A method for preparing high-performance rare earth polishing powder from lanthanum cerium sulfate

Abstract

The application discloses a method for preparing high-performance rare earth polishing powder from lanthanum cerium sulfate, and belongs to the technical field of rare earth polishing powder preparation. The method mainly comprises the following steps: precipitating lanthanum cerium sulfate solution and magnesium bicarbonate solution in a parallel flow feeding mode. The precipitated product is aged, washed, once separated from liquid, beaten, fluorinated, twice separated from liquid, dried at low temperature, calcined at high temperature, and broken and classified by air flow milling, so that a rare earth polishing powder product with good polishing and etching capacity is successfully prepared. The application selects lanthanum cerium sulfate as the original liquid, has a short separation process, low transformation cost, and is easy to popularize and promote in industrialization. The residual part of sulfate in the precipitated product can effectively adjust the hardness of the rare earth polishing powder particles and homogenize the morphology, so as to improve the cutting performance of the polishing powder. The magnesium salt wastewater and the fluorination wastewater generated in the application can be all reused to the production line for preparing the rare earth polishing powder, and zero wastewater discharge is realized in the whole process.

Description

A method for preparing high-performance rare earth polishing powder using lanthanum and cerium sulfate Technical Field

[0001] This invention relates to the field of rare earth polishing powder preparation technology, specifically a method for preparing high-performance rare earth polishing powder using lanthanum and cerium sulfate. Background Technology

[0002] As a commonly used polishing material, rare earth polishing powder has many advantages, such as uniform particle size, moderate hardness, high grinding efficiency, long cutting life, good polishing quality, and environmental friendliness and ease of cleaning. It is widely used in many fields, including mobile phone cover plates, optical glass, LCD displays, crystal ornaments, integrated circuits, and precision optical components. In recent years, high-performance rare earth polishing powder has gradually evolved into a key polishing material in the electronics and microelectronics information industry. With the continuous development and expansion of the LCD and 3C industries, this has not only greatly increased the added value of rare earth products but also promoted the development of my country's rare earth industry to a higher level.

[0003] The raw materials for rare earth polishing powder production vary, and the preparation processes differ significantly. Developing a polishing powder preparation process that achieves both high polishing precision and high erosion yield while maintaining low production costs and a short process flow is a continuous endeavor. The selection of raw materials and precipitants in the rare earth polishing powder production process often significantly determines the type of wastewater and its treatment method. Achieving a green polishing powder preparation process is a crucial challenge that urgently needs to be addressed now and for some time to come. Currently, the preparation of rare earth polishing powder precursors (taking lanthanum-cerium carbonate as an example) utilizes a third-generation acid process (taking Baotou mixed rare earth ore as an example). Its main steps include concentrated sulfuric acid-enhanced roasting, water leaching, neutralization and impurity removal (MgO), and P... 507 / P 204 Extraction and separation, ammonium bicarbonate precipitation, etc. However, the introduction of ammonium bicarbonate will inevitably generate a large amount of ammonia nitrogen wastewater, and the environmental treatment cost of ammonia nitrogen wastewater is high and the emission standards are high, which is not suitable for the concept of developing green and friendly rare earth polishing powder under the dual carbon background.

[0004] Chinese patent CN 112080207 A discloses a rare earth polishing powder and its preparation method. This patent precisely calculates the amount of Y₂O₃ added, reducing the lattice constant of CeO₂. The formation of oxygen vacancies significantly enhances the wear resistance, grinding force, and reactivity of the polishing powder. In preparing rare earth fluorocarbonates, this patent uses lanthanum chloride, samarium chloride, and yttrium chloride solutions as raw materials, adds phosphoric acid and hydrofluoric acid for fluorination, then adds cerium chloride solution, and selects ammonium bicarbonate solution as the precipitant. However, this patent has the following drawbacks: firstly, the extraction and conversion production using rare earth chloride as raw material has high costs; secondly, using ammonium bicarbonate solution as the precipitant inevitably generates a large amount of ammonia nitrogen wastewater in the solid-liquid separation process of the precipitated product, and the treatment of ammonia nitrogen wastewater remains a challenging problem.

[0005] Chinese patent CN 107674592 A discloses a samarium-cerium rare earth polishing powder and its preparation method. The samarium-cerium rare earth polishing powder prepared by this patent, when measured on an RL-13B polishing machine, exhibits a polishing rate approximately 30% higher than that of normal lanthanum-cerium polishing powder. Its polishing yield is comparable to that of the lanthanum-cerium polishing powder in comparative tests. Furthermore, compared to other rare earth polishing powders, it significantly improves the ease of cleaning the polished glass and has a longer service life. In a specific embodiment, the patent first adds 200L of cerium chloride solution and 60L of samarium chloride solution to a 1000L reactor, then adds 11Kg of hydrofluoric acid, followed by the addition of ammonium bicarbonate solution until precipitation is complete. However, this patent also has the shortcoming of not fully considering the economic and environmental benefits of the polishing powder preparation process. Summary of the Invention

[0006] The purpose of this invention is to address a series of problems in the current lanthanum-cerium polishing powder preparation process, such as the long process of preparing the original rare earth chloride solution (extraction transformation), high cost, high cost of environmental wastewater recycling, difficulty in achieving wastewater discharge standards, and long preparation process. This invention provides a method for preparing high-performance rare earth polishing powder using lanthanum-cerium sulfate, thereby solving the problems mentioned in the background art.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for preparing high-performance rare earth polishing powder using lanthanum and cerium sulfate includes the following steps:

[0009] Step 1: Add the lanthanum sulfate and cerium sulfate solution and the magnesium bicarbonate solution together in a feeding manner to allow them to undergo a precipitation reaction;

[0010] Step 2: The precipitated product from Step 1 is subjected to a series of processes including static aging, washing, primary solid-liquid separation, water addition and pulping, fluorination reaction, secondary solid-liquid separation, low-temperature drying, high-temperature calcination, and air jet mill crushing and classification to obtain a rare earth polishing powder with polishing capacity.

[0011] Step 3: The magnesium salt wastewater, the product of the first solid-liquid separation obtained in Step 2, can be reprocessed into magnesium bicarbonate solution through alkali conversion and carbonation processes, which can be recycled in Step 1.

[0012] Step 4: Collect the fluorination wastewater, the secondary solid-liquid separation product obtained in Step 2, which can be used for pulping in the next batch of fluorination reaction to reduce the amount of tap water used.

[0013] Step 5: After preparing the rare earth polishing powder obtained in Step 2 into a slurry, evaluate its polishing performance using K9 glass with a specification of Φ75*15mm, and use polishing powder prepared with lanthanum chloride and cerium chloride as raw materials for comparative grinding performance testing.

[0014] Furthermore, in step one, the temperature of the precipitation reaction is controlled at 25℃~35℃, and the pH of the precipitation reaction system is controlled at 4~5.

[0015] Furthermore, in step two, the settling and aging time is controlled to be 1.5h to 2.5h; after the aging is completed, the precipitated product needs to be washed 2 to 3 times.

[0016] Furthermore, in step two, calcium oxide is added to the magnesium salt wastewater, the product of the first solid-liquid separation, to generate calcium hydroxide. Then, carbon dioxide is introduced to carbonize it, resulting in a high-purity magnesium bicarbonate alkaline solution. This solution is then recycled and reused as a precipitant.

[0017] Furthermore, in step two, the solid-liquid ratio is maintained at 1:1 during the water addition and pulping process, and the volume of hydrofluoric acid added during the fluorination reaction is controlled at 5.5% to 7% of the total rare earth content, and stirring continues for a certain period of time after the acid addition is completed.

[0018] Furthermore, in step two, the low-temperature drying process uses an XSG-1200 type rapid rotary flash dryer to dry and remove water from the fluoride salt at a low temperature, with the temperature controlled between 250℃ and 350℃; the high-temperature calcination involves calcining the obtained semi-oxide in a roller kiln at a high temperature, with the temperature controlled between 930℃ and 1010℃; in both the low-temperature drying and high-temperature calcination stages, the exhaust gas is treated through bag filters and spray towers.

[0019] Furthermore, in step two, the air jet mill crushing and grading process uses an OLM-3.5 type air jet mill to crush and grade the rare earth oxides after high-temperature calcination. The resulting lanthanum cerium rare earth polishing powder has a central particle size of 1.0μm to 2.5μm.

[0020] Furthermore, in step five, the rare earth polishing powder is prepared by controlling the solid-liquid ratio to 1:8 to 10 during the slurry preparation. The polishing time for each polishing session is 30 minutes. The mass difference before and after polishing is measured, and the particle size change of the polishing powder particles before and after each polishing session is statistically analyzed.

[0021] Furthermore, in step two, the rare earth polishing powder has a microstructure of polygons with certain angles, and its grain size is distributed between 2502 and 3502.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] The use of lanthanum-cerium sulfate solution in this invention significantly simplifies the subsequent extraction and transformation process. Its low raw material cost and the ability of residual sulfate ions to control the hardness of the polishing powder make it the preferred raw material solution for preparing high-performance rare earth polishing powder. In this invention, the magnesium salt wastewater generated from the primary solid-liquid separation and the fluorination wastewater generated from the secondary solid-liquid separation can be completely recycled into the production line for preparing high-performance rare earth polishing powder, achieving zero wastewater discharge throughout the entire process. This demonstrates both the economic efficiency and environmental friendliness of this invention. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the process of the present invention.

[0025] Figure 2 shows the macroscopic microstructure of the two polishing powders prepared in Example 1 of this invention.

[0026] Figure 3 is a comparative analysis of the polishing performance of the two polishing powders prepared in Example 1 of this invention.

[0027] Figure 4 is a comparison of white light interference 3D images of the K9 glass surface after grinding tests using the two polishing powders prepared in Example 1 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] Example

[0031] This embodiment provides a method for preparing high-performance rare earth polishing powder using lanthanum and cerium sulfate, including the following steps:

[0032] Step 1: Add the lanthanum sulfate and cerium sulfate solution and the magnesium bicarbonate solution together in a feeding manner to allow them to undergo a precipitation reaction;

[0033] Step 2: The precipitated product from Step 1 is subjected to a series of processes including static aging, washing, primary solid-liquid separation, water addition and pulping, fluorination reaction, secondary solid-liquid separation, low-temperature drying, high-temperature calcination, and air jet mill crushing and classification to obtain a rare earth polishing powder with polishing capacity.

[0034] Step 3: The magnesium salt wastewater, the product of the first solid-liquid separation obtained in Step 2, can be reprocessed into magnesium bicarbonate solution through processes such as alkali conversion and carbonation, which can be recycled in Step 1.

[0035] Step 4: Collect the fluorination wastewater, the secondary solid-liquid separation product obtained in Step 2, which can be used for pulping in the next batch of fluorination reaction to reduce the amount of tap water used.

[0036] Step 5: After preparing the rare earth polishing powder obtained in Step 2 into a slurry, evaluate its polishing performance using K9 glass with a specification of Φ75*15mm, and use polishing powder prepared with lanthanum chloride and cerium chloride as raw materials for comparative grinding performance testing.

[0037] In step one, the temperature of the precipitation reaction is controlled at 25℃~35℃, and the pH of the precipitation reaction system is controlled at 4~5. The main chemical components of the lanthanum-cerium sulfate solution are La: 24.236%~34.945%, Ce: 64.92%~75.01%, Pr: <0.01%, Nd: <0.01%; its rare earth content is 21.3%~26.5%, and its pH is 0.64~0.79. The magnesium bicarbonate solution has a content of 5.10g / L~5.63g / L (calculated as MgO) and a pH of 6.53~6.95.

[0038] In step two, the settling and aging time is controlled to be 1.5h to 2.5h; after the aging is completed, the precipitated product needs to be washed 2 to 3 times.

[0039] In step two, calcium oxide is added to the magnesium salt wastewater, the product of the first solid-liquid separation, to generate calcium hydroxide. Then, carbon dioxide is introduced to carbonize it, resulting in a high-purity magnesium bicarbonate alkaline solution. This solution is then recycled and reused as a precipitant.

[0040] In step two, the solid-liquid ratio is maintained at 1:1 during the water addition and pulping process, and the volume of hydrofluoric acid added during the fluorination reaction is controlled at 5.5% to 7% of the total rare earth content, and stirring is continued for a certain period of time after the acid addition is completed.

[0041] In step two, the low-temperature drying process uses an XSG-1200 type rapid rotary flash dryer to dry and remove water from the fluoride salt at a low temperature, with the temperature controlled between 250℃ and 350℃; the high-temperature calcination involves calcining the obtained semi-oxide in a roller kiln at a high temperature, with the temperature controlled between 930℃ and 1010℃; in both the low-temperature drying and high-temperature calcination stages, the exhaust gas is treated through bag filters and spray towers.

[0042] In step two, the air jet mill crushing and grading process uses an OLM-3.5 type air jet mill to crush and grade the rare earth oxides after high-temperature calcination. The resulting lanthanum cerium rare earth polishing powder has a central particle size of 1.0μm to 2.5μm.

[0043] In step two, the mass percentage content of the main non-rare earth impurities in the obtained rare earth polishing powder is as follows: sulfur (S): 0.68-1.1%, calcium oxide (CaO): 0.45-0.68%, magnesium oxide (MgO): 0.27-0.42%, and phosphate (PO4). 3- : 0.33~0.55%; central grain size is 1.0μm~2.5μm, the microstructure is a polygon with certain angularity, and the grain size is distributed in 2502~3502.

[0044] In step four, the non-rare earth impurities in the recyclable fluorinated wastewater are: CaO: 0.55-15 mg / L, magnesium oxide (MgO): 0.69-11.5 mg / L, fluoride ions (F-): 0.15-1.0%; and its pH is 6.03-6.99.

[0045] In step five, the rare earth polishing powder is prepared by controlling the solid-liquid ratio to 1:8 to 10 during the slurry preparation. The polishing time for each polishing session is 30 minutes. The mass difference before and after polishing is measured, and the particle size change of the polishing powder particles before and after each polishing session is statistically analyzed.

[0046] Specifically, the performance evaluation of the rare earth polishing powder in step five involves using an M200 precision planar grinding and polishing machine and an optical 3D surface profilometer to assess the polishing performance of the prepared rare earth polishing powder. K9 glass (Φ75*15mm) is used for polishing tests. The solid-liquid ratio should be maintained at 1:8, 1:9, or 1:10 when preparing the grinding slurry, and no additives are used in the preparation of the polishing slurry. Grinding tests are performed every 30 minutes, and the weight difference of the K9 glass before and after polishing is measured. The particle size of the polishing slurry before and after polishing is measured using a Malvern 2000 particle size analyzer, and the scratches on the glass surface are statistically analyzed using a high-definition microscope. After accumulating four grinding cycles, the total amount of erosion is calculated, and the roughness of the polished surface is evaluated using a 3D surface profilometer.

[0047] In this embodiment, a lanthanum-cerium sulfate solution, obtained from the pre-classification of Baotou mixed rare earth ore through concentrated sulfuric acid-enhanced roasting, water leaching, neutralization and impurity removal, and P507 transformation, is used as the raw material for preparing high-performance rare earth polishing powder. In this method, a magnesium bicarbonate solution, obtained from the product (magnesium sulfate wastewater) separated from the smelting of Baotou mixed rare earth ore through alkali conversion and carbonization, is used as the precipitant for preparing high-performance rare earth polishing powder. First, compared to methods using lanthanum-cerium rare earth chloride as the raw material for preparing rare earth polishing powder, the choice of lanthanum-cerium sulfate solution significantly reduces the cost of further extraction and transformation to lanthanum-cerium rare earth chloride, and also greatly simplifies the process. Second, the residual sulfate ions in the precipitate can regulate the hardness of the polishing powder, which can significantly improve its grinding performance. Furthermore, compared to the method of preparing lanthanum-cerium polishing powder using ammonium bicarbonate as a precipitant, the magnesium salt wastewater precipitated by magnesium bicarbonate solution can be recycled and reused, truly achieving zero wastewater discharge in the polishing powder preparation process. This demonstrates both the economic efficiency and the green environmental protection of this invention.

[0048] Example 1

[0049] Step 1: In a 12m 3 The selected lanthanum sulfate and cerium bicarbonate solutions (with a seed crystal addition of 5%) were continuously added to a steel-lined fiberglass reaction tank in a feed-by-feed manner, allowing a precipitation reaction to occur at room temperature. The lanthanum sulfate solution had the following chemical composition: La: 34.84%, Ce: 65.03%, Pr: <0.01%, Nd: <0.01%, rare earth content: 23.5%, and pH: 0.72. The magnesium bicarbonate solution had a content of 5.33 g / L (calculated as MgO) and a pH: 6.85. To increase the crystal nucleation rate during the precipitation reaction, the stirring frequency should be maintained at a relatively high speed, adjusted according to the actual liquid level. The feeding ratio of the two liquids was strictly controlled, specifically maintaining the pH of the precipitation reaction system at 4.5.

[0050] The chemical composition of the lanthanum chloride solution used in the comparative experiment was approximately La: 35% and Ce: 65%. The ammonium bicarbonate precipitation of lanthanum chloride was performed using the existing precipitation process of Gansu Rare Earth Company.

[0051] Step 2: After the precipitation is completed, in order to ensure the reaction is complete, it should be stirred continuously for more than 30 minutes, and then allowed to stand and age for 1.5 hours. After aging, tap water is added for washing, and the washing is performed twice. After washing, the sulfate content in the carbonate is 0.68%.

[0052] Step 3: Add slaked lime (CaO concentration of 100.5 g / L) to the magnesium salt wastewater after solid-liquid separation for alkali conversion. The alkali conversion reaction is MgSO4 + Ca(OH)2 = Mg(OH)2 + CaSO4, and the conversion time is 35 min. Then, CO2 gas is passed into the alkali conversion slurry at a flow rate of not less than 100 L / h for carbonization, and the carbonization temperature is 25℃. This allows for the preparation of a Mg(HCO3)2 solution with a content of 5.33 g / L (calculated as MgO) for the next batch of precipitation.

[0053] Step 4: Perform fluorination by pulping at a solid-liquid ratio of 1:1. The amount of hydrofluoric acid added is 5.5% of the total amount of carbonate rare earth oxides. The acid addition time needs to be more than 40 minutes. After the acid addition is completed, continue stirring for 30 minutes.

[0054] Step 5: Solid-liquid separation of the fluorination product is performed by plate and frame filtration, with a filtration time of not less than 25 minutes per plate. The separated fluorination wastewater contains extremely low levels of non-rare earth impurities (calcium, magnesium, aluminum, etc.) (calcium: 8.5 mg / L, magnesium: 11 mg / L, aluminum: 3.5 mg / L), and has a pH of 6.88, making it perfectly suitable as tap water for use in the next batch of pulping.

[0055] Step 6: The fluoride salts after plate and frame filtration were dried at a low temperature (300℃) using an XSG-1200 rapid rotary flash dryer. The total rare earth content of the resulting semi-oxide was 70.5%. The semi-oxide was then calcined at a high temperature (980℃) using a roller kiln (50m). After calcination, the total rare earth content of the oxide was 91.5%, and the fluorine content was 3.94%.

[0056] Step 7: The rare earth oxides are crushed and classified using an OLM-3.5 airflow crusher. In this embodiment, the center particle size of the rare earth polishing powder after classification is 1.8 μm and the grain size is 3022.

[0057] Step 8: As shown in Figures 1-4, the polishing performance of the prepared rare earth polishing powder was evaluated using an M200 precision planar grinding and polishing machine and an optical 3D surface profilometer. The polishing performance of lanthanum-cerium rare earth polishing powder prepared under the same conditions using lanthanum-cerium rare earth chloride as the raw material and ammonium bicarbonate as the precipitant was compared with that of the powder. A polishing slurry with a solid-liquid ratio of 1:10 was prepared for grinding tests. The initial polishing capacity of the rare earth polishing powder prepared in this invention was 99 mg·30 min. -1 The initial polishing capacity of rare earth polishing powder of the same particle size, prepared by precipitating lanthanum and cerium rare earth chloride with ammonium bicarbonate for reference, was 84 mg·30 min. -1After 120 minutes of cumulative grinding, the rare earth polishing powder prepared by this invention achieved an etching amount of 352 mg, while the rare earth polishing powder prepared by precipitating lanthanum, cerium, and rare earth chloride with ammonium bicarbonate achieved an etching amount of 299 mg. With increasing grinding time, the center particle size of the two lanthanum, cerium, and rare earth polishing powders decreased to 1.658 μm and 1.503 μm, respectively, indicating that the polishing powder prepared by this invention has a better grinding life.

[0058] The surface of K9 glass after four polishing cycles using two different polishing powders was observed under a high-definition microscope. No obvious scratches were found, indicating good polishing quality. 3D white light interferometry images and profile curves obtained using an optical surface profilometer showed that the surface roughness Sa of the polishing powder prepared by the method of this invention was 1.642 nm after polishing K9 glass, while the surface roughness Sa of the polishing powder prepared using lanthanum cerium chloride (used as a reference) was 2.174 nm.

[0059] Example 2

[0060] Step 1: In a 12m 3 The selected lanthanum sulfate and cerium bicarbonate solutions (with a seed crystal content of 6%) were continuously added to a steel-lined fiberglass reaction tank in a feed-by-feed manner, allowing a precipitation reaction to occur at room temperature. The lanthanum sulfate and cerium sulfate solution had the following chemical composition: La: 24.964%, Ce: 75.03%, Pr: <0.01%, Nd: <0.01%, rare earth content: 24.11%, and pH: 0.76. The magnesium bicarbonate solution had a content of 5.28 g / L (calculated as MgO) and a pH of 6.66. The pH of the precipitation reaction system was maintained at 4.0.

[0061] The chemical composition of the lanthanum chloride solution used in the comparative experiment was approximately La: 25% and Ce: 75%. The ammonium bicarbonate precipitation of lanthanum chloride was performed using the existing precipitation process of Gansu Rare Earth Company.

[0062] Step 2: After the precipitation is complete, to ensure a thorough reaction, continue stirring for at least 30 minutes, then allow it to stand and age for 2 hours. After aging, add tap water for washing, repeating the washing process three times. After washing, the sulfate content in the carbonate should be 0.73%.

[0063] Step 3: Add slaked lime (CaO concentration of 100.5 g / L) to the magnesium salt wastewater after solid-liquid separation for alkali conversion for 35 min. Then, introduce CO2 gas into the alkali conversion slurry at a flow rate of not less than 100 L / h for carbonization at a temperature of 25℃. This will prepare a Mg(HCO3)2 solution for the next batch of precipitation, with a content of approximately 5.30 g / L (calculated as MgO).

[0064] Step 4: Perform fluorination by pulping at a solid-liquid ratio of 1:1. The amount of hydrofluoric acid added is 6% of the total amount of carbonate rare earth oxides. The acid addition time needs to be more than 40 minutes. After the acid addition is completed, continue stirring for 30 minutes.

[0065] Step 5: Solid-liquid separation of the fluorination product is performed by plate and frame filtration, with a filtration time of not less than 25 minutes per plate. The separated fluorination wastewater contains extremely low levels of non-rare earth impurities (calcium, magnesium, aluminum, etc.) (calcium: 14 mg / L, magnesium: 26 mg / L, aluminum: 3.9 mg / L), and has a pH of 6.83, making it perfectly suitable as tap water for use in the next batch of pulping.

[0066] Step 6: The fluoride salts after plate and frame filtration were dried at a low temperature (300℃) using an XSG-1200 rapid rotary flash dryer. The total rare earth content of the resulting semi-oxide was approximately 69.98%. The semi-oxide was then calcined at a high temperature (1010℃) using a roller kiln (50m). After calcination, the total rare earth content of the oxide was 95.5%, and the fluorine content was 3.68%.

[0067] Step 7: The rare earth oxides are crushed and classified using an OLM-3.5 airflow crusher. In this embodiment, the center particle size of the rare earth polishing powder after classification is 1.812 μm and the grain size is 3362.

[0068] Step 8: The polishing performance of the two rare earth polishing powders prepared was evaluated using an M200 precision planar grinding and polishing machine and an optical 3D surface profilometer. A polishing slurry with a solid-liquid ratio of 1:9 was prepared for grinding tests. The initial polishing capacity of the rare earth polishing powder prepared in this invention was 101 mg·30 min. -1 The initial polishing capacity of rare earth polishing powder of the same particle size, prepared by precipitating lanthanum and cerium rare earth chloride with ammonium bicarbonate for reference, was 90 mg·30 min. -1 After 120 minutes of cumulative grinding, the rare earth polishing powder prepared in this invention achieved an etching amount of 360 mg, while the rare earth polishing powder prepared by precipitating lanthanum and cerium rare earth chloride with ammonium bicarbonate achieved an etching amount of 312 mg. High-resolution microscopy was used to observe the surface of K9 glass after four grinding cycles with both polishing powders, revealing no obvious scratches and indicating good polishing quality. 3D white light interferometry images and contour curves obtained using an optical surface profilometer showed that the surface roughness Sa of the polishing powder prepared in this invention after polishing K9 glass was 2.012 nm, while the surface roughness Sa of the polishing powder prepared with lanthanum and cerium chloride (used as a reference) after polishing K9 glass was 2.619 nm.

Claims

1. A method for preparing high-performance rare earth polishing powder using lanthanum and cerium sulfate, characterized in that, Includes the following steps: Step 1: Lanthanum sulfate and cerium sulfate solution and magnesium bicarbonate solution are added together in a feeding manner to induce a precipitation reaction. Step 2: The precipitated product from Step 1 is subjected to a series of processes including settling and aging, washing, primary solid-liquid separation, water addition and slurrying, fluorination reaction, secondary solid-liquid separation, low-temperature drying, high-temperature calcination, and air jet mill crushing and classification to obtain a rare earth polishing powder with high polishing properties. The low-temperature drying process uses an XSG-1200 type rapid rotary flash dryer to dry the fluoride salts at a low temperature of 250℃~350℃. The high-temperature calcination involves using a roller kiln to calcine the obtained semi-oxides at a high temperature of 930℃~1010℃. During both the low-temperature drying and high-temperature calcination stages, the exhaust gas is treated through bag filters and spray towers. Step 3: Calcium oxide is added to the magnesium salt wastewater from the primary solid-liquid separation to generate calcium hydroxide, which is then carbonized by introducing carbon dioxide to obtain a high-purity product. A magnesium bicarbonate alkaline solution of a certain degree is used again as a precipitant for recycling in step one; Step four: The fluorination wastewater obtained from the secondary solid-liquid separation in step two is collected and supplied to the next batch of fluorination reaction for slurrying to reduce the amount of tap water used; Step five: The rare earth polishing powder obtained in step two is slurried and then polished using K9 glass with a specification of Φ75*15mm, and polishing performance is evaluated using polishing powder prepared with lanthanum cerium chloride as raw material for grinding performance comparison test; In step one, the amount of seed crystals added in the precipitation reaction is controlled to be 5%~10% of the total rare earth, the temperature of the precipitation reaction is controlled to be 25℃~35℃, and the pH of the precipitation reaction system is controlled to be 4~5; In step two, the solid-liquid ratio is maintained at 1:1 in the water addition and slurrying process, and the volume of hydrofluoric acid added in the fluorination reaction is controlled to be 5.5%~7% of the total rare earth, and stirring is continued for a certain period of time after the acid addition is completed.

2. The method for preparing high-performance rare earth polishing powder from lanthanum and cerium sulfate according to claim 1, characterized in that: In step two, the settling and aging time is controlled to be 1.5h to 2.5h; after the aging is completed, the precipitated product needs to be washed 2 to 3 times.

3. The method for preparing high-performance rare earth polishing powder from lanthanum and cerium sulfate according to claim 1, characterized in that: In step two, the air jet mill crushing and grading process uses an OLM-3.5 type air jet mill to crush and grade the rare earth oxides after high-temperature calcination. The resulting lanthanum cerium rare earth polishing powder has a central particle size of 1.0μm~2.5μm.

4. The method for preparing high-performance rare earth polishing powder from lanthanum and cerium sulfate according to claim 1, characterized in that: In step five, the rare earth polishing powder is prepared by controlling the solid-liquid ratio to 1:8~10 during the slurry preparation. The polishing time for each polishing session is 30 minutes. The mass difference before and after polishing is measured, and the particle size change of the polishing powder particles before and after each polishing session is statistically analyzed.

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