Methods and equipment for processing lithium-containing substances.

Abstract

The invention relates to a method for processing lithium-containing substances comprising a soaking step S01 for soaking lithium in an acid solution by soaking the lithium-containing substance in an acid solution to obtain a lithium soaking solution, a first heavy metal and fluorine precipitation step S02 for adding a first calcium compound to the lithium soaking solution to produce a metal hydroxide precipitate and a fluorine precipitate, a first liquid-solid separation step S03 for removing the precipitated metal hydroxide precipitate and the precipitated fluorine precipitate from the lithium soaking solution, a second fluorine precipitation step S04 for adding a second calcium compound to the lithium soaking solution after removing the precipitates to cause the dissolved fluorine to precipitate, and a second liquid-solid separation step S05 for removing the precipitated dissolved fluorine precipitate and the unreacted second calcium compound from the lithium soaking solution.

Description

Method for treating lithium-containing material and device for treating lithium-containing material

[0001] The present invention relates to a method for treating a lithium-containing material and an apparatus for treating a lithium-containing material. This application claims priority based on Japanese Patent Application No. 2023-166485 filed in Japan on September 27, 2023, and Japanese Patent Application No. 2024-167391 filed in Japan on September 26, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, lithium has been recovered and reused from lithium-containing materials such as crushed lithium-ion batteries.

[0003] One known method for recovering lithium from lithium-containing materials involves roasting lithium-ion battery waste, immersing the resulting battery slag in an acidic solution, leaching the lithium into the acidic solution, and recovering lithium from the resulting lithium leachate. The leached liquid also contains metals other than lithium, such as cobalt and aluminum, but adding an alkali such as sodium hydroxide or calcium hydroxide to neutralize the leached liquid causes the metals other than lithium to precipitate, and further performing solid-liquid separation to separate the lithium solution from the other substances (Patent Document 1).

[0004] Furthermore, as a method for separating lithium from a lithium aqueous solution containing 200 mg / L or more of lithium, 20 mg / L or more of fluorine, and having a pH of 10.5 or more, there is known a method in which calcium hydroxide is added to the lithium aqueous solution to solidify the fluorine contained in the lithium aqueous solution, and the solidified fluorine is removed to obtain a fluorine-free lithium aqueous solution. In this method, carbon dioxide is further added to the lithium aqueous solution to solidify the remaining calcium, and the solidified calcium is removed to obtain a fluorine-free lithium aqueous solution (Patent Document 2).

[0005] Patent No. 6998241 Patent No. 6869444

[0006] However, as shown in Patent Document 1, if an alkaline agent such as sodium hydroxide is added to the lithium aqueous solution for the neutralization treatment of the lithium leachate, it becomes difficult to separate the sodium ions from the lithium ions, making it impossible to recover a highly pure lithium compound. Also, as shown in Patent Document 2, if the treatment for removing fluorine is carried out in only one stage, the removal of fluorine is insufficient, and a lithium compound of a purity suitable for reuse cannot be obtained.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and apparatus for treating a lithium-containing material that can recover lithium at high purity from the lithium-containing material.

[0008] In order to solve the above problems, a method for treating a lithium-containing material according to a first aspect of the present invention includes: a leaching step of adding an acidic solution containing an inorganic acid to a lithium-containing material to leach lithium into the acidic solution; a heavy metal and first fluorine precipitation step of adding a first calcium compound to the lithium leachate obtained in the leaching step to precipitate heavy metal ions as hydroxides and to precipitate fluorine; a first solid-liquid separation step of separating hydroxides of the heavy metal ions and the precipitate of fluorine from the lithium leachate after the heavy metal and first fluorine precipitation step; a second fluorine precipitation step of adding a second calcium compound to the lithium leachate after the first solid-liquid separation step to precipitate dissolved fluorine; and a second solid-liquid separation step of separating the precipitate of dissolved fluorine and unreacted second calcium compound from the lithium leachate to obtain a lithium-containing liquid after the second fluorine precipitation step.

[0009] According to the method for treating a lithium-containing material of Aspect 1 of the present invention, in the heavy metal and first fluorine precipitation step, a first calcium compound is added to precipitate heavy metals such as cobalt, nickel, and manganese dissolved in the lithium leachate, as well as fluorine. Then, in the first solid-liquid separation step, these precipitates are separated from the lithium leachate. This results in a lithium leachate with high lithium purity, free of heavy metals and fluorine. Furthermore, in the second fluorine precipitation step, a second calcium compound is added to the lithium leachate to precipitate heavy metals and dissolved fluorine that were not completely removed in the first fluorine precipitation step and the first solid-liquid separation step. Then, in the second solid-liquid separation step, the precipitated dissolved fluorine and unreacted components of the second calcium compound added in the second fluorine precipitation step are removed. This allows for the removal of fluorine in an amount that would be impossible to remove in a single-stage fluorine removal process, thereby obtaining a lithium-containing solution with higher lithium purity than conventional solutions. In both precipitation steps, a calcium compound is used to adjust the pH of the lithium leaching solution, so the amount of sodium mixed into the lithium leaching solution can be reduced compared to when sodium hydroxide (a sodium compound) is used for neutralization as described in Patent Document 1.

[0010] A method for treating a lithium-containing material according to Aspect 2 of the present invention is characterized in that, in the method for treating a lithium-containing material according to Aspect 1, it further comprises a calcium precipitation step of adding a soluble carbonate compound to the lithium-containing liquid after the second solid-liquid separation step to precipitate calcium as calcium carbonate, and a third solid-liquid separation step of separating the calcium carbonate from the lithium-containing liquid after the calcium precipitation step. According to the method for treating a lithium-containing material according to Aspect 2 of the present invention, calcium ions, which are calcium ions in a dissolved state that are part of the calcium compounds added in the first and second fluorine precipitation steps and remain in the lithium leaching solution, can be separated from the lithium-containing liquid as calcium carbonate, thereby making it possible to obtain a lithium-containing liquid having an even higher lithium purity.

[0011] A method for treating a lithium-containing material according to Aspect 3 of the present invention is characterized in that, in the method for treating a lithium-containing material according to Aspect 1 or Aspect 2, the fluorine precipitate and the unreacted second calcium compound separated in the second solid-liquid separation step are used as the first calcium compound in the heavy metal and first fluorine precipitation steps. According to the method for treating a lithium-containing material according to Aspect 3 of the present invention, the unreacted second calcium compound recovered in the second solid-liquid separation step is used in the heavy metal and first fluorine precipitation steps, thereby reducing chemical costs. Furthermore, since the precipitates produced in the first fluorine precipitation step and the second fluorine precipitation step can be combined, sludge treatment costs can be reduced.

[0012] A method for treating a lithium-containing material according to Aspect 4 of the present invention is characterized in that, in the method for treating a lithium-containing material according to Aspect 2 or Aspect 3, the calcium carbonate separated in the third solid-liquid separation step is used as the second calcium compound in the second fluorine precipitation step. According to the method for treating a lithium-containing material according to Aspect 4 of the present invention, the calcium carbonate recovered in the third solid-liquid separation step is used in the second fluorine precipitation step, thereby making it possible to reduce chemical costs and the amount of sludge.

[0013] A method for treating a lithium-containing material according to Aspect 5 of the present invention is characterized in that, in the method for treating a lithium-containing material according to any one of Aspects 1 to 4, the solid content containing calcium fluoride separated in the second solid-liquid separation step is used as seed crystals in the second fluorine precipitation step. According to the method for treating a lithium-containing material according to Aspect 5 of the present invention, the solid content recovered in the second solid-liquid separation step is used as seed crystals in the second fluorine precipitation step, and therefore the solid concentration in the second fluorine precipitation step is increased, thereby making it possible to increase the fluorine removal efficiency and, in addition, reduce the amount of sludge.

[0014] A method for treating a lithium-containing material according to Aspect 6 of the present invention is characterized in that, in the method for treating a lithium-containing material according to any one of Aspects 2 to 5, the calcium carbonate separated in the third solid-liquid separation step is used as seed crystals in the calcium precipitation step. According to the method for treating a lithium-containing material according to Aspect 6 of the present invention, the calcium carbonate removed in the third solid-liquid separation step is used as seed crystals in the calcium precipitation step, and therefore the solid concentration in the calcium precipitation step is increased, thereby making it possible to enhance the calcium removal efficiency and, in addition, to reduce the amount of sludge.

[0015] A method for treating a lithium-containing material according to Aspect 7 of the present invention is characterized in that, in the method for treating a lithium-containing material according to any one of Aspects 2 to 6, a sodium compound is added after the addition of the second calcium compound in the second fluorine precipitation step. According to the method for treating a lithium-containing material according to Aspect 7 of the present invention, the sodium compound is used supplementarily, and as a result, the amount of sodium mixed into the lithium leaching solution can be reduced compared to the case where sodium hydroxide (sodium compound) described in Patent Document 1 is mainly used.

[0016] A method for treating a lithium-containing material according to Aspect 8 of the present invention is the method for treating a lithium-containing material according to any one of Aspects 1 to 6, characterized in that a soluble aluminum compound is added in the second fluorine precipitation step. According to the method for treating a lithium-containing material according to Aspect 8 of the present invention, the soluble aluminum compound acts as an inorganic flocculant to improve separability, making it easier to remove the fluorine precipitate produced in the second fluorine precipitation step. In addition, aluminum hydroxide produced by hydrolysis of soluble aluminum has the effect of adsorbing fluorine, making it possible to obtain a lithium-containing solution with a higher lithium purity.

[0017] A method for treating a lithium-containing material according to Aspect 9 of the present invention is characterized in that, in the method for treating a lithium-containing material according to any one of Aspects 2 to 7, a soluble aluminum compound is added in the calcium precipitation step. According to the method for treating a lithium-containing material according to Aspect 9 of the present invention, the soluble aluminum compound acts as an inorganic flocculant to improve separability by settling, and calcium carbonate produced in the calcium precipitation step can be more easily removed, thereby making it possible to obtain a lithium-containing solution having a higher lithium purity.

[0018] A method for treating a lithium-containing material according to Aspect 10 of the present invention is characterized in that, in the method for treating a lithium-containing material according to any one of Aspects 1 to 8, an anionic polymer flocculant is added in the second solid-liquid separation step. According to the method for treating a lithium-containing material according to Aspect 10 of the present invention, the sedimentation property is dramatically improved by the polymer flocculant, and the fluorine precipitate and calcium carbonate can be more easily removed in the second solid-liquid separation step, so that a lithium-containing liquid having a higher lithium purity can be obtained.

[0019] A method for treating a lithium-containing material according to Aspect 11 of the present invention may be configured such that an anionic polymer flocculant is added in the third solid-liquid separation step in the method for treating a lithium-containing material according to any one of Aspects 2 to 9. According to the method for treating a lithium-containing material according to Aspect 11 of the present invention, the polymer flocculant dramatically improves separability, making it easier to remove calcium carbonate in the third solid-liquid separation step, and therefore a lithium-containing liquid having a higher lithium purity can be obtained.

[0020] A method for treating a lithium-containing material according to Aspect 12 of the present invention is the method for treating a lithium-containing material according to any one of Aspects 1 to 10, characterized in that in the heavy metal and first fluoride precipitation step, the pH is adjusted to a range of 9 or more and 11 or less by adding the first calcium compound. According to the method for treating a lithium-containing material according to Aspect 12 of the present invention, in the heavy metal and first fluoride precipitation step, many heavy metal ions are easily separated as hydroxide precipitates, and a lithium-containing solution with high lithium purity can be obtained.

[0021] Furthermore, a method for treating a lithium-containing material according to Aspect 13 of the present invention is the method for treating a lithium-containing material according to any one of Aspects 1 to 11, characterized in that in the second fluorine precipitation step, the pH is adjusted to a range of 6.5 or more and 8 or less by adding the second calcium compound. According to the method for treating a lithium-containing material according to Aspect 13 of the present invention, fluorine is more likely to precipitate in the second fluorine precipitation step. Therefore, it becomes possible to remove a larger amount of fluorine, and a lithium-containing solution having a high lithium purity can be obtained.

[0022] Furthermore, a method for treating a lithium-containing material according to Aspect 14 of the present invention is the method for treating a lithium-containing material according to any one of Aspects 2 to 12, characterized in that in the calcium precipitation step, the pH is adjusted to a range of 9 or more and 11 or less by adding the soluble carbonate compound. According to the method for treating a lithium-containing material according to Aspect 14 of the present invention, calcium carbonate is more likely to precipitate in the calcium precipitation step. As a result, more calcium can be removed, and a lithium-containing solution having a high lithium purity can be obtained. Furthermore, lithium can be prevented from precipitating as carbonate in the calcium precipitation step, and a decrease in the lithium concentration of the lithium-containing solution can be prevented.

[0023] A method for treating a lithium-containing material according to Aspect 15 of the present invention may be configured such that, in the method for treating a lithium-containing material according to any one of Aspects 1 to 13, the lithium-containing material is a fine powder obtained by pulverizing lithium ion batteries. According to the method for treating a lithium-containing material according to Aspect 15 of the present invention, high-purity lithium can be recovered from waste lithium ion batteries.

[0024] A sixteenth aspect of the present invention provides an apparatus for treating a lithium-containing material, comprising: a leaching tank that generates a lithium leach solution by adding an acidic solution containing an inorganic acid to a lithium-containing material to cause lithium to leach into the acidic solution; a heavy metal and first fluorine precipitation tank that adds a first calcium compound to the lithium leach solution to precipitate heavy metal ions as hydroxides and also to precipitate fluorine; a first solid-liquid separator that separates the hydroxides of the heavy metal ions and the precipitate of fluorine from the lithium leach solution; a second fluorine precipitation tank that adds a second calcium compound to the lithium leach solution to precipitate dissolved fluorine; and a second solid-liquid separator that separates the precipitate of dissolved fluorine and the unreacted second calcium compound from the lithium leach solution to obtain a lithium-containing liquid.

[0025] According to the lithium-containing material treatment device of Aspect 16 of the present invention, in the heavy metal and first fluorine precipitation tank, a first calcium compound is added to precipitate heavy metals such as cobalt, nickel, and manganese dissolved in the lithium leach solution, and fluorine, and these precipitates are then removed in the first solid-liquid separator. As a result, a lithium leach solution with high lithium purity from which heavy metals and fluorine have been removed is obtained. Furthermore, in the second fluorine precipitation tank, a second calcium compound is added to the lithium leach solution to precipitate heavy metals and dissolved fluorine that were not completely removed in the first fluorine precipitation tank and the first solid-liquid separator. The precipitated dissolved fluorine and unreacted components of the second calcium compound added in the second fluorine precipitation tank are then removed in the second solid-liquid separator. This makes it possible to remove an amount of fluorine that would be difficult to remove in a single-stage fluorine removal process, thereby obtaining a lithium-containing solution with higher lithium purity.

[0026] A lithium-containing material treatment apparatus according to Aspect 17 of the present invention is the lithium-containing material treatment apparatus according to Aspect 15, characterized in that it further comprises a calcium precipitation tank in which a soluble carbonate compound is added to the lithium-containing liquid to precipitate calcium as calcium carbonate, and a third solid-liquid separator in which the calcium carbonate is separated from the lithium-containing liquid. According to the lithium-containing material treatment apparatus according to Aspect 17 of the present invention, the second calcium compound added in the second fluorine precipitation tank is removed, and therefore a lithium-containing liquid having an even higher lithium purity can be obtained.

[0027] According to the present invention, it is possible to provide a method and an apparatus for treating a lithium-containing material that can recover lithium with high purity from the lithium-containing material.

[0028] 1 is a flow diagram showing a method for treating a lithium-containing material according to one embodiment of the present invention; 2 is a block diagram showing a treatment device for a lithium-containing material according to one embodiment of the present invention; 3 is a diagram showing the result of powder X-ray diffraction of a precipitate formed by adding 25% NaOH to a lithium-containing liquid and stirring the mixture in an example;

[0029] Hereinafter, a method and apparatus for treating a lithium-containing material according to an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiments are specifically described to provide a better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified.

[0030] Fig. 1 is a flow diagram showing a method for treating a lithium-containing material according to one embodiment of the present invention. As shown in Fig. 1, the method for treating a lithium-containing material according to this embodiment includes a leaching step S01, a heavy metal and first fluorine precipitation step S02, a first solid-liquid separation step S03, a second fluorine precipitation step S04, a second solid-liquid separation step S05, a calcium precipitation step S06, and a third solid-liquid separation step S07.

[0031] (Leaching Step S01) In the leaching step S01, lithium-containing material such as crushed lithium-ion battery material is immersed in an acidic solution to leach lithium into the acidic solution, thereby obtaining a lithium leachate. As the acidic solution, for example, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid can be used alone or in combination. In this embodiment, sulfuric acid is used as the acid. In this embodiment, the lithium-containing material is mixed with sulfuric acid and stirred for 60 minutes to dissolve the lithium in the lithium-containing material, thereby obtaining a lithium leachate.

[0032] The pH of the lithium leachate is not particularly limited and may be, for example, 1 to 2. Note that metals other than lithium, fluorine, etc., are also leached into the leachate. The metals contained in the leachate vary depending on the lithium-containing material used, but examples include cobalt, nickel, manganese, iron, aluminum, etc., which are used as positive electrode active materials, and copper, aluminum, iron, etc., which are used as battery current collectors and exterior materials.

[0033] (Heavy Metal and First Fluoride Precipitation Step S02) In the heavy metal and first fluoride precipitation step S02, a first calcium compound is added to the lithium leachate obtained in the leaching step S01 to produce a metal hydroxide precipitate and a fluoride precipitate (e.g., calcium fluoride). The first calcium compound is added, for example, while stirring the lithium leachate. The first calcium compound is not particularly limited as long as it is basic, and solid calcium compounds such as calcium carbonate, calcium hydroxide, calcium oxide, or mixtures thereof can be used. The pH of the lithium leachate when producing the metal hydroxide and calcium fluoride precipitates is adjusted to 8.0 to 12.0. The pH is preferably 9.0 to 11.0, more preferably 9.5 to 10.5, and particularly preferably 10.0, because this facilitates separation of heavy metal ions as hydroxide precipitates, resulting in a high-purity lithium leachate, and reduces the amount of calcium compound added, thereby reducing chemical costs. As a result, heavy metal ions precipitate as metal hydroxides, and fluoride ions precipitate as calcium fluoride. Here, heavy metals are metals with a specific gravity of 4.0 g / cm ３The term "metals" refers to the above metals, including, for example, nickel, cobalt, manganese, iron, titanium, zinc, and copper. Other compounds may also be precipitated, such as compounds of aluminum or silicon.

[0034] (First solid-liquid separation step S03) In the first solid-liquid separation step S03, heavy metals, metal hydroxide precipitates precipitated in the first fluorine precipitation step S02, and fluorine precipitates are removed from the lithium leaching solution. As a method for removing the precipitates, a solid-liquid separation method such as gravity settling separation, centrifugation, or filter cloth filtration using a filter press or the like can be used.

[0035] (Second Fluorine Precipitation Step S04) In the second fluorine precipitation step S04, a second calcium compound is added to the lithium leachate from which the precipitate has been removed in the first solid-liquid separation step S03 to precipitate dissolved fluorine. The second calcium compound is not particularly limited as long as it is a basic calcium compound capable of controlling the pH to 5.0 to 9.0, and solid calcium compounds such as calcium carbonate, calcium hydroxide, calcium oxide, or mixtures thereof can be used. The pH of the lithium leachate used to produce a precipitate of dissolved fluorine (e.g., calcium fluoride) is adjusted by first adding aluminum sulfate to the pH to 5.0 or less, and then adding the second calcium compound to adjust the pH to 5.0 to 9.0. The pH is preferably 6.5 to 8.0, more preferably 7.0 to 7.5, and particularly preferably 7.0, because this facilitates the precipitation of calcium fluoride and results in a lithium leachate of even higher purity. This allows the heavy metals and dissolved fluorine compounds that could not be completely removed in the first fluorine precipitation step S02 and the first solid-liquid separation step S03 to be precipitated as calcium fluoride. Note that a portion of the unreacted second calcium compound is precipitated together with calcium fluoride.

[0036] In the second fluorine precipitation step S04, a sodium compound may be added after the addition of the second calcium compound. If only a calcium compound is added, it takes a long time for the pH to stabilize at the target pH, but by adding a sodium compound after the calcium compound, the pH can be stabilized at the target pH more quickly.

[0037] In the second fluorine precipitation step S04, an inorganic flocculant may be added to the lithium leachate. The inorganic flocculant improves separability by sedimentation, making it easier to separate the precipitate of dissolved fluorine and the unreacted second calcium compound in the second solid-liquid separation step S05 described below, thereby obtaining a lithium-containing solution with a higher lithium purity. As the inorganic flocculant, for example, commercially available soluble aluminum compounds such as aluminum sulfate (aluminum sulfate) and polyaluminum chloride (PAC) can be used. Furthermore, aluminum hydroxide, which is produced by hydrolysis of soluble aluminum, has the effect of adsorbing fluorine, so that a lithium-containing solution with a higher lithium purity can be obtained.

[0038] (Second solid-liquid separation step S05) In the second solid-liquid separation step S05, the precipitate of dissolved fluorine precipitated in the second fluorine precipitation step S04 and the unreacted second calcium compound are removed from the lithium leaching solution to obtain a lithium-containing solution. As a method for removing the precipitate, a solid-liquid separation method such as gravity settling separation, centrifugation, or filter cloth filtration using a filter press or the like can be used.

[0039] In the second solid-liquid separation step S05, a polymer flocculant may be added. The polymer flocculant promotes the formation of flocs, dramatically improving sedimentation properties and making it easier to separate the precipitate of dissolved fluorine and the unreacted second calcium compound, thereby obtaining a lithium-containing solution with a higher lithium purity. As the polymer flocculant, a polymer flocculant used in general water treatment, for example, an anionic polymer flocculant whose main component is polyacrylamide, may be used.

[0040] (Calcium Precipitation Step S06) In the calcium precipitation step S06, a soluble carbonate compound is added to the lithium-containing liquid from which the precipitate has been removed in the second solid-liquid separation step S05, thereby precipitating the dissolved calcium as calcium carbonate. The pH of the lithium-containing liquid when producing the calcium carbonate precipitate is adjusted to 8 to 12. The pH is preferably 9 to 11, more preferably 9.5 to 10.5, and particularly preferably 10.0, because this facilitates calcium carbonate production, allows a high-purity lithium-containing liquid to be obtained, and prevents lithium from precipitating as a carbonate salt, thereby preventing a decrease in the lithium concentration in the lithium-containing liquid. As the soluble carbonate compound, for example, sodium carbonate or sodium bicarbonate can be used in the form of a solution or powder. Carbon dioxide gas can also be blown into the reaction tank in the calcium precipitation step S06 to solubilize the dissolved calcium, thereby allowing it to react with the dissolved calcium.

[0041] In the calcium precipitation step S06, an inorganic flocculant may be added to the lithium-containing liquid. The inorganic flocculant improves separability by sedimentation, making it easier to remove calcium carbonate precipitate in the third solid-liquid separation step S07 described below, thereby obtaining a lithium-containing liquid with a higher lithium purity. As the inorganic flocculant, for example, commercially available soluble aluminum compounds such as aluminum sulfate (aluminum sulfate) and polyaluminum chloride (PAC) can be used.

[0042] (Third solid-liquid separation step S07) In the third solid-liquid separation step S07, the calcium carbonate precipitate precipitated in the calcium precipitation step S06 is removed from the lithium-containing solution. As a method for removing the precipitate, a solid-liquid separation method such as a gravity settling separation method, a centrifugal separation method, or a filter cloth filtration method using a filter press or the like can be used.

[0043] In the third solid-liquid separation step S07, a polymer flocculant may be added. The polymer flocculant dramatically improves sedimentation properties, making it easier to separate the calcium carbonate precipitate, thereby obtaining a lithium-containing solution with a higher lithium purity. As the polymer flocculant, a polymer flocculant commonly used in water treatment, such as an anionic polymer flocculant whose main component is polyacrylamide, can be used.

[0044] Here, in the treatment of lithium-containing materials, it may be necessary to reduce chemical costs and the amount of sludge generated. In that case, the method may include at least one of a first recycling step S08 in which the precipitate of dissolved fluorine and the unreacted second calcium compound separated and recovered in the second solid-liquid separation step S05 are used as the heavy metal and the first calcium compound to be added in the first fluorine precipitation step S02, a second recycling step S09 in which the calcium carbonate precipitate removed in the third solid-liquid separation step S07 is used as the second calcium compound to be added in the second fluorine precipitation step S04, a third recycling step S10 in which the solid content removed in the second solid-liquid separation step S05 is used as seed crystals in the second fluorine precipitation step S04, and a fourth recycling step S11 in which the calcium carbonate precipitate removed in the third solid-liquid separation step S07 is used as seed crystals in the calcium precipitation step S06.

[0045] (First Recycle Step S08) In the first reuse step S08, the precipitate of dissolved fluorine and the unreacted second calcium compound (the precipitate and the unreacted second calcium compound are collectively referred to as the solid content in the description of this step) removed from the lithium-containing liquid in the second solid-liquid separation step S05 are used as the first calcium compound to be added to precipitate metal ions and fluoride ions in the heavy metal and first fluorine precipitation step S02. The solid content may be added entirely in the heavy metal and first fluorine precipitation step S02, or only a portion of the solid content may be added. Alternatively, only the solid content may be added in the heavy metal and first fluorine precipitation step S02, or another calcium compound may be added in addition to the solid content. By reusing the unreacted second calcium compound in this step, chemical costs can be reduced. Furthermore, since the precipitates generated in the first fluorine precipitation step and the second fluorine precipitation step can be combined, sludge treatment costs can be reduced.

[0046] (Second Reuse Step S09) In the second reuse step S09, the calcium carbonate precipitate removed from the lithium-containing liquid in the third solid-liquid separation step S07 is used as a second calcium compound to be added to precipitate dissolved fluoride ions in the second fluorine precipitation step S04. The calcium carbonate precipitate removed in the third solid-liquid separation step S07 may be added entirely to the second fluorine precipitation step S04, or only a portion of it may be added. Alternatively, only the calcium carbonate precipitate removed in the third solid-liquid separation step S07 may be added to the second fluorine precipitation step S04, or another calcium compound may be added in addition to the calcium carbonate precipitate removed in the third solid-liquid separation step S07. By reusing the calcium carbonate precipitate that would otherwise be discarded in this step, chemical costs and the amount of sludge generated can be reduced.

[0047] (Third Recycle Step S10) In the third reuse step S10, the solids removed from the lithium-containing solution in the second solid-liquid separation step S05 are added to the lithium leaching solution to be used as seed crystals in the second fluorine precipitation step S04. All of the solids separated in the second solid-liquid separation step S05 may be added to the second fluorine precipitation step S04, or only a portion of them may be added. Because the solids are used as seed crystals in the second fluorine precipitation step, the solid concentration in the second fluorine precipitation step increases, making it possible to improve the fluorine removal efficiency and reduce the amount of sludge.

[0048] (Fourth Recycle Step S11) In the fourth reuse step S11, the calcium carbonate precipitate removed from the lithium-containing liquid in the third solid-liquid separation step S07 is added to the lithium-containing liquid to be used as seed crystals in the calcium precipitation step S06. All of the calcium carbonate precipitate removed in the third solid-liquid separation step S07 may be added to the calcium precipitation step S06, or only a portion of it may be added. By reusing the calcium carbonate precipitate that would otherwise be discarded in this step, the solid concentration in the calcium precipitation step increases, making it possible to improve the calcium removal efficiency and, in addition, reduce the amount of sludge.

[0049] The above-described steps enable the recovery of highly pure lithium from lithium-containing materials.

[0050] Fig. 2 is a block diagram showing an apparatus for treating a lithium-containing material according to one embodiment of the present invention. As shown in Fig. 2, the apparatus for treating a lithium-containing material 1 of this embodiment includes at least a leaching tank 10, a heavy metal and first fluorine precipitation tank 20, a first solid-liquid separator 30, a second fluorine precipitation tank 40, and a second solid-liquid separator 50. The apparatus for treating a lithium-containing material 1 of this embodiment may further include a calcium precipitation tank 60 and a third solid-liquid separator 70.

[0051] In this embodiment, the leaching tank 10 is required to immerse a lithium-containing material in an acidic solution to leach lithium into the acidic solution and obtain a lithium leachate. The heavy metal and first fluorine precipitation tank 20 is required to add a first calcium compound to the lithium leachate to produce a metal hydroxide precipitate and a fluorine precipitate. The first solid-liquid separator 30 is required to remove the metal hydroxide precipitate and the fluorine precipitate from the lithium leachate. The second fluorine precipitation tank 40 is required to add a second calcium compound to the lithium leachate to precipitate dissolved fluorine. The second solid-liquid separator 50 is required to remove the dissolved fluorine precipitate and unreacted second calcium compound from the lithium leachate to obtain a lithium-containing solution. The calcium precipitation tank 60 is required to add a soluble carbonate compound to the lithium-containing solution to precipitate dissolved calcium as calcium carbonate. The third solid-liquid separator 70 is required to remove the calcium carbonate precipitate from the lithium-containing solution.

[0052] According to the method for treating a lithium-containing material of the present embodiment configured as described above, the leaching step S01, the first fluorine precipitation step S02, and the first solid-liquid separation step S03 are performed to remove metal ions and fluoride ions, and then the second fluorine precipitation step S04 and the second solid-liquid separation step S05 are performed, thereby performing the step of removing fluorine in two stages. Therefore, a lithium-containing solution having a higher lithium purity can be obtained as compared with the conventional art which has only one stage of the step of removing fluorine.

[0053] Furthermore, by carrying out the calcium precipitation step S06 and the third solid-liquid separation step S07, the calcium added in the second fluorine precipitation step S04 can be removed, and therefore a lithium-containing liquid with a higher lithium purity can be obtained.

[0054] In the present embodiment, when the first recycling step S08 is used, it is possible to reduce the cost of chemicals and the amount of sludge.

[0055] In the present embodiment, when the second reuse step S09 is used, it is possible to reduce the cost of chemicals and the amount of sludge.

[0056] In the present embodiment, when the third recycling step S10 is used, the solid concentration of the fluorine precipitate in the lithium leaching solution increases in the second fluorine precipitation step S04, which makes it possible to enhance the fluorine removal efficiency and reduce the amount of sludge.

[0057] In the present embodiment, in the case of the configuration using the fourth reuse step S11, the solid concentration of calcium carbonate in the lithium-containing liquid increases in the calcium precipitation step S06, so that the calcium removal efficiency can be increased and, in addition, the amount of sludge can be reduced.

[0058] In the present embodiment, in the case where an inorganic flocculant is added in the second fluorine precipitation step S04, the separability of settling is improved by the inorganic flocculant, and the precipitate of dissolved fluorine and the unreacted second calcium produced in the second fluorine precipitation step S04 are more easily removed, so that a lithium-containing solution having a higher lithium purity can be obtained.

[0059] In the present embodiment, in the case where an inorganic flocculant is added in the calcium precipitation step S06, the separability of sedimentation is improved by the inorganic flocculant, and the calcium carbonate precipitate generated in the calcium precipitation step S06 becomes easier to remove, so that a lithium-containing solution having a higher lithium purity can be obtained.

[0060] In the present embodiment, in the case where a polymer flocculant is added in the second solid-liquid separation step S05, the formation of aggregated flocs is promoted by the polymer flocculant, and the sedimentation property is dramatically improved. As a result, the precipitate of dissolved fluorine and the unreacted second calcium are more easily separated in the second solid-liquid separation step S05, and therefore a lithium-containing liquid having a higher lithium purity can be obtained.

[0061] In the present embodiment, in the case where a polymer flocculant is added in the third solid-liquid separation step S07, the polymer flocculant promotes the formation of flocs, dramatically improving the sedimentation separability, and making it easier to separate the calcium carbonate precipitate in the third solid-liquid separation step S07, so that a lithium-containing liquid having a higher lithium purity can be obtained.

[0062] In the present embodiment, when the pH is adjusted to 9 to 11 when generating the metal hydroxide precipitate and the fluorine precipitate in the heavy metal and first fluorine precipitation step S02, many heavy metal ions can be easily separated as hydroxide precipitate in the heavy metal and first fluorine precipitation step S02. Therefore, a lithium-containing solution with high lithium purity can be obtained.

[0063] In the present embodiment, in the case where the pH is adjusted to 6.5 to 8 when a precipitate of dissolved fluorine is generated in the second fluorine precipitation step S04, dissolved fluorine is more likely to precipitate in the second fluorine precipitation step S04. Therefore, it becomes possible to remove a larger amount of fluorine, and a lithium-containing solution with high lithium purity can be obtained.

[0064] In the present embodiment, when the pH is adjusted to 9 to 11 when calcium carbonate precipitate is generated in the calcium precipitation step S06, calcium carbonate is more likely to be generated in the calcium precipitation step S06. As a result, more calcium can be removed, and a lithium-containing solution with high lithium purity can be obtained. Furthermore, it is possible to prevent lithium from precipitating as carbonate in the calcium precipitation step S06, and to prevent a decrease in the lithium concentration of the lithium-containing solution.

[0065] Furthermore, according to the lithium-containing material treatment apparatus of this embodiment configured as described above, in the heavy metal and first fluorine precipitation tank 20, a first calcium compound is added to precipitate heavy metals such as cobalt, nickel, and manganese dissolved in the lithium leach solution, and fluorine, and these precipitates are then removed in the first solid-liquid separator 30. This allows for the production of a lithium leach solution with high lithium purity from which heavy metals and fluorine have been removed. Furthermore, in the second fluorine precipitation tank 40, a second calcium compound is added to the lithium leach solution to precipitate heavy metals and dissolved fluorine that were not completely removed in the first fluorine precipitation tank 20 and the first solid-liquid separator 30. The precipitated dissolved fluorine and unreacted components of the second calcium compound added in the second fluorine precipitation tank 40 are then removed in the second solid-liquid separator 50. This allows for the removal of fluorine in an amount that would be difficult to remove in a single-stage fluorine removal process, thereby obtaining a lithium-containing solution with higher lithium purity.

[0066] In the present embodiment, in the case of a configuration including the calcium precipitation tank 60 in which a soluble carbonate compound is added to the lithium leaching solution to precipitate calcium as calcium carbonate, and the third solid-liquid separator 70 in which calcium carbonate is separated from the lithium-containing solution, the second calcium compound added in the second fluorine precipitation tank 40 is removed, so that a lithium-containing solution having an even higher lithium purity can be obtained.

[0067] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention.

[0068] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below.

[0069] 80 g of sintered and pulverized powder of a lithium-ion battery having the composition shown in Table 1 was suspended in 320 mL of water, and 75 g of 47% sulfuric acid was added and stirred for 60 minutes to leach lithium and heavy metals, yielding a lithium leachate (Leaching Step S01). The pH of the lithium leachate was 1.8. Subsequently, a 30% suspension was prepared from the lithium leachate using 30 g of calcium hydroxide, and 45 mL of the suspension was added and stirred (Heavy Metal and First Fluorine Precipitation Step S02). The pH rose to 11.0. Suction filtration was then performed to separate the leach residue and the lithium leachate (First Solid-Liquid Separation Step S03). The composition of the sintered and pulverized powder of a lithium-ion battery was analyzed by X-ray fluorescence analysis for all elements except lithium and fluorine, by ICP atomic emission spectroscopy for lithium, and by ion chromatography for fluorine.

[0070] 1000 mL of the lithium leachate was sampled and 2 mL of liquid aluminum sulfate was added as an inorganic flocculant. The pH of the lithium leachate was 4.6. Furthermore, 10 g of calcium carbonate was added as seed crystals to the lithium leachate. The pH of the lithium leachate was 6.0. After these additions, 25% sodium hydroxide was added to adjust the pH to 7.0, and the mixture was stirred for 1 hour (second fluorine precipitation step S04). 0.5 mL of a 0.05% by mass solution of polymer flocculant (DiaFloc A825B) was added, and the mixture was stirred to obtain a floc-like solid. After natural settling, 950 mL of a clear supernatant was obtained in approximately 2 minutes (second liquid separation step S05).

[0071] After settling, 950 mL of the supernatant of the lithium-containing solution was taken, and 1.5 mL of liquid aluminum sulfate was added. Calcium carbonate was added to the solution to a concentration of 10 g / L. The pH of the lithium-containing solution was 4.9. Further addition of 1.9 g of sodium carbonate resulted in a pH of 8.5, forming a white precipitate. 2 mL of 25% NaOH was added to adjust the pH to 10.0, and the solution was stirred for 60 minutes (calcium precipitation step S06). Subsequently, 1.9 mL of a 0.05 wt% solution of polymer flocculant (DiaFloc AP825B) was added, and the solution was stirred to obtain a floc-like solid. Natural settling resulted in 900 mL of clear supernatant in approximately 2 minutes (third liquid separation step S07). The compositions of the lithium leaching solution and the supernatant obtained in each step were measured by ICP atomic emission spectroscopy, and the results are shown in Table 2.

[0072]

[0073]

[0074] Example 1: 150 g of sintered and pulverized powder of lithium-ion batteries was suspended in 815 mL of water, and 91 g of 47% sulfuric acid was added and stirred for 60 minutes to leach lithium and heavy metals, yielding a lithium leachate (leaching step S01). The pH of the lithium leachate at this time was 1.8. Subsequently, 60 g of calcium hydroxide was added to the lithium leachate to prepare a 30% suspension, and 200 mL of the suspension was added and stirred (heavy metal and first fluorine precipitation step S02). The pH rose to 10.8. Subsequently, suction filtration was performed to separate the leach residue and the lithium leachate (first liquid separation step S03).

[0075] 1000 mL of the lithium leachate was sampled and 0.5 mL of liquid aluminum sulfate was added as an inorganic flocculant. The pH of the lithium leachate was 5.6. Furthermore, 10 g of calcium carbonate was added as seed crystals to the lithium leachate. The pH of the lithium leachate was 6.0. After these additions, 25% sodium hydroxide was added to adjust the pH to 6.5, and the mixture was stirred for 1 hour (second fluorine precipitation step S04). 1 mL of a 0.05% by mass solution of a polymer flocculant (DiaFloc AP825B) was added, and the mixture was stirred to obtain a floc-like solid. After natural settling and separation, a clear supernatant (950 mL) was obtained in approximately 2 minutes (second liquid separation step S05). The composition of this supernatant was measured by ICP atomic emission spectroscopy.

[0076] Examples 2 to 8 In Examples 2 to 8, the experiments were conducted under the same conditions as in Example 1, except that the amount of liquid aluminum sulfate added in S04 of Example 1 and the pH of the lithium leaching solution when liquid aluminum sulfate, calcium carbonate, and sodium hydroxide were added and stirred were changed to different values ​​(pH 6.0 to 8.5).

[0077] In Comparative Example 1, after adding liquid aluminum sulfate in the second fluorine precipitation step S04, calcium carbonate was not added, but 25% sodium hydroxide was added to adjust the pH of the lithium leaching solution to 7.0. The other conditions were the same as in Examples 1 to 8.

[0078] The experimental results of Examples 1 to 8 and Comparative Example 1 are shown in Table 3. The pH of the lithium leaching solution in Table 3 refers to the pH of the lithium leaching solution when liquid aluminum sulfate, calcium carbonate, and sodium hydroxide were added and stirred in S04. The raw water refers to the lithium leaching solution after the first solid-liquid separation step S03.

[0079]

[0080] As shown in Table 3, the fluorine concentrations in the lithium-containing solutions of Examples 1 to 8, in which calcium carbonate was added, were lower than that of Comparative Example 1, in which calcium carbonate was not added. These results demonstrate that performing the fluorine removal step in two stages makes it possible to obtain a lithium-containing solution with a low fluorine concentration, i.e., a high lithium purity. Furthermore, it was found that when the pH of the lithium leaching solution is 6.5 or higher and 8.0 or lower, a lithium-containing solution with a lower fluorine concentration can be obtained than when the pH is outside this range.

[0081] Example 9: 950 mL of the supernatant liquid of the lithium-containing liquid after sedimentation in Example 5 was taken, 0.5 mL of liquid aluminum sulfate was added, and 25 mL of returned precipitate (a solid composed primarily of calcium carbonate, recovered in the process described below) was added. The pH of the lithium-containing liquid at this time was 6.2. Further, 1.0 g of sodium carbonate was added, and the pH became 9.5, producing a white precipitate. Further, 0.5 mL of 25% NaOH was added to adjust the pH to 10.0, and the mixture was stirred for 60 minutes (calcium precipitation step S06). Subsequently, 1 mL of a 0.05% by mass solution of a polymer flocculant (DiaFloc AP825B) was added, and the pH was adjusted to 10.0 and stirred for 60 minutes to obtain a floc-like solid. After natural sedimentation, 970 mL of clear supernatant liquid was obtained in approximately 2 minutes (third liquid separation step S07). The supernatant liquid was collected and filtered through a 0.45 μm membrane filter, and its composition was analyzed by ICP atomic emission spectroscopy. A portion of the solid matter was collected and identified by powder X-ray diffraction and X-ray fluorescence analysis. The results of powder X-ray diffraction are shown in FIG. 3, and the results of X-ray fluorescence analysis are shown in Table 4. These results revealed that the main component of the solid matter was calcium carbonate.

[0082]

[0083] Example 10 In Example 10, only the amount of sodium carbonate added to the lithium-containing solution after sedimentation and separation in Example 6 was changed to a value different from that in Example 9, and the other conditions were the same as those in Example 9. The composition of the supernatant liquid is shown in Table 5.

[0084]

[0085] As shown in Table 5, by adding sodium carbonate and precipitating the dissolved calcium, a lithium-containing solution with a low calcium concentration could be obtained.

[0086] As a result of the above confirmatory experiments, it was confirmed that according to the present invention, lithium can be recovered with high purity from lithium-containing materials.

[0087] REFERENCE SIGNS LIST 1 lithium-containing material treatment device 10 leaching tank 20 heavy metal and first fluorine precipitation tank 30 first solid-liquid separator 40 second fluorine precipitation tank 50 second solid-liquid separator 60 calcium precipitation tank 70 third solid-liquid separator

Claims

1. A method for treating a lithium-containing material, comprising: a leaching step of adding an acidic solution containing an inorganic acid to a lithium-containing material to cause lithium to leach into the acidic solution; a heavy metal and first fluorine precipitation step of adding a first calcium compound to the lithium leachate obtained in the leaching step to cause heavy metal ions to precipitate as hydroxides and to cause fluorine to precipitate; a first solid-liquid separation step of separating the hydroxides of the heavy metal ions and the fluorine precipitate from the lithium leachate after the heavy metal and first fluorine precipitation step; a second fluorine precipitation step of adding a second calcium compound to the lithium leachate after the first solid-liquid separation step to cause dissolved fluorine to precipitate; and a second solid-liquid separation step of separating the precipitate of dissolved fluorine and unreacted second calcium compound from the lithium leachate to obtain a lithium-containing liquid after the second fluorine precipitation step.

2. The method for treating a lithium-containing material according to claim 1, further comprising: a calcium precipitation step of adding a soluble carbonate compound to the lithium-containing liquid after the second solid-liquid separation step to precipitate calcium as calcium carbonate; and a third solid-liquid separation step of separating the calcium carbonate from the lithium-containing liquid after the calcium precipitation step.

3. The method for treating lithium-containing material as described in claim 1, characterized in that the precipitate of dissolved fluorine and the unreacted second calcium compound separated in the second solid-liquid separation process are used as the first calcium compound in the heavy metal and first fluorine precipitation process.

4. The method for treating a lithium-containing material according to claim 2, characterized in that the calcium carbonate separated in the third solid-liquid separation step is used as the second calcium compound in the second fluorine precipitation step.

5. The method for treating a lithium-containing material according to claim 1, characterized in that the solid matter separated in the second solid-liquid separation step is used as seed crystals in the second fluorine precipitation step.

6. The method for treating a lithium-containing material according to claim 2, characterized in that the calcium carbonate separated in the third solid-liquid separation step is used as seed crystals in the calcium precipitation step.

7. The method for treating a lithium-containing material according to claim 1, characterized in that in the second fluorine precipitation step, a sodium compound is added after the second calcium compound is added.

8. The method for treating a lithium-containing material according to claim 1, characterized in that a soluble aluminum compound is added in the second fluorine precipitation step.

9. The method for treating lithium-containing material according to claim 2, characterized in that a soluble aluminum compound is added in the calcium precipitation step.

10. The method for treating lithium-containing material according to claim 1, characterized in that an anionic polymer flocculant is added in the second solid-liquid separation step.

11. The method for treating lithium-containing material according to claim 2, characterized in that an anionic polymer flocculant is added in the third solid-liquid separation step.

12. A method for treating lithium-containing material as described in claim 1, characterized in that in the heavy metal and first fluoride precipitation step, the pH is adjusted to within the range of 9 to 11 by adding the first calcium compound.

13. A method for treating lithium-containing material as described in claim 1, characterized in that in the second fluorine precipitation step, the pH is adjusted to within the range of 6.5 to 8.0 by adding the second calcium compound.

14. The method for treating a lithium-containing material according to claim 2, wherein in the calcium precipitation step, the pH is adjusted to within the range of 9 to 11 by adding the soluble carbonate compound.

15. A method for treating a lithium-containing material according to any one of claims 1 to 14, wherein the lithium-containing material is a fine powder obtained by pulverizing a lithium ion battery.

16. An apparatus for treating a lithium-containing material, comprising: a leaching tank for adding an acidic solution containing an inorganic acid to a lithium-containing material to cause lithium to leach into the acidic solution and produce a lithium leachate; a heavy metal and first fluorine precipitation tank for adding a first calcium compound to the lithium leachate to precipitate heavy metal ions as hydroxides and to precipitate fluorine; a first solid-liquid separator for separating the hydroxides of the heavy metal ions and the fluorine precipitate from the lithium leachate; a second fluorine precipitation tank for adding a second calcium compound to the lithium leachate to precipitate dissolved fluorine; and a second solid-liquid separator for separating the dissolved fluorine precipitate and unreacted second calcium compound from the lithium leachate to obtain a lithium-containing liquid.

17. The lithium-containing material treatment device according to claim 16, further comprising: a calcium precipitation tank for adding a soluble carbonate compound to the lithium-containing liquid to precipitate calcium as calcium carbonate; and a third solid-liquid separator for separating the calcium carbonate from the lithium-containing liquid.

Images