Method for direct lithium extraction using a discontinuous simulated moving bed

Abstract

Provided herein is a method of direct lithium extraction in which lithium ions are removed from a lithium-containing brine by adsorption onto a lithium-selective adsorbent, followed by eluting the adsorbed lithium. The process described herein is a discontinuous simulated moving bed process, in which brines or eluants are routed through a plurality of zones or columns, in turn, to reproduce the effect of lithium extraction via a simulated moving bed system. The discontinuous moving bed system, however, is based on a more efficient design that provides significant economies in resource use as well as construction and operation costs.

Description

[0001] DI83884-WO-PCT PATENT

[0002] Title of the Invention

[0003] Method for Direct Lithium Extraction using a Discontinuous Simulated Moving Bed

[0004] CROSS-REFERENCE TO RELATED APPLICATION

[0005] The present application claims priority to U.S. Provisional Appln. No. 63 / 684,553, filed on August 19, 2024, which is incorporated herein by reference in its entirety.

[0006] Field of the Invention

[0007] Provided herein is a method for direct lithium extraction. In particular, lithium ions are removed from a lithium-containing brine by adsorption onto a lithium selective adsorbent, followed by eluting the adsorbed lithium. The process described herein is a discontinuous simulated moving bed process, in which brines or eluants are routed through a plurality of zones or columns, in turn, to reproduce the effect of lithium extraction via a simulated moving bed system. The discontinuous moving bed system, however, is based on a more efficient design that provides significant economies in resource use as well as construction and operation costs.

[0008] Background of the Invention

[0009] Several patents, patent applications and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents, patent applications, and publications is incorporated by reference herein.

[0010] Direct Lithium Extraction (DLE) is envisioned to address the gap between lithium supply and demand which is expected to be significant in coming years. DLE will do this by accelerating the processing rate of Li-containing brine resources, which traditionally rely on extremely slow evaporation processes. In addition, DLE is facilitating the harvesting of unconventional Li brine resources, such as geothermal and oil field brines. However, highly efficient processes must be developed in order for DLE to be economically feasible. These processes must reach high lithium recovery, high product purity, high lithium productivity, as well as low operating costs such as those resulting from heating, electricity, and chemical usage. Importantly, capital costs must also be controlled.

[0011] Several configurations for direct lithium extraction processes are known. For example, continuous counter-current adsorption / desorption is described in U.S. Patent Nos. 10,604,414 and 11 ,365,128; similar systems are described in Chinese Patent No. CN201825992; and the use of fast rinses to further improve efficiency is described in Chinese Patent Nos. CN107058735, CN201825992, and CN111041201 . A counter current adsorption / desorption process that utilizes physical separation of the sorbent from one column / tank to the next is described in U.S. Patent Appln. Publn No. 20130001168A1.

[0012] More specifically, conventional processes using a single column are simple in implementation and generally have lower capital costs, but suffer from very poor efficiency due to poor utilization of the sorbent. The mass transfer zones in the adsorption circuit are typically quite large, unless prohibitively low flow rates are used. The result is that extremely large adsorption circuits with large quantities of sorbent are needed to process large quantities of brine. To address these deficiencies, lead-lead-lag systems can be utilized, in which the lead and lag columns are placed in the adsorption (brine) circuit and a single column is used in the desorption (elution) circuit. Examples of such systems are described generally in Adsorption Basics: Part 1. Gabelman, A., P.E., www.aiche.org / cep, July 2017, American Institute of Chemical Engineers. This operation mode allows for improved utilization of the sorbent capacity and improved system efficiency; however, the separation of the lithium product stream from the brine is not optimal in the desorption column.

[0013] Further optimization is achieved by utilizing multi-column arrangements in the desorption circuit as well. These systems have improved purity of lithium in the product stream. The full systems, sometimes referred to as counter current adsorption / desorption or continuous counter current ion exchange, have greatly improved efficiency. One example of such a system is described in U.S. Patent No. 9,126,843, issued to Rezkallah. However, these systems often have drawbacks such as high complexity, high pressure drops within the circuit (which can limit the size of the system due to sorbent mechanical limitations), large footprints to accommodate the large number of columns, and high capital costs due to the complexity, advanced valves, and / or large number of values required. This can sometimes restrict their use to very large plants.

[0014] Interrupted simulated moving bed systems, sometimes called improved simulated moving bed (ISMB) systems, address these drawbacks. Mitsubishi Chemical Aqua Solutions describes an example of one such system in a video entitled “ISMB™ chromatographic separation system,” available at https: / / www.youtube.com / watch?v=mEs6YZJWXsO (last accessed on May 14, 2025). In ISMB systems, a closed-loop internal recycle step is implemented between each cycle sub-step, which results in further improved separation performance. This then allows for comparable performance while utilizing fewer columns (lower complexity, fewer valves, less pressure drop) and overall lowered capital expenditures. This situation is optimal for the DLE market which is rapidly growing and seeks to quickly commercialize operations at a variety of sites world wide. Such a competitive market will see great benefit from DLE extraction plants that have lowered capital expenditures.

[0015] Finally, a simulated moving bed (SMB) process is described in Inti. Patent Appln. Publn. No. WO2023117597A1 , and a sequential simulated moving bed (SSMB) process for extracting lithium using an ion exchange mechanism rather than an adsorption / desorption process is described in Inti. Patent Appln. Publn. No. WO2012163791 A1.

[0016] Nevertheless, there remains a need for DLE methods that are capable of processing a wider variety of lithium brines and that are characterized by improved yield and improved economic efficiency, both in capital expenditure and operating cost. Summary of the Invention

[0017] Accordingly, provided herein are methods for the direct extraction of lithium from lithium-containing brines, by means of a discontinuous simulated moving bed (DSMB) process. This DSMB system typically contains four columns but may contain more. The columns contain a lithium-selective adsorbent media. In the DSMB process, brine is received as a feed and lithium-depleted brine is produced as a waste product. The lithium is extracted from the adsorbent by sending eluant into the system, thus producing a lithium-rich eluate. Typically in SMB systems, the feed (brine) and eluant (water, or water with low levels of lithium) are fed to opposite sides of the column carousel. Product (lithium) extract and lithium-depleted brine (raffinate) are removed between these points. The location of these points is periodically moved in a direction which is opposite to the direction of liquid flow, thus producing the simulated motion. In the methods provided herein, between these periodic valving steps, an additional step is used in which liquid flow to and from the system is stopped (and therefore the process is discontinuous). During this step, the liquid flow is continued but only within the internal column circuit. This allows for further separation to occur prior to removal of the product and raffinate.

[0018] More specifically, in the processes provided herein, lithium is recovered from a lithium-containing brine in a process comprising the steps of: a) directing a first aliquot of the lithium-containing brine through a first zone of a system comprising at least four zones, wherein each zone comprises at least one column, wherein each of the columns contains a lithium-selective adsorbent; and wherein each of said columns has a resin bed volume; b) adsorbing lithium from the lithium-containing brine onto the lithiumselective adsorbent in the first zone to produce a lithium-loaded adsorbent and a lithium-depleted brine; c) discharging the lithium-depleted brine from the first zone; d) ceasing the flow of the lithium-containing brine and ceasing the discharge of the lithium-depleted brine; e) maintaining a first residual liquid in the system; and optionally adding a first solution to the first residual liquid to produce a first altered residual liquid; f) circulating a volume of the first residual liquid or the first altered residual liquid through the system; g) directing an eluant through the first zone containing the lithium- loaded sorbent to desorb the lithium from the lithium-loaded sorbent into a lithium-enriched eluate; h) discharging a portion of the lithium-enriched eluate from the first zone; i) ceasing the flow of eluant and ceasing the discharge of the lithium- enriched eluate; j) maintaining a second residual liquid in the system; and optionally adding a second solution to the second residual liquid to produce a second altered residual liquid; k) circulating a volume of the second residual liquid or the second altered residual liquid through the system; l) directing a second aliquot of the lithium-containing brine through a second zone that is adjacent to or not adjacent to the first zone; and m) repeating step (b) through step (I) with the second zone.

[0019] Brief Description of the Drawings

[0020] FIGS. 1 A and 1 B are schematic diagrams depicting the status and function of the components of a discontinuous simulated moving bed apparatus suitable to perform the steps of the process described herein;

[0021] FIGS. 2A, 2B, and 2C are flow charts of three embodiments of the processes described herein;

[0022] FIG. 3 is a graph of the concentration of various cations vs. the bed volume of brine in the lithium-depleted brine leaving a column / zone; and FIG. 4 is a graph of the concentration of various cations vs. the bed volume of eluant in the lithium-enriched eluate leaving a column / zone.

[0023] Detailed Description of the Invention

[0024] Provided herein are methods for direct lithium extraction (DLE). In the methods described herein, a lithium-containing brine is treated by directing it through an adsorption column or an adsorption bed comprising lithium-selective adsorbent media.

[0025] Suitable brines for treatment with the processes described herein are aqueous solutions of one or more ions. The brine stream may be used as obtained from a natural source such as a salt lake, a salar, or a geothermal brine; alternatively, it may be derived from clay mining or a hard rock deposit. The brine stream may be generated synthetically by acid-digesting a lithium-containing material such as, but not limited to, lithium-ion batteries, solar panels, solar storage devices, computers, laptops, and like devices. Alternatively, the brine stream can be a processed feed which is generated by processing a natural resource brine or a synthetically generated brine. In addition, some preferred synthetic brines are described in U.S. Patent No. 11 ,371 ,118, for example.

[0026] One preferred synthetic brine is Solution F, an aqueous solution comprising: 0.01 to 200 g / L of lithium; 0 to 151 g / L sodium; 0 to 260 g / L potassium; 0 to 187 g / l magnesium; 0 to 270 g / L calcium; 0 to 315 g / L sulfate; 0 to 10 g / L boron; and 0 to 234 g / L chloride. Solution F preferably has a pH of from 1 .0 to 12.0. When passed through a bed or column, its temperature is preferably from about 5 °C to about 120 °C.

[0027] More preferably, the brine comprises 0.025 to 5 g / L of lithium; 0 to 151 g / L sodium; 0 to 20 g / L potassium; 0 to 150 g / l magnesium; 0 to 40 g / L calcium; 0 to 50 g / L sulfate; 0 to 5 g / L boron; and 0 to 234 g / L chloride. This brine preferably has a pH of from 3.0 to 11 .0. When passed through a bed or column, its temperature is preferably from about 5 °C to about 120 °C.

[0028] Still more preferably, the brine comprises 0.050 to 2 g / L of lithium; 5 to 135 g / L sodium; 1 to 15 g / L potassium; 0 to 150 g / l magnesium; 1 to 40 g / L calcium; 0 to 25 g / L sulfate; 0 to 2.5 g / L boron; and 0 to 234 g / L chloride. This brine preferably has a pH of from 4.0 to 10.0. When passed through a bed or column, its temperature is preferably from about 5 °C to about 120 °C.

[0029] Still more preferably, the brine comprises 0.010 to 1 g / L of lithium; 15 to 115 g / L sodium; 1 to 10 g / L potassium; 0 to 10 g / l magnesium; 1 to 10 g / L calcium; 0 to 20 g / L sulfate; 0 to 1 g / L boron; and 0 to 234 g / L chloride. This brine preferably has a pH of from 4.5 to 8.0. When passed through a bed or column, its temperature is preferably from about 5 °C to about 120 °C.

[0030] Another preferred synthetic brine resembles a naturally sourced brine, for example those of the Imperial Valley in California. Such a brine preferably has a composition profile similar to that of the brine used in the working example, below. Other preferred brines are described in the Table below, which is excerpted from Table 1 on page 6 of Ventura et al., Selective Recovery of Lithium from Geothermal Brines, Energy Research and Development Division Final Project Report, March 2020, Report No. C EC-500-2020-02 (available at https: / / www.enerqv.ca.aov / sites / default / files / 2021 -05 / CEC-500-2020-020.pdf, last accessed on June 24, 2024), internal citations omitted, wherein the symbol is not defined but is presumed to signify “not measured” or “not measurable.”

[0031] More preferably, the brine includes about 65 to 75 g / L Na cations; 250 to 350 mg / L Li cations; 35 to 45 g / L Ca cations; 20 to 30 g / L K cations; 600 to 700 mg / L Sr cations; and 150 to 250 g / L of Cl anions, titrated to pH ~6.5 with aqueous HCI. Table: Typical Geothermal Brine Compositions in the Imperial Valley

[0032] Dissolved solids (ma / L) Salton Sea Westmorland Brawlev

[0033] Lithium (Li) 211.00 48.00 100.00

[0034] Sodium (Na) 52,000.00 10,000.00 22,000.00

[0035] Potassium (K) 14,000.00 1 ,400.00 3,800.00

[0036] Magnesium (Mg) 160.00 188.00 34.00

[0037] Calcium (Ca) 24,000.00 690.00 8,100.00

[0038] Strontium (Sr) 500.00 - 340.00

[0039] Barium (Ba) 433.00 - 363.00

[0040] Arsenic (As) 11.00 - 2.60

[0041] Boron (B) 350.00 63.00 140.00

[0042] Copper (Cu) 4.00 0.07 0.11

[0043] Iron (Fe) 2,300.00 0.30 65.00

[0044] Manganese (Mn) 1 ,200.00 2.80 190.00

[0045] Nickel (Ni) 4.00

[0046] Lead (Pb) 100.00 3.80 1.10

[0047] Zinc (Zn) 660.00 0.04 14.00

[0048] Chloride (Cl) 145,000.00 18,000.00 46,000.00

[0049] Sulfate (SO4) 84.00 57.00

[0050] Bicarbonate (HCO3) 140.00 2,900.00 49.00

[0051] Fluoride (F) 9.00 2.24

[0052] Suitable eluants for use in the processes provided herein are described in U.S. Patent No. 11 ,371 ,118, for example. One preferred eluant for lithium-selective adsorbents is Solution E, an aqueous solution comprising 0 to 1 g / L, preferably 0.05 g / L to 0.5 g / L, more preferably 0.06 g / L to 0.25 g / L of lithium. Suitable eluants have a pH of 4 to 10, more preferably 5 to 9, more preferably 6 to 8. Another preferred eluant for lithium-selective ion exchangers is acidic process water that contains very little if any lithium. Suitable eluants have a pH of 0.1 to 8.0, more preferably 0.5 to 5, even more preferably 1 to 3. The pH of the process water may be adjusted with a dilute aqueous acid, such as H2SO4, acetic acid, or more preferably HCI.

[0053] As used herein, the term “adsorb”, whether alone or in combined form such as for example “adsorption” and “adsorbent”, refers to the action of selectively sequestering lithium ions from a solution or to a material that selectively sequesters lithium ions from a solution. Accordingly, the term “adsorb” includes any selective sequestration regardless of its mechanism, which may be accomplished by adsorption, ion exchange, intercalation, another mechanism, or a combination of two or more mechanisms. Accordingly, suitable lithiumselective adsorbents for use in the processes described herein include, without limitation, a lithium aluminum intercalate, a lithium aluminum layered double hydroxide chloride, a layered double hydroxide modified activated alumina, a layered double hydroxide modified activated boehmite, a layered double hydroxide loaded or synthesized within the pores of a porous support such as an ion exchange resin or copolymer or molecular sieve or zeolite or another porous material, a blend of lithium aluminum intercalates with polymers, an immobilized crown ether, or a combination of two or more of these adsorbents. Also suitable are lithium-specific ion exchange media, including, without limitation, a lithium manganese oxide, a lithium manganese oxide that has been blended with at least one polymer, a lithium titanium oxide, a lithium titanium oxide that has been blended with at least one polymer, an immobilized crown ether, or a combination of two or more of these ion exchange media. Preferably, the adsorbent contains lithium halides intercalated between layers of aluminum hydroxide. More preferred are adsorbents of the formula LiX 2AI(OH)3 nH2O, wherein n is an integer from 0 to 10, inclusive, and wherein X is a halogen anion, preferably a chlorine anion. Suitable lithium-selective adsorbents of this type are described in U.S. Pat. No. 11 ,371 ,118, for example.

[0054] Suitable lithium-selective adsorbents may further comprise one or more polymers, for example to function as binders, supports or scaffolds within the adsorbent. Suitable polymers include, without limitation, those described in U.S. Patent No. 11 ,371 ,118. Preferred polymers include polystyrene, polyacrylic acid, polymethylmethacrylate, polyacrylamide, polyvinylidene fluoride, polyvinyl fluoride, polyvinylchloride, polyvinyl alcohol, polytetrafluoroethylene, related polymers, and combinations of two or more of these polymers.

[0055] Upon treatment by the methods provided herein, the adsorbent beds or columns will produce an eluate having a concentration of lithium ions that is greater than the concentration of lithium ions in the brine. The eluate may further comprise some of the soluble non-lithium species that were present in the brine. Examples of such species include one or more of boric acid and its salts, or ions of potassium, sodium, magnesium, chloride, and sulfate.

[0056] Referring now to the drawings, wherein like reference numerals designate corresponding structures throughout the views, and referring in particular to FIG. 1A, a simulated moving bed system is depicted. The system includes four zones, labelled 1 , 2, 3, and 4. Each zone includes one or more beds or columns, and each of these beds or columns contains lithium-selective media.

[0057] In this connection, the terms “bed” and “column”, whether used alone or in combined form, such as, for example, “bed volume” and “column volume”, are synonymous and used interchangeably herein. It follows that, when a bed or a column is described herein, it is to be understood that either a bed or a column is suitable for that use, unless specifically stated otherwise in limited circumstances. Moreover, as used herein the terms “bed volume” and “column volume” refer to the capacity of the empty bed or column. Stated alternatively, the terms “bed volume” and “column volume” refer to the sum of the volumes of the particles of adsorbent material, the interstitial fluid within the layer of adsorbent material, the supernatant fluid layer outside of the layer of adsorbent material, if any, and the void volume outside of the adsorbent layer and the supernatant layer, if any, within the bed or column. For example, in a cylindrical column with a height of 100 cm and a diameter of 10 cm, the column volume is 7854 cm3(=K*52*100), regardless of the sum of the volumes of adsorbent and fluid that are contained within the column, which may well be less than 7854 cm3. A related term, “free volume,” refers to the total bed or column volume of the discontinuous moving bed system excluding the volume of the adsorbent particles. Finally, as used herein, the term “finite,” as used herein when referring to a quantity, for example as in “finite volume,” refers to a positive real number that is not equal to zero.

[0058] Still referring to Figure 1A, in Step 1 Solution F (lithium brine feed) is fed to the top of zone 4 while a lithium-depleted brine solution (Solution G) is removed from the bottom of zone 4. Preferably but not necessarily simultaneously, Solution E (eluant) is fed to the top of zone 2 while lithium-enriched eluate (Solution H) is simultaneously removed from the bottom of zone 2. Zones 1 and 3 sit idle during this step, that is, there is no fluid flow in these zones.

[0059] As used herein, the term “simultaneous” and “simultaneously” refer to two processes or steps that overlap in time, i.e., one process is not completed before the second process begins. In addition, the flow rates described herein are expressed in units of bed volume per hour (BV / h). Suitable flow rates for the adsorption, elution and circulation steps described herein are from 0.1 to 20 BV / h, preferably from 0.5 to 15 BV / h, more preferably from 1.5 to 10 BV / h or from 1 to 12 BV / h.

[0060] Referring now to Step 2 in FIG. 1 A, the addition of Solutions E and F, as well as the removal of lithium-depleted brine (Solution G) and lithium-enriched eluate (Solution H) is stopped. The system is run in circulation mode, in which liquid removed from the bottom of zone 4 is fed to the top of zone 3, liquid removed from the bottom of zone 3 is fed to the top of zone 2, liquid removed from the bottom of zone 2 and is fed to the top of zone 1 , and liquid removed from the bottom of zone 1 is fed to the top of zone 4. A recirculation pump is used to circulate the liquid through the columns. It is within the skill of the art to select an appropriate pump, an appropriate location for the pump within the system, and appropriate piping and connections to effectuate the pressure changes produced by the pump. For example, in some preferred embodiments (not depicted), the pump is located between two zones.

[0061] Referring now to Step 3 in FIG. 1 A, the circulation of Step 2 is stopped. Lithium brine feed (Solution F) is fed to the top of zone 1 , and lithium-depleted brine (Solution G) is removed from the bottom of zone 1. Simultaneously, eluant (Solution E) is fed to the top of zone 3, and lithium-enriched eluate (Solution H) is removed from the bottom of zone 3. Zones 2 and 4 sit idle during this step, that is, there is no fluid flow in these zones.

[0062] Still referring to FIG. 1A, in Step 4 the addition of liquids to the system and the elution of liquids from the system is ceased while the circulation of liquid through the system, as described above with respect to Step 2, is repeated.

[0063] Referring now to Step 5 in FIG 1 B, the circulation of Step 4 is stopped. Lithium brine feed (Solution F) is fed to the top of zone 2, and lithium-depleted brine (Solution G) is removed from the bottom of zone 2. Simultaneously, eluant (Solution E) is fed to the top of zone 4, and lithium-enriched eluate (Solution H) is removed from the bottom of zone 4. Zones 1 and 3 sit idle during this step, that is, there is no fluid flow in these zones.

[0064] Still referring to Fig. 1 B, in Step 6 the addition of liquids to the system and the elution of liquids from the system is ceased while the circulation of liquid through the system, as described above with respect to Step 2, is repeated.

[0065] Referring now to Step 7 in FIG. 1 B, the circulation of Step 6 is stopped. Lithium brine feed (Solution F) is now fed to the top of zone 3, and lithium-depleted brine (Solution G) is removed from the bottom of zone 3. Simultaneously, eluant Solution E is fed to the top of zone 1 and lithium-enriched eluate (Solution H) is removed from the bottom of zone 1 . Zones 2 and 4 sit idle during this step, that is, there is no fluid flow in these zones.

[0066] Still referring to FIG. 1 B, in Step 8 the addition of liquids to the system and the elution of liquids from the system is ceased while the circulation of liquid through the system, as described above with respect to Step 2, is repeated.

[0067] Steps 1 through 8, which constitute one cycle of the process described herein, may be repeated, for example up to 10 times, up to 25 times, up to 50 times, up to 75 times, up to 100 times, or more than 100 times. Preferably, the cycles are repeated until the system arrives at a steady state, that is, until the composition of the lithium-enriched eluate (Solution H) becomes relatively constant.

[0068] The process described herein is a simulated moving bed process because the positions of the lithium brine feed and eluant inlets and the lithium-depleted brine and lithium-enriched eluate outlets are moved throughout the process during operation to simulate the movement of the stationary adsorbent phase. It is a discontinuous simulated moving bed process because the flow of liquids into and out of the system is paused during the recirculation steps.

[0069] The liquid that is circulated through the system in Steps 2, 4, 6, and 8 is referred to herein as a “residual liquid.” The circulated liquid in Step 2 is the “first residual liquid,” the circulated liquid in Step 4 is the “second residual liquid,” and so on. Optionally, a solution may be added to a residual liquid to produce an altered residual liquid. For example, a first solution may be added to the first residual liquid to produce a first altered residual liquid, a second solution may be added to the second residual liquid to produce a second altered residual liquid, and so on. One or more solutions may be added to one or more residual liquids. Stated alternatively, solution(s) may be added to the residual liquid of only one circulation step, of more than one circulation step, or of every circulation step in the process. The solutions may be the same or different. Preferably, the solution(s) are independently selected from the group consisting of the lithium- depleted brine, lithium-enriched brine, eluant, lithium-enriched eluate, water, and an intermediate stream between two zones or between two columns in a zone.

[0070] Notably, in some preferred processes, in step (f), in step (k), or in both step (f) and step (k), one or more of the first residual liquid, the first altered residual liquid, the second residual liquid, or the second altered residual liquid flows from the second zone to the first zone.

[0071] Also notably, in some preferred processes, no fluids are added to or removed from the residual liquid(s) that are circulated within the system before the lithium- rich eluate is discharged from the system. When present, however, the volume(s) of the solutions(s) are independently selected and range from a finite value greater than 0% up to 100% of the volume of the first zone, or from a finite value greater than 0% up to 100% of the volume of the free volume of the system.

[0072] The residual liquid or the altered residual liquid has a finite volume that is preferably no greater than the free volume of the system. In some preferred processes, the volume(s) of one or more of the (optionally altered) residual liquid(s) are substantially equal to the free volume of the system. More specifically, the volume of the first residual liquid (which may optionally be altered), the volume of a plurality of the residual liquids (one or more of which may optionally be altered), or the volume of each residual liquid (which may optionally be altered) may be substantially equal to the free volume of the system.

[0073] In some preferred processes, the residual liquid(s) or the altered residual liquid(s) are circulated within the system at a rate of from 0.1 to 20 BV / h, preferably from 0.5 to 15 BV / h, more preferably from 1 .5 to 10 BV / h. The circulation rate of each residual liquid and altered residual liquid is independently selected, and the circulation rates may be the same or different. Referring now to FIGS. 2A, 2B, and 2C, the term “Direct Lithium Extraction,” as used only in the flowcharts of FIGS. 2A, 2B, and 2C, refers to the cycle(s) described above with reference to FIGS. 1 A and 1 B. The Direct Lithium Extraction process depicted in FIGS 1 A and 1 B may be supplemented with one or more additional steps to provide a desirable lithium-enriched product. Some preferred additional steps, and some preferred permutations of the process described herein when the one or more additional steps are included, are depicted in the flowcharts of FIGS. 2A, 2B, and 2C.

[0074] For example, in Fig. 2A, the brine is first subjected to a pre-treatment that may include, for example, one or more of filtration, pH adjustment, impurity precipitation, dilution, or temperature adjustment. Next, the pre-treated brine is passed through a lithium adsorbent bed or a bed of ion exchange resin. The adsorbed or ionically bound lithium is eluted to provide a lithium-enriched eluate. Divalent and multivalent cations are removed from the lithium-enriched eluant by one or more of nanofiltration, ion exchange, or chemical treatment to produce a lithium solution that comprises a preponderance of monovalent ions. Preferably, this monovalent ion solution comprises less than 5,000 ppm, less than 1 ,000 ppm, or less than 500 ppm of divalent and multivalent cations. Next, the monovalent ion solution is polished, for example by one or more of ion exchange or impurity adsorption. Finally, the polished monovalent ion solution is concentrated or “dewatered” by methods including one or more of evaporation, distillation, nanofiltration, or reverse osmosis to produce a concentrated lithium solution that preferably includes at least 500, 1000, 2500, or 5,000 ppm of lithium.

[0075] FIG. 2B depicts an alternative process, in which the individual steps are as described above with respect to FIG. 2A, and the order of the process steps is the same, except that the monovalent ion solution is concentrated first and then polished. Finally, FIG. 2C depicts a second alternative process in which the individual steps are as described above with respect to FIG. 2A. In the process of FIG. 20, however, the brine is concentrated immediately after the pre-treatment step, then proceeds to the direct lithium extraction step. The lithium-rich eluate obtained from direct lithium extraction undergoes removal of divalent and multivalent ions, then polishing, then a second concentration step. Although not depicted, it is clear that the second concentration step may precede the polishing step, analogously to the difference in the processes depicted in FIGS. 2A and 2B.

[0076] Advantageously, in the methods provided herein, the lithium-containing fractions elute from the adsorbent zones with a lower content of impurities. The reason is that the lithium ions are adsorbed on the columns in the zones and are substantially immobile until they are exposed to the eluant, which releases them from the adsorbent. In contrast, in a chromatographic method, the lithium- containing fraction and the fractions containing other ions may be mobile simultaneously. Thus, it is likely that a greater portion of the eluate of an adsorption / desorption process will include a lower concentration of mixed ions compared to the eluate of a chromatographic process. As a result, the chromatographic eluate is expected to require further purification steps.

[0077] Moreover, the recirculation steps in the methods described herein allow more contact time between the adsorbent media and the various liquids for improved efficiency of adsorption and desorption.

[0078] The following example is provided to describe the invention in further detail. This example, which sets forth specific embodiments and a preferred mode presently contemplated for carrying out the invention, is intended to illustrate and not to limit the invention. EXAMPLE

[0079] The lithium-selective adsorbent (“direct lithium extraction” or “DLE” adsorbent) was macroporous ion exchange resin beads loaded with LiCI(AI(OH)3)2, as described in U.S. Patent No. 11 ,371 ,118.

[0080] A jacketed column (inner diameter (ID) = 25mm) was loaded with 80 mL of DLE adsorbent and then preheated to 80 °C. The column was initially filled with sufficient eluant (water containing 200 mg / L Li, as LiCI) to submerge the bed. Into the top of the bed were then pumped alternating cycles of brine and eluant, both of which were pre-heated to 80 °C; this flow into the top of the column then generated an effluent or eluate which exited via the bottom of the column. The brine was composed of water containing 70799 mg / L Na cations, 295 mg / L Li cations, 39318 mg / L Ca cations, 25129 mg / L K cations, 642 mg / L Sr cations, and 203576 mg / L of Cl anions, titrated to pH ~6.5 with aqueous HCI. The eluant was composed of water containing 200 mg / L Li cations and 938 mg / L Cl anions, titrated to pH -7 with aqueous HCI or aqueous NaOH, as appropriate. In each brine half-cycle, the column was treated with ~28.83 BV of brine at 7.69 BV / h, followed by an eluant half-cycle in which the column was treated with -3.73 BV of eluant at 1 .86 BV / h. These half-cycles were alternated for 5 cycles and fractions of the eluate of the fifth full cycle were collected at various time points. These samples were diluted by a factor of 1000 (brine) or by a factor of 400 (eluate) with 5% (w / v) aqueous HNO3, and their composition was analyzed by inductively coupled plasma (ICP) spectroscopy using an Agilent 5800 ICP-OES (optical emission spectrometer) in radial view vertical torch mode, available from Agilent Technologies, Inc., of Santa Clara, California. A high total dissolved solids torch was used to accommodate the relatively high salinity of the samples tested.

[0081] The results of the ICP analyses are shown in Figures 3 and 4. In cycle 5, approximately 2.86 g of Li was captured by the column during the adsorption / brine half-cycle, and approximately 2.78 g of Li was released by the column during the desorption / eluant half-cycle. Figure 3 depicts the concentration profile of the eluate as it exited a column after the fifth cycle. These results show that magnesium, strontium, calcium, sodium, and potassium ions began to pass through the column almost immediately, and their concentrations remained constant, near the concentrations in the unprocessed brine, from the first through the thirtieth bed volume. In contrast, the concentration of lithium ions quickly decreased to a trace level and remained below its initial concentration after approximately 29 BV of brine were passed through the column. In particular, lithium adsorption is still occurring after 25 BV have passed though the column. These results indicate that the column was effective to retain lithium ions selectively.

[0082] Figure 4 depicts the lithium concentration profile of the lithium-enriched eluate as it exited a column after the fifth cycle. The lithium level began to rise as the eluant made its way through the column and desorbed lithium from the lithiumselective media. The level reached a peak before beginning to decline once the majority of the adsorbed lithium ions were eluted from the lithium-selective media.

[0083] These results establish that lithium can be extracted and isolated directly and efficiently from a Salton Sea-type brine using a lithium-selective adsorbent.

[0084] While certain of the preferred embodiments of the present invention have been described and specifically exemplified above, it is not intended that the invention be limited to such embodiments. Rather, it is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

CLAIMS:

1. A process for the recovery of lithium from a lithium-containing brine, said process comprising the steps of: a) directing a first aliquot of the lithium-containing brine through a first zone of a system comprising at least four zones, wherein each zone comprises at least one column, wherein each of the columns contains a lithium-selective adsorbent; and wherein each of said columns has a resin bed volume; b) adsorbing lithium from the lithium-containing brine onto the lithiumselective adsorbent in the first zone to produce a lithium-loaded adsorbent and a lithium-depleted brine; c) discharging the lithium-depleted brine from the first zone; d) ceasing the flow of the lithium-containing brine and ceasing the discharge of the lithium-depleted brine; e) maintaining a first residual liquid in the system; and optionally adding a first solution to the first residual liquid to produce a first altered residual liquid; f) circulating a volume of the first residual liquid or the first altered residual liquid through the system; g) directing an eluant through the first zone containing the lithium- loaded sorbent to desorb the lithium from the lithium-loaded sorbent into a lithium-enriched eluate; h) discharging a portion of the lithium-enriched eluate from the first zone; i) ceasing the flow of eluant and ceasing the discharge of the lithium- enriched eluate; j) maintaining a second residual liquid in the system; and optionally adding a second solution to the second residual liquid to produce a second altered residual liquid;k) circulating a volume of the second residual liquid or the second altered residual liquid through the system; l) directing a second aliquot of the lithium-containing brine through a second zone that is adjacent to or not adjacent to the first zone; and m) repeating step (b) through step (I) with the second zone.

2. The process of claim 1 , further comprising the steps of repeating step (b) through step (I) with one or more of the third, fourth, or additional zones.

3. The process of claim 1 or claim 2, further comprising a cycle or a plurality of cycles, wherein one cycle comprises repeating step (b) through step (I) for each of the at least four zones of the system.

4. The process of any preceding claim, wherein one or both of the first solution and the second solution are added to the first residual liquid or to the second residual liquid to produce the first altered residual liquid, the second altered residual liquid, or both the first altered residual liquid and the second altered residual liquid.

5. The process of any preceding claim, wherein the first solution and the second solution are independently selected from the group consisting of the lithium-depleted brine, lithium-enriched brine, eluant, lithium-enriched eluate, water, and an intermediate stream between two zones or between two columns in a zone.

6. The process of any preceding claim, wherein the first solution, the second solution, or both the first and the second solution are present; and wherein the volume of the first solution and the volume of the second solution are independently from 0% to 100% of the volume of the first zone.

7. The process of any preceding claim, wherein the volume of the first residual liquid is substantially equal to the free volume of the system.

8. The process of any preceding claim, wherein the volume of the second residual liquid is substantially equal to the free volume of the system.

9. The process of any preceding claim, wherein the volume of the circulated first residual liquid is a finite volume that is no greater than the free volume of the system.

10. The process of any preceding claim, wherein the volume of the circulated second residual liquid is a finite volume that is no greater than the free volume of the system.

11. The process of any preceding claim, wherein the steps of the lithium- containing brine being directed through the first zone and the eluant being directed through the second zone are carried out simultaneously.

12. The process of any preceding claim, wherein, in step (f), in step (k), or in both step (f) and step (k), one or more of the first residual liquid, the first altered residual liquid, the second residual liquid, or the second altered residual liquid flows from the second zone to the first zone.

13. The process of any preceding claim, wherein no fluids are added to or removed from the residual liquid(s) that are circulated within the system before the lithium-rich eluate is discharged from the system.

14. The process of any preceding claim, wherein the residual liquid(s) or the altered residual liquid(s) are circulated within the system at a rate of from 0.1 to 20 BV / h, preferably from 0.5 to 15 BV / h, more preferably from 1 .5 to 10 BV / h.

15. The process of any preceding claim, wherein the lithium-selective adsorbent is selected from the group consisting of a lithium aluminum intercalate; a lithium aluminum layered double hydroxide chloride; a layered double hydroxide modified activated alumina; a layered double hydroxide modified activated boehmite; a layered double hydroxide loaded or synthesized within an ion exchange resin or copolymer or molecular sieve or zeolite or another porous material; a lithium manganese oxide; a lithium titanium oxide; an immobilized crown ether; and a combination of two or more of these lithium selective adsorbents; and optionally wherein the lithium selective adsorbent(s) are blended with one or more polymers selected from the group consisting of polystyrene, polyacrylic acid, polymethylmethacrylate, polyacrylamide, polyvinylidene fluoride, polyvinyl fluoride, polyvinylchloride, polyvinyl alcohol, polytetrafluoroethylene, and related polymers.

16. The process any preceding claim, wherein the lithium-containing brine comprises at least 10 mg / L of lithium and at least 5000 mg / L of non-lithium cations.

17. The process of any preceding claim, wherein the lithium-containing brine has a pH value of 1 or more.

18. The process of any preceding claim, wherein the eluant comprises no more than 5000 mg / L of lithium and no more than 5000 mg / L of non-lithium cations.

19. The process of any preceding claim, wherein the lithium-containing brine is subjected to a pretreatment in which the concentrations of one or more non-lithium components are reduced.

20. The process of any preceding claim, wherein the lithium-enriched eluate comprises one or more polyvalent cations, and wherein the lithium- enriched eluate is subjected to a post-treatment in which the concentrations of the one or more polyvalent cations are reduced.

21. The process of any preceding claim, wherein the lithium-enriched eluate is subjected to a dewatering step.

22. The process of claim 21 , wherein the dewatering step includes one or a plurality of steps independently selected from the group consisting of a reverse osmosis step, a nanofiltration step, a distillation step, and an evaporation step.

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