Ti4O7 ceramic membrane electrode for electrochemical disinfection and preparation method

Abstract

The invention relates to a preparation method of a Ti4O7 ceramic membrane electrode for electrochemical disinfection, which comprises the following steps: 1) preparing 7wt.% of polyvinyl alcohol as a binder, adding a dopant and Ti4O7 powder into the prepared binder, carrying out ball milling to obtain ink, and removing bubbles from the ink under a vacuum condition; the dopant contains at least one of Pr < 3 + >, Nd < 3 + > or Sm < 3 + >; 2) filling the prepared ink into a charging barrel of a direct-writing 3D printer, and carrying out 3D printing to prepare a green body; the invention discloses a Ti4O7 ceramic membrane electrode and a preparation method thereof.The Ti4O7 ceramic membrane electrode has the advantages that the Ti4O7 ceramic membrane electrode is high in electrochemical disinfection efficiency and fine in pore structure, and the problem of membrane electrode blockage in operation procedures can be solved by the aid of the Ti4O7 ceramic membrane electrode.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a Ti4O7 ceramic membrane electrode for electrochemical disinfection and a preparation method thereof. Background Art

[0002] Pathogens (including bacteria and viruses) exposed to the water environment have been a constant threat to public health. Disinfection of wastewater containing pathogenic microorganisms can effectively cut off the spread of infectious diseases. Traditional sewage treatment technologies, such as chlorination, ultraviolet irradiation, membrane filtration, and ozone oxidation, have problems such as low treatment efficiency and secondary pollution. Electrochemical oxidation provides an alternative solution for the inactivation of pathogens in wastewater, with advantages including strong operability, no disinfection by-products, and high treatment efficiency.

[0003] Anode materials, as the core of electrochemical oxidation technology, have a key impact on the efficiency of pollutant treatment. Ti4O7 has high electrical conductivity, strong electrochemical stability and low preparation cost. In addition, Ti has wide biocompatibility and is safe and non-toxic. These advantages make electrochemical oxidation technology with Ti4O7 as anode widely used in the removal of pollutants in sewage. In particular, Ti4O7 reactive electrochemical membrane (REM) electrodes operated in flow-through mode can provide a large number of reaction sites and enhance mass transfer efficiency, showing great potential in pollutant removal and wastewater disinfection. However, the efficiency of Ti4O7REM in the process of inactivating bacteria is limited by two factors: (i) REM blockage caused by the attachment or interception of microorganisms; (ii) low charge transfer efficiency and hydroxyl radical (·OH) yield of Ti4O7.

[0004] 3D printing (additive manufacturing) technology can achieve precise control of the microstructure of the material, such as porosity, pore size distribution and void interconnectivity, and can solve the problem of unstable performance during operation caused by the random distribution of pore morphology characteristics of Ti4O7REM electrodes prepared by traditional template methods. In addition, the use of doping engineering can increase the concentration of oxygen vacancies in Ti4O7 electrodes, thereby improving their hydroxyl radical yield and low interfacial charge transfer efficiency. Recent studies have shown that rare earth elements La and Ce doped Ti4O7 electrodes exhibit higher oxidation efficiency for FLO and PFOS than pure Ti4O7.

[0005] At present, the methods for preparing Ti4O7 by 3D printing are mostly photocuring stereolithography and selective laser sintering technologies, which involve the steps of laying powder and cleaning, resulting in a large amount of waste of raw materials. The ink direct writing technology used in the present invention can greatly reduce the waste of raw materials and improve the efficiency of 3D printing. Summary of the invention

[0006] In view of the above problems, the present invention discloses a method for preparing a Ti4O7 ceramic membrane electrode for electrochemical disinfection, and the specific scheme is: A method for preparing a Ti4O7 ceramic membrane electrode for electrochemical disinfection comprises the following steps: 1) Prepare 7 wt.% polyvinyl alcohol as a binder, add dopant and Ti4O7 powder into the prepared binder, and perform ball milling to obtain ink. Remove bubbles from the ink under vacuum conditions; the dopant contains Pr 3+ 、Nd 3+ or Sm 3+ At least one of; 2) Loading the prepared ink into the barrel of a direct writing 3D printer to prepare a blank by 3D printing; 3) The printed body is subjected to debinding treatment in air atmosphere at a debinding temperature of 300°C; 4) Sinter the debinded green body in a vacuum furnace to obtain Ti4O7 ceramic membrane electrode; the vacuum degree during sintering is ≤ 10 - 2 Pa, and the sintering temperature is 1400℃.

[0007] Preferably, in step 1), polyvinyl alcohol 1788 is used to prepare the binder.

[0008] Furthermore, in step 1), the dopant Pr 3+ 、Nd 3+ or Sm 3+ The total mass is 1 wt.% of Ti4O7.

[0009] Furthermore, in step 2), a 22G dispensing needle is selected for 3D printing, and the printing speed is 100 mm min -1 , the extrusion pressure was set to 10,000-12,000 Pa, and the substrate temperature was set to 40-70 °C.

[0010] Furthermore, in step 3), the green body is heated at 1 °C min -1 Raise the temperature to 300℃ for heat preservation and debinding.

[0011] Furthermore, in step 3), the heat preservation and debinding time is 5 hours.

[0012] Furthermore, in step 1), the amount of Ti4O7 added is twice the mass of the binder.

[0013] The present invention also intends to protect the Ti4O7 ceramic membrane electrode prepared by the preparation method of the present invention.

[0014] The invention is used to prepare electrode materials for electrochemical oxidation method. Specifically, the prepared electrodes are used to electro-oxidatively disinfect pathogens such as bacteria and viruses in water.

[0015] Ti4O7 electrochemical membrane electrodes have a stronger electrochemical disinfection efficiency than flat electrodes, especially the electrochemical disinfection efficiency of Ti4O7 doped with rare earth elements is higher. However, while improving the efficiency, the sterilization process is easily blocked due to the irregularity of the pore structure.

[0016] In the process of electrochemical disinfection, to realize the practical application of electrochemical membrane electrodes, it is not feasible to simply improve the electrochemical disinfection efficiency of the electrode. Only by optimizing the electrode performance and structure at the same time can the long-term application of Ti4O7 ceramic membrane electrodes be realized.

[0017] In the present invention, the green body is 3D printed by direct ink writing, and the binder content is relatively high. The debinding process is critical to the realization of the present invention. During the debinding process, the green body further shrinks in volume and gradually densifies. The control of this process has a great influence on the pore structure of the ceramic membrane electrode after sintering.

[0018] In the conventional process of preparing porous ceramics by direct writing with ink, the debinding temperature is generally controlled at 400-600°C. For example, in the method for preparing ceramic porous parts by 3D printing disclosed in Patent 201711478724.7, the debinding temperature selected is 600°C. However, the debinding process is used to prepare ceramic membrane electrodes, and the sterilization efficiency of the obtained electrodes is low. The inventors found that the tolerance temperature of Ti4O7 is 324°C. When the debinding temperature is high, the oxidation of Ti4O7 causes the electrode performance to decrease. The present invention improves the debinding process, reduces the debinding temperature to 300°C, reduces the heating rate, and extends the insulation time, which not only ensures that the debinding is complete, but also ensures that the obtained ceramic membrane electrode has a good pore structure, a high sterilization efficiency, and is not prone to clogging. It also solves the problem of Ti4O7 oxidation causing electrode performance to decrease during the debinding process.

[0019] The rare earth element doped Ti4O7 ceramic membrane electrode of the present invention is prepared by using ink direct writing technology, has high electrochemical disinfection efficiency, and has a good pore structure, which can solve the problem of membrane electrode clogging during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 The electrochemical disinfection efficiency of Pr-doped and undoped Ti4O7 against enteropathogenic Escherichia coli in Example 1.

[0022] Figure 2The electrochemical disinfection efficiency of Nd-doped and undoped Ti4O7 against enteropathogenic Escherichia coli in Example 2.

[0023] Figure 3 The electrochemical disinfection efficiency of Sm-doped and undoped Ti4O7 against enteropathogenic Escherichia coli in Example 3.

[0024] Figure 4 SEM detection images of the Ti4O7 electrode prepared in Example 2: (a) optical photograph of Ti4O7REM; (b) SEM of the Ti4O7REM surface; (c) SEM of the Ti4O7REM waterproof layer; (d) SEM of the Ti4O7REM cross-section; (e)-(f) SEM of 3D printed extruded lines at different magnifications.

[0025] Figure 5 This is a comparison chart of membrane flux experiments of the undoped Ti4O7 electrode of Comparative Example 1, the Nd-doped Ti4O7 electrode prepared using the template method of Comparative Example 2, and the 3D printing technology of Example 2. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with the specific embodiments of the present invention. The description herein is only used to explain the present invention, but is not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work, any modifications, equivalent substitutions, improvements, etc., should be included in the protection scope of the present invention.

[0027] Example 1 7g of polyvinyl alcohol 1788 was dissolved in 93g of deionized water and stirred in a water bath at 80°C for 2h to completely dissolve. Then 40g of Ti4O7 powder and 0.7019g of PrCl3 were added to 20.5g of the prepared polyvinyl alcohol 1788 solution and stirred at 300rpm for 6h using a planetary ball mill to mix evenly. The obtained mixture was then placed in a vacuum stirring device to remove bubbles in the ink, and the vacuum degree was <10 -2 Pa. Load the prepared ink into the barrel of the direct writing 3D printer, select a 22G dispensing needle, and print at a speed of 100 mm min -1 The extrusion pressure was set to 12,000 Pa and the substrate temperature was set to 50 °C. The printed body was placed in a muffle furnace and the heating rate was set to 1 °C min -1 The debinding temperature is 300 °C and the holding time is 5 h. The debinding green body is sintered in a vacuum furnace with a heating rate of 5 °C min-1, a sintering temperature of 1400 °C, a holding time of 3 h, and a vacuum degree of ≤ 10 -2The electrochemical disinfection efficiency of the Pr-doped 3D Ti4O7 electrode against enteropathogenic Escherichia coli was compared with that of the undoped electrode. Figure 1 shown.

[0028] Example 2 7g of polyvinyl alcohol 1788 was dissolved in 93g of deionized water and stirred in a water bath at 80°C for 2h to completely dissolve. Then 40g of Ti4O7 powder and 0.9947g of NdCl3·6H2O were added to 20.5g of the prepared polyvinyl alcohol 1788 solution and stirred at 300rpm for 6h using a planetary ball mill to mix evenly. The obtained mixture was then placed in a vacuum stirring device to remove bubbles in the ink, and the vacuum degree was <10 -2 Pa. Load the prepared ink into the barrel of the direct writing 3D printer, select a 22G dispensing needle, and print at a speed of 100 mm min -1 The extrusion pressure was set to 12,000 Pa and the substrate temperature was set to 50 °C. The printed body was placed in a muffle furnace and the heating rate was set to 1 °C min -1 The debinding temperature was 300 °C and kept at this temperature for 5 h. The debinding green body was sintered in a vacuum furnace at a heating rate of 5 °C min -1 , sintering temperature is 1400 ℃, holding time is 3 h, vacuum degree needs to be ≤ 10 -2 The Nd-doped 3D Ti4O7 electrode was obtained, and its electrochemical disinfection efficiency against enteropathogenic Escherichia coli was compared with that of the undoped electrode. Figure 2 The electrode prepared in this embodiment and the SEM test results are shown in Figure 4 As shown, it can be seen that the electrode prepared by this method has a good pore structure.

[0029] Example 3 7g of polyvinyl alcohol 1788 was dissolved in 93g of deionized water and stirred in a water bath at 80°C for 2h to completely dissolve. Then 40g of Ti4O7 powder and 0.6829g of SmCl3 were added to 20.5g of the prepared polyvinyl alcohol 1788 solution and stirred at 300rpm for 6h using a planetary ball mill to mix evenly. The obtained mixture was then placed in a vacuum stirring device to remove bubbles in the ink, and the vacuum degree was <10 -2 Pa. Load the prepared ink into the barrel of the direct writing 3D printer, select a 22G dispensing needle, and print at a speed of 100 mm min -1 The extrusion pressure was set to 12,000 Pa and the substrate temperature was set to 50 °C. The printed body was placed in a muffle furnace and the heating rate was set to 1 °C min -1The debinding temperature was 300 °C and kept at this temperature for 5 h. The debinding green body was sintered in a vacuum furnace at a heating rate of 5 °C min -1 , sintering temperature is 1400℃, holding time is 3 h, vacuum degree needs to be ≤ 10 -2 The Sm-doped 3D Ti4O7 electrode was obtained, and its electrochemical disinfection efficiency against enteropathogenic Escherichia coli was compared with that of the undoped electrode. Figure 3 shown.

[0030] By comparison, it can be seen that the disinfection efficiency of the electrode after doping is significantly improved, and the disinfection efficiency of the Nd-doped electrode in Example 2 is the highest.

[0031] Comparative Example 1 7g of polyvinyl alcohol 1788 was dissolved in 93g of deionized water and stirred in a water bath at 80°C for 2h to completely dissolve. Then 40g of Ti4O7 powder was added to 20.5g of the prepared polyvinyl alcohol 1788 solution and stirred at 300rpm for 6h using a planetary ball mill to mix evenly. The obtained mixture was then placed in a vacuum stirring device to remove bubbles in the ink, and the vacuum degree was <10 -2 Pa. Load the prepared ink into the barrel of the direct writing 3D printer, select a 22G dispensing needle, and print at a speed of 100 mm min -1 The extrusion pressure was set to 12,000 Pa and the substrate temperature was set to 50 °C. The printed body was placed in a muffle furnace and the heating rate was set to 1 °C min -1 The debinding temperature was 300 °C and kept at this temperature for 5 h. The debinding green body was sintered in a vacuum furnace at a heating rate of 5 °C min -1 , sintering temperature is 1400 ℃, holding time is 3h, vacuum degree needs to be ≤ 10 -2 Pa. An undoped 3D Ti4O7 electrode was obtained, and the electrochemical disinfection efficiency of the undoped 3D Ti4O7 electrode against enteropathogenic Escherichia coli was compared with that of the doped electrodes of Examples 1-3.

[0032] Comparative Example 2 Template method for preparing Ti4O7: 4.5 g Ti4O7 powder and 1.5 g NaCl (pore former) were wet mixed for 6 h using a planetary ball mill, followed by drying and pressing (10 MPa) to obtain a green body with a diameter of 30 mm. Then, the green body was sintered using a vacuum sintering furnace according to the following procedure: heating from room temperature to 1000°C at a heating rate of 10°C / min, and from 1000°C to 1200°C at a heating efficiency of 5°C / min. Maintain at 1200°C for 2 h. The vacuum degree was maintained at 10 -2The obtained ceramic was boiled in boiling water for 5 h to remove the residual NaCl and then dried to obtain a Ti4O7 electrode.

[0033] like Figure 5 The flux of the electrode membrane prepared by the template method in Comparative Example 2 is significantly lower than that in Example 2 and Comparative Example 1.

[0034] In addition, in another comparative example, Nd doping was performed to prepare an electrode according to the method of Example 2, except that during debinding, the green body was heated to 600°C at a heating rate of 3.5°C / min and kept warm for 1 hour, and the sintering process was consistent with that of Example 2. The disinfection efficiency of the obtained Nd-doped electrode was significantly lower than that of Example 2.

Claims

1. A method for preparing a Ti4O7 ceramic membrane electrode for electrochemical disinfection, characterized in that: The following steps are involved: 1) Prepare 7 wt.% polyvinyl alcohol as a binder, add dopant and Ti4O7 powder into the prepared binder, perform ball milling to obtain ink, and remove bubbles from the ink under vacuum conditions; the dopant contains Pr 3+ 、Nd 3+ or Sm 3+ At least one of; 2) Loading the prepared ink into the barrel of a direct writing 3D printer to prepare a blank by 3D printing; 3) The printed body is subjected to debinding treatment in air atmosphere at a debinding temperature of 300°C; 4) Sinter the debinded green body in a vacuum furnace to obtain Ti4O7 ceramic membrane electrode; the vacuum degree during sintering is ≤ 10 -2 Pa, and the sintering temperature is 1400℃.

2. The method for preparing the Ti4O7 ceramic membrane electrode for electrochemical disinfection according to claim 1, characterized in that: In step 1), the dopant Pr 3+ 、Nd 3+ or Sm 3+ The total mass is 1 wt.% of Ti4O7.

3. The method for preparing the Ti4O7 ceramic membrane electrode for electrochemical disinfection according to claim 1, characterized in that: In step 2), select 22G dispensing needle for 3D printing and print speed of 100 mm min -1 , the extrusion pressure was set to 10,000-12,000 Pa, and the substrate temperature was set to 40-70 °C.

4. The method for preparing the Ti4O7 ceramic membrane electrode for electrochemical disinfection according to claim 1, characterized in that: In step 3), the green body is heated at 1 °C min -1 Raise the temperature to 300℃ for heat preservation and debinding.

5. The method for preparing the Ti4O7 ceramic membrane electrode for electrochemical disinfection according to claim 4, characterized in that: Step 3) The heat preservation and debinding time is 5 hours.

6. The method for preparing the Ti4O7 ceramic membrane electrode for electrochemical disinfection according to claim 1, characterized in that: In step 1), the amount of Ti4O7 added is twice the mass of the binder.

7. A Ti4O7 ceramic membrane electrode prepared by the method for preparing a Ti4O7 ceramic membrane electrode for electrochemical disinfection as described in any one of claims 1 to 6.

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