Selective separation method for lithium ions and multivalent ions in multi-ion coexistence system

Abstract

The invention provides a selective separation method for lithium ions and multivalent ions in a multi-ion coexistence system, belongs to the technical field of metal ion separation, and aims at solving the problem that multivalent metal ions are not fully utilized in an existing leaching solution lithium extraction method. The method comprises the following steps: adjusting the pH value of the multi-ion coexistence system containing at least one of Al < 3 + > and Fe < 3 + >, Li < + > and Mg < 2 + > to be 10-13; reacting for 20 minutes to 2 hours at the temperature of 25 to 80 DEG C to enable at least one of Al < 3 + > and Fe < 3 + > and Mg < 2 + > to generate a magnesium-based composite hydroxide precipitate; and carrying out solid-liquid separation, wherein the obtained magnesium-based composite hydroxide is used for deeply removing heavy metal ions in heavy metal-containing wastewater. The method is simple in process, lithium is extracted, and meanwhile high-value utilization of multivalent metal resources is achieved.

Description

Selective Separation Methods for Lithium Ions and Multivalent Ions in Multi-Ion Coexistence Systems Technical Field

[0001] This invention relates to the field of metal ion separation technology, specifically to a method for selectively separating lithium ions from multivalent ions in a multi-ion coexistence system. Background Technology

[0002] For different resource types such as salt lake brines, hard rock lithium deposits, and clay-type lithium deposits, various lithium extraction processes have been developed, including precipitation, extraction, adsorption, membrane separation, and selective migration of solid electrolytes. Regardless of the specific unit operation used, a core issue is to achieve effective separation and purification of lithium ions from coexisting cations in complex electrolyte systems.

[0003] In recent years, clay-type lithium deposits have become a promising source of lithium resources, attracting considerable attention. Their complex mineral composition means lithium often coexists with abundant magnesium, aluminum, and iron compounds. To improve leaching selectivity and reduce the environmental burden of traditional processes, organic or inorganic acid leaching processes have been increasingly introduced into the lithium extraction process from clay deposits. When leaching clay deposits with organic acids (such as oxalic acid and citric acid) or inorganic acids (such as sulfuric acid and hydrochloric acid), lithium is leached from the minerals, while magnesium is also leached... 2+ Al 3+ Fe 3+ Isovalent metals also enter the leachate in large quantities in the form of ions or complexes, and coexist with Cl in the system. - SO4 2- Even organic ligands and other anions together form complex multi-component systems. Compared with traditional salt lake brines, this type of leachate exhibits a "monovalent (Li)" characteristic. + ), divalent (Mg) 2+ etc.), trivalent (Al) 3+ Fe 3+ The significant characteristic of lithium is the coexistence of various metals, complex valence states, and intertwined complexation / precipitation equilibria, which makes the efficient separation and purification of lithium more difficult.

[0004] Existing lithium extraction processes from clay ore leaching solutions often follow the traditional approach of "magnesium removal—calcium removal—impurity removal—lithium extraction" from salt lakes, which is problematic for magnesium extraction. 2+ Fe 3+ Al 3+ The process for treating polyvalent metals involves a stepwise process of neutralization precipitation, filtration, and re-purification, supplemented by advanced impurity removal methods such as extraction, adsorption, or membrane separation, resulting in a complex process flow. Furthermore, the design focus of this type of process route remains on optimizing the separation and purification of lithium ions, while neglecting the removal of coexisting Mg in the leachate. 2+ Al 3+ Fe 3+Polyvalent metals are treated merely as impurities to be removed, rather than as resources that can be co-converted and utilized for high value, resulting in their being discarded and underutilized. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system. This method utilizes reaction-separation coupling technology to control the reaction pathway, thereby enabling the separation of Mg ions from multi-ion coexistence systems. 2+ Fe 3+ Al 3+ Multivalent metals are synergistically converted into magnesium-based composite hydroxides, achieving simultaneous one-step separation of multivalent ions and lithium ions within a single operating unit. Furthermore, the prepared magnesium-based composite hydroxides are directly applied to the deep polishing treatment of heavy metals in wastewater containing heavy metals (such as acidic mine wastewater), realizing the high-value utilization of multivalent metal resources in multi-ion coexistence systems and the organic integration of wastewater heavy metal treatment, thus constructing an integrated technical route of "resource separation - functional materials - heavy metal treatment".

[0006] To solve the above technical problems, the technical solution of the present invention is as follows: A method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system, comprising the following steps: Step (1), introducing lithium ions into a system containing Al... 3+ and Fe 3+ At least one of them, Li + Mg 2+ Add a pH adjuster to adjust the pH to 10-13 in a multi-ion coexistence system, and maintain the temperature at 25-80°C. o React at C for 20 min–2 h to allow the Al in the multi-ion coexistence system to react. 3+ and Fe 3+ At least one of them, Mg 2+ Co-precipitation and self-assembly reactions occur to generate magnesium-based composite hydroxide precipitate; step (2) solid-liquid separation is performed to obtain lithium-rich separation liquid and magnesium-based composite hydroxide wet solid phase; step (3) the magnesium-based composite hydroxide wet solid phase is washed and dried to obtain magnesium-based composite hydroxide material, and the magnesium-based composite hydroxide material is mixed with heavy metal-containing wastewater to deeply remove heavy metal ions from the heavy metal-containing wastewater.

[0007] Optionally, in step (1), the multi-ion coexistence system is at least one of salt lake, brine and mineral leachate.

[0008] Optionally, the mineral leachate is a clay-type lithium ore leachate.

[0009] Optionally, in step (1), the pH adjuster is an alkaline adjuster and / or a carbonate adjuster.

[0010] Optionally, the alkalinity regulator is at least one of sodium hydroxide, potassium hydroxide, and ammonia water, and the carbonate regulator is at least one of sodium carbonate, sodium bicarbonate, and ammonium carbonate.

[0011] Optionally, in step (1), the magnesium-based composite hydroxide is at least one of MgAlFe LDH, MgAl LDH and MgFe LDH.

[0012] Optionally, in step (3), the washing is a water wash.

[0013] Optionally, in step (3), the drying process includes: drying in an oven at a temperature of 60-80°C. o C, drying time 5-10h.

[0014] Optionally, in step (3), the solid-liquid ratio of the magnesium-based composite hydroxide material to the heavy metal-containing wastewater is 1-5 g: 1 L.

[0015] Optionally, in step (3), the conditions for deep removal of heavy metal ions from wastewater containing heavy metals include: pH 6-7 and time of 30 min until the heavy metal ions reach adsorption equilibrium.

[0016] The above-described solution of the present invention includes at least the following beneficial effects: The above-described solution of the present invention utilizes reaction coupling separation technology to simultaneously separate multivalent ions and lithium ions in one step, and simultaneously uses the magnesium-based composite hydroxide generated from the multivalent ions for the removal of heavy metals from wastewater containing heavy metals (e.g., mining wastewater), specifically: by introducing Al... 3+ and Fe 3+ At least one of them, Li + Mg 2+ In a multi-ion coexistence system, a pH adjuster is added to regulate the pH of the system to 10-13, and the temperature is maintained at 25-80°C. o Reacting at C for 20 min to 2 h will cause the original Al in the solution to... 3+ and Fe 3+ At least one of them, Fe 3+ Co-precipitation and self-assembly reactions occur, generating magnesium-based composite hydroxides in situ, preferably ternary MgAlFe layered bimetallic hydroxides (MgAlFe-LDH). These hydroxides are separated from the system in solid form, achieving simultaneous separation of multivalent ions and lithium ions in a single operating unit. The resulting lithium-rich separation solution can be used as a raw material solution for subsequent lithium salt preparation, while the resulting solid-phase magnesium-based composite hydroxide is used as an adsorbent for deep "polishing" removal of heavy metals in wastewater containing heavy metals (such as acidic mine wastewater). This achieves the organic integration of high-value utilization of multivalent metal resources in multi-ion coexistence systems and heavy metal treatment of wastewater containing heavy metals. Attached Figure Description

[0017] Figure 1 is a flowchart of a method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system according to an embodiment of the present invention. Detailed Implementation

[0018] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0019] As shown in Figure 1, this invention proposes a method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system, comprising the following steps: Step (1), introducing lithium ions into a system containing Al... 3+ and Fe 3+ At least one of them, Li + Mg 2+ Add a pH adjuster to adjust the pH to 10-13 in a multi-ion coexistence system, and maintain the temperature at 25-80°C. o React at C for 20 min–2 h to allow the Al in the multi-ion coexistence system to react. 3+ and Fe 3+ At least one of them, Mg 2+ Coprecipitation and self-assembly reactions occur, generating magnesium-based complex hydroxide precipitates; in step 1, by adjusting the pH, temperature, and reaction time of the system, the original Al in the multi-ion coexistence system is reduced. 3+ and Fe 3+ At least one of them, Mg 2+ Coprecipitation and self-assembly reactions occur, generating Mg in situ. 2+ As the main component, and also containing Al 3+ and Fe 3+ At least one magnesium-based composite hydroxide is precipitated from the solution in solid form, while lithium ions remain in the liquid phase, thereby achieving one-step simultaneous separation of multivalent metal ions and lithium ions in a multi-ion coexistence system.

[0020] Step (2) Solid-liquid separation is performed to obtain a lithium-rich separation liquid and a magnesium-based composite hydroxide wet solid phase. The lithium-rich separation liquid is used for subsequent lithium purification. The lithium-rich separation liquid contains almost no multivalent ions, providing a cleaner feed liquid for subsequent lithium purification. Step (3) The magnesium-based composite hydroxide wet solid phase is washed and dried to obtain a magnesium-based composite hydroxide material. The magnesium-based composite hydroxide material is mixed with heavy metal-containing wastewater to deeply remove heavy metal ions from the heavy metal-containing wastewater. In step (3), the magnesium-based composite hydroxide material deeply removes heavy metal ions from the mine wastewater through adsorption, ion exchange and surface precipitation, achieving polishing treatment of the mine wastewater. Subsequently, through solid-liquid separation, deeply purified effluent and heavy metal-loaded solid are obtained. The solid can be solidified / disposed of or reused as needed.

[0021] For example, in step (1), the multi-ion coexistence system is at least one of salt lake, brine and mineral leachate.

[0022] For example, the mineral leachate is a clay-type lithium ore leachate.

[0023] For example, a method for preparing a leaching solution of clay-type lithium ore includes: crushing and grinding the clay-type lithium ore, mixing it with an acid medium for leaching, and filtering to obtain a leaching solution of clay-type lithium ore; wherein the leaching solution contains Al in the clay-type lithium ore. 3+ Fe 3+ Li + Mg 2+ It may also contain Na. + K + Monovalent metal ions.

[0024] For example, the acid medium is an organic acid and / or an inorganic acid, such as an inorganic acid, or the organic acid is at least one of acetic acid, oxalic acid, and citric acid, and the inorganic acid is at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0025] For example, the concentration of the acid medium is 1-3 mol / L.

[0026] For example, the mass ratio of acidic medium to clay-type lithium ore is 1-10:1.

[0027] For example, in step (1), the pH adjuster is an alkaline adjuster and / or a carbonate adjuster.

[0028] For example, the alkalinity regulator is at least one of sodium hydroxide, potassium hydroxide, and ammonia water, and the carbonate regulator is at least one of sodium carbonate, sodium bicarbonate, and ammonium carbonate.

[0029] Exemplarily, in step (1), the magnesium-based composite hydroxide is at least one of MgAlFe LDH, MgAl LDH, and MgFeLDH. For compounds containing Fe... 3+ Li + Mg 2+ In a multi-ion coexistence system, MgFe LDH is generated, which is beneficial for systems containing Al. 3+ Li + Mg 2+ In a multi-ion coexistence system, MgAl LDH is generated. For systems containing Al... 3+ Fe 3+ Li + Mg 2+ The multi-ion coexistence system produces MgAlFe LDH.

[0030] For example, in step (2), the solid-liquid separation method is vacuum filtration.

[0031] For example, in step (3), the washing is a water wash.

[0032] For example, in step (3), the drying includes: in an oven at a temperature of 60-80 degrees Celsius. o C, drying time 5-10h.

[0033] For example, in step (3), the solid-liquid ratio of the magnesium-based composite hydroxide material to the heavy metal-containing wastewater is 1-5 g: 1 L.

[0034] For example, in step (3), the conditions for deep removal of heavy metal ions from wastewater containing heavy metals include: pH 6-7 and time of 30 min until the heavy metal ions reach adsorption equilibrium.

[0035] For example, the heavy metal-containing wastewater is acidic mine wastewater or acidic metal ore beneficiation tailings.

[0036] The selective separation method for lithium ions and multivalent ions in a multi-ion coexistence system of the present invention utilizes reaction-coupled separation technology to selectively separate lithium ions and multivalent ions in a multi-ion coexistence system. It can be widely applied to the efficient separation and resource utilization of multivalent metal ions and lithium ions in complex multi-component systems such as salt lakes / brines / mineral leachates. It has the following advantages: (1) In complex leachate systems where monovalent, divalent, and trivalent ions coexist, the "reaction-coupled separation technology" is used to generate magnesium-based composite hydroxides in situ by adjusting the pH of the system, thereby achieving the separation of Mg 2+ Al 3+ Fe 3+ Simultaneous separation of lithium ions in a single reaction unit eliminates the need for multi-stage extraction / multi-stage precipitation.

[0037] (2) Directly utilizing the Mg in the leachate itself 2+ Al 3+ Fe 3+ The co-precipitation self-assembles into magnesium-based composite hydroxides, requiring only the addition of alkali or carbonate to adjust the pH, without the need for external metal sources such as aluminum salts. The process is simple, has low reagent consumption, and lithium is mainly retained in the liquid phase, which is beneficial for obtaining lithium-rich solutions with high lithium retention.

[0038] (3) Mg, which was originally an impurity 2+ Al 3+ Fe 3+ The process involves targeted conversion into magnesium-based composite hydroxides that can be used for the deep removal of heavy metals from acidic mine wastewater, achieving the coupled utilization of "lithium extraction and separation + by-product materials + wastewater polishing," thereby improving the resource utilization level of associated elements while also taking into account environmental benefits.

[0039] The following specific embodiments further illustrate the method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to the present invention.

[0040] Example 1 This example provides a method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system, including: Step 1, crushing and grinding clay-type lithium ore, leaching it in a 2 mol / L hydrochloric acid medium, with a mass ratio of acid medium to clay-type lithium ore of 5:1, filtering to obtain a clear leachate, the main ionic composition of the leachate is shown in Table 1.

[0041] Step 2: Add 5 M NaOH solution to the leachate obtained in Step 1 to adjust the pH of the system to 12.25. o The reaction was carried out at C for 1.5 hours, which reduced the original Mg in the leachate. 2+ Al 3+ Fe 3+ Coprecipitation and self-assembly reactions occur, generating Mg in situ. 2+ As the main component, and also containing Al 3+ and Fe 3+ The magnesium-based composite hydroxide MgAlFe LDH precipitates from the solution in solid form, while lithium remains in the liquid phase, thus achieving a one-step simultaneous separation of multivalent metal ions and lithium ions in the leachate.

[0042] Step 3: The slurry from Step 2 is filtered to perform solid-liquid separation, yielding a lithium-rich separation liquid and a wet solid phase of magnesium-based composite hydroxide (MgAlFe LDH). The lithium-rich separation liquid contains Mg... 2+ Al 3+ Fe 3+ The concentration and lithium retention rate are shown in Table 3, providing a cleaner feed solution for subsequent lithium purification; after washing with water, the wet solid phase is dried in an oven at 70°C. oC. After drying for 8 hours, a magnesium-based composite hydroxide material is obtained.

[0043] Step 4: The magnesium-based composite hydroxide material obtained in Step 3 is added to acidic mining wastewater (the heavy metal ion content in the mining wastewater is shown in Table 2). The initial pH is 6.5, the solid-liquid ratio is 1 g / L, and the adsorption time is 1 h. The material removes heavy metal ions from the wastewater through adsorption, ion exchange, and surface precipitation, achieving a polishing treatment of the mining wastewater. Subsequently, solid-liquid separation is performed to obtain deeply purified effluent and a solid loaded with heavy metals. The solid can be solidified / disposed of or reused as needed. The heavy metal concentration in the mining wastewater after adsorption is shown in Table 4.

[0044] Example 2 This example provides a method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system. The steps are as follows: Step 1, after crushing and grinding clay-type lithium ore, leach it in a 1 mol / L hydrochloric acid medium. The mass ratio of the acid medium to the clay-type lithium ore is 6:1. Filter to obtain a clear leachate.

[0045] Step 2: Add 5 M NaOH solution to the leachate from Step 1 to adjust the pH of the system to 11.5. o The reaction was carried out at C for 2 hours, which reduced the original Mg in the leachate. 2+ Al 3+ Fe 3+ Coprecipitation and self-assembly reactions occur, generating Mg in situ. 2+ As the main component, and also containing Al 3+ and Fe 3+ The magnesium-based composite hydroxide MgAlFe LDH precipitates from the solution in solid form, while lithium remains in the liquid phase, thus achieving a one-step simultaneous separation of multivalent metal ions and lithium ions in the leachate.

[0046] Step 3: The slurry from Step 2 is filtered to perform solid-liquid separation, yielding a lithium-rich separation liquid and a wet solid phase of magnesium-based composite hydroxide (MgAlFe LDH). The lithium-rich separation liquid contains Mg... 2+ Al 3+ Fe 3+ The concentration and lithium retention rate are shown in Table 3, providing a cleaner feed solution for subsequent lithium purification. The wet solid phase, after washing with water, was dried in an oven at 70°C. o C. After drying for 8 hours, a magnesium-based composite hydroxide material is obtained.

[0047] Step 4: The magnesium-based composite hydroxide obtained in Step 3 is added to acidic mining wastewater (the heavy metal ion content in the mining wastewater is shown in Table 2). The initial pH is 6.5, the liquid-to-solid ratio is 1 g / L, and the adsorption time is 2 h. This allows the material to deeply remove heavy metal ions from the wastewater through adsorption, ion exchange, and surface precipitation, achieving a polishing treatment of the mining wastewater. Subsequently, solid-liquid separation is performed to obtain deeply purified effluent and a solid loaded with heavy metals. The solid can be solidified / disposed of or reused as needed. The heavy metal concentrations before and after adsorption are shown in Table 4.

[0048] Example 3 This example provides a method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system similar to Example 1. The difference is that the pH of the system is adjusted to 13 in step 2.

[0049] Example 4 This example provides a method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system similar to Example 1. The difference is that the adsorption time is increased to 5 hours in step 4.

[0050] Comparative Example 1 This comparative example provides a method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system similar to Example 1. The difference is that pure water is used for leaching in step 1, and no solid phase is precipitated after pH adjustment in step 2, and heavy metal removal steps cannot be performed subsequently.

[0051] Comparative Example 2 provides a method for selectively separating lithium ions and multivalent ions in a multi-ion coexistence system similar to Example 1. The difference is that in step 2, the pH is adjusted to 8, and no magnesium-based composite hydroxide precipitate is obtained, and subsequent heavy metal removal steps cannot be performed.

[0052] Table 1. Main ionic composition of the leachate from the examples

[0053] Table 2 Composition of mining wastewater used in the examples and comparative examples

[0054] Table 3 Ion concentrations in lithium-rich separation solutions of the examples and comparative examples

[0055] Table 4. Heavy metal concentrations in mine wastewater after adsorption

[0056] As can be seen from Tables 3 and 4, the selective separation method of lithium ions and multivalent ions in the multi-ion coexistence system of the present invention can separate multivalent ions and lithium ions simultaneously in one step. At the same time, the magnesium-based composite hydroxide generated by multivalent ions can be used for heavy metal removal from wastewater containing heavy metals, achieving efficient lithium extraction while realizing the effective utilization of multivalent metal ions.

[0057] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for selectively separating lithium ions from multivalent ions in a multi-ion coexistence system, characterized in that, Includes the following steps: Step (1), to the Al 3+ and Fe 3+ At least one of them, Li + Mg 2+ Add a pH adjuster to adjust the pH to 10-13 in a multi-ion coexistence system, and maintain the temperature at 25-80°C. o React at C for 20 min–2 h to allow the Al in the multi-ion coexistence system to react. 3+ and Fe 3+ At least one of them, Mg 2+ Co-precipitation and self-assembly reactions occur to generate magnesium-based composite hydroxide precipitate; step (2) solid-liquid separation is performed to obtain lithium-rich separation liquid and magnesium-based composite hydroxide wet solid phase; step (3) the magnesium-based composite hydroxide wet solid phase is washed and dried to obtain magnesium-based composite hydroxide material, and the magnesium-based composite hydroxide material is mixed with heavy metal-containing wastewater to deeply remove heavy metal ions from the heavy metal-containing wastewater.

2. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (1), the multi-ion coexistence system is at least one of salt lake, brine and mineral leachate.

3. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 2, characterized in that, The mineral leaching solution is a clay-type lithium ore leaching solution.

4. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (1), the pH adjuster is an alkaline adjuster and / or a carbonate adjuster.

5. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 4, characterized in that, The alkalinity regulator is at least one of sodium hydroxide, potassium hydroxide, and ammonia water, and the carbonate regulator is at least one of sodium carbonate, sodium bicarbonate, and ammonium carbonate.

6. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (1), the magnesium-based composite hydroxide is at least one of MgAlFe LDH, MgAl LDH and MgFe LDH.

7. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (3), the washing is water washing.

8. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (3), the drying process includes: drying in an oven at a temperature of 60-80°C. o C, drying time 5-10h.

9. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (3), the solid-liquid ratio of the magnesium-based composite hydroxide material to the heavy metal-containing wastewater is 1-5 g: 1 L.

10. The method for selective separation of lithium ions and multivalent ions in a multi-ion coexistence system according to claim 1, characterized in that, In step (3), the conditions for deep removal of heavy metal ions from wastewater containing heavy metals include: pH 6-7 and time of 30 min until the heavy metal ions reach adsorption equilibrium.

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