A method for preparing titanium dioxide electrochemical composite separation membrane

Abstract

This invention proposes a method for preparing a titanium dioxide electrochemical composite separation membrane. Using tetrabutyl titanate as a titanium source, a hydrothermal method is used to prepare titanium dioxide nanocrystals. This nanocrystal is then used as a membrane modification material. The titanium dioxide nanocrystals are then loaded onto a ceramic membrane support using a sol-gel method to produce the titanium dioxide electrochemical composite separation membrane. This preparation method is simple, low-cost, flexible, controllable, and easy to manage.

Description

Technical Field

[0001] The present invention relates to the technical field of multifunctional membrane separation, and in particular to a method for preparing a titanium dioxide electrochemical composite separation membrane. Background Art

[0002] Membrane separation technology is widely used in various water and wastewater treatment applications, such as desalination, oil-water separation, and disinfection, due to its advantages such as simple operation, low energy consumption, stable effluent quality, low cost, and small ecological footprint. However, traditional separation membranes can only physically retain pollutants in water but cannot completely remove them. These trapped pollutants can deposit and adsorb on the membrane surface or within the membrane pores, causing membrane fouling and seriously affecting membrane filtration efficiency and effluent quality.

[0003] Electrochemical composite separation membranes integrate membrane separation technology and electrochemical advanced oxidation technology. During the filtration process, electrochemical separation membranes perform the dual functions of separation membrane and electrode, utilizing electrochemical reactions to oxidize and decompose organic pollutants, thereby reducing membrane fouling and even enabling membrane self-cleaning. This effectively improves membrane filtration efficiency and effluent quality, and extends the membrane's service life. The preparation methods for electrochemical composite separation membranes are primarily categorized into three categories: membrane casting, membrane modification, and membrane integration. Membrane modification, which involves modifying a porous substrate membrane with a conductive material, is currently the most commonly used method for preparing electrochemical composite separation membranes. Commonly used conductive materials include carbon materials (such as carbon nanotubes and graphene), platinum, and lead dioxide. However, carbon and platinum have low oxygen evolution overpotentials, making them susceptible to oxygen evolution reactions under anodic polarization conditions. Furthermore, carbon materials are susceptible to oxidative corrosion, and platinum is very expensive. Lead dioxide and boron-doped diamond have higher oxygen evolution overpotentials and can generate hydroxyl radicals through the oxidation of water molecules, which facilitates the mineralization of organic pollutants. However, lead dioxide is highly toxic, making it unsuitable as an electrochemical water treatment material. Therefore, it is necessary to develop new conductive materials that can be used to modify separation membranes. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a titanium dioxide electrochemical composite separation membrane in order to address the problem of limited preparation materials of existing electrochemical composite separation membranes.

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a titanium dioxide electrochemical composite separation membrane, which uses tetrabutyl titanate as a titanium source, adopts a hydrothermal method to prepare titanium dioxide nanocrystals, and uses this as a membrane modification material. The titanium dioxide nanocrystals are loaded on a ceramic membrane support by a sol-gel method to obtain a titanium dioxide electrochemical composite separation membrane.

[0006] The preparation method further specifically comprises:

[0007] The first step is the preparation of titanium dioxide nanocrystals;

[0008] The second step is the preparation of titanium dioxide nano-single crystal dispersion;

[0009] The third step is the preparation of polyethylene oxide solution;

[0010] The fourth step is the preparation of titanium dioxide nano single crystal coating slurry;

[0011] Step 5: Loading of titanium dioxide nanocrystals.

[0012] In the first step, tetrabutyl titanate is added to a hydrofluoric acid aqueous solution at room temperature, stirred for reaction, and then transferred to an oven for further reaction. The mixture is then cooled, centrifuged to collect the powder, washed, vacuum dried, and ground to obtain titanium dioxide nanocrystals.

[0013] In the second step, the titanium dioxide nano-single crystal powder obtained in the first step is added to deionized water, and then triethanolamine is added, and ultrasonic reaction is carried out to obtain a titanium dioxide nano-single crystal dispersion.

[0014] In the third step, ethylene oxide is added to hot water under stirring and ultrasonically reacted to obtain an ethylene oxide solution.

[0015] In the fourth step, the ethylene oxide obtained in the third step is easily added to the titanium dioxide nano-single crystal dispersion in the second step to obtain a titanium dioxide nano-single crystal coating slurry.

[0016] In the fifth step, the titanium dioxide nano-single crystal coating slurry obtained in the fourth step is loaded on the alumina ceramic membrane support by using an immersion pulling method, and then dried and sintered to obtain the loaded titanium dioxide nano-single crystal.

[0017] The present invention also provides a titanium dioxide nano single crystal load prepared by the method.

[0018] The present invention also provides a membrane assembly for membrane separation, which includes the above-mentioned titanium dioxide nanocrystal load as a working electrode and a counter electrode, the distance between the two is between 0.1-5 mm, and is connected to a DC power supply through a wire.

[0019] The present invention also provides a method for membrane separation using the above membrane assembly, which comprises:

[0020] Voltage is applied by a DC power supply and cross-flow filtration is adopted. The influent water passes through the titanium dioxide electrochemical composite separation membrane under the action of the transmembrane pressure difference.

[0021] Beneficial effects of the present invention

[0022] 1. The titanium dioxide electrochemical composite separation membrane provided by the present invention has good electrochemical activity, and the preparation method is simple, low-cost, flexible and controllable, and easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flux variation curve of the titanium dioxide electrochemical composite separation membrane prepared by the present invention when treating sodium alginate. DETAILED DESCRIPTION

[0024] The present invention uses tetrabutyl titanate as titanium source, adopts hydrothermal method to prepare titanium dioxide nano single crystal, uses it as membrane modification material, adopts sol-gel method to load titanium dioxide nano single crystal on ceramic membrane support, and obtains titanium dioxide electrochemical composite separation membrane.

[0025] The specific steps are as follows:

[0026] The first step is the preparation of titanium dioxide nano-single crystals: at room temperature (10-15°C), 10-40 mL of tetrabutyl titanate is slowly added to 10-20 mL of a hydrofluoric acid aqueous solution with a mass fraction of 20-30 wt.%, and the mixed solution is transferred to a polytetrafluoroethylene reactor and magnetically stirred for 0.5-1 hour. Afterwards, the light yellow precursor is transferred to an oven and reacted at 150-220°C for 18-32 hours. After the reaction is completed, it is cooled to room temperature and the white powder is collected by centrifugation. Rinse repeatedly with anhydrous ethanol, 0.1M NaOH solution and deionized water to remove the unreacted fluoride ions, and then transfer the centrifugal product to a vacuum drying oven and dry at 40-80°C for 12-24 hours. After drying, grind to obtain titanium dioxide nano-single crystal powder;

[0027] The second step is to prepare a titanium dioxide nano-single crystal dispersion: 0.2-0.8 g of titanium dioxide nano-single crystal powder is added to 15-20 mL of deionized water, and 1-5 mL of triethanolamine is added. The resulting mixture is sonicated for 3-8 hours to obtain a uniformly mixed homogeneous dispersion.

[0028] Step 3: Preparation of polyethylene oxide solution: 1-5 g polyethylene oxide (Mw = 300,000-2,000,000) is slowly dissolved in 100 mL of hot water under stirring, and ultrasonicated for 3-6 hours to accelerate the dissolution of polyethylene oxide and remove bubbles in the solution, ultimately forming a solution with a certain viscosity;

[0029] Step 4: Preparation of a titanium dioxide nano-single crystal coating slurry: 60-90 mL of the polyethylene oxide solution was transferred into the titanium dioxide nano-single crystal dispersion to obtain a titanium dioxide nano-single crystal coating slurry with a concentration of 1-10 mg / mL;

[0030] Step 5: Loading the titanium dioxide nanocrystals: The titanium dioxide nanocrystal coating slurry is loaded onto the alumina ceramic membrane support using the dip-coating method. The membrane is then dried at room temperature for 0.5-2 hours, at 80-120°C for 0.5-2 hours, and sintered at 600-1000°C for 0.1-0.5 hours. This step is repeated 15-30 times.

[0031] The present invention also provides a method for membrane separation using the titanium dioxide electrochemical composite separation membrane, comprising the following steps:

[0032] In the first step, the titanium dioxide electrochemical composite separation membrane prepared above is sealed in a membrane assembly, with the separation membrane serving as the working electrode and the titanium dioxide modified layer facing the water inlet side; titanium sheets, titanium mesh, stainless steel sheets, and graphite sheets are used as counter electrodes, with the electrode spacing between the working electrode and the counter electrode being 0.1 to 5 mm. The working electrode and the counter electrode are connected to a DC power supply via wires;

[0033] In the second step, a voltage of 1 to 3 V is applied through a DC power supply, and a cross-flow filtration method is adopted. The incoming water passes through the titanium dioxide electrochemical composite separation membrane under the action of the trans-membrane pressure difference, realizing membrane filtration assisted by electrochemistry.

[0034] The following examples and drawings are used to describe the embodiments of the present invention in detail, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0035] Example 1

[0036] Preparation of titanium dioxide nanocrystals: At room temperature (10-15°C), 25 mL of tetrabutyl titanate was slowly added to 15 mL of a 24 wt.% hydrofluoric acid aqueous solution. The mixed solution was transferred to a polytetrafluoroethylene reactor and magnetically stirred for 0.5 hours. After that, the light yellow precursor was transferred to an oven and reacted at 180°C for 24 hours. After the reaction, it was cooled to room temperature and the white powder was collected by centrifugation. The product was repeatedly rinsed with anhydrous ethanol, 0.1M NaOH solution, and deionized water to remove unreacted fluoride ions. The centrifuged product was then transferred to a vacuum drying oven and dried at 60°C for 18 hours. After drying, it was ground to obtain titanium dioxide nanocrystal powder.

[0037] Preparation of titanium dioxide nano-single crystal dispersion: 0.5 g titanium dioxide nano-single crystal powder was added to 18 mL of deionized water, and 2 mL of triethanolamine was added. The resulting mixture was ultrasonicated for 5 h to obtain a uniformly mixed homogeneous dispersion.

[0038] Preparation of polyethylene oxide solution: 2 g of polyethylene oxide (Mw = 2000000) was slowly dissolved in 100 mL of hot water under stirring, and ultrasonicated for 5 h to accelerate the dissolution of polyethylene oxide and remove bubbles in the solution, ultimately forming a transparent homogeneous solution.

[0039] Preparation of titanium dioxide nano-single crystal coating slurry: 80 mL of polyethylene oxide solution was transferred into the titanium dioxide nano-single crystal dispersion to obtain a titanium dioxide nano-single crystal coating slurry with a concentration of 5 mg / mL.

[0040] Titanium dioxide nanocrystal loading: A titanium dioxide nanocrystal coating slurry was loaded onto an alumina ceramic membrane support using the dip-coating method. The membrane was then dried at room temperature for 1 hour, dried at 100°C for 1 hour, and sintered at 800°C for 0.5 hours. This process was repeated 20 times to obtain a titanium dioxide electrochemical composite separation membrane.

[0041] Example 2: Experimental results of membrane separation using the titanium dioxide electrochemical composite separation membrane prepared in Example 1

[0042] The titanium dioxide electrochemical composite separation membrane prepared in Example 1 was sealed in a membrane assembly. The separation membrane served as the working electrode, with the titanium dioxide modified layer facing the water inlet. A titanium mesh served as the counter electrode. The interelectrode spacing between the working and counter electrodes was 1 mm. Both electrodes were connected to a DC power supply via wires.

[0043] By applying a 1.5V voltage through a DC power supply, using a cross-flow filtration method, with a 10mg / L sodium alginate solution as the influent, the membrane filtration is realized through the titanium dioxide electrochemical composite separation membrane under the action of a transmembrane pressure difference of 50kPa. Figure 1 It can be seen that when the applied voltage is 0V, the membrane flux drops severely during the 60-min filtration process, and the standard water flux of the membrane is about 0.45 after 60 minutes of operation. When the applied voltage is 1.5V, the decline in membrane flux during the filtration process is significantly alleviated, and the standard water flux of the membrane is about 0.8 after 60 minutes of operation.

[0044] All of the above are intended to be primary implementations of this intellectual property and do not constitute limitations on other implementations of such new products and / or methods. Those skilled in the art will utilize this important information and modify the above to achieve similar implementations. However, all modifications or adaptations based on this invention to new products are reserved.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a titanium dioxide electrochemical composite separation membrane, characterized in that: Titanium dioxide nanocrystals were prepared by hydrothermal method using tetrabutyl titanate as titanium source and used as membrane modification material. Titanium dioxide nanocrystals were loaded on ceramic membrane support to obtain titanium dioxide electrochemical composite separation membrane. Specifically include: The first step is the preparation of titanium dioxide nanocrystals; The second step is the preparation of titanium dioxide nano-single crystal dispersion; The third step is the preparation of polyethylene oxide solution; The fourth step is the preparation of titanium dioxide nano single crystal coating slurry; Step 5: Loading of titanium dioxide nanocrystals; The fourth step is to add the ethylene oxide solution obtained in the third step to the titanium dioxide nano single crystal dispersion in the second step to obtain a titanium dioxide nano single crystal coating slurry. In the fifth step, the titanium dioxide nano-single crystal coating slurry obtained in the fourth step is loaded on an alumina ceramic membrane support by an immersion pulling method, dried, and sintered to obtain a titanium dioxide electrochemical composite separation membrane.

2. The method for preparing a titanium dioxide electrochemical composite separation membrane according to claim 1, wherein: In the first step, tetrabutyl titanate is added to a hydrofluoric acid aqueous solution at room temperature, stirred for reaction, and then transferred to an oven for further reaction. The mixture is then cooled, centrifuged to collect the powder, washed, vacuum dried, and ground to obtain titanium dioxide nanocrystals.

3. The method for preparing a titanium dioxide electrochemical composite separation membrane according to claim 1, wherein: In the second step, the titanium dioxide nano-single crystal powder obtained in the first step is added to deionized water, and then triethanolamine is added, and ultrasonic reaction is carried out to obtain a titanium dioxide nano-single crystal dispersion.

4. The method for preparing a titanium dioxide electrochemical composite separation membrane according to claim 1, wherein: In the third step, ethylene oxide is added to hot water under stirring and ultrasonically reacted to obtain an ethylene oxide solution.

5. A titanium dioxide electrochemical composite separation membrane prepared by the method according to any one of claims 1 to 4.

6. A membrane module for membrane separation, characterized in that: The invention comprises the titanium dioxide electrochemical composite separation membrane according to claim 5 as a working electrode and a counter electrode, the distance between the two is between 0.1 and 5 mm, and the electrodes are connected to a DC power supply via a wire.

7. A method for membrane separation using the membrane assembly according to claim 6, characterized in that: include: Voltage is applied by a DC power supply and cross-flow filtration is adopted. The influent water passes through the titanium dioxide electrochemical composite separation membrane under the action of the transmembrane pressure difference.

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