Method for extracting lithium by adsorbing magnesium sulfate subtype salt lake original brine and application thereof

Abstract

The invention relates to the field of salt lake lithium resource recycling, and discloses a method for extracting lithium from magnesium sulfate subtype salt lake original brine through adsorption and application of the method. The method comprises the following steps: (1) pretreating original brine of the magnesium sulfate subtype salt lake to obtain brine with the suspended matter concentration of less than or equal to 4mg / L; (2) carrying out boron removal treatment on the brine obtained after treatment in the step (1) by using ion exchange resin to obtain boron-removed qualified liquid of which the B < 3 + > concentration is less than or equal to 20mg / L; and (3) adjusting the pH value of the boron-removed qualified liquid to 6.4-6.8, and then carrying out adsorption and lithium extraction by using an aluminum adsorbent. The method for adsorbing and extracting lithium from the magnesium sulfate subtype salt lake original brine has the characteristics of high lithium ion recovery rate, high lithium extraction efficiency and the like, can still keep good adsorption and lithium extraction efficiency under long-term operation, and is particularly suitable for industrial application in preparation of battery-grade lithium hydroxide and battery-grade lithium salt from the magnesium sulfate subtype salt lake original brine.

Description

Technical Field

[0001] The invention relates to the field of recycling and utilizing lithium resources in salt lakes, and in particular to a method for extracting lithium by adsorption from raw brine of magnesium sulfate subtype salt lakes and an application thereof. Background Art

[0002] With the vigorous development of the new energy industry, the demand for related lithium products is in short supply. Therefore, how to make full use of salt lake lithium resources has become a concern of the entire industry. The adsorption method uses the selective adsorption of lithium ions by adsorbents to achieve effective separation of lithium ions and impurity ions. It has the advantages of simple process flow, low environmental pollution, and environmental protection. Although the adsorption method for lithium extraction has many advantages, the composition of the original brine of the magnesium sulfate subtype salt lake is unique, which makes the adsorption method for lithium extraction lead to low lithium ion recovery rate and low lithium extraction efficiency in the long-term operation, which seriously affects the industrial application of salt lake lithium resources. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of low lithium ion recovery rate and low lithium extraction efficiency in the long-term operation of magnesium sulfate subtype salt lake original brine using adsorption method in the prior art, and to provide a method for extracting lithium by adsorption from magnesium sulfate subtype salt lake original brine and its application. The method has the advantages of high lithium ion recovery rate and high lithium extraction efficiency in the case of long-term operation, and is particularly suitable for industrial application in the preparation of battery-grade lithium hydroxide and battery-grade lithium salt from magnesium sulfate subtype salt lake original brine.

[0004] The inventor of the present invention has found through in-depth research that the original brine of magnesium sulfate subtype salt lake contains a large amount of boron elements, wherein the boron elements exist in the form of boric acid or borate, have a high solubility in aqueous solution, and are difficult to further reduce. In addition, during the adsorption process, boron will be intercalated into the adsorbent along with lithium, which is an important reason for the low lithium ion recovery rate and low lithium extraction efficiency in the long-term operation of the original brine of magnesium sulfate subtype salt lake to extract lithium. In the existing salt lake lithium extraction method, the boron element is removed and collected after a series of pretreatments such as nanofiltration and adsorption. Although this method can effectively extract boron, the long-term original brine adsorption process will increase the lithium loss during the front-end pretreatment, reduce the adsorption efficiency of the adsorbent, and increase the energy consumption and cost of the subsequent process. For this reason, in the present invention, boron is removed before adsorption and lithium extraction, which can not only effectively avoid the above problems, but also because of the characteristics of the original brine components of magnesium sulfate subtype salt lakes, no additional alkali adjustment process is required, which can effectively reduce the process energy consumption and cost, thereby completing the present invention.

[0005] To this end, the present invention provides a method for extracting lithium by adsorption from raw brine of magnesium sulfate subtype salt lake, the method comprising the following steps:

[0006] (1) pretreating the original brine of magnesium sulfate subtype salt lake to obtain brine with a suspended matter concentration of ≤4 mg / L;

[0007] (2) using a boron removal ion exchange resin to remove boron from the brine obtained after the treatment in step (1) to obtain B 3+ Qualified boron removal solution with a concentration of ≤20mg / L;

[0008] (3) The pH value of the qualified boron removal solution is adjusted to 6.4-6.8, and then an aluminum-based lithium adsorbent is used to adsorb and extract lithium.

[0009] Preferably, in step (1), the magnesium sulfate subtype salt lake original 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.

[0010] Preferably, in step (1), the pretreatment process includes filtering the magnesium sulfate subtype salt lake original 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 treatment process is implemented 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 in sequence, and a plurality of resin adsorption columns formed by the boron removal ion exchange resin are continuously operated in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, wherein in the adsorption zone, the brine obtained after the treatment in step (1) enters the resin adsorption column through an upper feeding method for adsorption to obtain the boron removal qualified liquid.

[0013] Preferably, in the water washing zone, pure water is used to wash the resin adsorption column by upper feeding.

[0014] Preferably, in the acid desorption zone, hydrochloric acid is used to desorb the resin adsorption column by top feeding.

[0015] Preferably, in the water washing acid zone, pure water is used to wash the resin adsorption column by upper feeding.

[0016] Preferably, in the qualified liquid top water zone, the qualified boron removal liquid is used to evacuate the adsorption particles in the resin adsorption column by a bottom feeding method.

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

[0018] Preferably, the number of resin adsorption columns configured in the first continuous ion exchange device is 15, and during continuous operation, the adsorption zone has 8 resin adsorption columns, which are connected in a four-in-parallel and two-in-series manner, the water washing zone has 3 resin adsorption columns, which are connected in a three-column series manner, the acid desorption zone has 2 resin adsorption columns, which are connected in a two-column series manner, and the water washing acid zone and the qualified liquid top water zone each have one resin adsorption column.

[0019] Preferably, the process of adsorption and lithium extraction is implemented in a second continuous ion exchange device, which includes an adsorption zone, a water washing zone, a desorption zone and a qualified liquid top water zone arranged in sequence, and a number of adsorption columns formed by the aluminum-based lithium adsorbent are continuously operated in the adsorption zone, the water washing zone, the desorption zone and the qualified liquid top water zone, wherein, in the adsorption zone, the qualified boron removal liquid after pH adjustment enters the adsorption column through an upper feeding method for adsorption to obtain a qualified lithium extraction liquid.

[0020] Preferably, the qualified solution for 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.

[0021] Preferably, in the water washing zone, pure water is used to wash the adsorption column by upper feeding.

[0022] Preferably, in the desorption zone, pure water is desorbed from the adsorption column by upper feeding.

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

[0024] Preferably, the number of adsorption columns configured in the second continuous ion exchange device is 30, and during continuous operation, the adsorption zone has 16 adsorption columns, which are connected in an eight-in-two series manner, the water washing zone has 5 adsorption columns, which are connected in a five-column series manner, the desorption zone has 8 adsorption columns, which are connected in a two-in-four series manner, and the qualified liquid top water zone has 1 adsorption column.

[0025] The second aspect of the present invention also provides a method for preparing battery-grade lithium hydroxide from magnesium sulfate subtype salt lake original brine, the method comprising: extracting lithium by adsorption 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 produced during the bipolar membrane electrodialysis process is used in the acid desorption zone of the first continuous ion exchange device, or is used to adjust the pH value of the qualified boron removal solution.

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

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

[0029] According to the method of the present invention, boron is removed before the adsorption lithium extraction process, which can effectively avoid the problem of low lithium extraction efficiency of the adsorbent caused by the boron element in the long-term operation of the salt lake lithium extraction process. Under the condition of 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 original brine of magnesium sulfate subtype salt lakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the process flow of extracting lithium by adsorption from the original brine of magnesium sulfate subtype salt lake described in the present invention;

[0031] Figure 2 This is a graph showing the change in adsorption capacity when the method of the present invention is used for long-term lithium adsorption extraction in Example 1;

[0032] Figure 3 This is a graph showing the change in adsorption capacity during long-term operation of direct adsorption and lithium extraction from the original halogen without boron removal in Comparative Example 4. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0034] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0035] In the description of the present application, the terms "first" and "second" are only used to distinguish between devices and cannot be understood as indicating relative importance or implicitly indicating the number of the indicated technical features.

[0036] The method for extracting lithium by adsorption from raw brine of magnesium sulfate subtype salt lake of the present invention comprises the following steps:

[0037] (1) pretreating the original brine of magnesium sulfate subtype salt lake to obtain brine with a suspended matter concentration of ≤4 mg / L;

[0038] (2) using a boron removal ion exchange resin to remove the boron from the brine obtained after the treatment in step (1) to obtain B 3+ Qualified boron removal solution with a concentration of ≤20mg / L;

[0039] (3) The pH value of the qualified boron removal solution is adjusted to 6.4-6.8, and then an aluminum-based lithium adsorbent is used to adsorb and extract lithium.

[0040] According to the method of the present invention, boron is removed before the adsorption process to reduce the influence of the boron element on the adsorption efficiency of lithium extraction, significantly enhance the effect of adsorption of lithium extraction from the original brine of the magnesium sulfate subtype salt lake, and maintain good adsorption efficiency of lithium extraction during long-term operation.

[0041] In the method described in the present invention, in step (1), the magnesium sulfate subtype salt lake original 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 of the present invention, in step (1), preferably, the pretreatment process includes filtering the magnesium sulfate subtype salt lake raw brine 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 raw brine can remove soluble impurities and macromolecular organic matter contained therein, so that the suspended matter concentration therein is ≤4 mg / L, which is convenient for the subsequent adsorption treatment process.

[0043] In the method described in the present invention, in step (2), preferably, the boron removal process is implemented 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 in sequence, and a plurality of resin adsorption columns formed by the boron removal ion exchange resin are continuously operated in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, wherein, in the adsorption zone, the brine obtained after the treatment in step (1) enters the resin adsorption column through the upper feeding method for adsorption to obtain the boron removal qualified liquid. This operation can remove more than 95% of the boron ions in the original brine, so that the B in the qualified liquid 3+ ≤20mg / L, Li in the boron-removed qualified solution obtained after boron removal + It can be fully utilized to obtain better lithium extraction effect.

[0044] Further preferably, in the water washing zone, pure water is used to wash the resin adsorption column through the upper feeding method; in the acid desorption zone, hydrochloric acid is used to desorb the resin adsorption column through the upper feeding method; in the water washing acid zone, pure water is used to wash the resin adsorption column through the upper feeding method; in the qualified liquid top water zone, the boron removal qualified liquid is used to evacuate the adsorption particles in the resin adsorption column by the lower feeding method.

[0045] In a specific embodiment, the first continuous ion exchange device is a dynamic circulation device. In a relatively static state, the device comprises the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, and all resin adsorption columns are circulated through all areas in sequence. Specifically, the original brine is transported from the raw material tank to the resin adsorption column in the adsorption zone by the upper feeding method for adsorption, and is qualified after being adsorbed and removed by two-stage resin columns, and the boron removal qualified liquid enters the qualified liquid tank. Subsequently, the adsorption column arrives at the water washing zone, and pure water washes the resin adsorption column by the upper feeding method, and the original brine remaining in the adsorption column is pushed out to prevent boron loss, and the front section of the water outlet returns to the raw material tank for re-adsorption. Then it arrives at the acid desorption zone, and dilute hydrochloric acid is used to desorb the boron element complexed in the resin by the upper feeding method. The high-boron desorption liquid after desorption can be transported to the rear end for the preparation of industrial-grade boric acid. In the water washing and acidizing area, pure water is used to wash the resin adsorption column by upper feeding, and the effluent can be mixed with concentrated hydrochloric acid to form dilute hydrochloric acid and then enter the acid desorption area for recycling. Finally, in the qualified liquid top water area, the qualified boron removal liquid is used to evacuate the adsorption particles in the resin adsorption column by lower feeding to make them evenly distributed.

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

[0047] In the method described in the present invention, in the first continuous ion exchange system, the resin adsorption columns in different functional zones can be adjusted according to actual conditions, and the number of adsorption columns in each functional zone can be increased or decreased within the range allowed by the equipment to improve the adsorption efficiency.

[0048] In a preferred embodiment, the number of resin adsorption columns configured in the first continuous ion exchange device is 15, and during continuous operation, the adsorption zone has 8 resin adsorption columns, which are connected in a four-parallel and two-series manner, the water washing zone has 3 resin adsorption columns, which are connected in a three-column series manner, the acid desorption zone has 2 resin adsorption columns, which are connected in a two-column series manner, and the water washing acid zone and the qualified liquid top water zone each have one resin adsorption column.

[0049] In the method described in the present invention, in step (3), by adjusting the pH value of the qualified deboronation solution to a weak acidity (specifically, the pH value is 6.4-6.8), it is beneficial for the aluminum-based lithium adsorbent to adsorb and desorb lithium ions. 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 deboronation solution can be a hydrochloric acid solution. The concentration of the hydrochloric acid solution can be 3-10wt%, preferably 4-8wt%, and more preferably 5-7wt%. The hydrochloric acid used here can be a hydrochloric acid solution produced during bipolar membrane electrodialysis. In a specific operating example, the process of pH value adjustment includes: adding a hydrochloric acid solution produced by a bipolar membrane electrodialysis process to the qualified deboronation solution at a volume ratio of 1000:1, and adjusting the pH value of the qualified deboronation solution to 6.4-6.8.

[0050] In the method described in the present invention, in step (3), the qualified lithium extraction solution obtained after lithium extraction by adsorption 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 the present invention, in step (3), preferably, the process of adsorption and lithium extraction is implemented in a second continuous ion exchange device, the second continuous ion exchange device includes an adsorption zone, a water washing zone, a desorption zone and a qualified liquid top water zone arranged in sequence, and a plurality of adsorption columns formed by the aluminum-based lithium adsorbent are continuously operated in the adsorption zone, the water washing zone, the desorption zone and the qualified liquid top water zone, wherein, in the adsorption zone, the qualified boron removal liquid after pH adjustment enters the adsorption column through the upper feeding method for adsorption to obtain a qualified lithium extraction liquid.

[0052] Further preferably, in the water washing zone, pure water is used to wash the adsorption column by an upper feeding method; in the desorption zone, pure water is used to desorb the adsorption column by an upper feeding method; in the qualified liquid top water zone, the qualified lithium extraction liquid absorbs the residual liquid in the adsorption column by a lower feeding method.

[0053] In a specific embodiment, the second continuous ion exchange device is a dynamic circulation device. When in a relatively static state, the device comprises the adsorption zone, the water washing zone, the desorption zone and the qualified liquid top water zone, and all adsorption columns circulate through all areas in sequence. Specifically, the above-feeding method of ... Finally, in the qualified liquid top water zone, the tail liquid after boron removal and lithium extraction is used as a feed to absorb the remaining desorption liquid in the adsorption column to avoid contamination of the next link. Preferably, the pure water used in the desorption zone is 40°C pure water.

[0054] In the method described in the present invention, in the second continuous ion exchange system, the adsorption columns in different functional zones can be adjusted according to actual conditions, and the number of adsorption columns in each functional zone can be increased or decreased within the range allowed by the equipment to improve the adsorption efficiency.

[0055] In a preferred embodiment, the number of adsorption columns configured in the second continuous ion exchange device is 30, and during continuous operation, the adsorption zone has 16 adsorption columns, which are connected in an eight-in-two series manner, the water washing zone has 5 adsorption columns, which are connected in a five-column series manner, the desorption zone has 8 adsorption columns, which are connected in a two-in-one and four-in-one manner, 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 original brine, the method comprising: extracting lithium by adsorption 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 is used in the acid desorption zone of the first continuous ion exchange device, or is used to adjust the pH value of the boron removal qualified solution. In this preferred embodiment, consumption can be reduced and the overall process cost can be reduced.

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

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

[0060] In a more preferred embodiment, Figure 1 As shown in the figure, the process of extracting lithium by adsorption from the original brine of magnesium sulfate subtype salt lake and preparing battery-grade lithium hydroxide or battery-grade lithium salt includes:

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

[0062] S2 (ion exchange and boron removal): boron removal treatment is performed on the brine obtained after the above filtration using a boron removal ion exchange resin to obtain B 3+ A qualified boron-removed liquid with a concentration of ≤20 mg / L, wherein the boron-removal process is implemented in the first continuous ion exchange device, the hydrochloric acid used in the acid desorption zone of the first continuous ion exchange device can use the hydrochloric acid solution produced in the subsequent bipolar membrane electrodialysis process, and the high-boron desorption liquid obtained after desorption in the acid desorption zone can be used to prepare industrial-grade boric acid;

[0063] S3 (adjusting pH): adjusting the pH value of the qualified boron removal solution obtained after the above boron removal treatment to 6.4-6.8, and the hydrochloric acid used for adjusting the pH value can be the hydrochloric acid solution produced in the subsequent bipolar membrane electrodialysis process;

[0064] S4 (Lithium extraction by adsorption): The above-mentioned pH-adjusted boron removal qualified solution is subjected to lithium extraction by adsorption using an aluminum-based lithium adsorbent to obtain Li +A qualified solution for lithium extraction with a concentration of ≥500 mg / L, wherein the process of lithium extraction by adsorption is implemented in the second continuous ion exchange device, and in the adsorption zone of the second continuous ion exchange device, the tail brine after lithium extraction by adsorption can be transported to the salt pan for drying and comprehensive utilization; in the water washing zone of the second continuous ion exchange device, pure water is used to rinse the adsorption column by upper feeding, and the qualified boron removal solution remaining in the adsorption column is pushed out and returned for re-adsorption and lithium extraction;

[0065] S5 (purification and concentration): the qualified lithium extraction solution obtained after the above-mentioned adsorption and lithium extraction is purified and concentrated by multi-stage nanofiltration to obtain battery-grade lithium salt;

[0066] Alternatively, the qualified lithium extraction liquid is purified and concentrated by multi-stage nanofiltration, and then subjected to bipolar membrane electrodialysis treatment 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 liquid.

[0067] The following examples further illustrate the method for extracting lithium by adsorption from raw brine of magnesium sulfate subtype salt lake and its application. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0068] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0069] Example 1

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

[0071] (1) Pretreatment of raw brine

[0072] The original brine of magnesium sulfate subtype salt lake is pretreated through a multi-media filter to obtain brine with a suspended matter concentration of 3 mg / L;

[0073] (2) Boron removal treatment

[0074] In the first continuous ion exchange device in this step, 15 resin adsorption columns formed by boron removal ion exchange resin are configured, and an adsorption zone, a water washing material zone, an acid desorption zone, a water washing acid zone and a qualified liquid top water zone are sequentially configured, and the resin adsorption column is continuously operated in the adsorption zone, the water washing material zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone. During the continuous operation process, the adsorption zone has 8 resin adsorption columns, and is connected in a four-parallel and two-series manner, the water washing material zone has 3 resin adsorption columns, which are connected in a three-column series manner, the acid desorption zone has 2 resin adsorption columns, which are connected in a two-column series manner, and the water 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 in the first continuous ion exchange device, and after the boron is removed by the two-stage resin column of the adsorption zone in the above feeding mode, a boron-removed qualified liquid is obtained and enters the boron-removed qualified liquid tank, and a mixed sample in the boron-removed qualified liquid is taken to detect the boron element of 18 mg / L; in the water washing material zone, pure water is used to wash the resin adsorption column by the upper feeding mode, and the original brine remaining in the adsorption column is pushed out to prevent boron loss, and the front end of the water outlet is returned to the raw material tank for re-adsorption and boron removal; in the acid desorption zone, dilute hydrochloric acid is used to desorb the boron element complexed in the resin by the upper feeding mode, and the high-boron desorption liquid after desorption is transported to the rear end for the preparation of industrial-grade boric acid; in the water washing acid zone, pure water is used to wash the resin adsorption column by the upper feeding mode, and 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 said boron-removed qualified liquid is used to evacuate the adsorption particles in the resin adsorption column by the lower feeding mode to make them evenly distributed;

[0076] (3) Lithium extraction by adsorption

[0077] In the second continuous ion exchange device in this step, 30 adsorption columns formed by aluminum-based lithium adsorbents are configured, and adsorption zones, water-washing zones, desorption zones and qualified liquid top water zones are configured in sequence, and the adsorption columns are continuously operated in the adsorption zones, water-washing zones, desorption zones and qualified liquid top water zones. During the continuous operation, the adsorption zone has 16 adsorption columns, which are connected in eight parallel and two series, the water-washing zone has 5 adsorption columns, which are connected in five columns in series, the desorption zone has 8 adsorption columns, which are connected in two parallel and four series, and the qualified liquid top water zone has 1 adsorption column.

[0078] The hydrochloric acid produced by bipolar membrane electrodialysis is added to the qualified deboronation liquid obtained in step (2) at a volume ratio of 1000:1, and the pH value of the qualified deboronation liquid is adjusted to 6.8. The qualified deboronation liquid with a pH value of 6.8 is then transported to the adsorption zone of the second continuous ion exchange device, and after being adsorbed and extracted with lithium by two-stage adsorption columns in the above feeding method, it enters the tail liquid tank. After detection, the lithium content in the tail brine is 10 mg / L, and the tail brine can be transported to the salt field for drying and comprehensive utilization; then, the adsorption column is quickly rinsed with pure water in the upper feeding method, and the qualified deboronation liquid remaining in the adsorption column is pushed out and returned to the qualified deboronation liquid tank for re-adsorption and lithium extraction; then, the adsorption column is desorbed by 40° C. pure water in the upper feeding method, and the lithium adsorbed in the adsorption column is desorbed into the pure water to obtain a qualified lithium extraction liquid, and the obtained qualified lithium extraction liquid is transported to a storage tank for storage, and finally, the tail liquid after the deboronation and lithium extraction is used to absorb the residual desorption liquid in the adsorption column in the lower feeding method to avoid contamination of the next link. After 70 cycles of operation, the qualified lithium extraction solution was tested to contain the following components: Li + =732mg / L, Mg 2+ =0.421 g / L, Na + =0.591 g / L, K + =0.141 g / L, B 3+ =16 mg / L. The calculated lithium ion recovery rate and lithium extraction efficiency are shown in Table 1.

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

[0080] Example 2

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

[0082] (1) Pretreatment of raw brine

[0083] The original brine of magnesium sulfate subtype salt lake is pretreated through a multi-media filter to obtain brine with a suspended matter concentration of 2 mg / L;

[0084] (2) Boron removal treatment

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

[0086] The brine filtered in step (1) is transported to the adsorption zone in the first continuous ion exchange device, and after the boron is removed by the two-stage resin column of the adsorption zone in the above feeding mode, a qualified boron removal liquid is obtained and enters the qualified boron removal liquid tank, and a mixed sample of the qualified boron removal liquid is taken to detect the boron element of 15 mg / L; in the water washing material zone, pure water is used to wash the resin adsorption column by the upper feeding mode, and the original brine remaining in the adsorption column is pushed out to prevent boron loss, and the front end of the water outlet is returned to the raw material tank for re-adsorption and boron removal; in the acid desorption zone, dilute hydrochloric acid is used to desorb the boron element complexed in the resin by the upper feeding mode, and the high-boron desorption liquid after desorption is transported to the rear end for the preparation of industrial-grade boric acid; in the water washing acid zone, pure water is used to wash the resin adsorption column by the upper feeding mode, and 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 liquid top water zone, the qualified boron removal liquid is used to evacuate the adsorption particles in the resin adsorption column by the lower feeding mode to make them evenly distributed;

[0087] (3) Lithium extraction by adsorption

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

[0089] The hydrochloric acid produced by bipolar membrane electrodialysis is added to the qualified deboronation liquid obtained in step (2) at a volume ratio of 1000:1, and the pH value of the qualified deboronation liquid is adjusted to 6.4. The qualified deboronation liquid with a pH value of 6.4 is then transported to the adsorption zone in the second continuous ion exchange device, and after being adsorbed and extracted with lithium by two-stage adsorption columns in the above feeding method, it enters the tail liquid tank. After detection, the lithium content in the tail brine is 14 mg / L, and the tail brine can be transported to the salt field for drying and comprehensive utilization; then, the adsorption column is quickly rinsed with pure water in the upper feeding method, and the qualified deboronation liquid remaining in the adsorption column is pushed out and returned to the qualified deboronation liquid tank for re-adsorption and lithium extraction; then, the adsorption column is desorbed by 40° C. pure water in the upper feeding method, and the lithium adsorbed in the adsorption column is desorbed into pure water to obtain a qualified lithium extraction liquid, and the obtained qualified lithium extraction liquid is transported to a storage tank for storage, and finally, the tail liquid after the deboronation and lithium extraction is used to absorb the residual desorption liquid in the adsorption column in the lower feeding method to avoid contamination of the next link. After 70 cycles of operation, the qualified lithium extraction solution was tested to contain the following components: Li + =693mg / L, Mg 2+ =0.413 g / L, Na + =0.522 g / L, K + =0.111 g / 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 salt lake original brine used in this example contains the following components: Li + =311mg / L, Mg 2+ =33.723 g / L, Na + =70.93g / L, K + =12.522g / L, B 3+ =0.526 g / L, and pH is 7.6.

[0092] (1) Pretreatment of raw brine

[0093] The original brine of magnesium sulfate subtype salt lake is pretreated through a multi-media filter to obtain brine with a suspended matter concentration of 4 mg / L;

[0094] (2) Boron removal treatment

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

[0096] The brine filtered in step (1) is transported to the adsorption zone in the first continuous ion exchange device, and after the boron is removed by the two-stage resin column of the adsorption zone in the above feeding mode, a qualified boron removal liquid is obtained and enters the qualified boron removal liquid tank, and a mixed sample of the qualified boron removal liquid is taken to detect the boron element of 10 mg / L; in the water washing material zone, pure water is used to wash the resin adsorption column by the upper feeding mode, and the original brine remaining in the adsorption column is pushed out to prevent boron loss, and the front end of the water outlet is returned to the raw material tank for re-adsorption and boron removal; in the acid desorption zone, dilute hydrochloric acid is used to desorb the boron element complexed in the resin by the upper feeding mode, and the high-boron desorption liquid after desorption is transported to the rear end for the preparation of industrial-grade boric acid; in the water washing acid zone, pure water is used to wash the resin adsorption column by the upper feeding mode, and 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 liquid top water zone, the qualified boron removal liquid is used to evacuate the adsorption particles in the resin adsorption column by the lower feeding mode to make them evenly distributed;

[0097] (3) Lithium extraction by adsorption

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

[0099] The hydrochloric acid produced by bipolar membrane electrodialysis is added to the qualified deboronation liquid obtained in step (2) at a volume ratio of 1000:1, and the pH value of the qualified deboronation liquid is adjusted to 6.6. The qualified deboronation liquid with a pH value of 6.6 is then transported to the adsorption zone in the second continuous ion exchange device, and after being adsorbed and extracted with lithium by two-stage adsorption columns in the above feeding method, it enters the tail liquid tank. After detection, the lithium content in the tail brine is 21 mg / L, and the tail brine can be transported to the salt field for drying and comprehensive utilization; then, the adsorption column is quickly rinsed with pure water in the upper feeding method, and the qualified deboronation liquid remaining in the adsorption column is pushed out and returned to the qualified deboronation liquid tank for re-adsorption and lithium extraction; then, the adsorption column is desorbed by 40° C. pure water in the upper feeding method, and the lithium adsorbed in the adsorption column is desorbed into pure water to obtain a qualified lithium extraction liquid, and the obtained qualified lithium extraction liquid is transported to a storage tank for storage, and finally, the tail liquid after the deboronation and lithium extraction is used to absorb the residual desorption liquid in the adsorption column in the lower feeding method to avoid contamination of the next link. After 70 cycles of operation, the qualified lithium extraction solution was tested to contain the following components: Li + =639mg / L, Mg 2+ =0.398 g / L, Na + =0.24 g / L, K + =0.054 g / 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 of Example 1 is followed, except that in step (3), the pH value of the boron removal qualified solution is adjusted to 6.

[0102] As a result, the lower pH environment has an adverse effect on the adsorbent structure, causing its lithium extraction efficiency to decrease significantly under long-term cycling conditions.

[0103] After 70 cycles of operation, the qualified lithium extraction solution was tested to contain the following components: Li + =759mg / L, Mg 2+ =0.41 g / 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 followed, except that in step (3), the pH value of the boron removal qualified solution is adjusted to 7.5.

[0106] As a result, the higher pH environment adversely affects the adsorbent structure, 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 to contain the following components: Li + =401mg / 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 removal solution obtained after the boron removal treatment has a B 3+ The concentration is 70mg / L.

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

[0111] After 150 cycles of operation, the qualified lithium extraction solution was tested to contain the following components: Li + =572mg / L, Mg 2+ =0.34 g / L, Na + =0.31 g / 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) filtering the original brine of the magnesium sulfate subtype salt lake through a multi-media filter to obtain brine with a suspended matter concentration of 3 mg / L;

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

[0115] As a result, the boron removal operation was not performed, and under long-term cycle conditions, incomplete boron removal would lead to a significant decrease in the lithium ion recovery rate.

[0116] After 70 cycles of operation, the qualified lithium extraction solution was tested to contain the following components: Li + =394mg / 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 This is a graph showing the change in adsorption capacity of the raw halide without boron removal for direct adsorption and lithium extraction in Comparative Example 4. After 40 "adsorption-desorption" cycles, the adsorption capacity of the adsorbent decreases significantly, and decreases by about 50% after 70 cycles.

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

[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] It can be seen from the data in Table 1 that the method for extracting lithium by adsorption from raw brine of magnesium sulfate subtype salt lakes of the present invention is to remove boron before the adsorption lithium extraction process, so as to reduce the influence of low lithium extraction efficiency of the adsorbent caused by the boron element, and both the lithium ion recovery rate and the lithium extraction efficiency can reach more than 90% at the same time. It has the characteristics of high lithium ion recovery rate and high lithium extraction efficiency, and can maintain good lithium extraction efficiency by adsorption under long-term operation. It is suitable for industrial application in the preparation of battery-grade lithium hydroxide and battery-grade lithium salts from raw brine of magnesium sulfate subtype salt lakes.

[0122] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for extracting lithium by adsorption from raw brine of magnesium sulfate subtype salt lake, characterized in that: The method comprises the following steps: (1) pretreating the original brine of magnesium sulfate subtype salt lake to obtain brine with a suspended matter concentration of ≤4 mg / L; (2) using a boron removal ion exchange resin to remove the boron from the brine obtained after the treatment in step (1) to obtain B 3+ Qualified boron removal solution with a concentration of ≤20mg / L; (3) The pH value of the qualified boron removal solution is adjusted to 6.4-6.8, and then an aluminum-based lithium adsorbent is used to adsorb and extract lithium.

2. The method according to claim 1, characterized in that In step (1), the magnesium sulfate subtype salt lake original 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.

3. The method according to claim 1 or 2, characterized in that: In step (1), the pretreatment process includes filtering the magnesium sulfate subtype salt lake original brine using a filter; Preferably, the filter is at least one of a disc ceramic membrane filter, a multi-media multi-filter and a security filter.

4. The method according to claim 1, characterized in that In step (2), the boron removal treatment process is implemented 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 in sequence, and a plurality of resin adsorption columns formed by the boron removal ion exchange resin are continuously operated in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, wherein: In the adsorption zone, the brine obtained after the treatment in step (1) enters the resin adsorption column through the upper feeding method for adsorption to obtain the boron-removed qualified liquid.

5. The method according to claim 4, characterized in that In the water washing area, pure water is used to wash the resin adsorption column by upper feeding; In the acid desorption zone, hydrochloric acid is used to desorb the resin adsorption column by upper feeding method; In the water washing acid zone, pure water is used to wash the resin adsorption column by upper feeding method; In the qualified liquid top water zone, the qualified boron removal liquid is fed downward to disperse the adsorption particles in the resin adsorption column.

6. The method according to claim 5, characterized in that The concentration of hydrochloric acid used in the acid desorption zone is 3-10 wt %, preferably 5-7 wt %.

7. The method according to any one of claims 4 to 6, characterized in that: The number of resin adsorption columns configured in the first continuous ion exchange device is 15, and during continuous operation, the adsorption zone has 8 resin adsorption columns, which are connected in a four-in-parallel and two-in-series manner, the water washing zone has 3 resin adsorption columns, which are connected in a three-column series manner, the acid desorption zone has 2 resin adsorption columns, which are connected in a two-column series manner, and the water washing acid zone and the qualified liquid top water zone each have one resin adsorption column.

8. The method according to claim 1, characterized in that In step (3), the process of adsorption and lithium extraction is implemented in a second continuous ion exchange device, which comprises an adsorption zone, a water washing zone, a desorption zone and a qualified liquid top water zone arranged in sequence, and a plurality of adsorption columns formed by the aluminum-based lithium adsorbent are continuously operated in the adsorption zone, the water washing zone, the desorption zone and the qualified liquid top water zone, wherein: In the adsorption zone, the qualified boron removal solution after pH adjustment enters the resin adsorption column through the upper feeding method for adsorption to obtain the qualified lithium extraction solution.

9. The method according to claim 8, characterized in that 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.

10. The method according to claim 8, characterized in that In the water washing zone, pure water is used to wash the adsorption column by upper feeding; In the desorption zone, pure water desorbs the adsorption column by upper feeding; In the qualified liquid top water zone, the qualified lithium extraction liquid absorbs the residual liquid in the adsorption column by a bottom feeding method.

11. The method according to any one of claims 8 to 10, characterized in that: The number of adsorption columns configured in the second continuous ion exchange device is 30, and during continuous operation, the adsorption zone has 16 adsorption columns, which are connected in an eight-in-two series manner, the water washing zone has 5 adsorption columns, which are connected in a five-column series manner, the desorption zone has 8 adsorption columns, which are connected in a two-in-four series manner, and the qualified liquid top water zone has 1 adsorption column.

12. A method for preparing battery-grade lithium hydroxide from magnesium sulfate subtype salt lake raw brine, characterized in that: The method comprises: extracting lithium by adsorption according to the method described in any one of claims 1 to 11, purifying and concentrating the obtained qualified lithium extraction solution and performing bipolar membrane electrodialysis.

13. The method according to claim 12, characterized in that 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 is used to adjust the pH value of the boron removal qualified solution.

14. A method for preparing battery-grade lithium salt from magnesium sulfate subtype salt lake original brine, characterized in that: The method comprises: extracting lithium by adsorption according to the method described in any one of claims 1 to 11, and purifying and concentrating the obtained qualified lithium extraction solution.

15. The method according to claim 14, characterized in that The purification and concentration process adopts at least one of multi-stage nanofiltration, MVR concentration and electrodialysis concentration.

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