Lithium purification process

Abstract

Various embodiments of a lithium purification process are disclosed having a number of innovative features. In some embodiments, the process includes dissolving crystallized lithium carbonate in a brine in a first vessel, passing the solution to a second vessel, and crystallizing the dissolved lithium carbonate in the second vessel. In some embodiments, the brine includes high levels of impurities such as the brine includes at least 3 wt% Na, at least 0.4 wt% K, at least 2.6 wt% Ca, or at least 0.5 wt% Mg. In some embodiments, the solution in the second vessel is recirculated to the first vessel at a high flow rate.

Description

Lithium Purification ProcessTECHNICAL FIELD

[0001] This relates to lithium purification, particularly purification of lithium carbonate or lithium hydroxide for use in batteries.BACKGROUND

[0002] Lithium carbonate (Li2CO3) is used for the production of batteries for portable electronics, vehicles, and the like. This use case accounts for more than 80% of all lithium produced globally and requires as a raw material more than 99% pure lithium carbonate or lithium hydroxide (LiOH) (or related hydrates).

[0003] Lithium carbonate is a feedstock for the production of lithium-ion batteries, in particular, low-cost lithium-iron phosphate batteries. Purity requirements for battery-grade lithium carbonate are exceedingly stringent — requiring purities >99.5%, compared to pharmaceutical-grade purity of only 98%. Conventional processes for the purification of crude lithium are resultantly costly (due to reagent usage, and plant capital expenditure) and involves many discrete steps to remove impurities that naturally occur in lithium brine deposits (e.g., Na, Mg, K, Ca, Si and B, among others).

[0004] Conventional battery-grade lithium carbonate production is costly and involves many steps. Lithium-containing brines are first concentrated from 100’s of ppm to ~6g / L (1 M), in evaporation ponds. The energy cost of water evaporation is mitigated by using the sun’s heat to evaporate water from the brines, but this process takes 18 to 24 months to complete. Impurities are selectively precipitated during evaporation while highly soluble lithium salts remain in solution. Trace impurities that remain are removed with stoichiometric reagents (e.g., calcium hydroxide (Ca(OH)2), sodium oxalate (Na2C2O4)), solvents, or ion exchange resins, then the brine is reacted with sodium carbonate (Na2CO3) or potassium carbonate (K2CO3) to yield crude lithium carbonate (<95%). Water usage is substantial, with 5-50 m3required per ton of lithium carbonate, and an additional reactive crystallization step with carbon dioxide (CO2) is needed to upgrade this technical-grade material for battery applications (99% purity). Conventional methods to exploit high grade brines cost ~$5,580 / ton of lithium carbonate, with reagents contributing -24% of the cost.

[0005] Conventional evaporation-based methods for producing lithium carbonate are incompatible with low-grade brines found in North America. North American brine concentrations vary between 50 and ~800 ppm Li, while high-grade brines located in South America can exceed 1300 ppm Li. The comparatively lower temperatures, and solar irradiance in North America relative to South America reduce the viability of evaporation as a concentration method. It is currently not economical to extract North American lithium brines.

[0006] The accepted minimum cost for producing “technical grade” (< 95% purity) lithium carbonate from the best South American salar brine is about $3,000 / tonne. Upgrading this technical grade material to battery grade adds at least $1,000- $2,000 / tonne to the minimum cost. Reducing the cost of purification could render North American lithium reserves cost-competitive with established South American brine operations.GENERAL DESCRIPTION

[0007] The subject matter described in this document and recited in the claims represents a technological improvement to processes for purifying lithium, especially those capable of achieving lithium purity levels required for use in batteries. In general, the process is simpler and more cost effective than conventional lithium purification processes.

[0008] The lithium purification process can include a number of steps. In some embodiments, a lithium purification process includes techniques for carbonating and refining aqueous lithium feeds to generate high-purity lithium carbonate (Li2CO3) suitable for batteries. The lithium purification process can include a variety of methods for softening lithium chloride (LiCl) feeds to produce a brine including crude lithium carbonate.

[0009] In some embodiments, the lithium purification process includes a lithium carbonate recrystallization technology that produces battery-grade lithium carbonate (99.9 wt%) from crude lithium carbonate (20-95 wt%) in a single step, using a simple two-vessel continuous-loop crystallization process. This technology reduces the requirement for pre-processing of crude lithium feeds and is designed to simplify plant design for lithium carbonate purification.

[0010] There are a number of ways to reduce the cost of lithium extraction including, for example: i) decreasing the amount that brines must be concentrated prior to carbonation and / or ii) reducing the amount of reagents used in the feed purification process, or the number of purifications required. In some embodiments, the lithium purification process reduces the amount of reagents used in the purification process. In particular, the lithium purification process can include a lithium carbonate recrystallization technology designed for purifying crude lithium carbonate produced from low-grade brines, such as those found in North America. One purpose of this technology is to reduce the feed purification burden, thereby reducing plant footprint, reagent utilization, and increasing product throughput.

[0011] In some embodiments, the lithium purification process is a continuous recrystallization process having a set of operating conditions that enables low quality lithium carbonate (<20% purity) to be purified to battery grade in a single step. In some embodiments, the lithium purification process includes a recrystallization — thedifferential temperature between reactors is the driving force for crystallization. In some embodiments, the lithium purification process uses ammonium carbonate as a softening agent to produce crude lithium carbonate from lithium chloride brines. Carbon dioxide used to make the ammonium carbonate solution can be sourced from industrial waste products.

[0012] In some embodiments, a lithium purification process includes: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein a temperature of the first solution in the first vessel is more than 40°C and / or a temperature of the second solution in the second vessel is more than 65°C.

[0013] In some embodiments, a lithium purification process includes: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying at least a portion of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein the brine includes at least 3 wt% Na, at least 0.4 wt% K, at least 2.6 wt% Ca, or at least 0.5 wt% Mg. The brine can also include no more than 25 wt% Na and / or no more than 10 wt% Ca. In some embodiments, all or substantially all the Na, K, Ca, Mg, and Li in the brine are dissolved in the first solution.

[0014] In some embodiments, a lithium purification process includes: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein the amount of the second solution is conveyed from the second vessel to the first vessel at a flow rate that is: (i) at least 1% of a total volume of the first vessel and the second vessel per minute and / or (ii) at least the same as an overall mass flow rate of crystallization.

[0015] In some embodiments, a lithium purification process includes: reacting a lithium feed and carbon dioxide to form a softened brine including solid lithiumcarbonate, the lithium feed including lithium hydroxide and / or an alkaline solution of lithium chloride; conveying the softened brine to a first vessel; dissolving the solid lithium carbonate in the softened brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel.

[0016] In some embodiments, a lithium purification process includes: reacting a lithium feed and a carbonate source to form a softened brine including solid lithium carbonate, the carbonate source being formed by reacting a hydroxide and carbon dioxide; conveying the softened brine to a first vessel; dissolving the solid lithium carbonate in the softened brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel.

[0017] The general description is provided to give a general introduction to the described subject matter as well as a synopsis of some of the technological improvements and / or advantages it provides. The general description and background are not intended to identify essential aspects of the described subject matter, nor should they be used to constrict or limit the scope of the claims. For example, the scope of the claims should not be limited based on whether the recited subject matter includes any or all aspects noted in the general description and / or addresses any of the issues noted in the background.DESCRIPTION OF DRAWINGS

[0018] The preferred and other embodiments are described in association with the accompanying drawings in which:

[0019] Fig. 1 is a process flow diagram of one embodiment of a lithium purification process.

[0020] Fig. 2 is a process flow diagram showing one embodiment of a lithium continuous preferential crystallization (Ei-CPC) process. Ei-CPC reduces reagent usage, and is more impurity tolerant than conventional lithium refining.

[0021] Fig. 3 is a block flow diagram of one embodiment of a lithium chloride feed softening process using sodium carbonate.

[0022] Fig. 4 is a block flow diagram of one embodiment of a lithium chloride feed softening process using ammonium carbonate.

[0023] Fig. 5 is a block flow diagram of one embodiment of a lithium chloride feed softening process using carbon dioxide.

[0024] Fig. 6 is a plot of Mg, Li, and Ca solution concentrations of a lithium chloride brine during a softening process. The plot shows the concentration of Mg impurity in solution decreases with heating while Ca precipitates upon addition of sodium carbonate.

[0025] Fig. 7 shows lithium carbonate formation data in the form of turbidity (turbidity and crystal morphology) in the softening stage of the crystallization process.

[0026] Fig. 8 shows lithium carbonate formation data in the form of crystal morphology in the softening stage of the crystallization process.

[0027] Fig. 9 is a bar graph showing the maximum lithium carbonate yield predicted by a model at various lithium concentrations. The upper horizontal axis represents the lithium concentration (before crystallization) of a solution generated from mixing lithium chloride with the ammonium hydroxide / carbon dioxide solution. The lower axis represents the lithium concentration in the original input lithium chloride feed solution (assuming the lithium chloride solution and the ammonium hydroxide / carbon dioxide solution are mixed in a 1:1 ratio).

[0028] Fig. 10 is a block flow diagram of the lithium chloride softening process using ammonium carbonate. NH4C1 is removed through evaporative crystallization from the mother liquor.

[0029] Fig. 11 is a block flow diagram illustrating the conversion of a crude lithium chloride or sulfate feed into battery grade lithium carbonate. The Li-CPC technology purifies crude lithium carbonate (more than 20 wt%) to battery grade material through a two-reactor recirculating reactor.

[0030] Figs. 12A-12B are block flow diagrams illustrating the conversion of a crude lithium chloride or sulfate feed into battery grade lithium carbonate. The Li-CPC technology purifies crude lithium carbonate (more than 20 wt%) to battery grade material through a two-reactor recirculating reactor.

[0031] Figs. 13-14 are in-situ microscopy images of the lithium carbonate crystals formed in the hot reactor during the recrystallization. Fig. 13 is from the earlier stages of crystallization. Fig. 14 is from the end of the crystallization.DETAILED DESCRIPTION OF EMBODIMENTS

[0032] Lithium extraction is a set of chemical processes where lithium is isolated from a sample and converted into a saleable form that is generally stable yet readilyconvertible such as lithium carbonate (Li2CO3). Lithium extraction begins by removing lithium from a lithium source and forming a crude brine. Brines having a low concentration of lithium (e.g., 100s of ppm of lithium) are concentrated to increase lithium levels, and impurities are removed by chemical softening, ion exchange, solvent extraction, or a combination thereof. The lithium is softened to convert various lithium salts to lithium carbonate, which is then purified.

[0033] Fig. 1 shows a block diagram of one embodiment of the lithium purification process. It should be appreciated that the process can exclude some of the steps and / or include additional steps.

[0034] The process begins with a lithium source 100. It should be appreciated that any suitable lithium source can be used for the lithium extraction process. Pure elemental lithium is not found in nature because of its high reactivity. Instead, lithium is present as a constituent of salts (e.g., lithium chloride (LiCl)) or other compounds. Lithium salts can be found in underground deposits of brine, mineral ore, and clay, as well as in seawater and geothermal well brines / water. Most lithium extraction processes entail some form of mining to reach underground deposits of lithium-rich minerals or brines.

[0035] While lithium is relatively abundant both on land and in the sea, lithium occurs in very low concentrations, and only concentrates in brines or ores under specific geological conditions. Only a few sources, primarily in Australia and South America, are currently considered economically viable. The lithium extraction landscape will change as new technologies such as those described in this document make extraction from alternative lithium sources more cost-competitive.

[0036] The lithium source 100 undergoes lithium feed pre-processing 102 to concentrate the lithium and remove impurities. The crude brine can be processed using any suitable method to make it suitable for the lithium purification technology described as follows. Although there is no hard line of demarcation, it is generally the case that pre-processing refers to those steps taken before the brine is softened. This can include processes such as concentration (e.g., solar evaporation, thermal evaporation, or reverse osmosis), filtration, ion-exchange, solvent extraction, chemical treatment, and the like.

[0037] The pre-processed lithium then undergoes lithium feed softening 104. In the softening step 104, the lithium salts are reacted with various reactants to convert them to lithium carbonate. Suitable softening processes include reacting with sodium carbonate, ammonium carbonate, or carbon dioxide. Example 2 describes various lithium feed softening processes that can be used.

[0038] After softening 104, the lithium carbonate undergoes a crystallization process 106 to achieve a high purity product. A preferred crystallization method is acontinuous preferential crystallization (Li-CPC) process using two vessels. The crude lithium carbonate is dissolved in a first vessel, pumped to a second vessel to crystallize purified lithium carbonate, with the depleted solution recirculated back to the first vessel to dissolve more crude lithium carbonate. The temperature of the vessels and recirculation flow rate are controlled to provide greater than 99.5% purity lithium carbonate.

[0039] The first vessel can be maintained at a temperature of more than 40°C, more than 60°C, or more than 75°C. The second vessel can be maintained at a temperature of more than 65°C, more than 75°C, or more than 80°C. The temperature of the second vessel is preferably at least 5°C higher than the temperature of the first vessel or at least 10°C higher than the first vessel. The temperature differential between the first and second vessels provides the driving force for crystallization of the lithium carbonate in the second vessel.

[0040] The amount of the second solution conveyed from the second vessel to the first vessel can be recirculated at various flow rates. In some embodiments, the recirculation flow rate is at least 1% of the total volume of the first vessel and the second vessel per minute, at least 2% per minute, or at least 5% per minute (or 5 30%, no more than 30%, and the like). The higher recirculation flow rates can enable faster replenishment of the lithium carbonate in the first vessel, higher overall throughput, and improved impurity removal.

[0041] In some embodiments, the recirculation flow rate is at least the same as the overall mass flow rate of crystallization in the second vessel or more than the overall mass flow rate of crystallization, for example at least 3% more, at least 5% more, or at least 10% more.

[0042] In some embodiments, the first vessel and / or the second vessel can be replaced by multiple vessels positioned in parallel. For example, the first vessel can be replaced by two vessels piped in parallel to each other. Likewise, the second vessel can be replaced by two vessels piped in parallel to each other and in series to the first vessels.

[0043] The output of the crystallization 106 is purified lithium carbonate 108 suitable for use in manufacturing lithium ion batteries. Compared to conventional lithium purification methods, this process is simpler, higher yielding, and more tolerant of impurities in the input lithium source.Examples

[0044] The following examples are provided to further illustrate the disclosed subject matter. They should not be used to constrict or limit the scope of the claims in any way.Example 1 — Process Overview

[0045] The process begins with a suitable lithium source, which optionally undergoes pre-processing and softening. The final step in the lithium extraction process is crystallization, converting crude lithium carbonate (Li2CO3) to battery-grade material.

[0046] Crystal formation is carefully controlled to produce high quality crystals, while excluding impurities from the crystals. If the solution is too dilute, few crystals form, and mass recovery is low. By contrast, if the concentration is high, then rapid nucleation causes impurities to be trapped in the crystal. The small difference in lithium carbonate solubility between hot and cold solutions (13 g / L at 20°C vs 8.6 g / L at 80°C in water; lithium carbonate exhibits inverse solubility) results in a maximum theoretical yield of only 34% through a single batch crystallization process (starting from a saturated solution at 20°C and heating to 80°C). The lithium purification process described in the examples below allows higher yields by coupling two reactors — a first or dissolving vessel or decanter and a second or crystallization vessel or decanter. Recycling the feed through each of the reactors produces yields of at least 75%.

[0047] The lithium purification process uses continuous preferential crystallization (CPC) to purify crude lithium carbonate isolated from lithium containing brines. CPC is a process used to separate mixtures of chemicals with similar solubilities. CPC works by separating the dissolution and crystallization of the crude material into two reactors. Dissolution of the crude mixture is carried out in the first reactor, then the saturated solution flows to a second reactor where it is cooled (or heated) to drive the solution into supersaturation. Seeding the supersaturated mixture drives crystallization of the desired product.

[0048] Fig. 2 is a process flow diagram of a lithium continuous preferential crystallization process (Li-CPC). The use of a second re -crystallizing reactor dramatically increases the impurity tolerance of the crystallization process under the processing conditions, enabling 20% input material to be purified to at least 99.9%. In comparison, a typical metallurgical crystallization process using a single reactor, mixed-suspension mixed product removal (MSMPR) process is highly dependent on the purity of the feed solution to achieve acceptable results. Another notable advantage of the lithium purification process is that there are no additional reagents that must be added during the purification step.Example 2 — Lithium Feed Softening

[0049] Softening converts the lithium chloride or lithium sulphate feedstock to lithium carbonate. This simple metathesis reaction replaces the chloride / sulfate ion with a carbonate, precipitating the insoluble lithium carbonate product. This processcan be controlled through seeding, reaction temperature, and concentration to reject a portion of the impurities present in the feed from the crude lithium carbonate product. Crystal sizes of at least 50 microns are targeted to facilitate filtration and isolation. Figs. 3-5 are block diagrams showing different methods of lithium chloride softening. Three distinct softening methods are described in this document:A. Softening with Sodium Carbonate (Na2C03)

[0050] This approach to softening uses mined sodium carbonate as the carbonate source, producing soluble sodium chloride (NaCl) or sodium sulfate (Na2SO4) as the reaction byproduct according to equation 1-2 below:Na2CO3(aq) + 2LiCl(aq) -> Li2CO3(s) + 2NaCl(aq) [1]Na2CO3(aq) + Li2SO4(aq) -> Li2CO3(s) + Na2SO4(aq) [2]

[0051] Lithium chloride brine containing Na, Mg, and Ca impurities is softened with sodium carbonate to produce crude lithium carbonate as input for the Li-CPC process. The softening process is monitored with online ion chromatography (IC) and an online turbidity to monitor the lithium carbonate precipitation, as well as removal of Mg and Ca impurities (Fig. 6).

[0052] Sodium carbonate is added to accommodate 1.4 molar equivalents of carbonate with respect to all carbonate forming solids (i.e., magnesium carbonate (MgCO3), calcium carbonate (CaCO3), and lithium carbonate), sufficient to precipitate all carbonate forming solids The addition of sodium carbonate precipitates crude lithium carbonate and calcium carbonate immediately, forming a slurry. The concentration of dissolved Li+and Ca2+ions decreases accordingly, as measured by IC (Fig. 6). However, Mg2+concentration increases slightly during softening because Mg is an impurity in the industrial grade sodium carbonate salt used to soften the brine. Nevertheless, the magnesium and calcium levels as measured by online IC remain below 15 ppm at the end of the softening process.

[0053] Softening the lithium chloride with sodium carbonate shows that high sodium concentrations solubilize lithium carbonate through the diverse ion effect. Sodium thereby reduces the yield of lithium carbonate because solubilized lithium remains dissolved and is therefore lost during filtration. Sodium carbonate is mined, shipped, and the carbonate ion is released as carbon dioxide with exposure to acid during battery manufacturing. Although softening lithium chloride with sodium carbonate is acceptable, it would be preferable to eliminate the use of sodium salts in the softening step, and source carbonate from carbon dioxide to reduce carbon dioxide emissions associated with softening lithium chloride or sulfate brines.B. Softening with Ammonium Carbonate ((NH4)2CO3)

[0054] This approach involves softening lithium chloride brines with non-sodium carbonate salts. A sodium-free softening solution is prepared by reacting carbon dioxide gas with aqueous ammonium hydroxide (NH40H) to form ammonium carbonate. Lithium chloride solutions are softened with ammonium carbonate to produce the lithium carbonate product according to equations 3-7 below:NH3(aq) + H2O(1) NH4OH(aq) [3]CO2(g) CO2(aq) [4]C O2(aq) + H2O (1) H2C O3(aq) [5]2NH4OH(aq) + H2CO3(aq) (NH4)2CO3(aq) + 2H2O(1) [6](NH4)2CO3(aq) + 2LiCl(aq) Li2CO3(s) + 2NH4Cl(aq) [7]

[0055] The lithium chloride feed is softened as follows. An ammonium hydroxide / carbon dioxide solution is prepared by bubbling carbon dioxide into a 12 M ammonium hydroxide solution. The amount of carbon dioxide is added until total carbon concentration reached 4 M. The ammonium hydroxide / carbon dioxide solution is added slowly to the concentrated lithium chloride solution to avoid high levels of supersaturation, which can cause fouling of the reactor. The volume ratio of ammonium hydroxide / carbon dioxide solution to lithium chloride solution is chosen such that the lithium, carbon, and nitrogen concentrations provides the highest yield. For example, 4.5 M total nitrogen, 1.5 M total carbon, and 17,000 mg / L lithium achieved a high yield. Solid formed almost immediately as the ammonium hydroxide / carbon dioxide solution is dosed into the lithium chloride solution, and turbidity in the solution increased steadily throughout the addition (Figs. 7-8). The temperature of the reactor is then increased from 25°C to 70°C to drive the crystallization to completion. The crude solid is isolated by filtration and washed with water.

[0056] A 71% yield of the lithium from the original lithium chloride solution is isolated as the crude lithium carbonate solid, which formed as particles around 100 microns in diameter. This material is highly filterable and is low in impurities. However, recrystallization may be needed to remove B, Na, Ca, and Mg.

[0057] Lithium chloride solutions below -5,000 mg / L lithium results in less than a 20% yield, regardless of the concentration of carbon and nitrogen used. It should be noted that if a 1:1 mixture of lithium chloride solution with the ammonium hydroxide / carbon dioxide solution is assumed, then this 5,000 mg / L lithium mixed solution would correspond to a 10,000 mg / L lithium solution of lithium chloride feed going into the softening process. The low yield at this lithium concentration is consistent with what has been reported in the literature, where others have found thatsimilar lithium concentrations gave low yields of lithium carbonate using carbon dioxide and ammonium hydroxide to soften lithium chloride. Increasing the lithium chloride concentration results in higher yields, with a general preference in most cases for higher concentrations of nitrogen in the carbonating solution (see Fig. 9).

[0058] The concentration of carbon needed for the highest yield is between 1 and 2 mol / L; concentrations of carbon above this range are associated with increased speciation of bicarbonate, which negatively impacts the yield. To recover 50% of the lithium from the lithium chloride solution, the lithium concentration in the mixed solution should be around 10,000 mg / L (corresponding to 20,000 mg / L lithium in the lithium chloride feed). At lithium concentrations around 24,000 mg / L in the mixed solution, yields of up to 80% can be attained. The optimized ammonium carbonate softening process block flow diagram is provided in Fig. 10.

[0059] The primary challenge identified with this softening approach is the increased solubility of lithium carbonate in the concentrated ammonium chloride matrix. The lithium concentration in the feed solution resultantly is increased from -5000 mg / L to 42,000 mg / L to achieve a yield of at least 70% in a single pass.C. Softening with Carbon Dioxide (C02)

[0060] This approach to brine softening involves directly adding carbon dioxide to alkaline solutions of lithium chloride (LiCl), or lithium hydroxide (LiOH). Controlled crystallization of lithium carbonate can be achieved with sparging of carbon dioxide into lithium hydroxide brines from electrodialysis effluent, or produced from pH adjusting a lithium chloride feed. This approach is demonstrated for brines ranging in concentration from 10 g / L up to 25 g / L lithium. The feeds are either lithium hydroxide, or lithium chloride that is pH-adjusted with NaOH (to a concentration of -2 g / L Na).Procedure (lithium hydroxide feed):

[0061] 100 ml of aqueous lithium hydroxide solution (25 g / L lithium) is added to a thermostated reactor vessel with overhead stirring (Rushton turbine impeller, 500 rpm). The solution is heated to 70°C and the temperature is held throughout the duration of the crystallization. 100 mg of lithium carbonate seed crystals are added to the stirring solution. Carbon dioxide gas is added to the stirring solution via a dip tube placed as close to the impeller as possible at a flow rate of 5 SCCM. Carbon dioxide dosing is carried out for 60 hours and the turbidity of the slurry is monitored. After 60 hours, the turbidity readings began to level off and then decrease. The solid is isolated by filtration to afford 90% of the total amount of lithium available in the feed recovered as lithium carbonate.Table 1 — Lithium hydroxide feed compositionTable 2 — Washed lithium carbonate composition produced from carbon dioxidesparged lithium hydroxideExample 3 — Lithium Continuous Preferential Crystallization Process

[0062] Crude lithium carbonate is recrystallized by first loading crude lithium carbonate into the dissolving reactor. Water is added to the crude material to slurry the solid, and the dissolver is heated to a temperature 10-90°C (impurity rejection is highest when the temperature of the dissolving reactor is at least 60°C). A block flow diagram of the process is shown in Fig. 11.

[0063] Crude lithium carbonate dissolves, and the lithium saturated water is pumped to the crystallizing reactor, set at a temperature at least 10°C higher than the temperature of the dissolving reactor. This temperature differential and the flow rate of saturated solution set the driving force for the crystallization. The saturated solution is seeded with pure lithium carbonate (no more than 0.1 wt% of the solution) to initiate crystallization. The lithium depleted solution is pumped back to the dissolving reactor to dissolve additional crude lithium carbonate. The flow of lithium saturated solution to the crystallizer, and lithium depleted solution to the dissolver is continuous.

[0064] Crystallization is monitored online using a variety of process analytical technologies (PATs). Figs. 12A-12B illustrate the conversion of crude lithium chloride into battery grade lithium carbonate using two recycling reactors — e.g., a first, cold, or dissolving reactor and a second, hot, or crystallizing reactor. At location A in Fig. 12A, the hot reactor turbidity increases indicating that lithium carbonate crystallization has begun. At location B, the cold reactor turbidity decreases as solid crude lithium carbonate dissolves to replenish the solution with Li+(aq). At location C in Figs. 12A- 12B, the cold reactor turbidity reaches zero or approximately zero indicating that all the crude lithium carbonate has dissolved. At location D, the Li+(aq) concentrationdecreases sharply because there is no more crude lithium carbonate to replenish the solution. At location E in Fig. 12A, the turbidity and lithium ion concentration in the hot reactor have reached equilibrium indicating the reaction is complete.

[0065] In-situ microscopy images allowed for the evaluation of crystal quality throughout the crystallization process. Real-time imaging of the solid phase also enabled primary nucleation of lithium carbonate and control crystal growth to be monitored. Dissolved metal ion concentrations are monitored by online ion chromatography (IC) during the crystallization process using an autosampler. The steady readout of ion concentrations in real time allow the user to make process decisions in real time, informing decision making such as when solid product should be isolated. Throughout the crystallization process, turbidity measurements are recorded in both reactors to monitor the progress of solid dissolution and crystallization in the cold and hot reactors with a webcam and EasyViewer, respectively. The reprocessed lithium carbonate crystallized as narrow needles, as is typical for lithium carbonate produced via the recrystallization process described in this document (see Figs. 13-14).

[0066] Crude lithium carbonate from a variety of sources is recrystallized to demonstrate the versatility of the technology. Table 1 below summarizes the results from a selection of these experiments:Table 3 — Concentration and purity of input lithium carbonate, and purified output material.Example 4 — Comparison to Conventional Process

[0067] The process described in US Pat. App. Pub. No. 2017 / 0113942 (’942 publication) is tested using high concentration lithium chloride solutions (20,000 mg / L to 70,000 mg / L Li). With this high concentration solution, it is possible to recover 60% of the lithium as lithium carbonate solid. High concentrations of lithium are found to increase the process yield. In comparison, the lithium purification process described in this document can achieve >60% yields with initial lithium concentrations of 25,000 mg / L, and >80% with 50,000 mg / L starting solutions.

[0068] It should also be noted that the lithium purification process described above uses a different source of carbon dioxide than the ’942 publication. The source of carbon dioxide reported in the ’942 publication is limestone (CaCO3). The limestone is calcined into quicklime (CaO) thereby releasing carbon dioxide that is then fed into the ammonia solution. The quicklime is treated with water to generate slaked lime (Ca(OH)2).

[0069] It should also be noted that the lithium purification process described above treats the ammonium chloride (NH4C1) byproduct differently than the ’942 publication. In the ’942 publication, slaked lime from the carbon dioxide generation process is reacted with ammonium chloride to regenerate ammonia (NH3) gas and produce calcium chloride (CaCl2), which is removed from the process as a solid. In the lithium purification process described above, the ammonium chloride is removed through crystallization. The ammonium chloride is concentrated to supersaturation and the solid is removed from the system.Example 5 — Advantages of the Lithium Purification Process

[0070] The lithium purification process described in U.S. Pat. App. Pub. No. 2021 / 0180153 (the ’153 publication) is the first conceptualization of continuous recrystallization for refining lithium carbonate. The lithium purification process described herein represents an advance compared to that described in the ’153 publication because the continuous recrystallization purification technology has higher flexibility, increased recovery efficiency, broader operating conditions, and / or modified reactor architecture.Flexibility

[0071] The lithium purification process can process a wider range of brine compositions than lithium recrystallization methods such as the process described in the ’153 publication. The ’153 publication describes a brine composition of 0.1-6 wt% Li; 0.1-3 wt% Na; 0.001-0.4 wt% K; 0.01-2.6 wt% Ca; 0.01-0.5 wt% Mg. The lithium purification process using Li-CPC can process brines having a composition of: 0.1-18 wt% Li; 0-10 wt% Na; 0-4 wt% K; 0-20 wt% Ca; and / or 0-3 wt% Mg. The wide operating window of the lithium purification process allows processing of brine inputs having impurity concentrations that change over time. This is challenging for conventional processes because the impurity profile of the brine defines the solubility of the lithium carbonate productRecovery Efficiency

[0072] The lithium purification process can achieve up to a 76% recovery yield (or at least 50-76% recovery) with a throughput ranging from 5-400 mg / mL / h.Operating Conditions

[0073] The lithium purification process operates with the highest throughput and product purity with; i) high flow rate between the reactors, ii) dissolver temperature of at least 75°C, and iii) crystallizer temperature of at least 80-95°C. Notably, these conditions contrast with those reported in the ’153 publication, which describes cold reactor temperatures of no more than 40°C, and crystallizer temperatures below 65°C. Indeed, the ‘153 publication teaches that the dissolver temperature is more preferable between 10°C and 20°C, where lithium carbonate has its highest solubility. In contrast, the process described in this document shows the highest throughput and product purity at higher dissolver temperatures where lithium carbonate has lower solubility. In particular, magnesium is rejected most effectively from the product when dissolver temperatures exceed 60°C, and most preferably, when above 75°C.

[0074] A high flow rate between the reactors (5-20% of total reactor volume per minute), enables high Mg removal, which is counterintuitive to conventional crystallization methodology where a higher flow rate increases the crystallization rate at the detriment of product purity. By way of comparison, we found that 65% Mg was removed using a low flow rate, and 91% Mg removed using a high flow rate. The high flow rates of the present process are in distinct contrast to the ‘153 publication which teaches that the maximum flow rate is less than or equal to the rate of crystallization.

[0075] Mg removal can also be increased by adding small amounts of NaOH sufficient to adjust the pH to values to at least 10. This high pH environment precipitates MgOH-MgCO3salts that sequester the Mg impurity in the dissolving crystallizer.Reactor Architecture

[0076] The lithium purification process establishes the viability of refining highly impure carbonates using as few as two reactors, subject to certain operating conditions. This is contrary to the description in the ’153 publication, which suggests that a series of multiple reactors are needed to process brines of diminishing purity.Illustrative Embodiments

[0077] The following is a description of various embodiments of the disclosed subject matter. Each embodiment may include one or more of the various features, characteristics, or advantages of the disclosed subject matter. The embodiments are intended to illustrate a few aspects of the disclosed subject matter and should not be considered a comprehensive or exhaustive description of all possible embodiments.

[0078] Pl. A lithium purification process comprising: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate;conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein a temperature of the first solution in the first vessel is more than 40°C and / or a temperature of the second solution in the second vessel is more than 65°C.

[0079] P2. The lithium purification process of Pl wherein the temperature of the first solution in the first vessel is at least 60°C.

[0080] P3. The lithium purification process of any one of Pl to P2 wherein the temperature of the second solution in the second vessel is at least 75°C.

[0081] P4. The lithium purification process of any one of Pl to P3 wherein the temperature of the second solution in the second vessel is at least 5°C higher than the temperature of the first solution in the first vessel.

[0082] P5. The lithium purification process of any one of Pl to P4 wherein the temperature of the first solution in the first vessel is at least 60°C and the temperature of the second solution in the second vessel is at least 10°C higher than the temperature of the first solution in the first vessel.

[0083] P6. The lithium purification process of P5 wherein the temperature of the first solution in the first vessel is at least 75°C.

[0084] P7. The lithium purification process of any one of Pl to P6 wherein the brine includes at least 3 wt% Na, at least 0.4 wt% K, at least 2.6 wt% Ca, or at least 0.5 wt% Mg.

[0085] P8. The lithium purification process of any one of Pl to P7 wherein the lithium purification process does not include any other vessels that dissolve lithium carbonate at a different temperature than the first vessel.

[0086] P9. The lithium purification process of any one of Pl to P8 wherein the lithium purification process does not include any other vessels that crystallize lithium carbonate at a different temperature than the second vessel.

[0087] P10. The lithium purification process of any one of Pl to P9 wherein the amount of the second solution is continuously conveyed from the second vessel to the first vessel at a flow rate of at least 1% of a total volume of the first vessel and the second vessel per minute.

[0088] Pll. The lithium purification process of any one of Pl to P10 wherein the amount of the second solution is continuously conveyed from the second vessel to the first vessel at a flow rate that is at least the same as the overall mass flow rate of crystallization.

[0089] P12. The lithium purification process of any one of Pl to Pll wherein the brine is a softened brine, the lithium purification process comprising reacting a lithium feed and carbon dioxide to form the softened brine, the lithium feed including lithium hydroxide and / or an alkaline solution of lithium chloride.

[0090] P13. The lithium purification process of any one of Pl to P12 wherein the brine is a softened brine, the lithium purification process comprising reacting a lithium feed and a carbonate source to form the softened brine, the carbonate source being formed by reacting a hydroxide and carbon dioxide.

[0091] P14. A lithium purification process comprising: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying at least a portion of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein the brine includes at least 3 wt% Na, at least 0.4 wt% K, at least 2.6 wt% Ca, or at least 0.5 wt% Mg.

[0092] P15. The lithium purification process of P14 wherein the brine includes at least one of the Na, K, Ca, or Mg in an amount that is at least 5% more than that recited in P14.

[0093] P16. The lithium purification process of P14 wherein the brine includes at least one of the Na, K, Ca, or Mg in an amount that is at least 5-500% more than that recited in P14.

[0094] P17. A lithium purification process comprising: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein the amount of the second solution is continuously conveyed from the second vessel to the first vessel at a flow rate that is: (i) at least 1% of a total volume of the first vessel and the second vessel per minute and / or (ii) at least the same as an overall mass flow rate of crystallization.

[0095] P18. The lithium purification process of P17 wherein the flow rate is at least2% of the total volume of the first vessel and the second vessel per minute.

[0096] P19. The lithium purification process of any one of P17 to P18 wherein the flow rate is at least 5% of the total volume of the first vessel and the second vessel per minute.

[0097] P20. The lithium purification process of any one of P17 to P19 wherein the flow rate is more than the overall mass flow rate of crystallization.

[0098] P21. The lithium purification process of any one of P17 to P20 wherein the flow rate is at least 3% more than the overall mass flow rate of crystallization.

[0099] P22. The lithium purification process of any one of P17 to P21 wherein the flow rate is at least 5% more than the overall mass flow rate of crystallization.

[0100] P23. The lithium purification process of any one of P17 to P22 wherein the flow rate is at least 10% more than the overall mass flow rate of crystallization.

[0101] P24. A lithium purification process comprising: reacting a lithium feed and carbon dioxide to form a softened brine including solid lithium carbonate, the lithium feed including lithium hydroxide and / or an alkaline solution of lithium chloride; conveying the softened brine to a first vessel; dissolving the solid lithium carbonate in the softened brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel.

[0102] P25. The lithium purification process of P24 wherein reacting the lithium feed and the carbon dioxide includes bubbling the carbon dioxide in the lithium feed.

[0103] P26. A lithium purification process comprising: reacting a lithium feed and a carbonate source to form a softened brine including solid lithium carbonate, the carbonate source being formed by reacting a hydroxide and carbon dioxide; conveying the softened brine to a first vessel; dissolving the solid lithium carbonate in the softened brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel.

[0104] P27. The lithium purification process of P26 wherein the hydroxide includes ammonium hydroxide.

[0105] P28. The lithium purification process of any one of P26 to P27 wherein the carbonate source includes ammonium carbonate.General Terminology and Interpretative Conventions

[0106] Articles such as “the,” “a,” and “an” shall be interpreted as connoting the singular or plural. Also, the word “or” when used without a preceding “either” (or other similar language indicating that “or” is unequivocally meant to be exclusive - e.g., only one of x or y, etc.) shall be interpreted to be inclusive (e.g., “x or y” means one or both x or y).

[0107] The term “and / or” shall also be interpreted to be inclusive (e.g., “x and / or y” means one or both x or y). In situations where “and / or” or “or” are used as a conjunction for a group of three or more items, the group shall be interpreted to include one item alone, all the items together, or any combination or number of the items.

[0108] The phrase “based on” shall be interpreted to refer to an open set of conditions unless unequivocally stated otherwise (e.g., based on only a given condition). For example, a step described as being based on a given condition can be based on the recited condition and one or more unrecited conditions.

[0109] The term “can,” when used as an auxiliary verb, shall refer to an optional or noncompulsory capability of the described subject matter that is not required to be present in any given embodiment.

[0110] The terms have, having, contain, containing, include, including, and characterized by shall be interpreted to be synonymous with the terms comprise and comprising — i.e., the terms are inclusive or open-ended and do not exclude additional unrecited subject matter. The use of these terms shall also be understood as disclosing and providing support for narrower alternative embodiments where these terms are replaced by “consisting of,” “consisting of the recited subject matter plus impurities and / or trace amounts of other materials,” or “consisting essentially of.”

[0111] Certain features described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described in certain combinations and even initially claimed as such, one or more features from a claimed combination can be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0112] Many aspects or features are described as being optional, e.g. through the use of the term “can” or otherwise. For the sake of brevity and legibility, this document does not explicitly recite each combination and / or permutation that may be obtained by choosing from the set of optional aspects or features. However, this document is to be interpreted as explicitly disclosing all such combinations and / or permutations. Forexample, something described as having three optional aspects may be embodied in seven different ways, namely with only one of the three aspects, with any two of the three aspects, or with all three of the aspects.

[0113] Any methods described in this document should not be interpreted to require the steps to be performed in a specific order unless expressly stated otherwise or doing so is literally impossible. The methods should also be interpreted to provide support to perform the recited steps in any sequence unless expressly stated otherwise.

[0114] The example configurations described in this document do not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” shall be interpreted to mean “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.”

[0115] Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, or the like, used in the specification (other than the claims) are understood to be modified in all instances by the term “approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should be construed in light of the number of recited significant digits and / or by applying ordinary rounding techniques.

[0116] All disclosed ranges are to be understood to encompass and provide support for claims that recite any subranges or any individual values subsumed by each range. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any subranges or individual values that are between and / or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth), which values can be expressed alone or as a minimum value (e.g., at least 5.8) or a maximum value (e.g., no more than 9.9994).

[0117] All disclosed numerical values are to be understood as being variable from 0- 100% in either direction and thus provide support for claims that recite such values (either alone or as a minimum or a maximum - e.g., at least <value> or no more than <value>) or any ranges or subranges that can be formed by such values. For example, a stated numerical value of 8 should be understood to vary from 0 to 16 (100% in either direction) and provide support for claims that recite the range itself (e.g., 0 to 16), any subrange within the range (e.g., 2 to 12.5) or any individual value within that range expressed individually (e.g., 15.2), as a minimum value (e.g., at least 4.3), or as a maximum value (e.g., no more than 12.4).

[0118] The terms recited in the claims should be given their ordinary and customary meaning as determined by reference to relevant entries in widely used general dictionaries and / or relevant technical dictionaries, commonly understood meanings by those in the art, etc., with the understanding that the broadest meaning imparted by any one or combination of these sources should be given to the claim terms (e.g., two or more relevant dictionary entries should be combined to provide the broadest meaning of the combination of entries, etc.) subject only to the following exceptions: (a) if a term is used in a manner that is more expansive than its ordinary and customary meaning, the term should be given its ordinary and customary meaning plus the additional expansive meaning, or (b) if a term has been explicitly defined to have a different meaning by reciting the term followed by the phrase “as used in this document shall mean” or similar language (e.g., “this term means,” “this term is defined as,” “for the purposes of this disclosure this term shall mean,” etc.). References to specific examples, use of “i.e.,” use of the word “invention,” etc., are not meant to invoke exception (b) or otherwise restrict the scope of the recited claim terms. Other than situations where exception (b) applies, nothing contained in this document should be considered a disclaimer or disavowal of claim scope.

[0119] None of the limitations in the claims shall be interpreted as invoking 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly recited in the claim.

[0120] Unless explicitly stated otherwise or otherwise apparent from context, terms such as “processing,” “computing,” “calculating,” “determining,” “displaying,” or the like, refer to the action and processes of an electronic computing device including a processor and memory.

[0121] The subject matter recited in the claims is not coextensive with and should not be interpreted as coextensive with any embodiment, feature, or combination of features described or illustrated in this document. This is true even if only a single embodiment of the feature or combination of features is illustrated and described.Composition Related Terminology and Interpretative Conventions

[0122] Values expressed as a percentage, parts of, or a ratio are by weight unless expressly stated otherwise.

[0123] The description of a group or class of materials as suitable or preferred for a given purpose shall be understood as disclosing that a single member of the group or class or a mixture of any two or more members of the group or class are equally suitable or preferred.

[0124] The description of constituents in chemical terms refers to the constituents: (a) at the time of addition to any combination specified in the description and / or (b) generated in situ by chemical reactions with other constituents. The description of theconstituents does not preclude other chemical interactions among the constituents of a mixture once mixed unless expressly stated otherwise.

[0125] The description of materials in ionic form additionally implies the presence of sufficient counter ions to produce electrical neutrality for the composition.Incorporation by Reference

[0126] The entire content of each document listed below is incorporated by reference into this document (the documents below are collectively referred to as the “incorporated documents”). If the same term is used in both this document and one or more of the incorporated documents, then it should be interpreted to have the broadest meaning imparted by any one or combination of these sources unless the term has been explicitly defined to have a different meaning in this document. If there is an inconsistency between any incorporated document and this document, then this document shall govern. The incorporated subject matter should not be used to limit or narrow the scope of the explicitly recited or depicted subject matter.Priority patent documents incorporated by reference:- U.S. Prov. App. No. 63 / 606,069, titled “Lithium Purification Process,” filed on 4 Dec 2023.Additional documents incorporated by reference:- U.S. Pat. Pub. No. 2021 / 0180153 (App. No. 17 / 115,140), titled “Process and Method for Refining Lithium Carbonate Starting from an Impure Lithium Chloride Solution,” filed on 8 Dec 2020, published on 17 Jun 2021.

Claims

WHAT IS CLAIMED IS:

1. A lithium purification process comprising: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein a temperature of the first solution in the first vessel is more than 40°C.

2. The lithium purification process of claim 1 wherein the temperature of the first solution in the first vessel is at least 60°C.

3. The lithium purification process of any one of claims 1 to 2 wherein the temperature of the second solution in the second vessel is at least 75°C.

4. The lithium purification process of any one of claims 1 to 3 wherein the temperature of the second solution in the second vessel is at least 5°C higher than the temperature of the first solution in the first vessel.

5. The lithium purification process of any one of claims 1 to 4 wherein the temperature of the first solution in the first vessel is at least 60°C and the temperature of the second solution in the second vessel is at least 10°C higher than the temperature of the first solution in the first vessel.

6. The lithium purification process of claim 5 wherein the temperature of the first solution in the first vessel is at least 75°C.

7. The lithium purification process of any one of claims 1 to 6 wherein the brine includes at least 3 wt% Na, at least 0.4 wt% K, at least 2.6 wt% Ca, or at least 0.5 wt% Mg.

8. The lithium purification process of any one of claims 1 to 7 wherein the lithium purification process does not include any other vessels that dissolve lithium carbonate at a different temperature than the first vessel.

9. The lithium purification process of any one of claims 1 to 8 wherein the lithium purification process does not include any other vessels that crystallize lithium carbonate at a different temperature than the second vessel.

10. The lithium purification process of any one of claims 1 to 9 wherein the amount of the second solution is conveyed from the second vessel to the first vessel ata flow rate of at least 1% of a total volume of the first vessel and the second vessel per minute.

11. The lithium purification process of any one of claims 1 to 10 wherein the amount of the second solution is conveyed from the second vessel to the first vessel at a flow rate that is at least the same as an overall mass flow rate of crystallization.

12. The lithium purification process of any one of claims 1 to 11 wherein the brine is a softened brine, the lithium purification process comprising reacting a lithium feed and carbon dioxide to form the softened brine, the lithium feed including lithium hydroxide and / or an alkaline solution of lithium chloride.

13. The lithium purification process of any one of claims 1 to 12 wherein the brine is a softened brine, the lithium purification process comprising reacting a lithium feed and a carbonate source to form the softened brine, the carbonate source being formed by reacting a hydroxide and carbon dioxide.

14. A lithium purification process comprising: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying at least a portion of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein the brine includes at least 3 wt% Na, at least 0.4 wt% K, at least 2.6 wt% Ca, or at least 0.5 wt% Mg.

15. The lithium purification process of claim 14 wherein the brine includes at least one of the Na, K, Ca, or Mg in an amount that is at least 5% more than that recited in claim 14.

16. The lithium purification process of claim 14 wherein the brine includes at least one of the Na, K, Ca, or Mg in an amount that is at least 5-500% more than that recited in claim 14.

17. A lithium purification process comprising: conveying a brine including solid lithium carbonate to a first vessel; dissolving the solid lithium carbonate in the brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel;crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel; wherein the amount of the second solution is conveyed from the second vessel to the first vessel at a flow rate that is: (i) at least 1% of a total volume of the first vessel and the second vessel per minute and / or (ii) at least the same as an overall mass flow rate of crystallization.

18. The lithium purification process of claim 17 wherein the flow rate is at least2% of the total volume of the first vessel and the second vessel per minute.

19. The lithium purification process of any one of claims 17 to 18 wherein the flow rate is at least 5% of the total volume of the first vessel and the second vessel per minute.

20. The lithium purification process of any one of claims 17 to 19 wherein the flow rate is more than the overall mass flow rate of crystallization.

21. The lithium purification process of any one of claims 17 to 20 wherein the flow rate is at least 3% more than the overall mass flow rate of crystallization.

22. The lithium purification process of any one of claims 17 to 21 wherein the flow rate is at least 5% more than the overall mass flow rate of crystallization.

23. The lithium purification process of any one of claims 17 to 22 wherein the flow rate is at least 10% more than the overall mass flow rate of crystallization.

24. A lithium purification process comprising: reacting a lithium feed and carbon dioxide to form a softened brine including solid lithium carbonate, the lithium feed including lithium hydroxide and / or an alkaline solution of lithium chloride; conveying the softened brine to a first vessel; dissolving the solid lithium carbonate in the softened brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel.

25. The lithium purification process of claim 24 wherein reacting the lithium feed and the carbon dioxide includes bubbling the carbon dioxide in the lithium feed.

26. A lithium purification process comprising: reacting a lithium feed and a carbonate source to form a softened brine including solid lithium carbonate, the carbonate source being formed by reacting a hydroxide and carbon dioxide; conveying the softened brine to a first vessel; dissolving the solid lithium carbonate in the softened brine in the first vessel to form a first solution including dissolved lithium carbonate; conveying an amount of the first solution to a second vessel fluidically linked to the first vessel; crystallizing the dissolved lithium carbonate in the first solution in the second vessel to form crystallized lithium carbonate and a second solution; and conveying an amount of the second solution from the second vessel to the first vessel.

27. The lithium purification process of claim 26 wherein the hydroxide includes ammonium hydroxide.

28. The lithium purification process of any one of claims 26 to 27 wherein the carbonate source includes ammonium carbonate.

Images