A method for separating monovalent and polyvalent ions in water and a method for extracting lithium from salt lakes

Abstract

The present application relates to the technical field of membrane separation, and in particular to a method for separating monovalent and multivalent ions in water and a method for extracting lithium from salt lake. The method for separating monovalent and multivalent ions in water comprises the following steps: (A) performing first electrodialysis on pretreated liquid to be treated to obtain first electrodialysis dilute liquid and first electrodialysis concentrated liquid; (B) returning the first electrodialysis dilute liquid to step (A) to perform the first electrodialysis, and performing nanofiltration on the first electrodialysis concentrated liquid to obtain nanofiltration water and nanofiltration concentrated water; (C) performing second electrodialysis on the nanofiltration water and the nanofiltration concentrated water to obtain second electrodialysis concentrated liquid. The method for separating monovalent and multivalent ions in water has the advantages of short process, simple operation, small amount of fresh water, high water resource utilization rate, good separation effect of monovalent and multivalent ions, no requirement for the concentrations of monovalent and multivalent ions, etc.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a method for separating monovalent and polyvalent ions in water and a method for extracting lithium from salt lakes. Background Technology

[0002] Lithium, often called "white oil," has important applications in nuclear energy, energy storage materials, ceramics manufacturing, and the pharmaceutical industry. The lithium resource supply system mainly consists of two forms: lithium extraction from ore and lithium extraction from brine lakes, with brine lakes accounting for nearly 60%. With the increasing demand for lithium resources, brine lake lithium extraction technology has attracted much attention. However, the complex composition of brine poses significant challenges to lithium extraction technology, especially the separation of lithium from divalent calcium and magnesium ions.

[0003] Currently, the separation of monovalent and divalent ions in water often requires a combination of complex purification processes, which significantly increases production costs. Furthermore, it necessitates extensive post-processing, such as purification and concentration, which further increases operating time and costs. Large quantities of chemical reagents are added, introducing new impurities, such as pH adjustment with acid or alkali solutions, extraction with organic solvents, or removal of calcium and magnesium ions with oxalic acid. Incomplete separation of monovalent and divalent ions, low concentration efficiency, and low purity of enriched lithium ions are also issues. Adsorption and membrane methods require large amounts of fresh water for washing the adsorbent or diluting the solution, necessitating the design of separate freshwater systems and increasing investment costs.

[0004] The main methods for extracting lithium from salt lakes include chemical precipitation, extraction, adsorption, and membrane separation. However, most of these technologies have certain problems or limitations. Chemical precipitation is mainly suitable for brines with low magnesium-to-lithium ratios, but it involves many steps, has a long production cycle, and is prone to lithium loss, resulting in low lithium yield. Extraction yields high lithium yields, but the extractant is greatly affected by pH, requires highly corrosion-resistant equipment, and carries the risk of organic solvents entering the extract. Adsorption is commonly used in salt lake resources with high magnesium-to-lithium ratios and low lithium concentrations. It has high selectivity for lithium ions and a large adsorption capacity, but different adsorbent systems have problems such as high water or acid / alkali consumption and adsorbent solubility. Membrane methods mainly include nanofiltration, reverse osmosis, and electrodialysis. These processes are automated and have high production efficiency, but different membrane processes also have problems such as long process flows, high water consumption, and high investment costs.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for separating monovalent and polyvalent ions in water. This method employs a membrane coupling process of electrodialysis-nanofiltration-electrodialysis, which solves the problems of complex separation processes, high water consumption, and poor separation effect of monovalent and polyvalent ions in water.

[0007] The second objective of this invention is to provide a method for lithium extraction from salt lakes, which does not require a specific Ca / Mg to Li ratio or a specific Li concentration in the feed solution, and can improve the separation of monovalent lithium ions and divalent calcium and magnesium ions while simultaneously concentrating Li ions.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] This invention provides a method for separating monovalent and polyvalent ions in water, comprising the following steps:

[0010] (A) The pretreated solution is subjected to a first electrodialysis to obtain a first electrodialysis dilute solution and a first electrodialysis concentrate;

[0011] (B) The first electrodialysis dilute solution is returned to step (A) for the first electrodialysis, and the first electrodialysis concentrate is subjected to nanofiltration to obtain nanofiltration permeate and nanofiltration concentrate;

[0012] (C) The nanofiltration permeate and the nanofiltration concentrate are subjected to a second electrodialysis to obtain a second electrodialysis concentrate.

[0013] Furthermore, the liquid to be treated includes at least one of raw brine, old brine, adsorption desorption solution, nanofiltration permeate, and reverse osmosis concentrate.

[0014] Furthermore, the monovalent ion includes Li + Na + and K + At least one of the following; the multivalent ion includes Ca 2+ Mg 2+ Fe 2+ Cu 2+ Zn 2+ Mn 2+ SO4 2- CO3 2- Fe 3+ And Al 3+ At least one of them.

[0015] Preferably, the monovalent ion includes Li + The multivalent ions include Ca 2+ and / or Mg 2+ .

[0016] Furthermore, the preprocessing includes filtering.

[0017] Preferably, the filtration includes at least one of sand filtration, microfiltration, ultrafiltration, and multi-media filtration.

[0018] Furthermore, the electrodialysis membrane of the first electrodialysis includes a monovalent selective ion exchange membrane.

[0019] Furthermore, the first electrodialysis includes primary electrodialysis and / or multi-stage electrodialysis.

[0020] Furthermore, the nanofiltration includes at least one of the following: single-stage, single-stage multi-stage, multi-stage single-stage, and multi-stage multi-stage.

[0021] Preferably, the method for separating monovalent and polyvalent ions in water further includes performing ion exchange or reverse osmosis after nanofiltration.

[0022] Furthermore, the electrodialysis membrane of the second electrodialysis includes a monovalent selective ion exchange membrane.

[0023] Preferably, the second electrodialysis includes single-stage electrodialysis and / or multi-stage electrodialysis.

[0024] Furthermore, when the concentration of the multivalent ions in the nanofiltration permeate is <50ppm, the nanofiltration permeate enters the first-stage electrodialysis concentration chamber of the second electrodialysis, and the nanofiltration concentrate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and then undergoes separation and concentration.

[0025] When the concentration of the multivalent ions in the nanofiltration permeate is ≥50ppm, the nanofiltration permeate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and the pure water enters the first-stage electrodialysis concentrate chamber of the second electrodialysis. After separation and concentration, the first-stage electrodialysis concentrate of the second electrodialysis is obtained. The first-stage electrodialysis concentrate of the second electrodialysis enters the second-stage electrodialysis concentrate chamber of the second electrodialysis, and the nanofiltration concentrate enters the second-stage electrodialysis dilute chamber of the second electrodialysis, and then undergoes separation and concentration.

[0026] The present invention also provides a method for lithium extraction from salt lakes, including the separation method for monovalent and polyvalent ions in water as described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The method for separating monovalent and polyvalent ions in water of the present invention adopts a membrane coupling process of electrodialysis-nanofiltration-electrodialysis, which has a short process, is easy to operate, has easy-to-control process conditions, and saves space.

[0029] (2) The nanofiltration permeate and nanofiltration concentrate of the present invention are used as the concentrate and dilute solution of the second electrodialysis, which makes full use of the water resources in the system, reduces water waste, realizes the recycling of water resources in the system, and greatly improves the water resource utilization rate and reduces the amount of fresh water used.

[0030] (3) The present invention improves the separation effect of monovalent ions and polyvalent ions by repeatedly reducing the concentration of polyvalent ions through multi-stage processes; in particular, it improves the separation effect of monovalent lithium ions and divalent calcium and magnesium ions.

[0031] (4) The present invention adopts the whole membrane method, which does not require the addition of reagents, thus avoiding environmental pollution and equipment corrosion.

[0032] (5) The method for separating monovalent and polyvalent ions in water of the present invention can be used in the field of lithium extraction from salt lakes. It can effectively separate monovalent Li ions and divalent Ca and Mg ions, break the limitation on the ion concentration in the feed liquid, and has no requirements on the ratio of Ca and / or Mg to Li. It does not limit the concentration of Li in the feed liquid, can effectively improve the separation effect of monovalent and divalent ions, and at the same time achieve the concentration of Li ions. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the lithium extraction method from salt lakes according to the present invention. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0036] The following describes in detail a method for separating monovalent and polyvalent ions in water and a method for extracting lithium from salt lakes according to embodiments of the present invention.

[0037] In some embodiments of the present invention, a method for separating monovalent and polyvalent ions in water is provided, comprising the following steps:

[0038] (A) The pretreated solution is subjected to a first electrodialysis to obtain a first electrodialysis dilute solution and a first electrodialysis concentrate;

[0039] (B) The first electrodialysis dilute solution is returned to step (A) for the first electrodialysis, and the first electrodialysis concentrate is subjected to nanofiltration to obtain nanofiltration permeate and nanofiltration concentrate;

[0040] (C) The nanofiltration permeate and nanofiltration concentrate are subjected to a second electrodialysis to obtain a second electrodialysis concentrate.

[0041] This invention employs a membrane coupling process of electrodialysis-nanofiltration-electrodialysis, which significantly shortens the preparation process compared to traditional methods. The process is continuous, controllable, and easy to operate. The entire separation process uses a membrane method, eliminating the need for chemical reagents, which greatly reduces reagent investment and production costs, mitigates environmental pollution and corrosion of production equipment, and has outstanding environmental advantages.

[0042] This invention improves the separation efficiency of monovalent and polyvalent ions by repeatedly reducing the concentration of polyvalent ions through a multi-stage process, especially improving the separation efficiency of monovalent lithium ions and divalent calcium and magnesium ions. Furthermore, it has no requirements on the ion concentration in the feed solution, and can separate monovalent and polyvalent ions from solutions of any concentration. During the separation process, nanofiltration permeate and nanofiltration concentrate are used as feed solutions for the concentrate and dilute chambers of the second electrodialysis unit, respectively, achieving the recycling of water resources within the system. This fully utilizes the water resources in the system, reduces water waste, is environmentally friendly, significantly improves water resource utilization, and reduces freshwater consumption.

[0043] The method for separating monovalent and polyvalent ions in water according to the present invention comprises an electrodialysis-nanofiltration-electrodialysis process.

[0044] In some specific embodiments of the present invention, in step (B), the first electrodialysis dilute solution is returned to step (A) for the first electrodialysis, and the first electrodialysis concentrate is subjected to nanofiltration to obtain nanofiltration permeate containing monovalent ions and nanofiltration concentrate containing polyvalent ions.

[0045] Electrodialysis is an electrically driven process that utilizes the selective permeability of ion exchange membranes (i.e., cation exchange membranes allow only cations to pass through while repelling anions, and anion exchange membranes allow only anions to pass through while repelling cations) under the influence of a direct current electric field. This allows charged ions in the solution to migrate in a directional manner, thereby achieving the separation, concentration, and purification of salts in the solution. During electrodialysis, the characteristics of the monovalent selective ion exchange membrane cause monovalent ions to migrate from the dilute compartment to the concentrated compartment, while polyvalent ions in the dilute compartment cannot pass through the monovalent selective ion exchange membrane and are retained in the dilute compartment.

[0046] Nanofiltration is a pressure-driven process that lies between ultrafiltration and reverse osmosis. Its operating pressure is lower than that of reverse osmosis, and nanofiltration membranes also have selective separation properties, with low rejection rates for monovalent ions but high rejection rates for divalent and high-valent ions, thereby achieving the separation of monovalent and multivalent ions.

[0047] The membrane coupling process of electrodialysis-nanofiltration-electrodialysis of the present invention utilizes the characteristics of electrodialysis monovalent ion selective exchange membrane and nanofiltration membrane to perform multiple separations of monovalent and polyvalent ions in water. This solves the problems of incomplete separation of monovalent and polyvalent ions, especially monovalent lithium ions and divalent calcium and magnesium ions, in existing processes, as well as problems such as high water consumption, large amount of reagents added, and limitations on the concentration of monovalent and polyvalent ions in the influent. Moreover, this process has the advantages of short process, simple operation, water saving, and environmental friendliness.

[0048] In some embodiments of the present invention, the liquid to be treated includes at least one of raw brine, old brine, adsorption desorption liquid, nanofiltration permeate, and reverse osmosis concentrate.

[0049] In some embodiments of the present invention, the monovalent ion includes Li + Na + and K + At least one of the following; multivalent ions include Ca 2+ Mg 2+ Fe 2+ Cu 2+ Zn 2+ Mn 2+ SO4 2- CO3 2- Fe 3+ And Al 3+ At least one of the following; preferably, the monovalent ion includes Li. + Multivalent ions include Ca 2+ and / or Mg 2+ .

[0050] The separation method of this invention can effectively separate monovalent lithium ions from divalent calcium and magnesium ions in water.

[0051] In some embodiments of the present invention, pretreatment includes filtration. Pretreatment removes impurities and suspended solids from the liquid to be treated.

[0052] In some embodiments of the present invention, filtration includes at least one of sand filtration, microfiltration, ultrafiltration and multi-media filtration.

[0053] In some embodiments of the present invention, the electrodialysis membrane of the first electrodialysis includes a monovalent selective ion exchange membrane. The monovalent selective ion exchange membrane utilizes the membrane's properties to allow only monovalent ions to pass through while intercepting high-valent ions, thereby achieving the separation of monovalent and high-valent ions.

[0054] In some embodiments of the present invention, the first electrodialysis includes primary electrodialysis and / or multi-stage electrodialysis; preferably, the first electrodialysis includes at least one of primary electrodialysis, secondary electrodialysis, tertiary electrodialysis and quaternary electrodialysis.

[0055] In some embodiments of the present invention, nanofiltration includes at least one of single-stage, single-stage multi-stage, multi-stage single-stage, and multi-stage multi-stage.

[0056] In some embodiments of the present invention, the method for separating monovalent and polyvalent ions in water further includes performing ion exchange or reverse osmosis after nanofiltration.

[0057] In some specific embodiments of the present invention, the ion exchange resin used for ion exchange includes calcium magnesium exchange resin.

[0058] The method for separating monovalent and polyvalent ions in water according to the present invention can be a process flow of electrodialysis-nanofiltration-calcium magnesium exchange resin-electrodialysis, or the process flow can also be electrodialysis-nanofiltration-reverse osmosis-electrodialysis.

[0059] In some embodiments of the present invention, the electrodialysis membrane of the second electrodialysis includes a monovalent selective ion exchange membrane.

[0060] In some embodiments of the present invention, the second electrodialysis includes primary electrodialysis and / or multi-stage electrodialysis; preferably, the second electrodialysis includes at least one of primary electrodialysis, secondary electrodialysis, tertiary electrodialysis and quaternary electrodialysis.

[0061] In some embodiments of the present invention, when the concentration of multivalent ions in the nanofiltration permeate is <50ppm, the nanofiltration permeate enters the first-stage electrodialysis concentration chamber of the second electrodialysis, and the nanofiltration concentrate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and then is separated and concentrated.

[0062] In some embodiments of the present invention, when the concentration of multivalent ions in the nanofiltration permeate is <50 ppm, the nanofiltration permeate and the nanofiltration concentrate are subjected to first-stage electrodialysis of the second electrodialysis to obtain the first-stage electrodialysis concentrate of the second electrodialysis; preferably, when the concentration of multivalent ions in the nanofiltration permeate is <50 ppm, the second electrodialysis further includes: the first-stage electrodialysis concentrate of the second electrodialysis is subjected to at least one of second-stage electrodialysis, third-stage electrodialysis and fourth-stage electrodialysis in sequence until the obtained electrodialysis concentrate reaches the target value.

[0063] When the concentration of multivalent ions in nanofiltration permeate is <50ppm, monovalent ions and multivalent ions can be well separated in the subsequent multi-stage electrodialysis separation and concentration process. Therefore, nanofiltration permeate directly enters the first-stage electrodialysis concentration chamber of the second electrodialysis process, and nanofiltration concentrate enters the first-stage electrodialysis dilute chamber of the second electrodialysis process for concentration and separation.

[0064] In some embodiments of the present invention, when the concentration of multivalent ions in the nanofiltration permeate is ≥50ppm, the nanofiltration permeate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and the pure water enters the first-stage electrodialysis concentrate chamber of the second electrodialysis. After separation and concentration, the first-stage electrodialysis concentrate of the second electrodialysis is obtained. The first-stage electrodialysis concentrate of the second electrodialysis enters the second-stage electrodialysis concentrate chamber of the second electrodialysis, and the nanofiltration concentrate enters the second-stage electrodialysis dilute chamber of the second electrodialysis, and then is separated and concentrated.

[0065] When the concentration of multivalent ions in the nanofiltration permeate is ≥50ppm, the nanofiltration permeate and nanofiltration concentrate are subjected to secondary electrodialysis in the second electrodialysis process to obtain the secondary electrodialysis concentrate of the second electrodialysis process; preferably, when the concentration of multivalent ions in the nanofiltration permeate is ≥50ppm, the second electrodialysis process further includes the secondary electrodialysis concentrate of the second electrodialysis process being subjected to at least one of tertiary electrodialysis and quaternary electrodialysis processes until the obtained electrodialysis concentrate reaches the target value.

[0066] The pretreated solution obtained in this invention first undergoes electrodialysis. Utilizing the characteristics of a monovalent selective ion exchange membrane, monovalent ions (such as lithium ions) migrate from the dilute compartment to the concentrated compartment, while multivalent ions (such as calcium and magnesium ions) in the dilute compartment are retained because they cannot pass through the membrane. The concentrated solution from the first electrodialysis in the concentrated compartment then undergoes nanofiltration. Based on the permeability of the nanofiltration membrane to monovalent ions and its retention properties for multivalent ions, multivalent ions in the solution are removed a second time, reducing the ratio of multivalent ions to monovalent ions.

[0067] When the concentration of multivalent ions in the obtained nanofiltration permeate is <50ppm, the nanofiltration permeate enters the first-stage electrodialysis concentration chamber in the second electrodialysis process, and the obtained nanofiltration concentrate enters the first-stage electrodialysis dilute chamber in the second electrodialysis process. Similarly, a monovalent selective ion exchange membrane is used to allow monovalent ions in the concentrate to enter the concentration chamber, thereby increasing the monovalent ion content in the concentration chamber and reducing the ratio of multivalent ions to monovalent ions, so that multivalent ions and monovalent ions can be better separated.

[0068] Excessive concentration of polyvalent ions in nanofiltration permeate can affect the subsequent separation of monovalent and polyvalent ions. Directly entering the second electrodialysis concentration chamber for concentration will lead to the enrichment of polyvalent ions in the concentrate, resulting in incomplete separation of monovalent and polyvalent ions in the solution. Therefore, when the concentration of multivalent ions in the nanofiltration permeate is ≥50ppm, the nanofiltration permeate enters the first-stage electrodialysis dilute chamber of the second electrodialysis process, while pure water (externally supplied) enters the first-stage electrodialysis concentrate chamber. Utilizing the characteristics of the monovalent selective ion exchange membrane, monovalent ions migrate to the first-stage electrodialysis concentrate chamber, while multivalent ions do not migrate, resulting in the first-stage electrodialysis concentrate of the second electrodialysis process. The first-stage electrodialysis concentrate of the second electrodialysis process then enters the second-stage electrodialysis concentrate chamber, and the nanofiltration concentrate enters the second-stage electrodialysis dilute chamber. Utilizing the characteristics of the monovalent selective ion exchange membrane, monovalent ions in the nanofiltration concentrate migrate to the second-stage electrodialysis concentrate chamber, increasing the monovalent ion content in the concentrate chamber and thus reducing the ratio of multivalent to monovalent ions, resulting in better separation of multivalent and monovalent ions. After the second electrodialysis is completed, subsequent second electrodialysis, third-stage, and fourth-stage separation and concentration can be carried out according to the target values ​​(monovalent ion concentration, polyvalent ion concentration, separation coefficient between monovalent and polyvalent ions, etc.) until the target values ​​are reached.

[0069] The present invention also provides a method for lithium extraction from salt lakes, including the above-mentioned method for separating monovalent and polyvalent ions in water.

[0070] The electrodialysis-nanofiltration-electrodialysis coupling process of this invention can effectively separate calcium and magnesium and concentrate lithium from high-calcium, magnesium and lithium-containing brine in salt lakes, with high calcium and magnesium ion separation efficiency and lithium ion concentration efficiency; it does not require solution dilution, does not limit the lithium concentration of the feed liquid, and has no requirements on the ratio of Ca and / or Mg to Li; the lithium-rich permeate from nanofiltration and the high-calcium and magnesium concentrate are used as the feed liquid for the concentrate chamber and dilute chamber of the next stage of electrodialysis, realizing the recycling of water resources within the system, improving water resource utilization, with low water consumption, and a simple separation process.

[0071] See Figure 1 In some specific embodiments of the present invention, the method for lithium extraction from salt lakes includes the following steps:

[0072] (A) The brine from the salt lake is pretreated to obtain a treated solution. The treated solution is subjected to a first electrodialysis to obtain a dilute solution containing Ca and / or Mg (the first electrodialysis dilute solution) and a concentrated solution containing Li (the first electrodialysis concentrated solution).

[0073] (B) The dilute solution containing Ca and / or Mg is returned to step (A) for first electrodialysis, and the concentrated solution containing Li is subjected to nanofiltration to obtain nanofiltration permeate containing Li and nanofiltration concentrate containing Ca and / or Mg.

[0074] (C) The nanofiltration permeate containing Li and the nanofiltration concentrate containing Ca and / or Mg are subjected to a second electrodialysis to obtain a lithium-rich concentrate (second electrodialysis concentrate) and a dilute solution containing Ca and / or Mg.

[0075] Example 1

[0076] The method for extracting lithium and separating monovalent and divalent ions from salt lake brine provided in this embodiment includes the following steps:

[0077] (A) After ultrafiltration, the salt lake brine is subjected to first-stage electrodialysis. The first-stage electrodialysis is used to separate monovalent and divalent ions to obtain the first-stage electrodialysis concentrate and the first-stage electrodialysis dilute solution.

[0078] (B) The first electrodialysis dilute solution is returned to step (A) for the first electrodialysis. The first electrodialysis concentrate is subjected to nanofiltration. The first concentrate is separated into monovalent and divalent ions using a two-stage, two-part process to obtain nanofiltration permeate and nanofiltration concentrate.

[0079] (C) The polyvalent ions in the nanofiltration permeate are <50 ppm; the nanofiltration permeate enters the first-stage electrodialysis concentration chamber of the second electrodialysis, the nanofiltration concentrate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and the resulting first-stage electrodialysis concentrate enters the second-stage electrodialysis concentration and dilute chambers of the second electrodialysis for second-stage electrodialysis concentration. The second electrodialysis uses two-stage electrodialysis to separate monovalent and divalent ions and concentrate Li ions to obtain the second electrodialysis concentrate, which is a lithium-rich, low-calcium-magnesium solution.

[0080] The ion concentrations (g / L) of each solution in this embodiment are shown in Table 1; the ratios in Table 1 refer to the concentrations of Li in each solution. + Concentration and Mg 2+ and Ca 2+ The ratio of total concentration.

[0081] Table 1

[0082]

[0083] Example 2

[0084] The method for extracting lithium from salt lake brine and separating monovalent and divalent ions provided in this embodiment is the same as in Embodiment 1, except that the two-stage electrodialysis of the second electrodialysis is replaced with a three-stage electrodialysis.

[0085] The Li in the second electrodialysis concentrate obtained in this embodiment + Mg 2+ and Ca 2+ The concentrations were 11.205 g / L, 0.003 g / L, and 0.000 g / L, respectively, which can be directly used to prepare high-purity lithium salts.

[0086] Example 3

[0087] The method for extracting lithium and separating monovalent and divalent ions from salt lake brine provided in this embodiment is the same as in Embodiment 1, except that the salt lake brine is different. In step (B), nanofiltration is performed in a single-stage process, and the polyvalent ion concentration in the nanofiltration permeate is ≥50 ppm. In step (C), the second electrodialysis is performed in a three-stage electrodialysis separation and concentration process. Specifically, the nanofiltration permeate enters the first-stage electrodialysis dilute chamber of the second electrodialysis process, and pure water (externally supplied) enters the first-stage electrodialysis concentration chamber of the second electrodialysis process to receive Li ions from the nanofiltration permeate while simultaneously separating divalent ions. The first-stage electrodialysis concentrate of the second electrodialysis is obtained; the first-stage electrodialysis concentrate of the second electrodialysis enters the concentration chamber of the second electrodialysis, and the nanofiltration concentrate enters the dilute chamber of the second electrodialysis. The Li ions in the nanofiltration concentrate are further recovered and concentrated, and separated from the divalent ions to obtain the second-stage electrodialysis concentrate; the second-stage electrodialysis concentrate of the second electrodialysis enters the concentration and dilute chambers of the third electrodialysis, and the Li ions are further concentrated and the polyvalent ions are separated to obtain the second electrodialysis concentrate, which is a lithium-rich, low-calcium-magnesium solution.

[0088] In this embodiment, the ion concentrations (g / L) of each solution are shown in Table 2. The ratios in Table 2 refer to the concentrations of Li in each solution. + Concentration and Mg 2+ and Ca 2+ The ratio of total concentration.

[0089] Table 2

[0090]

[0091] Example 4

[0092] The method for extracting lithium and separating monovalent and divalent ions from salt lake brine provided in this embodiment refers to Embodiment 3, except that in step (B), nanofiltration adopts a two-stage, two-section process, and the polyvalent ions in the nanofiltration permeate are <50ppm; in step (C), the second electrodialysis adopts a single-stage electrodialysis separation and concentration process. Specifically, the nanofiltration permeate enters the first-stage electrodialysis concentration chamber of the second electrodialysis, and the nanofiltration concentrate enters the first-stage electrodialysis dilute chamber of the second electrodialysis. The resulting second-stage electrodialysis concentrate is a lithium-rich, low-calcium-magnesium solution.

[0093] In this embodiment, the ion concentrations (g / L) of each solution are shown in Table 3. The ratios in Table 3 refer to the concentrations of Li in each solution. + Concentration and Mg 2+ and Ca 2+ The ratio of total concentration.

[0094] Table 3

[0095]

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating monovalent and polyvalent ions in water, characterized in that, Includes the following steps: (A) The pretreated solution is subjected to a first electrodialysis to obtain a first electrodialysis dilute solution and a first electrodialysis concentrate; (B) The first electrodialysis dilute solution is returned to step (A) for the first electrodialysis, and the first electrodialysis concentrate is subjected to nanofiltration to obtain nanofiltration permeate and nanofiltration concentrate; (C) The nanofiltration permeate and the nanofiltration concentrate are subjected to a second electrodialysis to obtain a second electrodialysis concentrate; When the concentration of the multivalent ions in the nanofiltration permeate is <50ppm, the nanofiltration permeate enters the first-stage electrodialysis concentration chamber of the second electrodialysis, and the nanofiltration concentrate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and then is separated and concentrated. When the concentration of the multivalent ions in the nanofiltration permeate is ≥50ppm, the nanofiltration permeate enters the first-stage electrodialysis dilute chamber of the second electrodialysis, and the pure water enters the first-stage electrodialysis concentrate chamber of the second electrodialysis. After separation and concentration, the first-stage electrodialysis concentrate of the second electrodialysis is obtained. The first-stage electrodialysis concentrate of the second electrodialysis enters the second-stage electrodialysis concentrate chamber of the second electrodialysis, and the nanofiltration concentrate enters the second-stage electrodialysis dilute chamber of the second electrodialysis, where it is then separated and concentrated. The monovalent ion is Li + The multivalent ion is Ca 2+ and / or Mg 2+ .

2. The method for separating monovalent and polyvalent ions in water according to claim 1, characterized in that, The liquid to be treated includes at least one of raw brine, old brine, adsorption desorption solution, nanofiltration permeate, and reverse osmosis concentrate.

3. The method for separating monovalent and polyvalent ions in water according to claim 1, characterized in that, The pretreatment includes filtering.

4. The method for separating monovalent and polyvalent ions in water according to claim 3, characterized in that, The filtration includes at least one of sand filtration, microfiltration, ultrafiltration, and multi-media filtration.

5. The method for separating monovalent and polyvalent ions in water according to claim 1, characterized in that, The electrodialysis membrane of the first electrodialysis includes a monovalent selective ion exchange membrane.

6. The method for separating monovalent and polyvalent ions in water according to claim 5, characterized in that, The first electrodialysis includes primary electrodialysis and / or multi-stage electrodialysis.

7. The method for separating monovalent and polyvalent ions in water according to claim 1, characterized in that, The nanofiltration includes at least one of the following: single-stage, single-stage multi-stage, multi-stage single-stage, and multi-stage multi-stage.

8. The method for separating monovalent and polyvalent ions in water according to claim 1, characterized in that, The method for separating monovalent and polyvalent ions in water further includes performing ion exchange or reverse osmosis after nanofiltration.

9. The method for separating monovalent and polyvalent ions in water according to claim 1, characterized in that, The electrodialysis membrane of the second electrodialysis includes a monovalent selective ion exchange membrane.

10. A method for lithium extraction from salt lakes, characterized in that, This includes the method for separating monovalent and polyvalent ions in water as described in any one of claims 1 to 9.

Images