Method for extracting lithium and separating calcium and magnesium from lithium-containing brine

Abstract

The invention discloses a method for extracting lithium and separating calcium and magnesium from lithium-containing brine, and belongs to the technical field of extraction of lithium from brine. The method for extracting lithium and separating calcium and magnesium from the lithium-containing brine comprises the following steps: adding a NaAlO2 solution into the lithium-containing brine, adjusting the pH value to 9.5-11.5, mixing and reacting, and filtering to obtain a lithium-containing filtrate and a solid product containing calcium and magnesium; removing impurities from the lithium-containing filtrate by using divalent cation exchange resin (calcium and magnesium removal), and then adding sodium carbonate to obtain Li2CO3; adding an acid solution into the calcium-magnesium-containing solid product to dissolve the calcium-magnesium-containing solid product, adjusting the pH value to 4-5, mixing, reacting, and filtering to obtain a calcium-magnesium-containing filtrate; adding sodium sulfate into the filtrate containing calcium and magnesium, mixing and reacting, and filtering to obtain filtrate containing magnesium and CaSO4; and adjusting the pH value of the magnesium-containing filtrate to 12-13 to obtain Mg (OH) 2. The method provided by the invention not only is beneficial to extraction of lithium resources in the brine, but also is beneficial to comprehensive utilization of lithium-containing new energy mineral resources.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from brine, and particularly to a method for extracting lithium and separating calcium and magnesium from lithium-containing brine. Background Art

[0002] In recent years, due to the rapid development of industries such as new energy batteries, electric vehicles, and automobiles, the raw material demand for lithium (Li) and its salts as key new energy materials has gradually increased. The efficient and sustainable development of lithium-containing mineral resources is one of the important research directions in the current lithium resource supply chain.

[0003] Brine lithium is an important source of lithium resources. The cost of separating and extracting lithium ions from brine is relatively low, so it has received extensive attention and become a research hotspot. At present, the methods for extracting lithium from brine mainly include evaporation crystallization, precipitation method, extraction method, adsorption method, and membrane separation method, and the main research object is brine with a relatively high magnesium-lithium ratio. There is relatively little research on extracting lithium from brine with a relatively high calcium-lithium ratio. At present, the main process route in the technology for extracting lithium from brine is: raw brine → evaporation and concentration to remove sodium and potassium salts → acidification to remove boron → removal of calcium and magnesium → lithium precipitation. Such processes usually place the lithium extraction process at the back end. During processes such as evaporation crystallization to separate salts and boron removal, lithium ions are lost in an entrained form, resulting in a decrease in lithium recovery rate; moreover, the calcium and magnesium concentrations in the concentrated brine increase, leading to an increase in the operation load of calcium and magnesium removal; in addition, lithium will be lost with the precipitation entrainment, further increasing the loss of lithium, thus causing waste of lithium resources in the brine. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for extracting lithium and separating calcium and magnesium from lithium-containing brine to solve the problems existing in the above-mentioned prior art. The present invention adds a sodium aluminate (NaAlO2) solution to lithium-containing brine (raw brine), controls the conditions, first selectively precipitates and separates calcium and magnesium in the raw brine, and then separates and enriches lithium ions, overcoming the problem of waste of lithium resources.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: A method for extracting lithium from lithium-containing brine, comprising the following steps:

[0007] Add a NaAlO2 solution to the lithium-containing brine, adjust the pH to 9-11, filter after mixing and reacting to obtain a lithium-containing filtrate and a solid product;

[0008] After removing impurities from the lithium-containing filtrate using a divalent cation exchange resin, add sodium carbonate to obtain Li2CO3;

[0009] The function of the divalent cation exchange resin is to remove trace calcium and magnesium ions present in the brine 1.

[0010] Further, the concentration of the NaAlO2 solution is 50-100 g / L; the volume ratio of the NaAlO2 solution to the lithium-containing brine is (35-70):1000;

[0011] The cation components in the lithium-containing brine include: Li + , Ca 2+ and Mg 2+ ; The mass concentration ratio of Li + , Ca 2+ and Mg 2+ in the original lithium-containing brine is (70-90):(1200-5000):(190-320).

[0012] The second technical solution of the present invention: A method for extracting lithium from lithium-containing brine and separating calcium and magnesium, comprising the following steps:

[0013] Add a NaAlO2 solution to the lithium-containing brine, adjust the pH to 9.5-11.5, filter after mixing and reacting to obtain a lithium-containing filtrate and a solid product containing calcium and magnesium;

[0014] The cation components in the lithium-containing brine include: Li + , Ca 2+ and Mg 2+ ;

[0015] Use a divalent cation exchange resin to remove impurities from the lithium-containing filtrate and then add sodium carbonate to obtain Li2CO3;

[0016] Add an acid solution to the solid product containing calcium and magnesium to dissolve it, then adjust the pH to 4-5, filter after mixing and reacting to obtain a filtrate containing calcium and magnesium;

[0017] Add sodium sulfate to the filtrate containing calcium and magnesium, filter after mixing and reacting to obtain a magnesium-containing filtrate and CaSO4;

[0018] Adjust the pH of the magnesium-containing filtrate to 12-13 to obtain Mg(OH)2.

[0019] Further, the concentration of the NaAlO2 solution is 50-100 g / L; the volume ratio of the NaAlO2 solution to the lithium-containing brine is (35-70):1000;

[0020] The mass concentration ratio of Li + , Ca 2+ and Mg 2+ in the original lithium-containing brine is (70-90):(1200-5000):(190-320).

[0021] Further, the acid solution includes an HCl solution with a concentration of 1.0 - 2.0 mol / L; the dosage ratio of the calcium- and magnesium-containing solid product to the acid solution is 1 g : 25 - 50 mL.

[0022] Further, the pH regulator used to adjust the pH to 4 - 5 includes a NaOH solution with a concentration of 1.0 - 2.0 mol / L.

[0023] Further, the pH regulator used to adjust the pH to 12 - 13 includes a NaOH solution with a concentration of 1.0 - 2.0 mol / L.

[0024] The present invention discloses the following technical effects:

[0025] (1) The method of the present invention can improve the lithium recovery rate and avoid waste of lithium resources.

[0026] (2) The method of the present invention realizes the direct separation of Li from the raw brine in the first-step reaction by selective precipitation + from Ca 2+ , Mg 2+ , and prepares Li2CO3. At the same time, the step-by-step separation and enrichment of Ca 2+ , Mg 2+ are realized, the full utilization of high-calcium lithium ratio brine resources is achieved, and the recovery of Al in the reactants is realized to a certain extent. In addition, the process flow of the present invention is simple, and the reagents are cheap and easily available, which is beneficial to reducing the cost of extracting lithium from brine.

[0027] (3) The method of the present invention is not only beneficial to the extraction of lithium resources in brine, but also beneficial to the comprehensive utilization of lithium-containing new energy mineral resources.

[0028] (4) Compared with the traditional process for extracting lithium from old brine, the method of the present invention shortens the lithium extraction process, is beneficial to improving the separation efficiency of lithium in the raw brine, reducing lithium loss, and is beneficial to the efficient extraction and enrichment of lithium resources in brine. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 It is a schematic flow chart of extracting lithium and separating calcium and magnesium used in the embodiment;

[0031] Figure 2 It is the XRD spectrum of the solid phase 1# obtained in step (2) of Example 1;

[0032] Figure 3 XRD pattern of Li2CO3 prepared in step (3) of Example 1;

[0033] Figure 4 XRD pattern of solid phase 3# obtained in step (6) of Example 1;

[0034] Figure 5 XRD pattern of solid phase 4# obtained in step (7) of Example 1. Detailed implementation manners

[0035] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0038] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0039] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0040] In the first aspect of the present invention, a method for extracting lithium from lithium-containing brine is provided, including the following steps:

[0041] Add a NaAlO₂ solution to the lithium-containing brine, adjust the pH to 9.5 - 11.5, filter after mixing and reacting to obtain a lithium-containing filtrate and a solid product;

[0042] After removing impurities from the lithium-containing filtrate using a divalent cation exchange resin (for calcium and magnesium removal), add sodium carbonate to obtain Li₂CO₃;

[0043] In a specific embodiment of the present invention, the cation components in the lithium-containing brine include: Li + , Ca 2+ and Mg 2+ ; the mass concentration ratio of Li + , Ca 2+ and Mg 2+ in the lithium-containing raw brine is (70 - 90):(1200 - 5000):(190 - 320).

[0044] The concentration of the NaAlO₂ solution is 50 - 100 g / L; the volume ratio of the NaAlO₂ solution to the lithium-containing brine is (35 - 70):1000.

[0045] In a second aspect of the present invention, a method for extracting lithium from lithium-containing brine and separating calcium and magnesium is provided, including the following steps:

[0046] (1) Add a NaAlO₂ solution to the lithium-containing brine (raw brine), adjust the pH to 9.5 - 11.5, stir and react at room temperature for 3 - 6 h to obtain a solid mixture. After suction filtration and washing, the solid phase is dried at 60 °C to constant weight, denoted as solid phase 1#, and the liquid phase is denoted as brine 1#, for later use;

[0047] The cation components in the lithium-containing brine include: Li + , Ca 2+ and Mg 2+ ; the mass concentration ratio of Li + , Ca 2+ and Mg 2+ in the lithium-containing raw brine is (70 - 90):(1200 - 5000):(190 - 320);

[0048] The concentration of the NaAlO₂ solution is 50 - 100 g / L; the volume ratio of the NaAlO₂ solution to the lithium-containing brine is (35 - 70):1000;

[0049] The reaction of the lithium-containing brine with the NaAlO₂ solution, the specific principle is that Ca 2+ , Mg 2+ in the lithium-containing brine and NaAlO₂ react under alkaline conditions (pH = 9.5 - 11.5) to form a mixture of hydrocalumite, hydrotalcite, Al(OH)₃, Ca(OH)₂ and Mg(OH)₂, Ca 2+and Mg 2+ exist in the form of insoluble substances and are separated from the lithium-containing brine by filtration. Lithium does not undergo an obvious reaction under alkaline conditions with pH = 9.5 - 11.5 and continues to exist in the brine 1# in the form of ions. This step can achieve the separation of Li + from Ca 2 + and Mg 2+ , facilitating the subsequent direct preparation of Li2CO3 from brine 1#;

[0050] mainly involves the following reactions:

[0051]

[0052] (2) After the brine 1# is purified by a divalent cation exchange resin (for calcium and magnesium removal), it is evaporated and concentrated. The liquid phase obtained after filtration is denoted as brine 2#, and the solid phase is a sodium-potassium mixed salt. Saturated sodium carbonate solution is added to brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product;

[0053] The concentration of Li + in brine 2# is 2.0 - 2.5 g / L;

[0054] The purpose of purifying the brine 1# by a divalent cation exchange resin (for calcium and magnesium removal) is to remove the residual trace amounts of Ca 2+ and Mg 2+ in the brine. After evaporation and concentration, brine 2# is obtained, and saturated sodium carbonate solution is added to prepare Li2CO3;

[0055] mainly involves the following reactions:

[0056]

[0057] (3) After the solid phase 1# is mixed with a HCl solution with a concentration of 1.0 - 2.0 mol / L and stirred until completely dissolved, the resulting liquid is denoted as solution 1#;

[0058] The dosage ratio of the solid phase 1# to the HCl solution is 1 g: 25 - 50 mL;

[0059] The reaction of the solid phase 1# with the HCl solution can dissolve georgeite, hydrotalcite, Al(OH)3, and Mg(OH)2, enabling Ca, Mg, and Al to exist in the form of ions;

[0060] mainly involves the following reactions:

[0061]

[0062] (4) Add a NaOH solution with a concentration of 1.0 - 2.0 mol / L to Solution 1#, adjust the pH to 4 - 5, stir and react for 3 - 6 h. The solid phase obtained after filtration is denoted as Solid Phase 2#, and the liquid phase is denoted as Solution 2#;

[0063] Adding NaOH to the obtained Solution 1# to adjust the pH = 4 - 5 aims to preferentially separate Al 3+ in the form of Al(OH)3 (Solid Phase 2#);

[0064] The main reactions involved are as follows:

[0065]

[0066] (5) Add saturated sodium sulfate solution to Solution 2#, stir and react at room temperature for 3 - 6 h, then filter to obtain Solid Phase 3# and Solution 3#;

[0067] The main cation components in Solution 2# are Ca 2+ and Mg 2+ . Adding saturated sodium sulfate solution can separate Ca 2+ in the form of CaSO4 (Solid Phase 3#);

[0068] The main reactions involved are as follows:

[0069]

[0070] (6) Add a NaOH solution with a concentration of 1.0 - 2.0 mol / L to Solution 3# to adjust the pH to 12 - 13, stir and react at room temperature for 3 - 6 h, and obtain Solid Phase 4# after filtration and washing;

[0071] The main cation component in Solution 3# is Mg 2+ . Adding NaOH to adjust the pH = 12 - 13 can separate Mg 2+ in the form of Mg(OH)2;

[0072] The main reactions involved are as follows:

[0073]

[0074] The flow chart for lithium extraction and calcium and magnesium separation is shown in Figure 1 .

[0075] The reaction in the first step of the present invention realizes the separation of Li + from Ca 2+ and Mg 2+ . It can not only effectively shorten the lithium extraction process but also is beneficial to reducing Li + loss. At the same time, the present invention realizes the separation of Ca 2+ and Mg 2+ in the brine.The step-by-step separation uses simple, safe, and environmentally friendly reagents, and to a certain extent, the NaAlO2 introduced in the reactants is recovered in the form of Al(OH)3, realizing the full utilization of Al resources.

[0076] In the specific implementation of the present invention, the mass concentrations of Na + , K + , Ca 2+ , Mg 2+ and Li + in the involved liquid are all detected by ICP-OES, and the involved solid phases 1#-4# are all samples that have been fully washed, filtered, and dried with deionized water.

[0077] Example 1

[0078] A method for extracting lithium and separating calcium and magnesium from lithium-containing brine:

[0079] (1) Mix NaAlO2 and water at a dosage ratio of 0.06 g: 1 mL, stir at room temperature until fully dissolved to obtain a NaAlO2 solution, and set aside.

[0080] (2) Take 60 mL of the NaAlO2 solution in step (1) and add it to 1000 mL of raw brine, adjust the pH = 10, stir and react at room temperature for 4 h, after suction filtration and washing, the solid phase is dried to constant weight at 60 °C, denoted as solid phase 1#, and the liquid phase is denoted as brine 1#, and set aside.

[0081] Table 1 Main cation components and concentrations in raw brine

[0082] Component <![CDATA[Na + > <![CDATA[K + > <![CDATA[Ca 2+ > <![CDATA[Mg 2+ > <![CDATA[Li + > Concentration (mg / L) 16847.2 4428.8 2410.8 195.0 85.1

[0083] (3) After removing impurities from brine 1# through a divalent cation exchange resin (to remove calcium and magnesium), and through evaporation and concentration, the liquid phase obtained after filtration is denoted as brine 2#, and the solid phase is a sodium-potassium mixed salt. Add saturated sodium carbonate solution to brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product, with a purity of 99.5% and a lithium recovery rate of 93.8%.

[0084] Among them, the concentration of Li + in the evaporated brine 2# is 2.0 g / L.

[0085] (4) Mix the solid phase 1# and a 1.0 mol / L HCl solution at a dosage ratio of 1 g: 50 mL, stir and react until completely dissolved, and the obtained liquid is denoted as solution 1#.

[0086] (5) Add a NaOH solution with a concentration of 1.0 mol / L to Solution 1# to adjust the pH to 4.5, stir and react for 4 h. The solid phase obtained after filtration is denoted as Solid Phase 2# (Al(OH)3, purity 99.4%, Al recovery rate 98.0%), and the liquid phase is denoted as Solution 2#.

[0087] (6) Add a saturated sodium sulfate solution to Solution 2#, stir and react at room temperature for 4 h, then filter to obtain Solid Phase 3# (CaSO4, purity 99.2%, Ca recovery rate 97.0%) and Solution 3#.

[0088] (7) Add a NaOH solution with a concentration of 1.0 mol / L to Solution 3# to adjust the pH to 12.5, stir and react at room temperature for 4 h, then filter to obtain Solid Phase 4# (Mg(OH)2, purity 97.8%, Mg recovery rate 96.2%).

[0089] The flow chart for lithium extraction and calcium and magnesium separation is shown in Figure 1 .

[0090] The XRD pattern of Solid Phase 1# obtained in step (2) is shown in Figure 2 , and the XRD pattern of Li2CO3 prepared in step (3) is shown in Figure 3 , the XRD pattern of Solid Phase 3# obtained in step (6) is shown in Figure 4 , and the XRD pattern of Solid Phase 4# obtained in step (7) is shown in Figure 5 .

[0091] Example 2

[0092] A method for lithium extraction from lithium-containing brine and separation of calcium and magnesium:

[0093] (1) Mix NaAlO2 and water at a dosage ratio of 0.08 g:1 mL, stir at room temperature until fully dissolved to obtain a NaAlO2 solution for standby.

[0094] (2) Take 40 mL of the NaAlO2 solution in step (1) and add it to 1000 mL of the original brine (Table 1), adjust the pH to 11, stir and react at room temperature for 3 h. After suction filtration and washing, the solid phase is dried at 60 °C to constant weight, denoted as Solid Phase 1#, and the liquid phase is denoted as Brine 1# for standby.

[0095] (3) After removing impurities from Brine 1# through a divalent cation exchange resin (for calcium and magnesium removal), and through evaporation and concentration, the liquid phase obtained after filtration is denoted as Brine 2#, and the solid phase is a sodium-potassium mixed salt. Add a saturated sodium carbonate solution to Brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product, with a purity of 99.6% and a lithium recovery rate of 95.2%.

[0096] Among them, the concentration of Li + in Brine 2# after evaporation is 2.2 g / L.

[0097] (4) Mix solid phase 1# with an HCl solution with a concentration of 1.5 mol / L at a dosage ratio of 1 g: 30 mL, and stir and react until completely dissolved. The resulting liquid is denoted as solution 1#.

[0098] (5) Add a NaOH solution with a concentration of 1.5 mol / L to solution 1#, adjust the pH to 5, stir and react for 3 h, and the solid phase obtained after filtration is denoted as solid phase 2# ((Al(OH)3, purity 99.5%, Al recovery rate 98.8%)), and the liquid phase is denoted as solution 2#.

[0099] (6) Add a saturated sodium sulfate solution to solution 2#, stir and react at room temperature for 3 h and then filter to obtain solid phase 3# (CaSO4, purity 99.0%, Ca recovery rate 96.2%) and solution 3#.

[0100] (7) Add a NaOH solution with a concentration of 1.5 mol / L to solution 3# to adjust the pH to 12, stir and react at room temperature for 3 h, and the solid phase obtained after filtration is denoted as solid phase 4# (Mg(OH)2, purity 97.8%, Mg recovery rate 96.4%).

[0101] Example 3

[0102] A method for extracting lithium and separating calcium and magnesium from lithium-containing brine:

[0103] (1) Mix NaAlO2 with water at a dosage ratio of 0.05 g: 1 mL, and stir at room temperature until fully dissolved to obtain a NaAlO2 solution for standby.

[0104] (2) Take 70 mL of the NaAlO2 solution in step (1) and add it to 1000 mL of the original brine (Table 1), and adjust the pH to 10.5. Stir and react at room temperature for 5 h. After suction filtration and washing, the solid phase is dried at 60 °C to a constant weight and denoted as solid phase 1#, and the liquid phase is denoted as brine 1# for standby.

[0105] (3) After removing impurities from brine 1# through a divalent cation exchange resin (for removing calcium and magnesium), and through evaporation and concentration, the liquid phase obtained after filtration is denoted as brine 2#, and the solid phase is a sodium-potassium mixed salt. Add a saturated sodium carbonate solution to brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product, with a purity of 99.5% and a Li recovery rate of 94.0%.

[0106] Among them, the Li + concentration in the evaporated brine 2# is controlled to be 2.5 g / L.

[0107] (4) Mix solid phase 1# with an HCl solution with a concentration of 2.0 mol / L at a dosage ratio of 1 g: 25 mL, and stir and react until completely dissolved. The resulting liquid is denoted as solution 1#.

[0108] (5) Add a NaOH solution with a concentration of 2.0 mol / L to Solution 1#, adjust the pH to 4.8, stir and react for 5 h. The solid phase obtained after filtration is denoted as Solid Phase 2# (Al(OH)3, purity 99.4%, Al recovery rate 97.2%), and the liquid phase is denoted as Solution 2#.

[0109] (6) Add a saturated sodium sulfate solution to Solution 2#, stir and react at room temperature for 5 h, then filter to obtain Solid Phase 3# (CaSO4, purity 99.2%, Ca recovery rate 97.6%) and Solution 3#.

[0110] (7) Add a NaOH solution with a concentration of 2.0 mol / L to Solution 3# to adjust the pH to 13, stir and react at room temperature for 3 h, and the solid phase obtained after filtration is Solid Phase 4# (Mg(OH)2, purity 98.2%, Mg recovery rate 96.8%).

[0111] Example 4

[0112] A method for extracting lithium and separating calcium and magnesium from lithium-containing brine:

[0113] (1) Mix NaAlO2 and water at a dosage ratio of 0.09 g:1 mL, stir at room temperature until completely dissolved to obtain a NaAlO2 solution for standby.

[0114] (2) Take 45 mL of the NaAlO2 solution in step (1) and add it to 1000 mL of raw brine (Table 1), adjust the pH to 9.5, stir and react at room temperature for 6 h. After suction filtration and washing, the solid phase is dried at 60 °C to constant weight, denoted as Solid Phase 1#, and the liquid phase is denoted as Brine 1# for standby.

[0115] (3) After removing impurities from Brine 1# through a divalent cation exchange resin (to remove calcium and magnesium), and through evaporation and concentration, the liquid phase obtained after filtration is denoted as Brine 2#, and the solid phase is a sodium-potassium mixed salt. Add a saturated sodium carbonate solution to Brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product, with a purity of 99.6% and a Li recovery rate of 94.2%.

[0116] Among them, the Li + concentration control range in the evaporated Brine 2#: 2.0 g / L.

[0117] (4) Mix Solid Phase 1# and a HCl solution with a concentration of 1.5 mol / L at a dosage ratio of 1 g:35 mL, stir and react until completely dissolved, and the resulting liquid is denoted as Solution 1#.

[0118] (5) Add a NaOH solution with a concentration of 1.5 mol / L to Solution 1#, adjust the pH to 4.6, stir and react for 6 h. The solid phase obtained after filtration is denoted as Solid Phase 2# (Al(OH)3, purity 99.5%, Al recovery rate 98.6%), and the liquid phase is denoted as Solution 2#.

[0119] (6) Add a saturated sodium sulfate solution to Solution 2#, stir and react at room temperature for 6 h, then filter to obtain Solid Phase 3# (CaSO4, purity 99.0%, Ca recovery rate 96.2%) and Solution 3#.

[0120] (7) Add a 1.5 mol / L NaOH solution to Solution 3# to adjust the pH to 12.5, stir and react at room temperature for 3 h, and filter to obtain Solid Phase 4# (Mg(OH)2, purity 97.8%, Mg recovery rate 96.2%).

[0121] Example 5

[0122] A method for extracting Li from Li-containing brine and separating calcium and magnesium:

[0123] The composition of the brine is shown in Table 2, and the specific steps are as follows:

[0124] Table 2 Main cation components and concentrations in the original brine

[0125] Component <![CDATA[Na + > <![CDATA[K + > <![CDATA[Ca 2+ > <![CDATA[Mg 2+ > <![CDATA[Li + > Concentration (mg / L) 23265.2 7211.6 4441.8 299.4 86.2

[0126] (1) Mix NaAlO2 and water at a dosage ratio of 0.06 g:1 mL, stir at room temperature until completely dissolved to obtain a NaAlO2 solution for standby.

[0127] (2) Take 120 mL of the NaAlO2 solution in step (1) and add it to 1000 mL of the original brine, adjust the pH to 10, stir and react at room temperature for 4 h. After suction filtration and washing, the solid phase is dried to constant weight at 60 °C and denoted as Solid Phase 1#, and the liquid phase is denoted as Brine 1# for standby.

[0128] (3) After removing impurities from Brine 1# through a divalent cation exchange resin (for removing calcium and magnesium), and through evaporation and concentration, the liquid phase obtained after filtration is denoted as Brine 2#, and the solid phase is a sodium-potassium mixed salt. Add a saturated sodium carbonate solution to Brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product, with a purity of 99.5% and a Li recovery rate of 93.0%.

[0129] Among them, the concentration of Li in Brine 2# after evaporation + is 2.0 g / L.

[0130] (4) Mix Solid Phase 1# and a 1.0 mol / L HCl solution at a dosage ratio of 1 g:50 mL, stir and react until completely dissolved, and the resulting liquid is denoted as Solution 1#.

[0131] (5) Add a NaOH solution with a concentration of 1.0 mol / L to Solution 1# to adjust the pH to 4.5, stir and react for 4 h. The solid phase obtained after filtration is designated as Solid Phase 2# (Al(OH)3, purity 99.6%, Al recovery rate 97.2%), and the liquid phase is designated as Solution 2#.

[0132] (6) Add a saturated sodium sulfate solution to Solution 2#, stir and react at room temperature for 4 h, and then filter to obtain Solid Phase 3# (CaSO4, purity 98.6%, Ca recovery rate 95.8%) and Solution 3#.

[0133] (7) Add a NaOH solution with a concentration of 1.0 mol / L to Solution 3# to adjust the pH to 12.5, stir and react at room temperature for 4 h, and filter to obtain Solid Phase 4# (Mg(OH)2, purity 97.8%, Mg recovery rate 95.0%).

[0134] Example 6

[0135] A method for extracting lithium and separating calcium and magnesium from lithium-containing brine:

[0136] The composition of the brine is shown in Table 3, and the specific steps are as follows:

[0137] Table 3 Main cation components and concentrations in the raw brine

[0138] Component <![CDATA[Na + > <![CDATA[K + > <![CDATA[Ca 2+ > <![CDATA[Mg 2+ > <![CDATA[Li + <!-- 7 -->]]> Concentration (mg / L) 18418.6 3286.4 1210.8 218.6 76.8

[0139] (1) Mix NaAlO2 and water at a dosage ratio of 0.06 g:1 mL, stir at room temperature until completely dissolved to obtain a NaAlO2 solution for standby.

[0140] (2) Take 35 mL of the NaAlO2 solution in step (1) and add it to 1000 mL of the raw brine, adjust the pH to 10, stir and react at room temperature for 4 h. After suction filtration and washing, the solid phase is dried at 60 °C to constant weight, designated as Solid Phase 1#, and the liquid phase is designated as Brine 1# for standby.

[0141] (3) After removing impurities from Brine 1# through a divalent cation exchange resin (for removing calcium and magnesium), and through evaporation and concentration, the liquid phase obtained after filtration is designated as Brine 2#, and the solid phase is a sodium-potassium mixed salt. Add a saturated sodium carbonate solution to Brine 2#, and the solid phase obtained after the precipitation reaction is the Li2CO3 product, with a purity of 99.6% and a Li recovery rate of 94.4%.

[0142] Among them, the concentration of Li in the evaporated Brine 2# + is 2.0 g / L.

[0143] (4) Mix solid phase 1# with a HCl solution at a concentration of 1.0 mol / L in a dosage ratio of 1 g:50 mL, and stir and react until completely dissolved. The resulting liquid is denoted as solution 1#.

[0144] (5) Add a NaOH solution with a concentration of 1.0 mol / L to solution 1#, adjust the pH to 4.5, stir and react for 4 h. The solid phase obtained after filtration is denoted as solid phase 2# (Al(OH)3, purity 99.5%, Al recovery rate 96.0%), and the liquid phase is denoted as solution 2#.

[0145] (6) Add a saturated sodium sulfate solution to solution 2#, stir and react at room temperature for 4 h and then filter to obtain solid phase 3# (CaSO4, purity 99.0%, Ca recovery rate 96.2%) and solution 3#.

[0146] (7) Add a NaOH solution with a concentration of 1.0 mol / L to solution 3# to adjust the pH to 12.5, stir and react at room temperature for 4 h, and the solid phase obtained after filtration is solid phase 4# (Mg(OH)2, purity 98.8%, Mg recovery rate 95.4%).

[0147] Comparative Example 1

[0148] Same as Example 1, the only difference is that the dosage of the NaAlO2 solution in step (2) is 30 mL.

[0149] Comparative Example 2

[0150] Same as Example 1, the only difference is that the pH is adjusted to 8 in step (2).

[0151] Comparative Example 3

[0152] Same as Example 1, the only difference is that the stirring reaction time at room temperature in step (2) is 1 h.

[0153] Comparative Example 4

[0154] Same as Example 1, the only difference is that NaAlO2 is replaced with an equal amount of NaOH in step (2).

[0155] The changes in the lithium ion concentration in the brine after being treated in step (2) for each example and comparative example are shown in Table 4.

[0156] Table 4 Concentrations (mg / L) and ion removal rates of Li + 、Ca 2+ and Mg 2+ in the brine after being treated in step (2)

[0157]

[0158]

[0159] Comparing Examples 1-4 of the present invention with Comparative Examples 1-4, it can be seen that the present invention uses NaAlO2 to precipitate Ca 2 + and Mg 2+ in the form of hydrocalumite and hydrotalcite-magnesium. The removal rate of Ca 2+ in the original brine exceeds 97% and that of Mg 2+ exceeds 98%. Li + remains in the brine, and the loss of Li + is controlled within 5%.

[0160] Through the comparison between Example 1 and Examples 5 and 6, it is found that when the concentrations and ratios of Li + , Ca 2+ and Mg 2+ change to a certain extent, by appropriately adjusting the addition amount of NaAlO2, a separation effect equivalent to that of Examples 1-4 can still be achieved. Moreover, through the process route of the present invention, the recovery of Ca and Mg resources in the brine and the recovery of Al in the reagent can be realized.

[0161] The above-described embodiments are only descriptions of the preferred modes of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for extracting lithium from lithium-containing brine, characterized in that, It includes the following steps: Add a NaAlO₂ solution to the lithium-containing brine, adjust the pH to 9.5 - 11.5, filter after mixing and reacting, to obtain a lithium-containing filtrate and a solid product; Use a divalent cation exchange resin to remove impurities from the lithium-containing filtrate and then add sodium carbonate to obtain Li₂CO₃.

2. The method for extracting lithium from lithium-containing brine according to claim 1, wherein, The concentration of the NaAlO₂ solution is 50 - 100 g / L; the volume ratio of the NaAlO₂ solution to the lithium-containing brine is (35 - 70):1000; The cation components in the lithium-containing brine include: Li + , Ca 2+ and Mg 2+ ; the mass concentration ratio of Li + , Ca 2+ and Mg 2+ in the original lithium-containing brine is (70-90):(1200-5000):(190-320).

3. A method for extracting lithium and separating calcium and magnesium from lithium-containing brine, characterized in that, It includes the following steps: Add a NaAlO₂ solution to the lithium-containing brine, adjust the pH to 9.5 - 11.5, filter after mixing and reacting, to obtain a lithium-containing filtrate and a solid product containing calcium and magnesium; The cation components in the lithium-containing brine include: Li + , Ca 2+ and Mg 2+ ; Use a divalent cation exchange resin to remove impurities from the lithium-containing filtrate and then add sodium carbonate to obtain Li₂CO₃; Add an acid solution to the solid product containing calcium and magnesium to dissolve it, then adjust the pH to 4 - 5, filter after mixing and reacting, to obtain a filtrate containing calcium and magnesium; Add sodium sulfate to the filtrate containing calcium and magnesium, filter after mixing and reacting, to obtain a magnesium-containing filtrate and CaSO₄; Adjust the pH of the magnesium-containing filtrate to 12 - 13 to obtain Mg(OH)₂.

4. The method for extracting lithium from lithium-containing brine and separating calcium and magnesium according to claim 3, wherein, The concentration of the NaAlO₂ solution is 50 - 100 g / L; the volume ratio of the NaAlO₂ solution to the lithium-containing brine is (35 - 70):1000; Li in the original brine containing lithium + , Ca 2+ and Mg 2+ has a mass concentration ratio of (70 - 90):(1200 - 5000):(190 - 320).

5. The method for extracting lithium from lithium-containing brine and separating calcium and magnesium according to claim 3, characterized in that, The acid solution includes a HCl solution with a concentration of 1.0 - 2.0 mol / L; the dosage ratio of the solid product containing calcium and magnesium to the acid solution is 1 g:25 - 50 mL.

6. The method for extracting lithium from lithium-containing brine and separating calcium and magnesium according to claim 3, characterized in that, The regulator used to adjust the pH to 4 - 5 includes a NaOH solution with a concentration of 1.0 - 2.0 mol / L.

7. The method for extracting lithium from lithium-containing brine and separating calcium and magnesium according to claim 3, characterized in that, The regulator used to adjust the pH to 12 - 13 includes a NaOH solution with a concentration of 1.0 - 2.0 mol / L.

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