A lithium extraction method for reducing the dissolution loss of titanium-based adsorbent by continuous ion exchange

Abstract

The present invention discloses a lithium extraction method for reducing the dissolution loss of titanium-based adsorbent by continuous ionization and cross-exchange. The method adopts a continuous ionization and cross-exchange method to extract lithium. In the desorption process of the titanium-based adsorbent, a multi-stage segmented low-acid desorption method is adopted, and a low H + concentration, ensuring desorption while reducing the dissolution loss of the adsorbent; using LiCl solution washing or dilute acid decontamination combined with adsorption washing steps before desorption can effectively reduce the impurity content in the qualified solution, reduce water consumption, and improve production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from salt lakes, and in particular to a lithium extraction method for continuously ionizing and reducing the dissolution loss of a titanium-based adsorbent. Background Art

[0002] Lithium resources have become a vital strategic resource in my country. With the development of new energy industries, the lithium mining industry has become a crucial component in ensuring my country's energy security, and global lithium resource development has entered a rapid development phase. Lithium ore exists primarily in nature as solid lithium ore and salt lake brine-based lithium ore. According to statistics from the U.S. Geological Survey, global lithium resources amounted to approximately 86 million tons in 2020, of which brine resources accounted for approximately 65%.

[0003] Due to the huge differences in the composition and chemical properties of salt lake brines, there is a consensus on "one lake, one policy" for salt lake brine development. In the early days, salt lake brine development was mainly based on the salt solarization method. This method has a mature process and a simple principle, but it also has disadvantages such as large investment in salt field construction and low lithium recovery rate. With the explosion of downstream demand, the future trend is to shift from "extracting lithium from old brine" to "extracting lithium from raw brine" and from extensive to refined. Currently, lithium extraction methods such as adsorption, extraction, membrane, and electrochemical deintercalation have emerged. Among them, aluminum adsorption has been industrialized in Qinghai and other places. Due to the limitations of the use conditions of aluminum adsorbents (pH range, brine type) and problems such as impurities, titanium and manganese adsorbents have also become the focus of research and development.

[0004] Titanium and manganese adsorbents are both ion sieve adsorbents. + With H + An ion exchange reaction occurs, achieving the goal of selectively adsorbing Li. Using acid for desorption causes chemical dissolution of the adsorbent. Reducing adsorbent dissolution has become a key to the industry's promotion and application of ion-screen adsorbents.

[0005] In traditional column-type single column or series column desorption, the inlet is constantly exposed to acid, which will lead to increased dissolution of the adsorbent in this area and even cause structural damage. CN112777614A discloses a method for extracting lithium from salt lake brine by adsorption. The method uses titanium to adsorb lithium in the brine, and then uses acid with a H+ concentration of 0.001-0.2 mol / L for pre-desorption to desorb most of the Na (a small amount of lithium is lost, and the pH value is 5-7). Then, H + The desorption was carried out with an acid having a concentration of 0.05-0.6 mol / L (the pH value end point was 4-7), and the desorption liquid was used to enter the next lithium extraction process; then H + The desorption regeneration was carried out with an acid having a concentration of 0.05-0.3 mol / L (pH end point 1.5-4.0). +Desorption was performed using acid solutions with concentrations of 0.005 mol / L, 0.25 mol / L, and 0.2 mol / L, resulting in an endpoint pH of 1.9-2.0 and Ti concentrations of 7.1-15.8 mg / L in the desorption solution, indicating high dissolution losses. Reducing the acid usage and increasing the endpoint pH to reduce chemical dissolution losses will reduce lithium transfer and production capacity. Furthermore, dissolution losses of the adsorbent due to high acid exposure at the inlet are unavoidable. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention aims to provide a lithium extraction method that continuously ionizes and reduces the dissolution loss of titanium-based adsorbents.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A lithium extraction method for continuously ionizing and reducing the dissolution loss of a titanium-based adsorbent comprises the following steps:

[0009] S1. The resin column of the continuous ion exchange device is filled with titanium-based adsorbent, and brine is introduced into the adsorption zone for adsorption. After the resin column is saturated with adsorption, it enters the adsorption and washing zone to wash away the entrained brine and elute some of the co-adsorbed sodium, potassium, and magnesium elements.

[0010] S2. The washed resin column is transferred to the desorption zone for desorption; the desorption zone is provided with several desorption tanks, each of which corresponds to a plurality of parallel resin columns; the desorption tanks are connected in series in sequence, and the starting desorption tank of the liquid flow is the final desorption tank, and the end desorption tank of the liquid flow is the first desorption tank; the feed liquid in the desorption tank is simultaneously pumped into the corresponding parallel resin columns by the feed pump, and the outlet liquid of the resin columns corresponding to the other desorption tanks except the first desorption tank is returned to the original desorption tank; the outlet liquid of one of the resin columns corresponding to the first desorption tank is not returned to the first desorption tank, but is sent to the membrane treatment section as qualified liquid, and the outlet liquid of the remaining resin columns is returned to the first desorption tank; the H in the desorption tank is maintained by pumping acid into each desorption tank + The concentration is relatively stable;

[0011] S3. After desorption, the resin column enters the desorption washing area and is washed in multiple stages in series using pure water; the outflowing washing liquid flows into the final desorption tank.

[0012] Furthermore, in step S1, in the adsorption washing and impurity removal zone, four stages of washing are performed in series using LiCl solution or dilute acid, or three stages of washing are performed in series using LiCl solution or dilute acid followed by a single stage of washing using pure water, or two stages of washing are performed in series using LiCl solution or dilute acid followed by a second stage of washing using pure water.

[0013] Furthermore, the LiCl solution is obtained by diluting the purified liquid obtained by concentrating the qualified liquid in step S2 through reverse osmosis and removing calcium and magnesium through nanofiltration, or by diluting the concentrated liquid obtained by concentrating the qualified liquid in step S2 through reverse osmosis and removing calcium and magnesium through nanofiltration and then subjecting the purified liquid to electrodialysis, or by using LiCl solid.

[0014] Furthermore, the LiCl solution has a Li concentration of 0.01 g / L to 14 g / L, and the H + The concentration is 0.01mol / L-0.2mol / L.

[0015] Furthermore, in step S2, the number of series-connected desorption tanks is 1-3, and 2-3 resin columns are connected in parallel in each stage.

[0016] Furthermore, in step S2, the acid liquid pumped into each level of desorption tank is sulfuric acid or hydrochloric acid.

[0017] Furthermore, the H + The concentration is 0.5-12 mol / L, and the H + The concentration is 0.02-0.15mol / L.

[0018] Furthermore, in step S2, the adsorption wash water remaining in the first resin column of the desorption zone is directly discharged into the primary desorption tank, or by monitoring the outlet conductivity, the residual adsorption wash water with conductivity lower than the set value is used as the washing water after desorption.

[0019] Furthermore, in step S2, the resin column in which the outlet feed liquid does not return to the primary desorption tank is any resin column connected to the primary desorption tank except the first resin column transferred from the adsorption washing and impurity removal zone to the desorption zone.

[0020] Furthermore, in step S3, the residual pure water in the last-stage resin column of the desorption and washing zone is discharged and recovered by emptying or introducing tail brine into the resin column from bottom to top in a top-water manner.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention innovatively uses multi-stage segmented low-acid desorption and adds acid during the desorption process, achieving a high Li concentration in the qualified liquid during low-concentration acid desorption. This can significantly reduce the adsorbent loss during the desorption process, effectively extend the service life of the titanium-based adsorbent, reduce production costs, and significantly improve economic benefits.

[0023] 2. The present invention adopts a segmented method to add acid to the desorption tank during the desorption process to reduce the H + concentration, accelerating H + The consumption of adsorbent is reduced, thus avoiding the dissolution and structural damage of adsorbent caused by high acidity.

[0024] 3. The present invention recovers the residual washing water in the column after adsorption washing according to conductivity control, and adds this part of water to the post-desorption washing, thereby reducing the water consumption of the system.

[0025] 4. The present invention separates the qualified liquid open circuit and the adsorbent desorption process, and can flexibly control the qualified liquid Li concentration through the open circuit amount, significantly reducing the difficulty of process control.

[0026] 5. The present invention uses LiCl solution or dilute acid to elute the resin column after adsorption, which can effectively elute some of the co-adsorbed impurity ions, improve the water quality of the qualified liquid, and enhance the overall Li yield and product quality of the back end. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of an implementation device of Example 1 of the present invention;

[0028] Figure 2 Schematic diagram of the implementation device of Example 7 of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] Example 1

[0031] The alkaline salt lake brine used in this embodiment has the composition shown in Table 1.

[0032] Table 1

[0033] Components Li Na K Ca Mg pH Content g / L 0.25 19.11 3.92 0.01 0.94 9.27

[0034] The adsorption zone 31 is provided with 17 resin columns, column numbers 1-17, such as Figure 1 As shown; there are 4 resin columns in the adsorption, washing and impurity removal zone, namely Figure 1 Column numbers 27-30 are shown; the desorption zone is equipped with 6 resin columns, namely Figure 1 The columns shown are 21-26; the desorption and washing zone is equipped with 3 resin columns, namely Figure 1 Bars 18-20 shown.

[0035] The adsorption washing and impurity removal zone consists of four columns connected in series. The LiCl solution in the adsorption washing and impurity removal feed tank 38 is pumped into the adsorption washing and impurity removal zone, and the LiCl solution is used to perform four-stage series washing.

[0036] The six resin columns in the desorption zone are divided into two groups, with each group of three resin columns forming a parallel arrangement. Resin columns 21-23 and 24-26 are connected in parallel, connecting to the secondary desorption tank 33 and primary desorption tank 35, respectively. The feed temperature in both desorption tanks is maintained at 40°C. The desorbed acid is pumped simultaneously into the three parallel resin columns via a feed pump, with the inlet flow rate to each resin column being 12 BV / h. The outlet feed from each resin column returns to the desorption tank. The desorbed liquid in the secondary desorption tank 33 flows through an overflow pipe 34 to the primary desorption tank 35. After the primary desorption liquid is pumped into resin columns 24-26, the effluent from resin column 25 does not return to the primary desorption tank 35 but is directly routed to the membrane treatment section. A valve controls the flow rate to equal the sum of the overflow rate from the secondary desorption tank 33 and the acid flow rate pumped into the primary desorption tank 35. The outlet of the resin column 26 is linked to a conductivity meter. The feed liquid with a conductivity greater than 300uS / cm returns to the primary desorption tank 35 through the three-way valve 39, and the feed liquid with a conductivity less than 300uS / cm enters the adsorption washing and impurity removal feed tank 38 through the three-way valve 39 and mixes with the LiCl solution. The mixed LiCl solution contains 300mg / L Li and 350mg / L Na, which is used to wash the impurities entrained or desorbed in the adsorption washing and impurity removal zone.

[0037] H in the primary desorption tank 35 and the secondary desorption tank 33 + The concentration is 0.05mol / L. At the same time, acid is pumped from the acid tank 36 to the two desorption tanks to keep the pH value constant. The pumped acid H + The concentration is 1.9mol / L.

[0038] After desorption, the resin column enters the desorption and washing zone, where pure water is pumped from pure water tank 32 for series washing. In the desorption and washing zone, resin columns 19 and 20 are washed in series, with pure water pumped from pure water tank 32 from top to bottom into resin columns 19 and 20. The washing liquid flowing out of the lower outlet of resin column 20 flows into the secondary desorption tank 33. The residual pure water in resin column 18 is discharged and recovered by top-watering the tail brine from bottom to top. The post-desorption washing flow rate is 11 BV / h.

[0039] Example 2

[0040] The brine used in this embodiment and the operation method are the same as those in Example 1. The difference is that some connection relationships are changed in this embodiment.

[0041] The adsorption zone 31 is equipped with 16 resin columns, column numbers 1-16; the adsorption washing and impurity removal zone is equipped with 4 resin columns, column numbers 27-30; the desorption zone is equipped with 7 resin columns, column numbers 20-26; and the desorption washing zone is equipped with 3 resin columns, column numbers 17-19.

[0042] The 7 resin columns in the desorption zone are divided into three groups, 20-22, 23-24, and 25-26 are connected in parallel, and three-stage desorption tanks are set up accordingly. After the first-stage desorption liquid is pumped into the 25 and 26 resin columns, the effluent from the 25 column does not return to the first-stage desorption tank, but directly enters the membrane treatment system. + The concentrations are 0.03mol / L, 0.04mol / L, and 0.05mol / L respectively.

[0043] Example 3

[0044] The brine and process connection method used in this embodiment are the same as those in Example 1. The difference is that H + The concentrations were maintained at 0.03mol / L and 0.05mol / L respectively.

[0045] Example 4

[0046] The process and operation method used in this embodiment, H + The concentrations are the same as those in Example 1. The difference is that the brine composition used is shown in Table 2.

[0047] Table 2

[0048] Components Li Na K Ca Mg pH Content g / L 0.17 76.42 4.82 0.09 2.54 8.02

[0049] Example 5

[0050] The difference between this embodiment and Example 1 is that the purified liquid after four stages of nanofiltration is diluted as the rinse water for adsorption washing and impurity removal, containing 1000 mg / L Li and 1100 mg / L Na, and the Li concentration of the qualified liquid is controlled to be about 1.4 g / L by finely adjusting the amount of washing water after adsorption.

[0051] Example 6

[0052] The difference between this embodiment and Example 1 is that a 0.04 mol / L HCl solution is used as the rinse water for adsorption washing and impurity removal.

[0053] Example 7

[0054] Adsorption was performed using brine from Table 1. Figure 2 As shown, the adsorption zone 31 is equipped with 17 resin columns, column numbers 1-17; the adsorption washing and impurity removal zone is equipped with 4 resin columns, column numbers 27-30, which are divided into two stages. Resin columns 28-30 are washed with LiCl solution, and resin column 27 is washed with pure water. The desorption zone is equipped with 6 resin columns, namely Figure 2 The columns shown are 21-26; the desorption and washing zone is equipped with 3 resin columns, namely Figure 2 Bars 18-20 shown.

[0055] The adsorption-washing and impurity-removal zone consists of four columns connected in series. Pure water is pumped from adsorption-washing and impurity-removal pure water tank 37 to wash resin column 27. The wash then enters adsorption-washing and impurity-removal feed tank 38, where it is mixed with LiCl solution and then passed to resin columns 28-30 for a three-stage series washing. The mixed LiCl solution contains 300 mg / L Li and 350 mg / L Na. The six resin columns in the desorption zone are divided into two groups, with each group of three resin columns forming a parallel arrangement: resin columns 22-24 in parallel, and resin columns 21, 25-26 in parallel, connected to the secondary desorption tank 33 and the primary desorption tank 35, respectively. The feed temperature in both desorption tanks is 40°C. The desorbed acid solution is simultaneously pumped from the desorption tank to the three parallel resin columns via a feed pump. The inlet flow rate to each resin column is 12 BV / h, and the outlet feed from the resin column is returned to the desorption tank. The desorption liquid in the secondary desorption tank 33 flows to the first-stage desorption tank 35 through the overflow pipe 34. After the first-stage desorption liquid is pumped into the resin columns 21, 25-26, the effluent from the resin column 25 does not return to the first-stage desorption tank 35, but directly enters the membrane treatment section. The flow rate is controlled by a valve to be the same as the sum of the overflow flow rate of the secondary desorption tank 33 and the flow rate of the acid solution pumped into the first-stage desorption tank 35. The outlet of the resin column 26 is linked to a conductivity meter. The feed liquid with a conductivity greater than 300uS / cm returns to the first-stage desorption tank 35 through the three-way valve 39, and the feed liquid with a conductivity less than 300uS / cm enters the adsorption washing and impurity removal pure water tank 37 through the three-way valve 39 to wash the impurities entrained or desorbed.

[0056] H in the primary desorption tank 35 and the secondary desorption tank 33 + The concentration is 0.05mol / L. At the same time, acid is pumped from the acid tank 36 to the two desorption tanks to keep the pH value constant. The pumped acid H + The concentration is 5mol / L.

[0057] After desorption, the resin column enters the desorption and washing zone, where pure water is pumped in from pure water tank 32 for multi-stage series washing. In the desorption and washing zone, resin column 18 is washed individually, while resin columns 19 and 20 are washed in series. Pure water is pumped from pure water tank 32 from top to bottom into resin columns 18 and 19, and the washing liquid flowing out of the lower outlet of resin column 20 flows into the secondary desorption tank 33. The residual pure water in resin column 18 is discharged and recovered by top-watering the tail brine from bottom to top. The post-desorption washing flow rate is 11 BV / h.

[0058] Comparative Example 1

[0059] The adsorption zone is equipped with 20 resin columns, column numbers 1-20; the adsorption washing section is equipped with 4 resin columns, using pure water as eluent, column numbers 27-30; the desorption zone is equipped with 2 resin columns, column numbers 25-26; the desorption washing zone is equipped with 4 resin columns, column numbers 21-24.

[0060] The two resin columns in the desorption zone are connected in series, the desorption acid concentration is 0.3 mol / L, and the desorption temperature is 40° C. The desorption acid is pumped into the inlet of the resin column 25, and the qualified liquid is at the outlet of the resin column 26.

[0061] Table 3

[0062]

[0063] The above-mentioned dissolution loss and qualified liquid impurity content data are compared in Table 3. The water washing acid in the table is the effluent of the washing after desorption, which is the Ti concentration in the comprehensive sample of each column cycle. It can be seen from the table that the Ti concentration of the water washing acid and the feed liquid in each desorption tank of Examples 1-3 is relatively low. 3+ Hydrolysis begins at pH > 2. Ti solubility varies at different pH levels, and higher Ti concentrations will hydrolyze as the pH rises during desorption. Therefore, measuring Ti concentration in high-pH feed solutions does not reflect actual titanium dissolution loss. Therefore, the Ti concentration in the water-wash acid is used as the basis for assessing adsorbent dissolution loss. Calculations show that the annual adsorbent dissolution rate can be reduced by 70-80% using the methods of the examples compared to the comparative example.

[0064] The Li / Na and Li / K data for the qualified solution in Table 3 show that replacing the adsorption wash water with a LiCl solution or dilute acid effectively removes monovalent ions. Using a LiCl solution with a Li concentration of 300 mg / L reduces the Na content in the qualified solution by approximately 45%, effectively improving the impurity level in the qualified solution.

[0065] Comparative Example 2

[0066] The difference between this embodiment and Example 1 is that the flow rate of post-desorption washing is 8.5 BV / h.

[0067] Table 4

[0068] Example Washing flow rate after desorption BV / h Li concentration of qualified liquid mg / L Example 1 11 1550 Comparative Example 2 8.5 2070

[0069] The comparison of the Li concentration data of the qualified liquid after adjusting the desorption and washing flow rate is shown in Table 4. As can be seen from Table 4, the Li concentration in the qualified liquid is linearly related to the flow rate of the post-desorption washing. When a higher Li concentration of the desorption liquid is required, the Li concentration of the qualified liquid can be conveniently controlled by reducing the flow rate of the post-desorption washing.

[0070] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the scope of protection of the claims of the present invention.

Claims

1. A lithium extraction method for continuously ionizing and reducing the dissolution loss of titanium-based adsorbent, characterized in that: The steps include: S1. The resin column of the continuous ion exchange device is filled with titanium-based adsorbent, and brine is introduced into the adsorption zone for adsorption. After the resin column is saturated with adsorption, it enters the adsorption and washing zone to wash away the entrained brine and elute some of the co-adsorbed sodium, potassium, and magnesium elements. S2. The washed resin column is transferred to the desorption zone for desorption; the desorption zone is provided with several desorption tanks, each of which corresponds to a plurality of parallel resin columns; the desorption tanks are connected in series in sequence, and the starting desorption tank of the liquid flow is the final desorption tank, and the end desorption tank of the liquid flow is the first desorption tank; the feed liquid in the desorption tank is simultaneously pumped into the corresponding parallel resin columns by the feed pump, and the outlet liquid of the resin columns corresponding to the other desorption tanks except the first desorption tank is returned to the original desorption tank; the outlet liquid of one of the resin columns corresponding to the first desorption tank is not returned to the first desorption tank, but is sent to the membrane treatment section as qualified liquid, and the outlet liquid of the remaining resin columns is returned to the first desorption tank; the H in the desorption tank is maintained by pumping acid into each desorption tank + The concentration is relatively stable; the acid pumped into each level of desorption tank is sulfuric acid or hydrochloric acid; the H + The concentration is 0.5-12 mol / L, and the H + The concentration is 0.02-0.15 mol / L; S3. After desorption, the resin column enters the desorption washing area and is washed in multiple stages in series using pure water; the outflowing washing liquid flows into the final desorption tank.

2. The method according to claim 1, characterized in that In step S1, in the adsorption washing and impurity removal zone, four-stage washing is performed in series using LiCl solution or dilute acid, or three-stage washing is performed in series using LiCl solution or dilute acid followed by a single-stage washing using pure water, or two-stage washing is performed in series using LiCl solution or dilute acid followed by a second-stage washing using pure water.

3. The method according to claim 2, characterized in that The LiCl solution is obtained by diluting the purified liquid obtained by concentrating the qualified liquid in step S2 through reverse osmosis and removing calcium and magnesium through nanofiltration, or by diluting the concentrated liquid obtained by concentrating the qualified liquid in step S2 through reverse osmosis and removing calcium and magnesium through nanofiltration and then subjecting the purified liquid to electrodialysis, or by using LiCl solid.

4. The method according to claim 2, characterized in that The LiCl solution has a Li concentration of 0.01 g / L to 14 g / L, and the H + The concentration is 0.01mol / L-0.2mol / L.

5. The method according to claim 1, wherein In step S2, the number of series-connected desorption tanks is 1-3, and 2-3 resin columns are connected in parallel in each stage.

6. The method according to claim 1, characterized in that In step S2, the adsorption wash water remaining in the first resin column of the desorption zone is directly discharged into the primary desorption tank, or the outlet conductivity is monitored and the residual adsorption wash water with conductivity lower than the set value is used as the washing water after desorption.

7. The method according to claim 1, characterized in that In step S2, the resin column in which the outlet liquid does not return to the primary desorption tank is any resin column connected to the primary desorption tank except the first resin column transferred from the adsorption washing and impurity removal zone to the desorption zone.

8. The method according to claim 1, characterized in that In step S3, the residual pure water in the last-stage resin column of the desorption and washing zone is discharged and recovered by draining or introducing tail brine into the resin column from bottom to top in a top-water manner.

Images