Method for purifying lithium sulfate from lithium-containing solution of sulfate system

Abstract

The invention discloses a method for purifying lithium sulfate from a lithium-containing solution of a sulfate system, which comprises the following steps: S1, adding a lithium precipitation aid into the lithium-containing solution of the sulfate system, stirring and leaching, and carrying out lithium precipitation reaction to obtain lithium-rich slag and a lithium-poor solution; s2, adding water into the lithium-rich slag to make slurry, adding a lithium dissolving aid, stirring and leaching, carrying out lithium dissolving reaction to obtain lithium-poor slag and a lithium sulfate solution, and concentrating and crystallizing the lithium sulfate solution to obtain a lithium sulfate product; and S3, water is added into the lithium-poor slag for slurry making, a regeneration auxiliary agent is added for stirring leaching, a lithium precipitation auxiliary agent regeneration reaction is conducted, lithium dissolving auxiliary agent precursor slag and a lithium precipitation auxiliary agent solution are obtained, water is added into the lithium dissolving auxiliary agent precursor slag for slurry making, sulfuric acid is added for stirring leaching, a lithium dissolving auxiliary agent regeneration reaction is conducted, and a lithium dissolving auxiliary agent solution obtained after the reaction is completed is obtained. The method realizes preparation of lithium sulfate from the sulfate system lithium-containing solution through a new process, avoids using lithium carbonate as an intermediate product, and realizes accurate and efficient separation of lithium in the sulfate system lithium-containing solution.

Description

Technical Field

[0001] The invention relates to the field of metallurgy and renewable resource recovery technology for lithium element extraction, and in particular to a method for purifying lithium sulfate from a lithium-containing solution in a sulfate system. Background Art

[0002] With the development of the new energy vehicle industry, the market demand for lithium batteries continues to expand, and the market demand for lithium carbonate and lithium hydroxide continues to increase.

[0003] Lithium sulfate is an intermediate in the production of lithium carbonate and lithium hydroxide. In the process of lithium extraction, a large amount of lithium and other alkali metal elements are produced. Mixed sulfate system solution, such as lithium extraction leaching solution from lithium mica (mainly containing sodium and potassium), lithium precipitation mother liquor (mainly containing sodium) produced in the process of preparing lithium carbonate, etc. These solutions need to separate lithium from other alkali metal elements to produce lithium carbonate or lithium hydroxide. At present, it mainly relies on physical processes, through concentration and crystallization, using the difference in solubility of lithium and other alkali metal elements to separate sulfates of other alkali metal elements.

[0004] In particular, a large amount of sulfates such as sodium and potassium are used in the process of extracting lithium from lithium mica. The main components of the lithium-containing solution in the sulfate system include sodium sulfate, potassium sulfate, etc. in addition to lithium sulfate. When using the above process to produce lithium hydroxide, it is necessary to first concentrate and remove sodium and potassium, and then add sodium carbonate to produce lithium carbonate, so as to further separate lithium and sodium and potassium, and then dissolve the purified lithium carbonate in sulfuric acid to obtain lithium sulfate.

[0005] However, due to the decline in lithium prices, the price of lithium carbonate and lithium hydroxide has been inverted. The above process is not feasible to produce lithium sulfate and ultimately lithium hydroxide using lepidolite as raw material due to cost issues. Lepidolite smelters are in urgent need of a new process to produce lithium sulfate at a lower cost. Summary of the invention

[0006] In view of this, it is necessary to develop a new method for separating lithium from other alkali metal elements with low production cost from a lithium-containing solution of a sulfate system. Therefore, the present invention provides a method for purifying lithium sulfate from a lithium-containing solution of a sulfate system.

[0007] The scheme of the present invention is:

[0008] A method for purifying lithium sulfate from a sulfate system lithium-containing solution comprises the following steps:

[0009] The sulfate system lithium-containing solution is a solution in which the cation contains lithium and the anion is mainly sulfate; for example, the leaching solution or concentrated solution of lithium extraction from lepidolite;

[0010] S1. Separation of lithium

[0011] Adding a lithium precipitation auxiliary agent to a lithium-containing solution of a sulfate system and stirring and leaching, performing a lithium precipitation reaction at a certain temperature, a certain pH value, and a certain time to obtain a slurry after the reaction is completed, filtering and washing to obtain lithium-rich slag and lithium-poor solution;

[0012]

[0013] S2. Preparation of lithium sulfate

[0014] After adding water to the lithium-rich slag to make a slurry, a lithium dissolving aid is added and stirred for leaching. The lithium dissolving reaction is carried out at a certain temperature, a certain pH value, and a certain time to obtain a slurry after the reaction is completed. The slurry is filtered and washed to obtain lithium-poor slag and lithium sulfate solution. The lithium sulfate solution is concentrated and crystallized to obtain a lithium sulfate product.

[0015] Li 3 PO 4 +Fe 3+ →3Li + +FePO 4 ↓

[0016] S3, additive regeneration

[0017] The lithium-poor slag is slurried with water and a regeneration aid 1 is added to stir and leach, and a lithium precipitation aid regeneration reaction is carried out at a certain temperature, a certain pH value, and a certain time to obtain a slurry after the reaction is completed, which is filtered and washed to obtain a lithium-dissolving aid precursor slag and a lithium-precipitating aid solution; the lithium-dissolving aid precursor slag is slurried with water and a regeneration aid 2 is added to stir and leach, and a lithium-dissolving aid regeneration reaction is carried out at a certain temperature, a certain pH value, and a certain time to obtain a lithium-dissolving aid solution after the reaction is completed.

[0018]

[0019] Fe(OH) 3 K sp =1.1×10 -36

[0020] FePO 4 K sp =9.91×10 -16

[0021] Fe(OH) 3 +H + →Fe 3+ +3H 2 O

[0022] The produced lithium precipitation auxiliary solution and lithium dissolution auxiliary solution are returned to S1 and S2 for recycling respectively.

[0023] As a preferred technical solution, the concentration of lithium in the sulfate system lithium-containing solution in S1 is 2-30 g / L;

[0024] The lithium precipitation auxiliary agent is PO 4 3- With H + 、Na + , K + A compound composed of one or more of

[0025] The lithium precipitation reaction temperature is: 20-100°C;

[0026] The pH of the lithium precipitation reaction is: 8-12

[0027] The lithium precipitation reaction time is: 1-8h.

[0028] As a preferred technical solution, the lithium dissolving aid in S2 is SO 4 2- OH - with Fe 3+ A compound composed of one or more of

[0029] The lithium dissolving reaction temperature is: 20-100°C;

[0030] The pH of the lithium dissolution reaction is: ≤4

[0031] The lithium dissolving reaction time is: 1-8h.

[0032] As a preferred technical solution, the regeneration aid 1 and the regeneration aid 2 in S3 are one or more of sodium hydroxide, potassium hydroxide, and sulfuric acid;

[0033] The regeneration reaction temperature of the lithium precipitation auxiliary agent is: 20-100°C;

[0034] The pH of the lithium precipitation auxiliary agent regeneration reaction is: ≥9

[0035] The regeneration reaction time of the lithium precipitation auxiliary agent is: 1-8h.

[0036] The regeneration reaction temperature of the lithium dissolving agent is: 20-100°C;

[0037] The pH of the lithium dissolving auxiliary agent regeneration reaction is: ≥5;

[0038] The regeneration reaction time of the lithium dissolving auxiliary agent is: 1-8h.

[0039] Working principle:

[0040] The raw materials of the method of the present invention convert lithium ions into lithium salt-rich slag that is insoluble in water under the action of a lithium precipitation auxiliary agent; the lithium-rich slag is converted into lithium sulfate and lithium-poor slag under the action of a lithium dissolving auxiliary agent; the lithium-poor slag is converted into lithium precipitation auxiliary agent and lithium dissolving auxiliary agent precursor slag under the action of a regeneration auxiliary agent; the lithium dissolving auxiliary agent precursor slag is converted into a lithium dissolving auxiliary agent under the action of sulfuric acid. Thus, the purpose of generating lithium and separating alkali metal elements to generate lithium sulfate is achieved, and the purpose of recycling various auxiliary agents is achieved.

[0041] Compared with the prior art, the technical solution of the present invention has the following technical advantages or positive effects:

[0042] 1. The method of the present invention has strong adaptability to raw materials. The sulfate system lithium-containing solution is a solution in which cations contain lithium and anions are mainly sulfate, and the applicable range of lithium ion concentration is 2-30 g / L;

[0043] 2. The additives used in the method of the present invention can be recycled, with low cost and can be applied in large-scale industrialization;

[0044] 3. The method of the present invention is a new all-wet process with low production line investment, low production cost, obvious safety and environmental protection advantages and high production efficiency;

[0045] 4. The application of the method of the present invention provides a new idea for lithium mica smelting enterprises to efficiently and economically convert lithium sulfate, the raw material required for lithium hydroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0047] The present invention provides a method for purifying lithium sulfate from a lithium-containing solution of a sulfate system. In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0048] The method for purifying lithium sulfate from a sulfate system lithium-containing solution comprises the following steps:

[0049] S1. Separation of lithium

[0050] Adding a lithium precipitation auxiliary agent to a lithium-containing solution of a sulfate system, stirring and leaching, performing a lithium precipitation reaction, obtaining a slurry after the reaction is completed, filtering and washing, and obtaining lithium-rich slag and a lithium-poor solution;

[0051] S2. Preparation of lithium sulfate

[0052] After adding water to the lithium-rich slag to make a slurry, a lithium dissolving aid is added and stirred for leaching to carry out a lithium dissolving reaction to obtain a slurry after the reaction is completed, which is filtered and washed to obtain lithium-poor slag and a lithium sulfate solution; the lithium sulfate solution is concentrated and crystallized to obtain a lithium sulfate product;

[0053] S3, additive regeneration

[0054] The lithium-poor slag is slurried with water and a regeneration aid 1 is added to stir and leach, and a lithium precipitation aid regeneration reaction is carried out to obtain a slurry after the reaction is completed, which is filtered and washed to obtain a lithium-dissolving aid precursor slag and a lithium-precipitating aid solution; the lithium-dissolving aid precursor slag is slurried with water and a regeneration aid 2 is added to stir and leach, and a lithium-dissolving aid regeneration reaction is carried out to obtain a lithium-dissolving aid solution after the reaction is completed.

[0055] The produced lithium precipitation auxiliary solution and lithium dissolution auxiliary solution are returned to S1 and S2 for recycling respectively.

[0056] Example 1

[0057] 1.00 L of sulfate system lithium solution (main components and concentrations are Li 7.00 g / L, Na 14.10 g / L, K 5.10 g / L) was used, and the raw material regeneration aid 1 was NaOH 40.00 g, and the regeneration aid 2 was H 2 SO 4 49.00g, lithium precipitation auxiliary agent Na 3 PO 4 54.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2 SO 4 53.43g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.14%. The reaction conditions of the above purification method are shown in Table 1.

[0058] Table 1

[0059] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 20 12 8 Lithium dissolution reaction 20 4 8 Regeneration reaction of lithium precipitation additive 20 9 4 Regeneration reaction of lithium dissolving agent 20 5 8

[0060] Example 2

[0061] 3.50 L of sulfate system lithium solution (main components and concentrations are Li 2.00 g / L, Na 11.59 g / L, K 7.10 g / L) was used, and the raw material regeneration aid 1 was NaOH 40.00 g, and the regeneration aid 2 was H 2 SO 4 49.00g, lithium precipitation auxiliary agent Na 3 PO 4 54.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2SO 4 52.77g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 95.94%. The reaction conditions of the above purification method are shown in Table 2.

[0062] Table 2

[0063] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 60 12 3 Lithium dissolution reaction 80 3 3 Regeneration reaction of lithium precipitation additive 60 11 4 Regeneration reaction of lithium dissolving agent 50 2 5

[0064] Example 3

[0065] A sulfate system lithium solution (main components and concentrations are Li 30.00 g / L, Na 15.50 g / L, K 8.10 g / L) 0.23 L was used, and the raw material regeneration aid 1 was NaOH 40.00 g, and the regeneration aid 2 was H 2 SO 4 49.00g, lithium precipitation auxiliary agent Na 3 PO 4 54.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2 SO 4 54.42g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 98.94%. The reaction conditions of the above purification method are shown in Table 3.

[0066] Table 3

[0067] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 40 12 4 Lithium dissolution reaction 40 4 8 Regeneration reaction of lithium precipitation additive 40 11 5 Regeneration reaction of lithium dissolving agent 40 3 7

[0068] Example 4

[0069] Use 1.00L of sulfate system lithium solution (main components and concentrations are Li 7.00g / L, Na 10.00g / L, K 5.90g / L), and add raw material regeneration aid 1: KOH 56.00g, regeneration aid 2: H 2 SO 4 49.00g, lithium precipitation auxiliary agent K 3 PO 4 70.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2 SO 453.87g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.94%. The reaction conditions of the above purification method are shown in Table 4.

[0070] Table 4

[0071] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 20 12 3 Lithium dissolution reaction 20 1 4 Regeneration reaction of lithium precipitation additive 20 <![CDATA[OH - 1.5mol / L*]]> 2 Regeneration reaction of lithium dissolving agent 20 <![CDATA[H + 1.5mol / L*]]> 2

[0072] *OH - , H + The concentration is outside the pH range.

[0073] Example 5

[0074] 1.00 L of sulfate system lithium-containing solution (main components and concentrations are Li 7.00 g / L, Na 12.00 g / L, K 3.10 g / L) was used, and the raw material regeneration aid 1 was NaOH 20.00 g, KOH 28.00 g, and the regeneration aid 2 was H 2 SO 4 49.00g, lithium precipitation auxiliary agent Na 1.5 K 1.5 PO 4 62.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2 SO 4 53.76g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.74%. The reaction conditions of the above purification method are shown in Table 5.

[0075] Table 5

[0076] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 65 11 3 Lithium dissolution reaction 50 2 3 Regeneration reaction of lithium precipitation additive 70 12 2 Regeneration reaction of lithium dissolving agent 90 1 3

[0077] Example 6

[0078] 1.00 L of sulfate system lithium solution (main components and concentrations are Li 7.00 g / L, Na 14.50 g / L, K 3.10 g / L) was used, and the raw material regeneration aid 1 was NaOH 53.33 g, and the regeneration aid 2 was H 2 SO 4 65.33g, lithium precipitation aid Na 2 HPO 4 47.33g, lithium dissolving agent Fe 2 (SO 4) 3 66.67 g, Li 2 SO 4 53.77g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.76%. The reaction conditions of the above purification method are shown in Table 6.

[0079] Table 6

[0080] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 70 12 2 Lithium dissolution reaction 40 2 4 Regeneration reaction of lithium precipitation additive 50 11 3 Regeneration reaction of lithium dissolving agent 20 4 8

[0081] Example 7

[0082] Use 1.00L of sulfate system lithium solution (main components and concentrations are Li 7.00g / L, Na 16.09g / L, K 6.20g / L), and add raw material regeneration aid 1: KOH 93.33g, regeneration aid 2: H 2 SO 4 81.67g, lithium precipitation auxiliary agent KH 2 PO 4 45.33g, lithium dissolving agent Fe 2 (SO 4 ) 3 61.83 g, Li 2 SO 4 53.70g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.64%. The reaction conditions of the above purification method are shown in Table 7.

[0083] Table 7

[0084] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 90 12 1.5 Lithium dissolution reaction 60 4 6 Regeneration reaction of lithium precipitation additive 50 11 5 Regeneration reaction of lithium dissolving agent 20 3 6

[0085] Example 8

[0086] Use 1.00L of sulfate system lithium solution (main components and concentrations are Li 7.00g / L, Na 20.00g / L, K 5.10g / L), and add raw material regeneration aid 1, NaOH 20.00g, KOH 28.00g, and regeneration aid 2, H 2 SO 4 65.33g, lithium precipitation aid NaKHPO 4 52.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2SO 4 53.82g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.85%. The reaction conditions of the above purification method are shown in Table 8.

[0087] Table 8

[0088]

[0089]

[0090] Example 9

[0091] Use 1.00L of sulfate system lithium solution (main components and concentrations are Li 7.00g / L, Na 20.00g / L, K 5.10g / L), and add raw material regeneration aid 1: NaOH 53.33g, regeneration aid 2: H 2 SO 4 65.33g, lithium precipitation aid Na 3 PO 4 54.67 g, lithium dissolving agent Fe(OH)(SO 4 ) 2 44.17 g, Li 2 SO 4 53.71g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.66%. The reaction conditions of the above purification method are shown in Table 9.

[0092] Table 9

[0093] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 50 11 5 Lithium dissolution reaction 45 4 7 Regeneration reaction of lithium precipitation additive 50 10 4 Regeneration reaction of lithium dissolving agent 65 3 5

[0094] Example 10

[0095] Use 1.00L of sulfate system lithium solution (main components and concentrations are Li 7.00g / L, Na 20.00g / L, K 5.10g / L), and add raw material regeneration aid 1: NaOH 40.00g, regeneration aid 2: H 2 SO 4 49.00g, lithium precipitation auxiliary agent Na 3 PO 4 54.67g, lithium dissolving agent Fe 2 (SO 4 ) 3 66.67 g, Li 2 SO4 53.43g (Li 25.00g / L, Na and K content less than 0.001g / L), according to calculation, Li 2 SO 4 The direct recovery rate of Li is 97.14%. The reaction conditions of the above purification method are shown in Table 10.

[0096] Table 10

[0097] Reaction process Temperature / ℃ pH Time / h Lithium precipitation reaction 100 8 1 Lithium dissolution reaction 100 4 1 Regeneration reaction of lithium precipitation additive 100 9 1 Regeneration reaction of lithium dissolving agent 100 5 1

Claims

1. A method for purifying lithium sulfate from a sulfate system lithium-containing solution, characterized in that: The following steps are involved: S1. Separation of lithium Adding a lithium precipitation auxiliary agent to a lithium-containing solution of a sulfate system, stirring and leaching, performing a lithium precipitation reaction, obtaining a slurry after the reaction is completed, filtering and washing, and obtaining lithium-rich slag and a lithium-poor solution; S2. Preparation of lithium sulfate After adding water to the lithium-rich slag to make a slurry, a lithium dissolving aid is added and stirred for leaching to carry out a lithium dissolving reaction to obtain a slurry after the reaction is completed, which is filtered and washed to obtain lithium-poor slag and a lithium sulfate solution; the lithium sulfate solution is concentrated and crystallized to obtain a lithium sulfate product; S3, additive regeneration The lithium-poor slag is slurried with water and a regeneration aid 1 is added to stir and leach, and a lithium precipitation aid regeneration reaction is carried out to obtain a slurry after the reaction is completed, which is filtered and washed to obtain a lithium-dissolving aid precursor slag and a lithium-precipitating aid solution; the lithium-dissolving aid precursor slag is slurried with water and a regeneration aid 2 is added to stir and leach, and a lithium-dissolving aid regeneration reaction is carried out to obtain a lithium-dissolving aid solution after the reaction is completed. The produced lithium precipitation auxiliary solution and lithium dissolution auxiliary solution are returned to S1 and S2 for recycling respectively.

2. A method for purifying lithium sulfate from a sulfate system lithium-containing solution as claimed in claim 1, characterized in that: The sulfate system lithium-containing solution has sulfate ions as anions, lithium ions and alkali metal ions as cations, and the alkali metal elements are sodium and potassium or both. The concentration of lithium ions is 2-30 g / L.

3. A method for purifying lithium sulfate from a sulfate system lithium-containing solution as claimed in claim 1, characterized in that: Adding a lithium precipitation aid to the solution in S1; The lithium precipitation auxiliary agent is PO4 3- With H + 、Na + , K + A compound composed of one or more of The lithium precipitation reaction temperature is: 20-100°C; The pH of the lithium precipitation reaction is: 8-12 The lithium precipitation reaction time is: 1-8h.

4. A method for purifying lithium sulfate from a sulfate system lithium-containing solution as claimed in claim 1, characterized in that: Adding a lithium dissolving aid to the solution in S2; The lithium dissolving agent in S2 is SO4 2- OH - with Fe 3+ A compound composed of one or more of The lithium dissolving reaction temperature is: 20-100°C; The pH of the lithium dissolution reaction is: ≤4 The lithium dissolving reaction time is: 1-8h.

5. A method for purifying lithium sulfate from a sulfate system lithium-containing solution as claimed in claim 1, characterized in that: The regeneration aid 1 in S3 is one or more of sodium hydroxide and potassium hydroxide, and the regeneration aid 2 is sulfuric acid; The regeneration reaction temperature of the lithium precipitation auxiliary agent is: 20-100°C; The pH of the lithium precipitation auxiliary agent regeneration reaction is: ≥9 The regeneration reaction time of the lithium precipitation auxiliary agent is: 1-8h; The regeneration reaction temperature of the lithium dissolving agent is: 20-100°C; The pH of the lithium dissolving agent regeneration reaction is: ≤5 The regeneration reaction time of the lithium dissolving auxiliary agent is: 1-8h.

Images