A centrifugal adsorption method for extracting lithium from salt lakes

Abstract

The present invention provides a centrifugal adsorption method for extracting lithium from salt lakes, belonging to the technical field of lithium extraction from salt lakes. The present invention first loads an adsorbent into a centrifuge drum and turns on the centrifuge; then, lithium-containing brine is added to the centrifuge drum to adsorb the lithium-containing brine; after adsorption is completed, an eluent is added to obtain a lithium-containing eluent, which is then subjected to electrodialysis treatment. The present invention utilizes centrifugal force to increase the flow rate of the brine and eluent, accelerates the adsorption and desorption mass transfer process, reduces the adsorption and desorption time, and improves production efficiency; impurities entrained in the adsorbent are reduced, and the resulting lithium-containing desorption liquid has high purity; at the same time, the use of large amounts of acid and alkali is avoided, saving raw material logistics costs.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from salt lakes, and in particular to a centrifugal adsorption method for extracting lithium from salt lakes. Background Art

[0002] In recent years, with the rapid development of new energy vehicles and chemical energy storage, the demand for lithium has surged. Sichuan, Hubei, Jiangxi, and Hunan in my country are mainly lithium ore resources, accounting for 15% of my country's lithium resources; Qinghai and Tibet are mainly salt lake resources, accounting for 85% of my country's lithium resources. Therefore, lithium extraction from salt lakes has attracted more and more attention. Salt lake brine mainly contains Li + 、Na + , K + , Ca 2+ Mg 2+ Isocations and SO4 2- 、Cl - 、CO3 2- Therefore, the mining of lithium resources is technically difficult.

[0003] Adsorption is a new technology for extracting lithium from salt lakes. Compared to precipitation, roasting, and extraction methods, it boasts high extraction efficiency, relatively low costs, and strong environmental advantages. An adsorbent selectively adsorbs lithium ions from brine, which are then eluted with water or an eluent to separate the lithium ions from impurities and associated ions.

[0004] The adsorbents used for lithium extraction from salt lakes primarily include manganese-based and aluminum-based adsorbents. After the brine comes into contact with the adsorbent, the lithium ions in the brine bind to the adsorbent and, after saturation, are eluted. The eluent is typically an acid of a certain concentration, such as sulfuric acid or hydrochloric acid. However, the adsorption-desorption process is typically performed in large adsorption towers. Due to the large amount of adsorbent loaded, the brine or eluent flows very slowly within the tower, making mass transfer difficult. The adsorption and elution of lithium ions consume considerable time, resulting in low production efficiency.

[0005] Due to the slow mass transfer process, washing impurities from the adsorbent becomes difficult. Therefore, the lithium-containing desorbate obtained after desorption must be subjected to a large-scale nanofiltration membrane system for impurity removal, resulting in high equipment and operating costs. After impurity removal, it is then concentrated to obtain a lithium-containing concentrate. The lithium-containing concentrate is then precipitated with sodium carbonate to produce crude lithium carbonate. However, my country's salt lake lithium resources are primarily distributed in Tibet and Qinghai. The natural environment is relatively harsh, supporting infrastructure is lacking, the adsorption method consumes large amounts of acid and alkali, and the transportation cost of raw materials is high. These factors further restrict the further development of downstream industries. Summary of the Invention

[0006] In view of this, the present invention provides a centrifugal adsorption method for extracting lithium from salt lakes, which solves the problem of low adsorption-desorption efficiency of salt lake brine in an adsorption tower, resulting in many limiting factors in the salt lake lithium extraction process.

[0007] The centrifugal adsorption method for extracting lithium from salt lakes of the present invention comprises the following steps:

[0008] (1) The adsorbent is loaded into a centrifuge drum and the centrifuge is turned on; the centrifuge is selected from any one of a vertical centrifuge and a horizontal centrifuge.

[0009] (2) adding lithium-containing brine into a centrifuge drum to adsorb the lithium-containing brine; the adsorbed brine is discharged from the centrifuge drum;

[0010] (3) adding an eluent to the centrifuge drum to obtain a lithium-containing eluent;

[0011] (4) The lithium-containing eluent is subjected to electrodialysis to obtain a lithium hydroxide solution and a dilute acid solution, respectively. The lithium hydroxide solution is then concentrated to obtain a crude lithium hydroxide product; the dilute acid solution can be used for the elution process of step (3).

[0012] Preferably, step (2) further includes step (2-1), adding deionized water to the centrifuge drum twice to wash the impurities remaining in the brine, and then continuing centrifugation for 5 minutes; the volume mass ratio of the total amount of deionized water added to the adsorbent is 3.4~4L:6~7kg.

[0013] Preferably, the separation factor of the centrifuge in step (1) is 200-600.

[0014] Preferably, the adsorbent in step (1) is any one of an aluminum-based adsorbent or a manganese-based adsorbent, and the adsorption capacity of the adsorbent is 2 g / kg to 20 g / kg.

[0015] The manganese adsorbent is prepared by mixing manganese trioxide as a manganese source and lithium carbonate as a lithium source at a molar ratio of 1.25:1. The manganese trioxide and lithium carbonate are ground into 100-200 mesh and then calcined at 700-800°C to obtain a composition of Li4Mn5O 12 The precursor is then washed with 1% sulfuric acid to obtain a precursor.

[0016] The aluminum-based adsorbent was prepared according to the reference "Cheng Penggao, Huang Chuanfeng, Gan Shantian, et al. Preparation of aluminum-based lithium adsorbent and its application in lithium extraction from Taihe underground brine [J]. Inorganic Salt Industry, 2021. DOI: 10.19964 / j.issn.1006-4990.2020-0439". The preparation method is as follows:

[0017] 1) Accurately weigh AlCl3 and LiCl in a molar ratio of 1.25:1, mix and dissolve;

[0018] 2) Add the NaOH solution dropwise to the mixture of AlCl3 and LiCl at 75°C with a stirring speed of 100-200 r / min; control the reaction endpoint pH to 6-7;

[0019] 3) Filtering to separate the solid and liquid to obtain a filter cake, which is then dried to obtain an aluminum-based lithium adsorbent. The adsorbent is composed of: LiCl2Al(OH)3·nH2O.

[0020] Preferably, the lithium content in the lithium-containing brine in step (2) is 0.05 g / L to 5 g / L.

[0021] Preferably, during the adsorption process in step (2), the introduction rate of the lithium-containing brine is controlled so that it just covers the adsorbent.

[0022] Preferably, the eluent in step (3) is any one of dilute hydrochloric acid, dilute sulfuric acid and deionized water; the mass concentration of the dilute hydrochloric acid and dilute sulfuric acid is 0.1% to 5%.

[0023] Preferably, the ratio of the adsorbent, lithium-containing brine and eluent is 75-90 L: 6-7 kg: 10-11 L.

[0024] Preferably, the introduction rate of the eluent in step (3) is controlled at 16 to 18 L / min.

[0025] A centrifuge is a mechanical device that uses centrifugal force to accelerate the separation of liquid and solid particles. The separation effect of a centrifuge can be expressed by the separation factor (Fr) as shown in formula (1):

[0026]

[0027] Where R is generally the drum radius (meters); ω is the angular velocity of the drum (radians per second); g is the acceleration due to gravity (9.81 meters per second); and n is the drum speed (revolutions per minute).

[0028] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a centrifugal adsorption method for extracting lithium from salt lakes. The present invention utilizes centrifugal force to increase the flow rate of brine and eluent, accelerates the adsorption and desorption mass transfer process, reduces the adsorption and desorption time, and greatly improves production efficiency; the adsorbent is loaded in the centrifuge drum, which is convenient for replacement and maintenance; the impurities entrained in the adsorbent are greatly reduced, and the obtained lithium-containing desorption liquid has high purity, reducing equipment investment; at the same time, the use of large amounts of acid and alkali is avoided, saving raw material logistics costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1Schematic diagram of the centrifugal adsorption method for extracting lithium from salt lakes in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the embodiments.

[0031] Example 1

[0032] A centrifugal adsorption method for extracting lithium from salt lakes, comprising the following steps:

[0033] (1) 600 kg of manganese-based adsorbent was loaded into the drum of a vertical centrifuge (φ1600*800 mm), the centrifuge was turned on, the speed was adjusted to 800 rpm, and the separation factor of the centrifuge was 573;

[0034] (2) 7500 L of lithium-containing brine was added to the centrifuge drum to adsorb the lithium-containing brine (containing 1.17 g / L of lithium); during the adsorption process, the introduction rate of the lithium-containing brine was controlled (on average about 18 L / min) so that it just covered the adsorbent, and the adsorbed brine was discharged from the centrifuge drum into the secondary brine tank;

[0035] (3) Add 340 L of washing water to the centrifuge drum twice. Continue centrifugation for 5 minutes after adding the washing water. The outflowing washing water enters the washing water tank.

[0036] (4) adding 1000 L of eluent (1% sulfuric acid by mass concentration) to the centrifuge drum at a rate of 18 L / min to obtain a lithium-containing eluent which enters an eluent tank;

[0037] (5) The lithium-containing eluate is subjected to bipolar membrane electrodialysis to obtain a lithium hydroxide solution (entering a lithium hydroxide tank) and a dilute acid solution, respectively. The lithium hydroxide solution is then distilled and concentrated to obtain 37.4 kg of crude lithium hydroxide monohydrate (lithium hydroxide content 53.8%). The fraction (fraction collection tank) is collected and used in the acid preparation or washing process; the dilute acid solution enters the acid tank and can be used for the elution process of step (4).

[0038] Example 2

[0039] A centrifugal adsorption method for extracting lithium from salt lakes, comprising the following steps:

[0040] (1) 700 kg of aluminum-based adsorbent was loaded into the drum of a vertical centrifuge (φ1600*800 mm), the centrifuge was turned on, the speed was adjusted to 500 rpm, and the separation factor of the centrifuge was 224;

[0041] (2) 9000 L of lithium-containing brine was added to the centrifuge drum to adsorb the lithium-containing brine (containing 1.17 g / L of lithium); during the adsorption process, the introduction rate of the lithium-containing brine was controlled (on average about 17 L / min) so that it just covered the adsorbent, and the adsorbed brine was discharged from the centrifuge drum into the secondary brine tank;

[0042] (3) Add 400 L of washing water to the centrifuge drum twice. Continue centrifugation for 5 minutes after adding the washing water. The outflowing washing water enters the washing water tank.

[0043] (4) adding 1100 L of eluent (2% hydrochloric acid) to the centrifuge drum at a rate of 16 L / min to obtain a lithium-containing eluent which enters an eluent tank;

[0044] (5) The lithium-containing eluate is subjected to bipolar membrane electrodialysis to obtain a lithium hydroxide solution and a dilute acid solution, respectively. The lithium hydroxide solution is then concentrated to obtain 40.9 kg of crude lithium hydroxide monohydrate (lithium hydroxide content 54.2%); the dilute acid solution enters an acid tank and can be used for the elution process of step (4).

[0045] Comparative Example 1

[0046] A method for extracting lithium from a salt lake, comprising the following steps:

[0047] 600 kg of manganese-based adsorbent was loaded into an adsorption tower (φ1600 x 800 mm). A lithium-containing brine (1.17 g / L lithium, totaling 9000 L) was introduced into the tower, and the effluent flowed out of the tower at an average rate of approximately 4 L / min.

[0048] A total of 340 L of washing water was introduced into the centrifuge drum twice, and the washing water flowed out of the adsorption tower.

[0049] 1000 L of eluent (hydrochloric acid with a mass concentration of 2%) was added to the adsorption tower at a rate of about 6 L / min. The eluent flowed out of the adsorption tower.

[0050] The obtained eluate was subjected to nanofiltration to remove magnesium ions, and then concentrated by reverse osmosis membrane. The concentrate was precipitated with sodium carbonate and filtered to obtain lithium carbonate (filter cake, containing 36.0 kg of dry lithium carbonate) and sodium chloride solution (filtrate).

[0051] The parameters of the adsorption process of Examples 1, 2 and Comparative Example 1 are shown in Table 1:

[0052] Table 1

[0053] project Example 1 Example 2 Comparative Example 1 Adsorption capacity g / kg 7.5 7.2 6.8 <![CDATA[Li in the eluent + Concentration, g / L]]> 4.4 4.5 3.9 Desorption rate, % 97 98 96 Single recovery rate of lithium in brine, % 53 52 50 Adsorption-washing-desorption time, min 490 623 2473 Li production capacity, t / (t·a) 6.81 5.41 1.53

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A centrifugal adsorption method for extracting lithium from salt lakes, characterized in that: The following steps are involved: (1) Load the adsorbent into the centrifuge drum and start the centrifuge; (2) adding lithium-containing brine into a centrifuge drum to adsorb the lithium-containing brine; the adsorbed brine is discharged from the centrifuge drum; (3) adding an eluent to the centrifuge drum to obtain a lithium-containing eluent; (4) The lithium-containing eluate is subjected to electrodialysis to obtain a lithium hydroxide solution and a dilute acid solution, respectively. The lithium hydroxide solution is then concentrated to obtain a crude lithium hydroxide product; The dilute acid solution can be used for the elution process in step (3).

2. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The step (2) further includes step (2-1), adding deionized water to the centrifuge drum twice to wash the impurities remaining in the brine, and then continuing to centrifuge for 5 minutes; the volume mass ratio of the total amount of deionized water added to the adsorbent is 3.4~4L:6~7kg.

3. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The separation factor of the centrifuge in step (1) is 200-600.

4. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The adsorbent in step (1) is any one of an aluminum-based adsorbent or a manganese-based adsorbent, and the adsorption capacity of the adsorbent is 2 g / kg to 20 g / kg.

5. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The lithium content in the lithium-containing brine in step (2) is 0.05 g / L~5 g / L.

6. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: During the adsorption process of step (2), the introduction rate of the lithium-containing brine is controlled so that it just covers the adsorbent.

7. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The eluent in step (3) is dilute hydrochloric acid or dilute sulfuric acid; the mass concentration of the dilute hydrochloric acid and dilute sulfuric acid is 0.1% to 5%.

8. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The ratio of the adsorbent, lithium-containing brine and eluent is 75-90 L: 6-7 kg: 10-11 L.

9. The centrifugal adsorption method for extracting lithium from salt lakes according to claim 1, characterized in that: The introduction rate of the eluent in step (3) is controlled at 16-18 L / min.

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