Li recovery process and on-site production of chemicals for li recovery process

Abstract

The present disclosure introduces a method for recycling the acid, base, and salt reagents required in Li recovery processes. A membrane electrolyzer containing oxygen-depolarized cathodes is implemented to produce the required chemicals on-site. The system can utilize a portion of the salt marsh brine or other lithium-containing brines or solid waste to produce hydrochloric or sulfuric acid, sodium hydroxide, and carbonate salts. The simultaneous production of acid and base enables the utilization of both chemicals in conventional processes for Li recovery from brines and mineral rocks. Desalted water can also be used in washing steps in the recovery process or returned to the evaporation ponds. The process can also be used to convert lithium salts directly to the high-value LiOH product. The process does not produce any solid effluents, which makes it easy to implement in existing industrial Li recovery facilities.

Description

[0001] Cross-references to related applications

[0002] This application is a divisional application of Chinese invention patent application No. 201980092809.2, filed on December 19, 2019.

[0003] This application claims priority to U.S. Provisional Application No. 62 / 784,324, filed December 21, 2018, and U.S. Provisional Application No. 62 / 907,486, filed September 27, 2019, the contents of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0004] This invention generally relates to methods for Li recovery and the on-site production of chemicals used in Li recovery methods. This invention can be used to improve the extraction of lithium from various sources, including brine sources or lithium ore sources, where hydrochloric acid, sodium hydroxide, and / or sulfuric acid may be required. This invention eliminates the need for outsourcing acid and alkali feedstocks by utilizing readily available brine on-site, whether the brine is from saline marsh brine, brine solutions generated during lithium ore refining, or brine generated during lithium-ion battery recycling. This invention can also be used to directly convert lithium-containing salts (e.g., lithium chloride or lithium sulfate) into higher-value lithium hydroxide products. This invention can also provide a gas diffusion electrode configured for use in a membrane electrolyzer and a method for producing the gas diffusion electrode. Furthermore, this invention can provide a membrane electrolyzer for treating salt-containing solutions. This invention can also provide a method for purifying, concentrating, or producing LiOH using a membrane electrolyzer. Background Technology

[0005] Lithium has received increasing attention over the past few decades due to the emergence of lithium-ion batteries (LIBs) as a primary source of energy storage for automotive and electronic applications. The electric vehicle (EV) market, heavily reliant on LIBs, has also expanded at a record pace over the past decade and is projected to share 20% of the transportation market with internal combustion engines. Renewable energy generation, including solar and wind power applications, is also expected to rely on LIBs for load balancing. Recycling (e.g., recycling Li from LIBs) is considered a secondary resource for lithium. Besides batteries, Li is used in glass and ceramics, chemicals and pharmaceuticals, metallurgy, and lubricants. Therefore, the demand for improved Li recycling methods and related equipment continues to grow. Summary of the Invention

[0006] As an aspect of the present invention, a gas diffusion electrode for a membrane electrolysis cell is disclosed herein. The gas diffusion electrode includes a diffusion layer configured to diffuse a gas; a hydrophilic catalyst layer disposed on a surface of the diffusion layer, the hydrophilic catalyst layer having a hydrophilicity greater than the diffusion layer and being capable of transporting negative ions; and an ion exchange membrane disposed on a surface of the hydrophilic catalyst layer, the ion exchange membrane being configured to exchange ions from the hydrophilic catalyst layer to an opposite surface of the ion exchange membrane.

[0007] According to another aspect of the present invention, a method of producing a gas diffusion electrode for a membrane electrolysis cell is also disclosed. The method includes disposing a hydrophilic catalyst layer on a surface of a diffusion layer, the hydrophilic catalyst layer having a hydrophilicity greater than the diffusion layer; and disposing an ion exchange membrane on a surface of the catalyst layer, the ion exchange membrane being configured to exchange ions from the catalyst layer to an opposite surface of the ion exchange membrane and prevent flooding of the catalyst layer.

[0008] According to another aspect of the present invention, a membrane electrolysis cell for treating a salt-containing solution is also disclosed. The membrane electrolysis cell includes an inlet through which the salt-containing solution is introduced to an interior of the membrane electrolysis cell; an anode positioned to extend within the interior of the membrane electrolysis cell and positioned in an anode compartment; a cathode including a gas diffusion electrode positioned to extend within the interior of the membrane electrolysis cell and positioned in a cathode compartment, the gas diffusion electrode including a diffusion layer configured to diffuse a gas and a hydrophilic catalyst layer disposed on a surface of the diffusion layer, the hydrophilic catalyst layer having a hydrophilicity greater than the diffusion layer and the hydrophilic catalyst layer being configured to transport negative ions; a gas inlet through which a gas containing O2 is introduced to contact the gas diffusion electrode; a first ion exchange membrane interposed between the anode compartment and the hydrophilic catalyst layer of the gas diffusion electrode, the first ion exchange membrane being configured to exchange ions received from the anode to an opposite surface of the first ion exchange membrane; and at least one outlet through which a product of the salt solution is removed from the interior of the membrane electrolysis cell.

[0009] Finally, according to yet another aspect of the present invention, a method of purifying or concentrating LiOH using a membrane electrochemical cell is disclosed. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 An exemplary process flow diagram showing recovery of Li from a brine operation is shown;

[0011] Figure 2 An exemplary process flow diagram showing recovery of Li from a rock mining operation is shown;

[0012] Figure 3 A schematic diagram illustrating an exemplary membrane electrolysis cell showing feed and product streams is shown;

[0013] Figure 4 The structure of the electrode and membrane assembly inside the first embodiment of a membrane electrolysis cell is shown;

[0014] Figure 5 The structure of the electrode and membrane assembly inside the second embodiment of a membrane electrolysis cell is shown;

[0015] Figure 6 The structure of the electrode and membrane assembly inside the third embodiment of a membrane electrolysis cell is shown;

[0016] Figure 7 The structure of the electrode and membrane assembly inside the fourth embodiment of a membrane electrolysis cell is shown;

[0017] Figure 8A An exemplary single layer gas diffusion electrode (GDE) is shown;

[0018] Figure 8B Details of the single layer gas diffusion electrode (GDE) of Figure 8A are shown.

[0019] Figure 9A And 9B Details of the contact interface between the catalyst layer and the anion diffusion membrane of an exemplary double layer gas diffusion electrode (GDE) are shown;

[0020] Figure 10 A first embodiment of a double layer gas diffusion electrode (GDE) is shown;

[0021] Figure 11 A second embodiment of a double layer gas diffusion electrode (GDE) is shown;

[0022] Figure 12 A schematic diagram showing the function of a double layer gas diffusion electrode is shown;

[0023] Figure 13 A schematic diagram showing exemplary process steps for manufacturing a gas diffusion electrode for use as an oxygen depolarized electrode is shown;

[0024] Figure 14 A schematic diagram showing an embodiment of a catalyst coated membrane prepared for use with an oxygen depolarized cathode is shown;

[0025] Figure 15A And 15B Top and side cross-sectional views of an embodiment of a flow field on a cathode compartment are shown;

[0026] Figure 16 A process flow diagram showing the use of an embodiment of a membrane electrolysis cell incorporated into a method for recovering Li from brine is shown;

[0027] Figure 17 Process flow diagram showing use of an embodiment of a membrane electrolysis cell incorporated into a method for extracting Li from mineral rock;

[0028] Figure 18 Process flow diagram showing use of an embodiment of in situ production of LiOH and Li2CO3 and HC1 from LiCl brine via LiCl -> LiOH + HC1 incorporated into a method of recovering Li from salt marsh brine;

[0029] Figure 19 Process flow diagram showing use of an embodiment of in situ production of LiOH and Li2CO3 and HC1 from LiCl brine via LiCl -> LiOH + HC1 incorporated into a method of recovering Li from salt marsh brine;

[0030] Figure 20 Process flow diagram showing use of an embodiment of in situ production of crystalline LiOH from mixed LiCl and NaCl brine via LiCl -> LiOH + HC1 and NaCl -> NaOH + HC1 conversion in the same tank incorporated into a method of recovering Li from salt marsh brine;

[0031] Figure 21 Process flow diagram showing use of an embodiment of in situ production of LiOH and H2SO4 from Li2SO4 via Li2SO4 -> LiOH + H2SO4 incorporated into a method of lithium recovery in mid-stream into hard rock mining operations;

[0032] Figure 22 Process flow diagram showing an embodiment of LiOH production from Li2CO3 in which HC1 is produced and recycled to dissolve Li2CO3 in a closed loop process;

[0033] Figure 23 Process flow diagram showing one embodiment of LiOH production incorporated into a method of recovering Li from lithium brine by selective adsorption of Li via LiCl -> LiOH + HC1 conversion using ion exchange resin such that the HC1 is used to regenerate the ion exchange resin;

[0034] Figure 24 Process flow diagram showing another embodiment of LiOH production incorporated into a method of recovering Li from lithium brine by selective adsorption of Li via LiCl -> LiOH + HC1 conversion using ion exchange resin such that the HC1 is used to regenerate the ion exchange resin;

[0035] Figure 25 Schematic diagram showing an embodiment of LiOH production from Li2CO3;

[0036] Figure 26 A current versus time plot of a membrane electrolyzer using a single layer GDE is shown, with pure oxygen applied at the cathode;

[0037] Figure 27 A current versus time plot of a membrane electrolyzer using a double layer GDE as the ODC is shown, with pure oxygen applied at the cathode; and

[0038] Figure 28 A current versus time plot of a membrane electrolyzer using a double layer GDE as the ODC is shown, with air applied at the cathode. DETAILED DESCRIPTION

[0039] Although the application is illustrated and described herein with reference to specific embodiments, the application is not intended to be limited to the details shown. Rather, various modifications can be made in the details within the scope and range of equivalents of the claims.

[0040] According to one aspect, the application can provide a unique gas diffusion electrode that can use ambient, non-dried, humid air as a source of oxygen. According to one embodiment, the gas diffusion electrode is used only at the cathode of the membrane electrolyzer disclosed herein.

[0041] According to further aspects of the application, the application can improve the extraction of Li from various sources, including brine sources or lithium ore sources, where hydrochloric acid, sodium hydroxide, and / or sulfuric acid can be required; eliminate the need to outsource acid and base feedstocks by utilizing on-site available brines, whether from a salt marsh brine or a brine solution produced in a lithium ore refining process or a brine produced in a lithium ion battery recycling process; convert lithium-containing salts (such as lithium chloride or lithium sulfate) directly into the more valuable lithium hydroxide product; provide a gas diffusion electrode configured for use in a membrane electrolyzer and a method of producing the gas diffusion electrode; provide a membrane electrolyzer for treating a salt-containing solution; and / or provide a method of purifying or concentrating or producing LiOH using a membrane electrolyzer.

[0042] As used herein, the term "hydrophobic" means a lack of affinity for water, repulsion of water, or inability to adsorb or absorb water. In particular, a hydrophobic substance is one that has a contact angle greater than 90° when a drop of water is placed on it.

[0043] As used herein, the term "hydrophilic" means having an affinity for water and being able to adsorb or absorb water. In particular, a hydrophilic material is one that has a contact angle less than 90° between a drop of water and the material.

[0044] As used herein, the terms "oxygen-depolarized cathode" or "ODC" and "gas diffusion cathode" or "GDC" are used interchangeably and / or refer to the same structure, which is used, for example, as a cathode in a membrane electrolysis cell.

[0045] Extraction of lithium from brine

[0046] The growing demand for lithium requires matching production levels. In its free metal form, lithium is extremely reactive. Therefore, it is usually found in mineral compounds, which make up about 0.007% of the Earth's crust, the main source of lithium. Natural sources of lithium include igneous rocks, springs, ocean water, and salt marsh brines, which are underground reservoirs containing high concentrations of dissolved salts, such as lithium, potassium, and sodium. These are usually located below the dry lake bed surface, known as salt marshes.

[0047] Most lithium production comes from brine sources, and most lithium is recovered from lithium-bearing salt marsh brines or salt lake brines that occur in the Earth's crust. The concentration of lithium in seawater is about 0.17 mg / L. Geothermal water and oil well brines are also another source of recoverable lithium. Brines containing lithium salts that can be generated during lithium-ion battery recycling are also a source of recoverable lithium. Recovering lithium from these brines is less costly than mining lithium from mineral rocks.

[0048] While the following disclosure presents embodiments relating to the recovery of lithium from salt marsh brines or from lithium brines generated in the process of recovering lithium from lithium ores, the lithium salt solutions (also referred to herein as "brines") can also be derived from lithium-ion battery recycling processes.

[0049] The first attempt to commercially extract lithium from a salt lake was reported in 1936 at Searles Lake in the United States. Since then, the extraction of lithium from salt lakes has increased. When considering brines as a source of Li recovery, brine concentration, pond accessibility, and location of solar evaporation, ratios of alkaline earth and alkali metals to lithium, and chemical complexity are important factors.

[0050] Industrial scale recovery of lithium from brines can begin with a series of multistage, continuous solar pond evaporation of water from the brine. The lithium concentration of the world's major brine extraction operations ranges from 0.06 to 0.15 wt.% elemental lithium. This concentration reaches about 6 wt.% at the end of the evaporation cycle when lithium carbonate (Li2CO3) is prepared or LiOH is produced as the desired end product. During the evaporation stages, salts with lower solubility than the lithium salts precipitate out of the brine. Rock salt such as (NaCl) precipitates first, followed by sylvite (KCl), carnallite (NaCl-KCl), and other salts. KCl is the main byproduct in most brine recovery operations.

[0051] Some salt brine containing higher Mg, Ca and B contents require additional treatment steps to remove these elements. Removal of magnesium and calcium is preferred in order to use the final product for battery applications. Boron contamination is also detrimental to the quality of the final product and must be removed during the extraction process to achieve LIB quality requirements. During the evaporation stage, some Mg compounds such as carnallite (KCI-MgCI2-6H2O) and nesquehonite (MgCI2-6H2O) precipitate in the brine at about 4.4 wt.% elemental lithium concentration. After further evaporation to reach 5-6 wt.% Li, co-precipitation of compounds such as carnallite lithium (LiCI-MgCI2-6H2O) with lithium carbonate or lithium chloride results in a final product with Mg contamination. In order to obtain a pure lithium carbonate or lithium chloride product, removal of these contaminants is preferred.

[0052] Processes for removing Ca, Mg and B from brine include solvent extraction and precipitation stages. For example, boron can be removed by a solvent extraction process or precipitation of boric acid. In the solvent extraction method, an extractant such as a higher aliphatic alcohol or other organic solvent is used in an acidic environment to remove boron from the brine. Under acidic conditions, boron compounds form boric acid, which precipitates out of the brine.

[0053] A number of systems have been reported to develop processes for removing boron from lithium-containing brine. For example, U.S. Patent No. 3,855,392 describes the use of higher aliphatic alcohols to extract boron from magnesium brine. Similarly, U.S. Patent No. 4,980,136 describes the use of higher aliphatic alcohols having 6 to 16 carbon atoms dissolved in kerosene at a pH of 1 to 2 to extract boron from brine. U.S. Patent No. 3,424,563 and U.S. Patent No. 5,939,038 describe the use of glycols (which are organic molecules containing two OH groups in their structure) as extractants for removing boron. U.S. Patent No. 4,261,960 discloses a boron, magnesium and calcium removal process that includes the use of slaked lime (Ca(OH)2) and calcium chloride solution to precipitate calcium borate hydrate and magnesium hydroxide and calcium sulfate dihydrate from the brine.

[0054] Magnesium and calcium can be removed from brine by several precipitation processes. Magnesium is removed from brine by converting the dissolved magnesium salts to magnesium hydroxide. Calcium hydroxide, lime (CaO) or slaked lime (Ca(OH)2) is added to the brine to increase the pH and form Mg(OH)2, which has limited solubility in water. During this process, sulfate ions also precipitate as CaS04, and boron precipitates as calcium borate hydrate. Precipitation of Mg(OH)2also facilitates further removal of boron by surface adsorption mechanisms.

[0055] Adjustment of pH can be done by different media. U.S. Patents Nos. 4,036,713 and 4,207,297 disclose the use of lithium hydroxide product from the recovery product to raise the pH of the initial brine, thereby precipitating magnesium hydroxide. These patents also disclose the use of other basic solutions, including sodium hydroxide or calcium hydroxide. U.S. Patent No. 6,143,260 discloses the use of lime liquor from a previous lithium precipitation stage to remove Mg by precipitation of Mg(OH)2. U.S. Patent No. 6,048,507 discloses a bicarbonate treatment process, which includes mixing the impure lithium carbonate brine with CO2 gas under pressure to precipitate unwanted iron, magnesium, and calcium species. Further removal of Fe, Mg, and Ca ions is done by a selective ion exchange process.

[0056] U.S. Patent No. 5,993,759 describes a multi-stage process for purifying high Mg content lithium carbonate brine using soda ash, lime, and an organic extractant. The process starts with an acidification step, where hydrochloric acid (HC1) is used to maintain the pH between 0 and 4 to produce boric acid (H3BO3), which is removed by crystallization. The resulting boron-lean brine is further purified using an organic solvent extractant to obtain a boron-free brine. The resulting brine, which is diluted with mother liquor, is then treated by the addition of sodium carbonate (soda ash), which produces magnesium carbonate in the form of a solid precipitate. The remaining magnesium in the brine is further precipitated using calcium hydroxide, which forms Mg(OH)2. In this stage, any calcium introduced into the brine also precipitates as calcium carbonate due to the presence of sodium carbonate in the brine. The final step of adding soda ash results in the precipitation of lithium carbonate.

[0057] U.S. Patent No. 8,691,169 discloses that the order in which these compounds are added to the brine plays an important role in producing high purity lithium carbonate. The disclosure indicates that the addition of calcium hydroxide prior to the brine removal step removes all soluble magnesium in the brine after evaporation, as well as some boron and surface ions. The remaining boron in the brine is removed by solvent extraction. The resulting magnesium- and boron-free brine is then carbonated with soda ash to obtain a high purity lithium carbonate precipitate. The resulting Li2CO3 is further purified by the addition of carbonic acid, which forms lithium bicarbonate, and then the precipitation of pure lithium carbonate is achieved by heating the bicarbonate-containing brine. The final stage disclosed is the removal of all sodium and calcium impurities from the final precipitate product.

[0058] The final lithium product is produced from the resulting brine, where most of the Mg, B, Ca, and other species have been removed. Soda ash (sodium carbonate, i.e., Na2CO3) is the reagent that converts the solute lithium ions into a Li2CO3 precipitate. This precipitate can be used at an industrial grade or a high purity grade. Depending on the nature of the process, the initial composition of the brine, and the customer requirements, the Li recovery process can be designed and modified. For industrial grade lithium carbonate, the common recovery process of pond evaporation and concentration, selective removal of contaminants, and carbonation is sufficient.

[0059] For high purity and battery grade products, several additional processing stages have been proposed. For example, U.S. Patent No. 9,169,125 B2 discloses the use of spray drying, washing, and carbonation after removal of contaminants to obtain a purified lithium carbonate product. The bicarbonation of lithium carbonate can be used to purify the final product.

[0060] U.S. Patent No. 8,691,169 B2 discloses the use of carbonic acid to form lithium bicarbonate from lithium carbonate. The resulting bicarbonate is then decomposed into a purified carbonate salt by exposing it to heat at 50 to 95 °C. Another method to further purify the brine prior to lithium carbonate precipitation is the use of ion exchange resins. The use of this method in the process can result in a lithium carbonate product with a purity of up to 99.9%.

[0061] WO Patent Application Publication No. 2013 / 036983 discloses the use of ion exchange resins throughout the recovery process. Also disclosed therein is an ion exchange resin for the removal of boron, which replaces the solvent extraction method. Also disclosed is an ion exchange resin for the removal of trace amounts of soluble divalent and trivalent species containing magnesium, calcium, and iron from the brine in the last stages of recovery. U.S. Patent No. 8,641,992 discloses an ion exchange resin through which magnesium ions are selectively removed from the brine.

[0062] Generally, the process for recovering lithium from brine can be as shown in Figure 1 The first stage of recovery includes multiple pond evaporation concentration steps that remove high amounts of sodium and potassium salts, such as NaCl and KCl and possibly other salts, by precipitation, as these salts have lower solubility than the desired lithium salts. Thus, evaporation increases the concentration of lithium in the brine. In this evaporation stage, some magnesium is also removed as precipitated MgCl2. The next stage involves the removal of boron, calcium, magnesium, which are the main sources of impurities in the brine. Repeated pH adjustment, solvent extraction, and precipitation steps are used to remove the B, Ca, and Mg ions to ensure maximum removal of the ions. Ion exchange removal of the remaining trace amounts of monovalent, divalent, and trivalent ionic species other than lithium further purifies the brine. The introduction of soda ash Na2CO3 to convert the dissolved lithium salts into lithium carbonate Li2CO3 is the last major step in the production of industrial grade and high purity lithium carbonate.

[0063] As expected, almost every brine recovery operation, regardless of the source of the brine, relies heavily on the use of reagents throughout the process stages. Generally, more than 50% of the total operating cost of a typical lithium production comes from the cost of these reagents. The main reagents that affect the cost of recovery are soda ash (Na2C03), lime (mainly CaC03) and slaked lime (Ca(OH)2), caustic soda (NaOH), hydrochloric acid (HC1), extractants such as higher aliphatic alcohols or other organic solvents, and sulfuric acid (H2S04).

[0064] Soda ash or sodium carbonate (Na2C03) is a main component of the lithium recovery process because it is important to each of the lithium recovery stages. It is used to remove calcium from the brine through precipitation of CaC03. It is also the only reagent used to produce lithium carbonate.

[0065] Lime, mainly CaC03, is heated and then hydrated to produce slaked lime or calcium hydroxide (Ca(OH)2), which can be used to remove magnesium and some sulfate ions. Depending on the use of lime in the initial evaporation ponds or lithium carbonate processing plant, different grades of lime can be used. For example, using slaked lime to remove magnesium chloride and magnesium sulfate and other sulfate ions from the brine occurs according to the following reaction:

[0066] 1)

[0067] 2)

[0068] 3)

[0069] Caustic soda or sodium hydroxide (NaOH) is another chemical reagent that can be used in different stages of the processing plant. It can be used as a stripping agent to regenerate the solvent after the removal of boron by extraction using an organic solvent. It is also the most suitable alkali hydroxide for removing magnesium because it produces very high purity Mg(OH)2 as a byproduct. Another important use of NaOH is to adjust the pH during water treatment and for regenerating ion exchange resins.

[0070] Similar to caustic soda, hydrochloric acid (HC1) can be used as a reagent in multiple process steps throughout the recovery process. It can be used as a pH modifier in the boron solvent extraction step, as the initial stages of solvent extraction typically require an acidic environment. Another use of HC1 is in the concentration ponds, also known as evaporation ponds, where its addition prevents the unwanted precipitation of lithium carbonate. HC1 is also the main reagent used to convert lithium carbonate to lithium chloride when needed. HC1 is also used to regenerate the acid exchange resins used to selectively remove ions from the brine. Sulfuric acid (H2S04) can be stored in a concentrated form of 98% and can be used for descaling and cleaning of the lithium carbonate processing plant.

[0071] The main component of reagent cost, in terms of total reagent cost, is caustic soda, which accounts for nearly 50%; lime is about 15%, caustic soda (NaOH) is about 7% and hydrochloric acid accounts for 1%. In some cases where the Mg:Li ratio is high, this contribution of caustic soda can be as high as 80% of the total reagent cost. On-site production of these chemicals is very beneficial in reducing operating costs.

[0072] As an aspect of the present invention, an electrodialysis multi-compartment system is disclosed herein that allows for the on-site production of caustic soda (NaOH) and hydrochloric acid (HC1) from existing brine in an evaporation pond. The caustic soda is then converted to sodium carbonate (caustic soda) and sodium bicarbonate (NaHC03) using readily available carbon dioxide (C02) on site. The system is fully controllable and allows for the desired product concentrations to be reached. The ability to adjust the NaOH and HC1 concentrations reduces the operating costs associated with transporting and storing concentrated solutions.

[0073] Extraction of lithium from rock mining

[0074] Several minerals contain lithium in their structure. For example, at least four minerals have been found to be of interest as viable sources of lithium. These are lepidolite (K(Li, Al, Rb)2(Al, Si)4O 10 (F, OH)2), spodumene (LiAl(Si03)2), petalite (LiAlSi40 10 ) and eucryptite ((Li, Na)AlP04(F, OH)). Of these, spodumene is generally the most important ore in commercial lithium production. (Helvaci, C., 2003. Presence and distribution of lithium in borate deposits and some recent lake waters of West-Central Turkey. Int. Geol. Rev. 45(2), 1-14). The anticipated growth in demand for lithium batteries for hybrid and all-electric vehicles over the next century has led to interest in lithium production (Tahil, 2007, 2008; Bradbury, 2008).

[0075] A variety of methods have been developed to obtain lithium from lithium ores (Victor, K. A., 1953. Method of recovering lithium compounds from lithium minerals. U.S. Patent 2793933; Walter, R., Bichowsky, Francis R., 1935. Method of recovering lithium from its ores. U.S. Patent 2020854; Robinson, G. P., 1961. Recovery of lithium from ore. U.S. Patent 2983576; Moon, K. S., Fuerstenau, D. W., 2003. Surface crystal chemistry in selective flotation of spodumene (LiAl[SiO3]2) from other aluminosilicates. Int. J. Miner. Process. 72(1-4), 11-24; Saeki, S., Lee, J., Zhang, Q., Saito, F., 2004. Co-grinding LiCoO2 with PVC and water leaching of metal chlorides formed in ground product. Int. J. Miner. Process. 74(Supplement 1), S373-S378; A., Maras, I., Ioglu, D., Bilici, M. S. U., G., 2006. Extraction of lithium from boron clays by using natural and waste materials and statistical modelling to achieve cost reduction. Miner. Eng. 19(5), 515-517; Jandova, J., Dvorak, P., Vu, H. N., 2010. Processing of zinnwaldite waste to obtain Li2CO3. Hydrometallurgy 103(1-4), 12-18; Brandt, F., Haus, R., 2010. New concepts for lithium minerals processing. Miner. Eng. 23(8), 659-661; Chen, Y., Tian, Q., Chen, B., Shi, X., Liao, T., 2011. Preparation of lithium carbonate from spodumene by a sodium carbonate autoclave process. Hydrometallurgy 109(1-2), 43-46). Lithium can be extracted from lepidolite using the sulfuric acid and lime process (Distin, P. A., Phillips, C. V., 1982. The acid extraction of lithium from the granites of South West England. Hydrometallurgy 9(1), 1-14). However, the extraction of lithium by the sulfuric acid process typically uses high concentrations of acid and the purification process can be complex. The lime process uses limestone and can require a large amount of energy.

[0076] Wadman and von Girsewalt (Ellestad, Reuben B., Clarke, Fremont F., 1955. Extraction of lithium from its ores. Min. Eng. 7, 1045) extracted lithium from lithium silicate ores (lepidolite (K(Li, Al, Rb)2(Al, Si)4O 10(F,OH)2), spodumene (LiAl(SiO3)2) and an excess of an alkali metal sulfate (typically K2SO4) are ground together in a ratio of at least 1 to 1 and the mixture is heated to a relatively high temperature. Ion exchange occurs at the elevated temperature, forming lithium sulfate, which is dissolved by leaching with water along with the excess potassium sulfate. Successful operation of this process requires thorough mixing and careful temperature control. In addition, the high consumption of K2SO4 can increase costs. Using a mixture of an alkali metal sulfate and an alkali metal oxide as reactants, results show that favorable results are obtained when the lithium mica is roasted with a mixture of Na2SO4, K2SO4 and CaO.

[0077] To process spodumene as described in U.S. Patent No. 2,516,109, the a- spodumene feedstock is first converted to the β-phase by roasting at 1100-1300 °C. A typical process for extracting lithium from spodumene minerals is shown in Figure 2 Tahil (Tahil, W., 2010. How much lithium does a Li ion EV battery really need? Meridian Int. Res., (March 5, 2010)) reports roasting spodumene in a kiln at about 1100 °C. The calcine is mixed with sulfuric acid and roasted at 250 °C, followed by leaching in water to produce an aqueous solution of lithium sulfate. The reaction of β-spodumene with H2SO4 is shown as reaction 4). (Mcketta, J. J., 1988. Lithium and lithium compounds. Encyclopedia of Chemical Processing and Design vol. 28. Marcel Dekker)

[0078] 4) Li2O AI2O3 4SiO2(s) + H2SO4(conc) → Li2SO4(s) + AI2O3 4SiO2(s)

[0079] Lithium carbonate can be recovered by adding sodium carbonate to the solution after pH adjustment, purification and evaporation, as shown in reaction 5.

[0080] 5) Li2SO4(aq.) + Na2CO3(s) → Li2CO3(s) + Na2SO4(aq.)

[0081] The first continuous plant in the world to convert spodumene concentrate into lithium carbonate by calcination, roasting the calcine with H2SO4 and subsequent water leaching was commissioned by Galaxy Resources in China in 2012 (Clarke, G.M., 2013. Lithium-ion batteries: raw material considerations. Am. Inst. Chem. Eng. 44-52). One of the disadvantages of the sulphuric acid process to treat lepidolite, petalite and amtholite is the need for high concentrations of acid and complex purification processes, while spodumene needs to be converted to the more leachable β-phase at higher temperatures.

[0082] Overall, reagent costs also account for 45% of the total operating costs in the rock mining process. Implementing methods to reduce such costs is the next important step in the lithium recovery process. Since a large amount of chemical reagents are used in these processes, the most logical approach is to recover them after the process. Electrochemical technology provides a flexible solution for the recovery of chemicals.

[0083] Electrochemical process for on-site reagent recovery

[0084] The use of membrane electrolysis cells (also known as electrodialysis cells) has been successfully implemented to produce chemicals from brackish or saltwater streams as described herein. The process involves the use of a series of ion exchange membranes that are stacked in a specific order with respect to the components of the saltwater stream being treated and the desired outputs. Membranes are designed to allow specific charged ionic species to permeate through. Cation exchange membranes transport cationic species, while anion exchange membranes only allow anions to transport through the membrane structure. Bipolar membranes are another type of membrane that split water molecules into H + and OH - components. The movement of ions is achieved by applying an external voltage using cathodes and anodes. Under the applied voltage, anions move towards the positively charged anode, while cations move towards the negatively charged cathode. By carefully placing the membranes, it is possible to produce the desired chemical species, such as acids, bases and salts. During the electrolysis process using aqueous catholyte and anolyte, gaseous species such as H2 and O2 can be produced at the electrodes due to the electrolysis of water.

[0085] Electrochemical desalination technology relies on the membrane electrolysis principle described above. A concentrated saltwater or salt stream is passed through a separation device. An electric current (DC) applied between the anode and the cathode produces ionic species. Anions from the input salt solution migrate through the anion exchange membrane and combine with H + ions produced at the anode and produce an acid. Similarly, cations from the input salt solution migrate through the cation exchange membrane and combine with OH - ions produced at the cathode and produce a base.

[0086] U.S. Patent No. 2,829,095 discloses an example of a salt splitting process in which a combination of anion and cation exchange membranes are used to dissociate NaCl salt into Na + and Cl - ions. The sodium ions then combine with OH - ions from the cathode and produce NaOH. The chloride ions, on the other hand, combine with H + produced at the anode and produce HC1. The total voltage required to achieve splitting includes the potential for water decomposition and the potential drop across the membranes and electrolyte solutions.

[0087] Another example of this process is the conversion of brine (NaCl) to NaOH and chlorine gas in the chlor-alkali process described in U.S. Patent No. 4,217,186. In this process, NaCl brine is fed into the anolyte compartment, while water (or NaOH) is fed into the catholyte compartment. Upon application of voltage, sodium ions migrate through the cation exchange membrane toward the cathode, where they combine with OH - ions produced by the electrolytic splitting of water at the cathode to form NaOH. According to reaction 6), chlorine gas is evolved in the anode compartment, while hydrogen gas is produced at the cathode.

[0088] 6) 4Cl - → 2Cl2+ 4e - E 0 = 1.36 V

[0089] The chlor-alkali process can be modified to reduce the overall cell voltage and, thus, the energy consumption. To eliminate H2 generation at the cathode and reduce the overall energy consumption of the electrolytic cell, oxygen depolarized cathodes (ODC) have shown to reduce the electrolytic cell voltage required for the chlor-alkali process. An example of this application is disclosed in U.S. Patent No. 4,191,618. Depolarization of the cathode with oxygen gas results in the formation of only hydroxyl ions, thus preventing the formation of hydrogen gas. In the case of hydrogen evolution, the cathode reaction in the chlor-alkali process is as follows:

[0090] 7) 4H2O + 4e - → 2H2+ 4OH - E 0 = -0.83 V

[0091] Using oxygen depolarized cathodes, in which O2 gas is applied to the cathode, the cathode reaction changes to a hydroxyl formation reaction according to the following reaction:

[0092] 8) 2H2O + O2+ 4e - → 4OH - E 0 = 0.401 V

[0093] Overall, the use of ODCs and the application of pure oxygen at the cathode in the chlor-alkali process means that the overall cell voltage is about 1 V lower than 3.3 V in a chlor-alkali cell. In most ODC cases, the running cell requires pure O2.

[0094] As will be described in detail below, the novel gas diffusion electrodes disclosed herein allow the five-compartment membrane electrolysis cell to be operated with a stream of air applied at the cathode instead of pure oxygen. In this case, the anodic reaction is not the evolution of chlorine because there is no chloride solution there. In contrast, oxygen is evolved in the water oxidation reaction:

[0095] 9) 2H2O(l)→ O2(g) + 4H + (aq.) + 4e -

[0096] WIPO Patent Application Publication No. 2015 / 149185 Al describes a membrane electrolysis cell assembled using a combination of anion and cation exchange membranes. The cell is used to convert a stream of carbon dioxide gas and brine into carbonate, hydrochloric acid, and desalinated water.

[0097] The present disclosure relates to an in-situ process for producing chemical reagents from salt marsh brine or other lithium-containing brines (such as those produced from lithium-ion battery recycling operations and rock minerals) during a conventional lithium extraction process. The process describes an electrochemical method for converting a waste chemical stream into valuable reagent chemicals needed during a lithium extraction operation. The disclosed electrochemical method involves a multi-compartment membrane electrolysis cell that can be incorporated into the current process for extracting lithium from salt marsh brines and lithium-containing ores without interfering with the process streams of either type of recycling process. The disclosed method is unique in that it allows the connection of unique membrane electrolysis cell feed and product streams to the commonly used lithium extraction process, as well as the special design of a gas diffusion electrode (GDE) to be used as a cathode and optionally also as an anode for the cell.

[0098] In the following description of embodiments of the invention, a membrane electrolysis cell will be described, followed by a detailed discussion of the details of a gas diffusion electrode used as an oxygen depolarized cathode. Finally, the specific use of a membrane electrolysis cell containing a GDE as a cathode in lithium production will be described.

[0099] Membrane electrolysis cell

[0100] A generalized schematic of the feed and product streams of the membrane electrolysis cell of the present invention is shown in Figure 3 .

[0101] The solution being treated, also referred to herein as a brine feed, is fed to a depletion (also referred to as a salt depletion chamber or compartment) chamber, where cations and anions migrate from the solution in the depletion chamber to an adjacent product chamber (which can also be referred to herein as an acid accumulation compartment or a base accumulation compartment), thereby reducing the ionic concentration of the solution. The solution can be any brine solution, such as a saltwater, seawater, or wastewater, or any solution being treated to reduce the ionic concentration therein, such as industrial effluents from oil and gas, mining, forestry, lithium-ion battery recycling processes, etc. Any type of aqueous or non-aqueous stream composed of ionic or non-ionic species (which can be made ionic by the addition of other chemicals or by processing) can potentially be used as a brine feed.

[0102] As noted above, in electrodialysis, a potential gradient can be generated between the anode and the cathode. In an aqueous environment, the anode and the cathode typically undergo the following half-cell reactions, respectively:

[0103] 10) H2O(l) → 2H + (aq.) + ½ O2(g) + 2e - (anode reaction)

[0104] 11) 2H + (aq.) + 2e - → H2(g) (cathode reaction)

[0105] The dialysis cell (also referred to as a membrane electrolytic cell) of the disclosed embodiments includes multiple compartments, forming a “stack” of compartments, and the walls of the compartments include ion exchange barriers separating the compartments. The ion exchange barriers in the membrane electrolytic cell (also referred to herein as membranes) typically do not require regeneration, thereby reducing the need for input of chemicals in the ion exchange process. If necessary, inorganic fouling of the ion exchange barriers and fouling of the ion exchange barriers can be managed by polarity reversal, periodic flushing, and / or acid washing.

[0106] The ion exchange barriers of the membrane electrolytic cell include cation exchange barriers that selectively allow the migration of cations and anion exchange barriers that selectively allow the migration of anions. The ion exchange barriers can be water permeable. The ion exchange barriers can be ion exchange membranes and can include, but are not limited to, commercially available bipolar membranes and membranes with chemical modifications. Non-limiting examples of such modifications are: (i) perfluorinated membranes with fixed pyridine or sulfonic acid groups; (ii) polyether ketones; (iii) polysulfonones; (iv) polyphenylene ethers; (v) polystyrenes; (vi) styrene-divinylbenzene; (vii) polystyrene / acrylic-based fabrics with sulfonate and quaternary ammonium cations; (viii) polyfluorinated sulfonic acid polymers; or (ix) resin-polyvinylidene fluoride fabrics. In alternative embodiments, other ion exchange barriers such as are known in the art can be used.

[0107] The membrane electrolysis cell (also referred to as an electrodialysis cell) of the embodiments generally includes a cathode and an anode, which can be constructed of electrically conductive porous or non-porous substrates and coated with one or more catalysts. Ion exchange barriers (e.g., ion exchange membranes) can alternatively or additionally be coated with one or more catalysts. These catalysts can increase the rate of reactions in the electrolysis cell. Suitable catalysts include, but are not limited to, noble or non-noble transition metals and compounds thereof (e.g., oxides, nitrides, etc.). The catalysts can be supported on, for example, metals, metal oxides, metal nitrides, etc., or not. A mixture of one or more catalysts, optional binders, and other optional additives (e.g., hydrophilic and / or hydrophobic additives to control liquid and bubble removal) can be applied to the cathode or anode or both and / or the ion exchange barriers by various techniques known in the art, such as, for example, spraying, sputtering, screen printing, etc. Fluids can be flowed in the cell through flow fields (open channels, such as serpentine, inter-digitated, etc.), porous closed channels, or open pockets. The cell can be operated under pressure or pressure differential.

[0108] In operation, an electrical potential can be applied between the cathode and the anode to promote electrochemical reactions to occur at the electrodes and the migration of ions through the ion exchange membranes. In a membrane electrolysis cell (also referred to as an electrodialysis cell), an electrical potential can be applied between the conductors to create an electric field to enhance the migration of ions through the ion exchange membranes and chambers without any electrochemical reactions occurring. However, the application of an electrical potential between the conductors is not necessary for operation, as ions can diffuse through the ion exchange membranes under the influence of other transport mechanisms, such as concentration gradients.

[0109] In embodiments of the membrane electrolysis cell, a manifold assembly can be used to deliver solutions into and out of the chambers of the membrane electrolysis cell, which can include conduits, optional valves, and other equipment known in the art for delivering solutions into and out of the chambers of the membrane electrolysis cell.

[0110] As Figure 3 As schematically shown, a feed brine stream is supplied to the cell. Other inputs include air and / or oxygen and / or carbon dioxide and / or hydrogen or mixtures of these gases and electrical power. Product streams can include desalinated water, acid, base, and / or carbonate salts. Depending on the composition of the feed brine, the acid material can be hydrochloric acid (HC1) or sulfuric acid (H2SO4). Depending on the nature of the feed brine, the base product can be sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH) or mixtures. Carbonate and bicarbonate salts can also be produced when carbon dioxide is fed into the gas feed stream. These salts can also be produced separately by passing carbon dioxide into the sodium hydroxide product at a later stage.

[0111] The first embodiment of the membrane electrolysis cell consists of five compartments, as shown in Figure 4 The cell contains an oxygen depolarized cathode (ODC) in the cathode compartment (described in detail later), a dimensionally stable anode (DSA) in the anode compartment, and two anion and two cation exchange membranes stacked in an alternating fashion, thereby defining the compartments of the cell.

[0112] The electrochemical processes involved in the first membrane electrolysis cell are the cathodic reaction on the ODC, the anodic reaction on the DSA, acid formation in the acid accumulation compartment, base formation in the base accumulation compartment, and salt splitting in the salt depletion compartment. The use of the first anion exchange membrane near the cathode compartment allows the transport of the hydroxide ions produced by the cathode into the base compartment. Another important use of this membrane is to avoid flooding of the gas diffusion electrode cathode (i.e., the ODC) in contact with the base solution. The first cation exchange membrane between the salt depletion compartment and the base accumulation compartment is able to transport the salt cations (Na + in the case of NaCl or Na2SO4 as the feed brine, or Li in the case of LiCl or Li2SO4) from the salt depletion compartment into the base accumulation compartment. The combination of sodium ions with hydroxide ions results in the formation of sodium hydroxide in the base accumulation compartment. The anodic reaction results in the production of protons (H + ), which then enter the acid accumulation compartment through the second cation exchange membrane. The protons then combine with the anions transported from the salt depletion compartment through the second anion exchange membrane to form an acid. Depending on the nature of the salt, the anion formed is Cl - in the case of NaCl, SO4 2- (sulfate) in the case of Na2SO4, hydrochloric acid (HC1), or sulfuric acid (H2SO4). Furthermore, if LiCl is fed to the salt depletion compartment, HC1 will accumulate in the acid accumulation compartment, and LiOH will form in the base accumulation compartment. Finally, if Li2SO4 is used as the brine feed stream, sulfuric acid (H2SO4) and LiOH will form in the acid accumulation compartment and the base accumulation compartment, respectively.

[0113] The second embodiment of the membrane electrolysis cell is shown in Figure 5 In this second embodiment, the membrane electrolysis cell includes four compartments. In this embodiment, as in the first embodiment, the cathode is an oxygen depolarized cathode housed in a cathode compartment defined by a first anion exchange membrane. The cathode compartment is in fluid communication with a base accumulation compartment through the first anion exchange membrane. The base accumulation compartment is defined by the first anion exchange membrane and a cation exchange membrane. As can be seen in Figure 4 , the base compartment is thus in fluid communication with a salt compartment, which can also be referred to as a salt depletion compartment, through the cation exchange membrane. The cation exchange membrane defines an anode compartment that houses the anode. The anode is thus in fluid communication with the salt compartment through the cation exchange membrane.

[0114] In Figure 4 The first embodiment of the membrane electrolysis cell, shown in + Cations migrate through the cation exchange membrane to the negatively charged cathode compartment and remain in the base accumulation compartment as they cannot pass through the first anion exchange membrane. Similarly, OH - Anions accumulate in the base accumulation compartment as they will migrate away from the negatively charged cathode and toward the positively charged anode through the anion exchange membrane. Like Na + OH - Ions remain in the base accumulation compartment as they cannot pass through the cation exchange membrane. Thus, NaOH is formed in the base accumulation compartment. As Figure 5 Cl - Anions migrate from the salt compartment to the anode through another anion exchange membrane. Cl - Anions combine to form Cl2, i.e., chlorine gas, at the anode. Note that since the membrane electrolysis cell is in an aqueous environment, some water oxidation reactions will occur at the anode compartment as the anode compartment and the salt (also referred to as salt depletion) compartment are separated by an anion exchange membrane.

[0115] Importantly, one skilled in the art can appreciate that if LiCl in aqueous solution is used instead of the exemplary NaCl as the brine feed stream, LiOH will be produced in the base accumulation compartment. In the case of LiCl, chlorine gas will still be produced at the anode. Similar to the first embodiment of the membrane electrolysis cell, Na2SO4or Li2SO4can also be used as the brine feed stream in the second embodiment of the membrane electrolysis cell, thus NaOH and LiOH will be produced in the base accumulation compartment, respectively, and H2SO4will be produced at the anode.

[0116] The third embodiment of the membrane electrolysis cell is shown in Figure 6 which includes three compartments. As shown, the anode is housed in the salt depletion compartment, which third embodiment includes two additional compartments; a cathode compartment and a base accumulation compartment. Thus, the brine feed is essentially fed onto the anode. As in the first and second embodiments, the cathode comprises a double layer oxygen depletion cathode, which is preferably fed with oxygen in the form of air, more preferably in the form of humidified air.

[0117] Thus, as Figure 6 shown, OH -Ions are generated at the cathode, and they migrate out of the negatively charged cathode, through the anion exchange membrane defining the cathode compartment, and into the alkali accumulation compartment. For an exemplary NaCl aqueous solution as the feed brine, such as... Figure 6 As shown, Na formed in the anode / salt consumption compartment + Ions migrate from the positively charged anode, pass through the cation exchange membrane that defines the anode / salt consumption compartment, and enter the alkali accumulation chamber. NaOH is thus formed in the alkali accumulation chamber.

[0118] like Figure 6 As shown, Cl is formed at the anode. - Anions are generated, thus chlorine gas is produced at the anode. Similar to the first and second embodiments of the membrane electrolyzer, if the feed brine contains an aqueous LiCl solution, LiOH will form in the alkali accumulation compartment and Cl2 will be generated at the anode. If the feed brine is an aqueous Na2SO4 solution, NaOH will form in the alkali compartment, while H2SO4 will form at the anode. Finally, if the feed brine is an aqueous Li2SO4 solution, LiOH will form in the alkali compartment, while H2SO4 will form at the anode.

[0119] A fourth embodiment of the membrane electrolyzer is shown in Figure 7 In this embodiment, a single ion exchange membrane is present, which may be a cation exchange membrane. As in all other embodiments, the cathode is an ODC using O2, but air can be used as the O2 source. As in the previous embodiments, an aqueous NaCl solution is shown as an exemplary feed brine, but those skilled in the art will understand that, depending on the type of ions in the feed brine, similar ion transport to that of NaCl will occur. In this fourth embodiment, a brine containing NaCl is fed into the anode compartment. + Ions thus move through the cation exchange membrane into the cathode compartment. Since the cathode contains ODC, OH- is formed at the cathode. - The ions then form a base, NaOH, in the cathode compartment. In this embodiment, it is clear that the cathode compartment and the base compartment are identical. Figure 4 As shown, Cl - Ions combine at the anode to form chlorine gas.

[0120] Any membrane electrolyzer described herein may optionally include any of the following features:

[0121] • Flow field to improve the transport of oxygen and water into and out of the membrane electrolyzer;

[0122] • The concentrations of the generated acid and base can be controlled by combining the characteristics of the designed ion exchange membrane with the feedback loop.

[0123] Gas diffusion electrode

[0124] As briefly mentioned above, one important component of the membrane electrolysis cells disclosed herein is a unique gas diffusion electrode used as an oxygen depolarized cathode. This gas diffusion electrode allows the membrane electrolysis cell to be operated using air as the source of oxygen at the cathode. This is a major economic and safety advance in the ability to incorporate these cells into lithium recovery processes.

[0125] A gas diffusion electrode is schematically illustrated in Figure 8A and 8B Typically, in these gas diffusion electrodes that can be used as oxygen depolarized cathodes, the catalyst is deposited directly on the surface of a gas diffusion layer (GDL), as shown in Figure 8A Typically, the catalyst is either hydrophobic or hydrophilic. As shown in Figure 8B a small water droplet spreading out over the surface of the catalyst indicates that the catalyst is hydrophilic. It should be understood that in Figure 8B and subsequent figures, the small water droplet, whether it is spreading out to indicate a hydrophilic surface or is shown as sitting on top of the surface to indicate a hydrophobic surface, does not indicate that water is actually present on the surface. The small water droplet is simply a convenient way to indicate whether the surface shown is hydrophilic or hydrophobic.

[0126] As shown in Figure 8A and 8B In a single layer GDE or ODC, the layer includes a catalyst on a gas diffusion layer, optionally with an anion exchange membrane on the side of the GDL (not shown) opposite the catalyst.

[0127] Implementation of an ODC in a membrane electrolysis cell requires a large change in the cell design. A porous gas diffusion electrode (GDE) is typically used as the cathode. This is because a three-phase boundary is required, where three reactants (oxygen gas, liquid water, and electrons) must be present simultaneously. The most critical factor is the ease of access of oxygen gas to the active area where the reaction takes place.

[0128] It should be understood that the terms “upper”, “middle”, “lower”, and the like in the following discussion only relate to the relative position of the layers in the figures being discussed and do not necessarily apply to the structure being used.

[0129] One key feature of the gas diffusion electrode (GDE) of the present invention (also referred to herein as an oxygen depolarized cathode (ODC) or a gas diffusion cathode (GDC)) is that the catalyst layer is deposited directly on an anion exchange membrane, as shown in the cross-sectional view of Figure 9A This catalyst coated membrane (CCM) structure allows for better transport of ions (OH -or other anion). It should be understood that the catalyst coated membrane refers to an anion exchange membrane with a catalyst layer applied on one side at the interface between the cathode and the base compartment. Importantly, this gas diffusion electrode with a hydrophilic catalyst layer applied directly underneath the anion exchange membrane is only used on the cathode side of all membrane electrolysis cells disclosed herein.

[0130] Figure 9B A cross-sectional view of a double layer ODC is shown, which shows how the catalyst layer is in direct contact with the porous diffusion layer. The catalyst layer can be hydrophilic or hydrophobic depending on the operation. Looking closely Figure 9B , Figure 9B The uppermost layer in is an anion exchange membrane. In the case of the first embodiment of the membrane electrolysis cell described above (five-compartment), the anion exchange membrane will face the base accumulation compartment in the membrane electrolysis cell as described herein. Directly underneath the anion exchange membrane is a hydrophilic catalyst layer. This hydrophilic catalyst layer is disposed directly on a first gas diffusion layer (GDL). As shown in Figure 9B , underneath the first gas diffusion layer is an optional second gas diffusion layer. These gas diffusion layers are known in the art and are hydrophobic.

[0131] The gas diffusion layers can be made of, for example, carbon fiber paper, carbon felt, carbon cloth, porous metal structures, or other porous materials that can conduct electrons and provide gas diffusion capabilities. Depending on the voltage applied to the electrode, the reaction of reducing water to produce hydrogen gas can occur on many different materials. Without wishing to be bound by theory, the gas diffusion electrode as disclosed herein can ensure that any hydrogen produced due to the reduction of water can react with oxygen to produce water. This water can then be used to participate in the oxygen reduction at the cathode to produce OH - .

[0132] Finally, disposed directly on the second gas diffusion layer is an optional hydrophobic catalyst layer. Importantly, if this optional second catalyst layer is present, it is a hydrophobic catalyst layer. If the optional second gas diffusion layer is not present, the optional hydrophobic catalyst layer can be disposed directly on the side of the first gas diffusion layer opposite the desired hydrophilic catalyst layer. As known in the art, both the hydrophobic catalyst layer and the hydrophilic catalyst layer comprise commercially available platinum / carbon powder. The Pt / C catalyst, also known as an electrocatalyst, is mixed with an anion conductive ionomer. The addition of the anion conductive ionomer allows for better transport of OH - ions from the reaction site to the catalyst layer / membrane interface. It also serves as a binder for the platinum / carbon powder or other electrocatalyst. The binder can be a polymer that has both hydrophilic and hydrophobic properties. The binder can be a polymer that is completely hydrophobic or completely hydrophilic. For example, Nafion® (DuPont) ionomer is hydrophobic with hydrophilic pores, while (DuPont) can also be used as the binder, but is only hydrophobic. The specific properties of the binder should allow for gas diffusion, electrical conductivity, and ionic conductivity. In most cases, this is a balance of the amount of binder and the catalyst. If there is too much polymer, the electrons will not be able to conduct, but if there is too little binder, the catalyst layer will be unstable. The catalyst layer comprising this mixture is hydrophilic. The anion exchange ionomer can be an ionomer, i.e., a polymer with a certain amount of ionizable comonomer. The ionomer can be a dispersed solution in a liquid, which is combined with the catalyst and applied to the gas diffusion layer. An exemplary method of creating the ionomer binder can be to provide an ion exchange membrane in a solvent. This solution can be combined with the catalyst and applied to the gas diffusion layer to create the catalyst layer, thereby creating a gas diffusion electrode. Some ion exchange membranes can be provided as ionomers and do not need to be dissolved. Some such anion exchange membranes are commercially available. A non-limiting example of such a material is FAA-3 ionomer, which comprises a polyaromatic polymer, quaternary ammonium groups and has bromide ions (Br - ) as counterions; or, for example, an anion exchange ionomer from Ionomr (Vancouver, BC, Canada) is suitable.

[0133] The hydrophilic / hydrophobic nature of the gas diffusion electrode used as the oxygen depolarized cathode described herein is schematically shown in Figure 10 and 11 . The hydrophilicity or hydrophobicity of the catalyst layer is indicated by the small water droplets shown on the schematic. The anion exchange membrane is not shown in Figure 10 and 11 . Figure 10 One embodiment of the gas diffusion electrode is shown, where the optional hydrophobic catalyst layer is not present. However, since the gas diffusion layer itself is hydrophobic, the small water droplets located on the gas diffusion layer indicate that the layer is hydrophobic. The non-optional hydrophilic catalyst layer is shown disposed directly on top of the gas diffusion layer and under the anion exchange membrane (not shown), and it is reported as hydrophilic by the small water droplets partially absorbed in Figure 10 . Figure 11 Similar to Figure 10 , but the optional hydrophobic catalyst layer is indeed shown, indicated by the small water droplets not absorbed on the catalyst layer. Similar to Figure 10 , the anion exchange membrane is not shown, but it is understood to be present and disposed on the surface of the hydrophilic catalyst layer, opposite the side disposed on the gas diffusion layer.

[0134] The benefits of the double layer GDE (i.e. a hydrophilic catalyst layer deposited directly under the anion exchange membrane and on top of the gas diffusion layer) stem from the two different functions of its structure. First, the unique structure facilitates the reaction of oxygen reduction to hydroxide ion, reaction 12), rather than the formation of undesirable hydrogen gas through reaction 13).

[0135] 12) O2+ 2H2O + 4e - → 4OH -

[0136] 13) 2H2O + 2e - → 2OH - + H2

[0137] The formation of hydrogen gas is undesirable because: (a) when reaction 13) occurs, there is about 1 V of total cell voltage (i.e. additional energy consumption); and (b) since oxygen, hydrogen, and platinum catalyst are simultaneously present in the cathode compartment, hydrogen gas makes the operation of this cell unsafe.

[0138] Second, the specific configuration of the hydrophilic and hydrophobic layers in this double layer gas diffusion electrode allows for two simultaneous processes. First, and importantly, the hydrophobic diffusion layer and optional hydrophobic bottom catalyst layer (if present) ensure that the humidified gas stream (oxygen or air) is always readily accessible to the hydrophilic catalyst layer facing the anion exchange membrane, resulting in greatly improved mass transfer and increased output capacity of the membrane electrolysis cell. The hydrophobic catalyst layer at the bottom of the double layer gas diffusion electrode (if present) also ensures that any possible hydrogen gas formed at the hydrophilic catalyst layer facing the anion exchange membrane immediately combines with the incoming oxygen to form water. Hydrophobicity improves the reaction by pushing water away from the electrode and preventing catalyst sites from being flooded. If catalyst sites are flooded with water, oxygen will not be able to reach the cathode and the desired oxygen and water reduction reaction to produce anions will not occur. This is schematically shown in Figure 12 . Thus, the hydrophilic catalyst layer facing the anion exchange membrane provides optimal cell performance and reduced contact resistance, i.e. better ionic contact, while the other (optional) catalyst layer of the gas diffusion electrode must be hydrophobic (if present) to ensure that any water that can enter with the air or through the anion exchange membrane with oxygen and hydrogen chemical reactions at the platinum catalyst reacts with oxygen in the gas diffusion layer of the cathode. Thus, when hydrogen gas leaves the cell, it will come into contact with platinum in the hydrophobic catalyst layer on the bottom of the gas diffusion electrode. The platinum catalyzes the reaction of hydrogen and oxygen to water, which either reacts with oxygen through the oxygen reduction reaction to produce hydroxide ions or leaves the system in the form of water without reaction.

[0139] Figure 13 and 14 A process for producing a double layer gas diffusion electrode for use as an oxygen depolarized cathode is illustrated. AsFigure 13 As shown, the process begins with two separate layers of a hydrophobic gas diffusion layer. In the following discussion, these gas diffusion layers will be referred to as the "top" and the "bottom," referring only to their position within the diffusion layer. Figure 13 The relative position within.

[0140] The top gas diffusion layer is coated with catalyst ink to provide a hydrophilic catalyst layer. The ink is a mixture of Pt / C catalyst powder and anion exchange ionomer (used as a binder and anion transfer agent), as described above. The bottom gas diffusion layer is similarly coated with catalyst ink containing a hydrophobic agent (e.g., polytetrafluoroethylene (PTFE) dispersion). Therefore, the ink is Pt / C catalyst powder, anion exchange ionomer (which allows the catalyst layer to transport anions), and PTFE dispersion (…). A mixture of materials (such as this is an example of such materials) serves to make the catalyst layer hydrophobic. Next, two coated gas diffusion layers are placed together such that their uncoated sides face each other. An anion exchange membrane is disposed on the hydrophilic catalyst layer. In operation, it should be understood that the orientation of the completed oxygen depolarization cathode causes the hydrophilic catalyst layer to face the anion exchange membrane, which may face the alkali accumulation compartment, and thus the hydrophobic catalyst layer to face the incoming gas flow containing O2 (preferably air and more preferably humidified air). Regarding... Figure 13 As shown in the process, it is clear that another implementation of the method is to coat each side of a single gas diffusion layer, rather than using two separate gas diffusion layers, each coated separately and then placed together with the coated sides facing outwards.

[0141] Figure 14 An embodiment of a catalyst-coated membrane is shown that can be used with a cathode and will be applied in a manner similar to the bilayer ODC described above. Figure 14 The schematic illustration shows that this embodiment includes only the key elements of the ODC. These are Pt / C catalyst combined with anion exchange ionomers and hydrophobic agents as catalyst ink, which is coated onto an alkaline-stabilized anion exchange membrane. In this way, it is possible to allow O2 to flow through the catalyst layer while the anion exchange membrane faces the alkaline accumulation chamber. The main advantage of the catalyst-coated membrane is the increased contact resistance at the interface between the catalyst layer and the membrane. Functionally, it performs similarly to a bilayer GDE or ODC.

[0142] The oxygen diffusion cathode as described above can optionally include flow channels on the backside of the double layer ODC. The flow channels serve two purposes. First, it provides improved gas (air or oxygen) distribution. The flow channels can be serpentine, multi-serpentine, parallel flow, or cross flow. Second, the "landing" portion of the flow field also acts as a pressure point, thus providing uniform and adequate contact throughout the cell. An example of a serpentine flow field in the cathode compartment is shown in plan view in Figure 15A Figure 15B A cross-sectional side view of the channels formed by such serpentine flow channels is shown. The black squares are the points of contact of the flow field (i.e. gas) with the gas diffusion electrode / oxygen depolarized cathode.

[0143] Thus, unlike the single layer gas diffusion electrode, the double layer gas diffusion electrode of the present invention is preferably used as the oxygen depolarized cathode in all embodiments of the membrane electrolysis cell described herein, and as part of the inventive feature, it has two layers. It is this unique geometry that enables these ODCs to use air, rather than pure oxygen. In addition, the air can be humidified or wet, i.e. ambient non-dried air can be fed directly to the gas diffusion electrode. The ODCs can also use a waste gas stream containing oxygen as the oxygen source, for example, an oxygen rich stream generated from a nitrogen production process.

[0144] With respect to all embodiments of the ODC, it can have the following attributes:

[0145] • porous to allow diffusion of gases therein;

[0146] • capable of using humidified or wet, non-dried ambient air as the oxygen source;

[0147] • capable of using a waste gas stream containing oxygen as the oxygen source;

[0148] • electrically conductive to allow movement of electrons;

[0149] • ionically conductive to allow OH - product to diffuse out;

[0150] • it can contain a catalyst that can catalyze the oxygen reaction as shown in reaction 8).

[0151] • hydrophobic, i.e. the membrane can be hydrophobic;

[0152] • hydrophilic; the membrane can also be hydrophilic;

[0153] • the electrode can contain a double layer catalyst, i.e. each catalyst layer itself can have more than one layer, and each layer can contain a different catalyst to enhance their ion transport capabilities;

[0154] With respect to the dimensionally stable anode (DSA), it can have the following attributes: ​

[0155] • can also be a gas diffusion electrode to allow optional use of H2gas at the anode.

[0156] • electrically conductive to allow movement of electrons;

[0157] • ionically conductive;

[0158] • it can contain optional catalysts to catalyze reactions at the anode.

[0159] If hydrogen gas is applied to the anode, the reaction shows as reaction 14).

[0160] 14) H2→ 2H + + 2e -

[0161] Combining a membrane electrolysis cell including a gas diffusion electrode into a lithium recovery process

[0162] A brine lithium recovery process utilizing a membrane electrolytic cell is shown in Figure 16 . It can be seen that sodium chloride salt extracted from the evaporation stage of the lithium brine recovery process is fed as feed brine into the membrane electrolytic cell. As the feed brine passes through the cell, it undergoes a depletion process. Depletion is the result of Na + and OH - ions migrating out of the salt depletion compartment and into the base accumulation compartment and the acid accumulation compartment, respectively.

[0163] The ions that migrate out of the salt depletion compartment depend on the ion species in the feed brine that is fed to the membrane electrolytic cell. Thus, the desalted water removed from the salt depletion compartment can be re-concentrated and thus recycled using the readily available salt (NaCl) reservoir from the salt lake evaporation pond precipitates as feed brine. The concentration of the feed brine plays an important role in providing mass transfer of the feed brine as well as providing ions for acid and base generation. Although the membrane cell can operate at feed brine concentrations as low as 0.1 wt.% salt, it is beneficial to operate at the maximum available feed brine concentration.

[0164] The concentration of the product acid and base removed from the acid and base accumulation compartments, respectively, can be adjusted according to the requirements of each particular process. Sodium hydroxide (NaOH) concentrations in the range of 5-20 wt.% can be achieved using the membrane electrolytic cell disclosed herein. As shown in Figure 16 , typical uses of the NaOH produced in the membrane cell of the brine lithium recovery operation include, but are not necessarily limited to:

[0165] • neutralization and pH adjustment after solvent extraction processes to recover solvents;

[0166] • providing alkalinity for precipitation and hardness removal;

[0167] • regeneration of ion exchange resins for hardness and metal removal;

[0168] • Conversion of lithium carbonate to lithium hydroxide by causticization process.

[0169] All the above processes require caustic (NaOH) concentration in the range of 5-20 wt% which falls in the range achievable by membrane electrolysis cells.

[0170] Non-limiting examples of typical uses of hydrochloric acid that can be produced from membrane electrolysis cells in lithium brine recovery processes are as follows:

[0171] • pH adjustment in solvent extraction process to remove boron;

[0172] • Regeneration of ion exchange resins for hardness and metal removal;

[0173] • Conversion of lithium carbonate to lithium chloride.

[0174] The concentration of hydrochloric acid used for the above applications is in the range of 4-12 wt% which is achievable by membrane electrolysis cells.

[0175] The lithium hard rock mining operation process in conjunction with membrane electrolysis cells is shown in Figure 17 It can be seen that the sodium sulfate (Na2SO4) salt which is the largest byproduct of the lithium hard rock mining operation can be used as the feed brine for the membrane electrolysis cells. As shown in Figure 17 Feeding Na2SO4 to the membrane electrolysis cells will produce NaOH and H2SO4 as the base and acid respectively. These can be recycled and used as reagents in the lithium recovery process.

[0176] In the acid roasting process, sulfuric acid (H2SO4) is the main reagent necessary for the extraction of lithium from the ore. As shown in Figure 17 This chemical can be regenerated from the sodium sulfate byproduct which is readily available from the lithium mine hard rock mining operation.

[0177] Similarly, the sodium hydroxide produced can be used in multiple ways throughout the lithium production process. Non-limiting examples of the use of sodium hydroxide in the lithium hard rock mining operation are as follows:

[0178] • Provide alkalinity for precipitation and hardness removal;

[0179] • Regeneration of ion exchange resins for hardness and metal removal;

[0180] • Conversion of lithium sulfate to lithium hydroxide by adding NaOH in the process.

[0181] All the above processes require NaOH concentration in the range of 5-20 wt% which is in the range achievable by membrane electrolysis cells.

[0182] Figure 18A first embodiment is shown that uses a unique membrane electrolytic cell as disclosed herein to generate LiOH and HC1 from LiCl on-site. In Figure 14 The embodiment shown, a membrane electrolytic cell is used to convert LiCl to LiOH in the recovery of lithium from a salt marsh brine process. As Figure 18 Shown, the brine feed to the membrane electrolytic cell is a LiCl solution that is fed to a salt depletion chamber of the membrane electrolytic cell as Figures 3-7 Shown, oxygen gas, preferably in the form of air, is supplied to the cathode. The oxygen or air can optionally be humidified, for example by bubbling the gas through water prior to supplying the gas to the cathode. The air can optionally be purified. As shown, the output of the cell is LiOH removed from the base accumulation chamber Figures 3-7 ) and HC1 removed from the acid accumulation chamber Figures 3-7 ). Desalted water can optionally be removed from the cell, although this stream is not shown in Figure 18 . Whether desalted water is removed from the cell depends on the concentration of the feed brine (i.e. the aqueous LiCl solution) and the desired concentration of the LiOH and HC1 produced.

[0183] In a similar manner, water can optionally be supplied to the cell, rather than removed. Whether water is supplied to the cell depends on the concentration of the feed brine (i.e. the aqueous LiCl solution) and the desired concentration of the LiOH and HC1 produced. As Figure 18 shown, in this embodiment, the HC1 can be used to regenerate the ion exchange resin used to remove Ca, Mg, Na and K from the LiCl process stream entering the cell. The HC1 can also be used in a boron removal step to regenerate the ion exchange resin, which is typically after the evaporation / precipitation steps near the beginning of the process. As Figure 18 shown, the HC1 can be used for pH adjustment of the process stream, which produces CO2. The CO2 can be combined with a portion of the LiOH product stream, resulting in a stream comprising LiOH and Li2CO3. The LiOH / Li2CO3 stream can be fed to a precipitation step to remove Ca and Mg, as Figure 18 shown. Importantly, not all of the LiOH product stream is used in this precipitation step, as LiOH is the desired product. However, the ability to use LiOH in this manner significantly reduces the need to purchase base, such as NaOH or Na2CO3, to achieve precipitation removal of Ca and Mg.

[0184] As a reference, based on testing using a 6% LiCl stream for the brine feed, approximately 150-250 kWh / m 3 of LiCl brine is required to reduce the total salt content to 3% when air is used at the ODC.

[0185] Figure 19A second embodiment of a membrane electrochemical cell in the recovery of lithium from salt marsh brine is depicted. In this embodiment, an aqueous solution of LiCl is again the brine feed to the membrane electrolysis cell. In this embodiment, similar to the first embodiment, the membrane electrolysis cell is used to convert LiCl to LiOH. The aqueous solution of LiCl is fed to the salt depletion chamber of the membrane electrolysis cell shown in more detail in any of Figures 3-7 The oxygen, preferably in the form of air, is fed to the cathode. The oxygen or air can optionally be humidified, for example by bubbling the gas through water prior to feeding it to the cathode, and can optionally be purified. As shown, the output of the cell is LiOH removed from the base accumulation chamber Figures 3-7 and HC1 removed from the acid accumulation chamber Figures 3-7 As in the first embodiment, desalinated water can optionally be removed from the cell, although this stream is not shown in Figure 19

[0186] Whether desalinated water is removed from the cell depends on the concentration of the feed brine, i.e. the aqueous solution of LiCl, and the desired concentration of the LiOH and HC1 produced. In a similar manner, water can optionally be fed to the cell instead of being removed. Whether water is fed to the cell depends on the concentration of the feed brine, i.e. the aqueous solution of LiCl, and the desired concentration of the LiOH and HC1 produced. In this embodiment, all of the LiOH produced is removed, i.e. there is no recycle stream comprising LiOH.

[0187] However, the HC1 stream as in the first embodiment can be recycled and used in the lithium recovery process. As Figure 19 shown, just prior to feeding the process stream as the feed brine to the membrane electrolysis cell, the HC1 is used to regenerate the ion exchange resin used to remove Ca and Mg ions from the process stream. The HC1 produced can also be used to remove boron, B, after the precipitation step to regenerate the ion exchange resin.

[0188] Figure 20 A third embodiment showing the use of a membrane electrolysis cell in a lithium production process is shown. In this embodiment of the process, a mixed brine solution comprising both LiCl and NaCl is fed to the membrane electrolysis cell. The cell then produces HC1 and a mixed solution of LiOH and NaOH. This mixed solution of LiOH and NaOH is fed to a crystallization / separation step which produces crystallized LiOH and a mixed solution of NaOH and LiOH, wherein the concentration of LiOH is lower than the mixed solution of LiOH and NaOH fed to the crystallization / separation step. From Figure 20 It can be seen that this process is similar to Figure 16 and 18 ​the process, but using a membrane electrolysis cell for the existing operation to produce LiOH from the salt marsh brine. In an alternative embodiment, the membrane electrolysis cell can be applied to another waste stream or recycled lithium chloride stream that is free of sodium produced in a conventional lithium operation, and lithium chloride can be converted to lithium hydroxide and hydrochloric acid.

[0189] The steps are as follows:

[0190] Step 1 : A mixed lithium chloride and sodium chloride stream produced from a conventional salt marsh brine treatment operation is fed to a membrane electrolysis cell (electrochemical cell) to produce a mixed solution of lithium hydroxide and sodium hydroxide.

[0191] Step 2: The mixed lithium hydroxide and sodium hydroxide is sent to a crystallizer / separator where they are separated due to the large difference in solubility between the two salts (NaOH is more soluble in water than LiOH). The crystallization / separation unit can evaporate water and optionally recondense, or can simply effect some precipitation of LiOH by cooling the mixed solution of NaOH and LiOH. The more typical method is to simply evaporate water. Lithium hydroxide crystallizes while sodium hydroxide remains in solution. The crystallized lithium hydroxide is ready for market.

[0192] Step 3: Some lithium hydroxide remains in solution with sodium hydroxide and is recycled back into the process for the precipitation stage.

[0193] Step 4: Some lithium hydroxide and sodium hydroxide combine with carbon dioxide to produce a mixed lithium carbonate and sodium carbonate stream that is recycled back into the overall process and used for further precipitation, which can be seen in Figure 20 .

[0194] In summary, by incorporating an electrochemical cell (membrane electrolysis cell) into the overall process of recovering LiOH from salt marsh brine, these steps result in a closed or near-closed loop of sodium hydroxide, sodium carbonate, and lithium carbonate.

[0195] Turning next to Figure 21 , which shows a fourth embodiment of the use of a membrane electrolysis cell in a lithium production process. As shown in Figure 21 , in a process of producing lithium from a lithium-containing ore, a membrane electrolysis cell is used to convert Li2SO4 to LiOH. However, one skilled in the art will understand that the brine feed stream containing an aqueous solution of Li2SO4 does not necessarily have to come from a lithium ore-based process.

[0196] In certain brine recovery processes, it is necessary to convert a Li2SO4 solution to LiOH, and therefore a membrane electrolysis cell can also be used in such processes. As shown in Figure 21As shown, the membrane electrolysis cell uses aqueous Li2S04solution. As with other embodiments, also fed to the cell is a gas stream comprising oxygen. This stream, which is preferably air, is fed to the cathode. The oxygen or air can optionally be humidified, for example by bubbling the gas through water prior to feeding it to the cathode, and the air can optionally be purified. As shown, the output of the cell is LiOH removed from the base accumulation chamber Figures 3-7 ) and H2S04removed from the acid accumulation chamber Figures 3-7 ).

[0197] As with the first and second embodiments, desalinated water can optionally be removed from the cell, although this stream is not shown in Figure 21 . Whether desalinated water is removed from the cell depends on the concentration of the feed brine (i.e. aqueous Li2S04solution) and the desired concentration of the LiOH and H2S04produced. In a similar manner, water can optionally be fed to the cell instead of being removed. Whether water is fed to the cell depends on the concentration of the feed brine (i.e. aqueous Li2S04solution) and the desired concentration of the LiOH and H2S04produced.

[0198] In this embodiment, both LiOH and H2S04are recycled back into the lithium recovery process, which mitigates at least some of the need to purchase additional reagents. Importantly, only a portion of the LiOH is recycled, as of course LiOH is the desired end product. The H2S04is used in the acid roasting step of the ore production to produce the aqueous Li2S04brine solution after the water leaching step. A portion of the LiOH produced can be used to precipitate Ca and Mg from the aqueous Li2S04brine solution after the water leaching step, as Figure 20 shown.

[0199] Figure 22 An exemplary embodiment is shown in which a membrane electrolysis cell is used in a closed loop process in which lithium carbonate (Li2C03) produced from other methods, such as lithium carbonate produced from a brine operation by precipitation using sodium carbonate or lithium carbonate produced from jadarite (LiNaSiB30?OH), can be dissolved in hydrochloric acid to produce a lithium chloride solution, which is then converted to LiOH. The process as Figure 22 shown is carried out as follows:

[0200] Step 1 : Conversion of lithium carbonate produced from other methods to lithium chloride by dissolving it in hydrochloric acid.

[0201] Step 2: Electrochemical cell treatment of the lithium chloride to produce lithium hydroxide and hydrochloric acid.

[0202] Step 3: Recycling back of the hydrochloric acid for further conversion of lithium carbonate to lithium chloride, forming a fully or substantially closed loop system.

[0203] As shown in the following three exemplary implementation schemes ( Figure 23 , 24 As shown in (25), membrane electrolyzers can also be used in lithium recovery processes incorporating ion exchange resins. These ion exchange resins can be used directly to produce LiOH, or they can be used to recycle and / or recover other ionic substances during lithium recovery. The advantages of using these embodiments (and all embodiments disclosed herein) in terms of operational and capital cost savings are multifaceted.

[0204] As discussed above, lithium hydroxide is produced through an intensive process of treating lithium-rich brine, such as salt marsh brine. The water in the brine is evaporated over a period of 6 to 18 months to concentrate the lithium chloride in the solution to 5 wt% LiCl or higher, and to precipitate large amounts of sodium, calcium, and magnesium salts, which are generally more difficult to dissolve than LiCl.

[0205] The lithium chloride-rich brine must then undergo various purification steps. These purification steps may include, for example: removal of boron by solvents or other means; removal of calcium and magnesium by adding lime (calcium oxide and / or calcium hydroxide) and caustic soda, soda ash, and / or sodium bicarbonate or other substances; and further removal of calcium and magnesium by adding soda ash, i.e., sodium carbonate (Na₂CO₃). These processes produce a mixed stream of lithium chloride and sodium chloride, to which the addition of additional soda ash causes lithium carbonate to precipitate. The lithium carbonate can then be crystallized. Currently, this crystallized lithium carbonate is typically transported to a lithium hydroxide plant, where it is converted to lithium hydroxide by adding calcium hydroxide. The lithium hydroxide is then crystallized and sold. There are multiple process units associated with all these steps, and it is clear that procuring and maintaining these process units implies a significant capital investment and ongoing operating costs.

[0206] Many of these steps can be eliminated using ion exchange resins that selectively adsorb or bind lithium to selectively adsorb lithium from brine (or other sources) without time-consuming evaporation or removal of boron, calcium, magnesium, etc. For example, ion exchange resins used for selectively binding lithium and producing lithium chloride by desorbing lithium from the resin with HCl can be used. Membrane electrolyzers, as disclosed herein, can convert lithium chloride into lithium hydroxide and hydrochloric acid, which will be recycled back to the ion exchange resin while the desired lithium hydroxide is collected.

[0207] In another embodiment, the ion exchange resin used for selective lithium adsorption can also be used to produce lithium sulfate by regenerating the resin with sulfuric acid. Similarly, lithium sulfate is fed into an electrolytic cell to produce lithium hydroxide and sulfuric acid. The sulfuric acid is recycled back to the ion exchange resin to produce more lithium sulfate, while the desired lithium hydroxide is collected.

[0208] Ion exchange resins would eliminate a large amount of capital and operating expenditures and costs associated with lithium evaporation ponds and related downstream transportation.

[0209] Elimination of evaporation ponds would also save water that is lost to the atmosphere during the evaporation step. Producers would be able to pump the lithium-depleted brine back to the salt pan brine reservoir, thereby saving water that would be evaporated. This feature is important from both an environmental and a legal standpoint. For example, Chile, where most of the world's lithium brine is located, has strict limits on the amount of water that can be pumped and the amount of lithium brine that producers can pump. The purpose of this regulation is to protect the scarce water resources in the Chilean salt pan desert region. Thus, these limits effectively mean that producers are limited in the amount of lithium they can produce. However, if the lithium-depleted brine from the ion exchange process is pumped back to the reservoir, much less net brine is pumped, and thus the producers can increase the amount of lithium they produce without exceeding the government's limits on the amount of salt pan brine they can pump or the amount of water used in the operation. The use of ion exchange resins in the lithium recovery process also saves time because the evaporation step is slow. Furthermore, it is important to note that there is no need to purchase reagents needed to precipitate calcium and magnesium.

[0210] The largest cost associated with the direct production of lithium using ion exchange resins is the need to purchase HC1, which is needed to desorb or dissociate lithium ions from the active sites and regenerate the ion exchange resin. The electrochemical cells that are able to convert lithium chloride to lithium hydroxide and hydrochloric acid as described herein not only do not require the purchase of reagents needed to convert lithium chloride to lithium carbonate and then to lithium hydroxide, but these cells also produce the important HC1 needed to extract lithium from the ion exchange resins. Thus, the entire process from lithium chloride evaporation to lithium carbonate production and lithium carbonate conversion all the way to the production of lithium hydroxide for batteries can be simplified to the use of ion exchange resins and electrochemical cells only.

[0211] Furthermore, in a process that utilizes ion exchange resins to directly adsorb lithium from brine, another exemplary use of a membrane electrolytic cell is to deploy the ion exchange resins in the desert where the salt pan brine is pumped, while the membrane electrolytic cell is located in a different location. In this exemplary process, the ion exchange resins are removed, transported to the location of the membrane electrolytic cell, where the ion exchange resins are regenerated with HC1, thereby producing LiOH. The ion exchange resins are then transported back to the brine location in the desert. Thus, the spent ion exchange resins will move in one direction, while the regenerated ion exchange resins will move in the opposite direction. Thus, in any of the exemplary processes shown in FIGS. 1-24, the membrane electrolytic cell can be located in a different location than the ion exchange resins. Figure 22 、 23 or 24.

[0212] Non-limiting examples of suitable such ion exchange resins are those that selectively bind lithium or another noble metal based on the pH of the solution. For example, the resin can bind lithium in acid but not in base, or vice versa. This allows us to regenerate the resin and extract lithium from it. This allows the producer to regenerate the resin and extract lithium from it. The membrane electrolytic cell then produces a solution with the appropriate pH value by providing HC1 or NaOH to remove the bound ions. Such ion exchange resins can also include complexing metal resins, such as H n M n O n where H is hydrogen, M is a metal species, O is oxygen, and n is an integer. Non-limiting examples include LiAlO2, LiCuO2, and the like.

[0213] Thus, the following two embodiments demonstrate how a membrane electrolytic cell as disclosed herein can be incorporated into a lithium recovery process, where ion exchange resins are used to directly produce LiOH.

[0214] Figure 23 An exemplary embodiment is shown where a membrane electrolytic cell is used in a lithium production process where Li is selectively adsorbed from a lithium brine using ion exchange resins. This lithium brine is not necessarily a salt marsh brine - it can be a brine from other industrial processes, such as produced water from oil and gas operations, or geothermal brines or natural brine aquifers that sometimes contain lithium, or the brine can come from a lithium ion battery recycling process. As can be seen in Figure 23 the membrane electrolytic cell produces HC1 for use in regenerating the ion exchange resins from which the Li (as LiCl) was removed. The LiCl is fed to the membrane electrolytic cell to produce the desired LiOH. In an alternative embodiment, lithium sulfate can be produced by using sulfuric acid and producing lithium sulfate, which can be used to produce the desired lithium hydroxide in the membrane electrolytic cell. The steps in this process are as follows:

[0215] Step 1 : Treat the lithium-containing brine or solution with ion exchange resins or other adsorbents to adsorb lithium from the brine or solution.

[0216] Step 2: Regenerate the lithium-containing resin beads or adsorbents with hydrochloric acid to generate a lithium chloride solution. The resins or adsorbents are regenerated to the proton form by the HC1. Alternatively, the resins can be regenerated with sulfuric acid.

[0217] Step 3: Treat the lithium chloride solution through an electrochemical cell to generate lithium hydroxide and hydrochloric acid. Alternatively, a lithium sulfate solution can be treated through an electrochemical cell to produce lithium hydroxide and sulfuric acid.

[0218] Step 4: Sell the lithium hydroxide to the market or otherwise remove it from the process, while recycling the hydrochloric acid back to Step 2.

[0219] Figure 24 Another exemplary use of the membrane electrolysis cell disclosed herein is shown, where lithium-containing brine undergoes the following process: first boron is removed, then the brine is sent to ion exchange resin, then to the membrane electrolysis cell. As shown in this exemplary embodiment, the process steps after boron removal are: Figure 23

[0220] Step 1 : Treatment of lithium-containing brine or solution with ion exchange resin or other adsorbent to adsorb lithium from the brine or solution.

[0221] Step 2: Regeneration of lithium-containing ion exchange resin beads or other suitable lithium adsorbent with hydrochloric acid to produce a lithium chloride solution. The resin or adsorbent is regenerated to the proton form by the HC1. Note that the lithium- depleted solution can be pumped back to the salt pan reservoir or pond. As noted above, due to water conservation restrictions that are typically in place, particularly in Chile, given the amount of salt pan brine that can be pumped out of the natural reservoir, if the depleted solution is sent back to the reservoir, then the producer can produce more lithium without exceeding the legal limit of the amount of brine that they can pump.

[0222] Step 3: Treatment of the lithium chloride solution by the membrane electrochemical cell disclosed herein to produce lithium hydroxide and hydrochloric acid. Alternatively, treatment of lithium sulfate by the membrane electrochemical cell to produce lithium hydroxide and sulfuric acid.

[0223] Step 4: Sale of the lithium hydroxide to the market or otherwise removed from the process, while the hydrochloric acid or sulfuric acid is recycled back to Step 2.

[0224] Note that in the process as shown in Figure 24 air and electricity are sent to the membrane electrolysis cell. Thus, the overall reaction for the anodic and cathodic electrolysis is:

[0225] Anode: 2H2O→ O2+ 4H + + 4e -

[0226] Cathode: O2+ 2H2O + 4e - → 4OH -

[0227] Figure 25 Another exemplary embodiment of a method of use of the membrane electrolysis cell using the gas diffusion electrode of the present invention at the cathode of the cell is shown. In this method, lithium carbonate and / or lithium bicarbonate is directly converted to lithium hydroxide in the membrane electrolysis cell. In this case, the reactions are as follows:

[0228] Cathode: O2+ 2H2O + 4e - → 4OH -

[0229] ​Anode: 2H2O→ 4H++ 4e - + O2

[0230] Lithium carbonate will react with the protons generated at the anode, releasing lithium ions, carbon dioxide and water, as follows:

[0231] 2Li2CO3+ 4H + → 4Li + + 2CO2+ 2H2O

[0232] The released lithium ions will be transported towards the cathode, reaching the lithium hydroxide compartment, where they will combine with the hydroxide ions generated at the cathode and produce a lithium hydroxide solution.

[0233] It should be understood that in all the foregoing embodiments describing the use of the membrane electrolytic cell of the present invention in the lithium recovery process, the role of the GDE remains essentially the same among the various applications: producing OH - ions from the humidified oxygen / air gas stream. The cathode catalyst on the GDE always plays the same role, regardless of the salt used as feed brine (LiCl, NaCl, Na2SO4, Li2SO4).

[0234] Various non-limiting aspects of the present invention can be summarized as follows:

[0235] Aspect 1 : A method for recovering lithium from a lithium source, the method comprising the steps of:

[0236] receiving a salt-containing solution and a gas comprising O2 in a membrane electrolytic cell;

[0237] delivering recovered lithium and / or reagent materials used in the method for recovering lithium from the membrane electrolytic cell.

[0238] Aspect 2: The method of aspect 1, further comprising:

[0239] receiving by-products in the method for recovering Li in the membrane electrolytic cell; and

[0240] delivering reagent materials used in the method for recovering lithium from the membrane electrolytic cell.

[0241] Aspect 3: The method of aspect 1 or aspect 2, wherein the membrane electrolytic cell comprises

[0242] an inlet through which the salt-containing solution is received into an interior of the membrane electrolytic cell;

[0243] an anode positioned to extend within the interior of the membrane electrolytic cell and positioned in an anode compartment;

[0244] a cathode comprising a gas diffusion electrode positioned to extend within an interior of a membrane electrolysis cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse a gas and a hydrophilic catalyst layer disposed on a surface of the diffusion layer, the hydrophilic catalyst layer having a hydrophilicity greater than a hydrophilicity of the diffusion layer and configured to transport negative ions;

[0245] a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced to contact the gas diffusion electrode;

[0246] a first ion exchange membrane interposed between the anode compartment and the hydrophilic catalyst layer of the gas diffusion electrode, the first ion exchange membrane configured to exchange ions received from the anode to an opposite surface of the first ion exchange membrane; and

[0247] at least one outlet through which recovered lithium and / or reagent materials used in the method for recovering lithium are removed from the interior of the membrane electrolysis cell;

[0248] wherein during performance of the method, a salt-containing solution is received into the anode compartment and positive and negative salt ions are formed from the salt-containing solution in the anode compartment; and wherein the gas comprising O2 is reduced at the cathode to form OH - ;

[0249] wherein during performance of the method, the positive salt ions move through the first ion exchange membrane to the opposite surface of the first ion exchange membrane; and

[0250] wherein the positive salt ions combine with OH - to form the recovered Li and / or reagent materials used in the method for recovering Li.

[0251] Aspect 4: The method of aspect 3, the diffusion layer having a bilayer structure formed from a plurality of diffusion sub-layers, wherein the diffusion sub-layers are hydrophobic, and wherein water is transported away from the diffusion sub-layers.

[0252] Aspect 5: The method of aspect 3, the gas diffusion electrode further comprising a hydrophobic catalyst layer disposed on a surface of the diffusion layer opposite the hydrophilic catalyst layer, the hydrophobic catalyst layer having a hydrophilicity less than the diffusion layer and being capable of transporting negative ions, wherein OH - ions are transported through the hydrophobic catalyst layer.

[0253] Aspect 6: The method of aspect 5, the membrane electrolysis cell further comprising:

[0254] a second ion exchange membrane disposed on the hydrophilic catalyst layer of the gas diffusion electrode and configured to exchange ions received from the hydrophilic catalyst layer of the gas diffusion electrode to an opposite surface of the second ion exchange membrane;

[0255] wherein the first and second ion exchange membranes define a base accumulation compartment between the cathode compartment and the anode compartment;

[0256] wherein OH - ions are exchanged through the second ion exchange membrane to the opposite surface of the second ion exchange membrane into the base accumulation compartment;

[0257] wherein OH - ions combine with positive salt ions in the base accumulation compartment to form recovered Li and / or reagent materials used in the method for recovering Li;

[0258] wherein the recovered Li and / or reagent materials used in the method for recovering Li are removed from the base accumulation compartment.

[0259] Aspect 7: The method of Aspect 6, the membrane electrolysis cell further comprising:

[0260] a third ion exchange membrane interposed between the first ion exchange membrane and the anode compartment, wherein the first and third ion exchange membranes define a salt depletion compartment between the anode compartment and the base accumulation compartment, the third ion exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the third ion exchange membrane and into the anode compartment;

[0261] wherein a salt-containing solution is received into the salt depletion compartment and forms positive and negative salt ions from the salt-containing solution in the salt depletion compartment; and

[0262] wherein the negative salt ions are exchanged from the salt depletion compartment to the opposite surface of the third ion exchange membrane.

[0263] Aspect 8: The method of Aspect 7, the membrane electrolysis cell further comprising:

[0264] a fourth ion exchange membrane interposed between the third ion exchange membrane and the anode compartment, wherein the third and fourth ion exchange membranes define an acid accumulation compartment between the anode compartment and the salt depletion compartment, the fourth ion exchange membrane configured to exchange ions received from the anode compartment to an opposite surface of the fourth ion exchange membrane and into the acid accumulation compartment;

[0265] wherein H + ions are formed in the anode compartment and the H + ions are exchanged from the anode compartment to the opposite surface of the fourth ion exchange membrane into the acid accumulation compartment;

[0266] wherein H + ions and the negative salt ions together form an acid, wherein the acid comprises recovered Li and / or reagent materials used in the process for recovering Li; and

[0267] wherein the acid is removed from the acid accumulation compartment.

[0268] Aspect 9. The method of aspect 8, wherein the first and fourth ion exchange membranes comprise cation exchange membranes and the second and third ion exchange membranes comprise anion exchange membranes.

[0269] Aspect 10. The method of any of aspects 1-9, wherein the gas comprising O2 is air.

[0270] Aspect 11. The method of any of aspects 1-9, wherein the gas comprising O2 is a waste stream from a nitrogen production operation.

[0271] Aspect 12. The method of any of aspects 1-11, wherein the source of Li comprises salt marsh brine, and the recovered Li comprises at least one of LiOH, Li2CO3, and / or LiCl.

[0272] Aspect 13. The method of any of aspects 1-12, wherein in the receiving step, the byproduct of the process for recovering Li comprises NaCl precipitated from the salt marsh brine; and in the delivering step, the reagent materials used in the process for recovering Li comprise HC1 and NaOH.

[0273] Aspect 14. The method of any of aspects 1-13, wherein the reagent materials are used to regenerate and / or desorb ions from ion exchange resins used in the process for recovering lithium.

[0274] Aspect 15. The method of aspect 13, wherein at least one of HC1 and NaOH is used to regenerate and / or desorb ions from ion exchange resins used in the process for recovering lithium.

[0275] Aspect 16. The method of any of aspects 1-14, wherein the source of lithium comprises lithium ore and the recovered lithium comprises at least one of LiOH, Li2CO3, and / or Li2SO4.

[0276] Aspect 17. The method of aspect 16, wherein the recovered lithium comprises LiOH, and the method further comprises the step of recycling a portion of the LiOH to the process for recovering lithium.

[0277] Aspect 18. The method of aspect 17, further comprising the step of precipitating at least one of calcium and magnesium with the portion of LiOH.

[0278] Aspect 19. The method of aspect 17, further comprising a step of reacting a portion of the LiOH with CO2 to produce Li2CO3, and further comprising a step of precipitating at least one of calcium and magnesium with the Li2CO3.

[0279] Aspect 20. The method of any of aspects 1-16, wherein in the receiving step, a byproduct of the method for recovering Li comprises Na2SO4, and in the delivering step, a reagent material used in the method for recovering lithium comprises H2SO4 and NaOH.

[0280] Aspect 21. The method of any of aspects 1-14, wherein the source of lithium comprises a salt marsh brine, and in the receiving step, the salt-containing solution comprises LiCl, and in the delivering step, the recovered lithium comprises LiOH, and a reagent material used in the lithium recovery method comprises HC1.

[0281] Aspect 22. The method of aspect 21, further comprising recycling a portion of the LiOH to the method for recovering lithium.

[0282] Aspect 23. The method of aspect 21 or 22, further comprising a step of reacting a portion of the LiOH with CO2 to produce Li2CO3, and further comprising a step of precipitating at least one of calcium and magnesium with the Li2CO3.

[0283] Aspect 24. The method of any of aspects 1-14, wherein the source of lithium comprises a salt marsh brine, and in the receiving step, the salt-containing solution comprises LiCl and NaCl, and in the delivering step, the recovered lithium comprises LiOH, and a reagent material used in the lithium recovery method comprises HC1 and NaOH.

[0284] Aspect 25. The method of aspect 20, further comprising recycling a portion of the LiOH to the lithium recovery method.

[0285] Aspect 26. The method of any of aspects 1-16, wherein the source of lithium comprises a lithium ore, and in the receiving step, the salt-containing solution comprises Li2SO4 from the lithium ore, and in the delivering step, the recovered lithium comprises LiOH, and a reagent material used in the lithium recovery method comprises H2SO4.

[0286] Aspect 27. The method of aspect 18, wherein the salt-containing solution comprising LiCl is obtained by contacting a salt marsh brine with an ion exchange resin, wherein the ion exchange resin is configured to adsorb lithium from the salt marsh brine and desorb the adsorbed lithium in the presence of HC1 in the form of a solution comprising LiCl.

[0287] Aspect 28. The method of aspect 26, wherein the salt-containing solution comprising Li2SO4 is obtained by contacting a lithium-containing stream derived from a lithium ore with an ion exchange resin, wherein the ion exchange resin is configured to adsorb lithium from the lithium-containing stream derived from a lithium ore and desorb the adsorbed lithium in the presence of H2SO4 as a solution comprising Li2SO4.

[0288] Aspect 29. The method of aspect 22, wherein the ion exchange resin is further configured to adsorb lithium directly from a salt marsh brine.

[0289] Aspect 30. The method of aspect 22, wherein the method further comprises the step of removing boron from the salt marsh brine prior to contacting the salt marsh brine with the ion exchange resin.

[0290] Aspect 31. The method of any one of aspects 1-16, wherein the lithium source comprises Li2CO3.

[0291] Aspect 32. The method of aspect 31, wherein in the receiving step, the salt- containing solution comprises LiCl or Li2SO4.

[0292] Aspect 33. The method of aspect 32, wherein in the delivering step, the recovered lithium comprises LiOH, and the reagent material used in the lithium recovery process comprises HC1.

[0293] Aspect 34. The method of aspect 32, wherein in the delivering step, the recovered lithium comprises LiOH, and the reagent material used in the lithium recovery process comprises H2SO4.

[0294] Aspect 35. The method of aspect 33, wherein the method further comprises recycling the HC1 to dissolve Li2CO3 to produce LiCl.

[0295] Aspect 36. The method of aspect 34, wherein the method further comprises recycling the H2SO4 to dissolve Li2CO3 to produce Li2SO4.

[0296] Aspect 37. The method of any one of aspects 1-11, wherein the lithium source comprises a brine derived from a lithium-ion battery recycling process.

[0297] Aspect 38. A gas diffusion electrode for a membrane electrolysis cell, the gas diffusion electrode comprising:

[0298] a diffusion layer configured to diffuse a gas;

[0299] a hydrophilic catalyst layer disposed on a surface of the diffusion layer, the hydrophilic catalyst layer having a greater hydrophilicity than the diffusion layer and being capable of transporting negative ions;

[0300] an ion exchange membrane disposed on a surface of the hydrophilic catalyst layer, the ion exchange membrane configured to exchange ions from the hydrophilic catalyst layer to an opposite surface of the ion exchange membrane.

[0301] Aspect 39. The gas diffusion electrode of Aspect 38, the diffusion layer having a bilayer structure formed of a plurality of diffusion sub-layers.

[0302] Aspect 40. The gas diffusion electrode of Aspect 38 or Aspect 39, further comprising a hydrophobic catalyst layer disposed on a surface of the diffusion layer opposite the hydrophilic catalyst layer, the hydrophobic catalyst layer having a hydrophilicity less than the diffusion layer and being capable of transporting negative ions.

[0303] Aspect 41. The gas diffusion electrode of any of Aspects 38-40, the hydrophilic catalyst layer comprising platinum and carbon and an anion exchange ionomer.

[0304] Aspect 42. The gas diffusion electrode of Aspect 40 or Aspect 41, the hydrophobic catalyst layer comprising platinum and carbon and an anion exchange ionomer.

[0305] Aspect 43. The gas diffusion electrode of any of Aspects 40-42, the hydrophobic catalyst layer comprising PTFE.

[0306] Aspect 44. The gas diffusion electrode of any of Aspects 40-43, at least one of the hydrophilic catalyst layer and the hydrophobic catalyst layer configured as an oxygen depolarized cathode to catalyze the reaction: 02+ 2H20 + 4e - → 4OH - .

[0307] Aspect 45. The gas diffusion electrode of any of Aspects 38-44, the ion exchange membrane being an anion exchange membrane, thereby forming a cathode.

[0308] Aspect 46. A method of manufacturing a gas diffusion electrode for a membrane electrolysis cell, the method comprising:

[0309] disposing a hydrophilic catalyst layer on a surface of the diffusion layer, the hydrophilic catalyst layer having a hydrophilicity greater than the diffusion layer, and

[0310] disposing an ion exchange membrane on a surface of the catalyst layer, the ion exchange membrane configured to exchange ions from the catalyst layer to an opposite surface of the ion exchange membrane and to reduce or prevent flooding of the catalyst layer.

[0311] Aspect 47. The method of Aspect 46, further comprising disposing a hydrophobic catalyst layer on a surface of the diffusion layer opposite the hydrophilic catalyst layer, the hydrophobic catalyst layer having a hydrophilicity less than the diffusion layer.

[0312] Aspect 48. The method of Aspect 46 or Aspect 47, the diffusion layer having a bilayer structure formed from a plurality of diffusion sub-layers, the hydrophilic catalyst layer disposing step comprising disposing the hydrophilic catalyst layer on a surface of one diffusion sub-layer, and the hydrophobic catalyst layer disposing step comprising disposing the hydrophobic catalyst layer on an opposing surface of another diffusion sub-layer.

[0313] Aspect 49. The method of any of Aspects 46-48, further comprising combining the diffusion sub-layers to form the diffusion layer.

[0314] Aspect 50. The method of any of Aspects 46-49, at least one of the hydrophilic catalyst layer and the hydrophobic catalyst layer being formed from an ink, and at least one of the hydrophilic catalyst layer disposing step and the hydrophobic catalyst layer disposing step comprising applying the ink to a surface of the diffusion layer.

[0315] Aspect 51. A membrane electrolysis cell for treating a salt-containing solution, the membrane electrolysis cell comprising:

[0316] an inlet through which the salt-containing solution is introduced to an interior of the membrane electrolysis cell;

[0317] an anode positioned to extend within the interior of the membrane electrolysis cell and positioned in an anode compartment;

[0318] a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolysis cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse a gas and a hydrophilic catalyst layer disposed on a surface of the diffusion layer, the hydrophilic catalyst layer having a greater hydrophilicity than the diffusion layer, and the hydrophilic catalyst layer being configured to transport negative ions;

[0319] a gas inlet through which a gas comprising O2 is introduced to contact the gas diffusion electrode;

[0320] a first ion exchange membrane interposed between the anode compartment and the hydrophilic catalyst layer of the gas diffusion electrode, the first ion exchange membrane being configured to exchange ions received from the anode to an opposing surface of the first ion exchange membrane; and

[0321] at least one outlet through which a product of the salt solution is removed from the interior of the membrane electrolysis cell.

[0322] Aspect 52. The membrane electrolysis cell of Aspect 51, further comprising

[0323] a second ion exchange membrane disposed on the hydrophilic catalyst layer of the gas diffusion electrode and configured to exchange ions received from the hydrophilic catalyst layer of the gas diffusion electrode to an opposing surface of the third ion exchange membrane;

[0324] wherein the first and second ion exchange membranes define a base accumulation compartment between the cathode compartment and the anode compartment.

[0325] Aspect 53. The membrane electrolysis cell of Aspect 52, further comprising

[0326] a third ion exchange membrane, the third ion exchange membrane being between the first ion exchange membrane and the anode compartment, wherein the first and third ion exchange membranes define a salt depletion compartment between the anode compartment and the base accumulation compartment, the third ion exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposite surface of the third ion exchange membrane and into the anode compartment.

[0327] Aspect 54. The membrane electrolysis cell of Aspect 53, further comprising:

[0328] a fourth ion exchange membrane, the fourth ion exchange membrane being between the third ion exchange membrane and the anode compartment, wherein the third and fourth ion exchange membranes define an acid accumulation compartment between the anode compartment and the salt depletion compartment, the fourth ion exchange membrane being configured to exchange ions received from the anode compartment to an opposite surface of the fourth ion exchange membrane and into the acid accumulation compartment.

[0329] Aspect 55. The membrane electrolysis cell of Aspect 54, wherein the first and fourth ion exchange membranes comprise cation exchange membranes and the second and third ion exchange membranes comprise anion exchange membranes.

[0330] Aspect 56. The membrane electrolysis cell of any one of Aspects 51-55, wherein the hydrophilic catalyst layer comprises platinum and carbon and an anion exchange ionomer.

[0331] Aspect 57. A method of purifying or concentrating LiOH using a membrane electrolysis cell, the steps of the method comprising the steps of:

[0332] receiving, in the membrane electrolysis cell, a feed solution comprising LiOH and a gas comprising O2; and

[0333] delivering, from the membrane electrolysis cell, a product solution comprising a purified LiOH solution and / or a concentrated LiOH solution.

[0334] Aspect 58. A method of producing LiOH using a membrane electrolysis cell, the steps of the method comprising the steps of:

[0335] receiving, in the membrane electrolysis cell, a feed solution comprising LiCO3 and a gas comprising O2; and

[0336] delivering, from the membrane electrolysis cell, a product solution comprising a purified LiOH solution and / or a concentrated LiOH solution.

[0337] Example

[0338] Experiments were conducted to demonstrate the effectiveness of a two-layer gas diffusion electrode used as an oxygen depolarized cathode according to the present invention compared to a single layer ODC.

[0339] Figure 26 A plot of current versus time for a membrane electrolyzer using a single layer ODC is shown. As can be seen from the plot, after approximately 11 hours of testing, the single layer GDE using O2 at the cathode began to produce H2, which indicates that the GDE was ineffective at facilitating the following reaction: - O2 + 2H2O + 4e - → 4OH

[0340] Figure 27 and 28 demonstrate the effectiveness of a two-layer ODC using O2 at the cathode or air at the cathode as the source of oxygen, respectively. Using either O2 or air, it can be seen that no hydrogen was released even after more than 30 hours of continuous operation.

[0341] In some embodiments, the application herein can be construed to exclude any element or process not specifically mentioned that does not materially affect the basic and novel characteristic of the compositions or methods. Also, in some embodiments, the application can be construed to exclude any element or process not specified herein.

[0342] As previously described, although the present application is illustrated and described herein with reference to specific embodiments, the present application is not intended to be limited to the details described therein. Rather, various modifications can be made in the details within the scope and range of equivalents of the claims.

[0343] In this specification, the embodiments have been described in a manner which enables a clear and concise specification to be written, but it is intended that the application be interpreted by the terms of the appended claims in their broadest reasonable manner. Specifically, it is applied that all preferred features described herein apply to all aspects of the application described herein.

[0344] While preferred embodiments of the application have been shown and described herein, it is to be understood that these embodiments are merely exemplary of the application. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the spirit of the application. Therefore, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the application.

Claims

1. A method for recovering lithium from a lithium source, the method comprising the steps of: receiving, in a membrane electrolytic cell, a salt-containing solution comprising lithium ions and negative salt ions and a gas comprising O2; delivering recovered lithium and / or reagent materials used in the method for recovering lithium from the membrane electrolytic cell, wherein the membrane electrolytic cell comprises: an anode positioned to extend within an interior of the membrane electrolytic cell and positioned in an anode compartment; a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolytic cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse the gas comprising O2 and a catalyst layer disposed on a surface of the diffusion layer, the catalyst layer having a hydrophilicity greater than a hydrophilicity of the diffusion layer and the catalyst layer being configured to transport negative ions; a cation exchange membrane interposed between the anode compartment and the catalyst layer of the gas diffusion electrode, the cation exchange membrane being configured to exchange ions to an opposite surface of the cation exchange membrane; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange anions received from the catalyst layer of the gas diffusion electrode to an opposite surface of the first anion exchange membrane, wherein the cation exchange membrane and first anion exchange membrane define a base accumulation compartment interposed between the cathode compartment and the anode compartment; a second anion exchange membrane interposed between the cation exchange membrane and the anode compartment, wherein the cation exchange membrane and second anion exchange membrane define a salt depletion compartment interposed between the anode compartment and the base accumulation compartment, the second anion exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposite surface of the second anion exchange membrane; an inlet through which the salt-containing solution is received into the interior of the membrane electrolytic cell; a gas inlet positioned in the cathode compartment through which the gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which recovered lithium and / or reagent materials used in the method for recovering lithium are removed from the interior of the membrane electrolytic cell; wherein during performance of the method: a gas comprising O2 is reduced at the cathode to form OH - ions; said OH - ions are exchanged through the first anion exchange membrane to the opposite surface of the first anion exchange membrane into the base accumulation compartment; the salt-containing solution is received into the salt depletion compartment; the lithium ions are exchanged through the cation exchange membrane to an opposite surface of the cation exchange membrane into the base accumulation compartment; the lithium ions and the OH - ions together form LiOH in the base accumulation compartment; and the negative salt ions are exchanged from the salt depletion compartment to an opposite surface of the second anion exchange membrane; and wherein the Li source comprises salt marsh brine and the recovered Li comprises at least one of LiOH, Li2CO3 and / or LiCl.

2. The method of claim 1, wherein the membrane electrolytic cell further comprises: Another cation exchange membrane is disposed between the second anion exchange membrane and the anode compartment, wherein the second anion exchange membrane and the other cation exchange membrane define an acid accumulation compartment between the anode compartment and the salt consumption compartment, and the other cation exchange membrane is configured to exchange ions received from the anode compartment onto the opposite surface of the other cation exchange membrane and into the acid accumulation compartment; During the process of performing the aforementioned method: H + ions are formed in the anode compartment and the H + ions are exchanged from the anode compartment to the opposite surface of the other cation exchange membrane, into the acid accumulation compartment; and H + The ions and the negative salt ions together form a reagent material used in a method for recovering Li in the acid accumulation compartment.

3. A method for recovering lithium from a lithium source, the method comprising the following steps: The membrane electrolyzer receives a salt solution containing lithium ions and negative salt ions and a gas containing O2. Lithium recovered from the membrane electrolyzer and / or reagent materials used in the method for recovering lithium are delivered. The membrane electrolyzer comprises: The anode is positioned to extend inside the membrane electrolyzer and is located in the anode compartment; The cathode includes a gas diffusion electrode positioned to extend inside the membrane electrolyzer and positioned in a cathode compartment. The gas diffusion electrode includes a diffusion layer configured to diffuse a gas containing O2 and a catalyst layer disposed on the surface of the diffusion layer. The catalyst layer is more hydrophilic than the diffusion layer and is configured to transport negative ions. A cation exchange membrane is disposed between the anode compartment and the catalyst layer of the gas diffusion electrode, the cation exchange membrane being configured to exchange ions onto the opposite surface of the cation exchange membrane; A first anion exchange membrane is disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode to the opposite surface of the first anion exchange membrane, wherein the cation exchange membrane and the first anion exchange membrane define an alkali accumulation compartment between the cathode compartment and the anode compartment. A second anion exchange membrane is disposed between the cation exchange membrane and the anode compartment, wherein the cation exchange membrane and the second anion exchange membrane define a salt consumption compartment between the anode compartment and the alkali accumulation compartment, and the second anion exchange membrane is configured to exchange ions received from the salt consumption compartment to the opposite surface of the second anion exchange membrane. An inlet through which the salt-containing solution is received into the interior of the membrane electrolyzer; A gas inlet, positioned within the cathode compartment, through which O2-containing gas is introduced to contact the gas diffusion electrode; and At least one outlet through which recovered lithium and / or reagent materials used in the method for recovering lithium are removed from the interior of the membrane electrolyzer; During the process of performing the aforementioned method: a gas comprising O2 is reduced at the cathode to form OH - ions; said OH - ions are exchanged through the first anion exchange membrane to the opposite surface of the first anion exchange membrane into the base accumulation compartment; The salt-containing solution receives the salt-consuming compartment; The lithium ions are exchanged through the cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali accumulation compartment; the lithium ions and the OH - ions together form LiOH in the base accumulation compartment; and The negative salt ions are exchanged from the salt consumption compartment to the opposite surface of the second anion exchange membrane; and wherein the lithium source comprises a lithium ore and the recovered lithium comprises at least one of LiOH, Li2CO3, and / or Li2SO4.

4. The method of claim 3, wherein the membrane electrolytic cell further comprises: a further cation exchange membrane interposed between the second anion exchange membrane and the anode compartment, wherein the second anion exchange membrane and further cation exchange membrane define an acid accumulation compartment between the anode compartment and the salt depletion compartment, the further cation exchange membrane configured to exchange ions received from the anode compartment to an opposite surface of the further cation exchange membrane and into the acid accumulation compartment; wherein during performance of the method: H + ions are formed in the anode compartment and the H + ions are exchanged from the anode compartment to the opposite surface of the other cation exchange membrane, into the acid accumulation compartment; and H + The ions and the negative salt ions together form a reagent material used in a method for recovering Li in the acid accumulation compartment.

5. A method for recovering lithium from a lithium source, the method comprising the steps of: receiving a salt-containing solution comprising lithium ions and negative salt ions and a gas comprising O2 in a membrane electrolytic cell; delivering recovered lithium and / or reagent materials used in the method for recovering lithium from the membrane electrolytic cell, wherein the lithium source comprises a brine derived from a lithium-ion battery recycling process, and wherein, the membrane electrolytic cell comprises: an anode positioned to extend within an interior of the membrane electrolytic cell and positioned in an anode compartment; a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolytic cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse a gas comprising O2 and a catalyst layer disposed on a surface of the diffusion layer, the catalyst layer having a hydrophilicity greater than a hydrophilicity of the diffusion layer, and the catalyst layer configured to transport negative ions; a cation exchange membrane interposed between the anode compartment and the catalyst layer of the gas diffusion electrode, the cation exchange membrane configured to exchange ions received from the anode compartment to an opposite surface of the cation exchange membrane; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposite surface of the first anion exchange membrane; wherein the cation exchange membrane and first anion exchange membrane define a base accumulation compartment between the cathode compartment and the anode compartment; an inlet through which the salt-containing solution is received into the interior of the membrane electrolytic cell; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which recovered lithium and / or reagent materials used in the method for recovering lithium are removed from the interior of the membrane electrolytic cell; wherein during performance of the method: a gas comprising O2 is reduced at the cathode to form OH - ions; OH - ions are exchanged through the first anion exchange membrane to the opposite surface of the first anion exchange membrane into the base accumulation compartment; the salt-containing solution comprising lithium ions and negative salt ions is received into the anode compartment; the lithium ions are exchanged through the cation exchange membrane to an opposite surface of the cation exchange membrane into the base accumulation compartment; and said OH - ions and said lithium ions together form recovered lithium in said base accumulation compartment.

6. The method of claim 5, wherein the oxygen-containing gas is air.

7. The method of claim 5, wherein the oxygen-containing gas is a waste stream from a nitrogen generation operation.

8. A method for recovering lithium from a lithium source, the method comprising the steps of: receiving a salt-containing solution comprising lithium ions and negative salt ions and a gas comprising O2 in a membrane electrolytic cell; delivering recovered lithium and / or reagent materials used in the method for recovering lithium from the membrane electrolytic cell, wherein the lithium source comprises brine derived from a lithium-ion battery recycling process, and wherein the membrane electrolytic cell comprises: an anode positioned to extend within an interior of the membrane electrolytic cell and positioned in an anode compartment; a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolytic cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse the gas comprising O2 and a catalyst layer disposed on a surface of the diffusion layer, the catalyst layer having a hydrophilicity greater than a hydrophilicity of the diffusion layer, and the catalyst layer configured to transport negative ions; a cation exchange membrane interposed between the anode compartment and the catalyst layer of the gas diffusion electrode, the cation exchange membrane configured to exchange ions to an opposite surface of the cation exchange membrane; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposite surface of the first anion exchange membrane, wherein the cation exchange membrane and first anion exchange membrane define a base accumulation compartment interposed between the cathode compartment and the anode compartment; a second anion exchange membrane interposed between the cation exchange membrane and the anode compartment, wherein the cation exchange membrane and second anion exchange membrane define a salt depletion compartment interposed between the anode compartment and the base accumulation compartment, the second anion exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the second anion exchange membrane; an inlet through which the salt-containing solution is received into the interior of the membrane electrolytic cell; a gas inlet positioned in the cathode compartment through which the gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which recovered lithium and / or reagent materials used in the method for recovering lithium are removed from the interior of the membrane electrolytic cell; wherein during performance of the method: a gas comprising O2 is reduced at the cathode to form OH - ions; said OH - ions are exchanged through the first anion exchange membrane to the opposite surface of the first anion exchange membrane into the base accumulation compartment; the salt-containing solution is received into the salt depletion compartment; the lithium ions are exchanged through the cation exchange membrane to the opposite surface of the cation exchange membrane into the base accumulation compartment; said lithium ions and said OH - ions together in said alkali accumulation compartment form recovered lithium; and the negative salt ions are exchanged from the salt depletion compartment to the opposite surface of the second anion exchange membrane.

9. The method of claim 8, wherein the membrane electrolytic cell further comprises: another cation exchange membrane, the other cation exchange membrane being configured to exchange ions received from the anode compartment to an opposite surface of the other cation exchange membrane and into the acid accumulation compartment; wherein during the course of performing the method: H + ions are formed in the anode compartment and the H + ions are exchanged from the anode compartment to the opposite surface of the other cation exchange membrane, into the acid accumulation compartment; and H + The ions and the negative salt ions together form a reagent material used in a method for recovering Li in the acid accumulation compartment.

10. The method of claim 8 or 9, wherein the oxygen-containing gas is air.

11. The method of claim 8 or 9, wherein the oxygen-containing gas is a waste stream from a nitrogen generation operation.

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