Electrochemical preparation method of nano CeO2 powder

Abstract

The invention relates to an electrochemical preparation method of nano CeO2 powder, which comprises the following steps: 1) adding an electrolyte containing Ce < 3 + > into a cathode chamber and an anode chamber of an electrolysis device, and arranging a cation exchange membrane between the cathode chamber and the anode chamber; then, cerium carbonate powder is added into the anode chamber for electrolysis; 2) carrying out a heating reaction on the Ce (OH) 3 turbid liquid and air in a closed reaction kettle, and filtering after the reaction is finished to obtain a precursor, carrying out ultrasonic treatment on the electrolyte in the cathode chamber and the anode chamber continuously in the electrolysis process, so as to obtain a Ce (OH) 3 turbid liquid in the cathode chamber; the filtered filtrate returns to the cathode chamber; and (3) calcining the precursor, so as to obtain the nano CeO2 powder. The preparation method is simple to operate, low in cost and free of ammonia nitrogen / high-salinity wastewater discharge, has considerable economic benefits and meets the large-scale commercial application requirements.

Description

Technical Field

[0001] The invention relates to the field of materials, and in particular to an electrochemical preparation method of nano CeO2 powder. Background Art

[0002] As a very important, cheap and widely used rare earth oxide, CeO2 is widely used in three-way catalysis, chemical mechanical polishing, solid fuel cells, anti-corrosion coatings, plastic additives, etc. Especially in the field of chemical mechanical polishing and catalysis, higher requirements are placed on the morphology, size and uniformity of CeO2 powder particles.

[0003] For example, using Ce 3+ and Ce 4+ The mixture of the precipitate prepared by mixing the solution of the ions with the alkali solution and the solution is aged to finally obtain CeO2 nanocubes. This method is simple and easy, with high yield, and the obtained CeO2 nanocubes are of uniform size, high crystallinity and good dispersibility. However, this method inevitably produces nitrogen-containing high-salt wastewater (such as NaNO3), which requires further treatment. For example, a soluble cerium salt solution is mixed with an alkali solution without adding an organic solvent, a dispersant, or a surfactant to prepare nano CeO2 colloidal particles, which have a smaller particle size, and the obtained CeO2 particles have good dispersibility and particle consistency. However, the soluble cerium salt and the alkali solution selected in this process also produce high-salt wastewater during the reaction process. Patent CN116553596A discloses a CeO2 nanoparticle, a preparation method and application thereof. Using soluble Ce(NO3)3 as a raw material, concentrated ammonia water as a precipitant, a washing solvent is added, and ultrasonic dispersion is used to obtain CeO2 nanoparticles with a primary particle size of 3 to 6 nm. This method also produces nitrogen-containing high-salt wastewater. Therefore, the prior art generally has the disadvantages of complicated steps and the need to treat wastewater. It is necessary to develop a preparation process for nano CeO2 powder with low cost, simple preparation method and no high-salt wastewater discharge. Summary of the invention

[0004] In order to solve the technical problems in the prior art that high-cost soluble cerium salts are required as raw materials, the preparation method is complicated, and the amount of high-salt wastewater discharged is large, the present invention proposes an electrochemical preparation method for nano CeO2 powder. The invention directly uses solid cerium carbonate as a raw material for membrane electrolysis, and the product after electrolysis is hydrothermally treated to obtain nano CeO2 powder. The invention utilizes the membrane electrolysis process, the process is simple, the cost is low, the electrolyte and the solution after hydrothermal treatment can be recycled, there is no high-salt wastewater discharge, and finally obtains nano CeO2 powder with high purity, high crystallinity and uniform particle size distribution.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] An electrochemical preparation method of nano CeO2 powder comprises the following steps:

[0007] Step 1) Add Ce-containing 3+ An electrolyte, wherein a cation exchange membrane is provided between the cathode chamber and the anode chamber; then cerium carbonate powder is added to the anode chamber for electrolysis; during the electrolysis process, the electrolyte in the cathode chamber and the anode chamber is continuously subjected to ultrasonic treatment to obtain a Ce(OH)3 suspension in the cathode chamber;

[0008] Step 2) heating the Ce(OH)3 suspension and air in a closed reactor to react, filtering to obtain a precursor after the reaction is completed; and returning the filtered filtrate to the cathode chamber;

[0009] Step three) calcining the precursor to obtain the nano CeO2 powder.

[0010] Optionally, Ce in the electrolyte 3+ The concentration is 0.1~1.0mol / L.

[0011] Optionally, the electrolyte contains at least one of cerium chloride, cerium nitrate and cerium acetate.

[0012] Optionally, the solid-liquid ratio of the cerium carbonate powder added to the anode chamber in step 1) to the electrolyte in the anode chamber is 0.1 to 1.0 kg / L.

[0013] Optionally, the current density during the electrolysis process is 50-500 mA / cm 2 , the electrolysis temperature is 10~90℃.

[0014] Optionally, the volume of the Ce(OH)3 suspension added to the reactor in step 2) is 20 to 70% of the volume of the reactor.

[0015] Optionally, the temperature of the heating reaction in step 2) is 120-220° C. and the time is 1-24 hours.

[0016] Optionally, in the step 2), the precursor obtained by filtration is dried at a temperature of 70 to 110° C. for a time of 1 to 6 hours.

[0017] Optionally, in the step 3), the calcination temperature is 350-850° C. and the calcination time is 1-6 hours.

[0018] Preferably, in step 3), the calcination temperature is 350° C. and the calcination time is 1 h.

[0019] Preferably, in the step 3), the calcination temperature is 850° C. and the calcination time is 1 h.

[0020] Compared with the prior art, the present invention has the following advantages: (1) The present invention can prepare nano CeO2 powder with high crystallinity and uniform particle size distribution by a simple two-step method: electrolysis treatment-hydrothermal treatment method; (2) electrolysis is directly carried out using low-cost cerium carbonate as raw material, and the electrolysis process has a high degree of automation and is easy to realize industrial production; (3) The filtrate after the hydrothermal reaction is recycled, eliminating the problem of large amounts of ammonia nitrogen wastewater and high-salt wastewater that need to be treated in the process of converting soluble cerium salt into CeO2 in the prior art. Therefore, the preparation method is simple to operate, has low product cost, and a green and environmentally friendly process flow, has considerable economic benefits, and meets the needs of large-scale commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0022] Figure 1 is a schematic diagram of an electrolysis device;

[0023] Figure 2 is the X-ray diffraction pattern of the powder in Examples 1 to 3;

[0024] Figure 3 is a scanning electron microscope image of the powder in Examples 1 to 3. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0026] The preparation method is described in detail below with reference to different embodiments.

[0027] Embodiment 1:

[0028] The electrolysis device used in the present invention comprises: a cell body, a cathode chamber, an anode chamber, a cation exchange membrane, an ultrasonic cleaning machine, and a DC power supply. A cation exchange membrane is arranged inside the cell body, and the cation exchange membrane divides the cell body into an anode chamber and a cathode chamber, wherein the anode chamber is connected to the positive electrode of the DC power supply, and the cathode chamber is connected to the negative electrode of the DC power supply.

[0029] Step (1): prepare 0.1 mol / L cerium nitrate solution as cathode liquid and anode liquid, then add 0.1 kg / L cerium carbonate powder to the anode liquid; place the membrane electrolytic cell in an ultrasonic cleaning machine and turn on the ultrasound; 2The electrolysis was carried out for 120 min at a current density of 20°C, and a Ce(OH)3 suspension was obtained in the cathode chamber;

[0030] Step (2): The suspension in step (1) of Example 1 was transferred to a polytetrafluoroethylene-lined autoclave, deionized water was added to 2 / 3 of the autoclave for hydrothermal treatment, and heated at a constant temperature of 120° C. for 6 h;

[0031] Step (3): The solid-liquid mixture after the hydrothermal treatment in step (2) of Example 1 is filtered, and the filtrate is circulated back to the cathode chamber; the obtained solid is dried at 70°C for 6h, and then calcined at 350°C for 1h to finally obtain nano CeO2 powder.

[0032] In the above process, the reaction occurring during the electrolysis process is:

[0033] Anode main reaction: 2H2O-4e - =O2↑+4H + (1)

[0034] 6H + + Ce2(CO3)3 = 2Ce 3+ + 3H2O + 3CO2↑ (2)

[0035] Cathode main reaction: 2H2O+2e - =H2↑+2OH - (3)

[0036] Ce 3+ + 3OH - = Ce(OH)3↓ (4)

[0037] Ce 3+ Through the cation exchange membrane, it continuously enters the cathode chamber from the anode chamber. The overall reaction is:

[0038] 2Ce2(CO3)3 + 12H2O = 4Ce(OH)3↓ + 3O2↑ + 6H2↑+ 6CO2↑ (5)

[0039] The reactions that occur during the hydrothermal process are:

[0040] 4Ce(OH)3 + O2 = 4CeO2 + 6H2O (6)

[0041] During the calcination process, the crystallinity and particle size of CeO2 will change. Under low temperature conditions, the crystallinity of CeO2 is low and the particle size is small; as the temperature rises, the crystallinity of CeO2 increases and the particle size becomes larger; if the temperature continues to rise, sintering will occur, causing the CeO2 particle size to further increase. Therefore, by adjusting the calcination temperature, the crystallinity and particle size of CeO2 can be precisely controlled to meet the needs of different application fields.

[0042] Example 2

[0043] Step (1): prepare 0.5 mol / L cerium acetate solution as cathode liquid and anode liquid, then add 0.5 kg / L cerium carbonate powder to the anode liquid; place the membrane electrolytic cell in an ultrasonic cleaning machine and turn on the ultrasound; 2 The electrolysis was carried out for 60 min at a current density of 40°C, and a Ce(OH)3 suspension was obtained in the cathode chamber;

[0044] Step (2): The suspension in step (1) of Example 2 was transferred to a polytetrafluoroethylene-lined autoclave, deionized water was added to 2 / 3 of the autoclave for hydrothermal treatment, and heated at a constant temperature of 160° C. for 24 h;

[0045] Step (3): The solid-liquid mixture after the hydrothermal treatment in step (2) of Example 2 is filtered, and the filtrate is circulated back to the cathode chamber; the obtained solid is dried at 90°C for 2h, and then calcined at 550°C for 2h to finally obtain nano CeO2 powder.

[0046] Example 3

[0047] Step (1): prepare 1.0 mol / L cerium chloride solution as cathode liquid and anode liquid, then add 1.0 kg / L cerium carbonate powder to the anode liquid; place the membrane electrolytic cell in an ultrasonic cleaning machine and turn on the ultrasound; at 500 mA / cm 2 The electrolysis was carried out for 60 min at a current density of 80°C, and a Ce(OH)3 suspension was obtained in the cathode chamber.

[0048] Step (2): The suspension in step (1) of Example 3 was transferred to a polytetrafluoroethylene-lined autoclave, deionized water was added to 2 / 3 of the autoclave for hydrothermal treatment, and heated at a constant temperature of 180° C. for 6 h;

[0049] Step (3): The solid-liquid mixture after hydrothermal treatment in step (2) of Example 3 is filtered, and the filtrate is circulated back to the cathode chamber; the obtained solid is dried at 110°C for 1 hour, and then calcined at 850°C for 1 hour to finally obtain nano CeO2 powder.

[0050] The CeO2 powder finally obtained in the above embodiments was subjected to crystal phase and morphology test analysis, and the test results were as follows: Figure 2 and Figure 3 shown.

[0051] Depend on Figure 2 It can be seen that Examples 1-3 all successfully synthesized CeO2 crystal phases, and the crystallinity of the crystal phase increased with the increase of calcination temperature. Figure 3 It can be seen that the primary particle sizes of the CeO2 nanoparticles in Examples 1-3 are 15nm, 45nm and 110nm respectively, and the particle surface is rough, presenting a porous structure. Compared with the prior art (CN115259205A, CeO2 nanoparticles 20-50nm, smooth surface), the CeO2 nanoparticles of the present application have a higher specific surface area and roughness, and have obvious application advantages in mechanical polishing, catalysis and other fields.

[0052] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. An electrochemical preparation method of nano CeO2 powder, characterized in that: The following steps are involved: Step 1) Add Ce-containing 3+ An electrolyte, wherein a cation exchange membrane is provided between the cathode chamber and the anode chamber; then cerium carbonate powder is added to the anode chamber for electrolysis; during the electrolysis process, the electrolyte in the cathode chamber and the anode chamber is continuously subjected to ultrasonic treatment to obtain a Ce(OH)3 suspension in the cathode chamber; Step 2) heating the Ce(OH)3 suspension and air in a closed reactor to react, filtering to obtain a precursor after the reaction is completed; and returning the filtered filtrate to the cathode chamber; Step three) calcining the precursor to obtain the nano CeO2 powder.

2. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: Ce in the electrolyte 3+ The concentration is 0.1~1.0mol / L.

3. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: The electrolyte contains at least one of cerium chloride, cerium nitrate and cerium acetate.

4. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: In the step 1), the solid-to-liquid ratio of the cerium carbonate powder added to the anode chamber to the electrolyte in the anode chamber is 0.1 to 1.0 kg / L.

5. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: The current density during the electrolysis process is 50-500 mA / cm 2 , the electrolysis temperature is 10~90℃.

6. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: In the step 2), the volume of the Ce(OH)3 suspension added to the reactor is 20-70% of the volume of the reactor.

7. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: The temperature of the heating reaction in the step 2) is 120-220° C. and the time is 1-24 hours.

8. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: In the step 2), the precursor obtained by filtration is dried at a temperature of 70 to 110° C. for 1 to 6 hours.

9. The electrochemical preparation method of nano CeO2 powder according to claim 1, characterized in that: In the step 3), the calcination temperature is 350-850° C. and the calcination time is 1-6 hours.

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