Systems and methods for enriching lithium from seawater

Abstract

A cell (100) for increasing the lithium (Li) concentration in a stream includes a housing (102); a dense lithium selective membrane (108) located within the housing (102) and dividing the housing (102) into a first chamber (104) and a second chamber (106); a cathode electrode (105) located in the first chamber (104); an anode electrode (107) located in the second chamber (106); a first conduit loop (116) fluidly connected to the second chamber (106) and configured to supply a feed stream (110) to the second chamber (106); a second conduit loop (124) fluidly connected to the first chamber (104) and configured to circulate an enrichment stream (120) through the first chamber (104); and a power source (109) configured to apply a voltage between the cathode and anode electrodes to initiate an oxidation electrochemical reaction at the anode electrode and a reduction electrochemical reaction at the cathode electrode. The thickness of the dense lithium selective membrane is less than 400 nm.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 139,006, filed January 19, 2021, entitled “Method for Enriching Lithium from Seawater”, and U.S. Provisional Patent Application No. 63 / 251,340, filed October 1, 2021, entitled “System and Method for Enriching Lithium from Seawater,” the disclosures of which are incorporated herein by reference in their entirety. background Technical Field

[0004] The embodiments of the subject matter disclosed herein generally relate to systems and methods for enriching lithium (Li) from seawater, and more specifically to methods for enriching a stream of lithium ions from seawater while preventing other ions present in the seawater from entering the enriched stream using a continuous electric pump membrane (CEPM) process with a glass-type dense membrane.

[0005] Background Discussion

[0006] Lithium is rapidly becoming a strategically important commodity due to the rapidly growing demand for lithium-ion batteries. Commercial lithium is primarily produced from land resources such as salt lake brines and high-grade ores using chemical precipitation methods, which is technically and economically feasible only when the lithium concentration in the brine or ore is at the level of several hundred parts per million (ppm). However, onshore lithium reserves are finite and geographically unevenly distributed. In 2018, global lithium demand was 0.28 trillion tons (Li₂CO₃ equivalent). This demand is projected to increase to approximately 1.4 to 1.7 trillion tons (Li₂CO₃ equivalent) by 2030. Onshore lithium reserves are expected to be depleted by 2080.

[0007] The ocean contains 5,000 times more lithium than the land. The ocean provides an almost unlimited and location-independent supply of lithium. However, extracting lithium from seawater is very challenging because of its low concentration (about 0.2 ppm) and the presence of competing ions (sodium, magnesium, calcium, potassium, etc.) exceeding 13,000 ppm. To date, no known system or associated process has been able to efficiently extract lithium atoms from seawater at such low concentrations. In this regard, U.S. Patent No. 6,764,584B2[1] discloses a two-step process for producing lithium concentrates from brine or seawater, the contents of which are incorporated herein by reference in their entirety. The first step uses an adsorption process to enrich lithium to a level of 1,200 to 1,500 ppm, and the second step involves a two-stage electrodialysis process in series to increase the lithium concentration to about 1.5%. U.S. Patent No. 4,636,295[2] develops an electrodialysis method for recovering lithium from brine, the contents of which are also incorporated herein by reference in their entirety. The method includes an anode and cathode chambers separated by multiple alternating monopolar cation peroxide membranes and monopolar anion peroxide membranes. At approximately 10 A / m 2 Up to 500A / m 2 A current is applied within a certain range to drive lithium ions from the anode chamber to the cathode chamber. However, this method only works when the lithium concentration is above 30 ppm, so the process and system cannot be applied to seawater-based lithium brines. U.S. Patent No. 9,932,653B2[3] describes an electrorecovery process that also uses a lithium-selective membrane to recover lithium from the feed stream to the recovery stream, the contents of which are also incorporated herein by reference in their entirety. Mesh electrodes are directly connected to both sides of the membrane, with the anode facing the recovery stream. The process relies primarily on the concentration gradient to drive lithium ions through the membrane. Therefore, the process is slow, and the lithium concentration in the recovery stream is lower than that in the feed stream. U.S. Patent No. 10,689,766B2[4] improves this electrorecovery process by applying a lithium adsorption layer on the feed side of the lithium-selective membrane, the contents of which are also incorporated herein by reference in their entirety. This process increases the production speed, but does not disclose how lithium is enriched from the feed stream.

[0008] Lithium concentration is arguably the most critical factor determining the technological challenges of lithium extraction. When the lithium concentration in brine is sufficiently high, lithium ions can be easily obtained through conventional chemical precipitation. However, due to the extremely low lithium concentration in seawater (approximately 0.2 ppm), a process to enrich the lithium concentration in brine is urgently needed before conventional lithium extraction methods become feasible. Furthermore, the energy consumption of the enrichment process must be sufficiently low to make it economically viable, which is not the case with the technologies discussed above.

[0009] Therefore, it is necessary to develop new systems that can selectively enrich lithium from low concentrations while using a small amount of energy in the enrichment process. Summary of the Invention

[0010] According to the embodiment, there is a cell for increasing the lithium (Li) concentration in a stream. The cell includes a housing, a dense lithium-selective membrane located within the housing and dividing the housing into a first chamber and a second chamber, a cathode electrode located in the first chamber, an anode electrode located in the second chamber, a first conduit loop fluidly connected to the second chamber and configured to provide a feed flow to the second chamber, a second conduit loop fluidly connected to the first chamber and configured to circulate the enrichment flow through the first chamber, and a power source configured to apply a voltage between the cathode and anode electrodes to initiate an oxidation electrochemical reaction at the anode electrode and a reduction electrochemical reaction at the cathode electrode. The thickness of the dense lithium-selective membrane is less than 400 μm.

[0011] According to another embodiment, there is a multi-stage pool for increasing the lithium (Li) concentration in a stream, comprising multiple pools connected in series. Each pool has the structure described above. The enriched stream from the previous pool is the feed stream to the current pool.

[0012] According to another embodiment, there is a method for increasing the lithium (Li) concentration in a pool, the method comprising the steps of placing a dense lithium selective membrane in a housing to divide the housing into a first chamber and a second chamber, supplying a feed stream to the second chamber, wherein the feed stream contains seawater, supplying an enrichment stream to the first chamber, applying a voltage between a cathode electrode located in the first chamber and an anode electrode located in the second chamber to initiate an oxidation electrochemical reaction on the anode electrode and a reduction electrochemical reaction on the cathode electrode, and driving Li atoms from the seawater through the dense lithium selective membrane into the enrichment feed. The thickness of the dense lithium selective membrane is less than 400 μm. Attached Figure Description

[0013] To gain a more complete understanding of the present invention, reference is now made to the following description in conjunction with the accompanying drawings, wherein:

[0014] Figure 1 This is a schematic diagram of a pool that increases the lithium concentration in the flow by driving lithium ions from seawater through a dense lithium selective membrane.

[0015] Figure 2 The chemical structure of the dense lithium-selective film was explained;

[0016] Figure 3 This illustrates the migration of lithium ions through a dense lithium-selective membrane;

[0017] Figure 4 This is a schematic diagram of another pool that increases the lithium concentration in the stream by driving lithium ions from seawater through a dense lithium selective membrane.

[0018] Figure 5 This is a schematic diagram of another pool that increases the lithium concentration in the stream by driving lithium ions from seawater through a dense lithium selective membrane.

[0019] Figure 6 This is another schematic diagram of a pool that increases the lithium concentration in the flow by driving lithium ions from seawater through a dense lithium selective membrane.

[0020] Figure 7 It is a schematic diagram of a multi-stage pool that includes multiple pools connected in series;

[0021] Figure 8 This is a flowchart of a method for increasing lithium content in seawater streams;

[0022] Figure 9A and Figure 9B An electron microscope image of a dense lithium-selective film is shown;

[0023] Figure 10 The chemical analysis of the dense lithium selective film is explained;

[0024] Figure 11A and Figure 11B The physical structure of the copper hollow fiber used with the pool is explained;

[0025] Figure 12 This is an explanation Figure 7 A table showing the concentrations of lithium ions and other major ions at different stages in a multi-stage pool.

[0026] Figure 13 The chronocurrent curves for each stage are shown; integrating the area under the curve yields the total charge passing through the membrane at each stage, in coulombs.

[0027] Figure 14 The relationship between steady-state current and lithium feed concentration at different stages of the method is illustrated.

[0028] Figure 15 This illustrates the Faraday efficiency contributed by different ions in each stage;

[0029] Figure 16 This describes the X-ray diffraction pattern of the collected lithium product powder, which is theoretically a standard XRD pattern; and

[0030] Figure 17 This is a flowchart of a method for increasing lithium content in seawater streams. Detailed Implementation

[0031] The following description of the embodiments refers to the accompanying drawings. The same reference numerals in different drawings denote the same or similar elements. The following detailed description does not limit the invention. Rather, the scope of the invention is defined by the appended claims. For simplicity, the following embodiments are discussed in relation to a lithium enrichment method using seawater with a very low lithium concentration as a raw material, in the range of parts per billion (ppb). However, the embodiments discussed below are not limited to such low-concentration lithium seawater, but can be used for any brine with a lithium concentration of ppm.

[0032] Throughout the specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Therefore, the appearance of these phrases "in an embodiment" or "in an embodiment" in different places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in one or more embodiments in any suitable manner.

[0033] According to the implementation scheme, a continuous electric pump membrane (CEPM) process is introduced, and the system in which the CEPM process is implemented includes a first chamber separated from the second chamber by a lithium-selective membrane. The lithium-selective membrane is defined herein as any membrane that allows lithium atoms to pass through at a rate at least 10 times that of magnesium and sodium atoms. The enrichment method includes the step of selecting the lithium-selective membrane as a dense (defined herein as a material impermeable to water and gases) membrane, such as Li... x La 2 / 3-x / 3A TiO3 (LLTO) membrane, with x ranging from 0.23 to 0.67, is prepared from LLTO nanoparticles using a high-temperature sintering process; however, other materials, as discussed later, can also be used. This membrane is referred to herein as a glass-type dense lithium-selective membrane. The process includes the steps of introducing an initial enrichment stream into the first chamber and a feed stream into the second chamber; an optional step of adjusting the pH of the enrichment stream to 4.5 to 7 by adding an acid or acidic gas; connecting the cathode electrode to the first chamber and the anode electrode to the second chamber; applying a sufficiently high voltage to trigger an oxidation electrochemical reaction on the anode and a reduction electrochemical reaction on the cathode; and driving lithium ions from the feed stream through the lithium-selective membrane to enrich the enrichment stream, while the transport of other ions present in the seawater is substantially blocked by the lithium-selective membrane (e.g., a glass-type dense LLTO membrane). Furthermore, the method may also include Pt-Ru-coated copper hollow fibers as the cathode electrode or used outside the cathode electrode. In one application, CO2 is introduced from the internal channels of the copper hollow fibers, blown out through the porous walls of the fibers, and ultimately uniformly released into the first chamber. The typical redox electrochemical reactions occurring in the pool supporting this method involve hydrogen reduction and chlorine oxidation. In this case, hydrogen and chlorine are released from the cathode and anode, respectively, and collected as valuable byproducts. In one application, the lithium selectivity membrane can be a glass-type membrane. The term "glass-type" is defined as a material with no grain boundaries or with low-density grain boundaries in its microstructure. In one application, low density is defined as equal to or less than 10%, except 0%. Glass-type materials typically have a transparent or translucent appearance when irradiated with visible light. However, glass-type materials can also include materials that are opaque to visible light. In one embodiment, the lithium selectivity membrane comprises a ceramic material. In another embodiment, the lithium selectivity membrane is a hybrid membrane, i.e., containing both organic and inorganic materials.

[0034] The method can be further improved by creating a third chamber to completely contain the anolyte, i.e., removing the anolyte from the second chamber. The third chamber is separated from the second chamber by an anion exchange membrane and filled with a saturated NaCl solution to facilitate the release of chlorine gas as a valuable byproduct. The method can also be improved by using other redox electrochemical reactions to drive the enrichment process, such as redox reactions of Fe... 2+ / Fe 3+ In this case, a fourth chamber is created to completely house the cathode electrode. The fourth chamber is separated from the first chamber by an anion exchange membrane and is filled with an oxidizing agent solution of a redox pair, namely, Fe redox pair. 2+ / Fe 3+ Fe 3+ The anode electrode is placed in the third chamber, and the reducing agent solution of the redox couple, i.e., the Fe redox couple, is used. 2+ / Fe 3+ Fe 2+As the anolyte, the redox couple may also include Cl. - / ClO3 - ,Br - / BrO3 - I - I2, Ag / AgCl, Hg / Hg2Cl2, hydroquinone / 1,4-benzoquinone, etc.

[0035] In one application, multi-stage cells can be configured to stack membrane units of multiple cells to form a cascade system, thereby enriching lithium to a higher level. In this cascade system, the enriched stream from the previous stage is used as the feed stream for the current stage. Lithium is extracted from the enriched stream of the final stage using conventional chemical precipitation.

[0036] The lithium enrichment cells and related methods will now be discussed in more detail with reference to the figures shown in the attached diagram. Figure 1 A cell 100 supporting the CEPM process is shown. Cell 100 is a cell having a housing 102 that contains a first chamber 104 separated from a second chamber 106 by a dense lithium selector membrane 108 (referred to herein as the lithium selector membrane for simplicity). The lithium selector membrane 108 can be made not only of LLTO but also of other superionic conductors, including but not limited to NASICON (Li-100N). 1+x+y Al x M 2-x Si y P 3-y O 12 M = Ti, Ge, 0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.6), Li 11-x M 2-x P 1+x S 12 (M = Ge, Sn, Si) and Li x / 3 M 2z / 3-x / 3-4y / 3 N y O z (M = tetravalent metal ions and N = trivalent metal ions, 0 ≤ x ≤ 1.0, 0 ≤ y ≤ 1.0, 2.9 ≤ z ≤ 3.0). Lithium-selective films can be constructed in different forms. They can be formed by sintering nanoparticles at high temperatures to create dense, glassy (optional) films with a thickness of less than 400 micrometers. Nanoparticles can also be embedded in polymers or inorganic binders to form hybrid matrix films.

[0037] An anode electrode 107 is placed in a second chamber 106, and a cathode electrode 105 is placed in a first chamber 104. Both electrodes are connected to a power supply 109 (e.g., a DC power supply), with the anode connected to the positive terminal of the power supply. A feed stream 110 can be stored in a feed reservoir 112, which is pumped into the second chamber 106 via a proximate pipe loop 114 using a pump 114. Note that the feed reservoir 112 can be ocean, lake, or any natural body of water containing lithium diluted in brine; pump 114 is optional. An enrichment stream 120 can also optionally be circulated to the first chamber 104 by a pump 122 via a pipe loop 124. The enrichment stream 120 can be stored in an enrichment reservoir 126. The volume of the feed stream 110 is typically much larger than the volume of the enrichment stream 120. Acid 140 stored in an acid reservoir 142 can be supplied to the first chamber 104 via port 144 to make the enrichment stream 120 acidic. Acid 140 can be a polybasic acid or a weak acid, including phosphoric acid, carboxylic acid, acetic acid, citric acid and glycine, etc., which is used to form a buffer solution to stabilize the pH of the enrichment stream 120 in a preferred range of 4.5 to 7.0 throughout the enrichment process.

[0038] Feed stream 110 is a lithium-containing solution 150 to which a lithium concentration 150 needs to be enriched in the enrichment stream. It includes seawater and / or brine solutions. Enrichment stream 120 is a solution that receives lithium ions 150 from feed stream 110. Anode stream, to be discussed later. Figure 4 The discussion will focus on the solution in which the anode electrode 107 is placed when the anode electrode is separated from the feed stream. The cathode stream will be discussed later. Figure 6 The discussion focuses on the solution in which the cathode electrode 106 is placed when the cathode is separated from the enrichment stream. The initial concentration of the enrichment solution 120 may be less than, equal to, or higher than the concentration of the feed stream 110, but after the enrichment process, the lithium concentration of the enrichment solution 120 is higher than that of the feed stream 110.

[0039] In this embodiment, the lithium selective membrane 108 is based on a ceramic solid-state lithium electrolyte, preferably made of Li x La 2 / 3-x / It is made of 3TiO3 (LLTO). When the LLTO film is made dense (optionally glass-type), it allows Li... + Ions migrate through their perovskite-type lattice, but the larger ion size and / or incompatible valence states of other ions hinder the migration of all other major ions in seawater (i.e., Na+). + K + Mg 2+ Ca 2+ The transport of LLTO 108 (etc.). The crystal structure of LLTO 108 is as follows: Figure 2 As shown, the TiO6 octahedron is depicted extending between a La-poor layer 210 and a La-rich layer 220, where layer 220 has more La atoms than layer 210. When this structure is exposed to lithium ions, as... Figure 3 As shown, lithium ions 150 migrate through the lattice space 300 of LLTO 108 because the average diameter of the lattice space 300 is comparable to or slightly larger than the size of the lithium ions. In one application, the outer surface of the glass-type dense LLTO film is coated with a protective layer 310, which is preferably made of a cation exchange resin. It is manufactured to protect it from corrosion. The protective layer of the lithium selective membrane can be prepared from other anion exchange resins, including but not limited to DOWEX.

[0040] LLTO is one of the excellent solid-state lithium-ion superconductors. Its high lithium-ion conductivity and high selectivity for other ions can be explained by its crystal structure. For example... Figure 2 As shown, LLTO has a perovskite-type crystal structure. The lattice framework of LLTO consists of interconnected TiO6 octahedra, which form a spacer for Li. + and La 3+ A cubic cage or opening. Large La 3+ Ions act as supporting pillars, stabilizing the crystal structure. La 3+ The high price of La leads to the alternating arrangement of La-rich layers 220 and La-poor layers 210 along the c-axis, creating abundant vacancies 300 in the lattice, allowing Li to... + Embedded. Li + Transfer from one cage to another requires passing through a square window or lattice space of 300, the size of which is... to approximately For example This is defined by four adjacent TiO6 tetrahedra, such as Figure 3 As shown. Li + Size Slightly larger than the 300-inch window, it requires slight deformation within the LLTO frame to enlarge the window, which is possible due to the thermal vibrations of the TiO6 octahedron. Other ions present in the seawater feed (i.e., Na+) + K + Mg 2+ Ca 2+ The energy density of lithium ions (such as ions) is much higher than that of lithium ions, requiring substantially greater deformation and thus creating a higher energy barrier for their transport. Therefore, based on these properties of LLTO films, it is expected that LLTO films will allow Li-ion transport to proceed. + Rapid transport of Li, but it blocks all other major ions present in seawater. Furthermore, the thickness of membrane 108, which will be discussed later, contributes to enhancing Li... + Ions migrate and block other ions.

[0041] Inert electrodes made of carbon cloth, graphite, titanium, etc., with optional noble metal coatings (Pt, Ru, Ir, etc.), are used for the anode 107 and cathode 105. In the CEPM process, the power supply 109 applies a voltage higher than 1.75V to the electrodes, which triggers the following electrochemical reactions at the cathode and anode.

[0042] At the cathode, the following chemical reaction occurred:

[0043]

[0044] At the anode, the following reaction occurs:

[0045]

[0046] Hydrogen 160 is continuously generated from cathode 105 via reaction (1), thereby driving the transport of lithium 150 from feed stream 110 through LLTO membrane 108 and enrichment in enrichment stream 120. Simultaneously, chlorine 162 is generated from anode 107. However, in this case, chlorine 162 may be partially or completely dissolved in feed stream 110 of this embodiment. Figure 1 The display cell 100 has corresponding ports 161 and 163 for hydrogen 160 and chlorine 162, respectively. A controller 170, such as a processor, laptop, or any computing device, can be provided to coordinate all pumps and control the flow rate of each stream through the cell. Corresponding valves 180 can be provided along piping systems 116 and 124 to refresh the feed stream 110 and / or extract the enriched stream 120 for further processing to extract Li atoms.

[0047] To prevent the dissolution of chlorine 162 in the feed stream 110, Figure 4 In one embodiment shown, a third chamber 410 is formed within the second chamber, and the third chamber 410 is separated from the second chamber 106 by an anion exchange membrane 420, which primarily allows the transport of anions rather than cations. The anion exchange membrane may include, but is not limited to, [other types of membranes]. A series, AEMION TM and Ion exchange membrane.

[0048] In this embodiment, the anode electrode 107 is now entirely located within the third chamber 410. A saturated NaCl solution is used as the anolyte stream 412, which is loaded into a reservoir 414 and optionally circulated within the third chamber 410 using a pump 416. Since chlorine gas 162 has much lower solubility in the saturated NaCl solution 412, most of it will be released as chlorine gas and collected at port 163 as a valuable byproduct.

[0049] In another implementation scheme, such as Figure 5As shown, the cathode 105 of cell 500 is a copper hollow fiber cathode 505. The copper hollow fiber cathode 505 can be made of one or more noble metals such as Pt-Ru (2.0 mg / cm³). -2 The copper hollow fiber is coated to promote the hydrogen evolution reaction. It has a standard finger-like porous structure, allowing CO2 gas 510 to be introduced from outside the cell into the defined internal channels 507 within the cathode 505. The CO2 is blown out through the porous walls of the cathode 505 and ultimately uniformly released into the enrichment stream 120 within the first chamber 104. The released CO2 510 creates an acidic environment near the cathode 505, which improves the Faraday efficiency at high current densities. Acid 140 can also serve as an auxiliary solution to control the pH of the feed stream. Thus, CO2 gas 510 and acid 140 form a buffer solution, maintaining the pH of the enrichment stream 120 at 4.5 to 7.0 to protect the LLTO membrane 108 from alkaline corrosion.

[0050] When CO2 gas 510 is blown through the copper hollow fiber cathode 505, the electrochemical reaction at the cathode 505 undergoes the following changes:

[0051]

[0052]

[0053]

[0054] The electrochemical reaction at anode 107 will be as described in reaction (2). The hydrogen produced by reaction (1) or by reactions (3) and (4b) will be collected as a valuable byproduct, as discussed above.

[0055] exist Figure 6 In another embodiment shown, pool 600 is configured to drive the enrichment process using other redox electrochemical reactions. One example is the use of redox reactions on Fe... 2+ / Fe 3+ In this configuration, a fourth chamber 610 is formed within the first chamber, separated from the first chamber 104 by an anion exchange membrane 612. In this way, the fourth chamber completely accommodates the cathode electrode 105. Fe is used. 3+ The solution, as cathode stream 614, is loaded into reservoir 616 and circulated in fourth chamber 610 via pipe loop 620 using pump 618. Anode electrode 107 remains inserted in third chamber 410, but in this embodiment, anolyte stream 412 is fed by Fe... 2+Solution substitution. In this embodiment, auxiliary electrolyte 140 and / or auxiliary gas 510 are optionally added to enrichment stream 120 to improve its conductivity. Optionally, auxiliary gas 510 can be blown into first chamber 104 using gas distributor 630, which may have the same structure as cathode 505 but is not electrically connected to power supply 109. Power supply 109 applies a voltage higher than 0.8V to cell 102, which triggers the following electrochemical reaction at cathode:

[0056] F e 3+ +e - →Fe 2+ (7)

[0057] And triggers the following electrochemical reaction at the anode:

[0058] Fe 2+ -e - →Fe 3+ (8)

[0059] The auxiliary electrolyte 140 may include LiCl, NaCl, acetic acid, etc., and the auxiliary gas 510 may include SO2, Cl2 and NH3, etc.

[0060] The cells discussed in this article, ranging from 100 to 600, can be stacked in multiple stages to form a membrane cascade system 700, such as... Figure 7 As shown, to achieve a higher level of enrichment. As shown, the membrane cascade system 700 uses the enriched stream 120 from the first chamber 104 of the previous stage 702-1 as the feed stream 110 for the second chamber 106 of the next stage 702-2, and so on.

[0061] exist Figure 5 The shown pool 500 uses a lithium brine (red seawater) with a concentration of approximately 0.21 ppm (feed stream) to enrich the concentration of Li. More specifically, as Figure 8As shown, the enrichment method begins in step 800 by supplying a feed stream 110 to the second chamber 106 where the anode 107 is located. In step 802, an enrichment stream 120 is supplied to the first chamber 104 where the cathode 105 is located. While the feed stream 110 contains 0.21 ppm of Li atoms, the initial enrichment stream 120 can contain any number of Li atoms. In step 804, the pH of the enrichment stream 120 is adjusted to a desired range, for example, 4.5 to 7.0. This is achieved by introducing an acid 140 (e.g., a polybasic or weak acid) into the stream, for example, by introducing it directly into the first chamber 104 at port 144. In one application, a controller 170 automatically measures the pH in the first chamber 104 using a sensor 171 and controls the amount of acid 140 released from container 142 to achieve the target pH. Next, in step 806, controller 170 instructs power supply 109 to apply a voltage between anode 107 and cathode 105 to trigger an oxidation electrochemical reaction at the anode and a reduction electrochemical reaction at the cathode. The redox electrochemical reactions at the anode and cathode drive lithium ions 150 from feed stream 110 to be enriched in enrichment stream 120 through lithium selective membrane 108, while the transport of other ions present in seawater is essentially blocked due to the glass-type dense and thin LLTO membrane. Then, in step 808, a portion of the enriched feed is removed from pool 500, and Li is extracted using a conventional process for extracting Li atoms.

[0062] In this regard, the inventors note that a similar lithium enrichment process has been discussed in U.S. Patent No. 9,932,653 (see [reference to the patent]). Figure 3 The patent describes the process as unsuccessful in column 4, row 60, and column 5, row 4, because of "low selectivity for lithium ions 50". In other words, the patent's... Figure 3 The process described was found to be ineffective because lithium ions are hydrated as they flow from the electrode to the membrane through the solution. To overcome this problem, the authors of U.S. Patent No. 9,932,653 proposed placing the electrode directly on the membrane, as their method... Figure 1 As shown, it is described as successful in columns 5, lines 9-15, because "high [lithium ion concentration] was obtained". The inventors discovered that U.S. Patent No. 9,932,653... Figure 3 The processes shown are not efficient due to the properties of their membranes and the lack of pH control over the feed stream. By using the (optional glass-type) dense membranes discussed above and controlling the pH of the feed stream, the inventors discovered that... Figure 8 The discussed process is highly efficient, enabling the use of ppb of Li atoms in the feed stream while still enriching it, a feat unattainable by any known process or system in the art. This unexpected result arises from the density and / or thinness of the LLTO film 108.

[0063] Figure 8 An optional step in the method described is to create a third chamber to house the anode electrode, such as... Figure 4 As shown. The third chamber is separated from the second chamber by an anion exchange membrane and can be filled with NaCl solution to promote chlorine release. In an alternative step, a hollow fiber cathode coated with Pt-Ru can be used, and CO2 is introduced from the internal channels of the electrode and blown into the first chamber, as shown. Figure 5 As shown. In another optional step, which may be combined with or not combined with the preceding optional steps, a fourth membrane may be used to separate the cathode, as shown. Figure 6 As shown. In another optional step, two or more pools can be connected in series, as... Figure 7 As shown, the enriched feed from the previous cell is used as the feed stream for the next cell, thereby increasing the concentration of Li in the final enriched stream. For example, for a 5-stage system, the inventors obtained 9000 ppm of Li from a raw feed stream containing only 0.21 ppm of Li atoms, with a Li / Mg selectivity greater than 45 million.

[0064] Now we will discuss an example of preparing a dense and thin LLTO film 108 (optionally glass-type). First, LLTO nanoparticles with the chemical formula Li₂O₃ were prepared using a sol-gel process. 0.33 La 0.56 TiO3. Stoichiometric amounts of LiNO3 and La(NO3)3 were dissolved in a 25% aqueous citric acid solution, with 18 equivalents of citric acid used compared to LiNO3. Subsequently, stoichiometric amounts of tetrabutoxytitanium(IV) were added dropwise to the mixture under vigorous stirring (e.g., 1000 rpm), and the mixture was heated to 100 °C to obtain a homogeneous solution, which was then dried at 150 °C with continuous stirring. The final solution had a molar ratio of LiNO3:La(NO3)3, tetrabutoxytitanium(IV), and citric acid of 0.363:0.57:1.00:6.53. The resulting solid was sintered at 600 °C for 4 hours and then sintered in air at 1050 °C for 20 hours, with a heating and cooling rate of 2 °C / min. The resulting white LLTO powder was continuously ball-milled at 300 rpm for 12 hours to obtain nanoparticles with a diameter of approximately 200 nm. LLTO nanoparticles were granulated into disks with a diameter of 22 mm and a thickness of 70 μm, and then sintered at 1050 °C for 4 hours to release CO2 and NO. x Furthermore, it is melted at 1275℃ for 8 hours to reach a molten state, in order to form Figure 9A and Figure 9B The glass-type dense and thin LLTO film is shown. The heating and cooling rates during the sintering process were set to 2 °C / min. During the sintering process, approximately 10% of the LiNO3 was vaporized. Therefore, based on elemental analysis, the final chemical formula of the LLTO film is Li. 0.33La 0.57 TiO3. Figure 9A and Figure 9B The high-magnification SEM images shown indicate that the surface of film 108 is smooth and free of grain boundaries. The thickness of the LLTO film is less than 80 μm, more specifically, about 60 μm. In one embodiment, the inventors found that an LLTO film 108 with a thickness of about 55 μm produced the unexpected results discussed herein. The film preparation process was controlled to a thickness approximately 10 times thinner than reported in the literature, which allows for the realization of high Li- content in the pools discussed above. + One of the factors affecting permeability. X-ray powder diffraction measurements confirmed the LLTO structure, such as... Figure 10 As shown, all the reflection peaks match the standard LLTO pattern. Mechanical testing revealed that the film has a stress of 110 MPa and a ductility of 0.066%, indicating that the film is hard and brittle.

[0065] Copper hollow fiber 505 was prepared via a solvent-free phase separation method followed by a high-temperature sintering process. Copper powder (99%, particle size approximately 1 mm) was mixed with polysulfone (PSE), polyvinylpyrrolidone (MW approximately 10,000), and N-methylpyrrolidone (NMP, 99.5%) in a weight ratio of 64.4:6.2:1.5:27.9 to form a homogeneous doped solution, which was then rotated through a spinneret with a central hole. The resulting hollow fibers were sintered in air at 600 °C for 3 hours, followed by reduction at 650 °C in a hydrogen / argon atmosphere (volume ratio = 2:8) for 6 hours. A Pt / Ru catalyst (50% on Kejenblack) was wetted with deionized water and then... The solution (12.5% ​​in dimethylformamide) was mixed at a weight ratio of 7:3. The Pt / Ru:Nafion mixture was prepared at 2.0 mg cm⁻¹. 2 The horizontal spray is applied to the surface of the copper hollow fiber.

[0066] In an experiment using a 5-stage 700 cell, an LLTO membrane 108 (membrane area = 2.01 cm²) was used. 2 ) and AEM membrane 420 (membrane area = 2.01cm²) 2 Fumasep FAA-3-20 (FuelCellStore, USA) was assembled into each cell 702-I and sealed with an O-ring. The solution volume circulating as the feed stream was 25 L in the first stage and 2.5 L in the remaining stages. In all stages, the solution volumes in the cathode and anode chambers were fixed at 2.5 ml and 25 ml, respectively. A catalytic Pt-Ru carbon cloth gas diffusion electrode (FuelCellStore, USA) was used as the anode, and a Pt-Ru coated copper hollow fiber element 630 (see [link to product]) was used. Figure 11A and Figure 11BA copper hollow fiber cathode 505 was used as the cathode. The copper hollow fiber cathode 505 was connected to a CO2 cylinder, controlling the CO2 flow rate at 6.0 mL / min. Concentrated H3PO4 was further used as an auxiliary solution 140 to control the pH of the enrichment stream 120 from 4.5 to 7.0. Released Cl2 was adsorbed by a CH2Cl2 solution to avoid air pollution, while hydrogen was collected by a gas sampling bag. A constant voltage of 3.25 V was applied using a potentiostat.

[0067] In the first stage, red seawater was used as the feed stream 110, and deionized water was used as the initial enrichment stream 120. In the second to fifth stages, the lithium-rich solution from the previous stage was used as both the feed stream and the initial enrichment stream. The run time for each stage was fixed at 74,500 seconds. Figure 12 Table 1 lists the concentrations of major ions in the seawater after each stage. Except for lithium, which continuously enriched from seawater levels (0.21 ppm) to approximately 9000 ppm in the final stage, the concentrations of all other ions decreased significantly and remained almost constant after the second stage. After the fifth stage, the nominal Li / Mg selectivity reached over 45 million, indicating the high efficiency of the pool discussed in this paper.

[0068] The nominal Li / Mg selectivity β is calculated using the following formula:

[0069]

[0070] Where C Li,5th C Mg,5th C Li,sw and C Mg,sw Li in the fifth enrichment current and the first ocean current, respectively + and Mg 2+ The molar concentration. The selectivity of a single stage can be calculated using the same formula, but the value for the fifth stage is replaced by the value for the first stage.

[0071] Figure 13 The current recorded over time for each stage is shown. It can be seen that the current rises sharply in the initial stage and then remains relatively stable, due to the adsorption of ions on the electrodes and membrane. Only in the fifth stage does the current decrease slightly over time. The steady-state current increases with increasing lithium concentration in the feed stream. Figure 14 The number of ions passing through the membrane at each stage is shown. Li + The quantity of Na+ increased rapidly from the first to the fifth stage, confirming that the transport rate also increases with increasing feed concentration. For other ions, only the first stage had a large amount of Na+ at approximately 300 ppm. + Through the membrane, almost everything else is blocked. Figure 15The results show that the overall Faraday efficiency across all stages is close to 100%. In the first stage, approximately 47.06% of the electrical energy is used for lithium transport, while in the remaining stages, almost 100% of the electrical energy is used for lithium migration. Based on these data, the total electricity required to enrich 1 kg of lithium from seawater to 9000 ppm in five stages is estimated to be 76.34 kWh. Simultaneously, 0.876 kg of H2 and 31.12 kg of Cl2 are collected from the cathode and anode, respectively. Considering the US electricity price of $0.065 / kWh, the total electricity cost for this process is approximately $5.00. Furthermore, based on the 2020 prices of hydrogen and Cl2 (i.e., $2.5 / kg to $8.0 / kg and $0.15 / kg, respectively), the value of the byproducts could reach approximately $6.90 to $11.70, which well offsets the total energy cost. These unexpected results—the high electrical efficiency of lithium ion transport across membrane 108 and the low cost fully compensated by byproducts—are due to the dense and thin (optional glass-type) LLTO membrane used in the pool. Furthermore, it was noted that the total concentration of other salts was below 500 ppm after the first stage, meaning that the remaining water after lithium harvesting can be treated as freshwater. Therefore, this method could potentially be combined with seawater desalination to further improve its economic viability.

[0072] It is further noted that total energy consumption is directly proportional to the number of stages. However, Figure 13 The stable current curves shown suggest that extending the processing time for each stage would allow for greater enrichment of lithium concentration, thus reducing the number of stages. This approach would come at the cost of low productivity. The exceptionally slow transfer rate in the first stage (see...) Figure 13 This indicates that the parameters for the first stage of lithium enrichment need to be adjusted based on the energy-productivity trade-off. In this experiment, the duration of the first stage was determined based on the purity of the product, requiring a Mg concentration of approximately 2.0 ppm. Therefore, as shown in Table 1, when the Mg in the enrichment stream... 2+ The first stage is stopped when the concentration reaches approximately 1.5 ppm. Under these conditions, the lithium concentration reaches approximately 75 ppm. Therefore, in one embodiment, the duration of the first stage is determined based on the Mg concentration in the enrichment stream. For this embodiment, the processor 170 can be connected to a sensor that determines the Mg concentration in the enrichment stream.

[0073] Lithium can be precipitated from the fifth-stage enrichment stream as Li3PO4 by adjusting the pH to 12.25 with a 10.0 M NaOH solution. The precipitate is separated by centrifugation, washed with deionized water, and then dried under vacuum. Figure 16As shown, the collected white powder was characterized by XRD spectroscopy. The XRD pattern was in excellent agreement with the standard pattern of Li3PO4 (PDF#25-1030), and no impurity signals were found. Further quantitative elemental analysis showed that the purity of Li3PO4 was 99.94% ± 0.03%, and the contents of Na, K, Mg, and Ca in the product were 194.53 ppm ± 7.80 ppm, 0.99 ppm ± 0.02 ppm, 25.16 ppm ± 0.83 ppm, and 17.18 ppm ± 0.57 ppm, respectively, which meet the purity requirements for lithium battery grade.

[0074] The implementation scheme discussed in this paper describes a continuous electropump membrane process that successfully enriched lithium from seawater samples from the Red Sea. The success of this implementation scheme relies on a thin and dense (glass-type) LLTO membrane, which provides efficient separation between lithium and other interfering ions, and also exhibits high lithium permeability. In one application, the anode chamber is separated from the feed chamber by an anion exchange membrane, and a saturated NaCl solution is used in the anode chamber to allow the release of Cl2. This is necessary to prevent highly soluble Cl2 from dissolving in the large feed stream. In another application, the use of CO2 and phosphate buffer stabilizes the pH and extends the membrane lifetime. In fact, the LLTO membrane was found to last for 200 hours with negligible performance degradation. Furthermore, the use of hollow copper fibers increased the Faraday efficiency to approximately 100% across all stages. The combination of enrichment with conventional precipitation methods makes the method less sensitive to interference from soluble ions. Energy consumption is significantly reduced. Cost analysis shows that the value of byproducts well outweighs the energy costs.

[0075] Now Figure 17 The method for enhancing Li in one of the pools discussed above is discussed. The method includes step 1700 of placing a (optionally glass-type) dense and thin LLTO membrane in a housing to divide the housing into a first chamber and a second chamber, step 1702 of supplying a feed stream to the second chamber, wherein the feed stream contains seawater, step 1704 of supplying an enrichment stream to the first chamber, step 1706 of applying a voltage between a cathode electrode located in the first chamber and an anode electrode located in the second chamber to initiate an oxidation electrochemical reaction on the anode electrode and a reduction electrochemical reaction on the cathode electrode, and step 1708 of driving Li atoms in the seawater through the dense lithium selective membrane into the enrichment feed.

[0076] The method may further include the steps of injecting acid into the enrichment stream to maintain a pH of 4.5 to 7.0, and / or adding a first anion exchange membrane to the second chamber to form a third chamber, thereby placing the anode electrode in the third chamber, and / or supplying an anolyte stream to the third chamber, the anolyte stream being different from the feed stream and the enrichment stream, the anolyte stream being configured not to absorb chlorine generated by the anode electrode, thereby trapping chlorine at the port formed in the third chamber. In one application, the cathode electrode is made of copper hollow fibers coated with Pt-Ru, the copper hollow fibers forming internal channels to receive CO2 from outside the shell.

[0077] The method may further include the steps of adding a second anion exchange membrane to the first chamber to form a fourth chamber, thereby placing a cathode electrode in the fourth chamber, and / or supplying a cathode stream to the fourth chamber, the cathode stream being different from the feed stream and the enrichment stream, and / or adding copper hollow fibers located in the first chamber, wherein the copper hollow fibers are coated with Pt-Ru and the copper hollow fibers form internal channels, and / or supplying CO2 from outside the housing to the internal channels and releasing CO2 in the enrichment stream.

[0078] The disclosed embodiments provide systems and methods for enriching lithium from marine brine having very low lithium concentrations. It should be understood that this description is not intended to limit the invention. Rather, embodiments of the invention are intended to cover alternatives, modifications, and equivalent configurations that are included within the spirit and scope of the invention as defined in the appended claims. Furthermore, numerous specific details are set forth in the detailed description of the embodiments to provide a full understanding of the claimed invention. However, those skilled in the art will understand that various embodiments can be practiced without these specific details.

[0079] Although the features and elements of the embodiments of the present invention are described in specific combinations in the embodiments, each feature or element can be used alone without the other features and elements of the embodiments, or in various combinations with or without the other features and elements disclosed herein.

[0080] This specification uses examples of the disclosed subject matter to enable any person skilled in the art to practice the same subject matter, including making and using any device or system and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims and may include other examples as would occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims.

[0081] References

[0082] [1] U.S. Patent No. 6,764,584B2

[0083] [2] U.S. Patent No. 4,636,295

[0084] [3] U.S. Patent No. 9,932,653B2

[0085] [4] U.S. Patent No. 10,689,766B2

Claims

1. A cell (100) for increasing the lithium (Li) concentration in a stream, the cell (100) comprising: Shell (102); A dense lithium selective membrane (108) located inside the housing (102) and dividing the housing (102) into a first chamber (104) and a second chamber (106); Cathode electrode (105) located in the first chamber (104); The anode electrode (107) is located in the second chamber (106); A first conduit loop (116) is fluidly connected to the second chamber (106) and is configured to supply a feed stream (110) to the second chamber (106); A second conduit loop (124) is fluidly connected to the first chamber (104), configured to circulate enriched flow (120) through the first chamber (104); and A power supply (109) is configured to apply a voltage between the cathode and anode electrodes to initiate an oxidation electrochemical reaction at the anode electrode and a reduction electrochemical reaction at the cathode electrode. The thickness of the dense lithium selective film is less than 400 μm, and The cathode electrode is made of copper hollow fiber coated with platinum-ruthenium (Pt-Ru), and the cathode electrode forms an internal channel to receive CO2 from outside the housing and release CO2 in the enrichment stream.

2. The cell according to claim 1, wherein the dense lithium selective membrane is a glass-type Li x La 2 / 3-x / 3 TiO3 (LLTO) film, where x is 0.23 to 0.

67.

3. The pool according to claim 1, further comprising: The fluid is connected to a port in the first chamber, which is used to inject acid into the enriched stream to maintain the pH at 4.5 to 7.

0.

4. The pool according to claim 3, further comprising: The first anion exchange membrane is arranged in the second chamber to form the third chamber, thereby placing the anode electrode in the third chamber.

5. The pool according to claim 4, wherein an anode stream is supplied to the third chamber, the anode stream being different from the feed stream and the enrichment stream, the anode stream being configured not to absorb chlorine generated by the anode electrode, thereby capturing the chlorine at the port formed in the third chamber.

6. The pool according to claim 4, further comprising: A second anion exchange membrane is arranged in the first chamber to form the fourth chamber, thereby placing the cathode electrode in the fourth chamber.

7. The pool according to claim 6, wherein a cathode stream is supplied to the fourth chamber, the cathode stream being different from the feed stream and the enrichment stream.

8. A multistage cell (700) for increasing the lithium (Li) concentration in a stream, said multistage cell (700) comprising: Multiple pools connected in series (702-I), Each of the multiple pools (702-I) includes: Shell (102); A dense lithium selective membrane (108) located in the housing (102) divides the housing (102) into a first chamber (104) and a second chamber (106); Cathode electrode (105) located in the first chamber (104); The anode electrode (107) is located in the second chamber (106); A first conduit loop (116) is fluidly connected to the second chamber (106) and is configured to supply a feed stream (110) to the second chamber (106); A second conduit loop (124) is fluidly connected to the first chamber (104), configured to circulate enriched flow (120) through the first chamber (104); and A power supply (109) is configured to apply a voltage between the cathode and anode electrodes to initiate an oxidation electrochemical reaction at the anode electrode and a reduction electrochemical reaction at the cathode electrode. The thickness of the dense lithium selective film is less than 400 μm. The cathode electrode is made of copper hollow fibers coated with platinum-ruthenium (Pt-Ru), and forms an internal channel to receive CO2 from outside the housing and release CO2 in the enrichment stream. The enriched flow from the previous pool is the feed flow to the current pool.

9. A method for increasing the lithium (Li) concentration in a pool, the method comprising: A dense lithium selective membrane (108) is arranged (1700) in the housing (102) to divide the housing (102) into a first chamber (104) and a second chamber (106); A feed stream (110) comprising seawater is supplied (1702) to the second chamber (106); Supply (1704) enriched flow (120) to the first chamber (104); A voltage (1706) is applied between the cathode electrode (105) located in the first chamber (104) and the anode electrode (107) located in the second chamber (106) to initiate an oxidation electrochemical reaction on the anode electrode and a reduction electrochemical reaction on the cathode electrode. and Li atoms from seawater (1708) are driven through a dense lithium-selective membrane into the enriched feed. The thickness of the dense lithium selective film is less than 400 μm, and The cathode electrode is made of copper hollow fiber coated with platinum-ruthenium (Pt-Ru), and the cathode electrode forms an internal channel to receive CO2 from outside the housing and release CO2 in the enrichment stream.

10. The method of claim 9, wherein the dense lithium selective film is a glass-type Li x La 2 / 3-x / 3 TiO3 (LLTO) film, where x is 0.23 to 0.

67.

11. The method of claim 9, further comprising: Inject acid into the enriched stream to maintain the pH at 4.5 to 7.

0.

12. The method of claim 9, further comprising: A first anion exchange membrane is added to the second chamber to form a third chamber, thereby placing the anode electrode in the third chamber.

13. The method of claim 12, further comprising: An anode stream is supplied to the third chamber, which is different from the feed stream and the enrichment stream. The anode stream is configured not to absorb chlorine generated by the anode electrode, thereby capturing the chlorine at the port formed in the third chamber.

14. The method of claim 12, further comprising: A second anion exchange membrane is added to the first chamber to form a fourth chamber, thereby placing the cathode electrode in the fourth chamber.

15. The method of claim 14, further comprising: A cathode stream is supplied to the fourth chamber, which is different from the feed stream and enrichment stream.

16. A cell (100) for increasing the lithium (Li) concentration in a stream, the cell (100) comprising: Shell (102); A dense lithium selective membrane (108) located inside the housing (102) and dividing the housing (102) into a first chamber (104) and a second chamber (106); Cathode electrode (105) located in the first chamber (104); The anode electrode (107) is located in the second chamber (106); A first conduit loop (116) is fluidly connected to the second chamber (106) and is configured to supply a feed stream (110) to the second chamber (106); A second conduit loop (124) is fluidly connected to the first chamber (104), configured to circulate enriched flow (120) through the first chamber (104); and A power supply (109) is configured to apply a voltage between the cathode and anode electrodes to initiate an oxidation electrochemical reaction at the anode electrode and a reduction electrochemical reaction at the cathode electrode. The thickness of the dense lithium selective film is less than 400 μm. The dense lithium selective membrane is configured to be sufficiently dense that it is impermeable to water and gas. The cathode electrode is made of copper hollow fiber coated with platinum-ruthenium (Pt-Ru), and the cathode electrode forms an internal channel to receive CO2 from outside the housing and release CO2 in the enrichment stream.

17. The cell of claim 16, wherein the dense lithium selective membrane is a glass-type Li x La 2 / 3-x / 3 TiO3 (LLTO) film, where x is 0.23 to 0.67.

Images