CN113926430B - Preparation method and application of MOF derivative/LDH double-site adsorption membrane - Google Patents
Preparation method and application of MOF derivative/LDH double-site adsorption membrane Download PDFInfo
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Abstract
The invention discloses a preparation method and application of a MOF derivative/LDH double-site adsorption membrane, firstly electrodepositing a metal hydroxide/metal oxide precursor on a pretreated stainless steel wire mesh, and hydrothermally synthesizing the MOF membrane by an in-situ growth method; calcining the MOF film in a muffle furnace, and controlling the calcining temperature and the calcining time to obtain the required MOF derivative; and finally, placing the MOF derivative into electrolyte containing metal nitrate, and applying reduction potential on the surface of the MOF derivative by an electrochemical method to prepare a layer of uniform LDH nanosheets, thereby obtaining the MOF derivative/LDH double-site adsorption membrane material. The double-site adsorption membrane material is used for electrically controlling and extracting bromide ions, and the selective extraction performance of the membrane on the bromide ions is effectively improved; the extraction of bromide ions is realized through potential regulation and control, and other chemical reagents are not needed to be added; in the regeneration process of the composite membrane, no secondary pollution is generated.
Description
Technical Field
The invention relates to a preparation method and application of a MOF derivative/LDH double-site adsorption membrane, and belongs to the technical field of efficient utilization of salt lake resources.
Background
Bromine is an important chemical raw material as a halogen element with high added value, and is widely applied to various fields such as medicines, bactericides, flame retardants, rubber and the like. Currently, with the continued development of the global industry, the demand is increasing dramatically. Bromine exists in the form of ions in seawater, underground brine, oilfield water, salt lake brine and other resources, and the content of bromine is limited. Therefore, on the basis of reasonably utilizing bromine resources, the exploration of a high-efficiency and environment-friendly bromine ion extraction technology has important significance.
Heretofore, methods for extracting bromine mainly include an air blowing method, a solvent extraction method, an ion exchange method, a membrane separation method, an adsorption method, and the like. The bromine extraction technologies have different advantages, but the bromine extraction technologies have the problems of secondary pollution, high investment cost, low efficiency, poor selectivity and the like. Compared to the extraction techniques described above, electronically controlled ion Exchange (ESIX) technology is considered a novel efficient, environmentally friendly ion separation technique, which has received increasing attention due to its high selectivity, high efficiency even at very low concentrations, and low cost advantages. During ESIX, reversible intercalation and deintercalation of target ions can be achieved by electrochemically controlling the oxidation and reduction states of the thin film electrodes on the conductive substrate.
Two-dimensional Layered Double Hydroxide (LDHs) materials have obvious advantages in the fields of capacitance storage and ion separation due to the adjustable structure, unique layered structure and interlayer anion exchange performance. However, because of the high electron and ion transport resistance of LDHs in solution, it is difficult to directly prepare LDHs thin films on conductive substrates, which limits their application in ESIX systems. Therefore, to overcome these drawbacks, we should design a suitable material as the base layer to improve the conductivity, ion storage capacity and film forming properties of LDHs. In recent years, MOF derivatives have been considered as an electrode material having a great potential because they can retain the original morphology and high specific surface area of the MOF precursor while having excellent electron/ion transport ability and excellent cycle stability. Therefore, the anchoring of LDHs with the same metal active center on the surface of the MOF derivative is beneficial to the preparation of the LDHs film, and abundant active sites can be exposed, so that the electrochemical performance is effectively improved. Furthermore, studies have demonstrated that MOF/LDH heterostructures can effectively optimize the electron structure and promote electron/ion transport, thus synergistically improving their electrocatalytic properties. In light of the above, it is contemplated to combine the separation layer LDH and the basal layer MOF derivative to obtain a novel in-situ grown two-site adsorption membrane electrode and apply the same to the field of electrically controlled bromide ion extraction.
Disclosure of Invention
The invention aims to provide a preparation method and application of a MOF derivative/LDH double-site adsorption membrane, provides a double-site adsorption mechanism for selective extraction of bromide ions in an ESIX process of an LDHs-based material, and provides a theoretical basis for designing the LDHs-based membrane electrode material with specific recognition sites.
In the invention, electrochemical induction of metal center coordination of a laminate of LDH in the MOF derivative/LDH double-site adsorption membrane and interlayer anion exchange form a double-site adsorption mechanism, and the composite membrane shows higher extraction amount of bromide ions and excellent cycle stability, and simultaneously shows good selectivity under the existence of nitrate ions and iodide ions.
The invention provides a preparation method of a MOF derivative/LDH double-site adsorption membrane, which comprises the following steps: firstly, electrochemically depositing a metal hydroxide/metal oxide precursor on a pretreated stainless steel wire net, and hydrothermally synthesizing an MOF film under high temperature and high pressure by an in-situ growth method; then, calcining the prepared MOF film in a muffle furnace, and controlling the calcining temperature and the calcining time to obtain the required MOF derivative; and finally, placing the MOF derivative into an electrolyte containing metal nitrate, and applying a reduction potential on the surface of the MOF derivative by an electrochemical deposition method to prepare a layer of uniform LDH nanosheets, thereby obtaining the MOF derivative/LDH double-site adsorption membrane.
As a further improvement of the technical scheme of the invention, the method for electrochemically depositing the metal hydroxide/metal oxide precursor is one of a constant voltage method, a constant current method, a pulse method and a cyclic voltammetry method. When a constant voltage method is adopted, the voltage range of the electrochemical deposition metal hydroxide/metal oxide precursor is-1.0 to-1.5V, and the deposition time is 30-60 min; when a constant current method is adopted, the current range of the electrochemical deposition metal hydroxide/metal oxide precursor is-18 to-24 mA, and the deposition time is 40-60 min.
As a further improvement of the technical scheme of the invention, the metal hydroxide/metal oxide precursor is one of metal hydroxide/metal oxide containing Ni, co, cu, fe, zn element.
As a further improvement of the technical scheme, the temperature of the MOF for hydrothermal synthesis is 120-150 ℃ and the time is 10-14 hours; when the MOF derivative is prepared, the calcination temperature is 350-450 ℃, and the calcination time is 2-4 hours.
The electrolyte of the metal nitrate consists of any two of nickel nitrate, cobalt nitrate, ferric nitrate, manganese nitrate and aluminum nitrate, wherein the molar ratio of the two nitrates is 1:9-9:1, and the concentration of the nitrates is 0.1-0.3M; the metal elements in the formed LDH nanosheets are any two of Ni, co, mn, al and Fe.
As a further improvement of the technical scheme of the invention, when LDH is deposited by an electrochemical method, the deposition potential is-1.0 to-1.5V, and the electrodeposition time is as follows: and (5) 10-30 min.
The invention provides an application of the MOF derivative/LDH double-site adsorption membrane prepared by the preparation method in electric control for extracting bromide ions, and the application is implemented in an electric control ion exchange system under a three-electrode system. The MOF derivative/LDH double-site adsorption film is used as a working electrode, a platinum sheet and a saturated calomel electrode are respectively a counter electrode and a reference electrode, and the counter electrode and the reference electrode are placed in an aqueous solution containing bromide ions with a certain concentration to assemble an electric control ion exchange system. The process is controlled by constant voltage, and bromide ions in the solution are electrically extracted by utilizing a MOF derivative/LDH double-site adsorption membrane. Specifically, oxidation potential is applied to the working electrode through the circuit control system, bromide ions in the solution can be selectively placed in the membrane, and the adsorption balance time is 2-4 hours. According to the method disclosed by the invention, the effective extraction of the bromide ions in the solution can be realized.
As a further improvement of the technical scheme of the invention, the concentration of the bromide ions is 50-200 ppm; the constant voltage is 0.6-1.2V; the application time is 2-4 h.
The invention has the beneficial effects that:
(1) The invention combines the pore structure of the conductive substrate layer MOF derivative with the double-site adsorption characteristic of the selective separation layer LDH and applies the conductive substrate layer MOF derivative to an electric control ion exchange system, thereby effectively improving the selective extraction performance of bromide ions.
(2) Due to the in-situ growth strategy, the MOF derivative/LDH double-site adsorption membrane has excellent cycle performance and electrochemical stability, and can realize repeated cycle extraction of bromide ions.
(3) The bromine extraction process of the MOF derivative/LDH double-site adsorption membrane is realized through potential regulation and control, and other chemical reagents are not needed to be added. When a reduction potential is applied, bromide ions are released into the solution. Therefore, no secondary pollution is generated in the regeneration process of the composite membrane material.
Drawings
FIG. 1 shows XRD curves of Ni-MOF derivatives (Ni-MOF (D))/NiCo LDH composite membrane electrodes prepared in example 1 of the present invention. In the figure, (a) and (b) are XRD patterns of stainless steel wire gauze, ni-MOF (D), niCo LDH and Ni-MOF (D)/NiCo LDH film.
FIG. 2 is an SEM image of a Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 1 of the present invention. In the figure, (A) is an SEM image of a stainless steel wire mesh substrate, and (B) and (C) are Ni (OH) under different magnifications respectively 2 SEM images of the nanosheets, (D) and (E) are SEM images of the Ni-MOF at different magnifications, respectively, (F) and (G) are SEM images of the Ni-MOF (D) at different magnifications, and (H) and (I) are SEM images of the Ni-MOF (D)/NiCo LDH composite membrane electrode at different magnifications.
FIG. 3 is a graph showing the effect of extraction test on aqueous solutions containing 50 ppm, 100 ppm and 200 ppm bromide ions for Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 3 of the present invention. In the figure, (a) is a graph of bromide concentration in solution over time; (b) Is a graph of the adsorption capacity of Ni-MOF (D)/NiCo LDH composite membrane electrode to bromide ions with time.
FIG. 4 is a comparative graph of the selective extraction test of Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 3 of the present invention in aqueous solution containing 200 ppm of each of bromide ion, nitrate ion and iodide ion.
FIG. 5 is a graph showing the effect of the Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 3 of the present invention in 5 cycles of adsorption/desorption test in an aqueous solution containing 200 ppm of bromide ions and a sodium nitrate solution of 0.1. 0.1M.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. The described embodiments are only some, but not all, embodiments of the invention. All other embodiments, based on the examples of the invention, which are within the scope of this patent, are within the reach of a person skilled in the art without making any inventive effort.
Example 1:
(1) Dissolving 4.0711 g nickel nitrate hexahydrate and 0.3704 g ammonium fluoride in 200 mL of aqueous solution to prepare a mixed aqueous solution A;
(2) Dissolving 0.237 and g nickel chloride hexahydrate and 0.166 and g terephthalic acid in an N, N-dimethylformamide solvent of 35 and mL to prepare a mixed solution, sequentially and slowly dropwise adding 2.5 and mL deionized water and 2.5 and mL absolute ethyl alcohol under the condition of stirring at room temperature, and stirring at a constant speed for 30 min to obtain a solution B;
(3) Dissolving 4.3619 g nickel nitrate hexahydrate and 1.4552 g cobalt nitrate hexahydrate in 200 mL aqueous solution to prepare 0.075M nickel nitrate hexahydrate and 0.025M cobalt nitrate hexahydrate mixed aqueous solution C;
(4) Dissolving 0.0745 g potassium bromide in 1L water to prepare 50 ppm bromide ion solution D;
(5) Three-electrode system (working electrode with effective area of 2×2 cm) 2 Is 2×2 cm to the counter electrode 2 A reference electrode is a saturated calomel electrode) is placed in the solution A, constant deposition current is set to be 18 mA, and deposition time is set to be 40 min;
(6) And vertically placing the prepared nickel hydroxide nanosheet precursor into the solution B, transferring the precursor into a polytetrafluoroethylene lining, heating to 125 ℃, and keeping the temperature at 2 h.
(7) The prepared Ni-MOF film was put into a muffle furnace and calcined at 450 ℃ for 2 h.
(8) Placing the obtained Ni-MOF (D) film as a working electrode into a C solution, and setting unipolar pulse signals as follows: the pulse voltage is-1.5V, the pulse on-off time ratio is 1 s/1 s, and the pulse times are 1000 times.
(9) The bromide ion-containing solution D is selectively extracted based on the Ni-MOF (D)/NiCo LDH double-site adsorption membrane, and after 3 h of the adsorption process, the adsorption of the bromide ions in the solution by the composite membrane reaches equilibrium. The concentration of the bromine ions left in the solution after being adsorbed by the composite membrane is measured by an ion chromatograph to be 8.57 ppm, and the calculated bromine ion extraction amount is 41.96 mg g -1 。
(9) And the adsorption film to be regenerated is used as a working electrode, a counter electrode and a saturated calomel electrode to form a three-electrode system. And (3) placing the three-electrode system into a sodium nitrate solution of 0.1M, applying a reduction potential on the working electrode, releasing bromide ions adsorbed on the Ni-MOF (D)/NiCo LDH double-site adsorption membrane into the sodium nitrate solution, taking out the working electrode, flushing out electrolyte remained on the surface of the hybridization membrane material by using water, and drying at normal temperature to obtain the regenerated adsorption membrane.
(10) After 5 adsorption and desorption cycles, the bromine ion extraction amount still can reach 38.90 mg g -1 。
FIG. 1 shows XRD curves of Ni-MOF (D)/NiCo LDH composite membrane electrodes prepared in this example. As can be seen from figure (a), the three strong diffraction peaks at 43.6 °, 50.8 ° and 74.6 ° correspond to the characteristic peaks of the stainless steel mesh substrate, and the XRD pattern of the Ni-MOF matches well with the simulated Ni-MOF characteristic peaks. In the graph (a), the Ni-MOF (D) obtained by calcination showed diffraction peaks at 37.2 DEG and 62.8 DEG corresponding to monoclinic crystal planes of nickel oxides (111) and (220). Subsequently, when NiCo LDH was electrodeposited on the Ni-MOF (D) surface, diffraction peaks corresponding to the (003), (006), (009) and (111) planes at 10.6 °, 22.5 °, 34.0 ° and 60.3 ° appeared, demonstrating successful material compounding.
FIG. 2 is an SEM image of a Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in this example. In the figure, figure (a) illustrates that the pretreated stainless steel mesh substrate has a smooth surface. Fig. (b, c) are nickel hydroxide nanoplatelets deposited on a stainless steel mesh substrate, providing rich nucleation sites for subsequent hydrothermal synthesis of Ni-MOF. FIG. d, e shows that the Ni-MOF has a flower-ball structure and is uniformly distributed on the electrode surface. Panels (f, g) show that the Ni-MOF (D) obtained by calcination still retains the structure of the flower sphere, and the nano-sheets on the flower sphere are more prominent and smooth, which is beneficial for the later growth of NiCo LDH. Panel (h, i) is an image of Ni-MOF (D)/NiCo LDH film at different magnifications. It can be seen that the Ni-MOF (D) film surface appeared to be uniform, small-sized nanoflakes, which correspond to the formation of NiCo LDH. In addition, the outer layer of the film can be seen to be completely covered by the NiCo LDH nanoplatelets, indicating that NiCo LDH is well deposited on the Ni-MOF (D) film surface.
Example 2:
(1) Dissolving 4.0711 g nickel nitrate hexahydrate and 0.3704 g ammonium fluoride in 200 mL of aqueous solution to prepare a mixed aqueous solution A;
(2) Dissolving 0.237 and g nickel chloride hexahydrate and 0.166 and g terephthalic acid in an N, N-dimethylformamide solvent of 35 and mL to prepare a mixed solution, sequentially and slowly dropwise adding 2.5 and mL deionized water and 2.5 and mL absolute ethyl alcohol under the condition of stirring at room temperature, and stirring at a constant speed for 30 min to obtain a solution B;
(3) Dissolving 4.6527 g nickel nitrate hexahydrate and 1.1642 g cobalt nitrate hexahydrate in 200 mL to prepare a mixed aqueous solution C of 0.08M nickel nitrate hexahydrate and 0.02M cobalt nitrate hexahydrate;
(4) Dissolving 0.0745 g potassium bromide in 500 mL water to prepare 100 ppm bromide ion solution D;
(5) Three-electrode system (working electrode with effective area of 2×2 cm) 2 Is 2×2 cm to the counter electrode 2 A reference electrode is a saturated calomel electrode) is placed in the solution A, constant deposition current is set to be-20 mA, and deposition time is set to be 50 min;
(6) And vertically placing the prepared nickel hydroxide nanosheet precursor into the solution B, transferring the precursor into a polytetrafluoroethylene lining, heating to 125 ℃, and keeping the temperature at 2 h.
(7) The prepared Ni-MOF film was put into a muffle furnace and calcined at 450 ℃ for 2 h.
(8) Placing the obtained Ni-MOF (D) film material as a working electrode into a C solution, and setting unipolar pulse signals as follows: the pulse voltage is-1.5V, the pulse on-off time ratio is 1 s/1 s, and the pulse times are 1000 times.
(9) The bromide ion-containing solution D is selectively extracted based on the Ni-MOF (D)/NiCo LDH double-site adsorption membrane, and after 3 h of the adsorption process, the adsorption of the bromide ions in the solution by the composite membrane reaches equilibrium. The concentration of the bromine ions remained in the solution after being adsorbed by the composite membrane is measured by an ion chromatograph to be 25.13 ppm, and the calculated bromine ion extraction amount is 71.64 mg g -1 。
(9) And the adsorption film to be regenerated is used as a working electrode, a counter electrode and a saturated calomel electrode to form a three-electrode system. And (3) placing the three-electrode system into a sodium nitrate solution of 0.1M, applying a reduction potential on the working electrode, releasing bromide ions adsorbed on the Ni-MOF (D)/NiCo LDH double-site adsorption film into the sodium nitrate solution, taking out the working electrode, flushing out electrolyte remained on the surface of the hybridization film material by using water, and drying at normal temperature to obtain the regenerated adsorption film.
(10) After 5 adsorption and desorption cycles, the extraction amount of the bromide ions can still reach 66.41 mg g -1 。
Example 3:
(1) Dissolving 4.0711 g nickel nitrate hexahydrate and 0.3704 g ammonium fluoride in 200 mL of aqueous solution to prepare a mixed aqueous solution A;
(2) Dissolving 0.237 and g nickel chloride hexahydrate and 0.166 and g terephthalic acid in an N, N-dimethylformamide solvent of 35 and mL to prepare a mixed solution, sequentially and slowly dropwise adding 2.5 and mL deionized water and 2.5 and mL absolute ethyl alcohol under the condition of stirring at room temperature, and stirring at a constant speed for 30 min to obtain a solution B;
(3) Dissolving 5.2343 g nickel nitrate hexahydrate and 0.5821 g cobalt nitrate hexahydrate in 200 mL of aqueous solution to prepare 0.09M nickel nitrate hexahydrate and 0.01M cobalt nitrate hexahydrate of mixed aqueous solution C;
(4) Dissolving 0.1489 g potassium bromide in 500 mL water to prepare 200 ppm bromide ion solution D;
(5) Three-electrode system (working electrode with effective area of 2×2 cm) 2 Is 2×2 cm to the counter electrode 2 Is a saturated calomel electrode as a reference electrode) is placed in A solutionSetting constant deposition current to be-24 mA in the liquid, wherein the deposition time is 40 min;
(6) And vertically placing the prepared nickel hydroxide nanosheet precursor into the solution B, transferring the precursor into a polytetrafluoroethylene lining, heating to 125 ℃, and keeping the temperature at 2 h.
(7) The prepared Ni-MOF film was put into a muffle furnace and calcined at 450 ℃ for 2 h.
(8) Placing the obtained Ni-MOF (D) film material as a working electrode into a C solution, and setting unipolar pulse signals as follows: the pulse voltage is-1.5V, the pulse on-off time ratio is 1 s/1 s, and the pulse times are 1000 times.
(9) The bromide ion-containing solution D is selectively extracted based on the Ni-MOF (D)/NiCo LDH double-site adsorption membrane, and after 3 h of the adsorption process, the adsorption of the bromide ions in the solution by the composite membrane reaches equilibrium. The concentration of the bromine ions remained in the solution after being adsorbed by the composite membrane is 68.96 ppm by an ion chromatograph, and the calculated bromine ion extraction amount is 126.30 mg.g -1 。
(9) And the adsorption film to be regenerated is used as a working electrode, a counter electrode and a saturated calomel electrode to form a three-electrode system. And (3) placing the three-electrode system into a sodium nitrate solution of 0.1M, applying a reduction potential on the working electrode, releasing bromide ions adsorbed on the Ni-MOF derivative/NiCo LDH double-site adsorption membrane into the sodium nitrate solution, taking out the working electrode, flushing out electrolyte remained on the surface of the hybrid membrane material by using water, and drying at normal temperature to obtain the regenerated adsorption membrane.
(10) After 5 adsorption and desorption cycles, the extraction amount of the bromide ions can still reach 117.08 mg g -1 。
FIG. 3 is a graph showing the effect of extraction test on aqueous solutions containing 50 ppm, 100 ppm and 200 ppm bromide ions for Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 3 of the present invention.
In the graph, (a) is a graph showing the relation of the concentration of bromide ions in a solution with time, when the initial concentration of bromide ions in the solution is 50 ppm, the concentration is reduced to 8.57 ppm when the equilibrium is reached, and the corresponding adsorption quantity is 41.96 mg g -1 . When the concentration was increased to 200 ppm, bromide was addedThe adsorption quantity is up to 126.30 mg g -1 . (b) Is a graph of the adsorption capacity of Ni-MOF (D)/NiCo LDH composite membrane electrode to bromide ions with time. Along with the increase of the initial concentration of the bromide ions, the conductivity in the solution is increased, so that the migration rate of the bromide ions in an electric field is effectively improved, and the adsorption quantity is improved.
FIG. 4 is a graph showing the results of bromine extraction test performed on Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 3 of the present invention in a mixed solution of 200 ppm of each of bromide ion, nitrate ion and iodide ion. According to the interlayer anion exchange sequence bromide > nitrate > iodide inherent to LDHs, niCo LDH as a selective separation layer preferentially adsorbs bromide in solution. Since the prepared NiCo LDH is intercalated with nitrate ions, it is difficult to re-adsorb a large amount of nitrate ions, resulting in the lowest nitrate ion partition coefficient. As calculated from fig. 4, the separation coefficients of bromide ion for nitrate ion and iodide ion were 8.29 and 4.83, respectively.
FIG. 5 is a graph showing the effect of the Ni-MOF (D)/NiCo LDH composite membrane electrode prepared in example 3 of the present invention on 5 cycles of adsorption/desorption test in an aqueous solution containing 200 ppm of bromide ions and a sodium nitrate solution of 0.1. 0.1M. It can be seen that the bromide adsorption capacity can still maintain 92.7% of the initial adsorption capacity after 5 adsorption/desorption cycles, indicating that the membrane has excellent recycling property.
Claims (9)
1. The preparation method of the MOF derivative/LDH double-site adsorption membrane is characterized by comprising the following steps of: firstly, electrochemically depositing a metal hydroxide/metal oxide precursor on a pretreated stainless steel wire net, and hydrothermally synthesizing an MOF film under high temperature and high pressure by an in-situ growth method; then, calcining the prepared MOF film in a muffle furnace, and controlling the calcining temperature and the calcining time to obtain the required MOF derivative; finally, placing the MOF derivative into an electrolyte containing metal nitrate, and applying a reduction potential on the surface of the MOF derivative by an electrochemical deposition method to prepare a layer of uniform LDH nanosheets, so as to obtain the MOF derivative/LDH double-site adsorption membrane; the temperature of the MOF for hydrothermal synthesis is 120-150 ℃ and the time is 10-14 h.
2. The method for preparing a MOF derivative/LDH double site adsorption membrane according to claim 1, wherein: the method for electrochemically depositing the metal hydroxide/metal oxide precursor is one of a constant voltage method, a constant current method, a pulse method and a cyclic voltammetry.
3. The method for preparing a MOF derivative/LDH double site adsorption membrane according to claim 2, wherein: when a constant voltage method is adopted, the voltage range of the electrochemical deposition metal hydroxide/metal oxide precursor is-1.0 to-1.5V, and the deposition time is 30-60 min; when a constant current method is adopted, the current range of the electrochemical deposition metal hydroxide/metal oxide precursor is-18 to-24 mA, and the deposition time is 40-60 min.
4. The method for preparing a MOF derivative/LDH double site adsorption membrane according to claim 1, wherein: the metal center ion of the metal hydroxide/metal oxide precursor is one of the metal hydroxide/metal oxide of Ni, co, cu, fe, zn elements.
5. The method for preparing a MOF derivative/LDH double site adsorption membrane according to claim 1, wherein: when the MOF derivative is prepared, the calcination temperature is 350-450 ℃, and the calcination time is 2-4 hours.
6. The method for preparing a MOF derivative/LDH double site adsorption membrane according to claim 1, wherein: the electrolyte of the metal nitrate consists of any two of nickel nitrate, cobalt nitrate, ferric nitrate, manganese nitrate and aluminum nitrate, wherein the molar ratio of the two nitrates is 1:9-9:1, and the concentration of the nitrates is 0.1-0.3M; the metal elements in the formed LDH nano-sheets are any two of Ni, co, mn, al, fe.
7. The method for preparing a MOF derivative/LDH double site adsorption membrane according to claim 1, wherein: when LDH is deposited by an electrochemical method, the deposition potential is-1.0 to-1.5V, and the deposition time is as follows: and (5) 10-30 min.
8. Use of a MOF derivative/LDH double site adsorption membrane prepared by the preparation method of any one of claims 1 to 7 for electrically controlled extraction of bromide ions.
9. The use according to claim 8, characterized in that: the method is implemented in an electric control ion exchange system under a three-electrode system, the MOF derivative/LDH double-site adsorption membrane is adopted as a working electrode, a platinum sheet and a saturated calomel electrode are respectively a counter electrode and a reference electrode, and the counter electrode and the reference electrode are placed in a bromine ion aqueous solution with the concentration of 50-200 ppm to assemble the electric control ion exchange system; the process is controlled by constant voltage, the constant voltage is 0.6-1.2V, oxidation potential is applied to the working electrode through a circuit control system, bromide ions in the solution can be selectively placed in the membrane, and the adsorption balance time is 2-4 h.
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