A nano-hybrid membrane for separating volatile vapor state components and a method for preparing the same

Abstract

The application belongs to the technical field of traditional Chinese medicine volatile component separation, and specifically discloses a nano hybrid membrane for separating volatile vapor state components and a preparation method thereof. Firstly, alkyl modification is performed on graphene oxide, and the modified material is used as a filler to prepare a nano hybrid membrane. The introduction of alkyl chains increases the compatibility of the filler and PDMS, and reduces the phenomenon of interface gap on the contact surface of the filler and the polymer. Then, the alkylated graphene oxide is embedded in the polymer membrane. By changing the alkylization degree of the graphene oxide and the addition amount of the filler, the polymer chain packing state and the free volume in the membrane are regulated, so that the selectivity of the membrane material for traditional Chinese medicine volatile components is increased, the prepared nano hybrid membrane is more suitable for separating traditional Chinese medicine volatile components, and the addition of the nano filler in the application can enhance the mechanical strength of the polymer membrane and inhibit the deformation degree of the membrane.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of separation of volatile components of traditional Chinese medicine, and particularly relates to a nano-hybrid membrane for separating volatile vapor components and a preparation method thereof. BACKGROUND

[0002] The volatile components of traditional Chinese medicine refer to components with aromatic smell and easy to volatilize in traditional Chinese medicine, mainly including volatile oil components. The volatile oil has small molecular weight, strong lipid solubility, can easily pass through the biological membrane in vivo, has high bioavailability, and can be quickly absorbed to take effect. Pharmacological experiments show that the volatile oil of traditional Chinese medicine has anti-inflammatory, anti-allergic, anti-microbial, anti-mutation and anti-cancer, insect repellent effect, enzyme inhibition effect, effect on central nervous system, effect on respiratory system, and has broad application prospects. The current common methods for separating the volatile components of traditional Chinese medicine include fractional distillation, extraction, chromatography and the like. However, due to the low content of volatile components in medicinal materials, the existing separation technical means has a complicated separation process, low separation efficiency, and it is difficult to realize high-efficiency separation of volatile components, and problems such as organic solvent pollution and recovery also limit the application of these technologies in industrial production, and the separation of volatile components of traditional Chinese medicine has become one of the difficult problems to be solved.

[0003] In recent years, due to the advantages of simple operation and low energy consumption, the membrane separation technology has a very wide application in the separation of volatile components. At present, the membrane materials used for separating the volatile oil of traditional Chinese medicine mainly include ultrafiltration membrane, nanofiltration membrane; steam permeation membrane and pervaporation membrane are usually used for separating alcohol and water and other organic mixtures or concentrating and recovering representative aromatic compounds in plants. For example, Gopika recovers turmeric volatile oil from curcumin byproducts by using nanofiltration membrane, Du et al. separate and obtain perilla volatile components from perilla essential oil aqueous solution by using polyether-based amide (PEBA) and polydimethylsiloxane (PDMS) membranes through pervaporation method. In order to improve the upper limit of the separation performance of the membrane, some researchers try to prepare hybrid membranes with mixed matrix to separate organic matter, such as the patent application with publication number CN109289531A prepares a polydimethylsiloxane\mesoporous nanosilicon composite membrane for separating dyes from organic solvents, and the patent application with publication number CN109876682A proposes a preparation method of carbon nanotube hybrid pervaporation membrane for separating volatile components in tea leaves, and there is almost no report on the use of steam permeation hybrid membrane for separating volatile components of traditional Chinese medicine.

[0004] Therefore, in view of the above problems, it is urgent to develop a high-efficiency and stable steam permeation hybrid membrane for separating volatile components in the steam of traditional Chinese medicine extraction liquid, so as to realize the high-efficiency separation of water vapor and volatile components of traditional Chinese medicine on the gas level. SUMMARY

[0005] In order to solve the above problems, the application provides a nano-hybrid membrane for separating volatile vapor components, which comprises a polymer support layer and a polymer separation layer of modified inorganic nanomaterial deposited on the surface of the polymer support layer.

[0006] Further, the polymer support layer is a fluorine-containing hydrophobic porous polymer membrane.

[0007] Further, the polymer separation layer of modified inorganic nanomaterial is filled with silanized graphene oxide.

[0008] In addition, the application provides a preparation method of the nano-hybrid membrane for separating volatile vapor components, which comprises the following steps:

[0009] The graphene oxide is modified by using a silane coupling agent to obtain silanized graphene oxide.

[0010] The silanized graphene oxide is added into a mixed solution of polydimethylsiloxane and a solvent, and then a crosslinking agent and a catalyst are added after dispersion, and the polymer separation layer of modified inorganic nanomaterial is obtained after stirring, defoaming and drying.

[0011] The polymer separation layer of modified inorganic nanomaterial is deposited on the surface of the polymer support layer, and then the nano-hybrid membrane is obtained after the solvent is volatilized, dried and crosslinked and solidified.

[0012] Further, the graphene oxide has a sheet diameter of 0.5-5 microns, a thickness of 0.8-1.2 microns and an oxygen content of 30-37%.

[0013] Further, the modification of the graphene oxide by using the silane coupling agent to obtain the silanized graphene oxide comprises the following steps:

[0014] The silane coupling agent is diluted with anhydrous ethanol to obtain solution A with a volume fraction of 0.4-1.0%;

[0015] The graphene oxide is dispersed in anhydrous ethanol to obtain solution B, and the material-liquid ratio of the graphene oxide and the anhydrous ethanol is 5-10 mg: 5-10 mL;

[0016] The solution A is added dropwise into the solution B under the condition of 70-100 DEG C, and then the supernatant is removed after centrifugation for 4-6 hours of magnetic stirring, and the precipitate is washed and vacuum dried for 4-8 hours to obtain the silanized graphene oxide.

[0017] Further, the silane coupling agent comprises one or more combinations of 3-aminopropyl triethoxysilane, dodecyltrimethoxysilane and hexadecyltrimethoxysilane.

[0018] Further, the mass ratio of the silanized graphene oxide and the polydimethylsiloxane is 1-5:1000.

[0019] Further, the solvent is n-heptane; the mass ratio of the solvent and the polydimethylsiloxane is 1:9;

[0020] The mass ratio of the polydimethylsiloxane: crosslinking agent: catalyst is 10:1:0.2;

[0021] The crosslinking agent is tetraethyl orthosilicate, and the catalyst is dibutyltin dilaurate.

[0022] The nanohybrid membrane can be applied in the separation process of volatile components of traditional Chinese medicine.

[0023] The beneficial effects of the present application are:

[0024] The present application first alkylates the graphene oxide, and uses the modified material as a filler to prepare a nanohybrid membrane, the prepared nanohybrid membrane is a vapor permeation membrane, and realizes the separation process based on the principle of "adsorption-diffusion". Compared with a pure polymer membrane, the nanohybrid membrane has better separation performance. The alkylization of the oxygen-containing groups in the graphene oxide increases the hydrophobicity of the material, and reduces the adhesion of water molecules on the membrane surface in the "adsorption" process. The introduction of the alkyl chain increases the compatibility of the filler and PDMS (polydimethylsiloxane), reduces the phenomenon of interface voids on the contact surface of the filler and the polymer, and simultaneously, due to the affinity between the modified material and the to-be-separated substances, the volatile components have an advantage in the "diffusion" process.

[0025] The nanohybrid membrane prepared by the present application has good mechanical strength. In the separation process of the vapor permeation membrane, the feed liquid side of the membrane is under a larger vapor pressure, and the permeation side of the membrane is under a negative pressure. Long-time operation will cause a certain degree of deformation of the membrane, which may change or damage the original structure of PDMS, and reduce the separation effect. However, the addition of the nanofiller in the present application can enhance the mechanical strength of the polymer membrane and inhibit the degree of deformation of the membrane.

[0026] The present application embeds alkylated graphene oxide in a polymer membrane, and is suitable for the separation system of traditional Chinese medicine extract containing volatile components. By changing the degree of alkylization of the graphene oxide and the addition amount of the filler, the accumulation state of the polymer chain and the free volume in the membrane are regulated, so as to increase the selectivity of the membrane material for the volatile components of traditional Chinese medicine, and make the prepared nanohybrid membrane more suitable for separating the volatile components of traditional Chinese medicine.

[0027] Additional features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0029] Figure 1 A flow chart of a preparation method of a nano-hybrid membrane for separating volatile vapor components is shown in the present application;

[0030] Figure 2 A comparison chart of separation effects of the nano-hybrid membranes prepared in embodiments 1-3 and the commercially available hydrophobic membranes in the comparative examples is shown. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0032] The nano-hybrid membrane in the present application is a vapor permeation membrane. Different from the "mechanical screening" principle of nanofiltration membranes, the pervaporation membrane and the vapor permeation membrane realize the separation process through the "adsorption-diffusion" principle. Compared with the pervaporation membrane, the vapor permeation membrane uses steam as the feed in the separation process, and does not directly contact with the liquid, which greatly reduces the swelling and shrinkage of the vapor permeation membrane and weakens the concentration polarization phenomenon. In addition, in the volatile oil extraction process, the volatile oil is extracted from the medicinal parts in the form of condensable gas mixed with water vapor, which can be coupled with the vapor permeation membrane separation process.

[0033] Based on this, the present application prepares a nano-hybrid membrane for separating volatile vapor components in traditional Chinese medicine. The preparation method mainly includes three steps of modifying graphene oxide, preparing a polymer separation layer of modified inorganic nanomaterials and preparing a nano-hybrid membrane, as shown in Figure 1

[0034] ​Modified graphene oxide: the graphene oxide is modified by using silane coupling agent to obtain silanized graphene oxide;

[0035] Preparation of polymer separation layer of modified inorganic nanomaterial: the silanized graphene oxide is added into a mixed solution of polydimethylsiloxane and solvent, and after being uniformly dispersed, a crosslinking agent and a catalyst are added, and after stirring and defoaming, a polymer separation layer of modified inorganic nanomaterial is obtained;

[0036] Preparation of nanohybrid film: the polymer separation layer of modified inorganic nanomaterial is deposited on the surface of a polymer support layer, and after the solvent is volatilized, drying and crosslinking and curing are performed to obtain a nanohybrid film.

[0037] The specific technical solutions are as follows:

[0038] Step 1: modification of graphene oxide;

[0039] The silane coupling agent 20-30 μL is diluted with anhydrous ethanol, and is ready for use; the silane coupling agent is one or a combination of 3-aminopropyl triethoxysilane, dodecyltrimethoxysilane and hexadecyltrimethoxysilane, and the volume fraction of the diluted silane coupling agent is 0.4-1.0%.

[0040] 5-10 mg of graphene oxide is added into 5-10 mL of anhydrous ethanol, and is ultrasonically dispersed for 30 min; the graphene oxide has a sheet diameter of 0.5-5 μm, a thickness of 0.8-1.2 μm, and an oxygen content of about 30-37%.

[0041] The diluted silane coupling agent is added dropwise under the condition of 70-100°C, and after magnetic stirring for 4-6 h, centrifugation is performed, the supernatant is removed, the precipitate is washed with anhydrous ethanol for three times, and is dried in a vacuum drying oven at 55°C for 4-8 h to obtain silanized graphene oxide. The centrifuge speed is 5000-10000 r / min, and the single centrifugation time is 3 min.

[0042] Step 2: preparation of polymer separation layer of modified inorganic nanomaterial;

[0043] The silanized graphene oxide is added into a mixed solution of polydimethylsiloxane and solvent, and is ultrasonically dispersed, and a crosslinking agent and a catalyst are added, and after stirring and defoaming, a casting solution (i.e. the polymer separation layer of modified inorganic nanomaterial) is obtained; the mass ratio of the silanized graphene oxide and the polydimethylsiloxane is 1-5:1000.

[0044] The solvent includes n-heptane.

[0045] The crosslinking agent is tetraethyl orthosilicate.

[0046] The catalyst is dibutyltin dilaurate.

[0047] The mass ratio of the polydimethylsiloxane:crosslinking agent: catalyst is = 10:1:0.2.

[0048] Step 3: Preparation of a nano-hybrid membrane:

[0049] The obtained casting solution is uniformly deposited on the surface of a fluorine-containing hydrophobic porous polymer film (polymer support layer), and after the solvent is volatilized, the membrane is placed in a vacuum drying oven, and after crosslinking and curing, a nano-hybrid membrane is obtained.

[0050] The preferred technical solution is: 3-aminopropyl triethoxysilane is selected as the silane coupling agent, the volume fraction of the diluted silane silane coupling agent is 0.5%, the reaction conditions are stirring at 80°C for 4h and drying in a vacuum drying oven at 55°C for 6h, the kinematic viscosity of the polydimethylsiloxane is 40cSt, and the modified graphene oxide:polydimethylsiloxane is 1-5:1000.

[0051] The above method is described in detail in combination with the following examples.

[0052] Example 1

[0053] The embodiment provides a preparation method of a nano-hybrid membrane for separating volatile vapor components, including the following steps:

[0054] Take 20μL of 3-aminopropyl triethoxysilane and dilute it with anhydrous ethanol, and the volume fraction after dilution is 0.5%. Take 5.0mg of graphene oxide and put it into 10.0mL of anhydrous ethanol, and ultrasonically disperse it for 30min. Under the condition of 80°C, add the 3-aminopropyl triethoxysilane diluted with anhydrous ethanol drop by drop, magnetically stir for 4h, centrifuge, remove the supernatant, wash the precipitate with anhydrous ethanol three times, and put it into a vacuum drying oven at 55°C for 6h to obtain silanized graphene oxide.

[0055] Put 1g of hydroxyl-terminated polydimethylsiloxane with a kinematic viscosity of 40cSt into an appropriate amount of n-heptane, and magnetically stir at room temperature for 2h to uniformly dissolve it. The mass ratio of polydimethylsiloxane to n-heptane is 1:9.

[0056] Precisely take 1.50mg of modified graphene oxide and add it to the polydimethylsiloxane solution (silanized graphene oxide:polydimethylsiloxane=1.5:1000), ultrasonically disperse it, and then add crosslinking agent tetraethyl orthosilicate and catalyst dibutyltin dilaurate according to a certain mass ratio (polydimethylsiloxane:crosslinking agent: catalyst=10:1:0.2), ultrasonically stir at room temperature for 2h, and degas to obtain a casting solution (i.e. a polymer separation layer of modified inorganic nanomaterials).

[0057] The obtained casting solution was uniformly deposited on the surface of a fluorinated hydrophobic porous polymer membrane (in this embodiment, a PTFE membrane with a pore size of 0.2 micrometers from Shanghai Funai Technology Co., Ltd. was selected). After being placed at room temperature for 12 hours and the solvent was allowed to evaporate, the membrane was placed in a vacuum drying oven and crosslinked and cured at 80°C for 5 hours to obtain a nano-hybrid membrane loaded with 1.50 mg of modified nanomaterials.

[0058] Example 2

[0059] Unlike Example 1, the ratio of silanized graphene oxide to polydimethylsiloxane was 3.0:1000, and all other conditions remained unchanged to obtain a nano-hybrid film loaded with 3.0 mg of modified nanomaterials.

[0060] Example 3

[0061] Unlike Example 1, the ratio of silanized graphene oxide to polydimethylsiloxane was 4.5:1000, and the other conditions remained unchanged to obtain a nano-hybrid film loaded with 4.5 mg of modified nanomaterials.

[0062] Comparative analysis of commercially available PTFE hydrophobic membranes

[0063] The nano-hybrid membranes in Examples 1-3 and commercially available PTFE hydrophobic membrane materials were fixed with membrane modules. Under the same temperature conditions, the extract containing volatile gaseous components was vaporized and passed through the membrane. The permeate was collected by a collection device and the separation factor was calculated using the following formula.

[0064] α=(Y i ×X W ) / (Y W ×X i )

[0065] Where α is the separation factor, Y i Y w These represent the mass percentages of volatile oil and water in the collected permeate, respectively; X i X w These represent the mass percentages of volatile oil and water in the raw material liquid, respectively.

[0066] Test results show that the hybrid membrane with modified nanomaterials has a significantly improved separation effect compared with commercially available PTFE hydrophobic membranes, specifically as follows: Figure 2 As shown in the figure. Simultaneously, observations during the experiment revealed that when the PTFE hydrophobic membrane was subjected to prolonged conditions of 80–100°C, a certain degree of membrane deformation occurred. The nano-hybrid membrane prepared by this invention exhibited significantly improved deformation under the same conditions, indicating that the mechanical strength of the nano-hybrid membrane prepared by the method of this invention is greatly enhanced.

[0067] Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood that modifications can be made to the foregoing embodiments, or additional implementations can be implemented, without departing from the spirit and scope of the inventive subject matter. Accordingly, the present application is not limited to the implementations described herein, but is intended to be defined by the claims set forth below, and equivalents thereof.

Claims

1. A nano-hybrid membrane for separating volatile gaseous components, characterized in that, The nanohybrid membrane comprises a polymer support layer and a polymer separation layer of modified inorganic nanomaterials deposited on the surface of the polymer support layer; wherein, the polymer separation layer of modified inorganic nanomaterials uses silanized graphene oxide as a filler, and the polymer separation layer of modified inorganic nanomaterials is prepared according to the following steps: Silanized graphene oxide is added to a mixed solution of polydimethylsiloxane and solvent, dispersed, and then a crosslinking agent and catalyst are added. After stirring and degassing, a polymer separation layer of modified inorganic nanomaterial is obtained; the mass ratio of silanized graphene oxide to polydimethylsiloxane is 1~5:1000.

2. The nano-hybrid membrane for separating volatile gaseous components according to claim 1, characterized in that, The polymer support layer is a fluorinated hydrophobic porous polymer membrane.

3. A method for preparing a nano-hybrid membrane for separating volatile gaseous components, characterized in that, Includes the following steps: Silane coupling agents were used to modify graphene oxide to obtain silanized graphene oxide. Silanized graphene oxide was added to a mixed solution of polydimethylsiloxane and solvent, dispersed, and then a crosslinking agent and catalyst were added. After stirring and degassing, a polymer separation layer of modified inorganic nanomaterials was obtained; the mass ratio of silanized graphene oxide to polydimethylsiloxane was 1~5:1000. The polymer separation layer of the modified inorganic nanomaterial is deposited on the surface of the polymer support layer. After the solvent evaporates, the mixture is dried, crosslinked, and cured to obtain a nano-hybrid film.

4. The method for preparing a nano-hybrid membrane for separating volatile gaseous components according to claim 3, characterized in that, The graphene oxide has a sheet diameter of 0.5~5μm, a thickness of 0.8~1.2μm, and an oxygen content of 30~37%.

5. The method for preparing a nano-hybrid membrane for separating volatile gaseous components according to claim 3, characterized in that, Modifying graphene oxide using a silane coupling agent to obtain silanized graphene oxide includes the following steps: Dilute the silane coupling agent with anhydrous ethanol to a volume fraction of 0.4-1.0% in solution A; Solution B is obtained by dispersing graphene oxide in anhydrous ethanol, wherein the ratio of graphene oxide to anhydrous ethanol is 5~10 mg: 5~10 mL. Under conditions of 70 ~ 100℃, solution A is added dropwise to solution B, and after magnetic stirring for 4 ~ 6 h, the supernatant is removed by centrifugation, the precipitate is washed and vacuum dried for 4 ~ 8 h to obtain silanized graphene oxide.

6. The method for preparing a nano-hybrid membrane for separating volatile gaseous components according to claim 3, characterized in that, The silane coupling agent includes one or more combinations of 3-aminopropyltriethoxysilane, dodecyltrimethoxysilane, and hexadecyltrimethoxysilane.

7. The method for preparing a nano-hybrid membrane for separating volatile gaseous components according to claim 3, characterized in that, The solvent is n-heptane; the mass ratio of the solvent to polydimethylsiloxane is 1:

9. The mass ratio of polydimethylsiloxane:crosslinking agent:catalyst is 10:1:0.2; The crosslinking agent is tetraethyl orthosilicate, and the catalyst is dibutyltin dilaurate.

8. The application of a nano-hybrid membrane for separating volatile gaseous components in the separation process of volatile components in traditional Chinese medicine, characterized in that, The nanohybrid membrane is prepared according to the method described in claim 1 or 2 or according to any one of claims 3-7.

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