METHOD FOR RECOVERING LITHIUM FROM LITHIUM-CONTAINING SOLUTION

Abstract

A method for recovering lithium from a lithium-containing solution is provided. A lithium-containing solution with an adjusted pH value or an unadjusted pH value is mixed with a meta-aluminate, and the pH value is adjusted to weak acid/neutral, so that lithium can be separated from the lithium-containing solution in the form of a precipitate of Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O. Then, the precipitate is converted into a lithium adsorbent of (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O and a Li.sub.aX-containing filtrate through desorption of lithium. High-purity Li.sub.2CO.sub.3 is obtained by performing precipitation of lithium on the Li.sub.aX-containing filtrate.

Claims

1. A method for recovering lithium from a lithium-containing solution, comprising: (1) precipitating lithium from the lithium-containing solution by a) or b): a) adjusting a pH value of the lithium-containing solution to 5-6, mixing the adjusted lithium-containing solution with a meta-aluminate solution, and standing for aging, to obtain a precipitation solution containing a first precipitate of Li(OH).Math.2Al(OH).sub.3nH.sub.2O, wherein n=1-3; and adjusting a pH value of the precipitation solution to 6-7, and performing filtering and washing on the regulated precipitation solution, to obtain a precipitate of Li.sub.aX.Math.2Al(OH).sub.3nH.sub.2O and a first filtrate; or b) mixing the lithium-containing solution with a meta-aluminate solution to obtain a first mixture, adjusting a pH value of the first mixture to 5-7, standing for aging, and performing filtering and precipitating on the regulated first mixture after the aging, to obtain a precipitate of Li.sub.aX.Math.2Al(OH).sub.3nH.sub.2O and a first filtrate, wherein X represents an anion of an acid solution used in the regulating of the pH value of the first mixture, n=1-3 and a=1 or 2; (2) desorption of lithium: mixing the precipitate of Li.sub.aX.Math.2Al(OH).sub.3nH.sub.2O with water to obtain a second mixture and stirring the second mixture, and filtering the second mixture to obtain a lithium adsorbent of (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O and a first Li.sub.aX-containing filtrate, wherein m=0.1-0.9; and (3) precipitation of lithium: evaporating and concentrating the first Li.sub.aX-containing filtrate to obtain a concentrated first Li.sub.aX-containing filtrate, adding a carbonate into the concentrated first Li.sub.aX-containing filtrate to obtain a third mixture, and stirring the third mixture, and performing filtering and washing on the third mixture, to obtain a precipitate of Li.sub.2CO.sub.3.

2. The method according to claim 1, further comprising: adding the lithium adsorbent to the first filtrate, stirring at 20-60° C. such that a lithium ion is absorbed in the first filtrate, and performing filtering and washing on the first filtrate to obtain a second precipitate of Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O; and performing the desorption of lithium on the second precipitate to obtain a lithium-desorbed filtrate, and precipitating lithium from the lithium-desorbed filtrate.

3. The method according to claim 1, wherein the acid solution comprises one of sulfuric acid, hydrochloric acid, nitric acid, or acetic acid.

4. The method according to claim 1, wherein a D50 particle size of the lithium adsorbent is 20-100 μm.

5. The method according to claim 1, wherein of the desorption of lithium comprises: mixing the first precipitate of Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with water in a mass ratio of 1:1 to 1:50 to obtain the second mixture, and stirring the second mixture at 20-60° C. for 1-24 hours.

6. The method according to claim 1, wherein the first Li.sub.aX-containing filtrate is evaporated and concentrated to obtain a concentration of lithium of 15-25 g/L.

7. The method according to claim 1, wherein in step (3), the carbonate is added into the first concentrated Li.sub.aX-containing filtrate at 50-90° C.

8. The method according to claim 1, wherein step (1) further comprises: during the adjusting of the pH value, collecting carbon dioxide produced by the lithium-containing solution and injecting the collected carbon dioxide into an alkaline solution to obtain a carbonate, wherein the alkaline solution comprises NaOH or KOH, and the carbonate comprises Na.sub.2CO.sub.3 or K.sub.2CO.sub.3.

9. The method according to claim 1, wherein in step (1), the lithium-containing solution is mixed with the meta-aluminate solution in a molar ratio of Li:Al of 1.05:2 to 1.3:2.

10. The method according to claim 1, wherein in step (3), a molar ratio of lithium in the first Li.sub.aX-containing filtrate to a carbonate ion in the carbonate is 1.05:2 to 1.3:2.

11. The method according to claim 1, wherein in step (3), a second filtrate is obtained when obtaining the precipitate of Li.sub.2CO.sub.3, and the method further comprises: adding the second filtrate to the lithium-containing solution.

12. The method according to claim 1, wherein the filtering is performed under a negative pressure of 0.04-0.07 MPa, and a mesh number of a filter medium for the filtering is 300-5000.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 is a process flowchart of lithium recovery according to Embodiment 1 of the disclosure; and

[0056] FIG. 2 is a process flowchart of lithium recovery according to Embodiment 2 of the disclosure.

DETAILED DESCRIPTION

[0057] The technical solution of the embodiments of the disclosure is described in detail with a plurality of embodiments in the following.

Embodiment 1

[0058] Referring to the process flowchart shown in FIG. 1, the recovery of lithium from a lithium-containing solution includes the following steps.

[0059] (1) Neutralization with acid: a 10 wt % HCl solution is slowly added to a lithium-containing solution at a stirring rate of 300 rpm until the pH value is reduced to 6.0, and stirred for 0.5 h.

[0060] (2) Precipitation of aluminum salt: a 5 wt % NaAlO.sub.2 is prepared with pure water at a constant temperature of 60° C. and a stirring rate of 300 rpm, and stirred for 30 min. A meta-aluminate solution with a flow rate of 500 mL/min is added to the aluminum salt solution in a molar ratio of Li:Al of 1.1:2 by using a peristaltic pump at a stirring rate of 300 rpm and a constant temperature of 60° C. Flow rates of the lithium salt and the aluminum salt are determined according to concentrations of the lithium-containing solution and the meta-aluminate solution and the molar ratio of Li:Al. After the mixing is finished, stirring is further performed for 30 min to make reactants in the solution react completely.

[0061] (3) Standing for aging: the solution after the reaction is further aged at 25° C. for 12 h, to obtain a precipitation solution containing a first precipitate of Li(OH).Math.2Al(OH).sub.3.Math.nH.sub.2O.

[0062] (4) Neutralization and conversion: a 10 wt % HCl solution is slowly added to the precipitation solution for neutralization at a stirring rate of 300 rpm, to obtain a precipitate of Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O. The pH value is monitored during the neutralization, and the stirring is further performed for 30 min after the pH value is adjusted to 6.0.

[0063] (5) Filtering and washing 1: a precipitate is filtered out by using a vacuum filter with a 500-mesh filter cloth under a negative pressure of 0.04 MPa. The precipitate is spray-washed with pure water during the filtering with a ratio of a spraying water amount per unit time to a lithium adsorbent of 0.5 L/kg. A filtrate after the filtering and washing is filtered again by using a precise bag filter with a precision of 3 μm.

[0064] The collected tiny particles are returned for aging, and a first filtrate is obtained.

[0065] (6) Desorption of lithium: the filtered and washed Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O is mixed with water in a mass ratio of 1:20 at a constant temperature of 40° C., and stirred at a rate of 300 rpm for 3 h. Filtering and washing are performed, to obtain a lithium adsorbent of (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O (with a D50 particle size of 36.86 μm) and a Li.sub.aX-containing filtrate. A mesh number of the filter medium is 500, and the negative pressure of the filter is 0.04 MPa. A filtrate after the filtering is filtered again by using the precise bag filter with a precision of 3 μm. Tiny particles are collected and returned for aging.

[0066] (7) Precipitation of lithium: the Li.sub.aX-containing filtrate is evaporated and concentrated to a 22 g/L concentration of lithium in the filtrate. The evaporated and concentrated solution is heated to and kept at 90° C., and 10 wt % Na.sub.2CO.sub.3 is added at a stirring rate of 300 rpm, where the added amount is 1.2 times a theoretical calculation amount. After the addition is finished, the stirring is further performed for 0.5 h, and standing is performed for 2 h.

[0067] (8) Filtering and washing 2: a precipitate of Li.sub.2CO.sub.3 is filtered out by using a vacuum filter with a 300-mesh filter medium under a negative pressure of 0.04 MPa. The precipitate is spray-washed with pure water during the filtering with a ratio of a spraying water amount per unit time to Li.sub.2CO.sub.3 of 0.5 L/kg. A second filtrate is obtained and added to the lithium-containing solution in step (1).

[0068] (9) Drying: the precipitate is dried in a blast drying oven at 130° C. for 120 min, to obtain a Li.sub.2CO.sub.3 product.

[0069] An adsorption of balance lithium is also included as follows: the lithium-desorbed precipitate (that is, the lithium adsorbent) in step (6) is added to the first filtrate containing balance lithium obtained in step (5) at a stirring rate of 300 rpm with a solid-liquid ratio of the lithium adsorbent to the first filtrate of 1:20 (that is, 1 kg of adsorbent is added per 20 L of filtrate), and stirred at a constant temperature of 40° C. for 90 min.

[0070] Filtering and washing 3: a remaining liquid after the adsorption of balance lithium is filtered by using a vacuum filter with a 500-mesh filter medium under a negative pressure of 0.04 MPa. LiCl.Math.2Al(OH).sub.3.Math.nH.sub.2O after the adsorption of balance lithium is filtered out. The filtered matter is spray-washed with pure water during the filtering with a ratio of a spraying water amount per unit time to the adsorbent of 0.5 L/Kg. Lithium-desorbed is performed on the filtered matter. The filtrate is filtered for a second time by using a precise bag filter with a precision of 3 μm, and the second time filtered matter is returned for aging, and the filtrate is discharged. A second precipitate of Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O is obtained.

[0071] The second precipitate is mixed with water and stirred to undergo the above desorption of lithium to obtain a second lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O (with a D50 particle size of 36.86 μm) and a second Li.sub.aX-containing filtrate (parameters in this process are the same as the parameters adopted for the desorption of lithium in step (6)).

[0072] The second Li.sub.aX-containing filtrate is subjected to the precipitation of lithium, and filtered, washed, and dried to obtain Li.sub.2CO.sub.3 (parameters in this process are the same as the parameters adopted in step (7) precipitation of lithium, step (8) filtering and washing 2, and step (9) drying).

Embodiment 2

[0073] Referring to the process flowchart shown in FIG. 2, the recovery of lithium from a lithium-containing solution includes the following steps.

[0074] (1) Precipitation of aluminum salt: a 5 wt % NaAlO.sub.2 is prepared with pure water at a constant temperature of 60° C. and a stirring rate of 300 rpm, and stirred for 30 min. A meta-aluminate solution with a flow rate of 500 mL/min is added to the aluminum salt solution in a molar ratio of Li:Al of 1.1:2 by using a peristaltic pump at a stirring rate of 300 rpm and a constant temperature of 60° C. Flow rates of the lithium salt and the aluminum salt are determined according to concentrations of the lithium-containing solution and the meta-aluminate solution and the molar ratio of Li:Al. In addition, a 10 wt % HCl solution is slowly added to the lithium-containing solution until the pH value is reduced to 6.0, and stirred for 30 min, so that reactants in the solution react completely, to obtain a precipitate of Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O.

[0075] Subsequent operations of standing for aging, filtering and washing 1, adsorption of balance lithium, desorption of lithium, precipitation of lithium, filtering and washing 2, filtering and washing 3, and drying are all the same as those in Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 40.11 μm is obtained.

Embodiment 3

[0076] The difference between Embodiment 3 and Embodiment 1 is that: in the process of precipitation of aluminum salt in step (2), the molar ratio of Li:Al is 1.3:2. Other conditions and operations are all consistent with those of Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 41.28 um is obtained.

Embodiment 4

[0077] The difference between Embodiment 4 and Embodiment 1 is that: in the process of precipitation of aluminum salt in step (2), the molar ratio of Li:Al is 1.2:2. Other conditions and operations are all consistent with those of Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 38.19 um is obtained.

Embodiment 5

[0078] The difference between Embodiment 5 and Embodiment 1 is that: in the process of desorption of lithium in step (6), the temperature is controlled to 20° C. Other conditions and operations are all consistent with those of Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 43.87 um is obtained.

Embodiment 6

[0079] The difference between Embodiment 6 and Embodiment 1 is that: in the process of desorption of lithium in step (6), the temperature is controlled to 60° C. Other conditions and operations are all consistent with those of Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 40.41 um is obtained.

Embodiment 7

[0080] The difference between Embodiment 7 and Embodiment 1 is that: in the process of precipitation of lithium in step (7), the added amount of Na.sub.2CO.sub.3 is 1.05 times the theoretical calculation amount. Other conditions and operations are all consistent with those of Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 37.13 μm is obtained.

Embodiment 8

[0081] The difference between Embodiment 8 and Embodiment 1 is that: in the process of precipitation of lithium in step (7), the added amount of Na.sub.2CO.sub.3 is 1.3 times the theoretical calculation amount. Other conditions and operations are all consistent with those of Embodiment 1. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 39.51 μm is obtained.

Embodiment 9

[0082] In Embodiment 9, compared with Embodiment 1, the pressure of all vacuum filtering is adjusted to 0.06 MPa, and other conditions remained unchanged. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 44.64 μm is obtained.

Embodiment 10

[0083] In Embodiment 10, compared with Embodiment 1, the step of filtering again by using a precise bag filter in the filtering and washing 1, filtering and washing 2, and filtering and washing 3 are omitted, and other conditions remained unchanged. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 35.49 μm is obtained.

Embodiment 11

[0084] The difference between Embodiment 11 and Embodiment 1 is that: after the neutralization and conversion in step (4), the balance lithium remaining in the first filtrate is not adsorbed by using the lithium adsorbent, and the first filtrate is directly discharged after precise filtering. A lithium adsorbent (1-m)Li.sub.aX.Math.2Al(OH).sub.3.Math.nH.sub.2O with a D50 particle size of 38.11 μm is obtained.

[0085] The technical solution provided in the disclosure is evaluated from the recovery rate of lithium, the purity of Li.sub.2CO.sub.3, the adsorption capacity of the lithium adsorbent, and the concentration of lithium in the discharged liquid. The recovery rate of lithium is determined based on the concentration of lithium (the concentration of Li′: 1.568 g/L) in the discharged liquid and the lithium-containing solution. The purity of Li.sub.2CO.sub.3 is determined by determining the content of carbonate ion by potentiometric titration. The concentration of lithium in the discharged liquid is determined by using an inductively coupled plasma (ICP) spectrometer. Test results of the embodiments are recorded in Table 1.

[0086] The testing method for the adsorption capacity of the lithium adsorbent is as follows. A lithium-containing brine with a high magnesium-lithium ratio is used for testing, where a concentration of Li.sup.+ is 0.0233 wt %, a concentration of Mg.sup.2+ is 7.8540 wt %, and the mass ratio of Mg:Li in the brine is 337:1. 10 g of lithium adsorbent is weighted, and is used for adsorption in a solid-liquid ratio of 1:50 at room temperature with a stirring rate of 300 rpm and an adsorption time of 90 min. The difference in the concentration of lithium in the brine before and after adsorption is the adsorption capacity of the lithium adsorbent.

TABLE-US-00001 TABLE 1 Test results of embodiments and comparative embodiments Concentration Recovery Adsorption of Li.sup.+ in D50 particle size Experiment rate of Purity of capacity discharged of lithium number lithium Li.sub.2CO.sub.3 (mg Li/g) liquid (mg/L) adsorbent (μm) Embodiment 1 98.5% 99.3% 9.66 22.8 36.86 Embodiment 2 98.4% 99.3% 7.96 25.3 40.11 Embodiment 3 93.4% 99.4% 9.89 103.2 41.28 Embodiment 4 95.8% 99.4% 9.73 65.3 38.19 Embodiment 5 85.6% 99.3% 5.61 225.3 43.87 Embodiment 6 89.0% 99.4% 6.68 171.8 40.41 Embodiment 7 95.0% 99.4% 9.59 26.3 37.13 Embodiment 8 98.6% 99.0% 9.69 21.3 39.51 Embodiment 9 98.5% 99.6% 9.63 24.3 44.64 Embodiment 10 95.1% 98.1% 9.58 76.8 35.49 Embodiment 11 67.7% 99.3% 9.61 505.8 38.11

[0087] The test results of Embodiments 1-11 in Table 1 are analyzed by comparison in the following:

[0088] (1) It can be learned by comparing the test results of Embodiments 1 and 2 that: the adsorption capacity of the lithium adsorbent prepared in Embodiment 2 is lower than that in Embodiment 1. However, because the balance lithium content of the first filtrate in Embodiment 2 is lower than that in Embodiment 1, the final recovery rates of lithium in the foregoing two embodiments are not much different.

[0089] (2) It can be learned by comparing the test results of Embodiments 1, 3, and 4 that: in the step of precipitation of aluminum salt, appropriately excessive lithium in the lithium-containing solution is beneficial for the meta-aluminate to react completely, and there is no aluminum remaining in the system after the reaction, thereby improving the purity of lithium carbonate.

[0090] (3) It can be learned by comparing the test results of Embodiments 1, 5, and 6 that: within the same period of time, a low desorption of lithium temperature leads to a small desorption of lithium amount, resulting in decreases in the recovery rate of lithium and in the adsorption capacity of the adsorbent. A high desorption of lithium temperature leads to a large desorption of lithium amount and a high recovery rate of lithium.

[0091] (4) It can be learned by comparing the test results of Embodiments 1, 7, and 8 that: appropriately excessive sodium carbonate can ensure the level of the lithium ion involved reaction level in the system, thereby increasing the recovery rate of lithium.

[0092] (5) It can be learned by comparing the test results of Embodiments 1 and 9 that: an increase in the negative pressure of the vacuum filtering can improve the purity of the Li.sub.2CO.sub.3 prepared.

[0093] (6) It can be learned by comparing the test results of Embodiments 1 and 10 that: the loss of tiny particles can be avoided by filtering again, which can further increase the recovery rate of lithium, and prevent the tiny particles from entering the step of precipitation of lithium, resulting in a decrease in the purity of lithium carbonate.

[0094] (7) It can be learned by comparing the test results of Embodiments 1 and 11 that: in Embodiment 11, compared with Embodiment 1, the balance lithium remaining in the first filtrate does not undergo adsorption, and therefore the recovery rate of Embodiment 1 is higher than the recovery rate of Embodiment 11.

[0095] The foregoing descriptions are exemplary embodiments of the disclosure. It should be noted that, a person of ordinary skill in the art can further make several improvements and refinements without departing from the principle of the disclosure, and the improvements and refinements shall fall within the protection scope of the disclosure.