Process for producing lithium compounds using reverse osmosis

Abstract

A method for extracting lithium from a lithium-containing solution, as well as the resulting composition, is provided. The method includes feeding the lithium-containing solution to a lithium capture step, the lithium capture step being operable to capture lithium from the lithium salt-containing solution. The method further includes recovering lithium from the lithium capture step to produce a lithium-rich stream. In a particularly preferred method, the lithium capture step is performed to increase the lithium to sodium ratio to at least greater than 1:1. Optionally, the lithium-rich stream can be purified to remove divalent ions and borate ions. The lithium-rich stream is then concentrated by feeding the lithium-rich stream to a reverse osmosis step to produce a concentrated lithium-rich stream.

Description

[Technical Field]

[0001] This disclosure generally relates to the field of recovering lithium from lithium-containing solutions. More specifically, this disclosure relates to the preparation of various lithium compounds, and in particular to the preparation of concentrated lithium solutions using reverse osmosis. [Background technology]

[0002] Depending on the source of the brine, it can contain various metal ions, particularly alkali metals and alkaline earth metals, at varying concentrations. Geothermal brine is of particular interest for several reasons. First, because high-temperature geothermal pools are stored underground under high pressure, geothermal brine can provide an energy source. When high-temperature geothermal pools are released to atmospheric pressure, they can provide flash steam. Flash steam can be used, for example, to power a power plant. Additionally, geothermal brine typically contains various useful metals such as lithium, lead, silver, and zinc, each of which can be recovered from the brine for further use.

[0003] Furthermore, smack-over brines are also of interest, as these brines are used to extract bromine and salts, such as calcium and magnesium chloride. The brines also contain significant concentrations of lithium in certain wells, for example, up to 100-400 mg / kg. Since the wells are used for bromine production, useful chemicals can be extracted from previously "mined" brines. Lithium can be recovered from the ore, as the ore is calcined with sulfuric acid and the products can be leached with water.

[0004] Typically, the economic recovery of lithium from natural, primarily chloride brines (which can vary greatly in composition) depends not only on the overall lithium content but also on the concentrations of interfering ions, particularly calcium and magnesium, which can significantly impact the performance and economic viability of lithium recovery. Magnesium can be difficult to remove because it is chemically similar to lithium in solution. Generally, at low concentrations, magnesium can be removed by precipitation with lime as magnesium carbonate. However, at higher magnesium concentrations, removal with lime becomes impractical.

[0005] Conventional processing of ore and brine allows for the removal of some of the interfering ions, but the need for simplified removal of interfering ions from brine remains due to the formation of lithium carbonate and other lithium compounds. [Overview of the project]

[0006] In some embodiments, the disclosure relates to systems, devices, and methods for the isolation and concentration of lithium from various sources. In some embodiments, a lithium-containing solution (e.g., from geothermal brine) is pretreated to reduce or remove silica and then further treated to make the solution suitable for concentration by reverse osmosis. In other embodiments, the treatment utilizes lithium-specific adsorbents that preferentially bind to lithium, and specific packing, recycling, and elution profiles are used to concentrate lithium ions significantly and specifically more than other ions (e.g., sodium, calcium, manganese, etc.). The osmotic pressure in the resulting solution is almost entirely a function of the lithium ion concentration, and the lithium can be further treated in various ways to lithium hydroxide or lithium carbonate.

[0007] In another embodiment, a method for extracting lithium from a lithium-containing solution includes supplying the lithium-containing solution to a lithium capture step, wherein the lithium capture step is operable to capture lithium from the lithium salt-containing solution; recovering lithium from the lithium capture step to generate a lithium-rich flow; optionally purifying the lithium-rich flow to remove divalent ions and borate ions; and concentrating the lithium-rich flow by supplying it to a reverse osmosis step to generate a concentrated lithium-rich flow.

[0008] In yet another embodiment, a method for extracting lithium from a lithium-containing solution includes supplying the lithium-containing solution to a lithium capture step, wherein the lithium capture step is operable to capture lithium from the lithium salt-containing solution; recovering lithium from the lithium capture step to generate a lithium-rich flow; purifying the lithium-rich flow to remove divalent ions and borate ions; concentrating the lithium-rich flow by supplying it to a reverse osmosis step to generate a concentrated lithium-rich flow; and purifying the concentrated lithium-rich flow by removing sodium and potassium ions to generate a concentrated lithium-rich flow having reduced sodium and potassium ion concentrations.

[0009] In some embodiments, a method for extracting lithium from a lithium-containing solution includes: supplying a lithium and silica-containing solution to a silica management process to produce a silica-lean lithium-containing solution; supplying the silica-lean lithium-containing solution to a lithium capture step, wherein the lithium capture step is operable to capture lithium from a lithium salt-containing solution, and at least a portion of the eluate obtained from the adsorbent in the lithium capture step is recycled back into the adsorbent to increase the lithium-to-sodium ratio in the lithium-rich stream; recovering lithium from the lithium capture step to produce a lithium-rich stream; purifying the lithium-rich stream to remove divalent ions and borate ions; concentrating the lithium-rich stream by supplying it to a reverse osmosis step to produce a concentrated lithium-rich stream; further concentrating the concentrated lithium-rich stream to produce a double-concentrated lithium-rich stream; and purifying the double-concentrated lithium-rich stream by removing sodium and potassium ions to produce a concentrated lithium-rich stream having reduced sodium and potassium ion concentrations.

[0010] In some embodiments, a method for extracting lithium from a lithium-containing solution includes: treating the lithium-containing solution in a lithium capture step by contacting the lithium-containing solution with an adsorbent material to capture lithium and generate an eluate of the adsorbent; recovering lithium from the eluate in the lithium capture step to generate a lithium-rich flow; concentrating the lithium-rich flow by treating the lithium-rich flow in a reverse osmosis step to generate a concentrated lithium-rich flow; and recycling at least a portion of the eluate back to the adsorbent, wherein the portion of the eluate includes a fraction from the peak lithium concentration region. In some embodiments, the concentrated lithium-rich flow is further concentrated by solvent extraction.

[0011] A patent or application file includes at least one color drawing. Copies of this patent or patent application publication, including the color drawing(s), will be provided by the Patent Office upon request and payment of the necessary fees. [Brief explanation of the drawing]

[0012] [Figure 1] This is a flowchart of a method for producing lithium hydroxide from geothermal brine according to one embodiment. [Figure 2] This is a flowchart of a method for producing lithium carbonate from geothermal brine according to one embodiment. [Figure 3] This is a flowchart of a method for concentrating the flow from the lithium capture step in a process for producing lithium hydroxide, according to one embodiment. [Figure 4] This is a flowchart of a method for concentrating the flow from the lithium capture step using reverse osmosis in a process for producing lithium carbonate, according to one embodiment. [Figure 5] This is a schematic diagram of a system for generating lithium carbonate from geothermal brine according to one embodiment. [Figure 6] This is a schematic diagram of a first embodiment of a system for generating lithium carbonate from geothermal brine, according to one embodiment. [Figure 7] This is a schematic diagram of a second embodiment of a system for generating lithium carbonate from geothermal brine according to one embodiment. [Figure 8] This is a schematic diagram of a third embodiment of a system for generating lithium carbonate from geothermal brine according to one embodiment. [Figure 9] An exemplary series of elution profiles for lithium from an adsorbent according to one embodiment is shown. [Figure 10] This shows an exemplary series of elution profiles for lithium and other ions from the adsorbent during the filling, washing, and stripping cycles. [Figure 11] Figure 10 shows an exploded view of a portion of it. [Figure 12] Exemplary series of elution profiles for lithium and other ions from an adsorbent during a filling, washing, and strip cycle according to one embodiment are shown. [Figure 13] An exploded view of a portion of FIG. 12 is shown. [Figure 14] A system for extracting lithium in a column according to one embodiment is shown. [Figure 15] A system for extracting lithium in a column according to one embodiment is shown. [Figure 16] Exemplary concentrations of lithium and other ions in depleted brine and lag brine according to one embodiment are shown. [Figure 17] Exemplary series of elution profiles for lithium and other ions in recycle filling, recycle cut, product cut, and recycle strip according to one embodiment are shown.

BEST MODE FOR CARRYING OUT THE INVENTION

[0013] Generally, the present disclosure relates to a process for producing lithium hydroxide and lithium carbonate from lithium salt-containing brine. In some embodiments, the process includes concentrating lithium (Li) via an adsorbent that enables selective lithium retention and recovery, as well as a further step of concentrating the lithium product recovered via reverse osmosis.

[0014] As used herein, the term "brine" refers to a solution of alkali and / or alkaline earth metal salt(s) in water, and the concentration of the salt can vary from trace amounts to the saturation point. Generally, brines suitable for the methods described herein can be aqueous solutions containing alkali metal or alkaline earth chlorides, bromides, sulfates, hydroxides, nitrates, etc., as well as natural brines. Brines can be obtained from natural sources, such as Chilean brine or Salton Sea geothermal resource brine, geothermal brine, seawater, mineral brines (e.g., lithium chloride or potassium chloride brine), alkali metal salt brines, and industrial brines, such as industrial brines recovered from ore leaching, mineral processing, etc. The methods are equally applicable to artificially prepared lithium salt solutions.

[0015] The method steps disclosed throughout this disclosure are not provided in any specific order and can be used interchangeably unless otherwise specified.

[0016] Thus, in some embodiments, the method includes the preparation and recovery of lithium carbonate from solutions containing various other monovalent, divalent, and polyvalent cations (e.g., potassium (K), sodium (Na), calcium (Ca), barium (Ba), magnesium (Mg), manganese (Mn), etc.) and various monovalent, divalent, and polyvalent anions (e.g., sulfate, chloride, nitrate, etc.) in addition to lithium.

[0017] In certain embodiments, silica can be present in the lithium salt-containing solution or geothermal brine and can be removed by various known methods (e.g., U.S. Patent No. 4,016,075) before use in the methods described herein. Thus, in certain embodiments, the method for preparing lithium carbonate described herein can include a silica management step.

[0018] The following methods and method steps are not in a specific order and need not be consecutive.

[0019] Figure 1 shows a flowchart of a method for producing lithium hydroxide from geothermal brine according to one embodiment. Method 100 generally includes processing a lithium salt containing brine, such as geothermal brine, in the following steps: silica control step 110, lithium capture step 120 (lithium salt extraction step), optional lithium concentration step 130, electrochemical production step of lithium hydroxide 140, evaporation / crystallization step 150, and isolation and drying step 160 of lithium hydroxide. As used herein, the term "lithium" refers to the ionic form of lithium, and such include lithium salts, such as lithium halides, lithium sulfate, and lithium nitrate, or some combination thereof. In some embodiments, the lithium salt is lithium chloride.

[0020] Figure 2 shows a flowchart of a method for producing lithium carbonate from geothermal brine according to one embodiment. The method 200 for producing lithium carbonate generally includes the following steps: a silica control step 210, a lithium capture step 220 (lithium salt extraction step), an electrochemical production step of lithium hydroxide 240, a carbonation step of lithium hydroxide 250, and an isolation step of lithium carbonate 260, which involve treating a lithium salt containing brine, such as geothermal brine. In this method 200, lithium hydroxide is converted to lithium carbonate.

[0021] In some embodiments, after the lithium capture step 220, the method may optionally include a step 230 of concentrating the lithium-containing solution. In some versions of method 200, after the optional step 230, the lithium-containing solution may react with sodium carbonate to produce lithium carbonate.

[0022] Referring to Figure 3, a method 300 is provided for the isolation and concentration of lithium ions from brine or other lithium-containing solutions, and for the optional subsequent production of lithium carbonate therefrom, according to another embodiment. The brine is supplied to a silica control step 310, where silica is removed from the brine to produce silica-free brine or a lithium-containing solution. After the silica control step 310, lithium ions are removed from the silica-free brine or lithium-containing solution in a lithium capture step 320 to form a lithium-ion-containing solution. The lithium-ion-containing solution produced from the lithium capture step 320 is concentrated via a reverse osmosis step 330 to produce a concentrated lithium-ion-containing solution. After the reverse osmosis step 330, optional further concentration of the lithium-containing solution may be present, followed by an optional purification step to remove sodium and potassium before the solution is supplied to an electrochemical production step 340 of lithium hydroxide.

[0023] Methods for removing sodium and potassium from lithium chloride solutions are well known, including those described in U.S. Patent No. 4,920,588, Nakajima, Yasushi et al., “Sodium Selective Ion-Exchange Properties of Zirconium Phosphate, HZr2(PO4)3, and Its Application for the Removal of Sodium Ions,” Analytical Sciences Vol.12, December 1996, pp.935-940, and Sun, Jian-Zhi, “Synthesis and Absorption Properties of Novel Na Specific Sorbent,” Journal of Chilean Chemical Society v.53(4), 2008 pp.1682-1683. Additionally, the purity of lithium hydroxide monohydrate can be improved by removing potassium and sodium impurities using adsorbents.

[0024] Optionally, the concentrated lithium-ion-containing solution from the reverse osmosis step 330 can then be fed through additional process steps to produce lithium hydroxide. In this optional process, the concentrated lithium-ion-containing solution from the reverse osmosis step 330 is fed through the electrochemical production step 340 of lithium hydroxide to produce a lithium hydroxide-containing solution. The lithium hydroxide-containing solution can optionally be treated in an evaporation / crystallization step 350 to remove water from the lithium hydroxide-containing solution and crystallize at least a portion of the lithium hydroxide. In an optional lithium hydroxide isolation and drying step 360, the lithium hydroxide is isolated, recovered, and dried.

[0025] Optionally, the lithium-ion-containing solution from lithium capture step 320 may also be supplied to a lithium-ion-containing solution purification step before the reverse osmosis step 330, or the purification of the lithium-ion-containing solution may occur after the reverse osmosis step 330. This optional purification of the lithium-ion-containing solution may include the removal of divalent ion impurities. The purification of the lithium-ion-containing solution is optional because it depends on the lithium-ion concentration from lithium capture step 320. If the lithium-ion-containing solution from lithium capture step 320 is pure enough to be supplied to the reverse osmosis step 330, optional purification is not necessarily required.

[0026] Referring to Figure 4, a method 400 is provided for the isolation of lithium ions from brine or other lithium-containing solutions and the subsequent production of lithium carbonate therefrom, according to another embodiment. The brine is supplied to a silica control step 410, where silica is removed from the brine to produce silica-free brine or a lithium-containing solution. The silica-free brine or lithium-containing solution is then processed in a lithium capture step 420. In the lithium capture step 420, lithium ions are removed from the silica-free brine or lithium-containing solution to obtain a lithium-ion-containing solution.

[0027] The lithium ion-containing solution obtained from the lithium capture step 420 can undergo further optional processing to obtain lithium carbonate. In an optional reverse osmosis step 430, the lithium ion-containing solution can be concentrated via reverse osmosis to produce a concentrated lithium ion-containing solution. In an optional electrochemical production step 440 of lithium hydroxide, the concentrated lithium ion-containing solution is supplied to an electrochemical cell to produce lithium hydroxide. The lithium hydroxide can then be supplied to the lithium hydroxide carbonation step 450, where it is converted to lithium carbonate. Finally, in the lithium carbonate isolation step 460, the lithium carbonate is isolated and recovered.

[0028] Referring to Figure 5, a multi-step process for the isolation and concentration of lithium ions from brine or other lithium-containing solutions is provided according to one embodiment. The brine is supplied to a silica control step (not shown), where silica is removed from the brine to produce silica-free brine or lithium-containing solution 500. The silica-free brine or lithium-containing solution 500 is then supplied to a lithium capture step 510. In the lithium capture step 510, lithium ions are removed from the silica-free brine or lithium-containing solution 500 to form a lithium-ion-containing solution 520. The lithium-ion-containing solution 520 from the lithium capture step 510 is then concentrated in a reverse osmosis step 530 to produce a concentrated lithium-ion-containing solution 540. The reverse osmosis permeate (line 505), which essentially contains water, is recycled back to lithium extraction as a condensed flow (line 590) produced by the concentration of lithium chloride resulting from the evaporation of water. Line 600 represents the concentrated lithium chloride flow.

[0029] The concentrated lithium ion-containing solution 540 can optionally undergo further processing. In an optional electrochemical production step of lithium hydroxide, the concentrated lithium ion-containing solution 540 is supplied to an electrochemical cell to produce lithium hydroxide. The lithium hydroxide can optionally be supplied to a lithium hydroxide carbonation step, where it is converted to lithium carbonate. In an optional lithium carbonate isolation step, the lithium carbonate is isolated and recovered. The lithium ion-containing solution from the lithium capture step can also optionally be supplied to a lithium ion-containing solution purification step before a reverse osmosis step 530 (not shown), or the lithium ion-containing solution purification step 550 may occur after the reverse osmosis step 530.

[0030] This optional lithium-ion-containing solution purification step 550 may include the removal of divalent ion impurities 580. The purification of the lithium-ion-containing solution is optional because it depends on the lithium-ion concentration from the lithium capture step 510. If the lithium-ion-containing solution 520 from the lithium capture step 510 is pure enough to be sent to the reverse osmosis step 530, the optional purification step 550 is not necessarily required. After the optional purification step 550, the purified lithium-ion-containing solution 560 may undergo an optional further lithium-containing solution concentration 570, followed by an optional purification step to remove sodium and potassium before the solution is supplied to the electrochemical production of lithium hydroxide.

[0031] Referring to Figure 6, in one embodiment of the method, a lithium salt-containing solution 610 is provided. As described above, the lithium salt-containing solution 610 can be obtained from various sources, including geothermal brine. The lithium salt-containing solution is supplied to a silica control process 612, which operates to significantly reduce the amount of silica that may be present in the lithium salt-containing solution 610, thereby producing a silicate precipitate 616 and a silica-lean lithium salt-containing solution 614. Preferably, after the silica control process 612, the silica concentration in the silica-lean lithium salt-containing solution 614 is less than about 150 ppm, more preferably less than about 100 ppm, even more preferably less than about 50 ppm, and even more preferably less than about 25 ppm. In certain embodiments, the silica concentration in the silica-lean lithium salt-containing solution 614 is less than about 20 ppm, less than about 10 ppm, or even less than about 5 ppm. It should be understood that silica control process 612 may be omitted or replaced from the process with respect to brine that does not contain silica or has a substantially low initial silica concentration.

[0032] In certain embodiments, the silica control process 612 may include the step of contacting a lithium salt-containing solution 610 with activated alumina to remove at least a portion of the silica present. The alumina containing the bound silica can be regenerated by contacting the alumina with sodium hydroxide. Alternatively, the lithium salt-containing solution can be contacted with aluminum chloride, which is converted to aluminum hydroxide when contacted with brine, and can be used to precipitate silica present in the lithium salt-containing stream. In further embodiments, iron(II) that may be present in certain lithium-containing brines can be oxidized with an oxidizing agent such as air, hypochlorite, hydrogen peroxide, oxygen, ozone, or similar oxidizing agents to produce iron(III) chloride, which precipitates iron hydroxide after adjusting the pH from an initial pH of about 2.5–3.5 to above about 5. The iron hydroxide can adsorb silica from the lithium-containing brine. In preferred embodiments, the pH is adjusted to about 5–6 to induce precipitation of silica and iron. In alternative embodiments, the pH is adjusted to at least about 4.5 to induce precipitation of silica and iron. In certain embodiments, it is preferable that the pH does not increase above about 6 to prevent precipitation of other ionic species present in the lithium-containing brine. In yet another embodiment, iron(II) is added to the lithium chloride-containing solution and oxidized to iron(III) by known means, for example, by contacting iron(II) with an oxidizing agent such as air, oxygen, ozone, hypochlorite, hydrogen peroxide, or other suitable oxidizing agents. Contacting the silica present in the lithium chloride-containing solution with the iron(III) compound forms a precipitate when the pH is adjusted to about 4.5–6 by the addition of lime or a similar base. In preferred embodiments, the pH is adjusted to about 5–6. In alternative embodiments, the pH needs to be adjusted to at least about 4.5 for silica and iron to precipitate. In certain embodiments, it is preferable that the pH does not increase above about 6 to prevent precipitation of other ionic species.

[0033] In addition, the silica control process 612 may include any known means for removing any portion of the silica present in the transport stream while simultaneously maintaining the initial lithium concentration. In one embodiment, the lithium chloride-containing solution 610 can be brought into contact with aluminum chloride, iron chloride, aluminum hydroxide, etc., to form a precipitate having silicon dioxide. Contact can be facilitated by known means such as a mixing device. The solid silica precipitate 616 removed from the lithium chloride-containing solution 610 can be collected and removed from the mixing device (or other device) by known means such as screening or filtration to produce a lithium chloride-containing stream 614 that is substantially free of silica.

[0034] Various membranes can be used to selectively remove specific undesirable ions from the lithium-containing solution 614.

[0035] A silica-lean lithium chloride-containing stream 614 that is substantially free of silica (measured as SiO2) may be fed to a lithium capture (or lithium extraction) step 618. In certain embodiments, the silica-lean lithium chloride-containing stream 614 may be fed to a lithium capture process 618 which includes at least one intercalated lithium adsorbent column configured to absorb and isolate lithium chloride from the silica-lean lithium chloride-containing solution while simultaneously allowing other ions such as calcium, magnesium, and / or sodium to pass through the wastewater stream 622 through the use of a selective molecular sieve, membrane, or other similar material. In embodiments including two or more intercalated lithium adsorbent columns, the majority of the lithium is removed in the first intercalated lithium adsorbent column, and the overall lithium loss during the recovery process can be minimized using any subsequent "polishing" intercalated lithium adsorbent column.

[0036] In certain embodiments, the intercalated lithium adsorbent column may operate as follows: In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 800 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 700 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 600 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 500 μm. Lithium alumina intercalate particles having an average diameter of less than 400 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 300 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 200 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of less than 100 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 100 to 150 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 150 to 200 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 200-250 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 250-300 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 300-350 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 350-400 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 400-450 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 450-500 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 500-550 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 550-600 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 600-650 μm.In some embodiments, the lithium alumina intercalate particles have an average diameter of about 650–700 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 700–750 μm. In some embodiments, the lithium alumina intercalate particles have an average diameter of about 750–800 μm. In a particular embodiment, the lithium alumina intercalate particles have an average diameter of about 200–800 μm. Alternatively, the lithium alumina intercalate particles have an average diameter of about 300–500 μm, alternatively, about 400–700 μm, or alternatively, about 350–650 μm.

[0037] In some embodiments, lithium alumina intercalate particles can be added to a column having a particle size of less than about 400 microns. The column may be coated and insulated, or include means for providing heating or cooling to the column. The column may include a method for distributing the liquid and support for the extraction medium, and may include frit ends having a pore size of about 25–50 μm, although other similar means such as glass wool or perforated plate supports, and fractal fluid distributors can also be used instead of frit ends. In some embodiments, the operating temperature of the column can be maintained at a temperature higher than room temperature (20°C), preferably above about 70°C, more preferably between about 95°C and about 110°C.

[0038] The column is kept moist before its first use and removed by circulating at least about 1 bed volume, preferably about 2 bed volumes, of deionized strip water 20 containing about 1000 ppm lithium chloride (or other lithium salt) at a flow rate of about 1 to 4 bed volumes / hour, preferably about 1.5 to 2.5 bed volumes / hour. The column is then brought into contact with about 1 bed volume of saturated sodium chloride solution containing about 200 ppm lithium chloride and then operated.

[0039] In some embodiments, during column packing (i.e., during the step of capturing the desired lithium salt), a high ionic strength solution 614 containing lithium chloride (or other lithium salt) is supplied to the lithium capture process 618, and the lithium concentration of the effluent in the wastewater flow 622 is measured to determine the point at which the column becomes saturated with lithium chloride. During the lithium ion capture step, the lithium concentration in the wastewater flow 622 remains fairly constant and relatively low, for example, approximately 0 to 100 ppm. At this point, the lithium capture process 618 reaches or approaches the saturation point with lithium ions, however, the concentration of lithium in the effluent increases, indicating that the column has little or no capacity for additional lithium ions. Upon reaching this saturation point, the flow of the lithium chloride solution into the lithium capture process 618 is stopped, and the column becomes flush with about 1 to 5 bed volumes of deionized water, preferably about 1 to 2.5 bed volumes, most preferably about 1 to 1.5 bed volumes, generating a lithium chloride-rich flow 624. It should be understood that the apparatus may include various valves and control devices to control the flow of lithium-containing solution or strip solution into the column.

[0040] In a particular embodiment, after the column is packed and before the collection of captured lithium chloride (or other lithium salts), the column may be flush with a 26% saturated sodium chloride solution containing about 200 ppm lithium chloride in about one bed volume.

[0041] In some embodiments, during the lithium capture process 618 for isolating lithium chloride, after removing lithium chloride (or other lithium salts) from the lithium-containing transport stream, the intercalated lithium adsorbent column can be regenerated and lithium chloride recovered therefrom. Specifically, at least about 0.5 equivalents of strip water 620 may be supplied to the column(s) used in the lithium capture process 618 to remove absorbed lithium chloride and produce a lithium chloride-rich solution 624. In certain embodiments, about 1-2 equivalents of strip water 620, or more equivalents, may be used during column regeneration. In preferred embodiments, the strip water may contain lithium ions for column regeneration. Optionally, low ionic strength liquids such as alcohol and water / alcohol mixtures may be used to regenerate the column. Generally, the amount of water utilized from the recovery of lithium chloride from the column is minimized by recycling the product stream to maximize lithium content without affecting the volume of the extraction medium. In this context, it should be noted that the strip solution (typically concentrated with lithium) exiting the column is also referred to herein as the eluate.

[0042] The lithium chloride-rich stream 624 may have a lithium concentration of about 1% to 6% by weight, preferably more than about 1% by weight, and more preferably more than about 3% by weight, based on the total weight of the lithium chloride-rich stream 624. In an alternative embodiment, the lithium chloride-rich stream 624 may have a lithium concentration of more than about 0.5% by weight. The lithium chloride-rich stream 624 can undergo lithium concentration 626 by various means including evaporation, reverse osmosis, solvent extraction, or a combination of these processes to produce a concentrated lithium chloride stream 630 having lithium in the range of 10% to 42% by weight, based on the total weight of the concentrated lithium chloride stream 630. In a preferred embodiment, the concentrated lithium chloride stream 630 has a lithium concentration of at least 20% by weight, more preferably 30% by weight, and even more preferably 42% by weight, based on the total weight of the concentrated lithium chloride stream 630. In most cases, the concentrations of sodium and potassium in the concentrated lithium chloride stream 630 are less than 1% by weight of the stream 630.

[0043] In certain embodiments, the lithium chloride-rich stream 624 and / or concentrated lithium chloride stream 630 may optionally undergo a purification or concentration step before being supplied to the electrolysis process 632. Optionally, the purification step may be used to remove calcium, magnesium, or other divalent ions such as zinc and manganese that may be present in the lithium chloride (or other lithium salt)-rich stream 624 and / or concentrated lithium chloride stream 630. Removal of calcium, magnesium, and / or other alkaline earth metals can be achieved by known means such as increasing the pH and treating the solution by ion exchange, preferably by using a selective chelating ion exchange resin, or by adding a base such as lime, sodium hydroxide, or lithium hydroxide, and / or by adding lithium carbonate, sodium carbonate, potassium carbonate, ammonium carbonate, or other suitable carbonates that can precipitate magnesium and iron hydroxide, as well as calcium carbonate. In alternative embodiments, ion exchange means may be used to facilitate the removal of calcium, magnesium, and / or other alkaline earth metals. Other bases such as sodium hydroxide and other alkali metal hydroxides may also be used. For certain brines, it may be beneficial at this point to remove boron from the product stream by known means such as precipitation, solvent extraction, or ion exchange. Methods for the isolation and purification of lithium chloride (or other lithium salts) from brines, including geothermal brines, are known in the art, as described, for example, in U.S. Patent Nos. 9,012,357, 8,901,032, 8,753,594, 8,637,428, 6,280,693, 4,348,295, and 4,461,714, and U.S. Patent Application Publications 2014 / 0239224 and 2018 / 0056283, each of which is incorporated herein by reference in whole. In some embodiments, such as those focusing on the removal of magnesium ions, the divalent ion removal step should occur in the lithium chloride-rich stream 624.

[0044] Alternative adsorbent materials for lithium extraction can also be combined with reverse osmosis to enhance lithium recovery performance. In some embodiments, adsorbent materials may include lithium oxide, lithium cobaltate, lithium phosphate, lithium iron phosphate, lithium fluorophosphate, lithium vanadium fluorophosphate, lithium manganese cobalt nickel oxide, lithium alumina, activated alumina, boehmite, cobalt nickel oxide, lithium titanate, lithium manganese oxide, or mixtures thereof. Adsorbent materials may be provided in various forms (e.g., powder). In some embodiments, a matrix based on an adsorbent composition (e.g., activated alumina lithium intercalate adsorbent) can be prepared by mixing the adsorbent material with a polymer, plastic, or other organic or inorganic binder material.

[0045] This optional purified lithium chloride-rich stream 624 and / or concentrated lithium chloride stream 630 may include the removal of sodium and potassium before the concentrated lithium chloride stream 630 is supplied to the electrochemical cell 632.

[0046] In certain embodiments, the process may optionally include one or more filtering or separation and purification steps prior to the step of supplying a concentrated lithium chloride solution 630 or brine to the electrochemical cell 632.

[0047] Optionally, the process may include steps to increase the concentration of the lithium chloride stream. Specifically, the lithium concentration step 626 may be used, for example, to remove a portion of the water in the lithium chloride stream by evaporation, thereby producing a more concentrated lithium chloride (or other lithium salt) solution 630. Exemplary concentration methods may include solvent extraction, electrodialysis, vapor evaporation, or solar evaporation. In further embodiments, the lithium concentration is obtained by reverse osmosis. In such a method, the reverse osmosis apparatus is supplied with a lithium chloride-rich stream 624. In some embodiments, the lithium chloride-rich stream supplied to the reverse osmosis apparatus has at least 1% by weight of lithium chloride. In some embodiments, the lithium chloride-rich stream supplied to the reverse osmosis apparatus has at least 2% by weight of lithium chloride. In further embodiments, the lithium chloride-rich stream has 1000 mg / kg or less of sodium chloride. In further embodiments, the lithium chloride-rich stream has 100 mg / kg or less of calcium equivalent. The calcium equivalent includes divalent cations such as calcium, manganese, magnesium, strontium, and barium. The sodium equivalent includes sodium and potassium. To calculate the equivalent weight, the molecular weight of the components was determined. For example, to calculate the calcium equivalent of manganese, the manganese concentration was divided by the molecular weight of manganese, and then multiplied by the molecular weight of calcium.

[0048] In a further embodiment, the lithium chloride-rich stream has boron content of 30 mg / kg or less. In a further embodiment, the reverse osmosis apparatus is also supplied with a recycled stream from either a strip water stream from a lithium adsorbent column or a strip water stream from depleted brine.

[0049] In further embodiments, the lithium capture process includes the step of supplying silica-lean lithium chloride to the lithium adsorbent material for lithium capture until the lithium adsorbent material is saturated with lithium, thereby producing a saturated lithium adsorbent material. In some embodiments, the lithium adsorbent material is an intercalated lithium adsorbent. In further embodiments, the recovered lithium salt step includes stripping the saturated lithium adsorbent material with water to produce a lithium-rich flow. In some embodiments, the saturated lithium adsorbent material is stripped with about 1 to 4 bed volumes of water. In some embodiments, the saturated lithium adsorbent material is stripped with about 1 to 3 bed volumes of water. In some embodiments, the saturated lithium adsorbent material is stripped with about 1 to 2 bed volumes of water. In some embodiments, the water is purified water. In some embodiments, the water is deionized water. In some embodiments, the water is recycled from a downstream process such as a lithium chloride concentration step.

[0050] In some embodiments, the water 628 removed from the lithium chloride solution can be recovered, for example, by evaporation and subsequent concentration and resupplied to the intercalated lithium adsorbent column(s) of the lithium capture step 618, or supplied to any other step in this or related process that requires a water supply. Alternatively, the water 628 can be supplied to a geothermal well. In embodiments using the concentration step, the overall concentration of the concentrated lithium chloride-rich solution 630 can be increased to more than 25% by weight of lithium chloride, preferably up to about 40% by weight of lithium chloride.

[0051] The concentrated lithium chloride-rich solution 630 can be supplied to an electrochemical cell 632 comprising at least one anode, one cathode, and a permeable membrane for the electrochemical preparation of lithium hydroxide. Electrochemical cells suitable for large-scale production are commercially available from companies such as Ineos, DeNora, Chlorine Engineers, and Asahi Glass, to name a few examples. Specifically, chloride ions are oxidized to chlorine (Cl) at the anode, and water is reduced to hydroxide ions and hydrogen gas at the cathode. Preferably, the concentrated lithium chloride-rich solution 630 is substantially free of other ions, particularly those that may interfere with the electrochemical reaction. Optionally, the lithium chloride-rich stream may be supplied directly to the electrochemical reaction without first being subjected to silica control and lithium ion sequestration steps, provided that the lithium chloride-rich stream is substantially free of non-lithium ions, particularly non-lithium ions that may interfere with the electrochemical reaction, such as silica, calcium, and magnesium. In certain embodiments, the concentration of sodium and / or potassium ions in the concentrated lithium chloride-rich solution 630 is less than about 5% by weight, preferably less than about 3% by weight, and more preferably less than 1%. Cations such as calcium and magnesium, if all are present, preferably have a total concentration of less than about 20 ppb by weight, more preferably less than about 10 ppb by weight, and more preferably less than 5 ppb by weight. Higher concentrations of interfering ions do not necessarily impede the operation of the electrochemical cell; rather, they may reduce the overall lifespan of the cell components, particularly the membrane, and / or the overall effectiveness of the production of the lithium hydroxide solution.

[0052] Similar to what is described above regarding the presence of non-lithium interfering cations, the electrochemical cell 632 preferably has a total non-chloride anion content of less than about 5% by weight, preferably less than about 3% by weight, and more preferably less than about 1% by weight.

[0053] The cathode of the electrochemical cell 632 may be any suitable material, including nickel, catalytic nickel, stainless steel, coated stainless steel, mild steel, and the like. Other exemplary catalysts include mixed ruthenium and nickel compounds, platinum, and other similar compounds having potentially low hydrogen content. The total surface area of ​​the cathode can be adjusted based on the size of the reactor and the desired yield. The cathode liquid delivered to the electrochemical cell 632 may be any suitable material having sufficient ions to carry the electric current. Water may be used, and in certain embodiments, the addition of lithium carbonate or lithium hydroxide to the water may be beneficial for the operation of the cell.

[0054] The anode of the electrochemical cell 632 may be any suitable material, such as a titanium mesh coated with ruthenium oxide, a titanium mesh coated with platinum, or a titanium mesh coated with carbon. Preferably, the anode is a dimensionally stable anode, which allows for reduced power consumption. A dimensionally stable ruthenium-iridium oxide on a titanium or similar corrosion-resistant metal anode is particularly suitable for chlorine environments because the titanium substrate is corrosion-resistant. In some embodiments, the anode is a dimensionally stable anode selected from those heavily coated with ruthenium oxide, platinum, or carbon. The total area of ​​the anode can be adjusted based on the size of the reactor and the desired yield. The anode solution of the electrochemical cell 632 may be any suitable material, comprising a lithium chloride solution having a concentration of about 1% to saturated, preferably 5% to 40% to 10% to 35% to 15% to 25% to 1

[0055] The materials for constructing the electrochemical cell 632 can be any material that is chemically resistant to chlorine, activated chlorine, oxygenated chlorine species, and other soluble species that may be present in the brine solution on the anode side and lithium hydroxide on the cathode side. Exemplary materials for constructing the electrochemical cell 632 include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), HALAR (an alternating copolymer of ethylene and chlorotrifluoroethylene (CTFE)), and other fluorinated or partially fluorinated materials.

[0056] The membrane of the electrochemical cell 632 can be any suitable semipermeable cation-selective membrane that selectively allows cations to pass through and inhibits the passage of anions. Such membranes are known in the art. One exemplary membrane is the material of Nafion® (EIDuPont de Nemours & Co.®), particularly the Nafion® 300, 400, and 900 / 9000 series. Other suitable membranes may be supplied by Flemion®, but any suitable membrane material may be used if the material is chemically resistant to both chlorine and lithium hydroxide. The membrane may be placed between the anode and cathode solutions to be electrolyzed.

[0057] During operation of electrochemical cell 632, the current is approximately 500-10,000 A / m. 2 The current density can be applied at a voltage of approximately 1.5 to 5 volts. In some embodiments, it can be approximately 2000 to 7000 A / m 2 A current density of approximately 2000-4000 A / m² is applied. In further embodiments, approximately 2000-4000 A / m² is applied. 2 The current density is applied.

[0058] The electrochemical cell 632 can operate at temperatures of about 60°C to 100°C, preferably about 70°C to 95°C, and more preferably about 80°C to 90°C. The cell 632 can be operated at atmospheric pressure or slightly above atmospheric pressure.

[0059] The operation of the electrochemical cell 632 generates lithium hydroxide in solution and releases chlorine and hydrogen gases, respectively, as products, which can be removed from the electrochemical cell via lines 634 and 636.

[0060] The current efficiency of the electrochemical cell 632 can be described in several ways as being at least about 60%, preferably at least about 70%, more preferably at least about 80%, more preferably at least about 90%, more preferably at least about 95%, and even more preferably up to about 99.9% for the production of lithium hydroxide. Electrolysis may be operated continuously until the lithium hydroxide content reaches about 17 wt%, at which point the lithium hydroxide solution may be removed and supplied to the carbonation reactor. At lithium hydroxide concentrations greater than about 17 wt%, lithium hydroxide monohydrate in the solution may begin to precipitate. The electrochemical cell 632 can also be operated under conditions designed to produce lower concentrations of lithium hydroxide solution, and the lower concentrations of lithium hydroxide solution may be recycled to and from the carbonation reactor. In certain embodiments, the electrochemical cell 632 may also include a transport line (not shown) for supplying water, low concentrations of lithium hydroxide, low concentrations of lithium carbonate, or a combination thereof to the cell. The preferred range for operating conditions is 2 to 1% by weight of lithium hydroxide, and most preferably 3 to 8% by weight.

[0061] After the lithium chloride-rich stream 624 and / or concentrated lithium chloride stream 630 are processed in the electrochemical cell 632, the lithium hydroxide solution 636 is supplied from the electrochemical cell 632 to the carbonation reactor / absorber 638, for example, upward, and can be brought into contact with carbon dioxide gas 644. The carbonation reactor / absorber 638 may include a series of trays or other similar means designed to allow lithium hydroxide 636 to be supplied to the top of the reactor, flow downward through the reactor, and thereby be introduced near the bottom of the carbonation reactor / absorber 638 into contact with upward carbon dioxide gas 644. In alternative embodiments, the carbonation reactor / absorber 638 may include various mixing means designed to facilitate efficient mixing of liquids and gases. Optionally, the carbonation reactor / absorber 638 may be a jacketed batch reactor with thermostat heating. This reaction produces solid lithium carbonate. The concentration of the lithium carbonate slurry is preferably at least about 1.5% by weight of lithium carbonate, more preferably at least about 6% by weight of lithium carbonate. Carbon dioxide can be captured and recycled to the carbonation reactor / absorber 638 via line 642.

[0062] In certain embodiments, lithium carbonate can be produced by the reaction of lithium chloride with sodium carbonate in water, and the mixture is heated with stirring, preferably to a temperature of about 90°C to 95°C. This reaction produces solid lithium carbonate and a sodium chloride solution, the sodium chloride solution can be separated from the desired solid lithium carbonate by filtration.

[0063] In a particular embodiment, the process product is a concentrated solution of lithium chloride, which is produced according to the silica control process 612, the lithium capture process 618, and the lithium concentration 626. The resulting solution preferably has a lithium chloride concentration of 30% to 42% by weight, preferably about 36% by weight. This lithium chloride can be further concentrated to produce crystalline lithium chloride by evaporation processes known in the art.

[0064] The lithium carbonate-containing slurry 640 can be fed to a filter 646, which is operable to separate the lithium carbonate-containing slurry 640 into a stream of water 652, which can optionally be re-fed to the filter 646, and a solid lithium carbonate product 650. The filter 646 may include, for example, a series of screens or filters and a water supply 648. Optionally, the water can be recycled back into the process via line 652. Optionally, the lithium carbonate can be concentrated from the lithium carbonate-containing slurry 640 by centrifugation or decantation thickening. The water collected during the separation of the solid from the lithium carbonate-containing slurry 640 via the filter 646 can be fed to an electrochemical cell 632, recycled to an optional purification step, or returned to a silica control 612 as a base to further increase the pH. In certain embodiments, the solid lithium carbonate may be held on a band or belt filter and fed to a washing step, preferably using hot water having a temperature of about 90°C to 95°C to wash the solid. In certain embodiments, the aqueous solution collected via filter 646 may have a pH greater than about 9, possibly about 10–12. Alternatively, sufficient acid can be added to the aqueous solution to achieve a pH of about 5–8.5, and the acidified water can then be fed to the intercalated lithium adsorbent column. Alternatively, the solution can be returned directly to the cathode side of the electrolytic cell without prior neutralization. Further recycling possibilities include using the strip water in the regeneration of the ion exchange process to purify the lithium chloride stream.

[0065] In some embodiments, the solid lithium carbonate 650 is supplied to a drying station 654 which may optionally include heating means and lines for supplying nitrogen or other inert gas to the dryer. The dried lithium carbonate product 656 can then be recovered, packaged, and transported for further use.

[0066] Referring here to Figure 7, another embodiment for the production of lithium carbonate is provided. In some embodiments, a lithium chloride stream 730 is provided by the process described above and as shown in Figure 6. In other embodiments, a sodium chloride stream 760 is provided to an electrochemical cell 732 as described above. The sodium chloride stream 760 is then subjected to electrolysis to produce a sodium hydroxide stream 762, and a chlorine gas stream 764, and a hydrogen gas stream 765. The reaction conditions for the production of sodium hydroxide by electrolysis of sodium chloride are known in the art.

[0067] In certain embodiments, the efficiency of sodium hydroxide production by electrolysis of sodium chloride is at least about 70%, alternatively at least about 80%, alternatively at least about 90%, or alternatively at least about 95%. In certain embodiments, the sodium hydroxide solution 762 is produced at a concentration of at least about 10% by weight, more preferably at least about 30% by weight, and most preferably about 32–35% by weight.

[0068] The chlorine gas streams 764 and hydrogen gas streams 765 from the electrochemical cell 732 can be burned and washed with water to produce hydrochloric acid, which can be used in the process or, alternatively, purified, compressed, and sold commercially.

[0069] A sodium hydroxide stream 762 is supplied to the carbonation reactor / absorber 738, and the sodium hydroxide stream 762 comes into contact with, for example, upward carbon dioxide vapor 744. The carbonation reactor / absorber 738 may include a series of trays designed to allow the sodium hydroxide stream 762 to be supplied to the top of the reactor and flow downward through the reactor, thereby coming into contact with upward-flowing carbon dioxide gas 744, which may be introduced near the bottom of the reactor, to produce a sodium carbonate solution or slurry 766. In alternative embodiments, the carbonation reactor / absorber 738 may include various mixing means designed to facilitate the mixing of liquids and gases. The concentration of the solution is preferably at least 15% by weight of sodium carbonate, more preferably at least 25% by weight of sodium carbonate. Carbon dioxide can be captured and recycled to the carbonation reactor / absorber 738 via line 742.

[0070] A sodium carbonate solution or slurry 766 is supplied to the reactor 768, where the solution comes into contact with a lithium chloride solution 730 to produce a slurry 770 containing lithium carbonate and sodium chloride solutions. The step of contacting the sodium carbonate solution 766 and the lithium chloride solution 730 in the reaction vessel can be performed at a temperature above about 60°C, preferably above about 80°C, and more preferably about 90°C to 95°C. In certain embodiments, the reaction vessel 768 may be a stirred tank reactor. Alternatively, the reaction vessel 768 may be a standard crystallizer. In some embodiments, the lithium carbonate is present as a precipitate, while the sodium chloride remains in aqueous solution.

[0071] A slurry 770 containing solid lithium carbonate and an aqueous sodium chloride solution is fed to a separator 772, which may include various means for separating the solid from the liquid to produce a lithium carbonate product stream 774 and a sodium chloride brine solution 776, including, for example, a centrifuge, a sedimentation tank, a filter, a screen, etc. To achieve improved product quality, the lithium carbonate may be treated to remove sodium, potassium, and / or chloride ions trapped in the interstitial space of the lithium carbonate precipitate by washing with water, preferably hot water, or similar means. In certain embodiments, the separator 772 may be a band filter or a rotating drum and may optionally be supplied through a countercurrent washing system for removing residual sodium chloride. The separator 772 may also include a water inlet 778 to provide water for washing the separated solid lithium carbonate. The separator 772 may also include means for drying and / or removing water from the solid lithium carbonate, including, for example, a centrifuge, a heater, a blower, a press, etc. The separator 772 may include a vacuum filter for removing water. In certain embodiments, it is desirable to optimize the washing step to maximize the purity of lithium carbonate while minimizing the amount of water used for washing. The sodium chloride solution 776 can be recycled to the electrochemical cell 732 for electrolysis. The lithium carbonate product 774 may have a water content of less than about 5% by weight, preferably less than about 2% by weight, and more preferably less than about 0.5% by weight.

[0072] The brine solution 776 from the separator 772 may contain sodium chloride and lithium carbonate. Generally, depending on the amount of water used during the process and washing process, the ratio of sodium chloride to lithium carbonate is at least about 20:1, more preferably at least about 25:1, and even more preferably at least 30:1. In certain embodiments, the ratio of sodium chloride to lithium carbonate in the brine solution may be about 35:1.

[0073] In certain embodiments, the brine solution 776 can be acidified with hydrochloric acid (not shown) to a pH of less than about 4, preferably about 3, and recycled to the electrochemical cell 732. The hydrochloric acid can be supplied from the electrochemical cell 732. Such a method of producing lithium carbonate is advantageous because the process eliminates or nearly eliminates the generation of waste. Specifically, in certain embodiments, unused metal salts, e.g., sodium chloride, and carbon dioxide are recycled, and the total yield can be quantitative or nearly quantitative. The brine solution 776 can be subjected to purification to achieve desired specifications for the delivery of sodium chloride anode liquid to the electrochemical cell 732, if required. Similar to the process described in detail above in Figure 6, in certain embodiments, the lithium chloride-rich stream 724 and / or concentrated lithium chloride stream 30 can optionally undergo a purification or concentration step before being supplied to the electrochemical cell 732.

[0074] Referring here to Figure 8, another alternative embodiment for the production of lithium carbonate is provided. This method is a single-step process in which sodium carbonate is produced and reacts with recovered lithium chloride, but may require additional input and produce a waste lithium chloride stream that may contain a small amount of lithium carbonate present therein.

[0075] A lithium chloride stream is provided as described above. In some embodiments, a sodium chloride stream 860 is supplied to an electrochemical cell 832. The sodium chloride stream 860 is subjected to electrolysis to produce a sodium hydroxide stream 862, a chlorine gas stream 864, and a hydrogen gas stream 865, respectively.

[0076] The sodium hydroxide stream 862 is supplied to the mixer 880, where it is mixed with the lithium chloride stream 830. The mixing of the sodium hydroxide stream 862 and the lithium chloride stream 830 can be carried out by known means, such as by a stirrer or mixer, using ultrasound, or similar means. The mixer 880 produces a mixed stream 882 containing sodium hydroxide and lithium chloride in aqueous solution. In certain embodiments, the lithium chloride stream 830 may preferably have a lithium chloride concentration of at least about 20% by weight, more preferably at least about 28% by weight, and even more preferably about 42% by weight. Similarly, in certain embodiments, the sodium hydroxide stream 862 may preferably have a sodium hydroxide concentration of at least about 15% by weight, more preferably at least about 25% by weight, and even more preferably about 35% by weight.

[0077] The mixed flow 882 is then supplied to the carbonation reactor / absorber 884, which may include a series of trays designed to allow the mixed flow containing lithium chloride and sodium hydroxide to be supplied to the top of the reactor and flow downward through the reactor, thereby allowing the mixed flow to come into sufficient contact with the upward-flowing carbon dioxide gas 844 and be introduced near the bottom of the reactor to produce a lithium carbonate slurry 890. Preferably, the carbonation reactor / absorber 884 is maintained at a temperature of about 90°C to 100°C. In alternative embodiments, the carbonation reactor / absorber 884 may include various mixing means designed to facilitate the mixing of liquids and gases. For example, the concentration of lithium carbonate in the flow 890 is preferably at least 4% by weight, more preferably at least 8% by weight. Carbon dioxide can be recycled to the carbonation reactor / absorber 884 via line 842.

[0078] The lithium carbonate solution 890 is supplied to the separator 892, where solid lithium carbonate is determined via line 894. A solution containing sodium chloride and optionally a small amount of lithium carbonate is produced as flow 896. The sodium carbonate solution 890, containing solid lithium carbonate and an aqueous sodium chloride solution, is supplied to the separator means 892, which may include various means for separating the solid from the liquid, including, for example, a centrifuge, a sedimentation tank, a filter, a screen, etc. The separator means 892 may also include a water inlet and a water outlet (not shown) for washing the separated solid lithium carbonate. The separator 892 may also include means for drying and / or removing water from the solid lithium carbonate, including, for example, a centrifuge, a heater, a blower, a press, etc. The solid sodium carbonate product may be recovered via line 894. Optionally, a portion of the sodium chloride flow 896 may be recycled to the electrochemical cell 832. Optionally, the sodium chloride solution may be recycled to the washing step of the lithium extraction medium. In certain embodiments, the sodium chloride required for the process can be produced by geothermal energy, smackover, or selective crystallization of sodium chloride from other brines.

[0079] In certain embodiments, the intended process may include means for neutralizing any lithium carbonate present in the sodium chloride solution, such as by neutralizing the solution by adding an effective amount of hydrochloric acid or a similar acid. In embodiments where lithium carbonate can be effectively removed, the solution can be recycled into an electrochemical cell, although any lithium carbonate present inside may cause problems with the performance of the electrochemical cell.

[0080] In a further embodiment for an exemplary reverse osmosis system, a lithium-containing solution from a lithium capture process is delivered to the reverse osmosis system using a pump. From the reverse osmosis system, water is delivered to the permeate. The concentrated lithium-containing stream is delivered to the concentrate. The permeate may then be delivered back to the reverse osmosis system using a pump. Additionally, the concentrated lithium-containing stream may be delivered back to further processing through the lithium capture process and using the reverse osmosis system. If the reverse osmosis system includes a cascade system, a lithium-containing solution from a lithium capture process is delivered to a first reverse osmosis system using a first pump. From the first reverse osmosis system, a first stream of water is delivered to the permeate, and the first concentrated lithium-containing stream is delivered to a second reverse osmosis system using a second pump. From the second reverse osmosis system, a second stream of water is delivered to the permeate, and the second concentrated lithium-containing stream is delivered to a third reverse osmosis system using a third pump. From the third reverse osmosis system, a third stream of water is delivered to the permeate, and the third concentrated lithium-containing stream is delivered to the concentrate. Various embodiments of the present invention may include any number of reverse osmosis systems in the cascade function. In some embodiments, there are three reverse osmosis systems in the cascade. In some embodiments, there are four reverse osmosis systems in the cascade. In some embodiments, there are five reverse osmosis systems in the cascade. In some embodiments, there are six reverse osmosis systems in the cascade. In some embodiments, there are seven reverse osmosis systems in the cascade. In some embodiments, there are eight reverse osmosis systems in the cascade. In some embodiments, there are nine reverse osmosis systems in the cascade. In some embodiments, there are ten reverse osmosis systems in the cascade.

[0081] Those skilled in the art will understand how to select a suitable reverse osmosis membrane for use in the present invention. Reverse osmosis membranes may include those supplied by Dow Chemical (Filmtec), Hydranautics, Osmonics (Desal), and Toray. Preferred reverse osmosis membranes typically include those that are spiral-shaped. Preferred reverse osmosis membranes are also described in Table 1. The list provided in Table 1 is provided as an example and is not intended to limit the reverse osmosis membranes used in embodiments of the present invention. Potential suppliers, along with descriptions of the membranes, are shown in Table 1 below. Less preferred membranes are those made from cellulose triacetate due to low flux. [Table 1-1] [Table 1-2]

[0082] In further embodiments, the lithium capture process is optimized by a series of recycling steps associated with the lithium capture process. For example, a portion of the strip may be recycled. Additionally, a portion of the filling may be recycled. The purpose of recycling is to improve the purity of the lithium chloride in the product and maximize its concentration before any purification or concentration steps. [Examples]

[0083] Example 1: Carbonation of sodium hydroxide Carbonation of sodium hydroxide was carried out using a 3-liter jacketed reactor with a heating system (manufactured by Syrris Reactor Systems, UK). The reaction was carried out at a temperature of approximately 95°C using 1 liter of 9.5 M sodium hydroxide solution (27.5% solid). Carbon dioxide was supplied at a rate of 3 L / min for approximately 1 hour (totaling approximately 8 moles, approximately 1.7 molar equivalents) to ensure the complete conversion of sodium hydroxide. At the end of the carbonation of the sodium hydroxide solution, a clear solution of sodium carbonate was obtained, at which point the carbonation reaction was stopped, and heating of the sodium carbonate solution was continued for several minutes. Lithium carbonate seeds were added to the clear solution and then reacted with a lithium chloride solution (404 g of lithium chloride in 1000 mL). The experimental yield was 95%. The yield varied for other similar reactions depending on the experimental conditions, and in some cases it was as high as approximately 100%. The purity of the isolated lithium carbonate was approximately 96.6% before washing.

[0084] Prior to the initial washing of the product stream, the lithium carbonate contained the following impurities: Na (71 mg / kg), Ca (2.8 mg / kg), Mg (2.1 mg / kg), Fe (0.3 mg / kg), Ba (0.1 mg / kg), Mn (0.08 mg / kg), and Sr (0.03 mg / kg) to a purity of approximately 78.4%. After washing with approximately 2-3 volume equivalents of water, the sodium concentration was reduced to an undetectable level, and the lithium carbonate contained the following impurities: Mg (5.9 mg / kg), Ca (2.9 mg / kg), Ba (0.4 mg / kg), Fe (0.4 mg / kg), Mn (0.07 mg / kg), and Sr (0.07 mg / kg) to a purity of over 99%. Washing conditions may affect the amount of sodium carbonate / chloride contained in the lithium carbonate product.

[0085] Example 2: Electrochemical cell efficiency The electrolysis process converts a purified, concentrated lithium chloride solution into a concentrated lithium hydroxide solution, and then into lithium bicarbonate. The limiting factor in determining the efficiency of the electrochemical cell is the concentration of lithium hydroxide in the cathode solution, due to the reverse migration of hydroxide across the membrane. Therefore, the experiment was designed to operate the electrochemical cell at four different hydroxide concentrations to map the effect of lithium hydroxide concentration and determine the maximum achievable concentration. The experiment was designed to measure the current efficiency and energy utilization of the dialysis process as a function of hydroxide concentration. Within the electrochemical cell, under the applied field, lithium cations migrate from the anode solution to the cathode solution, and the water present at the cathode is converted into H2 and OH. - It is electrolyzed. Theoretically, each electron passing through the external circuit corresponds to an increase of one lithium hydroxide molecule in the cathode solution, leading to an increase in the concentration of lithium hydroxide over time. The main inefficiency in the process is the OH from the cathode solution to the anode solution. - The reverse movement of ions occurs in the cathode solution's OH - It depends on the concentration. Therefore, the experiment reported here involves adding water at a known rate to the OH of the cathode solution. - The experiment was conducted with the intention of maintaining a constant concentration. The efficiency of the reaction was measured by comparing the actual rate of water addition with the theoretical rate of addition.

[0086] Example 3. Electrolysis of lithium hydroxide from lithium chloride. Experimental preparation. The electrolysis system consists of an electrolytic cell with a flow system for the anode and cathode solutions. Electrolysis of lithium chloride solution was performed using an FM01 electrolytic cell manufactured by ICI (a scale model of the FM21 electrolytic cell commercially available in the chlorine-alkali industry). The electrolytic cell contained lanthanum blade-style electrodes (anode: ruthenium oxide-coated titanium, and cathode: nickel) and a Nafion® 982 film. The active surface area of ​​each electrode was approximately 64 cm². 2(4×16 cm), and the cell gap (the measured distance from the anode to the cathode) was about 12 - 13 mm. The FM01 electrolytic cell was operated with a flow parallel to the direction of 16 cm (as it was intended to operate, compared with the flow direction parallel to the 4 cm dimension) to improve the management of chlorine and hydrogen gases released from the electrodes. In addition, the flow of the anolyte and catholyte is usually conveyed from the opposite side of the cell, but in this experiment, the anolyte and catholyte were conveyed from the same side of the electrochemical cell.

[0087] The anolyte flow system included a transfer tank, a pump, a degassing tank, a chlorine scrubber, and a collection tank. A lithium chloride solution with a concentration of about 21 wt% was placed in the anolyte transfer tank and heated to about 90 °C. The heated solution was pumped into the anode chamber of the cell in single - pass mode at a flow rate of about 20 cm 3 / min corresponding to a superficial velocity of about 0.13 cm / s. After leaving the cell, the lithium chloride solution and the attached chlorine gas (produced at the anode) were passed through a degassing tank equipped with a chlorine scrubber to remove chlorine. Then, the lithium chloride solution was pumped into the collection tank for storage.

[0088] The catholyte flow system included a transfer tank, a pump, and a water transfer system. Lithium hydroxide was placed in the transfer tank, heated to about 95 °C, and conveyed to the cathode chamber of the electrochemical cell in recirculation mode at a flow rate of about 50 mL / min corresponding to a superficial velocity of about 0.33 cm / s. To maintain a constant lithium hydroxide concentration, a peristaltic pump was used to continuously add water to the system. The addition rate was monitored by the weight loss of the water tank. Nitrogen was blown into the catholyte recirculation tank to minimize the reaction of lithium hydroxide and carbon dioxide in the air.

[0089] Table 2 summarizes the experimental conditions used in the test to determine the effect of the concentration of the catholyte.

Table 2

[0090] During operation of the electrochemical cell, samples were collected every 30 minutes at the cathode inlet and outlet, and the anode outlet port. The cell voltage was monitored at the cell terminals using a handheld multimeter. The cell efficiency and energy consumption were calculated using the difference between the inlet and outlet cathode hydroxide concentrations and the cell voltage. The results of the cathode concentration are summarized in Table 3. The cell voltage was maintained at approximately 4.3–4.4V for all experimental runs. Current efficiency was observed to decrease with increasing lithium hydroxide concentration. While we do not wish to be bound by any one theory, this decrease in current efficiency may be due to an increase in the reverse movement of hydroxide anions across the membrane from the cathode to the anode as the lithium hydroxide concentration increases. This also results in an increase in energy consumption, since all experiments were conducted at the same current density and the cell voltage was essentially constant. The experiments suggest that a favorable concentration of lithium hydroxide in the electrochemical cell may be approximately 1–2 moles.

[0091] Table 3 summarizes the test results. As shown, the lithium hydroxide production efficiency increases as the lithium hydroxide concentration decreases, reaching a maximum efficiency of approximately 80-88% for a lithium hydroxide solution with a concentration of approximately 1 mole (2.4 wt%). Since the cell voltage is relatively independent of the lithium hydroxide concentration, the efficiency also drives the decreasing energy requirement for approximately 5 kWh / kg of lithium hydroxide produced at a concentration of approximately 1 mole. The lithium hydroxide production rate increases with lower initial lithium hydroxide concentrations. [Table 3]

[0092] Example 4: Carbonation A chemical reactor was used to carbonate lithium hydroxide using a 3 L Syrris automated batch reactor system (Syrris Ltd., 27 Jarman Way, UK) with controls for sensing pH, temperature, reagent addition, and sample extraction. The electrolysis studies detailed above suggest that the electrolysis of lithium chloride yields at most 1 mole or 2.4 wt% lithium hydroxide solution. Indeed, this concentration has been found to be ideal for conducting carbonation studies under our experimental conditions without clogging issues.

[0093] Carbonation reaction dynamics. The carbonation reaction dynamics of lithium hydroxide were determined by monitoring the pH and metal ion concentration in the solution (using atomic absorption) as the reaction progressed. Approximately 84 g of lithium hydroxide monohydrate was dissolved in 2000 mL of water to prepare a solution with a concentration of approximately 1 mole (approximately 2.4 wt%). The reactor jacket was heated with a 30:70 water-glycol mixture to maintain the temperature of the lithium hydroxide solution at approximately 95°C. This solution was continuously stirred at 250 RPM with a mechanical stirrer during carbonation. The carbonation gas tube was initially maintained at a depth of at least 6 cm in the caustic solution, and the gas flow rate was continuously monitored using a flow meter (Matheson Tri-Gas, USA). As carbonation progressed, the pH of the solution increased slightly, and completion of the reaction was determined by a sudden drop in the pH of the solution immediately after the flow of carbon dioxide to the reactor stopped. The decrease in pH is consistent with the formation of lithium bicarbonate, which is less stable at higher temperatures. Therefore, the lithium bicarbonate formed in lithium carbonate was decomposed by heating the solution and / or continuing to stir the solution. The decomposition of lithium bicarbonate resulted in a stable increase in pH over time. The lithium ion concentration was monitored during the reaction and it was shown that excessive carbonation of the solution could lead to the formation of bicarbonate.

[0094] During carbonation, a slightly molar excess of carbon dioxide was added to the lithium hydroxide solution to address poor mixing of carbon dioxide into the solution. After the carbonation reaction was complete, the solution was thermally filtered because the solubility of lithium carbonate in water decreases with increasing temperature. The filtered solid was first dried at approximately 60°C for about 18 hours, and then at approximately 120°C for about 24 hours to ensure that any residual lithium bicarbonate present in the solid was converted back to lithium carbonate. The carbonation reaction was repeated several times with 1 mole of lithium hydroxide solution, with or without lithium carbonate seeding, under slightly different experimental conditions. These results are shown in Table 4. Seeding the lithium hydroxide solution with lithium carbonate crystals improved the yield. At higher carbon dioxide flow rates (e.g., above 3 L / min), the yield of the carbonation reaction remained high. As shown in Table 3, carbon dioxide transport was maintained at approximately 2 L / min, but the total amount of carbon dioxide added varied from approximately 1.25 to 2.5 moles (i.e., approximately 0.625 to 1.25 molar equivalents). Experiment 1 in Table 3 involved the addition of nitrogen gas to the carbonation vessel. Experiments 3–5 in Table 3 involved the addition of approximately 0.6%–1.2% by weight of lithium hydroxide seed. The results indicate that the increased reaction rate may allow for a reduction in reactor size and, consequently, a reduction in overall costs. [Table 4]

[0095] Example 5: Concentration of lithium chloride using reverse osmosis A solution containing synthetic lithium chloride was subjected to reverse osmosis at 72-80°F.

[0096] Test 1: In the first pass, a lithium chloride-containing solution (LiCl 16,000 ppm, KCl 500 ppm, NaCl 1,000 ppm, Ca 3 ppm, and B 1 ppm) was pumped from a transport tank to a reverse osmosis system via Line 1 at a pressure of 600 psi at 72°F. The transport pump speed was approximately 4 gpm. The permeate (reverse osmosis purified water) was collected and transported to a permeate tank. The weight of the permeate was measured at the end of each pass through the reverse osmosis unit. The residual solution containing 99% of Li, Na, K, Ca, Mn, and Cl ions (concentrate) was recovered into a concentrate tank. The weight of the concentrate solution in the concentrate tank was measured at the end of the test. In each pass, the pressure was increased until either the maximum pressure (1200 psig) or the maximum recovery rate (15%) was achieved.

[0097] Test 2: In the second test, the concentrate from Test 1 was transferred to a transport tank and mixed with any remaining unused transport from the previous test. The second pass was carried out in the same manner, except that the temperature was 77°F and the applied pressure was approximately 740 psi. Again, the concentrate was recovered from the concentrate tank and the permeate was transported to the permeate tank. Tests 3-7 were repeated in the same manner as Test 2, except that the pressure gradually increased as the transport and concentrate solution became more concentrated with lithium and other salts (Table 5).

[0098] Reverse osmosis experiments were performed to determine the flux and specific flow rate as a function of the transport concentration. A synthetic brine mimicking the lithium chloride-rich flow from the lithium capture step was supplied to the reverse osmosis process. Samples were taken at the beginning and end of each pass. The concentrate from a pass was the transport for subsequent passes. The initial artificial brine for pass 1 contained LiCl 16,000 ppm, KCl 500 ppm, NaCl 1,000 ppm, Ca 3 ppm, and B 1 ppm. Flux (F) was measured in gallons / square feet / day (gfd). Specific flow rate (gfd / psi) is a function of the transport concentration. The pump flow rate was 4 gpm. The achievable lithium chloride concentrations were measured at a maximum reverse osmosis transport pressure of 1200 psi at a given temperature, as shown in Table 4. The flux remained constant, indicating no problems with the passage of fouling or salt at a given pressure. The data are shown in Table 5. [Table 5]

[0099] Based on this, the theoretical reverse osmosis pressure was determined.

[0100] Example 6: Further optimization of the lithium chloride capture step for delivery to reverse osmosis The following experiments were conducted to determine the optimal process for the lithium capture step and to provide a transport for the subsequent reverse osmosis process.

[0101] A standard 2.6 cm × 53 cm laboratory column was prepared using an adsorbent prepared as described in U.S. Patent No. 8,901,032. The resulting adsorbent was screened to an average particle size of approximately 300–500 microns, then slurryed with deionized water, poured into the column, and backwashed with a saturated salt solution to remove fine particles. The column was packed with lithium from geothermal brine.

[0102] The geothermal brine was Hudson Ranch's geothermal brine used in the silica control process. The silica control process was a continuous process for silica management. The silica control system included three stirred reaction vessels supplied in series. Geothermal brine was supplied to the first reaction vessel at a rate of approximately 6 gpm. Approximately 30 cfm of air was supplied to each reactor and dispersed through the geothermal brine. After the addition of air to the first reaction vessel, the pH dropped to approximately 2.3–3.5. The brine supplied to each of the three reactors was maintained at a temperature of approximately 95°C.

[0103] Geothermal brine from the first reactor was also supplied to the second reactor. An aqueous calcium hydroxide slurry containing approximately 15–25 wt% calcium hydroxide was supplied to the second reactor at a wet-base rate of approximately 0.5 lb / min. This raised the pH in the second reactor to approximately 4.8–6.5. The brine in the second vessel, which had been in contact with the calcium hydroxide slurry, was again brought into contact with air. The addition of the calcium hydroxide slurry initiated the precipitation of iron(III) hydroxide and iron silicate. The brine was then supplied from the second vessel to the third reaction vessel, where it was again brought into contact with air. Air was supplied to all vessels at a constant rate of approximately 30 cfm. Each of the three reactors included means for stirring to ensure thorough mixing of the brine, base, and air oxidizer. The continuous addition of air and base to the reaction vessel results in the precipitation of iron and silica at a rate of up to approximately 0.5 lb / min, depending on the concentrations of iron and silica in the geothermal brine.

[0104] Next, geothermal brine containing iron(III) hydroxide and iron silicate precipitates was supplied from the third reaction vessel to the purifier. Water was added to the purifier. An aqueous solution of Magnafloc 351 coagulant at concentrations of approximately 0.005% to 1% by weight, such as approximately 0.025% by weight, was supplied to the purifier at a rate of approximately 0.01 gpm.

[0105] Two flows were generated from the purifier. The first purifier product flow contained geothermal brine with reduced concentrations of silica and iron, which was then transported to the lithium capture step. The second purifier product flow contained solid silica-iron waste, as well as some geothermal brine.

[0106] Figure 14 shows one embodiment of system 1400 for extracting lithium from an adsorbent column having three regeneration solutions. System 1400 includes a column 1410, a packing tank 1420, a depletion brine tank 1425, a recycle cut tank 1430, a product cut tank 1440, and a strip tank 1460. A packing (line 1), for example, a lithium-containing brine solution, was delivered to column 1410. Lithium was stripped from the packing (line 1) in column 1410 by sequentially treating column 140 with three regeneration solutions, starting with a recycle cut (line 2) used to replace the lithium-containing brine solution from column 1410, followed by recycle strips (lines 5 and 6) used to initiate stripping of the column, and finally a freshly prepared strip solution (line 7) made from DI water with 500 mg / kg of Li added to complete the elution of Li from column 1410. Each cycle includes a lithium-containing brine solution (line 1), a recycle cut (line 2), a recycle strip (lines 5 and 6), and a strip solution (line 7). The materials and flow rates are shown in Table 8. This was repeated for at least 50 cycles.

[0107] The recycle cut (line 2) from column 1410 is recycled to the packing tank 1420. The recycle cut (line 3), shown in Table 8, is defined as the peak region of the strip, where lithium is at its highest concentration, but impurities such as sodium, potassium, calcium, manganese, and boron are also at their highest concentrations. This is recycled and transported to column 1410 immediately after the packing step. The depleted brine (line 3) exiting column 1410 can be sent to the depleted brine tank 1425.

[0108] The product cut (line 4) from column 1410 is sent to product cut tank 1440 for further processing (e.g., a reverse osmosis system). The product cut (line 4), as shown in Table 8, is the portion of the strip that is retained (e.g., in product cut tank 1440) for processing by the reverse osmosis system. In some embodiments, the product cut (line 4) should have an average concentration of Li (about 1%) greater than 1600 mg / kg, Na less than 1000 mg / kg, divalent ions less than 500 mg / kg expressed as Ca, and B less than 100 mg / kg, preferably less than 50 mg / kg.

[0109] A recycled strip (line 5) from column 1410 may be sent to a recycled strip tank 1430 and then to column 1410 as a recycled strip (line 6). In some embodiments, the recycled strip (line 5) is processed in the recycled strip tank 1430 and then sent to column 1410 as a modified recycled strip (line 6). The recycled strips (lines 5 and 6), as shown in Table 8, are defined as portions of the Li strip following the product cut (line 4), which have lithium concentrations in the range of 700–1500 mg / kg and are too low to be transferred to the product cut tank 1440 or a reverse osmosis system. These recycled strips (lines 5 and 6) are recycled to become carriers for producing a product cut with the lowest levels of impurities such as sodium, potassium, calcium, manganese, and boron.

[0110] The strip solution (line 7) can be supplied from the strip tank 1460 to the column 1410. The strip solution (line 7) can be added to the packing (line 1), the recycled strip (line (6)), or transported independently to the column 1410. The strip solution (line 7) may include freshly prepared DI water with 500 mg / kg of Li added to complete the elution of Li from the column 1410.

[0111] As shown in Table 8, the fill-recycle (not shown in Figure 14) is defined as the portion of the Li-fill and strip curve containing Li at concentrations ranging from 200 to approximately 4000 mg / kg, with impurities such as sodium, potassium, calcium, manganese, and boron at concentrations ranging from approximately 30% of their concentration in the transport brine to their maximum transport brine concentration. This is recycled back into the transport tank, mixed with the geothermal brine, and transported to the column during the subsequent fill-up step.

[0112] Figure 15 shows one embodiment of system 1500 for extracting lithium from brine in a column from an adsorbent having a regeneration solution. In this embodiment, system 1500 includes a lead column 1505 (e.g., a lithium extraction column) and a lag column 1510. In some embodiments, both the lead column 1505 and the lag column 1510 are lithium extraction columns. For example, each of the lead column 1505 and the lag column 1510 may contain an adsorbent for extracting lithium from a brine solution. In some embodiments, the lead column 1505 and the lag column 1510 are arranged in series.

[0113] During column packing (i.e., during the lithium capture step), a brine solution containing lithium chloride (or other lithium salt) is supplied to the lead column 1505. The brine solution may be supplied to the lead column 1505 from a brine tank 1520. The lead column 1505 extracts lithium from the brine solution 1520 until the column is saturated with lithium (e.g., until the lead column is packed). In some embodiments, after the brine solution has been processed in the lead column 1505, the processed brine solution (e.g., brine with little or no lithium) is sent to a depletion brine tank 1530. In some embodiments, the processed brine solution is sent to the depletion brine tank 1530 when the brine has a lithium concentration below a threshold amount. For example, when the lithium concentration in the processed brine solution is less than 30 mg / kg, the processed brine solution is sent to a lag column to extract additional lithium. Initially, lithium is almost completely captured within the lead column 1505, as illustrated in the packing curve of the graph described herein. For example, during packing, the lithium concentration is approximately 15-20 mg / kg. As the adsorbent in the lead column 1505 becomes saturated with lithium, the lithium concentration increases until the lead column 1505 is completely filled with lithium, and there are no more accessible lithium sites in the adsorbent. Finally, the lithium concentration becomes equal to the Li in the transport, known as a breakthrough. Once a breakthrough occurs, the brine solution can be sent to the lag transport tank 1535 for further processing in the lag column 1510.

[0114] Figure 16 shows the concentrations of lithium and other elements in depleted brine and lag brine. When the lithium concentration in depleted brine reaches a threshold amount after extraction, it is considered lag brine to be sent to the lag column. For example, when the lithium concentration in the treated brine solution is greater than 30 mg / kg, the brine solution is sent to the lag column to extract additional lithium.

[0115] In some embodiments, the solution from the recycle cut tank 1550 is transported to the lead column 1505, which then pushes the brine solution through the lead column 1505. In some embodiments, the brine solution in the lead column 1505 is pushed through the column with the solution from the recycle cut tank 1550. The recycle cut replaces the brine, and as the brine leaves the column, it produces a mixed phase with a low lithium concentration and high impurities, which can be used as a recycle fill / cut. In some embodiments, the recycle fill / cut can be sent to a transport brine tank 1520 to be mixed with the transport brine, or to a strip makeup 1560 to be combined with or mixed with a strip solution 1540.

[0116] After the recycle cut 1550 is passed through the lead column 1505, it is replaced by the strip solution 1540. For example, if the lead column 1505 is filled with brine solution and the recycle cut 1550 pushes the brine through the column, the strip solution 1540 is added to the lead column 1505. The strip solution 1540 may be supplied to the lead column 1505 from a strip solution tank. In some embodiments, the strip solution 1540 extracts lithium from the adsorbent in the lead column 1505. At the outlet of the lead column 1505, the recycle cut 1550 is produced, which has a high (peak) Li content, but also high sodium and potassium content. The recycle cut 1550 is sent to the recycle cut tank, but as the strip solution 1540 comes through the lead column 1505, it produces a solution with lower sodium, potassium, and calcium content and a relatively high Li content, which is removed from the column as product 1545. For example, if the strip solution 1540 extracts enough lithium to meet the specifications for product 1545, the product cut can be supplied to the product tank. As the strip solution 1540 continues through the lead column 1505, the Li content decreases and impurities are reduced. This solution can be used as strip recycle 1555 and sent to a recycled strip tank. The strip recycle 1555 can be recycled directly to the lead column 1505 or mixed with other solutions that are transported to the lead column 1505. The concentrations of lithium and impurities in the lead column 1505 are shown in Figure 17. In some embodiments, this marks the end of the filling cycle. The brine is then transported back to the lead column 1505, pushing the strip solution 1540 into the strip recycle tank. The brine eventually reaches the outlet of the lead column 1505, where there is first a mixed phase of strip and brine, which is recycled filling / cut 1550, and is sent to a transport tank to be mixed with brine transporter (not shown in the drawings).Figure 15 shows an arrow leading to the base of the column, although in some embodiments the lead column 1505 is transported from the top. The arrow does not indicate the location or direction of the flow transport through the lead column 1505. In some embodiments, the brine and strip flow downwards for both the pack and the strip, but it is entirely feasible for both the pack and the strip to flow upwards, as well as for the pack to flow downwards and the strip to flow upwards, or vice versa. [Table 6]

[0117] Table 9 shows the concentrations of selected components in the geothermal brine before the start of each cycle. This brine was sampled before lithium extraction. [Table 7]

[0118] Figure 9 shows exemplary lithium packing curves for various cycles. When the lithium concentration is in the range of approximately 500–800 mg / kg, it is considered the tail fraction. The tail fraction can be recycled as a transport material for product cut. The product cut is the portion of the strip that is retained for processing by the reverse osmosis system. It has an average concentration of approximately 1600 mg / kg of Li, less than approximately 1000 mg / kg of Na, less than approximately 500 mg / kg of divalent ions and boron, preferably less than approximately 100 mg / kg, expressed as less than 200 calcium equivalents. The recycle cut is the peak region of the strip, where lithium is at its highest concentration, but impurities such as sodium, potassium, calcium, manganese, and boron are also at their highest concentrations. This is recycled and transported to the column instead of the washing step described in the example above.

[0119] Table 10 shows the concentrations in the lithium chloride product cut after lithium extraction in cycles 52–63. This product cut is then transported directly to the reverse osmosis process, or to the purification process followed by the reverse osmosis process. [Table 8]

[0120] Example 7: Additional example for optimizing the lithium chloride capture step for transport to reverse osmosis Conventional / Comparative: The column was packed to a depth of 48 cm with an adsorbent produced by the method described in U.S. Patent No. 8,901,032B1, and the column diameter was 2.64 cm. Lithium was extracted and recovered from geothermal brine according to the following sequence: The flow rate (packing volume) of the geothermal brine was 60 ml / min, and 5.065 liters of geothermal brine were passed through the column. This was followed by a sodium chloride (washing) solution at a rate of 62 mol / min until 0.3 liters of solution had passed through the column, and finally, a strip solution of water containing 500 mg / kg passed through the column at a rate of 12 ml / min until 0.9 liters of solution had passed through the column. Input data to the column are shown in Table 11, and output data are shown in Table 12, Figure 10 (Li concentration at the outlet is read from the primary Y-axis for Li, Mn, Zn, Ba and Zn, and from the secondary Y-axis for Na, K and Ca) and Figure 11.

[0121] Figure 11 illustrates one embodiment in which the peak lithium concentration region contains the most concentrated lithium solution extracted from the adsorbent. However, in some embodiments, the peak lithium concentration region may also contain impurities. For example, the peak lithium concentration region may contain large amounts of sodium and potentially other impurities (e.g., calcium and potassium). The peak lithium concentration region may have the highest lithium concentration, but it may also have the highest concentrations of impurities such as sodium, potassium, calcium, manganese, and boron.

[0122] In some embodiments, the process may include recycling a cut from the peak lithium concentration region (also referred to herein as a “recycle cut”) to remove these impurities and produce a purer lithium solution. The recycling can be obtained from the peak lithium concentration region during the stripping process. By using one or more recyclings of the peak lithium concentration solution, the peak lithium concentration can be shifted to a later time after the strip cycle. Thus, this process can produce a purer, concentrated lithium stream (see, for example, Figure 13, “product cut”) that can be delivered to a reverse osmosis unit.

[0123] For example, comparing Figure 11 with Figure 13, the lithium concentration is significantly higher in Figure 13 at bed volume (BV) 13-14, while at similar positions in Figure 11 (approximately BV 19.5-20.5), the lithium concentration is lower and the sodium concentration is significantly higher. The high sodium content prevents the use of reverse osmosis in these solutions, as reverse osmosis is limited to an operating pressure of approximately 1000-2000 psi. The high sodium content results in a higher osmotic pressure that must be overcome for reverse osmosis to have any practical applications. Therefore, by utilizing one or more recycled cuts of a highly concentrated lithium solution as part of the stripping process (e.g., stripping lithium from the adsorbent), the peak lithium concentration region can be shifted within the strip cycle, resulting in a purer lithium solution with fewer impurities that can then be transported to the reverse osmosis unit. [Table 9] [Table 10-1] [Table 10-2]

[0124] The present invention's method, suitable for use in combination with reverse osmosis: The column was packed to a depth of 19.3 inches with an adsorbent produced by the method described in U.S. Patent No. 8,901,032B1, and the column diameter was 1 inch. Lithium was extracted and recovered from geothermal brine according to the following sequence: The flow rate (packing volume) of the geothermal brine was 50 ml / min, and 3.058 liters of geothermal brine were passed through the column. Subsequently, a total of 0.1 liters of recycled strips were transported to the column at the same flow rate according to the flow diagram in Figure 5. Subsequently, recycled strips were transported to the column at a rate of 11 ml / min for a total of 0.26 liters, and finally the transport strip solution was transported to the column. The results of the extraction and obtained strip procedure are shown in Figure 13, along with Figure 12 (Li concentrations at the outlet are read from the primary Y-axis for Li, Mn, Zn, Ba and Zn, and from the secondary Y-axis for Na, K and Ca) and Table 13. [Table 11]

[0125] It should be noted that the use of sodium chloride washing is not economical and results in a solution with too high a sodium content. Without washing, the lithium chloride stream is contaminated with Na, Ca, and K at excessively high average concentrations. In fact, it should be understood that while a very significant reduction in sodium ions is observed, ions such as Mn and Ca remain at similar concentrations (which can be purified by known chemical means such as pH adjustment with lithium hydroxide and carbonate, as well as ion exchange to remove impurities). In the comparative example, the sodium ion concentration is 16 g / kg or 0.7 Molal, and the Li concentration is 2.6 g / kg, corresponding to 0.36 Molal. Under these conditions, the osmotic pressure is high, and the high sodium content is shown to prevent satisfactory concentration by reverse osmosis. Furthermore, there is significant salt consumption in the salt washing methodology. In contrast, in the method of the present invention, the amount of sodium in the product cut is 0.46 g / kg or 0.02 Molal, while for Li it is 1.8 g / kg, which is 0.25 Molal. Therefore, the osmotic pressure is almost entirely a function of the Li content and not of the sodium content, and thus it is economically feasible to concentrate LiCl to 0.5 wt% to approximately 5 wt% LiCl. Table 14 provides typical product compositions of the comparative method (Example 101) and the method of the present invention (Example 102). [Table 12]

[0126] Therefore, among other advantages, it should be understood that recycling lithium-rich fractions, as described above, offers many benefits, especially when the resulting lithium solution is subjected to a downstream reverse osmosis concentration step. In particular, as illustrated in Figure 11, conventional elution methods that utilize the lithium peak region (and even the region behind the peak) will inevitably be rich in sodium as well. Thus, high lithium recovery is associated with high sodium concentrations. Unfortunately, such high sodium concentrations negatively impact reverse osmosis because sodium contributes substantially to the osmotic pressure. As can be seen from the table above, sodium ions are six times more abundant than lithium ions using conventional elutions. In contrast, when the product (or fractions that at least partially overlap with the product cut) is recycled to an adsorbent, the ionic strength is sufficient to maintain (and even additionally bind) lithium on the adsorbent, largely due to the increased lithium concentration relative to sodium. From another perspective, the ionic strength is obtained by the increase in lithium accompanying the decrease in sodium, which favorably affects the product composition when eluted in a suitable eluate with low or depleted sodium. As can be seen from the table above, the lithium concentration is currently about four times that of sodium. Therefore, partial recycling as described above allows for an increase in the ratio of lithium to other undesirable cations (especially sodium) while maintaining overall lithium recovery.

[0127] The method described herein is suitable for recovering lithium from brines or solutions having low or high lithium concentrations, in addition to brines or solutions containing polyvalent ions or significant concentrations of other ions.

[0128] As is understood in the art, not all equipment or devices are shown in the drawings. For example, those skilled in the art will recognize that various holding tanks and / or pumps may be used in this method.

[0129] Unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" refer to multiple objects.

[0130] The following event or situation may or may not occur. The description includes examples of when the event or situation occurs and examples of when it does not.

[0131] In this specification, a range may be expressed as from about one specific value to and / or from about another specific value. When such a range is expressed, it should be understood that another embodiment is from one specific value to and / or other specific values, along with all combinations within the above range.

[0132] Wherever patents or publications are referenced in this application, unless they conflict with the descriptions made herein, the disclosures of those references are intended to be incorporated by reference to more fully describe the latest technology to which the present invention relates.

[0133] As used herein, the enumeration of the terms "about" and "approximately" in relation to a range of values ​​should be interpreted as including both the upper and lower limits of the enumerated range.

[0134] Although the present invention is described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the principles and scope of the invention. Accordingly, the scope of the invention should be determined by the following claims and their appropriate legal equivalents. Specific embodiments of the present invention are as follows. [Aspect 1] A method for extracting lithium from a lithium-containing solution, The lithium-containing solution is treated in the lithium capture step by contacting the lithium-containing solution with an adsorbent material to capture lithium and generate an eluate of the adsorbent, In the lithium capture step, lithium is recovered from the eluate to generate a lithium-rich flow, The lithium-rich flow is concentrated by processing it in the reverse osmosis step to produce a concentrated lithium-rich flow, The method comprising recycling at least a portion of the eluate back into the adsorbent, wherein the portion of the eluate includes a fraction from the peak lithium concentration region. [Aspect 2] The method according to embodiment 1, wherein the lithium-rich flow includes divalent ions and borate ions. [Aspect 3] The method according to embodiment 2, further comprising purifying the lithium-rich stream to remove divalent ions and borate ions. [Aspect 4] The method according to embodiment 1, further comprising treating the lithium-containing solution in a silica control step for removing silica from the lithium-containing solution and producing a silica-lean lithium solution, and then supplying the silica-lean lithium solution to the lithium capture step. [Aspect 5] The method according to embodiment 1, wherein the portion of the eluent has a higher lithium-to-sodium ratio compared to the lithium-containing solution. [Aspect 6] The method according to embodiment 1, wherein the region having the peak lithium concentration contains the highest concentration of lithium. [Aspect 7] The method according to embodiment 1, wherein the reverse osmosis step is a cascade reverse osmosis system. [Aspect 8] The lithium capture step is followed by a purification step to reduce the concentration of at least one of calcium, magnesium, manganese, or zinc in the lithium-rich stream, wherein the purification step is Contacting the lithium-rich stream with a base or carbonate such that at least a portion of the calcium, magnesium, manganese, or zinc precipitates as a solid carbonate, The method according to embodiment 1, comprising separating the solid carbonate from a purified lithium-rich stream, wherein the purified lithium-rich stream has a lower concentration of at least one of calcium, magnesium, manganese, or zinc. [Aspect 9] The lithium capture step is followed by a purification step to reduce the concentration of at least one of calcium, magnesium, manganese, or zinc in the lithium-rich stream, wherein the purification step is The lithium-rich flow is brought into contact with a base and / or carbonate, wherein at least a portion of the calcium, magnesium, manganese, or zinc precipitates as a solid carbonate. The solid carbonate is separated from the purified lithium-rich stream, The obtained lithium-containing solution is treated with an ion-selective medium to further remove trace concentrations of divalent ions and boron, The method according to embodiment 1, wherein the purified lithium-rich stream has a lower concentration of at least one of calcium, magnesium, manganese, zinc, or boron. [Aspect 10] The method according to embodiment 1, wherein the lithium capture step substantially enables the selective isolation of lithium and prevents the co-extraction of other cations present in the lithium-containing solution. [Aspect 11] The method according to embodiment 1, wherein the lithium capture step includes a step of contacting the lithium-containing solution with the lithium adsorbent material until the lithium adsorbent material for capturing lithium is saturated with lithium, thereby producing a saturated lithium adsorbent material. [Aspect 12] The method according to embodiment 11, wherein the step of recovering lithium includes stripping the saturated lithium adsorbent material with water to generate the lithium-rich flow. [Aspect 13] The method according to embodiment 11, wherein the lithium adsorbent material is an intercalated lithium adsorbent. [Aspect 14] The method according to embodiment 11, wherein the temperature is maintained above approximately 70°C during the step of bringing the lithium adsorbent material and the lithium-containing solution into contact. [Aspect 15] The lithium-containing solution is treated in a silica control step for removing silica and producing a silica-lean lithium solution, and then the silica-lean lithium solution is supplied to the lithium capture step, wherein the lithium capture step is operable to capture the lithium from the silica-lean lithium-containing solution. The lithium is recovered from the lithium capture step to generate a lithium-rich flow, The method according to embodiment 1, further comprising a reverse osmosis step of concentrating the lithium-rich flow. [Aspect 16] A method for extracting lithium from a lithium-containing solution, To provide a lithium-containing solution containing divalent ions and borate ions, The process involves treating the lithium-containing solution in a lithium capture step, wherein the lithium capture step includes contacting the lithium-containing solution with an adsorbent material to capture lithium. The lithium is recovered from the lithium capture step to generate a lithium-rich flow, The lithium-rich stream is purified to remove divalent ions and borate ions, The lithium-rich flow is concentrated by processing it in the reverse osmosis step to produce a concentrated lithium-rich flow, The method comprises purifying the concentrated lithium-rich stream by removing sodium and potassium ions to produce a concentrated lithium-rich solution having reduced sodium and potassium ion concentrations, and recycling at least a portion of the eluate of the adsorbent back into the adsorbent. [Aspect 17] The method according to embodiment 16, further comprising further concentration of the concentrated lithium-rich stream by solvent extraction. [Aspect 18] The method according to embodiment 16, further comprising further concentration of the concentrated lithium-rich flow by evaporation. [Aspect 19] The method according to embodiment 16, wherein the portion of the eluent has a higher lithium-to-sodium ratio compared to the lithium-containing solution. [Aspect 20] A method for extracting lithium from a lithium-containing solution, To provide a lithium-containing solution containing silica, divalent ions, and borate ions, In the silica management process, the lithium-containing solution is treated to produce a silica-lean lithium-containing solution, The lithium capture step involves processing the silica-lean lithium-containing solution, wherein the lithium capture step involves capturing lithium from the silica-lean lithium-containing solution by contacting the silica-lean lithium-containing solution with an adsorbent, and at least a portion of the eluate obtained from the adsorbent in the lithium capture step is recycled back into the adsorbent to increase the lithium-to-sodium ratio in the lithium-rich flow. The lithium is recovered from the lithium capture step to generate the lithium-rich flow, The lithium-rich stream is purified to remove divalent ions and borate ions, The lithium-rich flow is supplied to the reverse osmosis step to concentrate the lithium-rich flow and generate a concentrated lithium-rich flow. Further concentrating the aforementioned concentrated lithium-rich flow to generate a lithium-rich flow that is twice as concentrated, The method comprising purifying the 2x concentrated lithium-rich stream by removing sodium and potassium ions to produce a concentrated lithium-rich solution having reduced sodium and potassium ion concentrations.

Claims

1. A method for extracting lithium from a lithium-containing solution, The lithium-containing solution is treated in the lithium capture step by contacting the lithium-containing solution with an adsorbent material to capture lithium and generate an eluate of the adsorbent, In the lithium capture step, lithium is recovered from the eluate of the adsorbent that has adsorbed lithium from the lithium-containing solution to generate a lithium-rich flow. The lithium-rich flow is concentrated by processing it in the reverse osmosis step to produce a concentrated lithium-rich flow, The method comprising recycling at least a portion of the eluate back into the adsorbent, wherein the portion of the eluate includes a fraction from the peak lithium concentration region.

2. The method according to claim 1, wherein the lithium-rich flow includes divalent ions and borate ions.

3. The method according to claim 2, further comprising purifying the lithium-rich stream to remove divalent ions and borate ions.

4. The method according to claim 1, further comprising treating the lithium-containing solution in a silica control step for removing silica from the lithium-containing solution and producing a silica-lean lithium solution, and then supplying the silica-lean lithium solution to the lithium capture step.

5. The method according to claim 1, wherein the portion of the eluent has a higher lithium-to-sodium ratio compared to the lithium-containing solution.

6. The method according to claim 1, wherein the region having the peak lithium concentration contains the highest concentration of lithium.

7. The method according to claim 1, wherein the reverse osmosis step is a cascade reverse osmosis system.

8. The lithium capture step is followed by a purification step to reduce the concentration of at least one of calcium, magnesium, manganese, or zinc in the lithium-rich stream, wherein the purification step is Contacting the lithium-rich stream with a base or carbonate such that at least a portion of the calcium, magnesium, manganese, or zinc precipitates as a solid carbonate, The method according to claim 1, comprising separating the solid carbonate from a purified lithium-rich stream, wherein the purified lithium-rich stream has a lower concentration of at least one of calcium, magnesium, manganese, or zinc.

9. The lithium capture step is followed by a purification step to reduce the concentration of at least one of calcium, magnesium, manganese, or zinc in the lithium-rich stream, wherein the purification step is The lithium-rich flow is brought into contact with a base and / or carbonate, wherein at least a portion of the calcium, magnesium, manganese, or zinc precipitates as a solid carbonate. The solid carbonate is separated from the purified lithium-rich stream, The obtained lithium-rich flow is treated with an ion exchange medium to further remove trace concentrations of divalent ions and boron, The method according to claim 1, wherein the purified lithium-rich stream has a lower concentration of at least one of calcium, magnesium, manganese, zinc, or boron.

10. The method according to claim 1, wherein the lithium capture step substantially enables the selective isolation of lithium and prevents the co-extraction of other cations present in the lithium-containing solution.

11. The method according to claim 1, wherein the lithium capture step includes a step of contacting the lithium-containing solution with the lithium adsorbent material until the lithium adsorbent material for capturing lithium is saturated with lithium, thereby generating a saturated lithium adsorbent material.

12. The method according to claim 11, wherein the step of recovering lithium includes stripping the saturated lithium adsorbent material with water to generate the lithium-rich flow.

13. The method according to claim 11, wherein the lithium adsorbent material is an intercalated lithium adsorbent.

14. The method according to claim 11, wherein the temperature is maintained above 70°C during the step of bringing the lithium adsorbent material and the lithium-containing solution into contact.

15. The lithium-containing solution is treated in a silica control step for removing silica and producing a silica-lean lithium solution, and then the silica-lean lithium solution is supplied to the lithium capture step, wherein the lithium capture step is operable to capture the lithium from the silica-lean lithium-containing solution. The lithium is recovered from the lithium capture step to generate a lithium-rich flow, The method according to claim 1, further comprising concentrating the lithium-rich flow using a reverse osmosis step.

16. A method for extracting lithium from a lithium-containing solution, To provide a lithium-containing solution containing divalent ions and borate ions, The process involves treating the lithium-containing solution in a lithium capture step, wherein the lithium capture step includes contacting the lithium-containing solution with an adsorbent material to capture lithium. The lithium is recovered from the lithium capture step to generate a lithium-rich flow, The lithium-rich stream is purified to remove divalent ions and borate ions, The lithium-rich flow is concentrated by processing it in the reverse osmosis step to produce a concentrated lithium-rich flow, By removing sodium and potassium ions, the concentrated lithium-rich stream is purified to produce a concentrated lithium-rich solution having reduced sodium and potassium ion concentrations. The method comprising recycling at least a portion of the eluate of the adsorbent back into the adsorbent.

17. The method according to claim 16, further comprising further concentration of the concentrated lithium-rich stream by solvent extraction.

18. The method according to claim 16, further comprising further concentration of the concentrated lithium-rich flow by evaporation.

19. The method according to claim 16, wherein the portion of the eluent has a higher lithium-to-sodium ratio compared to the lithium-containing solution.

20. A method for extracting lithium from a lithium-containing solution, To provide a lithium-containing solution containing silica, divalent ions, and borate ions, In the silica management process, the lithium-containing solution is treated to produce a silica-lean lithium-containing solution, The lithium capture step involves processing the silica-lean lithium-containing solution, wherein the lithium capture step involves capturing lithium from the silica-lean lithium-containing solution by contacting the silica-lean lithium-containing solution with an adsorbent, and at least a portion of the eluate obtained from the adsorbent in the lithium capture step is recycled back into the adsorbent to increase the lithium-to-sodium ratio in the lithium-rich flow. The lithium is recovered from the lithium capture step to generate the lithium-rich flow, The lithium-rich stream is purified to remove divalent ions and borate ions, The lithium-rich flow is supplied to the reverse osmosis step to concentrate the lithium-rich flow and generate a concentrated lithium-rich flow. The aforementioned concentrated lithium-rich flow is further concentrated to generate a lithium-rich flow that is twice as concentrated. The method comprising purifying the twice-concentrated lithium-rich stream by removing sodium and potassium ions to produce a concentrated lithium-rich solution having reduced sodium and potassium ion concentrations.

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