Method for producing lithium hydroxide monohydrate

Abstract

Described herein are one or more methods for producing lithium hydroxide monohydrate and related systems. The one or more methods generally include feeding the slurry to one or more gravity separators and separating the slurry into an underflow slurry and an overflow slurry using the one or more gravity separators. The slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities.

Description

Technical Field

[0001] The present disclosure generally relates to the production of lithium hydroxide monohydrate. More specifically, the present disclosure relates to one or more methods and related systems for producing lithium hydroxide monohydrate. Background Art

[0002] This section introduces information that may be relevant to or provide context for some aspects of the technology described herein and / or claimed below. This information is background that helps to better understand what is disclosed herein. Such background may include discussion of "related" technology. The relevance of such technology in no way means that it is also "prior" technology. Related technology may or may not be prior art. The discussion should be understood from this perspective, and not as an admission of prior art.

[0003] In recent years, lithium has become increasingly important as an element in various applications, especially in high energy density batteries. Lithium is found in various sources around the world, including brines, mineral deposits (such as spodumene and lepidolite), and clays. Such lithium sources can be further processed to produce lithium hydroxide monohydrate, which is increasingly used in battery applications, especially in the automotive industry. Such battery applications may require lithium hydroxide monohydrate with low impurity levels, including calcium, sodium, chlorides, and sulfates. If one or more purification steps are not adopted, it may be difficult to produce lithium hydroxide monohydrate with low impurity content. One way to remove such impurities is to use ion exchange and / or soda ash treatment to remove impurities such as calcium. However, purification involving ion exchange and / or soda ash methods may have some disadvantages, such as the additional time and cost required to produce the desired lithium hydroxide monohydrate product, as well as the need for additional raw materials and waste streams.

[0004] Therefore, there is an ongoing need to develop new methods for producing lithium hydroxide monohydrate and related systems. Summary of the invention

[0005] In general, the present disclosure provides a method comprising: (A) feeding a slurry into one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; and (B) using one or more gravity separators to separate the slurry into an underflow slurry and an overflow slurry based on particle size. The method may further include feeding the underflow slurry into one or more centrifuges to form a separated underflow. The method may further include dissolving and recrystallizing the separated underflow to re-form a recrystallized underflow. The method may further include washing the recrystallized underflow to form purified lithium hydroxide monohydrate.

[0006] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the gravity separator comprises one or more hydrocyclones.

[0007] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the gravity separator comprises one or more settling tanks.

[0008] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the separated underflow has a calcium content of less than about 60 ppm.

[0009] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

[0010] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein in step (A), the content of lithium hydroxide monohydrate in the slurry is in the range of about 10 wt % to about 50 wt % based on the total weight of the slurry.

[0011] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the insoluble impurities include one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

[0012] One or more aspects of the present disclosure include the method described in any of the preceding paragraphs, wherein the insoluble impurities include one selected from the group consisting of CaCO3, Ca(OH)2, Li2CO3, CaSO4, and any combination of two or more of the foregoing.

[0013] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, wherein the aqueous solution has a calcium content greater than about 300 ppm.

[0014] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein the cut point of the gravity separator is about 50 microns or less.

[0015] One or more aspects of the present disclosure include the method of any preceding paragraph, wherein no ion exchanger is used.

[0016] One or more aspects of the present disclosure include the method of any of the preceding paragraphs, wherein no soda ash treatment is used.

[0017] Although multiple embodiments are disclosed, other embodiments will be apparent to those skilled in the art from the following detailed description. It will be apparent that certain embodiments as disclosed herein are capable of modification in various obvious respects, all without departing from the spirit and scope of the claims as set forth herein. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and non-restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a detailed description of the preferred embodiments of the disclosed embodiment, reference will now be made to the accompanying drawings, in which:

[0019] Figure 1 Methods of producing lithium hydroxide monohydrate according to certain aspects of the present disclosure are shown.

[0020] Although the claimed subject matter is susceptible to various modifications and alternative forms, the accompanying drawings show by way of example specific embodiments described in detail herein. However, it should be understood that the description of specific embodiments herein is not intended to limit the claimed subject matter to the specific forms disclosed, but on the contrary, the present invention will cover all modifications, equivalents and alternative forms falling within the spirit and scope defined by the appended claims.

[0021] definition

[0022] In order to more clearly define the terms used in the present disclosure, the following definitions are provided. Unless otherwise stated, the following definitions apply to the present disclosure. Terms that do not appear below have their common and customary meanings understood by those of ordinary skill in the art related to the technical field of the present disclosure in the context of the present disclosure. If any definition or usage provided by any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided in the present disclosure shall prevail.

[0023] In the present disclosure, features of the subject matter are described such that combinations of different features are contemplated within a particular aspect. For each aspect and each feature disclosed herein, all combinations that do not adversely affect the designs, systems, compositions, processes, or methods described herein are contemplated, with or without explicit description of a particular combination. In addition, unless explicitly stated otherwise, any aspect or feature disclosed herein may be combined to describe an inventive design, system, composition, process, or method consistent with the present disclosure.

[0024] In the present disclosure, although compositions and methods are often described in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps, unless otherwise specified. For example, a slurry consistent with aspects of the disclosed subject matter may comprise; or consist essentially of; or consist only of: lithium hydroxide monohydrate and one or more insoluble impurities.

[0025] Unless otherwise specified, the terms "a / an" and "the" are intended to include plural alternatives, such as at least one, one or more, and one or more than one. For example, unless otherwise specified, disclosure of "slurry" is intended to cover one slurry, or a mixture or combination of more than one solvent.

[0026] Unless otherwise specified, the term "contacting" is used herein to describe systems, compositions, processes and methods in which components are contacted, combined or brought together in any order, in any manner and for any length of time. For example, the components can be combined by blending or mixing using any suitable technique.

[0027] The term "particle size" refers to the median diameter or the median of a particle size distribution as determined by laser diffraction or other suitable methods known to those of ordinary skill in the art.

[0028] The term "cut point" refers to the particle size at which a particle has approximately a 50% chance of entering the underflow or overflow of a gravity separator.

[0029] The term "about" means that the amount, size, formulation, parameter and other quantities and characteristics are not and need not be exact, but may be approximate, including larger or smaller as necessary to reflect tolerances, conversion factors, rounding, measurement errors, etc. and other factors known to those skilled in the art. In general, the amount, size, formulation, parameter or other quantity or characteristic is "about" or "approximately", whether or not such explicit statement is made. The term "about" also includes amounts that vary due to different equilibrium conditions of the composition produced by a particular initial mixture. Whether or not modified by the term "about", the claims include equivalent values ​​of the quantities.

[0030] Various numerical ranges are disclosed herein. When any type of range is disclosed or claimed herein (e.g., "ranging from ...", "in a range of from ...", "in the range of from ...", "in a range of from ...", "in a range of from ..."), it is intended to disclose or claim each possible number separately so that such a range can be reasonably covered, including the endpoints of the range and any sub-ranges and combinations of sub-ranges covered therein, unless otherwise stated. For example, in some aspects, the disclosure describes that the content of lithium hydroxide monohydrate in the slurry is in the range of about 25% by weight to about 30% by weight based on the total weight of the slurry. By disclosing that the content of lithium hydroxide monohydrate can be in the range of about 25% by weight to about 30% by weight, the purpose is to indicate that the content of lithium hydroxide monohydrate can be any content within the range, for example, it can be equal to about 25% by weight, about 26% by weight, about 27% by weight, about 28% by weight, about 29% by weight, or about 30% by weight. In addition, the content of lithium hydroxide monohydrate can be in any range of about 25 wt % to about 30 wt % (for example, the content of lithium hydroxide monohydrate can be in the range of about 27 wt % to about 29 wt %), and this also includes any combination of ranges between about 25 wt % to about 30 wt %. Likewise, all other ranges disclosed herein should be interpreted in a similar manner to this example.

[0031] The embodiments disclosed herein may provide materials that are listed as suitable for satisfying specific features of the embodiments defined by the term "or". For example, specific features of the disclosed subject matter may be disclosed as follows: Feature X can be A, B, or C. It is also contemplated that for each feature, the statement may also be formulated as a list of alternatives, such that the statement "Feature X is A, alternatively B, or alternatively C" is also an embodiment of the present disclosure, whether or not the statement is explicitly recited.

[0032] Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the subject matter described herein, typical methods and materials are described herein.

[0033] All publications and patents mentioned herein are incorporated herein by reference for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications and that might be used in connection with the presently described subject matter. DETAILED DESCRIPTION

[0034] The following illustrative aspects of the claimed subject matter will now be disclosed. For clarity, not all features of actual implementations are described in this specification. It should be appreciated that in the development of any such actual implementation, a large number of implementation-specific decisions should be made to achieve the developer's specific goals, such as compliance with system-related constraints and business-related constraints, which goals will vary between different implementations. In addition, it should be appreciated that such development efforts, while complex and time-consuming, will still be a routine task for those of ordinary skill in the art who benefit from this disclosure.

[0035] A. Process for producing lithium hydroxide monohydrate

[0036] Aspects of the subject matter disclosed herein relate to one or more methods for producing lithium hydroxide monohydrate (LHM). One such method may include:

[0037] (A) passing a slurry into one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; and

[0038] (B) Separating the slurry into underflow slurry and overflow slurry based on particle size using one or more gravity separators.

[0039] Figure 1 A representative method flow diagram of systems and / or methods consistent with certain aspects of the present disclosure is shown. Figure 1 and steps (A) and (B), at 50t, the slurry can be fed into one or more gravity separators by using any suitable power device (e.g., a pump) to carry out a separation process 500. One or more gravity separators separate the slurry 50 into an underflow slurry 60 and an overflow slurry 51. The overflow slurry 51 can be further filtered to remove insoluble impurities in the overflow slurry 51 to form a filtered overflow slurry, which can be recycled in the process to further optimize. One or more gravity separators 500 can be any suitable gravity separator capable of separating slurries based on particle size. Non-limiting examples of suitable gravity separators can include separators utilizing cyclonic action (e.g., hydrocyclones), settling tanks, or separators of both. In certain aspects, one or more gravity separators can include one or more hydrocyclones, or two or more hydrocyclones. A non-limiting example of a suitable hydrocyclone includes the FX-100 hydrocyclone provided by Weihai Haiwang Hydrocyclone Co., LTD.

[0040] Although not wishing to be bound by theory, it is believed that many of the insoluble impurities (e.g., calcium-containing compounds) present in the slurry have sufficiently different particle sizes than lithium hydroxide monohydrate so that they can be separated by one or more gravity separators. For example, where one or more hydrocyclones are used as gravity separators, the slurry can enter the inlet of a hydrocyclone having a conical chamber to form a vortex within the conical chamber. At least a portion of the coarser particles (e.g., lithium hydroxide monohydrate) can settle out and be discharged from the hydrocyclone as an underflow slurry, and at least a portion of the finer particles (e.g., calcium-containing compounds) can remain suspended and be discharged from the hydrocyclone as an overflow slurry. In this way, the slurry can be fully separated based on particle size, or at least in part based on particle size or a measure indicative of particle size.

[0041] One or more gravity separators can adopt various operating and size parameters to ensure the desired separation of the slurry based on particle size. In some aspects, the size and configuration of one or more gravity separators can be designed to have a cut point of less than about 100 microns, or less than about 75 microns, or less than about 50 microns, or less than about 25 microns, or less than about 10 microns. The temperature can be in the range of about 20°C to about 80°C, or in the range of about 50°C to about 60°C. The pressure can be in the range of about 0.5 bar to about 3 bar, or about 0.7 bar to about 1 bar, or about 0.9 bar. The slurry can be fed to one or more gravity separators at any suitable flow rate according to the desired cut point and / or the desired lithium hydroxide monohydrate productivity. In some aspects, the inner diameter of one or more gravity separators can be in the range of about 10mm to about 400mm. For example, the inner diameter of one or more gravity separators can be about 100mm, the height is about 1069mm, and the bottom discharge port size is about 18mm. The slurry can be fed at about 7m 3 / hour to about 9m 3 / hour, or about 8m 3 The flow rate of the overflow slurry from the one or more gravity separators can be about 3m / h. 3 / hour to about 4m 3 In some aspects, the size of the underflow slurry discharge port of the gravity separator can be varied in order to achieve a desired flow distribution between the overflow slurry and the underflow slurry.

[0042] In at least some aspects of the present disclosure, the lithium hydroxide monohydrate content of slurry 50 is in a range of about 10 wt % to about 50 wt % based on the total weight of the slurry, or in a range of about 25 wt % to about 30 wt % based on the total weight of the slurry.

[0043] The slurry 50 can be formed by a variety of processes. Figure 1 As shown, a slurry 50 can be formed in a causticizing process 100 by contacting an aqueous solution 10 containing lithium sulfate with sodium hydroxide 11 under conditions sufficient to produce a solution 20 containing lithium hydroxide and sodium sulfate. In certain aspects, the aqueous solution 10 containing lithium sulfate has a calcium content greater than about 300 ppm. The solution 20 containing lithium hydroxide and sodium sulfate can be subjected to a filtering process 200 to remove certain impurities 21 to form a filtered solution 30 containing lithium hydroxide and sodium sulfate. The filtered solution 30 can have a calcium content of less than about 30 ppm, or alternatively less than about 20 ppm. The filtered solution 30 can be subjected to a freeze crystallization process 300 to remove sodium sulfate decahydrate solid 31. Subsequently, the solution 40 containing lithium hydroxide and other impurities is fed to an evaporative crystallizer 400 to form a slurry 50. As another example, a slurry 50 can be formed by contacting lithium hydroxide monohydrate containing insoluble impurities with water.

[0044] The insoluble impurities in the slurry 50 may include one or more calcium-containing compounds, one or more carbonate-containing compounds, or both. Non-limiting examples of insoluble impurities may include calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), lithium carbonate (Li2CO3), calcium sulfate (CaSO4), or any combination of two or more of the foregoing.

[0045] The insoluble impurity content described herein, such as the amount of calcium present (in ppm), can be determined by ICP-OES (Inductively Coupled Plasma-Optical Emission Spectroscopy).

[0046] In at least some aspects of the present disclosure, the method may further include:

[0047] (C) feeding the underflow slurry into one or more centrifuges to form a separated underflow.

[0048] Now refer to step (C) and Figure 1 , a separation process 600 including one or more separators (e.g., centrifuges) can be used to separate the mother liquor 61 from the underflow slurry to form a separated underflow 70. The mother liquor can be recycled back to the causticizing process 100. The one or more centrifuges can be any suitable centrifuge capable of forming a separated underflow with a desired moisture content. Non-limiting examples of suitable centrifuges can include pusher centrifuges, such as the HR-400 centrifuge manufactured by Saideli, China.

[0049] In at least some aspects of the present disclosure, the separated underflow 70 has a moisture content of no more than about 10 wt%, or alternatively no more than about 5 wt%, or alternatively about 5 wt%. "Moisture content" refers to the amount of water remaining on the lithium hydroxide monohydrate solids in the centrifuge. The separated underflow has a calcium content of less than about 60 ppm, alternatively less than about 50 ppm, or alternatively less than about 30 ppm.

[0050] In at least some aspects of the present disclosure, the method may further include:

[0051] (D) dissolving and recrystallizing the separated underflow to reform a recrystallized underflow.

[0052] Refer to step (D) and Figure 1 700, the separated bottom stream 70 is dissolved in a solution comprising water, lithium hydroxide or both to form a concentrated lithium hydroxide solution. The concentrated lithium hydroxide solution can be fed to a second evaporative crystallizer to produce lithium hydroxide monohydrate solid, which can be separated as a recrystallized bottom stream by one or more hydrocyclones and / or centrifuges, and in some applications does not require subsequent re-dissolution.

[0053] In at least some aspects of the present disclosure, the method may further include:

[0054] (E) washing the recrystallized underflow to form purified lithium hydroxide monohydrate.

[0055] Refer to step (E) and Figure 1 700, washing the recrystallized underflow can further reduce the amount of calcium and other impurities that may be present. As used herein, the term "washing" is intended to include any process in which a liquid (e.g., water) contacts the recrystallized underflow. One or more washes may be required to significantly reduce impurities in the recrystallized underflow. In at least some aspects of the present disclosure, after the washing step, the purified lithium hydroxide monohydrate 80 has a calcium content of less than about 25 ppm, or less than about 20 ppm.

[0056] In at least some aspects of the present disclosure, the methods described herein may be practiced without ion exchange, without soda ash treatment, or without both ion exchange and soda ash treatment.

[0057] In at least some aspects of the present disclosure, at least a portion of the material (e.g., slurry, material for slurry, or both) subjected to the methods disclosed herein is not purified by (i) ion exchange, (ii) soda ash treatment, or both (i) and (ii).

[0058] Example

[0059] Having generally described the subject matter, the following examples are given as specific embodiments of the subject matter of the present disclosure and demonstrate its practice and advantages. It should be understood that these examples are given by way of illustration only and are not intended to limit the appended claims in any way.

[0060] Comparative Example 1 (Operation without Hydrocyclone)

[0061] A slurry containing 25 to 30 weight percent lithium hydroxide monohydrate is discharged from the evaporative crystallizer and fed to a cooling crystallizer. The slurry is then fed by gravity flow from the cooling crystallizer to a scraper discharge centrifuge (LGZ1250 manufactured by Saideli, China) to separate the slurry into an aqueous mother liquor and separated lithium hydroxide monohydrate solids in a batch operation. Each batch produces about 250 to about 280 kilograms of separated lithium hydroxide monohydrate solids. The separated lithium hydroxide monohydrate solids are redissolved, recrystallized and washed to form purified lithium hydroxide monohydrate.

[0062] Example 1 (Operation using a hydrocyclone)

[0063] The slurry containing 25 to 30 wt% lithium hydroxide monohydrate was discharged from the evaporative crystallizer and sent to a cooling crystallizer. The slurry was then pumped into a conical stainless steel hydrocyclone. The FX-100 hydrocyclone (manufactured by Haiwang, China) had an inner diameter of 100 mm, a height of 1069 mm, and a bottom discharge port size of 18 mm. The slurry was fed at 8 m 3 The flow rate of the overflow at the top of the hydrocyclone is 3m / h. 3 / hour to 4m 3 / hour. The underflow from the bottom of the hydrocyclone is fed into a pusher centrifuge (HR-400 manufactured by Saideli, China), which separates the slurry into an aqueous mother liquor and separated lithium hydroxide monohydrate solids. The separated lithium hydroxide monohydrate solids are redissolved, recrystallized and washed to form purified lithium hydroxide monohydrate.

[0064] The data and results of Comparative Example 1 and Example 1 are summarized in Table 1 below.

[0065]

[0066] Therefore, the hydrocyclone described herein and the method for producing lithium hydroxide monohydrate using the hydrocyclone can be used to produce separated lithium hydroxide monohydrate with reduced calcium content. For example, as shown in the above examples, the hydrocyclone described herein and the method for producing lithium hydroxide monohydrate using the hydrocyclone can be used to produce separated lithium hydroxide monohydrate with a calcium content of about 27 ppm, which is about 77% less than the process without the hydrocyclone. In addition, the hydrocyclone described herein and the method for producing lithium hydroxide monohydrate using the hydrocyclone can be used to produce purified lithium hydroxide monohydrate with a calcium content of about 11 ppm, which is about 83% less than the process without the hydrocyclone.

[0067] Additional Notes

[0068] The subject matter is described above with reference to many aspects and specific embodiments. Based on the above detailed description, many variations will occur to those skilled in the art. All such obvious variations are within the full intended scope of the appended claims. Other aspects of the subject matter disclosed herein may include, but are not limited to, the following (aspects are described as "comprising", but alternatively, may be "consisting essentially of" or "consisting of"):

[0069] Aspect 1. A method for producing lithium hydroxide monohydrate, the method comprising the following steps: (A) feeding a slurry into one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; and (B) using the one or more gravity separators to separate the slurry into an underflow slurry and an overflow slurry based on particle size.

[0070] Aspect 2. The method as defined in aspect 1, wherein the method further comprises (C) sending the underflow slurry to one or more centrifuges to form a separated underflow.

[0071] Aspect 3. The method as defined in any one of aspects 1-2, wherein the method further comprises (D) dissolving and recrystallizing the separated underflow to reform a recrystallized underflow.

[0072] Aspect 4. The method as defined in any one of aspects 1-3, wherein the method further comprises (E) washing the bottom flow of the recrystallization to form purified lithium hydroxide monohydrate.

[0073] Aspect 5. The method as defined in any one of aspects 1 to 4, wherein the gravity separator comprises one or more hydrocyclones.

[0074] Aspect 6. The method as defined in any one of aspects 1 to 5, wherein the gravity separator comprises one or more settling tanks.

[0075] Aspect 7. The method as defined in any one of aspects 2-6, wherein the separated underflow has a calcium content of less than about 60 ppm.

[0076] Aspect 8. The method as defined in any one of aspects 4-7, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

[0077] Aspect 9. The method as defined in any one of aspects 1 to 8, wherein in step (A), the content of lithium hydroxide monohydrate in the slurry is in the range of about 10 wt % to about 50 wt % based on the total weight of the slurry.

[0078] Aspect 10. The method as defined in any one of aspects 1 to 9, wherein the insoluble impurities comprise one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

[0079] Aspect 11. A method as defined in any one of Aspects 1-10, wherein the insoluble impurities include one selected from the group consisting of CaCO3, Ca(OH)2, Li2CO3, CaSO4, and any combination of two or more of the foregoing.

[0080] Aspect 12. The method as defined in any one of aspects 1-11, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, wherein the aqueous solution has a calcium content greater than about 300 ppm.

[0081] Aspect 13. The method as defined in any one of aspects 1 to 12, wherein the cut point of the gravity separator is about 50 microns or less.

[0082] Aspect 14. A method as defined in any one of aspects 1 to 13, wherein no ion exchanger is used.

[0083] Aspect 15. A method as defined in any one of aspects 1 to 14, wherein no soda ash treatment is used.

[0084] Aspect 16. A method for producing lithium hydroxide monohydrate, the method comprising the following steps: (A) feeding a slurry into one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; (B) using the one or more gravity separators to separate the slurry into an underflow slurry and an overflow slurry based on particle size; (C) feeding the underflow slurry into one or more centrifuges to form a separated underflow; and (D) dissolving and recrystallizing the separated underflow to re-form a recrystallized underflow.

[0085] Aspect 17. The method as defined in aspect 16, wherein the gravity separator comprises one or more hydrocyclones.

[0086] Aspect 18. The method as defined in aspect 16, wherein the gravity separator comprises one or more settling tanks.

[0087] Aspect 19. A method as defined in the preceding aspect, wherein the separated underflow has a calcium content of less than about 60 ppm.

[0088] Aspect 20. A method as defined in any preceding aspect, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

[0089] Aspect 21. The method as defined in any of the preceding aspects, wherein in step (A), the content of lithium hydroxide monohydrate in the slurry is in the range of about 10 wt % to about 50 wt % based on the total weight of the slurry.

[0090] Aspect 22. A method as defined in any of the preceding aspects, wherein the insoluble impurities comprise one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

[0091] Aspect 23. A method as defined in any of the preceding aspects, wherein the insoluble impurities comprise one selected from the group consisting of CaCO3, Ca(OH)2, Li2CO3, CaSO4, and any combination of two or more of the foregoing.

[0092] Aspect 24. A method as defined in any preceding aspect, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, wherein the aqueous solution has a calcium content greater than about 300 ppm.

[0093] Aspect 25. A method as defined in any preceding aspect, wherein the cut point of the gravity separator is about 50 microns or less.

[0094] Aspect 26. A method as defined in any preceding aspect, wherein the cut point of the gravity separator is about 100 microns or less.

[0095] Aspect 27. A method as defined in any preceding aspect, wherein no ion exchanger is used.

[0096] Aspect 28. A method as defined in any preceding aspect, wherein no soda ash treatment is used.

[0097] Aspect 29. A method for producing lithium hydroxide monohydrate, the method comprising the following steps: (A) feeding a slurry into one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; and (B) using the one or more gravity separators to separate the slurry into an underflow slurry and an overflow slurry based on the specific gravity of different particles.

[0098] Aspect 30. A method for producing lithium hydroxide monohydrate as described in any of the preceding aspects, wherein in step (B), the separation is performed using the one or more gravity separators to separate into an underflow slurry and an overflow slurry at least partially based on the specific gravity of different particles.

Claims

1. A method for producing lithium hydroxide monohydrate, the method comprising the following steps: (A) passing a slurry into one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; and (B) separating the slurry into an underflow slurry and an overflow slurry based on particle size using the one or more gravity separators.

2. The method of claim 1, further comprising: (C) sending the underflow slurry to one or more centrifuges to form a separated underflow.

3. The method of claim 2, further comprising: (D) dissolving and recrystallizing the separated underflow to reform a recrystallized underflow.

4. The method of claim 3, further comprising: (E) washing the underflow of the recrystallization to form purified lithium hydroxide monohydrate.

5. The method of any one of claims 1-4, wherein the gravity separator comprises one or more hydrocyclones.

6. The method of any one of claims 1-4, wherein the gravity separator comprises one or more settling tanks.

7. The process of any one of claims 2-6, wherein the separated underflow has a calcium content of less than about 60 ppm.

8. The method of any one of claims 4-7, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

9. The method of any one of claims 1 to 8, wherein in step (A), the content of lithium hydroxide monohydrate in the slurry is in the range of about 10 wt % to about 50 wt % based on the total weight of the slurry.

10. The method of any one of claims 1-9, wherein the insoluble impurities include one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

11. The method of any one of claims 1 to 10, wherein the insoluble impurities include one selected from the group consisting of CaCO3, Ca(OH)2, Li2CO3, CaSO4, and any combination of two or more thereof.

12. The method of any one of claims 1-11, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, wherein the aqueous solution has a calcium content greater than about 300 ppm.

13. The method of any one of claims 1-12, wherein the gravity separator has a cut point of about 50 microns or less.

14. The process of any one of claims 1 to 13, wherein no ion exchanger is used.

15. The method of any one of claims 1 to 14, wherein no soda ash treatment is used.

16. A method for producing lithium hydroxide monohydrate, the method comprising the steps of: (A) feeding a slurry to one or more gravity separators, wherein the slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities; (B) separating the slurry into an underflow slurry and an overflow slurry based on particle size using the one or more gravity separators; (C) feeding the underflow slurry into one or more centrifuges to form a separated underflow; as well as (D) dissolving and recrystallizing the separated underflow to reform a recrystallized underflow.

17. The method of claim 16, wherein the gravity separator comprises one or more hydrocyclones.

18. The method of claim 16, wherein the gravity separator comprises one or more settling tanks.

19. The process of claim 17 or claim 18, wherein the separated underflow has a calcium content of less than about 60 ppm.

20. The method of claim 17 or claim 18, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

21. The method of claim 17 or claim 18, wherein in step (A), the content of lithium hydroxide monohydrate in the slurry is in the range of about 10 wt% to about 50 wt% based on the total weight of the slurry.

22. The method of claim 17 or claim 18, wherein the insoluble impurities include one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

23. The method of claim 17 or claim 18, wherein the insoluble impurities include one selected from the group consisting of CaCO3, Ca(OH)2, Li2CO3, CaSO4, and any combination of two or more thereof.

24. The method of claim 17 or claim 18, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, wherein the aqueous solution has a calcium content greater than about 300 ppm.

25. The method of claim 17, wherein the gravity separator has a cut point of about 50 microns or less.

26. The method of claim 17, wherein the gravity separator has a cut point of about 100 microns or less.

27. The method of claim 17, wherein no ion exchanger is used.

28. The method of claim 17 or claim 27 wherein no soda ash treatment is used.

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