Method and system for extracting lithium from salt lake based on membrane separation

Abstract

The application relates to a salt lake lithium extraction method and system based on membrane separation, wherein the method comprises the following steps: performing primary filtration on desorption qualified liquid stored in a qualified liquid tank to obtain corresponding filtered liquid; the desorption qualified liquid is a liquid obtained after salt lake liquid is subjected to adsorption treatment; STRO membranes in an STRO system are used to perform secondary filtration on the filtered liquid to obtain concentrated lithium-containing liquid and STRO produced water; an RO membrane system is used to separate and treat the STRO produced water to obtain lithium-containing concentrated liquid and fresh water, and the lithium-containing concentrated liquid is returned to the qualified liquid tank. By arranging two membrane separation process flows, the desorption qualified liquid is separated and filtered through the two membrane separation flows, so that the salt lake lithium extraction is no longer dependent on the influence of weather changes, and can be carried out in a closed space, thereby effectively ensuring the stability of the lithium extraction process.

Description

Technical Field

[0001] This disclosure relates to the field of lithium extraction technology, and in particular to a method and system for lithium extraction from salt lakes based on membrane separation. Background Technology

[0002] Lithium, as an important emerging industrial resource and strategic resource, and its compounds are widely used in many fields such as high-energy batteries, aerospace, pharmaceuticals, petrochemicals, electronics, and steel, especially in the field of new energy in recent years. Currently, my country's lithium products are mainly extracted from ores and brine, covering lithium carbonate, lithium chloride, lithium hydroxide, and metallic lithium. From a cost perspective, the cost of lithium extraction from lepidolite is higher than that from spodumene, which is higher than that from salt lakes. With the gradual decrease in lithium carbonate prices, ore-based lithium extraction faces significant cost pressures, thus highlighting the advantages of brine-based lithium extraction.

[0003] In related technologies, the current main process for lithium extraction from brine is the gradient solar pool method. This method requires exposing the brine to the sun for lithium extraction, which makes the process highly susceptible to weather changes and cannot guarantee the stability of the output. Summary of the Invention

[0004] In view of this, this disclosure proposes a membrane separation-based lithium extraction method from salt lakes, which can effectively improve the stability of lithium extraction.

[0005] According to one aspect of this disclosure, a method for lithium extraction from salt lakes based on membrane separation is provided, comprising:

[0006] The desorbed qualified liquid stored in the qualified liquid tank is subjected to primary filtration to obtain the corresponding filtrate; wherein, the desorbed qualified liquid is the liquid obtained after adsorption treatment of the salt lake liquid;

[0007] The filtrate was subjected to secondary filtration using a STRO membrane in a STRO system to obtain a concentrated lithium-containing solution and STRO permeate.

[0008] The STRO permeate is separated using an RO membrane system to obtain lithium-containing concentrate and fresh water, and the lithium-containing concentrate is then returned to the qualified liquid tank.

[0009] In one possible implementation, after the qualified desorption liquid stored in the qualified liquid tank is subjected to primary filtration, the process further includes pressurizing the qualified desorption liquid.

[0010] In one possible implementation, the filtrate is pressurized before secondary filtration using a STRO membrane in a STRO system.

[0011] In one possible implementation, when the filtrate is subjected to secondary filtration using a STRO membrane in a STRO system, the STRO membrane employs an internal circulation design.

[0012] In one possible implementation, when using a STRO membrane in a STRO system to perform secondary filtration of the filtrate, the following is included:

[0013] The filtrate is directed to the first STRO membrane, and the filtrate is filtered once by the first STRO membrane to obtain lithium-containing liquid and STRO permeate.

[0014] The STRO permeate obtained by filtration through the first STRO membrane is directed to the RO membrane system, and the lithium-containing solution obtained by filtration through the first STRO membrane is directed to the second STRO membrane;

[0015] The lithium-containing liquid obtained by the first STRO membrane is filtered again by the second STRO membrane to obtain the concentrated lithium-containing liquid and the STRO permeate, and the STRO permeate is then directed to the RO membrane system.

[0016] In one possible implementation, when using an RO membrane system to separate the STRO permeate to obtain lithium-containing concentrate and desalinated water, the following steps are included:

[0017] The STRO permeate is directed to a third STRO membrane, where it is separated to obtain fresh water and concentrated water; the fresh water is then recycled.

[0018] The concentrated water is directed to the fourth STRO membrane, where it is separated to obtain the fresh water and the concentrated water.

[0019] The fresh water is recycled, and the concentrated water is directed to the qualified liquid tank for mixing with the qualified analytical solution and then filtered and separated again.

[0020] In one possible implementation, the process of pressurizing the STRO permeate before directing it to the third STRO membrane is further included.

[0021] According to another aspect of this application, a membrane separation-based lithium extraction system from salt lakes is also provided, comprising a primary filtration unit, a STRO separation unit, and an RO separation and processing unit.

[0022] The primary filtration unit, the STRO separation unit, and the RO separation processing unit are connected in sequence;

[0023] The primary filtration unit is used to perform primary filtration on the desorbed qualified liquid stored in the qualified liquid tank to obtain the corresponding filtrate; wherein, the desorbed qualified liquid is the liquid obtained after adsorption treatment of the salt lake liquid;

[0024] The STRO separation unit is used to perform secondary filtration of the filtrate using the STRO membrane in the STRO system to obtain concentrated lithium-containing liquid and STRO permeate.

[0025] The RO separation and treatment unit is used to separate the STRO permeate using an RO membrane system to obtain lithium-containing concentrate and fresh water, and to return the lithium-containing concentrate to the qualified liquid tank.

[0026] In one possible implementation, the STRO filter unit is provided with a first booster module;

[0027] The first pressurization module corresponds to the STRO membrane configured in the STRO system, and each first pressurization module is correspondingly set between the inlets of the corresponding STRO membrane for pressurizing the filtrate flowing into the STRO membrane.

[0028] In one possible implementation, the RO separation unit is provided with a second filter, a second pressurization module, and a membrane separation assembly;

[0029] The inlet of the second filter is connected to the outlet of the STRO permeate tank for storing the STRO permeate, the inlet of the second booster module is connected to the outlet of the second filter, and the outlet of the second booster module is connected to the inlet of the membrane separation assembly.

[0030] Lithium extraction is based on membrane separation technology. By setting up two membrane separation processes, the qualified desorbed liquid is separated and filtered through the two membrane separation processes. This makes lithium extraction from salt lakes no longer dependent on weather changes and can be carried out in a closed space, thus effectively ensuring the stability of the lithium extraction process.

[0031] Other features and aspects of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0032] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this disclosure together with the specification and serve to explain the principles of this disclosure.

[0033] Figure 1 A process flow diagram of a membrane separation-based lithium extraction method from salt lakes according to a specific embodiment of this application is shown.

[0034] Figure 2 This paper shows a schematic diagram of the STRO membrane used in a membrane separation-based lithium extraction method from salt lakes according to a specific embodiment of this application.

[0035] Figure 3 This diagram illustrates the structure of a membrane separation-based lithium extraction system from salt lakes according to a specific embodiment of this application. Detailed Implementation

[0036] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0037] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0040] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0041] Figure 1 A process flow diagram of a membrane separation-based lithium extraction method from salt lakes according to a specific embodiment of this application is shown. Figure 1As shown, the method includes: step S100, performing primary filtration on the desorbed qualified liquid stored in the qualified liquid tank to obtain the corresponding filtrate. Here, those skilled in the art will understand that the desorbed qualified liquid mentioned in this step is the liquid obtained after adsorption treatment of the salt lake liquid. The salt lake liquid is the liquid extracted from a salt lake; the desorbed qualified liquid is obtained by adsorption treatment of the liquid extracted from the salt lake. In one possible implementation, the adsorption treatment of the salt lake liquid can be performed using conventional adsorption methods in the art, or a self-designed adsorption process can be used.

[0042] After the qualified solution obtained from the adsorption treatment is filtered through primary filtration, the filtrate obtained can be further filtered through the STRO membrane in the STRO system in step S200 to obtain concentrated lithium-containing solution and STRO permeate. The concentrated lithium-containing solution obtained is the extracted lithium-containing liquid.

[0043] It should be noted here that the STRO system specifically refers to a system that separates and filters the desorbed qualified solution using a STRO membrane. See also... Figure 2 The STRO membrane is a novel membrane module specifically developed for treating high-concentration wastewater. The membrane sheet uses an industrial antifouling RO membrane or nanofiltration membrane, while the grid channel employs a parallel grid structure, distinct from conventional spiral-wound membranes. Typical spiral-wound membranes consist of a membrane sheet wound around a central dialysis tube, with gaps formed by a grid. The grid of spiral-wound membranes is generally diamond-shaped, making the flow of wastewater or feed liquid through the grid less smooth, especially for wastewater containing suspended solids (SS). Therefore, when using traditional spiral-wound membranes for wastewater filtration and separation, strict softening and hardening treatment is usually required to prevent SS from entering the membrane module and causing physical blockage. Consequently, using the aforementioned traditional spiral-wound membrane is not easily feasible for lithium extraction from salt lakes based on membrane separation. In the lithium extraction method of this application embodiment, a novel membrane module (i.e., a STRO membrane) is employed. Because the STRO membrane uses a trapezoidal grid structure, the flow of wastewater or feed liquid within the channels formed by the grid is analogous to flow within a tubular membrane, resulting in significantly lower resistance compared to traditional diamond-shaped grids. Simultaneously, the internal transverse reinforcing ribs (i.e., transverse reinforcing ribs located inside the membrane) increase turbulence during feed liquid flow, reducing concentration polarization and thus enhancing the fouling resistance of the STRO membrane module. The lithium extraction method of this application embodiment, by employing such a STRO membrane module for lithium extraction from salt lakes, effectively ensures the smooth progress of lithium extraction from salt lakes.

[0044] Next, after secondary filtration of the filtrate using a STRO membrane through the above steps, step S300 is executed, where an RO membrane system is used to separate the STRO permeate, obtaining a lithium-containing concentrate and fresh water. The lithium-containing concentrate is then returned to a qualified liquid tank. It should be noted that the RO membrane system refers to a system that separates and filters the liquid to be separated using a set separation membrane. In the lithium extraction method of this application embodiment, the RO membrane system for separating the STRO permeate also uses a STRO membrane. That is, in the method of this application embodiment, when extracting lithium from salt lakes based on membrane separation, secondary filtration and separation are performed using a STRO membrane, ultimately effectively ensuring high-precision and high-concentration lithium extraction.

[0045] Therefore, the lithium extraction method based on membrane separation in this application embodiment is based on membrane separation technology. By setting up two membrane separation processes, the qualified desorbed liquid is separated and filtered through the two membrane separation processes. This makes the lithium extraction in the salt lake no longer dependent on the influence of weather changes and can be carried out in a closed space, thus effectively ensuring the stability of the lithium extraction process.

[0046] Among them, combined Figure 3 As shown, in the lithium extraction method of this application embodiment, after the qualified desorption liquid stored in the qualified liquid tank 111 is subjected to primary filtration, the method further includes pressurizing the qualified desorption liquid. It should be noted that a conventional filter can be used directly for primary filtration of the qualified desorption liquid; however, in this application, a safety filter 112 can be used.

[0047] Specifically, the desorbed qualified liquid stored in the qualified liquid tank 111 is drawn into the primary security filter 112 by the inlet pump 113 for primary filtration. The filtered qualified liquid is then pressurized by the high-pressure pump 122 and guided to the STRO membrane for secondary filtration.

[0048] In other words, in the method of this application embodiment, after the qualified desorption liquid is filtered in the first stage and before it is guided to the STRO membrane module for secondary filtration, the qualified desorption liquid after the first stage filtration needs to be pressurized.

[0049] More specifically, the qualified desorbate obtained by adsorption treatment of the brine lake solution has a salt content of 37 g / L, a lithium concentration of 5.31 g / L, and a sodium concentration of 1.64 g / L. Simultaneously, when pressurizing the qualified desorbate after primary filtration, the increased pressure should be greater than or equal to 90 bar. This is because in the lithium extraction method of this application embodiment, when the pressurized qualified desorbate is guided to the STRO membrane for filtration separation, the STRO membrane can be an SW3017 membrane. When the target concentration (lithium concentration 8.6 g / L) is achieved, the SW3017 membrane maintains a high desalination rate (desalination rate > 98%) while also having a high membrane flux (tested flux > 25 LMH at 90 bar pressure).

[0050] Furthermore, in one possible implementation, see [link to relevant documentation]. Figure 3 When using a STRO membrane for secondary filtration of the filtrate, the STRO membrane can be set up in two sections (i.e., a first STRO membrane and a second STRO membrane connected in sequence).

[0051] Correspondingly, the filtration process includes: First, the filtrate is directed to a first STRO membrane, where it is filtered once to obtain a lithium-containing solution and STRO permeate. Then, the STRO permeate obtained from the first STRO membrane is directed to an RO membrane system, and the lithium-containing solution obtained from the first STRO membrane is directed to a second STRO membrane. The second STRO membrane further filters the lithium-containing solution obtained from the first STRO membrane to obtain a concentrated lithium-containing solution and STRO permeate, which is then directed to the RO membrane system.

[0052] As mentioned above, the first STRO membrane can be an SW3017 membrane, and the second STRO membrane can be an SW3022 membrane. That is, the first and second STRO membranes are of different types, thus allowing for further separation and filtration of the filtrate after primary filtration using different types of STRO membranes, more effectively ensuring high-precision and high-concentration lithium extraction from the brine lake solution.

[0053] Furthermore, by setting up two STRO membranes, after the first separation and filtration is performed by the first STRO membrane (i.e., the first STRO membrane), the high-concentration influent is further concentrated by the second STRO membrane (i.e., the second STRO membrane), which makes the desalination rate more stable and the desalination rate decay rate low. When the target concentration (lithium concentration 12g / L) is reached, the desalination rate is >95%.

[0054] Furthermore, it should be noted that an internal circulation structure can be used when separating and filtering the qualified desorbed liquid after primary filtration using a STRO membrane. That is, the STRO membrane employs an internal circulation design. A circulation pump (e.g., a first circulation pump 123 and a second circulation pump 125 are respectively configured before the first STRO membrane and the second STRO membrane) is installed before the STRO membrane inlet. The circulation pump guides the filtrate obtained from primary filtration to the STRO membrane. After separation and filtration by the STRO membrane, the resulting STRO permeate is guided to the RO membrane system for further separation and treatment. A portion of the concentrated lithium-containing liquid obtained after separation and filtration by the STRO membrane is then returned to the STRO membrane for further separation and treatment via the circulation pump. This allows for multiple separation processes within the same STRO membrane module, which more effectively ensures the target concentration of the lithium-containing liquid.

[0055] Correspondingly, when using a STRO membrane for secondary filtration of the filtrate, if the STRO membrane adopts a two-stage membrane structure (i.e., setting a first STRO membrane and a second STRO membrane connected in sequence), the above-mentioned internal circulation structure can be used for each STRO membrane stage.

[0056] In other words, when using a STRO membrane for secondary filtration of the filtrate, a circulation pump is configured before the inlet of each STRO membrane. The circulation pump guides the liquid to be separated and filtered into the corresponding STRO membrane for separation and filtration. Then, the circulation pump returns a portion of the concentrated liquid obtained from the separation process to the STRO membrane to mix with the filtrate currently being guided into the STRO membrane and perform a second separation process.

[0057] It should also be noted that in the method of this application embodiment, when using a STRO membrane to perform secondary separation filtration of the filtrate, the number of STRO membrane segments (i.e., the number of STRO membrane components set) can be flexibly set according to the design. In the above possible implementation, two STRO membrane segments are used as an example for illustration. In other possible implementations, three segments or any other number of segments can be set, and no specific limitation is imposed here.

[0058] Preferably, when using a STRO membrane for secondary separation and filtration of the filtrate, the STRO membrane is set to have two segments (i.e., including a first STRO membrane and a second STRO membrane connected in sequence). At the same time, each STRO membrane segment adopts an internal circulation design, so that a portion of the concentrate from the outlet of the first STRO membrane column is returned to the inlet of the first circulation pump by the first circulation pump, and a portion of the concentrate from the outlet of the second STRO membrane column is returned to the inlet of the second circulation pump. This ensures sufficient flow rate and cross-flow velocity on the membrane surface, guarantees the system's recovery rate, and improves the system's anti-fouling ability. Finally, the highly concentrated lithium-containing concentrate enters the RO membrane system for further preparation.

[0059] Furthermore, it should be noted that in the above possible implementations, a high-pressure pump is also configured before each STRO membrane (e.g., a first high-pressure pump 122 and a second high-pressure pump 124 are configured before the first STRO membrane and the second STRO membrane, respectively). The filtrate flowing into the STRO membrane is pressurized by these high-pressure pumps. Specifically, the STRO high-pressure pump 122, configured before the inlet of the first STRO membrane, has a maximum pressurization of 85 bar, resulting in a maximum operating pressure of 90 bar for the first STRO membrane, a designed membrane flux of 10 LMH, a concentrate salt content of approximately 60 g / L, and a lithium concentration of approximately 8.6 g / L. The booster pump 124, configured before the second STRO membrane, has a maximum pressurization of 45 bar, resulting in a maximum operating pressure of 140 bar for the second STRO membrane, a designed membrane flux of 6 LMH, a concentrate salt content of approximately 84 g / L, and a lithium concentration of approximately 12 g / L.

[0060] In addition, when using a STRO membrane for secondary filtration of the filtrate, the pressure of the first-stage circulation pump 123 configured before the inlet of the first STRO membrane and the second-stage circulation pump 125 configured before the inlet of the second STRO membrane are both 3.5 bar to 5 bar.

[0061] Furthermore, in the membrane separation-based lithium extraction process of salt lakes in this application embodiment, some lithium in the desorbed qualified liquid permeates through the membrane into the product water. In order to improve the lithium recovery rate, the STRO product water obtained after secondary filtration of the filtrate by the STRO membrane in step S200 can be further separated and treated by the set RO membrane system, so that lithium can be extracted again from the STRO product water.

[0062] Specifically, in one possible implementation, when using an RO membrane system to separate the STRO permeate to obtain lithium-containing concentrate and fresh water, this can be achieved in the following way.

[0063] First, the STRO permeate is directed to the third STRO membrane, where it is separated. The STRO permeate has a salt content of approximately 1.8 g / L. A high-pressure pump installed before the third RO membrane provides a maximum pressurization of 12 bar, with an average membrane flux of 21 LMH, yielding both desalinated and concentrated water. The desalinated water is then recycled. Next, the concentrated water is directed to the fourth STRO membrane, where it is separated again, yielding both desalinated and concentrated water. An inter-stage booster pump is installed, providing a maximum pressurization of 6 bar, with an average membrane flux of 17 LMH. The desalinated water is again recycled, resulting in a final mixed desalinated water with a salt content below 40 mg / L. The concentrated water is directed to a qualified liquid tank for mixing with the eluent before further filtration and separation.

[0064] In other words, when using an RO membrane system to separate and treat STRO permeate, a two-stage membrane design can also be employed. Specifically, the RO membrane system consists of sequentially connected STRO membranes. The STRO permeate is guided into the RO membrane system, where the sequentially connected STRO membranes further separate and filter it, ultimately yielding concentrated water and desalinated water. The concentrated water, containing a small amount of lithium, is returned to the desorption qualified liquid tank and mixed with the desorption qualified liquid before being guided to the secondary filtration STRO membrane for further separation and filtration. The desalinated water, being almost lithium-free, can be recycled.

[0065] Furthermore, when using an RO membrane system to separate and treat STRO permeate, the process also includes pressurizing the STRO permeate. Specifically, a high-pressure pump (not shown in the figure) is installed before the inlet of each STRO membrane section in the RO membrane system. This high-pressure pump pressurizes the liquid that will flow into the corresponding STRO membrane, thereby ensuring the final separation and filtration effect of each STRO membrane section.

[0066] For more details, see Figure 3 As shown, when using an RO membrane system to separate and treat STRO permeate, the STRO permeate enters the STRO permeate tank 132, is pumped by the inlet pump 134 into the secondary security filter 133, and after filtration, is pressurized by the RO high-pressure pump 135 before entering the secondary RO membrane system for further brine separation to produce fresh water for reuse. The secondary RO system is designed with two filtration membranes 131 (i.e., the third and fourth STRO membranes connected sequentially). The concentrated water obtained after the first-stage RO separation and filtration enters the second-stage RO for further filtration. The concentrated water contains a small amount of lithium and is returned to the desorption qualified liquid tank to be mixed with the desorption qualified liquid before entering the STRO system for treatment.

[0067] The permeate from the high-pressure STRO system is pumped by the RO feed pump and filtered by the security filter before entering the secondary RO membrane system. To improve the overall recovery rate of the RO membrane system, the membrane system is designed in two stages. After the first stage of filtration, the water enters the second stage of RO. The RO high-pressure pump has a maximum boost pressure of 35 bar and a maximum designed operating pressure of 35 bar. The final lithium concentration in the permeate is <100 mg / L.

[0068] Accordingly, based on any of the aforementioned membrane separation-based lithium extraction methods from salt lakes, this application also provides a membrane separation-based lithium extraction system from salt lakes. Since the lithium extraction principle of the membrane separation-based lithium extraction system provided in this application is the same as or similar to the lithium extraction principle of the membrane separation-based lithium extraction method in this application, the repetitions will not be repeated.

[0069] See Figure 3The membrane separation-based lithium extraction system 100 provided in this application includes a primary filtration unit 110, a STRO separation unit 130-120, and an RO separation and treatment unit. The primary filtration unit 110, STRO separation unit 120, and RO separation and treatment unit 130 are sequentially connected. The primary filtration unit 110 is used to perform primary filtration on the desorbed qualified liquid stored in the qualified liquid tank 111 to obtain the corresponding filtrate; wherein the desorbed qualified liquid is the liquid obtained after adsorption treatment of the salt lake liquid. The STRO separation unit 120 is used to perform secondary filtration on the filtrate using the STRO membrane 121 in the STRO system to obtain concentrated lithium-containing liquid and STRO permeate. The RO separation and treatment unit 130 separates the STRO permeate to obtain concentrated lithium-containing liquid and fresh water, and returns the fresh water to the qualified liquid tank 111.

[0070] It should be noted that, in one possible implementation, when performing primary filtration of the desorbed qualified liquid in the primary filtration unit 110, the security filter 112 can be directly used.

[0071] Furthermore, the STRO separation unit 120 is equipped with a first pressurization module. Each first pressurization module corresponds to a STRO membrane configured in the STRO system, and each first pressurization module is correspondingly located between the inlets of the respective STRO membranes, used to pressurize the filtrate flowing into the STRO membranes.

[0072] It should be noted that the first pressurization module can be implemented directly using a booster pump or a high-pressure pump. Simultaneously, the STRO membrane in the STRO separation unit 120 can be configured with multiple sequentially connected STRO membrane segments, each segment sequentially separating and filtering the desorbed qualified liquid. Furthermore, it should be pointed out that a circulation pump can be configured at the inlet of each STRO membrane segment, enabling each segment to employ an internal circulation design. This allows a portion of the concentrated liquid after separation by each STRO membrane segment to be returned to the STRO membrane for further separation, thus more effectively improving the high-concentration lithium extraction.

[0073] Furthermore, the RO separation unit 130 includes a second filter 133, a second pressurization module, and a membrane separation assembly. The inlet of the second filter 133 is connected to the outlet of the STRO permeate tank used for storing STRO permeate, and is used to perform primary filtration of the STRO permeate before guiding the filtered STRO permeate to the second pressurization module. The inlet of the second pressurization module is connected to the outlet of the second filter, and is used to pressurize the STRO permeate after primary filtration. The outlet of the second pressurization module is connected to the inlet of the membrane separation assembly, thereby guiding the pressurized STRO permeate to the membrane separation assembly for further separation.

[0074] In one possible implementation, the second filter can also be a security filter. The membrane separation unit can be implemented using multiple sequentially connected STRO membranes.

[0075] See Figure 3 As shown, in one possible implementation, the membrane separation component in the STRO system 100 can also be configured as two segments. That is, the membrane separation component includes two sequentially connected filter membranes 131, such as a third STRO membrane and a fourth STRO membrane connected in sequence. The concentrate outlet of the third STRO membrane is directly connected to the inlet of the fourth STRO membrane, and the desalination outlets of the third and fourth STRO membranes are directly connected to the desalination recovery system. Furthermore, the concentrate outlet of the fourth STRO membrane is directly connected to the inlet of the desorption qualified tank.

[0076] It should be noted that, although... Figures 1 to 3 The membrane separation-based lithium extraction technology from salt lakes described in this application is presented as an example, but those skilled in the art will understand that this disclosure is not limited thereto. In fact, users can flexibly configure the structure of each part according to their personal preferences and / or actual application scenarios, as long as the membrane separation-based process for lithium extraction from salt lakes can be achieved.

[0077] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for lithium extraction from salt lakes based on membrane separation, characterized in that, include: The desorbed qualified liquid stored in the qualified liquid tank is subjected to primary filtration to obtain the corresponding filtrate; wherein, the desorbed qualified liquid is the liquid obtained after adsorption treatment of the salt lake liquid; The filtrate was subjected to secondary filtration using a STRO membrane in a STRO system to obtain a concentrated lithium-containing solution and STRO permeate. The STRO permeate is separated and treated using an RO membrane system to obtain lithium-containing concentrate and fresh water, and the lithium-containing concentrate is returned to the qualified liquid tank. When the filtrate is filtered in a secondary filtration process using a STRO membrane in a STRO system, the STRO membrane employs an internal circulation design. That is, the STRO membrane adopts an internal circulation design. By setting a circulation pump before the STRO membrane inlet, the circulation pump guides the filtrate obtained from the first-stage filtration to the STRO membrane. After the filtrate is separated and filtered by the STRO membrane, the resulting STRO permeate is guided to the RO membrane system for further separation and treatment. A portion of the concentrated lithium-containing liquid obtained after the filtrate is separated and filtered by the STRO membrane is then returned to the STRO membrane for further separation and treatment via the circulation pump. This allows for multiple separation and treatment operations within the same STRO membrane module. When the filtrate is filtered in two stages using the STRO membrane, the STRO membrane is configured as two segments, namely a first STRO membrane and a second STRO membrane connected in sequence, wherein the first STRO membrane is selected as an SW3017 membrane and the second STRO membrane is selected as an SW3022 membrane. When the RO membrane system is used to separate and treat the STRO permeate, the STRO permeate enters the STRO permeate tank, is pumped by the inlet pump into the secondary security filter, and after filtration, enters the secondary RO membrane system for further brine separation to obtain fresh water for reuse; wherein, the secondary RO membrane system consists of a third STRO membrane and a fourth STRO membrane connected in sequence. The process includes pressurizing the filtrate before performing secondary filtration using the STRO membrane in the STRO system. That is, the qualified desorption solution obtained by adsorption treatment of salt lake solution has a salt content of 37 g / L, a lithium concentration of 5.31 g / L, and a sodium concentration of 1.64 g / L; at the same time, when pressurizing the qualified desorption solution after primary filtration, the increased pressure should be greater than or equal to 90 bar.

2. The lithium extraction method according to claim 1, characterized in that, After the qualified desorption liquid stored in the qualified liquid tank is subjected to primary filtration, the process also includes pressurizing the qualified desorption liquid.

3. The lithium extraction method according to claim 1, characterized in that, When performing secondary filtration of the filtrate using a STRO membrane in a STRO system, the following steps are included: The filtrate is directed to the first STRO membrane, and the filtrate is filtered once by the first STRO membrane to obtain lithium-containing liquid and STRO permeate. The STRO permeate obtained by filtration through the first STRO membrane is directed to the RO membrane system, and the lithium-containing solution obtained by filtration through the first STRO membrane is directed to the second STRO membrane; The lithium-containing liquid obtained by the first STRO membrane is filtered again by the second STRO membrane to obtain the concentrated lithium-containing liquid and the STRO permeate, and the STRO permeate is then directed to the RO membrane system.

4. The lithium extraction method according to any one of claims 1 to 3, characterized in that, When the STRO permeate is separated and treated using an RO membrane system to obtain lithium-containing concentrate and desalinated water, the process includes: The STRO permeate is directed to the third STRO membrane, where it is separated to obtain fresh water and concentrated water; the fresh water is then recycled. The concentrated water is directed to the fourth STRO membrane, where it is separated to obtain the fresh water and the concentrated water. The fresh water is recycled, and the concentrated water is directed to the qualified liquid tank for mixing with the desorbed qualified liquid and then filtered and separated again.

5. The lithium extraction method according to claim 4, characterized in that, Before directing the STRO permeate to the third STRO membrane, the process also includes pressurizing the STRO permeate.

6. A membrane separation-based lithium extraction system from salt lakes, characterized in that, The method for realizing the membrane separation-based lithium extraction from salt lakes according to any one of claims 1 to 5 includes a primary filtration unit, a STRO separation unit, and an RO separation and processing unit. The primary filtration unit, the STRO separation unit, and the RO separation processing unit are connected in sequence; The primary filtration unit is used to perform primary filtration on the desorbed qualified liquid stored in the qualified liquid tank to obtain the corresponding filtrate; wherein, the desorbed qualified liquid is the liquid obtained after adsorption treatment of the salt lake liquid; The STRO separation unit is used to perform secondary filtration of the filtrate using the STRO membrane in the STRO system to obtain concentrated lithium-containing liquid and STRO permeate. The RO separation and treatment unit is used to separate and treat the STRO permeate using an RO membrane system to obtain lithium-containing concentrate and fresh water, and to return the lithium-containing concentrate to the qualified liquid tank. The RO separation unit is equipped with a second filter, a second pressurization module, and a membrane separation assembly. The inlet of the second filter is connected to the outlet of the STRO permeate tank for storing the STRO permeate, the inlet of the second booster module is connected to the outlet of the second filter, and the outlet of the second booster module is connected to the inlet of the membrane separation assembly.

7. The lithium extraction system according to claim 6, characterized in that, The STRO separation unit is equipped with a first booster module; The first pressurization module corresponds to the STRO membrane configured in the STRO system, and each first pressurization module is correspondingly set between the inlets of the corresponding STRO membrane for pressurizing the filtrate flowing into the STRO membrane.

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