Process for the preparation of LiOH

Abstract

The present invention relates to a process for the preparation of LiOH, said process comprising the steps of: (1) providing a mixture A containing Li2CO3; (2) treating the mixture A provided in (1) with carbonic acid, thereby at least partially converting the Li2CO3 contained therein to LiHCO3, and obtaining a mixture B containing LiHCO3; (3) subjecting at least a portion of the mixture B obtained in (2) to thermal conversion, and obtaining a mixture C containing Li2CO3; and (4) reacting the mixture C obtained in (3) with M(OH)2, thereby at least partially reacting the Li2CO3 contained therein to form LiOH, and obtaining a mixture D containing LiOH, wherein M represents an alkaline earth metal.

Description

Technical Field

[0001] This invention relates to a method for obtaining lithium hydroxide from lithium-containing minerals. introduction

[0002] WO 2019 / 220004 A1 relates to a method for obtaining lithium hydroxide from lithium-containing minerals by mixing the minerals with water and an alkali metal carbonate, leaching the resulting mixture at high temperature, and then subjecting it to a second leaching in an aqueous solution containing an alkaline earth metal hydroxide.

[0003] WO 2018 / 234614 A1 relates to a method for preparing lithium carbonate from lithium-containing minerals. The method includes: a leaching step of leaching the lithium-containing minerals in an aqueous solution containing an alkali metal carbonate, a carbonation step of reacting the leaching slurry with an alkaline earth metal compound in the presence of CO2, and a solid-liquid separation step of separating the carbonated mixture into solid and liquid components.

[0004] EP 2749535 A1 relates to a method for preparing high-purity lithium carbonate. The method includes reacting a first aqueous solution containing lithium carbonate with CO2 to form a second aqueous solution containing dissolved LiHCO3, further separating the second aqueous solution using a gas-liquid-solid separator to obtain a third aqueous solution. The third aqueous solution is then contacted with an ion-selective medium to prepare a fourth aqueous solution, from which high-purity lithium carbonate is precipitated.

[0005] CN 101948124 B relates to a method for obtaining lithium carbonate from spodumene, wherein, in a first step, α-spodumene is converted to β-spodumene, and the β-spodumene is further leached with an alkaline salt and water to obtain lithium carbonate. The lithium carbonate is further reacted with CO2 to convert it to lithium bicarbonate, and the lithium bicarbonate is further heat-treated to obtain lithium carbonate.

[0006] WO 2011 / 148040 A1 relates to a method for thermally processing α-spodumene into β-spodumene. The method involves treating a concentrate or ore in a fluidized bed reactor at a temperature of 800 to 100°C using an oxygen-containing gas.

[0007] CN 103183366 A relates to a method for obtaining lithium salts from spodumene by means of: soda ash leaching, and subsequent acid conversion of the resulting lithium carbonate into soluble lithium salts.

[0008] CN 113428882 A relates to a method for preparing battery-grade lithium carbonate from spodumene.

[0009] WO 2023 / 081961 A1 relates to a method for extracting a metal from a metal-containing material, the method comprising the step of dissolving the metal in the form of a carbonate or bicarbonate in a process stream using carbon dioxide. The metal is preferably lithium, and the metal-containing material may be spodumene. The metal-containing material may be calcined before contact with CO2. Furthermore, the method may include a leaching step using a carbonate-containing reagent. The method preferably includes a carbonation step of contacting carbon dioxide with an aqueous solution of Li2CO3 to obtain a solution containing LiHCO3. The solution containing LiHCO3 can be separated from the residue by filtration. The solution containing LiHCO3 is then decarbonated by heating, thereby forming pure Li2CO3. Optionally, preferably, the pure Li2CO3 is treated with slaked lime to obtain a LiOH solution and CaCO3.

[0010] CN 107265483 A relates to a method for preparing LiOH monohydrate. In step S120 of this document, an aqueous solution of Li2CO3 is contacted with carbon dioxide and converted into LiHCO3. Then, in step S140, the obtained LiHCO3 is pyrolyzed to Li2CO3, and in step 200, preferably, Li2CO3 is contacted with an aqueous solution containing lime to obtain a LiOH solution.

[0011] WO 2024 / 089394 A2 describes a method for preparing monohydrated LiOH or anhydrous LiOH from lepidolite. In step ix) of this document, a carbonate source is added to a lithium-containing solution to obtain a suspension containing Li₂CO₃, which is then filtered to obtain a first waste liquid and Li₂CO₃. In step x), Li₂CO₃ is converted to LiOH in water by adding Ca(OH)₂. Step x) preferably includes dissolving Li₂CO₃ in water by introducing CO₂ into the solution to generate LiHCO₃, followed by adding Ca(OH)₂ to obtain a suspension containing LiOH. The suspension is then filtered to recover a filter cake containing CaCO₃ and a solution containing LiOH.

[0012] Habashi Fathi, *Handbook of Extractive Metallurgy*, 1997, p. 2045, and Wietelmann Ulrich et al., *Ullmann's Encyclopedia of Industrial Chemistry*, 2000, p. 354, both describe methods for preparing LiOH from Li₂CO₃. In this method, Li₂CO₃ is reacted with CO₂ in water to produce LiHCO₃, followed by heating of the LiHCO₃ aqueous solution to obtain Li₂CO₃ and CO₂. Further reactions of Li₂CO₃ with Ca(OH)₂ to produce LiOH are also described.

[0013] CN 111635999 A describes a method for extracting lithium from lithium-containing brine. In a first step, lithium ions are extracted from the lithium-containing brine using an extractant, and the upper extract phase is separated. Preferred extractants specifically include alkyl phosphates, cyclohexanone, and n-butanol. In a second step, water and CO2 are added to the upper extract phase to obtain an aqueous solution of LiHCO3. Finally, Ca(OH)2 is added to obtain LiOH.

[0014] Although various methods exist for preparing lithium hydroxide from spodumene, further optimization of the processes is still needed. To meet the growing demand for high-purity lithium hydroxide in battery production, the following points should be particularly considered:

[0015] - The preparation of lithium hydroxide with consistently high purity enables the production of high-performance and long-lasting batteries.

[0016] - Optimization of preparation processes in terms of energy and raw material usage Detailed Implementation

[0017] Therefore, one object of the present invention is to provide a new, more efficient and environmentally friendly method for processing lithium-containing minerals to obtain high-purity lithium hydroxide.

[0018] In this case, it was found that introducing carbon dioxide into a suspension containing lithium carbonate lowered the pH of the liquid phase from 10-11 to approximately 7.5. Therefore, a pH change from alkaline to neutral occurs without the use of any process-independent foreign substances. During this process, more soluble lithium bicarbonate is formed, which remains in the aqueous phase. Impurities soluble under alkaline conditions can precipitate under these conditions and separate along with the suspended analcime. Furthermore, heavy metals not expected to dissolve in acidic media will leach from the solid under these conditions. Therefore, contamination of the lithium-containing solution by such compounds does not occur.

[0019] Furthermore, it was unexpectedly found that the pH of the lithium carbonate suspension before the introduction of carbon dioxide and the temperature during subsequent treatment of the mixture with carbonic acid independently enabled the method according to the invention to be significantly further optimized.

[0020] Furthermore, this reaction process allows for the separation of anticline from the reaction mixture before the addition of the alkaline earth metal hydroxide. Therefore, solid anticline is separated under mild conditions before the reaction becomes strongly alkaline. This avoids undesirable side reactions caused by the reaction of anticline with the alkaline earth metal hydroxide.

[0021] The introduction of carbon dioxide, the resulting pH change, and the transfer of lithium to the aqueous phase allow for more efficient separation of impurities or even prevention of their formation from the outset. This invention, as described herein, makes a significant contribution to improving the purity of the final product, lithium hydroxide. Furthermore, it broadens the range of raw materials (i.e., lithium ores from different sources) because it allows for more efficient separation of byproducts present in varying weight proportions.

[0022] Surprisingly, it was found that undesirable side reactions between analcime and alkaline earth metals can be avoided by separating the analcime in an early stage. Furthermore, it was discovered that by separating the analcime within a neutral pH range, impurities soluble under alkaline conditions can be separated. Additionally, it was also unexpectedly found that the temperature of subsequent treatment with alkaline earth metal hydroxides significantly affects the amount of impurities in the resulting LiOH solution. Specifically, an object of the present invention is to provide a method for obtaining lithium hydroxide in high yield and high purity.

[0023] This invention relates to a method for preparing LiOH, the method comprising:

[0024] (1) Provide a mixture A containing Li2CO3;

[0025] (2) Treat the mixture A provided in (1) with carbonic acid such that the Li2CO3 contained therein is at least partially converted into LiHCO3, and obtain a mixture B containing LiHCO3;

[0026] (3) At least a portion of the mixture B obtained in (2) is subjected to thermal conversion to obtain a mixture C containing Li2CO3;

[0027] (4) React the mixture C obtained in (3) with M(OH)2, such that the Li2CO3 contained therein is at least partially converted into LiOH, and obtain a mixture D containing LiOH, wherein M is an alkaline earth metal.

[0028] Preferably, the Li2CO3 content of mixture A in (1) is in the range of 0.1 wt% to 16.0 wt%, more preferably in the range of 5 wt% to 12 wt%, and alternatively and particularly preferably in the range of 1 wt% to 5 wt%. More preferably, the Li2CO3 content of mixture A in (1) based on the solid content of mixture A is in the range of 0.1 wt% to 16.0 wt%, and particularly preferably in the range of 5 wt% to 12 wt%.

[0029] Preferably, the Li content of mixture A in (1), calculated as elemental lithium, is in the range of 0.10 wt% to 3.00 wt%, more preferably in the range of 0.80 wt% to 2.25 wt%, and alternatively and particularly preferably in the range of 0.30 wt% to 2.25 wt%. More preferably, the Li content of mixture A in (1), calculated as elemental lithium and based on the solid content of mixture A, is in the range of 0.10 wt% to 3.00 wt%, and particularly preferably in the range of 0.80 wt% to 2.25 wt%.

[0030] Alternatively, preferably, mixture A further comprises water, and the water content of mixture A in (1) is in the range of 50% to 90% by weight, preferably in the range of 60% to 70% by weight. More preferably, the Li2CO3 content of mixture A in (1) is in the range of 0.01% to 8.0% by weight, preferably in the range of 1% to 5% by weight.

[0031] Preferably, the provision of mixture A according to (1) includes:

[0032] (1.a) Provide a mixture M0 containing one or more lithium-containing minerals;

[0033] (1.b) Calcine the mixture M0 to obtain a mixture M1 containing one or more calcined lithium-containing minerals;

[0034] (1.c) React the mixture M1 obtained in (b) with an alkali metal carbonate, such that the one or more calcined lithium-containing minerals are at least partially converted into Li2CO3, and obtain a mixture A containing Li2CO3.

[0035] When the method includes steps (1.a) to (1.c), preferably, the mixture M0 contains one or more lithium-containing minerals in the range of 50% to 100% by weight, preferably in the range of 60% to 95% by weight.

[0036] More preferably, one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein one or more lithium-containing minerals are preferably spodumene, and particularly preferably α-spodumene.

[0037] More preferably, during calcination in (1.b), the temperature is in the range of 800 to 1500°C, preferably in the range of 950 to 1100°C.

[0038] More preferably, the calcination in (1.b) is carried out for a time ranging from 0.1 to 16 h, preferably from 0.5 to 5 h.

[0039] More preferably, one or more calcined lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein one or more calcined lithium-containing minerals are preferably spodumene, and wherein one or more calcined lithium-containing minerals are particularly preferably β-spodumene.

[0040] More preferably, the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate, or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0041] More preferably, the weight ratio of one or more calcined lithium-containing minerals to alkali metal carbonates in (1.c) is in the range of 1:0.1 to 1:2, and more preferably in the range of 1:0.1 to 1:0.4.

[0042] More preferably, in (1.c), the molar ratio of lithium to sodium, calculated as elemental lithium and sodium, is in the range of 1:0.4 to 1:8, and more preferably in the range of 1:0.9 to 1:1.6.

[0043] More preferably, during the reaction in (1.c), the temperature is in the range of 150 to 350°C, and more preferably in the range of 200 to 250°C.

[0044] More preferably, during the reaction in (1.c), the pressure is in the range of 10 to 200 bar (absolute pressure), preferably in the range of 14 to 50 bar (absolute pressure), and more preferably in the range of 20 to 50 bar (absolute pressure).

[0045] More preferably, the reaction in (1.c) is carried out for a time ranging from 0.1 to 8 h, and preferably from 0.5 to 1.5 h.

[0046] More preferably, the reaction in (1.c) includes water, preferably an aqueous solution of an alkali metal carbonate.

[0047] More preferably, the method includes:

[0048] (1.d) Separate at least a portion of unreacted alkali metal carbonate from the mixture A obtained in (1.c) and obtain a mixture M2 containing unreacted alkali metal carbonate;

[0049] (1.e) The mixture M2 is provided as an alkali metal carbonate source for the reaction in (1.c).

[0050] Alternatively, preferably, the provision of mixture A according to (1) includes:

[0051] (1.a') Provide a mixture M0' containing one or more lithium-containing minerals;

[0052] (1.b') React the mixture MO' with an alkali metal carbonate to at least partially convert the one or more lithium-containing minerals into Li2CO3, and obtain a mixture A containing Li2CO3.

[0053] When the method includes steps (1.a') and (1.b'), preferably, the mixture M0' contains one or more lithium-containing minerals in the range of 50% to 100% by weight, preferably in the range of 60% to 95% by weight.

[0054] More preferably, the Li content of the mixture MO', calculated as elemental lithium, is in the range of 0.03 wt% to 4.0 wt%, and more preferably in the range of 2.00 wt% to 3.75 wt%.

[0055] More preferably, one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein one or more lithium-containing minerals are preferably spodumene, and particularly preferably α-spodumene.

[0056] More preferably, the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate, or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0057] More preferably, in (1.b'), the weight ratio of one or more lithium-containing minerals to alkali metal carbonates is in the range of 1:0.1 to 1:2, and preferably in the range of 1:0.2 to 1:0.4.

[0058] More preferably, the molar ratio of lithium to sodium in (1.b') is in the range of 1:0.4 to 1:8, and more preferably in the range of 1:0.9 to 1:1.4.

[0059] More preferably, the reaction in (1.b') is carried out for a time ranging from 0.1 to 10 h, and more preferably from 1 to 4 h.

[0060] More preferably, the reaction in (1.b') includes water, preferably water vapor. When the reaction in (1.b') includes water, preferably, during the reaction in (1.b'), the pressure is in the range of 10 to 200 bar (absolute pressure), more preferably in the range of 14 to 180 bar (absolute pressure), more preferably in the range of 14 to 50 bar (absolute pressure), and particularly preferably in the range of 20 to 50 bar (absolute pressure).

[0061] When the method includes steps (1.a') and (1.b'), preferably, the reaction in (1.b') includes:

[0062] (1.b'.1) Calcine the mixture M0' and the alkali metal carbonate to obtain mixture M1';

[0063] (1.b'.2) React the mixture M1' obtained in (1.b'.1) to obtain a mixture A containing Li2CO3.

[0064] When the method includes steps (1.b'.1) and (1.b'.2), preferably, during the calcination in (1.b'.1), the temperature is in the range of 900 to 1500°C, more preferably in the range of 1000 to 1200°C. More preferably, the reaction in (1.b'.2) contains water, preferably water vapor. When the reaction in (1.b') contains water, preferably, during the reaction in (1.b'.2), the pressure is in the range of 10 to 200 bar (absolute pressure), more preferably in the range of 14 to 180 bar (absolute pressure), more preferably in the range of 14 to 50 bar (absolute pressure), and particularly preferably in the range of 20 to 50 bar (absolute pressure).

[0065] Where the method includes steps (1.a') and (1.b'), preferably, the method includes:

[0066] (1.c') Separate unreacted alkali metal carbonates from the mixture A included in (1.b') and obtain a mixture M2' containing unreacted alkali metal carbonates;

[0067] (1.d') The mixture M2' is provided as an alkali metal carbonate source for the reaction in (1.b').

[0068] Preferably, during the treatment in (2), the temperature is in the range of 0 to 150°C, more preferably in the range of 15 to 100°C, more preferably in the range of 20 to 80°C, more preferably in the range of 25 to 70°C, more preferably in the range of 30 to 60°C, more preferably in the range of 35 to 50°C, and particularly preferably in the range of 40 to 45°C.

[0069] Preferably, the treatment in (2) is carried out in an aqueous solution, and CO2 is introduced into the aqueous solution.

[0070] In the case where the treatment in (2) is carried out in an aqueous solution and CO2 is introduced into the aqueous solution, preferably, the pH of the aqueous solution is in the range of 9 to 13, more preferably 10 to 12.5, more preferably 10.5 to 12, and particularly preferably 11 to 11.5 before the introduction of CO2.

[0071] More preferably, the pH of the aqueous solution is adjusted by adding an acid and / or a base before introducing CO2. In this case, preferably, the base contains one or more hydroxide salts, wherein the base preferably contains one or more alkali metal hydroxide salts, wherein the base preferably contains NaOH. In particular, preferably, the base consists of one or more hydroxide salts, wherein the base preferably consists of one or more alkali metal hydroxide salts, wherein the base is preferably NaOH.

[0072] Independently, when adjusting the pH by adding an acid, preferably, the acid contains one or more Brønsted acids, wherein the acid preferably contains one or more mineral acids, wherein the acid preferably contains H₂SO₄ and / or HCl, wherein the acid preferably contains H₂SO₄. In particular, preferably, the acid consists of one or more Brønsted acids, wherein the acid preferably consists of one or more mineral acids, wherein the acid preferably consists of H₂SO₄ and / or HCl, wherein the acid preferably consists of H₂SO₄.

[0073] A further alternative is that the pH of the aqueous solution is not adjusted by adding acid and / or base before the introduction of CO2, wherein the pH of the aqueous solution is not adjusted before the introduction of CO2.

[0074] More preferably, the pH of the aqueous solution is in the range of 9 to 13 before the introduction of CO2, and the temperature is in the range of 25 to 70°C during the treatment in (2).

[0075] More preferably, the pH of the aqueous solution is in the range of 10 to 12.5 before the introduction of CO2, and the temperature is in the range of 30 to 60°C during the treatment in (2).

[0076] More preferably, the pH of the aqueous solution is in the range of 10.5 to 12 before the introduction of CO2, and the temperature is in the range of 35 to 50°C during the treatment in (2).

[0077] Particularly preferably, the pH of the aqueous solution is in the range of 11 to 11.5 before the introduction of CO2, and the temperature is in the range of 40 to 45°C during the treatment in (2).

[0078] More preferably, CO2 is introduced into the aqueous solution at a pressure of 1 to 15 bar (absolute pressure), more preferably 1 to 10 bar (absolute pressure), more preferably 3 to 8 bar (absolute pressure), and particularly preferably 5 to 6 bar (absolute pressure). According to the invention, the pressure of CO2 refers to the partial pressure when CO2 is introduced into the aqueous solution, wherein the partial pressure corresponds to the total pressure of the gas flow when CO2 is introduced into the aqueous solution in its pure form.

[0079] Preferably, the process in (2) includes:

[0080] (2.1) Treat the mixture A provided in (1) with carbonic acid such that the Li2CO3 contained therein is at least partially converted to LiHCO3;

[0081] (2.2) Perform a solid-liquid separation step on the mixture obtained in (2.1) to obtain a solid mixture M4 containing unreacted Li2CO3 and a liquid mixture B containing LiHCO3.

[0082] In the case where the method includes steps (2.1) and (2.2), preferably, the processing in (2) further includes:

[0083] (2.3) Provide the mixture M4 as a Li2CO3 source for the treatment in (2).

[0084] Preferably, the process in (2.3) includes:

[0085] (2.3.1) Wash the solid mixture M4 obtained in (2.2) with water to obtain washing water containing Li2CO3;

[0086] (2.3.2) Provide at least a portion of the Li2CO3-containing wash water obtained in (2.3.1) for the thermal conversion in (3).

[0087] Independent of this context, preferably, the processing in (2.3) includes:

[0088] (2.3.1) Wash the solid mixture M4 obtained in (2.2) with water to obtain washing water containing Li2CO3;

[0089] (2.3.2) Provide at least a portion of the washing water containing Li2CO3 obtained in (2.3.1) for use in the treatment with carbonic acid in (2).

[0090] Preferably, the pH of the mixture B obtained in (2) is in the range of 5 to 9, more preferably in the range of 5 to 8.5, more preferably in the range of 6 to 8.5, more preferably in the range of 7 to 8.5, more preferably in the range of 7 to 8, and particularly preferably in the range of 7.5 to 8.

[0091] Preferably, the mixture B obtained in (2) contains less than 30.0% by weight of alkaline earth metal, more preferably less than 20.0% by weight of alkaline earth metal, more preferably less than 10.0% by weight of alkaline earth metal, more preferably less than 5.0% by weight of alkaline earth metal, more preferably less than 3.0% by weight of alkaline earth metal, and more preferably less than 1.0% by weight of alkaline earth metal, wherein the mixture B obtained in (2) is particularly preferably free of alkaline earth metal.

[0092] Preferably, the mixture B obtained in (2) contains less than 5.0% by weight of calcium, more preferably less than 3.0% by weight of calcium, particularly preferably less than 1.0% by weight of calcium, and wherein the mixture B obtained in (2) is particularly preferably free of calcium.

[0093] Preferably, during the thermal conversion in (3), the temperature is in the range of 50 to 200°C, preferably in the range of 70 to 150°C, and particularly preferably in the range of 70 to 110°C.

[0094] Preferably, during the thermal conversion in (3), the pressure is in the range of 0.1 to 10 bar (absolute pressure), preferably in the range of 0.2 to 6 bar (absolute pressure), and particularly preferably in the range of 0.3 to 1 bar (absolute pressure).

[0095] Preferably, the reaction in (3) further includes:

[0096] (3.1) React a portion of the mixture B obtained in (2) with M(OH)2, such that the LiHCO3 contained therein is at least partially converted to LiOH, and obtain a mixture D' containing LiOH, wherein M is an alkaline earth metal.

[0097] Preferably, the reaction in (4) includes:

[0098] (4.1) Perform a solid-liquid separation step on the mixture C obtained in (4) to obtain a suspension containing solid Li2CO3 and a solution containing Li2CO3;

[0099] (4.2) Provide at least a portion of the Li2CO3-containing solution obtained in (4.1) for use in the treatment with carbonic acid in (2);

[0100] (4.3) React the suspension containing solid Li2CO3 obtained in (4.1) with M(OH)2, such that the Li2CO3 contained therein is at least partially converted into LiOH, and obtain a mixture D containing LiOH, wherein M is an alkaline earth metal.

[0101] When the method includes step (4.1), preferably, the solid content of the suspension containing solid Li2CO3 obtained in (4.1) is in the range of 1% to 10% by weight, more preferably in the range of 3% to 9% by weight, and particularly preferably in the range of 4% to 8% by weight.

[0102] When the method includes step (4.1), preferably, the solid-liquid separation step in (4.1) is performed by cross-flow filtration of the mixture C obtained in (3).

[0103] Preferably, during the reaction in (4) and / or (3.1), the temperature is independently within the range of 10 to 100°C, more preferably within the range of 15 to 80°C, more preferably within the range of 20 to 60°C, more preferably within the range of 20 to 50°C, more preferably within the range of 25 to 45°C, more preferably within the range of 30 to 45°C, more preferably within the range of 35 to 45°C, and particularly preferably within the range of 38 to 42°C. More preferably, during the reaction in (4) and / or (3.1), the pressure is independently within the range of 0.5 to 1.5 bar (absolute pressure), preferably within the range of 0.8 to 1.2 bar (absolute pressure).

[0104] Preferably, during the thermal conversion in (3), the temperature is in the range of 50 to 200°C, preferably in the range of 70 to 150°C, and particularly preferably in the range of 70 to 110°C.

[0105] Preferably, during the thermal conversion in (3), the pressure is in the range of 0.1 to 10 bar (absolute pressure), preferably in the range of 0.2 to 6 bar (absolute pressure), and particularly preferably in the range of 0.3 to 1 bar (absolute pressure).

[0106] Preferably, the alkaline earth metal hydroxide M(OH)₂ used in (4) and / or (3.1) is dissolved or suspended in water independently of each other prior to the reactions in (4) and / or (3.1).

[0107] In (4) and / or (3.1), the alkaline earth metal hydroxide M(OH)2 used is dissolved or suspended in water before the reaction, and independently of each other, the weight percentage of alkaline earth metal hydroxide M(OH)2 in the aqueous solution or aqueous suspension is in the range of 1 wt% to 50 wt%, preferably in the range of 10 wt% to 30 wt%.

[0108] Preferably, the alkaline earth metal M in (4) and / or (3.1) is selected independently from the group consisting of barium, calcium and magnesium, wherein the alkaline earth metal M is preferably calcium.

[0109] Preferably, the method further includes:

[0110] (5) Separate MCO3 from the mixture D obtained from (4) and / or the mixture D' obtained from (3.1) to obtain a mixture E containing LiOH.

[0111] Preferably, the separation in (5) includes:

[0112] (5.1) Perform a solid-liquid separation step on the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) to obtain a solid mixture M5 containing CaCO3 and a liquid mixture E containing LiOH;

[0113] (5.2) Wash the solid mixture M5 obtained in (5.1) with water to obtain washing water containing LiOH.

[0114] (5.3) At least a portion of the LiOH-containing wash water obtained in (5.2) is provided for the reaction in (4), wherein the at least portion of the LiOH-containing wash water is preferably mixed with alkaline earth metal hydroxide M(OH)2 before being recycled into (4). Thus, the LiOH-containing wash water obtained in (5.2) is used to prepare an aqueous suspension of alkaline earth metal hydroxide M(OH)2, which is used for the reaction in (4) and recycled into (4) in this manner.

[0115] When the method includes steps (5.1) to (5.3), preferably, the separation in (5) further includes ion exchange, preferably cation ion exchange.

[0116] The invention is described in more detail through the following embodiments and combinations of embodiments derived from the indicated dependencies and references. Specifically, in various instances where a series of embodiments is referred to (e.g., in conjunction with terms such as "the method according to any one of embodiments 1 to 4"), it is intended to clearly disclose to those skilled in the art each embodiment within that series, i.e., the use of such terminology should be understood by those skilled in the art to be synonymous with "the method according to any one of embodiments 1, 2, 3, and 4". Furthermore, it is explicitly stated that the following series of embodiments is not a group of claims defining the scope of protection, but rather represents a suitable structured portion of the specification relating to the general and preferred aspects of the invention.

[0117] 1. A method for preparing LiOH, the method comprising:

[0118] (1) Provide a mixture A containing Li2CO3;

[0119] (2) Treat the mixture A provided in (1) with carbonic acid such that the Li2CO3 contained therein is at least partially converted into LiHCO3, and obtain a mixture B containing LiHCO3;

[0120] (3) At least a portion of the mixture B obtained in (2) is subjected to thermal conversion to obtain a mixture C containing Li2CO3;

[0121] (4) React the mixture C obtained in (3) with M(OH)2, such that the Li2CO3 contained therein is at least partially converted into LiOH, and obtain a mixture D containing LiOH, wherein M is an alkaline earth metal.

[0122] 2. The method according to embodiment 1, wherein the Li2CO3 content of the mixture A in (1) is in the range of 0.1 wt% to 16.0 wt%, preferably in the range of 5 wt% to 12 wt%, alternatively and particularly preferably in the range of 1 wt% to 5 wt%.

[0123] 3. The method according to embodiment 2, wherein the Li2CO3 content of the mixture A in (1) based on the solid content of the mixture A is in the range of 0.1 wt% to 16.0 wt%, particularly preferably in the range of 5 wt% to 12 wt%.

[0124] 4. The method according to embodiment 1 or 2, wherein the Li content of the mixture A in (1) is in the range of 0.10 wt% to 3.00 wt%, preferably in the range of 0.80 wt% to 2.25 wt%, alternatively and particularly preferably in the range of 0.30 wt% to 2.25 wt%.

[0125] 5. The method according to embodiment 4, wherein the mixture A in (1) is calculated as elemental lithium and the Li content based on the solid content of the mixture A is in the range of 0.10 wt% to 3.00 wt%, particularly preferably in the range of 0.80 wt% to 2.25 wt%.

[0126] 6. The method according to embodiment 1, wherein the mixture A further comprises water, and the water content of the mixture A in (1) is in the range of 50% to 90% by weight, preferably in the range of 60% to 70% by weight.

[0127] 7. The method according to embodiment 6, wherein the Li2CO3 content of the mixture A in (1) is in the range of 0.01% by weight to 8.0% by weight, preferably in the range of 1% by weight to 5% by weight.

[0128] 8. The method according to any one of embodiments 1 to 7, wherein the provision of the mixture A according to (1) comprises:

[0129] (1.a) Provide a mixture M0 containing one or more lithium-containing minerals;

[0130] (1.b) Calcine the mixture M0 to obtain a mixture M1 containing one or more calcined lithium-containing minerals;

[0131] (1.c) React the mixture M1 obtained in (b) with an alkali metal carbonate, such that the one or more calcined lithium-containing minerals are at least partially converted into Li2CO3, and obtain a mixture A containing Li2CO3.

[0132] 9. The method according to embodiment 8, wherein the mixture M0 contains one or more lithium-containing minerals in the range of 50% to 100% by weight, preferably in the range of 60% to 95% by weight.

[0133] 10. The method according to embodiment 8 or 9, wherein the one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more lithium-containing minerals are preferably spodumene, and wherein the one or more lithium-containing minerals are particularly preferably α-spodumene.

[0134] 11. The method according to any one of embodiments 8 to 10, wherein during calcination in (1.b), the temperature is in the range of 800 to 1500°C, preferably in the range of 950 to 1100°C.

[0135] 12. The method according to any one of embodiments 8 to 11, wherein the calcination in (1.b) is carried out for a time ranging from 0.1 to 16 h, preferably from 0.5 to 5 h.

[0136] 13. The method according to any one of embodiments 8 to 12, wherein the one or more calcined lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more calcined lithium-containing minerals are preferably spodumene, and wherein the one or more calcined lithium-containing minerals are particularly preferably β-spodumene.

[0137] 14. The method according to any one of embodiments 8 to 13, wherein the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate, or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0138] 15. The method according to any one of embodiments 8 to 14, wherein the weight ratio of the one or more calcined lithium-containing minerals in (1.c) to the alkali metal carbonate is in the range of 1:0.1 to 1:2, preferably in the range of 1:0.1 to 1:0.4.

[0139] 16. The method according to any one of embodiments 8 to 15, wherein the molar ratio of lithium to sodium in (1.c) based on elemental lithium and sodium is in the range of 1:0.4 to 1:8, preferably in the range of 1:0.9 to 1:1.6.

[0140] 17. The method according to any one of embodiments 8 to 16, wherein during the reaction in (1.c), the temperature is in the range of 150 to 350°C, preferably in the range of 200 to 250°C.

[0141] 18. The method according to any one of embodiments 8 to 17, wherein during the reaction in (1.c), the pressure is in the range of 10 to 200 bar (absolute pressure), more preferably in the range of 20 to 50 bar (absolute pressure), and most preferably in the range of 14 to 50 bar (absolute pressure).

[0142] 19. The method according to any one of embodiments 8 to 18, wherein the reaction in (1.c) is carried out for a time ranging from 0.1 to 8 hours, preferably from 0.5 to 1.5 hours.

[0143] 20. The method according to any one of embodiments 8 to 19, wherein the reaction in (1.c) comprises water, preferably an aqueous solution of an alkali metal carbonate.

[0144] 21. The method according to any one of embodiments 8 to 20, the method comprising:

[0145] (1.d) Separate at least a portion of unreacted alkali metal carbonate from the mixture A obtained in (1.c) and obtain a mixture M2 containing unreacted alkali metal carbonate;

[0146] (1.e) The mixture M2 is provided as an alkali metal carbonate source for the reaction in (1.c).

[0147] 22. The method according to any one of embodiments 1 to 7, wherein the provision of the mixture A according to (1) comprises:

[0148] (1.a') Provide a mixture M0' containing one or more lithium-containing minerals;

[0149] (1.b') React the mixture MO' with an alkali metal carbonate to at least partially convert the one or more lithium-containing minerals into Li2CO3, and obtain a mixture A containing Li2CO3.

[0150] 23. The method according to embodiment 22, wherein the mixture M0' contains one or more lithium-containing minerals in the range of 50% to 100% by weight, preferably in the range of 60% to 95% by weight.

[0151] 24. The method according to embodiment 22 or 23, wherein the Li content of the mixture Mo', calculated as elemental lithium, is in the range of 0.03 wt% to 4.0 wt%, preferably in the range of 2.00 wt% to 3.75 wt%.

[0152] 25. The method according to any one of embodiments 22 to 24, wherein the one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more lithium-containing minerals are preferably spodumene, and wherein the one or more lithium-containing minerals are particularly preferably α-spodumene.

[0153] 26. The method according to any one of embodiments 22 to 25, wherein the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate, or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0154] 27. The method according to any one of embodiments 22 to 26, wherein in (1.b'), the weight ratio of the one or more lithium-containing minerals to the alkali metal carbonate is in the range of 1:0.1 to 1:2, preferably in the range of 1:0.2 to 1:0.4.

[0155] 28. The method according to any one of embodiments 22 to 27, wherein the molar ratio of lithium to sodium in (1.b') is in the range of 1:0.4 to 1:8, preferably in the range of 1:0.9 to 1:1.4.

[0156] 29. The method according to any one of embodiments 22 to 28, wherein the reaction in (1.b') is carried out for a time ranging from 0.1 to 10 h, preferably from 1 to 4 h.

[0157] 30. The method according to any one of embodiments 22 to 29, wherein the reaction in (1.b') comprises water, preferably water vapor.

[0158] 31. The method according to embodiment 30, wherein during the reaction in (1.b'), the pressure is in the range of 10 to 200 bar (absolute pressure), preferably in the range of 14 to 180 bar (absolute pressure), more preferably in the range of 14 to 50 bar (absolute pressure), and particularly preferably in the range of 20 to 50 bar (absolute pressure).

[0159] 32. The method according to any one of embodiments 22 to 29, wherein the reaction in (1.b') comprises:

[0160] (1.b'.1) Calcine the mixture M0' and the alkali metal carbonate to obtain mixture M1';

[0161] (1.b'.2) React the mixture M1' obtained in (1.b'.1) to obtain a mixture A containing Li2CO3.

[0162] 33. The method according to embodiment 32, wherein during calcination in (1.b'.1), the temperature is in the range of 900 to 1500°C, preferably in the range of 1000 to 1200°C.

[0163] 34. The method according to embodiment 32 or 33, wherein the reaction in (1.b'.2) comprises water, preferably water vapor.

[0164] 35. The method according to embodiment 34, wherein during the reaction in (1.b'.2), the pressure is in the range of 10 to 200 bar (absolute pressure), preferably in the range of 14 to 180 bar (absolute pressure), more preferably in the range of 14 to 50 bar (absolute pressure), and particularly preferably in the range of 20 to 50 bar (absolute pressure).

[0165] 36. The method according to any one of embodiments 22 to 35, the method comprising:

[0166] (1.c') Separate unreacted alkali metal carbonates from the mixture A included in (1.b') and obtain a mixture M2' containing unreacted alkali metal carbonates;

[0167] (1.d') The mixture M2' is provided as an alkali metal carbonate source for the reaction in (1.b').

[0168] 37. The method according to any one of embodiments 1 to 36, wherein during the treatment in (2), the temperature is in the range of 0 to 150°C, preferably in the range of 15 to 100°C, more preferably in the range of 20 to 80°C, more preferably in the range of 25 to 70°C, more preferably in the range of 30 to 60°C, more preferably in the range of 35 to 50°C, and particularly preferably in the range of 40 to 45°C.

[0169] 38. The method according to any one of embodiments 1 to 37, wherein the treatment in (2) is carried out in an aqueous solution and CO2 is introduced into the aqueous solution.

[0170] 39. The method according to embodiment 38, wherein, prior to the introduction of CO2, the pH of the aqueous solution is in the range of 9 to 13, preferably 10 to 12.5, more preferably 10.5 to 12, and particularly preferably 11 to 11.5.

[0171] 40. The method according to embodiment 39, wherein the pH of the aqueous solution is adjusted by adding an acid and / or a base before introducing CO2.

[0172] 41. The method according to embodiment 40, wherein the base contains one or more hydroxide salts, wherein the base preferably contains one or more alkali metal hydroxide salts, wherein the base preferably contains NaOH.

[0173] 42. The method according to embodiment 41, wherein the base is composed of one or more hydroxide salts, wherein the base is preferably composed of one or more alkali metal hydroxide salts, wherein the base is preferably NaOH.

[0174] 43. The method according to any one of embodiments 40 to 42, wherein the acid contains one or more Brønsted acids, wherein the acid preferably contains one or more mineral acids, wherein the acid preferably contains H2SO4 and / or HCl, wherein the acid preferably contains H2SO4.

[0175] 44. The method according to embodiment 43, wherein the acid is composed of one or more Brønsted acids, wherein the acid is preferably composed of one or more mineral acids, wherein the acid is preferably composed of H2SO4 and / or HCl, wherein the acid is preferably composed of H2SO4.

[0176] 45. The method according to embodiment 39, wherein the pH of the aqueous solution is not adjusted by adding acid and / or base before the introduction of CO2, wherein the pH of the aqueous solution is not adjusted before the introduction of CO2.

[0177] 46. ​​The method according to any one of embodiments 39 to 45, wherein, prior to the introduction of CO2, the pH of the aqueous solution is in the range of 9 to 13, and during the treatment in (2), the temperature is in the range of 25 to 70°C.

[0178] Preferably, the pH of the aqueous solution is in the range of 10 to 12.5 before the introduction of CO2, and the temperature is in the range of 30 to 60°C during the treatment in (2).

[0179] More preferably, the pH of the aqueous solution is in the range of 10.5 to 12 before the introduction of CO2, and the temperature is in the range of 35 to 50°C during the treatment in (2).

[0180] Particularly preferably, the pH of the aqueous solution is in the range of 11 to 11.5 before the introduction of CO2, and the temperature is in the range of 40 to 45°C during the treatment in (2).

[0181] 47. The method according to any one of embodiments 38 to 46, wherein CO2 is introduced into the aqueous solution at a pressure of 1 to 15 bar (absolute pressure), preferably 1 to 10 bar (absolute pressure), more preferably 3 to 8 bar (absolute pressure), and particularly preferably 5 to 6 bar (absolute pressure).

[0182] 48. The method according to any one of embodiments 1 to 47, wherein the processing in (2) includes:

[0183] (2.1) Treat the mixture A provided in (1) with carbonic acid such that the Li2CO3 contained therein is at least partially converted to LiHCO3;

[0184] (2.2) Perform a solid-liquid separation step on the mixture obtained in (2.1) to obtain a solid mixture M4 containing unreacted Li2CO3 and a liquid mixture B containing LiHCO3.

[0185] 49. The method according to embodiment 48, wherein the processing in (2) further comprises: (2.3) providing the mixture M4 as a Li2CO3 source for the processing in (2).

[0186] 50. The method according to implementation scheme 49, wherein the processing in (2.3) includes:

[0187] (2.3.1) Wash the solid mixture M4 obtained in (2.2) with water to obtain washing water containing Li2CO3;

[0188] (2.3.2) Provide at least a portion of the washing water containing Li2CO3 obtained in (2.3.1) for the reaction in (3).

[0189] 51. The method according to implementation scheme 49 or 50, wherein the processing in (2.3) includes:

[0190] (2.3.1) Wash the solid mixture M4 obtained in (2.2) with water to obtain washing water containing Li2CO3;

[0191] (2.3.2) Provide at least a portion of the washing water containing Li2CO3 obtained in (2.3.1) for use in the treatment with carbonic acid in (2).

[0192] 52. The method according to any one of embodiments 1 to 51, wherein the pH of the mixture B obtained in (2) is in the range of 5 to 9, preferably in the range of 5 to 8, preferably in the range of 6 to 8.5, more preferably in the range of 7 to 8.5, more preferably in the range of 7 to 8, and particularly preferably in the range of 7.5 to 8.

[0193] 53. The method according to any one of embodiments 1 to 52, wherein the mixture B obtained in (2) contains less than 30.0% by weight of alkaline earth metal, preferably less than 20.0% by weight of alkaline earth metal, more preferably less than 10.0% by weight of alkaline earth metal, more preferably less than 5.0% by weight of alkaline earth metal, more preferably less than 3.0% by weight of alkaline earth metal, more preferably less than 1.0% by weight of alkaline earth metal, wherein the mixture B obtained in (2) is particularly preferably free of alkaline earth metal.

[0194] 54. The method according to any one of embodiments 1 to 53, wherein the mixture B obtained in (2) contains less than 5.0% by weight of calcium, preferably less than 3.0% by weight of calcium, particularly preferably less than 1.0% by weight of calcium, and wherein the mixture B obtained in (2) is particularly preferably free of calcium.

[0195] 55. The method according to any one of embodiments 1 to 54, wherein during the thermal conversion in (3), the temperature is in the range of 50 to 200°C, preferably in the range of 70 to 150°C, and particularly preferably in the range of 70 to 110°C.

[0196] 56. The method according to any one of embodiments 1 to 55, wherein during the thermal conversion in (3), the pressure is in the range of 0.1 to 10 bar (absolute pressure), preferably in the range of 0.2 to 6 bar (absolute pressure), and particularly preferably in the range of 0.3 to 1 bar (absolute pressure).

[0197] 57. The method according to any one of embodiments 1 to 56, wherein the reaction in (3) further comprises:

[0198] (3.1) React a portion of the mixture B obtained in (2) with M(OH)2, such that the LiHCO3 contained therein is at least partially converted to LiOH, and obtain a mixture D' containing LiOH, wherein M is an alkaline earth metal.

[0199] 58. The method according to any one of embodiments 1 to 57, wherein the reaction in (4) comprises:

[0200] (4.1) Perform a solid-liquid separation step on the mixture C obtained in (4) to obtain a suspension containing solid Li2CO3 and a solution containing Li2CO3;

[0201] (4.2) Provide at least a portion of the Li2CO3-containing solution obtained in (4.1) for use in the treatment with carbonic acid in (2);

[0202] (4.3) React the suspension containing solid Li2CO3 obtained in (4.1) with M(OH)2, such that the Li2CO3 contained therein is at least partially converted into LiOH, and obtain a mixture D containing LiOH, wherein M is an alkaline earth metal.

[0203] 59. The method according to embodiment 58, wherein the solid content of the suspension containing solid Li2CO3 obtained in (4.1) is in the range of 1% by weight to 10% by weight, preferably in the range of 3% by weight to 9% by weight, and particularly preferably in the range of 4% by weight to 8% by weight.

[0204] 60. The method according to embodiment 58 or 59, wherein the solid-liquid separation step in (4.1) is performed by cross-flow filtration of the mixture C obtained in (3).

[0205] 61. The method according to any one of embodiments 1 to 60, wherein during the reaction in (4) and / or (3.1), the temperature is independently within the range of 10 to 100°C, preferably within the range of 15 to 80°C, more preferably within the range of 20 to 60°C, more preferably within the range of 20 to 50°C, more preferably within the range of 25 to 45°C, more preferably within the range of 30 to 45°C, more preferably within the range of 35 to 45°C, and particularly preferably within the range of 38 to 42°C.

[0206] 62. The method according to any one of embodiments 1 to 61, wherein during the reaction in (4) and / or (3.1), the pressure is independently in the range of 0.5 to 1.5 bar (absolute pressure), preferably in the range of 0.8 to 1.2 bar (absolute pressure).

[0207] 63. The method according to any one of embodiments 1 to 62, wherein during the thermal conversion in (3), the temperature is in the range of 50 to 200°C, preferably in the range of 70 to 150°C, and particularly preferably in the range of 70 to 110°C.

[0208] 64. The method according to any one of embodiments 1 to 63, wherein during the thermal conversion in (3), the pressure is in the range of 0.1 to 10 bar (absolute pressure), preferably in the range of 0.2 to 6 bar (absolute pressure), and particularly preferably in the range of 0.3 to 1 bar (absolute pressure).

[0209] 65. The method according to any one of embodiments 1 to 64, wherein the alkaline earth metal hydroxide M(OH)2 used in (4) and / or (3.1) is dissolved or suspended in water independently of each other prior to the reaction in (4) and / or (3.1).

[0210] 66. The method according to embodiment 65, wherein, independently of each other, the weight percentage of alkaline earth metal hydroxide M(OH)2 in the aqueous suspension is in the range of 1 to 50% by weight, preferably in the range of 10% to 30% by weight.

[0211] 67. The method according to any one of embodiments 1 to 66, wherein the alkaline earth metal M in (4) and / or (3.1) is independently selected from the group consisting of barium, calcium and magnesium, wherein the alkaline earth metal M is preferably calcium.

[0212] 68. The method according to any one of embodiments 1 to 67, wherein the method further comprises:

[0213] (5) Separate MCO3 from the mixture D obtained from (4) and / or the mixture D' obtained from (3.1) to obtain a mixture E containing LiOH.

[0214] 69. The method according to embodiment 68, wherein the separation in (5) includes:

[0215] (5.1) Perform a solid-liquid separation step on the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) to obtain a solid mixture M5 containing CaCO3 and a liquid mixture E containing LiOH;

[0216] (5.2) Wash the solid mixture M5 obtained in (5.1) with water to obtain washing water containing LiOH.

[0217] (5.3) Provide at least a portion of the LiOH-containing wash water obtained in (5.2) for the reaction in (4), wherein the at least a portion of the LiOH-containing wash water is preferably mixed with alkaline earth metal hydroxide M(OH)2 before being recycled into (4).

[0218] 70. The method according to embodiment 69, wherein the separation in (5) further includes ion exchange, preferably cation ion exchange.

[0219] Experimental Section

[0220] As described in the introductory section of the detailed embodiments, it was unexpectedly found that the temperature at which Li₂CO₃ is treated with an alkaline earth metal hydroxide has a significant effect on the amount of LiOH solution obtained in this step of the method according to the invention. This effect is demonstrated by the following series of experiments, in which the reaction of lithium carbonate (Li₂CO₃) to lithium hydroxide (LiOH) using calcium hydroxide (Ca(OH)₂) at different temperatures was investigated. Specifically, temperatures of 50°C, 60°C, and 95°C were tested in this series of experiments.

[0221] As further described in the detailed description section, it was also unexpectedly found that the pH of the initial mixture containing Li₂CO₃ and the temperature during the subsequent treatment of the mixture with carbonic acid independently enabled significant additional optimization of the method according to the invention. These further effects of the method according to the invention were demonstrated by the following series of experiments. In this series, the reaction of lithium carbonate (Li₂CO₃) to lithium bicarbonate (LiHCO₃) was carried out using H₂CO₃ generated in situ from CO₂. CO₂ was continuously metered and added during the reaction at a maximum pressure of approximately 5 bar. This series of experiments included various pH values ​​adjusted before the addition of CO₂. For pH values ​​4 and 10.5, 96% sulfuric acid (H₂SO₄) was used. For pH value 13, 50% sodium hydroxide solution (NaOH) was used. For the experiments at pH value 11, neither acid nor alkali needed to be added.

[0222] A series of experiments for the preparation of LiOH from Li2CO3

[0223] Example 1: Reaction of a mixture containing Li₂CO₃ with Ca(OH)₂ at 40°C

[0224] In a batch manner, a Li₂CO₃ suspension obtained from the thermal decomposition of a LiHCO₃ solution is reacted with a Ca(OH)₂ suspension in water at 40°C under stirring. The LiHCO₃ solution originates from the pressure leaching of β-spodumene according to the present invention. Specifically, the process is as follows:

[0225] An initial Li₂CO₃ suspension (723.6 g; 23 g / L Li₂CO₃; 16 g Li₂CO₃; 222 mmol Li₂CO₃) was introduced and inert under a N₂ atmosphere. The suspension was heated to a target temperature of 40°C with stirring. Simultaneously, a pre-prepared Ca(OH)₂ suspension (97.9 g; 206 g / L Ca(OH)₂; 17.2 g Ca(OH)₂; 233 mmol Ca(OH)₂) was prepared by resuspending it at room temperature under a N₂ atmosphere. After 14 minutes, the target temperature of 40°C was reached, and the addition of Ca(OH)₂ began. 97.9 g of the suspension was added over a period of 30 minutes. The mixture was then stirred at 40°C for another 180 minutes. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0226] Example 2: Reaction of a mixture containing Li₂CO₃ with Ca(OH)₂ at 95°C

[0227] In a batch manner, a Li₂CO₃ suspension obtained from the thermal decomposition of a LiHCO₃ solution was reacted with a Ca(OH)₂ suspension in water at 95°C under stirring. The LiHCO₃ solution was derived from the pressure leaching of β-spodumene as described in Example 1. Specifically, the process is as follows:

[0228] An initial Li₂CO₃ suspension (704.2 g; 24 g / L Li₂CO₃; 17 g Li₂CO₃; 224 mmol Li₂CO₃) was introduced and inert under a N₂ atmosphere. The suspension was heated to a target temperature of 95°C with stirring. Simultaneously, a pre-prepared Ca(OH)₂ suspension (96.5 g; 206 g / L Ca(OH)₂; 17.3 g Ca(OH)₂; 234 mmol Ca(OH)₂) was prepared by resuspending it at room temperature under a N₂ atmosphere. After 27 minutes, the target temperature of 95°C was reached, and the addition of Ca(OH)₂ began. 96.5 g of the suspension was added over a period of 30 minutes. The mixture was then stirred at 95°C for another 180 minutes. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0229] Example 3: Reaction of a mixture containing Li₂CO₃ with Ca(OH)₂ at 50°C

[0230] In a batch manner, a Li₂CO₃ suspension obtained from the thermal decomposition of a LiHCO₃ solution was reacted with a Ca(OH)₂ suspension in water at 50°C under stirring. The LiHCO₃ solution was derived from the pressure leaching of β-spodumene as described in Example 1. Specifically, the process is as follows:

[0231] An initial Li₂CO₃ suspension (708.6 g; 24 g / L Li₂CO₃; 17 g Li₂CO₃; 225 mmol Li₂CO₃) was introduced and inertized under a N₂ atmosphere. The suspension was heated to a target temperature of 50°C with stirring. Simultaneously, a pre-prepared Ca(OH)₂ suspension (93.9 g; 206 g / L Ca(OH)₂; 17.5 g Ca(OH)₂; 236 mmol Ca(OH)₂) was prepared by resuspending it at room temperature under a N₂ atmosphere. After 11 minutes, the target temperature of 50°C was reached, and the addition of Ca(OH)₂ began. 93.9 g of the suspension was added over a period of 30 minutes. The mixture was then stirred at 50°C for another 180 minutes. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0232] Example 4: Reaction of a mixture containing Li₂CO₃ with Ca(OH)₂ at 60°C

[0233] In a batch manner, a Li₂CO₃ suspension obtained from the thermal decomposition of a LiHCO₃ solution was reacted with a Ca(OH)₂ suspension in water at 60°C under stirring. The LiHCO₃ solution was derived from the pressure leaching of β-spodumene as described in Example 1. Specifically, the process is as follows:

[0234] An initial Li₂CO₃ suspension (706.7 g; 24 g / L Li₂CO₃; 17 g Li₂CO₃; 225 mmol Li₂CO₃) was introduced and inert under a N₂ atmosphere. The suspension was heated to a target temperature of 60°C with stirring. Simultaneously, a pre-prepared Ca(OH)₂ suspension (89.2 g; 206 g / L Ca(OH)₂; 17.4 g Ca(OH)₂; 235 mmol Ca(OH)₂) was prepared by resuspending it at room temperature under a N₂ atmosphere. After 17 minutes, the target temperature of 60°C was reached, and the addition of Ca(OH)₂ began. 89.2 g of the suspension was added over a period of 30 minutes. The mixture was then stirred at 60°C for another 180 minutes. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0235] Discussion of the results of a series of experiments on the preparation of LiOH from Li₂CO₃

[0236] Table 1: Lithium yield determined by ICP-MS of Li in the filtrate and washing filtrate.

[0237]

[0238] As can be seen from the results in Table 1, Example 1 exhibited the highest yield at a reaction temperature of 40°C. Surprisingly, the results in Table 1 indicate that the effect of temperature is non-uniform. Thus, starting with the results at 40°C, the yield decreased as the temperature increased, then increased again, and then decreased again. This particularly unusual behavior reveals the complexity of the process that is unpredictable under any circumstances.

[0239] The precise composition of the filtrate was studied using ICP-MS. The following table shows the elemental composition of relevant elements in the filtrate.

[0240] Table 2: ICP measurements of filtrates from a series of experiments involving the reaction of a mixture containing Li2CO3 with Ca(OH)2.

[0241]

[0242] As can be seen from the results in Table 2, the results of Example 1, with a reaction temperature of 40°C, not only showed the highest yield but also surprisingly the lowest amounts of Na, Al, and K impurities. This was particularly true for Na and K, whose amounts nearly doubled and tripled, respectively, as the reaction temperature increased from 40°C to 50°C. For these impurities of interest, higher impurity levels were recorded as the reaction temperature increased. However, surprisingly, this did not necessarily apply to impurities Si and Ca. Thus, in the case of Si as an impurity, its amount increased with increasing temperature, rising sharply and exponentially at 60°C, only decreasing to the lowest value in the series at 95°C. In the case of Ca as an impurity, its amount initially increased at 50°C, decreasing to the lowest value only at 60°C, and then rising to the highest value at 95°C. Therefore, the example reacting at 95°C achieved the lowest (much lower) silicon value but the highest (equally much higher) calcium value. Conversely, the embodiment at 60°C achieved the highest (much higher) Si impurity level, but also the lowest (also much lower) Ca impurity value.

[0243] Therefore, based on temperature parameters, this series of experiments unexpectedly explains the complexity of the factors that play a role in the reaction of Li2CO3 with Ca(OH)2 suspension obtained by the thermal decomposition of LiHCO3 solution (which is derived from the pressure leaching of β-spodumene according to the invention), particularly in terms of the efficiency of the method and the purity of the obtained LiOH solution.

[0244] A series of experiments for the preparation of LiHCO3

[0245] Example 5: Preparation of LiHCO3 at pH 11 and 40°C

[0246] In a batch process, filter cakes containing Li₂CO₃ obtained from the pressure leaching of β-spodumene were resuspended in water with stirring and CO₂ was introduced at 40°C. For this purpose, the filter cake was initially loaded (500.6 g; 33.2% residual moisture; 19.9 mg / g Li₂CO₃; 35 g Li₂CO₃; 480 mmol Li₂CO₃) and resuspended using 1204 mL of H₂O. The suspension was heated to the target temperature of 40°C with stirring. After 8 minutes, the target temperature of 40°C was reached, and CO₂ at 5.5 bar was added. After a 10-minute reaction time, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 500 g of deionized water.

[0247] Example 6: Preparation of LiHCO3 at pH 4 and 40°C

[0248] In a batch manner, the filter cake containing Li₂CO₃ obtained by pressure leaching of β-spodumene as described in Example 5 was resuspended in water with stirring and CO₂ was introduced at 40°C. For this purpose, the filter cake (450.0 g; 36.0% residual water; 17.1 mg / g Li₂CO₃; 26 g Li₂CO₃; 355 mmol Li₂CO₃) was initially loaded and resuspended using 849 mL of H₂O. The initial pH of the suspension was 11.1. The target pH of 4.0 was achieved by adding 17 g of 96% H₂SO₄. The suspension was then heated to the target temperature of 40°C with stirring. After 16 minutes, the target temperature of 40°C was reached, and CO₂ at 5.2 bar was added. After a reaction time of 10 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0249] Example 7: Preparation of LiHCO3 at pH 13 and 40°C

[0250] In a batch manner, the filter cake containing Li₂CO₃ obtained by pressure leaching of β-spodumene as described in Example 5 was resuspended in water with stirring and CO₂ was introduced at 40°C. For this purpose, the filter cake (450.7 g; 36.0% residual water; 17.1 mg / g Li₂CO₃; 26 g Li₂CO₃; 355 mmol Li₂CO₃) was initially loaded and resuspended using 849 mL of H₂O. The initial pH of the suspension was 11.1. The target pH of 13.0 was achieved by adding 27 g of 50% NaOH. The suspension was then heated to the target temperature of 40°C with stirring. After 15 minutes, the target temperature of 40°C was reached, and CO₂ at 5.5 bar was added. After a reaction time of 10 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0251] Example 8: Preparation of LiHCO3 at pH 11 and room temperature

[0252] In a batch manner, the filter cake containing Li₂CO₃ obtained by pressure leaching of β-spodumene as described in Example 5 was resuspended in water with stirring and CO₂ was introduced at room temperature. For this purpose, the filter cake (450.1 g; 36.0% residual water; 17.1 mg / g Li₂CO₃; 26 g Li₂CO₃; 355 mmol Li₂CO₃) was initially loaded and resuspended using 849 mL of H₂O. CO₂ at 5.2 bar was added at 27°C. After a reaction time of 14 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0253] Example 9: Preparation of LiHCO3 at pH 10.5 and 100°C

[0254] In a batch manner, the filter cake containing Li₂CO₃ obtained by pressure leaching of β-spodumene as described in Example 5 was resuspended in water with stirring and CO₂ was introduced at 100°C. For this purpose, the filter cake (450.1 g; 36.0% residual water; 17.1 mg / g Li₂CO₃; 26 g Li₂CO₃; 355 mmol Li₂CO₃) was initially loaded and resuspended using 849 mL of H₂O. The initial pH of the suspension was 11.0. The target pH of 10.5 was achieved by adding 0.8 g of 96% H₂SO₄. The suspension was then heated to the target temperature of 100°C with stirring. After 21 minutes, the target temperature of 100°C was reached, and CO₂ at 5.3 bar was added. After a 10-minute reaction time, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0255] Discussion of the results of a series of experiments used to prepare LiHCO3

[0256] Table 3: Lithium yield determined by ICP-MS of Li in the filtrate and washing filtrate.

[0257]

[0258] As can be seen from the results in Table 3, Example 5, at pH 11 and 40°C, showed the highest yield. The yield of Example 6, at pH 4, was also relatively high. This is because sulfuric acid partially destroys the anabolic zeolite, thus extracting more lithium compared to experiments in the alkaline range. However, a drawback is the formation of lithium sulfate, which introduces new anions into the process, requiring subsequent separation. In contrast, the yield of the experiment according to Example 9, at pH 10.5 and 100°C, was lower.

[0259] Regarding the pH in the CO2 introduction step, it can be said that, as the comparison of the results of Examples 5, 6, and 7 performed at the same temperature shows, the highest yield can be achieved at pH 11. Higher and lower pH values ​​of the starting mixture both resulted in lower yields. Therefore, it was unexpectedly found that a significant optimization of the lithium yield could be achieved by adjusting the pH of the starting mixture.

[0260] Furthermore, it was unexpectedly found that optimization could also be achieved by adjusting the temperature during CO2 introduction. Therefore, a comparison of the results of Examples 5, 8, and 9, performed at pH 10.5 and 11 respectively, showed that Example 5 achieved the highest yield. In particular, the results of Example 8, performed at a lower temperature, and Example 9, performed at a higher temperature, showed that significant optimization of lithium yield could also be achieved by adjusting the temperature during CO2 introduction.

[0261] The precise composition of the filtrate was studied using ICP-MS. The table below shows the elemental composition of the filtrate based on relevant elements.

[0262] Table 4: ICP measurements of filtrates from a series of experiments used to prepare LiHCO3.

[0263]

[0264] As can be seen from the results in Table 4, the results of Example 5 not only show the highest Li yield (which is evident in Table 3) (yield in filtrate here), but also show the lowest levels of impurities, except for Al, such as Na, Si, Ca, and K. This optimization is again clearly seen in terms of pH (by comparing the corresponding results of Examples 5 to 7) and temperature (by comparing the corresponding results of Examples 5, 8, and 9).

[0265] Although the results of Example 5 show the highest value for Al impurities, this impurity still constitutes the smallest (much smaller) amount of impurities compared to Na, Si, Ca, and K impurities in all examples. Furthermore, lower Si impurities are preferable to higher Al impurities because silicon is difficult to separate.

[0266] References

[0267] - WO 2019 / 220004 A1

[0268] - WO 2018 / 234614 A1

[0269] - EP 2749535 A1

[0270] - CN 101948124 B

[0271] - WO 2011 / 148040 A1

[0272] - CN 103183366 A

[0273] - CN 113428882 A

[0274] - WO 2023 / 081961 A1

[0275] - CN 107265483 A

[0276] - WO 2024 / 089394 A2

[0277] - Habashi Fathi, Handbook of Extractive Metallurgy, 1997, p. 2045

[0278] - Wietelmann Ulrich et al., Ullmann's Encyclopedia of Industrial Chemistry, 2000, p. 354

[0279] - CN 111635999 A

Claims

1. A method for preparing LiOH, the method comprising: (1) Provide a mixture A containing Li2CO3; (2) Treat the mixture A provided in (1) with carbonic acid such that the Li2CO3 contained therein is at least partially converted into LiHCO3, and obtain a mixture B containing LiHCO3; (3) At least a portion of the mixture B obtained in (2) is subjected to thermal conversion to obtain a mixture C containing Li2CO3; (4) React the mixture C obtained in (3) with M(OH)2, such that the Li2CO3 contained therein is at least partially converted into LiOH, and obtain a mixture D containing LiOH, wherein M is an alkaline earth metal.

2. The method according to claim 1, wherein the Li2CO3 content of the mixture A in (1) is in the range of 0.1% by weight to 16.0% by weight based on the solid content of the mixture A.

3. The method according to claim 1 or 2, wherein the provision of mixture A according to (1) comprises: (1.a) Provide a mixture M0 containing one or more lithium-containing minerals; (1.b) Calcine the mixture M0 to obtain a mixture M1 containing one or more calcined lithium-containing minerals; (1.c) React the mixture M1 obtained in (b) with an alkali metal carbonate, such that the one or more calcined lithium-containing minerals are at least partially converted into Li2CO3, and a mixture A containing Li2CO3 is obtained; (1.d) Separate at least a portion of the unconverted alkali metal carbonate from the mixture A obtained in (1.c) and obtain a mixture M2 containing the unconverted alkali metal carbonate; (1.e) The mixture M2 is provided as an alkali metal carbonate source for the reaction in (1.c).

4. The method according to claim 1 or 2, wherein the provision of mixture A according to (1) comprises: (1.a') Provide a mixture M0' containing one or more lithium-containing minerals; (1.b') React the mixture MO' with an alkali metal carbonate to at least partially convert the one or more lithium-containing minerals into Li2CO3, and obtain a mixture A containing Li2CO3; (1.c') Separate the unconverted alkali metal carbonate from the mixture A obtained in (1.b') and obtain a mixture M2' containing the unconverted alkali metal carbonate; (1.d') The mixture M2' is provided as an alkali metal carbonate source for the reaction in (1.b').

5. The method according to any one of claims 1 to 4, wherein during the treatment in (2), the temperature is in the range of 0 to 150°C.

6. The method according to any one of claims 1 to 5, wherein the treatment in (2) is carried out in an aqueous solution and CO2 is introduced into the aqueous solution.

7. The method according to claim 6, wherein, Before the introduction of CO2, the pH of the aqueous solution was in the range of 9 to 13.

8. The method according to claim 7, wherein during the treatment in (2), the temperature is in the range of 25 to 70°C.

9. The method according to any one of claims 6 to 8, wherein CO2 is introduced into the aqueous solution at a pressure of 1 to 15 bar (absolute pressure).

10. The method according to any one of claims 1 to 9, wherein the processing in (2) comprises: (2.1) Treat the mixture A provided in (1) with carbonic acid such that the Li2CO3 contained therein is at least partially converted to LiHCO3; (2.2) Perform a solid-liquid separation step on the mixture obtained in (2.1) to obtain a solid mixture M4 containing unconverted Li2CO3 and a liquid mixture B containing LiHCO3.

11. The method according to any one of claims 1 to 10, wherein the pH of the mixture B obtained in (2) is in the range of 5 to 9.

12. The method according to any one of claims 1 to 11, wherein the mixture B obtained in (2) contains less than 30.0% by weight of alkaline earth metal.

13. The method according to any one of claims 1 to 12, wherein the reaction in (3) further comprises: (3.1) React a portion of the mixture B obtained in (2) with M(OH)2, such that the LiHCO3 contained therein is at least partially converted to LiOH, and obtain a mixture D' containing LiOH, wherein M is an alkaline earth metal.

14. The method according to any one of claims 1 to 13, wherein, During the reactions in (4) and / or (3.1), the temperature ranges from 10 to 100°C, independently of each other.

15. The method according to claim 14, wherein during the reaction in (4), the temperature is in the range of 10 to 50°C.

16. The method according to any one of embodiments 1 to 15, wherein the method further comprises: (5) Separate MCO3 from the mixture D obtained from (4) and / or the mixture D' obtained from (3.1) to obtain a mixture E containing LiOH.

17. The method of claim 16, wherein the separation in (5) comprises: (5.1) Perform a solid-liquid separation step on the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) to obtain a solid mixture M5 containing CaCO3 and a liquid mixture E containing LiOH; (5.2) Wash the solid mixture M5 obtained in (5.1) with water to obtain washing water containing LiOH. (5.3) Provide at least a portion of the LiOH-containing wash water obtained in (5.2) for the reaction in (4), wherein the at least a portion of the LiOH-containing wash water is preferably mixed with alkaline earth metal hydroxide M(OH)2 before being recycled into (4).

18. The method according to claim 17, wherein the separation in (5) further comprises ion exchange, preferably cation ion exchange.

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