Method and system for recovering lithium from brine

Abstract

Provided herein is a method and system for selectively recovering lithium with improved mass recovery and high purity. The method includes providing an initial feed having a dissolved mass of lithium ions and (i) an initial ratio of monovalent anions to lithium ions, (ii) an initial ratio of multivalent cations to lithium ions, and (iii) an initial ratio of monovalent anions to multivalent anions of less than 1; adding one or more salts to the initial feed to produce a conditioned feed having a pH of between 1 and 7 and a conditioned ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions; and passing a portion of the conditioned feed through a membrane filter unit to produce a first outlet stream into which at least half of the mass of lithium ions present in the initial feed is distributed and a second outlet stream into which at least half of the mass of lithium ions present in the initial feed is distributed, and the first outlet stream has a ratio of multivalent cations to lithium ions less than half the initial ratio of multivalent cations to lithium ions; and extracting the lithium ions from the first outlet stream.

Description

[0001] This application is a divisional application filed on September 21, 2023, with application number "202380067422.8" and title "Method and System for Recovering Lithium from Brine".

[0002] Cross-reference to related applications

[0003] This application claims priority to U.S. Provisional Application No. 63 / 409,404, filed September 23, 2022, pursuant to 35 USC §365(c), the entire contents of which are incorporated herein by reference.

[0004] Statement on Federally Funded Research

[0005] This invention was completed with the support of the U.S. government, under Government Contract No. DE-EE0009430 granted by the Office of Energy Efficiency and Renewable Energy of the U.S. Department of Energy. The U.S. government enjoys certain rights in this invention. Technical Field

[0006] This invention relates to a method and system for recovering lithium from naturally or synthetically produced brine. Specifically, the method includes adjusting the ion concentration of the feed prior to an ultrafiltration step. Background Technology

[0007] This specification references several patents, patent applications, and publications to provide a more comprehensive description of the technological advancements involved in this invention. The full disclosure of each of these patents, patent applications, and publications is incorporated herein by reference.

[0008] Lithium (Li) is a key component in high-energy-density lithium-ion batteries. Lithium-ion batteries are used in a variety of applications, including electric vehicles, computers, and energy storage devices. Global demand for lithium is expected to increase in the foreseeable future. Currently, industrial-scale Li extraction technologies employ chemical processing followed by evaporation-based processes to recover lithium from various natural and recycled sources; this is a time-consuming and space-consuming operation. Furthermore, significant amounts of water are required for Li recovery, and most natural Li sources are located in arid regions with limited clean water supplies. To accelerate the evaporation process and recover water, engineered processes such as thermal evaporation followed by condensation have been applied, but these remain energy-inefficient.

[0009] Various membrane-based methods for recovering lithium from natural and recycled sources have been described. U.S. Patent No. 10,450,633 ('633) describes a membrane-based method for recovering Li from an acidic solution. The processing steps described in '633 involve passing an acidic lithium solution through a nanofiltration (NF) membrane unit, wherein a portion of the acid and lithium solution permeates through the NF membrane. U.S. Patent No. 6,004,464 describes a method for recovering brine from a water softening resin unit, comprising acidifying a chloride-containing brine to a pH range of 0.5-6 and then adding a salt having monovalent cations and polyvalent anions (such as Na₂SO₄) to the pH-adjusted brine. CN 112,850,851 describes a method for separating Li from Na₂SO₄-type brine from a salt lake, the method involving the removal of chloride ions (Cl₂SO₄). - Salt is added to brine and pumped through an NF system within a pH range of 7.5–11.0 to obtain excellent Li + / Mg 2+ Separation. CN 108,063,295 describes a method for extracting Li and other heavy metals from a battery source using hydrochloric acid, wherein Li2SO4 is added to the acidic feed to react under stirring for about 30 minutes to generate LiCl and CaSO4, and LiCl and CaSO4 are further separated using an NF membrane.

[0010] However, for certain feeds, especially those containing polyvalent anions (e.g., SO42-), 2- CO3 2- For feedstocks located in water-scarce regions, better water management methods with high lithium recovery rates are still needed. Summary of the Invention

[0011] Therefore, this paper provides a method for recovering lithium ions, the method comprising providing an initial feed having a dissolved mass of lithium ions and (a) an initial ratio of monovalent anions to lithium ions, (b) an initial ratio of polyvalent cations to lithium ions and (c) an initial ratio of monovalent anions to polyvalent anions less than 1. The method comprises adding one or more salts to the initial feed to produce a regulated feed having a pH between 1 and 7 and a regulated ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions. The method further comprises passing a portion of the regulated feed through a membrane unit to produce a first outlet stream and a second outlet stream, wherein at least half the mass of lithium present in the initial feed is allocated to the first outlet stream, and the first outlet stream has a polyvalent cation to lithium ion ratio less than half of the initial ratio of polyvalent cations to lithium ions.

[0012] This document further provides a system for recovering lithium, the system comprising: means for providing an initial feed having a dissolved mass of lithium ions, wherein the initial feed contains (a) an initial ratio of monovalent anions to lithium ions, (b) an initial ratio of polyvalent cations to lithium ions and (c) an initial ratio of monovalent anions to polyvalent anions less than 1; means for adding one or more salts to the initial feed to produce a conditioned feed having a pH between 1 and 7 and a conditioned ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions; a membrane filter unit; and means for passing a portion of the conditioned feed through the membrane filter unit to produce a first outlet stream and a second outlet stream, wherein at least half the mass of lithium ions present in the initial feed is allocated to the first outlet stream, and the first outlet stream has a polyvalent cation to lithium ion ratio less than half of the initial ratio of polyvalent cations to lithium ions. The system may optionally further include: means for classifying the second outlet stream to form a portion rich in ions selected from monovalent anions and polyvalent cations, and means for recycling at least a portion of the enriched portion into the regulated feed.

[0013] The advantages and features characterizing the novelty of the invention are specifically pointed out in the appended claims and form a part of the claims. However, for a better understanding of the invention, its advantages, and the purposes achievable through its use, reference should be made to the accompanying drawings, which form another part of the invention, and to the accompanying descriptive text, in which one or more preferred embodiments of the invention are shown and described. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a system suitable for use in the method described herein for recovering lithium from an initial feed containing dissolved lithium in a brine solution;

[0015] Figure 2 This is a schematic diagram of another system suitable for use in the lithium recovery method described herein;

[0016] Figure 3 This is a schematic diagram of yet another system suitable for use in the lithium recovery method described herein; and,

[0017] Figure 4 This is a schematic diagram of yet another system suitable for use in the lithium recovery method described herein. Detailed Implementation

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While similar or equivalent methods and materials may be used in the practice or testing of the embodiments described herein, suitable methods and materials are described below.

[0019] As used herein, the terms “includes,” “including,” “has,” “having,” “contain,” “containing,” or any other variation thereof refer to non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0020] The connecting phrase "consistently composed of..." limits the scope of the claims to those specified materials or steps and those that do not substantially affect one or more basic and novel features of the claimed invention. "A claim 'consistently composed of...' falls between a closed claim written in the form of 'consistent with...' and a fully open claim written in the form of 'comprising'." Where an invention or part thereof is described using open-ended terms such as "comprising," it should be understood that, unless otherwise specified in specific circumstances, the description also includes a description of the invention using the terms "consistent with..." and "consistently composed of...".

[0021] Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive "or," not an exclusive "or." For example, conditions A or B are satisfied by any of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0022] Furthermore, the term "an" or "a type" is used to describe the elements and components of the invention. This is done merely for convenience and to give the general meaning of the invention. This description should be interpreted as including one or more types, and the singular form includes the plural form, unless it is obvious that it refers to something else.

[0023] As used herein, the term “about” means that a quantity, dimension, preparation, parameter, or other quantity and characteristic is not precise and need not be precise, but may be approximate and / or larger or smaller (as required), reflecting tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. In general, whether explicitly stated or not, a quantity, dimension, preparation, parameter, or other quantity or characteristic is “about” or “approximate”.

[0024] Furthermore, unless otherwise explicitly stated in the limited context, the ranges listed herein include their endpoints. Additionally, when quantities, concentrations, or other values ​​or parameters are given as ranges, one or more preferred ranges, or a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper or preferred value with any lower or preferred value, regardless of whether such pairings are disclosed individually.

[0025] However, when numerical ranges are listed herein, unless otherwise specified in the specific context, the range is intended to include its endpoints and all real numbers within that range. The scope of the invention is not intended to be limited to the specific values ​​listed when the range is defined. Finally, when the term "about" is used to describe the endpoints of a value or range, this disclosure should be understood to include the specific value or endpoint mentioned.

[0026] Finally, as used herein, the term "lithium," whether used alone or in combination, refers to lithium ions unless the context clearly describes lithium metal (Li). 0 ).

[0027] This article provides a method and system for selectively recovering lithium with good mass recovery rate and high purity. The method includes providing an initial feed having a dissolved mass of lithium ions. Preferably, the lithium concentration in the initial feed or in the water of interest used as the initial feed is between 0.05 g / L and 6 g / L, more preferably between 0.1 g / L and 3 g / L. For a given volume, the dissolved mass of lithium can be calculated by multiplying the volume by the concentration of dissolved lithium.

[0028] The initial feed may contain monovalent and polyvalent cations, monovalent and polyvalent anions, soluble organic matter, dissolved materials, and suspended particles, such as, but not limited to, colloidal silica and clay. Other monovalent cations that may be present in the initial feed besides lithium ions include cations of sodium (Na), potassium (K), cesium (Cs), and rubidium (Rb). Various polyvalent cations that may be present in the initial feed include ions of Mg, Ca, Mn, Fe, Cu, Al, Sr, Ba, Ti, Zn, Cd, and Pb in any oxidation state stable in aqueous solution. The initial feed may be derived from natural sources such as salt lakes or saline-alkali lands or geothermal brine, or from clay mining or hard rock deposits. The initial feed may be synthesized by acid digestion of lithium-containing materials (such as, but not limited to, lithium-ion batteries, solar panels, solar storage devices, computers, laptops, and similar devices). Alternatively, the initial feed may be a treated feed generated by processing natural resource brine or synthetically produced brine.

[0029] The initial feed has an initial ratio of monovalent anions to lithium ions. Some common monovalent anions include Cl...- ,Br - F - OH - and HCO3 - The initial ratio of monovalent anions to lithium ions depends on the source, extraction process, and preceding unit operations. Preferably, the initial feed is depleted of monovalent anions, wherein the initial ratio of monovalent anions to lithium ions is less than 1, more preferably less than 0.5, and even more preferably less than 0.2. In some cases, there may be no measurable amount of monovalent anions in the initial feed other than a small amount of hydroxide ions from water dissociation. For a given volume, the initial ratio of monovalent anions to lithium ions can be calculated by dividing the total molar concentration of dissolved monovalent anions by the molar concentration of dissolved lithium ions. For a given volume, the molar concentration can be calculated by measuring the dissolved mass of ions per unit volume and dividing it by the corresponding molar mass. For example, lithium ions (Li... + The molar concentration (in mol / L) of lithium ions can be calculated as the measured dissolved mass of lithium ions per L of solution divided by the molar mass of lithium ions (6.941 amu).

[0030] The initial feed has an initial ratio of polyvalent cations to lithium ions. The polyvalent cations in the initial feed typically include magnesium (Mg). 2+ ) and calcium (Ca 2+ However, the initial mixing ratio of polyvalent cations to lithium ions depends on the source, extraction process, and preceding unit operations. For a given volume, the initial ratio of polyvalent cations to lithium ions can be calculated by dividing the total molar concentration of dissolved polyvalent cations by the molar concentration of dissolved lithium ions. Preferably, the initial ratio of polyvalent cations to lithium ions is at least 0.10, more preferably at least 1.0, and even more preferably at least 10.0.

[0031] The initial feed has an initial ratio of monovalent anions to polyvalent anions of less than 1. For example, in a feed containing only chloride ions (35.45 amu) and sulfate ions (96.06 amu), a ratio of less than 1 corresponds to less than 27% chloride ions by mass. Common polyvalent anions include SO42-. 2- HPO4 2- PO4 3- and CO3 2- Advantageously, the anions in the initial feed can be in the form of SO42-. 2- With CO3 2- The combination of these components is predominant (more than 50% of the total molar concentration of anions), and more preferably, the anions are mainly SO42-. 2- Mainly.

[0032] Advantageously, the methods and systems described herein can be used to process several types of lithium-containing solutions. For example, many natural brine sources contain SO4. 2- As one of the key anions (e.g., sodium sulfate or magnesium sulfate subtype brine), sulfate subtype brine is typically characterized by a high Mg / Li ion ratio (e.g., >5). Brine extracted from hard rock, clay, or lithium-containing materials (e.g., lithium-ion batteries, solar panels, solar storage devices, computers, laptops, and similar devices) may also contain high levels of SO4. 2- Especially when H2SO4 is used as the extractant. More preferably, the initial feed is rich in polyvalent anions and depleted in monovalent anions, wherein the initial ratio of monovalent anions to polyvalent anions is less than 1, preferably less than 0.5, and even more preferably less than 0.2.

[0033] The initial feed pH range can be wide, for example, between pH 0 and pH 10 (inclusive). Particularly relevant examples of lower pH brine (pH range 0 to 3) include brine from hard rock extraction, clay mining, and brine from digestion of lithium-containing materials using an acid or an aqueous solution of that acid. Examples of higher pH brine (pH range 4 to 10) include brine from salt lakes, saline-alkali lands, or geothermal sources. The initial feed pH also depends on the processing conditions of any or all unit operations or steps involved prior to its production. The methods described herein include the step of adding one or more salts to the initial feed to produce a conditioned feed. As used herein, the term 'salt' refers to both solid salts and salts dissolved in water. One or more of dissolved salts, dispersed salts, suspended salts, or solid salts may be present in the initial feed or the conditioned feed. Solid salts may be in hydrated or anhydrous form. As used herein, the term 'salt' also refers to acids and bases. Non-limiting examples of acids include HCl, H₂SO₄, HNO₃, and H₃PO₄, and non-limiting examples of bases include NaOH, LiOH, KOH, Ca(OH)₂, and Mg(OH)₂. Adding a salt to any composition can be carried out in one or more steps by adding one or more salts in solid, suspended, dispersed, or dissolved form. When the salt is described herein as “dissolved,” the solution may also contain dispersed or suspended particles of the salt.

[0034] In the method described herein, the adjusted feed has a pH between 1 and 7 and an adjusted ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions. Preferably, the pH of the adjusted feed is greater than 2, and more preferably greater than 3. Preferably, the pH of the adjusted feed is less than 6. The adjusted ratio of monovalent anions to lithium ions (i.e., the ratio in the adjusted feed) is greater than 1, more preferably greater than 2, and still more preferably greater than 4.

[0035] In some preferred methods, the pH of the conditioned feed is lower than that of the initial feed. Non-limiting examples of suitable acids that can be added to the initial feed to lower the pH include HCl, HNO3, H2SO4, and H3PO4. Among these, HCl and HNO3 are preferred because chlorides and nitrates also increase the ratio of monovalent anions to lithium ions in the conditioned feed. These acids can be added in their pure form or as diluted aqueous solutions.

[0036] In other preferred methods, the pH of the adjusted feed is greater than the pH of the initial feed. Non-limiting examples of suitable bases that can be added to the initial feed to increase the pH include hydroxide salts (e.g., NaOH, KOH, LiOH, Mg(OH)₂, or Ca(OH)₂), carbonates (e.g., NaHCO₃, KHCO₃, Ca(HCO₃)₂, MgCO₃, or CaCO₃), and basic oxides such as quicklime (CaO). Among these, substances containing polyvalent cations can be used to both increase the pH and increase the adjusted ratio of polyvalent cations to lithium ions. These salts can be added in their pure form or as diluted aqueous solutions.

[0037] In some methods, precipitation and / or suspension can be caused by initial feed pH adjustment. The precipitated and / or suspended solids can then be removed by sedimentation, centrifugation, or by using filtration equipment (e.g., media filters, sand filters, ultrafiltration membranes, or microfiltration membranes). In particular, ultrafiltration is an advantageous method for removing solids from the adjusted feed. The adjusted feed is then defined as a solution containing dissolved ions that have crossed the surface of the ultrafiltration membrane.

[0038] In some preferred methods, an adjusted ratio of monovalent anions to lithium ions, greater than the initial ratio, can be achieved by adding common salts containing monovalent anions. For this purpose, the salt can be selected from the group consisting of: chloride salts in their hydrated or anhydrous form, such as, but not limited to, NaCl, KCl, MgCl2, CaCl2; or nitrates in their hydrated or anhydrous form, such as, but not limited to, NaNO3, KNO3, Mg(NO3)2, Ca(NO3)2; or carbonates in their hydrated or anhydrous form, such as, but not limited to, NaHCO3, KHCO3, Ca(HCO3)2, MgCO3, or CaCO3. Among these, salts containing polyvalent cations can also be used to simultaneously increase the adjusted ratio of polyvalent cations to lithium ions.

[0039] In order to maximize lithium ion throughput and reduce the ratio of polyvalent cations to lithium ions in the membrane permeate stream (the portion of the conditioned feed that passes through the ultrafiltration membrane), it has been found that the added salt preferably contains polyvalent cations to increase the conditioned ratio of polyvalent cations to lithium ions.

[0040] In some preferred methods, the adjustment of the initial feed pH and the adjustment of the ion ratio can be performed in a single step. This can be accomplished by adding a mixture of salts to the initial feed. For this purpose, salts containing monovalent anions (such as chloride or nitrate salts) are preferred. The salt can be dissolved in an acidic solution (to lower the initial feed pH to a preferred range for the adjusted feed) or dissolved in an alkaline solution (to raise the initial feed pH to a preferred range for the adjusted feed). More preferably, the monovalent anionic salt also contains polyvalent cations to increase the adjusted ratio of polyvalent cations to lithium ions. In other methods where the pH of the adjusted feed is greater than the pH of the initial feed, the adjustment of the initial feed pH and the adjustment of the ion ratio can be performed simultaneously by adding carbonates such as CaCO3 or MgCO3, either in their solid form or dissolved in water.

[0041] In some preferred methods, the initial feed pH and ion ratio can be adjusted in multiple steps. Ion adjustment can be achieved by adding a solid or dissolved salt containing monovalent anions (such as Cl-). - Or NO3 - Salt is added to the initial feed, and pH adjustment can be performed by adding acid or base separately to the initial feed in any order. In some methods, pH changes may induce precipitation. In preferred methods of this type, a filtration step (e.g., ultrafiltration) can be performed before, during, or after the addition of salt to remove solid precipitates or suspensions. For example, several examples of the invention described below illustrate the addition of salt to the initial feed, which alters the pH and causes precipitation.

[0042] The method described herein involves passing a conditioned feed (as described above) through a membrane unit to distribute it between a first outlet stream and a second outlet stream. The first outlet stream comprises liquid that has permeated through the membrane. In a preferred method, the first outlet stream contains a majority of monovalent cations from the conditioned feed, and the second outlet stream contains a majority of divalent anions from the conditioned feed. The membrane unit comprises an ultrafiltration membrane, and the conditioned feed is passed under pressure through at least one ultrafiltration membrane, wherein a portion of the conditioned feed permeates through the ultrafiltration membrane. As used herein, the term "membrane permeate" refers to the portion of the conditioned feed that has passed through the membrane, and the term "membrane retentate" refers to the remaining portion of the conditioned feed that has not passed through the membrane. Thus, in the absence of a permeate recirculation loop or a brine recirculation loop, the first outlet stream is the membrane permeate liquid, and the second outlet stream is the membrane retentate. As used herein, the term "ultrafiltration" refers to reverse osmosis and nanofiltration. Most preferably, the membrane unit comprises a nanofiltration membrane.

[0043] Membrane units may include membranes arranged in the form of flat sheets, hollow fibers, or tubular structures. Preferably, flat sheet membranes are disposed within helical winding modules. Multiple such helical winding membrane modules may be arranged in series and axially aligned within the chamber of a cylindrical pressure vessel to increase the available active membrane area. Membrane units may further include multiple pressure vessels arranged in parallel or series. Suitable membranes and units are well known in the art and are available from DuPont de Nemours, Inc. of Wilmington, DE, under the trade name FilmTec. TM The reverse osmosis membrane was commercially available. A suitable method for synthesizing the membrane is described in U.S. Patent No. 4,277,344 to Cadotte.

[0044] Now refer to the accompanying drawings, in which the same reference numerals designate the corresponding structures in all views, and in particular refer to... Figures 1 to 4 The systems described herein, and in particular the membrane units within these systems, can have more than one operating configuration or procedure. Not all operating configurations or procedures are depicted in the accompanying drawings. However, in each method and system described herein, a suitable additive flow allows the initial feed pH, the concentration of monovalent anions in the initial feed, and optionally the concentration of lithium ions in the initial feed to be altered to produce a regulated feed in which the ratio of monovalent anions to lithium ions is increased relative to the initial feed ratio.

[0045] Figure 1 A lithium recovery system 10 suitable for processing an initial feed containing lithium ions by passing it through a membrane unit 20 is shown. The membrane unit 20 contains at least one membrane module 22, symbolically represented by a combination of a rectangle and a diagonal that itself represents a membrane 24. The at least one membrane module 22 can have any size suitable for the parameters of the desired process. For example, it can be small (e.g., one or more small test cells containing a total area of ​​a few cm²). 2 The active membrane 24), or it may comprise a number of containers connected in series or in parallel, each container containing an area greater than 100 m². 2 Membrane 24. Alternatively, intermediate values ​​can be selected for the size of the module and the area of ​​one or more membranes 24.

[0046] System 10 can operate continuously or in a batch mode, in which the initial feed of discrete volumes is processed before re-batching. In the batching process (not shown), the initial feed can be adjusted, for example, within feed tank 12 at the start of the batching cycle. Alternatively, as... Figure 1As shown, at least one additive stream 32 can be continuously added to alter the initial feed stream 30 as it flows toward the membrane 24, thereby forming a regulated feed stream 34. In this way, the regulated feed stream 34 has a desired pH and composition as it passes through at least one membrane module 22. Within the membrane unit 20, a feed pump 26 provides pressure to permeate a portion of the regulated feed stream 34 through the membrane 24. The membrane permeate stream 44 passes through the membrane 24, and the membrane retainer stream 46 contains the remainder of the regulated feed stream 34. In the absence of any permeate recirculation or brine recirculation loop, the membrane permeate stream 44 becomes the first outlet stream 48 of the membrane unit 20, and the membrane retainer stream 46 becomes the second outlet stream 50 of the membrane unit 20.

[0047] Figure 2 A lithium recovery system 10 suitable for continuous operation is shown, which includes a recirculation loop that allows a portion of the membrane permeate stream 44 and / or membrane retentate stream 46 to be reintroduced for subsequent membrane treatment. Again, the membrane unit 20 contains at least one membrane module 22. In the continuous process, the initial feed stream 30 is combined with at least one additive stream 32 to allow for salt addition and pH adjustment. The regulated feed stream 34 flowing through the filter membrane 24 includes the initial feed stream 30 and at least one additive stream 32. Although two recirculation loops are shown, the continuous system may optionally include only the permeate recirculation loop 40, only the retentate recirculation loop 42, and exclude either one (e.g., Figure 1 (as depicted in the text), or both.

[0048] The order in which these recycle streams are added to or combined with the initial feed (before being added to the initial feed) is not limiting. For example, the initial feed stream 30 is mixed with the additive stream 32 before entering the membrane unit 20. However, within the membrane unit 20, the permeate recycle loop 40 may be added first to the combined streams 30 and 32, and then to the retentate recycle loop 42; the retentate recycle loop 42 may be mixed first with the combined streams 30 and 32, and then with the permeate recycle loop 40; or the permeate recycle loop 40 and the retentate recycle loop 42 may be mixed together, and this combined stream may then be mixed with the stream resulting from combining the initial feed stream 30 with at least one additive stream 32. Those skilled in the art will readily recognize that these and other configurations of the lithium recovery system 10 are suitable for practicing the methods described herein. In continuous processes (even those with permeate and / or retentate recycle loops (40, 42)), the regulated feed stream 34 passing through the membrane 24 can maintain a constant composition over time. In the illustrated embodiment, feed pump 26 pressurizes the combined regulated feed stream 34. In other cases (not depicted), the components constituting the regulated feed stream 34 can be pressurized individually. For example, additive stream 32 can be pressurized and injected after feed pump 26. In another example, pressurized retentate recirculation loop 42 can be directly mixed with pump 26 outlet to produce regulated feed 34 entering membrane module 22. Figure 2 As shown, the regulated feed stream 34 is divided by membrane 24 into a membrane permeate stream 44 that passes through the filter membrane 24 and a membrane retainer stream 46 that does not pass through the filter membrane. All fluid in the membrane permeate stream 44 that is not diverted (preferably controlled by optional valve 47') to the permeate recirculation loop 40 flows into the first outlet stream 48 of the membrane unit 20. Similarly, all fluid in the membrane retainer stream 46 that is not diverted (preferably controlled by optional valve 47') to the retainer recirculation loop 42 flows into the second outlet stream 50 of the membrane unit 20. In a preferred embodiment, the membrane system 10 includes the retainer recirculation loop 42 but not the permeate recirculation loop 40, because this allows the membrane unit 20 to achieve a higher recovery rate with a smaller amount of active membrane area.

[0049] Figure 3A configuration suitable for a semi-batch process is shown, in which permeate is continuously generated within a batch cycle and the feed tank 12 (containing at least a portion of the membrane retentate stream generated during the batch cycle) is periodically discharged. In such a process, the composition of the regulated feed 34 varies over time. In the illustrated configuration, fluid from the retentate recirculation loop 42 can be continuously mixed with the remainder of the feed volume. During the first portion of the batch cycle, the membrane permeate stream 44 can be continuously removed from the membrane unit 20 as a first effluent stream 48, while the membrane retentate stream 46 is mixed back into the feed tank 12 via the retentate recirculation loop 42. In subsequent portions of the batch cycle, one or more valves (52', 52") are arranged to intermittently discharge a more concentrated feed stream as a second effluent stream 50.

[0050] exist Figure 4 In the closed-loop reverse osmosis (CCRO) design described, the recirculation pump 28 is located within the retentate recirculation loop 42, wherein valves 52' and 52'" enable improved energy efficiency because the existing pressure of the retentate recirculation loop 42 is not lost when it is discharged through outlet 50 downstream of the high-pressure pump 26. Figure 4 The system is characterized by the periodic dumping of the retentate recycling loop 42 through the second outlet flow 50. Figure 3 and Figure 4 The arrangement in both provides at least one additive stream 32, which can form a regulated feed stream 34 with appropriate pH and ionic composition as it flows toward the membrane 24. However, the semi-batch process in these embodiments causes the composition of the regulated feed stream 34 flowing through the membrane 24 to change over time during batch cycling (the regulated feed osmotic pressure increases). Equivalent CCRO systems for other applications have been described in U.S. Patent Nos. 7,695,614 and 8,025,804, both granted to Efraty.

[0051] The composition of the first outlet flow 48 and the second outlet flow 50 of membrane unit 20 may vary over time. This time-dependent variation is important for... Figure 3 and Figure 4 The semi-batch configuration is inherent in membrane processes. However, even for more stable batch and continuous processes, the composition of the membrane permeate stream (or membrane retained stream) will vary to some extent (e.g., due to changes in pump pressure or less controlled conditions such as temperature). In the methods and systems described herein, the average composition of the first outlet stream can be understood as equal to the composition of the combined total output of the first outlet streams from the membrane unit.

[0052] Membrane unit 20 is configured and operated to provide a desired recovery rate, and the term "recovery rate" can be used in different ways. As used herein, the term "lithium recovery rate" refers to the mass of lithium contained in the combined total output of the first outlet stream over the same time period divided by the mass of lithium present in the initial feed to the membrane unit. (Ignoring any mass of lithium introduced by the additive stream, the lithium recovery rate can be approximated as the mass of lithium in the first outlet stream divided by the mass of lithium in both the first and second outlet streams.) Preferably, the lithium recovery rate of the membrane unit exceeds 50%, more preferably 75%, or even 90%. Furthermore, the volumetric recovery rate of the membrane unit is defined as the volume of the first outlet stream divided by the combined volume of the initial feed stream and the additive stream over the same time period. Equivalently, this volumetric recovery rate of the membrane unit can be calculated from the volumes of the first and second outlet streams, which is equal to the volume of the first outlet stream divided by the combined volume of the first and second outlet streams. Preferably, the volumetric recovery rate exceeds 70% or even 90%. In a preferred process, the lithium recovery rate of the membrane unit exceeds the volumetric recovery rate of the membrane unit.

[0053] The arrangement of membrane cells affects both lithium recovery and volumetric recovery. For example, when the same volume of regulated feed flows through a larger area of ​​tandem membranes, an increased volume of permeate is generated, thus improving the recovery rate of the membrane cell. Membrane cells can also include various internal loops for partially recycling the permeate and / or retained membrane streams, and these also affect the recovery rate. Although the presence of these internal loops is not considered in the recovery rate calculations above, their presence will affect both lithium recovery and volumetric recovery. For example, a substantially higher volumetric recovery rate can be achieved by recycling a portion of the retained membrane stream.

[0054] As the volumetric recovery rate of the membrane unit increases, the volume of the second outlet stream decreases. Therefore, the concentration of some well-retained ions (e.g., polyvalent anions) in the second outlet stream preferably becomes higher, and the lithium mass in the second outlet stream preferably decreases. A higher volumetric recovery rate affects the composition of both the first and second outlet streams because the components in the conditioned feed passing through the membrane unit are distributed between the first and second outlet streams. In a preferred embodiment, a portion of the conditioned feed is passed through the membrane unit to produce the first and second outlet streams, and at least half the lithium mass present in the initial feed is distributed to the first outlet stream, and the first outlet stream has a polyvalent cation to lithium ion ratio less than half of the initial ratio of polyvalent cations to lithium ions. In a more preferred embodiment, the first outlet stream has a polyvalent cation to lithium ion ratio less than 0.25 or even less than 0.1 of the initial ratio of polyvalent cations to lithium ions in the feed.

[0055] In some preferred embodiments, additional water may be combined with the initial feed stream and other salts to produce a conditioned feed stream having a reduced concentration of polyvalent anions compared to the initial feed. Preferably, the molar concentration (mol / L) of polyvalent anions in the conditioned feed is less than 90% of the molar concentration (mol / L) of polyvalent anions in the initial feed. More preferably, the molar concentration of polyvalent anions in the conditioned feed is less than 75% of the molar concentration of polyvalent anions in the initial feed. This may be advantageous, for example, when the osmotic pressure of the membrane retentate stream is otherwise higher than or close to the maximum pressure limit of the available pump or spiral wound module. In some embodiments, sufficient water is added during the process of adding one or more salts to the initial feed such that the molar concentration (mol / L) of polyvalent anions in the conditioned feed is less than 90%, more preferably less than 75%, of the molar concentration (mol / L) of polyvalent anions in the initial feed. The additional water may be derived from a portion of the solution in the permeate membrane. In some cases, the conditioned feed comprises the initial feed, added salt, and at least a portion of the liquid that has already permeated through the membrane. Most preferably, the additional water is obtained by separating the first outlet stream into a dilution portion and a concentration portion, such as by reverse osmosis, and at least a portion of the dilution portion is recycled. While the concentration of polyvalent anions in the conditioned feed is reduced compared to the initial feed, it is preferable that the flow rate of the membrane permeate stream exceeds the flow rate of the initial feed stream.

[0056] Different ultrafiltration membranes can be used to process conditioned feeds. The membrane preferably comprises a polymer layer selected from the group consisting of: fully aromatic polyamides, semi-aromatic polyamides, sulfonated polysulfones, sulfonated polyethersulfones, and polysulfonamides. The ultrafiltration membranes used in this invention are most preferably those prepared by interfacial polymerization. Although variations exist, common methods involve forming a thin film interfacial polymer layer on a porous support, typically polysulfone or polyethersulfone having a pore size between 0.001 and 0.5 μm. An aqueous polyfunctional amine is applied to the support surface, and a nonpolar solution containing a polyfunctional amine reactive monomer (e.g., hexane, Isoparium) is applied. TM Freon TM The polyfunctional amine reactive monomer and the polyfunctional amine monomer react at the interface to form a polyamide layer or film. This layer, often referred to as the polyamide “recognition layer” or “film layer,” provides the primary means for separating solutes (e.g., salts) from solvents (e.g., aqueous feeds) in composite membranes. It has been found that polyamide membranes prepared by this method exhibit pH dependence and mixed ion rejection, which is beneficial for improving lithium recovery under specified conditions.

[0057] A wide variety of monomers can be used at different concentrations and under different polymerization conditions. Polyfunctional amine monomers have at least two primary or secondary amino groups and can be aromatic (e.g., m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,3,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, and 2,4-diaminoanisole) or aliphatic (e.g., piperazine, ethylenediamine, propylenediamine, and tris(2-diaminoethyl)amine). Polyfunctional amine reactive monomers comprise at least two, preferably two to four, amine reactive moieties selected from acyl halides, sulfonyl halides, and acid anhydrides. These monomers can be aromatic or aliphatic (linear or cyclic). Individual substances can be used alone or in combination. Non-limiting examples of aromatic polyfunctional acyl halides include: pyromellitic trimethylolpropionate chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dimethylolpropionate chloride, naphthalenetrisulfonyl chloride, and naphthalenedimethylolpropionate chloride. Non-limiting examples of alicyclic polyfunctional acyl halides include: cyclopropanetricarboxylic acid chloride, cyclopentanetricarboxylic acid chloride, cyclohexanetricarboxylic acid chloride, cyclopentanedicarboxylic acid chloride, cyclobutanedicarboxylic acid chloride, cyclohexanedicarboxylic acid chloride, and tetrahydrofurandicarboxylic acid chloride. Non-limiting examples of aliphatic halides include adipyl chloride, malonyl chloride, glutaryl chloride, and sebacyl chloride. Fully aromatic polyamides can be produced by reacting an aromatic polyfunctional amine (e.g., m-phenylenediamine, p-phenylenediamine) with an aromatic polyfunctional amine reactive monomer (e.g., pyromellitic tricarboxylic acid chloride, terephthaloyl chloride). Semi-aromatic polyamides can be produced by selecting an aliphatic polyfunctional amine (e.g., piperazine, ethylenediamine) or an aliphatic polyfunctional amine reactive monomer (e.g., cyclopropanetricarboxylic acid chloride, cyclopentanetricarboxylic acid chloride) to form a film (while another monomer contains an aromatic ring). Polysulfonamide membranes can be produced by using aromatic or aliphatic polyfunctional amine monomers and monomers containing polyfunctional sulfonyl halides (non-limiting examples are 1,3,5-benzenetrisulfonyl chloride, 1,3,5-naphthalenetri(sulfonyl chloride)) to form a membrane.

[0058] During the reaction process, various reactive and non-reactive additives may be present that can affect the membrane's performance characteristics: surfactants and phase transfer catalysts, cosolvents / solvents, organic molecules, inorganic salts, and nanoparticles. Similarly, the membrane can also be modified after the reaction by various post-treatments, including reactive and non-reactive polymer coatings, reactions of modified end groups, plasma treatment, expansion agents, surfactants, and exposure to chlorine or inorganic acids (e.g., hot phosphoric acid).

[0059] Compared to the first effluent stream (i.e., the permeate stream), the second effluent stream (i.e., the retained stream from the membrane unit) is typically rich in multivalent ions (both cations and anions). In some embodiments, specific ions within the second effluent stream can be further separated from other ions in the same stream. Preferably, the second effluent stream is further fractionated to form a portion rich in ions selected from monovalent anions and multivalent cations. Preferably, enrichment can be achieved by passing at least a portion of the second effluent stream through a distillation column, an ion exchange resin column, or a membrane system. In a more preferred method, the fractionation process of the second effluent stream uses components selected from membranes and ion exchange columns. For example, a nanofiltration membrane can be used to separate monovalent anions from multivalent anions, thereby forming a permeate portion rich in monovalent anions. In another example, the second effluent stream rich in multivalent anions can be fractionated by passing the second effluent stream through a cation exchange resin column and then regenerating the column to produce a regenerated portion richer in divalent cations. In some methods, it is advantageous to use HCl or HNO3 to regenerate the cation exchange resin because the ion exchange process will produce a high concentration of monovalent anions (Cl-). - Or NO3 - The flow of ions containing both ions and polyvalent cations. In some methods, the enriched fraction may be diluted with water or any aqueous solution before, during, or after fractionation.

[0060] Furthermore, a portion of the second effluent stream enriched with ions selected from monovalent anions and polyvalent cations can be recycled to combine with the initial feed upstream of the membrane. This enriched portion can facilitate the addition of salt to the initial feed to adjust its composition during the production of a conditioned feed. Recycling this portion of the second effluent stream reduces the amount of new salt that needs to be brought to the site for lithium recovery.

[0061] In some preferred methods, lithium dissolved in the first outlet stream can be concentrated by dehydration. For the purposes of this invention, "dehydration" means reducing the volume of water per unit mass of dissolved lithium to cause an increase in the concentration of dissolved lithium ions. For example, thermal evaporation of water from the first outlet stream can be performed using an evaporator or a distillation column. More preferably, the first outlet stream can be passed through a second membrane system (e.g., reverse osmosis) to selectively allow water to pass through preferentially over ions, thereby complementaryly producing a stream with a higher lithium ion concentration. In a less direct process, the first outlet stream can be passed through a cation exchange medium in which cations are preferentially adsorbed. The cation exchange medium is then regenerated, i.e., by unloading or desorbing the cations, for example, by treatment with an acid solution, to produce a more concentrated (dehydrated) 'eluted' stream. In some methods, concentrating lithium by dehydrating the first outlet stream is particularly useful in terms of energy and waste management.

[0062] The first effluent or permeate stream may include monovalent cations other than lithium. Non-limiting examples of other monovalent cations are cations of Na, K, Cs, and Rb. Due to the high purity requirements (99.5% purity) of battery-grade lithium, it is desirable to remove other monovalent cations (along with polyvalent cations) from the first effluent stream. The purity of battery-grade lithium is defined as the content of lithium salts (typically lithium carbonate) in the final solid product, expressed as wt.%. In this invention, a preferred method further includes a process of fractionating the first effluent stream into two solutions, one of which comprises an increased molar concentration of lithium ions compared to the molar concentration of lithium ions in the first effluent stream and a decreased molar concentration of other (non-lithium) monovalent cations compared to the molar concentration of other (non-lithium) monovalent cations in the first effluent stream. The fractionation of the first effluent stream can be performed before, during, or after any step of concentrating (by dehydration) dissolved lithium ions to be allocated to the first effluent stream.

[0063] The classification of the first effluent stream can be accomplished through various processes. In some preferred embodiments, the first effluent stream can be passed through a lithium-selective medium. Common, non-limiting examples of lithium-selective media are inorganic lithium intercalations, including but not limited to iron phosphate, lithium aluminum hydroxide chloride, lithium manganese oxide, and lithium titanium oxide. Lithium ions can be adsorbed into these media and then desorbed with a suitable eluent (e.g., water). Lithium ions in these materials can also be extracted by ion exchange methods, where additives are used to replace lithium. In this embodiment, common additives are acids, such as sulfuric acid or hydrochloric acid. The eluent solution may include an increased molar concentration of lithium ions compared to the molar concentration of lithium ions in the first effluent stream and a decreased molar concentration of non-lithium monovalent cations compared to the molar concentration of non-lithium monovalent cations in the first effluent stream.

[0064] In some methods, the first effluent stream can be fractionated by passing through an ion-exchange medium. Suitable common media include, but are not limited to, poly(co-styrene-divinylbenzene), poly(co-methylmethacrylate-divinylbenzene), media that can be further functionalized to contain cation-binding groups (such as sulfonic acids, carboxylic acids, weak bases), and combinations of two or more of these media. The ion-exchange medium is preferably suitable for cation exchange, such that the fractionation of monovalent cations can be achieved chromatographically, i.e., lithium and other monovalent cations flow through the medium at different rates and have different retention times. This process can be aided by using additional elution solutions to separate lithium ions from other monovalent cations. Suitable elution solutions include, but are not limited to, solutions of acids such as sulfuric acid or hydrochloric acid.

[0065] In some other methods, the first effluent stream is fractionated by selective precipitation of one or more monovalent cations, followed by filtration or decantation. In this method, the anions are selected such that the resulting lithium anion salt has a lower solubility than other monovalent cation-anion salts present in the first effluent stream. Suitable anions include, but are not limited to, carbonate and oxalate. Alternatively, the method may involve the selective precipitation of salts of non-lithium monovalent cations. In this method, fractionation can be achieved where the lithium anion salt has a higher solubility than other monovalent cation-anion salts, leading to their precipitation. Suitable salts with lower solubility include, but are not limited to, sodium chloride and sodium bromide.

[0066] The following examples are provided to further describe the invention in detail. These examples, which illustrate specific embodiments and preferred modes of carrying out the invention as currently considered, are intended to be illustrative and not limiting.

[0067] Example

[0068] Description of the initial feed water production

[0069] By Li + Na + K + Ca 2+ Mg 2+ Fe 2+ Mn 2+ 、Sr 2+ Zn 2+ And Al 3+ SO4 2- The initial feed was prepared by dissolving salt in deionized water (DIW). The pH of the initial feed was adjusted to 1.4 to 1.5 by adding an appropriate amount of 98% sulfuric acid solution. The dissolved mass of lithium was 0.33 g / L. The initial feed cation concentration (mol / L) was measured as Li. + =0.05, Na + =0.08, K + =0.004, Ca 2+ =0.01, Mg 2+ =0.21, Fe 2+ =0.014, Mn 2+ =0.001, Sr 2+ =0.002, Zn 2+ =0.0007 and Al 3+ =0.02. The main anion in the initial feed is SO42-. 2- The ion concentration was 0.378 mol / L.

[0070] The initial feed contains no monovalent anions except for a small amount of hydroxide ions from water dissociation. Therefore, the initial ratio of monovalent anions to lithium ions is zero. Similarly, the initial ratio of monovalent anions to polyvalent anions is zero. The initial ratio of polyvalent cations to lithium ions is 5.4. In Examples 1 and 2, the initial feed was used as the feed stream for the filtration tests; that is, there was no separate conditioned feed.

[0071] Description of the manufacture of conditioned feed water

[0072] In Examples 3 through 14, conditioned feeds are prepared by adding one or more salt solutions to the initial feed solution. Details of conditioned feed preparation are provided in specific examples. Ion concentrations (mol / L) are used to calculate the conditioned ratio of monovalent anions to lithium ions.

[0073] Description of filtration test plan and analytical measurement

[0074] The filtration tests in Examples 1 through 14 were performed to measure and compare lithium throughput, mass recovery, and the ratio of multivalent cations to lithium ions in the membrane permeate stream of specific membranes operating under different feed and operating conditions.

[0075] The test was conducted in a cross-flow configuration by pressurizing the feed using a pump and passing it through membrane samples contained in standard membrane filtration cells. Each cell contained an active area of ​​42 cm² cut from a flat membrane sheet. 2 A rectangular membrane sample. The membrane unit contains six membrane filtration cells, and therefore, the total active area in contact with the feed is 252 cm². 2 (0.27ft 2 In these examples, each membrane filter cell with a membrane is considered a membrane module, and all six cells / modules combined are considered membrane units. These six membrane filter cells are positioned in two parallel groups, with three cells connected in series in each group. The active side of the membrane is exposed to the feed solution. A feed volumetric flow rate of 2 liters / minute is maintained for each group throughout the test. The portion of the feed that has passed through the membrane (membrane permeate) is collected from the permeate lines of each individual membrane filter cell. The portion of the feed that has not passed through the membrane (membrane retentate) is recirculated back to the feed tank upstream of the pump throughout the test period. Unless otherwise specified in any specific example, the membrane permeate is also recirculated back to the feed tank upstream of the pump during the permeate collection period. All filtration tests are conducted within a feed temperature range of 23°C to 27°C.

[0076] The permeate streams collected from individual membrane filtration cells were weighed using an analytical balance, and the membrane flux (volume per unit area per unit time) was calculated by correcting the measured permeate weight for permeate collection time and membrane active area. The flux value was averaged over the six permeates collected (one from each membrane filtration cell) and expressed in liters / m³.2 Reporting is done in units of / h (LMH). Flux is calculated using a permeate density of 1 g / ml.

[0077] The ion concentrations (mol / L) of both the permeate and feed streams were analyzed. The feed stream was collected from the feed tank, and the permeate stream was also collected simultaneously. When both the retentate and permeate streams were recycled back to the feed tank, the ion concentration of the feed stream did not change significantly during the experimental period. In some cases (e.g., Example 14), the ion concentration of the feed stream varied over time due to continuous collection of the permeate stream or due to occasional addition of water to the feed tank to reduce osmotic pressure.

[0078] To measure the ion concentration in the permeate stream, all six membrane permeate streams were mixed to prepare a 'mixed permeate' stream. Cation mass concentration was analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES) on an iCap 7600 ICP-OES analyzer available from Thermo Scientific of Waltham, MA. The ion concentration was calculated by dividing the ICP-OES mass concentration by the corresponding molar mass of the ion. These ion concentrations were used to calculate the ratio of multivalent ions to lithium ions in the (mixed) permeate stream. Ion throughput (fraction, abbreviated as "fr.") was calculated as the ratio of the molar concentration of ions in the (mixed) permeate stream to the corresponding molar concentration in the feed stream (both measured using ICP-OES).

[0079] The membrane unit volumetric recovery rate is calculated by dividing the volume of permeate liquid produced by the membrane unit by the volume of liquid supplied to the membrane unit during the same time period and is reported as a percentage (%). In most cases shown here, the membrane unit recovery rate is less than 2%, and these tests are specifically designed to demonstrate how the relative concentrations of different ions in the permeate can be altered by changing the regulated feed. It can be recognized that both the volumetric recovery rate and the fraction of lithium ions recovered (into the permeate stream) can be increased by using a larger tandem membrane area, passing less feed solution through the membrane unit at the same average flux, or recirculating the membrane retainer stream while continuing to extract permeate.

[0080] In a specific example (Example 14), the membrane retentate stream of the membrane unit is recycled, and the system recovery rate is measured and reported. For this example, the lithium-ion mass recovery rate is also calculated and expressed as a fraction by dividing the mass of lithium ions dissolved in the permeate stream (first outlet stream) by the mass of lithium ions dissolved in the initial feed. The mass of lithium ions dissolved in the permeate stream is calculated by multiplying the permeate volume (the volume of the collected first outlet stream) by the mass concentration of dissolved lithium ions as measured by ICP-OES. The mass of lithium ions dissolved in the initial feed is calculated by multiplying the mass of the Li-containing reagent used to prepare the initial feed by the weight fraction of Li ions in the reagent.

[0081] Examples (1 and 2) illustrate control cases in which the initial feed is fed directly into the membrane without the addition of any salt (i.e., without any pH and / or ion ratio adjustment).

[0082] Example 1: The membrane used in this example is a composite membrane with a piperazine-based polyamide barrier layer, which is used in FilmTec's commercial SR90 element. The initial feed described earlier is supplied to the membrane unit.

[0083] Example 2: In Example 2, a membrane sample was cut from a Duracid polysulfonamide membrane sheet available from Suez. The initial feed was used as the feed for the membrane unit.

[0084] Examples 3 through 6 illustrate the effects of adding salt to the initial feed before the membrane unit to provide a specified regulated feed pH and / or ion ratio.

[0085] Example 3: In Example 3, the initial feed was prepared as described above, except that no Fe was added. 2+ Zn 2+ or Sr 2+ Besides ions. Therefore, in this example, the initial feed cation concentration, in mol / L, is Li. + =0.05, Na + =0.08, K + =0.004, Ca 2+ =0.01, Mg 2+ =0.21, Mn 2+ =0.001 and Al 3+ =0.02. The initial feed pH was adjusted to 1.4 to 1.5 by adding an appropriate amount of 98% sulfuric acid solution to the salt solution. The dominant anion in the initial feed was SO42-. 2-The ion concentration was 0.368 mol / L. The initial feed contained no monovalent anions except for a small amount of hydroxide ions from water dissociation. Therefore, the initial ratio of monovalent anions to lithium ions was zero. Similarly, the initial ratio of monovalent anions to polyvalent anions was zero. The initial ratio of polyvalent cations to lithium ions was 5.1.

[0086] Lithium hydroxide powder (Li(OH)·H₂O, 41.95 g) was dissolved in deionized water to produce a Li(OH)₂ solution (1 L, 1 mol / L). As described above, an appropriate amount of this salt solution was added to the initial feed to raise the pH. Any precipitates formed during pH adjustment were removed using a Fisherbrand 0.2 μa PES membrane filter, and the filtrate pH was measured to be 4.2. The filtrate collected after removal of the precipitated solids was the adjusted feed, and this adjusted feed was passed through the membrane.

[0087] The conditioned feed was tested using a similar membrane and testing procedure as described in Example 1. The conditioned ratio of monovalent anions to lithium ions was zero because no other monovalent anions were present except for a small amount of hydroxide ions from water dissociation. The lithium ion concentration in the conditioned feed was 0.15 mol / L.

[0088] Example 4: This is similar to Example 3. However, after removing the precipitated solids, a conditioned feed is formed by adding 0.03 mol / L MgCl₂·6H₂O salt in solid form to the filtrate. The feed will contain Cl₂… - The filtrate (solution pH 4.4) containing ions is sent to the membrane unit. The Cl in the conditioned feed... - The ion concentration is 0.06 mol / L. The adjusted ratio of monovalent anions to lithium ions is 0.4. The adjusted feed lithium concentration is 0.14 mol / L.

[0089] Example 5: This is similar to Example 4, except that the adjusted feed (solution pH 4.2) contains Cl. - The ion concentration is 0.3 mol / L or higher. The adjusted ratio of monovalent anions to lithium ions is 2.1. The adjusted feed lithium concentration is 0.14 mol / L.

[0090] Example 6: This is similar to Example 4, except that the adjusted feed (solution pH 4.2) contains Cl. - The ion concentration is 0.6 mol / L. The adjusted ratio of monovalent anions to lithium ions is 4.3. The adjusted feed lithium concentration is 0.14 mol / L.

[0091] The feed composition and filtration performance of Examples 1 to 6 are reported in Table 1. As can be seen from the data in Table 1, when the pH and the ratio of monovalent anions to lithium ions are adjusted by adding specific salts, the Li in the permeate stream... + The permeability increased and the ratio of polyvalent cations to lithium ions in the permeate decreased.

[0092] Table 1

[0093]

[0094] Examples (7 to 8) illustrate the applicability of the present invention under different feed pH values.

[0095] Example 7: Example 7 uses the same conditions as Example 5 (membrane, initial feed preparation, conditioned feed preparation, and testing), except that: the conditioned feed pH is pH 6.6, and the Cl in the conditioned feed... - The ion concentration is 0.3 mol / L, the adjusted ratio of monovalent anions to lithium ions is 2.0, and the adjusted lithium concentration in the feed is 0.15 mol / L.

[0096] Example 8: Example 8 uses the same conditions as Example 5 (membrane, initial feed preparation, conditioned feed preparation, and testing), except that: the conditioned feed pH is pH 3.5, and the Cl in the conditioned feed... - The ion concentration is 0.3 mol / L, the adjusted ratio of monovalent anions to lithium ions is 3.0, and the adjusted lithium concentration in the feed is 0.10 mol / L.

[0097] The feed composition and filtration test performance of Examples 7 and 8 are reported in Table 2.

[0098] Table 2

[0099]

[0100] Examples (9 to 13) illustrate the use of different types and amounts of salt to form conditioned feeds with different pH and / or ion ratios.

[0101] Example 9: Example 9 used the same conditions as Example 3 (membrane, initial feed preparation, conditioned feed preparation, and testing procedures), except that a solid Mg(OH)₂ salt was added to the initial feed for pH adjustment. After removing the precipitate formed during pH adjustment, the pH of the conditioned feed solution was measured to be 4.2. The conditioned ratio of monovalent anions to lithium ions was zero because no other monovalent anions were present except for a small amount of hydroxide ions from water dissociation. The conditioned feed lithium concentration was 0.044 mol / L.

[0102] Example 10: Example 10 is similar to Example 9, except that 0.015 mol MgCl₂·6H₂O salt is added per L of filtrate after the removal of the precipitated solid. It contains Cl - The filtrate of ions forms a regulated feed (solution pH 4.3), which passes through the membrane surface. The regulated feed contains Cl... - The ion concentration is 0.03 mol / L. The adjusted ratio of monovalent anions to lithium ions is 0.7. The adjusted feed lithium concentration is 0.044 mol / L.

[0103] Example 11: In this example, the conditions are similar to those in Example 10, except that the adjusted feed (solution pH 4.2) contains Cl. - The ion concentration is 0.16 mol / L and the adjusted ratio of monovalent anions to lithium ions is 3.6 or higher. The adjusted feed lithium concentration is 0.044 mol / L.

[0104] Example 12: In this example, the conditions are similar to those in Example 10, except that the Cl in the adjusted feed (solution pH 4.2) is... - The ion concentration is 0.32 mol / L, the adjusted ratio of monovalent anions to lithium ions is 7.0, and the adjusted feed lithium concentration is 0.043 mol / L.

[0105] Example 13: In this example, the conditions are similar to those in Example 9, except that after removing the precipitated solid, 0.30 mol / L NO3 will be in the form of Mg(NO3)2·6H2O salt. - Added to the filtrate, excluding the filtrate. Contains NO3. - The filtrate for ion exchange is a regulated feed (solution pH 4.2) that passes through the membrane surface. The regulated ratio of monovalent anions to lithium ions is 6.8. The regulated feed lithium concentration is 0.044 mol / L.

[0106] The feed composition and filtration test performance of Examples 9 to 13 are reported in Table 3.

[0107] Table 3

[0108]

[0109] Example 14 demonstrates the mass recovery rate of Li in a system with a larger volumetric recovery rate.

[0110] Example 14: Preparation of Li + =0.043 and Mg 2+The initial feed is sulfate-based with a cation concentration of 0.173 mol / L. The initial feed also contains sulfuric acid and has an initial pH of 1.55. The initial feed contains no monovalent anions except for a small amount of hydroxide ions from water dissociation. Therefore, the initial ratio of monovalent anions to lithium ions is zero. Similarly, the initial ratio of monovalent anions to polyvalent anions is zero. The initial ratio of polyvalent cations to lithium ions is 4.0.

[0111] Furthermore, the recirculation system was configured to reasonably simulate the performance of a continuous filtration system with a larger membrane area. In this example, the ion ratio was adjusted by adding MgCl2·6H2O salt in powder form to the initial feed. The adjusted feed contained Cl... - The ion concentration was 0.4 mol / L. An appropriate amount of Mg(OH)₂ powder was then added to raise the solution pH. A Fisherbrand 0.2 μa PES membrane filter was used to remove the solids precipitated during pH adjustment, and the filtrate pH was measured to be 4.3. This filtrate is the 'adjusted feed' to the membrane unit. Monovalent anions (Cl₂) - The adjusted ratio of lithium ions to ions is 9.3. The adjusted feed lithium concentration is 0.043 mol / L. The adjusted feed was tested using a similar membrane as described in Example 1.

[0112] The adjusted feed (10.1L, 10378g) was pumped through a system containing six 252cm... 2 The membrane unit is a flat sheet sample with combined active area. Throughout the test, the first outlet flow (i.e., the permeate stream leaving the membrane unit) is collected in a bucket, while the membrane retentate stream is recycled to the feed tank (upstream of the feed pump, such as...). Figure 3 (As shown in the diagram). As the osmotic pressure in the feed tank increased, the feed-side pressure was adjusted to increase the permeate flow. After 9 hours of operation, 5.45 L of permeate (weighing 5401 g) was collected. This collected solution is referred to as permeate A.

[0113] After permeate A is collected, 0.5 L of deionized water (DIW) is added to the feed tank, and the permeate stream is collected for another 1.5 hours. The volume of the collected solution is 0.71 L (705.4 g) and is referred to as permeate B. Further, another 0.5 L of DIW is added to the feed tank, and the permeate stream is collected for another 3 hours. The volume of the collected solution is 1.0 L (1003.7 g) and is referred to as permeate C.

[0114] The data on membrane unit volume recovery rate and Li mass recovery rate are presented in Table 4.

[0115] Table 4

[0116]

[0117] When permeates A, B, and C are combined, the membrane unit volume recovery is 70.9% of the conditioned feed volume or 64.5% of the combined conditioned feed and added DIW volume. The Li mass recovery is 0.82, and the polyvalent cation (Mg) recovery is also high. 2+ The ratio of ions to lithium ions is 0.2 (i.e., 0.05 times the same ratio of 4.0 in the initial feed).

[0118] The method described herein is particularly useful for selectively recovering lithium from brine feeds with high recovery rates and purity. Another advantage of the method is the presence of polyvalent anions (e.g., SO42-) in the initial feed containing lithium ions. 2- CO3 2- ) can be permeated by monovalent anions (e.g., Cl-) in the permeate of the membrane system. - NO3 - This exchange creates a composition that may be more beneficial for downstream lithium recycling operations.

[0119] While certain preferred embodiments of the invention have been described and specifically illustrated above, the invention is not intended to be limited to such embodiments. Rather, it should be understood that although many features and advantages of the invention, along with details of its structure and function, have been set forth in the foregoing description, this disclosure is merely illustrative and changes may be made in detail, particularly in terms of the shape, size, and arrangement of parts, to the full extent indicated by the broad, general meaning of the terms in the appended claims, within the principles of the invention.

Claims

1. A system for recovering lithium, the system comprising: An apparatus for providing an initial feed having a dissolved mass of lithium, wherein the initial feed contains (i) an initial ratio of monovalent anions to lithium ions, (ii) an initial ratio of polyvalent cations to lithium ions and (iii) an initial ratio of monovalent anions to polyvalent anions less than 1. Apparatus for adding one or more salts to the initial feed to produce an adjusted feed having a pH between 1 and 7 and an adjusted ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions. Membrane filter unit; as well as A means for passing a portion of the regulated feed through the membrane filter unit to generate a first outlet stream and a second outlet stream, wherein at least half the mass of lithium present in the initial feed is allocated to the first outlet stream, and the first outlet stream has a multivalent cation to lithium ion ratio of less than half of the initial ratio of multivalent cations to lithium ions.

2. The system of claim 1, further comprising: A means for classifying the second outlet stream to form a portion rich in ions selected from monovalent anions and polyvalent cations, and a means for recycling at least a portion of the enriched portion to form the regulated feed.

3. The system of claim 1, further comprising: A device for extracting lithium from the first outlet stream.

4. A system for recovering lithium, the system comprising: An initial feed having a dissolved mass of lithium, wherein the initial feed contains (i) an initial ratio of monovalent anions to lithium ions, (ii) an initial ratio of polyvalent cations to lithium ions and (iii) an initial ratio of monovalent anions to polyvalent anions less than 1. One or more salts are added to the initial feed to produce an adjusted feed having a pH between 1 and 7 and an adjusted ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions. Membrane filter unit; as well as Piping, pumps, and optional valve assemblies are used to pass a portion of the regulated feed through the membrane filter unit to produce a first outlet flow and a second outlet flow. At least half of the mass of lithium present in the initial feed is allocated to the first outlet stream, and the first outlet stream has a multivalent cation to lithium ion ratio that is less than half of the initial ratio of multivalent cations to lithium ions.

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