Method for extracting lithium from spodumene smelting slag

Abstract

The invention discloses a method for extracting lithium from spodumene smelting slag, which relates to the technical field of lithium slag solid waste recovery. The method comprises the following steps: S1: mixing lithium slag, fluoride and sulfuric acid to obtain a mixed solution; S2: heating and stirring the mixed solution, and then performing solid-liquid separation to obtain solid product leaching slag and liquid product leaching solution; S3: purifying and removing impurities, evaporating and concentrating, precipitating lithium, filtering, washing and drying the leaching solution in sequence to obtain a lithium carbonate product. The method realizes efficient leaching of lithium from spodumene smelting slag by adding fluoride as a leaching aid, and the process does not require high-temperature heat treatment, has a simple process and low production cost.

Description

Technical Field

[0001] The invention relates to the technical field of lithium slag solid waste recovery, in particular to a method for extracting lithium from spodumene smelting slag. Background Art

[0002] The main mineral raw materials for lithium extraction include spodumene, lepidolite, petalite, ferrolithium mica and apatite, among which spodumene has the largest production capacity. The mainstream process of lithium extraction from spodumene is to first roast natural spodumene at 950-1100°C to transform the monoclinic α-spodumene into the tetragonal β-spodumene. Due to the crystal transformation, the physical and chemical properties of the mineral also change significantly, the chemical activity increases, and it can react with acids and alkalis in various ways, which is suitable for lithium extraction. Spodumene extraction produces about 8-10 tons of lithium slag for every ton of lithium carbonate produced. A large amount of lithium slag causes serious harm to the environment. At present, the resource utilization of lithium slag is mainly used in the field of building materials, but its economic value is low, and the effect of increasing the value of lithium slag is limited. The problem of lithium slag treatment has not been well solved.

[0003] In the process of lithium extraction from spodumene, a small amount of lithium will inevitably remain in the lithium slag, part of which exists in the form of α-lithium that has not been completely transformed into a crystalline form, and part of which exists in the form of β-lithium that has not been completely leached. The lithium oxide content in lithium slag is generally around 0.5%. Extracting lithium from lithium slag and preparing it into high-value-added lithium carbonate products has significant economic value. How to recycle lithium in lithium slag and prepare lithium carbonate products is currently a research hotspot.

[0004] In this regard, Chinese patent CN112408435A discloses a method for recycling and treating lithium slag resources, wherein spodumene sulfuric acid lithium extraction slag is mixed with spodumene to prepare lithium carbonate and lithium hydroxide. This process requires an acidification and roasting process, which has high energy consumption and produces a large amount of acid mist that is difficult to handle. Chinese patent CN114737066A provides a method for extracting lithium from lithium ore leaching slag, wherein lithium slag is mixed evenly with a sulfate additive and then ground and activated, and then subjected to heat treatment, leaching, impurity removal and lithium precipitation steps to obtain lithium carbonate. This process requires a heat treatment step, which has a high temperature, a long time, and a high industrial cost. Chinese patent CN116532235A provides a method for comprehensive utilization of spodumene smelting slag resources, which can make the lithium leaching rate ≥65% through a grinding + heated acid leaching process. This method is simple to operate but the lithium leaching rate is not high.

[0005] It can be seen that the current lithium slag extraction technology has the disadvantages of high energy consumption or low lithium leaching rate. Therefore, there is an urgent need for a method of extracting lithium from spodumene smelting slag with low energy consumption, low cost and high extraction efficiency. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for extracting lithium from spodumene smelting slag, so as to at least achieve the effects of low energy consumption, low cost and high extraction efficiency.

[0007] Provided is a method for extracting lithium from spodumene smelting slag.

[0008] The method for extracting lithium from spodumene smelting slag comprises the following steps:

[0009] S1: mixing lithium slag, fluoride and sulfuric acid to obtain a mixed solution;

[0010] S2: heating and stirring the mixed solution, and then performing solid-liquid separation to obtain a solid product leaching residue and a liquid product leaching solution;

[0011] S3: The leaching solution is purified and impurity-removed, evaporated and concentrated, lithium precipitated, filtered, washed and dried in sequence to obtain a lithium carbonate product.

[0012] In some implementations, in step S1, the lithium slag is smelting slag after spodumene undergoes high-temperature crystal transformation.

[0013] In some examples, the lithium slag is acid-process lithium slag.

[0014] In some embodiments, in step S1, the fluoride comprises CaF 2 、NaF、KF、MgF 2 、LiF、Na 3 AlF 6 and Ca 5 (PO 4 ) 3 At least one of F.

[0015] In some embodiments, in step S1, the sulfuric acid is dilute sulfuric acid.

[0016] In some examples, the mass fraction of the dilute sulfuric acid is 15-30%.

[0017] Exemplarily, the liquid-to-solid ratio of the dilute sulfuric acid and the lithium slag is 1 to 4:1.

[0018] In some embodiments, in step S1, the mass ratio of the lithium slag to the fluoride is 100:0.2-1.

[0019] In some examples, the mass ratio of the lithium slag to the fluoride is 100:0.2-1.

[0020] In some embodiments, in step S2, the temperature of the heating and stirring is 60-95°C;

[0021] In some examples, the heating and stirring time is 1-4 hours.

[0022] In some embodiments, in step S3, the purification and impurity removal adopts conventional leaching solution purification and impurity removal methods, including ion precipitation method, displacement precipitation method and co-precipitation method.

[0023] In some embodiments, in step S3, the purification and impurity removal method is: adjusting the pH of the leachate to 4-5, then adding a flocculant and filtering to obtain neutralized slag and neutralized liquid; adjusting the pH of the neutralized liquid to 10-11, filtering to obtain calcium magnesium slag and purified liquid; the purified liquid enters the subsequent evaporation and concentration step.

[0024] In some examples, calcium carbonate is used to adjust the pH of the leachate.

[0025] In some examples, sodium hydroxide is used to adjust the pH of the neutralization solution.

[0026] In some examples, the flocculant includes: polyacrylamide.

[0027] In some examples, the amount of the flocculant added is 25-40 g / t (calculated as lithium slag).

[0028] In some embodiments, in step S3, after the evaporation and concentration, a liquid product purified liquid and a solid product calcium-magnesium slag are obtained, and the purified liquid enters the subsequent lithium precipitation step.

[0029] In some embodiments, in step S3, the lithium precipitation is carried out by adding sodium carbonate to perform a precipitation reaction.

[0030] The beneficial effects of the present invention are:

[0031] The present invention provides a method for realizing efficient leaching of lithium element in lithium slag by adding fluoride at low temperature. The method has simple process, low energy consumption cost and high lithium extraction efficiency for spodumene smelting slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a simplified process flow diagram of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0034] Example 1

[0035] Lithium slag obtained from lithium extraction by spodumene acid process (Li 2 O content 0.743%), the specific method is as follows:

[0036] 1) Take 1 kg of the lithium slag and add 2 g of CaF at a mass fraction of 0.2%2 Then add 2L of 20% dilute sulfuric acid at a liquid-to-solid ratio of 2:1 to the lithium slag.

[0037] 2) heating in a water bath at 95°C and stirring for 1 hour, and then filtering to obtain leaching residue and leaching liquid; washing the leaching residue and testing the leaching residue, and the Li 2 O content is 0.104%, so the Li 2 The O content is 0.639% and the lithium leaching rate reaches 86.00%.

[0038] 3) adding sodium carbonate to the leaching solution after purification, impurity removal, evaporation and concentration to obtain lithium carbonate precipitate, washing and drying the lithium carbonate precipitate to obtain a lithium carbonate product;

[0039] The purification and impurity removal method is as follows: firstly, calcium carbonate is added to adjust the pH to 4-5, then polyacrylamide is added in an amount of 40 g / t (based on lithium slag), and neutralized slag and neutralized liquid are obtained by filtering; sodium hydroxide is added to the neutralized liquid to adjust the pH to 10-11, then sodium carbonate is added, and calcium-magnesium slag and purified liquid are obtained by filtering, and the purified liquid enters the subsequent lithium precipitation step;

[0040] The method for precipitating lithium is to add sufficient amount of sodium carbonate for precipitation.

[0041] Example 2

[0042] Lithium slag obtained from lithium extraction by spodumene acid process (Li 2 O content 0.584%), the specific method is as follows:

[0043] 1) Take 2 kg of the lithium slag, add 20 g of NaF at a mass fraction of 1%, and then add 8 L of dilute sulfuric acid with a mass fraction of 15% at a liquid-to-solid ratio of 4:1 to the lithium slag.

[0044] 2) heating in a water bath at 80°C and stirring for 2h, then filtering to obtain leaching residue and leaching solution; washing the leaching residue and testing the leaching residue, and finding out the Li 2 O content is 0.066%, so the Li 2 The O content is 0.518% and the lithium leaching rate reaches 88.70%.

[0045] 3) adding sodium carbonate to the leaching solution after purification, impurity removal, evaporation and concentration to obtain lithium carbonate precipitate, washing and drying the lithium carbonate precipitate to obtain a lithium carbonate product;

[0046] The purification and impurity removal method is as follows: firstly, calcium carbonate is added to adjust the pH to 4-5, then polyacrylamide is added in an amount of 25 g / t (based on lithium slag), and neutralized slag and neutralized liquid are obtained by filtering; sodium hydroxide is added to the neutralized liquid to adjust the pH to 10-11, then sodium carbonate is added, and calcium-magnesium slag and purified liquid are obtained by filtering, and the purified liquid enters the subsequent lithium precipitation step;

[0047] The method for precipitating lithium is to add sufficient amount of sodium carbonate for precipitation.

[0048] Example 3

[0049] Lithium slag obtained from lithium extraction by spodumene acid process (Li 2 O content 0.510%), the specific method is as follows:

[0050] 1) Take 3 kg of the lithium slag and add 15 g of Na 3 AlF 6 Then add 9L of 30% dilute sulfuric acid at a liquid-to-solid ratio of 3:1 to the lithium slag.

[0051] 2) heating in a water bath at 70°C and stirring for 3h, then filtering to obtain leaching residue and leaching solution; washing the leaching residue and testing the leaching residue, and finding out the Li 2 O content is 0.082%, so the Li 2 The O content is 0.428% and the lithium leaching rate reaches 83.92%.

[0052] 3) After purifying and removing impurities from the leaching solution and evaporating and concentrating it, sodium carbonate is added to obtain a lithium carbonate precipitate, and the lithium carbonate precipitate is washed and dried to obtain a lithium carbonate product.

[0053] The purification and impurity removal method is as follows: firstly, calcium carbonate is added to adjust the pH to 4-5, then polyacrylamide is added in an amount of 30 g / t (based on lithium slag), and neutralized slag and neutralized liquid are obtained by filtering; sodium hydroxide is added to the neutralized liquid to adjust the pH to 10-11, then sodium carbonate is added, and calcium-magnesium slag and purified liquid are obtained by filtering, and the purified liquid enters the subsequent lithium precipitation step;

[0054] The method for precipitating lithium is to add sufficient amount of sodium carbonate for precipitation.

[0055] Comparative Example 1

[0056] Lithium slag obtained from lithium extraction by spodumene acid process (Li 2 O content 0.443%), the difference is that no fluoride leaching agent is added as in Example 1, and the specific method is as follows:

[0057] 1) Take 1 kg of the lithium slag, and add 2 L of dilute sulfuric acid with a mass fraction of 20% according to a liquid-to-solid ratio of 2:1 between the lithium slag and the lithium slag.

[0058] 2) heating and stirring at 80°C for 1 hour and then filtering to obtain leaching residue and leaching liquid; washing and testing the leaching residue, and the Li 2 O content is 0.210%, so the Li 2 The O content is 0.233% and the lithium leaching rate reaches 52.60%.

[0059] 3) adding sodium carbonate to the leaching solution after purification, impurity removal, evaporation and concentration to obtain lithium carbonate precipitate, washing and drying the lithium carbonate precipitate to obtain a lithium carbonate product;

[0060] The purification and impurity removal method is as follows: firstly, calcium carbonate is added to adjust the pH to 4-5, then polyacrylamide is added in an amount of 40 g / t (based on lithium slag), and neutralized slag and neutralized liquid are obtained by filtering; sodium hydroxide is added to the neutralized liquid to adjust the pH to 10-11, then sodium carbonate is added, and calcium-magnesium slag and purified liquid are obtained by filtering, and the purified liquid enters the subsequent lithium precipitation step;

[0061] The method for precipitating lithium is to add sufficient amount of sodium carbonate for precipitation.

[0062] Comparative Example 2

[0063] Lithium slag obtained from lithium extraction by spodumene acid process (Li 2 O content 0.443%), the difference from Example 1 is that the leaching temperature is higher, and the specific method is as follows:

[0064] 1) Take 1 kg of the lithium slag and add 2 g of CaF at a mass fraction of 0.2% 2 Then add 2L of 20% dilute sulfuric acid at a liquid-to-solid ratio of 2:1 to the lithium slag.

[0065] 2) heating and stirring at 180°C in an autoclave for 1 hour and then filtering to obtain leaching residue and leaching liquid; washing and testing the leaching residue, and the Li 2 O content is 0.155%, so the Li 2 The O content is 0.288% and the lithium leaching rate reaches 65.01%.

[0066] 3) adding sodium carbonate to the leaching solution after purification, impurity removal, evaporation and concentration to obtain lithium carbonate precipitate, washing and drying the lithium carbonate precipitate to obtain a lithium carbonate product;

[0067] The purification and impurity removal method is as follows: firstly, calcium carbonate is added to adjust the pH to 4-5, then polyacrylamide is added in an amount of 40 g / t (based on lithium slag), and neutralized slag and neutralized liquid are obtained by filtering; sodium hydroxide is added to the neutralized liquid to adjust the pH to 10-11, then sodium carbonate is added, and calcium-magnesium slag and purified liquid are obtained by filtering, and the purified liquid enters the subsequent lithium precipitation step;

[0068] The method for precipitating lithium is to add sufficient amount of sodium carbonate for precipitation.

[0069] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for extracting lithium from spodumene smelting slag, characterized in that: The following steps are involved: S1: mixing lithium slag, fluoride and sulfuric acid to obtain a mixed solution; S2: heating and stirring the mixed solution, and then performing solid-liquid separation to obtain a solid product leaching residue and a liquid product leaching solution; S3: sequentially purifying and removing impurities, evaporating and concentrating, precipitating lithium, filtering, washing and drying the leaching solution to obtain a lithium carbonate product; The lithium slag is smelting slag after spodumene undergoes high-temperature crystal transformation; The fluoride includes at least one of CaF2, NaF, KF, MgF2, LiF, Na3AlF6 and Ca5(PO4)3F.

2. The method according to claim 1, characterized in that: In step S1, the sulfuric acid is dilute sulfuric acid.

3. The method according to claim 2, characterized in that: The mass fraction of the dilute sulfuric acid is 15-30%.

4. The method according to claim 3, characterized in that: The liquid-to-solid ratio of the dilute sulfuric acid to the lithium slag is 1-4:1, and the unit is L:kg.

5. The method according to claim 1, characterized in that: In step S1, the mass ratio of the lithium slag to the fluoride is 100:0.2-1.

6. The method according to claim 1, characterized in that: In step S2, the heating and stirring temperature is 60-95°C; And / or, the heating and stirring time is 1-4h.

7. The method according to claim 1, characterized in that In step S3, the purification and impurity removal method is: adjusting the pH of the leaching solution to 4-5, then adding a flocculant and filtering to obtain neutralized slag and neutralized liquid; adjusting the pH of the neutralized liquid to 10-11, filtering to obtain calcium magnesium slag and purified liquid; the purified liquid enters the subsequent evaporation and concentration step.

8. The method according to claim 1, characterized in that: In step S3, the lithium precipitation is carried out by adding sodium carbonate to perform a precipitation reaction.

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