Hydrophobic Ti3C2Tx and application thereof in deionized water treatment of membrane-free capacitor

Abstract

The invention relates to the technical field of flowing electrode preparation and capacitive deionization application, in particular to hydrophobic Ti3C2Tx and application thereof in membrane-free capacitive deionization water treatment.The method includes the steps that flowing electrode slurry prepared from the hydrophobic Ti3C2Tx serves as a negative flowing electrode, flowing electrode slurry prepared from BMIM Ac serves as a positive flowing electrode, and the flowing electrode slurry and the positive flowing electrode are placed in a reactor; the negative flow electrode and the positive flow electrode are respectively in direct contact with seawater, brackish water or wastewater, and an electric field is applied between the negative flow electrode and the positive flow electrode to realize ion adsorption. Hydrophobic Ti3C2Tx is prepared to serve as a flowing electrode, FCDI membrane-free is achieved according to density difference layering, the liquid-liquid interface energy of ions is smaller than the solid-liquid interface energy, seawater desalination, brackish water desalination and wastewater treatment are achieved more efficiently, and the membrane-free reactor overcomes the defects of FCDI membrane pollution, membrane blockage, high cost and frequent membrane replacement.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of flow electrodes and capacitive deionization applications, and particularly relates to hydrophobic Ti3C2T x and its application in membrane-free capacitive deionization water treatment. Background Art

[0002] FCDI (Flow-Electrode Capacitive Deionization) is a new type of water treatment technology, mainly used in the fields of seawater desalination, brackish water desalination, and wastewater treatment. It is an improved version of the traditional capacitive deionization (CDI) technology, which improves the ion removal rate by using a flow electrode. FCDI introduces a flow electrode on the basis of traditional CDI, that is, the electrode flows in the form of a suspension. The flow electrode can continuously update the electrode surface and provide continuously active sites for adsorbing ions, thereby improving the ion removal rate. Among them, the ion exchange membrane in FCDI has the advantages of selective transport, preventing short circuit, improving efficiency, maintaining electrical neutrality, extending the electrode life, and optimizing system design, and plays a role in ensuring the efficient and stable operation of the system.

[0003] However, the ion exchange membrane in FCDI has the disadvantages of high cost, easy pollution, temperature limitation, selectivity limitation, and limited life. Many influencing factors need to be comprehensively considered in practical applications. During the capacitive deionization process, a large number of ions passing through the ion exchange membrane will cause problems such as pollution and blockage, reducing the service life of the ion exchange membrane, affecting the efficiency of the reactor, and possibly requiring frequent replacement of the ion exchange membrane, increasing the process cost. A large number of researchers have developed other membranes to replace it, including MOF membranes, hydrogel membranes, and bio-based membranes. Although these membranes can reduce the process cost to a certain extent, the problems existing in the use of the membranes themselves are difficult to solve. And the interfacial energy at the solid-liquid interface is usually high because the interaction between the molecules on the solid surface and the liquid molecules is weak. This means that ions need to overcome a relatively high energy barrier to pass through the solid-liquid interface. At the solid-liquid interface, the migration of ions is usually restricted by the solid surface, which may lead to a slow migration rate of ions. Therefore, the energy required for ions to pass through the solid-liquid interface is relatively high. These disadvantages also limit the water treatment capacity of FCDI to a certain extent. Generally, the flow electrode uses sodium salt deionized water as the electrolyte and activated carbon as the electrode material. These substances can be mixed with the ion solution, so the system cannot operate stably without a membrane. And currently, there is a lack of a membrane-free flow electrode capacitive deionization technology that can achieve stable operation. Summary of the Invention

[0004] The present invention aims to solve the problem of the current lack of a membrane-free flow electrode capacitive deionization technology that can achieve stable operation effects, and provides a hydrophobic Ti3C2T x and its application in membrane-free capacitive deionization water treatment.

[0005] In a first aspect, the present invention provides a preparation method of a hydrophobic Ti3C2T x comprising the following steps:

[0006] S1. Under the protection of an inert gas, Ti3AlC2 powder and ZnCl2 powder are mixed evenly, and then heat treatment is carried out under the protection of the inert gas;

[0007] S2. After the heat treatment reaction ends, residual ZnCl2 is removed by washing with deionized water; a mixture of Ti3C2T x and Zn is obtained by filtration; through ultrasonic dispersion with deionized water, centrifugation separation, and vacuum drying, hydrophobic Ti3C2T x is obtained.

[0008] As a further improvement of the technical solution of the present invention, in step S1, the mass ratio of the Ti3AlC2 powder to the ZnCl2 powder is 1:6.

[0009] As a further improvement of the technical solution of the present invention, in step S1, the heat treatment temperature is 550 °C and the time is 5 h.

[0010] In a second aspect, the present invention provides the application of the hydrophobic Ti3C2T x obtained by the preparation method of the hydrophobic Ti3C2T x as a flow electrode in capacitive deionization water treatment.

[0011] As a further disclosure of the application technical solution of the present invention, during capacitive deionization water treatment, it is a membrane-free treatment.

[0012] As a further disclosure of the application technical solution of the present invention, a flow electrode slurry prepared with hydrophobic Ti3C2T x is used as the negative electrode flow electrode, and a flow electrode slurry prepared with BMIM Ac is used as the positive electrode flow electrode. They are placed in a reactor. The negative electrode flow electrode and the positive electrode flow electrode are located at opposite positions in the reactor. There is water to be treated between the negative electrode flow electrode and the positive electrode flow electrode. The negative electrode flow electrode and the positive electrode flow electrode are in direct contact with the water to be treated respectively. An electric field is applied between the negative electrode flow electrode and the positive electrode flow electrode to achieve ion adsorption.

[0013] As a further disclosure of the application technical solution of the present invention, the preparation method of the negative electrode flow electrode is: dissolving BMIM TFSI in a tetrahydrofuran solution, and adding hydrophobic Ti3C2T xAfter thorough mixing, the obtained slurry is BMIM TFSI+Ti3C2T x flow electrode slurry; the preparation method of the positive flow electrode is: dissolving BMIM Ac in a tetrahydrofuran solution, adding AC and mixing thoroughly, and the obtained slurry is BMIM Ac+AC flow electrode slurry.

[0014] As a further disclosure of the application technical solution of the present invention, according to the density difference stratification, one of the negative flow electrode and the positive flow electrode floats on the upper layer of the water to be treated, and the other flow electrode sinks to the lower layer of the water to be treated.

[0015] As a further disclosure of the application technical solution of the present invention, after the capacitive deionization water treatment is completed, a reverse electric field is applied between the negative flow electrode and the positive flow electrode to achieve ion desorption and ion enrichment.

[0016] As a further disclosure of the application technical solution of the present invention, the reactor includes at least one FCDI device for adsorption and / or at least one FCDI device for desorption; each FCDI device includes an FCDI device and a power supply. Each FCDI device has a cavity inside, and the cavity is divided into an upper cavity, a middle cavity and a lower cavity by a first partition plate and a second partition plate. The first partition plate has a first fluid channel connecting the upper cavity and the middle cavity, and the second partition plate has a second fluid channel connecting the middle cavity and the lower cavity. Both ends of the power supply are electrically connected to the inside of the upper cavity and the lower cavity respectively.

[0017] As a further disclosure of the application technical solution of the present invention, when the reactor includes at least one FCDI device for adsorption and at least one FCDI device for desorption; the FCDI device for adsorption includes a first FCDI device, a first power supply, a first pump body, a third pump body, a first slurry pool and a treatment pool, and the FCDI device for desorption includes a second FCDI device, a second power supply, a second pump body, a fourth pump body, a second slurry pool and an enrichment pool;

[0018] The inlet pipe and the outlet pipe of the first pump body are respectively connected to the treatment pool and the inlet of the middle cavity of the first FCDI device, and the outlet of the middle cavity of the first FCDI device is communicated with the treatment pool;

[0019] The inlet pipe and the outlet pipe of the second pump body are respectively connected to the enrichment pool and the inlet of the middle cavity of the second FCDI device, and the outlet of the middle cavity of the second FCDI device is communicated with the enrichment pool;

[0020] The liquid inlet pipe and the liquid outlet pipe of the third pump body are respectively connected to the first slurry tank and the liquid inlet of the upper cavity of the first FCDI device, and the upper cavity of the second FCDI device is communicated with the first slurry tank; the liquid inlet pipe and the liquid outlet pipe of the fourth pump body are respectively connected to the second slurry tank and the liquid inlet of the lower cavity of the first FCDI device, and the lower cavity of the second FCDI device is communicated with the second slurry tank; and the upper cavities of the first FCDI device and the second FCDI device are communicated through a pipeline, and the upper cavity of the first FCDI device and the lower cavity of the second FCDI device are communicated through a pipeline.

[0021] A hydrophobic Ti3C2T provided by the present invention x and its application in membrane-free capacitive deionization water treatment have the following advantages compared with the prior art:

[0022] The hydrophobic Ti3C2T prepared by the present invention x As a flow electrode, the FCDI membrane-free is realized by stratification according to the density difference. The ion passing through the liquid-liquid interface energy is less than the solid-liquid interface energy, and seawater desalination, brackish water desalination and wastewater treatment are more efficiently realized. The membrane-free reactor improves the disadvantages of FCDI membrane pollution, membrane blockage, high cost and frequent membrane replacement. At the same time, the recovery of the electrode material and the ionic liquid also greatly reduces the cost of the whole system. Description of the Drawings

[0023] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments in line with the present invention, and are used together with the specification to explain the principles of the present invention.

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0025] Figure 1 The scanning electron microscope image of the hydrophobic Ti3C2T obtained in Example 1 of the present invention x

[0026] Figure 2 The X-ray diffraction pattern of the hydrophobic Ti3C2T obtained in Example 1 of the present invention x

[0027] Figure 3 The test result of the contact angle of the hydrophobic Ti3C2T obtained in Example 1 of the present invention x

[0028] Figure 4 The hydrophobic Ti3C2T obtained in Example 1 of the present invention​​​x Electrochemical characterization.

[0029] Figure 5 It is a schematic diagram of the connection between the FCDI device and the power supply.

[0030] Figure 6 It is a schematic diagram of the dynamic desalination of the brine to be treated.

[0031] Figure 7 It is a schematic diagram of the structure of the push-pull plate of the present invention.

[0032] Figure 8 It is a connection diagram of the adsorption process and the desorption process of the reactor in Example 4 of the present invention.

[0033] Figure 9 It is a schematic diagram of the result of the desalination test of the brine to be treated in Example 4 of the present invention.

[0034] Figure 10 It is the recovery rate of the electrode material, ionic liquid and tetrahydrofuran in the flow electrode slurry of the present invention.

[0035] In the figure: 11 - the first FCDI device, 12 - the first power supply, 13 - the first pump body, 14 - the second FCDI device, 15 - the second power supply, 16 - the second pump body, 17 - the third pump body, 18 - the fourth pump body, 19 - the treatment tank, 20 - the enrichment tank, 21 - the first slurry tank, 22 - the second slurry tank, 101 - the upper encapsulation plate, 102 - the first partition plate, 103 - the second partition plate, 104 - the first fluid channel, 105 - the second fluid channel, 106 - the lower encapsulation plate, 107 - the first push-pull plate, 108 - the second push-pull plate. Detailed implementation manners

[0036] In order to be able to more clearly understand the above-mentioned objects, features and advantages of the present invention, the solution of the present invention will be further described below. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0037] In the following description, many specific details are set forth in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0038] The present invention provides a specific embodiment of the preparation method of hydrophobic Ti3C2T x including the following steps:

[0039] S1. Under the protection of inert gas, the Ti3AlC2 powder and ZnCl2 powder are mixed evenly, and then heat treatment is carried out under the protection of inert gas;

[0040] After the heat treatment reaction ends, wash with deionized water to remove the residual ZnCl2; filter to obtain a mixture of Ti3C2T x and Zn; disperse ultrasonically with deionized water, separate by centrifuge, and obtain hydrophobic Ti3C2T through vacuum drying x .

[0041] In the present invention, the hydrophobic Ti3C2T x wherein T x represents a surface functional group. In the present invention, T x represents -Cl.

[0042] In some examples, in step S1, the inert gas can be selected from nitrogen, helium, argon, etc. Of course, in step S1, the inert gases used in the two stages of powder mixing and heat treatment can be the same inert gas or different inert gases. When the present invention is specifically implemented, the Ti3AlC2 powder and the ZnCl2 powder are mixed evenly in a glove box under a nitrogen atmosphere; the heat treatment is carried out under an argon atmosphere. During heat treatment, preferably, the mixed powder of Ti3AlC2 and ZnCl2 is placed in an alumina crucible for heat treatment. The present invention has no special requirements for the heat treatment container, but it is necessary to ensure that the mixed powder of Ti3AlC2 powder and ZnCl2 powder does not react with the heat treatment container.

[0043] In some examples, in step S2, in order to remove the residual ZnCl2, the number of times of washing with deionized water in the present invention is more than 5 times. When separating the mixture of hydrophobic Ti3C2T x and Zn by centrifuge, the rotation speed of the centrifuge used is 3000 rpm, the centrifugation time is 10 min, Zn precipitates at the bottom, and the upper layer solution (containing hydrophobic Ti3C2T x ) is taken. The rotation speed of the centrifuge is set to 6000 rpm again, the centrifugation time is 10 min, and the precipitate is taken for suction filtration. The solid obtained by suction filtration is hydrophobic Ti3C2T x . During vacuum drying, the drying temperature used is 40 °C.

[0044] In one example, in step S1, the mass ratio of the Ti3AlC2 powder to the ZnCl2 powder is 1:6.

[0045] In another example, in step S1, the heat treatment temperature is 550 °C and the time is 5 h.

[0046] The present invention further provides an application of the hydrophobic Ti3C2T x obtained by the preparation method of hydrophobic Ti3C2T x as a flow electrode in capacitive deionization water treatment.

[0047] In the present invention, the capacitive deionized water treatment can be membrane treatment. Preferably, the capacitive deionized water treatment is membrane-free treatment. The membrane herein includes any one of ion exchange membrane, MOF membrane, hydrogel membrane and bio-based membrane.

[0048] In the specific implementation, hydrophobic Ti3C2T x The prepared flow electrode slurry is used as the negative flow electrode, and the flow electrode slurry prepared by BMIM Ac is used as the positive flow electrode, which are placed in a reactor. The negative flow electrode and the positive flow electrode are located at relative positions in the reactor respectively, and there is water to be treated between the negative flow electrode and the positive flow electrode. The negative flow electrode and the positive flow electrode are in direct contact with the water to be treated respectively, and an electric field is applied between the negative flow electrode and the positive flow electrode to achieve ion adsorption.

[0049] Furthermore, after the capacitive deionized water treatment is completed, a reverse electric field is applied between the negative flow electrode and the positive flow electrode to achieve ion desorption and ion enrichment.

[0050] The water to be treated in the present invention includes seawater, brackish water, wastewater and the like.

[0051] In the present invention, the relative position can be an up-down position or a left-right position. In some examples, according to the density difference, one of the negative and positive flow electrodes floats on the upper layer of the water to be treated, and the other flow electrode sinks to the lower layer of the water to be treated.

[0052] Specifically, the preparation method of the negative electrode flow electrode is as follows: dissolving BMIM TFSI (Chinese name: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide)) in tetrahydrofuran solution, adding hydrophobic Ti3C2T x After thorough mixing, the obtained slurry is BMIM TFSI+Ti3C2T x Flow electrode slurry.

[0053] In some examples, when BMIM TFSI is dissolved in tetrahydrofuran solution, the volume ratio of BMIM TFSI to tetrahydrofuran solution is 8:15. The mass fraction of BMIM TFSI in the mixed solution of BMIM TFSI and tetrahydrofuran solution is 46%. x The amount of addition must ensure that the obtained TFSI+Ti3C2T x The density of the electrode slurry is greater than the density of the water to be treated (seawater, brackish water or wastewater). In the following example, the present invention is to dissolve 8 mL of BMIM TFSI in 15 mL of tetrahydrofuran solution and add 500 mg of hydrophobic Ti3C2T x, the slurry density obtained by ultrasonic mixing is 1.1 g / cm 3 .

[0054] Specifically, the preparation method of the positive flow electrode is as follows: Dissolve BMIM Ac (Chinese name: 1-butyl-3-methylimidazolium acetate) in a tetrahydrofuran solution, add AC (Chinese name: activated carbon) and mix well to obtain a slurry of BMIM Ac + AC flow electrode slurry.

[0055] In some examples, the volume ratio of BMIM Ac to the tetrahydrofuran solution is 8:15. The mass fraction of BMIM Ac in the mixture of BMIM Ac and the tetrahydrofuran solution is 40%. The addition amount of the AC needs to ensure that the density of the obtained BMIM Ac + AC flow electrode slurry is less than the density of the water to be treated (seawater, brackish water or wastewater). In the examples provided below, the present invention dissolves 8 mL of BMIM Ac in 15 mL of the tetrahydrofuran solution and adds 500 mg of AC, and the slurry density obtained by ultrasonic mixing is 0.9 g / cm 3 .

[0056] To illustrate the application in more detail, the present invention provides a reactor, which includes at least one FCDI device for adsorption and / or at least one FCDI device for desorption; each FCDI device includes an FCDI device and a power supply. Each FCDI device has a cavity inside, and the cavity is divided into an upper cavity, a middle cavity and a lower cavity by a first partition 102 and a second partition 103. The first partition 102 has a first fluid channel 104 connecting the upper cavity and the middle cavity, and the second partition 103 has a second fluid channel 105 connecting the middle cavity and the lower cavity. The two ends of the power supply are electrically connected to the inside of the upper cavity and the lower cavity respectively.

[0057] In some examples, the FCDI device for adsorption and the FCDI device for desorption can be the same FCDI device. During specific operation, just connect the two ends of the power supply in the positive and reverse directions (apply an electric field or a reverse electric field between the negative flow electrode and the positive flow electrode).

[0058] In some cases, in order to stably demarcate the fluids in the upper cavity, the middle cavity and the lower cavity, a first push-pull plate 107 is provided at the first fluid channel 104 of the first partition plate 102, and a second push-pull plate 108 is provided at the second fluid channel 105 of the second partition plate 103. Before applying an electric field (or a reverse electric field), when the fluids in the upper cavity, the middle cavity and the lower cavity enter the corresponding cavities respectively, the first push-pull plate 107 and the second push-pull plate 108 are closed; when the corresponding cavities are filled with the fluids, the first push-pull plate 107 and the second push-pull plate 108 are opened, and an electric field (or a reverse electric field) is applied. In some examples, after the first push-pull plate 107 and the second push-pull plate 108 are closed, the first push-pull plate 107 and the second push-pull plate 108 can be in sealing fit with the corresponding partition plates; in some examples, after the first push-pull plate 107 and the second push-pull plate 108 are closed, the first push-pull plate 107 and the second push-pull plate 108 are in clearance fit (non-sealing state) with the corresponding partition plates.

[0059] In the following embodiments, after the first push-pull plate 107 and the second push-pull plate 108 are opened, the first fluid channel 104 and the second fluid channel 105 are completely communicated with the adjacent cavity spaces. Of course, the opening and closing amounts of the push-pull plates can be adjusted according to specific situations, and the adjacent cavities can be completely communicated or partially communicated. For the convenience of opening or closing the push-pull plates, preferably, the push-pull plates are provided with push-pull rods.

[0060] The reactor provided by the present invention includes at least the following three situations, specifically:

[0061] ㈠ When the reactor only performs capacitive deionization water treatment (ion adsorption), the reactor includes at least one FCDI device for adsorption. The FCDI device for adsorption includes a first FCDI device 11 and a first power supply 12. The upper cavity of the first FCDI device 11 is filled with BMIM Ac+AC flow electrode slurry, the middle cavity is filled with water to be treated, and the lower cavity is filled with BMIM TFSI+Ti3C2T x flow electrode slurry; the first power supply 12 is respectively connected to the inside of the upper cavity and the inside of the lower cavity of the first FCDI device 11 through wires. In some cases, in order to improve the water treatment effect and the treatment capacity, the reactor further includes a first pump body 13 and a treatment pool 19. The middle cavity of the first FCDI device 11 is provided with a liquid inlet and a liquid outlet. The inlet pipe and the outlet pipe of the first pump body 13 are respectively connected to the treatment pool 19 and the liquid inlet of the middle cavity of the first FCDI device 11, and the liquid outlet of the middle cavity of the first FCDI device 11 is communicated with the treatment pool 19.

[0062] ㈡ When the reactor only performs enriched ion (ion desorption), the reactor includes at least one FCDI device for desorption. The FCDI device for desorption includes a second FCDI device 14 and a second power supply 15. The upper cavity of the second FCDI device 14 is filled with BMIM Ac+AC flow electrode slurry adsorbed with positive ions, the middle cavity is filled with deionized water, and the lower cavity is filled with BMIM TFSI+Ti3C2T x flow electrode slurry; the second power supply 15 is connected to the inside of the upper cavity and the inside of the lower cavity of the second FCDI device 14 through wires respectively. In some cases, in order to improve the enrichment amount, the reactor further includes a second pump body 16 and an enrichment pool 20. The middle cavity of the second FCDI device 14 has a liquid inlet and a liquid outlet. The inlet pipe and the outlet pipe of the second pump body 16 are respectively connected to the enrichment pool 20 and the liquid inlet of the middle cavity of the second FCDI device 14, and the liquid outlet of the middle cavity of the second FCDI device 14 is communicated with the enrichment pool 20.

[0063] ㈢ When the reactor needs to realize capacitive deionization water treatment and enriched ions, when the reactor includes at least one FCDI device for adsorption and at least one FCDI device for desorption; the FCDI device for adsorption includes a first FCDI device 11, a first power supply 12, a first pump body 13, a third pump body 17, a first slurry pool 21 and a treatment pool 19, and the FCDI device for desorption includes a second FCDI device 14, a second power supply 15, a second pump body 16, a fourth pump body 18, a second slurry pool 22 and an enrichment pool 20;

[0064] The upper cavity of the first FCDI device 11 is filled with BMIM Ac+AC flow electrode slurry, the upper cavity of the second FCDI device 14 is filled with BMIM Ac+AC flow electrode slurry adsorbed with positive ions, and the lower cavity of the first FCDI device 11 is filled with BMIM TFSI+Ti3C2T x flow electrode slurry, the lower cavity of the second FCDI device 14 is filled with BMIM TFSI+Ti3C2T x flow electrode slurry, the middle cavity of the first FCDI device 11 is filled with seawater, brackish water or wastewater (water to be treated), and the middle cavity of the second FCDI device 14 is filled with deionized water.

[0065] The first power supply 12 is connected to the inside of the upper cavity and the inside of the lower cavity of the first FCDI device 11 through wires respectively, and the second power supply 15 is connected to the inside of the upper cavity and the inside of the lower cavity of the second FCDI device 14 through wires respectively.

[0066] The liquid inlet pipe and the liquid outlet pipe of the first pump body 13 are respectively connected to the inlet of the middle cavity of the treatment tank 19 and the first FCDI device 11, and the outlet of the middle cavity of the first FCDI device 11 is communicated with the treatment tank 19. The liquid inlet pipe and the liquid outlet pipe of the second pump body 16 are respectively connected to the inlet of the middle cavity of the enrichment tank 20 and the second FCDI device 14, and the outlet of the middle cavity of the second FCDI device 14 is communicated with the enrichment tank 20.

[0067] The liquid inlet pipe and the liquid outlet pipe of the third pump body 17 are respectively connected to the inlet of the upper cavity of the first slurry tank 21 and the first FCDI device 11, and the upper cavity of the second FCDI device 14 is communicated with the first slurry tank 21. The liquid inlet pipe and the liquid outlet pipe of the fourth pump body 18 are respectively connected to the inlet of the lower cavity of the second slurry tank 22 and the first FCDI device 11, and the lower cavity of the second FCDI device 14 is communicated with the second slurry tank 22. And the upper cavities of the first FCDI device 11 and the second FCDI device 14 are communicated with each other through a pipeline, and the upper cavity of the first FCDI device 11 and the lower cavity of the second FCDI device 14 are communicated with each other through a pipeline.

[0068] It should be noted that when the reactor in the present invention needs to implement capacitive deionization water treatment and enrich ions, the capacitive deionization water treatment and the enrichment of ions can be carried out simultaneously, or the capacitive deionization water treatment can be carried out first and then the enrichment of ions. When the capacitive deionization water treatment and the enrichment of ions are carried out simultaneously, insulation measures can be set between the FCDI device for adsorption and the FCDI device for desorption as necessary. Further, the FCDI device has an upper encapsulation plate 101 and a lower encapsulation plate 106. Specifically, the upper encapsulation plate 101 and the lower encapsulation plate 106 are respectively located at the top and the bottom. Each encapsulation plate is made of an insulating material.

[0069] In some cases, independent valves can be set on each pipeline or pipe of the present invention according to actual conditions.

[0070] The specific embodiments of the present invention will be described in detail below.

[0071] Example 1:

[0072] A method for preparing a flow electrode, comprising the following steps:

[0073] Under the protection of nitrogen in a glove box, 1 g of Ti3AlC2 powder and 6 g of ZnCl2 powder are thoroughly ground and mixed. Under the protection of argon, the alumina crucible containing the mixed powder is placed in a tube furnace, and the temperature is raised to 550 °C at a heating rate of 5 °C / min and held for 5 h for reaction. After the reaction is completed, the temperature is lowered to room temperature at a cooling rate of 5 °C / min. The reaction product is obtained, including hydrophobic Ti3C2T x, ZnCl2, Zn.

[0074] Wash the product after the reaction with deionized water and filter by suction to obtain hydrophobic Ti3C2T x and the mixture of Zn. Add deionized water and disperse it by ultrasonic wave. Add the dispersion liquid to a centrifuge tube and centrifuge. The rotation speed of the centrifuge is 3000 rpm and the centrifugation time is 10 min. Zn precipitates at the bottom. Take the upper layer liquid (containing hydrophobic Ti3C2T x ), the rotation speed of the centrifuge is 6000 rpm and the centrifugation time is 10 min. Take the precipitate and filter by suction. The solid obtained by suction filtration is hydrophobic Ti3C2T x , and dry it in vacuum. The drying temperature is 40 °C.

[0075] Perform elemental analysis on the hydrophobic Ti3C2T x obtained in this example (see Table 1 for the results) and tests of scanning electron microscope, X-ray diffraction, and contact angle (see Figure 1 , 2 , 3) respectively.

[0076] Table 1

[0077]

[0078] Take 8 mL of BMIM TFSI and dissolve it in 15 mL of tetrahydrofuran solution. Add 500 mg of the hydrophobic Ti3C2T x obtained in this example. Ultrasonically form a uniform BMIM TFSI + Ti3C2T x flow electrode slurry as the negative flow electrode, and its density is 1.1 g / cm 3 .

[0079] Take 8 mL of BMIM Ac and dissolve it in 15 mL of tetrahydrofuran solution. Add 500 mg of AC. Ultrasonically form a uniform BMIM Ac + AC flow electrode slurry as the positive flow electrode, and its density is 0.9 g / cm 3 .

[0080] Example 2:

[0081] The hydrophobic Ti3C2T x prepared by the method described in Example 1 is mixed with polyvinylidene fluoride in a mass ratio of 9:1 in N-methylpyrrolidone and stirred evenly. The slurry is evenly coated on high-purity graphite paper with a coater and dried overnight in a vacuum oven at 80 °C, and then sliced to obtain an electrode.

[0082] Example 3:

[0083] The electrochemical performance of the electrode prepared in Example 2 was tested. The specific method was as follows: The prepared electrode was used as the working electrode, the Ag / AgCl electrode and the platinum electrode were used as the reference electrode and the counter electrode respectively, and BMIM TFSI with a mass fraction of 46% was used as the electrolyte. Its electrochemical performance (GCD test, i.e., constant current charge-discharge test) was tested under a three-electrode system. The results are shown in Figure 4 .

[0084] The calculation formula for the specific capacitance of the electrode is: , where represents the constant current charge-discharge current (A), is the discharge time (s), is the mass of the active substance on the electrode (g), is the voltage window (V).

[0085] Example 4:

[0086] 4.1 The negative flow electrode prepared in Example 1 was used as the Na + storage electrode, and the positive flow electrode was used as the Cl - storage electrode to conduct the capacitive deionization desalination performance test. Specifically:

[0087] The first push-pull plate 107 and the second push-pull plate 108 of the first FCDI device 11 were closed. The salt water to be treated in the treatment tank 19 was transported to the middle cavity of the first FCDI device 11 through the first pump body 13. The third pump body 17 transported the BMIM Ac+AC flow electrode slurry in the first slurry tank 21 to the upper cavity of the first FCDI device 11. The fourth pump body 18 transported the BMIM TFSI+Ti3C2T x flow electrode slurry to the lower cavity of the first FCDI device 11. After the slurry and the salt water to be treated filled the corresponding cavities, the first push-pull plate 107 and the second push-pull plate 108 of the first FCDI device 11 were opened.

[0088] The first power supply 12 was used to provide a voltage (1.6V) to the first FCDI device 11 for desalination (applying an electric field), and the slurry and the salt water to be treated remained in a dynamic flow state. The flow rates of the BMIM Ac+AC flow electrode slurry, the salt water to be treated (concentration 1.1mg / L), and the TFSI+Ti3C2T x flow electrode slurry in the first FCDI device 11 were 24mL / min, 22mL / min, and 20mL / min respectively.

[0089] As Figure 6 shown, Na + in the salt water to be treated was adsorbed by the BMIM Ac+AC flow electrode slurry, and Cl -Adsorbed by BMIM TFSI+Ti3C2T x The brine after desalination returns to the treatment tank 19 after being adsorbed by the flow electrode slurry.

[0090] 4.2 In the enrichment ion process of this embodiment, a constant voltage power supply is used to provide a reverse voltage to the reactor for enriching ions. Specifically:

[0091] Close the first push-pull plate 107 and the second push-pull plate 108 of the second FCDI device 14. The deionized water in the enrichment tank 20 is transported to the middle cavity of the second FCDI device 14 through the second pump body 16. Under the pressure of the third pump body 17, the BMIM Ac+AC flow electrode slurry adsorbed with Na + in the upper cavity of the first FCDI device 11 is transported to the upper cavity of the second FCDI device 14; under the pressure of the fourth pump body 18, the BMIM TFSI+Ti3C2T - flow electrode slurry adsorbed with Cl x in the lower cavity of the first FCDI device 11 is transported to the lower cavity of the second FCDI device 14; after the slurry and deionized water fill the corresponding cavities, open the first push-pull plate 107 and the second push-pull plate 108 of the second FCDI device 14.

[0092] Use the second power supply 15 to provide a voltage (1.6V) to the second FCDI device 14 for enriching ions, and the voltage used for enriching ions is a reverse voltage (applying a reverse electric field). The slurry and deionized water remain in a dynamic flow state, and the flow rate in each cavity of the second FCDI device 14 is adapted to that of the first FCDI device 11.

[0093] The BMIM Ac+AC flow electrode slurry adsorbed with Na + desorbs Na + into the deionized water under the action of the electric field; the BMIM TFSI+Ti3C2T - flow electrode slurry adsorbed with Cl x desorbs Cl - into the deionized water under the action of the electric field. The ion concentration in the enrichment tank 20 increases.

[0094] In this embodiment, the adsorption process and the desorption process are carried out synchronously. Of course, in some cases, the adsorption process and the desorption process can be carried out independently.

[0095] This embodiment uses a conductivity meter to monitor the conductivity changes in the treatment tank 19 and the enrichment tank 20 in real time, and calculates the brine concentration based on the conductivity changes.

[0096] The calculation formula for the salt ion removal rate is: , where and They are the initial concentration and the final concentration of the NaCl solution (mg / L), respectively.

[0097] The calculation formula for the salt ion adsorption rate is: , where V is the volume of the NaCl solution (L), is the desalination time ( ), is the contact area. In this embodiment, is 25 (0.0025 ).

[0098] Example 5:

[0099] According to Table 1 and Figure 1 it can be seen that the prepared hydrophobic Ti3C2T x mainly contains elements Ti, C, and Cl. The low content of Al element is due to the gasification and separation of AlCl3 generated during the reaction. The low content of Zn element indicates that there are few impurities. The structure presents a two-dimensional accordion structure, indicating that the hydrophobic Ti3AlC2 has been successfully etched.

[0100] From the XRD pattern ( Figure 2 ), it can be seen that the prepared hydrophobic Ti3C2T x has obvious characteristics of MXene (two-dimensional transition metal carbides). The peak of 002 shifts to the left, indicating that Al is etched, the layer spacing is opened, and a layered two-dimensional structure is formed.

[0101] Through the measurement of the contact angle ( Figure 3 ), the hydrophobic Ti3C2T x has good hydrophobicity. The surface functional group -Cl has an anti-wetting effect, which makes it have better stability as an electrode material for a flow electrode.

[0102] Example 6:

[0103] As Figure 4 shown, through the GCD test of the material, the specific capacitance of the hydrophobic Ti3C2T x is calculated to be 109 F / g, indicating excellent charge storage ability. Based on the curve, the energy density of the hydrophobic Ti3C2T x is calculated to be 139.52 Wh / kg, showing the potential of the hydrophobic Ti3C2T x in high-energy storage applications. An obvious plateau region appears in the charge-discharge curve, indicating the presence of pseudocapacitance behavior. The charge-discharge curve shows good symmetry, indicating that the electrode material has ideal capacitive behavior and low internal resistance.

[0104] Example 7:

[0105] Figure 5 It is a schematic diagram of the connection between the FCDI device and the power supply. During the feeding process, the first push-pull plate 107 or the second push-pull plate 108 (for the specific structure, refer to Figure 7 ) is closed, and the system is in an open circuit state, making the feeding more stable. After the feeding is completed, the first push-pull plate 107 or the second push-pull plate 108 is set to be open (i.e., pulled out), the flowing electrode slurry contacts the brine to be treated to form a conductive state, and a voltage is applied to start desalination.

[0106] As Figure 5 shown, in this embodiment, the contact surface between the first fluid channel 104 and the second fluid channel 105 is planar, and the contact surface (reaction area) is 5 5 .

[0107] Through the desalination test on the brine to be treated with a concentration of 1.1 g / L, Figure 9 almost all the salts in the brine to be treated are desorbed within 30 minutes. By calculation, the salt ion removal rate of this desalination method can be obtained up to 86.7%, and the salt ion adsorption rate is 2.4 . It shows that the present invention has good desalination ability and broad application prospects.

[0108] After the enrichment of ions is completed, the electrode materials (hydrophobic Ti3C2T x , AC) and ionic liquids (BMIM TFSI, BMIM Ac) in the flowing electrode slurry of BMIM TFSI + Ti3C2T and the flowing electrode slurry of BMIM Ac + AC are separated by a 0.2-μm nylon membrane, and washed with tetrahydrofuran. The obtained electrode materials can be washed with a large amount of deionized water and dried and recovered in a vacuum environment at 40°C. x

[0109] The results show that: the recovery rate of hydrophobic Ti3C2T x can reach 80.6%, the recovery rate of AC is 82.4%, and the loss is relatively low. The ionic liquids (BMIM TFSI, BMIM Ac) can be recovered by rotary evaporation to separate the ionic liquids and tetrahydrofuran. Due to the high stability of the ionic liquids, the recovery rate of BMIM TFSI is 85.8%, and the recovery rate of BMIM Ac is 83.2%. It shows that the flowing electrode slurry provided by this embodiment not only has good ability to treat brine, but also has stable properties and good recovery rate. It greatly reduces the process cost and has better economic benefits.

[0110] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although the foregoing embodiments have been described in detail, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the respective embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A method for preparing hydrophobic Ti3C2T x , characterized in that It includes the following steps: S1. Under the protection of inert gas, Ti3AlC2 powder and ZnCl2 powder are mixed evenly, and then heat treatment is carried out under the protection of inert gas; S2. After the heat treatment reaction is completed, wash with deionized water to remove the residual ZnCl2; filter to obtain a mixture of Ti3C2T x and Zn; disperse by ultrasonic wave with deionized water, separate by centrifuge, and obtain hydrophobic Ti3C2T x .

2. A preparation method of the hydrophobic Ti3C2T x as described in claim 1, characterized in that In step S1, the mass ratio of the Ti3AlC2 powder to the ZnCl2 powder is 1:6; the heat treatment temperature is 550 °C and the time is 5 h.

3. The hydrophobic Ti3C2T as claimed in any one of claims 1 to 2 x obtained by the preparation method x is used as a flow electrode in the application of capacitive deionization water treatment.

4. The application according to claim 3, wherein During the capacitive deionization water treatment, it is membrane-free treatment.

5. The application according to claim 3, wherein During capacitive deionization water treatment, a hydrophobic Ti3C2T x prepared flow electrode slurry is used as the negative flow electrode, and a flow electrode slurry prepared with BMIM Ac is used as the positive flow electrode. They are placed in a reactor. The negative flow electrode and the positive flow electrode are located at opposite positions in the reactor. There is water to be treated between the negative flow electrode and the positive flow electrode. The negative flow electrode and the positive flow electrode are in direct contact with the water to be treated respectively. An electric field is applied between the negative flow electrode and the positive flow electrode to achieve ion adsorption.

6. The application according to claim 5, wherein The preparation method of the negative electrode mobile electrode is as follows: dissolving BMIMTFSI in tetrahydrofuran solution, adding hydrophobic Ti3C2T x After thorough mixing, the obtained slurry is BMIM TFSI+Ti3C2T x Flow electrode slurry; the preparation method of the positive electrode flow electrode is: dissolving BMIM Ac in tetrahydrofuran solution, adding AC and mixing thoroughly, and the obtained slurry is BMIM Ac+AC flow electrode slurry.

7. The application according to claim 5, wherein Stratifying according to the density difference, one of the negative electrode flow electrode and the positive electrode flow electrode floats on the upper layer of the water to be treated, and the other flow electrode sinks to the lower layer of the water to be treated.

8. The application according to claim 5, wherein After the capacitive deionization water treatment is completed, a reverse electric field is applied between the negative electrode flow electrode and the positive electrode flow electrode to achieve ion desorption and ion enrichment.

9. The application according to claim 5, wherein The reactor includes at least one FCDI device for adsorption and / or at least one FCDI device for desorption; each FCDI device includes an FCDI device and a power supply. Each FCDI device has a cavity inside, and the cavity is divided into an upper cavity, a middle cavity and a lower cavity by a first partition and a second partition. The first partition has a first fluid channel connecting the upper cavity and the middle cavity, and the second partition has a second fluid channel connecting the middle cavity and the lower cavity. The two ends of the power supply are electrically connected to the inside of the upper cavity and the lower cavity respectively.

10. The application according to claim 9, characterized in that, When the reactor includes at least one FCDI device for adsorption and at least one FCDI device for desorption; the FCDI device for adsorption includes a first FCDI device, a first power supply, a first pump body, a third pump body, a first slurry pool and a treatment pool, and the FCDI device for desorption includes a second FCDI device, a second power supply, a second pump body, a fourth pump body, a second slurry pool and an enrichment pool; The inlet pipe and the outlet pipe of the first pump body are respectively connected to the treatment pool and the inlet of the middle cavity of the first FCDI device, and the outlet of the middle cavity of the first FCDI device is communicated with the treatment pool; The inlet pipe and the outlet pipe of the second pump body are respectively connected to the enrichment pool and the inlet of the middle cavity of the second FCDI device, and the outlet of the middle cavity of the second FCDI device is communicated with the enrichment pool; The inlet pipe and the outlet pipe of the third pump body are respectively connected to the first slurry pool and the inlet of the upper cavity of the first FCDI device, and the upper cavity of the second FCDI device is communicated with the first slurry pool; the inlet pipe and the outlet pipe of the fourth pump body are respectively connected to the second slurry pool and the inlet of the lower cavity of the first FCDI device, and the lower cavity of the second FCDI device is communicated with the second slurry pool; and the upper cavities of the first FCDI device and the second FCDI device are connected by a pipeline, and the lower cavities of the first FCDI device and the second FCDI device are connected by a pipeline.

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