Preparation method and application of PVA composite ZSM-5 molecular sieve-based hydrogel

Abstract

The present application relates to the technical field of oil-water / emulsion separation, in particular to a preparation method and application of PVA composite ZSM-5 molecular sieve-based hydrogel.The present application uses PVA as a matrix, introduces ZSM-5 molecular sieve and loads it on a stainless steel mesh (SSM) to construct ZSM-5 / PVA@SSM.ZSM-5 molecular sieve has a unique three-dimensional porous structure, which can construct continuous water transport channels in the hydrogel, reduce the mass transfer resistance of the water phase, and thus improve the water flux.ZSM-5 increases the roughness of the hydrogel surface, and together with the intrinsic hydrophilicity of PVA, it constructs a hydrophilic interface, quickly forms a hydration layer and inhibits oil droplet adsorption.ZSM-5 surface polar sites form hydrogen bonds with PVA hydroxyl groups, enhancing the interfacial bonding force and avoiding the shedding of the composite gel coating.SSM serves as a rigid support skeleton, providing stable mechanical support for the hydrogel coating and significantly improving the mechanical strength and reusability of the material.

Description

Technical Field

[0001] This invention relates to the field of oil-water / emulsion separation technology, specifically to a method for preparing and applying a PVA composite ZSM-5 molecular sieve-based hydrogel. Background Technology

[0002] Large amounts of oily wastewater are generated in daily life and industrial production, seriously endangering human health, marine life, and environmental protection. Therefore, exploring efficient oil-water separation methods is of great significance for sustainable development. Currently, oil pollutants in water are mainly removed through physical or chemical methods such as incineration, biodegradation, gravity sedimentation, air flotation, and oil separators. However, industrial wastewater and domestic sewage contain a large amount of emulsifiers. According to the Gibbs isotherm, the presence of emulsifiers reduces the interfacial tension between insoluble phases, thereby forming stable emulsions (oil-in-water and water-in-oil emulsions). Compared to oil-water separation, emulsion separation is more complex, and its separation process can be divided into demulsification and pollutant removal. Overall, the above-mentioned traditional oil-water separation technologies are difficult to effectively treat emulsified oil droplets. At the same time, these technologies suffer from low separation efficiency, high operating costs, complex equipment, and excessive energy consumption. In addition, due to the balance between permeability and selectivity, the low porosity of some two-dimensional (2D) materials (including fibrous membranes, biowoven fabrics, and polymer membranes) limits their application in emulsion separation. In recent years, three-dimensional (3D) porous materials, such as cotton fabrics, polymer foams, sponges, and aerogels, have been widely used in oily wastewater treatment. However, these materials generate a large amount of waste after use, and the oil phase recovery efficiency is low. As the composition of oily wastewater becomes increasingly complex, traditional materials struggle to meet practical requirements in terms of antifouling properties, long-term stability, and reusability. Therefore, developing novel oil-water separation materials with high efficiency, excellent stability, and low cost remains a significant challenge.

[0003] Hydrogels are typically used as coatings for various substrates to separate oil-water mixtures via gravity or vacuum filtration. Compared to oleophilic materials, hydrogels, being hydrophilic, effectively alleviate oil contamination and clogging problems, demonstrating great potential in oil-water separation. Research indicates that polyvinyl alcohol (PVA), a water-soluble synthetic polymer with hydrophilicity, biocompatibility, and corrosion resistance, is considered an ideal material for sustainable hydrogels. Furthermore, PVA possesses abundant hydroxyl groups, and its water content and hydrophilicity can be adjusted by modifying the type and amount of additives. For example, incorporating SiO2 nanoparticles into hydrogels enhances their surface energy and roughness, achieving superhydrophilicity and underwater superoleophobicity in PVA / PAM / SiO2 semi-IPN hydrogel-coated stainless steel mesh (SSM): an underwater oil contact angle of 156° and an oil-water separation flux of up to 1.2 × 10⁻⁶. 4 L·m -2 ·h -1The separation efficiency exceeds 98%. Besides inorganic nanoparticle modification, natural material composites also provide an effective path for optimizing the performance of PVA-based hydrogels. For example, PVA-tannic acid (TA) hydrogels, with their excellent underwater superoleophobic properties, can efficiently purify oily wastewater. After 60 separation cycles, its separation efficiency still remains at 99.20%. However, PVA hydrogels still face the following challenges in oil-water separation:

[0004] (1) Low water flux: The micropores or nanopores in the PVA hydrogel matrix are occupied by water molecules. These water molecules are bound by hydrophilic polymer chains, which restricts the flow and permeation of water in the matrix.

[0005] (2) Poor mechanical properties: PVA’s inherent hydrophilicity and good water solubility make PVA hydrogels very easy to swell or even partially dissolve in aqueous systems, resulting in poor mechanical properties.

[0006] (3) Poor oil resistance: Pure PVA hydrogels are not superhydrophilic and usually require the introduction of inorganic nanoparticles to construct a micro-nano rough surface to further improve the hydrophilicity of the gel. However, the increase in surface roughness leads to the accumulation of grease, which aggravates oil pollution.

[0007] Therefore, appropriate modification and optimization strategies are needed to prepare PVA-based hydrogels with high water flux, good mechanical properties and oil resistance. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing and applying PVA-composite ZSM-5 molecular sieve-based hydrogels, in order to solve the problems mentioned in the background art.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing PVA composite ZSM-5 molecular sieve-based hydrogel and its application.

[0010] A method for preparing a PVA composite ZSM-5 molecular sieve hydrogel includes the following steps:

[0011] Step 1: Add PVA to deionized water, stir and heat to obtain PVA solution;

[0012] Step 2: Add ZSM-5 to the PVA solution prepared in Step 1, stir and heat to obtain a homogeneous ZSM-5 / PVA mixture;

[0013] Step 3: The ZSM-5 / PVA mixture prepared in Step 2 is evenly coated onto the stainless steel mesh SSM, and after drying, ZSM-5 / PVA@SSM is obtained.

[0014] Furthermore, in step 1, the concentration of the PVA solution is 0.018 g·mL.-1 .

[0015] Furthermore, in step 1, the heating temperature is 95ºC and the stirring time is 3 hours.

[0016] Furthermore, in step 2, the amount of ZSM-5 molecular sieve added is 0.5 wt% of the PVA solution.

[0017] Furthermore, in step 2, the heating temperature is 95ºC and the stirring time is 2 hours.

[0018] Furthermore, in step 3, the drying temperature of ZSM-5 / PVA@SSM is 60ºC, and the processing time is 2 hours.

[0019] Furthermore, ZSM-5 / PVA@SSM is mainly composed of Fe, Al, C, N and Si elements, and has a rough, continuous porous structure on its surface, where N comes from non-metallic elements in the stainless steel network.

[0020] Furthermore, the ZSM-5 / PVA@SSM hydrogel is used for oil-water / emulsion separation applications.

[0021] Furthermore, the water flux of the ZSM-5 / PVA-0.5@SSM oil-water separator is 735.82 L·m. -2 ·h -1 After 30 cycles of separation, the separation efficiency remained above 96%. Furthermore, the separation efficiency for oil-in-water emulsions reached 99.80%, with a peak emulsion throughput of 1.086 × 10⁻⁶. 5 L·m -2 ·h -1 ·bar -1 .

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0023] This invention represents the first synthesis of a ZSM-5 / PVA@SSM composite hydrogel; ZSM-5 / PVA@SSM exhibits excellent separation efficiency in oil-water and emulsion separation. Specifically, the water flux of ZSM-5 / PVA-0.5@SSM is increased to 735.82 L·m⁻¹. -2 ·h -1 Even after 30 cycles, the separation efficiency remained above 96%. Furthermore, the separation efficiency for oil-in-water emulsions reached 99.80%, with a throughput of 1.086 × 10⁻⁶. 5 L·m -2 ·h -1 ·bar -1Mechanical property tests show that, compared to PVA hydrogel, the tensile strength of ZSM-5 / PVA-0.5 composite hydrogel is increased from 22.16 MPa to 26.97 MPa.

[0024] This invention relates to a ZSM-5 / PVA@SSM composite hydrogel using SSM as a substrate. The stability of the coating is further enhanced by the hydrogen bonding between PVA molecules and between PVA and ZSM-5. During the drying process, PVA segments crosslink to form a stable three-dimensional network. Simultaneously, the introduction of ZSM-5 optimizes the gel's micro-roughness and hydrophilicity, providing the necessary structural and performance basis for oil-water separation. Therefore, ZSM-5 / PVA@SSM has the following advantages:

[0025] 1) High water flux: ZSM-5 molecular sieve, as a Mobile five framework (MFI) type zeolite, possesses a rigid porous structure formed by the interlacing of 0.53nm×0.56nm linear channels and 0.51nm×0.55nm zigzag channels, along with excellent hydrophilicity, which can effectively improve the water flux and separation selectivity of the material. Simultaneously, the surface properties of the zeolite are modulated by the Si / Al ratio, which enhances the adsorption capacity of the composite hydrogel for water molecules.

[0026] 2) Strong mechanical properties: SSM has the advantages of good mechanical flexibility, corrosion resistance and low cost, which can provide a stable support skeleton for hydrogel composites, significantly improve the mechanical strength of the material and enhance the reusability of the material;

[0027] 3) Improved oil stain resistance: The combined effect of PVA and ZSM-5 can balance the hydrophilicity and structural stability of the material, reduce the adsorption of oil stains on the material surface, and effectively improve the oil stain resistance of the material. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 This is a schematic diagram illustrating the synthesis of the ZSM-5 / PVA@SSM composite hydrogel prepared according to the present invention.

[0030] Figure 2 The images show physical samples of different ZSM-5 / PVA mixtures from Example 1 and Comparative Examples 1-5.

[0031] Figure 3 This is a scanning electron microscope image of the stainless steel network used in this invention.

[0032] Figure 4The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.5@SSM composite hydrogel sample synthesized in Example 1.

[0033] Figure 5 The image shows a mapping diagram of the ZSM-5 / PVA-0.5@SSM composite hydrogel sample synthesized in Example 1.

[0034] Figure 6 The image shows a scanning electron microscope (SEM) image of the PVA@SSM hydrogel sample synthesized in Comparative Example 1.

[0035] Figure 7 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.1@SSM composite hydrogel sample synthesized in Comparative Example 2.

[0036] Figure 8 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.3@SSM composite hydrogel sample synthesized in Comparative Example 3.

[0037] Figure 9 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.7@SSM composite hydrogel sample synthesized in Comparative Example 4.

[0038] Figure 10 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.9@SSM composite hydrogel sample synthesized in Comparative Example 5.

[0039] Figure 11 The images show the XRD patterns of the composite hydrogel samples from Example 1 and Comparative Examples 1-5.

[0040] Figure 12 The images show the infrared curves of the composite hydrogel samples in Example 1 and Comparative Examples 1-5.

[0041] Figure 13 Atomic force microscopy images of the composite hydrogel samples in Example 1 and Comparative Examples 1-5.

[0042] Figure 14 The swelling ratio diagram shows the composite hydrogel samples in Example 1 and Comparative Examples 1-5.

[0043] Figure 15 The images show the contact angle test results of the composite hydrogel samples in Example 1 and Comparative Examples 1-5.

[0044] Figure 16 The stress-strain curves of the composite hydrogel samples in Example 1 and Comparative Examples 1-5 are shown.

[0045] Figure 17 The graph shows the tensile strength and elongation at break of the composite hydrogel samples in Example 1 and Comparative Examples 1-5.

[0046] Figure 18The graph shows the separation efficiency and water flux of the composite hydrogel samples in Example 1 and Comparative Examples 1-5 for separating petroleum ether / water mixtures.

[0047] Figure 19 The stability diagram of the ZSM-5 / PVA-0.5@SSM composite hydrogel sample synthesized in Example 1 for separating petroleum ether / water mixtures.

[0048] Figure 20 The graph shows the separation efficiency and water flux of the ZSM-5 / PVA-0.5@SSM composite hydrogel sample synthesized in Example 1 for separating different oil-in-water emulsions. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] All materials and their sources in this invention: ZSM-5 molecular sieve was purchased from Raodong Molecular Sieves Enterprise Store, model H-ZSM-5, crystal size 300~500nm, pore size 0.5~0.6nm; SSM stainless steel mesh was purchased from Hongmu Stainless Steel Filter Screen, 500 mesh, radius 29mm, thickness 0.08mm.

[0051] Example 1: A method for preparing PVA composite ZSM-5 molecular sieve-based hydrogel, comprising the following steps:

[0052] Step 1: Dissolve 12g of PVA powder in 68mL of deionized water and stir at 95℃ for 3h until the PVA dissolves to obtain a PVA solution; set aside.

[0053] Step 2: Weigh 0.4 g of ZSM-5 molecular sieve (0.5 wt% of the total mass of PVA solution) and add it to the PVA solution. Stir at 95℃ for 2 h to obtain a homogeneous ZSM-5 / PVA mixture; set aside.

[0054] Step 3: The ZSM-5 / PVA-0.5 mixture is evenly coated onto a stainless steel mesh and then placed in an oven at 60°C for 2 hours to prepare ZSM-5 / PVA-0.5@SSM.

[0055] Comparative Example 1: No ZSM-5 molecular sieve was added in this comparative example.

[0056] Step 1: Dissolve 12g of PVA powder in 68mL of deionized water and stir at 95℃ for 3h until the PVA dissolves to obtain a PVA solution; set aside.

[0057] Step 2: Apply the PVA solution evenly to the stainless steel mesh, and then place it in an oven at 60°C for 2 hours to prepare PVA@SSM.

[0058] Comparative Example 2: Adjust the amount of ZSM-5 molecular sieve added.

[0059] Step 1: Dissolve 12g of PVA powder in 68mL of deionized water and stir at 95℃ for 3h until the PVA dissolves to obtain a PVA solution; set aside.

[0060] Step 2: Weigh 0.08 g of ZSM-5 molecular sieve (0.1 wt% of the total mass of PVA solution) and add it to the PVA solution. Stir at 95℃ for 2 h to obtain a uniform ZSM-5 / PVA-0.1 mixture; set aside.

[0061] Step 3: The ZSM-5 / PVA-0.1 mixture is evenly coated onto a stainless steel mesh and then placed in an oven at 60°C for 2 hours to prepare ZSM-5 / PVA-0.1@SSM.

[0062] Comparative Example 3: Adjust the amount of ZSM-5 molecular sieve added.

[0063] Step 1: Dissolve 12g of PVA powder in 68mL of deionized water and stir at 95℃ for 3h until the PVA dissolves to obtain a PVA solution; set aside.

[0064] Step 2: Weigh 0.24 g of ZSM-5 molecular sieve (0.3 wt% of the total mass of PVA solution) and add it to the PVA solution. Stir at 95℃ for 2 h to obtain a homogeneous ZSM-5 / PVA-0.3 mixture; set aside.

[0065] Step 3: The ZSM-5 / PVA-0.3 mixture is evenly coated onto a stainless steel mesh and then placed in an oven at 60°C for 2 hours to prepare ZSM-5 / PVA-0.3@SSM.

[0066] Comparative Example 4: Adjust the amount of ZSM-5 molecular sieve added.

[0067] Step 1: Dissolve 12g of PVA powder in 68mL of deionized water and stir at 95℃ for 3h until the PVA dissolves to obtain a PVA solution; set aside.

[0068] Step 2: Weigh 0.56 g of ZSM-5 molecular sieve (0.7 wt% of the total mass of PVA solution) and add it to the PVA solution. Stir at 95℃ for 2 h to obtain a uniform ZSM-5 / PVA-0.7 mixture; set aside.

[0069] Step 3: The ZSM-5 / PVA-0.7 mixture is evenly coated onto a stainless steel mesh and then placed in an oven at 60 ℃ for 2 h to prepare ZSM-5 / PVA-0.7@SSM.

[0070] Comparative Example 5: Adjust the amount of ZSM-5 molecular sieve added.

[0071] Step 1: Dissolve 12g of PVA powder in 68mL of deionized water and stir at 95℃ for 3h until the PVA dissolves to obtain a PVA solution; set aside.

[0072] Step 2: Weigh 0.72 g of ZSM-5 molecular sieve (0.9 wt% of the total mass of PVA solution) and add it to the PVA solution. Stir at 95℃ for 2 h to obtain a homogeneous ZSM-5 / PVA-0.9 mixture; set aside.

[0073] Step 3: The ZSM-5 / PVA-0.9 mixture is evenly coated onto a stainless steel mesh and then placed in an oven at 60 ℃ for 2 hours to prepare ZSM-5 / PVA-0.9@SSM.

[0074] Figure 1 This is a schematic diagram of the synthesis of the sample in Example 1. The ZSM-5 / PVA-0.5@SSM composite hydrogel uses SSM as a substrate and utilizes the hydrogen bonding between PVA molecules and between PVA and ZSM-5 to further enhance the stability of the coating.

[0075] Figure 2 The images show actual samples of the mixtures with different ZSM-5 addition amounts in Example 1 and Comparative Examples 1-5. Different amounts of ZSM-5 resulted in significant differences in the appearance of the composite solutions. With increasing ZSM-5 content, the transparency of both the composite gel and the solution gradually decreased, changing from an initial colorless and transparent state to a light gray semi-transparent state. This change visually reflects the introduction and dispersion of ZSM-5 in the composite system.

[0076] Figure 3 This is a scanning electron microscope (SEM) image of a stainless steel mesh. SSM exhibits numerous micropores and a relatively smooth surface.

[0077] The physical properties of the ZSM-5 / PVA-0.5@SSM sample in Example 1 were characterized, and the results are as follows: Figure 4-5 As shown.

[0078] Figure 4The image shown is a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.5@SSM synthesized in Example 1. When the ZSM-5 content is 0.5 wt%, the ZSM-5 / PVA-0.5@SSM hydrogel has a compact structure and uniform pore distribution.

[0079] Figure 5 The image shows the mapping diagram of ZSM-5 / PVA-0.5@SSM synthesized in Example 1. In the elemental distribution diagram of ZSM-5 / PVA-0.5@SSM, Fe, Al, C, N, and Si are uniformly distributed. Fe and N elements mainly originate from SSM, while C originates from PVA. The Si and Al elements in ZSM-5 exhibit a dotted distribution, demonstrating that the molecular sieve is well dispersed in the PVA matrix.

[0080] Figure 6 The image shows a scanning electron microscope (SEM) image of the PVA@SSM hydrogel sample synthesized in Comparative Example 1. When the PVA hydrogel is uniformly coated on a stainless steel mesh, the hydrogel fills the pores of the mesh, and its surface is relatively smooth without obvious pores or structural defects.

[0081] Figure 7 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.1@SSM composite hydrogel sample synthesized in Comparative Example 2. When the ZSM-5 content is 0.1 wt%, the composite hydrogel forms an interconnected porous structure in the SSM pores, while the surface roughness of the coating is reduced.

[0082] Figure 8 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.3@SSM composite hydrogel sample synthesized in Comparative Example 3. When the ZSM-5 addition amount was 0.3 wt%, the surface roughness of the coating increased.

[0083] Figure 9 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.7@SSM composite hydrogel sample synthesized in Comparative Example 4. When the ZSM-5 content was 0.7 wt%, particle agglomeration occurred on the coating surface.

[0084] Figure 10 The image shows a scanning electron microscope (SEM) image of the ZSM-5 / PVA-0.9@SSM composite hydrogel sample synthesized in Comparative Example 5. When the ZSM-5 addition amount was 0.9 wt%, particle aggregation on the coating surface was intensified.

[0085] Figure 11The XRD patterns are shown for the composite hydrogel samples in Example 1 and Comparative Examples 1-5. For the PVA hydrogel, a fairly broad characteristic peak is observed at 20°, reflecting the typical semi-crystalline properties of the polymer material. This broad peak is maintained well in composite hydrogel systems with different ZSM-5 loadings. Compared to PVA, the intensity of the characteristic peak in the composite hydrogel system is relatively low, which is due to the lower ZSM-5 content in the composite hydrogel samples. The XRD results indicate that the introduction of ZSM-5 molecular sieves into the polymer matrix does not significantly affect its crystal structure.

[0086] Figure 12 Infrared curves of the composite hydrogel samples from Example 1 and Comparative Examples 1-5 are shown. For PVA, the curve is at 3441 cm⁻¹. −1 2832cm −1 and 1074cm −1 The adsorption bands at these locations represent the stretching vibrations of -OH, CH, and C-OH, respectively. At 1356 cm⁻¹... −1 The peak at θ represents the bending vibration of the COH plane. All four peaks are present in all composite hydrogels. In the ZSM-5 / PVA composite hydrogel, the -OH peak shifts to 3438 cm⁻¹. −1 3445cm −1 3445cm −1 3445cm −1 3449cm −1 and 3451cm −1 This is because hydrogen bonds are formed between ZSM-5 and PVA. The presence of hydrogen bonds creates a stable interfacial bond between the ZSM-5 particles and the PVA matrix, which enhances the structural stability of the composite coating.

[0087] Figure 13 Atomic force microscopy (AFM) images of the composite hydrogel samples from Examples 1 and Comparative Examples 1-5 are shown. The AFM images reveal the three-dimensional surface morphology and roughness of the ZSM-5 / PVA@SSM composite hydrogel. Figure 13 (af). With the increase of ZSM-5 addition, the surface roughness of the composite gel first increases and then decreases.

[0088] Figure 14 The diagram shows the swelling ratios of the composite hydrogel samples in Example 1 and Comparative Examples 1-5. The introduction of ZSM-5 molecular sieves into the PVA matrix effectively improved the swelling degree and swelling performance of the hydrogel. This is likely due to the porous nature of ZSM-5 itself, which constructs numerous hydrophilic mass transfer channels within the PVA matrix, enhancing the gel's water absorption capacity and reducing the water phase permeation resistance.

[0089] Figure 15The figures show the contact angle test results for the composite hydrogel samples in Example 1 and Comparative Examples 1-5. The PVA hydrogel itself contains a large number of hydroxyl groups (-OH), exhibiting strong hydrophilicity, with a contact angle of only 30.9°. When a small amount of ZSM-5 (0.1 wt%) is introduced, the contact angle increases slightly due to the Si-O-Si hydrophobic framework on the molecular sieve surface. When the doping amount is increased to 0.3 wt%, the ZSM-5 particles are uniformly dispersed in the PVA matrix, and the Si-OH on its surface forms hydrogen bonds with the -OH of PVA, enhancing the hydrophilicity of the gel. At this point, the contact angle reaches its lowest value (25.5°). As the ZSM-5 addition amount increases (0.5 wt%, 0.7 wt%, 0.9 wt%), more Si-O-Si hydrophobic framework is exposed on the gel surface. At this point, the contact angle increases, and the surface hydrophilicity gradually weakens, but it still maintains hydrophilicity (contact angles are all less than 90°).

[0090] Figure 16 The figures show the stress-strain curves of the composite hydrogel samples in Example 1 and Comparative Examples 1-5. The tensile stress-strain curves of the hydrogels all exhibit nonlinear changes, demonstrating typical viscoelastic behavior of polymer hydrogels.

[0091] Figure 17 The figures show the tensile strength and elongation at break of the composite hydrogel samples in Example 1 and Comparative Examples 1-5. Compared with the PVA hydrogel (22.16 MPa), the tensile strength of the composite hydrogels modified with ZSM-5 molecular sieve was improved, reaching a maximum of 26.97 MPa at an addition of 0.5 wt%. This is attributed to the uniform dispersion of ZSM-5 molecular sieve in the PVA matrix, which effectively exerted the reinforcing effect of the rigid filler.

[0092] Application example: The composite hydrogel prepared above was subjected to an oil-water separation test.

[0093] First, the oil component was stained with Sudan IV. Then, the pre-moistened composite hydrogel sample was placed in the middle of the oil-water separator and fixed with clamps. A simple 1:1 mixture of water and petroleum ether was prepared. The oil-water mixture was poured into the separator, and the oil-water separation efficiency and water flux were recorded. To evaluate the cyclic stability of the material, the optimal amount of ZSM-5 / PVA@SSM composite gel was subjected to 30 cycles of oil-water mixture (petroleum ether) cyclic separation tests, and the water flux and separation efficiency were recorded for each separation.

[0094] Emulsion separation test: An oil / water emulsion was prepared by adding oil components (dichloromethane, xylene, and n-hexane) to water at a volume ratio of 1:50. 0.1 g of cetyltrimethylammonium bromide surfactant was added to every 100 mL of water, and the mixture was sonicated for 1 hour to obtain a homogeneous emulsion. A composite gel was placed on a filter, and a certain volume of the emulsion was added to the device. The separation process was carried out under a pressure of 0.9 bar. The concentration of the oil components in the solutions before and after separation was analyzed by gas chromatography.

[0095] Figure 18 The graph shows the separation efficiency and water flux of the petroleum ether / water mixtures in Example 1 and Comparative Examples 1-5. Separation tests were conducted using a petroleum ether / water mixture as an example. With increasing ZSM-5 dosage, both separation efficiency and water flux initially increased and then decreased. The optimal oil-water mixture separation performance was achieved at a dosage of 0.5 wt%, with a separation efficiency of 99.08% and a water flux of 735.82 L·m⁻¹. -2 ·h -1 .

[0096] Figure 19 This is a stability diagram of the ZSM-5 / PVA-0.5@SSM synthesized in Example 1 for separating petroleum ether / water mixtures. After 30 separation cycles, the separation efficiency of the material for petroleum ether / water remained consistently above 96%, demonstrating good structural stability. This is mainly due to the fact that the ZSM-5 molecular sieve, acting as a rigid support unit, effectively maintains the stability of the mesh structure, avoiding coating deformation and pore collapse caused by water flow pressure and oil phase contamination. Simultaneously, ZSM-5 significantly enhances the surface hydrophilicity of the coating, thereby maintaining a high oil phase retention capacity during multiple cycles, thus keeping the separation efficiency at a high level.

[0097] Figure 20 The diagram shows the separation efficiency and water flux of ZSM-5 / PVA-0.5@SSM synthesized in Example 1 for separating different oil-in-water emulsions. This hydrogel consistently maintained a separation efficiency of over 96% for the three tested oil-in-water emulsions: dichloromethane / water, xylene / water, and n-hexane / water, demonstrating excellent emulsion separation capabilities.

[0098] In summary, this invention utilizes ZSM-5 molecular sieve to modify PVA, thereby constructing a ZSM-5 / PVA-0.5@SSM composite hydrogel. Specifically, by leveraging the unique porous structure of ZSM-5, interconnected mass transfer channels are formed within the composite hydrogel, which reduces the resistance to water phase transport and efficiently traps oil droplets through a sieving effect. Therefore, the ZSM-5 / PVA@SSM synthesized in this work achieves a maximum water flux of 735.82 L·m⁻¹. -2 ·h -1Furthermore, the optimal sample, ZSM-5 / PVA-0.5@SSM, achieved a separation efficiency of 99.80% for xylene emulsions in water. In addition, the polar sites on the ZSM-5 surface can form hydrogen bonds with the hydroxyl groups of the PVA molecular chains, effectively increasing the tensile strength (ZSM-5 / PVA-0.5 reaches 26.97 MPa) and significantly improving the material's mechanical strength. Moreover, the introduction of molecular sieves significantly increases surface roughness and improves surface wettability. The modified hydrogel exhibits good hydrophilicity, rapidly forming a hydration layer on the surface, mechanistically inhibiting oil droplet adsorption and adhesion, and endowing the material with excellent oil resistance. The rigid framework of SSM effectively inhibits the swelling and deformation of the PVA hydrogel; after 30 cycles, the separation efficiency remains stable above 96%, demonstrating excellent cycle life.

[0099] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0100] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a PVA composite ZSM-5 molecular sieve hydrogel, characterized in that: Includes the following steps: Step 1: Add PVA to deionized water, stir and heat to obtain PVA solution; Step 2: Add ZSM-5 to the PVA solution, stir and heat to obtain a ZSM-5 / PVA mixture; Step 3: Apply the ZSM-5 / PVA mixture onto the stainless steel mesh SSM and dry it to obtain ZSM-5 / PVA@SSM.

2. The preparation method according to claim 1, characterized in that: In step 1, the concentration of the PVA solution is 0.018 g·mL. -1 .

3. The preparation method according to claim 1, characterized in that: In step 1, the heating temperature is 95ºC and the stirring time is 3 hours.

4. The preparation method according to claim 1, characterized in that: In step 2, the amount of ZSM-5 molecular sieve added to the ZSM-5 / PVA mixture is 0.5 wt% of the total mass of the PVA solution.

5. The preparation method according to claim 1, characterized in that: In step 2, the heating temperature is 95ºC and the stirring time is 2 hours.

6. The preparation method according to claim 1, characterized in that: In step 3, the drying temperature of ZSM-5 / PVA@SSM is 60ºC and the drying time is 2 hours.

7. A PVA composite ZSM-5 molecular sieve hydrogel prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the PVA composite ZSM-5 molecular sieve hydrogel as described in claim 7 in the separation of oil / water emulsion systems, characterized in that: In the oil / water emulsion system, the oil component is at least one of dichloromethane, xylene, and n-hexane.

9. The application according to claim 8, characterized in that: In the oil / water emulsion system, the aqueous component is a mixture of water and a surfactant, wherein the surfactant is hexadecyltrimethylammonium bromide.

10. The application according to claim 8, characterized in that: The separation process is carried out under a pressure of 0.9 bar.

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