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] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under 35 U.S.C. §365(c) to U.S. Provisional Application No. 63 / 409,404, filed on September 23, 2022, the entire contents of which are incorporated herein by reference.

[0003] Statement Regarding Federally Funded Research

[0004] 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. Technical Field

[0005] The present invention relates to a method and system for recovering lithium from natural or synthetically generated brines. In particular, the method comprises adjusting the ion concentration of the feed prior to the ultrafiltration step. Background Art

[0006] Several patents, patent applications and publications are cited in this specification to more fully describe the state of the art to which the present invention relates. The entire disclosure of each of these patents, patent applications and publications is incorporated herein by reference.

[0007] 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. It is expected that the global demand for lithium will increase in the foreseeable future. Currently, industrial-scale Li extraction technology uses chemical treatment, followed by evaporation-based processes to recover lithium from different natural sources and recycled sources, which is time-consuming and requires large footprint operations. In addition, a large amount of water evaporation is required to recover Li, and most natural Li sources are in arid areas with limited clean water supplies. In order to accelerate the evaporation process and recover water, engineered processes such as thermal evaporation followed by condensation have been applied, but these are still energy inefficient.

[0008] Various membrane-based processes for recovering lithium from natural and recycled sources have been described. U.S. Pat. No. 10,450,633 ('633) describes a membrane-based process for recovering Li from an acid solution. The process steps described in '633 are passing the acidic lithium solution through a nanofiltration (NF) membrane unit, wherein the acid and a portion of the lithium solution permeate through the NF membrane. U.S. Pat. No. 6,004,464 describes a process for brine recovery from a water softening resin unit, the process comprising acidifying a chloride-containing brine to a pH range of 0.5-6 and then adding a salt having monovalent cations and multivalent anions (such as Na2SO4) to the pH adjusted brine. CN 112,850,851 describes a process for Li separation from a Na2SO4-type salt lake brine, the process involving the addition of chloride ions (Cl - ) salt is added to the brine and pumped through the NF system in the pH range of 7.5-11.0 to obtain excellent Li + / Mg 2+ 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 produce LiCl and CaSO4, which are further separated using a NF membrane.

[0009] However, for certain feeds, especially those containing polyvalent anions (e.g. SO 2- 、CO3 2- ) feeds and feeds located in water-scarce areas, there is still a need for better water management methods with high lithium recovery rates. Summary of the invention

[0010] Thus, a method for recovering lithium ions is provided herein, 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 multivalent cations to lithium ions, and (c) an initial ratio of monovalent anions to multivalent anions less than 1. The method comprises 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. The method further comprises passing a portion of the adjusted 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 the first outlet stream has a ratio of multivalent cations to lithium ions less than half of the initial ratio of multivalent cations to lithium ions.

[0011] Further provided herein is 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 an adjusted feed, the 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; a membrane filter unit; and means for passing a portion of the adjusted 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 less than half of the initial ratio of polyvalent cations to lithium ions. The system may optionally further comprise 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.

[0012] The advantages and features of novelty which characterize the invention are particularly pointed out in the appended claims and form a part thereof. However, for a better understanding of the invention, its advantages and objects attained by its use, reference should be made to the accompanying drawings which form another part hereof and to the accompanying descriptive matter, in which one or more preferred embodiments of the invention are shown and described. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of a system suitable for use in the process described herein for recovering lithium from an initial feed of a brine solution containing dissolved lithium;

[0014] Figure 2 is a schematic diagram of another system suitable for use in the lithium recovery method described herein;

[0015] Figure 3 is a schematic diagram of yet another system suitable for use in the lithium recovery methods described herein; and,

[0016] Figure 4 is a schematic diagram of yet another system suitable for use in the lithium recovery methods described herein. DETAILED DESCRIPTION

[0017] 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 the invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the embodiments described herein, suitable methods and materials are described below.

[0018] As used herein, the terms "includes," "including," "has," "having," "contain," "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 but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0019] The transitional phrase "consisting essentially of limits the scope of a claim to the specified materials or steps and those that do not materially affect one or more basic and novel features of the claimed invention. "A 'consisting essentially of' claim is intermediate between closed claims written in 'consisting of' format and fully open claims written in 'comprising' format." Where an invention or a portion of an invention is described using an open-ended term such as "comprising," it should be understood that the description also includes descriptions of inventions using the terms "consisting of" and "consisting essentially of," unless otherwise indicated in specific instances.

[0020] In addition, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, condition A or B is 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).

[0021] In addition, "a / an" is used to describe the elements and components of the present invention. This is done only for convenience and to give a general sense of the present invention. This description should be interpreted as including one / a kind or at least one / a kind, and the singular also includes the plural, unless it is obvious that it is otherwise intended.

[0022] As used herein, the term "about" means that amounts, dimensions, formulations, parameters, and other quantities and features are not and need not be exact, but may be approximate and / or larger or smaller (as desired), reflecting tolerances, conversion factors, rounding, measurement errors, etc., and other factors known to those skilled in the art. In general, an amount, dimension, formulation, parameter, or other quantity or feature is "about" or "approximate" whether or not expressly stated to be so.

[0023] In addition, unless otherwise expressly stated in the case of limitation, the ranges listed herein include their endpoints. In addition, when an amount, concentration, or other value or parameter is given as a range, one or more preferred ranges, or a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range or preferred value with any lower range or preferred value, regardless of whether such pairing is disclosed separately.

[0024] However, when numerical ranges are listed herein, unless otherwise indicated in specific cases, the ranges are intended to include their endpoints, as well as all real numbers within the range. It is not intended that the scope of the present invention be limited to the specific values ​​listed when defining the range. Finally, when the term "about" is used to describe a value or an endpoint of a range, the disclosure should be understood to include the specific value or endpoint mentioned.

[0025] Finally, as used herein, the term "lithium", alone or in combination, refers to lithium ions, unless the context clearly indicates that lithium metal (Li 0 ).

[0026] A method and system for selectively recovering lithium with good mass recovery and high purity is provided herein. 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.

[0027] The initial feed can include monovalent and multivalent cations, monovalent and multivalent 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 multivalent 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 can come 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 can be synthesized by acid digestion of lithium-containing materials (such as but not limited to lithium ion batteries, solar panels, solar energy storage devices, computers, laptop computers and similar devices). Alternatively, the initial feed can be a treated feed generated by treating natural resource brine or synthetically generated brine.

[0028] The initial charge 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, the extraction process, and the previous unit operations. Preferably, the monovalent anions in the initial feed are depleted, wherein the initial ratio of monovalent anions to lithium ions is less than 1, and 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, except for a small amount 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 ions per unit volume and dividing it by the corresponding molar mass. For example, lithium ions (Li + ) can be calculated as the measured mass of dissolved lithium ions per L of solution divided by the molar mass of lithium ions (6.941 amu).

[0029] The initial feed has an initial ratio of multivalent cations to lithium ions. The multivalent cations in the initial feed typically include magnesium (Mg 2+ ) and calcium (Ca 2+ ), but the initial mixture and ratio of polyvalent cations to lithium ions depends on the source, extraction process, and previous 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.

[0030] The initial feed has an initial ratio of monovalent anions to multivalent anions of 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 mass of anions. Common multivalent anions include SO4 2- 、HPO4 2- PO4 3- and CO3 2- Advantageously, the anions in the initial feed may be in the form of SO4 2- With CO3 2- (more than 50% of the total molar concentration of anions), and more preferably, the anions are exclusively SO4 2- For the main.

[0031] Advantageously, several lithium-containing solutions can be treated by the methods and systems described herein. For example, many natural brine sources contain SO4 2- As one of the key anions (e.g., sodium sulfate subtype or magnesium sulfate subtype brines), and sulfate subtype brines are generally characterized by a high Mg / Li ion ratio (e.g., >5). Brines extracted from hard rock, clay mining, or lithium-containing materials (such as, for example, lithium-ion batteries, solar panels, solar energy 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.

[0032] The pH range of the initial feed can be wide, for example, between pH 0 and pH 10 (including pH 0 and pH 10). Examples of particularly relevant lower pH brines (pH range of 0 to 3) include brines produced from hard rock extraction, clay mining, and brines obtained from digesting lithium-containing materials using an acid or an aqueous solution of the acid. Examples of higher pH (pH range of 4 to 10) brines include brines obtained from salt lakes or 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 before its generation. The method described herein includes the step of adding one or more salts to the initial feed to produce a regulated feed. As used herein, the term 'salt' refers to 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 in the regulated 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 salt to any composition can be performed in one or more steps via the addition of one or more salts in solid, suspended, dispersed, or dissolved form. When a salt is described herein as "dissolved," the solution may also include dispersed or suspended particles of the salt.

[0033] In the methods described herein, the adjusted feed has a pH between 1 and 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 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 (that is, the ratio in the adjusted feed) is greater than 1, more preferably greater than 2, and still more preferably greater than 4.

[0034] In some preferred methods, the pH of the adjusted 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, 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 adjusted feed. These acids can be added in their pure form or as a diluted aqueous solution.

[0035] 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 alkaline oxides such as quicklime (CaO). Among these, materials containing polyvalent cations can be used to increase both the pH and the adjusted ratio of polyvalent cations to lithium ions. These salts can be added in their pure form or as a diluted aqueous solution.

[0036] In some methods, precipitation and / or suspension can be caused by initial feed pH adjustment. Precipitation and / or suspension solids can be removed subsequently by sedimentation operation, by centrifugation or by using a filter device (e.g., media filter, sand filter, ultrafiltration membrane or microfiltration membrane). In particular, an advantageous method for removing solids from regulated feed is ultrafiltration. The regulated feed is then defined as a solution of ions having dissolved through the ultrafiltration membrane surface.

[0037] In some preferred methods, an adjusted ratio of monovalent anions to lithium ions greater than the initial ratio of monovalent anions to lithium ions can be achieved by adding common salts containing monovalent anions. For this purpose, the salt can be selected from the group 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.

[0038] In order to maximize the passage of lithium ions 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.

[0039] In some preferred methods, the adjustment of the initial feed pH and the adjustment of the ratio of ions can be performed in a single step. This can be done by adding a mixture of salts to the initial feed. For this purpose, salts containing monovalent anions (such as chloride salts or nitrates) are preferred. The salt can be dissolved in an acidic solution (to reduce the initial feed pH to the preferred range of the adjusted feed) or dissolved in an alkaline solution (to increase the initial feed pH to the preferred range of the adjusted feed). More preferably, the monovalent anion salt also contains polyvalent cations to increase the adjusted ratio of polyvalent cations to lithium ions. In other methods in which 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 in their solid form or dissolved in water.

[0040] In some preferred methods, the initial feed pH and ion ratio adjustments can be performed in multiple steps. Ion adjustments can be made by adding solid or dissolved mass salts containing monovalent anions (such as Cl - or NO3 - In some embodiments, the pH of the present invention may be adjusted by adding a salt (e.g., a salt) to the initial feed, and the pH adjustment may be performed by adding an acid or a base to the initial feed in any order. In some methods, the pH change may cause precipitation. In a preferred method of this type, a filtering step (e.g., ultrafiltration) may be performed to remove solid precipitates or suspensions before, during, or after the addition of the salt. For example, several examples of the present invention set forth below illustrate the addition of salt to the initial feed, which changes the pH and causes precipitation.

[0041] The method described herein includes passing the regulated feed (as described above) through a membrane unit to distribute it between a first outlet flow and a second outlet flow. The first outlet flow includes a liquid that has permeated the membrane. In a preferred method, the first outlet flow contains most of the monovalent cations from the regulated feed, and the second outlet flow contains most of the divalent anions from the regulated feed. The membrane unit includes an ultrafiltration membrane, and the regulated feed passes through at least one ultrafiltration membrane under pressure, wherein a portion of the regulated feed permeates through the ultrafiltration membrane. As used herein, the term "membrane permeate" refers to the portion of the regulated feed that passes through the membrane, and the term "membrane retentate" refers to the remaining portion of the regulated feed that does not pass through the membrane. Therefore, in the absence of a permeate recirculation loop or a brine recirculation loop, the first outlet flow is a membrane permeate liquid, and the second outlet flow is a membrane retentate. The term "ultrafiltration" as used herein refers to reverse osmosis and nanofiltration. Most preferably, the membrane unit includes a nanofiltration membrane.

[0042] The membrane unit may include a membrane in a flat sheet, hollow fiber or tubular configuration. Preferably, the flat sheet membrane is disposed in a spiral wound module. A plurality of such spiral wound membrane modules may be axially aligned in a series arrangement within a chamber of a cylindrical pressure vessel to increase the available active membrane area. The membrane unit may further include a plurality of pressure vessels arranged in parallel or in 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 Reverse osmosis membranes are commercially available. Suitable methods for synthesizing membranes are described in US Pat. No. 4,277,344 to Cadotte.

[0043] Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the several views, and in particular to Figures 1 to 4 The systems described herein, and in particular the membrane units in these systems, may have more than one operating configuration or operating procedure. Not all operating configurations or operating procedures are depicted in the accompanying drawings. However, in each of the methods and systems described herein, appropriate additive flows enable 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 changed to produce a regulated feed in which the ratio of monovalent anions to lithium ions is increased relative to the ratio of the initial feed.

[0044] Figure 1 A lithium recovery system 10 is shown that is suitable for processing an initial feed containing lithium ions by passing the initial feed through a membrane unit 20. The membrane unit 20 contains at least one membrane module 22, which is symbolically represented by a combination of a rectangle and a diagonal line 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, which contain a total area of ​​several cm 2 active membrane 24), or it may include a plurality of containers connected in series or in parallel, each container containing an area greater than 100m 2 Alternatively, intermediate values ​​may be selected for the size of the module and the area of ​​the membrane or membranes 24.

[0045] The system 10 can be operated continuously or in a batch mode in which discrete volumes of initial feed are processed before re-batching. In a batch process (not shown), the initial feed can be adjusted at the beginning of the batch cycle, for example, in the feed tank 12. Alternatively, as Figure 1, at least one additive stream 32 may be continuously added to modify the initial feed stream 30 as it flows toward the membrane 24, thereby forming an adjusted feed stream 34. In this manner, the adjusted 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 cause a portion of the adjusted feed stream 34 to permeate the membrane 24. A membrane permeate stream 44 passes through the membrane 24, and a membrane retentate stream 46 contains the remainder of the adjusted feed stream 34. In the absence of any permeate recirculation or brine recirculation loop, the membrane permeate stream 44 becomes a first outlet stream 48 of the membrane unit 20 and the membrane retentate stream 46 becomes a second outlet stream 50 of the membrane unit 20.

[0046] Figure 2 A lithium recovery system 10 suitable for continuous operation is shown, this time including a recirculation loop that enables a portion of a membrane permeate stream 44 and / or a membrane retentate 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, an initial feed stream 30 is combined with at least one additive stream 32 to enable the addition of salt and adjustment of pH. The conditioned feed stream 34 flowing through the filter membrane 24 includes the initial feed stream 30 and the at least one additive stream 32. Although two recirculation loops are shown, the continuous system may alternatively include only the permeate recirculation loop 40, only the retentate recirculation loop 42, and neither (e.g., Figure 1 ), or both.

[0047] The order in which these recycle streams are added to the initial feed or merged together (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 can be added to the combined streams 30 and 32 first, and then added to the retentate recycle loop 42; the retentate recycle loop 42 can be mixed with the combined streams 30 and 32 first, and then mixed with the permeate recycle loop 40; or the permeate recycle loop 40 and the retentate recycle loop 42 can be mixed together, and the combined stream can then be mixed with the stream generated by merging 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 a continuous process (even a process with a permeate and / or retentate 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 depicted), 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 retentate recycle loop 42 may be directly mixed with the pump 26 outlet to produce the conditioned feed 34 that enters the membrane module 22. Figure 2 As shown in FIG. 1 , the conditioned feed stream 34 is divided by the membrane 24 into a membrane permeate stream 44 that has passed through the filter membrane 24 and a membrane retentate stream 46 that has not passed through the filter membrane. All of the fluid in the membrane permeate stream 44 that is not diverted (preferably controlled by an optional valve 47″) to the permeate recirculation loop 40 flows into a first outlet stream 48 of the membrane unit 20. Similarly, all of the fluid in the membrane retentate stream 46 that is not diverted (preferably controlled by an optional valve 47′) to the retentate recirculation loop 42 flows into a second outlet stream 50 of the membrane unit 20. In a preferred embodiment, the membrane system 10 includes a retentate recirculation loop 42 but does not include a permeate recirculation loop 40 because this enables the membrane unit 20 to achieve a higher recovery rate with a smaller amount of active membrane area.

[0048] Figure 3A configuration suitable for a semi-batch process is shown in which permeate is continuously produced within a batch cycle and the feed tank 12 (including at least a portion of the membrane retentate stream produced during the batch cycle) is periodically discharged. In such a process, the composition of the conditioned feed 34 varies over time. In the case shown, 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 outlet stream 48, while the membrane retentate stream 46 is mixed back into the feed tank 12 through the retentate recirculation loop 42. In a subsequent portion of the batch cycle, one or more valves (52', 52") are arranged to intermittently discharge a more concentrated feed stream as a second outlet stream 50.

[0049] exist Figure 4 In the closed circuit reverse osmosis (CCRO) design depicted in FIG, the recirculation pump 28 is located within the retentate recirculation loop 42, wherein valves 52', 52" enable improved energy efficiency because the existing pressure of the retentate recirculation loop 42 is not lost when it is discharged through the outlet 50 downstream of the high pressure pump 26. Figure 4 The system is characterized by periodic dumping of the retentate recirculation loop 42 via the second outlet stream 50. Figure 3 and Figure 4 In both arrangements, at least one additive stream 32 is provided, which can form a regulated feed stream 34 having an 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 vary over time during the batch cycle (the regulated feed osmotic pressure increases). Comparable CCRO systems for other uses have been described in U.S. Pat. Nos. 7,695,614 and 8,025,804, both to Efraty.

[0050] The composition of the first outlet stream 48 and the second outlet stream 50 of the membrane unit 20 may vary with time. This time-dependent variation is important for Figure 3 and Figure 4 The semi-batch configuration in the process is inherent. However, even for more stable batch and continuous processes, the composition of the membrane permeate stream (or membrane retentate stream) will vary to some extent (e.g. due to changing pump pressures or less controlled conditions (like temperature)). In the methods and systems described herein, the average composition of the first outlet stream can be understood to be equal to the composition of the combined total output of the first outlet stream of the membrane unit.

[0051] 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 lithium mass contained in the combined total output of the first outlet flow divided by the lithium mass present in the initial feed sent to the membrane unit in the same time. (Ignoring any mass of lithium introduced by the additive flow, the lithium recovery rate can be approximated as the lithium mass in the first outlet flow divided by the lithium mass in both the first outlet flow and the second outlet flow.) Preferably, the lithium recovery rate of the membrane unit exceeds 50%, more preferably 75%, or even 90%. In addition, the volume recovery rate of the membrane unit is defined as the volume of the first outlet flow divided by the combined volume of the initial feed flow and the additive flow in the same time period. Equivalently, the volume recovery rate of the membrane unit can be calculated from the volume of the first outlet flow and the second outlet flow, which is equal to the volume of the first outlet flow divided by the combined volume of the first outlet flow and the second outlet flow. Preferably, the volume recovery rate exceeds 70% or even 90%. In a preferred process, the lithium recovery rate of the membrane unit exceeds the volume recovery rate of the membrane unit.

[0052] The arrangement of membrane unit will affect the lithium recovery rate and volume recovery rate.For example, when the regulated feed stream of the same volume flows through more series membrane areas, the membrane permeate stream of increased volume is produced and the recovery rate of membrane unit is improved.Membrane unit can also include various internal loops for making the partial recycling of membrane permeate stream and / or membrane intercept stream, and these all affect the recovery rate equally.Although the existence of these internal loops is not considered in the above recovery rate calculation, their existence will affect both the lithium recovery rate and the volume recovery rate.For example, when making a part of the membrane intercept stream be recycled, the substantially higher volume recovery rate of membrane unit can be realized.

[0053] When the volume recovery rate of the membrane unit is improved, the volume of the second outlet flow is reduced. Therefore, the concentration of some well-retained ions (such as multivalent anions) in the second outlet flow is preferably higher, and the lithium mass in the second outlet flow is preferably reduced. Since the components in the regulated feed through the membrane unit are distributed between the first outlet flow and the second outlet flow, the greater volume recovery rate affects the composition of the first outlet flow and the second outlet flow. In a preferred embodiment, a portion of the regulated feed is passed through the membrane unit to produce the first outlet flow and the second outlet flow, and at least half of the lithium mass present in the initial feed is distributed to the first outlet flow, and the first outlet flow has a ratio of multivalent cations to lithium ions less than half of the initial ratio of multivalent cations to lithium ions. In a more preferred embodiment, the first outlet flow has a ratio of multivalent cations to lithium ions less than 0.25 or even less than 0.1 of the ratio of multivalent cations to lithium ions in the initial feed.

[0054] In some preferred embodiments, additional water can be combined with the initial feed stream and other salts to produce an adjusted feed stream having a reduced polyvalent anion concentration compared to the polyvalent anion concentration in the initial feed. Preferably, the molar concentration (mol / L) of the polyvalent anions in the adjusted feed is less than 90% of the molar concentration (mol / L) of the polyvalent anions in the initial feed. More preferably, the molar concentration of the polyvalent anions in the adjusted feed is less than 75% of the molar concentration of the polyvalent anions in the initial feed. This may, for example, have advantages 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, enough water is added during the process of adding one or more salts to the initial feed so that the molar concentration (mol / L) of the polyvalent anions in the adjusted feed is less than 90% of the molar concentration (mol / L) of the polyvalent anions in the initial feed, more preferably less than 75%. The additional water may be derived from a portion of the solution of the permeable membrane. In some cases, the conditioned feed comprises the initial feed, added salt, and at least a portion of the liquid that has permeated through the membrane. Most preferably, the additional water is obtained by separating the first outlet stream into a dilute portion and a concentrated portion, such as by reverse osmosis, and recycling at least a portion of the dilute portion. While the concentration of polyvalent anions in the conditioned feed is reduced compared to the initial feed, it is preferred that the flow rate of the membrane permeate stream exceeds the flow rate of the initial feed stream.

[0055] Different ultrafiltration membranes can be used to process regulated feeds. The membrane preferably includes 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 prepared by interfacial polymerization. Although there are variations, common methods involve forming a thin film interfacial polymer layer on a porous support, typically a polysulfone or polyethersulfone with a pore size between 0.001 and 0.5 μm. An aqueous multifunctional amine is applied to the support surface and a non-polar solution (e.g., hexane, Isopar TM , Freon TM ) is applied thereon. Once in contact with each other, the multifunctional amine reactive monomer and the multifunctional amine monomer react at the interface to form a polyamide layer or film. This layer is generally referred to as a polyamide "discrimination layer" or "film layer" and provides the primary means for separating solutes (e.g., salts) from solvents (e.g., aqueous feeds) for the composite membrane. It has been found that the polyamide membranes prepared by this method exhibit pH dependence and mixed ion retention, which is beneficial to improve lithium recovery under specified conditions.

[0056] Various monomers can be used under 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 includes at least two, preferably two to four amine reactive parts selected from acyl halides, sulfonyl halides and anhydrides. These monomers can be aromatic or aliphatic (straight chain or cyclic). Each substance can be used alone or in combination. Non-limiting examples of aromatic polyfunctional acyl halides include: trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, naphthalene trisulfonyl chloride, naphthalene dicarboxylic acid chloride. Non-limiting examples of alicyclic polyfunctional acyl halides include: cyclopropane tricarboxyl chloride, cyclopentane tricarboxyl chloride, cyclohexane tricarboxyl chloride, cyclopentane dicarboxyl chloride, cyclobutane dicarboxyl chloride, cyclohexane dicarboxyl chloride, tetrahydrofuran dicarboxyl chloride. Non-limiting examples of aliphatic halides include adipoyl chloride, malonyl chloride, glutaryl chloride and sebacoyl chloride. Fully aromatic polyamides can be produced by reacting aromatic polyfunctional amines (e.g., m-phenylenediamine, p-phenylenediamine) with aromatic polyfunctional amine reactive monomers (e.g., trimesoyl chloride, terephthaloyl chloride). Semi-aromatic polyamides can be produced by selecting aliphatic polyfunctional amines (e.g., piperazine, ethylenediamine) or aliphatic polyfunctional amine reactive monomers (e.g., cyclopropane tricarboxyl chloride, cyclopentane tricarboxyl chloride) to form a film (where the other monomer contains an aromatic ring). Polysulfonamide membranes can be produced by using aromatic or aliphatic polyfunctional amine monomers and polyfunctional sulfonyl halide-containing monomers (non-limiting examples are 1,3,5-benzenetrisulfonyl chloride, 1,3,5-naphthalenetri(sulfonyl chloride)) to form the membrane.

[0057] Various reactive and non-reactive additives may be present during the reaction process that may affect the performance characteristics of the membrane: surfactants and phase transfer catalysts, co-solvents / solvents, organic molecules, inorganic salts and nanoparticles. Similarly, the membranes may also be modified after the reaction by different post-treatments including reactive and non-reactive polymer coatings, reaction of modified end groups, plasma treatment, swelling agents, surfactants and exposure to chlorine or inorganic acids (e.g. hot phosphoric acid).

[0058] Compared with the first outlet flow (that is, permeate flow), the second outlet flow (that is, the retentate flow from the membrane unit) is typically rich in multivalent ions (both cations and anions). In certain embodiments, the specific ions in the second outlet flow can be further separated from other ions in the same flow. Preferably, the second outlet flow is further classified to form a part rich in ions selected from monovalent anions and multivalent cations. Preferably, enrichment can be achieved by making at least a portion of the second outlet flow pass through a distillation column, an ion exchange resin column or a membrane system. In a preferred method, the process of the second outlet flow being classified uses a part selected from membrane and an ion exchange column. For example, a nanofiltration membrane can be used to separate monovalent anions from multivalent anions, thereby forming a permeation part rich in monovalent anions. In another example, this second outlet flow rich in multivalent anions can be classified by the following operation: make this second outlet flow pass through a cation exchange resin column and then regenerate this column to produce a regeneration part 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 cation exchange resin rich in monovalent anions (Cl - or NO3 - ) and multivalent cation ions. In some methods, the enriched portion can be diluted with water or any aqueous solution before, during or after fractionation.

[0059] In addition, a portion of the second outlet stream rich in ions selected from monovalent anions and multivalent cations can be recycled to combine with the initial feed upstream of the membrane. When producing a regulated feed, the enriched portion can help add salt to the initial feed for adjusting the composition of the initial feed. Recycling this portion of the second outlet stream reduces the amount of new salt that needs to be brought to the site for lithium recovery.

[0060] In some preferred methods, the lithium dissolved in the first outlet stream can be concentrated by dehydration. For the purposes of the present 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 in preference to ions, thereby complementarily producing a stream with a higher concentration of lithium ions. 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., the cations are unloaded or desorbed, for example, by treatment with an acid solution, to produce a more concentrated (dehydrated) 'elution' stream. In some methods, concentrating lithium by dehydrating the first outlet stream is particularly useful in terms of energy and waste management.

[0061] The first outlet 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 of battery-grade lithium (99.5% purity), it is desirable to remove other monovalent cations (along with multivalent cations) from the first outlet stream. The purity of battery-grade lithium is defined as the content of lithium salt (usually lithium carbonate) by wt.% in the final solid product. In the present invention, the preferred method further includes a process for fractionating the first outlet stream into two solutions, wherein one of the two solutions includes a molar concentration of lithium ions increased compared to the molar concentration of lithium ions in the first outlet stream and a molar concentration of other (non-lithium) monovalent cations reduced compared to the molar concentration of other (non-lithium) monovalent cations in the first outlet stream. The classification of the first outlet stream can be performed before, during or after any step for concentrating (by dehydration) the dissolved lithium ions distributed to the first outlet stream.

[0062] The classification of the first outlet flow can be accomplished by various processes. In some preferred embodiments, the first outlet flow can be passed through a medium that is selective for lithium. A non-limiting example of a common lithium selective medium is an inorganic lithium intercalation, examples of which (inorganic lithium intercalation) 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). The lithium ions in these materials can also be extracted by an ion exchange method, in which an additive is used to replace lithium. In this embodiment, a common additive is an acid, such as sulfuric acid or hydrochloric acid. The eluent solution can include a molar concentration of lithium ions increased compared to the molar concentration of lithium ions in the first outlet flow and a molar concentration of non-lithium monovalent cations reduced compared to the molar concentration of non-lithium monovalent cations in the first outlet flow.

[0063] In some methods, the first outlet 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-methyl methacrylate-divinylbenzene), media that can be further functionalized to contain cation binding groups (such as sulfonic acid, carboxylic acid, weak base), and combinations of two or more of these media. The ion exchange medium is preferably suitable for cation exchange so that the fractionation of monovalent cations can be achieved by chromatography, that is, lithium and other monovalent cations flow through the medium at different rates and have different retention times. The process can be assisted by using an additional elution solution that assists in separating 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.

[0064] In some other methods, the first outlet stream is fractionated by selectively precipitating one or more monovalent cations, followed by filtering or decanting. In this method, the anion is selected so that the resulting lithium anion salt has a lower solubility than other monovalent cation-anion salts present in the first outlet 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, classification can be achieved, wherein the solubility of the lithium anion salt is higher than that of other monovalent cation-anion salts, which results in their precipitation. Suitable lower solubility salts include, but are not limited to, sodium chloride and sodium bromide.

[0065] The following examples are provided to further describe the present invention in detail. These examples, which set forth specific embodiments and currently considered preferred modes for carrying out the invention, are intended to illustrate, not to limit, the present invention.

[0066] Examples

[0067] Description of the initial feed water production

[0068] By + 、Na + , K + , Ca 2+ Mg 2+ , Fe 2+ , Mn 2+ , Sr 2+ 、Zn 2+ and Al 3+ SO4 2- The salt was dissolved in deionized water (DIW) to prepare the initial feed. The initial feed pH was adjusted to a value of 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 SO4 2- , where the ion concentration is 0.378mol / L.

[0069] The initial feed did not contain any monovalent anions other than a small amount 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 multivalent anions was zero. The initial ratio of multivalent 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, that is, there was no separate conditioned feed.

[0070] Description of the production of conditioned feed water

[0071] In Examples 3 to 14, adjusted feeds were prepared by adding one or more salt solutions to the initial feed solution. Details of adjusted feed preparation are provided in the specific examples. Ion concentrations (mol / L) were used to calculate the adjusted ratio of monovalent anions to lithium ions.

[0072] Description of the filter test protocol and analytical measurements

[0073] The filtration tests in Examples 1 to 14 were conducted to measure and compare lithium passage, mass recovery, and ratio of multivalent cations to lithium ions in the membrane permeate stream for specific membranes operated under different feed and operating conditions.

[0074] The test was performed in a cross-flow configuration by using a pump to pressurize the feed and pass the feed through the membrane samples contained in standard membrane filtration cells. Each cell contained an active area of ​​42 cm cut from a flat membrane sheet. 2 The membrane unit contains six membrane filtration cells, and therefore, the total active area in contact with the feed is 252 cm 2 (0.27ft 2 ). In these examples, each membrane filtration pool with a membrane is considered as a membrane module, and all six pools / modules of the combination are considered as membrane units. These six membrane filtration pools are positioned in two parallel groups, and three pools in each group are connected in series. The active side of the membrane is exposed to the feed solution. A feed volume flow rate of 2 liters / minute is maintained for each group during the entire test. The portion of the feed that passes through the membrane (membrane permeate flow) is collected from a separate membrane filtration pool permeate line. The portion of the feed that does not pass through the membrane (membrane retentate flow) is recycled back to the feed tank upstream of the pump during the entire test period. Unless otherwise mentioned in any specific example, the membrane permeate flow is also recycled back to the feed tank upstream of the pump during the permeate flow collection period. All filtration tests are carried out in the feed temperature range of 23°C to 27°C.

[0075] The permeate streams collected from the 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 the permeate collection time and membrane active area. The flux values ​​were averaged for the six permeates collected (one for each membrane filtration cell) and reported in liters / m2 The units are reported as / h (LMH). Fluxes were calculated using a permeate flow density of 1 g / ml.

[0076] The ion concentration (mol / L) of both the permeate stream and the feed stream was analyzed. The feed stream was collected from the feed tank while the permeate stream was collected. When both the retentate stream and the permeate stream were recycled back to the feed tank, the feed stream ion concentration did not change significantly during the experimental time. In some cases (e.g., Example 14), the feed stream ion concentration changed over time due to the continuous collection of the permeate stream or due to occasional addition of water to the feed tank to reduce the osmotic pressure.

[0077] In order to measure the ion concentration in the permeate stream, all six membrane permeate streams are mixed to prepare a 'mixed permeate' stream. The iCap 7600 ICP-OES analyzer available from Thermo Scientific of Waltham, MA, is used to analyze the cation mass concentration by inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. The cation concentration is calculated by dividing the ICP-OES mass concentration by the corresponding ion molar mass. These ion concentrations are used to calculate the multivalent cations in the (mixed) permeate stream and the ion ratio of lithium. The ion pass rate (fraction, abbreviated as "fr.") is calculated as the ratio of the ion molar concentration (both of which are measured using ICP-OES) in the (mixed) permeate stream and the corresponding feed stream.

[0078] The membrane unit volume recovery is calculated as the volume of permeate liquid produced by the membrane unit divided by the volume of liquid provided to the membrane unit in the same time period and is reported in %. In most cases presented here, the membrane unit recovery was less than 2%, and these tests were specifically to demonstrate how the relative permeate concentrations of different ions can be changed by changing the conditioned feed. It can be appreciated that both the volume recovery and the fraction of lithium ions recovered (into the permeate stream) can be increased by using more membrane area in series, passing less feed solution through the membrane unit at the same average flux, or recycling the membrane retentate stream while continuing to extract the permeate.

[0079] In one specific example (Example 14), the membrane retentate stream of the membrane unit is recycled, and the recovery of the system is measured and reported. For this example, the lithium ion mass recovery is 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 and expressed as a fraction. The mass of lithium ions dissolved in the permeate stream is calculated by multiplying the permeate volume (the volume of the first outlet stream collected) by the mass concentration of dissolved lithium ions measured by ICP-OES. The mass of lithium ions dissolved in the initial feed is 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.

[0080] Examples (1 and 2) illustrate control cases where the initial feed was fed directly to the membrane without the addition of any salt (ie without any pH and / or ion ratio adjustment).

[0081] Example 1: The membrane used in this example is a composite membrane with a piperazine-based polyamide barrier layer, which is used in a commercial SR90 element from FilmTec. The initial feed described previously was supplied to the membrane unit.

[0082] Example 2: In Example 2, membrane samples were cut from sheets of Duracid polysulfonamide membrane available from Suez. The initial feed was used as the feed to the membrane unit.

[0083] Examples 3 to 6 illustrate the effect of adding salt to the initial feed prior to the membrane unit to provide a specified adjusted feed pH and / or ion ratio.

[0084] 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+ 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 pH of the initial feed was adjusted to 1.4 to 1.5 by adding an appropriate amount of 98% sulfuric acid solution to the salt solution. The main anion in the initial feed was SO4 2-, where the ion concentration is 0.368 mol / L. The initial feed does not contain any monovalent anions except a small amount of hydroxide from water dissociation. Therefore, the initial ratio of monovalent anions to lithium ions is zero. Similarly, the initial ratio of monovalent anions to multivalent anions is zero. The initial ratio of multivalent cations to lithium ions is 5.1.

[0085] Lithium hydroxide powder (Li(OH) · H2O, 41.95 g) was dissolved in deionized water to produce a Li(OH) solution (1 liter, 1 mol / liter). As described above, an appropriate amount of this salt solution was added to the initial feed to increase the pH. A Fisherbrand 0.2μa PES membrane filter was used to remove any precipitate generated during pH adjustment, and the filtrate pH was measured to be 4.2. The filtrate collected after removal of the precipitated solids was the conditioned feed, and the conditioned feed was passed through the membrane.

[0086] The conditioned feed was tested using similar membranes and testing procedures as described in Example 1. The conditioned ratio of monovalent anions to lithium ions was zero, since no other monovalent anions were present except for a small amount of hydroxide from water dissociation. The lithium ion concentration in the conditioned feed was 0.15 mol / L.

[0087] Example 4: This is similar to Example 3. However, after removing the precipitated solids, a conditioned feed was formed by adding 0.03 mol / LMgCl2.6H2O salt as a solid to the filtrate. - The filtrate (solution pH 4.4) of ions is 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.

[0088] Example 5: This is similar to Example 4, except that the Cl in the adjusted feed (solution pH 4.2) - The ion concentration was other than 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.

[0089] Example 6: This is similar to Example 4, except that the Cl in the adjusted feed (solution pH 4.2) - 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.

[0090] The feed compositions and filtration test performances of Examples 1 to 6 are reported in Table 1. As can be seen from the data in Table 1, when both the pH and the ratio of monovalent anions to lithium ions are adjusted by adding specific salts, the Li + The throughput rate increases and the ratio of multivalent cations to lithium ions in the permeate decreases.

[0091] Table 1

[0092]

[0093] Examples (7 to 8) illustrate the applicability of the present invention at different feed pH values.

[0094] Example 7: Example 7 used the same conditions as Example 5 (membrane, initial feed preparation, adjusted feed preparation and testing), except that the adjusted feed pH was pH 6.6, the Cl in the adjusted feed was - The ion concentration was 0.3 mol / L, the adjusted ratio of monovalent anions to lithium ions was 2.0, and the adjusted lithium concentration in the feed was 0.15 mol / L.

[0095] Example 8: Example 8 used the same conditions as Example 5 (membrane, initial feed preparation, adjusted feed preparation and testing), except that the adjusted feed pH was pH 3.5, the Cl in the adjusted feed was - The ion concentration was 0.3 mol / L, the adjusted ratio of monovalent anions to lithium ions was 3.0, and the adjusted lithium concentration in the feed was 0.10 mol / L.

[0096] The feed compositions and filtration test performances for Examples 7-8 are reported in Table 2.

[0097] Table 2

[0098]

[0099] Examples (9 to 13) illustrate the use of different types and amounts of salts to form conditioned feeds having different pH and / or ion ratios.

[0100] Example 9: Example 9 used the same conditions (membranes, initial feed preparation, adjusted feed preparation, and testing procedures) as Example 3, except that Mg(OH)2 salt in solid form was added to the initial feed for pH adjustment. After removing the precipitate generated during pH adjustment, the adjusted feed solution pH was measured to be 4.2. The adjusted ratio of monovalent anions to lithium ions was zero because no other monovalent anions were present except for a small amount of hydroxide from water dissociation. The adjusted feed lithium concentration was 0.044 mol / L.

[0101] Example 10: Example 10 is similar to Example 9, except that 0.015 mol MgCl2·6H2O salt is added to each L of filtrate after removing the precipitated solid. - The filtrate of ions forms the conditioned feed (solution pH 4.3), which passes 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.

[0102] Example 11: In this example, the conditions were similar to Example 10, except that the Cl in the adjusted feed (solution pH 4.2) - 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.

[0103] Example 12: In this example, the conditions were similar to those of Example 10, except that the Cl in the adjusted feed (solution pH 4.2) - 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.

[0104] Example 13: In this example, the conditions were similar to those of Example 9, except that 0.30 mol / L NO3 in the form of Mg(NO3)2·6H2O salt was added after removing the precipitated solid. - Add to the filtrate. With NO3 - The filtrate of ions is the adjusted feed (solution pH 4.2), which passes through the membrane surface. The adjusted ratio of monovalent anions to lithium ions is 6.8. The adjusted feed lithium concentration is 0.044 mol / L.

[0105] The feed compositions and filtration test performances for Examples 9 to 13 are reported in Table 3.

[0106] Table 3

[0107]

[0108] Example 14 demonstrates the Li mass recovery in a system with greater volumetric recovery.

[0109] Example 14: Preparation of Li + =0.043 and Mg 2+=0.173 cation concentration (mol / L) of sulfate-based initial feed. 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 a small amount 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 multivalent anions was zero. The initial ratio of multivalent cations to lithium ions was 4.0.

[0110] Again, the recirculation system was configured to reasonably simulate the performance of a continuous filtration system with more membrane area. In this example, ion ratio adjustment was performed by adding MgCl2·6H2O salt in powder form to the initial feed. The Cl in the conditioned feed - 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. A Fisherbrand 0.2μa PES membrane filter was used to remove the precipitated solids generated during the pH adjustment, and the filtrate pH was measured to be 4.3. The filtrate was the 'adjusted feed' fed to the membrane unit. Monovalent anions (Cl - The adjusted ratio of ) to lithium ions was 9.3. The adjusted feed lithium concentration was 0.043 mol / L. This adjusted feed was tested using a similar membrane as described in Example 1.

[0111] The conditioned feed (10.1 L, weight 10378 g) was pumped through a column containing six 2 During the entire test, the first outlet flow (i.e., the permeate flow leaving the membrane unit) was collected in a drum, while the membrane retentate flow was recycled to the feed tank (upstream of the feed pump, such as Figure 3 As the feed tank osmotic pressure increases, the feed side pressure is adjusted to increase the permeate flow. After 9 hours of operation, 5.45 L of permeate (weight 5401 g) was collected. The collected solution is called permeate A.

[0112] After permeate A was collected, 0.5 L of deionized water (DIW) was added to the feed tank, and the permeate flow was collected for another 1.5 hours. The collected solution volume was 0.71 L (weight 705.4 g) and was called permeate B. Further, another 0.5 L of DIW was added to the feed tank, and the permeate flow was collected for another 3 hours. The collected solution volume was 1.0 L (weight 1003.7 g) and was called permeate C.

[0113] The membrane unit volume recovery and Li mass recovery data are presented in Table 4.

[0114] Table 4

[0115]

[0116] 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 added DIW volume. The Li mass recovery was 0.82, and the multivalent cations (Mg 2+ ) to lithium ions is 0.2 (i.e. 0.05 times the same ratio of 4.0 in the initial charge).

[0117] The methods described herein are particularly useful in selectively recovering lithium from brine feeds at high mass recovery and purity. Another advantage of the methods of the present invention is that polyvalent anions (e.g., SO4 2- 、CO3 2- ) can be removed by monovalent anions (e.g. Cl - 、NO3 - ) to form a composition that may be more beneficial for downstream lithium recovery operations.

[0118] Although certain preferred embodiments of the present invention have been described and specifically illustrated above, the present invention is not intended to be limited to such embodiments. Rather, it should be understood that although many of the characteristics and advantages of the present invention have been set forth in the foregoing description, together with the details of the structure and function of the present invention, the present disclosure is illustrative only, and changes may be made in detail, especially in the shape, size and arrangement of parts, within the principles of the present invention to the full extent indicated by the broad general meaning of the terms expressing the appended claims.

Claims

1. A method for recovering lithium, the method comprising the following steps: providing an initial charge having a dissolved mass of lithium and a) the initial ratio of monovalent anions to lithium ions, b) the initial ratio of multivalent cations to lithium ions; and c) an initial ratio of monovalent anions to polyvalent anions of less than 1; One or more salts are added to the initial feed to form an adjusted feed having a pH between 1 and 7 and d) an adjusted ratio of monovalent anions to lithium ions that is greater than the initial ratio of monovalent anions to lithium ions; as well as 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 the first outlet stream has a ratio of multivalent cations to lithium ions that is less than half of the initial ratio of multivalent cations to lithium ions.

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

3. The method according to claim 1 or claim 2, wherein: The 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. The process of any one of claims 1, 2 or 3, further comprising combining the initial feed with additional water such that the molar concentration of polyvalent anions in the adjusted feed is less than 90% of the molar concentration of polyvalent anions in the initial feed.

5. A method as claimed in any preceding claim, wherein: The conditioned feed comprises the initial feed, added salt, and at least a portion of the liquid that has permeated across the membrane of the membrane unit.

6. A method as claimed in any preceding claim, wherein: The membrane includes a polymer layer selected from the group consisting of fully aromatic polyamides, semi-aromatic polyamides, sulfonated polysulfones, sulfonated polyethersulfones, and polysulfonamides.

7. A method as claimed in any preceding claim, further comprising the step of fractionating the second outlet stream to form a fraction enriched in ions selected from monovalent anions and multivalent cations, and wherein the fractionating step uses a component selected from the group consisting of ultrafiltration membranes and ion exchange resins.

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

9. A method as claimed in any preceding claim, further comprising concentrating the first outlet stream by dehydration to produce an increased concentration of dissolved lithium.

10. A method as claimed in any preceding claim, wherein: The first outlet stream comprises at least one monovalent cation other than lithium, and further comprises the step of fractionating the first outlet stream into two solutions, wherein one of the two solutions comprises 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 the monovalent cation compared to the molar concentration of the monovalent cation in the first outlet stream.

11. A method as claimed in any preceding claim, further comprising the step of extracting lithium from the first outlet stream.

12. A system for recovering lithium, the system comprising: means for providing an initial feed having a dissolution mass of lithium, wherein the initial feed contains (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; means 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 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 the first outlet stream, and the first outlet stream has a ratio of multivalent cations to lithium ions that is less than half of the initial ratio of multivalent cations to lithium ions.

13. The system of claim 12, further comprising: means for fractionating said 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 said enriched fraction to form said conditioned feed.

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

15. A system for recovering lithium, the system comprising: An initial charge having a dissolution mass of lithium, wherein the initial charge contains (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; one or more salts 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 that is greater than the initial ratio of monovalent anions to lithium ions; Membrane filter unit; as well as a conduit, a pump and optionally a valve assembly 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 into the first outlet stream, and the first outlet stream has 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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