A phosphate-type lithium ion sieve and its desorption method

Abstract

The present invention provides a phosphate-type lithium ion sieve, and the phosphate-type ion sieve is of olivine type with the chemical formula Li x M a N b PO4, where M is one or more of Na, K, Ca, Al, Mg, Cu, F, B, Ni, Co, Mn, Ti, Nb, Sn, Mo, W; N is one or more of Fe and Mn; 0 ≤ x < 1, 0 ≤ a ≤ 0.1, 0.9 ≤ b ≤ 1. The phosphate-type lithium ion sieve provided by the present invention has the advantages of high adsorption capacity, good stability, low adsorption temperature and short adsorption time, and can efficiently recover lithium from lithium-containing industrial wastewater and lithium-containing brine.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorbents, and particularly relates to a phosphate-type lithium ion sieve and a desorption method thereof. Background Art

[0002] With the rise of new energy technologies, lithium ion batteries prepared from lithium resources are widely used in electronic devices and electric vehicles. The increasing demand for lithium resources requires the rapid development of lithium extraction technologies from salt lakes and lithium mines at the source on the one hand, and on the other hand, it also faces the problem of lithium resource recovery after the end of the service life of lithium ion batteries. In current lithium extraction technologies using adsorbents, there are aluminum-based lithium ion sieves, manganese-based lithium ion sieves, titanium-based lithium ion sieves, etc. These lithium ion sieves have played a huge role in the development of lithium extraction technologies, but there are also some drawbacks. The most prominent one is the problem of low adsorption capacity. Secondly, there are also problems such as low adsorption speed and easy destruction of the structure. Therefore, it is necessary to develop an adsorption technology with high adsorption capacity, fast adsorption speed and stable structure to meet the future demand for lithium resources. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a phosphate-type lithium ion sieve and a desorption method thereof. The phosphate-type lithium ion sieve provided by the present invention has the advantages of high adsorption capacity, good stability and short adsorption time, and can efficiently recover lithium from lithium-containing industrial wastewater and lithium-containing brine.

[0004] The present invention provides a phosphate-type lithium ion sieve, which is of olivine type and has the chemical formula Li x M a N b PO 4 , where M is one or more of Na, K, Ca, Al, Mg, Cu, F, B, Ni, Co, Mn, Ti, Nb, Sn, Mo, W, N is one or more of Fe and Mn, 0 ≤ x < 1, 0 ≤ a ≤ 0.1, 0.9 ≤ b ≤ 1.

[0005] For the above-mentioned phosphate-type lithium ion sieve, the primary particle size is < 300 nm. The present invention also provides a preparation method of the above-mentioned phosphate-type lithium ion sieve, which includes the following steps:

[0006] Mix olivine-type doped or undoped phosphate, an oxidant, an acid and water for reaction to obtain a phosphate-type lithium ion sieve;

[0007] The phosphate is selected from one or more of lithium iron phosphate, lithium manganese phosphate and lithium manganese iron phosphate.

[0008] Preferably, the oxidant is selected from one or more of hydrogen peroxide, oxygen, ozone, sodium peroxide, hypochlorous acid, hypoiodous acid and peracetic acid.

[0009] Preferably, the acid is selected from one or more of phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and oxalic acid.

[0010] The present invention also provides a method for adsorbing lithium by the above-mentioned phosphate-type lithium ion sieve, which includes the following steps:

[0011] Mix the phosphate-type lithium ion sieve, the solution containing lithium ions, and a reducing agent, then adjust the pH>2, and perform stirring adsorption to obtain the phosphate-type lithium ion sieve adsorbed with lithium.

[0012] Preferably, the reducing agent is selected from one or more of oxalate, iodide, formaldehyde, sodium borohydride, and ascorbic acid.

[0013] Preferably, the temperature of the stirring adsorption is ≤50°C, and the time is 0.5-8h.

[0014] Preferably, the solution containing lithium ions is selected from industrial wastewater containing lithium or brine containing lithium.

[0015] Preferably, the pH is adjusted with an acid or a base. The acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and oxalic acid;

[0016] The base is selected from one or more of ammonia, aqueous ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, lithium hydroxide, etc.

[0017] Preferably, the molar ratio of the phosphate-type lithium ion sieve to the reducing agent is 1:(0.5-5).

[0018] Compared with the prior art, the present invention provides a phosphate-type lithium ion sieve. The phosphate-type lithium ion sieve is of olivine type, and its chemical formula is Li x M a N b PO 4 , M is one or more of Na, K, Ca, Al, Mg, Cu, F, B, Ni, Co, Mn, Ti, Nb, Sn, Mo, W, N is one or more of Fe and Mn, 0≤x<1, 0≤a≤0.1, 0.9≤b≤1. The phosphate-type lithium ion sieve provided by the present invention has the advantages of high adsorption capacity, good stability, low adsorption temperature, and short adsorption time, and can efficiently recover lithium from industrial wastewater containing lithium and brine containing lithium. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the XRD pattern of the phosphate-type lithium ion sieve;

[0020] Figure 2 is the SEM image of the phosphate-type lithium ion sieve. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention provides a phosphate-type lithium ion sieve, and the phosphate-type lithium ion sieve is of olivine type with the chemical formula Li x M a N b PO 4 , where M is one or more of Na, K, Ca, Al, Mg, Cu, F, B, Ni, Co, Mn, Ti, Nb, Sn, Mo, W; N is one or more of Fe and Mn; 0 ≤ x < 1; 0 ≤ a ≤ 0.1; 0.9 ≤ b ≤ 1.

[0022] The primary particle size of the phosphate-type lithium ion sieve is < 300 nm. Under this particle size condition, the particle size is small, the specific surface area is large, there are more active sites, and the ion transport path is shorter, which is beneficial to the rapid adsorption of lithium ions.

[0023] In the present invention, the preparation method of the phosphate-type lithium ion sieve comprises the following steps:

[0024] Mix olivine-type doped or undoped phosphate, an oxidant, an acid and water for reaction to obtain the phosphate-type lithium ion sieve;

[0025] The phosphate is selected from one or more of lithium iron phosphate, lithium manganese phosphate and lithium manganese iron phosphate.

[0026] Among them, the chemical formula of the olivine-type doped or undoped phosphate is Li y M m N n PO 4 , where M is one or more of Na, K, Ca, Al, Mg, Cu, F, B, Ni, Co, Mn, Ti, Nb, Sn, Mo, W; N is one or more of Fe and Mn; 0.5 ≤ y ≤ 1.05; 0 ≤ m ≤ 0.1; 0.9 ≤ n ≤ 1.

[0027] The oxidant is selected from one or more of hydrogen peroxide, oxygen, ozone, sodium peroxide, hypochlorous acid, hypoiodous acid and peracetic acid, and preferably hydrogen peroxide.

[0028] The acid is selected from one or more of phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, carbonic acid and oxalic acid, and preferably carbonic acid or concentrated sulfuric acid.

[0029] The molar ratio of the olivine-type doped or undoped phosphate, the oxidant and the acid is 1:(1 - 5):(1 - 5), and preferably 1:(2 - 4):(2 - 4).

[0030] The temperature of the reaction is 0 to 100 °C, preferably 0, 5, 10, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, or any value between 0 and 100 °C, preferably at room temperature conditions, and the time is 0.1 to 10 h, preferably 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 0.1 and 10 h.

[0031] After the reaction is completed, an olivine-type phosphate-based lithium ion sieve is obtained.

[0032] The present invention also provides an adsorption method using the above-mentioned phosphate-based lithium ion sieve, comprising the following steps:

[0033] The phosphate-based lithium ion sieve, a solution containing lithium ions, and a reducing agent are mixed and then the pH is adjusted to be > 2, followed by stirring and reacting to obtain a phosphate-based lithium ion sieve adsorbed with lithium.

[0034] Specifically, the present invention adds the phosphate-based lithium ion sieve to a solution containing lithium ions.

[0035] Among them, there are no special restrictions on the solution containing lithium ions, including but not limited to lithium-containing industrial wastewater, lithium-containing brine and other lithium-containing solutions. In the present invention, the concentration of lithium ions in the solution containing lithium ions is ≥ 10 mg / L. The method provided by the present invention can adsorb low-concentration lithium.

[0036] Then, a reducing agent is added. The reducing agent is selected from one or more of oxalate, iodide, formaldehyde, sodium borohydride, and ascorbic acid. Under the action of the above reducing agent, the adsorption reaction is promoted, and at the same time, the adsorption capacity and adsorption efficiency of the phosphate-based lithium ion sieve are improved.

[0037] Then, the pH of the above solution added with the reducing agent is adjusted to be > 2, preferably 4 to 9.

[0038] In the present invention, the pH is adjusted using an acid or a base. The acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and oxalic acid;

[0039] The base is selected from one or more of ammonia, aqueous ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, lithium hydroxide, etc.

[0040] After adjusting the pH, the solution is stirred for adsorption to obtain a phosphate-type lithium ion sieve adsorbed with lithium. The temperature of the stirring adsorption is ≤ 50 °C, and the time is 0.5 - 8 h. In some specific embodiments of the present invention, the temperature of the reaction is 0 - 50 °C, preferably 0, 5, 15, 20, 25, 30, 50, or any value within 0 - 50 °C. The reaction time is 0.5 - 4 h, preferably 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, or any value between 0.5 - 8 h. In some specific embodiments of the present invention, the stirring adsorption is carried out under normal temperature and pressure conditions.

[0041] In the present invention, the molar ratio of the phosphate-type lithium ion sieve to the reducing agent is 1:(0.5 - 5), preferably 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, or any value between 1:(0.5 - 5).

[0042] In the present invention, it also includes desorbing lithium from the phosphate-type lithium ion sieve adsorbed with lithium. The specific method includes the following steps:

[0043] The phosphate-type lithium ion sieve adsorbed with lithium, an oxidizing agent, an acid, and water are mixed for reaction to regenerate the phosphate-type lithium ion sieve.

[0044] The oxidizing agent is selected from one or more of hydrogen peroxide, oxygen, ozone, sodium peroxide, hypochlorous acid, hypoiodous acid, and peracetic acid.

[0045] The acid is selected from one or more of phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and oxalic acid.

[0046] The molar ratio of the phosphate-type lithium ion sieve adsorbed with lithium, the oxidizing agent, and the acid is 1:(1 - 5):(1 - 5), preferably 1:(2 - 4):(2 - 4).

[0047] The temperature of the reaction is 0 - 100 °C, preferably 0, 5, 10, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, or any value within 0 - 100 °C, preferably under normal temperature conditions, and the time is 0.1 - 10 h, preferably 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 0.1 - 10 h.

[0048] After the reaction ends, a lithium-depleted phosphate-type lithium ion sieve is obtained.

[0049] The phosphate-type lithium ion sieve provided by the present invention has the advantages of high adsorption capacity, good stability, low adsorption temperature, and short adsorption time, and can efficiently recover lithium from lithium-containing industrial wastewater and lithium-containing brine.

[0050] To further understand the present invention, a phosphate-type lithium ion sieve provided by the present invention and its desorption method will be described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0051] Example 1

[0052] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, and then introduce carbon dioxide and stir for 3 h to prepare the phosphate-type lithium ion sieve Li 0.05 Fe 0.96 PO 4 . The XRD pattern of the phosphate-type lithium ion sieve is shown in Figure 1 , Figure 1 which is the XRD pattern of the phosphate-type lithium ion sieve; the SEM pattern of the phosphate-type lithium ion sieve is shown in Figure 2 , Figure 2 which is the SEM pattern of the phosphate-type lithium ion sieve, and the primary particles are 200 nm.

[0053] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 300 ml of lithium chloride brine with a lithium concentration of 500 mg / L;

[0054] (3) Add 2 g of ascorbic acid to the solution in step (2);

[0055] (4) Add sodium hydroxide to the solution in step (3), adjust the pH to 8, and stir at 25 °C for 3 h to complete the adsorption;

[0056] (5) Mix the phosphate-type lithium ion sieve adsorbed with lithium with twice the molar amount of sulfuric acid aqueous solution and twice the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 3 h to obtain the de-lithiated phosphate-type lithium ion sieve.

[0057] The phosphate-type lithium ion sieve before and after adsorption and after desorption in Example 1 was tested by ICP-OES, and the results are shown in Table 1. The prepared phosphate-type lithium ion sieve is Li 0.05 Fe 0.96 PO 4 . After adsorbing lithium ions from the lithium-containing solution of lithium chloride brine, the composition is Li 0.97 Fe 0.97 PO 4 , the adsorption capacity is 40 mg of lithium / g of the phosphate-type lithium ion sieve, and the composition after desorption is Li 0.01 Fe 0.96 PO 4 .

[0058] Table 1

[0059]

[0060] Example 2

[0061] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, and then introduce carbon dioxide and stir for 3 h to prepare the phosphate-type lithium ion sieve Li 0.05 Fe 0.96 PO 4 , with a primary particle size of 200 nm;

[0062] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 300 ml of lithium sulfate brine with a lithium concentration of 600 mg / L;

[0063] (3) Add 2 g of ascorbic acid to the solution in step (2);

[0064] (4) Add ammonia water to the solution in step (3), adjust the pH = 7, and stir at 25 °C for 2 h to complete the adsorption;

[0065] (5) Mix the phosphate-type lithium ion sieve adsorbed with lithium with twice the molar amount of sulfuric acid aqueous solution and twice the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 3 h to obtain the de-lithiated phosphate-type lithium ion sieve.

[0066] Perform ICP-OES tests on the phosphate-type lithium ion sieve before and after adsorption and after desorption in Example 2, and the obtained results are shown in Table 2. The prepared phosphate-type lithium ion sieve is Li 0.05 Fe 0.96 PO 4 , and after adsorbing lithium ions from the lithium-containing solution of lithium chloride brine, the composition is Li 0.99 Fe 0.97 PO 4 , the adsorption capacity is 41 mg of lithium / g of phosphate-type lithium ion sieve, and the composition after desorption is Li 0.02 Fe 0.97 PO 4 .

[0067] Table 2

[0068]

[0069] Example 3

[0070] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, and then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare the phosphate-type lithium ion sieve Li 0.03 Fe 0.98 PO 4 , with a primary particle size of 230 nm;

[0071] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium sulfate brine with a lithium concentration of 300 mg / L;

[0072] (3) Add 6 g of sodium oxalate and 2 g of ascorbic acid to the solution in step (2);

[0073] (4) Add ammonia water and sulfuric acid solution to the solution in step (3), adjust the pH = 8, and stir at 25 °C for 1 h to complete the adsorption;

[0074] (5) Mix the phosphate-type lithium ion sieve adsorbed with lithium with twice the molar amount of hydrochloric acid and twice the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 3 h to obtain the de-lithiated phosphate-type lithium ion sieve.

[0075] The phosphate-type lithium ion sieve before and after adsorption and after desorption in Example 3 was tested by ICP-OES, and the results are shown in Table 3. The prepared phosphate-type lithium ion sieve was Li 0.03 Fe 0.98 PO 4 , and after adsorbing lithium ions from the lithium-containing solution of lithium chloride brine, the composition was Li 0.98 Fe 0.99 PO 4 , with an adsorption capacity of 44 mg of lithium / g of the phosphate-type lithium ion sieve, and the composition after desorption was Li 0.02 Fe 0.99 PO 4 .

[0076] Table 3

[0077]

[0078] Example 4

[0079] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare a phosphate-type lithium ion sieve with a primary particle size of 230 nm;

[0080] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium chloride brine with a lithium concentration of 300 mg / L;

[0081] (3) Add 8 g of sodium iodide to the solution in step (2);

[0082] (4) Add sodium hydroxide and oxalic acid solution to the solution in step (3), adjust the pH = 4, stir at 25 °C for 0.5 h to complete the adsorption, and test according to the method of Test Example 1. The adsorption capacity was 41 mg of lithium / g of the phosphate-type lithium ion sieve.

[0083] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with twice the molar amount of hydrochloric acid and twice the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 3 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.03 Fe 0.99 PO 4 .

[0084] Example 5

[0085] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare the phosphate-type lithium ion sieve with a primary particle size of 230 nm;

[0086] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium chloride brine with a lithium concentration of 300 mg / L;

[0087] (3) Add 6 g of sodium oxalate and 2 g of sodium iodide to the solution in step (2);

[0088] (4) Add sodium hydroxide and oxalic acid solution to the solution in step (3), adjust the pH = 4, stir at 25 °C for 0.5 h to complete the adsorption, and test according to the method of Test Example 1. The adsorption capacity is 43 mg of lithium / g of the phosphate-type lithium ion sieve.

[0089] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of hydrochloric acid and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.01 Fe 1.00 PO 4 .

[0090] Example 6

[0091] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare the phosphate-type lithium ion sieve with a primary particle size of 230 nm;

[0092] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium sulfate brine with a lithium concentration of 300 mg / L;

[0093] (3) Add 6 g of ascorbic acid and 2 g of sodium iodide to the solution in step (2);

[0094] (4) Add sodium hydroxide and oxalic acid solution to the solution in step (3), adjust the pH = 4, stir at 25 °C for 0.5 h to complete the adsorption, and test according to the method of Test Example 1. The adsorption capacity is 43 mg of lithium / g of the phosphate-type lithium ion sieve.

[0095] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of hydrochloric acid and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the lithium-depleted phosphate-type lithium ion sieve, Li 0.02 Fe 1.00 PO 4 。

[0096] Example 7

[0097] (1) Add 5 g of fluorine-doped lithium iron phosphate to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir, while introducing oxygen for 6 h to prepare the fluorine-doped phosphate-type lithium ion sieve, Li 0.01 FeF 0.01 PO 4 , with a primary particle size of 250 nm;

[0098] (2) Add 3 g of the fluorine-doped phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium sulfate brine with a lithium concentration of 300 mg / L;

[0099] (3) Add 6 g of ascorbic acid and 2 g of sodium iodide to the solution in step (2);

[0100] (4) Add sodium hydroxide and oxalic acid solution to the solution in step (3), adjust the pH = 4, stir at 25 °C for 0.5 h to complete the adsorption, and test according to the method of Test Example 1. The adsorption capacity is 42 mg of lithium / g of phosphate-type lithium ion sieve.

[0101] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of hydrochloric acid and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the lithium-depleted fluorine-doped phosphate-type lithium ion sieve, Li 0.01 Fe 0.98 F 0.01 PO 4 。

[0102] Example 8

[0103] (1) Add 5 g of lithium manganese phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, and then introduce carbon dioxide and stir for 3 h to prepare the phosphate-type lithium ion sieve Li 0.02 Mn 0.98 PO 4 , with a primary particle size of 210 nm;

[0104] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 300 ml of lithium sulfate brine with a lithium concentration of 600 mg / L;

[0105] (3) Add 2 g of ascorbic acid to the solution in step (2);

[0106] (4) Add ammonia water to the solution in step (3), adjust the pH to 7, stir at 25 °C for 2 h to complete the adsorption, and test according to the method of Test Example 1. The adsorption capacity is 41 mg of lithium per g of phosphate-type lithium ion sieve;

[0107] (5) Mix the phosphate-type lithium ion sieve adsorbed with lithium with twice the molar amount of sulfuric acid aqueous solution and twice the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 3 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.03 Mn 0.98 PO 4 。

[0108] Example 9

[0109] (1) Add 5 g of lithium iron manganese phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, and then pass in carbon dioxide and stir for 3 h to prepare the phosphate-type lithium ion sieve Li 0.01 Fe 0.62 Mn 0.37 PO 4 , with a primary particle size of 220 nm;

[0110] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 300 ml of lithium sulfate brine with a lithium concentration of 600 mg / L;

[0111] (3) Add 2 g of ascorbic acid to the solution in step (2);

[0112] (4) Add ammonia water to the solution in step (3), adjust the pH to 7, stir at 25 °C for 2 h to complete the adsorption, and test according to the method of Test Example 1. The adsorption capacity is 40 mg of lithium per g of phosphate-type lithium ion sieve;

[0113] (5) Mix the phosphate-type lithium ion sieve adsorbed with lithium with twice the molar amount of sulfuric acid aqueous solution and twice the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 3 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.01 Fe 0.62 Mn 0.37 PO 4 。

[0114] Comparative Example 1

[0115] (1) Add 3 g of commercially available iron phosphate (belonging to the P3121 space group) to 300 ml of lithium chloride brine with a lithium concentration of 500 mg / L;

[0116] (3) Add 2 g of ascorbic acid to the solution in step (2);

[0117] (4) Add sodium hydroxide to the solution in step (3), adjust the pH to 8, stir at 25 °C for 3 h to complete the adsorption, and perform ICP-OES testing according to Test Example 1. The measured adsorption capacity is < 2 mg lithium / g phosphate-type lithium ion sieve;

[0118] Comparative Example 2

[0119] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add sulfuric acid and ammonia water to adjust the pH to 3 - 6, and stir for 6 h to prepare a phosphate-type lithium ion sieve with a primary particle size of 400 nm;

[0120] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium chloride brine with a lithium concentration of 300 mg / L;

[0121] (3) Add 6 g of ascorbic acid to the solution in step (2);

[0122] (4) Add sodium hydroxide to the solution in step (3), adjust the pH to 8, stir at 25 °C for 3 h to complete the adsorption, and perform ICP-OES testing according to Test Example 1. The measured adsorption capacity is 30 mg / g;

[0123] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of sulfuric acid aqueous solution and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the lithium-depleted phosphate-type lithium ion sieve, Li 0.02 Fe 1.00 PO 4 .

[0124] Comparative Example 3

[0125] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then introduce carbon dioxide and stir for 3 h to prepare a phosphate-type lithium ion sieve with a primary particle size of 200 nm;

[0126] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium chloride brine with a lithium concentration of 300 mg / L;

[0127] (3) Add 2 g of sodium sulfite to the solution in step (2);

[0128] (4) Add sodium hydroxide to the solution in step (3), adjust the pH to 8, stir at 25 °C for 3 h to complete the adsorption, and perform ICP-OES testing according to Test Example 1. The measured adsorption capacity is 25 mg / g;

[0129] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of sulfuric acid aqueous solution and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.01 Fe 1.00 PO 4 。

[0130] Comparative Example 4

[0131] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare the phosphate-type lithium ion sieve with a primary particle size of 230 nm;

[0132] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium sulfate brine with a lithium concentration of 300 mg / L;

[0133] (3) Add 60 g of 10% hydrazine aqueous solution to the solution in step (2);

[0134] (4) Add ammonia water and sulfuric acid solution to the solution in step (3), adjust the pH = 8, stir at 25 °C for 1 h to complete the adsorption, and perform ICP-OES test according to Test Example 1. The measured adsorption capacity is 28 mg of lithium / g of phosphate-type lithium ion sieve;

[0135] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of hydrochloric acid and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.02 Fe 0.99 PO 4 。

[0136] Comparative Example 5

[0137] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare the phosphate-type lithium ion sieve with a primary particle size of 230 nm;

[0138] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium sulfate brine with a lithium concentration of 300 mg / L;

[0139] (3) Add 8 g of sodium bisulfite to the solution in step (2);

[0140] (4) Add ammonia water and sulfuric acid solution to the solution in step (3), adjust the pH = 8, stir at 25 °C for 1 h to complete the adsorption, and perform ICP-OES test according to Test Example 1. The measured adsorption capacity is 20 mg of lithium / g of phosphate-type lithium ion sieve.

[0141] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of hydrochloric acid and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.01 Fe 1.00 PO 4 。

[0142] Comparative Example 6

[0143] (1) Add 5 g of lithium iron phosphate and 5 ml of 30% hydrogen peroxide to 100 ml of water, then add 15 ml of concentrated sulfuric acid and stir for 3 h to prepare a phosphate-type lithium ion sieve with a primary particle size of 230 nm;

[0144] (2) Add 3 g of the phosphate-type lithium ion sieve prepared in step (1) to 500 ml of lithium sulfate brine with a lithium concentration of 300 mg / L;

[0145] (3) Add 4 g of sodium bisulfite and 4 g of sodium sulfite to the solution in step (2);

[0146] (4) Add ammonia water and sulfuric acid solution to the solution in step (3), adjust the pH to 8, stir at 25 °C for 1 h to complete the adsorption, and perform ICP-OES testing according to Test Example 1. The measured adsorption capacity is 21 mg of lithium per g of the phosphate-type lithium ion sieve.

[0147] (5) Mix the lithium-adsorbed phosphate-type lithium ion sieve with three times the molar amount of hydrochloric acid and three times the molar amount of hydrogen peroxide, with a solid-liquid ratio of 20 g / L, and react for 2 h to obtain the de-lithiated phosphate-type lithium ion sieve, Li 0.02 Fe 1.00 PO 4 。

[0148] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for adsorbing lithium using a phosphate-type lithium ion sieve, characterized in that, it includes the following steps: Mix the phosphate-type lithium ion sieve, the solution containing lithium ions, and a reducing agent, then adjust the pH > 2, and carry out stirring adsorption to obtain the phosphate-type lithium ion sieve adsorbed with lithium; The phosphate-type ion sieve is of the olivine type, with the chemical formula Li x M a N b PO 4 , where M is one or more of Na, K, Ca, Al, Mg, Cu, F, B, Ni, Co, Mn, Ti, Nb, Sn, Mo, W; N is one or more of Fe and Mn; 0 ≤ x < 1, 0 ≤ a ≤ 0.1, 0.9 ≤ b ≤ 1; The temperature for the lithium ion sieve to adsorb lithium is ≤ 50 °C; The primary particle size is < 300 nm; The reducing agent is selected from one or more of oxalate, iodide salt, and ascorbic acid.

2. The method according to claim 1, characterized in that, The preparation method of the phosphate-type lithium ion sieve includes the following steps: Mix olivine-type doped or undoped phosphate, an oxidizing agent, an acid, and water for reaction to obtain the phosphate-type lithium ion sieve; The phosphate is selected from one or more of lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate.

3. The method according to claim 2, characterized in that, The oxidizing agent is selected from one or more of hydrogen peroxide, oxygen, ozone, sodium peroxide, hypochlorous acid, hypoiodous acid, and peracetic acid; The acid is selected from one or more of phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and oxalic acid.

4. The method according to claim 1, characterized in that, The time for the stirring adsorption is 0.5 - 8 h.

5. The method according to claim 1, characterized in that, The solution containing lithium ions is selected from industrial wastewater containing lithium or brine containing lithium.

6. The method according to claim 1, characterized in that, The pH is adjusted using an acid or a base. The acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and oxalic acid; The base is selected from one or more of ammonia gas, ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, and lithium hydroxide.

7. The method according to claim 1, characterized in that, The molar ratio of the phosphate-type lithium ion sieve to the reducing agent is 1:(0.5 - 5).

Images