METHOD FOR RECOVERING LITHIUM AND METHOD FOR PRODUCING LITHIUM CARBONATE

Abstract

Disclosed is A method for recovering lithium from slag containing at least aluminum and lithium, the slag being provided by melting a lithium-ion secondary battery to be disposed of to obtain molten metal containing valuable metal and molten slag containing at least aluminum and lithium and separating the slag containing at least aluminum and lithium from the molten metal containing valuable metal. The condition of the melting of the lithium-ion secondary battery is adjusted such that the slag has an aluminum to lithium mass ratio, Al/Lo, of 6 or less. The method includes: contacting the slag with an aqueous liquid to obtain a leachate containing lithium leached from the slag; and contacting the leachate with a basic substance to cause unwanted metal contained in the leachate to precipitate in the form of a slightly soluble substance, followed by solid-liquid separation to obtain a purified solution having lithium dissolved therein.

Claims

1. A method for recovering lithium from slag containing at least aluminum and lithium, the slag being provided by melting a lithium-ion secondary battery to be disposed of to obtain molten metal containing valuable metal and molten slag containing at least aluminum and lithium and separating the slag from the molten metal containing valuable metal, wherein a condition of the melting of the lithium-ion secondary battery is adjusted such that the slag has an aluminum to lithium mass ratio, Al/Li, of 6 or less, the method comprising: contacting the slag with an aqueous liquid to obtain a leachate containing lithium leached from the slag, and contacting the leachate with a basic substance to cause unwanted metal contained in the leachate to precipitate in the form of a slightly soluble substance, followed by solid-liquid separation to obtain a purified solution having lithium dissolved therein.

2. The method for recovering lithium according to claim 1, wherein the amount of aluminum present in the melting of the lithium-ion secondary battery is controlled to adjust the aluminum to lithium mass ratio of the slag to 6 or less.

3. The method for recovering lithium according to claim 2, wherein the amount of aluminum present in the melting is controlled by any one of: method (1) comprising separating at least part of aluminum from the lithium-ion secondary battery before the melting by selective melting and removal of aluminum or by crushing and separation of aluminum to selectively remove aluminum, method (2) comprising carrying out the melting using a furnace of which a portion coming into contact with molten slag is made of an aluminum-free material, and method (3) comprising, not using a flux to accelerate slag formation in the melting, or using the flux which has an aluminum content that does not cause the aluminum to lithium mass ratio of the resulting slag to exceed 6.

4. The method for recovering lithium according to claim 1, wherein the slag to be contacted with the aqueous liquid to obtain the leachate containing lithium leached from the slag is crushed into grains having an average grain size of 5 mm or smaller.

5. The method for recovering lithium according to claim 1, wherein the contacting of the leachate with the basic substance is such that the resulting mixture of the leachate and the basic substance has a pH of 10 to 12.

6. The method for recovering lithium according to claim 1, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

7. A method for producing lithium carbonate from slag containing at least aluminum and lithium, the slag being provided by melting a lithium-ion secondary battery to be disposed of to obtain molten metal containing valuable metal and molten slag containing at least aluminum and lithium and separating the slag containing at least aluminum and lithium from the molten metal containing valuable metal, wherein a condition of the melting of the lithium-ion secondary battery is adjusted such that the slag has an aluminum to lithium mass ratio, Al/Li, of 6 or less, the method comprising: contacting the slag with an aqueous liquid to obtain a leachate containing lithium leached from the slag, contacting the leachate with a basic substance to cause an unwanted metal contained in the leachate to precipitate in the form of a slightly soluble substance, followed by solid-liquid separation to obtain a purified solution having lithium dissolved therein, and contacting the purified solution with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

8. The method for recovering lithium according to claim 2, wherein the slag to be contacted with the aqueous liquid to obtain the leachate containing lithium leached from the slag is crushed into grains having an average grain size of 5 mm or smaller.

9. The method for recovering lithium according to claim 3, wherein the slag to be contacted with the aqueous liquid to obtain the leachate containing lithium leached from the slag is crushed into grains having an average grain size of 5 mm or smaller.

10. The method for recovering lithium according to claim 2, wherein the contacting of the leachate with the basic substance is such that the resulting mixture of the leachate and the basic substance has a pH of 10 to 12.

11. The method for recovering lithium according to claim 3, wherein the contacting of the leachate with the basic substance is such that the resulting mixture of the leachate and the basic substance has a pH of 10 to 12.

12. The method for recovering lithium according to claim 4, wherein the contacting of the leachate with the basic substance is such that the resulting mixture of the leachate and the basic substance has a pH of 10 to 12.

13. The method for recovering lithium according to claim 8, wherein the contacting of the leachate with the basic substance is such that the resulting mixture of the leachate and the basic substance has a pH of 10 to 12.

14. The method for recovering lithium according to claim 9, wherein the contacting of the leachate with the basic substance is such that the resulting mixture of the leachate and the basic substance has a pH of 10 to 12.

15. The method for recovering lithium according to claim 2, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

16. The method for recovering lithium according to claim 3, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

17. The method for recovering lithium according to claim 4, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

18. The method for recovering lithium according to claim 5, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

19. The method for recovering lithium according to claim 8, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

20. The method for recovering lithium according to claim 9, further comprising contacting the purified solution having lithium dissolved therein with a carbonate or carbon dioxide to precipitate a carbonate of lithium in the solution.

Description

EXAMPLES

[0049] The invention will now be illustrated by way of Examples, but it should be understood that the invention is not construed as being limited thereto. All of the fluxes used in Examples and Comparative Examples were of the type that accelerates slag formation. Unless otherwise noted, all the percentages are by mass.

Chemical Composition Analysis

[0050] The amount of each metal element in the slag was determined by adding to the slag 10 times the mass of 60% nitric acid, 10 times the mass of 35% hydrochloric acid, and 30 times the mass of ultrapure water, mixing for 2 hours at 110° C. (dissolution treatment), and analyzing the resulting sample solution by ICP-AES. When insoluble matter remained after the dissolution treatment, the amounts of lithium and aluminum in the slag were calculated based on the weight of the slag under analysis having subtracted therefrom the weight of the insoluble matter separately measured as described below. The thus determined amount of lithium are shown in Tables 1 and 2. The Al/Li as calculated from the aluminum and the lithium concentration of the solution obtained by the dissolution treatment is also shown in Tables 1 and 2. The insoluble matter was separated from the liquid phase using a membrane filter, dried in a glass petri dish in an electric dryer at 50° C. for 2 hours, and weighed.

[0051] A leachate and a neutralization liquid were also analyzed for chemical composition by ICP-AES. The amount of lithium in lithium carbonate was determined by analyzing a solution of the lithium carbonate by ICP-AES as well.

Average Grain Size

[0052] The average grain size of slag was measured by the laser diffraction/scattering method using an analyzer available from Horiba, Ltd.

Example 1

[0053] Slag with an Al content of 13.0% and an Li content of 8.8% was used as a starting material. This slag was obtained as follows.

[0054] Method (1) was followed in carrying out the melting process. Scrap of LIBs having aluminum cans having been made harmless by the method described hereinabove was heated at 750° C. in a low-oxygen atmosphere with an oxygen concentration of 10 vol % or less and the rest of nitrogen and carbon dioxide to selectively melt aluminum. The aluminum melt was removed manually. The scrap after removal of aluminum was crushed in a hammer mill and sieved through a screen of 2 mm opening. The undersize from the screen was melted together with an aluminum-free flux (e.g., a calcium compound) by heating in a reducing atmosphere at 1400° C. in the presence of carbon. All the furnace material making up the furnace wall was magnesia. There was obtained slag having an Al/Li of 1.5. The slag was crushed to an average grain size of 0.5 to 1 mm.

[0055] To 10 g of the crushed slag was added 77 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of less than 1. To the resulting leachate containing the slag was added 64 g of calcium hydroxide having been diluted with water to 25% as a basic substance at 70° C. to adjust to a pH of 11 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 100 g of water therethrough. The filtrate was combined with the washing water to provide a purified solution. The lithium content of the purified solution was determined by the method described above. The lithium recovery from the slag was as shown in Table 1.

Example 2

[0056] Slag with an Al content of 13.9% and an Li content of 5.2% was used as a starting material. This slag was obtained in the same manner as in Example 1, except that, after the sieving, the oversize from the screen (2 mm opening) was subjected to a pneumatic gravity separator to remove residual aluminum, and that the undersize from the screen was subjected to the melting process together with the oversize from which aluminum has been removed and an aluminum-free flux (e.g., a calcium compound). The slag thus obtained had an Al/Li of 2.7. The slag was crushed to an average grain size of 0.5 to 1 mm.

[0057] To 10 g of the slag was added 41 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of 2.3. To the resulting leachate containing the slag was added 90 g of calcium hydroxide having been diluted with water to 5% as a basic substance at 70° C. to adjust to a pH of 11 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 100 g of water therethrough. The filtrate was combined with the washing water to provide a purified solution. The lithium content of the purified solution was determined by the method described above. The lithium recovery from the slag was as shown in Table 1.

Example 3

[0058] Slag with an Al content of 19.1% and an Li content of 5.5% was used as a starting material. This slag was obtained in the same manner as in Example 1, except that the crushed scrap from a hammer mill was melted together with an aluminum-free flux (e.g., a calcium compound). The resulting slag had an Al/Li of 3.5. The slag was crushed to an average grain size of 0.5 to 1 mm.

[0059] To 10 g of the slag was added 58 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of 1.1. To the resulting leachate containing the slag was added 83 g of calcium hydroxide having been diluted with water to 15% as a basic substance at 70° C. to adjust to a pH of 11 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 170 g of water therethrough. The filtrate was combined with the washing water to provide a purified solution. The lithium content of the purified solution was determined by the method described above. The lithium recovery from the slag was as shown in Table 1.

Example 4

[0060] Slag with an Al content of 27.9% and an Li content of 4.9% was used as a starting material. This slag was obtained in the same manner as in Example 1, except for using alumina as a flux in the melting process. The resulting slag had an Al/Li of 5.7. The slag was crushed to an average grain size of 0.5 to 1 mm.

[0061] To 10 g of the slag was added 140 g of sulfuric acid having been diluted with water to 30%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of less than 1 at that temperature. To the resulting leachate containing the slag was added 209 g of calcium hydroxide having been diluted with water to 15% as a basic substance at 70° C. to adjust to a pH of 11 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 100 g of water therethrough. The filtrate was combined with the washing water to provide a purified solution. The lithium content of the purified solution was determined by the method described above. The lithium recovery from the slag was as shown in Table 1.

Comparative Example 1

[0062] Slag with an Al content of 29.4% and an Li content of 3.9% was used as a starting material. This slag was obtained in the same manner as in Example 1, except that the LIB scrap was directly crushed in a hammer mill without the previous removal of aluminum by melting according to method (1), and that the crushed scrap was subjected to the melting process. The slag was crushed to an average grain size of 0.5 to 1 mm.

[0063] To 10 g of the slag was added 75 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of less than 1 at that temperature. To the resulting leachate containing the slag was added 110 g of calcium hydroxide having been diluted with water to 15% as a basic substance at 70° C. to adjust to a pH of 11 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 120 g of water therethrough. The filtrate was combined with the washing water to provide a purified solution. The lithium content of the purified solution was determined by the method described above. The lithium recovery from the slag was as shown in Table 1.

Comparative Example 2

[0064] Slag with an Al content of 28.6% and an Li content of 3.6% was used as a starting material. This slag was obtained in the same manner as in Example 1, except that the LIB scrap was directly crushed in a hammer mill without the previous removal of aluminum by melting according to method (1) and melted, and that a furnace made of alumina was used. The slag was crushed to an average grain size of 0.5 to 1 mm

[0065] To 10 g of the slag was added 75 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of less than 1 at that temperature. To the resulting leachate containing the slag was added 111 g of calcium hydroxide having been diluted with water to 15% as a basic substance at 70° C. to adjust to a pH of 11 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 120 g of water therethrough. Through the above steps, a purified solution was obtained. The lithium content of the resulting purified solution was determined by the method described above. The lithium recovery from the slag was as shown in Table 1.

TABLE-US-00001 TABLE 1 Li in Slag Li in Purified Li Recovery (mg) Al/Li Solution (mg) (%) Example 1 797 1.5 777 97 Example 2 518 2.7 452 87 Example 3 545 3.5 515 94 Example 4 490 5.7 310 63 Comp. Example 1 349 7.5  92 26 Comp. Example 2 299 7.9  96 32

[0066] It is seen from Table 1 that the lithium recovery is greatly increased by adjusting the Al to Li mass ratio to 6 or lower.

Examples 5 to 8

[0067] Slag with an Al content of 19.1% and an Li content of 5.5% was used as a starting material. This slag was obtained in the same manner as in Example 1, except that the crushed scrap from a hammer mill was melted together with an aluminum-free flux (e.g., a calcium compound). There was obtained slag with an Al/Li of 3.5. The slag was crushed to the average grain size shown in Table 2.

[0068] To 15 g of the slag was added 113 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of less than 1 at that temperature. The lithium content of the resulting leachate and the lithium recovery were as shown in Table 2.

TABLE-US-00002 TABLE 2 Grain Size Li in Slag Li in Li (mm) (mg) Leachate (mg) Recovery (%) Example 5 ≤1 818 800 98 Example 6 1-2 818 698 85 Example 7   2-3.4 818 528 65 Example 8 3.4-5   818 482 59

[0069] As shown in Table 2, the lithium recovery was as good as at least 59% when the slag grain size was 5 mm or smaller.

Example 9

[0070] Slag with an Al content of 13.9%, an Li content of 5.2%, a magnesium content of 3.7%, and a manganese content of 2.9% was used as a starting material.

[0071] The slag was obtained in the same manner as in Example 1, except for the following: the oversize from the screen (2 mm opening) was subjected to a pneumatic gravity separator to remove residual aluminum; and the undersize from the screen and the oversize from which residual aluminum has been removed were subjected to the melting process together with and an aluminum-free flux (e.g., a calcium compound). There was thus obtained slag having an Al/Li of 2.7. The slag was crushed to an average grain size of 0.5 to 1 mm.

[0072] To 18 g of the slag was added 68 g of sulfuric acid having been diluted with water to 40%, and the mixture was heated to 70° C. under atmospheric pressure to adjust to a pH of 1.8. To the resulting leachate containing the slag was added calcium hydroxide having been diluted with water to 5% as a basic substance at 70° C. to adjust to the pH shown in Table 3 at that temperature. The formed precipitate was collected by filtration (solid-liquid separation), and the solid phase was washed by passing 180 g of water therethrough. Through the above steps, a purified solution was obtained. The lithium, magnesium, and manganese contents of the resulting purified solution as determined by the method described above are shown in Table 3.

Examples 10 and 11

[0073] A purified solution was obtained in the same manner as in Example 9, except that the pH value of the leachate at 70° C. as adjusted by addition of a basic substance was changed as shown in Table 3. The lithium, magnesium, and manganese contents of the resulting purified solution as determined by the method described above are shown in Table 3.

TABLE-US-00003 TABLE 3 pH after Metal Content of Purified Solution (mg) Neutralization Mg Mn Li Example 9 11.5 N.D. N.D. 750 Example 10  5.5 2663 1482 878 Example 11  6.4 1662  658 814 N.D. = not detected

Example 12

[0074] The purified solution obtained in Example 9 was 10-fold concentrated under reduced pressure. To the concentrate was added 2.5 g of sulfuric acid having been diluted with water to 10% to adjust the pH at 70° C. to 7. Sodium carbonate was added thereto to cause the resulting mixture to react at 80° C. The precipitated lithium carbonate was collected by filtration under heating, and dried at 100° C. The lithium content of the lithium carbonate was determined, and the lithium recovery from the slag was found to be 52% as calculated from the lithium content. The purity of the lithium carbonate was found to be 98% from the results of analysis of impurity metals.

INDUSTRIAL APPLICABILITY

[0075] The invention allows for recovery of lithium, from the slag that is by-produced in melting waste LIBs for recovery of valuable metals, at higher efficiency than conventional techniques. The method of the invention enables effective utilization of the slag, which has been used only for building materials and the like in the past, through a few processes with low environmental burden.