Preparation method and application of a GO interlayer in-situ growth TiO2 composite film

Abstract

The application relates to the field of membrane separation technology, in particular to a preparation method and application of a GO interlayer in-situ growth TiO2 composite membrane, and the preparation method of the GO interlayer in-situ growth TiO2 composite membrane comprises the following steps: S1, preparing a titanium source; S2, dispersing; S3, film forming; and S4, near-infrared irradiation. The GO interlayer in-situ growth TiO2 composite membrane is loaded into a permeation separation device, one side of the membrane is seawater, the other side is deionized water, permeation separation is carried out under normal temperature and ultraviolet light irradiation, and selective separation of uranyl ions and vanadyl ions is realized. The in-situ growth of titanium dioxide nanoparticles in the GO interlayer is realized through the near-infrared irradiation technology, the uniform dispersion of the particles in the interlayer channel is ensured, the structural regularity and ion sieving performance of the membrane are significantly improved, and then the selective separation capacity of the membrane on the uranyl ions and vanadyl ions in seawater, the anti-organic pollution performance and the long-term operation stability are greatly enhanced.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a method for preparing and applying an in-situ grown TiO2 composite membrane between GO layers. Background Technology

[0002] Membrane separation technology has become a research hotspot in the field of uranium extraction from seawater due to its significant advantages such as continuous operation, ease of scale-up, and low energy consumption. Among them, graphene oxide (GO) membranes can construct regular nanoscale interlayer channels and have excellent ion sieving potential, showing promising application prospects in the field of ion separation. However, in actual seawater systems, GO membranes have inherent defects such as interlayer spacing fluctuations, decreased structural stability, and sensitivity to organic pollution, especially in systems where multiple metal ions such as uranium / vanadium coexist, resulting in insufficient separation selectivity.

[0003] To address the aforementioned issues, existing research has attempted to modify graphene oxide membranes by introducing metal oxides such as titanium dioxide, aiming to optimize the membrane's structural stability and separation performance.

[0004] CN104607069B discloses a composite desalination membrane, its preparation method, and its application. The method involves uniformly mixing an aqueous solution containing graphene oxide flakes with an aqueous solution containing titanium dioxide nanosheets, and then preparing a layered composite film of graphene oxide and titanium dioxide using vacuum filtration. However, titanium dioxide nanosheets have high surface energy and are prone to aggregation during aqueous solution mixing and filtration. This not only prevents uniform dispersion within the interlayer channels of graphene oxide but also leads to stacking or forming local agglomerates on the membrane surface, disrupting the regularity of the interlayer channels and causing a decrease in the membrane's ion sieving performance. Consequently, it fails to achieve efficient and selective separation of low-concentration uranyl ions and associated ions such as vanadium ions in seawater systems.

[0005] CN111186874B discloses a silanized reduced graphene oxide titanium dioxide composite material, its preparation method, and its application. The method involves mixing and stirring a tetrabutyl titanate solution with an aqueous dispersion of graphene oxide, removing the solvent, and then subjecting the mixture to a heating reaction and a hydrothermal reaction at 145℃~155℃ to prepare the silanized reduced graphene oxide titanium dioxide composite material. However, the hydrothermal reaction requires a high temperature, resulting in high energy consumption and complex operation.

[0006] Therefore, there is an urgent need to develop a low-temperature, controllable method for preparing composite films that can achieve uniform in-situ growth of TiO2 between GO layers. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing and applying an in-situ grown TiO2 composite film between GO layers, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing a TiO2 composite film grown in situ between GO layers, comprising the following steps: S1. Preparation of titanium source: Titanium tetrachloride is reacted with ammonia water to obtain titanium hydroxide precipitate, which is thoroughly washed with deionized water until chloride ions are completely removed. The titanium hydroxide precipitate is then dissolved in concentrated nitric acid to prepare a 0.8M to 1.2M titanium nitrate solution, which is directly used in step S2 without storage. S2. Dispersion: Mix 5 mg to 15 mg of graphene oxide with 0.5 ml to 2.0 ml of the titanium nitrate solution, and add deionized water to a total volume of 10 mL. Disperse the mixture by ultrasonication at 200 W to 400 W for 5 to 15 min to obtain a uniform dispersion. S3. Film formation: The dispersion is filtered onto a polymer substrate to form a wet film, and then vacuum dried at 70℃~85℃ for 60min~120min to obtain a precursor-supported film. S4. Near-infrared irradiation: A near-infrared light source is installed 2cm to 10cm directly above the precursor loaded film. The irradiation wavelength of the near-infrared light source is set to 780nm to 1100nm, the output power is 0.20W to 1.00W, and the irradiation time is 2h to 5h, so that titanium nitrate is converted in situ into TiO2 in the confined environment between the graphene oxide layers, thus obtaining the GO interlayer in situ grown TiO2 composite film.

[0009] Preferably, the graphene oxide has a sheet diameter of 10 μm to 50 μm and an oxygen-to-carbon ratio of 0.3 to 0.6.

[0010] Preferably, the polymer substrate is selected from any one of polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, or cellulose acetate.

[0011] Secondly, this invention provides an application of an in-situ grown TiO2 composite membrane between GO layers. The in-situ grown TiO2 composite membrane between GO layers is prepared by the above-mentioned preparation method. The in-situ grown TiO2 composite membrane between GO layers is loaded into a permeation separation device, with seawater on one side of the membrane and deionized water on the other side as the driving fluid. Permeation separation is carried out under room temperature and ultraviolet irradiation conditions to achieve selective separation of uranyl ions and vanadium ions.

[0012] Preferably, the ambient temperature is 25±2℃ and the wavelength of the ultraviolet irradiation is 365nm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves in-situ growth of titanium dioxide nanoparticles in the GO layer using near-infrared irradiation technology, ensuring uniform dispersion of particles in the interlayer channels, significantly improving the membrane's structural regularity and ion sieving performance, and thus greatly enhancing the membrane's selective separation ability of uranyl ions and vanadium ions in seawater, its resistance to organic pollution, and its long-term operational stability. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the operation of the near-infrared irradiation precursor loaded film in this invention.

[0015] Figure 2 The images show TEM images and elemental distribution maps of Ti, O, and C of the GO interlayer in-situ grown TiO2 composite film prepared in Example 1. Specifically, image a is a TEM image of the GO interlayer in-situ grown TiO2 composite film at a scale of 200 nm; image b is a TEM image of the GO interlayer in-situ grown TiO2 composite film at a scale of 20 nm; image c is an HRTEM image of the GO interlayer in-situ grown TiO2 composite film at a scale of 2 nm; image d is an HRTEM image of the GO interlayer in-situ grown TiO2 composite film at a scale of 5 nm; image e is a TEM image of the GO interlayer in-situ grown TiO2 composite film at a scale of 200 nm; image f is the Ti elemental distribution map corresponding to the region in image e; image g is the O elemental distribution map corresponding to the region in image e; and image h is the C elemental distribution map corresponding to the region in image e.

[0016] Figure 3 The images shown are TEM images and elemental distribution maps of Ti, O, and C after slicing the GO in-situ grown TiO2 composite film prepared in Example 1. Image a is a TEM image of the GO in-situ grown TiO2 composite film slice at a scale of 500 nm; image b is the Ti elemental distribution map for the corresponding region in image a; image c is the O elemental distribution map for the corresponding region in image a; image d is the C elemental distribution map for the corresponding region in image a; images e and f are TEM images of different regions of the GO in-situ grown TiO2 composite film slice at a scale of 100 nm; image g is a TEM image of the GO in-situ grown TiO2 composite film slice at a scale of 50 nm; and image h is a TEM image of the GO in-situ grown TiO2 composite film slice at a scale of 20 nm.

[0017] Figure 4 The results of Experiment Example 2 are shown in the upper left figure, which shows the change of ion permeability with the number of cycles; the lower left figure shows the change of uranium-vanadium separation factor with the number of cycles; the bar chart on the right shows the change of total degradation rate of dissolved organic matter (DOM) with the number of cycles; and the dotted line graph on the right shows the change of DOM rejection rate with the number of cycles. Detailed Implementation

[0018] 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.

[0019] Example 1 This embodiment provides a method for preparing an in-situ grown TiO2 composite film between GO layers, including the following steps: S1. Preparation of titanium source: Titanium tetrachloride is reacted with ammonia water to obtain titanium hydroxide precipitate, which is thoroughly washed with deionized water until chloride ions are completely removed. The titanium hydroxide precipitate is then dissolved in concentrated nitric acid to prepare a 1.0M titanium nitrate solution, which is directly used in step S2 without storage. S2. Dispersion: Mix 10 mg of graphene oxide with 1.0 ml of titanium nitrate solution, and add deionized water to a total volume of 10 mL. Disperse the mixture by ultrasonication at 300 W for 10 min to obtain a uniform dispersion. The graphene oxide has a sheet diameter of 30 μm and an oxygen-to-carbon ratio of 0.4. S3. Film formation: The dispersion is filtered onto a polyethersulfone substrate to form a wet film, and then vacuum dried at 80°C for 90 min to obtain the precursor-supported film. S4. Near-infrared irradiation: A near-infrared light source is installed 5 cm directly above the precursor loaded film. The irradiation wavelength of the near-infrared light source is set to 808 nm, the output power is 0.53 W, and the irradiation time is 3 h. This allows titanium nitrate to be converted in situ into TiO2 in the confined environment between the graphene oxide layers, thus obtaining the TiO2 composite film grown in situ between the GO layers.

[0020] Please see Figure 2 and Figure 3 TEM images show that the sample exhibits an ultrathin sheet morphology with transparent edges and localized wrinkles, rather than ordinary bulk particles. The clearly discernible lattice fringes in the HRTEM images indicate the formation of well-crystallized TiO2 domains between the layers. Notably, these lattice-ordered regions do not appear as independent large particles, but rather as dispersed localized crystalline regions embedded within the sheet matrix, indicating that the two-dimensional confined environment significantly inhibits crystal growth and induces confined nanocrystallization. Elemental distribution maps show that C, O, and Ti are uniformly distributed along the film thickness direction. Ti shows no localized aggregation and exhibits no significant segregation throughout the entire film, proving that titanium dioxide nanoparticles achieved confined in-situ growth between graphene oxide sheets, and that the titanium source precursor was successfully converted in-situ into TiO2 within the graphene oxide layers.

[0021] Example 2 This embodiment provides a method for preparing an in-situ grown TiO2 composite film between GO layers, including the following steps: S1. Preparation of titanium source: Titanium tetrachloride is reacted with ammonia water to obtain titanium hydroxide precipitate, which is thoroughly washed with deionized water until chloride ions are completely removed. The titanium hydroxide precipitate is then dissolved in concentrated nitric acid to prepare a 0.8M titanium nitrate solution, which is directly used in step S2 without storage. S2. Dispersion: Mix 5 mg of graphene oxide with 0.5 ml of titanium nitrate solution, and add deionized water to a total volume of 10 mL. Disperse the mixture by ultrasonication at 200 W for 5 min to obtain a uniform dispersion. The graphene oxide has a sheet diameter of 10 μm and an oxygen-to-carbon ratio of 0.3. S3. Film formation: The dispersion is filtered onto a polyvinylidene fluoride substrate to form a wet film, and then vacuum dried at 70°C for 60 min to obtain the precursor-supported film. S4. Near-infrared irradiation: A near-infrared light source is installed 2 cm directly above the precursor loaded film. The irradiation wavelength of the near-infrared light source is set to 780 nm, the output power is 0.20 W, and the irradiation time is 2 h. This allows titanium nitrate to be converted in situ into TiO2 in the confined environment between the graphene oxide layers, thus obtaining the GO interlayer in situ grown TiO2 composite film.

[0022] Example 3 This embodiment provides a method for preparing an in-situ grown TiO2 composite film between GO layers, including the following steps: S1. Preparation of titanium source: Titanium tetrachloride is reacted with ammonia water to obtain titanium hydroxide precipitate, which is thoroughly washed with deionized water until chloride ions are completely removed. The titanium hydroxide precipitate is then dissolved in concentrated nitric acid to prepare a 1.2M titanium nitrate solution, which is directly used in step S2 without storage. S2. Dispersion: Mix 15 mg of graphene oxide with 2.0 ml of titanium nitrate solution, and add deionized water to a total volume of 10 mL. Disperse the mixture by ultrasonication at 400 W for 15 min to obtain a uniform dispersion. The graphene oxide has a sheet diameter of 50 μm and an oxygen-to-carbon ratio of 0.6. S3. Film formation: The dispersion is filtered onto a polyacrylonitrile substrate to form a wet film, and then vacuum dried at 85°C for 120 min to obtain the precursor-supported film. S4. Near-infrared irradiation: A near-infrared light source is installed 10 cm directly above the precursor loaded film. The irradiation wavelength of the near-infrared light source is set to 1100 nm, the output power is 1.00 W, and the irradiation time is 5 h. This allows titanium nitrate to be converted in situ into TiO2 in the confined environment between the graphene oxide layers, thus obtaining the GO interlayer in situ grown TiO2 composite film.

[0023] Example 4 This embodiment provides a method for preparing an in-situ grown TiO2 composite film between GO layers, including the following steps: S1. Preparation of titanium source: Titanium tetrachloride is reacted with ammonia water to obtain titanium hydroxide precipitate, which is thoroughly washed with deionized water until chloride ions are completely removed. The titanium hydroxide precipitate is then dissolved in concentrated nitric acid to prepare a 0.9M titanium nitrate solution, which is directly used in step S2 without storage. S2. Dispersion: Mix 12 mg of graphene oxide with 0.8 ml of titanium nitrate solution, and add deionized water to a total volume of 10 mL. Disperse the mixture by ultrasonication at 360 W for 12 min to obtain a uniform dispersion. The graphene oxide has a sheet diameter of 20 μm and an oxygen-to-carbon ratio of 0.4. S3. Film formation: The dispersion is filtered onto a cellulose acetate substrate to form a wet film, and then vacuum dried at 75°C for 100 min to obtain the precursor-supported film. S4. Near-infrared irradiation: A near-infrared light source is installed 8 cm directly above the precursor loaded film. The irradiation wavelength of the near-infrared light source is set to 940 nm, the output power is 0.84 W, and the irradiation time is 4 h. This allows titanium nitrate to be converted in situ into TiO2 in the confined environment between the graphene oxide layers, thus obtaining the TiO2 composite film grown in situ between the GO layers.

[0024] Experimental Example 1: Membrane Separation Performance Test Experimental Procedure: The GO interlayer in-situ grown TiO2 composite membranes prepared in Examples 1-4 were loaded into a self-made membrane separation device. The device included a feed chamber and a receiving chamber. The feed chamber contained a feed solution containing uranium and vanadium, while the receiving chamber contained deionized water as the driving fluid. The feed chamber and receiving chamber were separated by a membrane clamping unit. The GO interlayer in-situ grown TiO2 composite membrane was fixed within this clamping unit in a circular area with an effective separation area of ​​1 cm in diameter. The device also included a xenon lamp source, whose emitted ultraviolet light, after passing through a filter, was perpendicularly irradiated onto the surface of the GO interlayer in-situ grown TiO2 composite membrane at a wavelength of 365 nm. A permeation separation experiment was conducted using 50 mL of spiked seawater as the feed solution and 50 mL of deionized water as the driving fluid. The spiked seawater contained 33 ppm uranyl ions, 26 ppm vanadate ions, and 10 ppm dissolved organic matter (DOM).

[0025] After 12 hours of permeation separation, the permeate and driving fluid were collected separately. The concentration of DOM in the solution was determined by ultraviolet spectrophotometer, and the concentrations of uranium and vanadium in the solution were determined by flame atomic absorption spectrometry. The above experiments were performed in parallel three times. The transmittance of uranium and vanadium, the average separation factor of uranium and vanadium (average transmittance of vanadium / average transmittance of uranium), the average rejection rate of DOM, and the average total degradation rate were calculated and recorded to evaluate the membrane separation performance of the in-situ grown TiO2 composite membrane in the GO interlayer. The experimental results are recorded in Table 1.

[0026] Table 1. Membrane separation performance test results .

[0027] As shown in Table 1, the GO interlayer in-situ grown TiO2 composite membranes prepared in Examples 1-4 exhibit excellent comprehensive separation performance: they demonstrate high efficiency in retaining uranium, good selective permeability for vanadium, and significant anti-fouling effects against DOM contamination. Among them, the GO interlayer in-situ grown TiO2 composite membrane prepared in Example 1 achieves the best performance, with significantly superior comprehensive performance compared to the other examples. This fully demonstrates the superiority and reliability of the preparation process, revealing its important application value and broad prospects in the field of seawater uranium extraction, making it worthy of promotion and application in practical engineering.

[0028] Experimental Example 2: Long-term Cyclic Stability Test Experimental Procedure: The GO interlayer in-situ grown TiO2 composite film prepared in Example 1 was subjected to 11 consecutive cycles under the same operating conditions as in Example 1, with each cycle lasting 12 hours. The separation factor of uranium and vanadium, as well as the total degradation rate and rejection rate of DOM, were recorded. The experimental results are as follows: Figure 4 As shown.

[0029] Please see Figure 4 After 11 runs, the separation factor of uranium and vanadium decreased slightly from the initial 37.85 to 28.27, the rejection rate of DOM remained above 92%, and the total degradation rate of DOM remained at around 18%, indicating that the in-situ grown TiO2 composite membrane in the GO interlayer has good structural and functional stability in the application of real seawater system.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a TiO2 composite film grown in situ between GO layers, characterized in that, Includes the following steps: S1. Preparation of titanium source: Titanium tetrachloride is reacted with ammonia water to obtain titanium hydroxide precipitate, which is thoroughly washed with deionized water until chloride ions are completely removed. The titanium hydroxide precipitate is then dissolved in concentrated nitric acid to prepare a 0.8M to 1.2M titanium nitrate solution, which is directly used in step S2 without storage. S2. Dispersion: Mix 5 mg to 15 mg of graphene oxide with 0.5 ml to 2.0 ml of the titanium nitrate solution, and add deionized water to a total volume of 10 mL. Disperse the mixture by ultrasonication at 200 W to 400 W for 5 to 15 min to obtain a uniform dispersion. S3. Film formation: The dispersion is filtered onto a polymer substrate to form a wet film, and then vacuum dried at 70℃~85℃ for 60min~120min to obtain a precursor-supported film. S4. Near-infrared irradiation: A near-infrared light source is installed 2cm to 10cm directly above the precursor loaded film. The irradiation wavelength of the near-infrared light source is set to 780nm to 1100nm, the output power is 0.20W to 1.00W, and the irradiation time is 2h to 5h, so that titanium nitrate is converted in situ into TiO2 in the confined environment between the graphene oxide layers, thus obtaining the GO interlayer in situ grown TiO2 composite film.

2. The method for preparing the GO interlayer in-situ grown TiO2 composite film according to claim 1, characterized in that, The graphene oxide has a sheet diameter of 10 μm to 50 μm and an oxygen-to-carbon ratio of 0.3 to 0.

6.

3. The method for preparing the GO interlayer in-situ grown TiO2 composite film according to claim 1, characterized in that, The polymer substrate is selected from any one of polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, or cellulose acetate.

4. An application of an in-situ grown TiO2 composite film between GO layers, characterized in that, The GO interlayer in-situ grown TiO2 composite membrane is prepared by the preparation method described in any one of claims 1 to 3. The GO interlayer in-situ grown TiO2 composite membrane is loaded into a permeation separation device, with seawater on one side of the membrane and deionized water on the other side as the driving fluid. Permeation separation is carried out under room temperature and ultraviolet irradiation conditions to achieve selective separation of uranyl ions and vanadium ions.

5. The application according to claim 4, characterized in that, The ambient temperature is 25±2℃, and the wavelength of the ultraviolet irradiation is 365nm.

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