Solar lithium enrichment device and lithium enrichment method based on magnesium-calcium selective barrier

Abstract

The solar lithium enrichment device comprises a lithium-rich salt collecting assembly, the lithium-rich salt collecting assembly is of an integrally-formed table-shaped cavity structure with the upper bottom end face closed and the lower bottom end face open, and the projection area of the lower bottom end face is larger than that of the upper bottom end face; the peripheral edge of the lower bottom end face is provided with a groove-shaped closing opening extending along the contour of the lower bottom end face, the upper bottom end face of the lithium-rich salt collecting assembly is provided with side edge water conveying layer penetrating openings which are parallel to each other, a middle water conveying layer penetrating opening is formed between the side edge water conveying layer penetrating openings which are parallel to each other, and the side edge water conveying layer penetrating openings are perpendicular to the middle water conveying layer penetrating opening; water and salt conveying assemblies are arranged in the side water conveying layer penetrating openings and the middle water conveying layer penetrating opening in a penetrating mode correspondingly, and a photo-thermal assembly is arranged on the water and salt conveying assembly located on the upper bottom end face. The problems that under a high-salt complex system, a membrane is prone to scaling pollution, the membrane material cost is high, a waste membrane easily causes solid waste pollution, and the system energy consumption and the equipment complexity are improved due to the need of high operation pressure difference are solved.

Description

Technical Field

[0001] This invention belongs to the field of salt lake brine treatment and inorganic salt separation technology, specifically relating to a solar lithium enrichment device and method based on magnesium-calcium selective barrier. Background Technology

[0002] In recent years, with the continuous development of solar energy utilization technology, solar interfacial evaporation technology has received widespread attention in fields such as seawater desalination, high-salinity wastewater treatment, and salting-out recovery due to its significant advantages, including simple structure, low energy consumption, and direct utilization of natural solar radiation. This type of technology typically constructs a highly efficient photothermal conversion interface, allowing water molecules to evaporate preferentially at the interface, thereby reducing solution volume and concentrating solute. However, existing solar interfacial evaporation processes mainly rely on the phase change mass transfer of water, acting on the entire solution system, and are essentially non-selective evaporation behaviors. Since the solute does not migrate with the vapor during evaporation but passively remains in the liquid phase, interfacial evaporation technology itself lacks the ability to distinguish between different metal ions, lacking effective selective control methods for monovalent and divalent metal ions, making it difficult to achieve efficient separation of lithium ions from divalent ions such as magnesium and calcium.

[0003] In lithium resource systems such as salt lake brines, magnesium ions (Mg²⁺) + ) and calcium ions (Ca²) + Magnesium ions (MgO) typically exist at concentrations far exceeding those of lithium ions. They not only preferentially precipitate to form insoluble salts during evaporation and concentration but also significantly interfere with the crystallization behavior of lithium salts, reducing the purity of lithium products and increasing the difficulty of subsequent separation and purification processes. Therefore, the core technical challenge for selective lithium salt enrichment based on solar interfacial evaporation lies not simply in increasing the evaporation rate, but in how to effectively shield, remove, or separate divalent ions such as magnesium and calcium from the brine during the evaporation process, thereby creating favorable conditions for lithium ion enrichment.

[0004] To address the aforementioned issues, existing technologies primarily rely on the differences in hydration radii and physical sizes of different ions in aqueous solutions. They employ membrane materials or filter media with specific pore size distributions to physically sieve or block divalent ions such as magnesium and calcium. While theoretically, this method can achieve a certain degree of ion separation through pore size control, it generally suffers from numerous limitations in practical applications. Firstly, brine systems are characterized by high salinity and complex composition, making membrane materials highly susceptible to inorganic salt scaling and organic fouling during long-term operation. This leads to a rapid decline in membrane flux, and the membrane materials themselves are costly to manufacture, with the accumulation of waste membranes causing significant solid waste pollution. Secondly, maintaining effective separation typically requires applying a large operating pressure differential, increasing system energy consumption and equipment complexity. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention aims to provide a solar-powered lithium enrichment device and method based on magnesium-calcium selective blocking. The device has a simple structure, can be driven by natural solar energy, and can achieve divalent ion blocking and improve lithium ion enrichment during the evaporation process. It solves the problems of easy fouling and pollution of membranes in high-salt complex systems, high cost of membrane materials, easy solid waste pollution caused by discarded membranes, and increased system energy consumption and equipment complexity due to the need for high operating pressure differential.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A solar lithium enrichment device based on magnesium-calcium selective barrier includes a lithium-rich salt collection component, a water-salt transport component, and a photothermal component. The lithium-rich salt collection component is a one-piece, form-fitted, table-shaped cavity structure with a closed upper end face and an open lower end face. The projected area of ​​the lower end face is larger than that of the upper end face. The circumferential edge of the lower end face has a groove-shaped constriction extending along its contour. The upper end face of the lithium-rich salt collection component has parallel side water delivery layer penetrations, and an intermediate water delivery layer penetration is formed between the parallel side water delivery layer penetrations. The side water delivery layer penetrations and the intermediate water delivery layer penetrations are perpendicular to each other. Water and salt transport components are respectively installed in the side water delivery layer penetrations and the intermediate water delivery layer penetrations. A photothermal component is installed on the water and salt transport components on the upper end face. A water and salt transport component baffle is provided on the lower surface of the lithium-rich salt collection component on the opposite inner side of the parallel side water delivery layer penetrations. The water-salt transport assembly includes a side water transport layer and a middle water transport layer. The side water transport layer and the middle water transport layer are respectively provided with through-holes. One end of the side water transport layer and the middle water transport layer extends into the cavity of the lithium-rich salt collection assembly and contacts the brine. The other end is in close contact with the side wall of the lithium-rich salt collection assembly. A divalent ion shielding layer is fitted on the end of the water-salt transport assembly that extends into the cavity of the lithium-rich salt collection assembly. The position of the divalent ion shielding layer is at least 5 mm above the liquid surface. The end of the water-salt transport assembly that is in close contact with the side wall of the salt collection device is a trapezoid with the short base facing downwards. The photothermal component includes a photothermal layer and a waterproof and moisturizing layer, which are sequentially disposed on the water and salt transport component from top to bottom.

[0007] Furthermore, the width of the intermediate water conveying layer is greater than the width of the side water conveying layer, and the intermediate water conveying layer and the side water conveying layer together cover the upper and lower end faces of the lithium-rich salt collection component.

[0008] Furthermore, the height of the divalent ion shielding layer is 2-5 mm, and the thickness is 1-3 mm.

[0009] Furthermore, the material of the divalent ion shielding layer is at least one of zeolite molecular sieve or alkaline cement, wherein the alkaline cement is 325 white cement, 425 white cement, 525 white cement or gray cement; and the zeolite molecular sieve is 4A, 5A or 13X zeolite.

[0010] Furthermore, in the trapezoidal structure, the long base is equal to the height, and the ratio of the long base to the short base is 2:1 to 5:1.

[0011] Furthermore, the lithium-rich salt collection component is nylon foam, polyethylene foam, or aerogel insulation board; the water-salt transport component is hydrophilic fiber fabric; the photothermal layer is a black inorganic coating with light absorption properties; and the waterproof and moisturizing layer is a flexible ethylene-based membrane material.

[0012] A lithium enrichment method based on a magnesium-calcium selective blocking solar lithium enrichment device includes the following steps: S1: Add the lithium salt solution to be treated into the cavity of the lithium-rich salt collection component. The lithium salt solution contacts the side water transport layer and the middle water transport layer in the water-salt transport component at one end that extends into the cavity. S2: The lithium salt solution is capillarily transported along the side water transport layer and the middle water transport layer. When the solution flows through the divalent ion shielding layer, the divalent metal ions are selectively blocked by the divalent ion shielding layer. The lithium ions continue to be transported upward along the side water transport layer and the middle water transport layer with the solution. A lithium-rich solution is obtained at the top and bottom end face of the lithium-rich salt collection component, thus realizing the separation of lithium ions and divalent metal ions. S3: Under sunlight, the solar thermal component converts solar energy into thermal energy, causing the lithium-rich solution to gradually accumulate and evaporate on the upper and lower end faces of the lithium-rich salt collection component. The lithium-rich solution continues to evaporate along the side water transport layer and the middle water transport layer on the outer surface of the side wall of the lithium-rich salt collection component, and lithium-rich salt solids are precipitated in the groove-shaped opening on the lower end face of the lithium-rich salt collection component and collected. S4: Dissolve the lithium-rich salt solid collected in step S3 in water, add a carbonate precipitant, and use a single-step carbonate precipitation method to precipitate lithium ions in the form of lithium carbonate; after solid-liquid separation, washing and drying, the purified lithium salt is obtained.

[0013] Further, in step S4, lithium-rich salt solid is added to water to form a lithium-rich salt solution with a mass fraction of 10–25 wt%. The lithium-rich salt solution is heated to 60–90 °C, and a carbonate precipitant is added under stirring. The actual amount of carbonate precipitant added is 1.02–1.10 times its theoretical reaction equivalent, calculated based on the molar number of lithium ions in the lithium-rich salt solution. After solid-liquid separation, the filter cake is washed with deionized water / deionized water at 50–95 °C 1–3 times. Subsequently, it is dried at 110–130 °C for 2–12 h.

[0014] Furthermore, when the divalent ion shielding layer reaches adsorption saturation or its performance deteriorates, the entire water-salt transport assembly is removed, and the divalent ion shielding layer is separated from the side water transport layer and the middle water transport layer by axial sliding for replacement.

[0015] Furthermore, the lithium-rich salt solution preferably has a mass fraction of 12–20 wt%; the carbonate precipitant is preferably anhydrous sodium carbonate.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention introduces a functional layer with selective adsorption capacity for divalent ions into a solar interfacial evaporation system. This layer enables the in-situ capture and fixation of magnesium and calcium ions in the brine during the evaporation and concentration process, thereby effectively reducing the risk of accumulation and precipitation of divalent ions in the interfacial region. Through the synergistic effect of photothermal evaporation and ion-selective adsorption, this invention can achieve relative enrichment of lithium ions in a simple, easy-to-build, low-cost, and low-pollution manner without introducing additional chemical reagents, applying external pressure, or complex control conditions. This significantly enhances the application value of solar interfacial evaporation systems in the field of lithium resource extraction. Specifically: 1. The overall structural design of this invention achieves high-efficiency Li under solar energy conditions. + With Mg² + / Ca² + Separation. Experimental data shows that after setting a divalent ion shielding layer, Mg²⁺ + / Li + Ca² + / Li + The significant decrease in the ratio values ​​(e.g., Mg / Li ratio from 2.55 to 0.48, Ca / Li ratio from 2.38 to 0.80) indicates the significant divalent ion blocking and lithium enrichment effect of this invention.

[0017] 2. This invention effectively inhibits Ca²⁺ + Mg² + Scaling behavior on the evaporation surface improves evaporation stability. COMSOL multiphysics simulations show that Ca²⁺… + The concentration of Ca and Mg at the front of the barrier layer is significantly accumulated, making it difficult to penetrate to the evaporation interface; scanning electron microscopy-electron energy scattering spectroscopy (SEM-EDS) further confirmed that Ca and Mg are largely retained at the barrier layer, and the evaporation surface of the water-salt transport component remains clean.

[0018] 3. The device of this invention has a simple structure and uses inexpensive materials, making it suitable for low-cost, large-scale applications. The water and salt transport components are made of hydrophilic fiber fabric, and the divalent ion shielding layer is made of zeolite molecular sieve or alkaline cement. It requires no complex equipment or energy consumption and can operate directly using natural solar energy in coastal areas, salt lakes, islands, and reefs, making it highly economical and versatile.

[0019] 4. The photothermal evaporation process of this invention does not involve chemical additives and will not cause additional pollution to water bodies. The process is green and sustainable, with no secondary pollution, and is environmentally friendly and safe. It can be applied to scenarios such as seawater lithium extraction, lithium enrichment in salt lakes, and resource utilization of concentrated brine, providing an important foundation for the renewable energy storage industry and has broad application prospects. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure of the bottom end face of the lithium-rich salt collection component of the present invention; Figure 3 This is a schematic diagram of the structure of the water and salt transport component of the present invention; Figure 4 This is a schematic diagram of the installation of the water-salt transport component and the divalent ion shielding layer of the present invention; Figure 5 This is a schematic diagram of the structure of the photothermal component of the present invention; Figure 6(a) is an overall physical diagram of the present invention, Figure 6(b) is a physical diagram of the installation of the lithium-rich salt collection component and the water-salt transport component, and Figure 6(c) is a physical diagram of the present invention viewed from below from inside the cavity structure of the lithium-rich salt collection component. Figure 7 The graph shows the changes in the proportion of each ion evaporated and precipitated before and after seawater treatment by a solar lithium enrichment device based on magnesium-calcium selective blocking. Figure 8 The ratio of each salting-out ion before and after seawater treatment is given by a solar lithium enrichment device based on magnesium-calcium selective blocking. Figure 9 shows the simulation of the principle and effect of the divalent ion shielding layer in blocking calcium and magnesium ions. Figure 9(a) is a schematic diagram of calcium and magnesium ion adsorption-exchange by 4A zeolite, and Figure 9(b) is a schematic diagram of magnesium ion adsorption, encapsulation and precipitation by alkaline cement. Figure 10 Simulation diagram of COMSOL multiphysics effect of divalent ion shielding layer on calcium and magnesium ion blocking; Figure 11 SEM-EDS distribution of elements such as Ca and Mg on the substrate after the water and salt transport components have been blocked.

[0021] Wherein: 1-Lithium-rich salt collection component, 1.1-Side water conveying layer penetration port, 1.2-Intermediate water conveying layer penetration port, 1.3-Water conveying layer baffle, 2-Water and salt transport component, 2.1-Side water conveying layer, 2.2-Intermediate water conveying layer, 2.3-Divalent ion shielding layer, 3-Photothermal component, 3.1-Photothermal layer, 3.2-Waterproof and moisture-retaining layer. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. In this invention, "path" refers to the direction in which the invention is situated. Figure 1 Description of the state's progression.

[0023] See Figure 1 A solar lithium enrichment device based on magnesium-calcium selective barrier includes a lithium-rich salt collection component 1, a water-salt transport component 2, and a photothermal component 3. The lithium-rich salt collection component 1 is a truncated cavity structure with a closed upper bottom end face and an open lower bottom end face. The projected area of ​​the lower bottom end face is larger than the projected area of ​​the upper bottom end face, and the circumferential edge of the lower bottom end face is provided with a groove-shaped constriction extending along its contour. The lithium-rich salt collection component 1 has parallel side water delivery layer penetrations 1.1 on its upper and lower end faces. An intermediate water delivery layer penetration 1.2 is formed between the parallel side water delivery layer penetrations 1.1 and the intermediate water delivery layer penetration 1.2. The side water delivery layer penetrations 1.1 and the intermediate water delivery layer penetration 1.2 are perpendicular to each other. Water and salt transport components 2 are respectively installed in the side water delivery layer penetrations 1.1 and the intermediate water delivery layer penetration 1.2. A photothermal component 3 is provided on the water and salt transport components 2 located on the upper and lower end faces. The lithium-rich salt collection component 1 is a nylon foam, polyethylene foam or aerogel insulation board.

[0024] In this embodiment, the lithium-rich salt collection component 1 is a frustum-shaped cavity structure; the lithium-rich salt collection component 1 is nylon foam, and the water-salt transport component 2 is hydrophilic fiber fabric.

[0025] See Figure 2 and Figure 3 The water-salt transport assembly 2 includes a side water transport layer 2.1 and a middle water transport layer 2.2. The side water transport layer 2.1 and the middle water transport layer 2.2 are respectively provided with side water transport layer penetration openings 1.1 and middle water transport layer penetration openings 1.2. A water transport layer baffle 1.3 is provided on the lower surface of the lithium-rich salt collection assembly 1 on the inner side of the parallel side water transport layer penetration openings 1. One end of each side water transport layer 2.1 and the middle water transport layer 2.2 extends into the cavity of the lithium-rich salt collection assembly 1 and contacts the liquid, while the other end is in close contact with the side wall of the lithium-rich salt collection assembly 1.

[0026] In this embodiment, the side water conveyance layers 2.1 are arranged in two sets of three in parallel, and the middle water conveyance layers 2.2 are arranged in two sets.

[0027] See Figure 4 The water-salt transport component 2, extending into the cavity of the lithium-rich salt collection component 1, is fitted with a divalent ion shielding layer 2.3. The height of the divalent ion shielding layer 2.3 is 2-5 mm, and its thickness is 1-3 mm. The position of the divalent ion shielding layer 2.3 is at least 5 mm above the liquid surface. The material of the divalent ion shielding layer 2.3 is at least one of zeolite molecular sieve or alkaline cement. The alkaline cement is 325 white cement, 425 white cement, 525 white cement, or gray cement. The zeolite molecular sieve is 4A, 5A, or 13X zeolite. The end of the water-salt transport component 2 that is in close contact with the side wall of the salt collection device 1 is a trapezoid with the short base facing downwards. In the trapezoidal structure, the long base and the height are equal, and the ratio of the long base to the short base is 2:1 to 5:1.

[0028] In this embodiment, the height of the divalent ion shielding layer 2.3 is 5 mm and the thickness is 2 mm; the position of the divalent ion shielding layer 2.3 is 5 mm above the liquid surface, the material is 4A zeolite, the width of the middle water conveying layer 2.2 is 30 mm, the width of the side water conveying layer 2.1 is 24 mm, the long base, height and short base of the trapezoid at one end of the middle water conveying layer 2.2 are 30 mm, 30 mm and 10 mm respectively, and the long base, height and short base of the trapezoid at one end of the side water conveying layer 2.1 are 24 mm, 24 mm and 8 mm respectively.

[0029] See Figure 5 The photothermal component 3 includes a photothermal layer 3.1 and a waterproof and moisture-retaining layer 3.2, which are sequentially disposed on the water and salt transport component 2 from top to bottom. The photothermal layer 3.1 is a black inorganic coating with light absorption properties, and the waterproof and moisture-retaining layer 3.2 is a flexible vinyl membrane material. The photothermal layer 3.1 has a photothermal conversion function, and the waterproof and moisture-retaining layer 3.2, after being attached, has a moisturizing effect on the space within the water and salt transport component 2, preventing the hydrophilic fiber fabric from drying out under strong light.

[0030] Referring to Figure 6(a), which is an overall physical diagram of the present invention, high-purity lithium salt is precipitated in the groove-shaped inlet of the lithium-rich salt collection component 1. Figure 6(b) is a physical diagram of the installation of the lithium-rich salt collection component and the water-salt transport component. Figure 6(c) is a physical diagram of the present invention from a bottom view inside the cavity structure of the lithium-rich salt collection component. Purple represents the water-salt transport component 2 of the present invention.

[0031] When the side water conveying layer 2.1 and the middle water conveying layer 2.2 extend into the cavity of the lithium-rich salt collection component 1 and come into contact with the liquid, the liquid flows through the divalent ion shielding layer 2.3. Due to the adsorption effect of the divalent ion shielding layer 2.3, divalent ions such as magnesium ions remain in the divalent ion shielding layer 2.3 and fail to flow out, while lithium ions are almost unimpeded by the divalent ion shielding layer and continue to flow. The outflowing liquid is a high-purity lithium ion solution. The water-salt transport component 2 extends out of the upper and lower end face of the lithium-rich salt collection component 1 and is attached to the photothermal component 3. When exposed to sunlight, it can convert solar energy into heat energy. When the lithium ion solution flows to the upper and lower end face of the lithium-rich salt collection component 1, the lithium ion-rich solution can be brought close to saturation under light. Simultaneously, a temperature difference is generated between the water-salt transport component 2 on the upper and lower end face of the lithium-rich salt collection component 1 and the interior of the side wall of the lithium-rich salt collection component 1. Since the side water transport layer 2.1 and the middle water transport layer 2.2 have good water absorption, under the action of the Marangoni effect, the solution flows upward along the water-salt transport component 2 to the outside of the side wall of the lithium-rich salt collection component 1, and continues to be evaporated by sunlight. Finally, high-purity lithium salt can be precipitated in the trough-shaped constriction of the lithium-rich salt collection component 1.

[0032] The device must be kept in a water-containing state within 1 hour after the adsorption material of the divalent ion shielding layer 2.3 is loaded to prevent the adsorption material from drying out. That is, it must be put into use within one hour after loading.

[0033] The present invention manufactures a solar-powered lithium enrichment device based on magnesium-calcium selective barrier, which can separate lithium from magnesium-lithium mixed solutions, seawater and salt lake water using only solar energy. It is applicable to seawater / salt lake desalination, lithium extraction from salt lakes, and refined salt refining.

[0034] like Figure 7 As shown in the figure, the evaporation and precipitation ratios of five ions (Na, Mg, Ca, K, and Li) in the original group and the group with barriers are compared: the precipitation ratios of each ion are generally higher in the original group (e.g., Na and Li are close to 95%), while in the group with barriers, the precipitation ratios of Mg, Ca, and K decrease significantly (Mg decreases from about 50% to 18%, and Ca decreases from about 50% to 28%), with only Na and Li maintaining relatively high precipitation ratios. This clearly demonstrates the effect of the divalent ion shielding layer on divalent ions (Mg²⁺). + Ca² + The inhibition effect of evaporation and precipitation is more significant.

[0035] like Figure 8As shown in the figure, this diagram illustrates the differences in the ratios of the four groups of ions—Mg / Li, Mg / K, Ca / Li, and Ca / K—between the original group and the group with barriers. In the original group, the ratios of Mg and Ca to Li and K are extremely high (e.g., Mg / Li reaches 255, Ca / Li reaches 238), while in the group with barriers, these ratios are significantly reduced (Mg / Li drops to 0.48, Ca / Li drops to 0.8). This further demonstrates that the divalent ion shielding layer significantly reduces the separation of divalent ions such as Mg and Ca, achieving selective separation of divalent and monovalent ions.

[0036] Figure 9(a) is a schematic diagram of calcium and magnesium ion adsorption-exchange by zeolite molecular sieve, and Figure 9(b) is a schematic diagram of magnesium ion adsorption, encapsulation, and precipitation by alkaline cement. The diagrams illustrate the working principle of the barrier by comparing the left and right sides: the left side of Figure 9(a) and Figure 9(b) "without barrier (zeolite)" treats ions only through ion exchange and adsorption; the right side "with barrier" adds a "divalent ion shielding layer", which, through adsorption, encapsulation, and reaction, etc., absorbs Mg²⁺ ions. + Ca² + Divalent ions are confined within the divalent ion shielding layer, while Na+ is allowed to... + Li + Monovalent ions pass through the water-salt transport components. This explains the mechanism by which the barrier measures preferentially suppress the migration / deposition of divalent ions.

[0037] like Figure 10 As shown in the figure, the ion concentration distribution simulation is performed at different times (0d, 5.1d, 35.1d, 49.8d): Initially, the divalent ion shielding layer 2.3 completely blocks divalent ions. As time progresses, the concentration of divalent ions in the divalent ion shielding layer 2.3 gradually increases and diffuses upwards, while the upper region of the water-salt transport component 2 maintains a low concentration. This indicates that the blocking measures can delay ion diffusion and maintain a low divalent ion concentration in the output liquid flow over a long period.

[0038] like Figure 11 As shown in the figure, the water-salt transport layer near the divalent ion shielding layer 2.3 was observed by SEM, demonstrating the selective transport effect of the divalent ion shielding layer 2.3 on Ca / Mg ions: Mg (red) and Ca (blue-green) elements migrate upward within the water-salt transport layer. Upon encountering the alkaline cement of the divalent ion shielding layer, they are adsorbed by chelating groups such as hydroxyl groups inside the shielding layer, forming chelated ions, and no longer continue to be transported upward. It can be seen that beyond the divalent ion shielding layer, there is no distribution of Ca / Mg elements in the water-salt transport layer as shown by EDS characterization, which effectively proves the shielding effect of the divalent ion shielding layer on Ca / Mg ions.

[0039] A lithium enrichment method based on a magnesium-calcium selective blocking solar lithium enrichment device includes the following steps: S1: Add the lithium salt solution to be treated into the cavity of the lithium-rich salt collection component 1. The lithium salt solution contacts the end of the side water transport layer 2.1 and the middle water transport layer 2.2 in the water-salt transport component 2 that extends into the cavity. S2: The lithium salt solution is capillarily transported along the side water transport layer 2.1 and the middle water transport layer 2.2. When the solution flows through the divalent ion shielding layer 2.3, the divalent metal ions are selectively blocked by the divalent ion shielding layer 2.3. The lithium ions continue to be transported upward along the side water transport layer 2.1 and the middle water transport layer 2.2 with the solution. A lithium-rich solution is obtained at the upper and lower end face of the lithium-rich salt collection component 1, realizing the separation of lithium ions and divalent metal ions. S3: Under sunlight, the solar thermal component 3 converts solar energy into thermal energy, causing the lithium-rich solution to gradually accumulate and evaporate on the upper and lower end face of the lithium-rich salt collection component 1. The lithium-rich solution continues to evaporate on the outer surface of the side wall of the lithium-rich salt collection component 1 along the side water transport layer 2.1 and the middle water transport layer 2.2, and lithium-rich salt solids are precipitated in the groove-shaped opening on the lower end face of the lithium-rich salt collection component 1 and collected. S4: Add lithium-rich salt solid to water to form a lithium-rich salt solution with a mass fraction of 10–25 wt%. Heat the lithium-rich salt solution to 60–90 °C and add a carbonate precipitant under stirring. The actual amount of carbonate precipitant added is 1.02–1.10 times its theoretical reaction equivalent, calculated based on the number of moles of lithium ions in the lithium-rich salt solution. After solid-liquid separation, wash the filter cake with deionized water / deionized water at 50–95 °C 1–3 times. Then dry at 110–130 °C for 2–12 h to obtain the separated and purified lithium salt.

[0040] When the divalent ion shielding layer 2.3 reaches adsorption saturation or its performance deteriorates, the entire water-salt transport assembly 2 is removed. The divalent ion shielding layer 2.3 is then separated from the side water transport layer 2.1 and the intermediate water transport layer 2.2 via axial sliding for replacement. The divalent ion shielding layer 2.3 is a natural inorganic material and can be directly treated as solid waste without causing environmental pollution. The separated side water transport layer 2.1 and intermediate water transport layer 2.2 can be reused after rinsing with clean water and then re-attached with a new adsorption layer before being put back into operation. The preferred mass fraction of the lithium-rich salt solution is 12–20 wt%; the preferred carbonate precipitant is anhydrous sodium carbonate.

[0041] Example 1 Steps S1-S3 remain unchanged. In step S4, lithium-rich salt solid is added to water to form a lithium-rich salt solution with a mass fraction of 10 wt%. The lithium-rich salt solution is heated to 60 °C, and anhydrous sodium carbonate is added under stirring. The actual amount of anhydrous sodium carbonate added is 1.02 times its theoretical reaction equivalent, calculated based on the number of moles of lithium ions in the lithium-rich salt solution. After solid-liquid separation, the filter cake is washed once with deionized water / deionized water at 50 °C. Then, it is dried at 110 °C for 2 hours to obtain the separated and purified lithium salt.

[0042] Example 2 Steps S1-S3 remain unchanged. In step S4, lithium-rich salt solid is added to water to form a lithium-rich salt solution with a mass fraction of 18 wt%. The lithium-rich salt solution is heated to 75 °C, and anhydrous sodium carbonate is added under stirring. The actual amount of anhydrous sodium carbonate added is 1.06 times its theoretical reaction equivalent, calculated based on the number of moles of lithium ions in the lithium-rich salt solution. After solid-liquid separation, the filter cake is washed twice with deionized water / deionized water at 70 °C. Subsequently, it is dried at 120 °C for 7 h to obtain the separated and purified lithium salt.

[0043] Example 3 Steps S1-S3 remain unchanged. In step S4, lithium-rich salt solid is added to water to form a lithium-rich salt solution with a mass fraction of 25 wt%. The lithium-rich salt solution is heated to 90 °C, and anhydrous sodium carbonate is added under stirring. The actual amount of anhydrous sodium carbonate added is 1.10 times its theoretical reaction equivalent, calculated based on the number of moles of lithium ions in the lithium-rich salt solution. After solid-liquid separation, the filter cake is washed three times with deionized water / deionized water at 95 °C. Subsequently, it is dried at 130 °C for 12 h to obtain the separated and purified lithium salt.

Claims

1. A solar lithium enrichment device based on magnesium-calcium selective barrier, characterized in that, It includes a lithium-rich salt collection component (1), a water-salt transport component (2), and a photothermal component (3). The lithium-rich salt collection component (1) is a truncated cavity structure with a closed upper bottom face and an open lower bottom face, formed integrally. The projected area of ​​the lower bottom face is larger than that of the upper bottom face. The circumferential edge of the lower bottom face is provided with a groove-shaped constriction extending along its contour. The upper bottom face of the lithium-rich salt collection component (1) is provided with parallel side water conveyance layer penetrations (1.1). An intermediate water conveyance layer penetration (1.2) is provided between the parallel side water conveyance layer penetrations (1.1). The side water conveying layer penetration (1.1) and the middle water conveying layer penetration (1.2) are perpendicular to each other; water and salt transport components (2) are respectively installed in the side water conveying layer penetration (1.1) and the middle water conveying layer penetration (1.2), and a photothermal component (3) is provided on the water and salt transport component (2) located on the upper bottom end face. On the opposite inner side of the parallel side water conveying layer penetration (1.1), a water and salt transport component baffle (1.3) is provided on the lower surface of the lithium-rich salt collection component (1). The water-salt transport assembly (2) includes a side water transport layer (2.1) and a middle water transport layer (2.2). The side water transport layer (2.1) and the middle water transport layer (2.2) are respectively provided with the side water transport layer through-hole (1.1) and the middle water transport layer through-hole (1.2). One end of the side water transport layer (2.1) and the middle water transport layer (2.2) extends into the cavity of the lithium-rich salt collection assembly (1) and contacts the brine. The other end is close to the side wall of the lithium-rich salt collection assembly (1). A divalent ion shielding layer (2.3) is provided at the end of the water-salt transport assembly (2) that extends into the cavity of the lithium-rich salt collection assembly (1). The position of the divalent ion shielding layer (2.3) is at least 5 mm above the liquid surface. The end of the water-salt transport assembly (2) that is close to the side wall of the salt collection device (1) is a trapezoid with the short bottom side facing downward. The photothermal component (3) includes a photothermal layer (3.1) and a waterproof and moisturizing layer (3.2), which are arranged sequentially from top to bottom on the water and salt transport component (2).

2. The solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 1, characterized in that, The width of the intermediate water conveying layer (2.2) is greater than the width of the side water conveying layer (2.1), and the intermediate water conveying layer (2.2) and the side water conveying layer (2.1) together cover the upper bottom surface of the lithium-rich salt collection component (1).

3. The solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 1, characterized in that, The height of the divalent ion shielding layer (2.3) is 2~5mm and the thickness is 1~3mm.

4. The solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 1, characterized in that, The material of the divalent ion shielding layer (2.3) is at least one of zeolite molecular sieve or alkaline cement, wherein the alkaline cement is 325 white cement, 425 white cement, 525 white cement or gray cement; and the zeolite molecular sieve is 4A, 5A or 13X zeolite.

5. A solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 1, characterized in that, In the trapezoidal structure, the long base is equal to the height, and the ratio of the long base to the short base is 2:1 to 5:

1.

6. The solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 1, characterized in that, The lithium-rich salt collection component (1) is a nylon foam, polyethylene foam or aerogel insulation board, the water and salt transport component (2) is a hydrophilic fiber fabric, the photothermal layer (3.1) is a black inorganic coating with light absorption properties, and the waterproof and moisturizing layer (3.2) is an ethylene-based flexible membrane material.

7. The lithium enrichment method of the solar lithium enrichment device based on magnesium-calcium selective barrier according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Add the lithium salt solution to be treated into the cavity of the lithium salt collection component (1), and the lithium salt solution contacts the end of the side water transport layer (2.1) and the middle water transport layer (2.2) in the water-salt transport component (2) that extends into the cavity; S2: The lithium salt solution is capillarily transported along the side water transport layer (2.1) and the middle water transport layer (2.2). When the solution flows through the divalent ion shielding layer (2.3), the divalent metal ions are selectively blocked by the divalent ion shielding layer (2.3). The lithium ions continue to be transported upward along the side water transport layer (2.1) and the middle water transport layer (2.2) with the solution. A lithium-rich solution is obtained at the top and bottom end face of the lithium-rich salt collection component (1), thereby realizing the separation of lithium ions and divalent metal ions. S3: Under sunlight, the photothermal component (3) converts solar energy into thermal energy, causing the lithium-rich solution to gradually accumulate and evaporate on the upper bottom end face of the lithium-rich salt collection component (1). The lithium-rich solution continues to evaporate on the outer surface of the side wall of the lithium-rich salt collection component (1) along the side water transport layer (2.1) and the middle water transport layer (2.2), and lithium-rich salt solids are precipitated in the groove-shaped opening on the lower bottom end face of the lithium-rich salt collection component (1) and collected. S4: Dissolve the lithium-rich salt solid collected in step S3 in water, add a carbonate precipitant, and use a single-step carbonate precipitation method to precipitate lithium ions in the form of lithium carbonate; after solid-liquid separation, washing and drying, the purified lithium salt is obtained.

8. The lithium enrichment method of the solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 7, characterized in that, In step S4, lithium-rich salt solid is added to water to form a lithium-rich salt solution with a mass fraction of 10–25 wt%. The lithium-rich salt solution is heated to 60–90 °C, and a carbonate precipitant is added under stirring. The actual amount of carbonate precipitant added is 1.02–1.10 times its theoretical reaction equivalent, calculated based on the molar number of lithium ions in the lithium-rich salt solution. After solid-liquid separation, the filter cake is washed with deionized water / deionized water at 50–95 °C 1–3 times. Subsequently, it is dried at 110–130 °C for 2–12 h.

9. The lithium enrichment method of the solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 7, characterized in that, When the divalent ion shielding layer (2.3) reaches adsorption saturation or its performance deteriorates, the water-salt transport assembly (2) is removed as a whole, and the divalent ion shielding layer (2.3) is separated from the side water transport layer (2.1) and the middle water transport layer (2.2) by axial slippage for replacement.

10. The lithium enrichment method of the solar lithium enrichment device based on magnesium-calcium selective barrier according to claim 8, characterized in that, The preferred mass fraction of the lithium-rich salt solution is 12–20 wt%; the preferred carbonate precipitant is anhydrous sodium carbonate.

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