Method for removing silicon from yttrium lutetium silicate leach

Abstract

The application discloses a method for removing silicon from yttrium lutetium silicate leaching solution, which comprises the following steps: firstly, mixing yttrium lutetium silicate waste with flake alkali uniformly, then baking, adding hot water to stir and react, and filtering to obtain rare earth hydroxide precipitate; then, washing the obtained rare earth hydroxide precipitate with sodium hydroxide solution for 2-3 times; then, placing the treated rare earth hydroxide precipitate in a reaction container, adding a small amount of pure water to stir, heating to 70-90 DEG C under water bath condition, and then keeping constant temperature, then slowly adding hydrochloric acid to dissolve the rare earth hydroxide precipitate to obtain a mixed solution, filtering to remove silicic acid colloid to obtain rare earth leaching solution; then, using an extractant prepared from N235, isooctanol and kerosene to extract the rare earth leaching solution to remove impurity iron, then heating and concentrating to make sodium chloride in the solution precipitate, filtering to remove the precipitated sodium chloride, and finally obtaining pure lutetium yttrium chloride solution. The application can effectively solve the problem that the content of silicon impurities in the yttrium lutetium silicate leaching solution is high and cannot be effectively removed.

Description

Technical Field

[0001] This invention belongs to the field of rare earth recycling technology, specifically relating to a method for removing silicon from yttrium silicate leaching solution. Background Technology

[0002] Lutetium yttrium silicate is a high-performance scintillation crystal used in large-scale nuclear medicine equipment and other high-end devices, boasting the most advanced and widely applied technology internationally. It is a crucial raw material for various radioactive detection, medical, and aerospace applications. For example, lutetium yttrium silicate scintillation crystal (LYSO) is considered the best-performing inorganic scintillation crystal material overall and is an ideal replacement for NaI(Tl) and BGO in SPECT and PET applications. However, the production and application of lutetium yttrium silicate crystals generate at least 20% scrap material. To achieve efficient and comprehensive utilization of rare earth resources and environmentally friendly development, the valuable rare earth elements in lutetium yttrium silicate waste are recycled.

[0003] Currently, the common method for recovering rare earth elements from lutetium yttrium silicate waste is acid leaching. For example, Chinese invention patent application CN201910693691.0, entitled "A Method for Recovering Rare Earth Elements from Cerium-Doped Luttium Yttrium Silicate Waste," discloses a method for recovering rare earth elements from lutetium yttrium silicate waste, which includes the following steps: mixing lutetium yttrium silicate waste with an inorganic alkaline reagent and performing alkaline fusion to obtain an enriched material; mixing the enriched material with an acid solution and performing acid dissolution to obtain an acid leaching solution; extracting the acid leaching solution with an extractant solution to obtain a rare earth extract; and back-extracting the rare earth extract to obtain recovered rare earth materials; wherein the extractant solution comprises a mixed solution of ether amide functional ionic liquid, additives, and diluents. The method provided by this invention disrupts the structure of cerium-doped lutetium yttrium silicate waste during the alkaline fusion process, reduces acid consumption during acid dissolution, and improves the extraction performance for rare earth elements through the addition of ether amide functional ionic liquid. Furthermore, the method is simple to operate, low in cost, and suitable for industrial production. However, during the leaching process of lutetium yttrium silicate waste, the presence of a large amount of silicate impurities coexisting with rare earth elements results in a high concentration of silicon impurities in the leachate. The presence of silicon impurities severely affects subsequent production and product quality. Therefore, it is still necessary to develop a method to effectively remove silicon from lutetium yttrium silicate leachate. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention discloses a method for removing silicon from lutetium yttrium silicate leachate, thus solving the problem of high silicon impurity content in lutetium yttrium silicate leachate, which cannot be effectively removed.

[0005] This invention is achieved using the following technical solution:

[0006] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0007] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Calcinate mixture A at 600°C for 6 hours. Then cool mixture A to 60-80°C and place it in a reaction vessel. Add 400-500 mL of hot water to each 100 g of mixture A and mix. Stir the reaction at 100-110°C for 3-4 hours. Then filter to obtain rare earth hydroxide precipitate.

[0008] (2) Wash the rare earth hydroxide precipitate obtained in step (1) with sodium hydroxide solution 2 to 3 times; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g: (30 to 35)mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 10 to 15 minutes at 40 to 50°C, then let stand to clarify, and then filter to remove the filtrate.

[0009] (3) Take 100-300g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 200-300mL of pure water and stir. Heat the mixture to 70-90℃ in a water bath and keep it at a constant temperature. Then slowly add 6mol / L hydrochloric acid to dissolve the rare earth hydroxide precipitate to obtain mixture B. When the pH of mixture B reaches 0.5-1.0, stop adding hydrochloric acid. After standing for 10-15min, filter to remove the silica colloid and obtain rare earth leachate.

[0010] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, and then add the extractant to the extraction tank. At the same time, add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant. Control the flow rate ratio of the extractant to the rare earth leachate to be 1:(2~3). After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0011] (5) Heat and concentrate the solution C obtained in step (4) to precipitate sodium chloride in solution C, and then filter to remove the precipitated sodium chloride to obtain pure lutetium yttrium chloride solution.

[0012] Furthermore, the concentration of the sodium hydroxide solution in step (2) is 0.1 mol / L. Using 0.1 mol / L sodium hydroxide as the washing solution aims to maintain the alkalinity balance of the solution, allowing it to quickly achieve clarification, shortening the washing time, and also dissolving other silicate impurities, thereby removing more silicon impurities.

[0013] Furthermore, in step (2), after the sodium hydroxide solution and rare earth hydroxide precipitate are mixed, they are stirred for 10 to 15 minutes at 40 to 50°C and a stirring speed of 100 to 300 r / min.

[0014] Furthermore, in step (3), the hydrochloric acid is added at a rate of 1 mL / min to 3 mL / min. By controlling the hydrochloric acid addition rate and the pH value of the solution within a suitable range, the viscosity and adsorption of the silica colloid can be reduced, ensuring the yield while effectively removing impurities such as silicon. If the hydrochloric acid is added too quickly, the acidity of the solution is difficult to control, resulting in excessive hydrochloric acid or local over-acidity, which increases the viscosity of the silica colloid and affects the filtration time.

[0015] Furthermore, in step (3), 100-300g of rare earth hydroxide precipitate treated in step (2) is placed in a reaction vessel, and a small amount of pure water is added and stirred at a stirring speed of 50-100r / min.

[0016] Furthermore, in step (5), the solution C obtained in step (4) is concentrated to two-thirds of its original volume at 60-70°C, and then modified polyacrylamide is added. The mass ratio of the added modified polyacrylamide to the volume of solution C is (1-3) g:1L. Then, it is rapidly cooled to 5-10°C at a cooling rate of 5°C / min and kept at the temperature for 1-2 hours. After standing for 5-10 minutes, the precipitated sodium chloride is removed by filtration to obtain pure lutetium yttrium chloride solution.

[0017] Furthermore, the modified polyacrylamide is prepared by taking polyacrylamide, formaldehyde, glycine, and sodium carbonate in a molar ratio of 1:1:1:0.15, wherein the molecular weight of the polyacrylamide is 60,000–80,000. First, the polyacrylamide, formaldehyde, and sodium carbonate are stirred and mixed. Then, the mixture is reacted at 45°C for 2 hours. Next, glycine is added, and the reaction continues for 3 hours to obtain solution D. Solution D is slowly added to an acetone solution for precipitation and purification. Finally, the solution is vacuum dried at 50°C for 24 hours to obtain the modified polyacrylamide. Modifying polyacrylamide with glycine allows it to disperse and swell rapidly at low temperatures, thereby improving its flocculation effect at low temperatures. Adding this to a cooled lutetium yttrium chloride solution promotes the flocculation and precipitation of sodium chloride crystals, improving the sodium chloride removal efficiency.

[0018] Compared with existing technologies, this technical solution has the following advantages:

[0019] 1. During the recycling and leaching process of lutetium yttrium silicate waste, a large amount of silicate impurities coexist with rare earth elements. The presence of a large amount of impurity silicon can severely affect subsequent production and product quality. Therefore, this invention employs a two-step silicon removal process to obtain a qualified lutetium yttrium chloride solution with low impurity content. First, in the initial washing and filtration, sodium hydroxide solution is added to the rare earth hydroxide precipitate for stirring and clarification. This method, compared to directly adding pure water, effectively maintains the alkalinity balance of the solution, allowing for rapid clarification and shortening the washing time. It also dissolves other small amounts of silicate impurities, thereby removing more impurity silicon. Next, hydrochloric acid is slowly added to the washed rare earth hydroxide precipitate to dissolve it, adjusting the final pH value of the solution to between 0.5 and 1.0. This generates silicate colloids from residual sodium silicate and other silicate impurities in the rare earth hydroxide, which are then filtered out, achieving separation of the rare earth solution from the impurity silicon. Finally, a composite extractant is used to remove impurity iron, and then sodium impurity is removed by controlling the solution to be a supersaturated sodium chloride solution.

[0020] 2. The process of this invention is simple and highly operable. The silicon content in the lutetium yttrium chloride solution after impurity removal is about 150 ug / mL, and the rare earth recovery rate is about 95%. The impurity removal effect is obvious and the rare earth recovery rate is high. It is suitable for the large-scale and automated recycling of lutetium yttrium silicate fertilizer. It not only provides a source of rare earth raw materials for production, but its finished products can also meet market demand, which has good economic benefits. Detailed Implementation

[0021] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0022] Example 1:

[0023] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0024] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Roast mixture A at 600°C for 6 hours. Then cool mixture A to 70°C and place it in a reaction vessel. Then add 450 mL of hot water to every 100 g of mixture A and mix. Then stir and react at 105°C for 3.5 hours. Then filter to obtain rare earth hydroxide precipitate.

[0025] (2) Wash the rare earth hydroxide precipitate obtained in step (1) twice with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:32mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 15min at 45℃ and a stirring speed of 200r / min, then let it stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0026] (3) Take 200g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 250mL of pure water and stir at a stirring speed of 60r / min. Heat the mixture to 75℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 2mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.8. After standing for 15min, filter to remove silica colloid and obtain rare earth leachate.

[0027] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, then add the extractant to the extraction tank, and at the same time add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant, and control the flow rate ratio of the extractant to the rare earth leachate to be 1:2.5. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0028] (5) Heat and concentrate the solution C obtained in step (4) to precipitate sodium chloride in solution C, and then filter to remove the precipitated sodium chloride to obtain pure lutetium yttrium chloride solution.

[0029] Example 2:

[0030] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0031] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Calcinate mixture A at 600°C for 6 hours. Then cool mixture A to 60°C and place it in a reaction vessel. Add 400 mL of hot water to every 100 g of mixture A and mix. Stir the reaction at 100°C for 3 hours and then filter to obtain rare earth hydroxide precipitate.

[0032] (2) Wash the rare earth hydroxide precipitate obtained in step (1) twice with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:30mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 10min at 40℃ and 100r / min, then let stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0033] (3) Take 100g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 200mL of pure water and stir at a stirring speed of 50r / min. Heat the mixture to 70℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 1mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.5. After standing for 10min, filter to remove silica colloid and obtain rare earth leachate.

[0034] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, then add the extractant to the extraction tank, and at the same time add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant, and control the flow rate ratio of the extractant to the rare earth leachate to be 1:2. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0035] (5) Heat and concentrate the solution C obtained in step (4) to precipitate sodium chloride in solution C, and then filter to remove the precipitated sodium chloride to obtain pure lutetium yttrium chloride solution.

[0036] Example 3:

[0037] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0038] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Roast mixture A at 600°C for 6 hours. Then cool mixture A to 75°C and place it in a reaction vessel. Then add 480 mL of hot water to every 100 g of mixture A and mix. Then stir and react at 105°C for 3.5 hours. Then filter to obtain rare earth hydroxide precipitate.

[0039] (2) Wash the rare earth hydroxide precipitate obtained in step (1) three times with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:33mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 12min at 48℃ and a stirring speed of 200r / min, then let it stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0040] (3) Take 200g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 280mL of pure water and stir at a stirring speed of 80r / min. Heat the mixture to 80℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 1.5mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.8. After standing for 12min, filter to remove silica colloid and obtain rare earth leachate.

[0041] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, then add the extractant to the extraction tank, and at the same time add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant, and control the flow rate ratio of the extractant to the rare earth leachate to be 1:2.5. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0042] (5) Heat and concentrate the solution C obtained in step (4) to precipitate sodium chloride in solution C, and then filter to remove the precipitated sodium chloride to obtain pure lutetium yttrium chloride solution.

[0043] Example 4:

[0044] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0045] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Calcinate mixture A at 600°C for 6 hours. Then cool mixture A to 80°C and place it in a reaction vessel. Add 500 mL of hot water to every 100 g of mixture A and mix. Stir and react at 110°C for 4 hours. Then filter to obtain rare earth hydroxide precipitate.

[0046] (2) Wash the rare earth hydroxide precipitate obtained in step (1) three times with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:35mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 15min at 50℃ and a stirring speed of 300r / min, then let it stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0047] (3) Take 300g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 300mL of pure water and stir at a stirring speed of 100r / min. Heat the mixture to 90℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 3mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 1.0. After standing for 15min, filter to remove silica colloid and obtain rare earth leachate.

[0048] (4) Prepare an extractant according to the volume ratio of N235: isooctyl alcohol: kerosene of 2:1:2, and then add the extractant to the extraction tank. At the same time, add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant. Control the flow rate ratio of the extractant to the rare earth leachate to be 1:3. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0049] (5) Heat and concentrate the solution C obtained in step (4) to precipitate sodium chloride in solution C, and then filter to remove the precipitated sodium chloride to obtain pure lutetium yttrium chloride solution.

[0050] Example 5:

[0051] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0052] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Calcinate mixture A at 600°C for 6 hours. Then cool mixture A to 70°C and place it in a reaction vessel. Add 420 mL of hot water to every 100 g of mixture A and mix. Stir and react at 105°C for 3 hours. Then filter to obtain rare earth hydroxide precipitate.

[0053] (2) Wash the rare earth hydroxide precipitate obtained in step (1) twice with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:32mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 15min at 45℃ and a stirring speed of 200r / min, then let it stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0054] (3) Take 200g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 220mL of pure water and stir at a stirring speed of 60r / min. Heat the mixture to 75℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 2mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.8. After standing for 15min, filter to remove silica colloid and obtain rare earth leachate.

[0055] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, then add the extractant to the extraction tank, and at the same time add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant, and control the flow rate ratio of the extractant to the rare earth leachate to be 1:2.5. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0056] (5) The solution C obtained in step (4) is concentrated to two-thirds of its original volume at 60°C. Then, modified polyacrylamide is added. The mass ratio of the modified polyacrylamide added to the volume of solution C is 1 g: 1 L. Then, it is rapidly cooled to 5°C at a cooling rate of 5°C / min and kept at a constant temperature for 1 h. After standing for 5 min, the precipitated sodium chloride is removed by filtration to obtain pure lutetium yttrium chloride solution. The modified polyacrylamide is prepared by taking polyacrylamide, formaldehyde, glycine and sodium carbonate in a molar ratio of 1:1:1:0.15. The molecular weight of the polyacrylamide is 60,000 to 80,000. Then, the polyacrylamide, formaldehyde and sodium carbonate are stirred and mixed. Then, the reaction is carried out at a temperature of 45°C for 2 h. Then, glycine is added and the reaction is continued for 3 h to obtain solution D. Solution D is slowly added to acetone solution for precipitation and purification. After vacuum drying at 50°C for 24 h, modified polyacrylamide is obtained.

[0057] Example 6:

[0058] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0059] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Roast mixture A at 600°C for 6 hours. Then cool mixture A to 70°C and place it in a reaction vessel. Then add 480 mL of hot water to every 100 g of mixture A and mix. Then stir and react at 105°C for 3.5 hours. Then filter to obtain rare earth hydroxide precipitate.

[0060] (2) Wash the rare earth hydroxide precipitate obtained in step (1) twice with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:32mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 15min at 45℃ and a stirring speed of 200r / min, then let it stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0061] (3) Take 200g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 220mL of pure water and stir at a stirring speed of 60r / min. Heat the mixture to 75℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 2mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.8. After standing for 15min, filter to remove silica colloid and obtain rare earth leachate.

[0062] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, then add the extractant to the extraction tank, and at the same time add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant, and control the flow rate ratio of the extractant to the rare earth leachate to be 1:2.5. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0063] (5) The solution C obtained in step (4) is concentrated to two-thirds of its original volume at 65°C. Then, modified polyacrylamide is added. The mass ratio of the modified polyacrylamide to the volume of solution C is 2g:1L. Then, it is rapidly cooled to 8°C at a cooling rate of 5°C / min and kept at the temperature for 1.5h. After standing for 8min, the precipitated sodium chloride is removed by filtration to obtain pure lutetium yttrium chloride solution. The modified polyacrylamide is prepared by taking polyacrylamide, formaldehyde, glycine and sodium carbonate in a molar ratio of 1:1:1:0.15. The molecular weight of the polyacrylamide is 60000-80000. Then, the polyacrylamide, formaldehyde and sodium carbonate are stirred and mixed. Then, the reaction is carried out at 45°C for 2h. Then, glycine is added and the reaction is continued for 3h to obtain solution D. Solution D is slowly added to acetone solution for precipitation and purification. After vacuum drying at 50°C for 24h, modified polyacrylamide is obtained.

[0064] Example 7:

[0065] A method for removing silicon from a yttrium lutetium silicate leaching solution, comprising the following steps:

[0066] (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.5. Calcinate mixture A at 600°C for 6 hours. Then cool mixture A to 70°C and place it in a reaction vessel. Add 420 mL of hot water to every 100 g of mixture A and mix. Stir and react at 105°C for 3.5 hours. Then filter to obtain rare earth hydroxide precipitate.

[0067] (2) Wash the rare earth hydroxide precipitate obtained in step (1) twice with sodium hydroxide solution; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g:32mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 15min at 45℃ and a stirring speed of 200r / min, then let it stand to clarify, and then filter to remove the filtrate; the concentration of the sodium hydroxide solution is 0.1mol / L.

[0068] (3) Take 200g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 280mL of pure water and stir at a stirring speed of 60r / min. Heat the mixture to 75℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 2mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.8. After standing for 15min, filter to remove silica colloid and obtain rare earth leachate.

[0069] (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, then add the extractant to the extraction tank, and at the same time add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant, and control the flow rate ratio of the extractant to the rare earth leachate to be 1:2.5. After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained.

[0070] (5) The solution C obtained in step (4) is concentrated to two-thirds of its original volume at 70°C. Then, modified polyacrylamide is added. The mass ratio of the modified polyacrylamide to the volume of solution C is 3g:1L. Then, it is rapidly cooled to 10°C at a cooling rate of 5°C / min and kept at the temperature for 2 hours. After standing for 10 minutes, the precipitated sodium chloride is removed by filtration to obtain pure lutetium yttrium chloride solution. The modified polyacrylamide is prepared by taking polyacrylamide, formaldehyde, glycine and sodium carbonate in a molar ratio of 1:1:1:0.15. The molecular weight of the polyacrylamide is 60,000 to 80,000. Then, the polyacrylamide, formaldehyde and sodium carbonate are stirred and mixed. Then, the mixture is reacted at 45°C for 2 hours. Then, glycine is added and the reaction is continued for 3 hours to obtain solution D. Solution D is slowly added to acetone solution for precipitation and purification. After vacuum drying at 50°C for 24 hours, modified polyacrylamide is obtained.

[0071] Comparative Example 1:

[0072] The only difference between this comparative example and the method for removing silicon from the yttrium lutetium silicate leaching solution described in Example 1 is that step (2) is omitted. The obtained rare earth hydroxide precipitate is not washed. 200g of the rare earth hydroxide precipitate is directly placed in a reaction vessel, a small amount of pure water is added, and the mixture is stirred at a stirring speed of 60r / min. The mixture is then heated to 75°C in a water bath and kept at a constant temperature. Then, hydrochloric acid with a concentration of 6mol / L is added at a rate of 2mL / min to dissolve the rare earth hydroxide precipitate and obtain a mixed solution B. When the pH of the mixed solution B reaches 0.8, the addition of hydrochloric acid is stopped. After standing for 15min, the rare earth leaching solution is obtained by filtration to remove the silica colloid.

[0073] Comparative Example 2:

[0074] The only difference between this comparative example and the method for removing silicon from the yttrium silicate leaching solution described in Example 1 is that, in step (2), the rare earth hydroxide precipitate obtained in step (1) is washed twice with pure water.

[0075] Experimental Example 1:

[0076] The lutetium silicate waste was treated according to the methods described in Examples 1-7 and Comparative Examples 1-2. The iron, sodium and silicon content in the obtained lutetium chloride yttrium solution was detected, and the specific results are shown in Table 1.

[0077] Table 1. Iron, sodium, and silicon content in lutetium yttrium chloride solution

[0078]

[0079] As can be seen from the above data, washing the rare earth hydroxide precipitate before dissolving it with hydrochloric acid can reduce the content of impurities such as iron, sodium, and silicon. Furthermore, the method described in this invention, which uses sodium hydroxide solution and limits the washing conditions (temperature, stirring speed, solid-liquid ratio, number of washes, washing time, etc.), yields significantly better results than washing with pure water.

[0080] Experimental Example 2:

[0081] The lutetium yttrium silicate waste was treated according to the method described in Example 1. In step (3), hydrochloric acid with a concentration of 6 mol / L was added at rates of 0.5 mL / min, 1.0 mL / min, 1.5 mL / min, 2 mL / min, 2.5 mL / min, 3.0 mL / min, 4.0 mL / min, and 5.0 mL / min to dissolve the rare earth hydroxide precipitate and obtain mixed solution B. After removing iron and sodium impurities, the iron, sodium, and silicon content in the obtained lutetium yttrium chloride solution was finally detected. The specific results are shown in Table 2.

[0082] Table 2. Iron, sodium, and silicon content in lutetium yttrium chloride solution

[0083]

[0084] As the data above shows, when the hydrochloric acid addition rate reaches 3.0 mL / min or higher, the content of impurities such as iron, sodium, and silicon in the obtained lutetium yttrium chloride solution does not decrease significantly, but the rare earth recovery rate drops sharply. This is because the rapid addition of a large amount of hydrochloric acid leads to excess hydrochloric acid or local over-acidity, thereby increasing the viscosity of the silica colloid. This causes the silica colloid to adhere to the rare earth hydroxide precipitate, forming a precipitate that is then filtered out, resulting in a significant loss of rare earth metals and reducing the rare earth recovery rate. Conversely, if the hydrochloric acid addition rate is too slow, the content of impurities such as iron, sodium, and silicon in the obtained lutetium yttrium chloride solution does not decrease significantly; instead, it prolongs the production time. Moreover, the hydrochloric acid dissolution process is carried out at 90°C, and the extended reaction time also requires more heat energy to maintain the reaction temperature, thus increasing production costs. Therefore, the method described in this invention can not only ensure the impurity removal effect and rare earth recovery rate but also control production cost consumption.

[0085] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for removing silicon from a yttrium lutetium silicate leaching solution, characterized in that: Includes the following steps: (1) Take yttrium lutetium silicate waste and caustic soda flakes and mix them evenly to obtain mixture A. The mass ratio of yttrium lutetium silicate waste to caustic soda flakes is 1:1.

5. Calcinate mixture A at 600°C for 6 hours. Then cool mixture A to 60-80°C and place it in a reaction vessel. Add 400-500 mL of hot water to each 100 g of mixture A and mix. Stir the reaction at 100-110°C for 3-4 hours. Then filter to obtain rare earth hydroxide precipitate. (2) Wash the rare earth hydroxide precipitate obtained in step (1) with sodium hydroxide solution 2 to 3 times; each time, the mass ratio of rare earth hydroxide precipitate to sodium hydroxide solution is 1g: (30 to 35)mL. After mixing the sodium hydroxide solution and rare earth hydroxide precipitate, stir for 10 to 15 minutes at 40 to 50°C, then let stand to clarify, and then filter to remove the filtrate. (3) Take 100-300g of rare earth hydroxide precipitate treated in step (2) and place it in a reaction vessel. Add 200-300mL of pure water and stir. Heat the mixture to 70-90℃ in a water bath and keep it at a constant temperature. Then add 6mol / L hydrochloric acid at a rate of 1mL / min-3mL / min to dissolve the rare earth hydroxide precipitate and obtain mixture B. Stop adding hydrochloric acid when the pH of mixture B reaches 0.5-1.

0. After standing for 10-15min, filter to remove silica colloid and obtain rare earth leachate. (4) Prepare an extractant according to the volume ratio of N235:isooctanol:kerosene of 2:1:2, and then add the extractant to the extraction tank. At the same time, add the rare earth leachate obtained in step (3) to the extraction tank in the opposite direction to the extractant. Control the flow rate ratio of the extractant to the rare earth leachate to be 1:(2~3). After the rare earth leachate is removed from the iron in the extraction tank, a clear and transparent solution C is obtained. (5) The solution C obtained in step (4) is concentrated to two-thirds of its original volume at 60-70℃. Then, modified polyacrylamide is added. The mass ratio of the modified polyacrylamide to the volume of solution C is (1-3) g:1L. Then, the solution is rapidly cooled to 5-10℃ at a cooling rate of 5℃ / min and kept at the temperature for 1-2 hours. After standing for 5-10 minutes, the precipitated sodium chloride is removed by filtration to obtain pure lutetium yttrium chloride solution. The modified polyacrylamide is prepared by taking polyacrylamide, formaldehyde, glycine and sodium carbonate in a molar ratio of 1:1:1:0.15, wherein the molecular weight of the polyacrylamide is 60,000 to 80,000. Then, the polyacrylamide, formaldehyde and sodium carbonate are stirred and mixed, and then reacted at 45°C for 2 hours. Glycine is then added and the reaction is continued for 3 hours to obtain solution D. Solution D is slowly added to acetone solution for precipitation and purification, and then vacuum dried at 50°C for 24 hours to obtain modified polyacrylamide.

2. The method for removing silicon from yttrium lutetium silicate leachate according to claim 1, characterized in that: The concentration of the sodium hydroxide solution in step (2) is 0.1 mol / L.

3. The method for removing silicon from yttrium lutetium silicate leachate according to claim 1, characterized in that: In step (2), the sodium hydroxide solution and rare earth hydroxide precipitate are mixed and stirred for 10 to 15 minutes at 40 to 50°C and a stirring speed of 100 to 300 r / min.

4. The method for removing silicon from yttrium lutetium silicate leachate according to claim 1, characterized in that: In step (3), 100-300g of rare earth hydroxide precipitate treated in step (2) is placed in a reaction vessel, pure water is added, and the mixture is stirred at a stirring speed of 50-100r / min.

Images