Method for producing high-purity cesium phosphate by using mother liquor after lithium extraction

Abstract

The invention discloses a method for producing high-purity cesium phosphate by using mother liquor after lithium extraction, which comprises the following steps: by using waste liquor generated after lithium extraction of lepidolite as a raw material, adding auxiliary materials such as an acidifying reagent, an aluminum precipitation and sulfur radical removal reagent and the like; the high-purity cesium phosphate is produced through the procedures of sodium and potassium mixed salt precipitation, acidification alum precipitation, recrystallization purification, aluminum precipitation sulfur radical removal, concentration crystallization, centrifugal drying and the like, the product purity reaches 99.9% or above, and the method is wide in raw material source, high in energy utilization rate, simple and feasible in process, small in equipment investment, low in cost, short in production period, high in efficiency, free of new waste, environmentally friendly and suitable for industrial production. The comprehensive recycling of the lithium precipitation mother liquor is effectively realized, the economic value of the lepidolite is improved, the production cost of extracting lithium from ore is reduced, the cesium source is saved, the pollution problem of waste liquid is also reduced, and the method can be comprehensively popularized and applied to the industrial production of extracting lithium from the lepidolite.

Description

Technical Field

[0001] The invention relates to the technical field of cesium phosphate production, and in particular to a method for producing high-purity cesium phosphate by utilizing mother liquor after lithium extraction. Background Art

[0002] Cesium phosphate is an inorganic compound with the chemical formula Cs3PO4, a molecular weight of 493.688, and a CAS registration number of 17893-64-0. With the widespread application of rubidium and cesium elements in high-tech fields, the demand for cesium phosphate is increasing year by year, which has promoted the progress of its industrial production. At present, there are very few reports on the preparation method of cesium phosphate. The traditional laboratory method usually uses 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 elements, it is particularly important to find an efficient and economical method for producing cesium phosphate.

[0003] Yichun, my country is rich in lepidolite resources. Lepidolite is the main carrier mineral rich in cesium, providing a natural raw material basis for the production of cesium phosphate. At the same time, as a scarce resource, cesium element, its high-purity cesium phosphate products are of great significance to meet the needs of scientific research and high-tech fields. Using the mother liquor after lithium extraction from lepidolite to produce cesium phosphate can not only realize the comprehensive utilization of resources, but also effectively alleviate the scarcity of cesium element.

[0004] At present, there are few literature reports on the production of cesium phosphate using the mother liquor after lithium extraction from lepidolite at home and abroad, and there is a technical gap. The technical research in this field needs to be deepened. Therefore, the development of a method for producing high-purity cesium phosphate using the mother liquor after lithium extraction can not only meet the demand for high-purity cesium salts in scientific research and high-tech fields, but also reduce the environmental pressure of lithium extraction enterprises and reduce the production cost of lithium extraction from ore, which has far-reaching significance for promoting scientific and technological progress and economic development in related fields. Summary of the invention

[0005] The present invention aims to provide a method for producing high-purity cesium phosphate by utilizing mother liquor after lithium extraction, utilizing waste liquor generated after lithium extraction from lepidolite as raw material, adding auxiliary materials such as acidifying agent, aluminum precipitation and sulfur removal agent, so as to produce high-purity cesium phosphate at low cost and high efficiency, realize comprehensive reuse of lithium precipitation mother liquor, reduce production cost of lithium extraction from ore, and reduce pollution of waste liquor.

[0006] To achieve the above object, the present invention provides the following technical solutions:

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

[0008] S1. Acidification: Add lithium precipitation mother liquor into a glass-lined reactor, add acid to adjust the pH to weak acidity, and obtain cesium mother liquor A;

[0009] S2, precipitating sodium-potassium mixed salt: heating and concentrating the cesium mother solution A obtained in step 1, cooling and crystallizing, centrifuging and filtering to separate the sodium-potassium mixed salt to obtain a cesium mother solution B, crushing and drying the sodium-potassium mixed salt and storing it in a warehouse; testing the cesium content of the cesium mother solution B, and proceeding to the next step if it is qualified, otherwise repeating this step until it is qualified;

[0010] S3, acidification and precipitation of alum: adding the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then adding an acidifying agent to adjust the pH of the solution to acidity, boiling at normal pressure, keeping warm and stirring, adding purified water to maintain the volume unchanged, cooling, natural crystallization, centrifugal filtration and separation, to obtain crude cesium alum and filtrate A, the filtrate A can be reused as a supplement of the acidifying agent;

[0011] S4, recrystallization and purification: add the crude cesium alum obtained in step 3 into a glass-lined reactor, add purified water, heat, stir and dissolve, and perform recrystallization and purification to obtain refined cesium alum and filtrate B, and the filtrate B is recycled;

[0012] S5, aluminum precipitation and sulfur removal: add the refined cesium alum obtained in step 4 to a glass-lined reactor, add purified water and stir to dissolve, add aluminum precipitation and sulfur removal reagent, etc., pass carbon dioxide, heat and boil for a certain period of time, centrifuge and separate the residue to obtain cesium mother liquor C, and the residue can be processed into building materials;

[0013] S6, concentration and crystallization: acidifying the cesium mother solution C obtained in step 5 and concentrating it under reduced pressure on a rotary evaporator, cooling and crystallizing after concentration, and centrifuging to obtain a wet cesium phosphate product and a filtrate C, and the filtrate C is recycled;

[0014] S7, drying: the wet cesium phosphate obtained in step 6 is placed in an oven for drying. After drying, the cesium phosphate finished product is obtained. Samples are taken for testing. After the test is qualified, the cesium phosphate is packed in bags and stored 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, and 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 the cesium mother solution A in step 2 is 8-9%, and the cesium content of the cesium mother solution B is greater than 40 g / L.

[0017] Preferably, the acidifying agent in step 3 refers to sulfuric acid, aluminum sulfate, potassium aluminum sulfate, the amount of aluminum sulfate is 1-2% of the cesium mother solution B, the amount of potassium aluminum sulfate is 1-6 times the cesium content of the cesium mother solution B, the solution pH is adjusted to ≤3, the normal pressure boiling time is more than 1 hour, and the heat preservation and stirring are performed for 1 hour.

[0018] Preferably, the amount of purified water added in step 4 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 and crystallization temperature after dissolution is lower than 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 sulfur removal reagent can be any one or a combination of calcium oxide, barium oxide, calcium hydroxide, barium hydroxide octahydrate, ammonia water, 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 and sulfur removal reagent is a composite of calcium hydroxide and barium hydroxide octahydrate, 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 solution C in step 6 is acidified using 85% phosphoric acid, the pH of the solution is adjusted to 1-5, and the liquid-to-solid ratio after concentration is less than 1:3.

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

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention uses waste liquid generated after lithium extraction from lepidolite as a raw material, adds auxiliary materials such as an acidifying agent, an aluminum precipitation sulfur radical removal agent, and the like, and produces high-purity cesium phosphate through the processes of precipitation of sodium-potassium mixed salt, acidification precipitation of alum, recrystallization purification, aluminum precipitation sulfur radical removal, concentration crystallization, centrifugal drying, and the like. The purity of the product reaches more than 99.9%. The method has wide raw material sources, high energy utilization rate, simple and feasible process, small equipment investment, low cost, short production cycle, high efficiency, no new waste generation, and is environmentally friendly. The method 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 sources, and reduces the pollution problem of waste liquid. The method can be fully promoted and applied to the industrialized production of lithium extraction from lepidolite. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart of the present invention; DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used 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 shown.

[0028] Embodiment 1:

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

[0030] S1, acidification: add 2400L lithium precipitation mother liquor into the glass-lined reactor with a pump. The lithium precipitation mother liquor is the alkaline waste liquid in the process of preparing lithium phosphate from lithium mica (the solution pH is between 6 and 12, and the main components are shown in Table 1). The lithium precipitation mother liquor is circulated several times before being added, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A, in which sodium ions and potassium ions react with sulfate ions respectively to synthesize sodium sulfate and potassium sulfate, so as to facilitate the subsequent precipitation of sodium potassium salt to reduce the sodium and potassium ion content in the solution and improve the purity of cesium;

[0031] S2, precipitating 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 centrifugal filtration to obtain a cesium mother liquor B, which is crushed and dried and then stored in a warehouse for other uses; the cesium content of the cesium mother liquor B is detected, and the cesium content of the cesium mother liquor B is required to be greater than 40g / L. If the cesium content is too low, it is not conducive to the precipitation of alum, and the qualified step is entered into the next step, otherwise this step is repeated until it is qualified. The cesium content detection value of this embodiment is 41.0g / L;

[0032] S3, acidification and precipitation of alum: add the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then add 3.2 kg of aluminum sulfate, 45 kg of potassium aluminum sulfate, and sulfuric acid, adjust the solution pH <3, boil at normal pressure for 2.5 hours, keep warm and stir for 1 hour, add purified water to maintain the volume unchanged, cool and crystallize, centrifuge and separate, obtain crude cesium alum and filtrate A, the weight of crude cesium alum is 25.6 kg, and filtrate A can be reused as an acidifying agent, wherein aluminum sulfate and potassium aluminum sulfate react with cesium ions in the solution to generate corresponding cesium alum precipitates, and 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 complex salt of potassium sulfate and aluminum sulfate containing crystal water. It can provide a specific chemical environment and contribute to 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. Potassium aluminum sulfate is relatively cheap and easy to obtain, and 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 purified water, heat and stir to dissolve for recrystallization and purification, the heating temperature is above 95°C, the stirring time is 3 hours, and after the solution is clear, cool and crystallize, the cooling temperature is below 15°C, centrifuge and filter to separate, and obtain 22.8Kg of refined cesium alum and filtrate B, and the filtrate B is recycled;

[0034] S5, precipitation of aluminum to remove sulfur radicals: add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 100L purified water to stir and dissolve, add 5.2Kg calcium hydroxide, 7.1Kg barium hydroxide octahydrate, pass carbon dioxide, the carbon dioxide passing rate is 28L / min, the passing time is 180 minutes, heat and boil for 45 minutes, centrifuge and separate the filter residue to obtain cesium mother liquor C, cesium mother liquor C is 98.6L, the filter residue can be processed into building materials, the filter residue main components are Al(OH)3, CaSO4, BaSO4, CaCO3 and BaCO3, the chemical reaction in this step is as follows:

[0035] 1) Calcium salt and barium salt are used to adjust and remove aluminum ions and part of sulfate in 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] Since Cs2SO4 is highly soluble, it exists in the solution as free cesium ions and sulfate ions;

[0039] 2) Remove sulfate from the solution. The chemical equation is as follows:

[0040] Ca 2+ +SO4 2- =CaSO4↓;

[0041] Ba 2+ +SO4 2- =BaSO4↓;

[0042] 3) Remove excess calcium hydroxide and barium hydroxide octahydrate. The chemical formula 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 solution C obtained in step 5 is treated with 85% phosphoric acid to adjust the solution pH to 2, and after acidification, it is concentrated under reduced pressure on a rotary evaporator until a large amount of crystals appear in the solution, and the rotation speed is appropriately reduced. When it is evaporated to contain only a small amount of liquid, that is, when the liquid-to-solid ratio is less than 1:3, the water bath is stopped from heating, and the water bath is continued to rotate and cool to 20°C, cooled and crystallized, and centrifuged to obtain 5.1Kg of cesium phosphate wet product and filtrate C, and the filtrate C is recycled, wherein the acidification reaction equation is:

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

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

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

[0052] S7, drying: the wet cesium phosphate obtained in step 6 is placed in a 316L stainless steel tray and put into an oven for drying at a temperature of 150°C for 6 hours. After drying, 4.6 kg of cesium phosphate product is obtained. 10 g of sample is taken for testing. The test results are shown in Table 2. After passing the test, the sample is packed in bags and stored in the warehouse.

[0053] Embodiment 2:

[0054] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, the chemical reaction mechanism is the same as that of Example 1, and comprises the following steps:

[0055] S1, acidification: add 2350L lithium precipitation mother liquor into a glass-lined reactor by pump, the lithium precipitation mother liquor is alkaline waste liquid in the process of preparing lithium phosphate from lithium mica (the solution pH is between 6 and 12, and the main components are shown in Table 1), the lithium precipitation mother liquor is circulated several times before adding, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A;

[0056] S2, precipitating sodium-potassium mixed salt: the cesium mother solution A obtained in step 1 is heated and concentrated to 206L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugal filtration to obtain a cesium mother solution B, which is crushed, dried and stored in a warehouse; the cesium content of the cesium mother solution B is detected, and the cesium content of the cesium mother solution B is required to be greater than 40g / L, and the next step is entered if it is qualified, otherwise the step is repeated until it is qualified. The cesium content detection value of this embodiment is 47.2g / L;

[0057] S3, acidification and precipitation of alum: add the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then add 4.4 kg of aluminum sulfate, 60 kg of potassium aluminum sulfate, and sulfuric acid, adjust the solution pH <2, boil at normal pressure for 1.5 hours, keep warm and stir for 1 hour, add purified water during this period to maintain the volume unchanged, cool and crystallize, centrifuge and separate, obtain crude cesium alum and filtrate A, the crude cesium alum weighs 32.1 kg, and the filtrate A can be reused as an acidifying agent;

[0058] S4, recrystallization and purification: add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 100L purified water, heat and stir to dissolve for recrystallization and purification, the heating temperature is above 95°C, the stirring time is 3 hours, and after the solution is clear, cool and crystallize, the cooling temperature is below 15°C, centrifuge and filter to separate, and obtain 28.8Kg of refined cesium alum and filtrate B, and the filtrate B is recycled;

[0059] S5, precipitation of aluminum to remove sulfur radicals: add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 125L purified water to stir and dissolve, add 7.26Kg calcium hydroxide, 10Kg barium hydroxide octahydrate, pass carbon dioxide, the carbon dioxide passing rate is 20L / min, the passing time is 120 minutes, heat and boil for 35 minutes, centrifuge and separate the filter residue to obtain cesium mother liquor C, cesium mother liquor C is 104.1L, and the filter residue can be processed into building materials;

[0060] S6, concentration and crystallization: the cesium mother solution C obtained in step 5 is treated with 85% phosphoric acid to adjust the solution pH to 2, acidified and concentrated on a rotary evaporator under reduced pressure until a large amount of crystals appear in the solution, the rotation speed is appropriately reduced, and the solution is evaporated to contain only a small amount of liquid, that is, when the liquid-to-solid ratio is less than 1:1, the water bath is stopped from heating, and the solution is cooled to 25°C by continuous rotation, cooled and crystallized, and centrifuged to obtain 6.6 kg of cesium phosphate wet product and filtrate C, and the filtrate C is recycled;

[0061] S7, drying: the wet cesium phosphate obtained in step 6 is placed in a 316L stainless steel tray and put into an oven for drying at 160°C for 6 hours. After drying, 6.0 kg of cesium phosphate finished product is obtained. 10 g of sample is taken for testing. The test results are shown in Table 2. After passing the test, the sample is packed in bags and stored in the warehouse.

[0062] Embodiment three:

[0063] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, the chemical reaction mechanism is the same as that of Example 1, and comprises the following steps:

[0064] S1, acidification: add 2200L lithium precipitation mother liquor into the glass-lined reactor by pump, the lithium precipitation mother liquor is the alkaline waste liquid in the process of preparing lithium phosphate from lithium mica (the solution pH is between 6 and 12, and the main components are shown in Table 1), the lithium precipitation mother liquor is circulated several times before adding, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A;

[0065] S2, precipitating sodium-potassium mixed salt: the cesium mother solution A obtained in step 1 is heated and concentrated to 180L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugal filtration to obtain a cesium mother solution B, which is crushed, dried and stored in a warehouse; the cesium content of the cesium mother solution B is detected, and the cesium content of the cesium mother solution B is required to be greater than 40g / L, and the next step is entered if it is qualified, otherwise the step is repeated until it is qualified. The cesium content detection value of this embodiment is 50.3g / L;

[0066] S3, acidification and precipitation of alum: add the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then add 4.7 kg of aluminum sulfate, 60 kg of potassium aluminum sulfate, and sulfuric acid, adjust the solution pH <3, boil at normal pressure for 1.5 hours, keep warm and stir for 1 hour, add purified water during this period to maintain the volume unchanged, cool and crystallize, centrifuge and separate to obtain crude cesium alum and filtrate A, the crude cesium alum weighs 30.7 kg, and the filtrate A can be reused as an acidifying agent;

[0067] S4, recrystallization and purification: add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 100L purified water, heat and stir to dissolve for recrystallization and purification, the heating temperature is above 95°C, the stirring time is 3 hours, and after the solution is clear, cool and crystallize, the cooling temperature is below 15°C, centrifuge and filter to separate, and obtain 28.4Kg of refined cesium alum and filtrate B, and the filtrate B is recycled;

[0068] S5, precipitation of aluminum to remove sulfur radicals: add the refined cesium alum obtained in step 4 to a glass-lined reactor, add 125L purified water to stir and dissolve, add 6.9Kg calcium hydroxide, 9.5Kg barium hydroxide octahydrate, pass carbon dioxide, the carbon dioxide passing rate is 16L / min, the passing time is 120 minutes, heat and boil for 45 minutes, centrifuge and separate the filter residue to obtain cesium mother liquor C, cesium mother liquor C is 100.2L, and the filter residue can be processed into building materials;

[0069] S6, concentration and crystallization: the cesium mother solution C obtained in step 5 is treated with 85% phosphoric acid to adjust the solution pH to 2, acidified and concentrated on a rotary evaporator under reduced pressure until a large amount of crystals appear in the solution, the rotation speed is appropriately reduced, and the solution is evaporated to contain only a small amount of liquid, that is, when the liquid-to-solid ratio is less than 1:1, the water bath is stopped from heating, and the solution is cooled to 25°C by continuous rotation, cooled and crystallized, and centrifuged to obtain 6.2 kg of cesium phosphate wet product and filtrate C, which is recycled;

[0070] S7, drying: the wet cesium phosphate obtained in step 6 is placed in a 316L stainless steel tray and put into an oven for drying at a temperature of 110°C for 5 hours. After drying, 5.7 kg of cesium phosphate product is obtained. 10 g of sample is taken for testing. The test results are shown in Table 2. After passing the test, the sample is packed in bags and stored in the warehouse.

[0071] Embodiment 4:

[0072] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, the chemical reaction mechanism is the same as that of Example 1, and comprises the following steps:

[0073] S1, acidification: add 2400L lithium precipitation mother liquor into the glass-lined reactor by pump, the lithium precipitation mother liquor is the alkaline waste liquid in the process of preparing lithium phosphate from lithium mica (the solution pH is between 6 and 12, and the main components are shown in Table 1), the lithium precipitation mother liquor is circulated several times before adding, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A;

[0074] S2, precipitating sodium-potassium mixed salt: heating and concentrating the cesium mother solution A obtained in step 1 to 200 L, cooling and crystallizing, centrifuging and filtering to separate the sodium-potassium mixed salt to obtain a cesium mother solution B, crushing and drying the sodium-potassium mixed salt and storing it in a warehouse; testing the cesium content of the cesium mother solution B, requiring the cesium content of the cesium mother solution B to be greater than 40 g / L, and proceeding to the next step if it is qualified, otherwise repeating this step until it is qualified, and the cesium content detection value of this embodiment is 65.6 g / L;

[0075] S3, acidification and precipitation of alum: add the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then add 6.3 kg of aluminum sulfate, 88.1 kg of potassium aluminum sulfate, and sulfuric acid, adjust the solution pH to less than 3, boil at normal pressure for 3.5 hours, keep warm and stir for 2 hours, add purified water during this period to maintain the volume unchanged, cool and crystallize, centrifuge and separate, obtain crude cesium alum and filtrate A, the weight of the crude cesium alum is 44.8 kg, and the filtrate A can be reused as an acidifying agent;

[0076] S4, recrystallization and purification: add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 150L purified water, heat and stir to dissolve for recrystallization and purification, the heating temperature is above 95°C, the stirring time is 3 hours, and the solution is cooled and crystallized, the cooling temperature is below 15°C, and centrifugal filtration is performed to obtain 41.1Kg of refined cesium alum and filtrate B, and the filtrate B is recycled;

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

[0078] S6, concentration and crystallization: the cesium mother solution C obtained in step 5 is treated with 85% phosphoric acid to adjust the solution pH to 2, acidified and concentrated on a rotary evaporator under reduced pressure until a large amount of crystals appear in the solution, the rotation speed is appropriately reduced, and the solution is evaporated to contain only a small amount of liquid, that is, when the liquid-to-solid ratio is less than 1:1, the water bath is stopped from heating, and the solution is cooled to 25°C by continuous rotation, cooled and crystallized, and centrifuged to obtain 9.2 kg of cesium phosphate wet product and filtrate C, and the filtrate C is recycled;

[0079] S7, drying: the wet cesium phosphate obtained in step 6 is placed in a 316L stainless steel tray and put into an oven for drying at a temperature of 100°C for 6 hours. After drying, 8.6 kg of cesium phosphate product is obtained. 10 g of sample is taken for testing. The test results are shown in Table 2. After passing the test, the sample is packed in bags and stored in the warehouse.

[0080] Embodiment five:

[0081] A method for producing high-purity cesium phosphate using mother liquor after lithium extraction, the chemical reaction mechanism is the same as that of Example 1, and comprises the following steps:

[0082] S1, acidification: add 2300L lithium precipitation mother liquor into the glass-lined reactor by pump, the lithium precipitation mother liquor is the alkaline waste liquid in the process of preparing lithium phosphate from lithium mica (the solution pH is between 6 and 12, and the main components are shown in Table 1), the lithium precipitation mother liquor is circulated several times before adding, and the pH is adjusted to 5 with sulfuric acid to obtain cesium mother liquor A;

[0083] S2, precipitating sodium-potassium mixed salt: the cesium mother solution A obtained in step 1 is heated and concentrated to 200 L, cooled and crystallized, and the sodium-potassium mixed salt is separated by centrifugal filtration to obtain a cesium mother solution B, which is crushed, dried, and stored in a warehouse; the cesium content of the cesium mother solution B is detected, and the cesium content of the cesium mother solution B is required to be greater than 40 g / L, and the next step is entered if it is qualified, otherwise the step is repeated until it is qualified. The cesium content detection value of this embodiment is 60.3 g / L;

[0084] S3, acidification and precipitation of alum: add the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then add 5.8 kg of aluminum sulfate, 81 kg of potassium aluminum sulfate, and sulfuric acid, adjust the solution pH to less than 3, boil at normal pressure for 2 hours, keep warm and stir for 2 hours, add purified water during this period to maintain the volume unchanged, cool and crystallize, centrifuge and separate, obtain crude cesium alum and filtrate A, the weight of the crude cesium alum is 40.7 kg, and the filtrate A can be reused as an acidifying agent;

[0085] S4, recrystallization and purification: add the crude cesium alum obtained in step 3 to a glass-lined reactor, add 150L purified water, heat and stir to dissolve for recrystallization and purification, the heating temperature is above 95°C, the stirring time is 3 hours, and the solution is cooled and crystallized, the cooling temperature is below 15°C, and centrifugal filtration is performed to obtain 37.4Kg of refined cesium alum and filtrate B, and the filtrate B is recycled;

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

[0087] S6, concentration and crystallization: the cesium mother solution C obtained in step 5 is treated with 85% phosphoric acid to adjust the solution pH to 2, acidified and concentrated on a rotary evaporator under reduced pressure until a large amount of crystals appear in the solution, the rotation speed is appropriately reduced, and the solution is evaporated to contain only a small amount of liquid, that is, when the liquid-to-solid ratio is less than 1:1, the water bath is stopped from heating, and the solution is cooled to 25°C by continuous rotation, cooled and crystallized, and centrifuged to obtain 8.6 kg of cesium phosphate wet product and filtrate C, and the filtrate C is recycled;

[0088] S7, drying: the wet cesium phosphate obtained in step 6 is placed in a 316L stainless steel tray and put into an oven for drying at a temperature of 185°C for 6 hours. After drying, 7.7 kg of cesium phosphate product is obtained. 10 g of sample is taken for testing. The test results are shown in Table 2. After passing the test, the sample is packed in bags and stored in the warehouse.

[0089] Table 1 Lithium Precipitation Mother Liquor Test Report

[0090]

[0091] Table 2 Product Cesium Phosphate Test Report

[0092]

[0093] Through the analysis of Tables 1 and 2, it can be seen that the purity of cesium phosphate produced by the mother liquor after lithium extraction from lepidolite in this method is more than 99.9%, which 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 sources, and reduces the pollution problem of waste liquid. It can be fully promoted and applied to the industrial production of lithium extraction from lepidolite.

[0094] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention 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: The following steps are involved: S1. Acidification: Add lithium precipitation mother liquor into a glass-lined reactor, add acid to adjust the pH to weak acidity, and obtain cesium mother liquor A; S2, precipitating sodium-potassium mixed salt: heating and concentrating the cesium mother solution A obtained in step 1, cooling and crystallizing, centrifuging and filtering to separate the sodium-potassium mixed salt to obtain a cesium mother solution B, crushing and drying the sodium-potassium mixed salt and storing it in a warehouse; testing the cesium content of the cesium mother solution B, and proceeding to the next step if it is qualified, otherwise repeating this step until it is qualified; S3, acidification and precipitation of alum: adding the cesium mother solution B obtained in step 2 into a glass-lined reactor by using a pump or a vacuum pump, then adding an acidifying agent to adjust the pH of the solution to a strong acid, boiling at normal pressure, and stirring at a temperature of 100 °C. During this period, purified water is added to maintain the volume unchanged, the solution is cooled and crystallized, and centrifuged and filtered to obtain crude cesium alum and filtrate A, which can be reused as a supplement of the acidifying agent; S4, recrystallization and purification: add the crude cesium alum obtained in step 3 into a glass-lined reactor, add purified water, heat, stir and dissolve, and perform recrystallization and purification to obtain refined cesium alum and filtrate B, and the filtrate B is recycled; S5, aluminum precipitation and sulfur removal: add the refined cesium alum obtained in step 4 into a glass-lined reactor, add purified water and stir to dissolve, add aluminum precipitation and sulfur removal reagent, introduce carbon dioxide, heat and boil for a certain period of time, centrifuge and separate the residue to obtain cesium mother liquor C, and the residue can be processed into building materials; S6, concentration and crystallization: acidifying the cesium mother solution C obtained in step 5 and concentrating it under reduced pressure on a rotary evaporator, cooling and crystallizing after concentration, and centrifuging to obtain a wet cesium phosphate product and a filtrate C, and the filtrate C is recycled; S7, drying: the wet cesium phosphate obtained in step 6 is placed in an oven for drying. After drying, the cesium phosphate finished product is obtained. Samples are taken for testing. After the test is qualified, the cesium phosphate is packed in bags and stored in the warehouse.

2. The method according to claim 1, characterized in that 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 element. 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 The concentration rate of the cesium mother solution A in step 2 is 8-9%, and the cesium content of the cesium mother solution B is greater than 40 g / L.

4. The method according to claim 1, characterized in that: The acidifying agent in step 3 refers to sulfuric acid, aluminum sulfate, and potassium aluminum sulfate. The amount of aluminum sulfate is 1 to 2% of the cesium mother solution B, and the amount of potassium aluminum sulfate is 1 to 6 times the cesium content of the cesium mother solution B. The solution pH is adjusted to ≤ 3, the normal pressure boiling time is more than 1 hour, and the temperature is kept warm and stirred for 1 hour.

5. The method according to claim 1, characterized in that 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 and crystallization temperature after dissolving is lower than 15° C.

6. The method according to claim 1, characterized in that The amount of purified water added in step 5 is 4 to 5 times that of refined cesium alum, the aluminum precipitation and sulfur removal reagent can be any one or a combination of calcium oxide, barium oxide, calcium hydroxide, barium hydroxide octahydrate, ammonia water, 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.

7. The method according to claim 6, characterized in that The aluminum precipitation and sulfur removal reagent is a composite of calcium hydroxide and barium hydroxide octahydrate, the amount of calcium hydroxide added is 0.22 to 0.25 times of the refined cesium alum, and the amount of barium hydroxide octahydrate added is 0.22 to 0.35 times of the refined cesium alum.

8. The method according to claim 1, characterized in that The cesium mother solution C in step 6 is acidified by using 85% phosphoric acid, and the pH of the solution is adjusted to 1-5. After concentration, the liquid-to-solid ratio is less than 1:

3.

9. The method according to claim 1, characterized in that: The oven temperature in step 7 is 60-250 0 C, drying time 6 hours.

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