Method and system for recovering lithium from brine

Abstract

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

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 365(c) to U.S. Provisional Patent Application No. 63 / 409,404, filed September 23, 2022, which is incorporated herein by reference in its entirety.

[0002] Statement Regarding Federally Sponsored Research This invention was made with U.S. government support under Government Contract No. DE-EE0009430 awarded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. The U.S. government has certain rights in this invention.

[0003] The present invention relates to a method and system for the recovery of lithium from natural or synthetically produced brines. In particular, the method involves adjusting the ionic concentration of the feed prior to an ultrafiltration step. [Background technology]

[0004] Several patents, patent applications and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains, and the entire disclosures of each of these patents, patent applications and publications are incorporated herein by reference.

[0005] Lithium (Li) is a key component of high-energy-density lithium-ion batteries. Lithium-ion batteries are used in a variety of applications, including electric vehicles, computers, and energy storage devices, among others. Global demand for lithium is expected to increase in the foreseeable future. Currently, industrial-scale Li extraction technologies use chemical treatment followed by evaporation-based processes to recover lithium from different natural and recycled sources, which are time-consuming and require large-footprint operations. Furthermore, large amounts of water evaporation are required to recover Li, and most natural Li sources are located in arid regions with limited availability of clean water. Although engineered processes such as thermal evaporation and subsequent condensation have been applied to speed up the evaporation process and recover water, these remain energy-inefficient.

[0006] Various membrane-based processes have been described for recovering lithium from natural and recycled sources. U.S. Pat. No. 10,450,633 ('633) describes a membrane-based process for recovering Li from an acid solution. The processing step described in '633 is passing the acidic lithium solution through a nanofiltration (NF) membrane unit, where fractions of the acid and lithium solution permeate the NF membrane. U.S. Pat. No. 6,004,464 describes a brine regeneration process from a water softening resin unit, which involves acidifying chloride-containing brine to a pH range of 0.5 to 6, and then adding a salt with monovalent cations and polyvalent anions (e.g., Na2SO4) to the pH-adjusted brine. Chinese Patent No. 112,850,851 describes a membrane-based process for recovering Li from an acid solution. - ) salts are added to the brine and pumped through the NF system in the pH range of 7.5 to 11.0 to obtain excellent Li + / Mg 2+Chinese Patent No. 108,063,295 describes a process for the extraction of Li and other heavy metals from battery sources using hydrochloric acid, in which LiSO is added to the acidic feed and reacted under stirring for about 30 minutes to produce LiCl and CaSO, which are further separated using an NF membrane. Summary of the Invention [Problem to be solved by the invention]

[0007] Nevertheless, certain feeds, especially polyvalent anions (e.g., SO4 2- , CO3 2- There remains a need for better water management processes with high lithium recovery rates for those containing uranium dioxide (CO₂) and those located in water-scarce regions. [Means for solving the problem]

[0008] Accordingly, provided herein is a method for recovering lithium ions, 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 that is less than 1. The method includes adding one or more salts to the initial feed to create a conditioned feed having a pH between 1 and 7 and an conditioned ratio of monovalent anions to lithium ions that is greater than the initial ratio of monovalent anions to lithium ions. The method further includes passing a portion of the conditioned feed through a membrane unit to produce a first outlet stream and a second outlet stream, wherein at least half of the mass of lithium present in the initial feed is distributed to the first outlet stream, and wherein the first outlet stream has a ratio of polyvalent cations to lithium ions that is less than half of the initial ratio of polyvalent cations to lithium ions.

[0009] Also provided herein is a system for recovering lithium, comprising: means for providing an initial feed having a dissolved mass of lithium ions, the initial feed containing (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 that is less than 1; means for adding one or more salts to the initial feed to produce a conditioned feed having a pH of 1 to 7 and an conditioned ratio of monovalent anions to lithium ions that is 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 of the mass of lithium ions present in the initial feed is distributed to the first outlet stream, and the first outlet stream has a ratio of polyvalent cations to lithium ions that is less than half of the initial ratio of polyvalent cations to lithium ions. The system may optionally further include means for fractionating the second outlet stream to form a fraction enriched in ions selected from monovalent anions and multivalent cations, and means for recycling at least a portion of the enriched fraction to the conditioned feed.

[0010] The advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and objects attained by its uses, reference should be made to the drawings which form a further part of this specification and to the accompanying descriptive matter which illustrates and describes one or more preferred embodiments of the invention. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a system suitable for use in the methods described herein for recovering lithium from an initial feed of brine solution containing dissolved lithium. [Figure 2] FIG. 1 is a schematic diagram of another system suitable for use in the lithium recovery methods described herein. [Figure 3] FIG. 1 is a schematic diagram of yet another system suitable for use in the lithium recovery methods described herein. [Figure 4] FIG. 1 is a schematic diagram of yet another system suitable for use in the lithium recovery methods described herein. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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 belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments described herein, suitable methods and materials are described below.

[0013] As used herein, the terms "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, refer to a non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to those elements and may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0014] The transitional phrase "consisting essentially of" limits the scope of a claim to those materials or steps specified and that do not materially affect the basic and novel characteristics of the claimed invention. A "consisting essentially of" claim occupies a middle ground between a closed claim written in a "consisting of" format and a fully open claim drafted in a "comprising" format. When an invention or a portion thereof is described in open-ended terms such as "comprising," this description should also be understood to include descriptions of the invention using the terms "consisting of" and "essentially consisting of," unless the specific circumstances clearly indicate otherwise.

[0015] Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, condition A or B can be satisfied by any one 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 A and B are both true (or exist).

[0016] Additionally, the use of "a" or "an" is used to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one, and the singular also includes the plural unless it is clear that this is meant otherwise.

[0017] As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not, and need not be, exact, but may be approximate and / or larger or smaller, as desired, to reflect tolerances, conversion factors, rounding, measurement error, etc., as well as other factors known to those of ordinary skill in the art. In general, an amount, size, formulation, parameter, or other quantity or characteristic is "about" or "approximately" whether or not it is expressly stated as such.

[0018] Additionally, ranges set forth herein include their endpoints, unless otherwise expressly stated under limited circumstances. Furthermore, when an amount, concentration, or other value or parameter is given as a range, one or more preferred ranges, or a list of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed from any pairing of any upper range value or preferred value with any lower range value or preferred value, regardless of whether such pairs are separately disclosed.

[0019] Furthermore, when a range of numerical values ​​is recited herein, unless otherwise stated under specific circumstances, the range is intended to include the endpoints thereof, and all real numbers within the range. The scope of the invention is not intended to be limited to the specific values ​​recited when defining a range. Finally, when the term "about" is used to describe a value or an endpoint of a range, it should be understood that the disclosure includes the specific value or endpoint referred to.

[0020] Finally, as used herein, the term "lithium" as used alone or in combination means lithium metal (Li 0 ) refers to lithium ion unless otherwise specified.

[0021] Provided herein are methods and systems for selectively recovering lithium with good mass recovery and high purity. The method includes providing an initial feed having a dissolved mass of lithium ions. Preferably, the concentration of lithium in the initial feed or in water of interest for use 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.

[0022] The initial feed may include 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. In addition to lithium ions, other monovalent cations that may be present in the initial feed 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 that is stable in aqueous solution. The initial feed may be derived from natural sources such as salt lakes or salars or geothermal brines, or from clay mining or hard rock deposits. The initial feed may be synthetically produced by acid decomposition of lithium-containing materials, such as, but not limited to, lithium-ion batteries, solar panels, solar thermal storage devices, computers, laptops, and similar devices. Alternatively, the initial feed may be a processed feed produced by processing natural resource brine or synthetically produced brine.

[0023] The initial feed has an initial ratio of monovalent anions to lithium ions. Some common monovalent anions include Cl, - , Br - , F - , O.H. - , 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 monovalent anion-depleted, with an initial ratio of monovalent anions to lithium ions of 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 small amounts of hydroxide 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 the ion per unit volume and dividing it by the corresponding molar mass. For example, the ratio of lithium ions (Li) in moles / L can be calculated by dividing the total molar concentration of dissolved monovalent anions by the molar concentration of dissolved lithium ions. + The molar concentration of lithium ion (Li ion) can be calculated as the measured dissolved mass of lithium ion per L of solution divided by the molar mass of lithium ion (6.941 amu).

[0024] The initial feed has an initial ratio of multivalent cations to lithium ions. The multivalent cations in the initial feed are generally magnesium (Mg 2+ ) and calcium (Ca 2+ ), although the initial mixture and ratio of polyvalent cations to lithium ions will depend 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.

[0025] The initial feed has an initial ratio of monovalent anions to polyvalent anions that is less than 1. For example, in a feed containing only chloride (35.45 amu) and sulfate (96.06 amu) anions, a ratio of less than 1 corresponds to less than 27% chloride by anion mass. Common polyvalent anions include SO42- , HPO4 2- , PO4 3- , and CO3 2- Advantageously, the anions in the initial feed include SO4 2- and CO3 2- (greater than 50% of the total molar concentration of anions), more preferably the anion is SO 2- is governed only by

[0026] Some lithium-containing solutions can be advantageously treated by the methods and systems described herein. For example, many natural brine sources contain SO4 as one of the key anions. 2- (e.g., sodium sulfate subtype or magnesium sulfate subtype brines), with sulfate subtype brines often characterized by high Mg / Li ion ratios, e.g., greater than 5. Brines extracted from hard rock, clay mining, or lithium-containing materials, such as, for example, lithium-ion batteries, solar panels, solar thermal storage devices, computers, laptops, and similar devices, also contain high levels of SO4, especially when H2SO4 is used as the extractant. 2- More preferably, the initial feed is enriched in polyvalent anions and depleted in monovalent anions, with an initial ratio of monovalent anions to polyvalent anions being less than 1, preferably less than 0.5, and even more preferably less than 0.2.

[0027] The initial feed pH range can be broad, for example, from pH 0 to pH 10, inclusive. Particularly relevant examples of lower pH brines (pH range 0-3) include brines produced from hard rock extraction, clay mining, and those resulting from the decomposition of lithium-containing materials using acid or aqueous acid solutions. Examples of higher pH brines (pH range 4-10) include those obtained from salt lakes or salars 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 creation. The methods described herein include adding one or more salts to the initial feed to create a conditioned feed. As used herein, the term 'salt' refers to solid salts and to 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 in the conditioned feed. Solid salts may be in hydrated or anhydrous forms. 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. The addition of salts to any composition can be done in one or more steps by adding one or more salts in solid, suspended, dispersed, or dissolved form. When a salt is described herein as "dissolved," the solution can also contain dispersed or suspended particles of the salt.

[0028] In the methods described herein, the conditioned feed has a pH of 1 to 7 and an adjusted ratio of monovalent anions to lithium ions that is greater than the initial ratio of monovalent anions to lithium ions. Preferably, the pH of the conditioned feed is greater than 2, more preferably greater than 3. Preferably, the pH of the conditioned feed is less than 6. The adjusted ratio of monovalent anions to lithium ions, i.e., the ratio in the conditioned feed, is greater than 1, more preferably greater than 2, and even more preferably greater than 4.

[0029] In some preferred methods, the pH of the conditioned feed is less than the pH of the initial feed. Non-limiting examples of suitable acids that can be added to the initial feed to lower the pH include HCl, HNO, HSO, and HPO. Of these, HCl and HNO 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 a dilute solution in water.

[0030] 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 for the purpose of raising the pH include hydroxide salts (e.g., NaOH, KOH, LiOH, Mg(OH)2, or Ca(OH)2), carbonate salts (e.g., NaHCO3, KHCO3, Ca(HCO3)2, MgCO3, or CaCO3), and alkaline oxides such as quicklime (CaO). Among these, species containing multivalent cations can be used both to raise the pH and to enhance the adjusted ratio of multivalent cations to lithium ions. These salts can be added in their pure form or as a dilute solution in water.

[0031] In some processes, precipitation and / or suspension may be caused by an initial feed pH adjustment. The precipitated and / or suspended solids may then be removed by settling, by centrifugation, or by using a filtration device (e.g., a media filter, a sand filter, an ultrafiltration membrane, or a microfiltration membrane). A particularly advantageous method for removing solids from the conditioned feed is ultrafiltration. The conditioned feed is then defined as a solution in the presence of dissolved ions that pass through the surface of an ultrafiltration membrane.

[0032] In some preferred methods, an adjusted ratio of monovalent anions to lithium ions greater than the initial ratio can be achieved by adding a common salt containing a monovalent anion. To this end, the salt can be selected from the group consisting of chloride salts, such as, but not limited to, NaCl, KCl, MgCl, and CaCl, in their hydrated or anhydrous forms; nitrates, such as, but not limited to, NaNO, KNO, Mg(NO), and Ca(NO), in their hydrated or anhydrous forms; and carbonates, such as, but not limited to, NaHCO, KHCO, Ca(HCO), MgCO, and CaCO, in their hydrated or anhydrous forms. Among these, salts containing polyvalent cations can be used to simultaneously increase the adjusted ratio of polyvalent cations to lithium ions.

[0033] In order to maximize the passage of lithium ions and to reduce the ratio of multivalent cations to lithium ions in the permeate stream (the portion of the conditioned feed that passes through the ultrafiltration membrane), it has been found that the added salt preferably contains multivalent cations to increase the conditioned ratio of multivalent cations to lithium ions.

[0034] In some preferred methods, adjusting the initial feed pH and adjusting 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, monovalent anion-containing salts such as chloride salts or nitrate salts are preferred. The salts can be dissolved in an acidic solution (to lower the initial feed pH to the range preferred for the adjusted feed) or in a basic solution (to raise the initial feed pH to the range preferred for the adjusted feed). More preferably, the monovalent anion salt also contains a polyvalent cation 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, adjusting the initial feed pH and adjusting the ion ratio can be performed simultaneously by adding carbonate salts such as CaCO3 or MgCO3 in their solid form or dissolved in water.

[0035] In some preferred methods, adjustment of the initial feed pH and ion ratios may be done in multiple steps. Ion adjustments include Cl - or NO3 - The pH adjustment can be performed by adding a solid or dissolved mass of a salt containing a monovalent anion, such as a salt, to the initial feed, and the pH adjustment can be performed by adding an acid or base to the initial feed separately in any order. In some methods, the pH change can induce precipitation. In preferred methods of this type, a filtration step (e.g., ultrafiltration) to remove solid precipitates or suspended matter can be performed before, during, or after completion of the salt addition. For example, some examples of the present invention presented herein below illustrate the addition of salt to the initial feed, which changes the pH and causes precipitation.

[0036] The methods described herein include passing a conditioned feed (as described above) through a membrane unit and distributing it between a first outlet stream and a second outlet stream. The first outlet stream contains the liquid that has permeated the membrane. In a preferred method, the first outlet stream contains a majority of the monovalent cations from the conditioned feed, and the second outlet stream contains a majority of the divalent anions from the conditioned feed. The membrane unit includes an ultrafiltration membrane, and the conditioned feed passes through at least one ultrafiltration membrane under pressure, where a portion of the conditioned feed permeates the ultrafiltration membrane. As used herein, the term "membrane permeate" refers to the portion of the conditioned feed that passes through the membrane, and the term "membrane reject" refers to the remaining portion of the conditioned feed that does not pass through the membrane. Thus, if there is no permeate recycle loop or brine recycle loop, the first outlet stream is the membrane permeate, and the second outlet stream is the membrane reject. As used herein, the term "ultrafiltration" refers to reverse osmosis and nanofiltration. Most preferably, the membrane unit comprises a nanofiltration membrane.

[0037] The membrane unit may include flat sheet, hollow fiber, or tubular shaped membranes. Preferably, flat sheet membranes are provided in a spiral-wound module. A plurality of such spiral-wound membrane modules may be axially aligned in a series configuration within the chamber of a cylindrical pressure vessel to increase the available active membrane area. The membrane unit may further include multiple pressure vessels arranged in parallel or series. Suitable membranes and units are well known in the art and are commercially available from DuPont de Nemours, Inc. of Wilmington, DE, under the trade name FilmTec™ reverse osmosis membranes. A suitable method for synthesizing membranes is described in U.S. Pat. No. 4,277,344 issued to Cadotte.

[0038] Referring now to the drawings, and particularly to Figures 1-4, in which like reference numerals indicate corresponding structure throughout the figures, the systems described herein, and particularly the membrane units in these systems, may have two or more operating configurations or operating procedures. Not all operating configurations or operating procedures are depicted in the figures. Nevertheless, in each of the methods and systems described herein, appropriate additive flows can modify 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 produce a conditioned feed having an increased ratio of monovalent anions to lithium ions compared to that of the initial feed.

[0039] FIG. 1 illustrates a lithium recovery system 10 suitable for processing an initial feed containing lithium ions by passing it through a membrane unit 20. The membrane unit 20 contains at least one membrane module 22, symbolically represented by a rectangle combined with a diagonal line, which itself represents a membrane 24. The at least one membrane module 22 may be of any size suitable for the desired process parameters. For example, it may be small (e.g., a few cm 2 The total area of ​​the active membrane 24 may be 100 m2 or more smaller test cells, each containing 100 m2 of active membrane 24. 2Alternatively, intermediate values ​​for module size and membrane 24 area may be selected.

[0040] System 10 can be operated continuously or in a batch mode in which discrete volumes of initial feed are processed before rebatching. In a batch process, the initial feed can be conditioned (not shown), for example, in feed tank 12, at the beginning of a batch cycle. Alternatively, as illustrated in FIG. 1, at least one additive stream 32 can be continuously added to modify initial feed stream 30 as it flows toward membrane 24, creating conditioned feed stream 34. In this manner, conditioned feed stream 34 has a desired pH and composition as it traverses at least one membrane module 22. Within membrane unit 20, feed pump 26 provides pressure to force a portion of conditioned feed stream 34 through membrane 24. A membrane permeate stream 44 passes through membrane 24, and a membrane reject stream 46 contains the remaining portion of conditioned feed stream 34. In the absence of any permeate recycle or brine recycle loop, membrane permeate stream 44 becomes a first outlet stream 48 of membrane unit 20, and membrane reject stream 46 becomes a second outlet stream 50 of membrane unit 20.

[0041] FIG. 2 illustrates a lithium recovery system 10 suitable for continuous operation, this time including a recycle loop that allows a portion of the membrane permeate stream 44 and / or the membrane reject stream 46 to be reintroduced for subsequent processing by the membrane. Again, the membrane unit 20 contains at least one membrane module 22. In a 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 conditioned feed stream 34 that flows across the filtration membrane 24 includes the initial feed stream 30 and at least one additive stream 32. While shown with two recycle loops, this continuous system may optionally include only a permeate recycle loop 40, only a reject recycle loop 42, neither (as depicted in FIG. 1), or both.

[0042] The order in which these recycled streams are added to the initial feed or combined together (before being added to the initial feed) is not limited. 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 rejects recycle loop 42; the rejects 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 rejects recycle loop 42 may be mixed together, and then this combined stream may be mixed with the stream resulting from combining the initial feed stream 30 and 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 a continuous process, even one with a permeate and / or rejects recycle loop (40, 42), the conditioned feed stream 34 passing through the membrane 24 can maintain a constant composition over time. In the illustrated embodiment, the feed pump 26 pressurizes the combined conditioned feed stream 34. In other cases (not shown), the components that make up the conditioned feed stream 34 may be pressurized separately. For example, the additive stream 32 may be pressurized and injected after the feed pump 26. In another example, the already pressurized rejects recycle loop 42 may be mixed directly with the effluent at pump 26 to create the conditioned feed 34 that enters the membrane module 22. As shown in FIG. 2 , the conditioned feed stream 34 is divided by the membrane 24 into a permeate stream 44 that passes through the filtration membrane 24 and a membrane rejects stream 46 that does not. All of the fluid from the permeate stream 44 that is not diverted to the permeate recycle loop 40 (preferably controlled by optional valve 47″) flows into a first outlet stream 48 of the membrane unit 20. Similarly, all of the fluid from membrane reject stream 46 that is not diverted to reject recycle loop 42 (preferably controlled by optional valve 47 ′) flows into second outlet stream 50 of membrane unit 20 .In a preferred embodiment, membrane system 10 includes a reject recycle loop 42 and does not include a permeate recycle loop 40 because this allows membrane unit 20 to achieve higher recovery rates with a smaller amount of active membrane area.

[0043] FIG. 3 illustrates a configuration suitable for a semi-batch process in which permeate is continuously produced within a batch cycle and the feed tank 12 is periodically discharged containing at least a portion of the membrane reject stream produced during the batch cycle. In such a process, the composition of the conditioned feed 34 changes over time. In the illustrated case, fluid from the reject recycle loop 42 may be continuously mixed with the remainder of the feed volume. During a first portion of the batch cycle, the membrane permeate stream 44 may be continuously removed from the membrane unit 20 as a first outlet stream 48, while the membrane reject stream 46 is mixed back to the feed tank 12 through the reject recycle loop 42. During a subsequent portion of the batch cycle, one or more valves (52′, 52″) are configured to intermittently discharge the more concentrated feed stream as a second outlet stream 50.

[0044] In the closed-circuit reverse osmosis (CCRO) design depicted in FIG. 4 , the recirculation pump 28 is positioned within the rejects recycle loop 42, and valves 52′, 52″ allow for improved energy efficiency because the rejects recycle loop 42 does not lose its existing pressure when it is discharged through an outlet 50 downstream of the high-pressure pump 26. The system of FIG. 4 features periodic dumping of the rejects recycle loop 42 via a second outlet stream 50. Both the arrangements of FIGS. 3 and 4 provide at least one additive stream 32 capable of creating a conditioned feed stream 34 with the appropriate pH and ionic composition as it flows toward the membrane 24. However, the semi-batch process in these embodiments changes the composition of the conditioned feed stream 34 flowing across the membrane 24 over time during the batch cycle (increasing conditioned feed osmolality). Comparable CCRO systems are described for other applications in U.S. Pat. Nos. 7,695,614 and 8,025,804, both issued to Efraty.

[0045] The first and second outlet streams 48, 50 of the membrane unit 20 can change in composition over time. This time-dependent variation is inherent in the semi-batch configurations of Figures 3 and 4. However, even for more stable batch and continuous processes, the composition of the membrane permeate stream (or membrane reject 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 to be equal to the total aggregate output composition of the first outlet stream of the membrane unit.

[0046] The membrane unit 20 is configured and operated to provide a desired recovery rate, and the term "recovery rate" can be used in various ways. As used herein, the term "lithium recovery rate" refers to the mass of lithium contained in the total combined output of the first outlet stream divided by the mass of lithium present in the initial feed sent to the membrane unit over the same time period. (Disregarding 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 for the membrane unit is greater than 50%, more preferably greater than 75%, or even greater than 90%. Furthermore, the volumetric recovery rate for the membrane unit is defined as the volume of the first outlet stream divided by the total volume of the initial feed stream and the additive stream over the same time period. Equivalently, this volumetric recovery rate for the membrane unit can be calculated from the volumes of the first and second outlet streams and is equal to the volume of the first outlet stream divided by the total volume of the first and second outlet streams. Preferably, the volumetric recovery is greater than 70% or even 90%. In a preferred process, the lithium recovery for the membrane unit exceeds the volumetric recovery for the membrane unit.

[0047] The configuration of the membrane units will affect lithium and volumetric recovery. For example, if the same volume of conditioned feed stream flows across successively more membrane areas, an increased volume of permeate stream is produced, and the recovery rate of the membrane unit increases. The membrane units may also include various internal loops for recycling portions of the permeate stream and / or membrane reject stream, as well as for recovering these effects. Although the presence of these internal loops is not considered in the recovery calculations above, their presence will affect both lithium recovery and volumetric recovery. For example, substantially higher volumetric recovery rates for a membrane unit may be achieved if a portion of the membrane reject stream is recycled.

[0048] When the volumetric recovery rate of the membrane unit increases, the volume of the second outlet stream decreases. As a result, the concentration of some sufficiently rejected ions (e.g., polyvalent anions) in the second outlet stream preferably becomes higher, and the mass of lithium in the second outlet stream preferably decreases. Because the components in the conditioned feed passing through the membrane unit are distributed between the first and second outlet streams, a greater volumetric recovery rate affects the composition of the first and second outlet streams. In a preferred embodiment, a portion of the conditioned feed passes through the membrane unit to produce first and second outlet streams, and at least half of the mass of lithium present in the initial feed is distributed to the first outlet stream, with the first outlet stream having a ratio of polyvalent cations to lithium ions that is less than half the initial ratio of polyvalent cations to lithium ions. In a more preferred embodiment, the first outlet stream has a ratio of polyvalent cations to lithium ions that is less than 0.25, or even less than 0.1, of the ratio of polyvalent cations to lithium ions in the initial feed.

[0049] In some preferred embodiments, additional water can be combined with the initial feed stream and other salts to create a conditioned feed stream having a reduced concentration of polyvalent anions compared to the concentration of polyvalent anions in the initial feed. Preferably, the molar concentration of polyvalent anions (mol / L) in the conditioned feed is less than 90% of the molar concentration of polyvalent anions (mol / L) 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 can be advantageous, for example, when the osmotic pressure of the membrane reject stream is above or near the maximum pressure limit of an otherwise 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 so that the molar concentration of polyvalent anions (mol / L) in the conditioned feed is preferably less than 90%, more preferably less than 75%, of the molar concentration of polyvalent anions (mol / L) in the initial feed. The additional water can be obtained from a portion of the solution that permeates the membrane. In some cases, the conditioned feed comprises the initial feed, the added salt, and at least a portion of the liquid that permeated the membrane. Most preferably, the additional water is obtained by separating the first outlet stream into a dilute and a concentrated fraction, such as by reverse osmosis, with at least a portion of the dilute fraction being recycled. Preferably, the flow rate of the membrane permeate stream exceeds the flow rate of the initial feed flow, while the concentration of polyvalent anions is reduced in the conditioned feed compared to the initial feed.

[0050] Various ultrafiltration membranes can be used to process the conditioned feed. The membranes preferably comprise 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 the present invention are most preferably those produced by interfacial polymerization. Although variations exist, a general approach involves forming a thin interfacially polymerized layer on a porous support, typically polysulfone or polyethersulfone with pore sizes between 0.001 and 0.5 μm. An aqueous polyfunctional amine is applied to the support surface, and a nonpolar solution (e.g., hexane, Isopar™, Freon™) containing a polyfunctional amine-reactive monomer is applied thereon. When contacted with each other, 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 "discriminating layer" or "thin film layer," provides the composite membrane with its primary means for separating solutes (e.g., salts) from solvents (e.g., aqueous feeds). Polyamide membranes produced by this approach have been found to exhibit pH-dependent and mixed-ion rejection that is favorable for improved lithium recovery under certain conditions.

[0051] A wide variety of monomers can be used at different concentrations and polymerization conditions. The polyfunctional amine monomer has 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). The polyfunctional amine-reactive monomer contains 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 species can be used alone or in combination. Non-limiting examples of aromatic polyfunctional acyl halides include trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, biphenyldicarboxylic acid chloride, naphthalene trisulfonyl chloride, and naphthalenedicarboxylic acid dichloride. 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 adipoyl chloride, malonyl chloride, glutaryl chloride, and sebacoyl chloride. Wholly aromatic polyamides can be produced by reacting aromatic polyfunctional amines (e.g., m-phenylenediamine, p-phenylenediamine) with aromatic polyfunctional amine-reactive monomers (e.g., trimesic acid chloride, terephthalic acid chloride). Semi-aromatic polyamides can be produced by selecting aliphatic polyfunctional amines (e.g., piperazine, ethylenediamine) or aliphatic polyfunctional amine-reactive monomers (e.g., cyclopropanetricarboxylic acid chloride, cyclopentanetricarboxylic acid chloride) to form a membrane (while other monomers contain aromatic rings).Polysulfonamide membranes can be created by forming the membrane using aromatic or aliphatic polyfunctional amine monomers and polyfunctional sulfonyl chloride-containing monomers (non-limiting examples are 1,3,5-benzenetrisulfonyl trichloride, 1,3,5-naphthalene tris(sulfonyl chloride)).

[0052] Various reactive and non-reactive additives can be present during the reaction that can affect the membrane's performance characteristics: surfactants and phase transfer catalysts, cosolvents / solvents, organic molecules, inorganic salts, and nanoparticles. Similarly, membranes can also be modified by different post-reaction treatments, including reactive and non-reactive polymer coatings, reactions to modify end groups, plasma treatments, swelling agents, surfactants, and exposure to chlorine or inorganic acids (e.g., hot phosphoric acid).

[0053] The second outlet stream, i.e., the reject stream from the membrane unit, is typically enriched in multivalent ions (both cations and anions) compared to the first outlet stream, i.e., the permeate stream. In some embodiments, certain ions in the second outlet stream can be further separated from other ions in the same stream. Preferably, the second outlet stream is further fractionated to form a portion enriched in ions selected from monovalent anions and multivalent cations. Preferably, this enrichment can be achieved by passing at least a portion of the second outlet stream through a distillation column, an ion exchange resin column, or a membrane system. In a more preferred method, the process for fractionating the second outlet 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 to form a permeate portion enriched in monovalent anions. In another example, this multivalent anion-enriched second outlet stream can be fractionated by passing it through a cation exchange resin column, followed by regenerating the column to produce a regenerated portion enriched in divalent cations. In some methods, the ion exchange process involves the addition of monovalent anions (Cl - or NO3 -It is advantageous to use HCl or HNO to regenerate the cation exchange resin, as this will produce a stream enriched in ions selected from cations ...

[0054] Additionally, a portion of the second outlet stream, enriched in ions selected from monovalent anions and polyvalent cations, can be recycled for combination with the initial feed upstream of the membrane. In creating the conditioned feed, this enriched portion can contribute to the salts added to the initial feed to adjust its composition. Recycling this portion of the second outlet stream reduces the amount of new salt that needs to be brought on-site for lithium recovery.

[0055] In some preferred methods, the dissolved lithium in the first outlet stream can be concentrated by dehydration. For purposes of the present invention, "dehydration" means reducing the volume of water per unit mass of dissolved lithium to increase the concentration of dissolved lithium ions. For example, thermal evaporation of water from the first outlet stream can be performed using an evaporator or distillation column. More preferably, the first outlet stream can be passed through a second membrane system (e.g., reverse osmosis) to selectively pass water over ions and complementary create a stream more concentrated in lithium ions. In a less direct process, the first outlet stream can be passed through a cation exchange medium to which cations are preferentially adsorbed. The cation exchange medium is then regenerated, i.e., cations are unloaded or desorbed, for example, by treatment with an acid solution, to produce a more concentrated (dehydrated) "eluate" stream. In some methods, concentrating lithium by dehydrating the first outlet stream is particularly useful in energy and waste management aspects.

[0056] The first outlet or permeate stream may contain monovalent cations other than lithium. Non-limiting examples of other monovalent cations are cations of Na, K, Cs, and Rb. Removal of other monovalent cations (along with polyvalent cations) from the first outlet stream is desirable due to the high purity requirements (99.5% purity) of battery-grade lithium. The purity of battery-grade lithium is defined as the lithium salt (typically lithium carbonate) content, in weight percent, in the final solid product. In the present invention, a preferred method further includes a process of fractionating the first outlet stream into two solutions, one of which contains an increased molar concentration of lithium ions compared to the molar concentration of lithium ions in the first outlet stream and a reduced molar concentration of other (non-lithium) monovalent cations compared to the molar concentrations of the other (non-lithium) monovalent cations in the first outlet stream. Fractionation of the first outlet stream can be performed before, during, or after an optional step to concentrate (by dehydration) the dissolved lithium ions partitioned into the first outlet stream.

[0057] Fractionation of the first outlet stream can be achieved by various processes. In some preferred embodiments, the first outlet stream can be passed through a medium that is selective for lithium. Non-limiting examples of common lithium-selective media are inorganic lithium intercalates, examples of which include, but are not limited to, iron phosphate, lithium aluminum chloride hydroxide, lithium manganese oxide, and lithium titanium oxide. Lithium ions can be adsorbed into these media and then desorbed with a suitable eluent, such as water. Lithium ions in these materials can also be extracted by ion exchange methods, in which an additive is used to replace lithium. A common additive in this embodiment is an acid, such as sulfuric acid or hydrochloric acid. The eluent solution can contain an increased molar concentration of lithium ions compared to the molar concentration of lithium ions in the first outlet stream and a decreased molar concentration of non-lithium monovalent cations compared to the molar concentration of non-lithium monovalent cations in the first outlet stream.

[0058] In some methods, the first outlet stream can be fractionated by passing it through an ion exchange medium. Suitable common media include, but are not limited to, poly(co-styrene-divinylbenzene), poly(co-methyl methacrylate-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, so that 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 the use of an additional eluent solution that aids in the separation of lithium ions from other monovalent cations. Suitable eluent solutions include, but are not limited to, solutions of acids such as sulfuric acid or hydrochloric acid.

[0059] In some other methods, the first outlet stream is fractionated by selective precipitation of one or more monovalent cations, followed by filtration or decantation. In this method, anions are selected so that the resulting lithium anion salt has a lower solubility than the other monovalent cation-anion salts present in the first outlet stream. Suitable anions include, but are not limited to, carbonate and oxalate. Alternatively, this method may involve selective precipitation of salts of non-lithium monovalent cations. In this method, fractionation may be achieved in which the solubility of lithium-anion salts is higher than that of other monovalent cation-anion salts, resulting in their precipitation. Suitable salts with lower solubility include, but are not limited to, sodium chloride and sodium bromide.

[0060] The following examples are provided to further illustrate the present invention. These examples, which set forth specific embodiments and preferred modes presently contemplated for carrying out the invention, are intended to illustrate, but not limit, the present invention. [Example]

[0061] Description of the production of the initial feed water 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 the salts in deionized water (DIW). The initial feed pH was adjusted to a value of 1.4-1.5 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 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 major anion in the initial feed was SO4 with an ion concentration of 0.378 mol / L. 2- It was.

[0062] The initial feed did not contain any monovalent anions other than small amounts of hydroxide 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 5.4. In Examples 1 and 2, the initial feed was used as the feed stream for the filtration tests, i.e., there was no separate conditioned feed.

[0063] Description of the preparation of conditioned feed water In Examples 3-14, conditioned feeds were prepared by adding one or more salt solutions to the initial feed solution. Details of the conditioned feed preparations are provided in the specific examples. Ion concentrations (mol / L) were used to calculate the conditioned ratio of monovalent anions to lithium ions.

[0064] Filtration Test Protocol and Analytical Measurement Description Filtration tests in Examples 1-14 were conducted to measure and compare lithium passage, mass recovery, and ratio of multivalent cations to lithium ions in the permeate stream of specific membranes operated at different feed and operating conditions.

[0065] Testing was performed in a cross-flow configuration by pressurizing the feed using a pump and forcing the feed through membrane coupons housed in standard membrane filtration cells. Each cell contained a 42 cm 2 membrane coupon cut from a flat membrane sheet. 2 The membrane unit contained six membrane filtration cells, and therefore the total active area in contact with the feed was 252 cm. 2 (0.27ft 2 ). In these examples, each membrane filtration cell with a membrane is considered a membrane module, and all six combined cells / modules are considered a membrane unit. These six membrane filtration cells were arranged in two parallel banks of three cells each connected in series. The membrane active side was exposed to the feed solution. A feed volumetric flow rate of 2 L / min per bank was maintained throughout the entire test. The portion of the feed that passed through the membrane, the membrane permeate stream, was collected from the individual membrane filtration cell permeate line. The portion of the feed that did not pass through the membrane, the membrane reject stream, was recycled back to the feed tank upstream of the pump throughout the entire test period. Unless otherwise noted in any example, the membrane permeate stream was also recycled back to the feed tank upstream of the pump except during the permeate stream collection period. All filtration tests were conducted at a feed temperature range of 23-27°C.

[0066] The permeate stream collected from each membrane filtration cell was 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 the permeate collection time and membrane active area. Flux values ​​were averaged over the six permeates collected (one from each membrane filtration cell) and expressed in liters / m 2 The flux is reported in units of 1000 vol / h (LMH). A permeate flow density of 1 g / ml was used for the flux calculations.

[0067] Ion concentrations (mol / L) were analyzed for both the permeate and feed streams. The feed stream was collected from the feed tank at the same time the permeate stream was collected. When both the reject and permeate streams were recycled back to the feed tank, the feed stream ion concentrations did not change significantly over the time of the experiment. In some cases (e.g., Example 14), the feed stream ion concentrations changed over time due to the continuous collection of the permeate stream or the occasional addition of water to the feed tank to reduce osmotic pressure.

[0068] To measure the ion concentrations in the permeate stream, all six membrane permeate streams were mixed to prepare a 'mixed permeate' stream. Cation mass concentrations were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) using an iCap 7600 ICP-OES analyzer available from Thermo Scientific, Waltham, MA. Cation concentrations were calculated by dividing the ICP-OES mass concentration by the corresponding ion molar mass. These ion concentrations were used to calculate the ion ratio of multivalent cations to lithium in the (mixed) permeate stream. The ion transmission (fraction, abbreviated as "fr") was calculated as the ratio of the ion molar concentration in the (mixed) permeate stream to the corresponding feed stream, both measured using ICP-OES.

[0069] Membrane unit volume recovery was calculated as the volume of permeate liquid produced by the membrane unit divided by the volume of liquid provided to the membrane unit over the same period and reported in percentage. In most cases exemplified here, membrane unit recovery was less than 2%, and these tests were specifically for the purpose of demonstrating how the relative permeate concentrations of different ions can be altered by changing the conditioned feed. It can be seen that both the volume recovery and the percentage of lithium ions recovered (into the permeate stream) can be increased by using more membrane area in series, by passing less feed solution through the membrane unit at the same average flux, or by recycling the membrane reject stream while continuing to withdraw permeate.

[0070] In one specific example (Example 14), the membrane reject stream of the membrane unit was recycled, and the system recovery was measured and reported. For this example, the lithium ion mass recovery was also calculated 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, expressed as a percentage. The mass of lithium ions dissolved in the permeate stream was calculated by multiplying the permeate volume (collected volume of the first outlet stream) by the mass concentration of dissolved lithium ions measured by ICP-OES. The mass of lithium ions dissolved in the initial feed was calculated by using the mass of the Li-containing reagent used to prepare the initial feed multiplied by the weight fraction of Li ions in the reagent.

[0071] Examples (1 and 2) illustrate a control case in which the initial feed was fed directly to the membrane without any added salt (ie, without any pH and / or ion ratio adjustment).

[0072] Example 1: The membrane used in this example is a composite membrane with a piperazine-based polyamide barrier layer used in FilmTec's commercially available SR90 element.The initial feed described above was fed to the membrane unit.

[0073] Example 2: In Example 2, membrane coupons were cut from sheets of Duracid polysulfonamide membrane commercially available from Suez. The initial feed was used as the feed to the membrane unit.

[0074] Examples 3-6 illustrate the effect of adding salt to the initial feed to provide a specific adjusted feed pH and / or ion ratio before the membrane unit.

[0075] Example 3: In Example 3, any Fe 2+ , Zn 2+ , or Sr 2+ The initial feed was prepared as described above, except that no cations were added. Therefore, in this example, the initial feed cation concentration in mol / L was 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 pH of the initial feed was adjusted to 1.4-1.5 by adding an appropriate amount of 98% sulfuric acid solution to the salt solution. The major anion in the initial feed was SO4 with an ion concentration of 0.368 mol / L. 2- The initial feed did not contain any monovalent anions other than small amounts of hydroxide 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.

[0076] Lithium hydroxide powder (Li(OH)·HO, 41.95 g) was dissolved in deionized water to produce a solution of Li(OH) (1 liter, 1 mole / liter). An appropriate amount of this salt solution was added to the initial feed, as described above, to raise the pH. Any precipitate formed during pH adjustment was removed using a Fisherbrand 0.2μ aPES membrane filter, and the filtrate pH was measured to be 4.2. The filtrate collected after removal of the precipitated solids was the conditioned feed, which was passed through the membrane.

[0077] This conditioned feed was tested using the same membrane and test procedure as described in Example 1. Because no other monovalent anions were present other than small amounts of hydroxide from water dissociation, the conditioned ratio of monovalent anions to lithium ions was zero. The lithium ion concentration in the conditioned feed was 0.15 mol / L.

[0078] Example 4: This is similar to Example 3. However, after removal of the precipitated solids, a conditioned feed was formed by adding 0.03 mol / L of MgCl 6H O salt in solid form to the filtrate. - This filtrate with ions (solution pH 4.4) was sent to the membrane unit. - The ion concentration was 0.06 mol / L. The adjusted ratio of monovalent anions to lithium ions was 0.4. The adjusted feed lithium concentration was 0.14 mol / L.

[0079] Example 5: This is the Cl in the adjusted feed (solution pH 4.2) - Similar to Example 4, except that the ion concentration was 0.3 mol / L. The adjusted ratio of monovalent anions to lithium ions was 2.1. The adjusted feed lithium concentration was 0.14 mol / L.

[0080] Example 6: This is the Cl in the adjusted feed (solution pH 4.2) -Similar to Example 4, except that the ion concentration was 0.6 mol / L. The adjusted ratio of monovalent anions to lithium ions was 4.3. The adjusted feed lithium concentration was 0.14 mol / L.

[0081] The feed compositions and filtration test performance for Examples 1-6 are reported in Table 1. As is evident from the data in Table 1, when both the pH and the monovalent anion to lithium ion ratio were adjusted by adding certain salts, the amount of Li in the permeate stream was significantly reduced. + Both the passage increased and the ratio of multivalent cations to lithium ions in the permeate decreased.

[0082] [Table 1]

[0083] Examples (7-8) illustrate the applicability of the present invention at different feed pH values.

[0084] Example 7: Example 7 is a case where the adjusted feed pH is pH 6.6 and the Cl content in the adjusted feed is - The same conditions (membrane, initial feed preparation, conditioned feed preparation, and testing) as in Example 5 are used, except that the ion concentration was 0.3 mol / L, the conditioned ratio of monovalent anions to lithium ions was 2.0, and the lithium concentration in the conditioned feed was 0.15 mol / L.

[0085] Example 8: Example 8 is a comparative example where the adjusted feed pH is pH 3.5 and the Cl content in the adjusted feed is - The same conditions (membrane, initial feed preparation, conditioned feed preparation, and testing) as in Example 5 are used, except that the ion concentration was 0.3 mol / L, the conditioned ratio of monovalent anions to lithium ions was 3.0, and the lithium concentration in the conditioned feed was 0.10 mol / L.

[0086] The feed compositions and filtration test performance for Examples 7-8 are reported in Table 2.

[0087] [Table 2]

[0088] Examples (9-13) illustrate the use of different types and amounts of salts to form conditioned feeds with different pH and / or ionic ratios.

[0089] Example 9: Example 9 uses the same conditions (membrane, initial feed preparation, adjusted feed preparation, and test procedure) as Example 3, except that solid form of Mg(OH) salt was added to the initial feed for pH adjustment. After removal of the precipitate formed during pH adjustment, the adjusted feed solution pH was measured to be 4.2. Because no other monovalent anions were present other than a small amount of hydroxide from water dissociation, the adjusted ratio of monovalent anions to lithium ions was zero. The adjusted feed lithium concentration was 0.044 mol / L.

[0090] Example 10: Example 10 is similar to Example 9, except that 0.015 mol of MgCl 6H O salt was added per L of filtrate after removal of the precipitated solids. - The filtrate with ions formed the conditioned feed (solution pH 4.3) which passed through the membrane surface. - The ion concentration was 0.03 mol / L. The adjusted ratio of monovalent anions to lithium ions was 0.7. The adjusted feed lithium concentration was 0.044 mol / L.

[0091] Example 11: In this example, the conditions were Cl in the conditioned feed (solution pH 4.2). - Similar to Example 10, except that the ion concentration was 0.16 mol / L and the adjusted ratio of monovalent anions to lithium ions was 3.6. The adjusted feed lithium concentration was 0.044 mol / L.

[0092] Example 12: In this example, the conditions were Cl in the conditioned feed (solution pH 4.2). - Similar to Example 10 except that the ion concentration was 0.32 mol / L, the adjusted ratio of monovalent anions to lithium ions was 7.0, and the adjusted feed lithium concentration was 0.043 mol / L.

[0093] Example 13: In this example, the conditions were: 0.30 mol / L NO3 in the form of Mg(NO3)2·6H2O salt after removal of precipitated solids; - Same as Example 9 except that NO3 was added to the filtrate. - The filtrate with ions was passed over the membrane surface as the conditioned feed (solution pH 4.2). The conditioned ratio of monovalent anions to lithium ions was 6.8. The conditioned feed lithium concentration was 0.044 mol / L.

[0094] The feed compositions and filtration test performance for Examples 9-13 are reported in Table 3.

[0095] [Table 3]

[0096] Example 14 illustrates Li mass recovery in a system with higher volumetric recovery.

[0097] Example 14: Li + =0.043 and Mg 2+ A sulfate-based initial feed was prepared with a cation concentration (mol / L) of 0.173. The initial feed also contained sulfuric acid, and the initial feed pH was 1.55. The initial feed did not contain any monovalent anions other than small amounts of hydroxide 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 4.0.

[0098] Here, a recirculation system was configured to reasonably simulate the performance of a continuous filtration system with a larger membrane area. In this example, ion ratio adjustment was performed by adding powdered MgCl 6H O salt to the initial feed. The Cl content in the adjusted feed was - The concentration of ions was 0.4 mol / L. An appropriate amount of Mg(OH)2 powder was then added to increase the solution pH. The precipitated solids formed during the pH adjustment were removed using a Fisherbrand 0.2μ aPES membrane filter, and the filtrate pH was measured to be 4.3. This filtrate was the 'conditioned feed' fed to the membrane unit. The monovalent anions (Cl) - The adjusted ratio of HCl to lithium ions was 9.3. The adjusted feed lithium concentration was 0.043 mol / L. This adjusted feed was tested using a membrane similar to that described in Example 1.

[0099] The adjusted feed (10.1 L, weighing 10378 g) was added to 252 cm 2 The solution was pumped through a membrane unit containing six flat-sheet coupons with a combined active area of ​​1000 sq. m. The first outlet stream, i.e., the permeate stream exiting the membrane unit, was collected in a bucket throughout the entire test, while the membrane reject stream was recycled to the feed tank (upstream of the feed pump, as shown in Figure 3). As the osmotic pressure in the feed tank increased, the feed-side pressure was adjusted to increase the permeate stream rate. After 9 hours of operation, 5.45 L of permeate (weighing 5401 g) was collected. This collected solution is referred to as Permeate A.

[0100] After collecting Permeate A, 0.5 L of deionized water (DIW) was added to the feed tank and the permeate stream was collected for another 1.5 hours. The collected solution volume was 0.71 L (weight 705.4 g) and is designated Permeate B. Another 0.5 L of DIW was added to the feed tank and the permeate stream was collected for another 3 hours. The collected solution volume was 1.0 L (weight 1003.7 g) and is designated Permeate C.

[0101] The membrane unit volume recovery and Li mass recovery data are shown in Table 4.

[0102] [Table 4]

[0103] When permeates A, B, and C were combined, the membrane unit volume recovery was 70.9% of the conditioned feed volume, or 64.5% of the combined conditioned feed and additional DIW volume. The Li mass recovery was 0.82, and the multivalent cations (Mg 2+ The ratio of Zn to lithium ions was 0.2 (i.e., 0.05 times the same ratio of 4.0 in the initial feed).

[0104] The methods described herein find particular utility in the selective recovery of lithium from brine feeds at high mass recovery and purity. Another advantage of the method is that it allows for the selective recovery of multivalent anions (e.g., SO4) in the initial feed containing lithium ions. 2- , CO3 2- ) in the permeate of the membrane system, - , NO3 - ) to form compositions that may be more beneficial for downstream lithium recovery operations.

[0105] Although some preferred embodiments of the present invention have been described and specifically exemplified above, it is not intended that the present invention be limited to such embodiments. Rather, while many of the features and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, it should be understood that the present disclosure is merely illustrative, and that changes may be made in details, particularly in the shape, size, and arrangement of parts, within the principles of the invention to the fullest extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. Dissolved mass of lithium, and a) an initial ratio of monovalent anions to lithium ions; b) an initial ratio of multivalent cations to lithium ions, and c) an initial ratio of monovalent anions to polyvalent anions that is less than 1; providing an initial supply having: One or more salts are added to the initial feed to achieve a pH of 1 to 7, and d) an adjusted ratio of monovalent anions to lithium ions that is greater than said initial ratio of monovalent anions to lithium ions. creating a conditioned supply having: passing a portion of the conditioned feed through a membrane unit to produce a first outlet stream and a second outlet stream, wherein at least half of the mass of lithium present in the initial feed is partitioned to the first outlet stream, the first outlet stream having a ratio of multivalent cations to lithium ions that is less than half of the initial ratio of multivalent cations to lithium ions; A method for recovering lithium, comprising:

2. 10. The method of claim 1, wherein the addition of one or more salts to the initial feed creates an adjusted ratio of multivalent cations to lithium ions that is greater than the initial ratio of multivalent cations to lithium ions.

3. 3. The method of claim 1 or claim 2, wherein a majority of the polyvalent anions in the initial feed are sulfate ions, and the ratio of monovalent anions to polyvalent anions in the initial feed is less than 0.

5.

4. 4. The method of any one of claims 1, 2, or 3, further comprising combining the initial feed with additional water such that the molar concentration of multivalent anions in the adjusted feed is less than 90% of the molar concentration of multivalent anions in the initial feed.

5. 5. The method of claim 1, wherein the conditioned feed comprises the initial feed, added salt, and at least a portion of the liquid that has permeated the membrane of the membrane unit.

6. 6. The method of any one of claims 1 to 5, wherein the membrane comprises a polymer layer selected from the group consisting of wholly aromatic polyamides, semi-aromatic polyamides, sulfonated polysulfones, sulfonated polyethersulfones, and polysulfonamides.

7. 7. The method of claim 1, further comprising fractionating the second outlet stream to form a portion enriched in ions selected from monovalent anions and multivalent cations, wherein the fractionating step uses a component selected from an ultrafiltration membrane and an ion exchange resin.

8. 8. The method of claim 7, wherein at least a portion of said enriched fraction is recycled and said conditioned feed comprises said initial feed and at least a portion of said enriched fraction.

9. 9. The method of any one of claims 1 to 8, further comprising concentrating the first outlet stream by dehydration to provide an increased concentration of dissolved lithium.

10. 10. The method of claim 1, wherein the first outlet stream comprises at least one monovalent cation other than lithium, further comprising the step of fractionating the first outlet stream into two solutions, one of the two solutions comprising an increased molar concentration of lithium ions relative to the molar concentration of lithium ions in the first outlet stream and a decreased molar concentration of the monovalent cations relative to the molar concentration of the monovalent cations in the first outlet stream.

11. 11. The method of any one of claims 1 to 10, further comprising extracting lithium from the first outlet stream.

12. 1. A system for recovering lithium, comprising: means for providing an initial feed having a dissolved mass of lithium, said initial feed containing (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 that is less than 1; means for adding one or more salts to said initial feed to produce a conditioned feed having a pH of 1 to 7 and an conditioned ratio of monovalent anions to lithium ions greater than said initial ratio of monovalent anions to lithium ions; a membrane filter unit; 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 of the mass of lithium present in the initial feed is distributed to a first outlet stream, the first outlet stream having a ratio of multivalent cations to lithium ions that is less than half of the initial ratio of multivalent cations to lithium ions; 1. A system for recovering lithium, comprising:

13. means for fractionating the second outlet stream to form a fraction enriched in ions selected from monovalent anions and multivalent cations; and means for recycling at least a portion of the enriched fraction to form the conditioned feed. The system of claim 12 further comprising:

14. means for extracting lithium from said first outlet stream. The system of claim 12 further comprising:

15. 1. A system for recovering lithium, comprising: an initial feed having a dissolved mass of lithium, said initial feed containing (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 that is less than 1; one or more salts added to the initial feed to produce a conditioned feed having a pH of 1 to 7 and an conditioned ratio of monovalent anions to lithium ions that is greater than the initial ratio of monovalent anions to lithium ions; a membrane filter unit; a pipeline, pump, and optionally a valve set for passing a portion of the conditioned feed through a membrane filter unit to produce a first outlet stream and a second outlet stream; 1. A system for recovering lithium, comprising: wherein at least half of the mass of lithium present in the initial feed is distributed to the first outlet stream, the first outlet stream having a ratio of multivalent cations to lithium ions that is less than half of the initial ratio of multivalent cations to lithium ions.

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