Method for extracting lithium from brine with high magnesium-lithium ratio by using lithium ion sieve expanded bed

Abstract

The invention discloses a method for extracting lithium from brine with a high magnesium-lithium ratio by using a lithium ion sieve expanded bed, the method for extracting lithium from the brine with the high magnesium-lithium ratio by using the lithium ion sieve expanded bed comprises adsorption lithium extraction and acid desorption operation, and the adsorption lithium extraction and acid desorption operation comprises the following steps: (S1) adjusting the expanded bed into an expansion mode, introducing expansion liquid into a first interface, the bed layer is expanded; (S2) introducing alkaline brine suspended with magnesium hydroxide crystal grains from the first interface to pass through the expanded bed layer so as to obtain lithium-poor brine, and discharging the lithium-poor brine from the second interface; (S3) introducing water into the treatment space from the first interface, flushing the treatment space to take away the alkaline brine suspended with magnesium hydroxide crystal grains and retained in the treatment space to obtain wastewater liquid, and discharging the wastewater liquid from the second interface; and (S4) adjusting the expanded bed from an expansion mode to a fixed mode, introducing a dilute acid solution into the treatment space from the second interface to desorb lithium ions adsorbed by the bed layer, obtaining a lithium-rich product solution, discharging the lithium-rich product solution from the first interface, and regenerating the bed layer at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of lithium extraction from brine, and in particular to a method for extracting lithium from brine with a high magnesium-to-lithium ratio by using a lithium ion sieve expanded bed. Background Art

[0002] As one of the important materials for green energy in the new century, the development and application of lithium has attracted wide attention. my country's lithium mineral resources are scarce and cannot meet the needs of industrial production. However, my country's salt lake brine contains a large amount of lithium valuable elements. Due to the low lithium grade, high magnesium-lithium ratio, and high content of alkali metals and alkaline earth metals in the brine, the cost and energy consumption of lithium extraction are high, which limits its industrialization process.

[0003] At present, there are various ways to extract lithium from brine. Among them, the solar pond heating lithium precipitation method and precipitation method are mainly suitable for carbonate-type brines with high lithium grade and low magnesium-lithium ratio; the solvent extraction method is suitable for brines with high lithium concentration; the adsorption method is suitable for brines with low lithium grade and high magnesium-lithium ratio. When using ion sieves to adsorb lithium ions in high magnesium-lithium ratio brines, the lithium ions replace the hydrogen ions in the ion sieves, and the replaced hydrogen ions enter the de-lithium brine, resulting in a decrease in the pH value of the de-lithium brine. The acidic environment is not conducive to the lithium ion adsorption operation. Therefore, before the lithium ion adsorption, it is usually necessary to add dilute alkali solution to the high magnesium-lithium ratio brine to increase the alkalinity.

[0004] Since high magnesium-to-lithium ratio brine is usually neutral and contains a very high content of magnesium ions, magnesium hydroxide crystals will be produced after adding dilute alkali solution. When the brine carrying magnesium hydroxide crystals passes through a fixed bed filled with ion sieve particles, the magnesium hydroxide crystals will block the bed layer formed by the accumulation of ion sieve particles, limiting large-scale industrial applications. Summary of the invention

[0005] In order to solve the above technical problems and achieve at least one advantage of the present invention, the present invention provides a method for extracting lithium from brine with a high magnesium-to-lithium ratio using a lithium ion sieve expanded bed, wherein the method for extracting lithium from brine with a high magnesium-to-lithium ratio using a lithium ion sieve expanded bed includes adsorption and lithium extraction and acid desorption operations, wherein the adsorption and lithium extraction and acid desorption operations use an expanded bed, the expanded bed includes a bed body and a bed layer filled inside the bed body, the bed layer is formed by stacking lithium ion sieve particles, the bed body includes a main body and an adjusting member, the adjusting member and the main body together form a processing space for accommodating the bed layer, and the adjusting member is movably arranged on the main body up and down to increase or decrease the processing space, The bottom end of the main body forms a first interface communicating with the processing space, and the adjustment member has a second interface opposite to the first interface and communicating with the processing space. The expansion bed has an expansion mode and a fixed mode. The adjustment member can be driven to move up and down to switch the expansion bed between the expansion mode and the fixed mode. The adjustment member moves up away from the first interface to keep the size of the processing space at the maximum. At this time, the expansion bed is in the expansion mode. The adjustment member moves down close to the first interface to keep the size of the processing space at the minimum. At this time, the expansion bed is in the fixed mode. The adsorption and lithium extraction and acid desorption operations include:

[0006] The lithium extraction operation is performed by adsorption, wherein the expanded bed is in the expansion mode and the lithium extraction operation comprises:

[0007] (S1) adjusting the expansion bed to the expansion mode, introducing an expansion liquid into the first interface, the flowing expansion liquid drives the lithium ion sieve particles in the processing space to float upward to expand the bed layer to increase the porosity, and obtain the treated expansion liquid and discharge it from the second interface;

[0008] (S2) introducing alkaline brine in which magnesium hydroxide crystals are suspended through the first interface to pass through the bed layer that remains expanded, wherein the alkaline brine and the lithium ion sieve particles undergo ion exchange so that lithium ions in the alkaline brine are adsorbed by the bed layer, and the magnesium hydroxide crystals neutralize hydrogen ions released by the ion exchange to obtain lithium-poor brine, which is discharged through the second interface;

[0009] (S3) introducing water into the treatment space from the first interface to flush the treatment space to remove the alkaline brine with magnesium hydroxide crystals suspended therein, obtain waste water and discharge it from the second interface;

[0010] An acid desorption operation, wherein the acid desorption operation uses the expanded bed in the fixed mode, and the acid desorption operation comprises:

[0011] (S4) The expanded bed is adjusted from the expansion mode to the fixed mode, and a dilute acid solution is introduced into the processing space from the second interface to desorb the lithium ions adsorbed by the bed layer to obtain a lithium-rich product solution which is discharged from the first interface, and the bed layer is regenerated at the same time.

[0012] According to an embodiment of the present invention, the lithium ion sieve particles are implemented as manganese-based ion sieve particles or titanium-based ion sieve particles.

[0013] According to an embodiment of the present invention, in the step (S2), the alkaline brine containing the magnesium hydroxide crystals suspended therein is introduced into the expanded bed at a flow rate higher than the minimum fluidization velocity of the lithium ion sieve particles.

[0014] According to an embodiment of the present invention, the dilute acid solution in the step (S4) is implemented as 0.2-0.5 mol / L hydrochloric acid.

[0015] According to an embodiment of the present invention, the acid desorption operation further comprises the following steps:

[0016] (S5) Water is introduced into the treatment space from the second interface to remove the dilute acid solution retained in the treatment space, and the acid recovery solution is obtained and discharged from the first interface.

[0017] According to an embodiment of the present invention, the expansion liquid in the step (S1) is implemented as a dilute alkali solution, which is introduced into the treatment space to neutralize the free hydrogen ions retained in the treatment space after the treatment in the step (S5).

[0018] According to an embodiment of the present invention, the swelling liquid in the step (S1) is implemented as a 0.01-0.05 mol / L potassium hydroxide solution.

[0019] According to one embodiment of the present invention, the method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed includes a pretreatment operation, in which a dilute alkali solution is added to the high magnesium-to-lithium ratio brine to obtain an alkaline brine in which magnesium hydroxide crystals are suspended.

[0020] According to one embodiment of the present invention, a dilute alkali solution having the same molar content of lithium ions as that in the high magnesium to lithium ratio brine is mixed with the high magnesium to lithium ratio brine to increase the alkalinity, and then the whole is heated to 30-50°C.

[0021] According to one embodiment of the present invention, the concentration of lithium ions in the high magnesium-to-lithium ratio brine is less than 300 mg / L, the concentration of magnesium ions is not less than 10 g / L, and the pH of the natural high magnesium-to-lithium ratio brine is 6.5-7.5.

[0022] Compared with the prior art, the method for extracting lithium from brine with a high magnesium-lithium ratio using a lithium ion sieve expanded bed of the present invention has the following technical effects:

[0023] 1. When the alkaline brine in which magnesium hydroxide crystals are suspended is subjected to the adsorption and lithium extraction and acid desorption operations, the voids in the expanded bed are sufficient to allow the magnesium hydroxide crystals to pass smoothly without clogging, and the alkaline brine can flow through the expanded bed in a manner close to plug flow to obtain a good adsorption effect.

[0024] 2. The hydrogen ions released by ion exchange are neutralized by magnesium hydroxide crystals, which promotes the lithium ion adsorption operation and increases the amount of lithium ions adsorbed.

[0025] 3. By recycling the acid recovery liquid and mixing it with an acid solution of a predetermined acidity to obtain a dilute acid solution for eluting the adsorbed lithium ions, resources can be reused and processing costs can be reduced.

[0026] 4. The expansion liquid is implemented as a dilute alkaline solution to neutralize the free hydrogen ions retained in the treatment space after the water washing treatment to prevent the free hydrogen ions from affecting the subsequent adsorption effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A step diagram of the adsorption and lithium extraction and acid desorption operations of the present invention is shown.

[0028] Figure 2 The graph shows the results of the measurement of lithium ion adsorption of the titanium-based lithium ion sieve particles on lithium-containing solutions with different pH values ​​in one embodiment.

[0029] Figure 3 The graph shows the test results of lithium ion outflow when titanium-based lithium ion sieve particles adsorb lithium ions on lithium-containing solutions with different pH values ​​in one embodiment.

[0030] Figure 4 The graph shows the results of measuring the adsorption amount of different cations by titanium-based ion sieve particles in one embodiment.

[0031] Reference numerals:

[0032] 10. Expansion bed; 11. Bed body; 111. Main body; 11101. First interface; 1101. Processing space; 112. Adjustment member; 11201. Second interface; 12. Bed layer. DETAILED DESCRIPTION

[0033] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0034] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0035] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0036] refer to Figure 1 A method for extracting lithium from brine with a high magnesium to lithium ratio using a lithium ion sieve expanded bed according to a preferred embodiment of the present invention will be described in detail below. The method for extracting lithium from brine with a high magnesium to lithium ratio using a lithium ion sieve expanded bed includes a pretreatment operation and an adsorption lithium extraction and acid desorption operation.

[0037] In the pretreatment operation, dilute alkali solution is added to brine with a high magnesium-lithium ratio to obtain alkaline brine with suspended magnesium hydroxide crystals, providing an alkaline environment for the subsequent adsorption and lithium extraction and acid desorption operations.

[0038] Preferably, a dilute alkali solution having the same molar content of lithium ions as that in the high magnesium to lithium ratio brine is mixed with the high magnesium to lithium ratio brine to increase the alkalinity, and then the whole is heated to 30-50° C. to increase the subsequent lithium extraction rate.

[0039] Preferably, solar energy is used for heating to save energy.

[0040] Preferably, the concentration of lithium ions in the high magnesium-to-lithium ratio brine is less than 300 mg / L, the concentration of magnesium ions is not less than 10 g / L, and the pH of the natural high magnesium-to-lithium ratio brine is 6.5-7.5.

[0041] Preferably, the dilute alkali solution in the pretreatment operation is implemented as sodium hydroxide, because sodium hydroxide is cheap, so the treatment cost is effectively reduced.

[0042] refer to Figure 1The adsorption and lithium extraction and acid desorption operations use an expanded bed 10, which includes a bed body 11 and a bed layer 12 filled inside the bed body 11, and the bed layer 12 is formed by stacking lithium ion sieve particles. The bed body 11 includes a main body 111 and an adjustment member 112, and the adjustment member 112 and the main body 111 together form a processing space 1101 for accommodating the bed layer 12, and the adjustment member 112 is movably arranged on the main body 111 to increase or decrease the processing space 1101. The bottom end of the main body 111 forms a first interface 11101 that is connected to the processing space 1101, and the adjustment member 112 has a second interface 11201 that is opposite to the first interface 11101 and is connected to the processing space 1101. The expansion bed 10 has an expansion mode and a fixed mode, and the adjustment member 112 can be driven to move up and down to switch the expansion bed 10 between the expansion mode and the fixed mode. The adjustment member 112 moves upward away from the first interface 11101 to keep the size of the processing space 1101 at the maximum, and the expansion bed 10 is in the expansion mode; the adjustment member 112 moves downward close to the first interface 11101 to keep the size of the processing space 1101 at the minimum, and the expansion bed 10 is in the fixed mode.

[0043] refer to Figure 1 The lithium extraction by adsorption and acid desorption operation includes a lithium extraction by adsorption operation and an acid desorption operation. The lithium extraction by adsorption operation uses the expanded bed 10 in the expansion mode, and the acid desorption operation uses the expanded bed 10 in the fixed mode.

[0044] The lithium extraction operation comprises the following steps:

[0045] (S1) adjusting the expansion bed 10 to the expansion mode, introducing an expansion liquid into the first interface 11101, and the flowing expansion liquid drives the lithium ion sieve particles in the processing space 1101 to float upward to expand the bed layer 12 to increase the porosity, so as to obtain a treated expansion liquid and discharge it from the second interface 11201;

[0046] (S2) alkaline brine in which magnesium hydroxide crystals are suspended is introduced through the first interface 11101 to pass through the bed layer 12 which is kept expanded, wherein the alkaline brine is subjected to ion exchange with the lithium ion sieve particles so that lithium ions in the alkaline brine are adsorbed by the bed layer 12, and the magnesium hydroxide crystals neutralize hydrogen ions released by the ion exchange to obtain lithium-poor brine which is discharged through the second interface 11201;

[0047] (S3) Water is introduced into the processing space 1101 from the first interface 11101 to flush the processing space 1101 to remove the alkaline brine with suspended magnesium hydroxide crystals retained in the processing space 1101, and wastewater is obtained and discharged from the second interface 11201.

[0048] The acid desorption operation comprises the following steps:

[0049] (S4) The expanded bed 10 is adjusted from the expansion mode to the fixed mode, and a dilute acid solution is introduced into the processing space 1101 from the second interface 11201 to desorb the lithium ions adsorbed by the bed layer 12 to obtain a lithium-rich product solution which is discharged from the first interface 11101, and at the same time, the bed layer 12 is regenerated for cyclic operation.

[0050] Since the expanded bed 10 combines the advantages of a fluidized bed and a fixed bed, when the alkaline brine containing suspended magnesium hydroxide crystals is subjected to the adsorption lithium extraction and acid desorption operations, the voids in the expanded bed 12 are sufficient to allow the magnesium hydroxide crystals to pass smoothly without clogging, and the alkaline brine can flow through the expanded bed 12 in a manner close to plug flow to obtain a good adsorption effect.

[0051] In addition, the hydrogen ions released by ion exchange are neutralized by magnesium hydroxide crystals, thereby promoting the lithium ion adsorption operation and increasing the amount of lithium ions adsorbed.

[0052] Preferably, the lithium ion sieve particles are implemented as manganese ion sieve particles or titanium ion sieve particles. Both manganese ion sieve particles and titanium ion sieve particles are prepared from precursors containing lithium ions, and lithium ions are stripped from the precursors to form spatial memory crystal sites that can only accommodate cations whose ions are not larger than the radius of lithium ions, thereby achieving selective adsorption of lithium ions.

[0053] Preferably, the lithium ion sieve particles are spherical particles, so that in the step (S2), the lithium ion sieve particles can be stably suspended in the expanded bed 10, reducing the possibility of back mixing.

[0054] Preferably, in the step (S2), the alkaline brine containing the magnesium hydroxide crystals suspended therein is introduced into the expanded bed 10 at a flow rate higher than the minimum fluidization velocity of the lithium ion sieve particles.

[0055] Preferably, the dilute acid solution in step (S4) is 0.2-0.5 mol / L hydrochloric acid.

[0056] In addition, the acid desorption operation also includes the following steps:

[0057] ( S5 ) Water is introduced into the processing space 1101 from the second interface 11201 to remove the dilute acid solution retained in the processing space 1101 , and the acid recovery solution is obtained and discharged from the first interface 11101 .

[0058] It is worth mentioning that by mixing the acid recovery liquid with an acid liquid of a predetermined acidity to obtain a dilute acid liquid for use in the step (S4), resources can be reused and processing costs can be reduced.

[0059] Preferably, the expansion liquid in the step (S1) is implemented as a dilute alkali solution, which is introduced into the processing space 1101 to neutralize the free hydrogen ions retained in the processing space 1101 after the treatment in the step (S5) to prevent the free hydrogen ions from affecting the subsequent adsorption effect.

[0060] Preferably, the swelling liquid in step (S1) is implemented as 0.01-0.05 mol / L potassium hydroxide solution.

[0061] In one embodiment, lithium carbonate and anatase titanium dioxide are calcined in a molten salt medium containing lithium chloride and lithium hydroxide to obtain an ion sieve precursor lithium titanate, which is then pretreated with acid to obtain metatitanate ion sieve powder. Finally, the metatitanate ion sieve powder, a binder containing polyvinyl butyral and polyacrylonitrile, lithium carbonate powder as a pore-forming agent, and N,N-dimethylacetamide as an organic solvent are mixed as raw materials and dispersed and acid-eluted in succession to obtain titanium-based ion sieve particles.

[0062] The titanium ion sieve particles prepared above were used to perform the following tests:

[0063] Test Example 1

[0064] The effect of the pH value of the lithium-containing solution on the titanium-based ion sieve particles was verified. That is, based on the fact that the pH values ​​of the lithium-containing solution and the solution after lithium ion adsorption remained unchanged, a predetermined amount of titanium-based ion sieve particles were added to multiple lithium-containing solutions with the same lithium ion concentration and different pH values. After constant temperature oscillation for 10 hours, a solution after lithium ion adsorption was obtained, the lithium content in the corresponding solution after lithium ion adsorption was detected, and the amount of lithium ion adsorption was calculated.

[0065] Depend on Figure 2 It can be seen that the pH value of the lithium-containing solution has a significant effect on the lithium ion adsorption of the titanium-based lithium ion sieve particles. Acidic lithium-containing solutions are not conducive to lithium ion adsorption, while alkaline lithium-containing solutions are conducive to lithium ion adsorption. When the pH value is 3, the titanium-based lithium ion sieve particles have almost no ability to adsorb lithium ions; when the pH value is higher than 7, the amount of lithium ion adsorption increases significantly.

[0066] Test Example 2

[0067] The effect of the pH value of the lithium-containing solution on the outflow of lithium ions after the titanium-based ion sieve particles adsorb lithium ions was verified, that is, based on the lithium content of the two feed solutions being 300 mg / L, one of which had a pH value of 7.5 and the other having a pH value of 11, the two feed solutions were respectively introduced into the two expanded beds 10, and the lithium content ratio of the effluent liquid to the feed solution was respectively measured.

[0068] Depend on Figure 3 It can be seen that when the pH value is 7.5, the lithium content ratio of the effluent to the feed liquid is higher than 0 at the beginning of the increase in the volume flow of the effluent. This is because the hydrogen ions released by ion exchange make the corresponding internal environment of the expanded bed 10 acidic, which limits the adsorption of lithium ions, resulting in the early discharge of lithium ions from the expanded bed 10, and the rapid increase in the discharge of lithium ions, resulting in a decrease in the recovery rate of lithium ions; when the pH value is 11, when the volume flow of the effluent is within 1L, the lithium content ratio of the effluent to the feed liquid remains at 0. This is because there is a predetermined amount of hydroxide ions in the lithium-containing solution, which can quickly neutralize the hydrogen ions released by the exchange of lithium ions and hydrogen ions, promote the adsorption of lithium ions, and delay the discharge time of lithium ions from the expanded bed 10, so that the recovery rate of lithium ions is significantly improved. Therefore, controlling the lithium-containing solution in the expanded bed 10 to be alkaline can improve the utilization rate of titanium-based ion sieve particles and enhance the recovery rate of lithium ions.

[0069] Test Example 3

[0070] A predetermined amount of titanium ion sieve particles was placed in a solution containing lithium ions, calcium ions, magnesium ions, potassium ions and sodium ions with a cation concentration of 20 mmol / L, and an ammonia-ammonium chloride buffer solution was used to adjust the pH to 9.2. The adsorption amount of the titanium ion sieve particles on different cations was measured. The measurement results are as follows: Figure 4 shown.

[0071] Depend on Figure 4 It can be seen that the adsorption capacity of titanium-based ion sieve particles for lithium ions is significantly better than that of other co-existing ions, indicating that titanium-based ion sieve particles have a higher selectivity for lithium ions.

[0072] Since the titanium-based ion sieve particles need to use hydrogen ions to replace the lithium ions in the ion sieve precursor lithium titanate during the preparation process, the formed titanium-based ion sieve particles only allow cations with an ionic radius less than or equal to that of lithium ions to pass through, and the ionic radius of lithium ions in the solution is 0.076nm, which is smaller than the ionic radius of calcium ions with an ionic radius of 0.100nm, potassium ions with an ionic radius of 0.138nm, and sodium ions with an ionic radius of 0.102nm. Although the ionic radius of magnesium ions with an ionic radius of 0.072nm is similar to that of lithium ions, the hydration energy of magnesium ions is greater than that of lithium ions. Magnesium ions require higher energy to dehydrate through the lattice on the surface of titanium-based ion sieve particles. Therefore, magnesium ions are more difficult to be adsorbed by titanium-based ion sieve particles than lithium ions.

[0073] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A method for extracting lithium from brine with a high magnesium-to-lithium ratio using a lithium ion sieve expanded bed, characterized in that: The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed includes adsorption lithium extraction and acid desorption operations, wherein the adsorption lithium extraction and acid desorption operations use an expanded bed, the expanded bed includes a bed body and a bed layer filled inside the bed body, the bed layer is formed by stacking lithium ion sieve particles, the bed body includes a main body and an adjustment member, the adjustment member and the main body together form a processing space for accommodating the bed layer, and the adjustment member is movably arranged on the main body to increase or decrease the processing space, the bottom end of the main body forms a first interface communicating with the processing space, and the adjustment member has a second interface opposite to the first interface and communicating with the processing space, the expanded bed has an expansion mode and a fixed mode, the adjustment member can be driven to move up and down to switch the expanded bed between the expansion mode and the fixed mode, the adjustment member moves up away from the first interface to keep the size of the processing space at the maximum, at this time the expanded bed is in the expansion mode, the adjustment member moves down close to the first interface to keep the size of the processing space at the minimum, at this time the expanded bed is in the fixed mode, the adsorption lithium extraction and acid desorption operations include: The lithium extraction operation is performed by adsorption, wherein the expanded bed is in the expansion mode and the lithium extraction operation comprises: (S1) adjusting the expansion bed to the expansion mode, introducing an expansion liquid into the first interface, the flowing expansion liquid drives the lithium ion sieve particles in the processing space to float upward to expand the bed layer to increase the porosity, and obtain the treated expansion liquid and discharge it from the second interface; (S2) introducing alkaline brine in which magnesium hydroxide crystals are suspended through the first interface to pass through the bed layer that remains expanded, wherein the alkaline brine and the lithium ion sieve particles undergo ion exchange so that lithium ions in the alkaline brine are adsorbed by the bed layer, and the magnesium hydroxide crystals neutralize hydrogen ions released by the ion exchange to obtain lithium-poor brine, which is discharged through the second interface; (S3) introducing water into the treatment space from the first interface to flush the treatment space to remove the alkaline brine with magnesium hydroxide crystals suspended therein, obtain waste water and discharge it from the second interface; An acid desorption operation, wherein the acid desorption operation uses the expanded bed in the fixed mode, and the acid desorption operation comprises: (S4) The expanded bed is adjusted from the expansion mode to the fixed mode, and a dilute acid solution is introduced into the processing space from the second interface to desorb the lithium ions adsorbed by the bed layer to obtain a lithium-rich product solution which is discharged from the first interface, and the bed layer is regenerated at the same time.

2. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 1, characterized in that: The lithium ion sieve particles are implemented as manganese-based ion sieve particles or titanium-based ion sieve particles.

3. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 1, characterized in that: In the step (S2), the alkaline brine containing magnesium hydroxide crystals suspended therein is introduced into the expanded bed at a flow rate higher than the minimum fluidization velocity of the lithium ion sieve particles.

4. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 1, characterized in that: The dilute acid solution in the step (S4) is implemented as 0.2-0.5 mol / L hydrochloric acid.

5. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 1, characterized in that: The acid desorption operation also includes the following steps: (S5) Water is introduced into the treatment space from the second interface to remove the dilute acid solution retained in the treatment space, and the acid recovery solution is obtained and discharged from the first interface.

6. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 5, characterized in that: The expansion liquid in the step (S1) is implemented as a dilute alkali solution, which is introduced into the treatment space to neutralize the free hydrogen ions retained in the treatment space after the treatment in the step (S5).

7. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 6, characterized in that: The swelling liquid in the step (S1) is implemented as 0.01-0.05 mol / L potassium hydroxide solution.

8. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 1, characterized in that: The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed includes a pretreatment operation, in which a dilute alkali solution is added to the high magnesium-to-lithium ratio brine to obtain an alkaline brine in which magnesium hydroxide crystals are suspended.

9. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 8, characterized in that: A dilute alkali solution having the same molar content of lithium ions as that in the high magnesium to lithium ratio brine is mixed with the high magnesium to lithium ratio brine to increase the alkalinity, and then the whole is heated to 30-50°C.

10. The method for extracting lithium from high magnesium-to-lithium ratio brine using a lithium ion sieve expanded bed according to claim 8, characterized in that: The concentration of lithium ions in high magnesium-to-lithium ratio brine is less than 300 mg / L, and the concentration of magnesium ions is not less than 10 g / L. The pH value of natural high magnesium-to-lithium ratio brine is 6.5-7.5.

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