Coordination cross-linked sepiolite hydrogel superwetted graphene membranes, methods of making and uses thereof

Abstract

The application belongs to the technical field of environmental functional material preparation, and provides a coordination cross-linking shell-imitating hydrogel super-wetting graphene film material, a preparation method and application thereof. A polyvinyl alcohol-tannic acid (PVA- TA) mixed solution is prepared by using a mixture of ethanol and water as a solvent; then, the solution is mixed with a GO solution to obtain a ternary self-assembled solution; the ternary self-assembled solution is deposited on a base film, and Fe 3+ is used for coordination cross-linking, so that the coordination cross-linking shell-imitating hydrogel super-wetting graphene film is obtained. Through various characterization methods, the physical morphology and wetting characteristics of the composite material are revealed, and the performance of the composite material in separating oil stains and soluble pollutants in water is studied.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials preparation technology, specifically relating to a shell-like hydrogel super-wetting graphene membrane material for separating oil and soluble pollutants in water, its preparation method, and its uses. Background Technology

[0002] In recent years, scientists both domestically and internationally have continued to explore and advance the development of superhydrophilic and underwater superoleophobic film materials. However, despite significant progress in this field, these materials still face several bottlenecks in practical applications, including but not limited to poor chemical stability, mechanical strength and toughness, and short service life, which urgently need to be addressed. Therefore, there is an urgent need to develop a robust and efficient biomimetic separation membrane material to extend membrane lifespan and improve its performance.

[0003] The nacreous layer of seashells is a multi-scale, multi-level "brick-and-mortar" layered organic-inorganic hybrid material formed by the alternating arrangement of 2D layered mineral CaCO3 and 1D flexible biomacromolecules. In marine environments, these nacreous materials exhibit excellent chemical stability and mechanical properties. Therefore, incorporating the concept of mimicking seashell structures into the design of underwater superoleophobic separation membrane materials holds promise for solving the problem of short lifespan caused by poor mechanical properties and stability of separation membranes.

[0004] Currently, research on shell-like layered composite materials mainly focuses on utilizing the interfacial interactions between inorganic and organic assembly units. Graphene oxide (GO) possesses a unique layered structure, good ductility, hydrophilicity, and excellent mechanical properties. It can self-assemble with polymers (such as polyvinyl alcohol (PVA), polyethyleneimine (PEI), and polydopamine (PDA)) through interfacial interactions to form macroscopic artificial shell-like layered materials. GO is an ideal inorganic assembly unit for constructing shell-like structures and is widely used in the preparation of graphene-based shell-like layered materials. For example, Wen et al. prepared a GO / CNC shell-like film with excellent mechanical properties by evaporation-induced assembly of GO with a small amount of cellulose nanocrystals (CNC) followed by reduction with hydroiodic acid. Putz et al. used a vacuum filtration self-assembly technique to adsorb PVA onto GO nanosheets, preparing a highly ordered and uniform layered graphene oxide polymer nanocomposite material. Compared with pure PVA or pure GO films, the mechanical properties of the prepared GO-PVA film were significantly improved.

[0005] Furthermore, considering the challenges of using superoleophobic films in complex environments, relying solely on the non-covalent interactions of the interfacial self-assembly process is insufficient to maintain the long-term stability of the shell-like micro-interface. Therefore, forming multiple synergistic effects through interfacial cross-linking (covalent or coordination bonds) is an effective strategy. Additionally, when this material is used to remove oil and soluble contaminants from water, its separation performance is insufficient, its stability is inadequate, and it is prone to breakage. Moreover, the ability to regulate the multiple properties of this material is insufficient, making it impossible to flexibly adjust its performance according to specific circumstances. Summary of the Invention

[0006] To address the problems existing in the above-mentioned technologies, this invention utilizes two-dimensional flexible GO (graphene oxide), flexible PVA (polyvinyl alcohol), and branched TA (tannic acid) as assembly units, and constructs a shell-like micro-interface using a vacuum filtration method. Subsequently, Fe... 3+ Coordination crosslinking was carried out using GO, PVA, TA, and Fe. 3+ The strong interfacial interactions between the graphene and the diatoms enable the construction of a high-strength, high-stability coordination crosslinked shell-like hydrogel superwetting graphene membrane material. This aims to overcome the shortcomings of existing technologies, improve the performance and service life of separation membranes, and provide new solutions for underwater oil spill treatment and other fields.

[0007] This invention first provides a coordination-crosslinked shell-like hydrogel superwetting graphene membrane, which is composed of Fe 3+ A cross-linked and coordinated shell-like hydrogel graphene composite film was obtained by depositing a ternary self-assembly solution onto a base film. The ternary self-assembly solution included a PVA-TA mixed solution and a GO aqueous solution.

[0008] This invention also provides a method for preparing a coordination crosslinked shell-like hydrogel superwetting graphene membrane, which is carried out according to the following steps:

[0009] Step 1: Mix ethanol and water to form a water-ethanol solvent, then prepare two solutions, PVA and TA. Then mix the PVA solution and TA solution according to the volume ratio to obtain a PVA-TA mixed solution.

[0010] Step 2: Prepare GO aqueous solution

[0011] Step 3: Mix the PVA-TA mixed solution and GO aqueous solution according to different volumes to obtain a ternary self-assembled solution.

[0012] Step 4: Deposit a ternary self-assembly solution on the base film to form a shell-like hydrogel graphene composite film.

[0013] Step 5: Utilizing Fe 3+ Cross-linking coordination is performed to allow the shell-like hydrogel graphene composite film to interact with Fe. 3+Once the cross-linking reaction is completed, a coordinated cross-linked shell-like hydrogel super-wetted graphene membrane can be obtained.

[0014] Preferably, in step 1, the volume ratio of water to ethanol in the water-ethanol solvent is 9:1 to 1:9, and a PVA solution with a mass fraction of 0.1-20% and a TA solution with a mass fraction of 0.1-10% are prepared respectively.

[0015] Preferably, in step 1, the PVA-TA mixed solution and the GO aqueous solution are thoroughly mixed at a volume ratio of 10:0.1 to 0.1:10 to form a light yellow PVA-TA mixed solution.

[0016] Preferably, in step 2, the concentration of the GO aqueous solution is 0.1-20 mg / L.

[0017] Preferably, in step 3, the GO aqueous solution and the PVA-TA alcohol aqueous solution are thoroughly mixed at a volume ratio of 1:1.

[0018] Preferably, in step 4, the base membrane includes at least one of the following substances: PVDF membrane, fiber membrane, quartz membrane, polytetrafluoroethylene membrane, and mixed matrix membrane.

[0019] Preferably, in step 5, Fe is used 3+ Fe 3+ Aqueous solution, the Fe 3+ The concentration of the aqueous solution is 0.2-10.0 mg / ml.

[0020] The preparation method of the super-wetted graphene membrane of the coordination crosslinked shell-like hydrogel provided by the present invention has the following uses: the prepared super-wetted graphene membrane of the coordination crosslinked shell-like hydrogel is used to separate oil and soluble pollutants in water.

[0021] The purpose of this invention is to provide a method for preparing a super-wetted graphene membrane using a coordination crosslinked shell-like hydrogel. This composite membrane has excellent separation and filtration performance, and is particularly suitable for underwater oil spill treatment and other fields.

[0022] The following is a summary of the characteristics of this preparation process: (1) Innovative application of self-assembled materials: This method uses PVA-TA self-assembled materials and GO assembly, and applies them to the preparation of hydrogel superwetting membranes. The application of this self-assembled material endows the composite membrane with excellent performance. (2) Importance of solvent selection: A water-ethanol mixed solvent is used in the preparation process, in which ethanol molecules break the hydrogen bonding between PVA and TA molecules and reduce the surface tension of the entire solution, allowing droplets to quickly wet the surface of the hydrophobic PVDF membrane (polyvinylidene fluoride). This feature helps to obtain efficient self-assembly effect. (3) Crosslinking stabilization: By impregnating the PVDF / GPT (GPT is an abbreviation for PVA, TA and GO) shell-like hydrogel composite membrane with Fe 3+ The cross-linking reaction in the aqueous solution increases the stability of the membrane surface. This step improves the durability and long-term performance of the composite membrane. (4) Preparation of multi-component self-assembly solution: A ternary self-assembly solution was obtained by mixing GO aqueous solution and PVA-TA alcohol aqueous solution, wherein different concentrations of PVA-TA were used to customize the membrane performance. The preparation of this multi-component self-assembly solution allows the properties of the membrane to be adjusted as needed. The preparation method provided by this invention can prepare high-performance coordination cross-linked shell-like hydrogel superwetting graphene membranes, which are expected to play an important role in multiple application fields, especially in environments involving underwater oil pollution treatment. The morphology and underwater oleophobic and hydrophobic properties of the composite material were revealed by various characterization methods, and its separation performance of pollutants in water was studied.

[0023] The present invention has the following beneficial effects:

[0024] Superior Separation Performance: The coordination-crosslinked shell-like hydrogel graphene composite membrane exhibits excellent separation and filtration performance, particularly excelling in underwater oil spill treatment. This facilitates the efficient removal of oil and soluble contaminants from water, improving treatment efficiency.

[0025] Long-term stability: Through cross-linking reaction, the surface stability of the composite film is enhanced, enabling it to be used for a long time in complex environments without losing performance or becoming damaged.

[0026] Multi-component performance regulation: The preparation process utilizes a multi-component self-assembly solution, allowing for customization of membrane properties as needed. Different concentrations of PVA-TA alcohol-water solutions can be used to adjust membrane performance, increasing flexibility and applicability.

[0027] Environmentally friendly: The preparation process uses a water-ethanol mixed solvent, which avoids adverse environmental impacts and improves droplet wetting performance.

[0028] In summary, this invention provides a high-performance hydrogel superwetting membrane with advantages such as excellent separation performance, long-term stability, and multi-functional performance regulation, and is expected to produce significant beneficial effects in multiple application fields such as liquid separation and filtration. Attached Figure Description

[0029] Figure 1 Macroscopic images (ac) and scanning electron microscope (df) of the upper surfaces of the original PVDF base film (a / d), the shell-like hydrogel graphene composite film (b / e), and the coordination-crosslinked shell-like hydrogel graphene composite film (c / f);

[0030] Figure 2 The underwater oil contact angle (a) of the composite membrane for different types of oil and the permeation flux and separation efficiency of the separated emulsion (b) are shown. Detailed Implementation

[0031] I. The present invention will be further described below with reference to the accompanying drawings:

[0032] The preparation method of the present invention includes the following steps:

[0033] Example 1:

[0034] Using water-ethanol at a volume ratio of 1:1 as the solvent, 1.0% PVA solution and 1.0% TA solution were prepared separately. These two solutions were then thoroughly mixed at a volume ratio of 1:1 to form a light yellow PVA-TA mixed solution. A 2.0 mg / L GO aqueous solution was then prepared and mixed with it at a volume ratio of 1:1, resulting in a ternary self-assembled solution. This solution was then deposited on a base film to form a shell-like hydrogel graphene composite film. Finally, a 2.0 mg / L Fe... 3+ In aqueous solution, make it react with Fe 3+ The cross-linking reaction was completed to obtain a coordinated cross-linked shell-like hydrogel superwetting graphene membrane.

[0035] Figure 1 The images show macroscopic views (ac) and scanning electron microscope (SEM) images (df) of the original PVDF base film (a / d), the shell-like hydrogel graphene composite film (b / e), and the coordinated crosslinked shell-like hydrogel graphene composite film (c / f). In the macroscopic images, significant color differences are observed, especially after coordination crosslinking, where the surface color of the film deepens. Furthermore, the SEM images clearly show that a dense shell-like hydrogel layer forms on the surface of both the shell-like hydrogel graphene composite film and the coordinated crosslinked shell-like hydrogel graphene composite film.

[0036] Figure 2The underwater oil contact angle of the coordination-crosslinked shell-like hydrogel graphene composite membrane was measured, showing that it exhibited contact angles exceeding 150° for various oils underwater, demonstrating excellent underwater superoleophobicity. Furthermore, the permeation flux for separating these different oil-containing emulsions all exceeded 450 L / m³. -2 h -1 bar -1 The separation efficiency is all above 99.5%.

[0037] Example 2:

[0038] Using water-ethanol at a volume ratio of 9:1 as the solvent, 0.1% PVA and 0.1% TA solutions were prepared separately. These two solutions were then thoroughly mixed at a volume ratio of 1:1 to form a light yellow PVA-TA mixed solution. A 0.1 mg / L GO aqueous solution was then prepared and mixed with the GO solution at a volume ratio of 1:1 to obtain a ternary self-assembled solution. This solution was then deposited on a base film to form a shell-like hydrogel graphene composite film. Finally, a 0.2 mg / ml Fe... 3+ In aqueous solution, make it react with Fe 3+ The cross-linking reaction was completed to obtain a coordinated cross-linked shell-like hydrogel superwetting graphene membrane.

[0039] Example 3:

[0040] A 20% PVA solution was prepared using water-ethanol (volume ratio 1:9) as the solvent. Then, a 1.0 mg / L GO aqueous solution was prepared and mixed with it at a volume ratio of 1:1 to obtain a binary self-assembled solution. This solution was then deposited onto a base film to form a shell-like hydrogel graphene composite film. Finally, a 1.0 mg / ml Fe... 3+ In aqueous solution, make it react with Fe 3+ The cross-linking reaction was completed to obtain a coordinated cross-linked shell-like hydrogel superwetting graphene membrane.

[0041] Example 4:

[0042] A 1.0% (w / w) TA solution was prepared using a 1:1 (v / v) water-ethanol mixture. Then, a 2.0 mg / L GO aqueous solution was prepared and mixed with the TA solution at a 1:1 (v / v) to obtain a binary self-assembled solution. This solution was then deposited onto a base film to form a shell-like hydrogel graphene composite film. Finally, a 2.0 mg / ml Fe... 3+ In aqueous solution, make it react with Fe 3+ The cross-linking reaction was completed to obtain a coordinated cross-linked shell-like hydrogel superwetting graphene membrane.

[0043] II. The present invention will be further described using n-hexane emulsion and methylene blue solution as examples:

[0044] Emulsion separation: First, a hexane emulsion is used for oil-water separation in a dead-end filter or a high-pressure flat-panel membrane device, and the separation efficiency is analyzed by testing the total organic carbon content.

[0045] Separation of water-soluble molecules: First, prepare a methylene blue solution, perform nanofiltration on an ultrafiltration cup device or a high-pressure flat sheet membrane device, and test and analyze the separation efficiency using a UV spectrophotometer.

[0046] A more detailed explanation follows:

[0047] Emulsion separation: First, the n-hexane emulsion is separated into oil and water on a dead-end filter or a high-pressure flat-panel membrane device. The permeation flux is calculated using formula (1). The separation efficiency is analyzed by testing the total organic carbon content and calculated according to formula (2).

[0048]

[0049] Permeation flux (L m) -2 h -1 Bar -1 () refers to the pressure (P, Bar) under a certain pressure (P, Bar) and the amount of energy produced per unit time (T, h) per unit area (A, m²) 2 The volume (V, L) of the liquid.

[0050]

[0051] Where Cp is the solute concentration in the permeate stream and Cf is the solute concentration in the feed solution.

[0052] Separation of soluble molecules in water: First, prepare a methylene blue solution and perform nanofiltration on an ultrafiltration cup device or a high-pressure flat sheet membrane device. Determine the wastewater flux by measuring the volume of the filtrate within a specified time and calculate the permeation flux using formula (1). Calculate the separation efficiency by measuring the UV absorption peak positions of the filtrate and the original solution from 200 to 800 nm using a spectrophotometer and calculating the UV absorption intensity, and then calculate according to formula (3).

[0053]

[0054] Where A 滤液 and A 原液 These refer to the absorption intensity of the permeate and the original solution at the point of maximum ultraviolet absorption, respectively.

Claims

1. A method for preparing a coordination-crosslinked shell-like hydrogel superwetting graphene membrane, characterized in that, Through Fe 3+ A cross-linked and coordinated shell-like hydrogel graphene composite film was obtained by depositing a ternary self-assembly solution onto a base film. The ternary self-assembly solution included a PVA-TA mixed solution and a GO aqueous solution. The preparation method of this coordination crosslinked shell-like hydrogel superwetting graphene membrane is carried out according to the following steps: Step 1: Mix ethanol and water to form a water-ethanol solvent, then prepare two solutions, PVA and TA. Then mix the PVA solution and TA solution according to the volume ratio to obtain a PVA-TA mixed solution. Step 2: Prepare an aqueous GO solution; Step 3: Mix the PVA-TA mixed solution and GO aqueous solution according to different volumes to obtain a ternary self-assembled solution; Step 4: Deposit a ternary self-assembly solution on the base film to form a shell-like hydrogel graphene composite film; Step 5: Utilizing Fe 3+ Cross-linking coordination is performed to allow the shell-like hydrogel graphene composite film to interact with Fe. 3+ After completing the crosslinking reaction, a coordinated crosslinked shell-like hydrogel superwetting graphene membrane can be obtained; in step 5, Fe is utilized. 3+ For Fe 3+ Aqueous solution, the Fe 3+ The concentration of the aqueous solution is 0.2-10.0 mg / ml.

2. The method for preparing the coordination crosslinked shell-like hydrogel superwetting graphene membrane according to claim 1, characterized in that, In step 1, the volume ratio of water to ethanol in the water-ethanol solvent is 9:1 to 1:9, and PVA solution with a mass fraction of 0.1-20% and TA solution with a mass fraction of 0.1-10% are prepared respectively.

3. The preparation method according to claim 1, characterized in that, In step 1, the PVA-TA mixed solution and GO aqueous solution are thoroughly mixed at a volume ratio of 10:0.1 to 0.1:10 to form a light yellow PVA-TA mixed solution.

4. The method for preparing the coordination crosslinked shell-like hydrogel superwetting graphene membrane according to claim 1, characterized in that, In step 2, the concentration of the GO aqueous solution is 0.1-20 mg / L.

5. The method for preparing the coordination crosslinked shell-like hydrogel superwetting graphene membrane according to claim 1, characterized in that, In step 3, the GO aqueous solution and the PVA-TA alcohol aqueous solution are thoroughly mixed at a volume ratio of 1:

1.

6. The method for preparing the coordination crosslinked shell-like hydrogel superwetting graphene membrane according to claim 1, characterized in that, In step 4, the base membrane includes at least one of the following substances: PVDF membrane, fiber membrane, quartz membrane, polytetrafluoroethylene membrane, and mixed matrix membrane.

7. The use of the coordination crosslinking shell-like hydrogel superwetting graphene membrane prepared by the method according to any one of claims 3-6, characterized in that, The prepared coordination crosslinked shell-like hydrogel superwetting graphene membrane was used to separate oil and water soluble pollutants.

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