A vs4 molecular sieve membrane, a solvothermal preparation method thereof and application of the molecular sieve membrane in organic dye interception

Abstract

The application provides a VS4 molecular sieve membrane, a solvothermal preparation method thereof and application of the VS4 molecular sieve membrane in organic dye interception, and the polycrystalline VS4 film layer has adjustable micro-morphology and good intergrowth. The preparation method comprises the following steps: sequentially loading a porous carrier and a precursor solution with a pH value of 8-11 into a reaction kettle to perform solvothermal reaction; after the reaction is completed, the temperature of the reaction liquid is cooled to room temperature, and the VS4 molecular sieve membrane is obtained through washing and drying. By adjusting the acid-base degree of the precursor solution and optimizing the solvothermal parameters to control the nucleation and growth kinetics of the VS4 crystal grains, the raw material supply at the interface between the reaction liquid and the carrier is ensured, the prepared VS4 molecular sieve membrane has good intergrowth, compactness and uniformity, exhibits excellent dye interception performance on organic dye molecules, and has good pressure resistance and long-term operation stability. In summary, the application develops the VS4 molecular sieve membrane and a solvothermal preparation process of the VS4 molecular sieve membrane, and provides a corresponding solution for the treatment of textile dye wastewater.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane separation, and particularly relates to a VS4 molecular sieve membrane, a solvothermal preparation method thereof, and application of the VS4 molecular sieve membrane in organic dye interception. BACKGROUND

[0002] The rapid development of urbanization and heavy industry has exacerbated global environmental pollution, seriously threatening public health and ecological safety. According to data from the World Health Organization, global water pollution continues to worsen and is considered a major cause of global disease and even death. In recent years, water pollution caused by organic dyes in the textile industry has attracted widespread attention. Dye wastewater not only has a complex composition, containing a large amount of toxic azo dyes and pigments, but also has a high colority and is difficult to degrade. However, traditional wastewater treatment technologies (such as solvent extraction, chemical oxidation, coagulation, adsorption, etc.) have disadvantages such as high energy consumption, low separation efficiency, and easy secondary pollution. Therefore, it is of great significance to develop a high-efficiency, clean, environmentally friendly, and sustainable dye wastewater treatment strategy for public health and water resource recovery. Membrane is a semi-permeable barrier that can realize the selective separation of chemical mixtures driven by concentration, temperature, pressure, or electric potential gradient. Compared with traditional separation technologies such as rectification, evaporation, and adsorption, membrane separation technology has the advantages of low energy consumption, high efficiency, small footprint, easy operation, and environmental friendliness, and has broad application prospects in the field of dye wastewater treatment.

[0003] Developing low-cost, high-performance, and reproducible membrane materials is the core and foundation of constructing high-performance polycrystalline molecular sieve membranes. Transition metal chalcogenides (TMCs) have the advantages of diverse material types, abundant resources, low cost, excellent mechanical properties, and electrical characteristics, and have broad application prospects in energy storage elements, semiconductor devices, optoelectronics, catalysis, and separation. However, among the TMCs material family, only layered transition metal dichalcogenides (TMDCs) have shown promise in molecular sieve membranes, but are limited by complex and poorly scalable preparation methods. Unlike layered TMDCs, VS4 has a unique one-dimensional chain structure, with van der Waals forces between parallel quasi-one-dimensional chains, and a chain spacing VS4 not only has the advantages of low price, environmental friendliness, and abundant resources, but also has a unique one-dimensional chain structure and excellent electrochemical properties, which lay the foundation for VS4 materials in the fields of electrochemistry and catalysis. However, there is currently no report on membrane separation. SUMMARY

[0004] VS4 has an open one-dimensional framework structure and a free interchain spacing comparable to the kinetic diameter of water molecules Good hydrophilic and other features are expected as a building block of molecular sieve membrane, realizing the mass transfer and transport of water molecules and effective interception of dye molecules, so as to be applied to the nanofiltration field such as dye separation. The application utilizes the solvothermal technology to prepare the VS4 molecular sieve membrane and applies it to the field of dye wastewater separation. By adjusting the pH of the precursor solution and optimizing the solvothermal parameters, the nucleation and growth process of VS4 grains on the surface of the porous carrier is controlled, the raw material supply at the interface between the reaction solution and the carrier is ensured, the heterogeneous nucleation density of VS4 on the surface of the carrier is improved, and the continuous and dense VS4 molecular sieve membrane is prepared on the commercialized porous carrier. The VS4 molecular sieve membrane prepared by the technology exhibits excellent dye interception performance for organic dye molecules (such as Congo red, methyl blue and methylene blue), and also has good pressure resistance and long-term operation stability, which provides a new solution for the removal of organic dyes in textile industry wastewater.

[0005] The technical scheme of the application is:

[0006] A VS4 molecular sieve membrane, comprising a polycrystalline VS4 membrane layer and a porous support carrier, wherein the polycrystalline VS4 membrane layer has adjustable micro-morphology and good intergrowth.

[0007] The thickness of the polycrystalline VS4 membrane layer is 500 nm-5 μm.

[0008] The XRD characteristic peaks of the polycrystalline VS4 membrane layer are pure phase VS4.

[0009] The application further provides a solvothermal preparation method of the VS4 molecular sieve membrane, comprising the following steps:

[0010] (1) fixing the porous carrier and placing it in a reaction kettle;

[0011] (2) mixing vanadium source solution and sulfur source solution uniformly to obtain a precursor solution; the solvents of the vanadium source solution and the sulfur source solution are organic solvents or mixed solvents of organic solvents / water, wherein the organic solvents are at least one of methanol, ethanol, propanol, N,N-dimethylformamide and ethylene glycol;

[0012] (3) adjusting the pH of the precursor solution to 8-11;

[0013] (4) loading the precursor solution into the above reaction kettle for solvothermal reaction;

[0014] (5) after the reaction is completed, cooling the reaction kettle to room temperature, and then washing and drying to obtain a continuous and dense VS4 molecular sieve membrane.

[0015] Preferably, the porous support in step (1) is selected from the group consisting of porous metal, porous carbide, porous metal oxide or porous non-metal oxide; and the structure is selected from the group consisting of flat plate structure, tubular structure, rolled structure or hollow fiber structure. Further, the porous support is porous metal oxide (e.g. porous alumina, porous zirconia and porous titania), and the structure is flat plate structure or tubular structure. Further, the porous support is porous alumina plate, hollow alumina tube and hollow fiber.

[0016] Preferably, the vanadium source in step (2) is at least one selected from the group consisting of ammonium metavanadate, sodium vanadate, vanadyl acetylacetonate and ammonium vanadyl bronze; and the sulfur source is at least one selected from the group consisting of thioacetamide and thiourea. Further, the vanadium source is ammonium metavanadate, and the sulfur source is thioacetamide, and the solvent is a binary solvent of ethylene glycol and water.

[0017] Preferably, the concentration of the vanadium source in the precursor solution in step (2) is 1-100 mM; the molar ratio of the sulfur source to the vanadium source is 5-100; and the volume ratio of the organic solvent to water in the solvent is greater than or equal to 0.2. Further, the concentration of the vanadium source is 2-10 mM, the molar ratio of the sulfur source to the vanadium source is 5-50; and the volume ratio of the organic solvent to water in the solvent is 0.5-1.

[0018] Preferably, the pH of the precursor solution in step (3) is adjusted by a NaOH solution with a mass fraction of 1-20%.

[0019] Preferably, the temperature of the solvothermal reaction in step (4) is 80-180℃.

[0020] Preferably, the single reaction period of the solvothermal reaction in step (4) is 2-48 h; and the solvothermal reaction time is 12-36 h.

[0021] The present application also provides the use of the VS4 molecular sieve membrane in organic dye rejection.

[0022] The dye rejection performance of the VS4 molecular sieve membrane is tested by using a dead-end or cross-flow dye rejection device under a test driving pressure of 1-50 bar. The prepared VS4 molecular sieve membrane shows excellent rejection rate (>90.0%) for Congo red, methylene blue and methyl blue dyes, and the water permeation flux is up to 72.18 L -1 m -2 h -1 bar -1 .

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The solvent-thermal method has the advantages of simple operation, short reaction period, high product purity, etc. Meanwhile, the pH value of the precursor solution and the solvent-thermal parameters can be optimized to precisely control the nucleation and growth of VS4, effectively increase the heterogeneous nucleation rate of VS4 on the carrier surface and ensure sufficient supply of raw materials at the carrier interface, thereby realizing good connection of the VS4 membrane layer and constructing a high-performance VS4 molecular sieve membrane. Therefore, the VS4 molecular sieve membrane prepared by the method has the following characteristics: ① The open framework channel and the free interchain distance equivalent to the kinetic diameter of water molecules can realize the mass transfer and transport of water molecules and the effective interception of dye molecules; ② The dye interception performance remains stable under different operating pressures (1-50 bar); ③ The dye separation performance is excellent, and the Congo red dye interception rate of the plate-type supported membrane is up to ~ 99.58%, the dye interception rate of the tubular supported membrane is greater than 90%, and the water flux is up to 72.18 L -1 m -2 h -1 bar -1 . BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 SEM image of the porous alumina sheet carrier in Example 1;

[0026] Figure 2 SEM image of the hollow alumina tube carrier in Example 2;

[0027] Figure 3 XRD pattern of the VS4 molecular sieve membrane prepared in Example 3;

[0028] Figure 4 SEM image of the VS4 molecular sieve membrane prepared in Example 3;

[0029] Figure 5 XRD pattern of the VS4 molecular sieve membrane prepared in Example 4;

[0030] Figure 6 SEM image of the VS4 molecular sieve membrane prepared in Example 4;

[0031] Figure 7 XRD pattern of the VS4 molecular sieve membrane prepared in Example 5;

[0032] Figure 8 SEM image of the VS4 molecular sieve membrane prepared in Example 5;

[0033] Figure 9 EDXS image of the VS4 molecular sieve membrane prepared in Example 5;

[0034] Figure 10 XRD pattern of the VS4 molecular sieve membrane prepared in Example 6;

[0035] Figure 11 SEM image of VS4 molecular sieve membrane prepared in Example 6;

[0036] Figure 12 XRD pattern of VS4 molecular sieve membrane prepared in Example 7;

[0037] Figure 13 SEM image of VS4 molecular sieve membrane prepared in Example 7;

[0038] Figure 14 Dead-end dye rejection performance plot of VS4 molecular sieve membrane prepared in Example 5;

[0039] Figure 15 Dead-end dye rejection long-term stability test of VS4 molecular sieve membrane prepared in Example 5;

[0040] Figure 16 Cross-flow dye rejection performance test of VS4 molecular sieve membrane prepared in Example 7;

[0041] Figure 17 Cross-flow dye rejection performance plot of VS4 molecular sieve membrane prepared in Example 7;

[0042] Figure 18 Cross-flow dye rejection long-term stability test of VS4 molecular sieve membrane prepared in Example 7;

[0043] Figure 19 XRD pattern of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 1;

[0044] Figure 20 SEM image of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 1;

[0045] Figure 21 SEM image of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 2;

[0046] Figure 22 XRD pattern of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 3;

[0047] Figure 23 SEM image of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 3;

[0048] Figure 24 XRD pattern of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 4;

[0049] Figure 25 SEM image of VS4 molecular sieve membrane prepared by solvothermal in Comparative Example 4. DETAILED DESCRIPTION

[0050] The application will be further described in detail below with reference to specific examples. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the application. These are all within the scope of protection of the application.

[0051] Example 1: Porous alumina sheet carrier

[0052] After fixing the porous alumina sheet carrier, it was placed in a reaction kettle, and SEM Figure 1 ) is the surface graph of the porous alumina sheet carrier.

[0053] Example 2: Hollow alumina tube carrier

[0054] After fixing the porous alumina tube carrier, it was placed in a reaction kettle, and SEM Figure 2 ) is the surface and cross-sectional graph of the hollow alumina tube carrier.

[0055] Example 3: Solvothermal preparation of VS4 molecular sieve membrane

[0056] (1) 0.312 g of ammonium metavanadate was added to 20 mL of deionized water, and heated and stirred under the condition of 60°C water bath until a clear light yellow solution was obtained; 1.001 g of thioacetamide was dissolved in 20 mL of ethylene glycol under ultrasonic action. Then the above metal source solution and sulfur source solution were mixed and stirred at room temperature to obtain a precursor solution.

[0057] (2) The pH of the above precursor solution was adjusted to 8 using a 15% mass fraction sodium hydroxide solution.

[0058] (3) The porous alumina sheet in Example 1 was fixed vertically in a reaction kettle containing the precursor solution, and then it was placed in a preheated to 160°C constant temperature air drying oven for 24 h.

[0059] (4) After the reaction was completed, the carrier was taken out and washed with a large amount of deionized water and ethanol, and then placed in a 70°C oven for drying.

[0060] XRD Figure 3 ) spectrum showed the characteristic diffraction peaks of VS4, confirming that VS4 was generated on the porous alumina sheet carrier. Combined with SEM Figure 4 ), it was further proved that under this condition, VS4 membrane with thickness of about 1.0 μm, good intergranular connectivity and dense and continuous membrane layer could be generated.

[0061] Example 4: Solvothermal preparation of VS4 molecular sieve membrane

[0062] The specific implementation steps are the same as those in Example 3, except that the pH of the precursor solution in step (2) is adjusted to 9.

[0063] XRD( Figure 5 ) spectrum shows characteristic diffraction peaks of VS4, confirming the formation of VS4 on the porous alumina sheet carrier. SEM( Figure 6 ) further proves that under this condition, VS4 film with a thickness of ~ 1.6 μm, good intergranular connectivity and continuous and dense membrane layer can be generated.

[0064] Example 5: Preparation of VS4 molecular sieve membrane by solvothermal method

[0065] The specific implementation steps are the same as those in Example 3, except that the pH of the precursor solution in step (2) is adjusted to 10.

[0066] XRD( Figure 7 ) spectrum shows characteristic diffraction peaks of VS4, indicating the formation of VS4 on the surface of the porous alumina sheet carrier. SEM( Figure 8 ) shows that under this condition, VS4 molecular sieve membrane with a thickness of ~ 2.5 μm, good intergranular connectivity and continuous and dense membrane layer is generated. EDXS( Figure 9 ) spectrum shows that there is a clear boundary between the VS4 membrane layer and the porous alumina carrier, indicating that the prepared VS4 membrane has not significantly penetrated into the pores of the porous alumina carrier.

[0067] Example 6: Preparation of VS4 molecular sieve membrane by solvothermal method

[0068] The specific implementation steps are the same as those in Example 3, except that the pH of the precursor solution in step (2) is adjusted to 11.

[0069] XRD( Figure 10 ) spectrum shows characteristic diffraction peaks of VS4, indicating the formation of VS4 on the surface of the porous alumina sheet carrier. SEM( Figure 11 ) shows that under this condition, VS4 molecular sieve membrane with a thickness of ~ 2.8 μm, good intergranular connectivity and dense membrane layer is generated.

[0070] Example 7: Preparation of VS4 molecular sieve membrane by solvothermal method

[0071] The specific implementation steps are the same as those in Example 5, except that in step (3), the carrier is replaced with the hollow alumina tube carrier in Example 2, and Teflon plugs and tapes are used to seal both ends of the carrier.

[0072] XRD( Figure 12 ) spectrum shows characteristic diffraction peaks of VS4, confirming the formation of VS4 on the surface of the hollow alumina tube carrier. SEM( Figure 13) shows that under this condition, VS4 molecular sieve membrane with thickness of ~2.5 μm, good intercrystalline connection and continuous and dense membrane layer is generated.

[0073] Example 8: Test of dye rejection performance of VS4 molecular sieve membrane

[0074] Dead-end dye rejection test is performed on the VS4 molecular sieve membranes prepared in Examples 3-6, and the test conditions are as follows: room temperature, transmembrane pressure difference of 3 bar, and Congo red dye concentration of 0.1 g / L. The dye rejection performance of the corresponding VS4 membranes to Congo red is shown in Table 1. The rejection rate of the VS4 membrane prepared in Example 3 to Congo red is 98.45%, and the water permeation flux is 10.67 Lm -2 h -1 bar -1 ; the rejection rate of the VS4 membrane prepared in Example 4 to Congo red is 99.28%, and the water permeation flux is 9.63 Lm -2 h -1 bar -1 ; the rejection rate of the VS4 membrane prepared in Example 5 to Congo red is 99.46%, and the water permeation flux is 9.97 Lm -2 h -1 bar -1 ; the rejection rate of the VS4 membrane prepared in Example 6 to Congo red is 99.58%, and the water permeation flux is 9.42 Lm -2 h -1 bar -1 . The above results show that the VS4 membranes prepared under the above pH conditions have good interconnection and density.

[0075] Table 1: Dye separation performance of VS4 membrane to Congo red

[0076]

[0077] Example 9: Test of dye rejection pressure change performance of VS4 molecular sieve membrane

[0078] Taking Congo red as an example, dead-end dye rejection pressure change performance test is performed on the VS4 molecular sieve membrane prepared in Example 5. The test conditions are as follows: room temperature, transmembrane pressure difference of 1-6 bar, and Congo red concentration of 0.1 g / L. When the operating pressure is increased to 6 bar( Figure 14 ), the water permeation flux of the membrane (~14.92 L -1 m -2 h -1 bar -1 ) and the Congo red rejection rate (~99.42%) do not show significant fluctuations, indicating that the membrane has good skeleton rigidity and pressure resistance.

[0079] Example 10: Test of long-term stability of dye rejection performance of VS4 molecular sieve membrane

[0080] The VS4 zeolite membrane prepared in Example 5 was tested for long-term stability of dead-end dye rejection using Congo red dye as an example. The test conditions were as follows: room temperature, transmembrane pressure difference of 6 bar, and Congo red dye concentration of 0.1 g / L. After 84 h of continuous testing, the water permeation flux of the membrane (~15.11 L -1 m -2 h -1 bar -1 ) and the Congo red dye rejection rate (~99.36%) did not decrease significantly Figure 15 ), indicating that the membrane has good long-term operation stability.

[0081] Example 11: Dye rejection performance test of VS4 zeolite membrane

[0082] The VS4 zeolite membrane prepared in Example 7 was tested for cross-flow dye rejection performance, and the test conditions were as follows: room temperature, transmembrane pressure difference of 1.0 bar, and dye concentration of 0.1 g / L. The tubular support membrane had a dye rejection rate of more than 95% for three kinds of dye molecules (CR, MEB, and MB), and had good dye rejection performance; the Congo red rejection rate reached 97.45%, and the water permeation flux was 31.96 L -2 m -1 h -1 bar Figure 16 .

[0083] Example 12: Dye rejection pressure change performance test of VS4 zeolite membrane

[0084] The VS4 zeolite membrane prepared in Example 7 was tested for cross-flow dye rejection pressure change performance using Congo red dye as an example, and the test conditions were as follows: room temperature, transmembrane pressure difference of 1-5 bar, and Congo red dye concentration of 0.1 g / L. When the driving pressure increased from 1 bar to 5 bar, the water permeation flux of the membrane increased to 72.18 L -1 m -2 h -1 bar -1 , and the Congo red dye rejection rate was 97.37% Figure 17 .

[0085] Example 13: Long-term stability test of dye rejection of VS4 zeolite membrane

[0086] The VS4 zeolite membrane prepared in Example 7 was tested for long-term stability of cross-flow dye rejection using Congo red dye as an example, and the test conditions were as follows: room temperature, transmembrane pressure difference of 1.0 bar, and Congo red dye concentration of 0.1 g / L. After 50 h of continuous testing, the membrane had stable water permeation flux and dye rejection rate Figure 18 .

[0087] Comparative Example 1: Solvothermal preparation of VS4 molecular sieve membrane

[0088] The specific implementation steps are the same as those of Example 3, except for the configuration and treatment of the precursor solution: 0.312 g of ammonium metavanadate and 1.001 g of thioacetamide were dissolved in 40 mL of N-methylpyrrolidone to obtain a precursor solution, and there was no pH adjustment step for the precursor solution.

[0089] XRD( Figure 19 ) spectrum showed characteristic diffraction peaks of VS4, indicating that VS4 was generated on the surface of the porous alumina sheet carrier. SEM( Figure 20 ) showed that VS4 was sparsely accumulated on the surface of the carrier in the form of particles with a size of ~ 270 nm, with a thickness of ~ 1 μm and poor cross-sectional connectivity. The results showed that it was difficult to prepare a dense VS4 molecular sieve membrane in N-methylpyrrolidone using the above precursor.

[0090] Comparative Example 2: Solvothermal preparation of VS4 molecular sieve membrane

[0091] The specific implementation steps are the same as those of Example 3, except for the following: no pH adjustment of the precursor solution in step (2), the reaction temperature range (140-180°C) and the reaction time range (12-36 h) in step (3).

[0092] SEM( Figure 21 ) showed that a large number of pinhole defects and bare porous alumina carriers were visible in the ethylene glycol-water solvent system. The above results showed that it was difficult to prepare a VS4 molecular sieve membrane with good connectivity in the ethylene glycol-water solvent system by only adjusting the reaction temperature and reaction time.

[0093] Comparative Example 3: Solvothermal preparation of VS4 molecular sieve membrane

[0094] The specific implementation steps are the same as those of Example 3, except that the precursor solution in step (2) is adjusted to be acidic (pH = 3-5) with a 15% mass fraction of hydrochloric acid solution.

[0095] XRD( Figure 22 ) spectrum showed characteristic diffraction peaks of VS4, indicating that VS4 was generated on the surface of the porous alumina carrier. SEM( Figure 23 ) showed that VS4 microspheres with a size of ~ 1 μm were sparsely dispersed on the surface of the porous α-Al2O3 carrier, and a large number of bare carrier surfaces were visible; the membrane thickness was about 600 nm, and the cross-sectional connectivity was poor. In an acidic environment, thioacetamide rapidly decomposes into hydrogen sulfide and accelerates escape, leading to explosive excess nucleation of VS4 in the bulk solution, which is not conducive to the heterogeneous nucleation of VS4 on the carrier surface.

[0096] Comparative Example 4: Solvothermal preparation of VS4 molecular sieve membrane

[0097] The procedure was the same as Example 3 except that the precursor solution was adjusted to pH = 12 in step (2).

[0098] XRD Figure 24 pattern showed the characteristic diffraction peaks of VS2, indicating the formation of VS2 on the surface of the porous alumina support. SEM Figure 25 showed that a large number of layered VS2 micrometer flowers were deposited on the surface of the film layer, and the film thickness was about 3.5 μm. The above results showed that the product prepared by the solvothermal method was two-dimensional layered VS2 when the alkalinity of the precursor solution was too strong.

Claims

1. A solvothermal preparation method for VS4 molecular sieve membranes, characterized in that: The VS4 molecular sieve membrane comprises a polycrystalline VS4 membrane layer and a porous support, wherein the polycrystalline VS4 membrane layer has a controllable microstructure and good intergrowth properties. The preparation method includes the following steps: (1) After fixing the porous carrier, place it in the reaction vessel; (2) Mix the vanadium source solution and the sulfur source solution evenly to obtain the precursor solution; the solvents of the vanadium source solution and the sulfur source solution are organic solvents or a mixture of organic solvent and water, wherein the organic solvent is ethylene glycol; (3) Adjust the pH of the precursor solution to 8-11; (4) The precursor solution is loaded into the above-mentioned reaction vessel for solvothermal reaction; (5) After the reaction is completed, the reaction vessel is cooled to room temperature, and after washing and drying, a continuous and dense VS4 molecular sieve membrane is obtained. The porous support mentioned in step (1) includes porous metals, porous carbides, porous metal oxides or porous non-metal oxides. Its structure includes flat plate structure, tubular structure, spiral structure or hollow fiber structure; The concentration of the vanadium source in the precursor solution described in step (2) is 1-100 mM; the molar ratio of the sulfur source to the vanadium source is 5-100; and the volume ratio of the organic solvent to water in the solvent is greater than or equal to 0.

2. In step (4), the solvothermal reaction temperature is 80-180 ℃; the reaction time of the solvothermal reaction is 2-48 h.

2. The solvothermal preparation method of VS4 molecular sieve membrane as described in claim 1, characterized in that: The thickness of the polycrystalline VS4 film is 500 nm-5 μm.

3. The solvothermal preparation method of a VS4 molecular sieve membrane according to claim 1, characterized in that: In step (2), the vanadium source solution contains at least one of ammonium metavanadate, sodium vanadate, acetylacetone vanadium oxide, and ammonium vanadium bronze; the sulfur source solution contains at least one of thioacetamide and thiourea.

4. The solvothermal preparation method of a VS4 molecular sieve membrane according to claim 1, characterized in that: The pH of the precursor solution in step (3) is adjusted by using a NaOH solution with a mass fraction of 1-20%.

5. The application of a VS4 molecular sieve membrane obtained by the method according to claim 1 in the retention of organic dyes.

6. The application of the VS4 molecular sieve membrane according to claim 5 in the retention of organic dyes, characterized in that: The test drive pressure was 1-50 bar, and the dye retention performance of the VS4 molecular sieve membrane was tested using a dead-end or cross-flow dye retention device.

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