METHOD FOR EXTRACTING LITHIUM FROM SALTY LAKE BRINE

Abstract

This disclosure provides a method for extracting lithium from salt lake brine, comprising: (1) flowing the salt lake brine through a lithium adsorbent at a variable rate, to allow the lithium ions present in the salt lake brine to be adsorbed onto said adsorbent, in order to obtain a lithium-rich adsorbent, wherein during the adsorption process the flow rate of the salt lake brine is gradually decreased, and a difference between the initial flow rate and the final flow rate of the salt lake brine is 0.5 - 3 BV / h; (2) washing the lithium-rich adsorbent; and (3) desorbing the lithium ions from the washed lithium-rich adsorbent with a lithium-ion eluent, to obtain a desorption solution.

Description

/ 1 LITHIUM EXTRACTION METHOD FROM LAKE BRINE SALTY FIELD

[0001] The present disclosure relates to the fields of environmental protection and resource recycling, and specifically, to a method for extracting lithium from salt lake brine. BACKGROUND

[0002] Most of China's lithium resources are stored in salt lake brine, which is mostly brine with a high magnesium-lithium ratio. Therefore, the extraction of lithium from brine with a high magnesium-lithium ratio has become a focus in the development of lithium resources in China. The newly developed adsorption method is widely used due to its good selectivity to lithium ions, simple process, ability to extract lithium from salt lake brine with a high magnesium-lithium ratio, low cost, and other advantages.

[0003] However, the lithium extraction process by the adsorption method has the problem of low adsorption efficiency for lithium, and the difficulty of producing a qualified desorption solution with a high lithium content at low temperature (such as in winter). SUMMARY

[0004] In view of this, the present disclosure provides a method for extracting lithium from salt lake brine, wherein a variable rate adsorption process is employed. 2100597 of 30 / 1 in the brine adsorption stage, greatly improving the adsorption efficiency of the lithium present in the brine and solving the problem of the difficulty in obtaining a qualified desorption solution with a high lithium content at low temperatures. This ensures uninterrupted production throughout the year.

[0005] The present disclosure provides a method for extracting lithium from salt lake brine, including the following steps: (1) flowing the salt lake brine through a lithium adsorbent at a variable speed, to allow lithium ions in the salt lake brine to be adsorbed on said adsorbent, so as to obtain a lithium-rich adsorbent, where during the adsorption process, the flow rate of the salt lake brine gradually decreases, and a difference between the initial flow rate of the salt lake brine and the final flow rate of the salt lake brine is 0.5-3 BV / h; (2) washing the lithium-rich adsorbent; and (3) desorbing lithium ions from the washed lithium-rich adsorbent with a lithium ion eluent, to obtain a desorption solution.

[0006] In the method for extracting lithium from salt lake brine provided in the present disclosure, a variable rate adsorption process is employed in which the flow rate of the brine gradually decreases in the stage of adsorbing the salt lake brine, so as to greatly improve the adsorption efficiency of lithium present in the brine, and achieve high-efficiency adsorption of lithium at low temperature (below zero degrees Celsius). As a result, a desorption solution having a lithium content of 500 mg / L or higher can be obtained without affecting the production capacity. With the same adsorption time (e.g., 180 min), while the production capacity is 2100597 of 30 / 1 remains unchanged, the lithium content in the desorption solution obtained by the lithium extraction method of the present disclosure is much higher than the lithium content in a desorption solution obtained by a conventional lithium extraction method using a brine adsorption process with a constant flow rate (generally around 400 mg / L).

[0007] In the present disclosure, the flow rate of the salt lake brine varies with time during the adsorption process, and the flow rate gradually decreases as the adsorption progresses. The difference between the initial flow rate of the salt lake brine and the final flow rate of the salt lake brine is 0.5-3 BV / h, for example, 0.8 BV / h, 1 BV / h, 1.2 BV / h, 1.5 BV / h, 1.8 BV / h, 2 BV / h or 2.5 BV / h. An appropriate difference between the initial flow rate and the final flow rate is conducive to improving the adsorption efficiency of lithium present in the brine.

[0008] The initial flow rate and the final flow rate may be defined according to the rate-varying brine adsorption process. If the brine flow rate is constantly decreasing, the initial flow rate is the flow rate of the brine that first passes through the lithium adsorbent when adsorption starts, and the final flow rate is the flow rate of the brine that finally passes through said adsorbent when adsorption is about to end. If the brine flow rate is discretely decreased in steps, i.e., the brine flow rate has n different values ​​(n is defined, and the flow rates may be Vi, V2,...and Vn) during the adsorption process, the first flow rate interval (the flow rate is Vi) is the initial flow rate of the brine, the last flow rate interval (i.e., the nth flow rate interval, the flow rate is. 2100597 of 30 / 1 Vn) is the final flow rate. If the total amount of brine to be adsorbed is Q (in Bv), the amount of brine flowing through the adsorbent in each flow rate interval can be Q / n. The flow rate of the first Q / n BV of salt lake brine through the lithium adsorbent is called the initial flow rate. The flow rate of the last Q / n BV of salt lake brine through the lithium adsorbent is called the final flow rate. For example, when 6 BV of salt lake brine needs to be adsorbed, and each BV of brine flows through the lithium adsorbent respectively at a flow rate of 2.5 BV / h, 2.3 BV / h, 2.1 BV / h, 2.0 BV / h, 1.8 BV / h, and 16 BV / h, where the initial flow rate of brine is 2.5 BV / h, the final flow rate is 1.6 BV / h, and the adsorption time of each brine was respectively 24 min, 26 min, 28.6 min, 30 min, 33 min, and 37.5 min.

[0009] In some embodiments of the present disclosure, the initial flow rate is 2.0-3.0 BV / h, and the final flow rate is 1.2-1.8 BV / h. Compared to a brine adsorption process with a constant flow rate, with such initial flow rate and final brine flow rate, the adsorption efficiency of lithium present in the brine can be increased by 5%-20%. BV generally refers to the filling volume of the lithium adsorbent, and 2.0-3.0 BV / h (same below) represents that the flow rate of the brine by volume is 2-3 times the volume of the lithium adsorbent per hour. In some embodiments, the initial flow rate may specifically be 2.0 BV / h, 2.1 BV / h, 2.2 BV / h, 2.3 BV / h, 2.4 BV / h, 2.5 BV / h, 2.6 BV / h, 2.7 BV / h, 2.8 BV / h, 2.9 BV / h, or 3.0 BV / h. The final flow rate may specifically be 1.2 BV / h, 1.3 BV / h, 1.4 BV / h, 1.5 BV / h, 1.6 BV / h, 1.7 BV / h, or 1.8 BV / h.

[0010] In some embodiments of the present disclosure, during the adsorption process, a total amount of the salt lake brine to be adsorbed is 6-8 BV. That is, the 2100597 of 30 / 1 volume of salt lake brine to be contacted with the lithium adsorbent is 6-8 times the loading volume of said adsorbent. The amount of salt lake brine to be adsorbed may vary depending on the lithium level in the salt lake brine (typically 180-300 ppm). In some embodiments of the present disclosure, the total adsorption time may be 2.5-4 h, for example, 2.8 h, 3 h, 3.5 h and 3.8 h.

[0011] In some embodiments of the present disclosure, in Step (1), before the salt lake brine flows through the lithium adsorbent at a variable rate, the method further includes filtering the brine to remove impurities (e.g., particulate impurities) therein. The filtration may sequentially include: high speed centrifugal filtration and backwash filtration. The high speed centrifugal filtration is primarily used to remove large particle sediments. The high speed centrifugal filtration may be carried out in a solid-liquid centrifugal separator at a centrifugation speed of 15,000-35,000 rpm.Backwash filtration is provided for additional polishing filtration, reducing solid impurities in the salt lake brine. This ensures that the material after filtration does not affect the adsorption function of the lithium adsorbent. The filtered impurities can be easily backwashed without frequently replacing filter consumables. Backwash filtration can be performed with a stainless steel mesh backwash filter.

[0012] In the present disclosure, lithium extraction from salt lake brine is achieved by adsorption. The lithium adsorbent may be packed in a carrier, such as an exchange column (e.g., a glass or stainless steel column) or an adsorption tower. As the salt lake brine flows through the carrier containing the lithium adsorbent, the adsorbent may be packed in a carrier such as an exchange column (e.g., a glass or stainless steel column) or an adsorption tower. 2100597 of 30 / 1 lithium adsorbent, and is brought into contact with said adsorbent, lithium ions contained therein may be adsorbed and fixed by the lithium adsorbent, during which said adsorbent is also transformed into a lithium-rich adsorbent with adsorbed lithium.

[0013] In one embodiment of the present disclosure, the lithium adsorbent used may include an adsorbent material and a binder. The adsorbent material may be, for example, an aluminum-based adsorbent material, a manganese-based adsorbent material (such as a combination of spinel-type manganese oxide and lithium ions), a titanium-based adsorbent material (such as a lithium metatitanate ion sieve adsorbent), and an iron-based adsorbent, etc. In some embodiments of the present disclosure, the adsorbent material is an aluminum-based adsorbent material. The aluminum-based adsorbent material may be a combination of aluminum hydroxide and a lithium-containing compound (such as lithium halide and lithium sulfate, etc.). The adsorbent material can adsorb lithium ions from a lithium-containing solution.After reaching saturated adsorption, lithium ions are eluted with water at a certain temperature to release them into a solution. In some embodiments, the aluminum-based adsorbent material may be represented by LiaX^mAl(OH)3mH2O, where X may be Cl-, and SO42-; a = 1 or 2; m is 1-5; and n is 1-5. In some embodiments, m may be 2. Furthermore, to provide higher lithium adsorption capacity of the lithium adsorbent of the present disclosure, before flowing the salt lake brine through said adsorbent at a variable rate, a desorption of the lithium ions from the lithium adsorbent is performed in order to allow the adsorbent material to have more lithium vacancies. The aluminum-based adsorbent material after lithium desorption can be expressed as (1-x)LiaX / mAl(OH)3mH2O, where 0 <x<1. El material adsorbente a base de aluminio puede sintetizarse por un método mecanoquímico, o por remojo,. 2100597 of 30 / 1 conversion by acidification and precipitation, etc. For example, LiCl-mAl(OH)3-nH2Ü can be prepared by soaking aluminum hydroxide in a LiCl solution, or by immersing aluminum hydroxide in a LiOH solution followed by acidification and conversion, or by coprecipitation of AlCl3 and a LiCl solution, or by crushing LiOH and aluminum hydroxide.

[0014] The binder may be one or more of the following resins: epoxy resin, phenolic resin, polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyvinylidene fluoride, ethylene-vinyl acetate copolymer, vinylidenechlorotrifluoroethylene fluoride copolymer (called VDF-CTFE copolymer) or fluoroolefin-vinyl ether copolymer (also called FEVE type fluorocarbon resin).

[0015] In some embodiments, the binder is at least one of the following: a vinylidene fluoride-chlorotrifluoroethylene copolymer or a fluoroolefin-vinyl ether copolymer. In this case, the lithium adsorbent also includes a wetting and dispersing agent, and the wetting and dispersing agent comprises one or more of polyethylene glycol, sodium polyacrylate, polyvinyl alcohol, or a formaldehyde condensate. Exemplary formaldehyde condensates may include, but are not limited to, one or more of a formaldehyde naphthalenesulfonate condensate, a formaldehyde methylnaphthalenesulfonate condensate, a formaldehyde benzylnaphthalenesulfonate condensate, a formaldehyde phenolsulfonate condensate, or the like.

[0016] By using vinylidene fluoride-chlorotrifluoroethylene copolymer and / or fluoroolefin-vinyl ether copolymer as a binder, the lithium adsorbent not only exhibits higher structural stability and mechanical strength, good corrosion resistance, low dissolution loss rate and long adsorbent life after multiple lithium absorption and desorption cycles, but also exhibits a porosity and a state of 2100597 of 30 / 1 suitable surface area with a narrow pore size. As a result, the lithium adsorbent has a high lithium adsorption efficiency; the adsorption rate and efficiency of the adsorbent will not be affected due to the reduction of the effective active surface area. The wettability of the wetting and dispersing agent also contributes to improving the adsorption efficiency and adsorption capacity of the adsorbent for lithium ions. Furthermore, with the synergistic effect of the excellent surface uniformity and cleaning effect of the two binders and the wettability of the wetting and dispersing agent, the lithium adsorbent is easy to clean after adsorbing lithium, and the lithium desorption process is convenient.This saves water in the cleaning and desorption process, reduces the rate of adsorbent dissolution loss in these processes, and lowers the desorption temperature, making it of great importance for industrialized lithium extraction in areas with significant energy shortages, such as salt lakes. The resulting solution is qualified with a low magnesium-to-lithium ratio and a high lithium content.

[0017] In some embodiments of the present disclosure, the molecular weight of the vinylidene fluoride-chlorotrifluoroethylene copolymer or the fluoroolefin-vinyl ether copolymer may be 100,000-800,000. An appropriate high molecular weight binder has a better bonding effect and reduces the risk of cracking and breakage of the lithium adsorbent during use, thereby extending its service life. In the vinylidene fluoride-chlorotrifluoroethylene copolymer, the copolymerization ratio of vinylidene fluoride and chlorotrifluoroethylene may be 1:(1-5). In some embodiments, the copolymerization ratio of vinylidene fluoride and chlorotrifluoroethylene may be 1:4. In some embodiments, the binder is a vinylidene fluoride-chlorotrifluoroethylene copolymer, or a blend of a vinylidene fluoride-chlorotrifluoroethylene copolymer and a fluoroolefin-ether copolymer. 2100597 30 / 1 vinyl.

[0018] In some embodiments of the present disclosure, a molecular weight of the formaldehyde condensate is 4,000-10,000; and a molecular weight of the sodium polyacrylate is 5,000-10,000.

[0019] In some embodiments of the present disclosure, the wetting and dispersing agent is polyethylene glycol. Polyethylene glycol has good wetting and dispersing capabilities. In some embodiments, a molecular weight of the polyethylene glycol is 10,000-30,000. Higher molecular weight polyethylene glycol is less soluble in water with the adsorbent, causing the adsorbent to have a longer useful life.

[0020] In one embodiment of the present disclosure, based on the weight of the lithium adsorbent, a content of the adsorbent material is 80-95 wt. %, a content of the binder is 4-17 wt. %, and a content of the wetting and dispersing agent is 1-5 wt. % With a combination of the adsorbent material, the binder, and the wetting and dispersing agent in a suitable ratio, the lithium adsorbent has good structural stability, adsorption effect, and desorption effect. In some embodiments, the content of the adsorbent material is 85-92 wt. % In some embodiments, the content of the binder is 5-15 wt. %, and in some embodiments, the content of the binder is 6-12 wt. % In some embodiments, the content of the wetting and dispersing agent is 1-3 wt. %.

[0021] In some embodiments of the present disclosure, the binder accounts for 812.5% ​​by weight of the adsorbent material. An appropriate amount of the binder can not only ensure high structural stability and long service life (not easy to break) of the lithium adsorbent, but also weaken its reducing effect on the adsorption capacity of the obtained lithium adsorbent. 2100597 of 30 / 1

[0022] In one embodiment of the present disclosure, the wetting and dispersing agent represents 1-5% by weight of the adsorbent material. At this time, the wetting and dispersing agent allows the adsorbent material to be more uniformly distributed in the lithium adsorbent particles, the structure to be more stable, and the lithium adsorbent particles to have better wettability and therefore a higher lithium adsorption / desorption rate. Furthermore, the wetting and dispersing agent can also dissolve relatively slowly in the brine, so as to slowly increase the porosity of the lithium adsorbent, thereby further improving the adsorption efficiency of said adsorbent without causing a significant impact on the dissolution loss rate of the adsorbent and obviously without reducing the lifetime thereof.

[0023] In some embodiments of the present disclosure, the ratio of the weight of an adsorbent material to the total weight of the binder and the wetting and dispersing agent is 8:1 or more. This contributes to the good structural stability and excellent adsorption and desorption performance of the lithium adsorbent. In some embodiments, the ratio may be in the range of (8-10):1. In some embodiments, the ratio may be 8.5, 9:1, or 9.5:1.

[0024] In one embodiment of the present disclosure, the lithium adsorbent may be columnar particles. The columnar particles of the lithium adsorbent may be formed in a simple manner and have surface uniformity to prevent wear and dust due to compression and friction against each other during use, and reduce loss. In some embodiments, the particle size of the lithium adsorbent is 1.2 mm-1.8 mm, and the length is 1.5 mm-2.5 mm. A lithium adsorbent with such a shape and size provides a more suitable path for diffusion of a liquid and ions, and when the adsorbent is compressed, it is easy to leave some space to facilitate the penetration of brine, thereby facilitating the improvement of the adsorption efficiency of lithium ions, contributing to ion exchange. 2100597 of 30 / 1 between lithium ions and water during the desorption process, thereby reducing the lithium desorption temperature and the amount of desorption water to ensure complete desorption of the adsorbed lithium.

[0025] According to the present disclosure, in Step (2), washing the lithium-rich adsorbent is performed mainly to remove impurities from the surface of the lithium-rich adsorbent that has adsorbed lithium ions. In one embodiment of the present disclosure, the washing includes a first wash, a second wash, and a third wash. The flow rate of a first detergent in the first wash, the flow rate of a second detergent in the second wash, and the flow rate of a third detergent in the third wash increase sequentially (i.e., the flow rate of the first detergent < the flow rate of the second detergent < the flow rate of the third detergent). An amount of the second detergent is greater than an amount of the first detergent and an amount of the third detergent. The amount of the first detergent and the amount of the third detergent may be the same or different.

[0026] The above-mentioned washing process of the lithium-rich adsorbent is carried out in three steps in which the flow rate is increased from slow to fast. In the first washing, the flow rate is slow, to avoid the difficulty of removing impurities from the brine caused by the formation of a coagulation layer due to a large amount of high-concentration brine at a high flow rate during washing on the support filled with the lithium-rich adsorbent, which greatly reduces the washing effect. In the second washing, the flow rate is moderate and the amount of detergent is large, to ensure a suitable washing time and that impurities such as magnesium adhered to the adsorbent can be completely dissolved and removed. In the third washing, the flow rate is fast, and the 2100597 of 30 / 1 detergent amount is less than the detergent amount of the second wash, to reduce the desorption of lithium adsorbed on the lithium-rich adsorbent in the detergent, and reduce the lithium loss during washing with water. Therefore, the previous washing process can remove impurities from the surface of the lithium-rich adsorbent, so that the weight ratio of magnesium to lithium in the desorption solution obtained by the subsequent desorption is relatively low; the amount of detergents used is small, and the lithium loss rate during washing (i.e., the weight percentage of lithium dissolved in the detergents relative to the total lithium adsorbed by the lithium-rich adsorbent) is 16% or less, or even 15%.

[0027] In some embodiments of the present disclosure, the difference between the flow rate of the detergent in the third wash and the flow rate of the detergent in the first wash may be 5-9 BV / h. At this time, a better washing effect can be obtained.

[0028] In some embodiments of the present disclosure, washing includes three steps, including a first wash, wherein the flow rate of a first detergent is 3-5 BV / h, and the amount of the first detergent is 0.5-1 BV; a second wash, wherein the flow rate of a second detergent is 6-8 BV / h, and the amount of the second detergent is 1-1.5 BV; and a third wash, wherein the flow rate of a third detergent is 912 BV / h, and the amount of the third detergent is 0.5-1 BV.The washing process can effectively remove impurities from the surface of the lithium-rich adsorbent, so that the weight ratio of magnesium to lithium in the desorption solution obtained by subsequent desorption is much lower, for example, as low as 2:1; and the lithium loss rate during washing is much lower, at less than 15%, which is much lower than the lithium loss rate of approximately 20% (or even 25%) caused by a high-speed washing process. 2100597 of 30 / 1 constant commonly used in industry.

[0029] In some embodiments, the amount of the first detergent may be 0.6 BV, 0.7 BV, 0.8 BV, or 0.9 BV; the amount of the second detergent may be 1 BV, 1.2 BV, 1.3 BV, 1.4 BV, or 1.5 BV; and the amount of the third detergent may be 0.6 BV, 0.7 BV, 0.8 BV, or 0.9 BV. Furthermore, in order to reduce the rate of lithium loss during washing, the total amount of each detergent in the washing process is controlled not to exceed 2.5 BV in some embodiments.

[0030] In some embodiments, the duration of the first wash is 6-20 min, and may further be 7-15 min (e.g., 9 min); the duration of the second wash is 7.5-15 min, and may further be 9-13 min (e.g., 11 min); and the duration of the third wash is 2.5-6.6 min (e.g., 4 min). In some embodiments, in Step (2), the total washing time may be controlled to 25 min or less, and may further be 20 min or less. As a result, a better washing effect of the impurities may be achieved, while reducing the lithium loss rate.

[0031] In some embodiments, the washing process includes:

[0032] i) a first wash of the lithium-rich adsorbent with a first detergent (i.e. the first wash detergent), to obtain a first wash effluent and a first adsorbent;

[0033] ii) a second washing of the first adsorbent with a second detergent (i.e. the second wash detergent), to obtain a second wash effluent and a second detergent; and

[0034] iii) a third wash of the second adsorbent with a third detergent (i.e. the detergent from the third wash), to obtain a third wash effluent and a third adsorbent. 2100597 of 30 / 1 third adsorbent is here the lithium-rich adsorbent after washing, and the desorption of the aforementioned Step (3) is also carried out with this.

[0035] In the present disclosure, the first detergent, the second detergent, and the third detergent contain a large amount of water, and each may be pure water, or recycled water (containing some inorganic metal ion impurities); and the composition of each detergent may be different. In some embodiments, the first detergent, the second detergent, and the third detergent are all pure water. In this case, the amount of pure water used is large, and the lithium loss rate during the washing process is slightly higher.

[0036] In some other embodiments, the first detergent and the second detergent are recycled water; and the third detergent is pure water, instead of recycled water, and for example, deionized water, distilled water, clean groundwater, and tap water, etc. By using recycled water in the first two washes, lithium desorption during the washing process is inhibited; and pure water is used in the last wash, the amount of pure water is small, and a good washing effect can be ensured. In some embodiments, each detergent does not contain organic substances, and has a conductivity of 300 μs / cm or less, furthermore 200 μs / cm or less, and furthermore 50 μs / cm or less.

[0037] Furthermore, the magnesium content in the first detergent, the second detergent, and the third detergent decreases sequentially. In some embodiments, the magnesium content in the first detergent is not more than 50 g / L, moreover, not more than 30 g / L, moreover, not more than 10 g / L; the magnesium content in the second detergent is not more than 5 g / L; and the magnesium content in the third detergent is not more than 100 mg / L. In some embodiments, the magnesium ion content in the first detergent is not more than 50 g / L, 2100597 of 30 / 1 and the lithium ion content is not more than 300 mg / L. In some embodiments, the first detergent further includes other metal ions, each with a concentration not more than 10 g / L (calcium, boron, sodium or potassium). The magnesium ion content in the second detergent is not more than 5 g / L, and the lithium ion content is not more than 250 mg / L.

[0038] In some embodiments of the present disclosure, an unqualified desorption solution (produced in a subsequent desorption step) with a lithium concentration of no more than 250 mg / L obtained in the desorption process of Step (3) may be used as a detergent in the second wash (i.e., the second detergent). After the desorption is completed, residual water in the support (such as an adsorption column) packed with the lithium adsorbent may also be discharged and used as a second detergent. A third wash effluent obtained after the third wash or a second wash effluent obtained after the second wash may be used as a detergent in the first wash (i.e., the first detergent). A first wash effluent obtained after the first wash may be fed back to and mixed with salt lake brine.As a result, throughout the entire washing process, only pure water is used in the third wash, so the amount of pure water used is small. This brings great economic and environmental benefits to the extraction of lithium from salt lake brine in water-scarce regions. For example, the second wash effluent generally contains magnesium ions with a concentration of no more than 50 g / L and other metal ions (calcium, lithium, boron, sodium, or potassium), each with a concentration of no more than 10 g / L. The lithium ion concentration can also be 100–200 ppm. The third wash effluent generally contains magnesium ions with a concentration of no more than 10 g / L and other metal ions (e.g., calcium, lithium, boron, sodium, or potassium), each with a concentration of no more than 0.5 g / L. 2100597 of 30 / 1 in addition, the concentration of lithium ions is less than 300 mg / L.

[0039] In Step (3) of the present disclosure, the washed lithium-rich adsorbent is eluted with a lithium ion eluent (also called a lithium desorbent), to desorb lithium ions adsorbed on the lithium-rich adsorbent, so that the lithium ions are eluted and released into the eluent to obtain a desorption solution. The desorption solution can be further treated and used (usually converted into lithium carbonate products). On the other hand, after lithium is desorbed from the lithium-rich adsorbent, the lithium adsorbent can be regenerated and then used in contact with salt lake brine for adsorption lithium extraction. In the lithium extraction method, steps (1)-(3) form a cycle.

[0040] In some embodiments of the present disclosure, the temperature of the lithium ion eluent (i.e., the “desorption process temperature”) may be 30-50°C. In some embodiments (e.g., when using a lithium adsorbent containing a vinylidene fluoride-chlorotrifluoroethylene copolymer and / or a vinyl fluoroolefin ether copolymer as a binder), the temperature may be 30-40°C, e.g., 28°C, 30°C, 32°C, 35°C, 38°C, or 40°C, and further 30-35°C. The lithium ion eluent may be deionized water, distilled water, clean groundwater, or tap water. It is also feasible to use an unqualified desorption solution that does not meet the lithium concentration requirements (generated at a later stage of desorption) for lithium desorption in an order from high to low, in order to obtain a qualified desorption solution with the maximum lithium content.

[0041] In some embodiments, the flow rate of the lithium ion eluent is 1.5-2.5 BV / h, for example, 1.8 BV / h, 2 BV / h and 2.2 BV / h. This may ensure that the content 2100597 of 30 / 1 of lithium ions in the desorption solution is relatively high, and the desorption time will not be too long. In some embodiments, the desorption time of lithium ions from the washed lithium-rich adsorbent is 2.5-4 h, for example, 2.8 h, 3 h, 3.5 h, and 3.8 h.

[0042] In the method of extracting lithium from salt lake brine described in the present disclosure, a variable rate adsorption process is employed in the stage of adsorbing the salt lake brine, to effectively improve the adsorption efficiency of lithium in brines, thereby solving the problem that it is difficult to obtain a qualified desorption solution with high lithium content at low temperature (brine usually does not freeze in winter at a temperature of up to minus ten degrees Celsius). This ensures uninterrupted production throughout the year. The method of extracting lithium from salt lake brine has a simple process and a high lithium extraction and recovery rate, making it suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0001] FIG. 1 shows a flow diagram of a method for extracting lithium from salt lake brine provided in an embodiment of the present disclosure; and

[0002] FIG. 2 shows a flow diagram of a method for extracting lithium from salt lake brine provided in another embodiment of the present disclosure. DETAILED DESCRIPTION

[0043] The technical solutions of the embodiments of the present disclosure are described in detail below in combination with multiple examples.

[0044] The composition of salt lake brine used for lithium extraction 2100597 of 30 / 1 in the following examples is shown in Table 1. Table 1 Salt lake brine composition Li (%) 0.0138 Na (%) 0.2325 Mg (%) 7.0719 K (%) 0.6241 Ca (%) 0.2970 B (%) 0.0133 Cl- (%) 22.7497 SO42- (%) 0.0577 Mg:Li 222.4

[0045] Example 1

[0046] A flow diagram of a method for extracting lithium from salt lake brine is shown in FIG. 1. The method includes the following steps:

[0047] (1) Adsorption:

[0048] A lithium adsorbent (including an aluminum-based adsorbent material LiCT2Al(OH)3mH2O and a polyvinylidene fluoride binder, in a weight ratio of 9:1) is packed in a glass adsorption column in an amount of 0.9 dm3.

[0049] The salt lake brine for lithium extraction is sequentially subjected to high speed centrifugal filtration and backwash filtration, and then flowed through the adsorption column packed with the lithium adsorbent at a variable rate, to allow lithium ions present therein to adsorb on the adsorbent and transform the adsorbent into a lithium-rich adsorbent. The temperature during 2100597 of 30 / 1 the adsorption process is 25 °C, the amount of brine to be adsorbed is 6 BV and 5400 ml in total. The flow rate (i.e., the initial flow rate) of the first BV of brine through the adsorption column is 2.5 BV / h, and the adsorption time is 24 min. The flow rate of the second BV of brine is 2.3 BV / h, and the adsorption time is 26 min. The flow rate of the third BV of brine is 2.1 BV / h and the adsorption time is 28 minutes. The flow rate of the fourth BV of brine is 2.0 BV / h, and the adsorption time is 30 minutes. The flow rate of the fifth brine BV is 1.8 BV / h, and the adsorption time is 33 min. The flow rate (i.e., final flow rate) of the sixth brine BV is 1.3 BV / h, and the adsorption time is 38 min. The total adsorption time of the adsorption process is about 3 h.

[0050] (2) Washing of the lithium-rich adsorbent:

[0051] The adsorption column with the lithium-rich adsorbent is washed with clean water to remove impurities adsorbed on the surface of the lithium-rich adsorbent. The entire washing process is carried out in three steps, in which the total amount of detergents is 2250 ml (i.e., 2.5 BV), and the total washing time is 20 min. The washing process includes the following:

[0052] a) First wash: A third wash effluent from a third wash of a previous cycle (having a composition with a Li+ content of 210 mg / L and a Mg2+ content of 10 g / L) is used as a first detergent to wash the lithium-rich adsorbent, where the amount of the first detergent is 0.6 BV, the flow rate is 4.5 BV / h, and the washing time is 8 min. After washing, a first adsorbent and a first wash effluent are obtained. The first wash effluent may be fed back to and mixed with the salt lake brine. 2100597 of 30 / 1

[0053] b) Second washing: An unqualified desorption solution collected at a later stage of a previous desorption cycle (having a composition with a Li+ content of 105 mg / L and a Mg2+ content of 150 mg / L) is used as a second detergent to wash the first adsorbent, where the volume amount of the second detergent is 1.3 BV (i.e., 1170 ml), the flow rate is 8.5 BV / h, and the washing time is 9 min. After washing, a second adsorbent and a second washing effluent are obtained. The second washing effluent has a magnesium to lithium weight ratio of 206:1, and can be collected and used in brine adsorption again, to reduce lithium loss.

[0054] c) Third wash: In this washing process, pure water is used as a third detergent, where the volumetric amount of pure water is 0.6 BV (5400 ml), the flow rate is 12 BV / h, and the washing time is 3 min. After washing, a third adsorbent and a third wash effluent are obtained. The third wash effluent can be stored in a pre-storage tank and used as the first detergent in a subsequent cycle.

[0055] (3) Desorption:

[0056] The third adsorbent was eluted with pure water (as a lithium ion eluent) at 50 °C to desorb the adsorbed lithium ions, where the water amount of 3.3 BV, the flow rate of 1.7 BV / h and the desorption time of 116 min. The liquid of the first two BV of the desorption process is collected and used as a qualified desorption solution (with a Li+ content greater than 500 mg / L), and the last 1.3 BV as an unqualified solution is recycled and used as a washing agent.

[0057] Example 2

[0058] Example 2 differs from Example 1 in that, during the adsorption process, 2100597 of 30 / 1 according to the adsorption order, the brine flow rate is 2.8 BV / h (initial flow rate), 2.6 BV / h, 2.4 BV / h, 2.1 BV / h, 1.8 BV / h and 1.5 BV / h (final flow rate), respectively; the adsorption time is 21.5 min, 23 min, 25 min, 28.5 min, 33 min and 40 min, respectively; the total adsorption time is 171 min (i.e., 2.85 h); and the other process conditions are the same as those in Example 1.

[0059] Example 3

[0060] Example 3 differs from Example 1 in that during the adsorption process, according to the adsorption order, the brine flow rate is 2 BV / h (initial flow rate), 1.8 BV / h, 1.6 BV / h, 1.4 BV / h, 1.3 BV / h, and 1.2 BV / h (final flow rate) respectively; the adsorption time is 30 min, 33.3 min, 37.5 min, 43 min, 46 min, and 50 min, respectively; the total adsorption time is about 240 min; and the other process conditions are the same as those in Example 1.

[0061] Example 4

[0062] Example 4 differs from Example 1 in that the initial flow rate of the brine is 3.5 BV / h, and the final flow rate is 2.0 BV / h. In particular, according to the order of adsorption, the flow rates of the 6 BV of brine to be adsorbed are 3.5 BV / h, 3.2 BV / h, 3.0 BV / h, 2.8 BV / h, 2.5 BV / h, and 2.0 BV / h, respectively; the adsorption time of each 1 BV of brine is 17 min, 18.75 min, 20 min, 21.4 min, 24 min, and 30 min, respectively; and the total adsorption time is about 240 min.

[0063] Example 5

[0064] Example 5 differs from Example 1 in that the amount of brine to be adsorbed is 7.5 BV and during the adsorption process the brine flow rate gradually decreases. Seven different flow rate ranges are included, the step of 2100597 of 30 / 1 decrease between adjacent flow rate intervals is 0.5 BV / h, the initial flow rate is 5 BV / h, and the final flow rate is 2 BV / h. The adsorption times of each 1.07 BV of brine are 12.9 min, 14.3 min, 16.1 min, 18.4 min, 21.4 min, 25.7 min, and 32.1 min, respectively; and the total adsorption time is about 140.9 min.

[0065] Example 6

[0066] Example 6 differs from Example 1 in that the flow rate in three washing steps is 5 BV / h, 8 BV / h and 12 BV / h respectively; the washing time is 7 min, 10 min and 3 min, respectively; and the total washing time is 20 min. The other process conditions are the same as those in Example 1.

[0067] Example 7

[0068] Example 7 differs from Example 1 in that a constant rate washing process is used for washing. The same flow rate of 7.5 BV / h is used in all three washing steps, the amount of detergent in each wash is 0.8 BV, 0.9 BV and 0.8 BV respectively, and the washing time is 384 s, 432 s and 384 s respectively. The total time of the washing process is 20 min, and the total amount of detergent is kept constant at 2.5 BV.

[0069] Example 8

[0070] Example 8 differs from Example 1 in that a constant rate washing process is used for washing. The same flow rate of 7.5 BV / h is used in all three washing steps, the amount of detergent used in each wash is 0.83 BV, and the time in each wash is 6.64 min. The total time of the washing process is 20 min, and the total amount of detergent is kept constant at 2.5 BV.

[0071] Example 9 2100597 of 30 / 1

[0072] Example 9 differs from Example 1 in that a constant rate washing process is used for washing. The same flow rate of 5 BV / h is used in all three washing steps, the amount of detergent used in each wash is 0.83 BV, and the time in each wash is 10 min. The total amount of detergent is kept constant at 2.5 BV, and the total time of the washing process is 30 min.

[0073] Example 10

[0074] A flow diagram of a method for extracting lithium from salt lake brine is shown in FIG. 2. Example 10 differs from Example 1 in that during the washing process, the detergent used in each wash is pure water (different from the first and second washes of Example 1 in which recycled water is used).

[0075] Example 11

[0076] Example 11 differs from Example 1 in that a different lithium adsorbent is used, the desorption temperature is 30°C, and the other process parameters are the same. The lithium adsorbent used in Example 11 includes the same adsorbent material as in Example 1, but a binder that is a vinylidenechlorotrifluoroethylene fluoride copolymer having a molecular weight of about 20,000, and also a wetting and dispersing agent that is polyethylene glycol having a molecular weight of 10,000, where the weight ratio of the adsorbent material, the binder, and the wetting and dispersing agent (polyethylene glycol) is 9:0.9:0.1.

[0077] Example 12

[0078] Example 12 differs from Example 11 in that in the method for extracting lithium from salt lake brine, the binder used in the lithium adsorbent is a FEVE type fluorocarbon resin. 2100597 of 30 / 1

[0079] Example 13

[0080] Example 13 differs from Example 11 in that in the method for extracting lithium from salt lake brine, the binder used in the lithium adsorbent is a VDF-CTFE copolymer and a FEVE type fluorocarbon resin in a weight ratio of 1:1.

[0081] Example 14

[0082] Example 14 differs from Example 11 in that the weight ratio of the adsorbent material, the binder and the polyethylene glycol is 9.5:0.4:0.1.

[0083] Example 15

[0084] The lithium adsorbent of Example 15 differs from that of Example 11 in that the molecular weight of the binder (VDF-CTFE copolymer) is 200,000.

[0085] Example 16

[0086] The lithium adsorbent of Example 16 differs from that of Example 11 in that the molecular weight of the binder (VDF-CTFE copolymer) is 600,000.

[0087] Example 17

[0088] The lithium adsorbent of Example 17 differs from that of Example 11 in that the wetting and dispersing agent used is sodium polyacrylate with a molecular weight of 6,000.

[0089] To highlight the beneficial effects of the examples of the present disclosure, the following comparative examples are provided.

[0090] Comparative Example 1

[0091] Comparative Example 1 differs from Example 1 in that a constant rate adsorption process is used for adsorption, in which the salt lake brine flows through the lithium adsorbent at a flow rate of 2.5 BV / h, and the adsorption time 2100597 of 30 / 1 is still 3 h.

[0092] Comparative Realization 2

[0093] Comparative Example 2 differs from Example 1 in that a constant rate adsorption process is used for the adsorption in Step (1), the salt lake brine is flowed through the lithium adsorbent at a flow rate of 25 BV / h, and the adsorption time remains 3 h; and a constant rate washing process is used for the washing in Step (2), wherein the same flow rate of 7.5 BV / h is used in all three washing steps, the amount of detergent used in each washing is 0.83 BV, and the time in each washing is 6.64 min. The total time of the washing process is 20 min, and the total amount of detergent is kept constant at 2.5 BV.

[0094] In order to provide strong support for the effect of the examples of the present disclosure, the adsorbed amount, the total adsorption time, the adsorption efficiency of lithium in the adsorption process, the lithium loss rate during washing, and the lithium content and the ratio of magnesium to lithium in the desorption solution finally obtained are determined in the method of each example and in the comparative example. The amount of adsorbed lithium is determined by a ratio of the weight of lithium adsorbed by the adsorbent (i.e., the difference between the weight of lithium element in the brine after adsorption and in the brine before adsorption) to the weight of the adsorbent. The adsorption efficiency is expressed by the ratio of the weight of lithium adsorbed by the lithium adsorbent to the weight of lithium in the original brine.The lithium loss rate during washing is a ratio of the weight of lithium element in the wash effluent obtained after washing (the wash effluent obtained after the final wash if there are multiple washing stages) to the total amount of lithium adsorbed by the lithium-rich adsorbent. 2100597 of 30 / 1

[0095] The above results are summarized in Table 2. Table 2. Summary of the results of each example and comparative example No. Amount of adsorbed lithium (mg / g) Total adsorption time (min) Adsorption efficiency (%) Lithium loss rate during washing (%) Lithium content in the desorption solution (mg / L) Ratio of magnesium to lithium in the desorption solution Amount of pure water for washing (non-recycled water) Example 1 2.5 180 80 13,543 2:1 0.6 BV Example 2 2.4 171 77 13,530 2:1 0.6 BV Example 3 2.7 240 86 13,577 1.9:1 0.6 BV Example 4 2.0 131.15 64 13,510 2.2:1 0.6 BV Example 5 2.2 140.9 70 13,518 2.1:1 0.6 BV Example 6 2.5 180 80 14,534 2.1:1 0.6 BV Example 7 2.5 180 80 17,529 3:1 0.8 BV Example 8 2.5 180 80 19,513 3.3:1 0.83 BV Example 9 2.5 180 80 20,501 3.2:1 0.83 BV Example 10 2.5 180 80 22,487 1.8:1 2.5 BV Example 11 2.55 180 82 13,556 2:1 0.6 BV Example 12 2.42 180 77.5 14,544 2:1 0.6 BV Example 13 2.48 180 79.4 13,548 2:1 0.6 BV Example 14 2.6 180 83 16,539 2:1 0.6 BV Example 15 2.58 180 82.6 13.1 563 2:1 0.6 BV Example 16 2.57 180 82.2 13.2 560 2:1 0.6 BV Example 17 2.52 180 80.6 13,551 2:1 0.6 BV Comparative Example 1 2.1 180 67 14,501 2.2:1 0.6 BV Comparative Example 2 2.1 180 67 20,440 3.4:1 0.83 BV,

[0096] In general, when lithium is extracted using the same adsorbent at the same temperature, the longer the total adsorption time, the higher the adsorption efficiency. As can be seen from Table 2, with the same adsorbent and the same total adsorption time, the adsorption efficiency of the variable rate adsorption process (Example 1) is much higher than the adsorption efficiency of the constant rate adsorption process. 2100597 of 30 / 1 (Comparative Examples 1-2). Examples 2-5 have a different adsorption time than Example 1; however, when the total adsorption time is short, Examples 2, 4, and 5 still have a fairly high adsorption efficiency. Furthermore, by using a washing process at a speed varying from slow to fast, the lithium loss rate during the washing process can be effectively reduced (Examples 1 and 6). In the constant-rate washing process (Examples 7-9), the lithium loss rate is slightly higher, and the ratio of magnesium to lithium in the obtained desorption solution is slightly higher (similar cases in Comparative Example 2 and Comparative Example 1). On the other hand, the lithium loss rate when using pure water for washing throughout the process (Example 10) is higher than the lithium loss rate when using recycled water and pure water for washing (Example 1).

[0097] Furthermore, it can be known from the comparison of Examples 11-14 with Example 1 that when an adsorbent having at least one of a vinylidene fluoride-chlorotrifluoroethylene copolymer and a fluoroolefin-vinyl ether copolymer as a binder and containing a wetting and dispersing agent is used, the desorption temperature is lower, and the lithium ion concentration in the lithium desorption solution is basically the same as that in Example 1. When the lithium ion concentration in the lithium desorption solution is comparable, energy can be largely saved with the lowering of the desorption temperature in the example. In the salt lake area where water and energy resources are scarce, the consumption of water and energy is of great significance to the cost and production capacity. The costs of running water and clean water, etc., are often 3 to 5 times higher than in other regions.Furthermore, Examples 15-16 differ from Example 11 in that the molecular weight of the VDF-CTFE copolymer binder is different. The binder in Examples 15-16 has a molecular weight in the range of 100,000 to 210,000,597. 800,000, and exhibits a desorption effect that is better than that of Example 11 where the binder has a molecular weight of 20,000 under the same other conditions. In Examples 17 and 11, the wetting and dispersing agents are different. The desorption effect in Example 11 where polyethylene glycol is used as the wetting and dispersing agent is slightly better than that of Example 17 where sodium polyacrylate is used as the wetting and dispersing agent.

[0098] In general, in the lithium extraction method provided in the examples of the present disclosure, a specific variable-speed adsorption process is used, to achieve high adsorption efficiency of the lithium present in the brine, and achieve high-efficiency lithium adsorption at low temperature. In this way, obtaining a reasonable lithium desorption solution is guaranteed.

[0100] The above are exemplary embodiments of the present disclosure. It should be noted that one skilled in the art may also make various improvements and modifications without departing from the principles of the present disclosure, and these improvements and modifications will fall within the scope of protection of the present disclosure. 2100597 of 30 / 1 2100597 of 30 DANIEL ALEJANDRO GUASCONI - 20184128102 Digitally signed by PORTALTRAMITES - INPI Date: 2022.12.27 15:09:49 -03:00 Reason: Digitally signed by the INPI Location: Buenos Aires, Argentina 2100597

Claims

1. A method for extracting lithium from salt lake brine, characterized in that the method comprises the following steps: (1) flowing the salt lake brine through a lithium adsorbent at a variable rate, to allow the lithium ions in the salt lake brine to adsorb onto the lithium adsorbent, to obtain a lithium-rich adsorbent, wherein during the adsorption process, the flow rate of the salt lake brine is gradually decreased, and the difference between the initial flow rate of the salt lake brine and the final flow rate of the salt lake brine is 0.5–3 BV / h; (2) washing the lithium-rich adsorbent; and (3) desorbing the lithium ions from the washed lithium-rich adsorbent with a lithium-ion eluent, to obtain a desorption solution. Nineteen claims follow.