is 25 wt%, the cross-linking effect of the addition of glutaraldehyde enables the pervaporation film to exert optimal thermal stability.

Further, wherein Ag ⁺ or Cu ²⁺ or Fe ³⁺ or other heavy metal ions chelate CS to promote the intermolecular interaction of the pervaporation film, thereby obtaining a highly compatible polymer matrix and enabling it to be in water The mixture of the organic solvent system absorbs more water and swells itself without losing its network structure.

Further, the present invention provides a pervaporation film formed according to the above production method.

The present invention further provides a highly selective and highly permeable pervaporation film for dehydration of an organic solvent, which uses glutaraldehyde as a crosslinking agent for polyvinyl alcohol and chitosan, and adds silver ions or copper ions. Or formed by iron ions.

The invention has the following beneficial effects:

The pervaporation film prepared by the invention has high mechanical strength, thermal stability and can exhibit excellent permeability and selectivity for dehydration of an organic solution; it can effectively promote water transmittance without losing its Selectivity.

DRAWINGS

Figure 1 shows (a) pure PVA, (b) pure CS, (c) PVA/CS, (d) PVA/CS-Ag ⁺ (Ag ⁺ : 1.17x10 ^-1 mol.) and (e) PVA/GA/ FTIR spectrum of CS-Ag ⁺ (Ag ⁺ : 1.17 x 10 ^-1 mol.).

Figure 2 is a graph showing (a) pure PVA, (b) pure chitosan, (c) PVA/CS, (d) PVA/CS-Ag ⁺ (Ag ⁺ : 1.17 x 10 ^-1 mol.), (e) PVA TGA map of /GA/CS-Ag ⁺ (Ag ⁺ : 1.17x10 ^-1 mol.).

Figure 3 shows the contact angles of PVA/GA/CS-Ag ⁺ pervaporation films with different contents of Ag ⁺ .

Figure 4 shows the effect of water concentration in a water/isopropanol mixture on the degree of swelling of PVA/GA/CS-Ag ⁺ films with different Ag ⁺ contents.

Figure 5 is a graph showing the permeation of a PVA/GA/CS-Ag ⁺ pervaporation film having different contents of Ag ⁺ at 30 ° C in various water/isopropanol mixtures.

Figure 6 shows the effect of Ag ⁺ content on the pervaporation efficiency of a water/isopropanol mixture at 30 ° C (90 wt% feed isopropanol concentration) through a PVA/GA/CS-Ag ⁺ pervaporation film.

Figure 7 is a graph showing the amount of PVA/GA/CS-Cu ²⁺ pervaporation film having different contents of Cu ²⁺ at 30 ° C in various water/isopropanol mixtures.

Figure 8 is a graph showing the permeation of a PVA/GA/CS-Fe ³⁺ pervaporation film having different contents of Fe ³⁺ at 30 ° C in various water/isopropanol mixtures.

Figure 9 is a graph showing the permeation of PVA/GA/CS-Ag ⁺ pervaporation films with different contents of Ag ⁺ at 30 ° C in various water/ethanol mixtures.

Figure 10 is a graph showing the permeation of PVA/GA/CS-Ag+ pervaporation films with different contents of Ag+ at 30 °C in various water/acetone mixtures.

Figure 11 shows the permeation of PVA/GA/CS-Cu ²⁺ pervaporation films with different contents of Cu ²⁺ at 30 ° C in various water/ethanol mixtures.

Figure 12 is a graph showing the amount of PVA/GA/CS-Cu ²⁺ pervaporation film having different contents of Cu ²⁺ at 30 ° C in various water/acetone mixtures.

Figure 13 is a graph showing the permeation of PVA/GA/CS-Fe ³⁺ pervaporation films with different contents of Fe ³⁺ at 30 ° C in various water/ethanol mixtures.

Figure 14 is a graph showing the permeation of PVA/GA/CS-Fe ³⁺ pervaporation films with different contents of Fe ³⁺ at 30 ° C in various water/acetone mixtures.

Figures 15a-h include (a) pure PVA, (b) PVA/CS, (c) PVA/GA/CS-Ag ⁺ (Ag: 2.4x10 ^-2 mol.), (d) PVA/GA/CS- Ag ⁺ (Ag ⁺ : 4.7x10 ^-2 mol.), (e) PVA/GA/CS-Ag+ (Ag ⁺ : 7.1x10 ^-2 mol.), (f) PVA/GA/CS-Ag ⁺ (Ag ⁺ : 9.4x10 ^-2 mol.), (g) SEM image of PVA/GA/CS-Ag ⁺ (Ag ⁺ : 1.17x10 ^-1 mol.) film and (h) EDS diagram (Ag ⁺ : 1.17x10 ^-1 mol .).

Figures 16a-e include (a) PVA/GA/CS-Cu ²⁺ (1.9x10 ^-2 mol.Cu ²⁺ ), (b) PVA/GA/CS-Cu ²⁺ (3.7x10 ^-2 mol.Cu) ²⁺ ), (c) PVA/GA/CS-Cu ²⁺ (5.6x10 ^-2 mol.Cu ²⁺ ), (d) PVA/GA/CS-Cu ²⁺ (7.5x10-2mol.Cu ²⁺ ) And (e) SEM image of PVA/GA/CS-Cu ²⁺ (9.3x10 ^-2 mol.Cu ²⁺ ) film.

Figures 17a-e include (a) PVA/GA/CS-Fe ³⁺ (1x10 ^-2 mol.Fe ³⁺ ), (b) PVA/GA/CS-Fe ³⁺ (2x10 ^-2 mol.Fe ³⁺ ), (c) PVA/GA/CS-Fe ³⁺ (3x10 ^-2 mol.Fe ³⁺ ), (d) PVA/GA/CS-Fe ³⁺ (4x10 ^-2 mol.Fe ³⁺ ) and (e SEM image of PVA/GA/CS-Fe ³⁺ (5x10 ^-2 mol.Fe ³⁺ ) film.

18a-1 to a-2 are AFM images of a pure PVA film.

19a to cc include (a-1 to a-2) CS/PVA ratio of 1/5, and (b-1 to b-2) CS/PVA ratio of 3/5, (c-1 to c-2) AFM map of different CS/PVA weight ratio films with a CS/PVA ratio of 5/5.

20a to cc include (a-1 to a-2) Ag ⁺ : 2.4 x 10 ^-2 mol., (b-1 to b-2) Ag ⁺ : 7.1 x 10 ^-2 mol, (c-1 to c- 2) Ag ⁺ : 1.17 x 10 ^-1 mol. AFM pattern of PVA/GA/CS-Ag ⁺ film with different Ag ⁺ addition amount.

21a to cc include (a-1 to a-2) Cu ²⁺ : 1.9x10 ^-2 mol. Cu ²⁺ , (b-1 to b-2) Cu ²⁺ : 5.6x10 ^-2 mol. Cu ^{2 +} , (c-1 to c-2) Cu ²⁺ : 9.3x10 ^-2 mol. AFM pattern of PVA/GA/CS-Cu2+ film with different Cu ²⁺ addition amount.

22a to cc include (a-1 to a-2) Fe ³⁺ : 1x10 ^-2 mol., (b-1 to b-2) Fe ³⁺ : 3x10 ^-2 mol., (c-1 to c) -2) Fe ³⁺ : 5 x 10 ^-2 mol. AFM pattern of PVA/GA/CS-Fe ³⁺ film with different Fe ³⁺ addition amount.

Detailed ways

The present invention will be further described in conjunction with the specific embodiments thereof, so that those skilled in the art can understand the present invention and can be practiced without departing from the scope of the invention.

The invention provides a high permeability and high selectivity pervaporation film for dehydration of an organic solution and a preparation method thereof, the method comprising:

Preparation materials: polyvinyl alcohol (PVA) (Mw ~ 125,000), chitosan (CS) (Mw ~ 30,000), 25 wt% glutaraldehyde (GA), and 99 wt% isopropanol (IPA), ethanol ( EtOH) and acetone (Acetone). All chemical reagents are reagent grade and require no further purification.

Preparation process: 5g of CS is dissolved in 45g of deionized water, stirred at room temperature for 7 to 10 hours, especially 8 hours, and then different weights of silver, copper, iron ions, that is, nitrates are added before In a solution, liquid A is formed and stirring is continued, in other words, the weight ratio of CS to deionized water of liquid A is 1:9. 5 g of PVA is dissolved in 45 g of deionized water and stirred at 70 ° C for 20 to 24 hours, preferably 24 hours, to form liquid B, in other words, the weight ratio of liquid B to PVA and deionized water is 1:9. The liquids A and B were thoroughly mixed and stirred for 2 hours to form a mixed solution C. Then, the mixed solution C was poured into a petri dish made of polyethylene, dried in an oven at a specified temperature of 40 ° C for 1 day, and glutaraldehyde was added to form PVA/GA/CS-M+ (M+ represents heavy metal ions). The pervaporation film, wherein the temperature of the oven is not too high or too low, so as not to affect the formation of the present invention.

The pervaporation film produced by the present invention measures the contact angle, the degree of swelling, the mechanical properties and the thermal stability. Further, the pervaporation film of the present invention can respectively recognize the functional groups of the present invention by Fourier transform infrared spectroscopy (FTIR) analysis, which is explained below.

Fourier transform infrared spectroscopy (FTIR): The functional groups of the pervaporation film and the identification of their interactions were expressed by FTIR spectroscopy (Perkin-Elmer spectrometer, FTS-1000). Measured in the infrared region of the wavelength region of 450-4000 cm ^-1 .

Thermogravimetric analysis (TGA, Thermogravimetric analysis): TGA test was performed using Perkin-Elmer Pyis-17GA at a scan rate of 10 ° C/min under an oxygen-filled environment at a temperature range of 25-800 ° C.

Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM & EDS): Scanning electron microscopy was used to observe the surface morphology of the film and to study the energy dispersion spectrum of the composition.

Atomic force microscopy is used to detect the roughness and microscopic surface structure of the film.

Contact angle: The surface of the sample exhibited characteristics of the chemical and physical properties of the pervaporation film by a contact angle analyzer (FTA125 contact angle analyzer). The contact angle of water is carried out by placing distilled water droplets on the surface of the pervaporation film.

Swelling degree: The obtained inventive product was cut into a 2 cm × 2 cm sample, placed in a precision balance (Ab304-S/FACT) to obtain its weight (Wd, dry film weight), and the dry film was placed in 100 g of various types. After maintaining the ratio of water/isopropanol mixture for 24 hours, the weight (Ws) of the wet film was obtained with a precision balance. The degree of swelling of the film is calculated by the following formula (1):

Pervaporation experiment: Pervaporation dehydration measurements were carried out in the apparatus as described above. The feed zone pressure was measured by a mercury pressure gauge and the pressure was maintained at a vacuum of about 2 torr using a vacuum pump, the effective area in contact with the feed mixture was about 7 cm ² , and the mixture was passed through an electronically controlled thermometer. The material temperature was maintained at 30 °C. The composition of the permeate was measured with a refractometer (RX-5000α). The pervaporation separation efficiency of the present invention was evaluated based on the amount of permeation and the separation factor (αsep).

Where W is the mass of the permeate (kg), A is the effective area of the pervaporation film (m2), t is the time of transmission (h), Pw and PIPA, PEtOH, PAcetone are permeate water and isopropyl Percentage by mass of alcohol, ethanol, acetone, and the like. Fw, FIPA, FEtOH, and FAcetone are the mass percentages of water, isopropanol, ethanol, acetone, etc. in the feed, respectively. The results obtained from the foregoing experiments can be further explained by the following analysis.

FTIR analysis: Figure 1 shows FT including PVA (a), CS (b), PVA / CS (c), PVA / CS - Ag ⁺ (d) and PVA / GA / CS - Ag ⁺ (e) pervaporation film -IR spectrum, in which a broad absorption band at 3100-3500 cm ^-1 is attributed to the stretching vibration of -OH. The peaks at 2833, 1324 and 843 cm ^-1 correspond to the stretching of CH and the bending of CH, respectively. The peak at 1086, 1415, 1719 cm ^-1 can be identified as a -CO group. In the chitosan map, the characteristic absorption band of 1570-1655 cm-1 is attributed to the amide I, II and -C=O groups. The peaks of 1077, 1320 and 1154 cm-1 represent the stretching and glycosidic groups of CON, respectively. The peak at 1719 cm ^-1 of PVA/GA/CS-Ag+ is smaller than the peak at the same position of (a), (c), and (d), which indicates that there is an interaction between GA and the film. Therefore, it was judged that the formation of an acetal (COC) bond was observed in the PVA/GA/CS-Ag+ film.

TGA analysis: thermogravimetric analysis of PVA, CS, PVA/CS, PVA/CS-Ag ⁺ and PVA/GA/CS-Ag ⁺ is shown in Figure 2. It proves that the introduction of silver ions (curve d) can greatly increase the heat resistance of the film, and the crosslinking effect (curve e) of glutaraldehyde can be used to better exert the optimum thermal stability of the film.

SEM Morphology & Elemental Analysis: Observing Figures 15a-h, Figures 16a-e and 17a-e, when a higher content of silver ions, copper ions or iron ions is added, the obtained pervaporation film has no PVA and CS mixed. The resulting agglomerate phenomenon has a coarser network structure, which indicates that the presence of CS chelated by heavy metal ions such as Ag ⁺ , Cu ²⁺ , Fe ³⁺ promotes PVA/GA/CS-M ⁺ pervaporation film The intermolecular interactions thus improve their compatibility.

AFM Atomic Force Microscopy Analysis: Looking at Figure 18 and Figures 19a-c, the surface of the pure PVA film is relatively flat. When more CS is added, a larger agglomerate is formed. 20a-c, 21a-c, and 22a-c, it can be seen that as the heavy metal ions such as Ag ⁺ , Cu ²⁺ , Fe ³⁺ increase, the agglomerates on the surface of the film become smaller and the surface roughness of the film It has also gradually increased, in line with the SEM test results.

Contact Angle Study: Water contact angles of PVA/GA/CS-Ag ⁺ pervaporation films with different levels of Ag ⁺ were measured. The observation results are shown in Fig. 3, showing that the contact angle decreases as the silver ion content increases. This silver ion has a high polarity, so in its presence, the PVA/GA/CS-Ag ⁺ pervaporation film has high hydrophilicity.

Swelling degree: In the present invention, chitosan chelated with heavy metal ions such as Ag ⁺ , Cu ²⁺ , Fe ^{3+ is} blended with PVA, and then cross-linked with glutaraldehyde to form a dehydration for organic aqueous solution. Pervaporation film. In general, crosslinkers can be used to prevent the polymer matrix from swelling due to water absorption, but this can result in a decrease in hydrophilic properties and a reduced flux of dehydration treatment. Due to the unshared electron pair of chitosan present in the amino nitrogen, it can adsorb heavy metal ions by chelation, and the polarity of the film is increased to greatly increase the water absorption of the film. Figure 4 shows the effect of water concentration in water/isopropanol mixture on the swelling degree of PVA/GA/CS-Ag ⁺ film with different contents of Ag ⁺ . The results show that PVA/GA/CS-Ag ⁺ penetration of higher silver ion content Evaporating the film and using a higher water/isopropanol ratio of the aqueous solution, the pervaporation film reflects a higher degree of expansion. The present inventors have found that the presence of CS chelated by heavy metal ions such as Ag ⁺ , Cu ²⁺ , Fe ³⁺ can promote the intermolecular interaction of PVA/GA/CS-M ⁺ pervaporation films, thereby obtaining better compatibility. The polymer matrix is capable of absorbing more water in a mixture of water/organic solvents while expanding itself without losing its network structure.

Pervaporation dehydration efficiency of PVA/GA/CS-Ag ⁺ film with different content of silver ions: water/different at 30 °C using PVA/GA/CS-Ag ⁺ film chelated with different content of silver ions Pervaporation dehydration process of propanol solution. The results show that the more the silver ions chelate, the higher the transmittance. This increase in polarity due to the addition of silver ions. Comparing Figure 4 with Figure 5, the results were found to be similar. In Figure 4, the increase in swelling is mainly due to an increase in water content; however, chelation of silver ions can also promote this effect. Similarly, more water content in the feed results in higher permeate, increased silver ion content, and a significant increase in permeate (Figure 5). We can conclude that the silver ions chelated on the CS molecule show the importance of dehydration of the isopropanol solution in the low water content feed, and the importance is also reflected in the very high water shown in Figure 6. Through concentration. No matter how many silver ions are introduced to prepare PVA/GA/CS-Ag ⁺ pervaporation film, the concentration of the permeate water can reach 99.99%, the silver ion concentration is 1.171×10 ^-1 mol., and the water permeation can reach 2kg. /m ² h.

Comparison of the present invention with known data: a PVA-based pervaporation film was used for dehydration of an isopropanol solution at 10 ° C with a 10 weight percent feed. The results are shown in Table 1. In general, when the selection ratio is increased, the amount of transmission is lowered. The invention utilizes GA as a crosslinking agent, and sequesters CS as a precursor by heavy metal ions such as Ag ⁺ , Cu ²⁺ and Fe ³⁺ , which greatly improves the selection ratio and the permeation amount. With a silver ion content of 1.17×10-1 mol. and a feed of 10% by weight of water, a high separation efficiency with a separation factor of up to 89,991 can be achieved.

Table 1: Comparison of studies on the separation efficiency of modified PVA pervaporation films reported in the known literature for the dehydration of isopropanol.

PVA, poly(vinyl alcohol); CA, citric acid; AA, amic acid; USF, urea formaldehyde/sulfuric acid; CS, chitosan; GA, glutaraldehyde; NaAlg, sodium alginate

Specifically, according to the foregoing method for preparing a pervaporation film of the present invention, silver ions may be replaced by copper ions, iron ions or other heavy metal ions, and the other methods are the same, thereby forming PVA/GA/CS-Cu ²⁺ or PVA/GA/CS-Fe ³⁺ (expressed as PVA/GA/CS-M ⁺ , where M ⁺ represents heavy metal ions) pervaporation film, the physical properties such as tensile strength are as follows:

Tensile strength: PVA/CS, PVA/CS-Ag ⁺ , PVA/GA/CS-Ag ⁺ , PVA/GA/CS-Cu ²⁺ and PVA/GA/CS-Fe ³ were evaluated according to the measure of tensile strength. ⁺ Mechanical properties of the pervaporation film, the test data of which is shown in Table 2. When chitosan is blended in PVA, the tensile strength can be almost doubled, showing that PVA has good compatibility with CS, and there is a strong interaction between them. When Ag ^{+ is} introduced into the film, the tensile strength of the film can be greatly increased. Even without the addition of a crosslinking agent, the Ag ⁺ chelated CS and PVA molecules have a non-negligible interaction force. Helps the formation of a more compatible polymer matrix. The addition of CS to chelate Ag ⁺ can greatly improve the separation efficiency of organic water-soluble nights, and can also improve the mechanical strength of the polymer matrix. This can be clarified by comparing PVA/GA/CS with PVA/GA/CS-Ag ⁺ pervaporation film, in which the introduction of silver ions can greatly increase the tensile strength by 64.7%, showing CS chelated with Ag ⁺ This has a strong interaction with the PVA, which also reflects an improvement in the heat resistance properties. In addition, it can be seen from the data in Table 2 that the addition of copper ions and iron ions also showed results and characteristics similar to the addition of silver ions.

Table 2: Tensile strength and tensile elongation of pervaporation films

In the pervaporation experiment, PVA/CS, PVA/CS-Ag ⁺ , PVA/GA/CS-Ag ⁺ , PVA/GA/CS-Cu ²⁺ and PVA/GA/CS-Fe ³⁺ films were evaluated. It can be confirmed from the experimental results of FIG. 5 to FIG. 8 that the addition of Cu ²⁺ and Fe ³⁺ can effectively promote the water permeation amount without losing the selectivity as with the addition of Ag ⁺ . Further, the pervaporation film of the present invention can be used for dehydration of an aqueous ethanol solution and an aqueous acetone solution in addition to an aqueous solution of isopropyl alcohol, which can be illustrated by the experimental results of Figs. 9 to 14. This also shows the wide application of dehydration for numerous organic solutions.

In summary, the present invention uses GA as a crosslinking agent, and silver ions, copper ions and iron ions are respectively chelated to CS as a precursor, and blended with PVA, can successfully prepare PVA/GA/CS-Ag ⁺ , Pervaporation films such as PVA/GA/CS-Cu ²⁺ and PVA/GA/CS-Fe ³⁺ . The invention is used for dehydration of organic solutions, and has good mechanical properties and heat resistance. The present invention is supplied with an organic solution at 30 ° C, and is introduced into a pervaporation film by using silver ions, copper ions, iron ions or the like, and can effectively promote the permeation rate of water without losing its selectivity. For example, the present invention has a film having an Ag ⁺ content of 1.171×10-1 mol., and it is found that at 30° C., dehydration of a high concentration isopropanol solution having a concentration of 90% by weight can be achieved up to The separation factor of 89991 and the permeation amount of up to ² kgm ² h; while the known technique uses the PVA-based pervaporation film in the same case, the results are shown in Table 1. Generally, when the permeation amount is increased, the selection is made. The sexual appearance is lowered, and thus the advantages of the present invention are known. In particular, the present invention also shows the effectiveness of dewatering of the feed at lower water levels, facilitating large scale purification applications.

The embodiments described above are merely preferred embodiments for the purpose of fully illustrating the invention, and the scope of the invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are within the scope of the present invention. The scope of the invention is defined by the claims.

Claims (9)

1. A method for preparing a highly permeable and highly selective pervaporation film for dehydration of an organic solution, comprising the steps of:

   Preparing polyvinyl alcohol, chitosan and glutaraldehyde;

   Dissolving a unit weight of the chitosan in nine unit weight of deionized water, stirring at room temperature for 7-10 hours to form a solution;

   Adding silver ions or copper ions or iron ions to the solution to form liquid A, and continuing to stir;

   Dissolving a unit weight of the polyvinyl alcohol in nine unit weight of deionized water, stirring at 70 ° C for 20 to 24 hours to form a liquid B;

   The liquid A and the liquid B are thoroughly mixed and stirred for at least 2 hours to form a mixed solution C;

   Stir at 70 ° C for at least 1 hour, place the mixed solution C in a Petri dish made of polyethylene, dry in an oven at a temperature of 25 ° C to 50 ° C for 1 day and add glutaraldehyde to form a usable organic solution. A highly selective permeation evaporation membrane for dehydration.
2. The preparation method according to claim 1, wherein the organic solution is a 99 wt% aqueous solution of isopropanol, an aqueous solution of ethanol, an aqueous solution of acetone or another aqueous solution of an organic solvent.
3. The preparation method according to claim 1, wherein the unit weight is 5 g, and the nine unit weight is 45 g.
4. The preparation method according to claim 1, wherein the chitosan is dissolved in ionized water at room temperature for 8 hours, and the PVA is dissolved in deionized water for 24 hours.
5. The preparation method according to claim 1, wherein when a relatively high concentration of silver ions or copper ions or iron ions is added, a film having a relatively uniform network structure can be obtained, which means CS chelated silver ions or Copper ions or iron ions interact with PVA to improve the compatibility of CS with PVA.
6. The preparation method according to claim 1, wherein the concentration of the glutaraldehyde is 25% by weight, and crosslinking by glutaraldehyde is added to impart optimum thermal stability to the pervaporation film.
7. The preparation method according to claim 1, wherein Ag+ or Cu2+ or Fe3+ or other heavy metal ions chelate CS to promote the intermolecular interaction of the pervaporation film, thereby obtaining a highly compatible polymer matrix, and It allows it to absorb more water in a mixture of water/organic solvent systems while swelling itself without losing its network structure.
8. A pervaporation film formed by the production method of claim 1.
9. A highly selective and highly permeable pervaporation film for dehydration of organic solvents, characterized in that it uses glutaraldehyde as a crosslinking agent for polyvinyl alcohol and chitosan, and adds silver ions or copper ions or Formed by iron ions.

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