Method for adsorbing lithium from original brine of magnesium sulfate sub-type salt lake and application thereof

Abstract

This invention relates to the field of lithium resource recovery and utilization in salt lakes, and discloses a method for lithium extraction by adsorption from magnesium sulfate subtype salt lake raw brine and its application. The method includes the following steps: (1) pretreating the magnesium sulfate subtype salt lake raw brine to obtain brine with a suspended solids concentration ≤4 mg / L; (2) using an ion exchange resin to remove boron from the brine obtained after step (1) to obtain B... 3+ (3) Adjust the pH of the boron removal qualified solution to 6.4-6.8, and then use an aluminum-based adsorbent for lithium adsorption. The method for lithium adsorption from magnesium sulfate subtype salt lake raw brine according to the present invention has the characteristics of high lithium ion recovery rate and high lithium extraction efficiency. It can still maintain good adsorption lithium extraction efficiency under long-term operation, and is particularly suitable for industrial applications in the preparation of battery-grade lithium hydroxide and battery-grade lithium salts from magnesium sulfate subtype salt lake raw brine.

Description

Technical Field

[0001] This invention relates to the field of lithium resource recovery and utilization in salt lakes, specifically to a method for lithium extraction by adsorption from magnesium sulfate subtype salt lake raw brine and its application. Background Technology

[0002] With the booming development of the new energy industry, the demand for related lithium products is far exceeding supply. Therefore, how to fully utilize salt lake lithium resources has become a major concern for the entire industry. Adsorption extraction utilizes the selective adsorption of lithium ions by adsorbents to achieve effective separation of lithium ions from impurity ions. It boasts advantages such as simple process flow, low environmental pollution, and environmental friendliness. However, despite the numerous advantages of adsorption lithium extraction, the unique composition of the original brine in magnesium sulfate subtype salt lakes leads to low lithium ion recovery rates and low extraction efficiency under long-term operation, severely impacting the industrial application of salt lake lithium resources. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of low lithium-ion recovery rate and low lithium extraction efficiency in the long-term operation of existing technologies for lithium extraction from magnesium sulfate subtype brine in salt lakes. This invention provides a method for lithium extraction from magnesium sulfate subtype brine through adsorption and its application. This method has the advantages of high lithium-ion recovery rate and high lithium extraction efficiency under long-term operation, and is particularly suitable for industrial applications in the preparation of battery-grade lithium hydroxide and battery-grade lithium salts from magnesium sulfate subtype brine in salt lakes.

[0004] Through in-depth research, the inventors of this invention discovered that the original brine of magnesium sulfate subtype salt lakes contains a large amount of boron, which exists in the form of boric acid or borate. This boron has high solubility in aqueous solution, making further reduction difficult. Furthermore, during adsorption, boron intercalates into the adsorbent along with lithium. This is a significant reason for the low lithium-ion recovery rate and low lithium extraction efficiency in the long-term operation of lithium extraction from magnesium sulfate subtype salt lake brine. In existing salt lake lithium extraction methods, boron is removed and collected after a series of pretreatments such as nanofiltration and adsorption. While this method effectively extracts boron, long-term adsorption from the original brine increases lithium loss during the initial pretreatment, reduces the adsorbent's adsorption efficiency, and increases energy consumption and cost in subsequent processes. Therefore, this invention removes boron before adsorption and lithium extraction. This not only effectively avoids the aforementioned problems but also, due to the characteristics of the original brine composition of magnesium sulfate subtype salt lakes, eliminates the need for additional alkali adjustment processes, effectively reducing process energy consumption and cost, thus completing this invention.

[0005] Therefore, the present invention provides a method for lithium extraction by adsorption from magnesium sulfate subtype salt lake raw brine, the method comprising the following steps:

[0006] (1) Pre-treat the original brine of magnesium sulfate subtype salt lake to obtain brine with suspended solids concentration ≤4mg / L;

[0007] (2) Boron removal treatment is performed on the brine obtained after step (1) using a boron removal ion exchange resin to obtain B. 3+ Boron removal solution with a concentration ≤20mg / L;

[0008] (3) Adjust the pH value of the qualified boron removal solution to 6.4-6.8, and then use an aluminum-based lithium adsorbent for adsorption and lithium extraction.

[0009] Preferably, in step (1), the magnesium sulfate subtype brine of the salt lake contains the following components: Li + ≥0.2g / L, Mg 2+ ≤85g / L, Na + ≤85g / L, K + ≤15g / L, B 3+ ≤0.6g / L, and pH≥7.2.

[0010] Preferably, in step (1), the pretreatment process includes filtering the magnesium sulfate subtype salt lake raw brine using a filter.

[0011] Preferably, the filter is at least one of a disc ceramic membrane filter, a multi-media multi-filter, and a security filter.

[0012] Preferably, in step (2), the boron removal process is carried out in a first continuous ion exchange device, which includes an adsorption zone, a water washing zone, an acid desorption zone, a water washing acid zone, and a qualified liquid top water zone arranged sequentially. Several resin adsorption columns formed by the boron removal ion exchange resin operate continuously in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone, and the qualified liquid top water zone. In the adsorption zone, the brine obtained after the treatment in step (1) is fed into the resin adsorption column for adsorption to obtain the qualified boron removal liquid.

[0013] Preferably, in the washing zone, pure water is used to wash the resin adsorption column via an upward feeding method.

[0014] Preferably, in the acid desorption zone, hydrochloric acid is used to desorb the resin adsorption column via a top-feed method.

[0015] Preferably, in the acid washing zone, pure water is used to wash the resin adsorption column via a top-feed method.

[0016] Preferably, in the qualified liquid top water zone, the boron removal qualified liquid is fed from the bottom to disperse the adsorbed particles in the resin adsorption column.

[0017] Preferably, the concentration of hydrochloric acid used in the acid desorption zone is 3-10 wt%, more preferably 5-7 wt%.

[0018] Preferably, the first continuous ion exchange device is equipped with 15 resin adsorption columns. During continuous operation, the adsorption zone has 8 resin adsorption columns connected in a four-parallel-two-series configuration, the water washing zone has 3 resin adsorption columns connected in a three-column-in-series configuration, the acid desorption zone has 2 resin adsorption columns connected in a two-column-in-series configuration, and the water washing acid zone and the qualified liquid top water zone each have 1 resin adsorption column.

[0019] Preferably, the lithium extraction process is carried out in a second continuous ion exchange device, which includes an adsorption zone, a washing zone, a desorption zone, and a qualified liquid top water zone arranged sequentially. Several adsorption columns formed by the aluminum-based lithium adsorbent operate continuously in the adsorption zone, the washing zone, the desorption zone, and the qualified liquid top water zone. In the adsorption zone, the qualified boron removal solution, after pH adjustment, enters the adsorption column through a top feed method for adsorption to obtain a qualified lithium extraction solution.

[0020] Preferably, the qualified lithium extraction solution contains the following components: Li + ≥500mg / L, Mg 2+ ≤0.5g / L, Na + ≤0.6g / L, K + ≤0.15g / L, B 3+ ≤0.07g / L.

[0021] Preferably, in the washing zone, pure water is used to wash the adsorption column via an upward feeding method.

[0022] Preferably, in the desorption zone, pure water desorbs the adsorption column by top feeding.

[0023] Preferably, in the qualified liquid top water zone, the qualified lithium extraction liquid absorbs the residual liquid in the adsorption column by bottom feeding.

[0024] Preferably, the second continuous ion exchange device is configured with 30 adsorption columns. During continuous operation, the adsorption zone has 16 adsorption columns connected in an eight-parallel-two-series configuration, the washing material zone has 5 adsorption columns connected in a five-column-series configuration, the desorption zone has 8 adsorption columns connected in a two-parallel-four-series configuration, and the qualified liquid top water zone has 1 adsorption column.

[0025] A second aspect of the present invention also provides a method for preparing battery-grade lithium hydroxide from magnesium sulfate subtype salt lake raw brine, the method comprising: performing adsorption lithium extraction according to the method described above, purifying and concentrating the obtained qualified lithium extraction solution, and performing bipolar membrane electrodialysis.

[0026] Preferably, the hydrochloric acid generated during the bipolar membrane electrodialysis process is used in the acid desorption zone of the first continuous ion exchange device, or to adjust the pH value of the qualified boron removal solution.

[0027] A third aspect of the present invention also provides a method for preparing battery-grade lithium salts from magnesium sulfate subtype salt lake raw brine, the method comprising: performing adsorption lithium extraction according to the method described above, and purifying and concentrating the obtained qualified lithium extraction solution.

[0028] Preferably, the purification and concentration process employs at least one of multi-stage nanofiltration, MVR concentration, and electrodialysis concentration.

[0029] According to the method of the present invention, boron removal is performed before the adsorption lithium extraction process, which can effectively avoid the problem of low lithium extraction efficiency of adsorbent caused by boron in the long-term operation of the salt lake lithium extraction process. Under long-term operation, it has the advantages of high lithium ion recovery rate and high lithium extraction efficiency, and is particularly suitable for industrial applications in the preparation of battery-grade lithium hydroxide and battery-grade lithium salts from magnesium sulfate subtype salt lake raw brine. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the process flow for lithium extraction from magnesium sulfate subtype salt lake raw brine as described in this invention.

[0031] Figure 2 This is a graph showing the change in adsorption capacity during long-term operation of lithium extraction using the method of the present invention in Example 1.

[0032] Figure 3 This is a graph showing the change in adsorption capacity during long-term operation of the original halogen without boron removal in Comparative Example 4, when it was directly subjected to adsorption for lithium extraction. Detailed Implementation

[0033] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] In the description of this application, the terms "first" and "second" are used only to distinguish devices and should not be construed as indicating relative importance or implying the number of technical features indicated.

[0036] The method for lithium extraction from magnesium sulfate subtype salt lake raw brine according to the present invention includes the following steps:

[0037] (1) Pre-treat the original brine of magnesium sulfate subtype salt lake to obtain brine with suspended solids concentration ≤4mg / L;

[0038] (2) Boron removal treatment is performed on the brine obtained after step (1) using a boron removal ion exchange resin to obtain B. 3+ Boron removal solution with a concentration ≤20mg / L;

[0039] (3) Adjust the pH value of the qualified boron removal solution to 6.4-6.8, and then use an aluminum-based lithium adsorbent for adsorption and lithium extraction.

[0040] According to the method of the present invention, boron removal is performed before the adsorption process to reduce the influence of boron on the adsorption lithium extraction efficiency, which significantly enhances the adsorption lithium extraction effect of magnesium sulfate subtype salt lake raw brine and can maintain good adsorption lithium extraction efficiency during long-term operation.

[0041] In the method described in this invention, in step (1), the magnesium sulfate subtype salt lake raw brine contains the following components: Li + ≥0.2g / L, Mg 2+ ≤85g / L, Na + ≤85g / L, K + ≤15g / L, B 3+ ≤0.6g / L, and pH≥7.2.

[0042] In the method described in this invention, in step (1), preferably, the pretreatment process includes filtering the magnesium sulfate subtype brine from the salt lake using a filter. More preferably, the filter is at least one of a disc ceramic membrane filter, a multi-media multi-filter, and a security filter. The pretreated brine can remove soluble impurities and macromolecular organic matter, reducing the suspended solids concentration to ≤4 mg / L, which facilitates subsequent adsorption treatment.

[0043] In the method described in this invention, in step (2), preferably, the boron removal process is carried out in a first continuous ion exchange device. The first continuous ion exchange device includes an adsorption zone, a washing zone, an acid desorption zone, a washing acid zone, and a qualified liquid top water zone arranged sequentially. Several resin adsorption columns formed by the boron removal ion exchange resin operate continuously in the adsorption zone, washing zone, acid desorption zone, washing acid zone, and qualified liquid top water zone. In the adsorption zone, the brine obtained after step (1) is fed into the resin adsorption column via a top-feed method for adsorption, resulting in the boron-removed qualified liquid. This operation can remove more than 95% of the boron ions from the original brine, reducing the boron content in the qualified liquid. 3+ ≤20mg / L, the Li in the qualified boron-removed solution obtained after boron removal is + It can be fully utilized to achieve better lithium extraction results.

[0044] More preferably, in the water washing zone, pure water is used to wash the resin adsorption column via top feeding; in the acid desorption zone, hydrochloric acid is used to desorb the resin adsorption column via top feeding; in the water washing acid zone, pure water is used to wash the resin adsorption column via top feeding; and in the qualified liquid top water zone, the boron removal qualified liquid is used to disperse the adsorbed particles in the resin adsorption column via bottom feeding.

[0045] In a specific implementation, the first continuous ion exchange device is a dynamic circulation device. In a relatively static state, the device includes the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone, and the qualified liquid top water zone. All resin adsorption columns circulate through all zones sequentially. Specifically, the raw brine is fed from the raw material tank to the resin adsorption columns in the adsorption zone for adsorption. After two stages of resin column adsorption to remove boron, it reaches the qualified level, and the boron-removed qualified liquid enters the qualified liquid tank. Subsequently, the adsorption column reaches the water washing zone, where pure water is fed from the top to wash the resin adsorption column, pushing out the raw brine remaining in the adsorption column to prevent boron loss. The effluent is returned to the raw material tank for re-adsorption. Then, it reaches the acid desorption zone, where dilute hydrochloric acid is fed from the top to desorb the boron element complexed in the resin. The desorbed high-boron desorption solution can be sent to the downstream for the preparation of industrial-grade boric acid. In the acid washing zone, pure water is fed from the top to wash the resin adsorption column. The effluent can be mixed with concentrated hydrochloric acid to form dilute hydrochloric acid, which is then recycled back into the acid desorption zone. Finally, in the qualified liquid top water zone, the qualified boron removal liquid is fed from the bottom to disperse the adsorbed particles in the resin adsorption column, ensuring uniform distribution.

[0046] In the method described in this invention, the concentration of hydrochloric acid used in the acid desorption zone can be 3-10 wt%, preferably 4-8 wt%, and more preferably 5-7 wt%. The hydrochloric acid used in the acid desorption zone can be a hydrochloric acid solution generated during bipolar membrane electrodialysis.

[0047] In the method described in this invention, in the first continuous ion exchange system, the resin adsorption columns of different functional zones can be adjusted according to the actual situation, increasing or decreasing the number of adsorption columns in each functional zone within the range allowed by the equipment, thereby improving the adsorption efficiency.

[0048] In a preferred embodiment, the first continuous ion exchange device is equipped with 15 resin adsorption columns. During continuous operation, the adsorption zone has 8 resin adsorption columns connected in a four-parallel-two-series configuration, the water washing zone has 3 resin adsorption columns connected in a three-column-series configuration, the acid desorption zone has 2 resin adsorption columns connected in a two-column-series configuration, and the water washing acid zone and the qualified liquid top water zone each have 1 resin adsorption column.

[0049] In the method described in this invention, in step (3), the pH value of the qualified boron removal solution is adjusted to a weakly acidic state (specifically, a pH value of 6.4-6.8). This is beneficial for the adsorption and desorption of lithium ions by the aluminum-based lithium adsorbent. When the pH value is too high or too low, it will cause irreversible damage to the structure of the aluminum-based lithium adsorbent. In a specific embodiment, the reagent used to adjust the pH value of the qualified boron removal solution can be a hydrochloric acid solution. The concentration of the hydrochloric acid solution can be 3-10 wt%, preferably 4-8 wt%, and more preferably 5-7 wt%. The hydrochloric acid used here can be a hydrochloric acid solution generated during the bipolar membrane electrodialysis process. In a specific operational example, the pH adjustment process includes adding a hydrochloric acid solution generated during the bipolar membrane electrodialysis process to the qualified boron removal solution at a volume ratio of 1000:1 to adjust the pH value of the qualified boron removal solution to 6.4-6.8.

[0050] In the method described in this invention, in step (3), the qualified lithium extraction solution obtained after adsorption lithium extraction contains the following components: Li + ≥500mg / L, Mg 2+ ≤0.5g / L, Na + ≤0.6g / L, K + ≤0.15g / L, B 3+ ≤0.07g / L.

[0051] In the method described in this invention, in step (3), preferably, the lithium extraction process is carried out in a second continuous ion exchange device. The second continuous ion exchange device includes an adsorption zone, a washing zone, a desorption zone, and a qualified liquid top water zone arranged sequentially. Several adsorption columns formed by the aluminum-based lithium adsorbent operate continuously in the adsorption zone, the washing zone, the desorption zone, and the qualified liquid top water zone. In the adsorption zone, the qualified boron removal solution after pH adjustment enters the adsorption column through a top feeding method for adsorption to obtain a qualified lithium extraction solution.

[0052] More preferably, in the washing zone, pure water washes the adsorption column by top feeding; in the desorption zone, pure water desorbs the adsorption column by top feeding; and in the qualified liquid top water zone, the qualified lithium extraction liquid absorbs the residual liquid in the adsorption column by bottom feeding.

[0053] In a specific embodiment, the second continuous ion exchange device is a dynamic circulation device. In a relatively static state, the device includes the adsorption zone, the washing zone, the desorption zone, and the qualified liquid top water zone. All adsorption columns circulate through all zones sequentially. Specifically, the qualified boron removal liquid is fed from the qualified boron removal liquid tank to the adsorption columns in the adsorption zone for lithium adsorption. After lithium adsorption and extraction through two stages of resin columns, it enters the tail liquid tank and is then transported to a salt field for drying and comprehensive utilization. Subsequently, the adsorption columns reach the washing zone, where pure water is fed from above to rapidly wash the adsorption columns, pushing out the qualified boron removal liquid remaining in the adsorption columns and returning it to the qualified boron removal liquid tank for re-adsorption and lithium extraction. Then, in the desorption zone, the adsorption columns are desorbed using pure water fed from above, desorbing the lithium adsorbed in the resin into the pure water to obtain a qualified lithium extraction liquid, which is then transported to a storage tank for storage. Finally, in the qualified liquid top water zone, the residual desorption liquid in the adsorption column is absorbed by feeding the tail liquid after boron removal and lithium extraction, thus avoiding contamination of the next stage. Preferably, the pure water used in the desorption zone is pure water at 40°C.

[0054] In the method described in this invention, in the second continuous ion exchange system, the adsorption columns of different functional zones can be adjusted according to the actual situation, increasing or decreasing the number of adsorption columns in each functional zone within the range allowed by the equipment, thereby improving the adsorption efficiency.

[0055] In a preferred embodiment, the second continuous ion exchange device is configured with 30 adsorption columns. During continuous operation, the adsorption zone has 16 adsorption columns connected in an eight-parallel-two-series configuration, the washing material zone has 5 adsorption columns connected in a five-column-series configuration, the desorption zone has 8 adsorption columns connected in a two-parallel-four-series configuration, and the qualified liquid top water zone has 1 adsorption column.

[0056] The present invention also provides a method for preparing battery-grade lithium hydroxide from magnesium sulfate subtype salt lake raw brine, the method comprising: performing adsorption lithium extraction according to the method described above, purifying and concentrating the obtained qualified lithium extraction solution, and performing bipolar membrane electrodialysis.

[0057] In a preferred embodiment, the hydrochloric acid produced during the bipolar membrane electrodialysis process is used in the acid desorption zone of the first continuous ion exchange device, or to adjust the pH value of the boron-removed qualified solution. This preferred embodiment reduces consumption and lowers the overall process cost.

[0058] The present invention also provides a method for preparing battery-grade lithium salts from magnesium sulfate subtype salt lake raw brine, the method comprising: performing adsorption lithium extraction according to the method described above, and purifying and concentrating the obtained qualified lithium extraction solution.

[0059] In the method described in this invention, the purification and concentration process can employ at least one of multi-stage nanofiltration, MVR concentration, and electrodialysis concentration.

[0060] In a preferred embodiment, such as Figure 1 As shown, the process of lithium extraction from magnesium sulfate subtype salt lake raw brine and the preparation of battery-grade lithium hydroxide or battery-grade lithium salts includes:

[0061] S1 (Pretreatment): The original brine of the magnesium sulfate subtype salt lake is filtered through a multi-media filter to obtain brine with a suspended solids concentration of ≤4mg / L;

[0062] S2 (Ion Exchange Boron Removal): Boron removal is performed on the brine obtained after filtration using a boron-removing ion exchange resin to obtain B. 3+ A qualified boron removal solution with a concentration ≤20mg / L, wherein the boron removal process is carried out in the first continuous ion exchange device, the hydrochloric acid used in the acid desorption zone of the first continuous ion exchange device can be the hydrochloric acid solution generated in the subsequent bipolar membrane electrodialysis process, and the high boron desorption solution obtained after desorption in the acid desorption zone can be used to prepare industrial grade boric acid.

[0063] S3 (Adjust pH): Adjust the pH of the qualified boron-removed solution obtained after the above boron removal treatment to 6.4-6.8. The hydrochloric acid used to adjust the pH can be the hydrochloric acid solution generated during the subsequent bipolar membrane electrodialysis process.

[0064] S4 (Lithium Extraction by Adsorption): An aluminum-based lithium adsorbent is used to adsorb and extract lithium from the above-mentioned qualified boron-removed solution after pH adjustment, yielding Li. +The lithium extraction solution has a concentration ≥500mg / L. The lithium extraction process is carried out in the second continuous ion exchange device. In the adsorption zone of the second continuous ion exchange device, the tail brine after lithium extraction can be transported to the salt field for sun drying and comprehensive utilization. In the washing zone of the second continuous ion exchange device, pure water is used to wash the adsorption column through the top feeding method to push out the qualified deboron removal solution remaining in the adsorption column and return it for re-adsorption and lithium extraction.

[0065] S5 (Purification and Concentration): The qualified lithium-extracting solution obtained after the above adsorption and lithium extraction is purified and concentrated by multi-stage nanofiltration to obtain battery-grade lithium salt.

[0066] Alternatively, the qualified lithium extraction solution can be purified and concentrated using multi-stage nanofiltration, and then subjected to bipolar membrane electrodialysis to obtain battery-grade lithium hydroxide. The hydrochloric acid produced during the bipolar membrane electrodialysis process can be used in the acid desorption zone of the first continuous ion exchange device, or used to adjust the pH value of the qualified boron removal solution.

[0067] The following examples further illustrate the method for lithium extraction from magnesium sulfate subtype salt lake raw brine according to the present invention and its application. The examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0068] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0069] Example 1

[0070] The magnesium sulfate subtype brine from the salt lake used in this embodiment contains the following components: Li + =241 mg / L, Mg 2+ =32.67g / L, Na + =67.45g / L, K + =14.06g / L, B 3+ =0.41g / L, and pH is 7.6.

[0071] (1) Pretreatment of raw brine

[0072] The original brine of the magnesium sulfate subtype salt lake was pretreated by a multi-media filter to obtain brine with a suspended solids concentration of 3 mg / L.

[0073] (2) Boron removal treatment

[0074] In this step, the first continuous ion exchange device is equipped with 15 resin adsorption columns formed by boron removal ion exchange resin. These columns are sequentially arranged in an adsorption zone, a washing material zone, an acid desorption zone, a washing acid zone, and a qualified liquid top water zone. The resin adsorption columns operate continuously within these zones. During continuous operation, the adsorption zone has 8 resin adsorption columns connected in a four-parallel, two-series configuration; the washing material zone has 3 resin adsorption columns connected in a three-column series configuration; the acid desorption zone has 2 resin adsorption columns connected in a two-column series configuration; and the washing acid zone and the qualified liquid top water zone each have 1 resin adsorption column.

[0075] The brine obtained after filtration in step (1) is transported to the adsorption zone of the first continuous ion exchange device. After boron removal by the two-stage resin columns in the adsorption zone via the top-feed method, the qualified boron-removed liquid is obtained and enters the qualified boron-removed liquid tank. The boron element in the mixed sample of the qualified boron-removed liquid is tested and found to be 18 mg / L. In the water washing zone, pure water is fed from the top to wash the resin adsorption column, pushing out the original brine remaining in the adsorption column to prevent boron loss. The effluent is returned to the raw material tank for re-adsorption and boron removal. In the acid desorption zone, dilute hydrochloric acid is fed from the top to desorb the boron element complexed in the resin. The desorbed high-boron desorption liquid is transported to the downstream end for the preparation of industrial-grade boric acid. In the acid washing zone, pure water is fed from the top to wash the resin adsorption column. The effluent is mixed with concentrated hydrochloric acid to form 6% dilute hydrochloric acid and then enters the acid desorption zone for recycling. In the qualified liquid top water zone, the qualified boron-removed liquid is fed from the bottom to disperse the adsorbed particles in the resin adsorption column, making them evenly distributed.

[0076] (3) Lithium extraction by adsorption

[0077] In this step, the second continuous ion exchange unit is equipped with 30 adsorption columns formed by aluminum-based lithium adsorbent, arranged sequentially in an adsorption zone, a washing material zone, a desorption zone, and a qualified liquid top water zone. The adsorption columns operate continuously within these zones. During continuous operation, the adsorption zone has 16 adsorption columns connected in an eight-parallel, two-series configuration; the washing material zone has 5 adsorption columns connected in a five-column series configuration; the desorption zone has 8 adsorption columns connected in a two-parallel, four-series configuration; and the qualified liquid top water zone has 1 adsorption column.

[0078] Hydrochloric acid produced by bipolar membrane electrodialysis was added to the qualified boron-removing solution obtained in step (2) at a volume ratio of 1000:1 to adjust the pH of the qualified boron-removing solution to 6.8. Then, the qualified boron-removing solution with pH 6.8 was transported to the adsorption zone of the second continuous ion exchange device. After lithium extraction by two-stage adsorption columns, the solution was fed into the tail liquid tank. The lithium content in the tail brine was found to be 10 mg / L. The tail brine can be transported to the salt field for drying and comprehensive utilization. Then, the adsorption column was quickly rinsed with pure water by top feeding to push out the qualified boron-removing solution remaining in the adsorption column and return it to the qualified boron-removing solution tank for re-adsorption and lithium extraction. Then, the adsorption column was desorbed with pure water at 40°C by top feeding to desorb the lithium adsorbed in the adsorption column into the pure water to obtain qualified lithium extraction solution. The obtained qualified lithium extraction solution was transported to the storage tank for storage. Finally, the tail liquid after boron removal and lithium extraction was used by bottom feeding to absorb the residual desorbed liquid in the adsorption column to avoid contamination of the next step. After 70 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =732mg / L, Mg 2+ =0.421 g / L, Na + =0.591g / L, K + =0.141g / L, B 3+ =16 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0079] Figure 2 The graph shows the change in adsorption capacity during long-term operation of lithium extraction using the method of the present invention in Example 1. As can be seen from the graph, a high adsorption capacity is still maintained after 60 cycles.

[0080] Example 2

[0081] The magnesium sulfate subtype brine from the salt lake used in this embodiment contains the following components: Li + =225mg / L, Mg 2+ =32.78g / L, Na + =70.46g / L, K + =13.457g / L, B 3+ =0.493g / L, and pH is 7.6.

[0082] (1) Pretreatment of raw brine

[0083] The original brine of the magnesium sulfate subtype salt lake was pretreated by a multi-media filter to obtain brine with a suspended solids concentration of 2 mg / L.

[0084] (2) Boron removal treatment

[0085] The configuration of the first continuous ion exchange device used in this embodiment is the same as that in Embodiment 1.

[0086] The filtered brine from step (1) is transported to the adsorption zone of the first continuous ion exchange device. After boron removal by the two-stage resin columns in the adsorption zone via the top-feed method, the boron-removed qualified solution is obtained and enters the boron-removed qualified solution tank. A mixed sample of the boron-removed qualified solution is tested and found to contain 15 mg / L of boron. In the water washing zone, pure water is fed from the top to wash the resin adsorption column, pushing out the original brine remaining in the adsorption column to prevent boron loss. The effluent is returned to the raw material tank for re-adsorption and boron removal. In the acid desorption zone, dilute hydrochloric acid is fed from the top to desorb the boron complexed in the resin. The desorbed high-boron desorption solution is transported to the downstream end for the preparation of industrial-grade boric acid. In the acid washing zone, pure water is fed from the top to wash the resin adsorption column. The effluent is mixed with concentrated hydrochloric acid to form 7% dilute hydrochloric acid and then enters the acid desorption zone for recycling. In the qualified solution top water zone, the boron-removed qualified solution is fed from the bottom to disperse the adsorbed particles in the resin adsorption column, making them evenly distributed.

[0087] (3) Lithium extraction by adsorption

[0088] The configuration of the second continuous ion exchange device used in this embodiment is the same as that in Embodiment 1.

[0089] Hydrochloric acid produced by bipolar membrane electrodialysis was added to the qualified boron-removing solution obtained in step (2) at a volume ratio of 1000:1 to adjust the pH of the qualified boron-removing solution to 6.4. Then, the qualified boron-removing solution with pH 6.4 was transported to the adsorption zone of the second continuous ion exchange device. After lithium extraction by two-stage adsorption columns, the solution was fed into the tail liquid tank. The lithium content in the tail brine was tested to be 14 mg / L. The tail brine can be transported to the salt field for drying and comprehensive utilization. Then, the adsorption column was quickly rinsed with pure water by top feeding to push out the qualified boron-removing solution remaining in the adsorption column and return it to the qualified boron-removing solution tank for re-adsorption and lithium extraction. Then, the adsorption column was desorbed by top feeding with pure water at 40°C to desorb the lithium adsorbed in the adsorption column into the pure water to obtain qualified lithium extraction solution. The obtained qualified lithium extraction solution was transported to the storage tank for storage. Finally, the tail liquid after boron removal and lithium extraction was used by bottom feeding to absorb the residual desorbed liquid in the adsorption column to avoid contamination of the next step. After 70 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =693mg / L, Mg 2+ =0.413 g / L, Na + =0.522g / L, K + =0.111g / L, B 3+ =17 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0090] Example 3

[0091] The magnesium sulfate subtype brine from the salt lake used in this embodiment contains the following components: Li + =311 mg / L, Mg 2+ =33.723 g / L, Na + =70.93g / L, K + =12.522g / L, B 3+ =0.526g / L, and pH is 7.6.

[0092] (1) Pretreatment of raw brine

[0093] The original brine of the magnesium sulfate subtype salt lake was pretreated by a multi-media filter to obtain brine with a suspended solids concentration of 4 mg / L.

[0094] (2) Boron removal treatment

[0095] The configuration of the first continuous ion exchange device used in this embodiment is the same as that in Embodiment 1.

[0096] The filtered brine from step (1) is transported to the adsorption zone of the first continuous ion exchange device. After boron removal by the two-stage resin columns in the adsorption zone via the top-feed method, the boron-removed qualified solution is obtained and enters the boron-removed qualified solution tank. A mixed sample of the boron-removed qualified solution is tested and found to contain 10 mg / L of boron. In the water washing zone, pure water is fed from the top to wash the resin adsorption column, pushing out the original brine remaining in the adsorption column to prevent boron loss. The effluent is returned to the raw material tank for re-adsorption and boron removal. In the acid desorption zone, dilute hydrochloric acid is fed from the top to desorb the boron complexed in the resin. The desorbed high-boron desorption solution is transported to the downstream end for the preparation of industrial-grade boric acid. In the acid washing zone, pure water is fed from the top to wash the resin adsorption column. The effluent is mixed with concentrated hydrochloric acid to form 5% dilute hydrochloric acid and then enters the acid desorption zone for recycling. In the qualified solution top water zone, the boron-removed qualified solution is fed from the bottom to disperse the adsorbed particles in the resin adsorption column, making them evenly distributed.

[0097] (3) Lithium extraction by adsorption

[0098] The configuration of the second continuous ion exchange device used in this embodiment is the same as that in Embodiment 1.

[0099] Hydrochloric acid produced by bipolar membrane electrodialysis was added to the qualified boron-removing solution obtained in step (2) at a volume ratio of 1000:1 to adjust the pH of the qualified boron-removing solution to 6.6. Then, the qualified boron-removing solution with pH 6.6 was transported to the adsorption zone of the second continuous ion exchange device. After lithium extraction by two-stage adsorption columns, the solution was fed into the tail liquid tank. The lithium content in the tail brine was measured to be 21 mg / L. The tail brine can be transported to the salt field for drying and comprehensive utilization. Then, the adsorption column was quickly rinsed with pure water by top feeding to push out the qualified boron-removing solution remaining in the adsorption column and return it to the qualified boron-removing solution tank for re-adsorption and lithium extraction. Then, the adsorption column was desorbed with pure water at 40°C by top feeding to desorb the lithium adsorbed in the adsorption column into the pure water to obtain qualified lithium extraction solution. The obtained qualified lithium extraction solution was transported to the storage tank for storage. Finally, the tail liquid after boron removal and lithium extraction was used by bottom feeding to absorb the residual desorbed liquid in the adsorption column to avoid contamination of the next step. After 70 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =639mg / L, Mg 2+ =0.398g / L, Na + =0.24g / L, K + =0.054g / L, B 3+ =14 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0100] Comparative Example 1

[0101] The method is implemented according to Example 1, except that in step (3), the pH value of the qualified boron removal solution is adjusted to 6.

[0102] As a result, the lower pH environment adversely affects the structure of the adsorbent, leading to a significant decrease in its lithium extraction efficiency under long-term cycling conditions.

[0103] After 70 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =759mg / L, Mg 2+ =0.41g / L, Na + =0.23g / L, K + =0.049g / L, B 3+ =16 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0104] Comparative Example 2

[0105] The method of Example 1 is implemented, except that in step (3), the pH value of the qualified boron removal solution is adjusted to 7.5.

[0106] As a result, the higher pH environment had an adverse effect on the structure of the adsorbent, leading to a significant decrease in its lithium-ion recovery rate under long-term cycling conditions.

[0107] After 70 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =401 mg / L, Mg 2+ =0.32g / L, Na + =0.22g / L, K + =0.023g / L, B 3+ =16 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0108] Comparative Example 3

[0109] The method of Example 1 is followed, except that in step (2), the boron-removing solution obtained after boron removal treatment has a different B content. 3+ The concentration is 70 mg / L.

[0110] As a result, under long-term cycling conditions, incomplete boron removal leads to a significant decrease in lithium-ion recovery rate.

[0111] After 150 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =572mg / L, Mg 2+ =0.34g / L, Na + =0.31g / L, K + =0.027g / L, B 3+ = 89 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0112] Comparative Example 4

[0113] (1) The original brine of magnesium sulfate subtype salt lake was filtered through a multi-media filter to obtain brine with a suspended solids concentration of 3 mg / L;

[0114] (2) The filtered brine is directly transported to the second continuous ion exchange device and processed according to the method of step (3) in Example 1.

[0115] As a result, without boron removal, incomplete boron removal under long-term cycling conditions leads to a significant decrease in lithium-ion recovery rate.

[0116] After 70 cycles of operation, the qualified lithium extraction solution was tested and found to contain the following components: Li + =394 mg / L, Mg 2+ =0.65g / L, Na + =0.43g / L, K + =0.12g / L, B3+ =438 mg / L. The calculated lithium-ion recovery rate and lithium extraction efficiency are shown in Table 1.

[0117] Figure 3 The graph shows the change in adsorption capacity of lithium extraction from the original halogen without boron removal in Comparative Example 4. After 40 cycles of "adsorption-desorption", the adsorption capacity of the adsorbent decreased significantly, and after 70 cycles, it decreased by about 50%.

[0118] pass Figure 2 and Figure 3 The comparison shows that by first removing boron and adjusting the pH value of the original brine before adsorption and lithium extraction, the problem of decreased adsorption capacity can be effectively solved. That is, the method of adsorption and lithium extraction from magnesium sulfate subtype salt lake original brine in this invention can still maintain good adsorption and lithium extraction efficiency under long-term operation, and is more suitable for industrial applications in the preparation of battery-grade lithium hydroxide and battery-grade lithium salts from magnesium sulfate subtype salt lake original brine.

[0119] Table 1

[0120] serial number <![CDATA[Li + Recovery rate (%) Lithium extraction efficiency (%) Example 1 91.38 94.64 Example 2 96.51 90.61 Example 3 93.73 92.45 Comparative Example 1 88.46 64.84 Comparative Example 2 78.92 74.82 Comparative Example 3 76.35 80.57 Comparative Example 4 69.65 73.59

[0121] As can be seen from the data in Table 1, the method for lithium extraction by adsorption from magnesium sulfate subtype salt lake raw brine of the present invention, which removes boron before the adsorption lithium extraction process, can reduce the impact of low lithium extraction efficiency caused by boron. The lithium ion recovery rate and lithium extraction efficiency can both reach over 90%, which has the characteristics of high lithium ion recovery rate and high lithium extraction efficiency. It can also maintain good adsorption lithium extraction efficiency under long-term operation, and is suitable for industrial applications in the preparation of battery-grade lithium hydroxide and battery-grade lithium salts from magnesium sulfate subtype salt lake raw brine.

[0122] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for lithium extraction from a raw brine of a magnesium sulfate sub-type salt lake by adsorption, characterized in that, The method includes the following steps: (1) The original brine of the magnesium sulfate subtype salt lake is pretreated. The pretreatment process includes filtering the original brine of the magnesium sulfate subtype salt lake using a filter to obtain brine with a suspended solids concentration ≤4mg / L. (2) Boron removal treatment is performed on the brine obtained after step (1) using a boron removal ion exchange resin to obtain B. 3+ A qualified boron removal solution with a concentration ≤20mg / L; the boron removal process is carried out in a first continuous ion exchange device, which includes an adsorption zone, a water washing zone, an acid desorption zone, a water washing acid zone, and a qualified solution top water zone arranged sequentially, and several resin adsorption columns formed by the boron removal ion exchange resin operate continuously in the adsorption zone, water washing zone, acid desorption zone, water washing acid zone, and qualified solution top water zone; (3) The pH value of the boron removal qualified solution is adjusted to 6.4-6.8, and then lithium is extracted by adsorption using an aluminum-based lithium adsorbent; the lithium extraction process is carried out in a second continuous ion exchange device, which includes an adsorption zone, a washing zone, a desorption zone, and a qualified solution top water zone arranged sequentially. Several adsorption columns formed by the aluminum-based lithium adsorbent operate continuously in the adsorption zone, the washing zone, the desorption zone, and the qualified solution top water zone. In the adsorption zone, the boron removal qualified solution after pH adjustment enters the resin adsorption column for adsorption by top feeding; in the washing zone, pure water washes the adsorption column by top feeding; in the desorption zone, pure water desorbs the adsorption column by top feeding to obtain a qualified lithium extraction solution; the qualified lithium extraction solution contains the following components: Li + ≥500mg / L, Mg 2+ ≤0.5g / L, Na + ≤0.6g / L, K + ≤0.15g / L, B 3+ ≤0.07g / L; In step (1), the magnesium sulfate subtype salt lake raw brine contains the following components: Li + ≥0.2g / L, Mg 2+ ≤85g / L, Na + ≤85g / L, K + ≤15g / L, B 3+ ≤0.6g / L, and pH≥7.

2.

2. The method according to claim 1, characterized in that, In step (1), the filter is at least one of a disc ceramic membrane filter, a multi-media multi-filter, and a security filter.

3. The method of claim 1, wherein, In step (2), the brine obtained after the treatment in step (1) is fed into the resin adsorption column in the adsorption zone for adsorption to obtain the qualified boron removal solution.

4. The method of claim 1, wherein, In the water washing zone, pure water is fed from the top to wash the resin adsorption column; in the acid desorption zone, hydrochloric acid is fed from the top to desorb the resin adsorption column; in the water washing acid zone, pure water is fed from the top to wash the resin adsorption column. In the qualified liquid top water zone, the boron removal qualified liquid is fed from the bottom to disperse the adsorbed particles in the resin adsorption column.

5. The method of claim 4, wherein, The concentration of hydrochloric acid used in the acid desorption zone is 3-10 wt%.

6. The method of claim 5, wherein, The concentration of hydrochloric acid used in the acid desorption zone is 5-7 wt%.

7. The method according to any one of claims 3-6, characterized in that, The first continuous ion exchange device is equipped with 15 resin adsorption columns. During continuous operation, the adsorption zone has 8 resin adsorption columns connected in a four-parallel-two-series configuration, the water washing zone has 3 resin adsorption columns connected in a three-column-in-series configuration, the acid desorption zone has 2 resin adsorption columns connected in a two-column-in-series configuration, and the water washing acid zone and the qualified liquid top water zone each have 1 resin adsorption column.

8. The method of claim 1, wherein, In the qualified liquid top water zone, the qualified lithium extraction liquid absorbs the residual liquid in the adsorption column by bottom feeding.

9. The method according to any one of claims 1 or 8, characterized in that, The second continuous ion exchange device is equipped with 30 adsorption columns. During continuous operation, the adsorption zone has 16 adsorption columns connected in an eight-parallel-two-series configuration, the washing material zone has 5 adsorption columns connected in a five-column-series configuration, the desorption zone has 8 adsorption columns connected in a two-parallel-four-series configuration, and the qualified liquid top water zone has 1 adsorption column.

10. A process for the preparation of battery grade lithium hydroxide from a raw brine of a magnesium sulfate sub-type salt lake characterized in that, The method includes: performing adsorption lithium extraction according to any one of claims 1-9, purifying and concentrating the obtained qualified lithium extraction solution, and performing bipolar membrane electrodialysis.

11. The method of claim 10, wherein, The hydrochloric acid produced during the bipolar membrane electrodialysis process is used in the acid desorption zone of the first continuous ion exchange device, or to adjust the pH value of the qualified boron removal solution.

12. A method of producing battery grade lithium salt from a raw brine of a magnesium sulfate sub-type salt lake, characterized in that, The method includes: performing adsorption lithium extraction according to any one of claims 1-9, and purifying and concentrating the obtained qualified lithium extraction solution.

13. The method of claim 12, wherein, The purification and concentration process employs at least one of the following methods: multi-stage nanofiltration, MVR concentration, and electrodialysis concentration.

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