A method for extracting lithium based on electrochemical salt lake brine

Abstract

The application discloses a method for extracting lithium from electrochemical salt lake brine, comprising the following steps: constructing an electrochemical reactor, wherein the electrochemical reactor comprises a reaction cavity, a cathode and an anode oppositely arranged in the reaction cavity, the anode is an iron electrode, the cathode is an iron electrode, a stainless steel electrode, a carbon electrode or a graphite electrode, the cathode and the anode are connected with an external power source through wires; an adsorption stage: after adjusting the conductivity and pH value of the salt lake brine to be treated, the salt lake brine is introduced into the iron electrochemical reactor, nitrogen is blown to adjust the dissolved oxygen value of the water body, after the iron electrochemical treatment, the power source is turned off, and the floc rich in lithium ions is collected by standing and centrifugation; a nitrogen aeration device is used to make the dissolved oxygen value in the reaction be 0.05-8.0 mg / L; a desorption stage: the water containing the floc is introduced into the reactor, the reactor is heated, oxygen is introduced into the reactor and an oxidant is added, and after the treatment, the solution rich in lithium ions is obtained by standing and centrifugation.

Description

Technical Field

[0001] This invention relates to a method for extracting lithium from salt lake brine based on electrochemical processes. Background Technology

[0002] Lithium is a metallic element with high electrical conductivity and good physicochemical properties, playing a vital role in the development of new energy, military, and battery industries. With the rapid development of science, technology, and the economy, the demand for lithium resources from numerous industries has increased dramatically. Currently, salt lake brines account for approximately 70% of the world's total lithium reserves, making them the most promising source for lithium production. However, lithium and magnesium are essentially symbiotic in salt lake brines because magnesium and lithium ions have very similar chemical properties and small differences in their hydration radii. Therefore, this presents a significant challenge to the efficient extraction of lithium from salt lakes with high Mg / Li mass ratios.

[0003] Currently, the main technologies for extracting lithium resources from salt lake brines include solvent extraction, precipitation, ion exchange adsorption, and membrane separation. These methods can effectively recover lithium from salt lake brines, but they all have several problems. For example, chemical extraction, precipitation, and ion exchange methods require the addition of large amounts of chemical reagents, which introduces a large number of impurities, and the separation and purification process leads to material consumption and environmental problems. Another example is adding aluminum salts (AlCl3) and strong bases (NaOH, KOH) to a lithium-containing solution, reacting with LiCl to generate LiCl·2Al(OH)3·xH2O to extract lithium. Membrane separation methods suffer from membrane fouling and high membrane costs, which also prevents the widespread application of this technology. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for extracting lithium from salt lake brine based on electrochemical methods. This method can achieve efficient extraction of lithium resources (lithium ions) from salt lake brine, and the extracted lithium ions have low impurity content and high purity.

[0005] Technical solution: The method for extracting lithium from salt lake brine based on electrochemical methods of the present invention includes the following steps:

[0006] (1) Constructing an electrochemical reactor: The electrochemical reactor includes a reaction chamber and a cathode and an anode located opposite each other in the reaction chamber, the distance between the anode and the cathode being 0.5 to 20 cm; the anode is an iron electrode; the cathode is any one of an iron electrode, stainless steel, carbon electrode or graphite electrode; the cathode and the anode are connected to an external power source through wires;

[0007] (2) Adsorption stage: After adjusting the conductivity and pH of the brine to be treated, the brine is introduced into a ferroelectrochemical reactor. Nitrogen gas is aerated to adjust the dissolved oxygen (DO) value of the water so that green rust flocs can be generated. After ferroelectrochemical treatment for 20-300 minutes, the power is turned off, and the flocs rich in lithium ions are collected by centrifugation. A nitrogen aeration device is used to maintain the dissolved oxygen value in the reaction at 0.05-8.0 mg / L. The green rust flocs are precisely generated in situ to adsorb the lithium in the brine. + Preferential adsorption;

[0008] (3) Desorption stage: The flocs are placed in water, and the water containing the flocs is passed into the reactor. The reactor is heated, and oxygen and an oxidant are introduced into the reactor at the same time. After treatment, the mixture is allowed to stand and centrifuged to obtain a lithium-ion-rich solution. The lithium-ion solution can be evaporated and concentrated to obtain the product.

[0009] In step (2), the conductivity of the salt lake brine is adjusted to 800-10000 μS / cm and the pH value is 4-9. The salt lake brine to be treated is pretreated by using Na2SO4 as the electrolyte and adjusting the conductivity to 800-10000 μS / cm and the pH value to 4-9, which is conducive to the electrochemical reaction. At the same time, the electrolysis current density is determined according to the concentration of lithium ions in the salt lake brine, and then the electrochemical reaction is carried out.

[0010] In step (2), the current density during the electrochemical reaction is 0.2–20 mA / cm². 2 .

[0011] In step (2), the aeration rate of the nitrogen aeration device is 0.5 to 50 L / min.

[0012] In step (3), during the phase change process of the green rust flocs, the temperature of the reactor is raised to 35℃~70℃; the aeration rate of the oxygen aeration device is 1~10L / min, the dissolved oxygen (DO) value in the reactor is controlled to be 10~20mg / L, and the reaction time is 10~180min.

[0013] In step (3), the oxidant is any one or a combination of several of H2O2, Cl2 or O3; the concentration of the added H2O2 oxidant is 0.1 to 20 mM, the concentration of the Cl2 oxidant is 0.5 to 3 M, and the concentration of the O3 oxidant is 10 to 300 mg / L.

[0014] The electrochemical treatment of salt lake brine is divided into two stages: an adsorption stage, in which lithium ions are adsorbed in situ by controlling the dissolved oxygen (DO) value of the solution during the electrochemical reaction to generate green rust flocs; and a desorption stage, in which lithium ions are desorbed into the recovery solution. During the phase transition of the green rust, the highly adsorbent but unstable green rust is transformed into poorly adsorbed iron hydroxide and iron(II,III) oxide, thereby desorbing the adsorbed lithium ions into the recovery solution, resulting in a high concentration of lithium ions in the recovery solution.

[0015] This invention desorbs adsorbed lithium ions by inducing a phase transition in the saturated green rust flocs produced during the electrochemical treatment of salt lake brine. Because green rust flocs have strong adsorption capacity, poor stability, and are easily oxidized, they are sensitive to temperature and oxidants. Therefore, by heating and introducing an oxidant into the green rust flocs produced after the electrochemical reaction, they can be transformed into iron oxide flocs with poor adsorption capacity but good stability, such as ferric hydroxide and magnetite. During the phase transition from green rust flocs to ferric hydroxide and magnetite, the change in floc structure leads to a decrease in adsorption capacity. At this point, the high capacity of lithium adsorbed by the green rust flocs during the adsorption stage will desorb into the recovery liquid due to the reduced adsorption capacity caused by the phase transition, thus enriching lithium in the recovery liquid. This achieves efficient extraction of lithium resources from salt lake brine, effectively solving the problem of the difficulty in developing lithium resources from salt lake brine. This is because the loose, porous structure of green rust flocs is highly resistant to lithium with small atomic radii. + It has high adsorption efficiency, Li + Compared to Na + Mg 2+ With a smaller atomic radius, therefore in Li + Na + and Mg 2+ Between, green rust on Li + It has high adsorption selectivity.

[0016] In the ferroelectrochemical treatment of salt lake brine of this invention, the metal cation Fe is electrolyzed at the anode. 2+ or Fe 3+ Electrolysis at the cathode produces H2 and OH. -In solution, green rust flocs are precisely generated in situ under continuous nitrogen aeration. These flocs, generated in situ via ferroelectrochemical processes, possess a large specific surface area and strong adsorption capacity, capable of adsorbing most lithium ions from salt lake brine. However, the green rust flocs themselves are unstable and easily oxidized. Temperature changes and the addition of oxidants can cause a phase transition, transforming them into other iron oxides, such as ferric hydroxide (FeOOH) or magnetite (Fe3O4). The adsorption capacity of ferric hydroxide and magnetite is relatively weaker than that of green rust. Therefore, during the phase transition of the green rust flocs, the adsorbed lithium ions are re-desorbed and enriched in the recovery solution (deionized water), thus achieving efficient extraction of lithium ions from the salt lake brine.

[0017] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: Ferroelectric chemical technology can precisely generate green rust flocs in situ. The in-situ generated green rust has an extremely high specific surface area and numerous active sites. These strongly adsorbent green rust flocs adsorb lithium ions from the salt lake brine. Compared to magnesium ions, green rust has a higher adsorption capacity for lithium ions, preferentially adsorbing them. The surface of the green rust flocs has a large number of hydroxyl groups, which have strong coordination exchange and coordination adsorption capabilities, adsorbing lithium ions from the brine through surface coordination adsorption. In the subsequent phase transition process, the green rust is oxidized to iron(II,III) oxide and / or iron(II,III) hydroxide. The adsorption efficiency of these flocs is much lower than that of green rust. Therefore, oxidation can desorb the high-capacity lithium ions adsorbed by the green rust into the recovery liquid, achieving a high enrichment of lithium in the recovery liquid, thereby realizing efficient and impurity-free extraction of lithium resources from salt lake brine. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an electrochemical reactor. Detailed Implementation

[0019] like Figure 1 As shown, the electrochemical reactor of the present invention includes a reaction chamber and a cathode and an anode located opposite each other in the reaction chamber. The distance between the anode and the cathode is 0.5 to 20 cm. The anode plate is a flat iron electrode, and the cathode plate is an iron electrode, stainless steel, carbon electrode or graphite electrode. The thickness of the electrode plates is 1 to 6 mm, the length is 300 to 800 mm, and the width is 200 to 1200 mm.

[0020] Example 1

[0021] This invention describes a lithium ion extraction process for salt lake brine with a lithium ion concentration of 100 mg / L, specifically comprising the following steps:

[0022] (1) The conductivity of the salt lake brine was adjusted to 800 μS / cm using Na2SO4 as an electrolyte, and the pH value of the salt lake brine was adjusted to 4.

[0023] (2) An iron electrode was used as the anode, and a stainless steel electrode as the cathode. The distance between the cathode and the anode was 0.5 cm, and the dimensions of the electrode plates were 300 × 200 × 3 mm. The nitrogen aeration rate was set to 0.5 L / min, the DO value of the solution was controlled at 0.05 mg / L during the electrochemical reaction, and the current density of the electrolysis reaction was 0.2 mA / cm². 2 Ferroelectrochemical reaction was carried out for 120 minutes. After the reaction, the treated water was allowed to stand for 10 minutes, centrifuged for 5 minutes, and lithium-ion-rich flocs were collected. At the same time, the clear liquid after centrifugation was discharged from the reactor.

[0024] (3) Add the flocs to the deionized water, add the deionized water containing the flocs to the reactor, heat the water bath to raise the temperature to 40°C, aerate with O2 for 60 min, the O2 aeration rate is 1 L / min, control the dissolved oxygen value in the reaction to 10 mg / L, after treatment, let the recovered liquid stand for 10 min, centrifuge for 5 min, and obtain a solution rich in lithium ions.

[0025] The lithium ion recovery rate was calculated to be 80.46%.

[0026] Comparative Example 1

[0027] Comparative Example 1 describes a method for recovering lithium from salt lake brine by electrochemically generating aluminum hydroxide flocs to adsorb lithium and form a precipitate. The method includes the following steps:

[0028] (1) The conductivity of the salt lake brine was adjusted to 800 μS / cm using Na2SO4 as the electrolyte, and the pH value of the salt lake brine was adjusted to 4; the lithium ion concentration in the salt lake brine was 100 mg / L.

[0029] (2) Using an aluminum electrode as the anode and a stainless steel electrode as the cathode, the distance between the anode and cathode is 0.5 cm, and the dimensions of the electrode plates are 300 × 200 × 3 mm; the current density of the electrolysis reaction is 0.2 mA / cm². 2 An electrochemical reaction was carried out for 3 hours. The resulting aluminum flocs reacted with LiCl in the lithium-containing solution to form LiCl·2Al(OH)3·xH2O precipitate.

[0030] The lithium ion recovery rate was calculated to be 65.25%.

[0031] Example 2

[0032] This invention relates to the lithium ion extraction treatment of salt lake brine with a lithium ion concentration of 600 mg / L, specifically including the following steps:

[0033] (1) The conductivity of the salt lake brine was adjusted to 10000 μS / cm using Na2SO4 as an electrolyte, and the pH value of the salt lake brine was adjusted to 9.

[0034] (2) An iron electrode was used as the anode and a stainless steel electrode as the cathode, with a distance of 20 cm between the cathode and anode. The dimensions of the electrode plates were 300×200×3 mm. The nitrogen aeration rate was set to 50 L / min, the DO value of the solution was controlled to 8 mg / L during the electrochemical reaction, and the current density of the electrolysis reaction was 20 mA / cm². 2 Ferroelectrochemical reaction was carried out for 90 minutes. After the reaction, the treated water was allowed to stand for 10 minutes, centrifuged for 5 minutes, and lithium-ion-rich flocs were collected. At the same time, the clear liquid after centrifugation was discharged from the reactor.

[0035] (3) Add the flocs to the deionized water, add the deionized water containing the flocs to the reactor, add the concentration of H2O2 oxidant to 0.1mM, the aeration rate of oxygen is 1L / min, control the dissolved oxygen value in the reaction to 10mg / L, heat the temperature to 40℃ for 60min, let the recovered liquid stand for 10min, centrifuge for 5min to obtain a lithium ion-rich solution.

[0036] The lithium ion recovery rate was calculated to be 90.21%.

[0037] Comparative Example 2

[0038] Comparative Example 2 describes a method for recovering lithium from salt lake brine by electrochemically generating aluminum hydroxide flocs to adsorb lithium and form a precipitate. The method includes the following steps:

[0039] (1) The conductivity of the salt lake brine was adjusted to 10000 μS / cm using Na2SO4 as the electrolyte, and the pH value of the salt lake brine was adjusted to 9; the lithium ion concentration in the salt lake brine was 600 mg / L.

[0040] (2) Using an aluminum electrode as the anode and a stainless steel electrode as the cathode, the distance between the cathode and the anode is 20 cm, and the dimensions of the electrode plates are 300 × 200 × 3 mm; the current density of the electrolysis reaction is 20 mA / cm². 2 An electrochemical reaction was carried out for 4 hours. The resulting aluminum flocs reacted with LiCl in the lithium-containing solution to form LiCl·2Al(OH)3·xH2O precipitate.

[0041] The lithium ion recovery rate was calculated to be 70.09%.

[0042] Example 3

[0043] This invention describes a lithium ion extraction process for salt lake brine with a lithium ion concentration of 400 mg / L, specifically including the following steps:

[0044] (1) The conductivity of the salt lake brine was adjusted to 6000 μS / cm using Na2SO4 as an electrolyte, and the pH value of the salt lake brine was adjusted to 7.

[0045] (2) An iron electrode was used as the anode, and a stainless steel electrode was used as the cathode. The distance between the cathode and the anode was 16 cm, and the dimensions of the electrode plates were 300×200×3 mm. The nitrogen aeration rate was set to 30 L / min, the DO value of the solution was controlled at 6.4 mg / L during the electrochemical reaction, and the current density of the electrolysis reaction was 15 mA / cm². 2 Ferroelectrochemical reaction was carried out for 120 minutes. After the reaction, the treated water was allowed to stand for 10 minutes, centrifuged for 5 minutes, and lithium-ion-rich flocs were collected. At the same time, the clear liquid after centrifugation was discharged from the reactor.

[0046] (3) Add the flocs to the deionized water, add the deionized water containing the flocs to the reactor, add the H2O2 oxidant at a concentration of 0.1 mM, the O2 aeration rate at 1 L / min, control the dissolved oxygen value in the reaction at 10 mg / L, heat to 50℃ for 30 min, let the recovered liquid stand for 10 min, centrifuge for 5 min, and obtain a lithium-ion-rich solution.

[0047] The lithium ion recovery rate was calculated to be 92.32%.

[0048] Comparative Example 3

[0049] Comparative Example 3 describes a method for recovering lithium from salt lake brine by electrochemically generating aluminum hydroxide flocs to adsorb lithium and form a precipitate. The method includes the following steps:

[0050] (1) The conductivity of the salt lake brine was adjusted to 6000 μS / cm using Na2SO4 as the electrolyte, and the pH value of the salt lake brine was adjusted to 7; the lithium ion concentration in the salt lake brine was 400 mg / L.

[0051] (2) Using an aluminum electrode as the anode and a stainless steel electrode as the cathode, the distance between the cathode and the anode is 16 cm, and the dimensions of the electrode plates are 300×200×3 mm; the current density of the electrolysis reaction is 15 mA / cm². 2An electrochemical reaction was carried out for 3 hours. The resulting aluminum flocs reacted with LiCl in the lithium-containing solution to form LiCl·2Al(OH)3·xH2O precipitate.

[0052] The lithium ion recovery rate was calculated to be 68.84%.

[0053] Example 4

[0054] This invention describes a lithium ion extraction process for brine from a salt lake with a lithium ion concentration of 300 mg / L, specifically comprising the following steps:

[0055] (1) The conductivity of the salt lake brine was adjusted to 4000 μS / cm using Na2SO4 as an electrolyte, and the pH value of the salt lake brine was adjusted to 5.

[0056] (2) An iron electrode was used as the anode, and a stainless steel electrode was used as the cathode. The distance between the cathode and the anode was 12 cm, and the dimensions of the electrode plates were 300×200×3 mm. The nitrogen aeration rate was set to 10 L / min, the DO value of the solution was controlled to 4 mg / L during the electrochemical reaction, and the current density of the electrolysis reaction was 12 mA / cm². 2 Ferroelectrochemical reaction was carried out for 80 minutes. After the reaction, the treated water was allowed to stand for 10 minutes, centrifuged for 5 minutes, and lithium-ion-rich flocs were collected. At the same time, the clear liquid after centrifugation was discharged from the reactor.

[0057] (3) Add the flocs to the deionized water, add the deionized water containing the flocs to the reactor, add the concentration of H2O2 oxidant to 0.1mM, the O2 aeration rate to 1L / min, control the dissolved oxygen value in the reaction to 10mg / L, heat to 60℃ for 30min, let the recovered liquid stand for 10min after treatment, centrifuge for 5min to obtain a lithium ion-rich solution.

[0058] The lithium ion recovery rate was calculated to be 94.37%.

[0059] Comparative Example 4

[0060] Comparative Example 4 describes a method for recovering lithium from salt lake brine by electrochemically generating aluminum hydroxide flocs to adsorb lithium and form a precipitate. The specific steps include:

[0061] (1) The conductivity of the salt lake brine was adjusted to 4000 μS / cm using Na2SO4 as the electrolyte, and the pH value of the salt lake brine was adjusted to 5; the lithium ion concentration in the salt lake brine was 300 mg / L.

[0062] (2) Using an aluminum electrode as the anode and a stainless steel electrode as the cathode, the distance between the cathode and the anode is 12 cm, and the dimensions of the electrode plates are 300×200×3 mm; the current density of the electrolysis reaction is 12 mA / cm². 2 An electrochemical reaction was carried out for 2 hours. The resulting aluminum flocs reacted with LiCl in the lithium-containing solution to form LiCl·2Al(OH)3·xH2O precipitate.

[0063] The lithium ion recovery rate was calculated to be 64.29%.

[0064] Example 5

[0065] This invention describes a lithium ion extraction process for salt lake brine with a lithium ion concentration of 200 mg / L, specifically including the following steps:

[0066] (1) The conductivity of the salt lake brine was adjusted to 2500 μS / cm using Na2SO4 as an electrolyte, and the pH value of the salt lake brine was adjusted to 6.

[0067] (2) An iron electrode was used as the anode and a stainless steel electrode as the cathode, with a distance of 8 cm between the cathode and anode. The dimensions of the electrode plates were 300×200×3 mm. The nitrogen aeration rate was set at 15 L / min, the DO value of the solution was controlled at 1.6 mg / L during the electrochemical reaction, and the current density of the electrolysis reaction was 10 mA / cm². 2 Ferroelectrochemical reaction was carried out for 60 minutes. After the reaction, the treated water was allowed to stand for 10 minutes, centrifuged for 5 minutes, and lithium-ion-rich flocs were collected. At the same time, the clear liquid after centrifugation was discharged from the reactor.

[0068] (3) Add the flocs to the deionized water, add the deionized water containing the flocs to the reactor, add the concentration of the added Cl2 oxidant to 0.5M, the O2 aeration rate to 1L / min, control the dissolved oxygen value in the reaction to 10mg / L, heat to 50℃ for 30min, after treatment, let the recovered liquid stand for 10min, centrifuge for 5min to obtain a lithium ion-rich solution.

[0069] The lithium ion recovery rate was calculated to be 92.48%.

[0070] Comparative Example 5

[0071] Comparative Example 5 describes a method for recovering lithium from salt lake brine by electrochemically generating aluminum hydroxide flocs to adsorb lithium and form a precipitate. The method includes the following steps:

[0072] (1) The conductivity of the salt lake brine was adjusted to 2500 μS / cm using Na2SO4 as the electrolyte, and the pH value of the salt lake brine was adjusted to 6; the lithium ion concentration in the salt lake brine was 200 mg / L.

[0073] (2) Using an aluminum electrode as the anode and a stainless steel electrode as the cathode, the distance between the cathode and the anode is 8 cm, and the dimensions of the electrode plates are 300×200×3 mm; the current density of the electrolysis reaction is 10 mA / cm². 2 An electrochemical reaction was carried out for 3 hours. The resulting aluminum flocs reacted with LiCl in the lithium-containing solution to form LiCl·2Al(OH)3·xH2O precipitate.

[0074] The lithium ion recovery rate was calculated to be 60.86%.

[0075] Example 6

[0076] This invention relates to the lithium ion extraction treatment of salt lake brine with a lithium ion concentration of 500 mg / L, specifically including the following steps:

[0077] (1) The conductivity of the salt lake brine was adjusted to 7800 μS / cm using Na2SO4 as an electrolyte, and the pH value of the salt lake brine was adjusted to 8.

[0078] (2) An iron electrode was used as the anode and a stainless steel electrode as the cathode, with a distance of 4 cm between the cathode and anode. The dimensions of the electrode plates were 300×200×3 mm. The nitrogen aeration rate was set to 20 L / min, the DO value of the solution was controlled to 5 mg / L during the electrochemical reaction, and the current density of the electrolysis reaction was 10 mA / cm². 2 Ferroelectrochemical reaction was carried out for 140 minutes. After the reaction, the treated water was allowed to stand for 10 minutes, centrifuged for 5 minutes, and lithium-ion-rich flocs were collected. At the same time, the clear liquid after centrifugation was discharged from the reactor.

[0079] (3) Add the flocs to the deionized water, add the deionized water containing the flocs to the reactor, add the concentration of O3 oxidant to 200 mg / L, the O2 aeration rate to 1 L / min, control the dissolved oxygen value in the reaction to 10 mg / L, heat to 70℃ for 30 min, after treatment, let the recovered liquid stand for 10 min, centrifuge for 5 min, and obtain a solution rich in lithium ions.

[0080] The lithium ion recovery rate was calculated to be 95.12%.

[0081] Comparative Example 6

[0082] Comparative Example 6 describes a method for recovering lithium from salt lake brine by electrochemically generating aluminum hydroxide flocs to adsorb lithium and form a precipitate. The method includes the following steps:

[0083] (1) The conductivity of the salt lake brine was adjusted to 7800 μS / cm using Na2SO4 as the electrolyte, and the pH value of the salt lake brine was adjusted to 8; the lithium ion concentration in the salt lake brine was 500 mg / L.

[0084] (2) Using an aluminum electrode as the anode and a stainless steel electrode as the cathode, the distance between the cathode and the anode is 4 cm, and the dimensions of the electrode plates are 300×200×3 mm; the current density of the electrolysis reaction is 10 mA / cm². 2 An electrochemical reaction was carried out for 4 hours. The resulting aluminum flocs reacted with LiCl in the lithium-containing solution to form LiCl·2Al(OH)3·xH2O precipitate.

[0085] The lithium ion recovery rate was calculated to be 75.79%.

[0086] Comparative Example 7

[0087] The treatment method of Comparative Example 7 was basically the same as that of Example 6, the only difference being that O3 oxidant was not added in step (3), but the O2 aeration rate was 1L / min, the dissolved oxygen value in the reaction was controlled at 10mg / L, and the temperature was heated to 70℃ for 120min. After treatment, the recovered liquid was allowed to stand for 10min and centrifuged for 5min to obtain a lithium-ion-rich solution. The lithium ion recovery rate was calculated to be 85.02%.

[0088] Comparative Example 8

[0089] The treatment method of Comparative Example 8 was basically the same as that of Example 6, except that in step (3), O3 oxidant and O2 exposure were not added. The solution was simply heated to 70°C for 120 min, and then the recovered liquid was allowed to stand for 10 min and centrifuged for 5 min to obtain a lithium-ion-rich solution. The lithium-ion recovery rate was calculated to be 74.03%.

[0090] Comparative Example 9

[0091] The treatment method of Comparative Example 9 was basically the same as that of Example 6, the only difference being that no heating was performed in step (3), the concentration of the added O3 oxidant was 200 mg / L, the O2 aeration rate was 1 L / min, the dissolved oxygen value in the reaction was controlled at 10 mg / L, and the treatment was carried out at room temperature for 120 min. After treatment, the recovered liquid was allowed to stand for 10 min and centrifuged for 5 min to obtain a lithium-ion-rich solution. The lithium-ion recovery rate was calculated to be 80.25%.

Claims

1. A method for extracting lithium from salt lake brine based on electrochemical processes, characterized in that, Includes the following steps: (1) Constructing an electrochemical reactor: The electrochemical reactor includes a reaction chamber and a cathode and an anode located opposite each other in the reaction chamber. The anode is an iron electrode. The cathode is any one of an iron electrode, a stainless steel electrode, a carbon electrode, or a graphite electrode. The cathode and anode are connected to an external power source through wires. (2) Adsorption stage: After adjusting the conductivity and pH value of the salt lake brine to be treated, it is introduced into the electrochemical reactor. Nitrogen gas is aerated to adjust the dissolved oxygen value of the water so that green rust flocs can be generated. After electrochemical treatment, the power is turned off, and the flocs rich in lithium ions are collected by settling and centrifugation. A nitrogen aeration device is used to make the dissolved oxygen value in the reaction 0.05~8.0mg / L. (3) Desorption stage: Water containing flocs is introduced into the reactor, the reactor is heated, oxygen is introduced into the reactor and an oxidant is added, and after treatment, the solution is allowed to stand and centrifuged to obtain a lithium-ion-rich solution; during the phase change process of the green rust flocs, the temperature of the reactor is raised to 35°C~70°C; the aeration rate of the oxygen aeration device is 1~10L / min, and the dissolved oxygen value in the reactor is controlled to be 10~20mg / L; the oxidant is any one or a combination of several of H2O2, Cl2 or O3; the concentration of the added H2O2 oxidant is 0.1~20mM, the concentration of the Cl2 oxidant is 0.5~3M, and the concentration of the O3 oxidant is 10~300mg / L.

2. The method for extracting lithium from salt lake brine based on electrochemical methods according to claim 1, characterized in that: In step (1), the distance between the anode and the cathode is 0.5~20cm.

3. The method for extracting lithium from salt lake brine based on electrochemical methods according to claim 1, characterized in that: In step (2), the conductivity of the salt lake brine is adjusted to 800~10000μs / cm and the pH value is 4~9.

4. The method for extracting lithium from salt lake brine based on electrochemical methods according to claim 1, characterized in that: In step (2), the current density during the electrochemical reaction is 0.2~20 mA / cm². 2 .

5. The method for extracting lithium from salt lake brine based on electrochemical methods according to claim 1, characterized in that: In step (2), the aeration rate of the nitrogen aeration device is 0.5~50L / min.

6. The method for extracting lithium from salt lake brine based on electrochemical methods according to claim 1, characterized in that: In step (2), the electrochemical reaction time is 20~300 min.

7. The method for extracting lithium from salt lake brine based on electrochemical extraction according to claim 1, characterized in that: In step (3), the desorption reaction time is 10~60 min.

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