Method and apparatus for producing high purity lithium hydroxide

Abstract

A method for producing battery-grade lithium hydroxide from aqueous solutions feedstocks includes extracting lithium from an aqueous solution with an extractant to form a lithium loaded organic phase, stripping the lithium loaded organic phase to form a stripping solution comprising lithium, processing the stripping solution comprising lithium to form a lithium loaded aqueous solution, and processing the lithium loaded aqueous solution to obtain a battery-grade lithium carbonate. The stripping includes contacting the lithium loaded organic phase with an acid solution or a hydrogen peroxide solution.

Description

METHOD AND APPARATUS FOR PRODUCING HIGH PURITYLITHIUM HYDROXIDEBACKGROUND

[0001] Lithium plays a pivotal role in modem society across multiple industries and applications. It is indispensable in battery technology, powering everything from smartphones to electric vehicles and energy storage systems due to its high energy density and rechargeability. As the world moves towards cleaner and more sustainable energy systems, lithium's versatility and efficiency in energy storage technologies continue to underpin advancements in achieving a low-carbon future.

[0002] Lithium primarily occurs in two main types of sources: brine deposits and hard rock (lithium -bearing minerals). Brine deposits, found predominantly in salt flats or salars, contain concentrated lithium-rich solutions that can be pumped to the surface and processed. These brines often coexist with other salts such as potassium and magnesium. Hard rock lithium deposits, on the other hand, consist of lithium-bearing minerals like spodumene and pegmatites. These minerals are mined from open pits or underground mines and then processed to extract lithium through a series of steps including crushing, grinding, and chemical treatment. Additionally, lithium recovery from secondary sources, such as recycled batteries and other lithium-containing products, is an emerging and increasingly important aspect of the lithium supply chain.

[0003] Lithium is produced into commercial products from the main sources through a complex process that may involve mining, mineral processing, roasting, leaching, solvent extraction, and precipitation. Commercial lithium products encompass a diverse array of materials critical to numerous industries worldwide. Lithium carbonate and lithium hydroxide are pivotal in lithium-ion battery manufacturing, powering electric vehicles and energy storage systems, while lithium metal finds applications in lightweight alloys for aerospace and defense. Lithium chloride serves as a desiccant in air conditioning systems, controlling humidity levels, and various lithium compounds contribute to pharmaceuticals, lubricants, and specialty chemicals. These products collectively support advancements inelectronics, healthcare, aerospace, and environmental sustainability, underlining lithium's indispensable role in modem technology and industry.

[0004] While lithium carbonate historically dominated the lithium market due to its broader use across industries, the shift towards lithium hydroxide in battery manufacturing, particularly for EVs and energy storage, indicates a rising market share for lithium hydroxide in recent years. This is mainly driven by its crucial role in the production of high- nickel content lithium-ion batteries. These batteries are preferred for electric vehicles (EVs) due to their higher energy density and performance characteristics.

[0005] During lithium hydroxide production from hard rocks, a low-concentration lithium sulfate solution is normally obtained first from the hard rocks by mineral processing, roasting, and leaching. The low-concentration solution is then concentrated by evaporation to enhance the lithium concentration. Afterwards, lithium hydroxide is produced from the solution by adding a base. One of the major disadvantages of this process is the high energy consumption associated with concentration step. Lithium hydroxide production can also start from lithium chloride, typically using electrochemical methods. Lithium concentration in the lithium chloride solution may also be low; thus, this process also requires concentration to increase lithium concentration. Therefore, energy consumption and operating costs of these conventional lithium hydroxide production processes are extremely high, failing to ensure a safe supply of affordable lithium hydroxide to support energy transition.

[0006] Overall, there remains a need for innovative technologies to efficiently concentrate and purify lithium from aqueous solutions, especially those with low lithium concentrations, and to produce battery-grade lithium hydroxide.SUMMARY

[0007] In accordance with the purpose(s) of the disclosure, as embodied and broadly described herein, the disclosure relates to two processing routes for producing battery-grade lithium hydroxide from lithium -containing solutions. These processes utilize solvent extraction and downstream processing techniques to enhance lithium concentration in solution and reduce operational costs associated with lithium hydroxide production.

[0008] A method for producing battery-grade lithium hydroxide from aqueous solutions feedstocks, includes extracting lithium from an aqueous solution with an extractant to form a lithium loaded organic phase, stripping the lithium loaded organic phase to form a stripping solution comprising lithium, wherein the stripping comprises contacting the lithium loaded organic phase with an acid solution or a hydrogen peroxide solution, processing the stripping solution comprising lithium to form a lithium loaded aqueous solution, and processing the lithium loaded aqueous solution to obtain a battery-grade lithium carbonate.

[0009] Other systems, methods, features, and advantages of the present disclosure will be apparent to those skilled in the art upon reviewing the accompanying drawings and detailed descriptions. It is understood that all such additional systems, methods, features, and advantages are encompassed by this disclosure, fall within the scope of the present invention, and are protected by the accompanying claims. Furthermore, all optional and preferred features and modifications described herein can be applied across all aspects of the invention. Moreover, the specific features of dependent claims, as well as optional and preferred features and modifications of the disclosed embodiments, can be combined and interchanged with each other.BRIEF DESCRIPTION OF THE FIGURES

[0010] FIG. 1 is a process flow diagram for lithium hydroxide production from solutions that contain lithium.

[0011] FIG. 2 is another process flow diagram for lithium hydroxide production from solutions that contain lithium.DETAILED DESCRIPTION

[0012] The disclosure is not limited to particular embodiments described, and as such may, of course, vary. The terminology used herein serves the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

[0013] As those having ordinary skill in the art will appreciate, different persons may refer to the same feature by different names. This document does not intend to distinguishbetween features that differ in name but not function. The figures are not necessarily drawn to scale. Certain features here may be shown in somewhat schematic form and some details may not be shown in the interest of clarity and conciseness.

[0014] Those having ordinary skill in the art will appreciate that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0015] While aspects of the present disclosure can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present disclosure can be described and claimed in any statutory class.

[0016] Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of organic chemistry, inorganic chemistry, biology, and the like, which are within the skill of the art. Such techniques are explained fully in the literature.

[0017] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to perform the methods and use the compositions and compounds disclosed and claimed herein. Effects have been made to ensure accuracy with respect to numbers (e.g., amounts, temperatures, etc.), but some errors and deviations should be accounted for.

[0018] Before the embodiments of the present disclosure are described in detail, it is to be understood that, unless otherwise indicated, the present disclosure is not limited to particular materials, reagents, reaction materials, manufacturing processes, dimensions, frequency ranges, applications, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequence, where this is logically possible. It is also possible that the embodiments of the present disclosure can be applied to additional embodiments involving measurements beyond the examples described herein, which are not intended to be limiting. It is furthermore possible that the embodiments of the present disclosure can be combinedor integrated with other measurement techniques beyond the examples described herein, which are not intended to be limiting.

[0019] As used in the discussion and the appended claims, the singular form “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. For example, reference to “a solvent extraction system,” “an oxidizing agent,” or “the black mass material” includes, but is not limited to, two or more such solvent extraction systems, oxidizing agents, or black mass materials, and the like.

[0020] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0021] It should be noted that ratios, temperatures, pH values, and other numerical data can be expressed herein in a range format. It will be further understood that the end points of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It will be also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particularly value in addition to the value itself. For example, if the value “60” is disclosed, then “about 60” is also disclosed. Ranges can be expressed herein as from “about” one particular value, and / or to “about” another value. Similarly, when values are expressed as approximations, by the use of the antecedent “about”, it will be understood that the particular value forms a further aspect. For example, if the value “about 60” is disclosed, then “60” is also disclosed.

[0022] When a range is expressed, a further aspect includes from one particular value and / or to the other particular value. For example, where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g., the phrase “x to y” includes the range from “x” to “y” as well as the ranges greater than “x” and less than “y”. In addition, the phrase “about x to y”, where “x” and “y” are numerical values, includes “about x” to “about y.”

[0023] It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and subrange is explicitly recited. To illustrate, a concentration range of “about 0.1 percent to 0.5percent” should be interpreted to include not only the explicitly recited concentration of about 0.1 percent to about 0.5 percent but also include individual concentrations (e.g., 1 percent, 2 percent, 3 percent, and 4 percent) and the sub-ranges (e.g., 0.5 percent, 1.1 percent, 2.2 percent, 3.3 percent, and 4.4 percent) within the indicated range. The term “about” can include traditional rounding according to significant figures of the numerical value. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to ‘about y’”.

[0024] Furthermore, the terms “about,” “several,” “multiple,” “a number of,” “some,” “at or about,” “substantially,” “mainly,” “primarily,” and “minimal” as used herein mean that the amount or value in question can be the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not to be exact but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art such that equivalent results or effects are obtained. In some circumstance, the value that provides equivalent results or effects cannot be reasonable determined. In such cases, it is generally understood, as used herein, that “about” and “at or about” mean the nominal value indicated ±10% variations unless otherwise indicated or inferred. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about,” “several,” “multiple,” “a number of,” “some,” “at or about,” “substantially,” “mainly,” “primarily,” and “minimal” whether or not expressly stated to be such. It is understood that where “about” or “at or about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0025] In the following discussion and in the claims, the terms “such as”, “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . ..”

[0026] As used herein, “contaminants” or “impurities” refers to undesired materials in the final products. Contaminants and impurities include, but are not limited to aluminum, copper, calcium, magnesium, titanium, silicon, zinc, sulfur, and fluoride.

[0027] As used herein, “undesired constituents” refers to contaminants, including but not limited to lithium, nickel, cobalt, manganese, iron, and phosphorus.

[0028] As used herein, “battery-grade” refers to the purity and other specifications of the products that meet the standards of being used for battery manufacturing.

[0029] As used herein, “solvent extraction” refers to metal separation and concentration by mixing two immiscible phases, typically an aqueous phase and an organic phase. During the mixing process, metal ions transfer from one phase to another.

[0030] As used herein, “aqueous phase” refers to the phase with higher density during the solvent extraction process. It is used interchangeably with “aqueous solution” and “solution” in this disclosure.

[0031] As used herein, “organic phase” refers to the phase with lower density during the solvent extraction process.

[0032] As used herein, “loaded organic phase” refers to an organic phase containing metal ions.

[0033] As used herein, “extractant” refers to the active organic compounds present in the organic phase that can selectively interact with selected types of metal ions.

[0034] As used herein, “diluent” refers to the organic chemicals used to dissolve the extractant.

[0035] As used herein, “scrubbing” refers to the removal of undesired constituents from a loaded organic phase by mixing with an appropriate aqueous solution.

[0036] As used herein, “stripping” refers to the removal of target valuables from the organic phase.

[0037] As used herein, “oil” or “organic compounds” refers to the chemicals present in the organic phase.

[0038] As used herein, “relatively pure water” refers to water with low concentrations of undesired impurities.

[0039] As used herein, “suspension” refers to a mixture of a liquid with solid particles dispersed within it.

[0040] The invention includes two processes for producing battery-grade lithium hydroxide. These processes include extracting lithium from a lithium -containing solution using solvent extraction to obtain a relatively pure solution of lithium salt, causticizing the solution by adding a base to convert the solution into a mixed solution containing lithium hydroxide and a secondary salt, which is then frozen in a gradient mode to precipitate the secondary salt from the solution, concentrating the solution to precipitate lithium hydroxide, and further purifying the resulting product to enhance its purity.

[0041] Referring to FIG. 1, a process flow diagram in accordance with embodiments disclosed herein. This process may be used to produce battery-grade lithium hydroxide from a lithium-containing solution.

[0042] Embodiments disclosed herein are directed to a process that can be used to extract and purify lithium hydroxide from a solution that contains lithium, with the production of battery-grade lithium hydroxide through simple steps.

[0043] The solution that contains lithium is referred to as an aqueous phase (A) 100 in the process flow diagram FIG. 1. Those having ordinary skill in the art will appreciate that the lithium solution may originate from different sources, such as leachates of primary and secondary sources (e.g., spodumene, clays, lithium-ion batteries, ceramics glass), natural liquid lithium sources (e.g., salt lake brines, geotherm brines, produced water, acid mine drainage), wastewater (e.g., industrial wastewater, municipal waste water), combinations of these sources, and lithium-containing streams from lithium recovery processes.

[0044] The aqueous phase (A) 100 may first undergo a pretreatment step 102 to remove undesired constituents for downstream processing. The specific undesired constituents may depend on a number of factors, such as the operating parameters and flowsheet design of the downstream processing. The undesired constituents may typically include, but are not limited to, iron, aluminum, copper, calcium, magnesium, and titanium. The undesired constituents may be removed through a single method or a combination of different methods. The methods that may be used include, but are not limited to, selective precipitation by adding a precipitant or adjusting the redox potential of the solution, selective adsorption by reacting with an efficient adsorbent, solvent extraction using extractants showing high affinity towards the undesired constituents.

[0045] An organic phase (O) 104 may be prepared by mixing a diluent and an extractant. The diluent serves as a solvent for the extractant and may include, but is not limited to, kerosene, n-hexane, and heptane. The extractant exhibits a higher affinity for lithium ions compared to contaminants. Those having ordinary skill in the art will appreciate that different types of extractant are available for the extraction of lithium, which can be classified into acidic extractants (e.g., di-(2-ethylhexyl) phosphoric acid (D2EHPA)), neutral extractants (e.g., tri-n-butyl phosphate (TBP)), amines and quaternary ammonium compounds (e.g., tricaprylmethylammonium chloride (Aliquat 336)), ionic liquids, and synergistic solvent extraction systems. Those having ordinary skill in the art will also appreciate that in addition to the diluent and extractant, some other chemicals, such as phase modifiers, stabilizers, surfactants, and / or anti-foaming agents, may be added to the organic phase to enhance its performance of lithium extraction.

[0046] The organic phase 104 may require pretreatment 106 to make its suitability for lithium extraction, with the specific pretreatment method depending on the extractant utilized. For instance, when an acidic extractant is used, the organic phase may react with a sodium hydroxide (NaOH) or an ammonia solution to neutralize the extractant. During the reaction process, hydrogen ions (H+) in the acidic functional groups of the extractant are replaced with sodium ions (Na+). Na+in the neutralized extractant are more easily replaced by lithium ions (Li+) than H+. Consequently, Li+in the aqueous phase can be more easily extracted into the organic phase.

[0047] Following the pretreatment of both the aqueous phase 102 and the organic phase 106, they are combined in a reactor to facilitate the extraction 108 of lithium ions from the aqueous phase into the organic phase. To achieve the desired purity and extraction efficiency, the extraction process may involve multiple extraction stages, and the extraction flowsheet may be configured in various ways, such as counter-current, co-current, and a combination of both. Those having ordinary skill in the art will appreciate that different types of reactors, such as mixer-settlers and centrifugal extractors, can be utilized for this step. After extraction, an organic phase loaded with lithium and possibly some impurities, as well as an aqueous phase depleted in lithium, are obtained. The aqueous phase depleted in lithium is referred to as raffinate 110 in the process flow diagram shown in FIG. 1.

[0048] The loaded organic phase obtained from the extraction step 108 may contain some impurities, such as sodium and / or potassium ions. These impurities may report to the final lithium carbonate product, reducing its quality. Consequently, the loaded organic phase may undergo a scrubbing step 112 to eliminate these undesired constituents. In this step, an aqueous solution 114, such as deionized water, a weak acid solution, or a weak base solution, is mixed with the loaded organic phase in a reactor. To achieve the desired purity and scrubbing efficiency, the scrubbing process may involve multiple scrubbing stages, and the scrubbing flowsheet may be configured in various ways, such as counter-current, cocurrent, and a combination of both. Those having ordinary skill in the art will appreciate that different types of reactors, such as mixer-settlers and centrifugal extractors, can be utilized for this step. Those having ordinary skill in the art will also appreciate that the scrubbing step is optional and is contingent upon the concentration and type of impurities present in the loaded organic phase. After scrubbing, a scrubbing solution 116 and an organic phase loaded with lithium but containing minimal impurities may be obtained. The loaded organic phase will be further processed as discussed next.

[0049] The loaded organic phase may be directed to a stripping step 118 to transfer the lithium in the organic phase to an aqueous solution. In this step, an acid solution 120, which includes, but is not limited to, H2SO4, HC1, HNO3, H3PO4, and / or organic acids, is mixed with the organic phase after scrubbing 112 and / or extraction 108 in a reactor. To achieve the desired stripping efficiency, the stripping process may involve multiple stripping stages, and the stripping flowsheet may be configured in various ways, such as counter-current, co-current, and a combination of both. Those having ordinary skill in the art will appreciate that different types of reactors, such as mixer-settlers and centrifugal extractors, can be utilized for this step. After stripping, a regenerated organic phase 122 and a stripping solution 124 containing lithium with minimal impurities may be obtained. The regenerated organic phase may be reused for the solvent extraction, while the stripping solution will be further processed as discussed next.

[0050] Embodiments disclosed herein are directed to a process for producing battery-grade lithium hydroxide from the stripping solution 124. The solution primarily contains lithium and some remaining acid.

[0051] The stripping solution may undergo a causticization / neutralization step 126 to neutralize the remaining acid and introduce a substantial quantity of hydroxide ions into the solution. In the neutralization step, a base 128, such as sodium hydroxide, ammonia, or calcium hydroxide / oxide, is added to the solution in a stirred reactor. The preferred solid to liquid ratio, temperature, and reaction duration range from about 1 :2 to about 1 :20, about 40 °C to about 90 °C, and about 1 minute to about 24 hours, respectively. This process facilitates the formation of dissolved lithium hydroxide species as lithium ions complex with hydroxide ions. In the meantime, the cations introduced with the base complex with the anions of the acid added during stripping 118. For instance, if H2SO4 and NaOH are used in the stripping step and the neutralization step, respectively, a lot of sodium in the solution may complex with sulfate, forming dissolved sodium sulfate species in the solution.

[0052] After neutralization, the solution may undergo gradient freezing 130 to precipitate the cations introduced with the base during neutralization 126 and the anions introduced with the acid during stripping 118 as salts, thereby leaving lithium and hydroxide ions in the solution. The gradient freezing step leverages temperature-dependent differences in the solubility patterns of chemical compounds. Compared with the impurities in the solution, lithium hydroxide remains more stable and dissolved in the solution when a significant temperature drop occurs. Thus, the methods described herein may include performing gradient freezing where the temperature of the solution undergoes step-wise temperature drops to exploit the differences in solubility between the impurities and the lithium hydroxide. A total temperature drop of the solution by about 20 °C to about 100 °C is preferred for the gradient freezing step. As a non-limiting example, gradient freezing may include several freezing steps, such as a primary freezing step by reducing the temperature of the solution to 10-20°C, medium freezing (to ~0°C), and deep freezing (to -5°C to -9°C). Thus, the gradient freezing may include one or more freezing steps that include reducing the temperature of the solution by 20°C to 100°C.

[0053] After gradient freezing, the resulting suspension is subjected to solid / liquid separation to eliminate precipitated salt impurities form the solution. Any solid / liquid separation methods, such as filter press, vacuum filter, and / or belt filter, may be used for this step. The solid after the separation may be referred to as filter cake, precipitates, orsimply solid, as discussed in the following discussion and in the claims. The fdter cake may be washed several times using relatively pure water to reduce the loss of lithium associated with the liquid entrapped within solid particles in the fdter cake. The solution after solid / liquid separation may be further process as discussed next.

[0054] After gradient freezing and solid / liquid separation, the solution is directed to a concentration step 132. This step aims to precipitate lithium hydroxide by concentrating lithium through the removal of water via evaporation. As water is removed, the lithium concentration in the solution increases, causing lithium hydroxide to precipitate. Mechanical vapor recompression is preferred in this step. Those having ordinary skill in the art will appreciate other evaporation methods, such as thermal vapor recompression, vacuum evaporation, rotary evaporation, and / or flash evaporation, can also be utilized in this step to precipitate lithium hydroxide from the solution. Once the concentration of lithium in the solution reduces to a certain level, the resulting suspension will be subjected to solid / liquid separation to separate the solid from the liquid. Any solid / liquid separation methods, such as filter press, vacuum filter, and / or belt filter, may be used for this step. The filter cake may be washed several times using relatively pure water to eliminate impurities associated with the liquid entrapped within solid particles in the filter cake. The solution after filtration may be recirculated to gradient freezing or previous steps.

[0055] After concentration, the resulting lithium hydroxide precipitate may undergo a further purification step 134 to enhance its purity level. In this step, the precipitate may be redissolved in a trace metal grade acid, such as H2SO4, HC1, HNO4, and / or H3PO4. The resulting solution may be re-processed through neutralization 126, gradient freezing & solid / liquid separation 130, and concentration 132 steps sequentially. After purification, a battery-grade lithium hydroxide product 136 is obtained.

[0056] Referring to FIG. 2, another process flow diagram in accordance with embodiments disclosed herein is shown. This process may be used to produce battery-grade lithium hydroxide from a lithium-containing solution.

[0057] Embodiments disclosed herein are directed to another process that can be used to extract and purify lithium from a solution that contains lithium, with the production of battery-grade lithium hydroxide through simple steps.

[0058] As shown in FIG. 2, the first part of the flow diagram is the same as that presented in FIG. 1. An aqueous solution 200 that contains lithium undergoes a pretreatment step 202 to remove impurities that will interfere with downstream processing. An organic phase 204 undergoes a pretreatment step 206 to enhance its capacity to extract target metals. After pretreatment, the aqueous solution and the organic phase are mixed in an extraction step 208 to transfer lithium from the former to the latter. After that, the organic phase loaded with lithium and some contaminants is subjected to scrubbing 212 using an aqueous solution 214 to eliminate contaminants from the organic phase, leading to a scrubbing solution 216. The organic phase after scrubbing is directed to a stripping step 218 to transfer lithium into a stripping solution 224, along with the production of a regenerated organic phase 222. Unlike the flow diagram shown in FIG. 1, the flow diagram of FIG. 2 uses hydrogen peroxide as the aqueous solution used for the stripping step.

[0059] Embodiments disclosed herein are directed to a method that uses hydrogen peroxide or other similar chemicals, which will not bring any contaminants, for stripping lithium from the organic phase. Embodiments disclosed herein are also directed to a process for producing lithium hydroxide from the stripping solution.

[0060] As shown in FIG. 2, the stripping solution first undergoes a de-oiling & decontamination step 226 to remove oil and potential impurities. Those having ordinarily skill in the art will appreciate that various methods for oil removal can be used for this step, such as coalescence, adsorption, electrocoagulation, and / or physical separation. Those having ordinary skill in the art will also appreciate that various methods for impurity removal can be used for this step, such as selective precipitation, selective adsorption, and / or membranebased technologies.

[0061] After de-oiling and de-contamination, the solution is further processed through the concentration step 228. This step aims to precipitate lithium hydroxide by concentrating lithium through the removal of water via evaporation. As water is removed, the lithium concentration in the solution increases, causing lithium hydroxide to precipitate. Mechanical vapor recompression is preferred in this step. Those having ordinary skill in the art will appreciate other evaporation methods, such as thermal vapor recompression, vacuum evaporation, rotary evaporation, and / or flash evaporation, can also be utilized in this step to precipitate lithium hydroxide from the solution. Once the concentration oflithium in the solution reduces to a certain level, the resulting suspension will be subjected to solid / liquid separation to separate the solid from the liquid. Any solid / liquid separation methods, such as filter press, vacuum filter, and / or belt filter, may be used for this step. The filter cake may be washed several times using relatively pure water to eliminate impurities associated with the liquid entrapped within solid particles in the filter cake. The solution after filtration may be recirculated to gradient freezing or previous steps.

[0062] After concentration, the resulting lithium hydroxide precipitate may undergo a further purification step 230 to enhance its purity level. In this step, the precipitate may be redissolved in a trace metal grade acid, such as H2SO4, HC1, HN04, and / or H3PO4. The resulting solution may be re-processed through de-oiling & de-contamination 226 and concentration 228 steps. After purification, a battery-grade lithium hydroxide product 232 is obtained.

[0063] In some aspects, the techniques described herein relate to a process for producing lithium hydroxide from a lithium containing aqueous solutions feedstocks, including: pretreating a lithium containing aqueous solution to remove undesired impurities for downstream processing; pretreating an organic phase to improve its efficiency in lithium extraction; extracting lithium from the pretreated aqueous solution to the pretreated organic phase by mixing the two phases, resulting in a lithium-loaded organic phase; scrubbing the lithium-loaded organic phase to remove co-extracted contaminants, yielding a high-purity lithium -loaded organic phase; stripping the lithium -loaded organic phase with an acid solution, leading to a stripping solution rich in lithium; causticizing the stripping solution by adding a base to introduce a substantial quantity of hydroxide ions into the solution; freeze the solution and precipitate the secondary salt, and solid / liquid separation to remove the secondary salts from the solution; concentrating the solution by evaporation to precipitate lithium hydroxide from the solution as lithium hydroxide; subjecting to further purification to purify the lithium hydroxide to achieve battery-grade quality by redissolving the crude lithium hydroxide and precipitate the purified lithium hydroxide .

[0064] In some aspects, the techniques described herein relate to a method, wherein the aqueous solution may come from different sources, which include, but is not limited to leachates of primary and secondary sources, natural liquid lithium sources, wastewater, and lithium-containing streams from lithium recovery processes.

[0065] In some aspects, the techniques described herein relate to a method, wherein various methods, such as selective precipitation, pH adjustment, selective adsorption, and solvent extraction, may be used individually or in combination to remove undesired contaminants from the aqueous solution.

[0066] In some aspects, the techniques described herein relate to a method, wherein the organic phase may be pretreated by reacting with acids or bases.

[0067] In some aspects, the techniques described herein relate to a method, wherein mixing of the aqueous solution and the organic phase can occur in various stages, which may be configured in various ways, such as counter-current, co-current, and a combination of both.

[0068] In some aspects, the techniques described herein relate to a method, wherein the use of scrubbing to remove co-extracted contaminants from the lithium-loaded organic phase is optional.

[0069] In some aspects, the techniques described herein relate to a method, wherein the acid solution used for stripping includes, but is not limited to, H2SO4, HC1, HN03, and H3PO4.

[0070] In some aspects, the techniques described herein relate to a method, wherein the based used for neutralizationincludes, but is not limited to, NaOH, ammonia, CaO, and Ca(OH)2.

[0071] In some aspects, the techniques described herein relate to a method, wherein the preferred temperature change for gradient freezing starts from 20 °C to 100 °C.

[0072] In some aspects, the techniques described herein relate to a method, wherein the preferred concentration method is mechanical vapor recompression.

[0073] In some aspects, the techniques described herein relate to a method, wherein the further purification step involves re-dissolving the solid product and re-subjecting to previous steps, such as neutralization, gradient freezing & solid / liquid separation, and / or concentration.

[0074] In some aspects, the techniques described herein relate to a process of producing lithium hydroxide from an organic phase loaded with lithium, including: stripping lithium from the organic phase with a chemical that does not introduce impurities to the resultingaqueous solution; de-oiling and de -contamination to remove oil and impurities from the aqueous solution; concentrating the aqueous solution to precipitate lithium hydroxide from it; subjecting to further purification for improving the lithium hydroxide to battery-grade quality.

[0075] In some aspects, the techniques described herein relate to a method, wherein the chemical used for the stripping step includes, but is not limited to, hydrogen peroxide.

[0076] In some aspects, the techniques described herein relate to a method, wherein the method used for the de-oiling step includes, but is not limited to, selective adsorption, coalescence, and electrocoagulation.

[0077] In some aspects, the techniques described herein relate to a method, wherein the method used for de -contamination step includes, but is not limited to, selective precipitation, selective adsorption, and membrane-based technologies.

[0078] In some aspects, the techniques described herein relate to a method and 15, wherein a combination of different methods may be used to achieve the desired de-oiling and decontamination efficiency.

[0079] In some aspects, the techniques described herein relate to a method, wherein the preferred concentration method is mechanical vapor recompression.

Claims

CLAIMSWhat is claimed is:

1. A method for producing battery-grade lithium hydroxide from aqueous solutions feedstocks, comprising: extracting lithium from an aqueous solution with an extractant to form a lithium loaded organic phase; stripping the lithium loaded organic phase to form a stripping solution comprising lithium, wherein the stripping comprises contacting the lithium loaded organic phase with an acid solution or a hydrogen peroxide solution; processing the stripping solution comprising lithium to form a lithium loaded aqueous solution; and processing the lithium loaded aqueous solution to obtain a battery-grade lithium carbonate.

2. The method of claim 1, wherein processing the stripping solution comprising lithium comprises: de -oiling the stripping solution comprising lithium; or neutralizing the stripping solution comprising lithium with a base.

3. The method of claim 1 or 2, wherein before extracting lithium from an aqueous solution, the method further comprises: pretreating the aqueous solution to remove impurities; and pretreating the extractant to improve efficiency lithium extraction efficiency.

4. The method of any one of the preceding claims, wherein the extracting the lithium to form the lithium loaded organic phase comprises: mixing the aqueous solution with the organic phase; and scrubbing the loaded organic phase from mixing the aqueous solution with the organic phase, with a scrubbing solution to remove co-extracted contaminants.

5. The method of claim 2, further comprising, after neutralizing the stripping solution: gradient freezing a solution formed from neutralizing the stripping solution to precipitate salts.

6. The method of claim 5, wherein the gradient freezing comprises step-wise reductions in a temperature of the solution formed from neutralizing the stripping solution by a total of 20°C to 100°C.

7. The method of any one of the preceding claims, wherein the aqueous solution is derived from at least one of leachates of primary and secondary sources, natural liquid lithium sources, wastewater, and lithium-containing streams from lithium recovery.

8. The method of any one of the preceding claims, wherein the extracting lithium from an aqueous solution occurs in various stages, and comprises counter-current flows, cocurrent flows, or a combination of both.

9. The method of any one of the preceding claims, wherein the processing the lithium loaded aqueous solution comprises: concentrating the lithium loaded aqueous solution to form a suspension comprising lithium hydroxide and a fdtrate, dissolving the lithium hydroxide with a trace metal grade acid to form a lithium hydroxide solution; and sequentially processing the lithium hydroxide solution.

10. The method of claim 9, wherein the trace metal grade acid is selected from the group consisting of H2SO4, HC1, HNO4, H3PO4 and combinations thereof.

11. The method of claim 9 or 10, wherein sequentially reprocessing comprises: gradient freezing the lithium hydroxide solution, neutralizing the lithium hydroxide solution, filtering the lithium hydroxide solution, or combinations thereof.

12. The method of any one of the preceding claims, wherein the base is added at a solid to liquid ratio of 1 :2 to 1 :20.

13. The method of any one of the preceding claims, wherein the neutralizing the stripping solution occurs at a temperature ranging from 40°C to 90°C.

14. The method of any one of the preceding claims, wherein the neutralizing the stripping solution occurs for a time ranging from 1 minute to 24 hours.

5. The method of any one of the preceding claims, wherein de-oiling the stripping solution comprises coalescence, adsorption, electrocoagulation, physical separation or combinations thereof.

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