Method for directly extracting lithium from lithium-containing brine by adopting adsorption process

Abstract

The invention discloses a method for directly extracting lithium from lithium-containing brine by adopting an adsorption process, which comprises the following steps of: feeding pretreated brine into a continuous countercurrent adsorption system comprising an N-stage continuous overflow adsorption stirring tank, and extracting lithium from the lithium-containing brine through N-stage continuous countercurrent adsorption, then the washed loaded adsorbent is fed into a continuous countercurrent desorption system containing M-stage continuous overflow desorption stirring tanks, and desorption of lithium is achieved through M-stage continuous countercurrent desorption; the lithium-rich liquid obtained through desorption is pretreated and then subjected to reverse osmosis, nanofiltration and further concentration, and finally the obtained concentrated liquid is prepared into the required lithium product. Compared with the traditional lithium extraction process, the method provided by the invention has the advantages of low equipment requirement, low investment, high adsorption and desorption rate, high adsorbent utilization rate and controllable desorption process, and can flexibly adapt to the change of lithium concentration and capacity of the brine.

Description

Technical Field

[0001] The invention relates to the technical field of lithium extraction from lithium-containing brine, and in particular to a method for directly extracting lithium from lithium-containing brine by adopting an adsorption process. Background Art

[0002] Lithium is known as the "white oil of the future". With the rapid development of the new energy industry and the continuous development and application of high-performance lithium materials, the demand for lithium is increasing. The supply of lithium ore resources will be insufficient, while salt lake brine contains rich lithium resources, accounting for 66% of the world's lithium reserves, and lithium resources in my country's salt lake brine account for 87% of the total reserves. Therefore, the development of lithium resources in salt lake brine is of great significance to the sustainable development of the lithium industry.

[0003] The processes for extracting lithium from lithium-containing brine include solvent extraction, precipitation, calcination, membrane separation and adsorption. Among them, the adsorption method is currently widely used in the salt lake lithium extraction industry due to its high lithium selectivity, environmental friendliness and easy automation control.

[0004] The core of the adsorption process for lithium extraction is the adsorbent and the adsorption equipment that matches it. In terms of adsorbents, the adsorption materials that can be used for the adsorption process for lithium extraction currently include organic adsorbents and inorganic adsorbents, among which inorganic adsorbents are more widely used, including aluminum adsorbents, titanium adsorbents and manganese adsorbents; from the use of adsorbents, there are two types: granular and powder. CN111825152A discloses a lithium extraction technology using powder adsorption. After the adsorbent is mixed with brine for adsorption, it is transported to a belt filter. The frame is provided with a reciprocating filter cloth, and along the forward direction of the filter cloth, there are: a solid-liquid separation zone, a salt washing zone, and a desorption zone. A lithium eluent collection port is provided below the desorption zone, and finally a lithium eluent with a magnesium-lithium ratio of less than 1:1 can be obtained. However, there are problems in the use of this technology, such as fine adsorbent powder particles, difficult solid-liquid separation, low adsorbent utilization, and serious process leakage. Therefore, most salt lakes currently use granulated adsorbents to extract lithium. For example, CN110743516A, CN115738892A and CN115845825A all disclose methods for granulating lithium adsorbents. In addition, Salt Lake Co., Ltd. and Zangge Lithium Industry use granulated aluminum adsorbents to extract lithium from the Chaerhan Salt Lake. Zijin Mining uses granulated titanium adsorbents to extract lithium from the Laguocuo Salt Lake. Tailixin uses granulated manganese adsorbents to conduct lithium extraction experiments on the Kushui Lake. However, after granulation, the adsorbent powder has a significantly reduced adsorption capacity. For example, the working adsorption capacity of the manganese adsorbent powder can reach 20 mg / g, and the saturated adsorption capacity after granulation is 6-8 mg / g. Due to the influence of fluid linear velocity and adsorption kinetics, the actual working capacity of the column loading process is only 3-5 mg / g. Under the premise of ensuring production capacity, it is necessary to increase the investment in initial equipment and adsorbents.

[0005] In terms of adsorbent supporting equipment, the current adsorption equipment is mainly fixed bed, simulated moving bed and continuous ion exchange equipment. For example, CN109354043A discloses a method for removing impurities and extracting lithium from ultra-low concentration lithium-containing brine. The adsorption and impurity removal device includes an adsorption tower and a valve array unit, thereby controlling the adsorption, elution and desorption operations of each resin layer; the device is generally based on a fixed bed or a simulated moving bed, but there are problems such as large floor space occupied by the fixed bed and the simulated moving bed, complex pipeline connection, and low adsorbent utilization. CN116377248A discloses a lithium extraction method for continuously ion exchange to reduce the dissolution loss of titanium-based adsorbents. The process adopts a continuous ion exchange lithium extraction device, which has the advantages of high automation level and high adsorbent utilization rate compared with fixed beds and simulated moving beds, but the investment amount is large. In addition, when using the above-mentioned lithium extraction equipment, due to the fixed defects of the equipment, there is an excessive desorption phenomenon of the adsorbent during the desorption process, especially the ion sieve type adsorbent, which may cause the adsorbent to aggravate the dissolution loss, even scale collapse, and cause irreversible damage to the adsorbent.

[0006] In summary, the current adsorption lithium extraction process has the following shortcomings: the powder adsorbent is difficult to filter, the working adsorption capacity of the granular adsorbent is low, the continuous separation and exchange is expensive, the fixed bed and simulated moving bed occupy a large area, the equipment connection is complex, and the adsorbent utilization rate is low. It is urgent to develop an efficient adsorption-desorption lithium extraction process with low investment, simple process, and little damage to the adsorbent, so as to provide technical support for the large-scale application of lithium extraction process by adsorption of lithium-containing brine. Summary of the invention

[0007] In view of the deficiencies of the prior art, the present invention aims to provide a method for directly extracting lithium from lithium-containing brine using an adsorption process.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for extracting lithium directly from lithium-containing brine using an adsorption process comprises the following steps:

[0010] Step 1: pre-treating the lithium-containing brine to remove impurities;

[0011] Step 2, feeding the brine pretreated in step 1 into a continuous countercurrent adsorption system comprising N-stage continuous overflow adsorption stirring tanks, and extracting lithium from the lithium-containing brine by N-stage continuous countercurrent adsorption; wherein, the lithium-containing brine is added from the first-stage overflow adsorption stirring tank and flows step by step into the next-stage overflow adsorption stirring tank, the tail brine flows out from the N-stage overflow adsorption stirring tank, the unloaded adsorbent is added from the N-stage overflow adsorption stirring tank and is gradually lifted to the upper-stage overflow adsorption stirring tank, and the loaded lithium adsorbent is discharged from the first-stage overflow adsorption stirring tank;

[0012] Step 3: washing the loaded adsorbent discharged from the first-stage overflow adsorption stirring tank with low-salt water to remove entrained brine;

[0013] Step 4, sending the washed loaded adsorbent in step 3 into a continuous countercurrent desorption system comprising M-stage continuous overflow desorption stirring tanks, and realizing lithium desorption through M-stage continuous countercurrent desorption; the loaded adsorbent is added from the M-stage overflow desorption stirring tank, and gradually promoted to the overflow desorption stirring tank of the previous stage, and the unloaded adsorbent after lithium desorption is discharged from the first-stage overflow desorption stirring tank; the desorption liquid is added from the first-stage overflow desorption stirring tank, and gradually flows into the overflow desorption stirring tank of the next stage, and the lithium-rich liquid flows out from the M-stage overflow desorption stirring tank;

[0014] Step 5, returning the unloaded adsorbent discharged from the first-stage overflow desorption stirring tank in step 4 to step 2 for recycling;

[0015] Step 6: The lithium-rich solution obtained in step 4 is first concentrated by reverse osmosis to produce low-salt water and concentrated water; the concentrated water is filtered to remove calcium and magnesium ions, and the nanofiltration water is further concentrated by high-pressure reverse osmosis, electrodialysis, solar pond, mechanical steam recompression or multi-effect evaporation to prepare the desired lithium product.

[0016] Furthermore, in step one, the lithium-containing brine includes one or more of salt lake brine, lithium-containing geothermal water, lithium-containing ore leachate, lithium-containing brine produced in the oil field exploitation process and lithium-containing leachate produced in the lithium battery recovery process; the lithium-containing brine is chloride type, sodium sulfate subtype or carbonate type, and the lithium concentration is 50-1000 mg / L; the pretreatment includes one or more of sand filtration, ultrafiltration, microfiltration, flocculation sedimentation, oxidation, and includes one or more of adjusting pH, removing sulfate, removing carbonate and heating.

[0017] Furthermore, in step 2, the adsorbent is one or a combination of molecular sieve type aluminum adsorbent, ion sieve type manganese adsorbent, ion sieve type titanium adsorbent, and the adsorbent is in the form of powder, magnetic powder or granules obtained by granulating the powder adsorbent; the particle size of the powder or magnetic powder adsorbent is 10μm-1000μm; the particle size of the granular adsorbent is 1000μm-10000μm; the lithium extraction capacity of the adsorbent in the continuous countercurrent adsorption system is adjusted by adding fresh adsorbent purchased from outside or produced on site, or by open-circuit regeneration of the adsorbent with degraded performance.

[0018] Furthermore, in step 2, the lithium working capacity of the adsorbent is 5-50 mg / g; when the adsorption capacity of the adsorbent decays to 25-50% of the adsorption capacity of the fresh adsorbent, an open circuit and regeneration treatment is performed, and the regeneration treatment method adopts a combination of one or more of solid-phase sintering method, precipitation method, and hydrothermal method.

[0019] Furthermore, in step 2, N=2-8, in each stage of the overflow adsorption stirring tank, the mass ratio of brine to adsorbent is 2-100:1, the adsorption temperature is -5-50°C, and after the brine and the adsorbent are fully contacted by one or more of mechanical stirring, aeration stirring or pump circulation stirring, the adsorbent is separated from the brine by one or more of thickening, bag filtration, magnetic separation, centrifugal filtration separation, and the separated adsorbent is lifted upward, and the separated brine overflows downward; the lifting speed of the adsorbent is such that the lifting amount of the adsorbent in each stage of the overflow adsorption stirring tank within 1 hour is 10-80% of the total mass of the adsorbent in the overflow adsorption stirring tank of this stage; the adsorption pH in each stage of the overflow adsorption stirring tank is 5-11, and according to the pH requirements of different adsorbents, the pH of the brine is first regulated before adsorption or acid or alkali is directly added to the overflow adsorption stirring tanks of each stage to adjust the pH of the brine.

[0020] Furthermore, in step three, the total dissolved solids TDS content in the low-salt water is less than 1000 mg / L, including one or more of reverse osmosis water, surface fresh water or evaporation condensation water; the mass of the low-salt water used for washing is 1-10 times the mass of the loaded adsorbent discharged from the first-stage countercurrent adsorption tank.

[0021] Furthermore, in step 4, M=2-8; in each stage of the overflow desorption stirring tank, the mass ratio of the desorption liquid to the adsorbent is 4-40, the desorption temperature is 5-50°C, and the pH value of the desorption liquid after desorption is 2.0-7.0; the desorption liquid and the adsorbent are fully mixed by one or more of mechanical stirring, aeration stirring and pump circulation stirring, and then the adsorbent and the desorption liquid are separated by thickening, filtration or magnetic separation, and the separated adsorbent is lifted upward, and the separated desorption liquid overflows downward; in each stage of the overflow desorption stirring tank, the lifting speed of the adsorbent is such that the lifting amount of the adsorbent within 1 hour is 50-300% of the total amount of the adsorbent in the overflow desorption stirring tank.

[0022] Furthermore, in step 4, when the adsorbent is a molecular sieve type adsorbent, low salt water is used as the desorption liquid;

[0023] When the adsorbent is an ion sieve type adsorbent, an acidic solution is used as the desorption liquid, and the acidic solution is prepared by low salt water, low lithium solution and acid; the low lithium solution includes one or more of the washed liquid of the adsorbent after desorption, nanofiltration water, electrodialysis fresh water and high pressure reverse osmosis water; the acid is a combination of one or more of hydrochloric acid, sulfuric acid and nitric acid; the desorption pH in each stage of the overflow desorption stirring tank is 1.0-5.0;

[0024] The low-salt water has a total dissolved solids (TDS) lower than 300 mg / L and includes one or more of reverse osmosis produced water, surface fresh water or evaporation condensate water.

[0025] Further, in step six, the lithium-rich solution obtained in step four is pretreated before being concentrated by reverse osmosis;

[0026] If the adsorbent is an aluminum-based adsorbent or a titanium-based adsorbent, the pretreatment of the lithium-rich solution includes removing suspended matter using an ultrafiltration membrane;

[0027] If the adsorbent is a manganese-based adsorbent, the pretreatment of the lithium-rich liquid includes adding alkali to adjust the pH to 7-9 for hydrolysis, then aerating and oxidizing for 2-30 minutes, and then filtering with a composite filter material to achieve manganese removal. After manganese removal, the manganese ion concentration in the lithium-rich liquid is less than 1 mg / L, and an ultrafiltration membrane is used to remove suspended matter from the lithium-rich liquid before it enters reverse osmosis concentration after manganese removal; the oxidant used in aeration oxidation is a combination of one or more of air, a mixed gas of air and sulfur dioxide, hydrogen peroxide, oxygen, ozone or chlorine; the composite filter material includes manganese sand, and includes one or more of activated carbon, quartz sand, fiber balls, anthracite and ceramsite.

[0028] Furthermore, in step six, the low-salt water produced by concentrating the lithium-rich solution by reverse osmosis is returned to step three for washing and / or returned to step four as desorption water;

[0029] The concentrated water produced by the concentration of lithium-rich liquid by reverse osmosis is subjected to nanofiltration to remove calcium and magnesium ions therein, and the lithium ion concentration is 7-10 g / L, and the total concentration of calcium and magnesium ions is less than 5 mg / L; the concentrated solution obtained by further concentrating the nanofiltration water has a lithium ion concentration of 25-50 g / L; the nanofiltration concentrated water is further dialyzed to recover lithium, the fresh water produced by dialysis is returned to the reverse osmosis, and the concentrated water produced by dialysis is returned to the continuous countercurrent adsorption system of step 2;

[0030] The concentrated solution is prepared into a lithium product by using an evaporation crystallization method or a chemical precipitation method, or a combined process of ion exchange deep purification, bipolar membrane and evaporation crystallization; the lithium product is crude, chemical grade or battery grade lithium sulfate, lithium chloride, lithium carbonate, lithium phosphate or lithium hydroxide monohydrate.

[0031] The beneficial effects of the present invention are:

[0032] 1) The present invention adopts a multi-stage continuous countercurrent adsorption-desorption process, which has low equipment requirements and low investment compared with fixed bed, simulated moving bed or continuous desorption and adsorption lithium extraction processes.

[0033] 2) The present invention has a fast adsorption rate, a high adsorbent utilization rate, and a controllable desorption process. If the adsorbent is an ion sieve type, the desorption process can achieve continuous acid replenishment, thereby extending the service life of the adsorbent.

[0034] 3) Compared with the traditional adsorption lithium extraction process (fixed bed, simulated moving bed, continuous ion exchange equipment), the adsorbent and brine or desorbent are in instantaneous multi-dimensional homogeneous contact during the adsorption and desorption process, with a fast adsorption rate and high desorption efficiency. However, in the traditional column adsorption and desorption process, the brine, desorbent and lithium extraction agent are in directional flow contact through the adsorption column, which has a low efficiency, especially for ion sieve type adsorbents, there are still problems such as low front-end adsorbent utilization and excessive desorption.

[0035] 4) Compared with the traditional adsorption lithium extraction process (fixed bed, simulated moving bed, continuous desorption equipment), the continuous countercurrent adsorption and desorption process adopted in the present invention can flexibly adapt to the changes in brine lithium concentration and production capacity by adjusting the brine flow rate, adsorbent concentration in the tank and adsorbent lifting speed.

[0036] 5) The present invention regenerates the attenuated adsorbent, which has the advantages of repeated resource recycling, no need to purchase adsorbent and low raw material investment cost, which can further increase the economic benefits of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is an overall flow chart of the method of embodiments 1-4 of the present invention;

[0038] Figure 2 The overall flow chart of the countercurrent adsorption process of the method of Examples 1-4 of the present invention;

[0039] Figure 3 The overall flow chart of the countercurrent desorption process of the method of Examples 1-4 of the present invention;

[0040] Figure 4 Schematic diagram of the lifting process of lithium-containing brine and adsorbent in countercurrent adsorption and desorption in the method of Example 1 of the present invention;

[0041] Figure 5 Schematic diagram of the lifting process of lithium-containing brine and adsorbent in the countercurrent adsorption and desorption method of Example 2 of the present invention;

[0042] Figure 6 Schematic diagram of the lifting process of lithium-containing brine and adsorbent in countercurrent adsorption and desorption in the method of Example 3 of the present invention;

[0043] Figure 7 Schematic diagram of the lifting process of lithium-containing brine and adsorbent in countercurrent adsorption and desorption according to the method of Example 4 of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0045] Example 1

[0046] This embodiment provides a method for extracting lithium directly from a salt lake using an adsorption process, such as Figure 1 As shown, the specific process is:

[0047] (1) Countercurrent adsorption process of manganese adsorbent powder

[0048] The manganese adsorbent powder (the crystal form of the manganese adsorbent is Li 1.6 Mn 1.6 O4) and pretreated lithium-containing brine (Li400mg / L, Na 100g / L, K 4.16g / L, Ca 17.7g / L, Mg1.25g / L, B 0.37g / L, Cl 190g / L, SO4 2- 0.56 g / L, pH value of brine is 5.8) in a continuous countercurrent adsorption system containing 3 continuous overflow adsorption stirred tanks ( Figure 2 ), and contact with the adsorbent. In this embodiment, the pretreatment adopts ultrafiltration process, the purpose of which is to remove suspended matter, colloid, macromolecules and other components and influencing factors that may affect the back-end adsorption in the lithium-containing brine.

[0049] like Figure 2 As shown, brine is added from the first-stage overflow adsorption stirring tank and flows out from the third-stage overflow adsorption stirring tank, unloaded adsorbent is added from the third-stage overflow adsorption stirring tank and gradually increased to the upper-stage overflow adsorption stirring tank, and loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank.

[0050] The separation and flow of brine and adsorbent between each level of overflow adsorption stirring tank is as follows: Figure 4 As shown. The adsorption residence time of each overflow adsorption stirring tank is 20min, the stirring speed is 100rpm, the mass ratio of brine to adsorbent is 15:1, and the adsorption temperature is 15°C. During the adsorption process of each overflow adsorption stirring tank, 1% NaOH solution is added to the overflow adsorption stirring tank to control the adsorption pH value to be around 6. During the adsorption process, the adsorbent and brine overflow into the thickener through the overflow port on the overflow adsorption stirring tank, and the supernatant in the thickener overflows into the next overflow adsorption stirring tank. 70% (mass percentage) of the adsorbent slurry in the bottom flow of the thickener is pumped back to the overflow adsorption stirring tank of this stage, and 30% is pumped into the overflow adsorption stirring tank of the previous stage. After the adsorption in the third-stage overflow adsorption stirring tank was completed, the lithium concentration of the tail brine was 16 mg / L. After the adsorption in the second-stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 148 mg / L. After the adsorption in the first-stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 343 mg / L. The adsorption capacity of the manganese-based adsorbent powder was calculated to be 19.2 mg / g, and the lithium adsorption rate was 96%.

[0051] (2) Countercurrent desorption process of manganese-loaded adsorbent powder

[0052] The countercurrent desorption process of the loaded adsorbent is as follows Figure 3 As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption stirring tank and a thickener. The loaded adsorbent washed with low brine is sent to a continuous countercurrent desorption system comprising a 3-stage overflow desorption stirring tank. The pH of the 1st stage overflow desorption stirring tank and the 2nd stage overflow desorption stirring tank is controlled to be 1.2 by adding 1mol / L hydrochloric acid, and the pH of the 3rd stage overflow desorption stirring tank is controlled to be about 3-4 by adding 1mol / L hydrochloric acid.

[0053] The initial acid concentration of the desorption liquid is 0.1 mol / L. It flows into the first-stage overflow desorption stirring tank and flows into the next-stage overflow desorption stirring tank step by step. The lithium-rich liquid flows out of the third-stage overflow desorption stirring tank. The loaded adsorbent is added from the third-stage overflow desorption stirring tank and is gradually increased to the previous-stage overflow desorption stirring tank. The unloaded adsorbent is discharged from the first-stage overflow desorption stirring tank, thus realizing three-stage continuous countercurrent lithium desorption.

[0054] After desorption in each overflow desorption stirring tank is completed, the adsorbent and desorption liquid overflow into the thickener through the overflow port on the overflow desorption stirring tank, and the supernatant desorption liquid in the thickener overflows into the next overflow desorption stirring tank. 80% (mass percentage) of the adsorbent slurry in the bottom flow of the thickener is pumped to the previous overflow desorption stirring tank, and 20% is returned to the overflow desorption stirring tank of this stage. The desorption time of each overflow desorption stirring tank is 20min, the stirring speed is 100rpm, the mass ratio of desorption liquid to adsorbent is 8:1, and the desorption temperature is 25℃. During the desorption process of each overflow desorption stirring tank, the pH value is controlled at about 1.5 by adding 1mol / L HCl solution.

[0055] After the desorption in the third-stage overflow desorption stirring tank was completed, the lithium concentration of the outflowing lithium-rich liquid was 1.91g / L, after the desorption in the second-stage overflow desorption stirring tank was completed, the lithium concentration of the outflowing desorption liquid was 1.63g / L, after the desorption in the first-stage overflow desorption stirring tank was completed, the lithium concentration of the outflowing desorption liquid was 526mg / L. The desorption capacity of the manganese-based adsorbent powder was calculated to be 19.1mg / g, and the lithium desorption rate was 99%.

[0056] (3) Process of purification and concentration of lithium-rich liquid and preparation of lithium carbonate

[0057] The obtained lithium-rich solution (Li 1.91g / L, Na 202mg / L, K 56mg / L, Ca 108mg / L, Mg 15.3mg / L, Mn53mg / L) was firstly adjusted to pH 9 by adding alkali, and then aerated for 2min. After the aeration, the composite filter material (composite filter material includes manganese sand and activated carbon) was used for filtration and separation. The manganese ion concentration in the lithium-rich solution after manganese removal was less than 1mg / L, and the suspended matter was removed by ultrafiltration membrane before the lithium-rich solution after manganese removal entered the reverse osmosis concentration. After the lithium-rich solution after manganese removal was concentrated by reverse osmosis and then calcium and magnesium were removed by nanofiltration, the lithium ion concentration was 7.5g / L, the sodium ion concentration was 0.79g / L, the potassium ion concentration was 0.22g / L, and the calcium and magnesium ion concentrations were 3.2mg / L in total. The nanofiltration water is further concentrated to a lithium concentration of 50 g / L using MVR (solar pond or mechanical vapor recompression technology), and then a resin is used to deeply remove calcium, magnesium and boron to obtain a purified liquid (calcium and magnesium ion concentrations totaling 2 mg / L, boron concentration 1 mg / L). The purified liquid is then subjected to lithium precipitation at 85°C using a 28% sodium carbonate solution to obtain a lithium carbonate product, and the lithium concentration in the lithium precipitation mother liquor is detected to be 1.25 g / L.

[0058] (4) Regeneration of attenuated manganese adsorbent powder

[0059] After a long period of circulation, when the adsorption capacity of the manganese-based adsorbent powder drops to 10 mg / g, the adsorbent is regenerated. The process is to mix the attenuated manganese-based adsorbent powder with lithium carbonate. The molar ratio of lithium to manganese in the mixed sample is 1:1. The evenly mixed sample is then calcined in a muffle furnace at a calcination temperature of about 500°C and a holding time of 6 hours. After the calcination, a lithium manganese oxide precursor is obtained, and the manganese-based adsorbent powder is obtained after activation.

[0060] Example 2

[0061] This embodiment provides a method for extracting lithium directly from a salt lake using an adsorption process, such as Figure 1 As shown, the specific process is:

[0062] (1) Countercurrent adsorption process of titanium adsorbent particles

[0063] Titanium adsorbent particles (particle size 1000 μm-5000 μm, dry basis bulk density 0.4 g / cm 3 , the titanium adsorbent crystal form is Li2TiO3) and the pretreated lithium-containing brine (Li230mg / L, Na 15.3g / L, K 2.23g / L, Ca 23mg / L, Mg0.76g / L, B 0.71g / L, Cl - 11.59g / L, SO4 2-19.14g / L, carbonate 3g / L, brine pH 9.1) was sent to a multi-stage countercurrent adsorption system consisting of 8 continuous overflow adsorption stirring tanks ( Figure 2 ). In this embodiment, the pretreatment adopts a sand filtration process, the purpose of which is to remove suspended matter, colloids, macromolecules and other components and influencing factors that may affect the back-end adsorption in the lithium-containing brine.

[0064] Brine is added from the first-stage overflow adsorption stirring tank, flows to the next-stage overflow adsorption stirring tank step by step, and flows out from the eighth-stage overflow adsorption stirring tank. The unloaded adsorbent is added from the eighth-stage overflow adsorption stirring tank, and gradually increases to the previous-stage overflow adsorption stirring tank. The loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank. The adsorption time of each overflow adsorption stirring tank is 30 minutes, the stirring speed is 200 rpm, the mass ratio of brine to adsorbent is 10:1, and the adsorption temperature is 10°C.

[0065] like Figure 5 As shown in the figure, after the adsorption of each overflow adsorption stirring tank is completed, the brine overflows to the next overflow adsorption stirring tank through the overflow port on the overflow adsorption stirring tank. A filter is used at the overflow port to prevent the adsorbent from overflowing with the brine. The adsorbent is pumped from the bottom of the overflow adsorption stirring tank to the previous overflow adsorption stirring tank through an air lifter. By controlling the flow rate of the air lifter, it is ensured that 40% of the mass percentage of the adsorbent in a single overflow adsorption stirring tank is lifted to the previous overflow adsorption stirring tank within 30 minutes.

[0066] After the adsorption of the eighth stage overflow adsorption stirring tank was completed, the lithium concentration of the tail brine was 5.8 mg / L, after the adsorption of the seventh stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 37.8 mg / L, after the adsorption of the sixth stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 63 mg / L, after the adsorption of the fifth stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 95 mg / L, after the adsorption of the fourth stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 120 mg / L, after the adsorption of the third stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 148 mg / L, after the adsorption of the second stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 177 mg / L, after the adsorption of the first stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 211 mg / L. The adsorption capacity of the titanium-based adsorbent particles was calculated to be 5.61 mg / g, and the lithium adsorption rate was 97.5%.

[0067] (2) Countercurrent desorption process of titanium-based adsorbent particles

[0068] The countercurrent desorption process of the loaded adsorbent is as follows Figure 3As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption stirring tank and an air lift. After the loaded adsorbent is washed with low brine, it is sent to a continuous countercurrent desorption system comprising a 3-stage overflow desorption stirring tank. The pH of the first-stage overflow desorption stirring tank and the second-stage overflow desorption stirring tank is controlled to be 1.5 by adding 1mol / L hydrochloric acid, and the pH of the third-stage overflow desorption stirring tank is controlled to be about 3-4 by adding 1mol / L hydrochloric acid.

[0069] The initial acid concentration of the desorption liquid is 0.1 mol / L. It flows into the first-stage overflow desorption stirring tank, flows into the next-stage overflow desorption stirring tank step by step, and flows out of the lithium-rich liquid from the third-stage overflow desorption stirring tank. The loaded adsorbent is added from the third-stage overflow desorption stirring tank, and is gradually lifted to the previous-stage overflow desorption stirring tank. The unloaded adsorbent is discharged from the first-stage overflow desorption stirring tank, realizing three-stage continuous countercurrent lithium desorption. After the desorption of each overflow desorption stirring tank is completed, the desorption liquid overflows to the next-stage overflow desorption stirring tank through the overflow port on the overflow desorption stirring tank. A filter is used at the overflow port to prevent the adsorbent from overflowing with the desorption liquid; the adsorbent is pumped from the bottom of the overflow desorption stirring tank to the previous-stage overflow desorption stirring tank through an air lift. By controlling the flow rate of the air lift, it is ensured that 80% of the adsorbent in a single overflow desorption stirring tank is lifted to the previous-stage overflow desorption stirring tank within 20 minutes. The desorption time of each overflow desorption stirring tank is 20 min, the stirring speed is 100 rpm, the mass ratio of desorption liquid to adsorbent is 4:1, the temperature is 40°C, and the pH value is controlled at about 1.5 by adding 1 mol / L HCl solution during the adsorption process of each overflow desorption stirring tank.

[0070] After the desorption in the third-stage overflow desorption stirring tank was completed, the lithium concentration of the outflowing lithium-rich liquid was 1.09g / L, the lithium concentration of the outflowing desorption liquid was 930.7mg / L after the desorption in the second-stage overflow desorption stirring tank was completed, and the lithium concentration of the outflowing desorption liquid was 480mg / L after the desorption in the first-stage overflow desorption stirring tank was completed. The desorption capacity of the titanium-based adsorbent particles was calculated to be 5.45mg / g, and the lithium desorption rate was 97%.

[0071] (3) Process of purification and concentration of lithium-rich liquid and preparation of lithium carbonate

[0072] The obtained lithium-rich solution (Li 1.09g / L, Na 368mg / L, K 73mg / L, Ca 128.2mg / L, Mg 187.9mg / L) was subjected to ultrafiltration membrane to remove suspended solids before reverse osmosis concentration, and then reverse osmosis concentration and nanofiltration to remove calcium and magnesium. The lithium ion concentration in the lithium-rich solution was about 7g / L, the sodium ion concentration was 2.36g / L, the potassium ion concentration was 0.47g / L, and the calcium and magnesium ion concentrations were 4.5mg / L in total. Subsequently, the nanofiltration produced water was concentrated to 50g / L using MVR, and then the resin was used to deeply remove calcium, magnesium and boron to obtain the purified solution (calcium and magnesium ion concentrations were 2mg / L in total, and boron concentration was 1mg / L). The purified solution was subjected to lithium precipitation at 80°C using a sodium carbonate solution with a mass percentage of 28% to obtain a lithium carbonate product, and the lithium concentration in the lithium precipitation mother liquor was detected to be 1.31g / L.

[0073] (4) Regeneration of attenuated titanium adsorbent powder

[0074] After a long period of circulation, when the adsorbent capacity drops to 2 mg / g, the adsorbent is regenerated. The process is to roast the attenuated titanium adsorbent and mix it with lithium carbonate. The molar ratio of lithium to titanium in the mixed sample is 2:1. The evenly mixed sample is then roasted in a muffle furnace at a roasting temperature of about 1000°C and a holding time of 6 hours. After the roasting is completed, a lithium titanium oxide precursor is obtained, and the titanium adsorbent powder is obtained after activation.

[0075] Example 3

[0076] This embodiment provides a method for extracting lithium directly from a salt lake using an adsorption process, such as Figure 1 As shown, the specific process is:

[0077] (1) Countercurrent adsorption process of aluminum adsorbent powder

[0078] The aluminum adsorbent powder (aluminum adsorbent crystal form is LiCl·2Al(OH)3·nH2O) and pre-treated lithium-containing brine (Li 400mg / L, Na 100g / L, K 4.16g / L, Ca 17.7g / L, Mg 1.25g / L, B 0.37g / L, Cl 190g / L, SO4 2- 0.56g / L, pH value of brine is 5.8) and sent to a continuous countercurrent adsorption system including a 3-stage overflow adsorption stirring tank (such as Figure 2). Brine is added from the first-stage overflow adsorption stirring tank, flows into the next-stage overflow adsorption stirring tank step by step, and flows out from the third-stage overflow adsorption stirring tank. The unloaded adsorbent is added from the third-stage overflow adsorption stirring tank, and is gradually lifted to the previous-stage overflow adsorption stirring tank. The loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank. In this embodiment, the pretreatment adopts a microfiltration process, the purpose of which is to remove suspended matter, colloids, macromolecules and other components and influencing factors that may affect the back-end adsorption in the lithium-containing brine.

[0079] like Figure 6 As shown, each stage of adsorption is completed by an overflow adsorption stirring tank and a plate and frame filter press. After the adsorption of each stage of the overflow adsorption stirring tank is completed, the brine and adsorbent in the upper part of each stage of the overflow adsorption stirring tank flow into the plate and frame filter press through the overflow port to complete the separation of brine and adsorbent. The water produced by the plate and frame filter press enters the next stage of the overflow adsorption stirring tank. 55% (mass percentage) of the adsorbent after the plate and frame filter press returns to the overflow adsorption stirring tank of this stage, and 45% of the adsorbent is transferred to the previous stage of the overflow adsorption stirring tank. The adsorption time for each stage is 40min, the stirring speed is 200rpm, the mass ratio of brine to adsorbent is 6.75:1, and the adsorption temperature is 20℃. The filtration time for each stage is 10min, and the mass percentage of 40% of the adsorbent in a single overflow adsorption stirring tank is increased within 40min. After the adsorption in the third-stage overflow adsorption stirring tank was completed, the lithium concentration of the outflowing tail brine was 55 mg / L. After the adsorption in the second-stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 244 mg / L. After the adsorption in the first-stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 334 mg / L. The adsorption capacity of the aluminum-based adsorbent powder was calculated to be 5.18 mg / g, and the lithium adsorption rate was 86.25%.

[0080] (2) Countercurrent desorption process of aluminum-based adsorbent powder

[0081] The countercurrent desorption process of the loaded adsorbent is as follows Figure 3 As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption stirring tank and a plate and frame filter press. The above-mentioned loaded adsorbent is washed and sent to a continuous countercurrent desorption system including an 8-stage overflow desorption stirring tank.

[0082] The desorption liquid is low-salt water (reverse osmosis water and / or pure water), which is added from the first-stage overflow desorption stirring tank and flows into the next-stage overflow desorption stirring tank step by step. The lithium-rich liquid (pH about 5) flows out from the eighth-stage overflow desorption stirring tank. The loaded adsorbent is added from the eighth-stage overflow desorption stirring tank and gradually raised to the previous-stage overflow desorption stirring tank. The unloaded adsorbent is discharged from the first stage to achieve 8-stage continuous countercurrent lithium desorption. The desorption time of each overflow desorption stirring tank is 20 minutes, the stirring speed is 200 rpm, the mass ratio of the desorption liquid to the adsorbent is 10:1, and the temperature is 40°C.

[0083] After desorption in each overflow desorption stirring tank is completed, the desorption liquid and adsorbent in the upper part of each overflow desorption stirring tank flow into the plate and frame filter press through the overflow port to complete the separation of the desorption liquid and the adsorbent. The desorption liquid produced by the plate and frame filter press enters the next overflow desorption stirring tank, and the loaded adsorbent after the plate and frame filter press is all returned to the overflow desorption stirring tank of the previous stage.

[0084] After the desorption of the eighth-stage overflow desorption stirring tank is completed, the lithium concentration of the outflowing lithium-rich liquid is 525 mg / L, the desorption of the seventh-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 360 mg / L, the desorption of the sixth-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 243.7 mg / L, the desorption of the fifth-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 181.2 mg / L, the desorption of the fourth-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 119.8 mg / L, the desorption of the third-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 88.7 mg / L, the desorption of the second-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 65.4 mg / L, the desorption of the first-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 33.2 mg / L, the desorption capacity of the aluminum-based adsorbent powder is calculated to be 5.13 mg / g, and the lithium desorption rate is 99%.

[0085] (3) Process of purification and concentration of lithium-rich liquid and preparation of lithium carbonate

[0086] The obtained lithium-rich solution (Li 525mg / L, Na 160mg / L, K 13mg / L, Ca 82mg / L, Mg 4.5mg / L) was subjected to ultrafiltration membrane to remove suspended solids before reverse osmosis concentration, and after reverse osmosis concentration and nanofiltration to remove calcium and magnesium, the lithium ion concentration in the lithium-rich solution was about 6g / L, the sodium ion concentration was 1.83g / L, the potassium ion concentration was 0.15g / L, and the calcium and magnesium ion concentrations were 3mg / L in total. Subsequently, the nanofiltration produced water was concentrated to 50g / L using MVR, and then the resin was used to deeply remove calcium, magnesium and boron to obtain the purified solution (calcium and magnesium ion concentrations were 1mg / L in total, and boron concentration was 1mg / L), and then 28% sodium carbonate solution was used to precipitate lithium in the purified solution at 80°C to obtain lithium carbonate products, and the lithium concentration in the lithium precipitation mother liquor was detected to be 1.18g / L.

[0087] (4) Regeneration of attenuated aluminum adsorbent powder

[0088] After the aluminum-based adsorbent powder has been circulated for a long period of time, when the adsorbent capacity drops to 2 mg / g, the adsorbent is regenerated. The process is to dissolve the attenuated aluminum-based adsorbent powder with hydrochloric acid to form an AlCl3 solution, then decompose the lithium carbonate with hydrochloric acid to form a LiCl solution, and then mix the two solutions to control the lithium-aluminum molar ratio to 0.5. Then, the temperature is raised to 75°C, and 5 mol / L sodium hydroxide solution is added dropwise to the mixed solution to control the end point pH to 6-7. After filtration, the solid is dried at 60°C to obtain an aluminum-based adsorbent precursor, and then the aluminum-based adsorbent powder is obtained after activation.

[0089] Example 4

[0090] This embodiment provides a method for extracting lithium directly from a salt lake using an adsorption process, such as Figure 1 As shown, the specific process is:

[0091] (1) Countercurrent adsorption process of magnetic manganese adsorbent powder

[0092] The magnetic manganese adsorbent powder (the crystal form of the manganese adsorbent is Li 1.6 Mn 1.6 O4) and pretreated lithium-containing brine (Li 230mg / L, Na 15.3g / L, K2.23g / L, Ca 23mg / L, Mg0.76g / L, B 0.71g / L, Cl 11.59g / L, SO4 2- 19.14g / L, carbonate 3g / L, brine pH 9.1) into a continuous countercurrent adsorption system consisting of two overflow adsorption stirring tanks. In each overflow adsorption stirring tank, the aeration intensity is 6m per cubic meter of liquid. 3 In this embodiment, the pretreatment adopts ultrafiltration process, the purpose of which is to remove suspended matter, colloid, macromolecules and other components and influencing factors that may affect the back-end adsorption in the lithium-containing brine.

[0093] Brine was added from the first-stage overflow adsorption stirring tank and flowed out from the second-stage overflow adsorption stirring tank, the unloaded adsorbent was added from the second-stage overflow adsorption stirring tank, and the loaded adsorbent was discharged from the first-stage overflow adsorption stirring tank. The adsorption time for each stage was 20 minutes, the mass ratio of brine to adsorbent was 60:1, and the adsorption temperature was 0°C.

[0094] like Figure 7As shown, each stage of adsorption is completed by an overflow adsorption stirring tank and a magnetic separator. After the adsorption of each stage of the overflow adsorption stirring tank is completed, the brine and the adsorbent in the overflow adsorption stirring tank are separated by a magnetic separator. The adsorbent obtained by magnetic separation is lifted to the previous overflow adsorption stirring tank by the magnetic separator, and the brine enters the next overflow adsorption stirring tank through the overflow port of the overflow adsorption stirring tank. A filter is set at the overflow port to ensure that the adsorbent remains in the overflow adsorption stirring tank. Ensure that 60% of the adsorbent in a single overflow adsorption stirring tank is lifted to the previous overflow adsorption stirring tank within 30 minutes.

[0095] After the adsorption in the second-stage overflow adsorption stirring tank was completed, the lithium concentration of the outflowing tail brine was 47.5 mg / L. After the adsorption in the first-stage overflow adsorption stirring tank was completed, the lithium concentration of the brine after adsorption was 171 mg / L. The adsorption capacity of the manganese-based adsorbent powder was calculated to be 18.25 mg / g, and the adsorption rate was 79.35%.

[0096] (2) Countercurrent desorption process of loaded magnetic manganese adsorbent powder

[0097] The countercurrent desorption process of the loaded adsorbent is as follows Figure 3 As shown in the figure, similar to the adsorption process, the desorption process is completed by the overflow desorption stirring tank and the magnetic separator. In each stage of the overflow desorption stirring tank, the aeration intensity is 3m per cubic meter of liquid. 3 / h.

[0098] The loaded adsorbent is washed with low salt water and then sent to a continuous countercurrent desorption system comprising a two-stage overflow desorption stirring tank. The desorption liquid is a 0.1 mol / L HCl solution. The pH of the first-stage overflow desorption stirring tank is controlled to be 1.5 by adding desorption liquid, and the pH of the second-stage overflow desorption stirring tank is controlled to be 3-4 by adding desorption liquid. Lithium-rich liquid flows out of the second-stage overflow desorption stirring tank. The loaded adsorbent is added from the second-stage overflow desorption stirring tank, and the unloaded adsorbent is discharged from the first-stage overflow desorption stirring tank, realizing two-stage continuous countercurrent lithium extraction and desorption. After the desorption of each overflow desorption stirring tank is completed, the adsorbent in the overflow desorption stirring tank is lifted to the previous overflow desorption stirring tank by a magnetic separator, ensuring that 80% of the adsorbent in a single overflow desorption stirring tank is lifted to the previous overflow desorption stirring tank within 30 minutes, and the desorption liquid overflows to the next level through the overflow port at the top of the overflow desorption stirring tank. A filter is set at the overflow port to ensure that the adsorbent remains in the overflow desorption stirring tank. The desorption time of each overflow desorption stirring tank is 30 minutes, the mass ratio of desorption liquid to adsorbent is 8:1, and the desorption temperature is 10°C.

[0099] After the desorption in the second-stage overflow desorption stirring tank is completed, the lithium concentration of the discharged lithium-rich liquid is 1.79g / L. After the desorption in the first-stage overflow desorption stirring tank is completed, the lithium concentration of the desorption liquid is 1.02g / L. The desorption capacity of the manganese-based adsorbent powder is calculated to be 17.9mg / g, and the lithium desorption rate is 98%.

[0100] (3) Process of purification and concentration of lithium-rich liquid and preparation of lithium carbonate

[0101] The obtained lithium-rich solution (Li 1.79g / L, Na 206mg / L, K 15mg / L, Ca 185mg / L, Mg 5.3mg / L, Mn83mg / L) was oxidized to remove manganese. First, the lithium-rich solution was adjusted to pH 9 by adding alkali, and aeration was performed for 30 minutes. After the aeration, a composite filter material (the composite filter material includes manganese sand and quartz sand) was used for filtration and separation. The manganese ion concentration in the lithium-rich solution after manganese removal is less than 1mg / L, and the suspended matter is removed by ultrafiltration membrane before the lithium-rich solution after manganese removal enters reverse osmosis concentration. After the lithium-rich solution after manganese removal is concentrated by reverse osmosis and then calcium and magnesium are removed by nanofiltration, the lithium ion concentration is 7.5g / L, the sodium ion concentration is 0.86g / L, the potassium ion concentration is 62.8mg / L, and the calcium and magnesium ion concentrations are 3mg / L in total. Subsequently, the nanofiltration water was concentrated to 50g / L using MVR, and then the resin was used to deeply remove calcium, magnesium and boron to obtain a purified liquid (the total concentration of calcium and magnesium ions was 2mg / L, and the boron concentration was 1mg / L). Then, a 28% sodium carbonate solution was used to precipitate lithium in the purified liquid at 85°C to obtain a lithium carbonate product, and the lithium concentration in the lithium precipitation mother liquor was detected to be 1.15g / L.

[0102] (4) Regeneration of attenuated magnetic manganese adsorbent powder

[0103] After the magnetic manganese adsorbent powder has been circulated for a long period of time, when the adsorbent capacity drops to 8 mg / g, the adsorbent is regenerated. The process is to mix the attenuated magnetic manganese adsorbent powder with lithium carbonate. The molar ratio of lithium to manganese in the mixed sample is 1:1. The evenly mixed sample is then calcined in a muffle furnace at a calcination temperature of about 500°C and a holding time of 6 hours. After the calcination, a magnetic lithium manganese oxide precursor is obtained, and the magnetic manganese adsorbent powder is obtained after activation.

[0104] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for extracting lithium directly from lithium-containing brine using an adsorption process, characterized in that: The steps include: Step 1: pre-treating the lithium-containing brine to remove impurities; Step 2, feeding the brine pretreated in step 1 into a continuous countercurrent adsorption system comprising N-stage continuous overflow adsorption stirring tanks, and extracting lithium from the lithium-containing brine by N-stage continuous countercurrent adsorption; wherein, the lithium-containing brine is added from the first-stage overflow adsorption stirring tank and flows step by step into the next-stage overflow adsorption stirring tank, the tail brine flows out from the N-stage overflow adsorption stirring tank, the unloaded adsorbent is added from the N-stage overflow adsorption stirring tank and is gradually lifted to the upper-stage overflow adsorption stirring tank, and the loaded lithium adsorbent is discharged from the first-stage overflow adsorption stirring tank; Step 3: washing the loaded adsorbent discharged from the first-stage overflow adsorption stirring tank with low-salt water to remove entrained brine; Step 4, sending the washed loaded adsorbent in step 3 into a continuous countercurrent desorption system comprising M-stage continuous overflow desorption stirring tanks, and realizing lithium desorption through M-stage continuous countercurrent desorption; the loaded adsorbent is added from the M-stage overflow desorption stirring tank, and gradually promoted to the overflow desorption stirring tank of the previous stage, and the unloaded adsorbent after lithium desorption is discharged from the first-stage overflow desorption stirring tank; the desorption liquid is added from the first-stage overflow desorption stirring tank, and gradually flows into the overflow desorption stirring tank of the next stage, and the lithium-rich liquid flows out from the M-stage overflow desorption stirring tank; Step 5, returning the unloaded adsorbent discharged from the first-stage overflow desorption stirring tank in step 4 to step 2 for recycling; Step 6: The lithium-rich solution obtained in step 4 is first concentrated by reverse osmosis to produce low-salt water and concentrated water; the concentrated water is filtered to remove calcium and magnesium ions, and the nanofiltration water is further concentrated by high-pressure reverse osmosis, electrodialysis, solar pond, mechanical steam recompression or multi-effect evaporation to prepare the desired lithium product.

2. The method according to claim 1, characterized in that: In step one, the lithium-containing brine includes one or more of salt lake brine, lithium-containing geothermal water, lithium-containing ore leachate, lithium-containing brine generated in the oil field exploitation process and lithium-containing leachate generated in the lithium battery recovery process. The lithium-containing brine is chloride type, sodium sulfate subtype or carbonate type, and the lithium concentration is 50-1000 mg / L; the pretreatment includes one or more of sand filtration, ultrafiltration, microfiltration, flocculation sedimentation, oxidation, and includes one or more of adjusting pH, removing sulfate, removing carbonate and heating.

3. The method according to claim 1, characterized in that In step 2, the adsorbent is one or a combination of molecular sieve type aluminum adsorbent, ion sieve type manganese adsorbent, ion sieve type titanium adsorbent, and the adsorbent is in the form of powder, magnetic powder or granules obtained by granulating the powder adsorbent; the particle size of the powder or magnetic powder adsorbent is 10μm-1000μm; the particle size of the granular adsorbent is 1000μm-10000μm; the lithium extraction capacity of the adsorbent in the continuous countercurrent adsorption system is adjusted by adding fresh adsorbent purchased from outside or produced on site, or by open-circuit regeneration of the adsorbent with degraded performance.

4. The method according to claim 3, characterized in that: In step 2, the lithium working capacity of the adsorbent is 5-50 mg / g; when the adsorption capacity of the adsorbent decays to 25-50% of the adsorption capacity of the fresh adsorbent, an open circuit and regeneration treatment is performed, and the regeneration treatment method adopts a combination of one or more of solid phase sintering method, precipitation method, and hydrothermal method.

5. The method according to claim 1, characterized in that In step 2, N=2-8, in each overflow adsorption stirring tank, the mass ratio of brine to adsorbent is 2-100:1, the adsorption temperature is -5-50°C, and after the brine and the adsorbent are fully contacted by one or more of mechanical stirring, aeration stirring or pump circulation stirring, the adsorbent is separated from the brine by one or more of thickening, bag filtration, magnetic separation, centrifugal filtration separation, and the separated adsorbent is lifted upward, and the separated brine overflows downward; the lifting speed of the adsorbent is such that the lifting amount of the adsorbent in each overflow adsorption stirring tank within 1 hour is 10-80% of the total mass of the adsorbent in the overflow adsorption stirring tank of this stage; the adsorption pH in each overflow adsorption stirring tank is 5-11. According to the pH requirements of different adsorbents, the pH of the brine is first regulated before adsorption, or acid or alkali is directly added to the overflow adsorption stirring tanks of each stage to regulate the pH of the brine.

6. The method according to claim 1, characterized in that In step three, the total dissolved solids TDS content in the low-salt water is less than 1000 mg / L, including one or more of reverse osmosis water, surface fresh water or evaporation condensation water; the mass of the low-salt water used for washing is 1-10 times the mass of the loaded adsorbent discharged from the first-stage countercurrent adsorption tank.

7. The method according to claim 1, characterized in that In step 4, M=2-8; in each overflow desorption stirring tank, the mass ratio of desorption liquid to adsorbent is 4-40, the desorption temperature is 5-50°C, and the pH value of the desorption liquid after desorption is 2.0-7.0; the desorption liquid and the adsorbent are fully mixed by one or more of mechanical stirring, aeration stirring and pump circulation stirring, and then the adsorbent and the desorption liquid are separated by thickening, filtration or magnetic separation, and the separated adsorbent is lifted upward and the separated desorption liquid overflows downward; in each overflow desorption stirring tank, the lifting speed of the adsorbent is such that the lifting amount of the adsorbent within 1 hour is 50-300% of the total amount of the adsorbent in the overflow desorption stirring tank.

8. The method according to claim 1, characterized in that: In step 4, when the adsorbent is a molecular sieve type adsorbent, low salt water is used as the desorption liquid; When the adsorbent is an ion sieve type adsorbent, an acidic solution is used as the desorption liquid, and the acidic solution is prepared by low salt water, low lithium solution and acid; the low lithium solution includes one or more of the washed liquid of the adsorbent after desorption, nanofiltration water, electrodialysis fresh water and high pressure reverse osmosis water; the acid is a combination of one or more of hydrochloric acid, sulfuric acid and nitric acid; the desorption pH in each stage of the overflow desorption stirring tank is 1.0-5.0; The low-salt water has a total dissolved solids (TDS) lower than 300 mg / L and includes one or more of reverse osmosis produced water, surface fresh water or evaporation condensate water.

9. The method according to claim 1, characterized in that: In step 6, the lithium-rich solution obtained in step 4 is pretreated before being concentrated by reverse osmosis; If the adsorbent is an aluminum-based adsorbent or a titanium-based adsorbent, the pretreatment of the lithium-rich solution includes removing suspended matter using an ultrafiltration membrane; If the adsorbent is a manganese-based adsorbent, the pretreatment of the lithium-rich liquid includes adding alkali to adjust the pH to 7-9 for hydrolysis, then aerating and oxidizing for 2-30 minutes, and then filtering with a composite filter material to achieve manganese removal. After manganese removal, the manganese ion concentration in the lithium-rich liquid is less than 1 mg / L, and an ultrafiltration membrane is used to remove suspended matter from the lithium-rich liquid before it enters reverse osmosis concentration after manganese removal; the oxidant used in aeration oxidation is a combination of one or more of air, a mixed gas of air and sulfur dioxide, hydrogen peroxide, oxygen, ozone or chlorine; the composite filter material includes manganese sand, and includes one or more of activated carbon, quartz sand, fiber balls, anthracite and ceramsite.

10. The method according to claim 1, characterized in that In step 6, the low-salt water produced by concentrating the lithium-rich solution by reverse osmosis is returned to step 3 for washing and / or returned to step 4 as desorption water; The concentrated water produced by the concentration of lithium-rich liquid by reverse osmosis is subjected to nanofiltration to remove calcium and magnesium ions, and the lithium ion concentration is 7-10g / L, and the total concentration of calcium and magnesium ions is less than 5mg / L; The nanofiltration water is further concentrated to obtain a lithium ion concentration of 25-50g / L in the concentrated solution; the nanofiltration concentrated water is further dialyzed to recover lithium, the fresh water produced by dialysis is returned to the reverse osmosis, and the concentrated water produced by dialysis is returned to the continuous countercurrent adsorption system in step 2; The concentrated solution is prepared into a lithium product by using an evaporation crystallization method or a chemical precipitation method, or a combined process of ion exchange deep purification, bipolar membrane and evaporation crystallization; the lithium product is crude, chemical grade or battery grade lithium sulfate, lithium chloride, lithium carbonate, lithium phosphate or lithium hydroxide monohydrate.

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