Photocatalytic self-cleaning two-dimensional vermiculite film and preparation method and application thereof

Abstract

The application discloses a kind of photocatalytic self-cleaning two-dimensional vermiculite films and its preparation method and application, preparation method includes the following steps: with thermal expansion stone as raw material preparation vermiculite nanodispersion, TiO2 solution is blended with vermiculite nanodispersion, ultrasonic, deposit on polycarbonate support substrate, dry, and be prepared.The photocatalytic self-cleaning two-dimensional vermiculite film prepared by the application has more adjustable nanochannel, improves the permeability of the film;At the same time, the preparation method is simple, low in cost, and has self-cleaning function, has more extensive application prospect, the application provides a possible way for developing two-dimensional nanofiltration membrane with controllable and stable dye desalination performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of film materials, and particularly relates to a photocatalytic self-cleaning two-dimensional vermiculite film and a preparation method and application thereof. BACKGROUND

[0002] Membrane separation technology has been rapidly developed due to its environmental protection and high efficiency, and is widely used in water treatment. Membrane separation is a high-tech field covering chemical engineering, materials science, process engineering and other disciplines. It is a separation medium with selectivity for a component in a mixture. A certain driving force is applied on both sides of the membrane, so that the components in the mixture are selectively transferred from one side of the membrane to the other side. There are many types of separation membranes, which cannot be classified by a simple method. Usually, classification is carried out from different angles. According to the separation process, there are microfiltration membrane (MF), ultrafiltration membrane (UF), nanofiltration membrane (NF), reverse osmosis membrane (RO), dialysis membrane (DL), gas separation membrane (GS), pervaporation membrane (PV) and ion exchange membrane (IE). Nanofiltration (NF) is a new type of membrane separation technology between reverse osmosis and ultrafiltration. Its molecular weight cut-off is between 200 and 2000, the membrane pore size is about 1 nm, and it is suitable for separating solute components with a size of about 1 nm.

[0003] Two-dimensional (2D) nanomaterials (such as graphene, transition metal carbides (MXenes), molybdenum disulfide, carbon nitride, vermiculite, etc.) show encouraging performance in the field of membrane separation technology. Due to its atomic thickness and controllable size, two-dimensional nanomaterials with unique nanogap and nanochannel have excellent permeation properties. By adjusting the size of two-dimensional nanosheets, surface physicochemical properties or adjusting the thickness of layered membranes, these membranes show extraordinary performance for separating liquids, gases and ions.

[0004] There are several processes for preparing photocatalytically self-cleaning membranes, including chemical vapor deposition (CVD), sol-gel deposition, and physical vapor deposition (PVD). CVD involves spraying a pre-prepared chemical vapor deposition liquid onto a substrate surface, followed by high-temperature heat treatment to form a thin film. Disadvantages of this process include high cost, the need for specialized equipment and materials, and the potential for pollutant generation, making it less suitable for environmental applications. Sol-gel deposition involves coating a pre-prepared titanium dioxide sol onto a substrate surface, followed by heat treatment to form a thin film. Disadvantages of this process include a complex preparation process, multiple treatments, and high cost. PVD involves high-temperature heat treatment of a pre-prepared material to generate a gas phase, which is then deposited onto the substrate surface as a thin film. Disadvantages of this process include the need for high temperatures and vacuum conditions, and the potential for waste and pollutant generation during production, making it less environmentally friendly. While these processes can produce photocatalytically self-cleaning membranes, they all have drawbacks, such as high cost, waste and pollutant generation, and environmental impact. Therefore, there is a need to find a new process that is low-cost, environmentally friendly in production, and produces thin films with high photocatalytic self-cleaning function. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a photocatalytic self-cleaning two-dimensional vermiculite membrane, its preparation method, and its applications.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for preparing a photocatalytic self-cleaning two-dimensional vermiculite film includes the following steps:

[0008] 1) Take TiO2 solution and vermiculite nano-dispersion, mix them, and sonicate to obtain dispersion I;

[0009] 2) The dispersion I obtained in step 1) is deposited on a polycarbonate support substrate and dried to obtain the desired product.

[0010] Further, the vermiculite nano-dispersion in step 1) was prepared by the following method:

[0011] a) Add thermally expanded stone to a saturated NaCl solution, stir, and wash with deionized water 4-7 times to obtain sodium ion intercalated expanded stone.

[0012] b) The sodium-intercalated expanded stone obtained in step a) is refluxed in 1-3 mol / L LiCl solution, filtered, and then washed 4-7 times with deionized water and 2-4 times with anhydrous ethanol to obtain lithium-intercalated expanded stone.

[0013] c) adding the lithium ion intercalated expanded stone prepared in step b) into deionized water, stirring, ultrasonicating, centrifuging, calibrating, and preparing a vermiculite nanodispersion.

[0014] Further, the concentration of the vermiculite nanodispersion is 0.1-0.3 mg / mL.

[0015] Preferably, the concentration of the vermiculite nanodispersion is 0.2 mg / mL.

[0016] Further, the particle size of the heat-expanded stone in step a) is 8-13 mm, the stirring temperature is 110-130 DEG C, and the stirring time is 45-50 h.

[0017] Further, the reflux in step b) is oil bath heating, the reflux temperature is 110-130 DEG C, and the reflux time is 22-25 h.

[0018] Further, the stirring time in step c) is 20-40 min, the ultrasonicating time is 20-40 min, the centrifuging speed is 10000-15000 r / min, and the centrifuging time is 15-25 min.

[0019] Further, in step 2), the concentration of the TiO2 solution is 0.05-0.15 mg / mL, and the volume ratio of the TiO2 solution to the vermiculite nanodispersion is 2-15:1-5; and the ultrasonicating time in step 2) is 8-12 min.

[0020] Preferably, in step 2), the concentration of the TiO2 is 0.1 mg / mL, and the volume ratio of the TiO2 solution to the vermiculite nanodispersion is 8:2.5.

[0021] Further, in step 2), the drying temperature is 50-70 DEG C, and the drying time is 10-15 h.

[0022] The photocatalytic self-cleaning two-dimensional vermiculite film is prepared by the above method.

[0023] The photocatalytic self-cleaning two-dimensional vermiculite film prepared by the above method is applied in dye desalination.

[0024] The present application has the following advantages:

[0025] 1) The present application has water purification function: the vermiculite used in the present application has exchangeable cations, which provides the possibility for TiO2 nanoparticles with photocatalytic properties to be embedded into the interlayer, thereby constructing a regular adjustable nanochannel with abundant and convenient transport carriers, and the size of the channel is adjusted by the titanium dioxide nanoparticles to improve the permeability.

[0026] 2) The present application is low in cost: the present application uses heat-expanded vermiculite as raw material, and prepares vermiculite nanosheets through a simple ion exchange method, which has the advantage of low cost. The method for preparing TiO2 intercalated vermiculite film is also relatively simple and can be completed through a simple device.

[0027] 3) The present application has a self-cleaning function: the photocatalytic self-cleaning two-dimensional vermiculite film prepared by the present application can decompose organic substances attached to the film under light, wherein the titanium dioxide nanoparticles generate electron and hole pairs, which can react with water molecules under the action of ultraviolet light to generate hydroxyl radicals, and can also react with organic pollutants and microorganisms to remove or degrade them. The free radicals generated by these reactions can effectively remove the pollutants on the surface of the film, thereby improving the recovery flux and stability of the film. Therefore, the application of ultraviolet treatment can effectively improve the performance of the film and prolong its service life, thereby improving the practical value of the film and realizing self-cleaning of the film. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Anti-pollution data of the photocatalytic self-cleaning two-dimensional vermiculite film. DETAILED DESCRIPTION

[0029] The following examples are used to explain the present application and are not intended to limit the scope of the present application. If specific conditions are not specified in the examples, they are carried out under conventional conditions or according to the manufacturer's recommendations. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0030] Example 1:

[0031] A method for preparing a photocatalytic self-cleaning two-dimensional vermiculite film, comprising the following steps:

[0032] 1) Preparation of vermiculite nanosheet dispersion: 2 g of heat-expanded stone (particle size: 8-13 mm) was added to a saturated NaCl solution, and stirred at 120°C for 48 h under magnetic stirring, washed with deionized water for 5 times, to obtain sodium ion intercalated expanded stone; the sodium ion intercalated expanded stone was further refluxed in 2 mol / L LiCl solution for 24 h, and the reflux was heated by oil bath, the heating temperature was 120°C, then filtered and washed with deionized water for 5 times, and washed with anhydrous ethanol for 3 times, until no Cl -1 was detected in the filtrate, to obtain lithium ion intercalated expanded stone. 0.5 g of lithium ion intercalated expanded stone was added to 200 mL of deionized water, and stirred for 30 min under magnetic stirring, and then treated by ultrasonic for 30 min. Then, the unpeeled stone pieces were removed by centrifugation at a centrifugal speed of 12000 r / min for 20 min, to obtain nearly transparent vermiculite nanosheet dispersion. Finally, the concentration of the vermiculite nanosheet dispersion was calibrated to be 0.2 mg / mL by drying and weighing method.

[0033] 2) Preparation of photocatalytic self-cleaning two-dimensional vermiculite film: 0.8 ml of TiO2 solution with a concentration of 0.1 mg / ml was added to the vermiculite nanosheet dispersion liquid containing 0.25 ml prepared in step 1), and deionized water was added for dispersion ultrasonic for 10 min. The above obtained dispersion liquid was deposited on a polycarbonate support substrate by vacuum assisted self-assembly using a suction filtration device, and the freshly prepared film was dried in a blast drying oven at 60 ℃ for 12 h to prepare a photocatalytic self-cleaning two-dimensional vermiculite film, which was marked as TiO2@VMT-0.8.

[0034] Example 2:

[0035] A preparation method of a photocatalytic self-cleaning two-dimensional vermiculite film, comprising the following steps:

[0036] 1) Preparation of vermiculite nanosheet dispersion liquid: the specific method is the same as that in Example 1.

[0037] 2) Preparation of photocatalytic self-cleaning two-dimensional vermiculite film: 0.6 ml of TiO2 solution with a concentration of 0.1 mg / ml was added to the vermiculite nanosheet dispersion liquid containing 0.25 ml prepared in step 1), and deionized water was added for dispersion ultrasonic for 10 min. The above obtained dispersion liquid was deposited on a polycarbonate support substrate by vacuum assisted self-assembly using a suction filtration device, and the freshly prepared film was dried in a blast drying oven at 60 ℃ for 12 h to prepare a photocatalytic self-cleaning two-dimensional vermiculite film, which was marked as TiO2@VMT-0.6.

[0038] Example 3:

[0039] A preparation method of a photocatalytic self-cleaning two-dimensional vermiculite film, comprising the following steps:

[0040] 1) Preparation of vermiculite nanosheet dispersion liquid: the specific method is the same as that in Example 1.

[0041] 2) Preparation of photocatalytic self-cleaning two-dimensional vermiculite film: 0.4 ml of TiO2 solution with a concentration of 0.1 mg / ml was added to the vermiculite nanosheet dispersion liquid containing 0.25 ml prepared in step 1), and deionized water was added for dispersion ultrasonic for 10 min. The above obtained dispersion liquid was deposited on a polycarbonate support substrate by vacuum assisted self-assembly using a suction filtration device, and the freshly prepared film was dried in a blast drying oven at 60 ℃ for 12 h to prepare a photocatalytic self-cleaning two-dimensional vermiculite film, which was marked as TiO2@VMT-0.4.

[0042] Comparative Example 1:

[0043] A preparation method of a two-dimensional vermiculite film, comprising the following steps:

[0044] 1) Preparation of Vermiculite Nanosheet Dispersion: The procedure is same as Example 1.

[0045] 2) Preparation of Two-dimensional Vermiculite Membrane: 0.25 ml of the vermiculite nanosheet dispersion prepared in step 1) was added to deionized water and dispersed ultrasonically for 10 min. The resulting dispersion was deposited on a polycarbonate support substrate by vacuum-assisted self-assembly using a filtration apparatus. The freshly prepared membrane was dried in a forced air oven at 60 °C for 12 hours to obtain a two-dimensional vermiculite membrane, noted as VMT-0.25.

[0046] Comparative Example 2:

[0047] A method for preparing a two-dimensional vermiculite membrane, comprising the steps of:

[0048] 1) Preparation of Vermiculite Nanosheet Dispersion: The procedure is same as Example 1.

[0049] 2) Preparation of Two-dimensional Vermiculite Membrane: 0.20 ml of the vermiculite nanosheet dispersion prepared in step 1) was added to deionized water and dispersed ultrasonically for 10 min. The resulting dispersion was deposited on a polycarbonate support substrate by vacuum-assisted self-assembly using a filtration apparatus. The freshly prepared membrane was dried in a forced air oven at 60 °C for 12 hours to obtain a two-dimensional vermiculite membrane, noted as VMT-0.20.

[0050] Comparative Example 3:

[0051] A method for preparing a two-dimensional vermiculite membrane, comprising the steps of:

[0052] 1) Preparation of Vermiculite Nanosheet Dispersion: The procedure is same as Example 1.

[0053] 2) Preparation of Two-dimensional Vermiculite Membrane: 0.15 ml of the vermiculite nanosheet dispersion prepared in step 1) was added to deionized water and dispersed ultrasonically for 10 min. The resulting dispersion was deposited on a polycarbonate support substrate by vacuum-assisted self-assembly using a filtration apparatus. The freshly prepared membrane was dried in a forced air oven at 60 °C for 12 hours to obtain a two-dimensional vermiculite membrane, noted as VMT-0.15.

[0054] Test Example 1: Permeability and Selectivity Test

[0055] The water flux permeability test of the photocatalytic self-cleaning two-dimensional vermiculite membranes prepared in Examples 1-3 above and the two-dimensional vermiculite membranes prepared in Comparative Examples 1-3 was carried out in dead-end filtration, and the selectivity test for removal of organic dyes such as Alizarin Blue (AB), Methylene Blue (MB), Congo Red (CR), and Eriochrome Black T (EBT) was carried out, and the test results are shown in Table 1 below.

[0056] Table 1 Permeability and selectivity data of two-dimensional vermiculite membrane and photocatalytic self-cleaning two-dimensional vermiculite membrane

[0057]

[0058] From the data in the above table, compared with the two-dimensional vermiculite membrane prepared by the comparative example, the photocatalytic self-cleaning two-dimensional vermiculite membrane prepared by the embodiment of the application has higher permeability, and the highest permeability can reach 260.9 L·m -2 ·h -1 ·bar -1 At the same time, the selectivity of different organic dyes is also improved to a certain extent, and the selectivity of the prepared photocatalytic self-cleaning two-dimensional vermiculite membrane is more than 95%, which proves that the photocatalytic self-cleaning two-dimensional vermiculite membrane prepared by the method of TiO2 intercalation significantly improves the permeability and selectivity.

[0059] Test example 2: photocatalytic performance test

[0060] The photocatalytic performance of the photocatalytic self-cleaning two-dimensional vermiculite membrane TiO2@VMT-0.8 prepared in example 1 was studied. In three cycles, the membrane was first tested for pure water flux for 0.5 hours, then the simulated pollutants (bovine serum albumin / soybean oil) were added, and the membrane flux was tested for 1 hour. The surface of the membrane was irradiated for 0.5 hours, and then the pure water flux was tested for 0.5 hours. The above steps were repeated three times.

[0061] The test results are shown in Figure 1 It was found that TiO2@VMT-0.8 had the characteristics of photocatalytic self-cleaning. After cleaning by irradiation, the flux recovery rate of the membrane was significantly improved from 63% to 97%, showing excellent anti-pollution performance.

[0062] The above description is only a preferred embodiment of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method for preparing a photocatalytic self-cleaning two-dimensional mica film, characterized by, It comprises the following steps: 1) blending TiO2 solution with vermiculite nanodispersion, ultrasonicating to obtain dispersion I; 2) depositing the dispersion I obtained in step 1) on a polycarbonate support substrate, drying to obtain a photocatalytic self-cleaning two-dimensional vermiculite film; The concentration of the vermiculite nanodispersion is 0.1-0.3 mg / mL; The concentration of the TiO2 solution is 0.05-0.15 mg / mL, and the volume ratio of the TiO2 solution to the vermiculite nanodispersion is 2-15:1-5; The vermiculite nanodispersion is prepared by the following method: a) adding heat-expanded stone to saturated NaCl solution, stirring, washing with deionized water to obtain sodium ion intercalated expanded stone; b) refluxing the sodium ion intercalated expanded stone obtained in step a) in 1-3 mol / L LiCl solution, filtering, then washing with deionized water, and then washing with anhydrous ethanol to obtain lithium ion intercalated expanded stone; c) adding the lithium ion intercalated expanded stone obtained in step b) to deionized water, stirring, ultrasonicating, centrifuging, and calibrating to obtain vermiculite nanodispersion.

2. The method of claim 1, wherein the photocatalytic self-cleaning two-dimensional mica film is prepared by the steps of: (a) preparing a mica film; (b) coating the mica film with a photocatalytic material; and (c) coating the mica film with a self-cleaning material. In step a), the particle size of the heat-expanded stone is 8-13 mm, the stirring temperature is 110-130 ℃, and the stirring time is 45-50 h.

3. The method of claim 1, wherein the photocatalytic self-cleaning two-dimensional mica film is prepared by the steps of: (a) preparing a mica film; (b) coating the mica film with a photocatalytic material; and (c) coating the mica film with a self-cleaning material. In step b), the reflux is oil bath heating, the reflux temperature is 110-130 ℃, and the reflux time is 22-25 h.

4. The method of claim 1, wherein the photocatalytic self-cleaning two-dimensional mica film is prepared by the steps of: (a) preparing a mica film; (b) coating the mica film with a photocatalytic material; and (c) coating the mica film with a self-cleaning material. In step c), the stirring time is 20-40 min, the ultrasonicating time is 20-40 min, the centrifuging speed is 10000-15000 r / min, and the centrifuging time is 15-25 min.

5. The method for preparing the photocatalytic self-cleaning two-dimensional vermiculite film according to claim 1, characterized in that, In step 1), the ultrasonicating time is 8-12 min.

6. The method for preparing the photocatalytic self-cleaning two-dimensional vermiculite film according to claim 1, characterized in that, In step 2), the drying temperature is 50-70 ℃, and the drying time is 10-15 h.

7. A photocatalytic self-cleaning two-dimensional vermiculite film prepared by the method of any one of claims 1-6.

8. The use of the photocatalytic self-cleaning two-dimensional vermiculite film of claim 7 in dye desalination.

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