Supported ionic liquid membrane contactor for lithium extraction from salt lake brine

Abstract

The application provides a supported ionic liquid membrane contactor for extracting lithium from salt lake brine, and belongs to the technical field of materials.The supported ionic liquid membrane contactor has an H-shaped cabin structure, the middle part of the cabin is provided with a crown ether polyamide / imine supported ionic liquid membrane which is constructed by using a crown ether polymer porous membrane as a supporting membrane material and combining an organic phosphorus-ionic liquid extraction system, the two ends of the cabin are respectively a feed phase for containing a magnesium-lithium solution and a receiving phase for containing an extractant, and based on the structure-activity relationship among the crown ether-lithium ion-magnesium ion-organic phosphorus-ionic liquid extraction system, the crown ether polyamide / imine supported ionic liquid membrane can realize efficient separation of magnesium ions and lithium ions in the salt lake brine with a high magnesium-lithium ratio while having excellent running stability.The method is simple in preparation, reduces the amount of extractant, can realize coupling and continuous operation of extraction and back extraction in the lithium extraction process, and is an environment-friendly and efficient separation method.

Description

Technical Field

[0001] The present invention belongs to the field of material technology, and in particular relates to a supported ion liquid membrane contactor for extracting lithium from salt lake brine. Background Art

[0002] Lithium (Li) is the lightest alkali metal with a density of only 0.534 g / cm 3 . Lithium has high electrochemical activity (electrode potential of -3.05V) and the highest specific heat capacity, and has extremely high commercial value in the fields of energy storage (batteries), new materials (ceramics, glass), etc. The quality of magnesium and lithium in salt lake brine is relatively high, which poses great difficulties for the extraction of lithium ions. Therefore, the development of efficient extraction of lithium resources from low-concentration, high Mg / Li ratio salt lake brine has always been a difficult problem and challenge for international salt lake lithium extraction. Existing lithium extraction methods mainly include adsorption, solvent extraction, membrane separation (including nanofiltration and electrodialysis technology), etc. Among them, the membrane technology separation method is considered to be one of the methods with the most development potential.

[0003] Supported ion liquid membranes (SILMs) are primarily extraction and separation technologies that combine an ionic liquid (IL) solvent extraction system with membrane separation. An ionic liquid organic phase (carrier molecules and solvent) is introduced into the pores of a base membrane through a specific method. Capillary forces and surface tension stabilize the organic carrier within the membrane, forming a liquid membrane phase. The ionic liquid organic carrier phase imbues the SILM with selective mass transfer properties. The liquid membrane phase separates the feed phase from the stripping phase. Target substances (such as metal ions) in the feed phase complex with the carrier molecules in the liquid membrane phase to form lipophilic metal-organic ligands, which are then transferred through the liquid membrane phase to the stripping phase, achieving efficient separation of the target substances. The SILM mass transfer process combines the extraction and stripping steps in a continuous permeation process, avoiding the complex operations of traditional solvent extraction systems. The SILM system significantly reduces the use of chemical reagents while offering advantages such as low cost, high efficiency, minimal product contamination, no phase separation issues, no need for demulsification, and ease of scalability. In recent years, SILM has shown broad application prospects in the separation of volatile organic compounds (VOCs), CO2 and heavy metals.

[0004] CN 201811557521 discloses a supported liquid membrane lithium extraction device and a membrane-based brine lithium extraction process. This patent describes a "sandwich" supported liquid membrane device using hydrophilic or hydrophobic polyvinylidene fluoride membrane, polyphenylsulfone membrane, or polytetrafluoroethylene membrane. This method primarily utilizes the recyclable organic extraction phase within the sandwich membrane layer. There is no strong interaction between the membrane material and the extractant. During lithium ion mass transfer, the membrane material merely serves as a support, which inevitably results in significant organic phase loss.

[0005] Journal of Membrane Science, 2007, 300 (1-2): 88-94 introduced a preparation method of ion liquid supported liquid membrane, using different ion liquids as extractant, using nylon membrane, polytetrafluoroethylene porous membrane as its support membrane material, however, the membrane holes on the surface of these porous membranes are larger, which cannot effectively intercept the ion liquid with small particle size. When treating salt lake water, the ion liquid is lost sharply due to direct contact with the aqueous solution, resulting in poor stability of the membrane and cannot be reused.

[0006] As can be seen from the above, the traditional SILM has the problem of serious loss of ion liquid in the membrane due to the lack of strong interaction between the membrane material and the ion liquid extractant, which reduces the lithium-magnesium separation and lithium extraction effect. Therefore, it is a problem to be solved in the art to provide a supported ion liquid membrane contactor for magnesium-lithium separation and lithium resource recovery of high magnesium-lithium salt lake brine, which has good lithium ion adsorption performance and magnesium-lithium selectivity. SUMMARY

[0007] The present application provides a supported ion liquid membrane contactor for magnesium-lithium separation and lithium resource recovery of high magnesium-lithium salt lake brine, which greatly increases the stability of the supported ion liquid membrane, so that the extraction and stripping process is completed in one step, effectively solving the problems of industrial complexity, low efficiency and high pollution in the traditional magnesium-lithium separation method.

[0008] The present application provides a supported ion liquid membrane contactor for lithium extraction of high magnesium-lithium ratio salt lake brine, which has an "H" type cabin structure, a crown ether polymeric porous membrane is used as a support membrane material in the middle of the cabin, and a crown ether polyamide / imine supported ion liquid membrane is constructed by combining an organic phosphorus-ionic liquid extraction system, the two ends of the cabin are respectively a feed phase for containing magnesium-lithium solution and a receiving phase for containing extractant, based on the structure-activity relationship between crown ether-lithium ion-magnesium ion-organic phosphorus-ionic liquid extraction system, the magnesium ion and lithium ion in high magnesium-lithium ratio salt lake brine are efficiently separated.

[0009] As a preferred, the crown ether polyamide / imine supported ion liquid membrane is constructed by using a crown ether polymeric porous membrane as a support membrane material and combining an organic phosphorus-ionic liquid extraction system, which is specifically:

[0010] The polyamide and polyimide containing dibenzocrown ether structure with high lithium ion adsorption performance are used as membrane materials, based on the non-solvent phase inversion method, they are dissolved in organic solvent by fully stirring under water bath condition of 40-80℃, and are degassed for 8-24h under the condition of 50-80℃ to configure into a homogeneous casting solution; then the casting solution is coated into a membrane, and is reduced to room temperature to gel, and then is immersed into a coagulation bath to solidify into a membrane, to obtain a crown ether polymeric porous membrane;

[0011] The organic phosphorus and the ionic liquid are mixed in a certain proportion to form a uniform organic phase, which serves as the loaded mixed organic phase of the crown ether polymer porous membrane;

[0012] The dried crown ether polymer porous membrane is immersed in an ionic liquid mixed organic phase by a direct impregnation method to obtain a crown ether polyamide / imine supported ionic liquid membrane.

[0013] The dried crown ether polymer porous membrane is obtained by drying the crown ether polymer porous membrane obtained in a coagulation bath in a vacuum freeze dryer for 8 to 10 hours.

[0014] In the above scheme, a polyamide or polyimide containing a dibenzocrown ether structure is used as a membrane material, and a crown ether polymer porous membrane is prepared by a non-solvent phase inversion method. The porosity of the crown ether polymer porous membrane is between 75% and 90%. + diameter Therefore, its crown ether polymer porous membrane can effectively adsorb lithium ions and has good lithium ion adsorption performance and magnesium-lithium selectivity.

[0015] Furthermore, a crown ether polymer porous membrane was used as the supporting membrane material and combined with an organophosphorus and ionic liquid solvent extraction system to prepare a crown ether polyamide / imine supported ion liquid membrane. Ionic liquids have high viscosity, and the selected organophosphorus and ionic liquid are both hydrophobic extractants. Relying on the physical and chemical interaction energies (such as van der Waals forces, electrostatic forces, and hydrogen bonds) between the crown ether-lithium ion-ionic liquid and the organophosphorus-lithium ion-ionic liquid, the prepared crown ether polyamide / imine supported ion liquid membrane will effectively reduce the loss of the loaded organic carrier, while increasing the operational stability of the SILM, and can achieve a one-step separation of lithium ions and magnesium ions, greatly improving the magnesium-lithium separation efficiency.

[0016] like Figure 1 As shown, the raw material or feed phase solution contains a magnesium-lithium solution, the receiving phase contains a stripping solution, and a crown ether polymer porous membrane is combined between the two phases to construct a crown ether polyamide / imide supported ion-liquid membrane contactor. During operation, the supported ion-liquid membrane contactor with an "H"-shaped compartment structure is placed on a multi-point magnetic stirrer, with stirring magnets in both the feed phase and the receiving phase.

[0017] Preferably, the stirring speed of the multi-point magnetic stirrer is 0 to 5000 rpm, and the extraction time is 30 to 6000 min.

[0018] Preferably, the crown ether polymer is selected from one of dibenzo-12-crown-4 polyamide, dibenzo-12-crown-4 polyimide, dibenzo-14-crown-4 polyamide, dibenzo-14-crown-4 polyimide, dibenzo-15-crown-5 polyamide, dibenzo-15-crown-5 polyimide, dibenzomonaaza-12-crown-4 polyamide, dibenzomonaaza-12-crown-4 polyimide, dibenzomonaaza-15-crown-5 polyamide, and dibenzomonaaza-15-crown-5 polyimide polymers.

[0019] Preferably, the porogen is selected from at least one of polyvinyl pyrrolidone with a molecular weight of 10-630 kDa, polyvinyl pyrrolidone with a molecular weight of 10-630 kDa and lithium chloride, and the content thereof is between 0 and 10 wt%.

[0020] Preferably, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, nitrogen methyl pyrrolidone, dimethyl sulfoxide and tetrahydrofuran;

[0021] The coagulation bath is selected from at least one of water, methanol, ethanol and acetic acid, and the content of acetic acid is between 1 and 15 wt%.

[0022] Preferably, the dissolution temperature, degassing temperature and coagulation bath temperature of the casting solution system are between 10°C and 80°C;

[0023] The casting solution is coated into a film using a doctor blade, wherein the thickness of the doctor blade is 50 to 600 μm.

[0024] Preferably, the dried crown ether polymer porous membrane is immersed in the ionic liquid mixed organic phase by direct impregnation to obtain the crown ether polyamide / imine supported ionic liquid membrane. Specifically:

[0025] The dried crown ether polymer porous membrane is placed in a culture dish pre-injected with an ionic liquid mixed organic phase, so that the ionic liquid mixed organic phase completely immerses the porous carrier membrane to ensure that the membrane pores are filled with ionic liquid. It is then placed in a vacuum negative pressure environment and soaked for 15-180 minutes. The porous carrier membrane is removed from the culture dish, the ionic liquid mixed organic phase attached to the surface is recovered, and the membrane liquid on the surface is removed to obtain a crown ether polyamide / imide supported ionic liquid membrane.

[0026] Preferably, the volume ratio of the organophosphorus compound to the ionic liquid is 9:1 to 1:1. It is understood that different ratios can affect the lithium ion extraction effect and the magnesium-lithium separation factor, so the volume ratio of the two is particularly critical. A ratio that is too high or too low cannot achieve good magnesium-lithium selectivity and lithium ion extraction efficiency.

[0027] The organophosphorus is selected from at least one of dibutyl phosphate, tributyl phosphate and trioctylphosphine oxide;

[0028] The ionic liquid is selected from alkyl-methylimidazolium bistrifluoromethanesulfonamide salt [Cnmim][NTf2], alkyl-methylimidazolium bistrifluoromethanesulfonamide salt [Cnmim][NTf2], alkyl-methylimidazolium hexafluorophosphate salt [Cnmim][PF6], and alkyl-methylimidazolium hexafluorophosphate salt [Cnmim][PF6], wherein n is at least one of any integer between 2 and 10.

[0029] Preferably, the feed phase is simulated brine containing Li + Mg 2+ 、Na + , K + At least one of which Li + and Mg 2+ The concentrations are 0.001 to 1.0 mmol / L respectively; the receiving phase is an inorganic acid, including at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and its concentration is 0.1 to 4.0 mol / L.

[0030] Preferably, after the contactor operates for 96 hours, the magnesium-lithium ratio in the receiving phase is ≤3, and the magnesium-lithium separation factor is 10-100.

[0031] The advantages and positive effects of the present invention are:

[0032] The present invention uses a crown ether porous membrane as a support membrane material in combination with an organophosphorus-ionic liquid extraction system to construct a crown ether polyamide or imine supported ion liquid membrane. This is combined with a magnesium-lithium solution in the feed phase and an extractant in the stripping phase to construct a crown ether polyamide / imine supported ion liquid membrane contactor. Compared to traditional supported ion liquid membrane systems, the resulting contactor significantly improves the stability of the supported ion liquid membrane, enabling a single-step extraction and stripping process, effectively addressing the complex industrial processes, low efficiency, and high pollution associated with traditional magnesium-lithium separation methods. This invention offers the advantages of high efficiency, environmental friendliness, high selectivity, and simple operation. Furthermore, the membrane material is recyclable, making it easy to industrialize and implement, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the experimental device of the present invention;

[0034] Figure 2 Surface and cross-sectional electron micrographs of TBP-[C4mim][NTf2] loaded on dibenzo-14-crown-4 polyimide in Example 2 of the present invention, as well as EDS images of P and S elements;

[0035] Figure 3The stress-strain properties and electronic photographs of the dibenzo-14-crown-4 polyimide prepared in Example 2 of the present invention are as follows: dry film without loading, wet film, hydrochloric acid immersion, and film loaded with TBP-[C4mim][NTf2];

[0036] Figure 4 In Examples 2 to 4 of the present invention, the magnesium-lithium ratio and magnesium-lithium selectivity in the stripping phase under different magnesium-lithium ratio conditions were studied by using different supported ion liquid membranes;

[0037] Figure 5 is the change in lithium ion and magnesium ion concentrations in the receiving phase of the dibenzodiazepine-12-crown-4 polyimide supported ionic liquid membrane in Example 5 of the present invention within 240 hours of stable operation;

[0038] Figure 6 The crown ether structure (dibenzo-14-crown-4 polyimide) in Example 2 of the present invention and TBP, [C4mim] + 、[NTf2]-、Li + The binding energy between them. DETAILED DESCRIPTION

[0039] Example 1

[0040] Take 2g of dibenzo-14-crown-4 polyamide polymer and 1g of PVP-K30, place them in a three-necked flask containing 23g of N,N-dimethylformamide (DMF) and fully dissolve them. Control the reaction temperature and stir in a 50°C water bath for 8 hours. After thorough stirring, place it in a 70°C oven for degassing for 12 hours to obtain a uniform casting solution. The uniformly degassed casting solution is evenly cast on a flat glass plate. Using an automatic film scraper with a 200μm scraper, a wet flat film is obtained. It is quickly immersed in deionized water for 24 hours to achieve complete phase separation. Finally, the membrane is placed in a vacuum freeze dryer and completely dried to obtain a dibenzo-14-crown-4 polyamide porous membrane with a sponge-like pore structure.

[0041] Take 9ml TBP and 1ml [C4mim] [PF6] in a volume ratio of 9:1 and mix thoroughly to obtain 10ml of uniform solution, which is then placed in a culture dish. Immerse the freeze-dried dibenzo-14-crown-4 polyamide porous membrane in the TBP-[C4mim] [PF6] mixed solution and fully immerse it in a vacuum drying oven for 12 hours. Wipe off the excess organic phase on the surface of the fully infiltrated membrane and hang it vertically for 12 hours to obtain a dibenzo-14-crown-4 polyamide supported ionic liquid membrane. Place it in Figure 1The middle position of the "H" type osmotic membrane pool device. The lithium ion concentration in the feed phase solution is 0.1 mol / L, and the magnesium ion concentration is 0.5 mol / L. The stripping phase is a 1.0 mol / L HCl solution. After 96 hours of operation, the lithium ion concentration in the receiving phase was monitored by inductively coupled plasma optical emission spectrometry (ICP-OES) to be 23.25 mmol / L and the magnesium ion concentration to be 9.61 mmol / L; the magnesium-lithium ratio in the receiving phase was 1.45, and the magnesium-lithium separation factor was 15.46.

[0042] Example 2

[0043] Take 4g of dibenzo-14-crown-4 polyimide polymer and 2g of PVP-K30, place them in a three-necked flask containing 21g of N,N-dimethylformamide (DMF) and fully dissolve them. Control the reaction temperature and stir for 8h in a 70℃ water bath. After being fully stirred, place it in a 50℃ oven for degassing for 12h to obtain a uniform casting liquid. The uniformly degassed casting liquid is evenly poured on a flat glass, and a wet flat film is obtained by using an automatic scraper under a 300μm scraper. It is quickly placed in deionized water and immersed for 24h to completely separate the phases. Finally, the membrane is placed in a vacuum freeze dryer and completely dried to obtain a dibenzo-14-crown-4 polyimide porous membrane with a sponge-like pore structure. Figure 2 As shown in a(1-3), the surface, cross section and locally enlarged SEM image of the obtained dibenzo-14-crown-4 polyimide polymer porous membrane are shown. It can be clearly seen that the cross section of the membrane is a sponge-like structure and the surface of the membrane presents a uniformly distributed pore structure.

[0044] Take 7ml TBP and 3ml [C4mim] [NTf2] in a volume ratio of 7:3 and mix them thoroughly to obtain 10ml of uniform solution, which is then placed in a culture dish. Immerse the freeze-dried dibenzo-14-crown-4 polyimide porous membrane in the TBP-[C4mim] [NTf2] mixed solution and fully immerse it in a vacuum drying oven for 12 hours. Wipe off the excess organic phase on the surface of the fully infiltrated membrane and hang it vertically for 12 hours to obtain a dibenzo-14-crown-4 polyimide supported ionic liquid membrane. Figure 2 b(1-3) shows the surface and cross-sectional SEM images of the porous membrane of dibenzo-14-crown-4 polyimide polymer loaded with TBP-[C4mim][NTf2]. Figure 2 As shown in c(1~3), EDS element analysis of the surface and cross section of the supported ionic liquid membrane shows that TBP-[C4mim][NTf2] is evenly distributed in the membrane voids. Figure 1The middle position of the "H" type permeation membrane cell device, the lithium ion concentration in the feed phase solution was 0.1 mol / L, and the magnesium ion concentration was 0.1 mol / L. The stripping phase was 0.5 mol / L HCl solution. As shown in Figure 4 Figure 1, the magnesium-lithium ratio was 3.5, and the contactor was operated for 96 h. The lithium ion concentration in the receiving phase was 26.36 mmol / L and the magnesium ion concentration was 2.40 mmol / L by using inductively coupled plasma optical emission spectrometer (ICP-OES) to monitor; the magnesium-lithium ratio in the receiving phase was 0.32, and the magnesium-lithium separation factor was 14.57.

[0045] Example 3

[0046] Take 3 g of dibenzo 12-crown-4 polyimide polymer and 1.5 g of PVP-K30, and place them in a three-necked flask containing 22 g of N,N-dimethylformamide (DMF) to fully dissolve, control the reaction temperature at 60°C water bath condition and stir for 8 h. After fully stirring and uniform, place it in a 60°C oven for 12 h to degas, and get a uniform casting solution. Pour the uniform degassed casting solution on a flat glass plate, and get a wet flat membrane by using an automatic film scraper under a 100 μm doctor blade, and quickly put it into deionized water for 24 h to make it completely phase separation. Finally, dry the membrane in a vacuum freeze dryer to get a sponge-like pore structure of dibenzo 12-crown-4 polyimide porous membrane.

[0047] Take 5 ml of TBP and 5 ml of [C4mim][NTf2] to fully mix to get 10 ml of uniform solution, and place it in a petri dish. The freeze-dried dibenzo 12-crown-4 polyimide porous membrane is immersed in the TBP-[C4mim][NTf2] mixed solution, and fully immersed in a vacuum drying oven for 12 h. Wipe the excess organic phase on the surface of the fully infiltrated membrane clean, and hang it vertically for 12 h to get a dibenzo 12-crown-4 polyimide supported ionic liquid membrane. Place it in a Figure 1 The middle position of the "H" type permeation membrane cell device, the lithium ion concentration in the feed phase solution was 0.1 mol / L, and the magnesium ion concentration was 1.0 mol / L. The stripping phase was 0.5 mol / L HCl solution. As shown in Figure 4 Figure 2, the magnesium-lithium ratio was 17.5, and the supported ionic liquid membrane contactor was operated for 96 h. The lithium ion concentration in the receiving phase was 24.39 mmol / L and the magnesium ion concentration was 16.61 mmol / L by using inductively coupled plasma optical emission spectrometer (ICP-OES) to monitor; the magnesium-lithium ratio in the receiving phase was 2.38, and the magnesium-lithium separation factor was 19.1.

[0048] Example 4

[0049] Take 1g of dibenzo-15-crown-5 polyamide polymer and 0.5g of PVP-K30, place them in a three-necked flask containing 24g of N,N-dimethylformamide (DMF) and fully dissolve them. Control the reaction temperature and stir in an 80℃ water bath for 8h. After being fully stirred, place it in an 80℃ oven for degassing for 12h to obtain a uniform casting solution. The uniformly degassed casting solution is evenly cast on a flat glass. Using an automatic scraper with a 300μm scraper, a wet flat film is obtained. It is quickly immersed in deionized water for 24h to achieve complete phase separation. Finally, the membrane is placed in a vacuum freeze dryer and completely dried to obtain a dibenzo-15-crown-5 polyamide porous membrane with a sponge-like pore structure.

[0050] Take 7ml TOPO and 3ml [C2mim] [NTf2] in a volume ratio of 7:3 and mix thoroughly to obtain 10ml of uniform solution, which is then placed in a culture dish. Immerse the freeze-dried dibenzo-15-crown-5 polyamide porous membrane in the TOPO-[C2mim] [NTf2] mixed solution and fully immerse it in a vacuum drying oven for 12 hours. Wipe off the excess organic phase on the surface of the fully infiltrated membrane and hang it vertically for 12 hours to obtain a dibenzo-15-crown-5 polyamide supported ionic liquid membrane. Place it in Figure 1 In the middle of the H-type permeation membrane pool, the lithium ion concentration in the feed phase solution is 0.1 mol / L, and the magnesium ion concentration is 0.1 mol / L. The stripping phase is 0.5 mol / L HCl solution. Figure 4 As shown, the magnesium-lithium ratio is 35.0, the contactor is operated for 240 hours, and the lithium ion concentration in the receiving phase is monitored by using an inductively coupled plasma optical emission spectrometer (ICP-OES) to be 42.26 mmol / L and the magnesium ion concentration is 3.48 mmol / L; the magnesium-lithium ratio in the receiving phase is 0.29, and the magnesium-lithium separation factor is 20.3.

[0051] Example 5

[0052] Take 4g of dibenzodiazepine-12-crown-4 polyimide polymer and 2.5g of PVP-K30, place them in a three-necked flask containing 21g of N,N-dimethylformamide (DMF) and fully dissolve them. Control the reaction temperature and stir in a 50℃ water bath for 8h. After being fully stirred, place it in a 65℃ oven for degassing for 12h to obtain a uniform casting solution. The uniformly degassed casting solution is evenly cast on a flat glass. Using an automatic scraper with a 300μm scraper, a wet flat film is obtained. It is quickly immersed in deionized water for 24h to achieve complete phase separation. Finally, the membrane is placed in a vacuum freeze dryer and completely dried to obtain a dibenzodiazepine-12-crown-4 polyimide porous membrane with a sponge-like pore structure.

[0053] Take 7ml DBBP and 3ml [C4mim] [NTf2] in a volume ratio of 7:3 and mix thoroughly to obtain 10ml of uniform solution, which is then placed in a culture dish. Immerse the freeze-dried dibenzodiazepine-12-crown-4 polyimide porous membrane in the DBBP-[C4mim] [NTf2] mixed solution and fully immerse it in a vacuum drying oven for 12 hours. Wipe off the excess organic phase on the surface of the fully infiltrated membrane and hang it vertically for 12 hours to obtain a dibenzodiazepine-12-crown-4 polyimide supported ionic liquid membrane. Place it in Figure 1 In the middle of the "H" type osmotic membrane pool, the lithium ion concentration in the feed phase solution is 0.1 mol / L, and the magnesium ion concentration is 1.0 mol / L. The stripping phase is 0.1 mol / L HCl solution. Figure 5 Figure 2 shows the changes in lithium and magnesium ion concentrations in the receiving phase of the contactor during 240 hours of stable operation. The lithium ion concentration in the receiving phase was monitored by inductively coupled plasma optical emission spectrometry (ICP-OES) to be 48.4 mmol / L and the magnesium ion concentration to be 4.45 mmol / L. The magnesium-to-lithium ratio in the receiving phase was 0.09, and the magnesium-lithium separation factor was 98.4.

[0054] Comparative Example 1

[0055] The international journal Journal of Membrane Science (2019, 580(62-76)) introduced a method for preparing an ionic liquid supported liquid membrane. A mixed solution of TBP:[C4mim][NTf2] with a volume ratio of 9:1 was used as the loaded organic phase. A porous polytetrafluoroethylene membrane (PVDF) was used as the supporting membrane material to construct the supported ionic liquid membrane. The lithium ion concentration in the feed phase solution was 0.078 mol / L, and the magnesium ion concentration was 0.02 mol / L. The stripping phase was a 1.0 mol / L Na2CO3 / NaHCO3 solution. After 96 hours of operation, the magnesium-lithium ratio decreased from 0.90 in the original solution to 0.73, and the magnesium-lithium separation factor was 1.66. The supported liquid membrane operated stably for approximately 48 hours.

[0056] As shown in Example 2, the crown ether polyamide / polyimide supported ion-liquid membrane prepared in the present invention uses a mixed solution of TBP:[C4mim][NTf2] in a volume ratio of 7:3 as the loaded organic phase; a dibenzo-14-crown-4 polyimide polymer porous membrane as the supporting membrane material to construct the supported ion-liquid membrane. The feed phase solution has a lithium ion concentration of 0.1 mol / L and a magnesium ion concentration of 0.1 mol / L; the stripping phase is a 0.5 mol / L HCl solution. After 96 hours of operation, the magnesium-lithium ratio decreased from 3.5 in the original solution to 0.32, and the magnesium-lithium separation factor was 14.57. The supported liquid membrane operated stably for approximately 96 hours.

[0057] Comparative Example 2

[0058] Use the porous membrane obtained in Example 1 as the supporting membrane material for the ionic liquid membrane. Take 9.5ml TBP and 0.5ml [C4mim] [PF6] in a volume ratio of 20:1 and mix them thoroughly to obtain 10ml of uniform solution, which is then placed in a culture dish. Immerse the freeze-dried dibenzo-14-crown-4 polyamide porous membrane in the TBP-[C4mim] [PF6] mixed solution and fully immersed it in a vacuum drying oven for 12h. Wipe off the excess organic phase on the surface of the fully infiltrated membrane and hang it vertically for 12h to obtain the dibenzo-14-crown-4 polyamide supported ionic liquid membrane. Place it in Figure 1 The middle position of the "H" type osmotic membrane pool device. The lithium ion concentration in the feed phase solution is 0.1 mol / L, and the magnesium ion concentration is 0.5 mol / L. The stripping phase is a 1.0 mol / L HCl solution. After 96 hours of operation, the lithium ion concentration in the receiving phase was monitored by inductively coupled plasma optical emission spectrometry (ICP-OES) to be 33.46 mmol / L and the magnesium ion concentration to be 119.32 mmol / L; the magnesium-lithium ratio in the receiving phase was 3.57, and the magnesium-lithium separation factor was 2.46.

[0059] Comparative Example 3

[0060] Use the porous membrane obtained in Example 3 as the supporting membrane material for the ionic liquid membrane. Take 2ml of TBP and 8ml of [C4mim][NTf2] in a volume ratio of 2:8 and mix them thoroughly to obtain 10ml of uniform solution, which is placed in a culture dish. Immerse the freeze-dried dibenzo-12-crown-4 polyimide porous membrane in the TBP-[C4mim][NTf2] mixed solution and fully immerse it in a vacuum drying oven for 12 hours. Wipe off the excess organic phase on the surface of the fully infiltrated membrane and hang it vertically for 12 hours to obtain the dibenzo-12-crown-4 polyimide supported ionic liquid membrane. Place it in Figure 1 In the middle of the H-shaped permeation membrane cell, the lithium ion concentration in the feed phase solution was 0.1 mol / L and the magnesium ion concentration was 1.0 mol / L. The stripping phase was a 0.5 mol / L HCl solution. After 96 hours of operation, the lithium ion concentration in the receiving phase was monitored by inductively coupled plasma optical emission spectrometry (ICP-OES) to be 11.36 mmol / L and 45.61 mmol / L. The magnesium-lithium ratio in the receiving phase was 4.01, and the magnesium-lithium separation factor was 8.17.

Claims

1. A supported ion liquid membrane contactor for lithium extraction from salt lake brine with a high magnesium to lithium ratio, characterized in that: The supported ion liquid membrane contactor has an "H"-shaped cabin structure. A crown ether polyamide / imide supported ion liquid membrane is provided in the middle of the cabin, using a crown ether polymer porous membrane as the supporting membrane material and combined with an organophosphorus-ionic liquid extraction system. The two ends of the cabin are respectively a feed phase for holding a magnesium-lithium solution and a receiving phase for holding an extractant. Based on the structure-activity relationship between the crown ether-lithium ion-magnesium ion-organophosphorus-ionic liquid extraction system, efficient separation of magnesium ions and lithium ions in salt lake brine with a high magnesium-to-lithium ratio is achieved. A crown ether polymer porous membrane is used as the supporting membrane material and combined with an organophosphorus-ionic liquid extraction system to construct a crown ether polyamide / imide supported ionic liquid membrane. Specifically: A polyamide or polyimide containing a dibenzocrown ether structure with high lithium ion adsorption performance is used as the membrane material. Based on the non-solvent phase inversion method, the polyamide or polyimide is dissolved in an organic solvent with a porogen at a certain temperature to prepare a homogeneous casting solution. The casting solution is coated to form a membrane, and then cooled to room temperature to cause gelation. The membrane is then immersed in a coagulation bath to solidify into a membrane, thereby obtaining a crown ether polymer porous membrane. The organic phosphorus and the ionic liquid are mixed in a certain proportion to form a uniform organic phase, which serves as the loaded mixed organic phase of the crown ether polymer porous membrane; The dried crown ether polymer porous membrane is immersed in the mixed organic phase by a direct impregnation method to obtain a crown ether polyamide / imine supported ionic liquid membrane.

2. The supported ion liquid membrane contactor according to claim 1, characterized in that: The crown ether polymer is selected from one of dibenzo-12-crown-4 polyamide, dibenzo-12-crown-4 polyimide, dibenzo-14-crown-4 polyamide, dibenzo-14-crown-4 polyimide, dibenzo-15-crown-5 polyamide, dibenzo-15-crown-5 polyimide, dibenzomonaaza-12-crown-4 polyamide, dibenzomonaaza-12-crown-4 polyimide, dibenzomonaaza-15-crown-5 polyamide, and dibenzomonaaza-15-crown-5 polyimide polymers.

3. The supported ion liquid membrane contactor according to claim 1, characterized in that: The porogen is selected from at least one of polyvinyl pyrrolidone with a molecular weight of 10-630 kDa, polyvinyl pyrrolidone with a molecular weight of 10-630 kDa and lithium chloride, and its content is between 0 and 10 wt%.

4. The supported ionic liquid membrane contactor according to claim 1, characterized in that: The organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, nitrogen methyl pyrrolidone, dimethyl sulfoxide and tetrahydrofuran.

5. The supported ionic liquid membrane contactor according to claim 1, characterized in that: The dried crown ether polymer porous membrane is immersed in the ionic liquid mixed organic phase by direct impregnation method to obtain the crown ether polyamide / imine supported ionic liquid membrane, specifically: The dried crown ether polymer porous membrane is placed in a culture dish pre-injected with an ionic liquid mixed organic phase, so that the ionic liquid mixed organic phase completely immerses the crown ether polymer porous membrane to ensure that the membrane pores are filled with ionic liquid. The membrane is placed in a vacuum negative pressure environment and soaked for 15-180 minutes. The crown ether polymer porous membrane is removed from the culture dish, the ionic liquid mixed organic phase attached to the surface is recovered, and the membrane liquid on the surface is removed to obtain a crown ether polyamide / imide supported ionic liquid membrane.

6. The supported ionic liquid membrane contactor according to claim 1, characterized in that: The volume ratio of the organophosphorus compound to the ionic liquid is 9:1 to 1:1; The organophosphorus is selected from at least one of dibutyl phosphate, tributyl phosphate and trioctylphosphine oxide; The ionic liquid is selected from alkyl-methylimidazolium bistrifluoromethanesulfonamide salt [Cnmim][NTf2], alkyl-methylimidazolium bistrifluoromethanesulfonamide salt [Cnmim][NTf2], alkyl-methylimidazolium hexafluorophosphate salt [Cnmim][PF6], and alkyl-methylimidazolium hexafluorophosphate salt [Cnmim][PF6], wherein n is at least one of any integer between 2 and 10.

7. The supported ionic liquid membrane contactor according to claim 1, characterized in that: The magnesium-lithium solution is a simulated brine containing Li + Mg 2+ 、Na + , K + At least one of which Li + and Mg 2+ The concentrations are 0.001 to 1.0 mol / L respectively; the extractant is an inorganic acid, including at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and its concentration is 0.1 to 4.0 mol / L.

8. The supported ionic liquid membrane contactor according to any one of claims 1 to 7, characterized in that: The magnesium-lithium ratio in the receiving phase is ≤3, and the magnesium-lithium separation factor is 10-100.

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