A hetero-membrane-based dual-channel coupled voltage-driven ion transport device and application thereof

Abstract

The application discloses a kind of based on hetero membrane two-channel coupling voltage-driven ion transport device and its application, the device includes source solution chamber, receiving solution chamber, hetero membrane and circuit system;Wherein: the hetero membrane is located between source solution chamber and receiving solution chamber;The selective layer and conductive layer are contained in the hetero membrane, first auxiliary electrode is provided in the source solution chamber, and second auxiliary electrode is provided in the receiving solution chamber;The circuit system includes two-channel coupling voltage supply device and voltage delivery channel: channel A and channel B;The two-channel coupling voltage supply device applies constant voltage to first auxiliary electrode and second auxiliary electrode by channel A;The two-channel coupling voltage supply device channel B is connected with the conductive layer, and pulse voltage is applied to the conductive layer by channel B.It solves the problems of low ion flux, low separation efficiency and complex operation discontinuity in the process of electrochemical ion separation.

Description

TECHNICAL FIELD

[0001] The present application relates to lithium resource recovery. More particularly, it relates to a hetero-membrane-based dual-channel coupled voltage-driven ion transport device and its application. BACKGROUND

[0002] The lithium grade in the positive electrode material of waste lithium batteries is higher than that in brine and ore, and has good recycling value. Extracting lithium resources from lithium-containing aqueous solution (salt lake, seawater, and waste battery positive electrode material leaching solution) can create objective economic and environmental benefits, and is of great significance for effective utilization of resources.

[0003] In recent years, high-efficiency ion separation technology based on electrochemical methods has attracted widespread attention from scholars at home and abroad. A variety of synthetic membrane materials have been applied to electro-controlled ion separation systems, such as organic conductive polymer membranes, inorganic membranes containing mixed valence transition metals, and organic-inorganic hybrid membranes. The oxidation / reduction process of the above electroactive ion exchange materials is used to control the insertion / release of ions. In the separation systems reported so far, the use of electroactive electrodes under the action of voltage to recover ions is achieved through frequent ion selective intercalation / deintercalation processes. However, the ion selective intercalation and deintercalation processes are carried out in stages, which means that the electrolyte solution needs to be switched relatively frequently, resulting in a complex operation process and low extraction efficiency. Based on inorganic materials, the electroactive electrode can extract lithium ions from mixed solutions through electrochemical intercalation under the action of pulse voltage, but the extraction efficiency of the electroactive electrode under the action of frequent voltage shows a significant decrease. Therefore, the electrode needs to be replaced after continuous operation for 100 to 1000 seconds to maintain a high Faraday extraction efficiency. In addition, in the transport process based on ion-gated membranes, such as conductive polymer membranes (polypyrrole membranes), ion flux can be improved by electrically modulating the oxidation-reduction state. However, the continuous ion intercalation / deintercalation process can cause the expansion, contraction, and rupture of the conductive polymer membrane, thereby weakening the controllable ion transport based on size confinement and reducing ion selectivity. Therefore, achieving continuous and controlled high-efficiency ion transport without liquid route switching is the key to effectively extracting target ions. SUMMARY

[0004] Based on the above problems, the purpose of the present application is to provide a hetero-membrane-based dual-channel coupled voltage-driven ion transport device and its application, to achieve continuous and controlled high-efficiency ion transport without liquid route switching, and to effectively extract target ions. This method solves the problems of low ion flux, low separation efficiency, and complex and discontinuous operation in existing electrochemical ion separation processes. This method uses dual-channel coupled voltage containing constant voltage and pulse voltage, hetero-membrane containing selective layer and conductive layer, ion selective transmembrane transport, and reversible intercalation-extraction process to achieve efficient, continuous, and selective separation of lithium ions.

[0005] On one hand, the present invention provides a dual-channel coupled voltage-driven ion transport device based on a heterostructure membrane, the device comprising a source solution chamber, a receiving solution chamber, a heterostructure membrane, and a circuit system; wherein:

[0006] The heterogeneous membrane is located between the source solution chamber and the receiving solution chamber to separate the source solution chamber and the receiving solution chamber;

[0007] The heterostructure includes a selective layer and a conductive layer, wherein the selective layer is located on the source solution chamber side and the conductive layer is located on the receiving solution chamber side;

[0008] The source solution chamber is provided with a first auxiliary electrode, and the receiving solution chamber is provided with a second auxiliary electrode;

[0009] The circuit system includes a dual-channel coupled voltage supply device and voltage delivery channels: channel A and channel B;

[0010] Channel A is connected to the first auxiliary electrode and the second auxiliary electrode, and the dual-channel coupling voltage supply device applies a constant voltage to the first auxiliary electrode and the second auxiliary electrode through channel A;

[0011] The dual-channel coupling voltage supply device has channel B connected to the conductive layer, and applies pulse voltage to the conductive layer through channel B.

[0012] Furthermore, the potential of the first auxiliary electrode is higher than the potential of the second auxiliary electrode. That is, the high potential of the constant voltage is applied to the first auxiliary electrode; the low potential of the constant voltage is applied to the second auxiliary electrode. The high potential of the constant voltage is applied to the first auxiliary electrode in the source solution chamber, and the low potential of the constant voltage is applied to the second auxiliary electrode in the receiving solution chamber. The constant electric field controls the direction of ion transport, enabling lithium ions to be selectively transported across the membrane from the source solution to the receiving solution.

[0013] Furthermore, the constant voltage has a value of 0.2 V.

[0014] Furthermore, the selective layer is made of lithium-ion selective ceramic material LAGP, and the conductive layer is made of MWCNTs-NH2 / PEDOT:PSS. PEDOT is a positively charged conductive polymer chain, and PSS acts as a large counterion to maintain charge balance within the conductive layer. When the pulse potential is low, the PEDOT in the conductive layer is reduced, and additional lithium ions from the source solution are transported across the membrane to the conductive layer, acting as counterions to maintain charge balance within the membrane. When the pulse potential is high, the PEDOT in the conductive layer is oxidized and becomes positively charged. Due to electrostatic interactions, the lithium ions stored in the conductive layer are released into the receiving solution.

[0015] Furthermore, the dual-channel coupled voltage supply device is a picoammeter.

[0016] Furthermore, in the source solution chamber, the source solution is a mixed solution containing equal concentrations of LiCl, NaCl, KCl, and MgCl2. For example, the concentrations of LiCl, NaCl, KCl, and MgCl2 in the source solution are all 0.01 M.

[0017] The receiving solution in the receiving solution chamber is an HCl solution. For example, the receiving solution has a concentration of 10... -3 M HCl.

[0018] Unless otherwise specified, the mixed solutions of LiCl, NaCl, KCl and MgCl2, and the HCl solution in this invention refer to aqueous solutions, that is, the solvent is water.

[0019] Furthermore, the pulse voltage is a square pulse voltage; the pulse low potential is 0 V, the pulse high potential is 0.05, 0.1, 0.15, 0.2, or 0.25 V, and the pulse period is 1 second. The storage-release process is induced by electrically modulating the conductive layer, accelerating the transmembrane transport of lithium ions.

[0020] Furthermore, both the first auxiliary electrode and the second auxiliary electrode are Ag / AgCl electrodes.

[0021] Furthermore, the preparation of the Ag / AgCl electrode includes the following steps:

[0022] The silver rod is polished and used as the anode, while the platinum sheet is used as the cathode.

[0023] The cathode and anode were placed in a 1 M KCl solution, and a constant voltage of 1 V was applied between the electrodes for electroplating for 20 min. The surface of the silver rod was gradually covered with AgCl, resulting in an Ag / AgCl electrode.

[0024] Furthermore, the device also includes a sealing device. The function of the sealing device is to prevent leakage. The sealing device is preferably a circular rubber ring.

[0025] Furthermore, the heterogeneous membrane is prepared by the following method:

[0026] 1 g of MWCNTs-NH2 powder was added to 10 mL of deionized water and sonicated for 30 min to disperse the multi-walled carbon nanotubes in water. 120 µL of ethylene glycol was added to 2 mL of PEDOT:PSS solution and stirred for 2 h. 2 mL of the PEDOT:PSS solution containing ethylene glycol was mixed with 6 mL of aminated multi-walled carbon nanotube dispersion (0.5 mg / mL) and then sonicated for 20 min to obtain a homogeneous solution, i.e., the conductive layer precursor solution.

[0027] A certain amount of conductive layer precursor solution was drop-coated onto the surface of a LAGP ceramic sheet, which was then placed on a heating plate and annealed at 60°C. After the solvent evaporated, a uniform conductive layer was formed on the selective layer, resulting in a heterogeneous film.

[0028] In another aspect, the present invention provides the application of the apparatus as described herein in the selective recovery of lithium ions.

[0029] Furthermore, the application includes the following steps:

[0030] A dual-channel coupled voltage supply device is used to apply a constant voltage to the first auxiliary electrode and the second auxiliary electrode through channel A, wherein the potential of the first auxiliary electrode is higher than the potential of the second auxiliary electrode;

[0031] While a constant voltage is applied, a pulsed voltage is applied to the conductive layer through channel B.

[0032] By repeatedly performing the pump-storage-release process under the action of a dual-channel coupled voltage, the transport flux of lithium ions can be increased.

[0033] By applying a dual-channel coupling voltage to the ion transport system and electrically controlling the redox state of the conductive layer, a pump-storage-release mechanism is induced. This mechanism involves the storage and release of lithium ions during continuous directional pumping, which can effectively improve lithium flux.

[0034] In other words, by applying a dual-channel coupling voltage to the ion transport system, while controlling the directional transport of lithium ions, the redox state of the conductive layer is electrically controlled to realize the pump-storage-release process, thereby accelerating the transmembrane transport flux of lithium ions and achieving continuous selective separation of lithium ions.

[0035] The beneficial effects of this invention are as follows:

[0036] This invention proposes a novel dual-channel coupled voltage-driven ion-selective transport device. This device eliminates the need for frequent solution changes, enabling continuous lithium-ion extraction, simplifying the operation process, and improving extraction efficiency. In this device, a selective layer controls ion selective transport, a conductive layer accelerates ion pumping, and reversible electro-regulation effectively increases lithium-ion flux. The device features simple system components, a significant increase in flux, a long service life, and is easily applicable to industrial applications.

[0037] In the application of this invention, a dual-channel coupled voltage ion transport device is used to efficiently separate lithium ions in a mixed solution. This is achieved by using the selective layer of a heterogeneous membrane to control the selective transport of lithium ions, and by electrically controlling the redox state of PEDOT in the conductive layer to realize the pump-storage-release process, thereby accelerating the transport flux of lithium ions. Attached Figure Description

[0038] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0039] Figure 1 A schematic diagram of the test apparatus components of the dual-channel coupled voltage-driven ion transport device of the present invention is shown.

[0040] Figure 2 A schematic diagram of the dual-channel coupled voltage-driven ion transport device of the present invention is shown.

[0041] Figure 3 The diagram illustrates the separation principle of the dual-channel coupled voltage-driven ion transport device of the present invention.

[0042] Figure 4 The image shows a scanning electron microscope (SEM) image of the heterostructure membrane in the dual-channel coupled voltage-driven ion transport device of the present invention.

[0043] Figure 5 The diagram shows the device under different driving forces and the lithium-ion transport flux.

[0044] In the figure: 1 is the source solution chamber, 2 is the heterogeneous membrane, 3 is the rubber ring, 4 is the receiving solution chamber, 5 is the auxiliary electrode, which is an Ag / AgCl electrode, 6 is the conductive layer, 7 is channel A of the dual-channel coupling voltage, i.e., constant voltage, and 8 is channel B of the dual-channel coupling voltage, i.e., pulse voltage. Detailed Implementation

[0045] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0046] like Figure 1 and2 As shown, a dual-channel coupled voltage-driven ion transport device applies a coupling voltage to an ion transport system equipped with a heterogeneous membrane 2. The ion transport system includes the heterogeneous membrane 2, a source solution chamber 1, a circular rubber ring 3, a receiving solution chamber 4, a coupling voltage circuit system, and auxiliary electrodes. The heterogeneous membrane 2 is fixed between the source solution chamber 1 and the receiving solution chamber 4, and the circular rubber ring 3 is fitted between the heterogeneous membrane 2 and the chamber to prevent liquid leakage.

[0047] In the above scheme, the heterostructure 2 in the dual-channel coupled voltage-driven ion transport system is composed of a selective layer and a conductive layer 6. The selective layer is a lithium-ion selective ceramic material LAGP, and the conductive layer 6 is MWCNTs-NH2 / PEDOT:PSS. The selective layer is located on the source solution chamber 1 side, and the conductive layer 6 is located on the receiving solution chamber 4 side.

[0048] In the above scheme, the auxiliary electrode 5 in the dual-channel coupled voltage-driven ion transport system is an Ag / AgCl electrode.

[0049] In the above scheme, the source solution is a mixed solution containing equal concentrations (0.01 M) of LiCl, NaCl, KCl, and MgCl2, and the receiving solution is a low concentration of 10... -3 M is an HCl solution.

[0050] In the above scheme, the electrical performance is tested by applying a dual-channel coupled voltage using a Keithley 2636 picoammeter (Keithley Instruments, Cleveland) and recording the membrane current value.

[0051] Example:

[0052] Includes the following steps:

[0053] (1) Add 1 g of MWCNTs-NH2 powder to 10 mL of deionized water and sonicate for 30 min to disperse the multi-walled carbon nanotubes in water. Add 120 µL of ethylene glycol to 2 mL of PEDOT:PSS solution and stir for 2 h. Mix 2 mL of PEDOT:PSS solution containing ethylene glycol with 6 mL of aminated multi-walled carbon nanotube dispersion (0.5 mg / mL) and sonicate for 20 min to obtain a homogeneous solution, i.e., the conductive layer precursor solution;

[0054] (2) A certain amount of conductive layer dispersion was drop-coated onto the surface of the LAGP ceramic sheet, and then placed on a heating plate and annealed at 60°C. After the solvent evaporated, a uniform conductive layer was formed on the selective layer, and the heterostructure was successfully constructed;

[0055] (3) Polish the silver rod and then electroplate it to prepare an Ag / AgCl electrode. Use the silver rod as the anode and the platinum sheet as the cathode. Place the cathode and anode in a 1 M KCl solution and apply a constant voltage of 1 V between the electrodes for electroplating. The electroplating time is 20 min. The surface of the silver rod is gradually covered with AgCl to obtain the Ag / AgCl electrode;

[0056] (4) The high potential of channel A of the dual-channel coupling voltage is applied to the auxiliary electrode in the source solution chamber, and the low potential of channel A is applied to the auxiliary electrode in the receiving solution chamber. A constant electric field (voltage value of 0.2 V) controls the direction of ion transport, enabling lithium ions to be selectively transported across the membrane from the source solution to the receiving solution.

[0057] (5) While applying a constant voltage (0.2 V), a pulse voltage is simultaneously applied to the transmission system. The square pulse voltage ranges between 0 V and 0.1 V, and the pulse duration is 1 s. The storage release process is induced by electrically modulating the conductive layer.

[0058] (6) The dual-channel coupled voltage ion-driven transport device was used to selectively extract lithium ions from the mixed solution. The extraction process took 20 min. The extraction was continuous and there was no need to replace the electrodes.

[0059] The schematic diagram of this embodiment is as follows: Figure 3 As shown, by applying a dual-channel coupling voltage to the transport system, a pump-storage-release process is achieved by controlling the directional transport of lithium ions and electrically modulating the redox state of the conductive layer. This pump-storage-release mechanism involves the storage and release of lithium ions during continuous directional pumping. The conductive layer is MWCNTs-NH2 / PEDOT:PSS, where PEDOT is a positively charged conductive polymer chain, and PSS acts as a large counter anion to maintain charge balance within the conductive layer. When the pulse potential is low, PEDOT in the conductive layer is reduced, and additional lithium ions from the source solution are transported across the membrane to the conductive layer to maintain charge balance within the membrane. When the pulse potential is high, PEDOT in the conductive layer is oxidized and becomes positively charged. Due to electrostatic interactions, lithium ions stored in the conductive layer are released into the receiving solution. The pump-storage-release process is repeated continuously under the action of the dual-channel coupling voltage, thereby increasing the lithium ion transport flux. Figure 5 As shown, comparing ion transport flux under different voltage driving conditions, the lithium flux achieved by dual-channel coupled voltage-driven ion transport is significantly higher than that under constant voltage or pulsed voltage driving conditions. The dual-channel coupled voltage-driven ion transport system accelerates lithium-ion transmembrane transport flux through a pump-storage-release mechanism, enabling continuous and selective separation of lithium ions.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An application of a heterogeneous membrane-based dual-channel coupled voltage-driven ion transport device in the selective recovery of lithium ions, characterized in that, The device includes a source solution chamber, a receiving solution chamber, a heterogeneous membrane, and a circuit system; wherein: The heterogeneous membrane is located between the source solution chamber and the receiving solution chamber to separate the source solution chamber and the receiving solution chamber; The heterostructure includes a selective layer and a conductive layer, wherein the selective layer is located on the source solution chamber side and the conductive layer is located on the receiving solution chamber side; The source solution chamber is provided with a first auxiliary electrode, and the receiving solution chamber is provided with a second auxiliary electrode; The circuit system includes a dual-channel coupled voltage supply device and voltage delivery channels: channel A and channel B; Channel A is connected to the first auxiliary electrode and the second auxiliary electrode, and the dual-channel coupling voltage supply device applies a constant voltage to the first auxiliary electrode and the second auxiliary electrode through channel A; Channel B is connected to the conductive layer, and the dual-channel coupling voltage supply device applies a pulse voltage to the conductive layer through channel B; The application includes the following steps: A dual-channel coupled voltage supply device is used to apply a constant voltage to the first auxiliary electrode and the second auxiliary electrode through channel A, wherein the potential of the first auxiliary electrode is higher than the potential of the second auxiliary electrode; While a constant voltage is applied, a pulsed voltage is applied to the conductive layer through channel B; The heterogeneous membrane was prepared by the following method: 1 g of MWCNTs-NH2 powder was added to 10 mL of deionized water and sonicated for 30 min to disperse the multi-walled carbon nanotubes in water; 120 µL of ethylene glycol was added to 2 mL of PEDOT:PSS solution and stirred for 2 h; 2 mL of PEDOT:PSS solution containing ethylene glycol was mixed with 6 mL of aminated multi-walled carbon nanotube dispersion and then sonicated for 20 min to obtain a homogeneous solution, i.e., the conductive layer precursor solution; The conductive layer precursor solution was drop-coated onto the surface of the LAGP ceramic sheet, which was then placed on a heating plate and annealed at 60°C. After the solvent evaporated, a uniform conductive layer was formed on the selective layer, resulting in a heterogeneous film.

2. The application according to claim 1, characterized in that, The constant voltage has a value of 0.2 V.

3. The application according to claim 1, characterized in that, In the source solution chamber, the source solution is a mixed solution containing equal concentrations of LiCl, NaCl, KCl, and MgCl2; in the receiving solution chamber, the receiving solution is an HCl solution.

4. The application according to claim 1, characterized in that, The pulse voltage is a square pulse voltage; the pulse low potential of the pulse voltage is 0 V, the pulse high potential is 0.05, 0.1, 0.15, 0.2 or 0.25 V, and the pulse period is 1 second.

5. The application according to claim 1, characterized in that, Both the first auxiliary electrode and the second auxiliary electrode are Ag / AgCl electrodes.

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