Short-distance and efficient electrochemical method for extracting lithium from original halogen and application of short-distance and efficient electrochemical method

Abstract

The invention discloses a short-range and efficient electrochemical method for extracting lithium from original brine and application of the short-range and efficient method. The method comprises the following steps: pre-separating and extracting lithium-containing brine by using an adsorbent to obtain a lithium-containing solution, and performing multi-stage concentration; extracting, separating and enriching the concentrated solution by using an electrochemical method to obtain a lithium-rich solution and a lithium-poor tail solution; and finally, concentrating the lithium-poor tail liquid, and performing secondary adsorption separation by using an adsorbent to complete lithium extraction. Compared with a mainstream adsorption-membrane separation coupling process, a complex multi-stage membrane process is omitted, a unique monovalent ion separation effect is achieved, and the lithium-rich liquid is high in purity, low in cost and short in process. Compared with an extraction method, the whole process is free of additional chemical reagents, free of organic pollution and environmentally friendly. Compared with an electrochemical method / electric de-intercalation method for directly extracting lithium, lithium / sodium separation is firstly realized through pre-adsorption, the sodium concentration is reduced, the separation effect is improved, the sodium intercalation influence is reduced, and the electrode stability is improved. And the high extraction rate of an adsorption method is combined, lithium-poor tail liquid is adsorbed again, and the lithium recovery rate is increased.

Description

Technical Field

[0001] This invention relates to the fields of adsorption, electrochemistry, and membrane separation technology, specifically to a short-range, high-efficiency electrochemical method for lithium extraction from raw halogen and its application. Background Technology

[0002] With the rapid development of the global new energy industry, lithium resources, as a crucial raw material supporting key areas such as electric vehicles and energy storage systems, are experiencing a continuous increase in market demand. Salt lakes, as the main storage sites for lithium resources, contain over 60% of the world's lithium reserves; therefore, lithium extraction technology from salt lakes has broad development prospects and enormous market potential.

[0003] However, the composition of salt lake brine is extremely complex. Besides being rich in lithium ions, it also contains large amounts of various impurity ions such as sodium, magnesium, calcium, potassium, borate, and sulfate. This complex composition makes it difficult for single extraction and separation methods to efficiently separate and enrich lithium. Currently, typical lithium extraction technologies from salt lakes include adsorption methods (such as aluminum-based adsorption), extraction methods, membrane methods, selective electrodialysis, and electrochemical / electrodeintercalation / deintercalation methods. Although these methods each have their own characteristics, they all have certain limitations in practical applications.

[0004] For example, Chinese patent CN 101928828 B discloses a method for extracting lithium from salt lake brine using an aluminum-based adsorbent. While this method can effectively extract lithium, the aluminum-based adsorbent also has a certain adsorption effect on ions such as borate, sodium, and potassium, resulting in a high content of impurity ions in the product solution after analysis, making it difficult to directly prepare battery-grade lithium carbonate. Another example is Chinese patent application CN 113293290 A, which proposes an electrochemical lithium extraction method. However, due to the high sodium and lithium content in the original salt lake brine and the electrode material's ability to intercalate / deintercalate sodium, the sodium ion concentration in the product solution is high, and long-term operation can lead to structural damage to the electrode material and accelerated electrode degradation. Yet another example is Chinese patent CN 115821040 B, which discloses an extraction lithium extraction technology. Although the extraction process can achieve good separation through multi-stage washing, environmental issues such as solvent loss of the extractant limit its large-scale application.

[0005] In summary, existing lithium extraction technologies from salt lakes, even with a single method, struggle to cope with complex brine compositions, the susceptibility of electrode materials to degradation due to impurity ions, and the environmental pollution risks associated with dissolution in some technologies. In other words, they cannot simultaneously achieve optimal separation efficiency, high-performance key materials, and a green and environmentally friendly process. Therefore, developing a highly efficient, environmentally friendly, and sustainable lithium extraction technology from salt lakes is an urgent problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a short-range, high-efficiency electrochemical method for lithium extraction from halogen and its application. This process achieves lithium separation and enrichment through the coupling of adsorption, membrane separation, and electrochemical technologies, effectively solving the technical problem that existing technologies cannot simultaneously achieve optimal separation performance, key material properties, and environmental friendliness.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A short-range, high-efficiency electrochemical method for lithium extraction from primary halides includes the following steps: S1: Lithium-containing brine is pre-separated and extracted using an adsorbent to obtain a lithium-containing solution; S2: The lithium-containing solution is concentrated in multiple stages to obtain a concentrated lithium-containing solution; S3: Electrochemical extraction, separation and enrichment of the concentrated lithium-containing solution are performed using an electrochemical method to obtain a lithium-rich solution and a lithium-poor tail liquid; S4: After concentrating the lithium-poor tail liquid, a concentrated lithium-poor tail liquid is obtained. An adsorbent is then used to adsorb and separate the concentrated lithium-poor tail liquid to complete the lithium extraction from the original brine.

[0008] Preferably, the adsorbent is at least one of aluminum-based adsorbents, titanium-based adsorbents, manganese-based adsorbents, and their corresponding derivatives.

[0009] Preferably, the lithium concentration in the lithium-containing solution is less than 0.025 g / L.

[0010] Preferably, in step S2, the concentration method includes one of the following: high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression.

[0011] Preferably, in step S2, the TDS in the concentrated lithium-containing solution is greater than 80 g / L.

[0012] Preferably, in step S3, the electrochemical extraction process employs a FePO4 / LiFePO4 symmetrical electrode system.

[0013] Preferably, the short-range, high-efficiency electrochemical lithium extraction method according to claim 1 is characterized in that, in step S3, the lithium concentration of the lithium-rich solution is greater than 6 g / L, and the lithium concentration of the lithium-poor tail liquid is greater than 0.15 g / L.

[0014] Preferably, during the electrochemical lithium extraction process, when the lithium concentration in the extract is greater than 0.4 g / L, the current density is controlled to be greater than 35 A / m2, and when the lithium concentration in the extract is between 0.15 g / L and 0.4 g / L, the current density is controlled to be less than 20 A / m2.

[0015] Preferably, in step S4, the concentration method includes one of high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression.

[0016] The above-mentioned short-range, high-efficiency electrochemical lithium extraction method is applied to lithium extraction from salt lakes.

[0017] Compared with the prior art, the method of the present invention has at least the following beneficial effects: This invention discloses a short-range, high-efficiency electrochemical method for lithium extraction from primary halides, which has many advantages: First, the process is simple and efficient. This method first uses an adsorbent to pre-separate and extract lithium-containing brine, obtaining a lithium-containing solution, which is then concentrated in multiple stages. Next, an electrochemical method is used to extract, separate, and enrich the concentrated solution, yielding a lithium-rich solution and a lithium-poor tailings. Finally, the lithium-poor tailings are concentrated and then subjected to adsorption for lithium extraction again. This method is simple and efficient, eliminating the need for complex multi-stage, multi-section ultrafiltration, nanofiltration, reverse osmosis, and electrodialysis membrane processes, significantly shortening the process and reducing operating costs.

[0018] Secondly, the separation effect is significantly improved. This scheme uses an adsorbent for pre-separation and extraction of lithium-containing brine, and the adsorbent has high selectivity for lithium ions. Through the pre-adsorption process, lithium ions are preferentially captured, while monovalent ions such as sodium remain in the brine, achieving preliminary separation of lithium and sodium. This step significantly reduces the concentration of sodium ions in the subsequent electrochemical lithium extraction process, creating conditions for efficient separation. In the electrochemical lithium extraction stage, this scheme utilizes the ion sieving characteristics of the electrode material's crystal structure to enhance lithium ion adsorption kinetics by creating vacancy defects through controllable delithiation. Simultaneously, selective lithium transport channels are constructed by controlling the valence state of transition metals, allowing lithium ions to preferentially embed into the electrode material under the action of an electric field, while monovalent ions such as sodium are effectively intercepted due to differences in size or charge characteristics. This selective transport mechanism significantly improves the lithium-sodium separation effect and reduces the sodium concentration in the lithium-rich solution. Moreover, this scheme increases the concentration of the lithium-containing solution through multi-stage concentration, further enhancing the separation efficiency of electrochemical lithium extraction. The lithium-poor tail liquid after electrochemical extraction is concentrated and then adsorbed again for lithium extraction, forming a closed-loop process of "adsorption-electrochemistry-re-adsorption". This design not only improves lithium recovery rate but also continuously removes residual monovalent ions through cyclic adsorption, ensuring the high purity of the final lithium-rich solution. Therefore, this solution possesses a unique monovalent ion separation effect, efficiently separating lithium ions from other impurity ions, resulting in an extremely high-purity lithium-rich solution. It effectively solves the problem of traditional methods' difficulty in efficiently separating impurities such as borate and monovalent cations.

[0019] In addition, this method extends the electrode's lifespan. Through pre-adsorption lithium extraction, lithium and sodium are separated first, reducing the sodium concentration in the lithium-containing solution and minimizing the impact of sodium intercalation on the electrode. This significantly improves the electrode's cycle stability during electrochemical lithium extraction and extends its lifespan.

[0020] Moreover, this solution requires no additional chemical reagents throughout the process, eliminating the risk of environmental pollution such as organic matter contamination and truly achieving green production. Simultaneously, leveraging the high extraction rate of the adsorption method, the lithium-poor tail liquid after electrochemical extraction is further concentrated and adsorbed for lithium extraction, effectively improving the overall lithium recovery rate. This fully utilizes the advantages of different processes, achieving a perfect balance between separation efficiency, key material performance, and environmentally friendly processes.

[0021] In summary, this invention addresses the existing challenges in lithium extraction from raw halides by proposing a short-process, highly efficient, and environmentally friendly coupled lithium extraction process. Compared to mainstream adsorption-membrane separation coupled processes, it eliminates the need for complex multi-stage membrane processes, possesses a unique monovalent ion separation effect, achieves higher purity of lithium-rich solutions, lower operating costs, and a shorter process. Compared to extraction methods, it introduces no additional chemical reagents and causes no organic pollution, making it environmentally friendly. Compared to direct lithium extraction via electrochemical / electrodeintercalation methods, this pre-adsorption lithium extraction first achieves lithium / sodium separation, reduces the sodium concentration in the lithium-containing solution, improves lithium-sodium separation efficiency, reduces the impact of sodium intercalation on electrode cycle life, and enhances electrode stability. Furthermore, this invention leverages the high extraction rate of adsorption methods by concentrating the lithium-poor tail liquid after electrochemical extraction and then re-adsorbing it for lithium extraction, improving lithium recovery rate. The entire process is coupled, fully utilizing the advantages of each process, solving the separation problems of adsorption methods, and overcoming the shortcomings of electrochemical methods in halides with high sodium / lithium ratios.

[0022] Furthermore, the adsorbent is at least one of aluminum-based adsorbents, titanium-based adsorbents, manganese-based adsorbents, and their corresponding derivatives. These adsorbents possess specific physicochemical properties and exhibit good selectivity and adsorption capacity for lithium ions. Different types of adsorbents and their derivatives can adapt to lithium-containing brines with different compositions and properties, improving the lithium capture efficiency in the pre-separation and extraction stages, providing high-quality lithium-containing solutions for subsequent processes, and thus enhancing the overall effectiveness and stability of the lithium extraction process.

[0023] Furthermore, the lithium concentration in the lithium-containing solution is less than 0.025 g / L. Specifying this condition helps standardize the treatment of lithium-containing brine during the pre-separation and extraction stages. Defining this concentration range optimizes the adsorbent's effectiveness, ensures the adsorption process occurs at a suitable lithium concentration, improves the adsorbent's selective adsorption capacity for lithium, and avoids the impact of excessively high or low lithium concentrations on adsorption efficiency and subsequent processes, thus guaranteeing the smooth progress of the entire lithium extraction process.

[0024] Furthermore, in step S2, the concentration method includes one of the following: high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression. Different concentration methods have their own characteristics and applicable scenarios, providing multiple options. Based on the actual properties of the lithium-containing solution, the processing scale, cost budget, and other factors, the most suitable concentration method can be flexibly selected to efficiently concentrate the lithium-containing solution to the required concentration, improve concentration efficiency, and reduce energy consumption and cost.

[0025] Furthermore, in step S2, the TDS in the concentrated lithium-containing solution is greater than 80 g / L. This requirement provides a suitable solution environment for subsequent electrochemical extraction, separation, and enrichment stages. A higher TDS concentration allows the ion concentration in the solution to reach a certain level, which is beneficial for ion migration and reaction during the electrochemical process, improving the efficiency and effectiveness of electrochemical lithium extraction, and enabling lithium ions to be extracted and enriched more effectively.

[0026] Furthermore, in step S3, the electrochemical extraction process employs a FePO4 / LiFePO4 symmetrical electrode system, which possesses unique electrochemical properties. FePO4 and LiFePO4 exhibit excellent lithium-ion insertion and extraction characteristics, providing a stable electrode reaction interface and improving the lithium-ion transport efficiency between electrodes. This enhances the extraction, separation, and enrichment of lithium during the electrochemical lithium extraction process, and may also improve the electrode's cycle stability and lifespan.

[0027] Furthermore, in step S3, the lithium concentration in the lithium-rich solution is greater than 6 g / L, and the lithium concentration in the lithium-lean tailings is greater than 0.15 g / L. These two concentration indicators are crucial for evaluating the effectiveness of the electrochemical extraction, separation, and enrichment stages. A higher lithium concentration in the lithium-rich solution means that lithium is effectively enriched, improving the utilization rate of lithium resources; specifying a lower limit for the lithium concentration in the lithium-lean tailings avoids over-extraction leading to resource waste, while ensuring the economic viability and feasibility of subsequent processing of the lithium-lean tailings, thus contributing to improving the overall lithium recovery rate of the process.

[0028] Furthermore, during the electrochemical lithium extraction process, when the lithium concentration in the extraction solution is greater than 0.4 g / L, the current density is controlled to be greater than 35 A / m. 2 When the lithium concentration in the extract is between 0.15 g / L and 0.4 g / L, the current density should be controlled to be between 20 A / m. 2 Here, the current density is controlled according to different lithium concentration ranges in the extract. When the lithium concentration in the extract is greater than 0.4 g / L, the current density is controlled to be >35 A / m. 2This can accelerate the migration rate of lithium ions during electrochemical extraction and improve extraction efficiency; when the lithium concentration in the extract is between 0.15 g / L and 0.4 g / L, the current density should be controlled to be between 20 A / m. 2 This avoids problems such as electrode polarization caused by excessive current density, ensuring the stability and selectivity of the electrochemical extraction process, thereby improving the quality and efficiency of the entire electrochemical lithium extraction process.

[0029] Furthermore, in step S4, the concentration method includes one of the following: high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression. Here, the appropriate concentration method is flexibly selected according to the actual situation to efficiently and economically concentrate the lithium-poor tail liquid to a concentration suitable for subsequent adsorption and separation, thereby improving the continuity and efficiency of the entire process and further enhancing lithium recovery. Attached Figure Description

[0030] To more clearly illustrate the present invention, the accompanying drawings used in the embodiments or technical description will be briefly described below. Obviously, the drawings described below are only embodiments of the present invention. Those skilled in the art can obtain other drawings from the following drawings without creative effort. Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is the lithium extraction capacity cycling curve of Example 2; Figure 3 This is the lithium extraction capacity cycling curve of Comparative Example 2. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] like Figure 1 As shown, this invention provides a short-range, high-efficiency electrochemical method for lithium extraction from primary halides, comprising the following steps: S1: Lithium-containing brine is pre-separated and extracted using an adsorbent to obtain a lithium-containing solution; in this step, the memory effect of lithium on the pore structure of the adsorbent is utilized, and the specific binding of surface hydroxyl groups with lithium is used to achieve selective extraction of lithium chloride. The adsorbent is at least one of aluminum-based adsorbents, titanium-based adsorbents, manganese-based adsorbents and their derivatives; aluminum-based adsorbents are preferred.

[0037] Specifically, the aluminum-based adsorbent is LiCl·mAl(OH)3·nH2O; derivatives of the aluminum-based adsorbent can be magnetic aluminum-based adsorbents.

[0038] Titanium-based adsorbents can be HP170 series high-selectivity, high-capacity lithium-ion sieve adsorbents; derivatives of titanium-based adsorbents can be nano-hybrid titanium-based lithium adsorbents, titanium-based lithium-ion sieves, and titanium-based lithium adsorbent microspheres, etc.

[0039] Manganese-based adsorbents can be spinel-type manganese-based lithium-ion sieves, and derivatives of manganese-based adsorbents can be manganese-based adsorbents doped with metal cations or co-doped with anions and cations.

[0040] The lithium-containing brine is at least one of the following: raw brine from a salt lake, old brine from a salt lake, oilfield water, and lithium-containing chloride water. The original brine of the salt lake is magnesium sulfate subtype brine, chloride type brine, or carbonate subtype brine; The lithium concentration in the lithium-containing solution is below 0.025 g / L; S2: The lithium-containing solution is concentrated in multiple stages to obtain a concentrated lithium-containing solution (i.e., concentrated lithium solution). The concentration methods include, but are not limited to, one of the following: high-pressure reverse osmosis, single-effect or multi-effect evaporation, and mechanical vapor recompression (MVR). The concentrated lithium-containing solution has a total dissolved solids (TDS) concentration (TDS) > 80 g / L. This step involves multi-stage concentration of the lithium-containing solution to improve its conductivity, facilitating subsequent electrochemical extraction and separation. S3: Electrochemical extraction, separation and enrichment of the concentrated lithium-containing solution are performed using an electrochemical method to obtain a lithium-rich solution and a lithium-poor tail liquid; Specifically, this step uses a LiFePO4 / FePO4 symmetrical electrode system for electrochemical lithium extraction. The lithium-containing solution to be extracted is placed in the cathode chamber, where a reduction reaction occurs to extract lithium from the lithium-containing solution, and FePO4 is converted into LiFePO4. The anode chamber is used to recover the lithium-rich solution, where an oxidation reaction occurs at the LiFePO4 anode to remove lithium ions from the material, thereby achieving lithium enrichment. That is, the electrochemical extraction process in the above steps uses a FePO4 / LiFePO4 symmetrical electrode system; The lithium concentration of the lithium-rich solution is controlled to be above 6 g / L; The lithium concentration in the lithium-poor tailings solution is >0.15 g / L; In addition, during the aforementioned electrochemical lithium extraction process, when the lithium concentration in the extraction solution is >0.4 g / L, the current density should be controlled to be >35 A / m. 2 When the lithium concentration in the extract is between 0.15 g / L and 0.4 g / L, the current density should be controlled to be between 20 A / m. 2 ; S4: Concentrate the lithium-poor tailings to obtain concentrated lithium-poor tailings; and use an adsorbent to adsorb and separate the concentrated lithium-poor tailings.

[0041] In this step, the low-concentration lithium-containing tail liquid extracted in step S3 is concentrated to increase the chloride ion content and lithium ion concentration of the solution, which facilitates further lithium extraction using the adsorption method.

[0042] The concentration methods used in this step include, but are not limited to, one of the following: high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression.

[0043] This invention addresses the problems of complex processes, poor separation effects, low lithium extraction rates, and environmental pollution encountered in current lithium extraction processes from raw brine. It proposes a short-process, high-efficiency electrochemical method for lithium extraction from raw brine. Compared to the mature and mainstream adsorption-membrane separation coupling process, this invention eliminates the complex combination of multi-stage, multi-section ultrafiltration, nanofiltration, reverse osmosis, and electrodialysis membrane processes. Furthermore, it possesses the monovalent ion separation effect that membrane processes lack, resulting in a higher purity lithium-rich solution, lower operating costs, and a shorter process flow. Compared to extraction methods, this invention eliminates organic pollution and introduces no additional chemical reagents throughout the process, making it more environmentally friendly. Compared to electrochemical or electro-deintercalation / extraction methods for directly extracting lithium from brine, this invention employs pre-adsorption lithium extraction, first performing lithium and sodium separation to reduce the sodium concentration in the lithium-containing solution. This improves the separation effect of lithium and sodium during electrochemical lithium extraction, reduces the sodium concentration in the lithium-rich solution, and also reduces the impact of sodium intercalation on electrode cycle life, thus improving electrode cycle stability. Furthermore, electrochemical methods alone struggle to extract lithium to extremely low concentrations, resulting in low extraction rates in a single pass. This invention combines the high extraction rate of adsorption methods with the further concentration of the lithium-poor tail liquid after electrochemical extraction, followed by adsorption extraction again, effectively improving the overall lithium recovery rate. This invention integrates the entire process, fully leveraging the high extraction rate of adsorption and the high lithium enrichment concentration and better separation effect of electrochemical methods. It also fully utilizes the characteristics of different processes, solving the problem of inefficient separation of borate and monovalent cations in adsorption methods, and overcoming the difficulties of poor lithium-sodium separation and poor recycling in high sodium / lithium ratio brines using electrochemical methods.

[0044] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0045] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0046] Example 1 S1: The raw material is 20L of brine from South America, which belongs to the magnesium sulfate subtype. The specific components are shown in Table 1-1. An aluminum-based adsorbent is used to adsorb and desorb in the adsorption system to obtain lithium-poor tail brine and lithium-containing desorption liquid (i.e. lithium-containing solution). The composition is shown in Table 1-1. S2: The above lithium-containing solution is concentrated by high-pressure reverse osmosis. The solution pH is first adjusted to 4.0 and the operating pressure is controlled at 6.5 MPa to obtain concentrated lithium-containing solution (concentrated lithium solution) and fresh water. The composition of the lithium-containing solution is shown in Table 1-1. S3: Using FePO4 / LiFePO4 as the electrode, the concentrated lithium-containing solution is added to the cathode chamber as the extraction solution. Considering conductivity, a lithium chloride solution containing 2 g / L of lithium is used as the initial circulating solution in the anode chamber. The current density is initially controlled at 35 A / m. 2 When the lithium concentration in the extract is below 0.4 g / L, the current density is adjusted to 15 A / m. 2 The working cutoff voltage was 0.5V and the lithium concentration of the extract was controlled to be >0.15g / L. The composition of the lithium-rich solution and the lithium-poor tail liquid obtained is shown in Table 1-1. S4: The above-mentioned lithium-poor tail liquid is further concentrated using a rotary evaporator to obtain concentrated lithium-poor tail liquid and distilled water. Then, the concentrated lithium-poor tail liquid is subjected to adsorption and desorption using the same process as step S1 (named S1-2) to obtain lithium-containing desorption liquid and tail liquid. The composition is shown in Table 1-1.

[0047] Table 1-1 Solution composition data for each step in Example 1

[0048] Note: The amount of water used in the adsorption and lithium extraction processes varies, mainly because a small amount of washing water was introduced during the experiment.

[0049] As can be seen from the data in the table above, according to the process described in this invention, the lithium concentration in the obtained lithium-rich solution reaches above 6 g / L, the Na concentration is <0.5 g / L, and the concentrations of impurity ions such as K, Ca, and Mg are all <0.1 g / L. The overall lithium recovery rate is calculated as 100% - lithium discharged from the system / lithium input to the system. Lithium discharged from the system includes lithium discharged from the lithium-poor brine in step S1, lithium discharged from the freshwater in step S2, and lithium discharged from the tail liquid in steps S1-2. The overall lithium recovery rate of the system is calculated to be 93.15%.

[0050] Comparative Example 1 S1, using the same brine as in Example 1; S2, Lithium extraction from the brine in step S1 is performed directly using the electrochemical method described in Example 1: FePO4 / LiFePO4 is used as the electrode, and the brine is added to the cathode chamber as the extraction solution. Considering conductivity, a lithium chloride solution containing 2 g / L of lithium is used as the initial solution in the anode chamber, and the current density is controlled at 35 A / m. 2 With a cutoff voltage of 0.5V, a lithium-rich solution and a lithium-poor brine (lithium-poor tail liquid) were obtained, the compositions of which are shown in Table 1-2. Table 1-2 Data on direct lithium extraction via electrochemical methods

[0051] As can be seen from the data in Table 1-2, the lithium-rich solution obtained by directly extracting lithium from the brine of the salt lake using electrochemistry has a high content of impurities such as Na, K, and Mg, and needs to be further refined before it can be used as a raw material solution for the synthesis of battery-grade lithium carbonate. According to the same calculation method as in Example 1, the overall yield of lithium directly extracted by electrochemistry is 60.78%, which is much lower than the overall lithium recovery rate in Example 1 of this invention.

[0052] Example 2 Using the same procedures as steps S1 and S2 in Example 1, a concentrated lithium-containing solution was prepared, the composition of which is shown in Tables 1-3. Table 1-3 Composition of Lithium-Containing Solutions

[0053] The lithium extraction cycle performance of the FePO4 / LiFePO4 electrode was tested in the above lithium-containing solution under the following conditions: current density 30 A / m. 2 With a cutoff voltage of 0.5V and using a 2mol / L lithium chloride solution as the initial solution at the anode, a 20-cycle test was conducted. The cycle performance of this electrode was as follows: Figure 2 As shown, its lithium extraction capacity retention rate after 20 cycles is 91%.

[0054] Comparative Example 2 Electrochemical lithium extraction was performed directly using the brine used in Comparative Example 1. The lithium extraction cycle performance was tested under the same conditions as in Example 2, and the data are as follows: Figure 3 As shown, its 20-cycle capacity retention rate is 86%, which is significantly lower than the capacity retention rate in the embodiments of the present invention.

[0055] Example 3 Using a certain old brine from Dongtai as raw material, the composition of which is shown in Table 1-4, a lithium-rich solution was obtained by adopting the same steps as in Example 1. The composition of the solution in each process is shown in Table 1-4 below.

[0056] As can be seen from the data in Tables 1-4, the lithium-rich solution obtained by the process in this embodiment has a lithium concentration >6 g / L, a magnesium concentration <0.52 g / L, and a boron concentration <0.23 g / L, which achieves further separation and enrichment of lithium from the qualified adsorption and desorption solution. Using the same calculation method as in Example 1, the overall lithium recovery rate of the system is calculated to be 98.5%.

[0057] Table 1-4 Component Data of Each Process in Example 3

[0058] Comparative Example 3 Lithium was extracted using the same brine as in Example 3, employing a selective electrodialysis process.

[0059] S1: Dilute a certain old brine from Dongtai. The composition of the diluted brine is shown in Table 1-5. S2: Selective lithium extraction is performed using Japanese Astom selective electrodialysis membranes, with 50 membrane pairs per stack and the stack voltage controlled between 0.375-0.5V. S3: Using three-stage continuous operation, the composition of the lithium-rich solution and lithium-poor brine is shown in Table 1-5.

[0060] Table 1-5 Comparative Example 3: Component Data for Each Process

[0061] The data in the table show that selective electrodialysis is ineffective in separating monovalent ions such as Na and K, and its separation effect on magnesium ions is also limited, with a Mg / Li mass ratio > 1.2 in lithium-rich solutions. Furthermore, the lithium yield of this process is low, with an overall recovery rate of 85.1%.

[0062] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A short-range, high-efficiency electrochemical method for lithium extraction from primary halides, characterized in that, Includes the following steps: S1: Lithium-containing brine is pre-separated and extracted using an adsorbent to obtain a lithium-containing solution; S2: The lithium-containing solution is concentrated in multiple stages to obtain a concentrated lithium-containing solution; S3: Electrochemical extraction, separation and enrichment of the concentrated lithium-containing solution are performed using an electrochemical method to obtain a lithium-rich solution and a lithium-poor tail liquid; S4: After concentrating the lithium-poor tail liquid, a concentrated lithium-poor tail liquid is obtained. An adsorbent is then used to adsorb and separate the concentrated lithium-poor tail liquid to complete the lithium extraction from the original brine.

2. The short-range, high-efficiency electrochemical lithium extraction method according to claim 1, characterized in that, The adsorbent is at least one of aluminum-based adsorbents, titanium-based adsorbents, manganese-based adsorbents, and their corresponding derivatives.

3. The short-range, high-efficiency electrochemical lithium extraction method according to claim 1, characterized in that, The lithium concentration in the lithium-containing solution is less than 0.025 g / L.

4. The short-range, high-efficiency electrochemical lithium extraction method from primary halides according to claim 1, characterized in that, In step S2, the concentration method includes one of the following: high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression.

5. The short-range, high-efficiency electrochemical lithium extraction method from primary halides according to claim 1, characterized in that, In step S2, the TDS in the concentrated lithium-containing solution is greater than 80 g / L.

6. The short-range, high-efficiency electrochemical lithium extraction method from primary halides according to claim 1, characterized in that, In step S3, the electrochemical extraction process employs a FePO4 / LiFePO4 symmetrical electrode system.

7. The short-range, high-efficiency electrochemical lithium extraction method according to claim 1, characterized in that, According to claim 1, a short-range, high-efficiency electrochemical method for lithium extraction from raw halogen is characterized in that, in step S3, the lithium concentration of the lithium-rich solution is greater than 6 g / L, and the lithium concentration of the lithium-poor tail liquid is greater than 0.15 g / L.

8. The short-range, high-efficiency electrochemical lithium extraction method from primary halides according to claim 1, characterized in that, In the electrochemical lithium extraction process, when the lithium concentration in the extract is greater than 0.4 g / L, the current density is controlled to be greater than 35 A / m2, and when the lithium concentration in the extract is between 0.15 g / L and 0.4 g / L, the current density is controlled to be less than 20 A / m2.

9. The short-range, high-efficiency electrochemical lithium extraction method from primary halides according to claim 1, characterized in that, In step S4, the concentration method includes one of the following: high-pressure reverse osmosis, single-effect evaporation, multi-effect evaporation, and mechanical vapor recompression.

10. The application of the short-range, high-efficiency electrochemical lithium extraction method according to any one of claims 1 to 9 in lithium extraction from salt lakes.

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