Solvent extraction for selective lithium recovery

Abstract

A lithium extraction process may include a solvent extraction unit configured to receive an aqueous feed stream from an upstream flow path, the aqueous feed stream including lithium cations and at least one additional monovalent cation species; a waste salt separation unit configured to receive a stream of aqueous wastewater from a first downstream flow path, the first downstream flow path connecting the waste salt separation unit with the solvent extraction unit in fluid communication; and a lithium carbonate generation unit configured to receive an aqueous lithium-rich stream from a second downstream flow path, the second downstream flow path connecting the lithium carbonate generation unit with the solvent extraction unit in fluid communication.

Description

Technical Field

[0001] The present disclosure relates to solvent extraction for selective lithium recovery. More specifically, the present disclosure relates to solvent extraction for selective lithium recovery from monovalent sulfate brines. Background Art

[0002] Lithium is a valuable mineral that is commonly used in the production of batteries, glass and ceramics, greases, and a variety of other products. Its largest use is in the production of lithium-ion batteries, which are commonly used in electric vehicles, grid storage, and portable electronic devices. Specifically, compounds of lithium carbonate (Li2CO3) and lithium hydroxide (LiOH) are used in the manufacture of batteries, and the processes require the compounds to have very high purity and contaminants not exceeding trace levels.

[0003] Due to the nature of the extraction process, it is difficult to achieve the required purity levels. Lithium exists in nature only as compounds, not as elements. Lithium deposits are typically present in low concentrations in certain rock formations, clays, and brines. In the case of rock and clay deposits, the ore is typically treated with an acid (such as sulfuric acid) to leach the lithium into solution; however, depending on the source, many additional elements are co-extracted. For example, aluminum, calcium, iron, potassium, magnesium, and sodium are typically co-extracted with the desired lithium from clays into the liquid leach brine. In the case of using sulfuric acid, the brine also contains a high sulfate concentration.

[0004] Most aluminum, calcium, iron, and magnesium are typically removed by a combination of chemical and physical precipitation techniques, and these elements are subsequently reduced to trace levels using purification techniques such as ion exchange. However, the resulting brine carries a mixture of lithium, potassium, and sodium, which cannot be directly used to produce lithium carbonate suitable for battery manufacture without multiple subsequent purification steps due to the impurity levels.

[0005] In common practice, multiple steps are required during lithium carbonate production to ensure the final product quality. Additionally, steps for removing sodium and potassium must be carried out after lithium carbonate is produced. These additional steps increase the process complexity and require additional equipment to construct. Additionally, these steps increase the consumption of energy and chemical inputs and result in lithium losses in the sulfates generated during waste salt separation (such as in zero liquid discharge units). Summary of the Invention

[0006] It should be understood that this summary of the invention is not an extensive overview of the present disclosure. This summary of the invention is exemplary and not restrictive, and it is neither intended to identify the key or important elements of the present disclosure nor to define its scope. The sole purpose of this summary of the invention is to explain and illustrate certain concepts of the present disclosure as an introduction to the following complete and extensive detailed description.

[0007] A lithium extraction process is disclosed, which includes: a solvent extraction unit configured to receive an aqueous feed stream from an upstream flow path, the aqueous feed stream containing lithium cations and at least one additional monovalent cation species; a waste salt separation unit configured to receive an aqueous wastewater stream from a first downstream flow path, the first downstream flow path connecting the waste salt separation unit and the solvent extraction unit in fluid communication; and a lithium carbonate production unit configured to receive an aqueous lithium-rich stream from a second downstream flow path, the second downstream flow path connecting the lithium carbonate production unit and the solvent extraction unit in fluid communication.

[0008] A method for extracting lithium is also disclosed, the method including: processing an aqueous feed stream containing lithium cations and at least one additional monovalent cation species with a solvent extraction unit, the processing including: contacting the aqueous feed stream with an organic solvent stream containing at least one extractant to: extract the lithium cations from the aqueous feed stream into the organic solvent stream; and generate an aqueous wastewater stream from the aqueous feed stream containing the at least one additional monovalent cation species; stripping the lithium cations from the organic solvent stream into an aqueous acid stream to produce an aqueous lithium-rich stream; and separating waste salt containing the at least one additional monovalent cation species from the aqueous wastewater stream in a linear process.

[0009] The various embodiments described in this disclosure may include additional systems, methods, features, and advantages that are not necessarily explicitly disclosed herein but will be apparent to those of ordinary skill in the art upon review of the following detailed description and the drawings. It is intended that all such systems, methods, features, and advantages be included within this disclosure and be protected by the appended claims. The features and advantages of such embodiments can be achieved and obtained by the systems, methods, features specifically pointed out in the appended claims. These and other features will become more fully apparent from the following description and the appended claims, or may be understood by practicing such exemplary embodiments as set forth below. Description of the Drawings

[0010] The features and components of the following drawings are shown to emphasize the general principles of this disclosure. The drawings are not necessarily to scale. For consistency and clarity, corresponding features and components throughout the drawings may be designated by matching reference numerals.

[0011] Figure 1 is the overall process flow diagram of the lithium extraction process.

[0012] Figure 2 is Figure 1 the detailed process flow diagram of the production loop of the lithium extraction process.

[0013] Figure 3 is a ternary phase diagram of lithium cations, sodium cations and potassium cations in the presence of sulfate anions.

[0014] Figure 4 is a detailed flow chart of an improved production loop of an improved lithium extraction process according to one aspect of the present disclosure.

[0015] Figure 5 is a detailed flow chart of an improved production loop of an improved lithium extraction process according to another aspect of the present disclosure.

[0016] Figure 6 is Figure 4 and 5 is a detailed flow chart of an exemplary solvent extraction unit of an improved production loop of aspects of. Detailed Description

[0017] The present disclosure can be more easily understood by reference to the following detailed description, examples, drawings and claims, as well as the description before and after. However, before disclosing and describing the inventive apparatus, system and / or method, it should be understood that the present disclosure is not limited to the specific apparatus, system and / or method disclosed, unless otherwise specified, and thus can of course vary. It should also be understood that the terms used herein are for the purpose of describing specific aspects only and are not intended to be limiting.

[0018] The following description is provided as an enabling teaching of the inventive apparatus, system and / or method in its best, currently known aspects. To this end, those skilled in the relevant art will recognize and understand that many changes can be made to the various aspects of the inventive apparatus, system and / or method described herein while still obtaining the beneficial results of the present disclosure. It is also obvious that some desired benefits of the present disclosure can be obtained by selecting some features of the present disclosure without utilizing other features. Therefore, those skilled in the art will recognize that many modifications and adaptations of the present disclosure are possible and, in some cases, even desirable and are part of the present disclosure. Accordingly, the following description is provided as an illustration of the principles of the present disclosure rather than a limitation thereof.

[0019] As used throughout this specification, unless the context clearly indicates otherwise, the singular forms "a / an" and "the" include plural referents. Thus, for example, unless the context otherwise indicates, reference to "an element" can include two or more such elements.

[0020] In this document, ranges may be expressed as from “about” a particular value and / or to “about” another particular value. When expressing such a range, on the other hand, includes from one particular value and / or to another particular value. Similarly, when a value is expressed as an approximation by use of the antecedent “about”, it should be understood that the particular value forms on the other hand. It should be further understood that each endpoint of each range is significant relative to the other endpoint and independent of the other endpoint.

[0021] For purposes of the present disclosure, a material property or dimension that is measured as being about X or substantially X on a particular measurement scale is measured within a range between X plus the industry standard upper tolerance for the specified measurement and X minus the industry standard lower tolerance for the specified measurement. Since tolerances may vary between different materials, processes, and different models, the tolerance for a particular measurement of a particular component may fall within the tolerance range.

[0022] As used herein, the term “optional” or “optionally” means that the subsequent described event or circumstance may or may not occur, and the description includes instances where the event or circumstance occurs and instances where the event or circumstance does not occur.

[0023] As used herein, the word “or” means any one member of a particular list and also includes any combination of members of that list. In addition, attention should be paid to conditional language, such as “can / could / might / may”, which, unless specifically stated otherwise or otherwise understood in the context in which it is used, is generally intended to convey that certain aspects include while other aspects do not include certain features, elements, and / or steps. Thus, such conditional language is generally not intended to imply that the features, elements, and / or steps are necessary in any case for one or more particular aspects, or that one or more particular aspects must include logic for determining whether these features, elements, and / or steps are included in any particular aspect or will be performed therein with or without user input or prompting.

[0024] Components that can be used to perform the disclosed methods and systems are disclosed. These and other components are disclosed herein, and it should be understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed, although specific references to each different individual and collective combination and arrangement of these components may not be explicitly disclosed, each combination and arrangement is specifically contemplated and described herein for all methods and systems. This applies to all aspects of the present application, including but not limited to the steps in the disclosed methods. Thus, if there are multiple additional steps that can be performed, it should be understood that each of these additional steps can be performed using any specific aspect or combination of aspects of the disclosed methods.

[0025] An improved lithium extraction process and associated methods, systems, apparatuses, and various equipment are disclosed. The improved lithium extraction process may include a solvent extraction unit. Those skilled in the art will understand that the disclosed improved lithium extraction process is described in several exemplary aspects. The specific terms or descriptions should not be considered to limit the scope of the present disclosure or any claims issued therefrom.

[0026] Figure 1 Depicts the current overall lithium extraction process 100 (also referred to as "current process 100"). Specifically, the current process 100 may be similar to the process of the Thacker Pass lithium mine in Nevada, USA. Figure 2 Is a detailed flowchart of the production loop 115 of the current process 100. In contrast, Figure 4 And Figure 5 Are detailed flowcharts of the improved lithium extraction processes 400, 500 according to various aspects of the present disclosure, respectively showing two aspects of the improved production loops 415, 515, each figure including a solvent extraction unit 480.

[0027] Turn to Figure 1 , the current process 100 may include multiple units 101, 103, 105, 107, 109, 111, 113, and the main processing stream 197 may carry lithium through the units 101, 103, 105, 107. The current process 100 may involve multiple input and output flow paths, as represented by the elements 150–164, which may correspond to the following:

[0028] 150: Raw water;

[0029] 151: Flocculant;

[0030] 152: Lime slurry;

[0031] 153: Limestone

[0032] 154: Ferric sulfate;

[0033] 155: Carbon dioxide;

[0034] 156: Treated water;

[0035] 157: Soda ash;

[0036] 158: Caustic soda;

[0037] 159: Molten sulfur;

[0038] 160: Electricity;

[0039] 161: Flow distribution;

[0040] 162: Coarse coal gangue stockpile;

[0041] 163: Waste rock storage facilities; and

[0042] 164: Clay tailings filter stack.

[0043] In aspects of the present invention, the initial primary process stream 197 can be a feed of lithium-containing solids, such as but not limited to clay. The current process 100 can include a beneficiation unit 101, a leaching unit 103, a filtration unit 105, a divalent removal unit 107, a lithium carbonate production unit 109, a waste salt separation unit 111, and an acid production unit 113. After passing through the leaching unit 103, the primary process stream 197 can be an aqueous sulfate brine; however, this chemical composition should not be considered limiting. The primary process stream 197 can be split into a separate lithium-rich stream 198 and a wastewater stream 199. This splitting of the primary process stream 197 can occur in the lithium carbonate production unit 109.

[0044] The beneficiation unit 101 can include multiple steps 102a–e. In step 102a, lithium-containing deposits can be mined to extract lithium-containing materials. The initially extracted materials can include the desired lithium ore as well as waste materials such as coal gangue, waste rock, and clay. In steps 102b–e, the extracted materials can be physically decomposed (crushed), sorted by size, and initially separated or concentrated to separate and extract the lithium ore from the associated waste materials. For example, in step 102b, the extracted materials can be fed through a feeder crusher, a mineral sieve, and a trough washer, which can crush the materials into smaller particle sizes and remove unwanted materials, such as lithium-free minerals. In step 102c, the materials can be further decomposed with a scrubber and initially sized via screening. In step 102c, waste rock can be sorted out from the primary process stream 197. In step 102d, the remaining materials can be classified by size, which can remove coarse coal gangue from the primary process stream 197. Finally, the materials can be mixed with water and a flocculant to produce a high-solid-concentration lithium stream.

[0045] In the leaching unit 103, the lithium ore can undergo an acid leaching step 104, in which the lithium ore can be mixed with acid from the acid production unit 113, and this mixing can extract lithium from the ore into the solution. The acid leaching step 104 can result in various elements (such as but not limited to, aluminum, calcium, iron, potassium, lithium, magnesium, and sodium) being leached into the solution. In an example of the present invention, the acid production unit 113 can generate sulfuric acid (H2SO4); however, different acids can be utilized.

[0046] After the leaching unit 103, limestone can be fed into the main process stream 197 in the filtration unit 105, where the neutralization and filtration step 106 can remove aluminum and iron from the main process stream 197.

[0047] The divalent removal unit 107 can remove magnesium and calcium from the main process stream 197 through the respective steps 108a–d. In step 108a, magnesium can be removed by evaporation and crystallization, such as in the form of magnesium sulfate (MgSO4). In step 108b, quicklime slurry can be added to the main process stream 197 to further remove magnesium by precipitation and filtration of magnesium precipitates. In step 108c, a flocculant, ferric sulfate, and soda ash solution (Na2CO3, also known as "sodium carbonate") can be added to the main process stream 197, and calcium can be removed using a reactor clarifier. In step 108d, residual divalent ions can be removed using a chelating ion exchanger. For example, divalent ions can be extracted from an aqueous solution using a renewable resin. The resin can be regenerated as needed with an acid (such as sulfuric acid, for example but not limited to from the acid generation unit 113) and / or a base / soluble base (such as, for example but not limited to, sodium hydroxide) injected into the ion exchanger, and the ion exchanger can release the divalent ions into an aqueous waste stream.

[0048] The main process stream 197 can flow from the divalent removal unit 107 to the production loop 115, which can include a lithium carbonate production unit 109 and a waste salt separation unit 111.

[0049] The lithium carbonate production unit 109 can include multiple steps 110a–e. Steps 110a–c relate to the production of lithium carbonate compounds, and here, the main process stream 197 can be split into a lithium-rich stream 198 and a wastewater stream 199. Step 110a is the first stage of lithium carbonate crystallization and centrifugation. In this stage, soda ash can be added to the main process stream 197. Centrifugation can separate the solid from the liquid centrate. In this step, as discussed below, approximately 100% of the centrate can be directed to the waste salt separation unit 111 (as shown by the flow path 117), and the centrate becomes part of the wastewater stream 199.

[0050] The lithium-rich stream 198 can carry solids from step 110a to the bicarbonation process in step 110b, where the lithium-rich stream 198 can be combined with or repulped with treated water and admixed with carbon dioxide. The lithium-rich stream 198 can then undergo a second stage of lithium carbonate crystallization and centrifugation, where solid lithium carbonate can be partially separated from the liquid centrate. In step 110c, about 33% of the centrate can be combined with the wastewater stream 199 that is directed to the waste salt separation unit 111, as shown by the flow path 119. The remaining liquid of the lithium-rich stream 198 and the lithium carbonate solids can be dried to remove the remaining water, cooled, and then stored in step 110d. The lithium carbonate can then be jet milled, magnetically filtered, and packaged in step 110e to produce a final salable product.

[0051] As described above, the waste salt separation unit 111 can receive the centrate from steps 110a, c of the lithium carbonate production unit 109, and the centrate can form the wastewater stream 199. The wastewater stream 199 can have a high concentration of sodium and potassium; however, the wastewater stream 199 can also carry a portion of the desired lithium. Sodium and potassium must be removed from the main process stream 197 to produce a battery-quality lithium product from the lithium carbonate production unit 109; however, steps 110a-c can also result in the undesired removal of lithium from the main process stream 197 to the wastewater stream 199.

[0052] In step 112a of the waste salt separation unit 111, the centrate can be treated with an acid (such as but not limited to sulfuric acid) from the acid production unit 113 to decarbonate the centrate. Once decarbonated, the wastewater stream 199 can be transferred to step 112b of the waste salt separation unit 111, where the wastewater stream 199 can undergo separation processes such as crystallization, evaporation, centrifugation, etc. The separation process can be a zero liquid process, which can produce solid sodium sulfate and potassium sulfate salts (and inadvertently, lithium sulfate salts). These salts can be separated for storage and / or removal from the ore.

[0053] As discussed in more detail below with reference to Figure 3 the ternary phase diagram of the sulfates of sodium, potassium, and lithium shown, the wastewater stream 199 cannot undergo complete separation without forming lithium-containing salts (such as potassium lithium sulfate) in addition to sodium sulfate and potassium sulfate salts, and for practical commercial purposes, the lithium-containing salts cause a loss of this portion of lithium. In the current process 100, the wastewater stream 199 can carry up to 15 - 30% or more of the lithium; thus, if all solids are completely separated from the wastewater stream 199, this will significantly reduce the recovery of the current process 100, which in turn will have a significant adverse impact on the profitability of the current process 100 due to the loss of lithium with the waste salts.

[0054] In order to avoid this loss of lithium, the crystallizer of step 112b can perform only a partial separation of spent salts from the wastewater stream 199. Since the sodium and potassium concentrations in the wastewater stream 199 are much higher than the lithium concentration, this partial separation results in the production of only sodium sulfate and potassium sulfate salts. The remaining liquid of the wastewater stream 199 (carrying the lithium portion and the remaining sodium and potassium) can be sent back to step 110a of the lithium carbonate production unit 109 through the recycling loop 121.

[0055] The recycle loop 121 may be a significant portion of a certain volume flow of the main process stream 197. Recycling this volume through steps 110a-c of the lithium carbonate production unit 109 may increase the percentage of lithium recovered by the current process 100, but at the expense of increased energy and reagent consumption (such as soda ash and sulfuric acid). Recycling this volume always requires equipment that is sized larger than that required to accommodate the larger flow rate.

[0056] Figure 2 It shows Figure 1 Detailed view of production loop 115 of current process 100 of FIG. Starting from the left side of the page, main process stream 197 is shown passing through ion exchange vessel 208 in step 108d of divalent removal unit 107. Ion exchange vessel 208 can strip residual divalent calcium ions and divalent magnesium ions (Ca and Mg, respectively) from main process stream 197. 2+ and Mg 2+ ), such as but not limited to using a regenerable ion exchange resin or other suitable media. When the exchange media is regenerated, divalent calcium ions and divalent magnesium ions can be removed from the ion exchange container 208, as shown in flow path 251.

[0057] The main process stream 197, now stripped of divalent ions, can exit the ion exchange vessel 208 along flow path 250, where the main process stream 197 can be mixed with soda ash, as illustrated by flow path 252 and recycle loop 121 from the spent salt separation unit 111. Similarly as discussed above, the recycle loop 121 can return lithium ions as well as remaining sodium and potassium ions that were not crystallized in the spent salt separation unit 111. Notably, the soda ash can add additional sodium to the main process stream 197.

[0058] The main process stream 197 can then enter the first crystallizer 210a of step 110a of the lithium carbonate production unit 109. In some aspects, the first crystallizer 210a can be a precipitator. Here, the lithium cation (Li + ) can react with carbonate anions (CO3 2-)The reaction forms lithium carbonate crystals. The main process stream 197 can advance from the first crystallizer 210a to the centrifuge 210b in step 110a of the lithium carbonate production unit 109 along the flow path 253. The centrifuge 210b can separate the solid lithium carbonate crystals from the liquid of the main process stream 197. The lithium carbonate carried by the lithium-rich stream 198 can advance along the flow path 254 to the bicarbonation vessel 210c in step 110b of the lithium carbonate production unit 109.

[0059] The centrate from the centrifuge 210b can be directed along the flow path 117, where the centrate can be combined with a first portion 219a of the centrate discharged from the centrifuge 210f in step 110c of the lithium carbonate production unit 109 along the flow path 119. These streams can together form a wastewater stream 199, which can be directed to the waste salt separation unit 111, which will be discussed in further detail below.

[0060] Returning to the bicarbonation vessel 210c, the lithium-rich stream 198 from the first crystallizer 210a can be rinsed with a second portion 219b of the centrate from the centrifuge 210f, while carbon dioxide (CO2) can be injected into the bicarbonation vessel 210c along the flow path 255. Treated water can also be injected into the bicarbonation vessel 210c along the flow path 262. These steps can dissolve the lithium carbonate solid into a solution of lithium bicarbonate (LiHCO3).

[0061] The lithium-rich stream 198 can advance from the bicarbonation vessel 210c to the filter 210d of the lithium carbonate production unit 109 along the flow path 256, where waste solids and solid contaminants can be separated from the lithium-rich stream 198 along the flow path 270. The lithium-rich stream 198 can flow along the flow path 257 to the second crystallizer 210e in step 110c of the lithium carbonate production unit 109, where the dissolved lithium bicarbonate can be converted back to solid lithium carbonate crystals. In aspects of the present invention, crystallization can be achieved by a precipitation process, such as a chemical crystallization process. In some aspects, crystallization can be achieved by a conventional crystallization process. Carbon dioxide can be removed by heating the lithium-rich stream 198, and the carbon dioxide can be recycled through the bicarbonation vessel 210c along the flow path 255. Bicarbonation steps and a second crystallization step may be required to achieve sufficient purity to produce battery-quality lithium carbonate.

[0062] Then the lithium-rich stream 198 can flow along the flow path 258 to the centrifuge 210f in step 110c of the lithium carbonate production unit 109, where the solid lithium carbonate crystals can be separated from the liquid as the centrate. As referred to above Figure 1As described in steps 110d, e of production unit 109 in [reference], the lithium-rich stream 198 carrying solid lithium carbonate can advance along flow path 259 to be dried, sized, filtered, and packaged (along with other steps) for sale. Similarly as described above, the centrate can be directed along flow path 119, where a first portion 219a of the centrate can be directed to waste salt separation unit 111, and a second portion 219b can be directed to bicarbonation vessel 210c.

[0063] The wastewater stream 199 can be a sulfate and carbonate brine containing large concentrations of sodium and potassium cations and a lower concentration of lithium cations, as well as other aqueous ions. The wastewater stream 199 can pass through decarbonation vessel 212a of step 112a of waste salt separation unit 111. Here, an acid (such as sulfuric acid) can be injected into decarbonation vessel 212a along flow path 260, where the acid can react with wastewater stream 199 to break down any remaining carbonate anions (from the soda ash injected along flow path 252) and release carbon dioxide gas. This carbon dioxide gas can be collected along flow path 255 and directed to bicarbonation vessel 210c. Adding sulfuric acid to wastewater stream 199 can lower the pH of wastewater stream 199 and increase the concentration of sulfate anions in the chemical composition of wastewater stream 199.

[0064] Then, the wastewater stream 199 can flow to a waste salt separation unit, such as zero liquid discharge ("ZLD") unit 212b of step 112b of waste salt separation unit 111. The removal of the remaining carbonate in step 112a can prevent loss of lithium carbonate in ZLD unit 212b. Referring to Figure 3 , a ternary phase diagram of lithium, sodium, and potassium cations in the presence of sulfate anions is shown. The ternary phase diagram indicates which salts will be produced when an aqueous solution undergoes a separation process (e.g., crystallization, centrifugation, evaporation, etc.) across the full spectrum of chemical components of lithium, sodium, potassium, and sulfate anions.

[0065] Specifically, the ternary phase diagram elucidates that the three corners 300a, b, c and three sides 301a, b, c correspond to the relative concentration ratios of lithium sulfate, sodium sulfate, and potassium sulfate, respectively. The relative concentration values of lithium, sodium, and potassium add up to 100%. Corners 300a, b, c reflect 100% lithium sulfate, 100% sodium sulfate, and 100% potassium sulfate, respectively. For example, corner 300a indicates the absence of sodium or potassium cations and the presence of only lithium cations (notably, the figure is shown on a dry basis and the water in the solution is omitted).

[0066] The sides 301a, b, c opposite these points reflect the absence of the corresponding cations. For example, the points along side 301a opposite corner 300a indicate the absence of lithium cations (i.e., only sodium and potassium cations are present in the chemical composition). Similarly, the points along side 301b indicate the absence of sodium cations, and the points along side 301c indicate the absence of potassium cations.

[0067] The ternary diagram of lithium sulfate, sodium sulfate, and potassium sulfate has six regions A - F, each region representing the type of salt that will form when a solution with specific ratios of lithium, sodium, and potassium concentrations undergoes a separation process.

[0068] For example, a solution with ratios of lithium, sodium, and potassium that fall into region A will initially produce Na2SO4·Li2SO4, which is a lithium - containing double salt. Region A generally corresponds to solutions with little or no potassium and lithium and sodium present in similar concentrations.

[0069] Solutions that fall into region B will initially produce Na2SO4, which is a single salt without lithium. Region B generally corresponds to solutions with very high sodium concentrations and little or no lithium and potassium present.

[0070] Solutions that fall into region C will initially produce LiKSO4, which is also a lithium - containing double salt that contains potassium. Region C generally corresponds to solutions with medium, low, or no sodium and lithium and potassium present in similar concentrations.

[0071] Solutions that fall into region D will initially produce Li2SO4·H2O, which is a lithium - containing hydrated salt. Region D generally corresponds to solutions with very high lithium concentrations and little or no sodium and potassium present.

[0072] Solutions that fall into region E will initially produce K2SO4·KNaSO4, which is a double salt without lithium. Region E generally corresponds to solutions with little or no lithium and potassium and sodium present in similar concentrations.

[0073] Solutions that fall into region F will initially produce K2SO4, which is a single salt without lithium. Region F generally corresponds to solutions with very high potassium concentrations and little or no sodium and lithium present.

[0074] Solutions that fall into region G will initially produce 2Li2SO4·Na2SO4·K2SO4, which is a lithium - containing triple salt. Region G generally corresponds to solutions with medium - to - low levels of potassium and lithium and sodium present in a relatively wide concentration range.

[0075] As previously mentioned, wastewater stream 199( Figure 1The initial chemical composition (as shown in ) typically contains high levels of sodium and potassium and relatively low levels of lithium. For example, the sodium concentration and potassium concentration (in ppm) can each be about 5 - 10 times (5 - 10×) the lithium concentration (in ppm). In an exemplary chemical composition, the ratio of sodium to potassium can be about 5:4. Thus, the initial chemical composition of the wastewater stream 199 will typically fall into one of regions B, E, or F at the start of the separation process. A series of boundary lines 302a–g surround regions B, E, and F. Boundary lines 302h, i are positioned between regions A, C, and G. Note that other boundary lines are shown but not labeled.

[0076] As the separation process proceeds, as the solvent (water) is removed, the concentrations of lithium, potassium, and sodium increase until the aforementioned salt crystals begin to form and drop out of solution. Using region B as an example, an initial chemical composition that falls within the interior of region B at the start of the separation process will initially produce solid Na2SO4 crystals. The formation of these sodium salts has the effect of reducing the ratio of sodium in the wastewater stream 199, which in turn increases the ratios of lithium and potassium in the wastewater stream 199. Thus, as the Na2SO4 crystals form, the concentration of the wastewater stream 199 will move in the direction towards side 301b until the concentration reaches one of the boundary lines 302a–c that define region B.

[0077] Once the concentration reaches a ratio located along one of the boundary lines 302a–c, the concentration will never cross the boundary lines 302a–c as the separation process continues. This is because continued separation produces salts corresponding to each region defined by the boundary lines 302a–c.

[0078] For example, if the concentration shifts to locate along boundary line 302a, continued separation will produce Na2SO4 crystals (as represented by region B) and Na2SO4·Li2SO4 double salt crystals (as represented by region A on the opposite side of boundary line 302a). Similarly, if the concentration shifts to locate along boundary line 302b, continued separation will produce Na2SO4 crystals (as represented by region B) and

[0079] 2Li2SO4·Na2SO4·K2SO4 triple salt crystals (as represented by region G on the opposite side of boundary line 302b). If the concentration shifts to locate along boundary line 302c, continued separation will produce Na2SO4 crystals (as represented by region B) and K2SO4·KNaSO4 double salt crystals (as represented by region E on the opposite side of boundary line 302c).

[0080] Once the concentration is located along the boundary line, continued separation will cause the concentration to shift along the corresponding boundary line until a final equilibrium is reached at the ternary points 303a–d. Note that only the ternary points 303a–d are labeled because these points delimit one of the regions B, E, and F. The ternary points 303a–d are each located at the intersection of three boundary lines. Ternary point 303a is located at the intersection of boundary lines 302a, b, i. Ternary point 303b is located at the intersection of boundary lines 302b, c, d. Ternary point 303c is located at the intersection of boundary lines 302d, e, h. Ternary point 303d is located at the intersection of boundary lines 302e, f, g.

[0081] The initial chemical composition of the wastewater stream 199 located in region B will always reach a final equilibrium at ternary point 303a or ternary point 303b, depending on the ratio of potassium to lithium present. The initial chemical composition of the wastewater stream 199 located in region E will always reach a final equilibrium at ternary point 303b, ternary point 303c, or ternary point 303d, depending on the ratio of potassium to sodium present. The initial chemical composition of the wastewater stream 199 located in region F will always reach a final equilibrium at ternary point 303d.

[0082] Once the concentration reaches a final equilibrium at the ternary points 303a–d, continued separation will produce solid salt crystals corresponding to each adjacent region of the ternary points 303a–d until complete separation is achieved. For example, continued separation will produce the salts of regions A, B, G at ternary point 303a, and it is worth noting that regions A and G result in the production of a lithium-containing double salt and a tritium salt, respectively. Continued separation will produce the salts of regions B, E, G at ternary point 303b, and it is worth noting that region G results in the production of a lithium-containing tritium salt. Continued separation will produce the salts of regions C, E, G at ternary point 303c, and it is worth noting that region G results in the production of a lithium-containing tritium salt, while region C results in a single salt containing both lithium and potassium. Continued separation will produce the salts of regions C, E, F at ternary point 303a, and it is worth noting that region C results in a single salt containing both lithium and potassium.

[0083] The salts corresponding to regions A, C, and G each contain lithium and are not commercially viable products. For practical commercial purposes, the lithium produced in these forms is effectively lost. Thus, in typical operation of the current process 100, the wastewater stream 199 typically exhibits an initial chemical composition located within region B, region E, or region F, and the wastewater stream 199 may only undergo a partial separation process to produce Na2SO4, K2SO4·KNaSO4, and / or K2SO4 waste salts without producing any lithium-containing salts. In other words, the separation process may only proceed to the extent that the chemical composition has not reached any of the boundary lines 302a–g or the ternary points 303a–d to avoid loss of lithium. A significant amount of solvent (water) may remain at the separation limit imposed by this process.

[0084] Return Figure 2 , the partially treated wastewater stream 199 can be transferred from the ZLD unit 212b to the centrifuge separator 212c, where solids (such as sodium and potassium salts) can be separated from the remaining liquid. These sodium and potassium waste salts can follow the flow path 261, where these sodium and potassium waste salts can be stored together with other waste products (such as clay tailings), while the remaining liquid of the wastewater stream 199 (still carrying a high concentration of sodium, lithium, and potassium) can be directed along the recycle loop 121. The recycle loop 121 can rejoin the main process stream 197, and the recycle stream can be reprocessed by at least a portion of the lithium carbonate production unit 109, which may result in an undesirable increase in sodium and potassium in the main process stream 197.

[0085] Figure 4 and Figure 5 respectively depict aspects of the improved production loops 415, 515 in accordance with various aspects of the present disclosure, each figure including a solvent extraction unit 480.

[0086] From Figure 4 starting, the improved production loop 415 of the improved lithium extraction process 400 is shown after the ion exchange vessel 208 in step 108d of the divalent removal unit 107. In some aspects, the portion of the improved lithium extraction process 400 upstream of the ion exchange vessel 208 may be substantially the same as the current lithium extraction process 100 ( Figure 1 as shown); however, the improved production loop 415 can be integrated into any lithium extraction process. Similarly as discussed above, the ion exchange vessel 208 can strip remaining calcium and magnesium ions from the main process stream 197, for example but not limited to using a renewable ion exchange resin or other suitable medium. When the exchange medium is regenerated, divalent calcium ions and divalent magnesium ions can be removed from the ion exchange vessel 208, as shown by the flow path 251. The main process stream 197 now stripped of divalent ions can leave the ion exchange vessel 208 along the flow path 250.

[0087] In aspects of the present invention, the ion exchange vessel 208 may also receive a recycle loop 406 from the lithium carbonate production unit 409 of the improved production loop 415, and the recycle loop may rejoin the main process stream 197.

[0088] In Figure 4 aspects, the main process stream 197 may pass through a solvent extraction unit 480, as shown by the flow path 250. The solvent extraction unit 480 is shown and discussed in more detail below with reference to Figure 6 The solvent extraction unit 480 may utilize a number of reagents. For example, the solvent extraction unit 480 may receive, for example but not limited to, an acid (such as sulfuric acid) along the flow path 401. The solvent extraction unit 480 may receive, for example but not limited to, a base (such as sodium hydroxide (NaOH)) along the flow path 402. The solvent extraction unit 480 may receive, for example but not limited to, one or more organic solvents along the flow path 403, each organic solvent comprising one or more extractants, diluents, or combinations thereof. In some aspects where multiple extractants are utilized, the flow path 403 may carry a mixture of extractants and one or more diluents. In some aspects where multiple extractants are utilized, the flow path 403 may represent multiple separate paths for individual extractants, which may or may not be mixed within the solvent extraction unit 480.

[0089] The solvent extraction unit 480 may have two separate streams: a waste stream 199 and a lithium-rich stream 198. The waste stream 199 and the lithium-rich stream 198 may each be aqueous streams. The solvent extraction unit 480 may selectively extract 99% or more of the lithium from the main process stream 197, while only a few percent of sodium and potassium may be extracted with the lithium, leaving most of the remaining sodium and potassium in the main process stream 197. For example but not limited to, in some aspects, 2% or less of sodium and / or potassium may be extracted with the lithium in the solvent extraction unit 480. The extracted lithium may then be concentrated into the lithium-rich stream 198. When optimized, as discussed in more detail below, the solvent extraction unit 480 may concentrate approximately 100% of the lithium from the main process stream 197 into the lithium-rich stream.

[0090] In the case where almost all of the lithium is extracted from the main process stream 197 but a significant concentration of sodium and potassium remains, the main process stream 197 may leave the solvent extraction unit 480 as the waste stream 199. The waste stream 199 may contain less than 1% of the lithium from the main process stream 197. When optimized, the solvent extraction unit 480 may produce a waste stream 199 containing less than 0.1% of the lithium from the main process stream 197.

[0091] Since the waste water stream 199 may contain little or no lithium, the separation process of the waste water stream 199 can be a linear process that begins immediately downstream of the solvent extraction unit 480 and extends to achieve complete separation or removal of all waste salts. "Linear process" means a process lacking any recycle loop (such as recycle loop 121). For example, the entire waste water stream 199 can be directed through the waste salt separation unit 411 of the modified production loop 415 to achieve substantially complete separation of the waste salts in the linear process without recycling any waste water stream 199.

[0092] In aspects of the present invention, the waste salt separation unit 411 can include a ZLD unit 412a and a centrifuge 412b. The waste salt separation unit 411 can substantially remove all the liquid from the waste water stream 199, leaving only lithium-free waste salts (such as various potassium and sodium salts). For example, in some aspects, less than 0.5% of the lithium from the main process stream 197 can be present in the waste salts. In some more preferred aspects, 0.2% or less of the lithium from the main process stream 197 can be present in the waste salts. Referring to Figure 3 the ternary phase diagram, the chemical composition of the waste water stream 199 entering the waste salt separation unit 411 can follow the side 301a (representing 0% lithium concentration) or fall into regions B, E, or F adjacent to said side.

[0093] Return Figure 4 , the lithium-rich stream 198 can be admixed with soda ash, as shown by the flow path 404. The lithium-rich stream 198 can enter the crystallizer 410a of the lithium carbonate production unit 409, where lithium carbonate crystals can be formed. As shown by the flow path 405, the lithium-rich stream 198 can be transferred from the crystallizer 410a to the centrifuge 410b, where the lithium carbonate can be separated from the liquid of the lithium-rich stream 198. This separation can remove most of the sodium added by the soda ash from the lithium-rich stream 198 as the centrate. The centrate can return to the ion exchange vessel 208 along the recycle loop 406. The lithium carbonate of the lithium-rich stream 198 can leave the centrifuge 410b along the flow path 407.

[0094] In some aspects of the modified production loop 415, the lithium-rich stream 198 from the centrifuge 410b can be directly prepared for sale (such as by drying, cooling, storing, jet milling, magnetic filtering, and / or packaging), similar to steps 110d, e of the lithium carbonate production unit 109 ( Figure 1Steps 110d, e as shown in and the lithium carbonate production unit 109). In some aspects of the improved production loop 415, before being prepared for sale, the lithium-rich stream 198 can be transferred from the centrifuge separator 410b to additional processing equipment. For example but not limited to, the lithium-rich stream 198 can pass through a bicarbonation vessel, a filter, a second crystallizer, and / or a second centrifuge separator, similarly as shown in the lithium carbonate production unit 109 of Figure 1 as shown in the lithium carbonate production unit 109 of.

[0095] Figure 5 An improved production loop 515 of an improved lithium extraction process 500 according to another aspect of the present disclosure is shown, and the improved production loop can include a solvent extraction unit 480. In step 108d of the divalent removal unit 107, the improved production loop 515 is shown after the ion exchange vessel 208. The portion of the improved lithium extraction process 500 upstream of the ion exchange vessel 208 can be substantially the same as the current lithium extraction process 100 ( Figure 1 as shown in); however, the improved production loop 415 can be integrated into any lithium extraction process. Similarly as discussed above, the ion exchange vessel 208 can strip residual calcium and magnesium ions from the main process stream 197, for example but not limited to using a renewable ion exchange resin or other suitable medium.

[0096] When the exchange medium is regenerated, divalent calcium ions and divalent magnesium ions can be removed from the ion exchange vessel 208, as shown by the flow path 251. The main process stream 197, now stripped of divalent ions, can leave the ion exchange vessel 208 along the flow path 250, where the main process stream 197 can be admixed with soda ash, as shown by the flow path 252.

[0097] Different from the aspect in Figure 5 where the wastewater stream 199 flows directly to the waste salt separation unit 511, a solvent extraction unit 480 can be integrated to receive the wastewater stream 199 before it enters the waste salt separation unit 511.

[0098] Returning to the main process stream 197, after leaving the ion exchange vessel 208 along the flow path 250, the main process stream 197 can then enter the first crystallizer 510a of the lithium carbonate production unit 509. The lithium carbonate production unit 509 of the improved production loop 515 can be similar to the lithium carbonate production unit 109 of the current process 100 of Figure 1 In the first crystallizer 510a, lithium cations can combine with carbonate anions (CO3 from soda ash 2-)React to form lithium carbonate crystals. The main process stream 197 can advance from the first crystallizer 510a to the centrifuge 510b of the lithium carbonate production unit 509 along the flow path 253. The centrifuge 510b can separate the solid lithium carbonate crystals from the liquid of the main process stream 197 which is the centrate. The lithium carbonate crystals of the lithium-rich stream 198 can advance along the flow path 254 to the bicarbonation vessel 510c of the lithium carbonate production unit 509.

[0099] The centrate from the centrifuge 510b can be directed along the flow path 117, where the centrate can be combined with the first portion 219a of the liquid or centrate discharged from the centrifuge 510f of the lithium carbonate production unit 509 along the flow path 119. These streams together can comprise a wastewater stream 199, which can be directed to the solvent extraction unit 480, which will be discussed in further detail below.

[0100] Returning to the bicarbonation vessel 510c, the lithium-rich stream 198 from the first crystallizer 510a can be rinsed with the second portion 219b of the centrate from the centrifuge 510f, while carbon dioxide can be injected into the bicarbonation vessel 510c along the flow path 255, and treated (deionized) water can be injected into the bicarbonation vessel 510c along the flow path 262. These steps can result in the formation of soluble lithium bicarbonate by the reaction of lithium carbonate crystals with carbon dioxide.

[0101] The lithium-rich stream 198 can advance from the bicarbonation vessel 510c to the filter 510d of the lithium carbonate production unit 509 along the flow path 256, where waste solids can be separated from the lithium-rich stream 198 along the flow path 270. The lithium-rich stream 198 can travel along the flow path 257 to the second crystallizer 510e of the lithium carbonate production unit 509, where the formation of lithium carbonate crystals can occur. This process can release carbon dioxide, which can be recycled along the flow path 255 to the bicarbonation vessel 510c.

[0102] Then the lithium-rich stream 198 can flow along the flow path 258 to the second centrifuge 510f of the lithium carbonate production unit 509, where the solid lithium carbonate crystals can be separated from the liquid which is the centrate. As described in steps 110d, e of the production unit 109 in Figure 1 above, the lithium-rich stream 198 carrying the solid lithium carbonate crystals can advance along the flow path 259 to be dried, sized, filtered and packaged (and other steps) for sale. Similarly as described above, the centrate can be directed along the flow path 119, where the first portion 219a of the centrate can be directed to the solvent extraction unit 480, and the second portion 219b can be directed to the bicarbonation vessel 510c.

[0103] The wastewater stream 199 can contain high concentrations of sodium and potassium cations and low concentrations of lithium cations, as well as other aqueous ions. The wastewater stream 199 can enter the solvent extraction unit 480. The solvent extraction unit 480 can utilize a number of reagents. For example, the solvent extraction unit 480 can receive, for example but not limited to, an acid (such as sulfuric acid) along the flow path 501. The solvent extraction unit 480 can receive, for example but not limited to, caustic soda or a base (such as sodium hydroxide) along the flow path 502. The solvent extraction unit 480 can receive one or more solvents along the flow path 503, such as but not limited to one or more extractants, one or more diluents, or a combination thereof. In some aspects, the extractant can be reactive and can be dissolved in the diluent.

[0104] Two separate streams can emerge from the solvent extraction unit 480: the wastewater stream 199 and the secondary lithium-rich stream 598. The wastewater stream 199 and the secondary lithium-rich stream 598 can each be aqueous streams. The solvent extraction unit 480 can selectively extract 99% or more of the lithium from the wastewater stream 199, while most of the sodium and potassium remain in the wastewater stream 199. The extracted lithium can then be concentrated into the secondary lithium-rich stream 598. When optimized, as discussed in more detail below, the solvent extraction unit 480 can concentrate approximately 100% of the lithium from the wastewater stream 199 into the secondary lithium-rich stream 598.

[0105] In the case where almost all of the lithium is extracted from the wastewater stream 199 but significant concentrations of sodium and potassium remain, the wastewater stream 199 can leave the solvent extraction unit 480, containing less than 1% of the lithium that entered the solvent extraction unit 480 in the wastewater stream. In some aspects, for example but not limited to, perhaps 98% or more of the sodium and / or potassium remains in the wastewater stream 199, while perhaps 0.5% or less of the lithium remains in the wastewater stream 199. When optimized, the solvent extraction unit 480 can leave less than 0.1% of the lithium in the wastewater stream 199.

[0106] Then, the wastewater stream 199 leaving the solvent extraction unit 480 can flow to the ZLD unit 512a of the waste salt separation unit 511 of the improved production loop 515, and then to the centrifuge 512b of the waste salt separation unit 511. In some aspects, centrifuges, crystallizers, evaporators, or other types of separation equipment and / or dryers can be used to completely separate the waste salt from the wastewater stream 199. It is noted that the wastewater stream 199 can be a linear process immediately downstream of the solvent extraction unit 480 to completely separate the waste salt from the wastewater stream 199, that is, the wastewater stream 199 can exclude a recirculation loop (such as Figure 1 the recirculation loop 121).

[0107] Reference Figure 3For the ternary phase diagram, the chemical composition of the wastewater stream 199 entering the waste salt separation unit 511 (after leaving the solvent extraction unit 480) can fall into regions B, E, or F along the side 301a (representing 0% lithium concentration) or adjacent to said side. Thus, the waste salt separation unit 511 can completely separate the waste salt from the wastewater stream 199, while the loss of lithium in the form of lithium sulfate salt is no more than trace amounts (such as less than 0.5%). The resulting waste salts (such as sodium sulfate salt and potassium sulfate salt) can follow the flow path 261, where the waste salts can be stored together with other waste products (such as clay tailings).

[0108] In aspects of the present invention, the secondary lithium-rich stream 598 can follow the flow path 562 to the secondary crystallizer 530. Soda ash can be admixed with the secondary lithium-rich stream 598, as shown by the flow path 563. The lithium and soda ash in the secondary lithium-rich stream 598 can react within the secondary crystallizer 530 to form lithium carbonate crystals. The secondary lithium-rich stream 598 can leave the secondary crystallizer 530 and be conveyed along the flow path 564 to the secondary centrifuge separator 532. The secondary centrifuge separator 532 can separate the lithium carbonate crystals from the liquid or centrate. During the centrifugation stage, the lithium carbonate crystals can be washed to further remove contaminants. The lithium carbonate crystals can follow the flow path 565 to be ready for sale, similarly as described in steps 110d, e of the lithium carbonate production unit 109 of the current lithium extraction process 100 ( Figure 1 as shown above).

[0109] The centrate can follow the flow path 566 to the lithium carbonate production unit 509. The centrate can carry most of the sodium added by the soda ash. In aspects of the present invention, the flow path 566 can direct the centrate to the bicarbonation vessel 510c. In other aspects, the flow path 566 can direct to different sections of the lithium carbonate production unit 509, such as the first crystallizer 510a or the second crystallizer 510e.

[0110] In some aspects, the secondary lithium-rich stream 598 can rejoin the main process stream, such as by admixing with the flow path 250, rather than passing through the secondary crystallizer 530 and the secondary centrifuge separator 532. Since the secondary lithium-rich stream 598 contains the least amount of sodium and potassium, the admixing of the secondary lithium-rich stream 598 can avoid significantly increasing the concentration of sodium ions and potassium ions within the main process stream 197.

[0111] Figure 6 is a flowchart of an exemplary aspect of the solvent extraction unit 480 according to one aspect of the present disclosure.

[0112] The solvent extraction unit 480 may include an extraction circuit 681 and a stripping circuit 683. In aspects of the present invention, the extraction circuit 681 may be a two-stage extraction process, but this should not be considered limiting. In various aspects, the extraction circuit 681 and / or the stripping circuit 683 may have more or fewer than two stages. In aspects of the present invention, the extraction circuit 681 and the stripping circuit 683 may be countercurrent circuits, but this should not be considered limiting.

[0113] As shown, an aqueous feed stream 600 may be supplied to the solvent extraction unit 480 along a flow path 601. For Figure 4 the improved production circuit 415, the aqueous feed stream 600 may be the main process stream 197 (see Figure 4 ) that is delivered to the solvent extraction unit 480 along a flow path 250. For Figure 5 the improved production circuit 515, the aqueous feed stream 600 may be the wastewater stream 199 that travels from the lithium carbonate production unit 509 (such as flow paths 117, 119) to the solvent extraction unit 480 (see Figure 5 ). Upon entering the solvent extraction unit 480, the aqueous feed stream 600 may carry a large amount of aqueous lithium.

[0114] An alkali 630 (such as, but not limited to, sodium hydroxide) may be added to the aqueous feed stream 600 to control the pH of the aqueous feed stream 600, as shown by flow path 631 and flow path 632a. In some aspects, the alkali 630 may be added to achieve a pH of 10.0 - 12.5 for the aqueous feed stream 600. In more preferred aspects, the alkali 630 may be added to achieve a pH of 10.5 - 12.0 for the aqueous feed stream 600. In the most preferred aspects, the alkali 630 may be added to achieve a pH of 11.0 - 11.5 for the aqueous feed stream 600. In practice, approximately a stoichiometric equivalent amount of the alkali 630 may be added relative to the amount of aqueous lithium in the aqueous feed stream 600 entering the solvent extraction unit 480.

[0115] A solvent stream 610 (also referred to as the "organic solvent stream") can be supplied to the solvent extraction unit 480, as shown by flow path 611. This stream can contain a solvent. The solvent can contain at least one diluent and at least one extractant. The at least one diluent can contain at least one organic diluent. The at least one extractant can be dissolved in the at least one diluent. The at least one diluent can carry the extractant and facilitate contact between the extractant and the sulfate aqueous brine solution. In some aspects, the solvent can further contain at least one modifier. In some aspects, adding at least one modifier can increase the efficiency of the solvent extraction unit 480. The at least one modifier can be utilized for purposes such as, but not limited to, helping to prevent the formation of unwanted phases, increasing the solubility of the extractant in the diluent, or reducing the aqueous phase loss caused by the extractant. During testing, organic solvent blends such as Cyanex 923 (manufactured by Solvay S.A., Brussels, Belgium) and Mextral 54-100 (manufactured by KopperChem, Chongqing, China) were tested. Cyanex 923 contains a blend of compounds such as trialkylphosphine oxides. Specifically, the Cyanex 923 extractant can contain a mixture of the following four trialkylphosphine oxides: R3P(O)R2R'P(O)RR'2P(O)R'3P(0), where R = [CH3(CH2)7]-n-octyl and R' = [CH3(CH2)7]-n-hexyl. Mextral 54-100 contains a mixture of β-diketone 1-benzoyl-2-nonanone (as the main component), surfactants, modifiers, stabilizers, and other compounds. In some aspects, these solvents are blended with a diluent such as Exxsol D80 (manufactured by ExxonMobil, Irving, TX, USA). Exxsol D80 is a dearomatized fluid. In practice, any organic solvent (or its blend) suitable for selectively binding lithium to remove it from the aqueous phase and into the organic phase in the presence of additional monovalent species (such as, but not limited to, sodium and potassium) can be utilized. In some aspects, the solvent can be paraffinic, for example, but not limited to, as opposed to aromatic.

[0116] The aqueous feed stream 600 and the solvent stream 610 can pass through the first extraction vessel 682a and the second extraction vessel 682b. In aspects of the present invention, the aqueous feed stream 600 and the solvent stream 610 can flow countercurrently through the first extraction vessel 682a and the second extraction vessel 682b. For example, the aqueous feed stream 600 can enter the first extraction vessel 682a along flow path 601, exit the first extraction vessel 682a and then enter the second extraction vessel 682b along flow path 602, and then exit the second extraction vessel 682b (and the solvent extraction unit 480) along flow path 603. In some aspects, additional base 630 can be injected into flow path 602 through flow path 632b to adjust the pH as needed. The aqueous feed stream 600 exiting along flow path 603 can be depleted of lithium such that the aqueous feed stream 600 becomes a wastewater stream.

[0117] Regarding Figure 4 the improved production loop 415, the aqueous feed stream 600 exiting along flow path 603 can form a wastewater stream 199 and flow to the ZLD unit 412a of the waste salt separation unit 411 (see Figure 4 ). Regarding Figure 5 the improved production loop 515, where the wastewater stream 199 can be treated by the solvent extraction unit 480, the aqueous feed stream 600 exiting along flow path 603 can flow to the ZLD unit 512a of the waste salt separation unit 511 (see Figure 5 ).

[0118] In contrast, the solvent stream 610 can enter the second extraction vessel 682b along flow path 611, exit the second extraction vessel 682b and then enter the first extraction vessel 682a along flow path 612, and then exit the first extraction vessel 682a and be directed along flow path 613 to the stripping loop 683. The solvent stream 610 entering the stripping loop 683 can carry substantially all of the lithium (dissolved in the organic phase) of the solvent extraction unit 480 that entered the aqueous feed stream 600 (dissolved in the aqueous phase). In some aspects, a first portion of the solvent stream 610 can be routed only through the first extraction vessel 682a and a second portion of the solvent stream 610 can be routed only through the second extraction vessel 682b rather than flowing the entire solvent stream 610 through both extraction vessels 682a, b. Then each portion of the solvent stream 610 can flow to the stripping loop 683. In some aspects, the solvent stream 610 can first pass through the first extraction vessel 682a, countercurrent to the aqueous feed stream 600, and then pass through the second extraction vessel 682b, countercurrent to the aqueous feed stream.

[0119] The solvent stream 610 can selectively extract lithium from the aqueous phase of the aqueous feed stream 600 into the organic phase of the solvent stream 610. The volume ratio (“O / A ratio”) of the organic phase (solvent stream 610) to the aqueous phase (aqueous feed stream 600) within the extraction circuit 681 can be from 5 / 1 to 1 / 5. Preferably, the O / A ratio can be from 1 / 2 to 1 / 1. Most preferably, the O / A ratio can be approximately 2 / 3. The O / A ratio in the extraction circuit 681 can affect the percentage of lithium extracted from the aqueous feed stream 600 into the solvent stream 610. In some aspects, 95% or more of the lithium can be absorbed from the aqueous phase into the organic phase, leaving 5% or less of the lithium in the aqueous feed stream 600 to exit along the flow path 603. In a preferred aspect, 99% or more of the lithium can be extracted from the aqueous phase into the organic phase, leaving 1% or less of the lithium in the aqueous feed stream 600 to exit along the flow path 603. In the most preferred aspect, 99.9% or more (substantially 100%) of the lithium can be extracted from the aqueous phase into the organic phase, leaving 0.1% or less of the lithium in the aqueous feed stream 600 to exit along the flow path 603. In the case where the O / A ratio is 2 / 3, substantially 100% of the lithium can be extracted into the organic phase. In some aspects, the O / A ratio can affect the number of stages required to completely absorb the lithium. For example but not limited to, in the case where the O / A ratio is 2 / 3, two extraction stages may be required to extract substantially 100% of the lithium into the organic phase. For example but not limited to, in the case where the O / A ratio is 1 / 2, three extraction stages may be required to absorb substantially 100% of the lithium into the organic phase. Over time, the preferred O / A ratio may be affected by the relative costs of the equipment and the extractant. For example but not limited to, if the extractant cost is high, it may be desirable to operate at a lower O / A ratio (i.e., lower extractant cost) through more stages (i.e., more equipment cost). For example but not limited to, if the extractant cost is low, it may be desirable to operate at a higher O / A ratio through fewer stages.

[0120] In the stripping circuit 683, the lithium-loaded solvent stream 610 can be contacted with the aqueous acid stream 620 supplied by the flow path 621. In an aspect of the present invention, the aqueous acid stream 620 can comprise sulfuric acid. In an aspect of the present invention, the solvent stream 610 can be contacted with the aqueous acid stream 620 in a stripping vessel 684. In some aspects, the solvent stream 610 can be contacted with the aqueous acid stream 620 in multiple phases comprising a plurality of stripping vessels. In an aspect of the present invention, the solvent stream 610 can be contacted with the aqueous acid stream 620 in countercurrent flow.

[0121] An aqueous acid stream 620 can strip lithium from the organic phase of the solvent stream 610 and restore the lithium back into the aqueous phase of the aqueous acid stream 620 to produce an aqueous lithium-rich stream 623. By supplying sulfuric acid in a 100% stoichiometric ratio of the amount of lithium in the solvent stream 610, approximately 100% of the lithium can be extracted into the aqueous acid stream 620. In practice, it may be desirable to supply at a 110% stoichiometric ratio of the amount of lithium in the solvent stream 610. The O / A ratio of the solvent stream 610 to the aqueous acid stream 620 within the stripping vessel 684 can be from 7 / 1 to 1 / 1. Preferably, the O / A ratio can be from 6 / 1 to 2 / 1. Most preferably, the O / A ratio can be approximately 4 / 1.

[0122] The aqueous lithium-rich stream 623 (carrying substantially 100% of the lithium initially introduced into the solvent extraction unit 480 in the aqueous feed stream 600) can leave the stripping vessel 684 and the solvent extraction unit 480 along the flow path 622. Referring Figure 4 to the improved production loop 415 of Figure 4 , the flow path 622 can route the lithium-rich stream 198 to the crystallizer 410a of the lithium carbonate production unit 409 (shown in Figure 5 ). Referring Figure 5 to the improved production loop 515 of

[0123] The solvent stream 610 can leave the stripping vessel 684 substantially free of lithium. Most of the solvent stream 610 can be recycled, as shown by the flow path 614, where the solvent stream 610 can rejoin the flow path 611 after leaving the stripping vessel 684. A small portion of the solvent stream 610 may be lost during the process, which can be supplemented by injecting additional extractant and / or diluent along the flow path 611 into the solvent extraction unit 480. In some aspects, any organic components present in the aqueous waste stream can subsequently be removed. In some aspects, techniques such as, but not limited to, activated carbon filters can be used to remove organic matter from the aqueous stream. This may be desirable, for example but not limited to, in aspects where the presence of organic matter in the water stream can cause problems in downstream processing steps (e.g., foaming, coloring, or other issues) and / or when local or federal environmental protection regulations applicable to aqueous waste control standards require it.

[0124] The following table contains an example of the experimental results of the chemical compositions of the aqueous feed stream 600 and the aqueous lithium-rich stream 623:

[0125] Composition of aqueous feed stream 600 Composition of aqueous lithium-rich stream 623 Concentration factor Lithium concentration 2410 ppm 18,000 ppm Approximately 7.47 times Sodium concentration 19,502 ppm 6,800 ppm Approximately 0.35 times Potassium concentration 15,476 ppm 600 ppm Approximately 0.04 times

[0126] In the illustrated example, the final lithium concentration in the aqueous lithium-rich stream 623 can be 7.47 times the initial lithium concentration in the aqueous feed stream 600. The concentration factor can vary, e.g., depending on the O / A ratios utilized in the extraction loop 681 and the stripping loop 683. In some aspects, the concentration factor of the lithium concentration can be greater than or equal to 3-fold. In a preferred aspect, the concentration factor of the lithium concentration can be greater than or equal to 5-fold. In a most preferred aspect, the concentration factor of the lithium concentration can be greater than or equal to 7-fold.

[0127] Notably, the concentration factors of the sodium concentration and the potassium concentration can be less than 1, indicating that the concentrations of those respective cations decrease from their initial concentrations in the aqueous feed stream 600 to their final concentrations in the aqueous lithium-rich stream 623.

[0128] In some aspects, the concentration factor of the sodium concentration can be less than or equal to 0.5-fold. In a preferred aspect, the concentration factor of the sodium concentration can be less than or equal to 0.35-fold. In a most preferred example, the concentration factor of the sodium concentration can be less than or equal to 0.10-fold.

[0129] In some aspects, the concentration factor of the potassium concentration can be less than or equal to 0.15-fold. In a preferred aspect, the concentration factor of the potassium concentration can be less than or equal to 0.10-fold. In a most preferred example, the concentration factor of the potassium concentration can be less than or equal to 0.04-fold.

[0130] Due to the high purity of the chemical composition of the aqueous lithium-rich stream 623, the aqueous lithium-rich stream 623 can be suitable for producing lithium carbonate or lithium hydroxide with sufficient purity to meet battery application standards. The improved lithium extraction processes 400, 500 can also be used to produce marketable lithium carbonate or lithium hydroxide from brines containing other monovalent cation species, such as rubidium and / or cesium.

[0131] As described above, the wastewater stream 199 leaving the solvent extraction unit 480 along the flow path 603 may be lithium-free, which allows for the complete separation of waste salts from the wastewater stream 199 in a linear process with no more than trace losses of lithium. By avoiding the need for a recycle loop in the treatment of the wastewater stream 199, resource consumption can be significantly reduced. For example, acid consumption (such as sulfuric acid consumption) can be reduced to save costs, or the saved acid can be reused in the acid leaching step 104, which can result in a 3-5% improvement in lithium recovery from lithium ore. Lithium losses during the separation of sodium salts and potassium salts can also be avoided, thereby increasing production efficiency. Soda ash consumption can be reduced by approximately 25-30%. The power consumption and total production cost of the entire facility can be reduced by about 7%.

[0132] In an exemplary aspect, a lithium extraction process can include a solvent extraction unit configured to receive an aqueous feed stream from an upstream flow path. The aqueous feed stream can include lithium cations and at least one additional monovalent cation species. The lithium extraction process can further include a waste salt separation unit configured to receive an aqueous wastewater stream from a first downstream flow path. The first downstream flow path can fluidly connect the waste salt separation unit to the solvent extraction unit. The lithium extraction process can further include a lithium carbonate production unit configured to receive an aqueous lithium-rich stream from a second downstream flow path. The second downstream flow path can fluidly connect the lithium carbonate production unit to the solvent extraction unit.

[0133] In a further exemplary aspect, the solvent extraction unit may include an extraction circuit configured to contact the aqueous feed stream with an organic solvent stream to extract the lithium cations from the aqueous feed stream into the organic solvent stream; and a stripping circuit configured to contact the organic solvent stream with an aqueous acid stream to strip the lithium cations from the organic solvent stream into the aqueous acid stream. In a further exemplary aspect, the at least one additional monovalent cation species includes sodium cations. In a further exemplary aspect, the at least one additional monovalent cation species includes potassium cations. In a further exemplary aspect, the aqueous feed stream may include an initial lithium cation concentration, the lithium-rich aqueous stream may include a final lithium cation concentration, and the final lithium cation concentration may be greater than or equal to three times the initial lithium cation concentration. In a further exemplary aspect, the final lithium cation concentration may be greater than or equal to five times the initial lithium cation concentration. In a further exemplary aspect, the final lithium cation concentration may be greater than or equal to seven times the initial lithium cation concentration. In a further exemplary aspect, the remaining lithium cation concentration in the aqueous wastewater stream may be equal to or less than 0.01 times the initial lithium cation concentration. In a further exemplary aspect, the aqueous feed stream may include an initial sodium cation concentration, the lithium-rich aqueous stream may include a final sodium cation concentration, and the final sodium cation concentration may be less than or equal to 0.5 times the initial sodium cation concentration. In a further exemplary aspect, the aqueous feed stream may include an initial sodium cation concentration, the lithium-rich aqueous stream may include a final sodium cation concentration, and the final sodium cation concentration may be less than or equal to 0.35 times the initial sodium cation concentration. In a further exemplary aspect, the aqueous feed stream may include an initial potassium cation concentration, the lithium-rich aqueous stream may include a final potassium cation concentration, and the final potassium cation concentration may be less than or equal to 0.5 times the initial potassium cation concentration. In a further exemplary aspect, the aqueous feed stream may include an initial potassium cation concentration, the lithium-rich aqueous stream may include a final potassium cation concentration, and the final potassium cation concentration may be less than or equal to 0.05 times the initial potassium cation concentration. In a further exemplary aspect, the waste salt separation unit may be configured to completely separate waste salts from the aqueous wastewater stream in a continuous process.

[0134] In another exemplary aspect, a method for extracting lithium can include processing an aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with a solvent extraction unit. Processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit can include contacting the aqueous feed stream with an organic solvent stream comprising at least one extractant to extract the lithium cations from the aqueous feed stream into the organic solvent stream; and generating an aqueous wastewater stream from the aqueous feed stream comprising the at least one additional monovalent cation species. Processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit can further include stripping the lithium cations from the organic solvent stream into an aqueous acid stream to produce an aqueous lithium-rich stream. The method for extracting lithium can further include separating waste salts from the aqueous wastewater stream in a linear process. The waste salts can include at least one additional monovalent cation species.

[0135] In a further exemplary aspect, the at least one additional monovalent cation species can include at least one of sodium cations and potassium cations. In a further exemplary aspect, processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit can further include enriching the final concentration of the lithium cations in the aqueous lithium-rich stream by 3-fold or more compared to the initial concentration of the lithium cations in the aqueous feed stream. In a further exemplary aspect, the remaining lithium cation concentration in the aqueous wastewater stream can be equal to or less than 0.01-fold of the initial lithium cation concentration. In a further exemplary aspect, processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit can further include enriching the final concentration of the lithium cations in the aqueous lithium-rich stream by 5-fold or more compared to the initial concentration of the lithium cations in the aqueous feed stream. In a further exemplary aspect, processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit can further include enriching the final concentration of the lithium cations in the aqueous lithium-rich stream by 7-fold or more compared to the initial concentration of the lithium cations in the aqueous feed stream. In a further exemplary aspect, the method for extracting lithium can further include processing the aqueous lithium-rich stream to produce at least one of lithium carbonate and lithium hydroxide.

[0136] In another exemplary aspect, a lithium extraction process can include a solvent extraction unit configured to receive an aqueous feed stream comprising lithium cations; a waste salt separation unit configured to receive an aqueous wastewater stream; and a lithium carbonate production unit configured to receive an aqueous lithium-rich stream.

[0137] Attention should be paid to conditional language, such as "can, could, might, or may", which generally, unless otherwise specifically stated or otherwise understood in the context in which it is used, is intended to convey that certain aspects include and other aspects do not include certain features, elements, and / or steps. Thus, such conditional language is generally not intended to imply that the features, elements, and / or steps are necessary for one or more particular aspects in any case, or that one or more particular aspects must include logic for determining whether these features, elements, and / or steps are included in or will be performed in any particular aspect, with or without user input or prompting.

[0138] It should be emphasized that the aspects described above are merely possible examples of embodiments, presented only to clearly understand the principles of the present disclosure. As understood by those skilled in the art of the present disclosure, any process description or block diagram in a flowchart should be understood to represent a module, section, or part of code that includes one or more executable instructions for implementing specific logical functions or steps in the process, and includes alternative embodiments, in which the functions may not be included or performed at all according to the functions involved, and the functions may not be performed in the order shown or discussed (including substantially simultaneously or in the reverse order). Various changes and modifications can be made to the aspects described above without materially departing from the spirit and principles of the present disclosure. In addition, the scope of the present disclosure is intended to cover any and all combinations and sub - combinations of all the elements, features, and aspects discussed above. All such modifications and changes are intended to be included within the scope of the present disclosure, and all possible claims for combinations of individual aspects or elements or steps are intended to be supported by the present disclosure.

Claims

1. A lithium extraction process, comprising: A solvent extraction unit configured to receive an aqueous feed stream from an upstream flow path, the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species; A waste salt separation unit configured to receive an aqueous wastewater stream from a first downstream flow path, the first downstream flow path fluidly connecting the waste salt separation unit to the solvent extraction unit; And A lithium carbonate production unit configured to receive an aqueous lithium-rich stream from a second downstream flow path, the second downstream flow path fluidly connecting the lithium carbonate production unit to the solvent extraction unit.

2. The lithium extraction process according to claim 1, wherein the solvent extraction unit comprises: An extraction circuit configured to contact the aqueous feed stream with an organic solvent stream to extract the lithium cations from the aqueous feed stream into the organic solvent stream; and A stripping circuit configured to contact the organic solvent stream with an aqueous acid stream to strip the lithium cations from the organic solvent stream into the aqueous acid stream.

3. The lithium extraction process according to claim 1, wherein the at least one additional monovalent cation species comprises sodium cations.

4. The lithium extraction process according to claim 1, wherein the at least one additional monovalent cation species comprises potassium cations.

5. The lithium extraction process according to claim 1, wherein: The aqueous feed stream comprises an initial lithium cation concentration; The aqueous lithium-rich stream comprises a final lithium cation concentration; and The final lithium cation concentration is greater than or equal to 3 times the initial lithium cation concentration.

6. The lithium extraction process according to claim 5, wherein the final lithium cation concentration is greater than or equal to 5 times the initial lithium cation concentration.

7. The lithium extraction process according to claim 5, wherein the final lithium cation concentration is greater than or equal to 7 times the initial lithium cation concentration.

8. The lithium extraction process according to claim 5, wherein the remaining lithium cation concentration in the aqueous wastewater stream is equal to or less than 0.01 times the initial lithium cation concentration.

9. The lithium extraction process according to claim 5, wherein: The aqueous feed stream comprises an initial sodium cation concentration; The aqueous lithium-rich stream comprises a final sodium cation concentration; and The final sodium cation concentration is less than or equal to 0.5 times the initial sodium cation concentration.

10. The lithium extraction process according to claim 5, wherein: The aqueous feed stream comprises an initial sodium cation concentration; The aqueous lithium-rich stream comprises a final sodium cation concentration; and The final sodium cation concentration is less than or equal to 0.35 times the initial sodium cation concentration.

11. The lithium extraction process according to claim 5, wherein: The aqueous feed stream comprises an initial potassium cation concentration; The aqueous lithium-rich stream comprises a final potassium cation concentration; and The final potassium cation concentration is less than or equal to 0.5 times the initial potassium cation concentration.

12. The lithium extraction process according to claim 5, wherein: the aqueous feed stream comprises an initial potassium cation concentration; the aqueous lithium-rich stream comprises a final potassium cation concentration; and the final potassium cation concentration is less than or equal to 0.05 times the initial potassium cation concentration.

13. The lithium extraction process according to claim 1, wherein the waste salt separation unit is configured to completely separate waste salts from the aqueous wastewater stream in a linear process.

14. A method for extracting lithium, the method comprising: processing an aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with a solvent extraction unit, the processing comprising: contacting the aqueous feed stream with an organic solvent stream comprising at least one extractant to: extract the lithium cations from the aqueous feed stream into the organic solvent stream; and generate an aqueous wastewater stream from the aqueous feed stream comprising the at least one additional monovalent cation species; stripping the lithium cations from the organic solvent stream into an aqueous acid stream to produce an aqueous lithium-rich stream; and separating waste salts from the aqueous wastewater stream in a linear process, the waste salts comprising the at least one additional monovalent cation species.

15. The method according to claim 14, wherein the at least one additional monovalent cation species comprises at least one of sodium cations and potassium cations.

16. The method according to claim 14, wherein processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit further comprises enriching the final concentration of the lithium cations in the aqueous lithium-rich stream by 3 times or more compared to the initial concentration of the lithium cations in the aqueous feed stream.

17. The method according to claim 16, wherein the remaining lithium cation concentration in the aqueous wastewater stream is equal to or less than 0.01 times the initial lithium cation concentration.

18. The method according to claim 14, wherein processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit further comprises enriching the final concentration of the lithium cations in the aqueous lithium-rich stream by 5 times or more compared to the initial concentration of the lithium cations in the aqueous feed stream.

19. The method according to claim 14, wherein processing the aqueous feed stream comprising lithium cations and at least one additional monovalent cation species with the solvent extraction unit further comprises enriching the final concentration of the lithium cations in the aqueous lithium-rich stream by 7 times or more compared to the initial concentration of the lithium cations in the aqueous feed stream.

20. The method according to claim 14, which further comprises processing the aqueous lithium-rich stream to produce at least one of lithium carbonate and lithium hydroxide.

21. A lithium extraction process, which comprises: a solvent extraction unit configured to receive an aqueous feed stream comprising lithium cations; a waste salt separation unit configured to receive an aqueous wastewater stream; and A lithium carbonate production unit, the lithium carbonate production unit being configured to receive an aqueous lithium-rich stream.

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