Method and device for extracting lithium from salt lake brine at high yield

Abstract

The invention relates to a method for extracting lithium from salt lake brine with high yield, which specifically comprises the following steps: adsorbing lithium in the salt lake brine by using a lithium extraction adsorbent, leaching and desorbing to obtain a lithium-containing desorption solution, and concentrating the lithium-containing desorption solution to obtain a lithium-containing concentrated solution; lithium phosphate can be prepared by adding a phosphate radical-containing agent to the lithium-containing desorption solution or concentrated solution and controlling the reaction temperature and pH value. In the preparation process, the lithium yield is high, the method is simple, and the obtained lithium phosphate can be used for preparing a battery material lithium iron phosphate.

Description

Technical Field

[0001] The invention relates to the field of lithium extraction from salt lakes, and in particular to a method and a device for extracting lithium from salt lake brine with high yield. Background Art

[0002] Lithium and its compounds are widely used in many fields such as batteries, medicine, aerospace, chemical industry and national defense due to their excellent performance. They play a vital role in economic development and are known as the "new energy of the 21st century". Lithium resources mainly come from lithium ore and salt lake brine. Salt lake brine has the highest lithium content, accounting for 66% of the world's lithium reserves. my country is a country with a large number of lithium resources, and its reserves are among the highest in the world. Among them, the salt lake lithium resource reserves in Qinghai and Tibet account for more than 85% of my country's total reserves.

[0003] The lithium extraction process from salt lake brine is simple, low-cost, and environmentally friendly, which meets market demand. At present, the research object of lithium extraction is mainly salt lake brine. However, in the prior art, most of them are lithium-rich solutions obtained from salt lake brine, and then CO2 is introduced into the lithium precipitation in a sodium carbonate solution or an alkaline environment to obtain lithium carbonate products. The lithium concentration in the lithium precipitation mother liquor of these lithium precipitation technologies is more than 1g / L, and the lithium loss during the lithium precipitation process is as high as more than 15%. A Chinese patent (application number 201811183552.5) ​​discloses a method for extracting lithium carbonate from salt lake brine. The invention has a low recovery rate of lithium carbonate, which is between 40% and 52%. A Chinese patent (application number 201410296274.X) discloses a method for purifying and separating lithium carbonate mixed salts using high-temperature brine. The yield of lithium carbonate produced by this invention is also low, about 50%.

[0004] A Chinese patent (application number 201910735486.6) discloses a method for extracting lithium from salt lake brine and preparing lithium phosphate and its use. The method of the present invention has an extraction rate of lithium from salt lake brine of >94%. However, the above invention is limited by the grade of brine and is only applicable to brine with a lithium concentration of 2 to 5 g / L. This brine is obtained by placing underground brine in a salt pan for more than 3 years, which is a long period. Using oxalic acid to remove calcium, magnesium and other ions in brine not only requires a large amount of drugs, which is not conducive to environmental protection, but also the large amount of precipitates generated will carry lithium ions, causing excessive lithium loss.

[0005] Therefore, developing a high-yield, environmentally friendly salt lake lithium extraction technology that is not limited by brine type and grade is of great significance to the new energy field. Summary of the invention

[0006] The object of the present invention is to provide a method for extracting lithium from salt lake brine with a high yield, comprising using a lithium extraction adsorbent to adsorb lithium in the salt lake brine, then eluting and desorbing to obtain a lithium-containing desorption liquid, and then concentrating the lithium-containing desorption liquid to obtain a lithium-containing concentrated liquid; lithium phosphate can be prepared by adding a phosphate-containing agent to the lithium-containing desorption liquid or the concentrated liquid and controlling the reaction temperature and pH value.

[0007] A method for extracting lithium from salt lake brine with high yield comprises the following steps:

[0008] Step 1, contacting salt lake brine with an adsorbent to adsorb lithium ions;

[0009] Step 2, eluting and washing the adsorbent obtained in step 1 to obtain a lithium-containing desorption liquid;

[0010] Step 3: The lithium-containing desorption liquid obtained in step 2 is concentrated or not concentrated, and a phosphate solution is added to separate the precipitate to obtain lithium phosphate.

[0011] In the step 1, the salt lake brine can be brine with chloride-type salt lake brine, magnesium sulfate-type salt lake brine, carbonate-type salt lake brine, deep underground brine, etc. as raw materials. It can be directly extracted from underground or the surface, or it can be brine from which salt is precipitated by evaporation and concentration. The lithium concentration in the salt lake brine is 0.02-5.0 g / L.

[0012] In the step 1, the adsorbent is at least one of an aluminum salt adsorbent, a titanium-based adsorbent or a manganese-based adsorbent.

[0013] In the step 2, the lithium concentration in the lithium-containing desorption solution is 0.4 to 12.0 g / L.

[0014] In the step 3, when the lithium ion concentration is 0.4-1.5 g / L, it needs to be concentrated.

[0015] The concentration process uses one or more combinations of reverse osmosis membranes, forward osmosis membranes, electrodialysis, and evaporation devices.

[0016] The phosphate solution refers to one or more combined solutions of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0017] The concentration of the phosphate solution is 15 to 50 wt%, preferably 25 to 40 wt%.

[0018] The amount of the phosphate solution is calculated based on a molar ratio of phosphate to lithium ion of 1:3, and the phosphate can be in excess of 3 to 15 wt%.

[0019] The pH value of the phosphate-containing solution can be controlled above 9.0, preferably 10.0 to 14.0.

[0020] The pH value is controlled by adding alkali.

[0021] The alkali refers to one or more combinations of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, ammonia water, ammonium carbonate, and ammonium bicarbonate.

[0022] The reaction temperature after adding the phosphate solution is controlled at 30-100°C.

[0023] The method further comprises step 5, wherein the mother liquor separated in step 4 is concentrated by using a high-pressure reverse osmosis membrane, and then divalent or multivalent cations are removed by using a cation exchange resin, and the obtained permeate is reused after adding phosphate.

[0024] A device for extracting lithium from salt lake brine with high yield, comprising:

[0025] Adsorption column, used for adsorption of lithium ions from salt lake brine;

[0026] A concentrator, connected to the liquid outlet of the adsorption column, for concentrating the lithium-containing eluent;

[0027] A precipitation reactor is connected to the concentration device and is used to perform lithium phosphate precipitation reaction on the obtained concentrated solution; and a phosphate adding tank and an alkali adding tank are connected to the precipitation reactor;

[0028] A solid-liquid separation device, connected to the precipitation reactor, is used to separate the precipitate after the lithium phosphate precipitation reaction;

[0029] A high-pressure reverse osmosis membrane is connected to the mother liquid outlet of the solid-liquid separation device and is used to concentrate the obtained mother liquid;

[0030] The cation exchange resin column has an inlet connected to the concentrate side of the high-pressure reverse osmosis membrane for removing divalent or multivalent cations from the concentrate, and an outlet connected to the phosphate addition tank.

[0031] The adsorption column is filled with one of aluminum salt adsorbent, titanium series adsorbent or manganese series adsorbent.

[0032] The concentration device is one or a combination of reverse osmosis membrane, forward osmosis membrane, electrodialyzer or evaporation device.

[0033] The phosphate adding tank is loaded with any one of the solutions of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate and ammonium phosphate.

[0034] The solid-liquid separation device is a centrifugal separation device, a sedimentation separation device or a membrane separation device, or a combination of these.

[0035] The cation exchange resin is filled with sodium type cation exchange resin.

[0036] Beneficial Effects

[0037] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention has a wider application scope and is almost not limited by the type and grade of brine. It can be applied to chloride-type salt lake brine, magnesium sulfate-type salt lake brine, carbonate-type salt lake brine, deep underground brine, etc. with a lithium concentration of 0.02-5.0 g / L as raw materials. It can be directly extracted from underground or the surface, or it can be brine from which salt is precipitated by evaporation and concentration. (2) During the lithium precipitation process, the lithium recovery rate is high, between 93.0% and 99.5%. (3) The preparation process described in the present invention is simple to operate, low in cost, does not require the consumption of a large amount of chemicals, and has no environmental hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of the method for extracting lithium from salt lake brine with high yield in Example 1.

[0039] Figure 2 It is the device diagram of this patent.

[0040] Among them, 1. adsorption column; 2. concentration device; 3a. phosphate adding tank; 3b. alkali adding tank; 4. precipitation reactor; 5. solid-liquid separation device; 6. high-pressure reverse osmosis membrane; 7. cation exchange resin column. DETAILED DESCRIPTION

[0041] The main process and implementation process of this patent are described as follows:

[0042] (1) sending salt lake brine into a device equipped with a lithium-extracting adsorbent for adsorption, and after the adsorption is completed, eluting and desorbing the lithium-extracting adsorbent, and collecting the lithium-containing desorbed liquid;

[0043] (2) the lithium-containing desorption liquid is sent to a concentration device for concentration to obtain a lithium-containing concentrated liquid;

[0044] (3) The lithium-containing desorption liquid or lithium-containing concentrated liquid is sent to a lithium precipitation device, a phosphate solution is added, and the reaction pH value and reaction temperature are controlled, and the reaction precipitate is collected, which is lithium phosphate.

[0045] (4) After the lithium phosphate is separated, the mother liquor obtained by separation is concentrated by a high-pressure reverse osmosis membrane, and then the divalent or multivalent cations are removed by a cation exchange resin. The obtained permeate is then added with phosphate and reused.

[0046] Optionally, the salt lake brine can be brine with chloride-type salt lake brine, magnesium sulfate-type salt lake brine, carbonate-type salt lake brine, deep underground brine, etc. as raw materials. It can be directly extracted from underground or the surface, or it can be brine from which salt is precipitated by evaporation and concentration. The lithium concentration in the salt lake brine is between 0.02 and 5.0 g / L.

[0047] Optionally, the lithium extraction adsorbent may be at least one of an aluminum salt adsorbent, a titanium-based adsorbent or a manganese-based adsorbent.

[0048] Optionally, the lithium concentration in the lithium-containing desorption liquid is 0.4-12.0 g / L; wherein, the lithium-containing desorption liquid with a lithium concentration of 0.4-1.5 g / L is sent to a concentration device; the lithium-containing desorption liquid with a lithium concentration of 1.5-12.0 g / L can be sent to a concentration device or directly sent to a lithium precipitation device.

[0049] Optionally, the concentration device may be a combination of one or more of a reverse osmosis membrane, a forward osmosis membrane, an electrodialysis device, and an evaporation device.

[0050] Optionally, the lithium concentration in the lithium-containing concentrated solution is 1.5 to 20.0 g / L.

[0051] Optionally, the phosphate-containing solution may be a combination solution of one or more of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0052] Wherein, the concentration of the phosphate solution is 15-50wt%.

[0053] More preferably, the concentration of the phosphate solution is 25-40 wt %.

[0054] The amount of the phosphate solution is calculated based on a molar ratio of phosphate to lithium ion of 1:3, and the phosphate can be in excess of 3 to 15 wt%.

[0055] More preferably, the phosphate radical may be in excess of 5 to 10 wt%.

[0056] Optionally, the pH value can be controlled above 9.0.

[0057] More preferably, the pH value can be controlled within the range of 10.0 to 14.0.

[0058] Optionally, the pH value control is achieved by adding one or more combinations of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, ammonia water, ammonium carbonate, and ammonium bicarbonate.

[0059] Optionally, the reaction temperature is controlled at 30-100°C.

[0060] More preferably, the reaction temperature is controlled at 60-90°C.

[0061] Optionally, the lithium yield in the lithium precipitation process is between 93.0% and 99.5%.

[0062] The purity of the lithium phosphate of the present invention is not less than 90%.

[0063] Based on the above process, the device structure provided by this patent is as follows Figure 2 As shown, including:

[0064] Adsorption column 1, used for adsorbing lithium ions from salt lake brine;

[0065] A concentrator 2, connected to the liquid outlet of the adsorption column 1, for concentrating the lithium-containing eluent;

[0066] The precipitation reactor 4 is connected to the concentration device 2 and is used to perform lithium phosphate precipitation reaction on the obtained concentrated solution; and the precipitation reactor 4 is connected to a phosphate adding tank 3a and an alkali adding tank 3b;

[0067] A solid-liquid separation device 5, connected to the precipitation reactor 4, is used to separate the precipitate after the lithium phosphate precipitation reaction;

[0068] A high-pressure reverse osmosis membrane 6 is connected to the mother liquid outlet of the solid-liquid separation device 5 and is used to concentrate the obtained mother liquid;

[0069] The cation exchange resin column 7 has an inlet connected to the concentration side of the high-pressure reverse osmosis membrane 6 for removing divalent or multivalent cations from the concentrate, and an outlet connected to the phosphate addition tank 3 .

[0070] The adsorption column 1 is filled with one of aluminum salt adsorbent, titanium adsorbent or manganese adsorbent.

[0071] The concentrating device 2 is one or a combination of reverse osmosis membrane, forward osmosis membrane, electrodialyzer or evaporation device.

[0072] The phosphate adding tank 3 is loaded with a solution of any one of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0073] The solid-liquid separation device 5 is a centrifugal separation device, a sedimentation separation device or a membrane separation device, or a combination of these.

[0074] The cation exchange resin 7 is filled with sodium type cation exchange resin.

[0075] Example 1

[0076] The brine used in this example is a chloride-type brine, in which the concentrations of the main ions sodium ion, calcium ion, lithium ion, boron element and chloride ion are 89.0 g / L, 20.5 g / L, 0.02 g / L, 0.21 g / L and 199.5 g / L respectively. Figure 1 The process of this embodiment is shown. The method of this embodiment includes the following steps:

[0077] The brine was sent to a device equipped with an aluminum adsorbent for adsorption. After the adsorption, elution and desorption were carried out in sequence to collect the lithium-containing desorption liquid with a lithium concentration of 0.4 g / L.

[0078] The lithium-containing desorption liquid is sent to a reverse osmosis membrane device for concentration to obtain a lithium-containing concentrated liquid with a lithium concentration of 1.5 g / L.

[0079] The lithium-containing concentrated solution is sent to the lithium precipitation device and heated to 60°C, and a phosphoric acid solution with a mass fraction of 25wt% is added to ensure that the phosphate radical is 5wt% in excess, and the pH value is adjusted to 10.0 with a sodium hydroxide solution, filtered, washed with hot water and separated, and dried to obtain a white powder, which is lithium phosphate with a purity of 90.1%. The separated mother liquor is concentrated using a high-pressure reverse osmosis membrane, and then divalent or multivalent cations (mainly Mg2+) are removed by a cation exchange resin, so that a mainly residual phosphate solution is obtained, and the concentration is increased, and then reused after adding phosphate.

[0080] Among them, the lithium yield in the lithium precipitation process is 93.3%.

[0081] Example 2

[0082] This example uses a magnesium sulfate subtype salt lake brine, in which the main ion concentrations of sodium ion, magnesium ion, lithium ion, boron element, chloride ion and sulfate ion are 91.0 g / L, 30.9 g / L, 0.3 g / L, 0.35 g / L, 190.4 g / L and 25.1 g / L respectively. The specific operation steps are as follows:

[0083] The brine was sent to a device equipped with a manganese adsorbent for adsorption. After the adsorption, elution and desorption were carried out in sequence to collect the lithium-containing desorption liquid with a lithium concentration of 0.8 g / L.

[0084] The lithium-containing desorption liquid is sequentially sent to a reverse osmosis membrane, a forward osmosis membrane, an electrodialysis device and an evaporation device for concentration to obtain a lithium-containing concentrated liquid with a lithium concentration of 20.1 g / L.

[0085] The lithium-containing concentrated solution is sent to the lithium precipitation device and heated to 90°C, and a disodium hydrogen phosphate solution with a mass fraction of 40wt% is added to ensure that the phosphate radical is 10wt% in excess, and the pH value is adjusted to 14.0 with a sodium carbonate solution, filtered, washed with hot water, and dried to obtain a white powder, which is lithium phosphate with a purity of 98.3%. The mother liquor obtained by separation is concentrated by a high-pressure reverse osmosis membrane, and then the divalent or multivalent cations (mainly Mg2+) are removed by a cation exchange resin, so that a mainly residual phosphate solution is obtained, and the concentration is increased, and then reused after adding phosphate.

[0086] Among them, the lithium yield in the lithium precipitation process is 99.5%.

[0087] Example 3

[0088] This example uses a carbonate salt lake brine, in which the concentrations of the main ions sodium ion, magnesium ion, lithium ion, boron element, chloride ion, carbonate and bicarbonate are 39.0 g / L, 1.3 g / L, 0.15 g / L, 0.75 g / L, 58 g / L, 2.1 g / L and 1.4 g / L respectively. The specific operation steps are as follows:

[0089] The brine was sent to a device equipped with a titanium-based adsorbent for adsorption. After the adsorption, elution and desorption were carried out in sequence to collect the lithium-containing desorption liquid with a lithium concentration of 12.2 g / L.

[0090] The lithium-containing desorption liquid is directly sent to the lithium precipitation device and heated to 80°C, and a sodium dihydrogen phosphate solution with a mass fraction of 30wt% is added to ensure that the phosphate radical is 8wt% in excess, and the pH value is adjusted to 12.0 with a potassium hydroxide solution, filtered, washed with hot water, and dried to obtain a white powder, which is lithium phosphate with a purity of 98.5%. The mother liquor obtained by separation is concentrated by a high-pressure reverse osmosis membrane, and then the divalent or multivalent cations (mainly Mg2+) are removed by a cation exchange resin, so that a mainly residual phosphate solution is obtained, and the concentration is increased, and then it is reused after adding phosphate.

[0091] Among them, the lithium yield in the lithium precipitation process is 99.2%.

[0092] Example 4

[0093] This example uses a brine that has been evaporated and concentrated to precipitate salt, wherein the concentrations of the main ions magnesium ion, sodium ion, lithium ion, boron element and chloride ion are 118g / L, 2.0g / L, 5.0g / L, 3.0g / L and 300g / L respectively. The specific operation steps are as follows:

[0094] The brine was sent to a device equipped with an aluminum adsorbent for adsorption. After the adsorption, elution and desorption were carried out in sequence to collect the lithium-containing desorption liquid with a lithium concentration of 1.2 g / L.

[0095] The lithium-containing desorption liquid is sequentially sent to a reverse osmosis membrane and an electrodialysis device for concentration to obtain a lithium-containing concentrated liquid with a lithium concentration of 10.3 g / L.

[0096] The lithium-containing desorption liquid is directly sent to the lithium precipitation device and heated to 70°C, and a sodium phosphate solution with a mass fraction of 35wt% is added to ensure that the phosphate radical is in excess of 7wt%, and the pH value is adjusted to 13.0 with a potassium carbonate solution, filtered, washed with hot water, and dried to obtain a white powder, which is lithium phosphate with a purity of 93.1%. The mother liquor obtained by separation is concentrated by a high-pressure reverse osmosis membrane, and then the divalent or multivalent cations (mainly Mg2+) are removed by a cation exchange resin, so that a mainly residual phosphate solution is obtained, and the concentration is increased, and then reused after adding phosphate.

[0097] Among them, the lithium yield in the lithium precipitation process is 99.0%.

[0098] Example 5

[0099] The difference between this embodiment and embodiment 3 is that the brine is sent to a device containing a manganese adsorbent for adsorption, and after the adsorption is completed, elution and desorption are performed in sequence to collect a lithium-containing desorption liquid with a lithium concentration of 6.2 g / L. The lithium yield in the lithium precipitation process is 98.3%.

[0100] The other conditions are exactly the same as those in Example 3.

[0101] Example 6

[0102] The difference between this embodiment and embodiment 5 is that the lithium-containing desorption liquid is directly sent to the lithium precipitation device and heated to 80°C, and a mixed solution of dipotassium hydrogen phosphate, potassium dihydrogen phosphate and potassium phosphate with a mass fraction of 30wt% is added to ensure that the phosphate radical is in excess of 8wt%, and the pH value is adjusted to 11.0 with an ammonia solution, filtered, washed with hot water, and dried to obtain a white powder, which is lithium phosphate with a purity of 98.1%. Among them, the lithium yield in the lithium precipitation process is 98.0%.

[0103] The other conditions are exactly the same as those in Example 5.

[0104] Example 7

[0105] The difference between this embodiment and embodiment 4 is that the lithium concentration of a brine used after evaporation and concentration to precipitate salt is 2.1g / L; the lithium-containing desorption liquid is directly sent to the lithium precipitation device and heated to 80°C, and a mixed solution of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and ammonium phosphate with a mass fraction of 30wt% is added to ensure that the phosphate radical is 6wt% in excess, and the pH value is adjusted to 11.0 with a mixed solution of ammonium carbonate and ammonium bicarbonate, filtered, washed with hot water, and dried to obtain a white powder, which is lithium phosphate with a purity of 93.1%. Among them, the lithium yield in the lithium precipitation process is 98.5%.

[0106] The other conditions are exactly the same as those in Example 4.

[0107] Comparative Example 1

[0108] The difference between this embodiment and embodiment 1 is that a sodium carbonate solution with a mass fraction of 25 wt% is added to the lithium-containing concentrated solution to obtain lithium carbonate with a purity of 90.1%, wherein the yield of lithium in the lithium precipitation process is 35.0%.

[0109] The other conditions are exactly the same as those in Example 1.

[0110] Comparative Example 2

[0111] The difference between this embodiment and embodiment 2 is that a sodium carbonate solution with a mass fraction of 25 wt% is added to the lithium-containing concentrated solution to obtain lithium carbonate with a purity of 95.6%, wherein the yield of lithium in the lithium precipitation process is 80.2%.

[0112] The other conditions are exactly the same as those in Example 2.

[0113] The main technical indicators in each embodiment of the present invention are shown in Table 1.

[0114] Table 1

[0115]

Claims

1. A method for extracting lithium from salt lake brine with high yield, characterized in that: The steps include: Step 1, contacting salt lake brine with an adsorbent to adsorb lithium ions; Step 2, eluting and washing the adsorbent obtained in step 1 to obtain a lithium-containing desorption liquid; Step 3: The lithium-containing desorption liquid obtained in step 2 is concentrated or not concentrated, and a phosphate solution is added to separate the precipitate to obtain lithium phosphate.

2. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: In the step 1, the salt lake brine can be brine with chloride-type salt lake brine, magnesium sulfate-type salt lake brine, carbonate-type salt lake brine, deep underground brine, etc. as raw materials. It can be directly extracted from underground or the surface, or it can be brine from which salt is precipitated by evaporation and concentration. The lithium concentration in the salt lake brine is 0.02-5.0 g / L.

3. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: In the step 1, the adsorbent is at least one of an aluminum salt adsorbent, a titanium-based adsorbent or a manganese-based adsorbent.

4. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: In the step 2, the lithium concentration in the lithium-containing desorption solution is 0.4-12.0 g / L; in the step 3, when the lithium ion concentration is 0.4-1.5 g / L, it needs to be concentrated.

5. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: The concentration process uses one or more combinations of reverse osmosis membranes, forward osmosis membranes, electrodialysis, and evaporation devices.

6. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: The phosphate solution refers to one or more combined solutions of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate; the concentration of the phosphate solution is 15-50wt%, preferably 25-40wt%; the amount of the phosphate solution is calculated based on a molar ratio of phosphate to lithium ion of 1:3, and the phosphate can be in excess of 3-15wt%.

7. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: The pH value of the phosphate solution can be controlled at above 9.0, preferably 10.0-14.0; the pH value is controlled by adding alkali; the alkali refers to one or more combinations of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, ammonia water, ammonium carbonate, and ammonium bicarbonate; the reaction temperature after adding the phosphate solution is controlled at 30-100°C.

8. The method for extracting lithium from salt lake brine with high yield according to claim 1, characterized in that: The method further comprises step 5, wherein the mother liquor separated in step 4 is concentrated by using a high-pressure reverse osmosis membrane, and then divalent or multivalent cations are removed by using a cation exchange resin, and the obtained permeate is reused after adding phosphate.

9. A device for extracting lithium from salt lake brine with high yield, characterized in that: include: An adsorption column (1) is used to adsorb lithium ions from salt lake brine; A concentrator (2), connected to the liquid outlet of the adsorption column (1), for concentrating the lithium-containing eluent; A precipitation reactor (4) is connected to the concentration device (2) and is used to perform a lithium phosphate precipitation reaction on the obtained concentrated solution; and a phosphate addition tank (3a) and an alkali addition tank (3b) are connected to the precipitation reactor (4); A solid-liquid separation device (5), connected to the precipitation reactor (4), is used to separate the precipitate after the lithium phosphate precipitation reaction; A high-pressure reverse osmosis membrane (6) is connected to the mother liquor outlet of the solid-liquid separation device (5) and is used to concentrate the obtained mother liquor; a cation exchange resin column (7) has an inlet connected to the concentration side of the high-pressure reverse osmosis membrane (6) and is used to remove divalent or polyvalent cations from the concentrated liquid, and an outlet connected to the phosphate addition tank (3).

10. The device for extracting lithium from salt lake brine with high yield according to claim 9, characterized in that: The adsorption column (1) is filled with one of aluminum salt adsorbent, titanium adsorbent or manganese adsorbent. The concentrating device (2) is one or a combination of reverse osmosis membrane, forward osmosis membrane, electrodialyzer or evaporation device. The phosphate adding tank (3) is loaded with a solution of any one of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate. The solid-liquid separation device (5) is a centrifugal separation device, a sedimentation separation device or a membrane separation device, or a combination of these. The cation exchange resin (7) is filled with sodium type cation exchange resin.

Images