Method for resource utilization of potassium-sodium-lithium mixed salt

Abstract

The application discloses a kind of potassium-sodium-lithium mixed salt resource utilization method, belong to industrial waste processing technical field.The application efficiently recovers low content lithium in mixed salt at lower cost, to separate potassium and sodium effectively with reasonable technology, and recover sodium carbonate, to prepare high-purity glauber's salt, lithium recovery rate is greater than 90%, sodium carbonate recovery rate is greater than 80%, potassium recovery rate is greater than 90%, lithium carbonate content in crude lithium is 10~60%, sodium bicarbonate purity is >99%, glauber's salt purity is >99%, and K2SO4 content in recovered potassium salt is >38% on average.The overall energy consumption of the process in the application is low, greatly reducing the investment cost, green and environmentally friendly, with excellent economic benefits, providing a systematic solution for the treatment of lithium-potassium-sodium mixed salt or lithium precipitation mother liquor.

Description

Technical Field

[0001] This invention belongs to the field of industrial waste treatment technology, specifically relating to a method for the resource utilization of potassium, sodium, and lithium mixed salts. Background Technology

[0002] When extracting lithium from spodumene or lepidolite ore, a lithium sulfate solution is obtained after roasting, leaching, and impurity removal. Lithium carbonate is then precipitated using excess sodium carbonate. The post-precipitation solution mainly consists of sodium sulfate, along with sodium carbonate, potassium introduced from the ore, dissolved lithium carbonate, and other impurities. One common treatment method for the post-precipitation solution is two-stage evaporation and crystallization. The first evaporation and crystallization precipitates relatively pure sodium sulfate solid; the sodium precipitate mother liquor undergoes a second evaporation and crystallization to obtain a slightly yellow mixed salt containing sodium sulfate, sodium carbonate, potassium sulfate, and a small amount of lithium. The current treatment of such mixed salts or the mother liquor from the first evaporation and crystallization is quite difficult, mainly due to several reasons: First, the lithium content in the mixed salt is only about 0.1%, and conventional lithium extraction processes, such as adsorption or extraction, are not economically viable due to the declining price of lithium salts; second, the uses of potassium-containing sodium sulfate are limited and difficult to process, while potassium-sodium separation processes still need improvement; third, some companies use sulfuric acid to neutralize sodium carbonate, converting high-value sodium carbonate into low-value sodium sulfate, which is unprofitable, and a low-cost sodium carbonate extraction process is urgently needed. To address the current difficulties in treating potassium-sodium-lithium mixed salts, this invention provides a systematic solution. Summary of the Invention

[0003] In view of the above-mentioned prior art, the present invention provides a method for the resource utilization of potassium-sodium-lithium mixed salts to solve the technical problem of difficult processing of potassium-sodium-lithium mixed salts.

[0004] To achieve the above objectives, the present invention provides a method for the resource utilization of potassium, sodium, and lithium mixed salts, comprising the following steps:

[0005] S1: Mix a potassium-sodium-lithium mixed salt with solvent one, wherein solvent one is either crystallization mother liquor two or water, and crystallization mother liquor two is obtained from subsequent S4; then heat the mixture to 70~100℃, keep it warm and stir for 20~100 min, filter while hot to obtain solid one and filtrate one; stir and cool filtrate one to 20~40℃ and keep it for 1~2 h, then filter to obtain potassium salt one and crystallization mother liquor one; under stirring, introduce CO2 into crystallization mother liquor one to carbonize the sodium carbonate in crystallization mother liquor one, filter to obtain solid three and filtrate three; wash and dry solid three to obtain sodium bicarbonate; adjust the pH of filtrate three to 6.5~7.5, then evaporate and crystallize to obtain potassium salt two;

[0006] S2: Mix solid one with solvent two, stir and dissolve at 40~65 ℃ for 30~60 min, filter while hot to obtain lithium-containing residue and filtrate two, wherein solvent two is a mixture of water and crystallization mother liquor two or water;

[0007] S3: Adjust the temperature of filtrate 2 to 32~45 ℃, and introduce CO2 while stirring to carbonize the sodium carbonate in filtrate 2. Filter to obtain solid 4 and filtrate 4. Wash and dry solid 4 to obtain sodium bicarbonate.

[0008] S4: Cool filtrate four to 5~10 ℃ and keep it at this temperature to crystallize until the amount of crystals no longer increases; then filter to obtain crystallization mother liquor two and crude sodium sulfate; heat the crude sodium sulfate to 40~60 ℃, then adjust the pH to neutral, keep it at this temperature for 45~90 min, filter to obtain solid five and filtrate five; dry solid five at 100~130 ℃ to obtain sodium sulfate.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, in the system obtained by mixing the potassium-sodium-lithium mixed salt in S1 with solvent 1, the mass ratio of water to potassium is 10~18:1.

[0011] Furthermore, in S2, the ratio of water to all solid solutions in the mixture of solid one and solvent two is 2 to 2.8.

[0012] Furthermore, in S1 and S3, the CO2 gas flow rate during sodium carbonate carbonation is 2–10 L / min. -1 . L -1 .

[0013] Furthermore, in both S1 and S3, the pH value at the endpoint of sodium carbonate carbonation was 7.5–8.3.

[0014] Furthermore, the drying temperature of solid five in S4 is 110~120 ℃, and the drying time is 40~60 min.

[0015] Furthermore, the potassium-sodium-lithium mixed salt contains 5-20 wt% potassium sulfate and 20-45 wt% sodium carbonate.

[0016] The processing technology of this invention can produce the following effects when used to awaken a mixed potassium, sodium, and lithium salt:

[0017] 1. Potassium-Sodium Separation: The inventors discovered through experiments that when sodium carbonate, potassium sulfate, and sodium sulfate coexist, the actual solubility of sodium sulfate decreases significantly at higher temperatures. Therefore, temperatures above 70°C are favorable for washing out potassium sulfate, while the dissolution of sodium sulfate is inhibited. The dissolved sodium ions, after carbonization, mostly precipitate as sodium bicarbonate, thus achieving potassium-sodium separation. When the potassium eluent (filtrate two) is cooled to 35-40°C, the solubility of potassium sulfate decreases, while the solubility of both sodium carbonate and sodium sulfate increases, precipitating potassium sulfate (K3Na(SO4)2) with a high potassium content. Further cooling to 25°C precipitates potassium sodium alum (K2SO4·Na2SO4·6H2O), while sodium carbonate and sodium sulfate show minimal precipitation. Then, a nearly saturated sodium carbonate solution enters a carbonization tower for carbonization, generating a large amount of sodium bicarbonate. After filtration and pH adjustment with sulfuric acid, the filtrate is evaporated and crystallized to obtain a potassium-sodium mixed salt with a potassium sulfate content greater than 20%, which can be used for the purification and preparation of potassium sulfate. The technical solution provided by this invention is suitable for potassium extraction from a potassium-sodium mixed salt with a potassium sulfate content of 5% to 20% and a sodium carbonate content of 20% to 50%.

[0018] 2. Lithium Extraction: The solid remaining after potassium extraction (Solid 1) is dissolved at 40-60 °C to obtain a near-saturated solution. After filtration, approximately 70% of the lithium carbonate enters the residue (Solid 2), where the lithium carbonate content is as high as 10-60%, resulting in a lithium enrichment of over 100 times. The lithium carbonate not remaining in the residue enters the solution and undergoes subsequent carbonation and other processes. Finally, the lithium is concentrated in the mother liquor (Crystallization Mother Liquor 2), which is returned to the dissolution process to reform lithium carbonate, which remains in the residue. Therefore, the lithium recovery rate is over 90%. Compared to other lithium extraction methods such as extraction and adsorption, this scheme's lithium recovery method is synergistically coupled with sodium carbonate recovery and sodium sulfate crystallization processes, offering advantages such as low cost, simple process, and high economic benefits.

[0019] 3. Sodium carbonate recovery: Sodium carbonate in the potassium washing solution (filtrate 2) and the lithium extraction solution (crystallization mother liquor 1) is recovered by carbonation. The reaction equation is as follows:

[0020] Na₂CO₃ + CO₂ + H₂O = 2NaHCO₃↓

[0021] During the carbonization stage, maintain a certain temperature to prevent sulfate crystallization caused by a drop in temperature during the initial reaction. +The common ion effect improves the yield of sodium bicarbonate. This invention uses two carbonization towers, one for the potassium washing solution and the other for the lithium extraction solution. The initial reaction temperature is controlled at 30-40℃, and the final pH value at the carbonization endpoint is controlled at 7.5-8.3, which effectively improves the purity and yield of the sodium bicarbonate product. Testing showed that the sodium bicarbonate obtained from both solutions had a purity of over 99%, with potassium content less than 0.012% and 0.002% respectively, sulfate ion content less than 0.07%, lithium content less than 0.0001%, and sodium carbonate recovery rate exceeding 80%.

[0022] 4. Preparation of high-quality sodium sulfate: After lithium extraction, the liquid is carbonized to extract sodium bicarbonate, and then cooled to 5-10℃. Na2SO4 precipitates out in large quantities as heptahydrate or decahydrate sodium sulfate. The lithium in the carbonized solution enters the mother liquor II for crystallization and is reused to dissolve the mixed salts, thus achieving efficient lithium recovery. The crude sodium sulfate is directly heated to 40℃-60℃ to convert it into anhydrous sodium sulfate. Some of the sodium sulfate dissolves in its own water of crystallization, and at the same time, potassium impurities in the sodium sulfate are also transferred into the solution. A small amount of sulfuric acid is added to adjust the pH of the slurry to neutral. After hot filtration and drying, high-quality sodium sulfate with a purity greater than 99% is obtained. The filtrate is combined with the carbonized liquid (filtrate IV) and then cooled for crystallization.

[0023] 5. Water Balance and Potassium Cycle Accumulation Issues: In the overall process design, to reduce energy consumption, most of the mother liquor is recycled after heat exchange. The mixed salt contains 10%~20% water, and all water in the process is recycled. After the process stabilizes, no additional water is added. However, the following three issues must be considered: First, the water balance between the potassium washing and extraction process, the lithium extraction process, and the product washing process; second, the potassium remaining in the mixed salt after potassium washing and extraction enters the sodium sulfate preparation process, and the potassium cycle accumulation problem needs to be solved; third, the accumulation of other small amounts of soluble impurities in the mixed salt needs to be addressed. The solution of this invention is as follows: the mother liquor produced in the crystallization section after carbonization in the potassium extraction process is completely evaporated and crystallized to obtain a mixed salt of potassium sulfate and sodium sulfate. The evaporated water vapor and mother liquor are combined and used as makeup water for flexible distribution, which can save some energy consumption. The crystallization mother liquor produced in the sodium sulfate process contains residual potassium. A portion of it is reacted with sodium hydroxide to convert a small amount of sodium bicarbonate into sodium carbonate, which is then returned to the potassium washing and extraction process (to prevent sodium bicarbonate from decomposing and releasing CO2 at higher temperatures). This effectively solves the problem of potassium accumulation. The sodium bicarbonate washing water is used in stages and then returned to the lithium extraction and dissolution process. This effectively solves the problem of water distribution balance in each process and potassium accumulation.

[0024] The beneficial effects of this invention are:

[0025] This invention efficiently recovers low-content lithium from mixed salts at a relatively low cost, effectively separates potassium and sodium and recovers sodium carbonate using reasonable technology, thereby producing high-purity sodium sulfate. The lithium recovery rate is greater than 90%, the sodium carbonate recovery rate is greater than 80%, and the potassium recovery rate is greater than 90%. The lithium carbonate content in the crude lithium is 10-60%, the sodium bicarbonate purity is >99%, the sodium sulfate purity is >99%, and the average K₂SO₄ content in the recovered potassium salt is >38%. The process in this invention has low overall energy consumption, significantly reducing investment costs, is environmentally friendly, and has excellent economic benefits, providing a systematic solution for the treatment of lithium-potassium-sodium mixed salts or lithium precipitation mother liquor. Attached Figure Description

[0026] Figure 1 This is a process flow diagram for the resource utilization of mixed potassium, sodium, and lithium salts. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0028] Example 1

[0029] A method for the resource utilization of mixed potassium, sodium, and lithium salts includes the following steps:

[0030] S1: Weigh 2 kg of potassium-sodium-lithium mixed salt (the composition of the mixed salt is shown in Table 1), add 1.2 kg of water, stir and mix evenly, and the resulting system contains w 总H2O / w K =16.6; The mixture was heated to 75°C, stirred for 40 min, and filtered while hot to obtain solid 1 (wet weight 1.31 Kg, water content 16.8%) and filtrate 1;

[0031] Table 1. Composition of potassium, sodium, and lithium mixed salts (%)

[0032] content / % 46.4 9.8 30.5 0.21 13

[0033] S2: Solid I is mixed with water, the water-to-solid ratio of the mixture is 2.48; then stirred and dissolved at 50 °C for 40 min, filtered while hot, to obtain 15.6 g of solid II (crude lithium carbonate) and 2.94 L of filtrate II; filtrate I is stirred and cooled to 25 °C and maintained for 1.5 h, then filtered, to obtain 161 g of potassium salt I (main components are K2SO4·Na2SO4·6H2O) and crystallization mother liquor I; crystallization mother liquor I is placed in a carbonization tower, heated to 30 °C, and then aerated with a microporous head at a rate of 3.5 L / min under stirring. -1 .L -1CO2 was introduced at a rate until the pH of the solution reached 8.2, and then filtered to obtain solid III and filtrate III. Solid III was washed (washing solution was water, and the water-to-solid ratio was 0.5:1) and dried at 50 °C to obtain sodium bicarbonate solid (422 g). The pH of filtrate III was adjusted to 7.0 with sulfuric acid (1 mol / L), and then evaporated to crystallize, yielding 285 g of potassium salt II (a mixture of potassium sulfate and sodium sulfate).

[0034] S3: Place filtrate two into the carbonization tower, heat to 38 ℃, and aerate at a rate of 3.5 L / min using a microporous aeration head while stirring. -1 .L -1 CO2 was introduced at a certain rate until the pH of the solution reached 8.0. Aeration was then stopped, and the solution was filtered to obtain solid IV and filtrate IV. Solid IV was washed (the washing liquid was water, and the water-to-solid ratio was 0.5:1) and dried at 50 °C to obtain sodium bicarbonate solid (342 g).

[0035] S4: Cool filtrate four to 8 ℃ and keep it at this temperature to crystallize until the amount of crystals no longer increases; then filter to obtain crystallization mother liquor two and crude sodium sulfate; add a small amount of concentrated sulfuric acid (98%) to the crude sodium sulfate, and at the same time raise the temperature to 40 ℃, then add sulfuric acid until the pH of the system is 7.0, keep the reaction at this temperature for 50 min, filter to obtain solid five and filtrate five; dry solid five at 120 ℃ for 40 min to obtain sodium sulfate (398 g).

[0036] Example 2

[0037] A method for the resource utilization of mixed potassium, sodium, and lithium salts includes the following steps:

[0038] S1: Weigh 2 kg of potassium-sodium-lithium mixed salt (the composition of the mixed salt is shown in Table 1), add 1.5 kg of the mother liquor obtained in Example 1 S4, then add 10 g of sodium hydroxide, stir and mix evenly, and the resulting system contains w 总H2O / w K =11.1; Heat the mixture to 90°C, stir for 40 min, and filter while hot to obtain solid one (wet weight 1.56 Kg, water content 17.5%) and filtrate one;

[0039] S2: Solid I was mixed with water and the mother liquor II obtained in Example 1 S4 (the mass ratio of water to mother liquor II was 1.8:1), and the water-to-solid ratio of the mixture was 2.51. The mixture was then stirred and dissolved at 50 °C for 40 min, and filtered while hot to obtain 26.8 g of solid II (crude lithium carbonate) and 3.34 L of filtrate II. Filtrate I was stirred and cooled to 25 °C and maintained for 1.5 h, then filtered to obtain 207 g of potassium salt I (mainly composed of K2SO4·Na2SO4·6H2O) and mother liquor I. Mother liquor I was placed in a carbonization tower, heated to 35 °C, and then aerated with a microporous aerator at a rate of 3.5 L / min under stirring. -1 .L -1 CO2 was introduced at a rate until the pH of the solution reached 8.3, and then filtered to obtain solid III and filtrate III. Solid III was washed (washing solution was water, and the water-to-solid ratio was 0.5:1) and dried at 50 °C to obtain sodium bicarbonate solid (427 g). The pH of filtrate III was adjusted to 7.5 with sulfuric acid (1 mol / L), and then evaporated to crystallize, yielding 336 g of potassium salt II (a mixture of potassium sulfate and sodium sulfate).

[0040] S3: Place filtrate two into the carbonization tower, heat to 38 ℃, and aerate at a rate of 3.5 L / min using a microporous aeration head while stirring. -1 .L -1 CO2 was introduced at a certain rate until the pH of the solution reached 8.0. Aeration was then stopped, and the solution was filtered to obtain solid 4 and filtrate 4. Solid 4 was washed (the washing liquid was water, and the water-to-solid ratio was 0.5:1) and dried at 50 °C to obtain sodium bicarbonate solid (404 g).

[0041] S4: Mix filtrate four with filtrate five obtained in Example 1 S4, then cool the mixture to 5 ℃ and keep it at this temperature to crystallize until the amount of crystals no longer increases; then filter to obtain crystallization mother liquor two and crude sodium sulfate; add a small amount of concentrated sulfuric acid (98%) to the crude sodium sulfate, and at the same time raise the temperature to 50 ℃, then add sulfuric acid until the pH of the system is 7.5, keep the reaction at this temperature for 35 min, filter to obtain solid five and filtrate five; dry solid five at 120 ℃ for 40 min to obtain sodium sulfate (685 g).

[0042] Example 3

[0043] A method for the resource utilization of mixed potassium, sodium, and lithium salts includes the following steps:

[0044] S1: Weigh 2 kg of potassium-sodium-lithium mixed salt (the composition of the mixed salt is shown in Table 2), add 1.2 kg of water, stir and mix evenly, and the resulting system contains w 总H2O / w K=14; Heat the mixture to 80°C, stir for 40 min, and filter while hot to obtain solid one (wet weight 1.40 Kg, water content 15.7%) and filtrate one;

[0045] Table 2. Composition of Potassium, Sodium, and Lithium Mixed Salts (%)

[0046] content / % 40.1 11.5 34.5 0.21 12

[0047] S2: Solid I is mixed with water, the water-to-solid ratio of the mixture is 2.45; then stirred and dissolved at 50 °C for 40 min, filtered while hot, to obtain 22.6 g of solid II (crude lithium carbonate) and 2.94 L of filtrate II; filtrate I is stirred and cooled to 25 °C and maintained for 1 h, then filtered, to obtain 204 g of potassium salt I (main components are K2SO4.Na2SO4.6H2O) and crystallization mother liquor I; crystallization mother liquor I is placed in a carbonization device, heated to 30 °C, and then aerated with a microporous aerator at 6 L / min under stirring. -1 .L -1 CO2 was introduced at a rate until the pH of the solution reached 8.2, and then filtered to obtain solid III and filtrate III. Solid III was washed (washing solution was water, and the water-to-solid ratio was 0.5:1) and dried at 55 °C to obtain sodium bicarbonate solid (526 g). The pH of filtrate III was adjusted to 6.5 with sulfuric acid (1 mol / L), and then evaporated to crystallize, yielding 298 g of potassium salt II (a mixture of potassium sulfate and sodium sulfate).

[0048] S3: Place the second filtrate in the carbonization tower, heat it to 38 ℃, and aerate it at a rate of 4 L / min using a microporous aeration head while stirring. -1 .L -1 CO2 was introduced at a certain rate until the pH of the solution reached 8.0. Aeration was then stopped, and the solution was filtered to obtain solid IV and filtrate IV. Solid IV was washed (the washing liquid was water, and the water-to-solid ratio was 0.5:1) and dried at 50 °C to obtain sodium bicarbonate solid (381g).

[0049] S4: Cool filtrate four to 10 ℃ and keep it at this temperature to crystallize until the amount of crystals no longer increases; then filter to obtain crystallization mother liquor two and crude sodium sulfate; add a small amount of concentrated sulfuric acid (98%) to the crude sodium sulfate, and at the same time raise the temperature to 50 ℃, then add sulfuric acid (1mol / L) until the pH of the system is 6.5, keep the reaction at this temperature for 60 min, filter to obtain solid five and filtrate five; dry solid five at 120 ℃ for 40 min to obtain sodium sulfate (398 g).

[0050] Experimental example:

[0051] 1. Product testing results

[0052] The test results of the products obtained by the method in the embodiments of the present invention are shown in Table 3.

[0053] Table 3. Detection results of Examples 1-3

[0054]

[0055] Note: 1 Example S2: Purity of sodium bicarbonate recovered by carbonization; 2 The purity of sodium bicarbonate recovered by carbonization in Example S3; 3 The weighted average of K2SO4% in the two recovered potassium salts.

[0056] As can be seen from Table 3, the processing method of this invention can directly obtain two products: industrial-grade sodium bicarbonate and high-quality sodium sulfate. Crude lithium carbonate can be used to prepare lithium carbonate. The available method is to add water to slurry, carbonize with CO2, remove impurities, and then pyrolyze to obtain battery-grade lithium carbonate. The potassium sulfate content in the two potassium-containing salts obtained is 35-60% and 18-25%, respectively, and can be used to prepare potassium sulfate.

[0057] 2. Economic Benefit Analysis of the Potassium-Sodium-Lithium Mixed Salt Resource Utilization Method in this Invention

[0058] The economic benefits of using the method of this invention to process 30,000 tons / year of lithium, sodium, and potassium mixed salt are shown in Table 4.

[0059] Table 4. Economic Benefit Analysis of Processing 30,000 Tons / Year of Lithium-Sodium-Potassium Mixed Salt

[0060]

[0061] As can be seen from Table 3, the method of the present invention for treating lithium, sodium and potassium mixed salt can generate good economic benefits and has great practical value.

[0062] Although specific embodiments of the present invention have been described in detail with reference to examples, they should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A method for the resource utilization of a mixed potassium, sodium, and lithium salt, characterized in that, Includes the following steps: S1: A potassium-sodium-lithium mixed salt is mixed with solvent one, wherein the components of the potassium-sodium-lithium mixed salt include potassium sulfate and sodium carbonate, and solvent one is crystallization mother liquor two, which is obtained from subsequent S4; then the mixed system is heated to 70~100℃, kept warm and stirred for 20~100 min, and filtered while hot to obtain solid one and filtrate one; filtrate one is stirred and cooled to 20~40℃ and kept for 1~2 h, and then filtered to obtain potassium salt one and crystallization mother liquor one; CO2 is introduced into crystallization mother liquor one under stirring to carbonize the sodium carbonate in crystallization mother liquor one, and filtered to obtain solid three and filtrate three; solid three is washed and dried to obtain sodium bicarbonate; the pH of filtrate three is adjusted to 6.5~7.5, and then evaporated and crystallized to obtain potassium salt two; S2: Mix solid one with solvent two, stir and dissolve at 40~65 ℃ for 30~60 min, filter while hot to obtain lithium carbonate-containing residue and filtrate two, wherein solvent two is a mixture of water and crystallization mother liquor two; S3: Adjust the temperature of filtrate two to 32~45 ℃, and introduce CO2 while stirring to carbonize the sodium carbonate in filtrate two. Filter to obtain solid four and filtrate four. The solid was washed and dried to obtain sodium bicarbonate; S4: Cool filtrate four to 5~10 ℃ and keep it at this temperature to crystallize until the amount of crystals no longer increases; then filter to obtain crystallization mother liquor two and crude sodium sulfate; heat the crude sodium sulfate to 40~60 ℃, then adjust the pH to neutral, keep it at this temperature for 45~90 min, filter to obtain solid five and filtrate five; dry solid five at 100~130 ℃ to obtain sodium sulfate.

2. The method for resource utilization of potassium, sodium, and lithium mixed salts according to claim 1, characterized in that: The mass ratio of water to potassium in the system obtained after mixing potassium, sodium, and lithium mixed salts with solvent S1 is 10~18:

1.

3. The method for resource utilization of potassium-sodium-lithium mixed salt according to claim 1, characterized in that: In both S1 and S3, the CO2 ventilation rate during sodium carbonate carbonation is 2~10 L / (min×L).

4. The method for resource utilization of potassium-sodium-lithium mixed salt according to claim 1, characterized in that: In both S1 and S3, the pH value at the endpoint of sodium carbonate carbonation is 7.5~8.

3.

5. The method for resource utilization of potassium-sodium-lithium mixed salt according to claim 1, characterized in that: The drying temperature of solid five in S4 is 110~120 ℃, and the drying time is 40~60 min.

6. The method for resource utilization of potassium-sodium-lithium mixed salt according to claim 1, characterized in that: The potassium-sodium-lithium mixed salt contains 5-20 wt% potassium sulfate and 20-45 wt% sodium carbonate.

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