A method for separating lithium, sodium and potassium using a lithium-selective membrane extraction material

Abstract

This invention discloses a method for separating lithium, sodium, and potassium using a lithium-selective membrane extraction material. The method includes preparing a lithium-selective extraction membrane without a modifier and preparing a modified lithium extraction membrane with a modifier: Polyvinyl chloride, 2-thiophenecarboxylic acid trifluoroacetone, and a co-extractant are added to a solvent and stirred until homogeneous. The mixture is then transferred to a flat-bottomed vessel, and a lithium-selective extraction membrane is prepared using a solvent evaporation method. A modifier is added during the preparation of the modified lithium extraction membrane. The lithium-selective extraction membrane or the modified lithium-selective extraction membrane is loaded in the middle of a two-liquid-pool device. Platinum electrodes connected to an external DC regulated power supply are installed in both pools. A lithium / sodium / potassium mixed solution is injected into the pool connected to the anode of the power supply, and an eluent for lithium recovery is injected into the pool connected to the cathode. Extraction is completed when the lithium concentration in both solutions no longer changes under a set voltage. This invention improves lithium extraction, mitigates membrane capacities in electro-membrane extraction systems, and results in a membrane with a high lithium extraction rate and high cycle stability.

Description

Technical Field

[0001] This invention belongs to the technical fields of materials chemistry, separation science, and hydrometallurgy, and relates to the preparation of a lithium selective membrane extraction material and its application in lithium extraction under the background of low-concentration liquid lithium resources. Background Technology

[0002] With the rapid development of the new energy industry, the market demand for lithium and its compounds is increasing, which has accelerated the development of liquid lithium resources. Liquid lithium resources, mainly composed of seawater, lithium product processing by-products, and leachate from waste lithium products, have large total lithium reserves but low average lithium concentrations. Furthermore, they contain coexisting ions, Na(I) and K(I), which have similar chemical properties. These characteristics make the selective extraction of Li(I) one of the challenges in lithium extraction from liquid resources.

[0003] Solvent extraction is an effective method for large-scale water treatment, and it has also shown promising results in lithium / sodium / potassium separation. For example, the 2-thiophenecarboxyltrifluoroacetone / trioctylphosphine oxide extraction system can achieve a Li(I) / Na(I) separation factor of 65 and a Li(I) / K(I) separation factor of 133 (Licheng Zhang, Journal of Molecular Liquids, 2019). However, the environmental pollution and economic issues caused by the volatilization and dissolution of large amounts of extractant during the treatment process have led to considerable skepticism regarding the practical application of this technology. Membrane extraction technology is a novel membrane technology developed based on solvent extraction. Compared with solvent extraction, membrane extraction technology loads the extractant onto a base polymer, which allows for the selective extraction of metal ions with only a small amount of extractant. Furthermore, by adjusting the membrane composition, the treatment effect of solvent extraction technology can be approximated. For example, in actual studies, the separation factor (SF) of Li(I) for Na(I) and K(I) in the 2-thiophenecarboxyltrifluoroacetone / trioctylphosphine oxide membrane extraction system can reach 54.25 and 50.60, respectively (Chunqing Cai, Journal of Membrane Science, 2019). Although this system has a low lithium permeability coefficient (1.0056 μm·s⁻¹). -1 Despite its relatively long processing time (120 hours), the relatively environmentally friendly processing method still attracts much attention.

[0004] External electric field coupled membrane extraction technology can significantly improve the extraction rate of ions. However, our previous studies have found that while applying an external electric field can significantly increase the lithium permeation coefficient (Meng Xiaorong, Hydrometallurgy, 2021), it also accelerates the leakage of the membrane substrate material. This is one of the main reasons for the reduced stability and selectivity of external electric field coupled extraction membrane technology. Therefore, how to maintain membrane stability while improving the membrane permeation coefficient remains one of the important problems to be solved in membrane extraction technology. Summary of the Invention

[0005] To address the issues of slow lithium mass transfer rate in traditional lithium membrane extraction systems and leakage of membrane substrate materials in external electric field coupled membrane extraction technology, this invention provides a method for preparing a highly efficient lithium selective membrane extraction material with good cyclic stability under an external electric field, as well as its electro-membrane lithium extraction technology. This provides a referable method for the efficient and stable extraction of lithium from liquid lithium resources in a lithium / sodium / potassium context.

[0006] The present invention is achieved through the following technical solution.

[0007] One aspect of the present invention provides a method for separating lithium, sodium, and potassium using a lithium-selective membrane extraction material, comprising the following steps:

[0008] Step 1, Preparation of lithium selective membrane extraction material:

[0009] Add 40%-50% polyvinyl chloride, 30%-40% 2-thiophenecarboxyltrifluoroacetone, and 10%-30% co-extractant to a solvent by mass ratio, stir until homogeneous, transfer the resulting homogeneous solution to a flat-bottomed vessel, and prepare a lithium selective extraction membrane by solvent evaporation method.

[0010] Step 2, Application of electro-membrane extraction:

[0011] The prepared lithium selective extraction membrane is loaded in the middle of a two-liquid-pool device. Platinum electrodes connected to an external DC regulated power supply are installed in the two liquid pools respectively. A lithium / sodium / potassium mixed solution is injected into the liquid pool on the anode side of the power supply, and a desorption solution for lithium recovery is injected into the liquid pool on the cathode side of the power supply. Extraction is completed when the lithium concentration in the solutions on both sides no longer changes under a set voltage.

[0012] Another aspect of the present invention provides a method for separating lithium, sodium, and potassium using a lithium-selective membrane extraction material, comprising the following steps:

[0013] Step 1, Preparation of modified lithium selective membrane extraction material:

[0014] Add 30%-50% polyvinyl chloride, 20%-40% 2-thiophenecarboxyltrifluoroacetone, 5%-23% co-extractant, and 5%-30% modifier to a solvent by mass ratio, stir until homogeneous, transfer the resulting homogeneous solution to a flat-bottomed vessel, and prepare a modified lithium selective extraction membrane by solvent evaporation method.

[0015] Step 2, Application of electro-membrane extraction:

[0016] The prepared modified lithium selective extraction membrane was loaded in the middle of a two-liquid pool device. Platinum electrodes connected to an external DC regulated power supply were installed in the two liquid pools respectively. A lithium / sodium / potassium mixed solution was injected into the liquid pool connected to the anode of the power supply, and a desorption solution for lithium recovery was injected into the liquid pool connected to the cathode of the power supply. Extraction was completed when the lithium concentration in the solutions on both sides no longer changed under the set voltage.

[0017] Preferably, the modifier is kerosene or dioctyl phthalate.

[0018] Preferably, the solvent is one or a mixture of two or more of dichloromethane, chloroform, tetrahydrofuran, or cyclohexanone; the solvent accounts for 80%-90% of the total mass of the mixture.

[0019] Preferably, the polyvinyl chloride is SG-8 type polyvinyl chloride.

[0020] Preferably, the co-extractant is trialkylphosphine oxide, tributyl phosphate, or 1,10-o-phenanthroline.

[0021] Preferably, the lithium / sodium / potassium mixed solution contains NH3·H2O and Li + Na + K + A mixed solution; the mixed solution is a chloride or nitrate salt of Li, Na, and K; Na + K + Concentration of Li + 1 to 5 times.

[0022] Preferably, the eluent is one of HCl, H2SO4 or HNO3 solution; the concentration of the eluent solution is 0.1 mol / L.

[0023] Preferably, the pH of the lithium / sodium / potassium mixed solution in the feed phase is maintained at 11.13, and the pH of the eluent is 1.

[0024] Preferably, the applied DC voltage is 10-40V and the separation time is 12-18h.

[0025] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0026] In one aspect, the present invention provides a method for preparing a lithium extraction membrane and an electro-membrane lithium extraction technology thereof. By leveraging the synergistic effect of a co-extractant on the lithium extraction of 2-thiophenecarboxylic acid trifluoroacetone, the lithium extraction rate of the prepared membrane is improved, thereby enhancing the stability of the prepared membrane under an external electric field and the lithium transport rate. Compared with traditional lithium membrane extraction technology, this method can extract lithium from aqueous solutions more efficiently and quickly, and also has a certain degree of cycle stability.

[0027] In another aspect, this invention provides a method for preparing a modified lithium selective extraction membrane and its application in lithium extraction and lithium / sodium / potassium separation under an external electric field. The lithium selective extraction membrane is prepared by adding different hydrophobic modifiers to the lithium extraction membrane, giving the membrane the hydrophobic properties of the modifiers, thereby reducing the contact between the carrier and water in the membrane and further improving the membrane's stability under an external electric field. Simultaneously, the selected modifiers do not affect the specific binding process between the carrier and lithium within the membrane, ensuring that the modified lithium selective extraction membrane still exhibits certain lithium / sodium and lithium / potassium selectivity and a high lithium extraction rate.

[0028] The method and technology provided by this invention can achieve efficient lithium extraction and have strong cycle stability. It is a highly stable lithium selective extraction membrane that can be used in lithium / sodium / potassium backgrounds. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 The infrared spectra of the lithium selective membrane extraction materials prepared in Examples 1-3 of this invention are shown. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0032] This invention provides a method for preparing a lithium-selective extraction membrane without adding a modifier, and for separating lithium, sodium, and potassium using the lithium-selective extraction membrane, comprising the following steps:

[0033] Step 1, Preparation of lithium selective extraction membrane:

[0034] Add 40%-50% polyvinyl chloride, 30%-40% 2-thiophenecarboxylic acid trifluoroacetone, and 10%-30% co-extractant to a solvent by mass ratio, stir for 8-14 hours until the mixture is clear and transparent as a homogeneous phase, transfer the resulting homogeneous solution to a flat-bottomed vessel, and prepare a lithium selective extraction membrane by solvent evaporation method.

[0035] The solvent is one or a mixture of two or more of dichloromethane, chloroform, tetrahydrofuran, or cyclohexanone; the solvent accounts for 80%-90% of the total mass of the mixture.

[0036] The polyvinyl chloride is SG-8 type polyvinyl chloride.

[0037] The co-extractant is trialkylphosphine oxide, tributyl phosphate, or 1,10-o-phenanthroline.

[0038] Step 2, Application of electro-membrane extraction:

[0039] The prepared lithium selective extraction membrane was loaded in the middle of a two-liquid-pool device. Platinum electrodes connected to an external DC regulated power supply were installed in the two liquid pools respectively. A lithium / sodium / potassium mixed solution was injected into the liquid pool on the anode side of the power supply. This lithium / sodium / potassium mixed solution contained NH3·H2O and Li. + Na + K + A mixed solution; pH 11.13; the mixture is a chloride or nitrate salt of Li, Na, and K, with Na... + K + Concentration of Li + The concentration is 1-5 times that of lithium. A solution for lithium recovery is injected into the liquid pool on the cathode side of the power supply. The solution concentration is 0.1 mol / L, and the solution is one of HCl, H2SO4, or HNO3, with a pH of 1. A voltage of 10-40V is applied across the electrodes, and separation is carried out for 12-18 hours. Extraction is complete when the lithium concentration in the solutions on both sides no longer changes.

[0040] This invention further provides the preparation of a lithium selective extraction membrane with a modifier, and a method for separating lithium, sodium, and potassium using the modified lithium selective extraction membrane, comprising the following steps:

[0041] Step 1, Preparation of modified lithium selective extraction membrane:

[0042] Add 30%-50% polyvinyl chloride, 20%-40% 2-thiophenecarboxyltrifluoroacetone, 5%-23% co-extractant, and 5%-30% modifier to a solvent by mass ratio, stir until homogeneous, transfer the resulting homogeneous solution to a flat-bottomed vessel, and prepare a modified lithium selective extraction membrane by solvent evaporation method.

[0043] The modifier is kerosene or dioctyl phthalate.

[0044] Step 2, Application of electro-membrane extraction:

[0045] The prepared modified lithium selective extraction membrane was loaded in the middle of a two-liquid-pool device. Platinum electrodes connected to an external DC regulated power supply were installed in the two liquid pools. A lithium / sodium / potassium mixed solution was injected into the liquid pool on the anode side of the power supply. This lithium / sodium / potassium mixed solution contained NH3·H2O and Li. + Na + K + A mixed solution; pH 11.13; the mixture is a chloride or nitrate salt of Li, Na, and K, with Na... + K + Concentration of Li + The concentration is 1-5 times that of lithium. A solution for lithium recovery is injected into the liquid pool on the cathode side of the power supply. The solution concentration is 0.1 mol / L, and the solution is one of HCl, H2SO4, or HNO3, with a pH of 1. A voltage of 10-40V is applied across the electrodes, and separation is carried out for 12-18 hours. Extraction is complete when the lithium concentration in the solutions on both sides no longer changes.

[0046] The specific embodiments of the present invention will be further described in detail below through examples.

[0047] Example 1:

[0048] Lithium extraction based on 2-thiophenecarboxyltrifluoroacetone / lithium trialkylphosphine oxide selective extraction membrane:

[0049] Step 1: Add 41.7% polyvinyl chloride, 33.3% 2-thiophenecarboxylic acid trifluoroacetone, and 25% trialkylphosphine oxide by mass ratio to dichloromethane solvent. The solvent accounts for 80% of the total mixture mass. After stirring the mixture for 8 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the 2-thiophenecarboxylic acid trifluoroacetone / trialkylphosphine oxide membrane extraction material.

[0050] Step 2: The prepared 2-thiophenecarboxyltrifluoroacetone / trialkylphosphine oxide lithium membrane extraction material was loaded into a self-made two-chamber mass transfer device. After leak testing confirmed that there were no problems, a platinum electrode connected to the anode of the power supply was inserted into the lithium-containing solution side, and a platinum electrode connected to the cathode of the power supply was inserted into the lithium recovery eluent side. A voltage of 40V was applied to both ends of the electrodes, and the separation was carried out for 12 hours. When the concentration of the solutions on both sides no longer changed, the two phase solutions were replaced and the lithium extraction process was repeated under the same voltage.

[0051] The lithium-containing solution consisted of 0.1 mol / L NH3·H2O and 20 mg / L Li. + The mixed solution, with lithium recovery eluent of 0.1 mol / L HCl, has an effective membrane area of ​​3.14 cm². 2The membrane thickness was 200 μm. During the 12-hour mass transfer process, samples were taken every 3-4 hours, and the pH of the two phases was adjusted using 0.1 mol / L NH3·H2O and 0.1 mol / L HCl to maintain the pH of the feed phase and the eluent phase at approximately 11 and 1, respectively.

[0052] When a voltage of 40V was applied, after 12 hours, the lithium extraction rate of the 2-thiophenecarboxylic acid trifluoroacetone / trialkylphosphine oxide lithium selective extraction membrane was 98.7%, the lithium recovery rate was 91.1%, and the permeability coefficient reached 33.20 μm·s. -1 At 40V, with only two phase solutions replaced and lithium extraction performed in 12-hour cycles, the membrane capacity loss rate was 39.3% after four cycles.

[0053] Example 2:

[0054] Lithium extraction based on 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium membrane extraction material:

[0055] Step 1: Add 50% polyvinyl chloride, 40% 2-thiophenecarboxylic acid trifluoroacetone, and 10% tributyl phosphate (by mass ratio) to chloroform solvent. The solvent accounts for 85% of the total mixture mass. After stirring the mixture for 10 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the 2-thiophenecarboxylic acid trifluoroacetone / tributyl phosphate lithium membrane extraction material. Use 0.1 mol / L NH3·H2O and 20 mg / L Li + The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 The film thickness is 200 μm.

[0056] Step 2: The prepared 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium membrane extraction material was loaded into a self-made two-chamber mass transfer device. After leak testing confirmed that there were no problems, a platinum electrode connected to the power supply anode was inserted into the lithium-containing liquid side, and a platinum electrode connected to the power supply cathode was inserted into the lithium recovery eluent side. A voltage of 10V was applied across the electrodes, and the separation was carried out for 14 hours. When the concentrations of the solutions on both sides no longer changed, the two phase solutions were replaced and the lithium extraction process was repeated under the same voltage.

[0057] The lithium-containing solution consisted of 0.1 mol / L NH3·H2O and 20 mg / L Li. + The mixed solution, with lithium recovery eluent of 0.1 mol / L HCl, has an effective membrane area of ​​3.14 cm². 2 The membrane thickness was 200 μm. During the 14-hour mass transfer process, samples were taken every 3-4 hours, and the pH of the two phases was adjusted using 0.1 mol / L NH3·H2O and 0.1 mol / L H2SO4 to maintain the pH of the feed phase and the eluent phase at approximately 11 and 1, respectively.

[0058] When a voltage of 10V was applied, the lithium extraction efficiency of the 2-thiophenecarboxylic acid trifluoroacetone / tributyl phosphate lithium membrane extraction material was 7.39 μm·s after 14 hours, with a permeability coefficient of 7.39 μm·s. -1 When a voltage of 10V was applied, the lithium extraction rate was 93.6% and the recovery rate was 92.1% after 14 hours, with a lithium permeability coefficient of 20.88 μm·s. -1 At 10V, with only two phase solutions replaced and lithium extraction performed in 14-hour cycles, the membrane capacity loss was 27.4% after four cycles.

[0059] Example 3:

[0060] Lithium extraction based on 2-thiophenecarboxyltrifluoroacetone / o-phenanthroline lithium membrane extraction material:

[0061] Step 1: Add 40% polyvinyl chloride, 30% 2-thiophenecarboxylic acid trifluoroacetone, and 30% 1,10-phenanthroline by mass ratio to tetrahydrofuran solvent. The solvent accounts for 90% of the total mixture mass. After stirring the mixture for 14 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the 2-thiophenecarboxylic acid trifluoroacetone / 1,10-phenanthroline lithium membrane extraction material. Use 0.1 mol / L NH3·H2O and 20 mg / L Li... + The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 The film thickness is 200 μm.

[0062] Step 2: The prepared 2-thiophenecarboxyltrifluoroacetone / o-phenanthroline lithium membrane extraction material was loaded into a self-made two-chamber mass transfer device. After leak testing confirmed that there were no problems, a platinum electrode connected to the power supply anode was inserted into the lithium-containing solution side, and a platinum electrode connected to the power supply cathode was inserted into the lithium recovery eluent side. A voltage of 20V was applied across the electrodes, and the separation was carried out for 18 hours. When the concentrations of the solutions on both sides no longer changed, the two phase solutions were replaced and the lithium extraction process was repeated under the same voltage.

[0063] The lithium-containing solution consisted of 0.1 mol / L NH3·H2O and 20 mg / L Li. + The mixed solution, with lithium recovery eluent of 0.1 mol / L HCl, has an effective membrane area of ​​3.14 cm². 2 The membrane thickness was 200 μm. During the 18-hour mass transfer process, samples were taken every 3-4 hours, and the pH of the two phases was adjusted using 0.1 mol / L NH3·H2O and 0.1 mol / L HNO3 to maintain the pH of the feed phase and the eluent phase at approximately 11 and 1, respectively.

[0064] When a voltage of 10V was applied, the lithium extraction efficiency of the 2-thiophenecarboxylic acid trifluoroacetone / o-phenanthroline lithium membrane extraction material was 6.55 μm·s after 18 hours. -1When a voltage of 40V was applied, the lithium extraction rate was 88.9% and the recovery rate was 77.0% after 18 hours. The lithium permeability coefficient was 16.86 μm·s. -1 At 20V, with only two phase solutions replaced and lithium extraction performed in 18-hour cycles, the membrane capacity loss was 33.9% after four cycles.

[0065] The infrared spectra of the lithium selective membrane extraction materials prepared in Examples 1-3 are shown below. Figure 1 As shown.

[0066] Example 4:

[0067] Preparation and stability testing of lithium selective extraction membranes using dioctyl phthalate as a modifier and trialkylphosphine oxide as a co-extractant:

[0068] Step 1: Add 38.46% polyvinyl chloride, 30.77% 2-thiophenecarboxyl trifluoroacetone, 23.08% trialkylphosphine oxide, and 7.69% dioctyl phthalate to tetrahydrofuran in the solvent dichloromethane. The solvent accounts for 80% of the total mixture mass. After stirring the mixture for 14 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the dioctyl phthalate modified 2-thiophenecarboxyl trifluoroacetone / trialkylphosphine oxide lithium selective extraction membrane.

[0069] Step 2: Load the prepared modified lithium membrane extraction material into a self-made two-chamber mass transfer device. After checking for leaks, insert a platinum electrode connected to the anode of the power supply into the lithium-containing liquid side and insert a platinum electrode connected to the cathode of the power supply into the lithium recovery eluent side. Apply a voltage of 40V to both ends of the electrodes and separate for 16 hours. When the concentration of the solutions on both sides no longer changes, replace the two phase solutions and repeat the lithium extraction process under the same voltage.

[0070] With 0.1 mol / L NH3·H2O and 20 mg / L Li + The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 The membrane thickness was controlled to be approximately 200 μm. Lithium extraction was performed at 40 V, with only the two-phase solutions replaced and cycles of 16 h. After four cycles, the capacitive loss rate of the dioctyl phthalate-modified 2-thiophenecarboxylic acid trifluoroacetone / trialkylphosphine oxide lithium selective extraction membrane was 31.9%.

[0071] Example 5:

[0072] Preparation and stability testing of lithium selective extraction membranes using dioctyl phthalate as a modifier and tributyl phosphate as a co-extractant:

[0073] A mixture of 45.45% polyvinyl chloride, 36.36% 2-thiophenecarboxylic acid trifluoroacetone, 9.10% tributyl phosphate, and 9.09% dioctyl phthalate by mass ratio was added to dichloromethane solvent. The solvent accounted for 80% of the total mass of the mixture. After stirring the mixture for 16 hours, it was transferred to a flat-bottomed container and allowed to stand to evaporate the solvent, thus obtaining a dioctyl phthalate-modified 2-thiophenecarboxylic acid trifluoroacetone / tributyl phosphate lithium selective extraction membrane.

[0074] Step 2: Load the prepared modified lithium membrane extraction material into a self-made two-chamber mass transfer device. After checking for leaks, insert a platinum electrode connected to the anode of the power supply into the lithium-containing liquid side and insert a platinum electrode connected to the cathode of the power supply into the lithium recovery eluent side. Apply a voltage of 40V to both ends of the electrodes and separate for 16 hours. When the concentration of the solutions on both sides no longer changes, replace the two phase solutions and repeat the lithium extraction process under the same voltage.

[0075] With 0.1 mol / L NH3·H2O and 20 mg / L Li + The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 The membrane thickness was controlled to be approximately 200 μm. Lithium extraction was performed at 40 V, with only the two-phase solutions replaced and cycles of 16 h. After four cycles, the capacitive loss rate of the dioctyl phthalate-modified 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium selective extraction membrane was 20.5%.

[0076] Example 6:

[0077] Preparation and stability testing of lithium selective extraction membranes using dioctyl phthalate as a modifier and o-phenanthroline as a co-extractant:

[0078] A mixture of 30.76% polyvinyl chloride, 40.47% 2-thiophenecarboxylic acid trifluoroacetone, 23.48% o-phenanthroline, and 5.29% dioctyl phthalate was added to dichloromethane solvent, with the solvent accounting for 80% of the total mixture mass. After stirring the mixture for 14 hours, it was transferred to a flat-bottomed container and allowed to stand to evaporate the solvent, thus obtaining a dioctyl phthalate-modified 2-thiophenecarboxylic acid trifluoroacetone / o-phenanthroline lithium selective extraction membrane.

[0079] Step 2: Load the prepared modified lithium membrane extraction material into a self-made two-chamber mass transfer device. After checking for leaks, insert a platinum electrode connected to the anode of the power supply into the lithium-containing liquid side and insert a platinum electrode connected to the cathode of the power supply into the lithium recovery eluent side. Apply a voltage of 40V to both ends of the electrodes and separate for 16 hours. When the concentration of the solutions on both sides no longer changes, replace the two phase solutions and repeat the lithium extraction process under the same voltage.

[0080] With 0.1 mol / L NH3·H2O and 20 mg / L Li +The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 The membrane thickness was controlled to be approximately 200 μm. Lithium extraction was performed at 40 V, with only the two-phase solutions replaced and cycles of 16 h. After four cycles, the capacitive loss rate of the dioctyl phthalate-modified 2-thiophenecarboxylic acid trifluoroacetone / lithium o-phenanthroline selective extraction membrane was 29.0%.

[0081] Compared to the lithium selective extraction membrane without the modifier, the capacity loss rate was improved, indicating that dioctyl phthalate modification can enhance the stability of the mass transfer system.

[0082] Example 7:

[0083] Preparation of 2-thiophenecarboxyltrifluoroacetone / lithium trialkylphosphine oxide selective extraction membrane modified with kerosene and its application in lithium / sodium / potassium separation:

[0084] Step 1: Add 31.25% polyvinyl chloride, 25% 2-thiophenecarboxylic acid trifluoroacetone, 18.75% trialkylphosphine oxide, and 25% kerosene to the solvent tetrahydrofuran. The solvent accounts for 85% of the total mixture mass. After stirring the mixture for 10 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the kerosene-modified 2-thiophenecarboxylic acid trifluoroacetone / trialkylphosphine oxide lithium selective extraction membrane. Control the membrane thickness to about 200 μm.

[0085] Step 2: The prepared kerosene-modified 2-thiophenecarboxyltrifluoroacetone / trialkylphosphine oxide lithium selective extraction membrane was loaded into a self-made two-chamber mass transfer device. After leak testing, a platinum electrode connected to the power supply anode was inserted into the lithium-containing solution side, and a platinum electrode connected to the power supply cathode was inserted into the lithium recovery eluent side. A voltage of 30V was applied across the electrodes, and separation was carried out for 12 hours. The lithium extraction process was completed when the concentration of the solutions on both sides no longer changed.

[0086] With 0.1 mol / L NH3·H2O and 20 mg / L Li + The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 When a voltage of 30V was applied, after 12 hours, the lithium extraction rate of the kerosene-modified 2-thiophenecarboxylic acid trifluoroacetone / trialkylphosphine oxide lithium selective extraction membrane was 95.3%, the lithium recovery rate was 90.6%, and the permeability coefficient reached 26.54 μm·s. -1 At 30V, with only two phase solutions replaced and lithium extraction performed in 12-hour cycles, the membrane capacity loss was 18.2% after four cycles.

[0087] The effective membrane area is 3.14 cm². 2 At that time, 0.1 mol / L HCl was used as the eluent, and the feed phase was Li.+ Na + K + A mixed solution with a concentration of 20 mg / L was subjected to lithium extraction at 30V for 12 hours. Li 25.4 μm·s -1 P Na 3.02 μm·s -1 P K 3.18 μm·s -1 S Li(I) / Na(I) It is 8.41, S Li(I) / K(I) The value was 7.99. 0.1 mol / L HCl was used as the eluent, and the feed phase consisted of 20 mg / L Li. + 100mg / L Na + K + The mixed solution was subjected to lithium extraction at 30V for 12 hours. Li 24.9 μm·s -1 P Na 3.25 μm·s -1 P K 3.36 μm·s -1 S Li(I) / Na(I) It is 7.66, S Li(I) / K(I) It is 7.41.

[0088] Example 8:

[0089] Preparation of 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium selective extraction membrane modified with kerosene and its application in lithium / sodium / potassium separation:

[0090] Step 1: Add 35.71% polyvinyl chloride, 28.57% 2-thiophenecarboxyltrifluoroacetone, 5.15% tributyl phosphate, and 30.57% kerosene to the solvent cyclohexanone. The solvent accounts for 90% of the total mixture mass. After stirring the mixture for 10 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the kerosene-modified 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium selective extraction membrane. Control the membrane thickness to about 200 μm.

[0091] Step 2: The prepared kerosene-modified 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium selective extraction membrane is loaded into a self-made two-chamber mass transfer device. After leak testing and confirmation of no problems, a platinum electrode connected to the anode of the power supply is inserted into the lithium-containing liquid side, and a platinum electrode connected to the cathode of the power supply is inserted into the lithium recovery eluent side. A voltage of 40V is applied across the electrodes, and separation is carried out for 15 hours. When the concentration of the solutions on both sides no longer changes, the lithium extraction process is complete.

[0092] With 0.1 mol / L NH3·H2O and 20 mg / L Li +The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 When a voltage of 40V was applied, after 15 hours, the lithium extraction rate of the kerosene-modified 2-thiophenecarboxyltrifluoroacetone / tributyl phosphate lithium selective extraction membrane was 91.8%, the lithium recovery rate was 88.3%, and the permeability coefficient was 19.02 μm·s. -1 At 40V, with only two phase solutions replaced and lithium extraction performed in 15-hour cycles, the membrane capacity loss was 16.0% after four cycles.

[0093] The effective membrane area is 3.14 cm². 2 At that time, 0.1 mol / L HCl was used as the eluent, and the feed phase was Li. + Na + K + A mixed solution with a concentration of 20 mg / L was subjected to lithium extraction at 40V for 15 hours. Li It is 18.48 μm·s -1 P Na 3.79 μm·s -1 P K 3.98 μm·s -1 S Li(I) / Na(I) It is 4.88, S Li(I) / K(I) The value was 4.64. 0.1 mol / L HCl was used as the eluent, and the feed phase consisted of 20 mg / L Li. + 100mg / L Na + K + The mixed solution was subjected to lithium extraction at 40V for 15 hours. Li It is 17.96 μm·s -1 P Na 3.93 μm·s -1 P K It is 4.21 μm·s -1 S Li(I) / Na(I) It is 4.57, S Li(I) / K(I) It is 4.26.

[0094] Example 9:

[0095] Preparation of 2-thiophenecarboxyltrifluoroacetone / lithium o-phenanthroline selective extraction membrane modified with kerosene and its application in lithium / sodium / potassium separation:

[0096] Step 1: Add 50.25% polyvinyl chloride, 20.25% 2-thiophenecarboxylic acid trifluoroacetone, 14.5% o-phenanthroline, and 15% kerosene to dichloromethane solvent. The solvent accounts for 80% of the total mixture mass. After stirring the mixture for 10 hours, transfer it to a flat-bottomed container and allow it to stand to evaporate the solvent to obtain the kerosene-modified 2-thiophenecarboxylic acid trifluoroacetone / o-phenanthroline lithium selective extraction membrane. Control the membrane thickness to about 200 μm.

[0097] Step 2: The prepared kerosene-modified 2-thiophenecarboxyltrifluoroacetone / o-phenanthroline lithium selective extraction membrane was loaded into a self-made two-chamber mass transfer device. After leak testing confirmed that there were no problems, a platinum electrode connected to the anode of the power supply was inserted into the lithium-containing liquid side, and a platinum electrode connected to the cathode of the power supply was inserted into the lithium recovery eluent side. A voltage of 20V was applied to both ends of the electrodes, and the separation was carried out for 18 hours. When the concentration of the solutions on both sides no longer changed, the lithium extraction process was completed.

[0098] With 0.1 mol / L NH3·H2O and 20 mg / L Li + The mixed solution is the feed phase, 0.1 mol / L HCl is the eluent, and the effective membrane area is 3.14 cm². 2 When a voltage of 20V was applied, after 18 hours, the lithium extraction rate of the kerosene-modified 2-thiophenecarboxyltrifluoroacetone / o-phenanthroline lithium selective extraction membrane was 88.1%, the lithium recovery rate was 76.9%, and the permeability coefficient was 16.16 μm·s. -1 At 20V, with only two phase solutions replaced and lithium extraction performed in 18-hour cycles, the membrane capacity loss was 20.2% after four cycles.

[0099] The effective membrane area is 3.14 cm². 2 At that time, 0.1 mol / L HCl was used as the eluent, and the feed phase was Li. + Na + K + A mixed solution with a concentration of 20 mg / L was subjected to lithium extraction at 20V for 18 hours. Li It is 15.37 μm·s -1 P Na 3.95 μm·s -1 P K 4.03 μm·s -1 S Li(I) / Na(I) It is 3.88, S Li(I) / K(I) The value was 3.81. 0.1 mol / L HCl was used as the eluent, and the feed phase consisted of 20 mg / L Li. + 100mg / L Na + K + The mixed solution was subjected to lithium extraction at 20V for 18 hours. Li It is 14.83 μm·s-1 P Na It is 4.12 μm·s -1 P K 4.39 μm·s -1 S Li(I) / Na(I) It is 3.60, S Li(I) / K(I) It is 3.38.

[0100] The lithium selective extraction membrane provided by this invention not only solves the problem of slow extraction rate of traditional lithium extraction membranes, but also improves the membrane tolerance problem in the electro-membrane extraction system, so that the prepared membrane has a high lithium extraction rate and cycle stability, and maintains a certain Li / Na, Li, K separation capability. This provides a reference method for the selective extraction of lithium from lithium / sodium / potassium solutions.

[0101] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for separating lithium, sodium, and potassium using a lithium-selective membrane extraction material, characterized in that, Includes the following steps: Step 1, Preparation of modified lithium selective membrane extraction material: Add 30%-50% polyvinyl chloride, 20%-40% 2-thiophenecarboxyltrifluoroacetone, 5%-23% co-extractant, and 5%-30% modifier to a solvent by mass ratio, stir until homogeneous, transfer the resulting homogeneous solution to a flat-bottomed vessel, and prepare a modified lithium selective extraction membrane by solvent evaporation method. The modifier is kerosene or dioctyl phthalate; The co-extractant is trialkylphosphine oxide, tributyl phosphate, or 1,10-o-phenanthroline; Step 2, Application of electro-membrane extraction: The prepared modified lithium selective extraction membrane was loaded in the middle of a two-liquid pool device. Platinum electrodes connected to an external DC regulated power supply were installed in the two liquid pools respectively. A lithium / sodium / potassium mixed solution was injected into the liquid pool connected to the anode of the power supply, and a desorption solution for lithium recovery was injected into the liquid pool connected to the cathode of the power supply. Extraction was completed when the lithium concentration in the solutions on both sides no longer changed under the set voltage.

2. The method for separating lithium, sodium, and potassium using the lithium-selective membrane extraction material according to claim 1, characterized in that, The solvent is one or a mixture of two or more of dichloromethane, chloroform, tetrahydrofuran or cyclohexanone; the solvent accounts for 80%-90% of the total mass of the mixture.

3. The method for separating lithium, sodium, and potassium using the lithium-selective membrane extraction material according to claim 1, characterized in that, The polyvinyl chloride is SG-8 type polyvinyl chloride.

4. The method for separating lithium, sodium, and potassium using the lithium-selective membrane extraction material according to claim 1, characterized in that, The lithium / sodium / potassium mixed solution contains NH3·H2O and Li + Na + K + A mixed solution; the mixed solution is a chloride or nitrate salt of Li, Na, and K; Na + K + Concentration of Li + 1 to 5 times.

5. The method for separating lithium, sodium, and potassium using the lithium-selective membrane extraction material according to claim 1, characterized in that, The eluent is one of HCl, H2SO4 or HNO3 solution; the concentration of the eluent solution is 0.1 mol / L.

6. The method for separating lithium, sodium, and potassium using the lithium-selective membrane extraction material according to claim 1, characterized in that, The pH of the lithium / sodium / potassium mixed solution was maintained at 11.13, and the pH of the eluent was 1.

7. The method for separating lithium, sodium, and potassium using the lithium-selective membrane extraction material according to claim 1, characterized in that, The applied DC voltage is 10-40V, and the separation time is 12-18h.

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