A method for producing high-purity cesium phosphate using mother liquor after lithium extraction

Abstract

This invention discloses a method for producing high-purity cesium phosphate using mother liquor after lithium extraction from lepidolite. The method utilizes the waste liquid generated after lithium extraction from lepidolite as raw material, and adds auxiliary materials such as acidifying reagents and aluminum precipitation and desulfurization reagents. Through processes including precipitation of sodium-potassium mixed salt, acidification precipitation of alum, recrystallization purification, aluminum precipitation and desulfurization, concentration crystallization, and centrifugal drying, high-purity cesium phosphate is produced with a product purity exceeding 99.9%. This method has a wide availability of raw materials, high energy utilization rate, simple and feasible process, low equipment investment, low cost, short production cycle, high efficiency, and does not generate new waste, making it environmentally friendly. It effectively realizes the comprehensive reuse of lithium precipitation mother liquor, improves the economic value of lepidolite, reduces the production cost of lithium extraction from ore, saves cesium resources, and reduces waste liquid pollution. It can be widely applied to the industrial production of lithium extraction from lepidolite.

Description

Technical Field

[0001] This invention relates to the field of cesium phosphate production technology, and in particular to a method for producing high-purity cesium phosphate using mother liquor after lithium extraction. Background Technology

[0002] Cesium phosphate is an inorganic compound with the chemical formula Cs3PO4, a molecular weight of 493.688, and a CAS registry number of 17893-64-0. With the widespread application of rubidium and cesium in high-tech fields, the demand for cesium phosphate is increasing year by year, driving its industrial production. Currently, there are very few reports on methods for preparing cesium phosphate. Traditional laboratory methods typically utilize the neutralization reaction of cesium carbonate and phosphoric acid to synthesize cesium phosphate; however, this method is not suitable for large-scale industrial production. With the increasing demand for cesium, finding an efficient and economical method for producing cesium phosphate has become particularly important.

[0003] Yichun, my country, is rich in lepidolite resources. Lepidolite is a major carrier mineral rich in cesium, providing a natural raw material basis for the production of cesium phosphate. Meanwhile, cesium is a scarce resource, and high-purity cesium phosphate products are of great significance for meeting the needs of scientific research and high-tech fields. Utilizing the mother liquor after lithium extraction from lepidolite to produce cesium phosphate not only achieves comprehensive resource utilization but also effectively alleviates the scarcity of cesium.

[0004] Currently, there are few domestic and international publications on the production of cesium phosphate from the mother liquor after lithium extraction from lepidolite, indicating a technological gap and requiring further in-depth research in this field. Therefore, developing a method for producing high-purity cesium phosphate from the mother liquor after lithium extraction would not only meet the demand for high-purity cesium salts in scientific research and high-tech fields, but also alleviate the environmental pressure on lithium extraction enterprises and reduce the production cost of lithium extraction from ore. This would have profound significance for promoting technological progress and economic development in related fields. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing high-purity cesium phosphate using mother liquor after lithium extraction. The method uses the waste liquid generated after lithium extraction from lepidolite as raw material, and adds auxiliary materials such as acidification reagent and aluminum precipitation desulfurization reagent to produce high-purity cesium phosphate at low cost and high efficiency. This method realizes the comprehensive reuse of lithium precipitation mother liquor, reduces the production cost of lithium extraction from ore, and reduces pollution from waste liquid.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction includes the following steps:

[0008] S1, Acidification: Lithium precipitation mother liquor is added to a glass-lined reactor, and acid is added to adjust the pH to weakly acidic to obtain cesium mother liquor A;

[0009] S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step 1 is heated and concentrated, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is pulverized, dried and stored in a warehouse. The cesium content of the cesium mother liquor B is tested. If it is qualified, it proceeds to the next step; otherwise, this step is repeated until it is qualified.

[0010] S3. Acidification and precipitation of cesium: The cesium mother liquor B obtained in step 2 is added to a glass-lined reactor using a pump or vacuum pump. Then, an acidification reagent is added to adjust the pH of the solution to acidic. The solution is boiled at normal pressure, kept warm and stirred. During this process, purified water is added to maintain a constant volume. The solution is cooled, allowed to crystallize naturally, and separated by centrifugation and filtration to obtain crude cesium alum and filtrate A. The filtrate A can be reused as a supplement to the acidification reagent.

[0011] S4. Recrystallization and purification: Add the crude cesium alum obtained in step 3 to the glass-lined reactor, add purified water, heat and stir to dissolve and recrystallize to obtain refined cesium alum and filtrate B. The filtrate B is recycled.

[0012] S5. Desulfurization of aluminum: The refined cesium alum obtained in step 4 is added to a glass-lined reactor. After adding purified water and stirring to dissolve it, aluminum desulfurization reagents are added, carbon dioxide is introduced, and the mixture is heated to boiling for a certain time. After centrifugation and filtration to separate the filter residue, cesium mother liquor C is obtained. The filter residue can be processed into building materials.

[0013] S6. Concentration and Crystallization: The cesium mother liquor C obtained in step 5 is acidified and concentrated under reduced pressure in a rotary evaporator. After concentration, it is cooled and crystallized, and then separated by centrifugation to obtain wet cesium phosphate and filtrate C. The filtrate C is recycled.

[0014] S7. Drying: Place the wet cesium phosphate obtained in step 6 into an oven to dry. After drying, the finished cesium phosphate product is obtained. Take a sample for testing. After passing the test, bag it and store it in the warehouse.

[0015] Preferably, the lithium precipitation mother liquor in step 1 can be an alkaline lithium precipitation mother liquor for producing lithium phosphate, or a lithium precipitation mother liquor for producing lithium carbonate, or other mother liquor containing cesium. The pH of the lithium precipitation mother liquor is adjusted to 5-6 with sulfuric acid or phosphoric acid.

[0016] Preferably, the concentration rate of cesium mother liquor A in step 2 is 8-9%, and the cesium content of cesium mother liquor B is greater than 40 g / L.

[0017] Preferably, the acidifying reagent in step 3 refers to sulfuric acid, aluminum sulfate, and potassium aluminum sulfate. The amount of aluminum sulfate is 1-2% of the cesium mother liquor B, and the amount of potassium aluminum sulfate is 1-6 times the cesium content of the cesium mother liquor B. The solution pH is adjusted to ≤3, the boiling time at normal pressure is more than 1 hour, and the solution is kept warm and stirred for 1 hour.

[0018] Preferably, in step 4, the amount of purified water added is 3 to 4 times that of crude cesium alum, the heating temperature is above 95°C, the stirring time is 3 hours, and the cooling crystallization temperature after dissolution is below 15°C.

[0019] Preferably, the amount of purified water added in step 5 is 4 to 5 times that of refined cesium alum, the aluminum precipitation and desulfurization reagent can be any one or a combination of several of calcium oxide, barium oxide, calcium hydroxide, barium hydroxide octahydrate, ammonia, liquid ammonia, and calcium carbonate, the carbon dioxide introduction rate is 15 to 35 L / min, the introduction time is 90 to 200 minutes, and the heating and boiling time is 10 to 60 minutes.

[0020] Preferably, the aluminum precipitation desulfurization reagent is a composite of calcium hydroxide and barium hydroxide octahydrate, wherein the amount of calcium hydroxide added is 0.22 to 0.25 times that of refined cesium alum, and the amount of barium hydroxide octahydrate added is 0.22 to 0.35 times that of refined cesium alum.

[0021] Preferably, the cesium mother liquor C acidification in step 6 is carried out using 85% phosphoric acid to adjust the pH of the solution to 1-5, and the liquid-to-solid ratio after concentration is <1:3.

[0022] Preferably, the oven temperature in step 7 is 90–250°C, and the drying time is 6 hours.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention utilizes the waste liquid generated after lithium extraction from lepidolite as raw material, and adds auxiliary materials such as acidifying reagents and aluminum precipitation and desulfurization reagents. Through processes including precipitation of sodium-potassium mixed salt, acidification precipitation of alum, recrystallization purification, aluminum precipitation and desulfurization, concentration crystallization, and centrifugal drying, high-purity cesium phosphate is produced with a product purity of over 99.9%. This method has a wide range of raw material sources, high energy utilization rate, simple and feasible process, low equipment investment, low cost, short production cycle, high efficiency, no new waste generation, and is environmentally friendly. It effectively realizes the comprehensive reuse of lithium precipitation mother liquor, improves the economic value of lepidolite, reduces the production cost of lithium extraction from ore, saves cesium resources, and reduces waste liquid pollution. It can be widely promoted and applied to the industrial production of lithium extraction from lepidolite. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention; Detailed Implementation

[0026] To make the technical problems solved, technical solutions, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0027] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, the process flow is as follows: Figure 1 As shown.

[0028] Example 1:

[0029] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction includes the following steps:

[0030] S1. Acidification: 2400L of lithium precipitation mother liquor is added to the glass-lined reactor using a pump. The lithium precipitation mother liquor is an alkaline waste liquid from the process of preparing lithium phosphate from lepidolite (the solution pH is between 6 and 12, and the main components are detailed in Table 1). The lithium precipitation mother liquor is circulated multiple times before being added, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A. Sodium ions and potassium ions react with sulfate ions respectively to synthesize sodium sulfate and potassium sulfate, which facilitates the subsequent precipitation of sodium and potassium salts to reduce the sodium and potassium ion content in the solution and improve the purity of cesium.

[0031] S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step 1 is heated and concentrated to 210L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is crushed, dried and stored in a warehouse for other uses. The cesium content of cesium mother liquor B is tested. The cesium content of cesium mother liquor B is required to be greater than 40g / L. If the cesium content is too low, it is not conducive to alum precipitation. If it is qualified, proceed to the next step. Otherwise, repeat this step until it is qualified. In this example, the cesium content test value is 41.0g / L.

[0032] S3. Acidification and Precipitation of Cesium Alum: Using a pump or vacuum pump, add the cesium mother liquor B obtained in step 2 to a glass-lined reactor. Then add 3.2 kg of aluminum sulfate and 45 kg of potassium aluminum sulfate, followed by sulfuric acid to adjust the pH of the solution to <3. Boil at normal pressure for 2.5 hours, maintain the temperature and stir for 1 hour, adding purified water to maintain a constant volume. Cool to crystallize, centrifuge, and filter to obtain crude cesium alum and filtrate A. The weight of crude cesium alum is 25.6 kg. Filtrate A can be reused as an acidifying agent. Aluminum sulfate and potassium aluminum sulfate react with cesium ions in the solution to generate corresponding cesium alum precipitates. The chemical equation is as follows: Cs + +Al 3+ +2SO4 2- +12H2O=CsAl(SO4)2·12H2O, the main component of crude cesium alum is CsAl(SO4)2·12H2O. Potassium aluminum sulfate, commonly known as alum, is a double salt of potassium sulfate and aluminum sulfate containing water of crystallization. It can provide a specific chemical environment that helps the selective precipitation of cesium ions. This selective precipitation can reduce the co-precipitation of other impurities and improve the purity of crude cesium alum. Moreover, potassium aluminum sulfate is relatively cheap and easy to obtain, and it is also convenient to use. In addition, aluminum sulfate and potassium aluminum sulfate themselves contain sulfate ions, which can replace sulfuric acid to a certain extent to adjust the pH value of the solution, thereby relatively reducing the amount of sulfuric acid used.

[0033] S4. Recrystallization and purification: Add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 100L of purified water, heat and stir to dissolve and recrystallize for purification. The heating temperature is above 95℃ and the stirring time is 3 hours. After dissolution, cool and crystallize. The cooling temperature is below 15℃. Centrifuge and filter to separate, and obtain 22.8Kg of refined cesium alum and filtrate B. The filtrate B is recycled.

[0034] S5. Desulfurization of Aluminum: The refined cesium sulfate obtained in step 4 is added to a glass-lined reactor. 100L of purified water is added and stirred to dissolve the sulfate. Then, 5.2Kg of calcium hydroxide and 7.1Kg of barium hydroxide octahydrate are added. Carbon dioxide is introduced at a rate of 28L / min for 180 minutes. After boiling for 45 minutes, the residue is separated by centrifugation and filtration to obtain cesium mother liquor C (98.6L). The residue can be processed into building materials. The main components of the residue are Al(OH)3, CaSO4, BaSO4, CaCO3, and BaCO3. The chemical reactions in this step are as follows:

[0035] 1) Calcium and barium salts are used to adjust and remove aluminum ions and some sulfate ions from the solution. The chemical equation is as follows:

[0036] 2CsAl(SO4)2·12H2O+3Ca(OH)2=Cs2SO4+2Al(OH)3↓+3CaSO4+12H2O;

[0037] 2CsAl(SO4)2·12H2O+3Ba(OH)2=Cs2SO4+2Al(OH)3↓+3BaSO4+12H2O;

[0038] Because Cs2SO4 has high solubility, it exists in solution as free cesium ions and sulfate ions;

[0039] 2) Removal of sulfate ions from the solution, the chemical equation is as follows:

[0040] Ca 2+ +SO4 2- =CaSO4↓;

[0041] Ba 2+ +SO4 2- =BaSO4↓;

[0042] 3) Removal of excess calcium hydroxide and barium hydroxide octahydrate, the chemical equation is as follows:

[0043] Ca(OH)2+CO2+H2O=CaCO3↓+2H2O;

[0044] Ba(OH)2+CO2+H2O=BaCO3↓+2H2O;

[0045] The amount of carbon dioxide introduced must be controlled and not excessive to avoid the following reactions:

[0046] Ba(OH)₂ + 2CO₂ = Ba(HCO₃)₂;

[0047] Ca(OH)₂ + 2CO₂ = Ca(HCO₃)₂;

[0048] S6. Concentration and Crystallization: The cesium mother liquor C obtained in step 5 is acidified by adjusting the pH of the solution to 2 with 85% phosphoric acid. The solution is then concentrated under reduced pressure in a rotary evaporator until a large amount of crystals appear. The rotation speed is appropriately reduced, and the solution is evaporated until only a small amount of liquid remains (i.e., the liquid-to-solid ratio is <1:3). Heating in the water bath is stopped, and the solution is cooled to 20°C. Crystallization is then carried out by centrifugation to obtain 5.1 kg of wet cesium phosphate and filtrate C. Filtrate C is recycled. The acidification reaction equation is:

[0049] 3Cs + +H3PO4=Cs3PO4+3H + ;

[0050] 3CsOH + H3PO4 = Cs3PO4 + 3H2O;

[0051] 3Cs2CO3+2H3P04=2Cs3P04+3H2O+3CO2↑;

[0052] S7. Drying: Place the wet cesium phosphate obtained in step 6 on a 316L stainless steel tray and put it into an oven to dry. The oven temperature is 150℃ and the drying time is 6 hours. After drying, 4.6Kg of cesium phosphate finished product is obtained. Take 10g of sample for testing. The test results are detailed in Table 2. After passing the test, bag it and store it in the warehouse.

[0053] Example 2:

[0054] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, with the same chemical reaction mechanism as in Example 1, includes the following steps:

[0055] S1. Acidification: 2350L of lithium precipitation mother liquor is added to the glass-lined reactor using a pump. The lithium precipitation mother liquor is an alkaline waste liquid from the process of preparing lithium phosphate from lepidolite (the solution pH is between 6 and 12, and the main components are detailed in Table 1). The lithium precipitation mother liquor is circulated multiple times before being added, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A.

[0056] S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step 1 is heated and concentrated to 206L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is pulverized, dried and stored in a warehouse. The cesium content of cesium mother liquor B is tested. The cesium content of cesium mother liquor B is required to be greater than 40g / L. If it is qualified, proceed to the next step. Otherwise, repeat this step until it is qualified. In this example, the cesium content test value is 47.2g / L.

[0057] S3. Acidification and precipitation of cesium alum: The cesium mother liquor B obtained in step 2 is added to a glass-lined reactor using a pump or vacuum pump. Then, 4.4 kg of aluminum sulfate and 60 kg of potassium aluminum sulfate are added, along with sulfuric acid. The pH of the solution is adjusted to <2. The solution is boiled at normal pressure for 1.5 hours, kept warm and stirred for 1 hour, during which purified water is added to maintain a constant volume. The solution is cooled and crystallized, then separated by centrifugation and filtration to obtain crude cesium alum and filtrate A. The weight of crude cesium alum is 32.1 kg. Filtrate A can be reused as an acidification reagent.

[0058] S4. Recrystallization and purification: Add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 100L of purified water, heat and stir to dissolve and recrystallize for purification. The heating temperature is above 95℃ and the stirring time is 3 hours. After dissolution, cool and crystallize. The cooling temperature is below 15℃. Centrifuge and filter to separate, and obtain 28.8Kg of refined cesium alum and filtrate B. The filtrate B is recycled.

[0059] S5. Desulfurization of aluminum: Add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 125L of purified water and stir to dissolve, then add 7.26Kg of calcium hydroxide and 10Kg of barium hydroxide octahydrate, and introduce carbon dioxide at a rate of 20L / min for 120 minutes. After heating and boiling for 35 minutes, centrifuge and filter to separate the filter residue to obtain cesium mother liquor C, which is 104.1L. The filter residue can be processed into building materials.

[0060] S6. Concentration and Crystallization: The cesium mother liquor C obtained in step 5 is acidified by adjusting the pH of the solution to 2 with 85% phosphoric acid. The solution is then concentrated under reduced pressure in a rotary evaporator until a large amount of crystals appear in the solution. The rotation speed is appropriately reduced and the solution is evaporated until it contains only a small amount of liquid, i.e., the liquid-to-solid ratio is <1:1. The water bath is then stopped and the solution is cooled to 25°C. After cooling and crystallization, the solution is separated by centrifugation to obtain 6.6 kg of wet cesium phosphate and filtrate C. Filtrate C is recycled.

[0061] S7. Drying: Place the wet cesium phosphate obtained in step 6 in a 316L stainless steel tray and put it in an oven to dry. The oven temperature is 160℃ and the drying time is 6 hours. After drying, 6.0Kg of cesium phosphate finished product is obtained. Take 10g of sample for testing. The test results are detailed in Table 2. After passing the test, bag it and store it in the warehouse.

[0062] Example 3:

[0063] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, with the same chemical reaction mechanism as in Example 1, includes the following steps:

[0064] S1. Acidification: 2200L of lithium precipitation mother liquor is added to the glass-lined reactor using a pump. The lithium precipitation mother liquor is an alkaline waste liquid from the process of preparing lithium phosphate from lepidolite (the solution pH is between 6 and 12, and the main components are detailed in Table 1). The lithium precipitation mother liquor is circulated multiple times before being added, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A.

[0065] S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step 1 is heated and concentrated to 180L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is pulverized, dried and stored in a warehouse. The cesium content of cesium mother liquor B is tested. The cesium content of cesium mother liquor B is required to be greater than 40g / L. If it is qualified, proceed to the next step. Otherwise, repeat this step until it is qualified. In this example, the cesium content test value is 50.3g / L.

[0066] S3. Acidification and precipitation of cesium alum: The cesium mother liquor B obtained in step 2 is added to a glass-lined reactor using a pump or vacuum pump. Then, 4.7 kg of aluminum sulfate and 60 kg of potassium aluminum sulfate are added, along with sulfuric acid. The pH of the solution is adjusted to <3. The solution is boiled at normal pressure for 1.5 hours, kept warm and stirred for 1 hour. During this time, purified water is added to maintain a constant volume. The solution is cooled and crystallized, then separated by centrifugation and filtration to obtain crude cesium alum and filtrate A. The weight of crude cesium alum is 30.7 kg. Filtrate A can be reused as an acidification reagent.

[0067] S4. Recrystallization and purification: Add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 100L of purified water, heat and stir to dissolve and recrystallize for purification. The heating temperature is above 95℃ and the stirring time is 3 hours. After dissolution, cool and crystallize. The cooling temperature is below 15℃. Centrifuge and filter to separate, and obtain 28.4Kg of refined cesium alum and filtrate B. The filtrate B is recycled.

[0068] S5. Desulfurization of aluminum: Add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 125L of purified water and stir to dissolve, then add 6.9Kg of calcium hydroxide and 9.5Kg of barium hydroxide octahydrate, and introduce carbon dioxide at a rate of 16L / min for 120 minutes. After heating and boiling for 45 minutes, centrifuge and filter to separate the filter residue to obtain cesium mother liquor C, which is 100.2L. The filter residue can be processed into building materials.

[0069] S6. Concentration and Crystallization: The cesium mother liquor C obtained in step 5 is acidified by adjusting the pH of the solution to 2 with 85% phosphoric acid. The solution is then concentrated under reduced pressure in a rotary evaporator until a large amount of crystals appear in the solution. The rotation speed is appropriately reduced and the solution is evaporated until it contains only a small amount of liquid, i.e., the liquid-to-solid ratio is <1:1. The water bath is then stopped from heating and the solution is rotated and cooled to 25°C. After cooling and crystallization, the solution is separated by centrifugation to obtain 6.2 kg of wet cesium phosphate and filtrate C. Filtrate C is recycled.

[0070] S7. Drying: Place the wet cesium phosphate obtained in step 6 in a 316L stainless steel tray and put it in an oven to dry. The oven temperature is 110℃ and the drying time is 5 hours. After drying, 5.7Kg of cesium phosphate finished product is obtained. Take 10g of sample for testing. The test results are detailed in Table 2. After passing the test, bag it and store it in the warehouse.

[0071] Example 4:

[0072] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, with the same chemical reaction mechanism as in Example 1, includes the following steps:

[0073] S1. Acidification: 2400L of lithium precipitation mother liquor is added to the glass-lined reactor using a pump. The lithium precipitation mother liquor is an alkaline waste liquid from the process of preparing lithium phosphate from lepidolite (the solution pH is between 6 and 12, and the main components are detailed in Table 1). The lithium precipitation mother liquor is circulated multiple times before being added, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A.

[0074] S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step 1 is heated and concentrated to 200L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is pulverized, dried and stored in a warehouse. The cesium content of cesium mother liquor B is tested. The cesium content of cesium mother liquor B is required to be greater than 40g / L. If it is qualified, proceed to the next step. Otherwise, repeat this step until it is qualified. In this example, the cesium content test value is 65.6g / L.

[0075] S3. Acidification and precipitation of cesium alum: The cesium mother liquor B obtained in step 2 is added to a glass-lined reactor using a pump or vacuum pump. Then, 6.3 kg of aluminum sulfate and 88.1 kg of potassium aluminum sulfate are added, followed by sulfuric acid to adjust the pH of the solution to <3. The solution is boiled at normal pressure for 3.5 hours, kept warm and stirred for 2 hours, during which purified water is added to maintain a constant volume. After cooling and crystallization, the solution is separated by centrifugation and filtration to obtain crude cesium alum and filtrate A. The weight of crude cesium alum is 44.8 kg. Filtrate A can be reused as an acidification reagent.

[0076] S4. Recrystallization and purification: Add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 150L of purified water, heat and stir to dissolve and recrystallize for purification. The heating temperature is above 95℃ and the stirring time is 3 hours. After dissolution, cool and crystallize. The cooling temperature is below 15℃. Centrifuge and filter to separate, and obtain 41.1Kg of refined cesium alum and filtrate B. The filtrate B is recycled.

[0077] S5. Desulfurization of aluminum: Add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 180L of purified water and stir to dissolve, then add 10.2Kg of calcium hydroxide and 14Kg of barium hydroxide octahydrate, and introduce carbon dioxide at a rate of 19L / min for 120 minutes. After heating to boiling for 30 minutes, centrifuge and filter to separate the filter residue to obtain cesium mother liquor C, which is 102.5L. The filter residue can be processed into building materials.

[0078] S6. Concentration and Crystallization: The cesium mother liquor C obtained in step 5 is acidified by adjusting the pH of the solution to 2 with 85% phosphoric acid. The solution is then concentrated under reduced pressure in a rotary evaporator until a large amount of crystals appear in the solution. The rotation speed is appropriately reduced and the solution is evaporated until it contains only a small amount of liquid, i.e., the liquid-to-solid ratio is <1:1. The water bath is then stopped and the solution is cooled to 25°C. After cooling and crystallization, the solution is separated by centrifugation to obtain 9.2 kg of wet cesium phosphate and filtrate C. Filtrate C is recycled.

[0079] S7. Drying: Place the wet cesium phosphate obtained in step 6 on a 316L stainless steel tray and put it into an oven to dry. The oven temperature is 100℃ and the drying time is 6 hours. After drying, 8.6Kg of cesium phosphate finished product is obtained. Take 10g of sample for testing. The test results are detailed in Table 2. After passing the test, bag it and store it in the warehouse.

[0080] Example 5:

[0081] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, with the same chemical reaction mechanism as in Example 1, includes the following steps:

[0082] S1. Acidification: 2300L of lithium precipitation mother liquor is added to the glass-lined reactor using a pump. The lithium precipitation mother liquor is an alkaline waste liquid from the process of preparing lithium phosphate from lepidolite (the solution pH is between 6 and 12, and the main components are detailed in Table 1). The lithium precipitation mother liquor is circulated multiple times before being added, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A.

[0083] S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step 1 is heated and concentrated to 200L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is pulverized, dried and stored in a warehouse. The cesium content of cesium mother liquor B is tested. The cesium content of cesium mother liquor B is required to be greater than 40g / L. If it is qualified, proceed to the next step. Otherwise, repeat this step until it is qualified. In this example, the cesium content test value is 60.3g / L.

[0084] S3. Acidification and precipitation of cesium alum: The cesium mother liquor B obtained in step 2 is added to a glass-lined reactor using a pump or vacuum pump. Then, 5.8 kg of aluminum sulfate and 81 kg of potassium aluminum sulfate are added, along with sulfuric acid. The pH of the solution is adjusted to <3. The solution is boiled at normal pressure for 2 hours, and then kept warm and stirred for 2 hours. During this time, purified water is added to maintain a constant volume. The solution is cooled and crystallized, then separated by centrifugation and filtration to obtain crude cesium alum and filtrate A. The weight of crude cesium alum is 40.7 kg. Filtrate A can be reused as an acidification reagent.

[0085] S4. Recrystallization and purification: Add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 150L of purified water, heat and stir to dissolve and recrystallize for purification. The heating temperature is above 95℃ and the stirring time is 3 hours. After dissolution, cool and crystallize. The cooling temperature is below 15℃. Centrifuge and filter to separate, and obtain 37.4Kg of refined cesium alum and filtrate B. The filtrate B is recycled.

[0086] S5. Desulfurization of aluminum: Add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 160L of purified water and stir to dissolve, then add 9.4Kg of calcium hydroxide and 13Kg of barium hydroxide octahydrate, and introduce carbon dioxide at a rate of 16L / min for 120 minutes. After heating to boiling for 15 minutes, centrifuge and filter to separate the filter residue to obtain cesium mother liquor C, which is 98.0L in volume. The filter residue can be processed into building materials.

[0087] S6. Concentration and Crystallization: The cesium mother liquor C obtained in step 5 is acidified by adjusting the pH of the solution to 2 with 85% phosphoric acid. The solution is then concentrated under reduced pressure in a rotary evaporator until a large amount of crystals appear in the solution. The rotation speed is appropriately reduced and the solution is evaporated until it contains only a small amount of liquid, i.e., the liquid-to-solid ratio is <1:1. The water bath is then stopped and the solution is cooled to 25°C. After cooling and crystallization, the solution is separated by centrifugation to obtain 8.6 kg of wet cesium phosphate and filtrate C. Filtrate C is recycled.

[0088] S7. Drying: Place the wet cesium phosphate obtained in step 6 on a 316L stainless steel tray and put it into an oven for drying. The oven temperature is 185℃ and the drying time is 6 hours. After drying, 7.7Kg of cesium phosphate finished product is obtained. Take 10g of sample for testing. The test results are detailed in Table 2. After passing the test, bag it and store it in the warehouse.

[0089] Table 1. Lithium-concentrated mother liquor test report

[0090]

[0091] Table 2. Cesium Phosphate Test Report for Products

[0092]

[0093] Analysis of Tables 1 and 2 shows that the cesium phosphate produced from the mother liquor after lithium extraction from lepidolite using this method has a purity of over 99.9%. This effectively realizes the comprehensive reuse of the lithium precipitation mother liquor, improves the economic value of lepidolite, reduces the production cost of lithium extraction from ore, saves cesium resources, and reduces the pollution problem of waste liquid. It can be widely promoted and applied to the industrial production of lithium extraction from lepidolite.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, characterized in that, Includes the following steps: S1, Acidification: Lithium precipitation mother liquor is added to a glass-lined reactor, and acid is added to adjust the pH to weakly acidic to obtain cesium mother liquor A; S2. Precipitation of sodium-potassium mixed salt: The cesium mother liquor A obtained in step S1 is heated and concentrated, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugation and filtration to obtain cesium mother liquor B. The sodium-potassium mixed salt is pulverized, dried and stored in a warehouse. The cesium content of the cesium mother liquor B is tested. If it is qualified, it proceeds to the next step; otherwise, this step is repeated until it is qualified. S3, Acidification and Precipitation of Alum: The cesium mother liquor B obtained in step S2 is added to the glass-lined reactor using a pump. Then, an acidification reagent is added to adjust the pH of the solution to strongly acidic. The solution is boiled at normal pressure, kept warm and stirred. During this process, purified water is added to maintain a constant volume. The solution is dissolved, cooled and crystallized. The solution is then separated by centrifugation and filtration to obtain crude cesium alum and filtrate A. The filtrate A is reused as a supplement to the acidification reagent. S4. Recrystallization and purification: Add the crude cesium alum obtained in step S3 to a glass-lined reactor, add purified water, heat and stir to dissolve, and recrystallize and purify to obtain refined cesium alum and filtrate B. The filtrate B is recycled. S5. Desulfurization of aluminum: The refined cesium alum obtained in step S4 is added to a glass-lined reactor. After adding purified water and stirring to dissolve it, a desulfurization reagent for aluminum precipitation is added. Carbon dioxide is introduced, and the mixture is heated to boiling for a certain time. After centrifugation and filtration to separate the filter residue, cesium mother liquor C is obtained. The filter residue is processed into building materials. S6. Concentration and Crystallization: The cesium mother liquor C obtained in step S5 is acidified and concentrated under reduced pressure in a rotary evaporator. After concentration, it is cooled and crystallized, and then separated by centrifugation to obtain wet cesium phosphate and filtrate C. The filtrate C is recycled. S7. Drying: Place the wet cesium phosphate obtained in step S6 into an oven to dry. After drying, the finished cesium phosphate product is obtained. Take a sample for testing. After passing the test, it is bagged and stored in the warehouse. The concentration rate of cesium mother liquor A in step S2 is 8-9%, and the cesium content of cesium mother liquor B is greater than 40 g / L; The acidifying reagents mentioned in step S3 refer to sulfuric acid, aluminum sulfate, and potassium aluminum sulfate. The amount of aluminum sulfate is 1 to 2% of the cesium mother liquor B, and the amount of potassium aluminum sulfate is 1 to 6 times the cesium content of the cesium mother liquor B. The solution pH is adjusted to ≤3, and the boiling time at normal pressure is more than 1 hour, followed by stirring at a constant temperature for 1 hour. The aluminum precipitation desulfurization reagent mentioned in step S5 is any one or a combination of several of calcium oxide, barium oxide, calcium hydroxide, barium hydroxide octahydrate, ammonia, liquid ammonia, and calcium carbonate. The cesium mother liquor C acidification in step S6 is carried out using 85% phosphoric acid to adjust the pH of the solution to 1-5, and the liquid-to-solid ratio after concentration is <1:

3.

2. The method according to claim 1, characterized in that, The lithium precipitation mother liquor mentioned in step S1 is an alkaline lithium precipitation mother liquor for producing lithium phosphate, or a lithium precipitation mother liquor for producing lithium carbonate. The pH of the lithium precipitation mother liquor is adjusted to 5-6 with sulfuric acid or phosphoric acid.

3. The method according to claim 1, characterized in that, In step S4, the amount of purified water added is 3 to 4 times that of crude cesium alum, the heating temperature is above 95°C, the stirring time is 3 hours, and the crystallization temperature after dissolution is below 15°C.

4. The method according to claim 1, characterized in that, In step S5, the amount of purified water added is 4 to 5 times that of refined cesium alum, the carbon dioxide introduction rate is 15 to 35 L / min, the introduction time is 90 to 200 minutes, and the heating and boiling time is 10 to 60 minutes.

5. The method according to claim 1, characterized in that, The aluminum precipitation desulfurization reagent is a composite of calcium hydroxide and barium hydroxide octahydrate, wherein the amount of calcium hydroxide added is 0.22 to 0.25 times that of refined cesium alum, and the amount of barium hydroxide octahydrate added is 0.22 to 0.35 times that of refined cesium alum.

6. The method according to claim 1, characterized in that, The oven temperature in step S7 is 60-250℃, and the drying time is 6 hours.

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