Processes for removing boron from lithium-containing brines

Abstract

A process is described to remove boron from lithium-containing process streams includes processing the source brine in a lithium adsorption step and a desorption step, raising the pH of a desorption effluent, and filtering the desorption effluent with one or more of a nanofiltration process and a reverse osmosis process to remove a portion of the boron. The permeate of the filtration is returned to the desorption process as a low boron recycled water stream. In one embodiment, a first reverse osmosis process operates at a low pH and low temperature and a second reverse osmosis process operates at a high pH and high temperature. The amount of boron retained by the second reverse osmosis process is greater than the amount of boron retained by the first reverse osmosis process.

Description

Docket No. 1710.00073WOPROCESSES FOR REMOVING BORON FROM LITHIUM-CONTAINING BRINESRELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Patent Application Serial No. 63 / 712,777, filed October 28, 2024, the disclosure of which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] This invention relates to new economical and practical process technology for recovering lithium values from lithium-containing brines while removing boron from the brines and recycle streams.BACKGROUND

[0003] As is well known, in recent years a need has arisen for more economical and efficient technology enabling production of high purity lithium or its salts from suitable sources. This is reflected by an increase in research activities devoted to this subject. It appears that this need has not been fulfilled yet by any published prior art.

[0004] Nanofiltration (NF) and Reverse Osmosis (RO) are two membrane processes used to concentrate or clean process streams. During these processes, undesirable ions like boron, calcium, and magnesium often flow through the membrane and remain in the product stream. These ions must then be extracted in downstream processes causing additional time and increased costs to be incurred.NON-LIMITING SUMMARY OF THE INVENTION

[0005] This summary lists several embodiments of the presently disclosed subject matter, and in many cases lists variations and permutations of these embodiments. This summary is merely exemplary of the numerous and varied embodiments. The mention of one or more representative features of a given embodiment is likewise exemplary. Such an embodiment can typically exist with or without the feature(s) mentioned; likewise, those features can be applied to other embodiments of the presently disclosed subject matter, whether listed in this summary or not. To avoid excessive repetition, this Summary does not list or suggest all possible combinations of such features.Docket No. 1710.00073WO

[0006] This invention utilizes a particular combination of separation techniques that has the capability of fulfilling the need for more efficient and economical process technology for recovering lithium and removing boron from various brine sources. Based on results presented hereinafter, it is believed reasonable to suggest that such combination and sequence of separation techniques will produce an aqueous solution of a lithium salt while removing boron from the brine streams. The techniques will allow recycled water from the streams to be used in a desorption process and / or in nanofiltration processes without a buildup of boron.

[0007] In one aspect, a process to remove boron from lithium-containing process streams, includes a source brine containing lithium and boron. The process includes processing the source brine in a lithium adsorption step and a desorption step, raising the pH of a desorption effluent, and filtering the desorption effluent with one or more of a nanofiltration process and a reverse osmosis process to remove a portion of the boron. The permeate of the filtration is returned to the desorption process as a low boron recycled water stream.

[0008] In a preferred embodiment, the pH of the desorption effluent is raised to a pH of higher than 9. In a preferred embodiment, more than 95 percent of the boron is removed from the desorption effluent during the filtration. In a preferred embodiment, the pH is raised after a first stage of the nanofiltration process but before a second stage of the nanofiltration process. In a preferred embodiment, the method includes performing purification and concentration processes on a concentrated retentate of the reverse osmosis process to produce one or more of LiCl, LiOH, and Li2CO3. In one embodiment, at least a portion of the low boron permeate of the filtering is recycled to one or more of stages of the nanofiltration process.

[0009] In another embodiment, the process includes processing the source brine in a lithium adsorption step and a desorption step, filtering a desorption effluent with one or more of a first nanofiltration process and a first reverse osmosis process, and raising the pH of a permeate of the filtration. After raising the pH, the process includes filtering the permeate in one or more of a second nanofiltration process and a second reverse osmosis process and returning a low boron permeate of the second filtering to the desorption process as a recycled water stream.

[0010] In a preferred embodiment, the pH of the permeate of the filtration is raised to a pH of higher than 9. In a preferred embodiment, more than 95 percent of the boron is removed from the desorption effluent during the second reverse osmosis filtration. In a preferred embodiment, the first nano filtration process is conducted with a pH of lower than 5. In a preferred embodiment, the method includes performing purification and concentrationDocket No. 1710.00073WO processes on a concentrated retentate of the reverse osmosis process to produce one or more of LiCl, LiOH, and Li2CO3. In one embodiment, at least a portion of the low boron permeate of the filtering is recycled to one or more of stages of the nanofiltration process.

[0011] In another embodiment, the process includes processing the source brine in a lithium adsorption step and a desorption step, heating a desorption effluent, filtering the heated desorption effluent with one or more of a first nanofiltration process and a first reverse osmosis process, cooling a boron rich permeate of the filtration, and raising the pH of the cooled permeate. After raising the pH, the process includes filtering the permeate in one or more of a second reverse osmosis process; and returning a low boron permeate of the second filtering to the desorption process as a recycled water stream.

[0012] In a preferred embodiment, the second reverse osmosis process operates at a temperature above 60 degrees C and at a pH above 9. In a preferred embodiment, the boron rich permeate of the filtration exchanges heat with the desorption effluent. In a preferred embodiment, the boron rich permeate of the filtration is cooled in a heat exchanger.

[0013] In a preferred embodiment, more than 95 percent of the boron is removed from the desorption effluent during the second reverse osmosis filtration. In a preferred embodiment, wherein the first reverse osmosis process operates at a temperature below 40 degrees C and at a pH below 5. In a preferred embodiment, the method includes performing purification and concentration processes on a concentrated retentate of the reverse osmosis process to produce one or more of LiCl, LiOH, and Li2CO3. In one embodiment, the raised temperature of the boron rich permeate processed in the second reverse osmosis process increases the amount of boron retained in the retentate.

[0014] In another embodiment, the process includes removing boron from lithium-containing process streams after processing with a chelating resin. The process includes providing a stream containing boron, processing the stream in a chelating resin process, and adjusting the pH of an effluent of the chelating resin process to above 7.0. After adjusting the pH, the process includes filtering the effluent with one or more of a nanofiltration process and a reverse osmosis process to remove a portion of the boron, returning a low boron permeate of the filtering as a recycled water stream; and collecting concentrated boron in the retentate of the filtering.

[0015] These and other steps will be discussed in greater detail below.Docket No. 1710.00073WO

[0016] Thus, the conduct of one or more additional steps beyond those described herein in performing a multi-step process of the invention falls within the scope of the claim coverage of this invention.

[0017] The above and other embodiments, objectives, features, and advantages of this invention will become still further apparent from the ensuing description, appended claims, and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The presently disclosed subject matter can be better understood by referring to the following example figures. The components in the figure are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the presently disclosed subject matter (often schematically). In the figures, like reference numerals designate corresponding parts throughout the different views. A further understanding of the presently disclosed subject matter can be obtained by reference to an embodiment set forth in the illustrations of the accompanying drawing. Although the illustrated embodiment is merely for purposes of example of systems for carrying out the presently disclosed subject matter, both the organization and method of operation of the presently disclosed subject matter, in general, together with further objectives and advantages thereof, may be more easily understood by reference to the drawings and the following description. The drawings are not intended to limit the scope of this presently disclosed subject matter, which is set forth with particularity in the claims as appended or as subsequently amended, but merely to clarify and provide examples of the presently disclosed subject matter.

[0019] FIG. 1 illustrates a general representation of the process of a system using nanofiltration and reverse osmosis.

[0020] FIG. 2 illustrates a general representation of the process using a pH adjustment before filtration in accordance with one or more embodiments.

[0021] FIG. 3 is a graph of a percent rejection of elements in a nanofiltration process at multiple pH levels.

[0022] FIG. 4 is a graph of a percent rejection of elements in a reverse osmosis process at multiple pH levels.

[0023] FIG. 5 illustrates a general representation of the process using multiple reverse osmosis or nanofiltration processes with a pH adjustment in accordance with one or more embodiments.Docket No. 1710.00073WO

[0024] FIG. 6 illustrates a general representation of the process using multiple reverse osmosis processes with a heat integration process in accordance with one or more embodiments.

[0025] FIG. 7 illustrates a general representation of the process using membrane filtration processes on effluent from resin adsorption processes in accordance with one or more embodiments.DETAILED DESCRIPTION

[0026] Following the Definitions provided below, illustrative aspects of the subject matter claimed even further below will be disclosed. In the interest of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve one of ordinary skill in the art’s specific goals, such as compliance with application-related, system-related and / or business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0027] Definitions

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the presently disclosed subject matter.

[0029] While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.

[0030] All technical and scientific terms used herein, unless otherwise defined below, are intended to have the same meaning as commonly understood by one of ordinary skill in the art. References to techniques employed herein are intended to refer to the techniques as commonly understood in the art, including variations on those techniques or substitutions of equivalent techniques that would be apparent to one of skill in the art. While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.

[0031] Components referred to by chemical name or formula anywhere in the specification or claims hereof, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical typeDocket No. 1710.00073WO(e.g., another component, a solvent, or etc.). It matters not what chemical changes, transformations and / or reactions, if any, take place in the resulting mixture or solution as such changes, transformations, and / or reactions are the natural result of bringing the specified components together under the conditions called for pursuant to this disclosure. Thus, the components are identified as ingredients to be brought together in connection with performing a desired operation or in forming a desired composition. Also, even though the claims hereinafter may refer to substances, components and / or ingredients in the present tense ("comprises", "is", etc.), the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixed with one or more other substances, components and / or ingredients in accordance with the present disclosure. The fact that a substance, component or ingredient may have lost its original identity through a chemical reaction or transformation during the course of contacting, blending or mixing operations, if conducted in accordance with this disclosure and with ordinary skill of a chemist, is thus of no practical concern.

[0032] In describing the presently disclosed subject matter, it will be understood that a number of techniques and steps are disclosed. Each of these has individual benefit and each can also be used in conjunction with one or more, or in some cases all, of the other disclosed techniques.

[0033] Accordingly, for the sake of clarity, this description will refrain from repeating every possible combination of the individual steps in an unnecessary fashion. Nevertheless, the specification and claims should be read with the understanding that such combinations are entirely within the scope of the invention and the claims.

[0034] Following long-standing patent law convention, the terms “a”, “an”, and “the” refer to “one or more” when used in this application, including the claims. Thus, for example, reference to "a cell" includes a plurality of such cells, and so forth.

[0035] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0036] As used herein, the term “about,” when referring to a value or to an amount of a composition, dose, mass, weight, temperature, time, volume, concentration, percentage, etc.,Docket No. 1710.00073WO is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed methods or employ the disclosed compositions.

[0037] The term “comprising”, which is synonymous with “including” “containing” or “characterized by” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. “Comprising” is a term of art used in claim language which means that the named elements are essential, but other elements can be added and still form a construct within the scope of the claim.

[0038] As used herein, the phrase “consisting of’ excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0039] As used herein, the phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

[0040] With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

[0041] As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D.

[0042] As used herein, the term “concentrated” when used in connection with a solution or in connection with a brine is meant to include a solution or brine that is saturated.General Procedure

[0043] FIG. 1 illustrates a general representation of the process of a system using nanofiltration and reverse osmosis.

[0044] The general procedure is as follows. Brine is removed from a source 100, such as the Smackover, oilfield, or other source of lithium rich brine. If necessary, the brine is routed to one or more pretreatment stages. Potential stages of pretreatment include bulk removal of oil via any number of commercially available technologies including at a minimum anyDocket No. 1710.00073WO combination of: oil / phase separators, hydrocyclone, inclined plate coalescers, coarse coalescers, induced gas flotation (IGF) units, deoiling cartridge filters, organoclay products, Macro Porous Polymer Extraction technology, crushed nut shell filtration bed, acid stripping followed by gravity settling, electrocoagulation technology, a light oil stripper and H2S stripper, as is known in the art. After the brine is pretreated, in some embodiments it may be sent to a processing unit to remove additional valuable materials. However, this step could occur anywhere along the process such as after the Lithium has been removed.

[0045] Once the brine is ready for the removal of lithium, it may be sent to a cooling tower for temperature, density, and / or concentration adjustment. The brine solutions of the Smackover, for example, come up from the ground at excessive temperatures. The brine solution temperature will in some embodiments be reduced to a temperature less than about 80°C to less than about 110°C, optionally the temperature will need to be reduced to less than about 105°C, preferably less than about 90°C, and more preferably less than about 82°C. The brine is then processed in the Lithium adsorption 102 and desorption 104 steps. After the adsorption 102 and desorption 104 steps, the desorb effluent brine is sent to an additional purification / concentration 110 step. The lithium enriched brine effluent leaving the additional purification / concentration 110 step is prepared for production and turned into a final product.Adsorption of Lithium from Brine and Desorption of the Lithium

[0046] Typically, the brine is introduced into a lithium adsorption step after the initial pretreatment steps. The lithium adsorption 102 step which is conducted by passing the lithium containing brine into and out of the sorbent bed - which is preferably placed in a column or other suitable contact vessel - at a brine temperature of about 40°C to about 110°C, preferably about 50 °C to about 90 °C, until lithium breakthrough is achieved in the effluent from the bed. “Breakthrough” is determined based on the goals and economics of the process being utilized. For example, “breakthrough” may occur when it is first determined that at least about 25% of the lithium has been adsorbed, more preferably more than about 80% of the lithium has been adsorbed, most preferably more than about 90% of the lithium has been adsorbed. The sorbent can recover lithium from brine of any concentration, although the higher the initial lithium concentration in the brine, the higher will be the sorbent take-up or load of sorbed lithium when breakthrough has occurred.

[0047] In the practice of processes for recovering lithium values from lithium-containing brines in accordance with this invention, a sorbent is used for treating the brine as receivedDocket No. 1710.00073WQ from its source, and if necessary or desired, after such brine has been pretreated as above. Any suitable sorbent can be used however in this novel process, such as described in CN111215040B, CN102631897 B, or U.S. Pat No. 10,648,061. Further, use may be made of known lithium sorbents disclosed for example in U.S. Pat. Nos. 5,599,516 and 6,280,693. These patents disclose polycrystalline hydrated alumina sorbents based on a hydrated alumina such as crystalline Gibbsite, bayerite, nordstrandite or bauxite. These sorbents are morphologically altered by the infusion therein of lithium salts which creates active lithium-specific sites within the crystal layers of the alumina. One example of infused sorbent particles, having the formula LiOH»2Al(OH)s and lithium loading up to 0.33 mol fraction, are converted to LiCl»2Al(OH)3 by neutralization with HC1, and can then be used in the present process of removing lithium values from brine.

[0048] One of the potential substances used in the practice of this invention is “hydrated alumina” which is also known in the art by a variety of terms such as alumina hydrate, alumina trihydrate, or aluminum hydroxide. This substance is also often identified by use of the acronym “ATH.” Typically, these materials are assigned the formula A1(OH)3 or AhO3*3H2O. Thus, these and any other named substance of the same chemical character as any of these named materials such as Gibbsite and Bayerite are deemed suitable for use in the process of this invention.

[0049] Continuing with Figure 1, after the brine has passed through a lithium adsorption step, it is then necessary to recover the adsorbed lithium through a lithium desorption 104 step. The lithium desorption 104 step generally is conducted by washing the sorbent with water or aqueous solutions such as a dilute lithium chloride or other lithium salt solution preferably containing about 50 mg Li / kg to about 300 mg Li / kg solution, at a temperature of about 40°C to about 100°C or higher if conducted under increased pressure, preferably greater than 50°C, and more preferably greater than 60°C. The desorption efficiency increases with the washing temperature. The higher the desorption efficiency, the less the amount of water required for Li desorption, and thereby the higher the lithium concentration in the eluent.

[0050] To increase the purity of the eluent, it is desirable to displace the holdup of brine remaining in the void space between the particles in the sorbent bed. This process typically involves use of at least about 1.2 to about 1.4 volumes of water per 1 volume of void space to be purged out before collecting high purity lithium chloride solution. Initial fractions can contain significantly increased levels of impurities relative to lithium compared to later fractions of the desorption effluent. Fractional selection of desorption segments can be fed to one or more processing steps suitable to the given TDS / Li ratio. This selection may occurDocket No. 1710.00073WO during or after the purge step. The purge which contains lithium values may be recycled back to the brine for a next sorption cycle. If available, optionally a concentrated salt solution such as but not limited to solutions made of one or more of NaCl, MgC12, KC1, CaC12 can be used to displace the brine prior to the desorption 104 step to minimize the lithium loss to the purge.Purification / Concentration of the Lithium Effluent

[0051] Continuing with Fig. 1, after the adsorption 102 step and the desorption 104 step, the desorption effluent containing lithium and boron among other impurities is processed in a series of a series of purification / concentration steps.

[0052] One of the available purification / concentration steps is a nanofiltration 106 process. Nanofiltration 106 is a filtration process that uses nanometer-sized pores in a membrane to allow smaller particles to pass through the membrane but not particles larger than the pore size. In examples, nanofiltration 106 membranes have pore sizes of about 1 to 10 nanometers, smaller than the pores in microfiltration and ultrafiltration, but a slightly larger than the pores in a reverse osmosis 108 process. Membranes used in example nanofiltration 106 processes are polymer thin films, such as polyamide or polyethelene terphthalate. In other examples, the thin films are composed of a metal, such as aluminum.

[0053] Nanofiltration 106 processes are able to remove certain elements from the brine. Nanofiltration 106 provides high rejection of multivalent ions, such as calcium, and low rejection of monovalent ions, such as lithium or sodium and low rejection of small non-ionic molecules such as boric acid, a boron compound. For example, in a typical nanofiltration 106 process, approximately 50% of the calcium in a brine is removed and 75% of the magnesium. The nanofiltration 106 process, however, removes less than 10% of any lithium, boron, or sodium in the brine.

[0054] The nanofiltration 106 system can be operated in a number of series or parallel configurations to accomplish the desired level of separation while maintaining a constant flux through the membrane. The nano filtration 106 system could be operated in single-pass operation, multiple-pass recirculation, and series configurations for removing elements from the lithium-containing stream. For example, a portion of permeate produced in a subsequent reverse osmosis unit operation is recycled back between each stage in the nanofiltration system to maintain the flux. In other examples, a recycled water stream, such as the permeate of a reverse osmosis 108 process may be used to maintain the flux.Docket No. 1710.00073WO

[0055] An additional or alternative purification / concentration step for the desorption effluent may include reverse osmosis. Reverse osmosis 108 may be used at any point of the purification / concentration process. For example, reverse osmosis 108 may be before or after nanofiltration 106.

[0056] Reverse osmosis 108 is a filtration process that uses high pressure to drive a fluid through specially engineered semi-permeable membranes. For example, reverse osmosis 108 processes often operate at pressures of 600 to 1200 psi to process brine. The pore size in a reverse osmosis membrane may be O.lnm to Inm. As such, reverse osmosis 108 typically removes particles that are smaller than the particles removed in a nanofiltration 106 process.

[0057] In a reverse osmosis 108 process operating under conventional conditions, approximately 50% of the boron in a brine is removed. The range of boron removed is typically between 40% and 60%. Nearly all of the remaining calcium, lithium, magnesium, and sodium are retained in the concentrate stream.

[0058] When using this step of a multi-step process, reverse osmosis process technology utilizes applied pressure to the aqueous solution concentrated, i.e., the lithium solution, to drive water from the lithium solution through a semi-permeable reverse osmosis membrane, producing a more concentrated lithium-containing solution and a separate second water stream. The pressure applied must be greater than the osmotic pressure of the lithium- containing solution for water to pass through the semi-permeable membrane.

[0059] While currently developed reverse osmosis 108 systems do require application of substantial pressure to achieve concentration, it is useful in that it produces a nearly pure water stream as a result of the water that permeates through the semi-permeable reverse osmosis membrane except for a portion of any boron in the brine. This water stream can then be utilized elsewhere on a plant site or recycled to the original source from which the lithium- containing solution was obtained. One advantage of using a reverse osmosis 108 step in the multi-step processes is that it can accommodate lithium solutions of a relatively wide range of concentrations from the nanofiltration step without significant loss of lithium values in the operations. Thus the lithium solution received by and subjected to pressurized reverse osmosis through a likely plurality of semi-permeable reverse osmosis membranes in units staged in series or parallel or both, with pressure applied to the lithium solution, may initially contain in the range of about 300 to about 5,000 ppm of lithium. Tn such a reverse osmosis 108 operation, water is forced across the semi-permeable reverse osmosis membranes while the ions contained within the feed solution are rejected and remain on the lithium solutionDocket No. 1710.00073WO side of the reverse osmosis membrane. Said reverse osmosis process technology provides for the concentration of the lithium solution.

[0060] The permeate stream of the reverse osmosis 108 process includes a portion of the boron that was not retained. The permeate stream may also include a trace concentration of lithium, calcium, magnesium, sodium, and other elements or compounds. The portion of the boron that is passed through the reverse osmosis 108 system, is returned in a recycle line with the water to the desorption 104 process. The boron in the recycled water passes through the desorption 104 process and re-enters the brine. Alternatively, the recycled water is introduced to the nanofiltration 106 process. Because the boron is repeatedly recycled, a buildup in the percentage of boron may occur. The boron must be purged or treated to prevent the buildup from reaching unsustainable levels. For example, a chelating resin may be used to remove boron from the recycle water stream. The chelating resin may be a polymer with a polyhydroxyl group, such as sorbitol, mannitol, or N-methyl-D-glucamine.

[0061] In an alternate example, a precipitation process is used at any point of the process, such as before nanofiltration 106. In the example, the precipitation process may perform a carbonate / hydroxide precipitation of magnesium / calcium prior to nanofiltration 106 to remove boron. For example, a powdered calcium hydroxide may be combined with the desorption effluent to reduce the residual boron concentration.Additional Purification / Concentration Steps

[0062] If needed, other optional purification / concentration steps 110 may be performed in addition to nanofiltration 106 and / or reverse osmosis 108. Generally, the enrichment process should result in a substantively concentrated and purified LiCl solution of quality sufficient to be further processed into either lithium metal, LiOH, LiCl, Li2CO3 or other valuable lithium minerals.

[0063] The stream entering the additional purification / concentration 110 process may include the desired lithium and a portion of the boron that was not removed in the reverse osmosis 108 process. The concentrate may further include calcium, magnesium, and sodium.

[0064] In order to make high purity lithium salts such as lithium chloride, lithium hydroxide, and lithium carbonate, it is desirable to remove the undesired impurities, such as magnesium, calcium, and / or boron, in the lithium chloride solution to as low as possible.

[0065] Typical conventional practice for the removal of divalent impurities generally requires the addition of a base, such as lime, sodium carbonate, sodium hydroxide to convert theDocket No. 1710.00073WO soluble divalent chlorides to insoluble divalent salts, which are then separated from the lithium chloride solution. Although the precipitation process generally can reduce the divalent impurities in the lithium chloride solution to less than about 5 ppm, the process requires the cost for the base and produces a large amount of solid waste. The use of a basic ion exchange resin is also a way of reducing the concentration of the divalent impurities, even to less than about 1 ppm, but the process is generally even more expensive, due to the costs for the resins and for its regeneration.

[0066] The additional purification / concentration 110 processes may include any suitable processes, procedures, equipment, chemicals, or other manners of purifying and concentrating the lithium compounds. For example, thermal evaporator techniques, such as thermal syphon, direct steam injection, or Mechanical Vapor Recompression, may be used. In other examples, electrodialysis or membrane distillation may be used. In other examples, crown ethers are capable of interacting with specific cations based on the structure of the ether and size of the cation. Any suitable process to purify or concentrate the lithium compounds may be used.

[0067] Systems such as the system described in FIG. 1, allow boron to be continuously recycled. Additional boron is added to the system in each cycle. Eventually, the boron must be removed before the percentage of boron becomes untenable. A process that removes a higher percentage of the boron from the brine before entering the recycled water stream would prevent the buildup of boron in the brine loop.

[0068] FIG. 2 illustrates a general representation of the process using a pH adjustment before filtration in accordance with one or more embodiments.

[0069] The process of FIG. 2 includes a pH adjustment step 202 before the desorption effluent enters the nanofiltration 106 and reverse osmosis 108 processes. A higher pH causes a percentage of boron rejected by the nanofiltration 106 process to increase. An illustration of the effect of pH on elements in the brine is provided in FIG. 3.

[0070] FIG. 3 is a graph of a percent rejection of elements in a nanofiltration 106 process at multiple pH levels. As illustrated, at pH levels of 3 to 5, substantially none of the boron is rejected. This boron is transmitted into the permeate. At a pH of 7, a small portion of the boron, less than 10%, is rejected. However, at pH levels above 7, the rejection rate increases sharply with a maximum rejection rate of nearly 80% at a pH above 9.

[0071] As seen in FIG. 3, the percentage of calcium and magnesium ions rejected is higher at lower pH levels while still maintaining a low rejection rate of lithium and sodium. At higher pH levels the calcium and magnesium rejection rates decrease and the boron rejection rateDocket No. 1710.00073WO increases. When the NF system operated at a pH of 3, sodium, lithium, and boron were allowed to pass through the membrane into the permeate stream. Calcium and magnesium were rejected and separated into the reject stream. This pH also maintained less than 10% loss of desirable ions like lithium to the reject stream.

[0072] To create FIG. 3, a commercially available 1812 nanofiltration membrane was installed as a nanofiltration unit and rinsed using water dosed with a small amount of acetic acid. After cleaning, the unit was charged with nominally 10 L of feed solution containing nominally 3% LiCl, 1% NaCl, 800 ppm CaCh, 1200 ppm MgCh, and 3400 ppm B(OH)s among other components and pH adjusted to 3.2 using hydrochloric acid. The material was allowed to recirculate for 3-10 minutes before taking a sample from the permeate and feed stream. The pH was then adjusted, and the procedure repeated for each data point on the graph of FIG. 3. Parts per million of the elements in the permeate and the reject of the example are provided in Table 1 and Table 2 below for pH levels of 3.2 and 10, respectively.

[0073] Table 1: Permeate and reject concentrations at a pH of 3.2 in nanofiltrationDocket No. 1710.00073WO

[0074] Table 2: Permeate and reject concentrations at a pH of 10 in nanofiltration

[0075] As illustrated in FIG. 3 and in Tables 1 and 2, a pH adjustment 202 process before the nanofiltration 106 process to change the pH a level above 7 allows additional boron to be rejected and reduces the boron that will eventually be retained in the recycle water stream. The boron that is rejected is collected in a boron rich nanofiltration reject stream. This stream may be treated or processed to collect the boron and any calcium, magnesium, or other rejected compounds.

[0076] The pH adjustment 202 may occur before or during the nanofiltration 106 process. For example, the nanofiltration 106 process may include multiple stages. The pH adjustment 202 may occur between two of the multiple stages. For example, the nanofiltration 106 may operate at a lower pH to reject a higher percentage of the calcium and magnesium. Then the pH is adjusted after a first stage to a higher pH to reject a higher percentage of boron.

[0077] In an example, sodium hydroxide or sodium carbonate may be added to the brine to increase the pH. Alternatively, calcium hydroxide or potassium hydroxide may be added to increase the pH. Any other suitable chemicals or processes may be used to increase the pH. In other examples, an acid, such as hydrochloric acid or citric acid may be used to lower a pH in the brine. Any other suitable chemicals or processes may be used to decrease the pH.

[0078] In another example, the pH may be lowered to remove additional calcium and magnesium in a first stage. Then the pH is increased to remove additional boron in a subsequent stage of the nanofiltration 106.

[0079] Returning to FIG. 2, the permeate of the nanofiltration 106 flows to the reverse osmosis 108 system. The pH may remain elevated from the previous pH adjustment 202 or an additional pH adjustment 202 may be performed before the reverse osmosis 108. For example, an additional percentage of sodium hydroxide may be added after the nanofiltration 106 and before the reverse osmosis 108 to increase the pH. The effect of the elevated orDocket No. 1710.00073WO reduced pH on the boron in the reverse osmosis 108 process is discussed in greater detail with respect to FIG. 4.

[0080] FIG. 4 is a graph of a percent rejection of elements in a reverse osmosis 108 process at multiple pH levels.

[0081] As illustrated, at pH levels of 4 to 8, a portion of the boron, approximately 45% to 60%, is rejected. However, at pH levels of 9 or above, the rejection rate increases sharply with a maximum rejection rate of nearly 95% or greater at a pH above 10. By operating the reverse osmosis 108 membrane at a pH of 5, boron is allowed to move through the membrane into the permeate stream while other ions are rejected and kept in the concentrate stream. As pH increases, lower amounts of boron is allowed to pass through the membrane and less boron separation is achieved. All pH levels allowed the reverse osmosis 108 to retain greater than 95% of desirable ions like lithium in the concentrated retentate stream.

[0082] To create FIG. 4, a commercially available 1812 RO membrane was installed in the reverse osmosis. A solution of 0.6% LiCl, 0.2% NaCl, 160 ppm CaCh, 240 ppm MgCh, 690 ppm B(OH)s was charged and the pH was adjusted to 4.0 with dilute hydrochloric acid. The material was allowed to recirculate for 3-10 minutes before taking a sample from the permeate and feed stream. The pH was then adjusted, and the procedure repeated. Parts per million of the elements in the permeate and the reject of the example are provided in Table 3 below for pH levels of 5.

[0083] Docket No. 1710.00073WO

[0084] Table 3: Permeate and reject concentrations at a pH of 5 in reverse osmosis

[0085] As illustrated in FIG. 4, a pH adjustment 202 process before the reverse osmosis 108 process to a level above 9 allows additional boron to be rejected and reduces the boron that will eventually be retained in the recycle water stream. The boron that is rejected is collected in a boron rich reverse osmosis reject stream. This stream may be treated or processed to collect the boron and any calcium, magnesium, or other rejected compounds. The pH adjustment 202 may occur before or during the reverse osmosis process.

[0086] Returning to FIG. 2, the retentate of the reverse osmosis 108 process is a concentrated lithium rich brine. The lithium rich brine flows to one or more additional purification / concentration 110 processes as described in FIG. 1. The permeate of the reverse osmosis 108 is transferred as recycled water to the desorption 104 as described in FIG. 1. However, the recycled water in FIG. 2 has a lower boron content than the recycled water stream of FIG. 1 because the pH adjustment caused a greater amount of boron to be retained by nanofiltration 106 and reverse osmosis 108. The boron is reduced to a level such that a buildup of boron does not occur or occurs more slowly. The reduced boron enables the system to avoid costly and time-consuming boron removal processes, such as with the addition of boron-removing chelating resins.

[0087] FIG. 5 illustrates a general representation of the process using multiple reverse osmosis or nanofiltration processes with a pH adjustment in accordance with one or more embodiments.

[0088] FIG. 5 illustrates an alternative process that uses pH adjustments 202 to improve the removal of boron from the recycled water stream. In FIG. 5, the process flows as described with respect FIG. 1 from adsorption 102 to desorption 104 to nanofiltration 106 to reverse osmosis 108. The concentrated retentate of the reverse osmosis 108 passes to the additional purification / concentration 110 processes as described in FIG. 1.

[0089] However, FIG. 5 includes steps to concentrate the boron salt from the recycled water line returning to the desorption 104 process. As described, the permeate of the first reverse osmosis 108 includes a portion of the boron from the brine. Before the boron containing permeate is returned as a recycle water stream to the desorption 104 process, a second reverse osmosis 502 or second nanofiltration 504 process is used with a pH adjustment 202.Docket No. 1710.00073WO

[0090] In the example, the boron containing permeate from the first reverse osmosis 108 has a pH adjustment 202 similar to the pH adjustment 202 described in FIG. 2. For example, sodium hydroxide may be added to the stream to raise the pH. The stream of boron containing permeate is fed to a second nanofiltration 504 process and / or a second reverse osmosis 502 process. This second filtration process occurs with the pH of the feed raised, such as to 9 or higher. As illustrated in FIG. 3 and FIG. 4, the amount of boron retained by the second nanofiltration 504 process and / or a second reverse osmosis 502 process will be much higher than the amount of boron retained by the first nanofiltration 106 and the first reverse osmosis 108.

[0091] The retained boron may be processed as a concentrated boron salt. The permeate that includes water and the smaller portion of the boron that passes through the filtration process are returned to the desorption 104 process as a recycled water stream. The boron is reduced to a level such that a buildup of boron does not occur. The reduced boron enables the system to avoid costly and time-consuming boron removal processes, such as with the addition of boron-removing chelating resins.

[0092] FIG. 6 illustrates a general representation of the process using multiple reverse osmosis processes with a heat integration process in accordance with one or more embodiments.

[0093] In FIG. 6, the process flows as described with respect FIG. 1 from adsorption 102 to desorption 104 processes. The desorption effluent leaves at an elevated temperature from these initial processing steps. In an example, the desorption effluent leaves at approximately 65 degrees C. In other examples, the desorption effluent leaves at approximately 60-70 degrees C. In other examples, the desorption effluent leaves at approximately 65-80 degrees C.

[0094] The higher temperature desorption effluent is fed to a heat integration 602 process. In an example, the heat integration 602 may be any suitable heat exchange process, such as a shell and tube heat exchanger or a plate heat exchanger. The higher temperature desorption effluent exchanges heat with another stream of the process or an external heating or cooling stream. For example, the higher temperature desorption effluent exchanges heat in the heat integration 602 system with a boron rich stream from the reverse osmosis 606 process that operates at a low temperature and a low pH. This stream is described in greater detail below.

[0095] The higher temperature desorption effluent leaves the heat integration 602 process at a lower temperature than the temperature at which the higher temperature desorption effluentDocket No. 1710.00073WO entered. For example, the higher temperature desorption effluent may leave at 35 degrees C. In other examples, the higher temperature desorption effluent leaves at 30-40 degrees C. In other examples, the higher temperature desorption effluent leaves at 40-50 degrees C. The cooled desorption effluent proceeds to the nanofiltration 106 process. The nanofiltration 106 process operates as described with respect to the nanofiltration 106 in FIG. 1. A small amount of boron (below 5%) is retained by the nanofiltration 106 unit.

[0096] The permeate stream of the nano filtration 106 proceeds to the reverse osmosis 606. The reverse osmosis 606 process operates at a low temperature and a low pH. The low pH of the reverse osmosis 606 allows 40-60% of the boron to pass through as permeate. The low temperature compounds the effect of the low pH to allow an even greater amount of boron to pass through as permeate, such as 50-70%.

[0097] The concentrated retentate of the reverse osmosis 502 passes as a lithium rich brine to the additional purification / concentration 110 processes as described in FIG. 1.

[0098] The boron rich permeate, which is still at a reduced temperature such as 35 degrees C, is transferred back to the heat integration 602 process. As the temperature of the boron rich permeate is cooler (such as 35 degrees C) than the desorption effluent entering the heat integration 602 system (such as 65 degrees C), then boron rich permeate may extract heat from the desorption effluent. In an example, the boron rich permeate exits the heat integration 602 process at 60 degrees C. In other examples, the boron rich permeate exits the heat integration 602 process at 40-60 degrees C or 50-60 degrees C. In other examples, additional heating and cooling components may be used to heat or cool the streams. For example, a chiller with a cooling refrigerant may be used to cool the desorption effluent. Steam or other heating media may be used to heat the boron rich permeate.

[0099] The heated boron rich permeate is transferred to a reverse osmosis 604 process that operates at a high pH and a high temperature. For example, the heated boron rich permeate is treated with a pH adjustment 202 before being fed to the reverse osmosis 604. The reverse osmosis 604 operating at a higher pH retains a higher percentage of the boron as described herein. Further, the elevated temperature of the reverse osmosis 604 allows an even higher percentage of the boron to be retained, such as 98-99%. The permeate of the reverse osmosis 604 is returned as recycled water to the desorption 104 process. The recycled water is substantially free of boron and does not require a purge or other removal of boron to prevent a buildup of boron in the brine loop.Docket No. 1710.00073WO

[0100] FIG. 7 illustrates a general representation of a process using membrane filtration processes on effluent from resin adsorption processes in accordance with one or more embodiments.

[0101] In certain processes as described herein and in conventional systems, users may find a need to use a boron selective adsorption resin to remove boron from a lithium containing process streams. For example, even though the methods and processes described herein remove boron more efficiently and at increased rates than conventional methods, residual boron may still be in the process streams and require removal to produce one or more of LiCl, LiOH, and Li2COs. Processes may use resin adsorption to remove additional quantities of boron. For example, a chelating resin may be used to remove boron from a recycle water stream. The chelating resin may be a polymer with a polyhydroxyl group, such as sorbitol, mannitol, or N-methyl-D-glucamine. After the boron is extracted, a process is needed to regenerate and wash the resin and recover water from the regeneration and wash solutions and / or recover water.

[0102] In the process of FIG. 7, boron containing streams 701 and resin regeneration and wash solutions 702 are provided to a boron removal resin process 704. For example, the boron rich stream 701 contacts the boron removal resin in the boron removal resin process 704. The boron in the stream 701 binds to functional groups in the resin in an ion exchange process. For example, boron ions may be exchanged with hydrogen or sodium on the resin. After the boron is removed by the resin, a boron depleted stream 703 containing lithium exits the boron removal resin process 704. This stream 703 is then converted to one or more of LiCl, LiOH, and Li2CO3- After the boron removal resin is saturated, aqueous solutions of acid and / or base along with dilution water may be introduced to contact the resin to break the bonds between the boron and the resin.

[0103] The boron is removed from the resin. The regeneration and wash solution effluent streams containing the concentrated boron may be subjected to one or more of the processes described herein to remove the boron from the resin effluent stream, recover water, and to further concentrate the boron.

[0104] For example, the pH of the regeneration and wash solution effluent stream may be increased to greater than 7 as described in pH adjustment 202 processes in FIG. 2. A higher pH causes a percentage of boron rejected by the nanofiltration and / or reverse osmosis 706 process to increase as described herein. After the pH adjustment 202, the regeneration and wash solution effluent stream may be subjected to one or more filtration processes in theDocket No. 1710.00073WO membrane filtration 706. For example, in membrane filtration 706, a nanofiltration process and / or a reverse osmosis process may concentrate the boron in the retentate as described herein. Any number or combination of nanofiltration process and / or a reverse osmosis processes may be used.

[0105] The boron containing concentrate / retentate from filtration 706 may be removed and repurposed, disposed of, or otherwise recycled. The low boron permeate of the filtration may then be recycled as recovered water 708. The recovered water 708 may be used for the regeneration of a sorbent material or for any other suitable purpose. For example, the sorbent material regenerated may be the boron selective sorbent, a divalent removal sorbent, or a lithium selective sorbent as may be used for the selective adsorption and isolation of lithium from a brine stream.

[0106] In other examples, the regeneration and wash solution effluent stream may include other materials, such as lithium. The process described in FIG. 7 may further concentrate lithium for recycle or reuse.

[0107] While the present invention has been described in terms of one or more preferred embodiments, it is to be understood that other modifications may be made without departing from the scope of the invention, which is set forth in the claims below.

Claims

Docket No. 1710.00073WOCLAIMSThat which is claimed is:

1. A process to remove boron from lithium-containing process streams, comprising: a. providing a source brine containing lithium and boron; b. processing the source brine in a lithium adsorption step and a desorption step; c. adjusting the pH of a desorption effluent of the desorption step to above 6.0; d. after adjusting the pH, filtering the desorption effluent with one or more of a nanofiltration process and a reverse osmosis process to remove a portion of the boron; and e. returning a low boron permeate of the filtering to the desorption process as a recycled water stream.

2. The process of claim 1, wherein the pH of the desorption effluent is adjusted to a pH of higher than 9.

3. The process of claims 1 or 2, wherein more than 95 percent of the boron is removed from the desorption effluent during the filtration.

4. The process of any of claims 1 to 3, wherein the pH is raised after a first stage of the nanofiltration process but before a second stage of the nanofiltration process.

5. The process of any of claims 1 to 4, further comprising performing purification and concentration processes on a concentrated retentate of the reverse osmosis process to produce one or more of LiCl, LiOH, and Li2CO3.

6. The process of any of claims 1 to 5, wherein at least a portion of the low boron permeate of the filtering is recycled to one or more of stages of the nanofiltration process.

7. A process to remove boron from lithium-containing process streams, comprising: a. providing a source brine containing lithium and boron; b. processing the source brine in a lithium adsorption step and a desorption step; c. filtering a desorption effluent with one or more of a first nanofiltration process and a first reverse osmosis process; d. raising a pH of the permeate of the one or more filtrations; e. after raising the pH, filtering the permeate in one or more of a second nanofiltration process and a second reverse osmosis process; andDocket No. 1710.00073WO f. returning a low boron permeate of the filtering in the one or more of the second nanofiltration process and the second reverse osmosis process to the desorption process as a recycled water stream.

8. The process of claim 7, wherein the pH of the permeate of the filtration is raised to a pH of higher than 9.

9. The process of claim 7 or 8, wherein more than 95 percent of the boron is removed from the desorption effluent during the second reverse osmosis filtration.

10. The process of any of claims 7 to 9, wherein the first nano filtration process is conducted with a pH of lower than 5.

11. The process of any of claims 7 to 10, further comprising performing purification and concentration processes on a concentrated retentate of the first reverse osmosis process to produce one or more of LiCl, LiOH, and Li2CO3.

12. The process of any of claims 7 to 11, wherein at least a portion of the low boron permeate of the second filtering is recycled to one or more of stages of the first or second nanofiltration process.

13. A process to remove boron from lithium-containing process streams, comprising: a. providing a source brine containing lithium and boron; b. processing the source brine in a lithium adsorption step and a desorption step; c. cooling a desorption effluent; d. filtering the cooled desorption effluent with one or more of a first nanofiltration process and a first reverse osmosis process; e. heating a boron rich permeate of the filtration; f. raising the pH of the cooled permeate; g. after raising the pH, filtering the permeate in a second reverse osmosis process; and h. returning a low boron permeate of the filtering in the second reverse osmosis process to the desorption process as a recycled water stream.

14. The process of claim 13, wherein the pH of the permeate of the first reverse osmosis process is raised to a pH of higher than 9.Docket No. 1710.00073WO15. The process of claim 13 or 14, the boron rich permeate of the filtration exchanges heat with the desorption effluent.

16. The process of any of claims 13 to 15, wherein the boron rich permeate of the filtration is heated in a heat exchanger.

17. The process of any of claims 13 to 16, wherein the first reverse osmosis process operates at a temperature below 40 degrees C and at a pH below 5.

18. The process of any of claims 13 to 17, wherein the second reverse osmosis process operates at temperature above 60 degrees C and at a pH above 9.

19. The process of any of claims 13 to 18, wherein the raised temperature of the boron rich permeate processed in the second reverse osmosis process increases an amount of boron retained in the retentate.

20. The process of any of claims 13 to 19, further comprising performing purification and concentration processes on a concentrated retentate of the first reverse osmosis process to produce one or more of LiCl, LiOH, and Li2CO3.

21. A process to remove boron from lithium-containing process streams, comprising: a. providing a stream containing boron; b. processing the stream in a chelating resin process to selectively remove the boron and produce one or more of LiCl, LiOH, and Li2COs; c. adjusting the pH of one or more effluents, the effluents comprising one or more of regeneration, wash solutions, purge solutions, and / or displacement solutions of the chelating resin process to above 7.0; d. after adjusting the pH, filtering the effluent with one or more of a nanofiltration process and a reverse osmosis process to remove a portion of the boron; e. returning a low boron permeate of the filtering as a recycled water stream; and f. collecting concentrated boron in the retentate of the filtering.

22. The process of claim 21, wherein the recycled water stream is returned within a lithium extraction process.

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