A method for preparing a mixed matrix pervaporation membrane

Abstract

The application discloses a preparation method of a mixed matrix pervaporation membrane. The membrane is composed of HSO3-UiO-66@HNTs, polyvinyl alcohol (PVA) and sulfosuccinic acid (SSA). In the preparation, PVP and HNTs are dispersed and dried in water to obtain PVP-HNTs; ZrCl4, BDC-SO3Na, PVP-HNTs and acetic acid are ultrasonically treated in DMF, and HSO3-UiO-66@HNTs fillers are prepared through hydrothermal reaction, washing and drying. Subsequently, PVA aqueous solution and an ethanol dispersion solution of the fillers are mixed, and SSA is added and ultrasonically treated at low temperature to obtain a casting solution. Finally, the casting solution is scraped on a polyether sulfone (PES) support layer, and a membrane is formed through drying and high-temperature crosslinking. The membrane is resistant to pollution and acid and alkali, can effectively remove small-molecule pollutants in pharmaceutical wastewater, and can realize high-flux purification of the pharmaceutical wastewater.

Description

Technical Field

[0001] This invention belongs to the field of water treatment membrane preparation technology, specifically relating to a method for preparing a mixed matrix pervaporation membrane. Background Technology

[0002] Tetracycline antibiotics (TCs), as key drugs in veterinary, human treatment, and agriculture, are widely popular due to their low cost, low toxicity, and broad-spectrum antibacterial activity, making them the second largest class of antibiotics produced and consumed globally. However, the metabolism of these drugs in humans and animals is incomplete, with over 70% of TCs still being released into the environment in their active form through urine and feces. Simultaneously, with the rapid expansion of the pharmaceutical industry, the problem of pharmaceutical wastewater discharge has become increasingly prominent, leading to pollution of some water bodies. TC residues may not only interfere with the synthesis and secretion of steroid hormones by inhibiting enzyme activity or regulating gene expression, thus affecting the growth and development of aquatic plants and animals, but may also accumulate through the food chain, ultimately posing a threat to human health, such as causing endocrine disorders, gene mutations, and enhanced antibiotic resistance. Currently, methods for treating pharmaceutical wastewater include advanced oxidation processes, adsorption, coagulation sedimentation, and biological treatment. Different methods are suitable for treating different types of drugs, and with increasingly stringent environmental protection requirements, exploring efficient, low-consumption, and pollution-free treatment methods is currently a research hotspot.

[0003] Chinese patent application number CN201510855579.4, entitled "Preparation method and application method of an antibiotic adsorption membrane", discloses an antibiotic adsorption membrane based on chitosan and copper nitrate composite and its preparation and application method. The membrane is low in cost, simple to prepare, has a high degradation rate and is easy to use. However, the membrane has the problems of limited adsorption capacity and difficult regeneration. Moreover, in complex aquatic environments, natural organic matter or common ions in the water will compete with the target pollutants for adsorption sites, thereby interfering with the removal effect of the target pollutants.

[0004] Chinese patent application CN202310093695.1, entitled "A Method for Preparing a Photo-Fenton Membrane Based on a Metal-Organic Framework Material," discloses a photo-Fenton membrane formed by synthesizing a Fe3O4@MIL-100(Fe) core-shell material via microwave radiation and loading it onto a PTFE membrane. This membrane possesses abundant porosity and a high specific surface area, enabling rapid adsorption and photo-Fenton degradation of various PPCPs (Polypropylene Pollutants), including sulfonamides, macrolides, quinolones, and anti-inflammatory drugs. However, the membrane material uses perfluorosulfonic acid as a binder, and the associated environmental risks introduced to some extent limit its potential for large-scale preparation and green application. Therefore, it is essential to develop a membrane with excellent removal efficiency, strong anti-fouling performance, and environmental friendliness. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing a mixed matrix pervaporation membrane.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: PVP and HNTs were dispersed in pure water, magnetically stirred until homogeneous, and then dried in a vacuum drying oven to obtain PVP-HNTs. ZrCl4, BDC-SO3Na, PVP-HNTs, and acetic acid were ultrasonically dispersed in DMF solution and then transferred to a hydrothermal reactor for high-temperature heating. The resulting product was centrifuged, washed, and soaked in a low-boiling-point solvent before vacuum drying to obtain HSO3-UiO-66@HNTs inorganic filler. PVA was dissolved in pure water by stirring in a water bath, and HSO3-UiO-66@HNTs was uniformly dispersed in ethanol by ultrasound. The two solutions were mixed together, magnetically stirred until homogeneous, and SSA was added and ultrasonically dispersed at low temperature to obtain a casting solution. An appropriate amount of the casting solution was uniformly coated onto a PES support layer and air-dried. The membrane was then placed in a vacuum drying oven for high-temperature cross-linking to prepare the HSO3-UiO-66@HNTs / PVA / SSA mixed matrix pervaporation membrane.

[0007] Specifically, the following steps are included: (1) PVP and HNTs were dispersed in 100ml of pure water at a ratio of (1g~2.5g):1g. After stirring magnetically at 60℃ overnight, the mixture was dried in a vacuum drying oven at 60℃ to obtain PVP-HNTs. ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of (0.343mmol~1.372mmol):(0.343mmol~1.372mmol):0.025g:20ml:(3ml~4ml). After being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 120℃~180℃ for 18h~24h to obtain HSO3-UiO-66@HNTs inorganic filler. (2) Prepare a PVA solution with a concentration of 5wt%~8wt%, add PVA to pure water and let stand for 0.5h, then stir at 90℃ for 2h to dissolve; (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication, and mix them in PVA solution at a concentration of 15wt%~25wt% and stir magnetically overnight; (4) Add SSA (SSA:PVA=1mol:10~20mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0008] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0009] In step (1), the ratio of PVP to HNTs is (1g~2.5g):1g. When the PVP concentration is too low, the amount of PVP is insufficient to completely cover the entire surface of HNTs, resulting in insufficient nucleation sites for HSO3-UiO-66 on HNTs. When the PVP concentration is too high, an excessively thick polymer layer is formed, blocking the pores of HNTs, hindering the diffusion of the HSO3-UiO-66 precursor, and inhibiting nucleation.

[0010] In step (1), the ratio of ZrCl4, BDC-SO3Na, PVP-HNTs, DMF, and acetic acid is (0.343mmol~1.372mmol):(0.343mmol~1.372mmol):0.025g:20ml:(3ml~4ml). Maintaining a 1:1 ratio between ZrCl4 and BDC-SO3Na ensures sufficient coordination between the metal center and the sulfonic acid functionalized ligand, forming a stable HSO3-UiO-66 framework, while avoiding excessive amounts of any one raw material that could lead to impurity formation. Fixing the amount of PVP-HNTs at 0.025g aims to control the loading of HSO3-UiO-66, ensuring ideal specific surface area and pore size distribution for HSO3-UiO-66@HNTs. Acetic acid, as a coordination modifier, slows the reaction rate through competitive coordination, promotes increased MOF crystallinity, and may enhance the regulation of framework defects, facilitating the subsequent exposure of sulfonic acid groups.

[0011] In step (1), the hydrothermal synthesis reaction temperature is 120℃~180℃. When the temperature is too low, although it is beneficial to form crystals with uniform size, the bonding force between HSO3-UiO-66 and the HNTs surface is too weak, and the heterogeneous nucleation rate is very slow. When the temperature is too high, although it accelerates nucleation and growth, it will cause PVP decomposition and crystal agglomeration, affecting the pore structure.

[0012] In step (1), the hydrothermal synthesis reaction time is 18-24 hours. If the reaction time is too short, the HSO3-UiO-66 precursor will not be fully adsorbed on the HNTs surface, resulting in incomplete crystallization and insufficient framework strength. If the reaction time is too long, HSO3-UiO-66 will grow excessively and agglomerate, reducing the effective specific surface area of ​​the material, or causing the pore structure to collapse or become blocked, thus reducing the porosity of the material.

[0013] The PVA solution concentration in step (2) is 5wt%~8wt%. PVA is the "skeleton" of the membrane. When the PVA concentration is too low, the membrane structure is incomplete, with a large number of cracks and pores, resulting in the inability to effectively retain pollutants and complete failure of separation performance. When the PVA concentration is too high, the membrane elongation at break decreases, excessive swelling occurs, and inorganic materials are difficult to disperse evenly in high-concentration PVA chains, forming defects.

[0014] The mass percentage of HSO3-UiO-66@HNTs to PVA in step (3) is 15wt%~25wt%. When the loading of HSO3-UiO-66@HNTs is too low, the membrane not only fails to overcome the bottleneck of "selectivity and flux trade-off", but also has insufficient electrostatic repulsion effect on pollutants, resulting in severe membrane fouling and pH sensitivity to pharmaceutical wastewater. When the loading of HSO3-UiO-66@HNTs is too high, it is prone to agglomeration and non-selective voids, while also damaging the continuity and toughness of the polymer matrix.

[0015] In step (4), the ratio of SSA to PVA is 1 mol: 10~20 mol. When the SSA content is too low, the degree of membrane swelling cannot be effectively controlled, the mechanical strength of the membrane is insufficient, and the hydrophilicity is not high. The cross-linking points firmly lock the polymer chains, severely restricting the movement and extension of the molecular chains, making the membrane excessively dense and causing a sharp drop in permeation flux.

[0016] 1. The hybrid matrix pervaporation membrane prepared by this invention can not only retain organic pollutants, but also efficiently remove anionic antibiotics such as tetracycline, achieving higher standards for pharmaceutical wastewater treatment. It is biodegradable and non-toxic, effectively overcoming the drawbacks of residual monomers in organic and inorganic flocculants that are toxic to organisms and cause secondary environmental pollution, thus improving biosafety and environmental friendliness.

[0017] 2. The mixed matrix pervaporation membrane prepared by this method has excellent resistance to acid and alkali corrosion, can effectively maintain the integrity of the membrane in harsh chemical environments, ensure stable separation performance, low performance degradation rate, and significantly extended service life.

[0018] 3. The mixed matrix pervaporation membrane prepared by this method has negative charge properties, which generate strong electrostatic repulsion against common anionic drug molecules in water. This effectively prevents the adsorption and accumulation of pollutants on the membrane surface, thereby significantly improving the membrane's antifouling ability and extending the cleaning cycle and service life. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the embodiments are ordinary commercially available products.

[0020] Example 1: (1) 2.5g PVP and 1g HNTs were dispersed in 100ml of pure water, and after being magnetically stirred overnight at 60℃, they were dried in a vacuum drying oven at 60℃ to obtain PVP-HNTs; ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of 0.686mmol:0.686mmol:0.05g:20ml:7ml, and after being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 160℃ for 20h to obtain HSO3-UiO-66@HNTs inorganic filler; (2) Prepare a 6wt% PVA solution by adding PVA to pure water and letting it stand for 0.5h, then stirring at 90℃ for 2h to dissolve it; (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication and mix them in PVA solution at a concentration of 20wt% overnight by magnetic stirring; (4) Add SSA (SSA:PVA=1mol:15mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0021] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0022] Example 2: (1) 2.5g PVP and 2.5g HNTs were dispersed in 100ml of pure water, and after being magnetically stirred overnight at 60℃, they were dried in a vacuum drying oven at 60℃ to obtain PVP-HNTs; ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of 0.686mmol:0.686mmol:0.05g:20ml:7ml, and after being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 160℃ for 20h to obtain HSO3-UiO-66@HNTs inorganic filler; (2) Prepare a PVA solution with a concentration of 8wt%. Add PVA to pure water and let it stand for 0.5h. Stir at 90℃ for 2h to dissolve. (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication and mix them in PVA solution at a concentration of 20wt% overnight by magnetic stirring; (4) Add SSA (SSA:PVA=1mol:15mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0023] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0024] Example 3: (1) 2.5g PVP and 1g HNTs were dispersed in 100ml of pure water, and after being magnetically stirred overnight at 60℃, they were dried in a vacuum drying oven at 60℃ to obtain PVP-HNTs; ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of 0.686mmol:0.686mmol:0.05g:20ml:7ml, and after being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 160℃ for 20h to obtain HSO3-UiO-66@HNTs inorganic filler; (2) Prepare a 6wt% PVA solution by adding PVA to pure water and letting it stand for 0.5h, then stirring at 90℃ for 2h to dissolve it; (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication and mix them in PVA solution at a concentration of 15wt% overnight by magnetic stirring; (4) Add SSA (SSA:PVA=1mol:15mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0025] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0026] Example 4: (1) 2.5g PVP and 1g HNTs were dispersed in 100ml of pure water, and after being magnetically stirred overnight at 60℃, they were dried in a vacuum drying oven at 60℃ to obtain PVP-HNTs; ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of 0.686mmol:0.686mmol:0.05g:20ml:7ml, and after being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 160℃ for 20h to obtain HSO3-UiO-66@HNTs inorganic filler; (2) Prepare a 6wt% PVA solution by adding PVA to pure water and letting it stand for 0.5h, then stirring at 90℃ for 2h to dissolve it; (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication and mix them in PVA solution at a concentration of 25wt% overnight by magnetic stirring; (4) Add SSA (SSA:PVA=1mol:15mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0027] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0028] Example 5: (1) PVP and HNTs were dispersed in pure water and magnetically stirred overnight at 60°C. Then, they were dried in a vacuum drying oven at 60°C to obtain PVP-HNTs. ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of 0.686mmol:0.686mmol:0.05g:20ml:7ml. After being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 160°C for 20h to obtain HSO3-UiO-66@HNTs inorganic filler. (2) Prepare a 6wt% PVA solution by adding PVA to pure water and letting it stand for 0.5h, then stirring at 90℃ for 2h to dissolve it; (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication and mix them in PVA solution at a concentration of 20wt% overnight by magnetic stirring; (4) Add SSA (SSA:PVA=1mol:10mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0029] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0030] Example 6: (1) PVP and HNTs were dispersed in pure water and magnetically stirred overnight at 60°C. Then, they were dried in a vacuum drying oven at 60°C to obtain PVP-HNTs. ZrCl4, BDC-SO3Na, PVP-HNTs, DMF and acetic acid were mixed in a ratio of 0.686mmol:0.686mmol:0.05g:20ml:7ml. After being ultrasonically dispersed evenly, the mixture was transferred to a hydrothermal reactor and heated at 160°C for 20h to obtain HSO3-UiO-66@HNTs inorganic filler. (2) Prepare a 6wt% PVA solution by adding PVA to pure water and letting it stand for 0.5h, then stirring at 90℃ for 2h to dissolve it; (3) Disperse HSO3-UiO-66@HNTs in ethanol by ultrasonication and mix them in PVA solution at a concentration of 20wt% overnight by magnetic stirring; (4) Add SSA (SSA:PVA=1mol:20mol) and disperse evenly by low-temperature ultrasonication to obtain casting solution.

[0031] (5) Take 0.7 ml of casting solution, evenly coat it onto the PES support layer and air dry it naturally. Place it in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

[0032] The relevant properties of the mixed matrix pervaporation membranes prepared in Examples 1 to 6 were measured respectively, and the data are detailed in Table 1.

[0033] Table 1. Relevant properties of mixed matrix pervaporation membranes As shown in Table 1 above, the mixed-matrix pervaporation membrane product prepared by this invention exhibits excellent overall performance and stable, reliable operation. This membrane demonstrates outstanding performance in tetracycline removal, exhibiting high removal efficiency, while also possessing a high water flux, significantly improving the efficiency of the separation process. Furthermore, the membrane material exhibits strong antifouling properties, effectively maintaining performance stability during long-term operation, and possesses good acid and alkali resistance, making it suitable for complex water quality environments. The entire preparation and application process is green, low-carbon, and environmentally friendly, with no toxic or harmful substances leaching out and no secondary pollution. It represents a highly efficient and sustainable solution for the preparation and use of mixed-matrix membranes.

[0034] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for preparing a mixed matrix pervaporation membrane, characterized in that, Polyvinylpyrrolidone (PVP) and halloysite nanotubes (HNTs) were dispersed in pure water and magnetically stirred overnight at 60°C. The mixture was then dried in a vacuum drying oven at 60°C to obtain PVP-HNTs. A mixed solution was prepared with zirconium chloride (ZrCl4), monosodium 2-sulfonic terephthalate (BDC-SO3Na), PVP-HNTs, N,N-dimethylformamide (DMF), and acetic acid in a ratio of 0.686 mmol:0.686 mmol:0.05 g:20 ml:7 ml. After ultrasonic dispersion, the solution was transferred to a hydrothermal reactor and heated at 160°C for 20 h to obtain HSO3-UiO-66@HNTs inorganic filler. The concentration of the prepared solution was... A 5wt%~8wt% polyvinyl alcohol (PVA) solution was prepared by adding PVA to pure water and letting it stand for 0.5 h, then stirring at 90℃ for 2 h to dissolve it. HSO3-UiO-66@HNTs were ultrasonically dispersed in ethanol and mixed with the PVA solution at a concentration of 15wt%~25wt%, and magnetically stirred overnight. Sulfosuccinic acid (SSA) crosslinking agent was added, and the mixture was ultrasonically dispersed at low temperature to obtain a casting solution. 0.7 ml of the casting solution was evenly coated onto a polyethersulfone (PES) support layer and air-dried. The mixture was then placed in a vacuum drying oven at 100℃ for 0.5 h to crosslink and prepare the HSO3-UiO-66@HNTs / PVA / SSA pervaporation membrane.

2. The method for preparing a mixed matrix pervaporation membrane according to claim 1, characterized in that, The mass ratio of PVP, HNTs, and pure water is 25:1:

100.

3. The method for preparing a mixed matrix pervaporation membrane according to claim 1, characterized in that, The ratio of HSO3-UiO-66@HNTs to ethanol is 0.2g:1ml.

4. The method for preparing a mixed matrix pervaporation membrane according to claim 1, characterized in that, The SSA addition ratio is SSA:PVA = 1 mol: 10~20 mol.

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