Process for producing lithium hydroxide monohydrate

Abstract

One or more processes and associated systems for producing lithium hydroxide monohydrate are described herein. One or more of the processes generally include feeding a 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 includes lithium hydroxide monohydrate and one or more insoluble impurities.

Description

[Technical field]

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

[0002] This section introduces information that may be relevant or provide context for some aspects of the technology described herein and / or claimed below. This information is background for better understanding what is disclosed herein. Such background may include a discussion of "related" art. The fact that such art is related does not mean that it is also "prior" art. Related art may or may not be prior art. This discussion should be read in this light, and not as an admission of prior art.

[0003] In recent years, lithium has gained importance as an element for use in various applications, especially for use in batteries with high energy density. Lithium is found in various sources around the world, including brines, mineral deposits (e.g., spodumene and lepidolite), and clays. Such lithium sources may be further processed to produce lithium hydroxide monohydrate, which is increasingly used for battery applications, especially in the automotive industry. Such battery applications may require lithium hydroxide monohydrate with low levels of impurities, including calcium, sodium, chloride, and sulfate, among others. It may be difficult to produce lithium hydroxide monohydrate with low impurity content without employing one or more purification steps. One method for removing such impurities includes using ion exchange and / or soda ash processing to remove impurities such as calcium. However, purification involving ion exchange and / or soda ash processes may suffer from drawbacks such as additional time and cost to produce the desired lithium hydroxide monohydrate product, as well as additional raw materials and waste streams.

[0004] Therefore, there is a continuing need to develop new processes and related systems for producing lithium hydroxide monohydrate. Summary of the Invention

[0005] In general, the disclosure provides a process that includes: (A) feeding a slurry, the slurry including lithium hydroxide monohydrate and one or more insoluble impurities, to one or more gravity separators; and (B) separating the slurry into an underflow slurry and an overflow slurry based on particle size using the one or more gravity separators. The process may further include feeding the underflow slurry to one or more centrifuges to form a separated underflow. The process may further include dissolving and recrystallizing the separated underflow to reform a recrystallized underflow. The process may further include washing the recrystallized underflow to form purified lithium hydroxide monohydrate.

[0006] One or more embodiments of the present disclosure include the process described in any of the preceding paragraphs, wherein the gravity separator includes one or more hydrocyclones.

[0007] One or more embodiments of the present disclosure include the process described in any of the preceding paragraphs, wherein the gravity separator comprises one or more settling tanks.

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

[0009] One or more embodiments of the present disclosure include the process described in 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 embodiments of the present disclosure include the process described in any of the preceding paragraphs, wherein in step (A), the slurry has a lithium hydroxide monohydrate content in the range of about 10 wt.% to about 50 wt.%, based on the total weight of the slurry.

[0011] One or more embodiments of the present disclosure include the process described in 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 embodiments of the present disclosure provide a process for preparing a soluble impurity comprising the steps of: 3 , Ca(OH) 2 , Li 2 CO 3 , CaSO 4 and any combination of two or more of the foregoing.

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

[0014] One or more embodiments of the present disclosure include the process of any of the preceding paragraphs, wherein the gravity separator has a cut point of about 50 micrometers or less.

[0015] One or more embodiments of the present disclosure include the process described in any of the preceding paragraphs, wherein no ion exchanger is used.

[0016] One or more embodiments of the present disclosure include the process described in any of the preceding paragraphs, wherein no soda ash treatment is used.

[0017] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, the specific embodiments disclosed herein can be modified in various obvious ways, all without departing from the spirit and scope of the claims presented herein. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

[0018] For a detailed description of the preferred embodiments of the disclosed embodiments, reference is now made to the accompanying drawing(s). [Brief description of the drawings]

[0019] [Figure 1] 1 illustrates a process for producing lithium hydroxide monohydrate, according to certain embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] While the claimed subject matter is susceptible to various modifications and alternative forms, the drawings(s) show, by way of example, specific embodiments described in detail herein. It should be understood, however, that the description of specific embodiments herein is not intended to limit the claimed subject matter to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope as defined by the appended claims.

[0021] definition The following definitions are provided to more clearly define the terms used in this disclosure. Unless otherwise indicated, the following definitions are applicable to this disclosure. Terms not listed below have their usual and customary meanings as understood by those skilled in the art in the relevant technical field of this disclosure in the context of this disclosure. To the extent that any definition or usage provided by any document incorporated by reference herein conflicts with the definition or usage provided herein, the definition or usage provided in this disclosure shall prevail.

[0022] In this disclosure, the subject features are described such that within a particular embodiment, combinations of different features may be envisioned. With respect to any and every embodiment and any and every feature disclosed herein, all combinations that do not adversely affect the designs, systems, compositions, processes, or methods described herein are contemplated, with or without the explicit description of the specific combination. In addition, unless otherwise expressly stated, any embodiment or feature disclosed herein may be combined to describe an inventive design, system, composition, process, or method consistent with this disclosure.

[0023] In this disclosure, compositions and methods are often described in terms of "comprising" various components or steps, but the compositions and methods can also "consist essentially of" or "consist of" various components or steps, unless otherwise specified. For example, a slurry consistent with aspects of the presently disclosed subject matter can include, alternatively consist essentially of, or alternatively consist of lithium hydroxide monohydrate and one or more insoluble impurities.

[0024] The terms "a," "an," and "the" are intended to include multiple alternatives, e.g., at least one, one or more, and one or more. For example, disclosure of a "slurry" is meant to include one slurry, or a mixture or combination of two or more slurries, unless otherwise specified.

[0025] The term "contacting" is used herein to describe systems, compositions, processes, and methods in which the components are contacted, combined, or brought together in any order, in any manner, and for any length of time, unless otherwise specified. For example, the components can be combined by blending or mixing, using any suitable technique.

[0026] The term "particle size" refers to the median diameter or median of a particle size distribution as determined by laser diffraction or other suitable methods known to those skilled in the art.

[0027] The term "cut point" refers to the particle size at which there is approximately a 50% chance that the particle will report either an underflow or an overflow of the gravity separator.

[0028] The term "about" means that amounts, sizes, formulations, parameters, and other quantities and features are not exact and need not be exact, but may be approximate, including being larger or smaller as necessary, to reflect tolerances, conversion factors, rounding, measurement errors, and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter, or other quantity or feature is "about" or "approximate" whether or not it is expressly stated as such. The term "about" also includes amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term "about", the claims include the equivalent of the quantity.

[0029] 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..."), the intention is to separately disclose or claim each possible number that such range may reasonably include, including the endpoints of such range, and any subranges and combinations of subranges contained therein, unless otherwise specified. For example, the disclosure recites that the slurry has a lithium hydroxide monohydrate content ranging from about 25% to about 30% by weight, based on the total weight of the slurry, in certain embodiments. By disclosing that the lithium hydroxide monohydrate content may range from about 25% to about 30% by weight, the intent is to recite that the lithium hydroxide monohydrate content may be any content within that range, e.g., equal to about 25%, about 26%, about 27%, about 28%, about 29%, or about 30% by weight. Further, by disclosing that the lithium hydroxide monohydrate content may be within any range from about 25% to about 30% by weight (e.g., the lithium hydroxide monohydrate content may range from about 27% to about 29% by weight), this also includes any combination of ranges from about 25% to about 30% by weight. Similarly, all other ranges disclosed herein should be interpreted in a similar manner to this example.

[0030] In embodiments disclosed herein, materials may be provided that are listed as being suitable for fulfilling a particular feature of an embodiment delimited by the term "or." For example, a particular feature of the presently disclosed subject matter may be disclosed as follows: feature X may be A, B, or C. It is also contemplated that for each feature, a statement that "feature X is A or alternatively B, or alternatively C" may also be expressed as an alternative listing, such that this statement is an embodiment of the present disclosure, regardless of whether this statement is explicitly stated.

[0031] 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, exemplary methods and materials are described herein.

[0032] All publications and patents mentioned herein are incorporated by reference herein, for the purpose of describing and disclosing, e.g., the constructs and methodology described in the publications that can be used in connection with the subject matter described herein.

[0033] Next, exemplary aspects of the claimed subject matter are disclosed below. For clarity, not all features of an actual implementation are described in this specification. It will be understood that in the development of any such actual embodiment, numerous implementation-specific decisions that will vary from implementation to implementation will have to be made to achieve the developer's particular goals, such as compliance with system-related and business-related constraints. Moreover, it will be understood that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0034] A. Process for Producing Lithium Hydroxide Monohydrate An embodiment of the subject matter disclosed herein relates to one or more processes for producing lithium hydroxide monohydrate (LHM). One such process may include: (A) feeding a slurry, the slurry comprising lithium hydroxide monohydrate and one or more insoluble impurities, to one or more gravity separators; and (B) separating the slurry into an underflow slurry and an overflow slurry based on particle size using one or more gravity separators.

[0035] An exemplary process flow diagram of a system and / or process consistent with certain embodiments of the present disclosure is shown in FIG. 1. Referring now to FIG. 1 and steps (A) and (B), at 50 (in the figure), the slurry may be subjected to a separation process 500 by feeding the slurry to one or more gravity separators using any suitable power device, such as a pump. The one or more gravity separators separate the slurry 50 into an underflow slurry 60 and an overflow slurry 51. The overflow slurry 51 may be subjected to further filtration to remove insoluble impurities from the overflow slurry 51 to form a filtered overflow slurry, which may be recycled in the process for further optimization. The one or more gravity separators 500 may be any suitable gravity separator capable of separating the slurry based on particle size. Non-limiting examples of suitable gravity separators may include separators using cyclonic action (e.g., hydrocyclones), settling tanks, or both. In some embodiments, the one or more gravity separators may include one or more hydrocyclones, or two or more hydrocyclones. A non-limiting example of a suitable hydrocyclone includes the FX-100 hydrocyclone available from Weihei Haiwang Hydrocycle Co., LTD.

[0036] Without wishing to be bound by theory, it is believed that many of the insoluble impurities present in the slurry (e.g., calcium-containing compounds) are sufficiently different in particle size compared to lithium hydroxide monohydrate to allow separation by one or more gravity separators. For example, in the case of one or more hydrocyclones as gravity separators, the slurry may enter an inlet of the hydrocyclone having a conical chamber and form a vortex inside the conical chamber. At least a portion of the coarse particles, such as lithium hydroxide monohydrate, may settle and exit the hydrocyclone as an underflow slurry, and at least a portion of the finer particles, such as calcium-containing compounds, may remain in suspension and exit the hydrocyclone as an overflow slurry. In this manner, the slurry may be sufficiently separated based on particle size or based at least in part on particle size or a measure indicative of particle size.

[0037] Various operating and size parameters for the one or more gravity separators can be utilized to ensure the desired separation of the slurry based on particle size. In some embodiments, the one or more gravity separators can be configured and shaped to have a cutoff point of less than about 100 micrometers, or alternatively less than about 75 micrometers, or alternatively less than about 50 micrometers, or alternatively less than about 25 micrometers, or alternatively less than about 10 micrometers. The temperature can be in the range of about 20° C. to about 80° C., or alternatively 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, alternatively in the range of about 0.7 bar to about 1 bar, or alternatively about 0.9 bar. The slurry can be fed to the one or more gravity separators at any suitable flow rate depending on the desired cutoff point and / or the desired rate of lithium hydroxide monohydrate production. In some embodiments, the one or more gravity separators can have an inner diameter in the range of about 10 mm to about 400 mm. For example, the one or more gravity separators may have an inner diameter of about 100 mm, a height of about 1069 mm, and a bottom discharge port size of about 18 mm. 3 / time ~ approx. 9m 3 / hour range of flow rate, or alternatively approximately 8m 3The overflow slurry from the one or more gravity separators may be fed to one or more gravity separators at a flow rate of about 3 m 3 / time ~ approx. 4m 3 In some embodiments, the size of the underflow slurry outlet of the gravity separator may be varied to achieve a desired flow distribution between the overflow and underflow slurries.

[0038] In at least some embodiments of the present disclosure, the slurry 50 has a lithium hydroxide monohydrate content in the range of about 10% to about 50% by weight, based on the total weight of the slurry, or alternatively, a lithium hydroxide monohydrate content in the range of about 25% to about 30% by weight, based on the total weight of the slurry.

[0039] The slurry 50 may be formed by a variety of processes. For example, as shown in FIG. 1, the slurry 50 may 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 an embodiment, 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 may be subjected to a filtration process 200 to remove certain impurities 21 to form a filtered solution 30 containing lithium hydroxide and sodium sulfate. The filtered solution 30 may have a calcium content less than about 30 ppm, or alternatively less than about 20 ppm. The filtered solution 30 may be subjected to a freeze crystallization process 300 to remove sodium sulfate decahydrate solids 31. The solution 40 containing lithium hydroxide and other impurities may then be fed to an evaporative crystallizer 400 to form the slurry 50. As another example, the slurry 50 may be formed by contacting lithium hydroxide monohydrate containing insoluble impurities with water.

[0040] 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 include calcium carbonate (CaCO 3 ), calcium hydroxide (Ca(OH) 2 ), lithium carbonate (Li 2 CO 3 ), calcium sulfate (CaSO 4 ), or any combination of two or more of the foregoing.

[0041] The insoluble impurity content described herein, such as the amount of calcium present (on a ppm basis), can be determined by ICP-OES (Inductively Coupled Plasma-Optical Emission Spectroscopy).

[0042] In at least some aspects of the present disclosure, the process may further include: (C) feeding the underflow slurry to one or more centrifuges to form a separated underflow.

[0043] Now referring to step (C) and FIG. 1 , a separation process 600 including one or more separators, such as centrifuges, can be used to separate the mother liquor 61 from the underflow slurry to form a separated underflow 70. The mother liquor may be recycled back to the recausticizing process 100. The one or more centrifuges may be any suitable centrifuge capable of forming a separated underflow having a desired water content. Non-limiting examples of suitable centrifuges may include pusher centrifuges, such as the HR-400 centrifuge manufactured by Saideli of China.

[0044] In at least some embodiments of the present disclosure, the separated underflow 70 has a water content of about 10% by weight or less, or alternatively about 5% by weight or less, or alternatively about 5% by weight. Reference to "water 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.

[0045] In at least some aspects of the present disclosure, the process may further include: (D) Dissolving and recrystallizing the separated underflow to reform the recrystallized underflow.

[0046] 1, at 700, the separated underflow 70 is dissolved in a solution containing 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 solids, which can be separated as recrystallized underflow by one or more hydrocyclones and / or centrifuges, and in certain applications, no subsequent redissolution is required.

[0047] In at least some aspects of the present disclosure, the process may further include: (E) washing the recrystallized underflow to form purified lithium hydroxide monohydrate.

[0048] With reference to step (E) and FIG. 1, at 700, the recrystallized underflow can be washed to further reduce the amount of calcium and other impurities that may be present. As used herein, the term washing is meant to include any process in which a liquid (e.g., water) contacts the recrystallized underflow. One or more washes may be required to substantially reduce the impurities in the recrystallized underflow. In at least some embodiments 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 alternatively less than about 20 ppm.

[0049] In at least some aspects of the present disclosure, the processes described herein may be carried out without ion exchange, without soda ash treatment, or without both ion exchange and soda ash treatment.

[0050] In at least some aspects of the present disclosure, at least a portion of the materials subjected to the processes disclosed herein (e.g., the slurry, the materials used in the slurry, or both) are not purified by (i) ion exchange, (ii) soda ash treatment, or both (i) and (ii). EXAMPLES

[0051] Having generally described the subject matter, the following examples are presented as specific embodiments of the subject matter of this disclosure and to demonstrate its practice and advantages. It is to be understood that the examples are presented by way of illustration and are not intended to limit the scope of the claims which follow in any manner.

[0052] Comparative Example 1 (run without hydrocyclone) A slurry having 25% to 30% by weight lithium hydroxide monohydrate was discharged from the evaporative crystallizer and fed to a cooling crystallizer. The slurry was then fed by gravity flow from the cooling crystallizer to a peeler centrifuge (LGZ1250 manufactured by Saideli, China) to separate the slurry into aqueous mother liquor and separate the lithium hydroxide monohydrate solids in a batch operation. Each batch produced about 250 kg to about 280 kg of separated lithium hydroxide monohydrate solids. The separated lithium hydroxide monohydrate solids were redissolved, recrystallized, and washed to form purified lithium hydroxide monohydrate.

[0053] Example 1 (run with hydrocyclone) The slurry having 25% to 30% by weight of lithium hydroxide monohydrate was discharged from the evaporative crystallizer and fed 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 pumped into a 8 m 3 The overflow from the top of the hydrocyclone was 3 m 3 / hour ~4m 3 The hydrocyclone had a flow rate of 1000000 / hr. The underflow from the bottom of the hydrocyclone was fed to a pusher centrifuge (HR-400 manufactured by Saideli, China) to subsequently separate the slurry into aqueous mother liquor and separate the lithium hydroxide monohydrate solids. The separated lithium hydroxide monohydrate solids were redissolved, recrystallized and washed to form purified lithium hydroxide monohydrate.

[0054] The data and results of Comparative Example 1 and Example 1 are summarized in Table 1 below. [Table 1]

[0055] In this manner, the hydrocyclone and process for producing lithium hydroxide monohydrate using a hydrocyclone described herein can be used to produce separated lithium hydroxide monohydrate having a reduced calcium content. For example, as illustrated by the above examples, the hydrocyclone and process for producing lithium hydroxide monohydrate using a hydrocyclone described herein can be used to produce separated lithium hydroxide monohydrate having a calcium content of about 27 ppm, which is about 77% reduced compared to a process without a hydrocyclone. Furthermore, in this manner, the hydrocyclone and process for producing lithium hydroxide monohydrate using a hydrocyclone described herein can be used to produce purified lithium hydroxide monohydrate having a calcium content of about 11 ppm, which is about 83% reduced compared to a process without a hydrocyclone. Additional Description

[0056] The subject matter has been described above with reference to numerous aspects and specific examples. Many variations will be suggested to those skilled in the art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. Other aspects of the subject matter disclosed herein can include, but are not limited to, the following (although an aspect may be described as "comprising", it may alternatively be "consisting essentially of" or "consisting of"):

[0057] Aspect 1. A process for producing lithium hydroxide monohydrate comprising: (A) feeding a slurry comprising lithium hydroxide monohydrate and one or more insoluble impurities to one or more gravity separators; and (B) separating the slurry into an underflow slurry and an overflow slurry based on particle size with the one or more gravity separators.

[0058] The process of claim 1, wherein the process further comprises: (C) feeding the underflow slurry to one or more centrifuges to form a separated underflow.

[0059] Embodiment 3. The process of any one of embodiments 1-2, wherein the process further comprises: (D) dissolving and recrystallizing the separated underflow to reform a recrystallized underflow.

[0060] Embodiment 4. The process of any one of embodiments 1-3, wherein the process further comprises: (E) washing the recrystallized underflow to form purified lithium hydroxide monohydrate.

[0061] Example 5. The process of any one of Examples 1-4, wherein the gravity separator comprises one or more hydrocyclones.

[0062] Example 6. The process of any one of Examples 1-5, wherein the gravity separator comprises one or more settling tanks.

[0063] Embodiment 7. The process of any one of embodiments 2-6, wherein the separated underflow has a calcium content of less than about 60 ppm.

[0064] Example 8. The process of any one of examples 4 to 7, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

[0065] Aspect 9. The process of any one of aspects 1 to 8, wherein in step (A), the slurry has a lithium hydroxide monohydrate content in the range of about 10% by weight to about 50% by weight, based on the total weight of the slurry.

[0066] Example 10. The process of any one of examples 1-9, wherein the insoluble impurities include one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

[0067] Aspect 11. The insoluble impurity is CaCO 3 , Ca(OH) 2 , Li 2 CO 3 , CaSO 4 and any combination of two or more of the foregoing.

[0068] Embodiment 12. The process of any one of embodiments 1-11, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, and the aqueous solution has a calcium content of greater than about 300 ppm.

[0069] Example 13. The process of any one of examples 1 to 12, wherein the gravity separator has a cut point of about 50 micrometers or less.

[0070] Embodiment 14. The process of any one of embodiments 1 to 13, wherein no ion exchanger is used.

[0071] Embodiment 15. The process of any one of embodiments 1-14, wherein no soda ash treatment is used.

[0072] Aspect 16. A process for producing lithium hydroxide monohydrate comprising: (A) feeding a slurry, the slurry comprising lithium hydroxide monohydrate and one or more insoluble impurities, to one or more gravity separators; (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 to one or more centrifuges to form a separated underflow; and (D) dissolving and recrystallizing the separated underflow to reform a recrystallized underflow.

[0073] Aspect 17. The process of aspect 16, wherein the gravity separator comprises one or more hydrocyclones.

[0074] Example 18. The process of example 16, wherein the gravity separator comprises one or more settling tanks.

[0075] Embodiment 19. The process of any of the preceding embodiments, wherein the separated underflow has a calcium content of less than about 60 ppm.

[0076] Aspect 20. The process of any of the preceding aspects, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

[0077] Aspect 21. The process of any of the preceding aspects, wherein in step (A), the slurry has a lithium hydroxide monohydrate content in the range of about 10% by weight to about 50% by weight, based on the total weight of the slurry.

[0078] Example 22 The process of any of the preceding examples, wherein the insoluble impurities include one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

[0079] Aspect 23. The insoluble impurity is CaCO 3 , Ca(OH) 2 , Li 2 CO 3 , CaSO 4

[0023] The process of any of the preceding aspects, comprising one selected from the group consisting of:

[0080] Embodiment 24. The process of any preceding embodiment, wherein the slurry is formed by contacting an aqueous solution comprising lithium sulfate with sodium hydroxide, and the aqueous solution has a calcium content of greater than about 300 ppm.

[0081] Embodiment 25. The process of any of the preceding embodiments, wherein the gravity separator has a cut point of about 50 micrometers or less.

[0082] Embodiment 26 The process of any of the preceding embodiments, wherein the gravity separator has a cut point of about 100 micrometers or less.

[0083] Embodiment 27 The process of any of the preceding embodiments, wherein no ion exchanger is used.

[0084] Embodiment 28. The process of any of the preceding embodiments, wherein no soda ash treatment is used.

[0085] Aspect 29. A process for producing lithium hydroxide monohydrate, comprising: (A) feeding a slurry, the slurry comprising lithium hydroxide monohydrate and one or more insoluble impurities, to one or more gravity separators; and (B) separating the slurry into an underflow slurry and an overflow slurry using the one or more gravity separators based on the specific gravities of various particles.

[0086] Aspect 30. The process for producing lithium hydroxide monohydrate of any of the preceding aspects, wherein in step (B), the separation into an underflow slurry and an overflow slurry is based at least in part on the specific gravities of the various particles using the one or more gravity separators.

Claims

1. A process for producing lithium hydroxide monohydrate, (A) A slurry comprising lithium hydroxide monohydrate and one or more insoluble impurities, the step of supplying the slurry to one or more gravity separators, and (B) The process comprising the step of separating the slurry into an underflow slurry and an overflow slurry based on particle size using one or more gravity separators.

2. (C) The process according to claim 1, further comprising supplying the underflow slurry to one or more centrifuges to form a separated underflow.

3. (D) The process according to claim 2, further comprising dissolving and recrystallizing the separated underflow to reshape the recrystallized underflow.

4. (E) The process according to claim 3, further comprising washing the recrystallized underflow to form purified lithium hydroxide monohydrate.

5. The process according to any one of claims 1 to 4, wherein the gravity separator includes one or more hydrocyclones.

6. The process according to any one of claims 1 to 4, wherein the gravity separator includes one or more sedimentation tanks.

7. The process according to claims 2 to 4, wherein the separated underflow has a calcium content of less than about 60 ppm.

8. The process according to claim 4, wherein the purified lithium hydroxide monohydrate has a calcium content of less than about 25 ppm.

9. The process according to claims 1 to 4, wherein in step (A), the slurry has a lithium hydroxide monohydrate content in the range of about 10% by weight to about 50% by weight, based on the total weight of the slurry.

10. The process according to claims 1 to 4, wherein the insoluble impurity comprises one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

11. The aforementioned insoluble impurity is CaCO 3 Ca(OH) 2 Li 2 CO 3 CaSO 4 The process according to claims 1 to 4, further comprising, and one selected from the group consisting of any two or more combinations of the foregoing.

12. The process according to claims 1 to 4, wherein the slurry is formed by contacting an aqueous solution containing lithium sulfate with sodium hydroxide, and the aqueous solution has a calcium content of more than about 300 ppm.

13. The process according to claims 1 to 4, wherein the gravity separator has a cutting point of about 50 micrometers or less.

14. The process according to claims 1 to 4, wherein no ion exchanger is used.

15. The process according to claims 1 to 4, wherein soda ash treatment is not used.

16. A process for producing lithium hydroxide monohydrate, (A) A slurry comprising lithium hydroxide monohydrate and one or more insoluble impurities, the step of supplying the slurry to one or more gravity separators, (B) Using one or more gravity separators, the step of separating the slurry into an underflow slurry and an overflow slurry based on particle size, (C) The steps of supplying the underflow slurry to one or more centrifuges to form separated underflow, and (D) The process comprising the step of dissolving and recrystallizing the separated underflow to reshape the recrystallized underflow.

17. The process according to claim 16, wherein the gravity separator comprises one or more hydrocyclones.

18. The process according to claim 16, wherein the gravity separator includes one or more sedimentation tanks.

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

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

21. The process according to claim 17 or 18, wherein in step (A), the slurry has a lithium hydroxide monohydrate content in the range of about 10% by weight to about 50% by weight, based on the total weight of the slurry.

22. The process according to claim 17 or claim 18, wherein the insoluble impurity comprises one or more calcium-containing compounds, one or more carbonate-containing compounds, or both.

23. The insoluble impurities are CaCO 3 , Ca(OH) 2 , Li 2 CO 3 , CaSO 4 The process according to claim 17 or claim 18, comprising one selected from the group consisting of and any combination of two or more of the foregoing.

24. The process according to claim 17 or claim 18, wherein the slurry is formed by contacting an aqueous solution containing lithium sulfate with sodium hydroxide, and the aqueous solution has a calcium content of more than about 300 ppm.

25. The process according to claim 17, wherein the gravity separator has a cutting point of about 50 micrometers or less.

26. The process according to claim 17, wherein the gravity separator has a cutting point of about 100 micrometers or less.

27. The process according to claim 17, wherein no ion exchanger is used.

28. The process according to claim 17 or claim 27, wherein soda ash treatment is not used.

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