Process for recovering lithium values from lithium-containing brines

Abstract

Producing a high purity lithium solution from a source brine containing at least 1 mg Li / kg of the brine, preferably 10 mg / kg, more preferably 25 mg Li / kg of the brine; if necessary, treating the source brine in a pre-treatment step; processing the treated brine in a lithium adsorption step; after the adsorption step, desorbing the adsorbed lithium in a desorption step; after the desorption step, processing the desorption effluent in an enrichment step. Designated optional steps and novel features can be used to increase lithium concentration and purity.

Description

Related applications

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 622,620, filed January 19, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to a new, economical, and practical method for recovering lithium from lithium-containing brines to obtain high-purity and high-yield water-soluble lithium salts, such as LiCl or Li2CO3, as well as other valuable minerals or elements. Background Technology

[0003] As is well known, there has been a growing demand in recent years for more economical and efficient technologies to produce high-purity lithium or its salts from suitable sources. This is reflected in the increased research activity on this subject. Furthermore, no publicly available technology appears to meet this need. This particular method is applicable to brine fields contaminated with organic pollutants (such as oil and gas and other hydrocarbons) and inorganic pollutants (such as H2S, FeS, Fe salts). Summary of the Invention

[0004] This invention describes several embodiments of the currently disclosed subject matter, and in many cases, variations and arrangements of these embodiments. This invention is merely exemplary for the numerous and different embodiments. References to one or more representative features of the given embodiments are also exemplary. Such embodiments may generally have or not have one or more of the mentioned features; similarly, those features can be applied to other embodiments of the currently disclosed subject matter, whether or not they are listed in this invention. To avoid excessive repetition, this invention does not list or propose all possible combinations of such features.

[0005] This invention utilizes a specific combination of separation techniques that can meet the need for more efficient and economical methods for recovering lithium from various brine sources. Based on the results presented below, it is reasonable to propose that such combinations and sequences of separation techniques will produce aqueous solutions of high-purity and high-yield lithium salts (such as lithium chloride) in an economical and practical manner.

[0006] The above methods are typically used in conjunction with initial lithium-containing brine containing preferably at least 100 ppm, but also including 50 ppm to 100 ppm or less, preferably 30 ppm to 50 ppm, of dissolved lithium. However, there are cases where one or more optional additional steps can be used according to the invention. Another preferred embodiment of the multi-step method of the invention is that the dissolved lithium source is derived from natural or industrial brine with a lithium concentration of at least about 100 ppm, preferably greater than about 180 ppm, and is concentrated with sodium salt, which enhances lithium recovery during the adsorption operation.

[0007] A preferred embodiment of this method involves first treating a lithium-containing brine to adjust its properties for further processing. For example, the pH, temperature, or density of the brine may need to be adjusted. In a preferred embodiment, the brine introduced into the next step should have a temperature below the bubble point of the solution at operating pressure. For an atmospheric system that may be about 110°C, preferably less than about 90°C, and more preferably less than about 82°C, it should have a TDS / Li ratio of less than about 5000 (e.g., but not limited to 25% salt and 50 ppm Li or better, or 10% salt and 20 ppm Li or better, or 1% salt and 2 ppm Li or better).

[0008] Next, the brine is introduced into the lithium adsorption step. In the highly preferred multi-step method of the present invention, the lithium adsorption step is carried out by introducing and removing the lithium-containing brine into the adsorbent bed (preferably placed in a column or other suitable contact container) at a brine temperature of 40°C-110°C, preferably 50°C-90°C, until lithium penetrates into the effluent from the bed. However, any suitable adsorbent, such as those described in CN111215040B, CN102631897 B, or US Patent No. 10,648,061, can be used in this novel method.

[0009] The brine is then subjected to a desorption process. The lithium desorption step of the preferred multi-step method of the present invention is performed by washing the adsorbent with water or other aqueous solution, preferably a diluted lithium chloride or other lithium salt solution (preferably containing 50 ppm-300 ppm Li), at a temperature of 40°C-100°C or even higher under increased pressure, preferably greater than 50°C, and more preferably greater than 60°C.

[0010] Another preferred embodiment of the multi-step method of the present invention is that the lithium eluent solution contains at least Ca2+ and / or Mg2+ impurities in the solution, and the weight ratio of dissolved Li+:Ca2+ and / or Li+:Mg2+ is enriched by at least 5 times, preferably at least 10 times, and more preferably 100 times. For example, if the brine has a starting point of 150 Ca:Li, the method increases this ratio to less than 30:1, preferably less than 15:1 Ca:Li, and more preferably 1.5:1. In another further preferred embodiment, the Ca:Li ratio can be further increased from the initial 150:1 to 0.6:1. By optimizing the embodiments, separation ratios can be achieved during the desorption process. For example, in a Ca:Li ratio of 0.6:1, multiple fractions can be obtained with different purity ratios (e.g., Ca:Li ratios of 2.5, 0.6, and 0.03).

[0011] Following desorption, brine is then prepared for the enrichment process. Further treatment of the brine may be necessary prior to the enrichment process. Specifically, impurities such as oils and greases, free halogens, and / or other free solids and impurities may need to be removed. Typically, the enrichment process should produce a sufficiently concentrated and purified LiCl solution of sufficient quality for further processing into lithium metal, LiOH, LiCl, Li₂CO₃, or other valuable lithium minerals. For example, in a preferred embodiment of Li₂CO₃, the desorption effluent should have a lithium concentration of 0.25% to 5%, preferably 0.5% to 3.5%, and more preferably 0.8% to 1.25%. For a preferred embodiment of LiCl production, the desorption effluent should have a lithium concentration of 1% to 13%, preferably 2% to 12%, and more preferably 4% to 8%, as well as suitable concentrations of contaminants such as boron, calcium, magnesium, and sodium. Suitable ratios of boron are lithium:boron greater than 500:1 or 2000:1 by mass, preferably greater than 5000:1 or 20000:1, and more preferably greater than 8000:1 or 40000:1. Suitable ratios of calcium are lithium:calcium greater than 50:1 or 200:1 by mass, preferably greater than 100:1 or 400:1, or more preferably greater than 160:1 or 800:1. Similarly, suitable ratios of magnesium are lithium:magnesium greater than 108:1 or 434:1 by mass, preferably greater than 217:1 or 869:1, or more preferably greater than 347:1 or 1739:1. Suitable strontium or other divalent content will follow the stated calcium or magnesium scheme, which is corrected for the mass difference of a divalent cation relative to calcium or magnesium. Suitable sodium ratios are less than 20:1 or 5:1 by mass, preferably 10:1 or 2.5:1, or more preferably less than 6.25:1 or 1.25:1. Suitable potassium or other monovalent content will follow the stated sodium scheme, which is corrected for the mass difference of a monovalent cation relative to sodium.

[0012] In one embodiment of the enrichment process, enrichment may include one or more of the following steps: nanofiltration, membrane distillation, reverse osmosis, cation and / or anion exchange resin purification, electrodialysis forward osmosis, osmosis-assisted reverse osmosis (OARO), ultrafiltration, chemical precipitation, evaporation or cooling crystallization or precipitation, solvent extraction and / or evaporation techniques. Each step may be performed in any order and may be repeated as needed to obtain a suitable brine effluent.

[0013] Finally, the lithium-rich brine effluent is processed into the final product. Typically, the final product of these lithium solutions is lithium metal, lithium sulfide, lithium phosphate, LiOH, LiBr, Li₂SO₄, LiCl, or Li₂CO₃. These steps can be performed using those known to those skilled in the art. As a result of the above process, preferably at least 25% or more, more preferably about 80% or more, or still more preferably about 90% or more of the lithium is extracted from the lithium source into the adsorbent. Complete recovery can occur during multiple passes of the process.

[0014] The above steps constitute the basic process of the proposed invention. A feature of this invention is the ability to customize the process, thereby further expanding the range of usable brine and generating additional economic benefits. A first optional additional process is a pretreatment step. Some brines (such as those from Smackover and oil fields) are frequently contaminated with materials unsuitable for lithium extraction. For example, the brine may contain hydrocarbons, solids, and H2S. Therefore, in another embodiment, a pretreatment step is performed on the initial brine, in which impurities are removed.

[0015] In another embodiment, the brine may contain additional economically beneficial materials. These materials include bromine and elemental sulfur, sulfur compounds, iodine, boron, and / or cesium, etc. Therefore, one embodiment of the invention is to provide a step for removing these additional economically beneficial materials. This step can be performed anywhere in the process, but is preferably performed before or after lithium removal. This step can be accomplished by any method known in the art.

[0016] In another embodiment, a recycling step can be added to the process. These recycling steps improve the overall lithium recovery rate and control the amount of liquid required for lithium removal performance, and help to achieve a net zero increase in the hydraulic pressure rate injected into the brine source formation. These and other steps will be discussed in detail below.

[0017] Therefore, in the multi-step process of carrying out the present invention, the performance of one or more additional steps other than those described herein falls within the scope of the claims of the present invention.

[0018] The above and other embodiments, objects, features and advantages of the invention will become more apparent from the following description, the appended claims and drawings. Attached Figure Description

[0019] The subject matter of this disclosure can be better understood by referring to the following exemplary figures. The components in the figures are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the subject matter (generally schematic). In the figures, the same reference numerals denote corresponding parts in different views. A further understanding of the subject matter of this disclosure can be obtained by referring to the embodiments illustrated in the figures. Although the illustrated embodiments are merely examples for the purpose of demonstrating systems for implementing the subject matter of this disclosure, the organization and operation of the subject matter of this disclosure, as well as its further purposes and advantages, can generally be more readily understood by referring to the figures and the following description. The figures are not intended to limit the scope of the subject matter of this disclosure, which is specifically set forth in the appended or subsequently amended claims, but are merely for illustrating and providing examples of the subject matter of this disclosure.

[0020] Figure 1 This is a general representation of the method of the present invention. Detailed Implementation

[0021] definition The terminology used herein is for the purpose of describing a particular implementation and is not intended to limit the subject matter currently disclosed.

[0022] While the following terms are considered to be well understood by one of ordinary skill in the art, the following definitions are set forth in order to explain the subject matter currently disclosed.

[0023] Unless otherwise defined below, all technical and scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art. References to techniques used herein are intended to refer to techniques commonly understood in the art, including variations or equivalents of those techniques that would be obvious to one of ordinary skill in the art. While the following terms are considered well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate the interpretation of the subject matter currently disclosed.

[0024] Any component mentioned anywhere in this specification or its claims by chemical name or formula (whether in the singular or plural) is confirmed to be present prior to contact with another substance (e.g., another component, solvent, etc.) mentioned by chemical name or chemical type. What kind of chemical change, transformation, and / or reaction (if any) occurs in the resulting mixture or solution is not important, as such change, transformation, and / or reaction is a natural result of bringing the specified components together under the conditions required by this disclosure. Therefore, a component is identified as an element aggregated together in conjunction with the desired operation or the formation of the desired composition. Furthermore, even though the claims below may refer to substances, components, and / or ingredients in the present tense (“comprising,” “is,” etc.), such substances, components, or ingredients are referred to as existing prior to their first contact, blending, or mixing with one or more other substances, components, and / or ingredients according to this disclosure. Therefore, the fact that a substance, component, or ingredient may lose its original properties during the contact, blending, or mixing process through chemical reaction or transformation is not of practical significance if carried out according to the contents of this disclosure and the ordinary skills of a chemist.

[0025] In describing the currently disclosed subject matter, it should be understood that many techniques and steps are disclosed. Each of these has its own individual benefits, and each can also be used in combination with one or more of the other disclosed techniques, or in some cases all of them.

[0026] Therefore, for clarity, this specification will avoid unnecessarily repeating every possible combination of the steps. However, the specification and claims should be read with the understanding that such combinations are fully within the scope of the invention and the claims.

[0027] According to long-standing patent law practice, when used in this application (including the claims), the terms "a" and "the" mean "a" or "a plurality of". Thus, for example, reference to "a cell" includes a plurality of such cells, and so on.

[0028] Unless otherwise stated, all figures used in the specification and claims to indicate the amount of ingredients, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in this specification and the appended claims are approximate values ​​that may vary depending on the desired properties sought to be obtained from the subject matter currently disclosed.

[0029] As used herein, the term “about” when referring to a value or amount of composition, dosage, mass, weight, temperature, time, volume, concentration, percentage, etc., is intended to cover variations from the specified amount by ±20% in some embodiments, ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, ±0.5% in some embodiments, and ±0.1% in some embodiments, because such variations are suitable for carrying out the disclosed methods or using the disclosed compositions.

[0030] The term "comprising," synonymous with "including," "containing," or "characterized in," is inclusive or open-ended and does not exclude additional, unlisted elements or method steps. "Comprising" is a technical term used in claims language, meaning that the specified element is essential, but other elements may be added and still form the concept within the scope of the claims.

[0031] As used herein, the phrase “consisting of” excludes any element, step, or component not specified in the claims. When the phrase “consisting of” appears in a clause of the body of the claims, rather than immediately following the preamble, it limits only the element set forth in that clause; it does not exclude other elements in the claims as a whole.

[0032] As used herein, the phrase “consistent essentially of” limits the scope of the claim to the specified material or step, plus those material or steps that do not substantially affect the essential and novel features of the claimed subject matter.

[0033] Regarding the terms “comprising,” “consisting of,” and “substantially composed of,” when one of these three terms is used herein, the currently disclosed and claimed subject matter may include the use of either of the other two terms.

[0034] As used herein, when used in the context of an entity list, the term "and / or" refers to entities that exist individually or in combination. Thus, for example, the phrase "A, B, C and / or D" includes A, B, C, and D individually, but also any and all combinations and subcombinations of A, B, C, and D.

[0035] As used herein, when used in conjunction with solutions or brine, the term "concentrated" is intended to include saturated solutions or brine.

[0036] General Procedure refer to Figure 1The general procedure is as follows: Remove the brine from its source (such as Smackover, oil fields, or other sources of lithium-rich brine). If necessary, send the brine to one or more pretreatment stages. Potential pretreatment stages include the removal of large amounts of oil using any number of commercially available technologies, including at least any combination of the following: oil / phase separators, hydrocyclones, inclined plate coalescers, coarse coalescers, induced gas flotation (IGF) units, deoiling cartridge filters, organoclay products, macroporous polymer extraction technologies, crushed nut shell filters, acid stripping followed by gravity settling, electrocoagulation, light oil stripping towers, and H2S stripping towers, as known in the art. After pretreatment, in some embodiments, the brine may be sent to a processing unit to remove additional valuable materials. However, this step can occur anywhere in the process, such as after lithium removal.

[0037] Once the brine is ready for lithium removal, it can be sent to a cooling tower for temperature and temperature, density, and concentration conditioning. For example, Smackover's brine solution emerges from the ground at excessively high temperatures. In some embodiments, the brine solution temperature will be reduced to less than about 80°C to less than about 110°C, optionally, the temperature will need to be reduced to less than about 105°C, preferably less than about 90°C, and more preferably less than about 82°C. The brine is then processed in lithium adsorption and desorption steps. Once lithium has been adsorbed and desorbed, the desorbed brine effluent is sent to an enrichment processing step.

[0038] Following the enrichment step, a lithium-rich brine effluent is prepared for production and conversion into the final product.

[0039] Initial brine adjustment Preferably, the brine received for processing has or is adjusted to have (i) a pH value in the range of about pH 3 to about pH 9, preferably about pH 3.5 to about pH 8, and more preferably about pH 4.0 to about pH 7.5, (ii) limited dissolved and free organic compounds, and (iii) no or minimal foreign solids, for example less than about 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%, optionally less than about 500 ppm, optionally less than about 100 ppm. Preferably, the brine has high osmotic strength, preferably resulting from salt content, but can be maintained by adding salt or other osmotic strength modifiers, including but not limited to salts having cations Na, Ca, Mg, and K, or by removing a portion of the solution water. Techniques for pretreating brine are well known to those skilled in the art, such as neutralization by adding acid or alkali, liquid-phase separation, and filtration.

[0040] To the extent desired for the removal of natural hydrocarbons or other organic matter at this stage, the brine is to be treated such that the natural hydrocarbons or other organic matter present as dissolved and free phase organic matter are less than about 0.3% by weight, preferably less than about 0.2% by weight, more preferably less than about 0.1% by weight, and most preferably less than about 180 ppm, and contain no heavy crude oil components. "Natural hydrocarbons or other organic matter" refers to hydrocarbons or organic matter present in the brine pumped from the formation, not hydrocarbons or organic matter added during the process. To the extent desired for the removal of solids, the solids content is desired to be less than about 1000 ppm, preferably less than about 500 ppm, and more preferably less than about 100 ppm.

[0041] In addition, removing halogenated oxidizing impurities may be beneficial. Oxidizing halogen species can include elemental chlorine, bromine, or iodine, as well as their molecular and ionic counterparts with destructive oxidation potentials. Other oxidizing agents, such as peroxides and ozone, should also be appropriately reduced or otherwise removed.

[0042] A preferred embodiment of this method involves first treating a lithium-containing brine to adjust its properties for further processing. For example, the pH, temperature, or density of the brine may need to be adjusted. In a preferred embodiment, the brine introduced to the next step should have a temperature below the bubble point of the solution under processing conditions and allow suitable building materials, for example, less than about 80°C to less than about 110°C, optionally, the temperature will be, for example, less than about 105°C, preferably less than about 90°C, and more preferably less than about 82°C, with a TDS / Li ratio of less than about 5000 (e.g., about 25% salt and 50 ppm Li or better).

[0043] Adsorption and desorption of brine effluent Typically, the brine is then introduced into the lithium adsorption step. The lithium adsorption step is carried out by introducing and removing lithium-containing brine into an adsorbent bed (preferably placed in a column or other suitable contact vessel) at a brine temperature of about 40°C to about 110°C, preferably about 50°C to about 90°C, until lithium penetrates into the effluent from the bed. "Penetration" is determined based on the objectives and economics of the process utilized. For example, "penetration" may occur when it is initially determined that at least about 25% of the lithium has been adsorbed, more preferably more than about 80%, and most preferably more than about 90%. The adsorbent can recover lithium from brine of any concentration, although a higher initial lithium concentration in the brine will result in a higher lithium loading absorbed or adsorbed by the adsorbent when penetration occurs.

[0044] In practice of the method for recovering lithium value from lithium-containing brine according to the present invention, the brine received from its source is treated with an adsorbent, and, if necessary or required, such brine is pretreated as described above. However, any suitable adsorbent, such as those described in CN111215040B, CN102631897 B, or U.S. Patent No. 10,648,061, can be used in this new method. Furthermore, known lithium adsorbents, such as those disclosed in U.S. Patent Nos. 5,599,516 and 6,280,693, can be used. These patents disclose polycrystalline hydrated alumina adsorbents based on hydrated alumina (such as crystalline gibbsite, bayerite, nordstrandite, or bauxite). These adsorbents are morphologically altered by the incorporation of lithium salts therein, which creates active lithium-specific sites within the crystalline layers of the alumina. An example of an injected adsorbent particle having the formula LiOH • 2Al(OH)3 and a lithium load of up to 0.33 molar fraction is converted to LiCl • 2Al(OH)3 by neutralization with HCl, and can then be used in the method of the present invention for removing lithium from brine.

[0045] One of the potential substances used in the practice of this invention is "hydrated alumina," which is also referred to in the art by various terms such as alumina hydrate, alumina trihydrate, or aluminum hydroxide. It is also frequently identified by the acronym "ATH." Typically, these materials are designated as Al(OH)3 or Al2O3•3H2O. Therefore, these and any other designated substances having the same chemical characteristics as any of these designated materials (such as gibbsite and diaspore) are considered suitable for use in the methods of this invention.

[0046] After the brine has passed through the lithium adsorption step, it needs to be passed through a lithium desorption step. The lithium desorption step is typically performed by washing the adsorbent with water or an aqueous solution (such as a diluted lithium chloride or other lithium salt solution preferably containing about 50 mg Li / kg to about 300 mg Li / kg) at a temperature of about 40°C to about 100°C or higher (preferably greater than 50°C, and more preferably greater than 60°C if carried out under increased pressure). The desorption efficiency increases with washing temperature. The higher the desorption efficiency, the less water is required for Li desorption, and thus the higher the lithium concentration in the eluent. To increase the purity of the eluent, it is desirable to displace the retention of brine in the interstitial spaces between the particles in the adsorbent bed. This typically involves using at least about 1.2 to about 1.4 volumes of water per volume of interstitial space to be purged before collecting the high-purity lithium chloride solution. The initial fraction can contain significantly higher levels of impurities relative to lithium compared to later fractions of the desorbed effluent. The desorption stage can be selectively fed to one or more processing steps suitable for a given TDS / Li ratio. This selection can occur during or after the purging step. The lithium-containing purge material can be recycled back into the brine for the next adsorption cycle. Optionally, if available, the brine can be displaced with a concentrated salt solution (such as, but not limited to, a solution made from one or more of NaCl, MgCl2, KCl, and CaCl2) before the desorption step to minimize lithium loss during purging.

[0047] In some implementations, thermal integration may be necessary to improve the overall energy efficiency of the DLE process. Thermal integration is considered to be the recovery of energy from Li-containing brine, desorption eluent, thermal evaporator products, and condensate, as well as within the direct LiCl process. The lithium desorption step is typically performed by washing the adsorbent with water or a diluted aqueous solution (such as a lithium chloride solution preferably containing about 50 ppm Li to about 300 ppm Li) at a temperature of about 40°C to about 100°C, preferably greater than 50°C, and more preferably greater than 65°C. For membrane processes, the desorption eluent should be cooled to below 40°C, preferably below 30°C. The heat in the desorption eluent can be used to preheat the water recovered from the membrane process before or simultaneously with the recirculation of the water to the desorption step. This water can also be preheated using other heat sources (e.g., lithium-containing or waste brine or streams from the thermal evaporator or LiCl crystallizer prior to adsorption).

[0048] After desorption, brine is then prepared for the enrichment process. Further treatment of the brine may be necessary prior to the enrichment process. Specifically, it may be necessary to remove impurities such as oils and greases, free halogens, and / or other free solids and impurities. The brine treatment can be carried out as discussed throughout the application. Preferably, the brine effluent should have oils and greases preferably less than about 5 ppm, and more preferably less than about 1 ppm. Furthermore, the amount of free halogens should be less than about 5 ppm, and more preferably less than about 1 ppm. Additionally, the total solids should preferably be less than about 10 ppm, more preferably less than about 5 ppm, and more preferably less than about 1 ppm. Residual sulfur compounds, including H₂S or other sulfides, should be reduced to less than about 100 ppm, preferably less than 50 ppm sulfur, and more preferably less than 20 ppm sulfur.

[0049] Enrichment steps Typically, the next step in this method is an enrichment step.

[0050] Typically, the enrichment process should produce a sufficiently concentrated and purified LiCl solution, of sufficient mass for further processing into lithium metal, LiOH, LiCl, Li₂CO₃, or other valuable lithium minerals. For example, in a preferred embodiment of Li₂CO₃, the desorption effluent should have a lithium concentration of 0.25% to 5%, preferably 0.5% to 3.5%, and more preferably 0.8% to 1.25%. For a preferred embodiment of LiCl production, the desorption effluent should have a lithium concentration of 1% to 13%, preferably 2% to 12%, and more preferably 4% to 8%, along with suitable concentrations of contaminants such as boron, calcium, magnesium, and sodium. Suitable boron ratios are greater than 500:1 lithium:boron or 2000:1 by mass, preferably greater than 5000:1 or 20000:1, and more preferably greater than 8000:1 or 40000:1. Suitable ratios for calcium are lithium:calcium greater than 50:1 or 200:1 by mass, preferably greater than 100:1 or 400:1, or more preferably greater than 160:1 or 800:1. Similarly, suitable ratios for magnesium are lithium:magnesium greater than 108:1 or 434:1 by mass, preferably greater than 217:1 or 869:1, or more preferably greater than 347:1 or 1739:1. Suitable strontium or other divalent ions will follow the stated calcium or magnesium scheme, which is corrected for the mass difference of a divalent cation relative to calcium or magnesium. Suitable ratios for sodium are sodium:lithium less than 20:1 or 5:1 by mass, preferably 10:1 or 2.5:1, or more preferably less than 6.25:1 or 1.25:1. The appropriate potassium or other monovalent content will follow the stated sodium scheme, which is corrected for the mass difference of a monovalent cation relative to sodium.

[0051] To prepare high-purity lithium salts (such as lithium chloride, lithium hydroxide, and lithium carbonate), it is desirable to remove undesirable impurities (such as Mg, Ca, and boron) from the lithium chloride solution to the lowest possible level, less than about 1 ppm. The concentration of the lithium chloride solution should also be increased to about 6% or higher, preferably about 8% or higher, and more preferably about 10% or higher.

[0052] Typical practices for removing divalent impurities usually involve adding an alkali (such as lime, sodium carbonate, or sodium hydroxide) to convert soluble divalent chlorides into insoluble divalent salts, which are then separated from the lithium chloride solution. While precipitation processes can generally reduce divalent impurities in lithium chloride solutions to less than about 5 ppm, this process requires the cost of alkali and generates significant amounts of solid waste. Using basic ion exchange resins is also a method for reducing divalent impurity concentrations, even to less than about 1 ppm, but this method is often even more expensive due to the cost of the resin and its regeneration.

[0053] Using nanofiltration to reduce divalent metal components in lithium chloride solutions is a preferred method, as it requires no additional consumable raw materials and generates no solid waste. Nanofiltration is generally effective for removing divalent metal impurities from diluted lithium chloride solutions formed during the initial adsorption and desorption steps of the method of this invention.

[0054] First, a nanofiltration system is used to remove most of the Ca and Mg present in the crude lithium chloride solution collected from the adsorbent bed. Nanofiltration is a pressure-driven membrane separation process that forms a transition between ultrafiltration and reverse osmosis. Nanofiltration is suitable for separating sizes ranging from approximately 10... -3 To about 10 -2 Micrometer-sized particles; that is, particles in the size range between those that can be separated by reverse osmosis and ultrafiltration, although there may be significant overlap between these technologies.

[0055] One side of the nanofiltration membrane in the flow contact unit. At a moderate pressure, preferably greater than about 25 psig, more preferably greater than about 50 psig, and most preferably greater than about 100 psig and less than about 1000 psig, more preferably about 800 psig, and most preferably less than about 500 psig, water is allowed to flow from the stream through the membrane to generate a permeate stream. Along with the water, the stream contains monovalent ions, particularly lithium and sodium, which permeate through the membrane under operating conditions. However, divalent impurities (including magnesium and calcium ions, etc.) do not readily permeate through the membrane because they are retained in the stream as concentrate or residue, thus effectively providing separation between monovalent lithium ions and divalent calcium and magnesium ions. The residue should typically contain about 50% or more of the initial divalent salt, preferably about 60% or more, and more preferably about 75%. Multistage nanofiltration can be used to further deplete the divalent salt in the permeate. Similarly, multistage nanofiltration can be used to increase the relative concentration of divalent salts in the nanofiltration residue or concentrate. For the optimal method, the majority of the initial lithium should permeate through the membrane and be recovered in the permeate solution. About 50% or more of the lithium, preferably about 60% or more, and more preferably 75% or more, should be recovered in the permeate solution. It should be noted that the flux through the membrane increases with temperature. While the method is preferably operated at temperatures between 25°C and 50°C, it is theoretically feasible over a wide range of temperatures. Furthermore, the method can be operated at a wide range of pressures and flow rates, depending on the desired flux and recovery rate.

[0056] Nanofiltration systems can operate in numerous series or parallel configurations to achieve the desired level of separation while maintaining a constant flux through the membrane. Nanofiltration systems can be operated in single-pass, multi-pass recirculation, and series configurations to remove divalent ions from lithium-containing streams. For example, a portion of the permeate produced in a subsequent reverse osmosis unit operation is recirculated between each stage of the nanofiltration system to maintain flux. The permeate solution leaving the nanofiltration system can be recirculated back to the initial lithium-containing brine or subjected to other treatment methods.

[0057] Typical practices for concentrating lithium chloride solutions require the use of reverse osmosis and / or evaporation. However, reverse osmosis capacity is limited to a maximum lithium chloride concentration of approximately 5%, as its osmotic pressure reaches the maximum feasible pressure applicable to reverse osmosis membranes (approximately 1200 psi). Concentration can be achieved through solar evaporation or thermal evaporation. The former requires the availability of large onshore sites, long evaporation times (on a monthly basis), and is dependent on climate conditions. Concentration via thermal evaporation incurs the investment costs of multi-stage evaporators with high energy consumption.

[0058] When using this step of the multi-step method of the present invention, the reverse osmosis process utilizes pressure applied to a concentrated aqueous solution (i.e., a lithium solution) to force water in the lithium solution through a semi-permeable reverse osmosis membrane, thereby producing a more concentrated lithium-containing solution and a separate second water stream. The applied pressure must be greater than the osmotic pressure of the lithium-containing solution to force water through the semi-permeable membrane.

[0059] While the currently developed reverse osmosis does require considerable pressure to achieve concentration, it is useful because it produces a nearly pure water stream due to water permeating through a semi-permeable reverse osmosis membrane. This water stream can then be used elsewhere on the plant site or recycled back to the original source from which the lithium-containing solution was obtained. One advantage of using the reverse osmosis step in the multi-step method of the present invention is that it can accommodate lithium solutions with a relatively wide concentration range from nanofiltration steps without significant loss of lithium value during operation. Thus, a lithium solution initially containing approximately 300 ppm to approximately 5000 ppm of lithium, received and subjected to pressurized reverse osmosis by possibly multiple semi-permeable reverse osmosis membranes in units connected in series, parallel, or both, under pressure, may initially contain approximately 300 ppm to approximately 5000 ppm of lithium. In this reverse osmosis operation, water is forced through the semi-permeable reverse osmosis membrane, while ions contained in the feed solution are repelled and retained on the lithium solution side of the reverse osmosis membrane. The reverse osmosis process technology provides concentration of the lithium solution.

[0060] Thermal evaporator (mechanical vapor recompression unit): After the RO step, a thermal evaporator equipped with thermal evaporation technology is used to further concentrate the stream. Methods include thermosiphon, direct steam injection, and mechanical vapor recompression. This unit utilizes heat and vapor recompression to enhance the evaporation process, resulting in further concentration of the solution.

[0061] Electrodialysis (a separation process based on the movement of ions under the influence of an electric field) can also be deployed as part of the enrichment step. This technique utilizes ion-selective membranes to allow specific ions (in this case, lithium and chloride ions) to migrate toward electrodes with opposite charges, resulting in their separation and subsequent concentration. Anion exchange resin technology can also be deployed in the enrichment step. This process utilizes specially designed anion exchange resins with a high affinity for chloride ions. When a lithium chloride solution passes through the resin bed, chloride ions selectively exchange with other anions present in the resin structure, thereby effectively concentrating lithium chloride in the eluent. The concentrated lithium chloride solution is then eluted through subsequent processing, yielding a product with enhanced purity and concentration.

[0062] Membrane distillation (MD) is a process that allows the concentration of a process stream by removing water as water vapor through a hydrophobic membrane. Membrane distillation can allow the removal of more water than reverse osmosis or forward osmosis at temperatures below those of standard thermal evaporation techniques. Membrane distillation technologies include, but are not limited to, vacuum MD, air-gap MD, purge gas MD, and direct contact MD. In membrane distillation, a heated stream is introduced into a permeable hydrophobic membrane. Water vapor, rather than bulk water or dissolved salts, is able to pass through the membrane and be introduced into a region of lower heat. This diffusion of water vapor is driven by water vapor pressure as it condenses in this lower-heat region.

[0063] Crown ethers can interact with specific cations based on their structure and the size of the cation. Crown ethers include soluble and insoluble crown ethers. Crown ethers can also be immobilized on solid scaffolds or other supports. Lithium cations can be selectively separated from sodium and potassium, for example, by using 12-crown-4, where 12 is the number of atoms forming the ring (crown) and 4 is the number of oxygen atoms present in the ring. Due to the solubility of soluble crown ethers in organic solvents, lithium cations can bind to the ring and then be transported to the organic solvent layer in a two-phase removal process. Once in the organic solvent, lithium can be removed from the ether, and lithium and the ether can be recovered as known to those skilled in the art. Alternatively, two-phase systems with 15-crown-5, 18-crown-6, and 21-crown-7 can selectively remove sodium, potassium, and cesium, respectively, while leaving lithium in aqueous solution. In addition to standard oxy-crown ethers, crown ethers can also contain other heteroatoms, such as nitrogen and / or sulfur, to allow tuning of the interaction between the ether and selective salts. Ethers and substituted ethers can also be used to separate and / or remove and / or recover transition metals of interest. This transition metal can be commercially valuable and can be converted into a marketable product or used elsewhere in the process. While ethers do not transport anions, the anions will associate with the corresponding cations and will also be removed along with them.

[0064] Removal of residual impurities If necessary, residual divalent impurities (less than about 1 ppm) remaining in the concentrated lithium chloride solution can be thoroughly removed by precipitation or crystallization and / or ion exchange resins. The concentrated lithium chloride solution can be purified first by chemical treatment with an alkali (such as an aqueous solution of sodium carbonate and / or sodium hydroxide) to precipitate residual divalent impurities Ca and Mg ions. The amount of alkali required is related to the stoichiometry of the reaction. The reaction can be carried out in a batch stirred tank or in a continuous stirred reaction system at a temperature of 20°C to 100°C, preferably 70°C to 100°C, because the solubility of divalent ions is inversely related to temperature. The separation of the divalent solid from the LiCl solution can be accomplished by any known method, such as using a filter, centrifuge, and / or decantation. The solid is sent to a disposal site or to another process for further processing. The resulting lithium chloride solution after separation of the divalent solid typically contains less than about 5 ppm of Ca and Mg.

[0065] Residual divalent impurities in lithium chloride solutions can be removed to less than about 1 ppm by passing the solution through a bed containing an ion exchange resin. Suitable commercially available resins for removing divalent ions include Amberlite. ® IRC 747 and 748 resins (manufactured by Rohm and Hass). Ion exchange resins may include more standard ion exchange resins that require acid and alkali for regeneration, or softening ion exchange resins that can be regenerated with concentrated monovalent salt solutions, or mixtures or series of both.

[0066] If boron (a typical contaminant present in lithium sources) is present, it can be removed using a boron-selective ion exchange resin. Suitable commercially available resins for boron removal include, for example, Amberlite. ® IRA 743 resin (manufactured by Rohm and Hass) and Diaion ® CRB03 and CRB05 resins (manufactured by Mitsubishi Chemical Corporation). Boron can be removed by other known processes, such as solvent extraction, chemical precipitation, or membrane processes.

[0067] Formation of LiCl or Li2CO3 In this patent application, we utilize an evaporative cooling crystallizer system specifically designed for the precipitation and removal of sodium chloride impurities and for optimizing the production of high-purity lithium chloride. The integration of solids handling equipment (including centrifuges and dryers) into the overall process design improves the efficiency and productivity of the entire system. The centrifuge enables efficient separation of the solid and liquid phases, while the dryer effectively removes residual moisture, resulting in a high-purity lithium chloride product that meets stringent industrial standards.

[0068] Once available with aboutA relatively pure and concentrated LiCl stream with a Li:Na ratio of 1:5 to 100:1 or better and a Li:non-Na impurity ratio of 100:1 or better can be subjected to one or more units during or after enrichment to provide a commercially available or otherwise usable LiCl salt or solution. The previously purified LiCl stream can be subjected to further evaporation. During this evaporation, selective crystallization of NaCl will allow advantageous removal of NaCl impurities, resulting in a high-purity LiCl solution. Optionally, cooling crystallization can be employed. This cooling crystallization can occur at a temperature in which the saturation temperature relative to sodium and / or lithium is 120°C or lower, optionally 45°C or lower. Alternatively, cryocooling crystallization can be employed, in which the solution is saturated or supersaturated relative to sodium and / or lithium, and the solution is brought to a temperature of about 15°C or lower, optionally about 5°C or lower, optionally about 2°C or lower. Optionally, cooling crystallization and cryocooling crystallization can be combined in one or more processes, wherein the solution is cooled in stages with or without a residence point at a given temperature. This high-purity solution can be used or sold as is, or further evaporated to provide crystalline LiCl or its hydrate. Then, if desired, the crystalline LiCl or its hydrate can be subjected to further drying techniques to provide marketable anhydrous lithium chloride or to be sold or used as is in a suitable process.

[0069] Alternatively, a fairly pure LiCl / NaCl / Na2CO3 solution, already free of Ca and Mg, can be subjected to a Li2CO3 precipitation process. Na2CO3 is introduced to precipitate LiCl as Li2CO3. The Na2CO3 and NaCl, plus up to 0.5 wt% Li2CO3, remain soluble in the mother liquor and should be recycled elsewhere. The Li2CO3 precipitate is then subjected to one or more filtration and drying steps and sold as a product. The wet filter cake or dried material can also be used in subsequent conversion steps to produce LiCl. A solution containing a nominal 0.5 wt% Li2CO3 is treated with CaCl2 to precipitate CaCO3. This solution can then be concentrated to obtain a saturated LiCl solution or crystalline LiCl. Alternatively, more Li2CO3 can be dissolved using weak LiCl, and CaCl2 can be added iteratively to produce a more concentrated LiCl stream.

[0070] Optional brine pretreatment Brine from oil fields or Smackover formations is often contaminated with impurities. Therefore, pretreatment of the brine fluid may be necessary before processing to meet the aforementioned criteria. A preferred method involves the use of hydrocyclones. A hydrocyclone is a cyclone separator that primarily separates product phases based on gravity differences, with an aqueous solution as the main feed fluid, and is known in the art. Hydrocyclones are particularly suitable for removing organic impurities such as petroleum and natural gas. Other known techniques for removing oils and greases can be used, including phase separators and API separators, centrifuges, coagulation / flocculation chemical demulsification, activated carbon filters, membrane filtration, skimmers, ion exchange resins, and integrated treatment systems, as well as combinations thereof.

[0071] In addition, lithium brines may contain H2S, which may also need to be removed. Known methods for H2S removal, such as H2S strippers, can be used. Furthermore, H2S can be removed by known techniques such as stripping, vacuum degassing, oxidative conversion, electrochemical conversion, and reaction with oxides of iron or other transition metals to form insoluble sulfides. Stripping can also use gases at standard temperatures and pressures, including standard liquids converted to gas at high temperatures.

[0072] Optional removal of other valuable materials Besides lithium, the brine used in this invention may contain other valuable materials. These materials include bromine and elemental sulfur, sulfur compounds, iodine and / or cesium, etc. Therefore, in order to utilize the brine effectively, it may be beneficial to remove these additional materials in a single process.

[0073] Bromine has a wide range of industrial applications. For example, it is used in the manufacture of brominated flame retardants such as tetrabromobisphenol A, decabromodiphenyl ethane, decabromodiphenyl ether, and brominated polystyrene. Bromine is also used, for example, in the manufacture of 1,2-dibromoethane as a gasoline additive, in the manufacture of compounds for photography (e.g., silver bromide, which is a photosensitive material in film), in the manufacture of dyes and pharmaceuticals, in the testing of unsaturation in organic compounds in analytical laboratories, as a disinfectant, and in gold extraction.

[0074] Brine produced in several regions of the world contains significant amounts of bromide salts, such as sodium bromide. Processes for producing bromine from brine and other bromide-containing solutions are well-known. For example, bromine can be produced by bromine distillation processes, such as the Kubierschky distillation process; see, for example, Kirk-Othmer, Encyclopedia of Chemical Technology, 4th edition, Vol. 4, pp. 548–553. Other methods for recovering bromine from bromide-containing solutions are described, for example, in U.S. Patent Nos. 3,181,934, 4,719,096, 4,978,518, 4,725,425, 5,158,683, and 5,458,781. For example, bromine can be recovered from brine by treating it with chlorine to oxidize the bromide to bromine. Methods for electrolyzing bromide to bromine are also known; however, electrolytic conversion is an expensive alternative compared to other methods.

[0075] A feature of this invention is that the removal of additional materials can occur in multiple steps of the process. For example, additional materials can be removed after pretreatment but before lithium removal and concentration. However, the removal of additional materials can be performed after lithium removal and concentration from the brine.

[0076] Optional recycling of brine materials A key optional feature of this invention is the multiple steps of recirculating the brine effluent throughout the process. These recirculation steps improve overall lithium recovery and control the amount of liquid required for lithium removal performance, and contribute to a net zero increase in the hydraulic pressure rate returned to the brine source formation.

[0077] For example, at least three (or more) possible recycling steps exist in this method. One option is that, after any nanofiltration step, the permeate or sludge can be recycled to a brine cooling tower or a desorption step. Another option is that, after any reverse osmosis step, the permeate or sludge can be recycled to a brine cooling tower or a lithium desorption step. Furthermore, after removing residual impurities, the permeate or sludge can be recycled to a cooling tower. Additionally, water generated during enrichment can be recycled to one or more stages of a multi-stage nanofiltration system. Another possible alternative is to recycle the boron resin waste regeneration solution to adjust the pH or permeability elsewhere in the enrichment or adsorption process, or to send it to a brine cooling tower. Finally, it may be advantageous to recycle the sludge volume for displacement or to send that volume to a separate purification step to achieve optimal lithium or heat recovery. The sludge volume is the material from the previous stage that remains in the column when switching from adsorption to desorption or vice versa.

[0078] Example The following embodiments are included to further illustrate various implementations of the subject matter currently disclosed. However, based on this disclosure, those skilled in the art will understand that many changes can be made to the specific implementations disclosed without departing from the spirit and scope of the subject matter currently disclosed and still obtaining the same or similar results.

[0079] Example 1: Lithium recovery from brine The lithium adsorbent was prepared as described in U.S. Patent No. 10,648,061. 805 g of the prepared adsorbent was packed into a vertical column with a bed aspect ratio of 48. A lithium-bearing brine containing 150 mg / kg Li and 31700 mg / kg Ca, along with other salts, was introduced into the adsorbent at a rate of 5.6 lb / h. The brine was then displaced with lithium in the form of 200 ppm lithium chloride at a pore volume of 1. The final fraction of the effluent, representing 17% by mass of the total brine feed, contained 115 mg / kg. The average lithium concentration in the effluent was 61 mg / kg, indicating that 60% of the lithium was removed from the brine. The bed was then desorbed with an additional 8.8 lb of a 200 mg / kg Li solution to obtain a desorbed solution containing 503 ppm Li, with a Ca / Li ratio of 6.7.

[0080] Example 2: Lithium recovery from brine The lithium adsorbent was prepared as described in U.S. Patent No. 10,648,061. 805 g of the prepared adsorbent was packed into a vertical column with a bed aspect ratio of 48. A lithium-bearing brine containing 180 mg / kg Li and 33,000 mg / kg Ca, 59,000 mg / kg Na, 3,000 mg / kg Mg, and other salts was introduced into the adsorbent at a rate of 3.3 lb / h. The final fraction of the effluent, representing 18% by mass of the total brine feed, contained 22 mg / kg Li. The average lithium concentration in the effluent was 14 mg / kg, indicating that 92% of the lithium was removed from the brine. The brine was then displaced with lithium in the form of 210 ppm lithium chloride. The bed was then desorbed with an additional 7.7 lb of a 190 mg / kg Li solution to obtain a desorbed solution containing 520 ppm Li, where the Ca:Li ratio was 1:4, the Na:Li ratio was 1:3, and the Mg:Li ratio was 1:15.

[0081] Example 3: Lithium recovery from brine The lithium adsorbent was prepared as described in U.S. Patent No. 10,648,061. 805 g of the prepared adsorbent was packed into a vertical column with a bed aspect ratio of 48. A lithium-bearing brine containing 175 mg / kg Li, 30,000 mg / kg Ca, 60,000 mg / kg Na, and <10,000 mg / kg of other cations was introduced into the adsorbent at a rate of 5.6 lb / h. The final fraction of the effluent, representing 19% by mass of the total feed brine, contained 81 mg / kg Li. The average lithium concentration in the effluent was 34 mg / kg, indicating that 80% of the lithium was removed from the brine. The brine was then displaced with lithium in the form of 200 ppm lithium chloride. The bed was then desorbed with an additional 7.7 lb of a 190 mg / kg Li solution to obtain a desorbed solution containing 495 ppm Li, where the Ca:Li ratio was 1:14 and the Na:Li ratio was 1:16.

[0082] Example 4: Lithium recovery from brine Suitable lithium-carrying brine was obtained from a commercial bromination process. The brine had been subjected to oil removal and stripping, H2S removal, bromide removal, and pH adjustment. The brine contained 33,000 ppm Ca, 175 ppm Li, 2,970 ppm Mg, and 57,560 ppm Na.

[0083] A 1”×48” column was packed with 653.2 g of the adsorbent prepared as described in U.S. Patent No. 10,648,061.

[0084] Nine kg of brine was subjected to an adsorption step by flowing it through a packed column at a nominal rate of 35 mL / min at approximately 50-70°C. The effluent concentration was 18 ppm. The waste brine was then replaced with a 200 ppm Li solution prepared from lithium chloride and water. The adsorbent was then subjected to a desorption step using another 200 ppm Li solution prepared from lithium chloride and water. The desorbed effluent contained 208 ppm Ca, 7 ppm B, 430 ppm Li, 10 ppm Mg, and 79 ppm Na.

[0085] Commercially available spiral-wound nanofiltration membranes and commercially available spiral-wound RO membranes are used to subject desorption products from multiple cycles to multi-pass nanofiltration and reverse osmosis. Typically, the material is subjected to five progressive nanofiltration stages, with permeate from one stage being passed through another, until the material passes through the fifth stage. At each stage, nominal 70% of the feed is forwarded as permeate, while nominal 30% is retained as concentrate. The final permeate nominally contains 300 ppm Li, 19 ppm Ca, <1 ppm Mg, and 20 ppm Na. The concentrate is then subjected to a separate nanofiltration stage and combined with concentrates from subsequent stages, and subjected to further nanofiltration stages. For example, the concentrate from the first stage is subjected to three rounds of nanofiltration. The final permeate from this sequence is combined with the second round of concentrate and subjected to further nanofiltration. The permeate produced by this sequence contains 39 ppm Ca, 313 ppm Li, 1.8 ppm Mg, and 36 ppm Na.

[0086] A commercially available spiral-wound membrane was used to subject the desorption products of a series of nanofiltration processes to reverse osmosis. The starting material contained 31 ppm Ca, 318 ppm Li, 1.2 ppm Mg, and 38 ppm Na. Reverse osmosis treatment produced a concentrate with 3387 ppm Li, 446 ppm Ca, 21 ppm Mg, and 138 ppm Na.

[0087] The reverse osmosis product underwent a divalent ion removal step using a commercially available resin capable of removing divalent ions from the brine. After treatment, the material contained <1 ppm Ca, 2774 ppm Li, <1 ppm Mg, and 2390 ppm Na. The product following the divalent ion removal step was then subjected to a treatment step in which the brine was treated with a resin capable of removing boron. The feed contained 7 ppm B, which was reduced to 1.6 after treatment.

[0088] The solution was then heated and evaporated until it reached a solution temperature of 146°C at ambient pressure. The solution was then cooled to precipitate sodium chloride. The resulting slurry was centrifuged, and the supernatant was decanted and filtered through a 2.7-micron filter. The supernatant had a density of 1.3 g / mL and contained 74,000 ppm Li, 1,117 ppm Na, 76 ppm B, 4.5 ppm Ca, and <1 ppm Mg.

[0089] Example 5: Lithium recovery from brine An aqueous solution containing 4.2% LiCl and 1.7% NaCl (by weight) was heated and evaporated at approximately ambient pressure until the solution temperature reached 140°C. The solution was then cooled to 40°C, causing some salt crystallization. The resulting slurry was filtered through an 8-micron filter. The filtrate was retained as the supernatant, containing 45.7% LiCl and 3400 mg / kg NaCl.

[0090] Example 6: Lithium recovery from brine An aqueous solution containing 2.0% LiCl and 8600 mg / kg NaCl by weight was heated and evaporated until a solution temperature of 137°C was reached. The solution was then cooled to 40°C, causing some salt crystallization. The resulting slurry was filtered through an 8-micron filter. The filtrate was retained as the supernatant, containing 32.8% LiCl and 6000 mg / kg NaCl. The salt-saturated supernatant was cooled to 1.2°C, further causing some salt crystallization. The resulting slurry was filtered through the same type of filter used in the previous step, while maintaining the solution temperature <2°C. The filtered supernatant contained 36.4% LiCl and 5200 mg / kg NaCl. The supernatant was then evaporated until a solution temperature of 137°C was reached. The solution was cooled to 40°C and the resulting slurry was filtered. The supernatant contained 45.2% LiCl and 5500 mg / kg NaCl. The supernatant was then cooled to 1.7°C and filtered again while cooling. The purity of the supernatant was then increased to 45.2% LiCl and 2400 ppm NaCl. The supernatant was then evaporated at 137°C. The solution was cooled to 40°C and filtered again. The final purity of the filtrate was 46.2% LiCl and 1900 mg / kg NaCl.

[0091] The invention is susceptible to considerable variation in its practice. Therefore, the foregoing description is not intended to limit the invention to the specific embodiments presented above and should not be construed as limiting the invention to the specific embodiments presented above.

Claims

1. A method for producing a high-purity lithium-containing aqueous solution from a dissolved lithium source, the method comprising: a. Source brine containing at least 1 mg Li / kg brine, preferably 10 mg / kg, more preferably 25 mg Li / kg brine; b. If necessary, treat the source brine in a pretreatment step; c. Processing the treated brine in the lithium adsorption step; d. Following the adsorption step, the adsorbed lithium is desorbed in a desorption step; and e. After the desorption step, the desorbed effluent is processed in an enrichment step.

2. The method of claim 1, wherein the concentration of the inlet brine solution is adjusted by one or more of the following: Introduce water or a water-based recirculation flow or nanofiltration / reverse osmosis permeate or concentrate, or Concentration, evaporation, or dehydration technologies, which include one or more of the following: Staged evaporation, membrane technology, thermal evaporation, vacuum evaporation, cooling tower evaporation including forced or induced ventilation, solar evaporation, forced air evaporation, or passive evaporation.

3. The method of claim 1 or 2, further comprising providing a solution made of one or more of NaCl, MgCl2, KCl, and CaCl2 prior to the desorption step to displace the brine thereby minimizing lithium loss.

4. A method for producing lithium salts, comprising the method of claim 1, followed by fractional crystallization of NaCl to produce LiCl or other commercially available lithium salt solutions, such as lithium bromide, lithium phosphate, lithium sulfate, lithium hydroxide, and solutions and hydrates thereof.

5. The method of claim 4, further comprising converting the LiCl solution into solid LiCl or its hydrate or a mixture thereof.

6. A method for producing Li2CO3, comprising the method of claim 1, followed by the introduction of Na2CO3 or K2CO3 or NaOH or KOH in the presence of CO2 to precipitate Li2CO3.

7. The method of any one of claims 1 to 6, further comprising an initial pretreatment step to remove impurities.

8. The method of claim 7, further comprising the brine produced by the pretreatment step as dissolved and free organic matter, preferably less than about 0.3 wt%, more preferably less than about 0.1 wt%, most preferably less than about 180 ppm, and free of heavy crude oil components.

9. The method of claim 7 or 8, further comprising the pretreatment step producing a brine containing less than about 100 ppm, preferably less than 50 ppm, and more preferably less than 20 ppm of residual sulfur compounds including H2S or other sulfides.

10. The method of any one of claims 7 to 9, further comprising the pretreatment step producing brine with less than about 500 ppm of free halogens, preferably less than about 200 ppm, and more preferably less than 20 ppm.

11. The method of any one of claims 7 to 10, further comprising the pretreatment step producing a brine with total undissolved solids of less than about 1000 ppm, more preferably less than about 100 ppm, and even more preferably less than about 10 ppm.

12. The method of any one of claims 1 to 12, further comprising a processing step prior to enrichment to remove impurities.

13. The method of claim 12, further comprising the brine produced by the said processing step containing less than about 100 ppm, preferably less than 50 ppm, and more preferably less than 20 ppm of residual sulfur compounds including H2S or other sulfides.

14. The method of claim 12 or 13, further comprising brine produced by the said processing step as dissolved and free organic matter, preferably less than about 0.3% by weight, more preferably less than about 0.1% by weight, most preferably less than about 180 ppm, and free of heavy crude oil components.

15. The method of any one of claims 12 to 14, further comprising the step of said treatment producing brine containing less than about 500 ppm of free halogens, preferably less than about 200 ppm, and more preferably less than 20 ppm.

16. The method of any one of claims 12 to 15, further comprising the brine produced by the said processing step having a total undissolved solids content of less than about 1000 ppm, more preferably less than about 100 ppm, and even more preferably less than about 10 ppm.

17. The method of any one of claims 1 to 16, further comprising the step of removing additional valuable materials, said valuable materials optionally including bromine and elemental sulfur, sulfur compounds, iodine and / or cesium.

18. The method of any one of claims 1 to 17, comprising recycling the lithium-poor brine effluent or any of the desorbed effluent during the method.

19. The method of claim 18, wherein the aqueous solution generated during enrichment is recycled to the desorption inflow.

20. The method of claim 18, wherein the aqueous solution generated during enrichment is recycled to one or more stages of a multi-stage nanofiltration system.

21. The method of claim 18, wherein the stagnation volume is replaced and recycled to adsorption or sent to a separate enrichment step.

22. The method of claim 18, wherein the solution used to regenerate the boron resin and the resulting solution are recycled to adjust the pH or osmotic strength elsewhere in the enrichment or adsorption or desorption process or in lithium-poor brine.

23. The method of any one of claims 1 to 22, wherein the enrichment step comprises one or more of the following steps: membrane technologies including nanofiltration, forward osmosis, reverse osmosis and osmosis-assisted reverse osmosis, electrodialysis, chemical precipitation, ion exchange resins including cation exchange resins and anion exchange resins, and evaporation or other dehydration or concentration techniques.

24. The method of claim 23, wherein NaCl is recovered from one or a combination of process streams and subjected to nanofiltration, reverse osmosis or selective precipitation, and is used to adjust the permeability of brine, desorb or enrich the solution, regenerate ion exchange resins, or provide minimized waste treatment costs as concentrated brine or provide zero liquid discharge solid waste.

25. The method of claim 23 or 24, further comprising an enrichment step of producing a brine effluent with a lithium concentration of 0.25% to 5%, preferably 0.5% to 3.5%, and more preferably 0.8% to 1.25%.

26. The method of claim 23 or 24, further comprising an enrichment step of producing a brine effluent with a lithium concentration of 1%-13%, preferably 2%-12%, and more preferably 4%-8%.

27. The method of any one of claims 1 to 26, further comprising the treatment of the source brine to produce brine with a pH value in the range of 1-9, preferably 3-8, more preferably 4.0-7.

5.

28. The method of any one of claims 1 to 27, wherein the effluent desorption solution contains at least 5 ppm Li, preferably 25 ppm Li, and more preferably 50 ppm Li.

29. The method of any one of claims 1 to 28, wherein the lithium-carrying source brine is subjected to two or more stages of adsorption in one or more contact containers (to further recover the initial Li).

30. The method of claim 29, wherein the desorption stage is selectively fed to one or more processing steps suitable for a given TDS / Li ratio.

31. The method of any one of claims 1 to 30, wherein in the adsorption step, at least about 50% of the lithium is adsorbed.

32. The method of any one of claims 1 to 31, wherein in the adsorption step, at least about 80% of the lithium is adsorbed.

33. The method of any one of claims 1 to 32, wherein in the adsorption step, at least about 90% of the lithium is adsorbed.

34. The method of any one of claims 1 to 33, wherein the treatment comprises fractionating the solution within one or more nanofiltration or RO units or any combination of two units, and the subsequent permeate is recycled elsewhere in the method.

35. The method of claim 29, wherein different adsorbent compositions are used in subsequent stages of the two or more stages.

36. The method according to any one of claims 1 to 36, wherein the lithium desorption step is performed by washing the adsorbent with water or a diluted aqueous solution, such as a lithium chloride solution preferably containing 50 ppm to 300 ppm Li, at a temperature of 40°C to 100°C, preferably greater than 50°C, and more preferably greater than 65°C.

37. The method of claim 36, wherein, for membrane processes, the desorption eluent should be cooled to below 40°C, preferably below 30°C.

38. The method of claim 36, wherein the heat in the desorption eluent can be used to preheat the water before or simultaneously with the water recovered from the membrane process and recycled to the desorption step.

39. The method according to any one of claims 1 to 38, wherein the temperature of the brine prior to the adsorption step is below about 110°C, preferably below about 90°C, and more preferably below about 82°C.

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