Application of metal vacancy-containing transition metal oxide in wastewater treatment

Abstract

The invention relates to application of transition metal oxide containing metal vacancies in wastewater treatment, and relates to the field of wastewater treatment products. According to the application of the transition metal oxide containing the metal vacancies in treatment of heavy metal ions in wastewater, the metal vacancies are introduced into the transition metal oxide, so that charge distribution on the surface of the transition metal oxide can be reconfigured, and then the electronic structure of active sites is optimized; the prepared transition metal oxide containing the metal vacancies can be used for treating heavy metal ions in wastewater, and particularly plays a role in treating the heavy metal ions in the wastewater as a membrane electrode material.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment products, and specifically relates to use of a transition metal oxide containing metal vacancies in wastewater treatment. Background Art

[0002] In the context of the continuous development of industrialization and urbanization, industries such as chemical, metallurgy, mining, electroplating and battery have discharged a large amount of wastewater containing low-concentration toxic heavy metal ions. These wastewaters have seriously polluted surface and groundwater resources, greatly reducing the amount of available water resources, and increasing the heavy metal content in the soil, posing a serious threat to the ecological environment and human health. In view of this, there is an urgent need to explore and research economical and efficient heavy metal ion wastewater treatment technology to address environmental pollution problems.

[0003] Adsorption, ion exchange and electrochemical methods have become the focus of heavy metal wastewater treatment in recent years. Although adsorption is fast and efficient, most adsorbents have problems such as difficulty in recovery, low affinity, and easy secondary pollution during regeneration, which restricts its widespread application; although ion exchange can effectively separate target ions, its chemical regeneration process will produce secondary pollution, and the selectivity of the regenerated ion exchanger is reduced, and it cannot be reused many times, increasing the treatment cost; although electrochemical method has the advantages of high absorption rate, economy and environmental protection, in the face of low-concentration heavy metal ion wastewater with low conductivity, metal deposition and hydrogen and oxygen evolution reactions are prone to occur on the electrode surface, reducing its energy efficiency in treating wastewater. Therefore, the development of a new energy-saving and environmentally friendly ion separation technology is of vital importance to solve the problem of low-concentration toxic heavy metal ion wastewater treatment.

[0004] As an innovative, environmentally friendly, efficient and low-cost new ion exchange method, the electrically switched ion exchange technology (ESIX) has attracted great attention from experts and scholars at home and abroad. This technology combines the principles of ion exchange, adsorption and electrochemistry to form a new type of ion selective separation technology. This technology deposits electroactive semiconductor ion exchange materials on a conductive substrate to form a nanoscale film, and exhibits the "potential response" characteristics by adjusting the redox state of the electroactive ion exchange material, thereby playing a role in controlling the capture and release of ions, and realizing the effective separation of ions in the solution. In addition, this electroactive ion exchange material can be recycled many times.

[0005] At present, commonly used electroactive ion exchange functional materials mainly include conductive polymers with conjugated structures (such as polyaniline) and inorganic materials. However, materials with this function are relatively scarce, and their low adsorption capacity limits their removal efficiency of target heavy metal ions, which has prompted the need for in-depth improvement of electroactive ion exchange materials. Summary of the invention

[0006] In view of the above-mentioned defects and problems of the prior art, the present invention develops a use of a transition metal oxide containing metal vacancies in wastewater treatment.

[0007] The application discloses the use of a transition metal oxide containing metal vacancies in treating heavy metal ions in wastewater.

[0008] Optionally, in the process of treating heavy metal ions in wastewater, the transition metal oxide containing metal vacancies is used to prepare a membrane electrode.

[0009] Optionally, in the process of treating heavy metal ions in wastewater, a transition metal oxide containing metal vacancies supported by a conductive polymer is used to prepare a membrane electrode; wherein a conductive polymer with excellent film-forming properties is inserted into the transition metal oxide containing metal vacancies to obtain the transition metal oxide containing metal vacancies supported by the conductive polymer.

[0010] Optionally, the metal oxide in the metal vacancy-containing transition metal oxide includes MoO3, TiO2 or CuO.

[0011] Optionally, the heavy metal ions in the wastewater include Pb 2+ .

[0012] Optionally, the method for preparing the transition metal oxide containing metal vacancies comprises:

[0013] Step 1: mixing a transition metal oxide and a stripping agent to obtain a transition metal oxide flake;

[0014] Step 2: passivating the transition metal oxide flakes with an encapsulant to obtain encapsulated flakes;

[0015] Step 3: Create trace metal vacancies in the encapsulated thin slices through an electron beam-induced chemical etching method to obtain a transition metal oxide containing metal vacancies.

[0016] Optionally, the method for preparing the transition metal oxide containing metal vacancies further comprises: modifying the transition metal oxide containing metal vacancies by plasma and / or a dopant; wherein the dopant may be polybenzenesulfonic acid or sodium polystyrene sulfonate.

[0017] Optionally, the method for preparing the membrane electrode comprises:

[0018] (a) mixing and grinding a transition metal oxide powder containing metal vacancies, a binder and conductive carbon black, and then mixing with an N-methylpyrrolidone solvent, and stirring until the slurry is uniform to form a film-forming solution;

[0019] (b) applying the membrane-forming solution onto a conductive substrate, and drying at 40-65° C. for 6-10 hours to obtain the membrane electrode.

[0020] Optionally, the membrane electrode preparation method satisfies at least one of the following features S1 to S4:

[0021] S1. In step (a), the metal vacancy-containing transition metal oxide powder, the adhesive and the conductive carbon black are mixed in a mass ratio of (6-12):(0.5-3):1;

[0022] S2, in step (b), drying at 50°C for 8h;

[0023] S3, the adhesive is selected from at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose;

[0024] S4. The conductive substrate is selected from one of stainless steel plate, carbon paper, platinum sheet, titanium plate, titanium mesh, graphite paper and carbon cloth.

[0025] Optionally, the device for treating heavy metal ions in wastewater using the transition metal oxide containing metal vacancies comprises:

[0026] An electrolytic cell containing an electrolyte, a power supply device and a three-electrode system, wherein the three-electrode system is inserted into the electrolytic cell, the power supply device is used to supply power to the three-electrode system, and the three-electrode system comprises a working electrode, a counter electrode and a reference electrode; the working electrode is a transition metal oxide film electrode containing metal vacancies;

[0027] During the process of treating heavy metal ions in wastewater, when a reduction potential is applied to the membrane electrode, the membrane electrode adsorbs the heavy metal ions in the wastewater; when an oxidation potential is applied to the membrane electrode, the membrane electrode desorbs the adsorbed heavy metal ions; wherein, -12V≤the reduction potential≤0V, and 0V≤the oxidation potential≤0.9V.

[0028] In summary, this application has the following beneficial effects:

[0029] By introducing defects (metal vacancies) into transition metal oxides, the charge distribution on the surface of the transition metal oxides can be reconfigured, thereby optimizing the electronic structure of the active sites. This allows the resulting transition metal oxides containing metal vacancies to have a larger adsorption capacity for metal ions, and can be used to efficiently treat heavy metal ions in wastewater, especially as membrane electrode materials to efficiently treat trace amounts of heavy metal ions in wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0031] Figure 1 This is a graph showing the adsorption data of various metal ions by the MoO3 / PPy membrane electrode within 120 minutes in Example 1 of the present application;

[0032] Figure 2 In Example 2 of the present application, under the action of MoO3 / PPy membrane electrode, Pb 2+ The concentration curve of changes with time;

[0033] Figure 3 This is the MoO3 / PPy membrane electrode adsorption / desorption cycle stability test in Example 2 of the present application;

[0034] Figure 4 Pb 2+ Schematic diagram of the adsorption mechanism and interfacial electron transfer mechanism of heavy metal ions represented by . DETAILED DESCRIPTION

[0035] The present application is further described in detail with reference to the following examples. It should be noted that if no specific conditions are specified in the following examples, the conventional conditions or the conditions recommended by the manufacturer are followed, and the raw materials used in the following examples can be obtained from common commercial sources unless otherwise specified.

[0036] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0037] In this application, "first aspect", "second aspect", "third aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0038] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0039] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0040] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0041] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically limited. .

[0042] In order to facilitate the description of the technical solution of this application, the following materials and steps are described before starting the experiment of this application:

[0043] The present application discloses the use of transition metal oxides containing metal vacancies in treating heavy metal ions in wastewater, especially selectively adsorbing trace amounts (concentration ≤ 20 ppm) of Pb in wastewater. 2+. In the process of treating heavy metal ions in wastewater, transition metal oxides containing metal vacancies can be used to make membrane electrodes. It should be noted that transition metal oxides containing metal vacancies refer to transition metal oxide crystal structures in which positions occupied by some metal atoms are made vacant through pretreatment, wherein the number of vacancies accounts for 0.1%-5% of the total number of metal atoms in the transition metal oxide crystal structure. The wastewater may be at least one of salt lake water, seawater, industrial wastewater, domestic sewage, and natural sewage. As an example, the wastewater may be wastewater from a fertilizer plant.

[0044] The preparation method of the transition metal oxide containing metal vacancies comprises:

[0045] Step 1: Mix transition metal oxide and a stripping agent to obtain transition metal oxide flakes; wherein the stripping agent includes tetrabutylammonium hydroxide or dioctadecyldimethylammonium chloride.

[0046] Step 2: passivating the transition metal oxide flakes with an encapsulant to obtain encapsulated flakes; wherein the encapsulant includes polyvinyl pyrrolidone.

[0047] Step 3: Create trace metal vacancies in the encapsulated thin film through an electron beam-induced chemical etching method to obtain a transition metal oxide containing metal vacancies.

[0048] Preferably, in order to improve the conductivity of the transition metal oxide containing metal vacancies as a membrane electrode, in some specific embodiments, the preparation method of the transition metal oxide containing metal vacancies further includes step 4: inserting a conductive polymer having excellent film-forming properties into the transition metal oxide containing metal vacancies to obtain a transition metal oxide containing metal vacancies supported by the conductive polymer. It is understood that the monomer of the conductive polymer can be an aniline monomer or a pyrrole monomer.

[0049] It should be noted that the transition metal oxide can be MoO3, TiO2 or CuO. As an example, when the transition metal oxide is MoO3 and the conductive polymer is polypyrrole PPy, the transition metal oxide containing metal vacancies supported by the conductive polymer can be expressed as MoO3 / PPy.

[0050] In other embodiments, the preparation method of the transition metal oxide containing metal vacancies further includes: modifying the transition metal oxide containing metal vacancies by plasma and / or dopants; wherein the dopant may be polybenzenesulfonic acid or sodium polystyrene sulfonate (PSS). It should be noted that plasma can change the microscopic morphology of the transition metal oxide containing metal vacancies and adjust the arrangement between nanoparticles, thereby improving the specific surface area and ion storage capacity of the transition metal oxide containing metal vacancies. The plasma in the present application may be low-temperature plasma, arc plasma or microwave plasma. The introduction of suitable dopants can significantly improve the performance of the transition metal oxide containing metal vacancies, enhance its electrical conductivity, electrochemical activity, stability and other important electrochemical properties, form a stable protective film on the surface of the material, and reduce the degradation or damage of the electrode material during long-term use.

[0051] The device for treating heavy metal ions in wastewater by using transition metal oxides containing metal vacancies comprises: an electrolytic cell filled with electrolyte, a power supply device and a three-electrode system, the three-electrode system is inserted into the electrolytic cell, the power supply device is used to supply power to the three-electrode system, the three-electrode system comprises a working electrode, a counter electrode and a reference electrode; the working electrode adopts a transition metal oxide film electrode containing metal vacancies, preferably, the working electrode adopts a MoO3 / PPy film electrode. More preferably, a 2cm×2.5cm blank graphite paper is used as the counter electrode, and an Ag / AgCl electrode is used as the reference electrode.

[0052] The method for preparing the membrane electrode in the above device includes:

[0053] (a) mixing a metal vacancy-containing transition metal oxide powder, a binder and conductive carbon black (CP), grinding the mixture sufficiently until a uniform powder is formed, mixing the mixture with an appropriate amount of N-methylpyrrolidone (NMP) solvent, and stirring the mixture until the slurry is uniform to form a film-forming solution;

[0054] (b) The membrane-forming liquid is evenly applied on the conductive substrate and dried at 40-65° C. for 6-10 hours to obtain a membrane electrode.

[0055] Wherein, in step (a), the transition metal oxide powder containing metal vacancies, the adhesive and the conductive carbon black can be mixed in a mass ratio of 6-12:0.5-3:1, for example, the transition metal oxide powder containing metal vacancies, the adhesive and the conductive carbon black can be mixed in a mass ratio of 8:1:1; and the adhesive can be at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose. As an example, the adhesive can be polyvinylidene fluoride (PVDF). In step (b), the conductive substrate can be one of stainless steel plate, carbon paper, platinum sheet, titanium plate, titanium mesh, graphite paper, and carbon cloth; as an example, the conductive substrate is 2cm×2.5cm graphite paper. It should be noted that the conductive substrate used for the working electrode and the counter electrode is generally the same. In this step, dry at 50°C for 8h. In addition, in the above step (a), the transition metal oxide powder containing metal vacancies can be replaced with an equal amount of electroactive MoO3 / PPy.

[0056] In the process of treating heavy metal ions in wastewater by transition metal oxides containing metal vacancies, a reduction potential is applied to the membrane electrode through a power supply device, and the membrane electrode adsorbs heavy metal ions in the wastewater; an oxidation potential is applied to the membrane electrode through a power supply device, and the membrane electrode can desorb the adsorbed heavy metal ions. Among them, -12V≤reduction potential≤0, 0≤oxidation potential≤0.9V. As an example, the reduction potential can be -0.7V, and the oxidation potential can be 0.8V.

[0057] Preparation example of transition metal oxide film electrode containing metal vacancies:

[0058] (1) Preparation of transition metal oxides containing metal vacancies:

[0059] Step 1: Add 5.0 g MoO3 and 1.5 g dioctadecyl dimethyl ammonium chloride into a beaker and evenly disperse in 150 mL deionized water. After fully mixing at 5°C for 24 hours, filter and vacuum dry to obtain transition metal oxide flakes. The average thickness of the transition metal oxide flakes is 0.02 mm.

[0060] Step 2: immerse the transition metal oxide flakes in polyvinyl pyrrolidone (PVP), passivate the transition metal oxide flakes with PVP, filter and vacuum dry to obtain encapsulated flakes, thereby achieving the protective effect on the surface of the transition metal oxide flakes.

[0061] Step 3: Apply about 10 7 e - / nm 2 The electron beam irradiation is used to create metal vacancy pairs in the encapsulated thin film, wherein the number of vacancies in the encapsulated thin film accounts for 3.1% of the total number of metal atoms in the transition metal oxide crystal structure.

[0062] Step 4: Add the flakes prepared with vacancies in step 3 to a solution of 0.9 g polypyrrole (PPy) and 0.6 g sodium polystyrene sulfonate (PSS), and continue stirring for 1 h. Place the mixture in a low-temperature water tank at 0°C for 8 h, filter and vacuum dry to obtain MoO3 / PPy powder.

[0063] (2) Preparation of membrane electrode

[0064] (a) Put MoO 3 / PPy powder, polyvinylidene fluoride (PVDF) and conductive carbon black (CP) were mixed at a mass ratio of 8:1:1, fully ground until a uniform black powder was formed, and then mixed with 10 mL of N-methylpyrrolidone (NMP) solvent and stirred overnight until the slurry was uniform to form a membrane-making solution.

[0065] (b) The film-forming solution was evenly applied on a 2 cm × 2.5 cm graphite paper by manual coating and dried at 50 °C for 8 h to obtain an electroactive MoO3 / PPy film electrode.

[0066] Example 1

[0067] Since actual lead-containing wastewater usually contains Pb 2+ In order to test the adsorption selectivity of the MoO3 / PPy membrane electrode prepared in the preparation example, the following experiment was carried out:

[0068] Prepare electrolyte: Pb 2+ 、Cd 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ and Cu 2+ are dissolved in deionized water to obtain a mixed solution. In the mixed solution, Pb 2+ 、Cd 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ and Cu 2+ The concentration of each is 20 ppm. The prepared electrolyte is placed in an electrolytic cell.

[0069] A three-electrode system was formed with MoO3 / PPy membrane electrode as working electrode, 2cm×2.5cm blank graphite paper as counter electrode, and Ag / AgCl electrode as reference electrode. The system was inserted into the prepared electrolyte, and a reduction potential of -0.7V was applied to the working electrode through a power supply device. The concentration of each ion in the electrolyte was detected every 20 minutes (measured by ion chromatography). Experimental data can be found in Figure 1 .

[0070] like Figure 1It can be seen that the MoO3 / PPy membrane electrode prepared in this application can achieve the adsorption of various metal ions in wastewater in a relatively short time, especially for Pb 2+ Excellent selectivity (after 120 min, Pb 2+ The concentration of Pb 2+ It has good adsorption performance and can be used for Pb in wastewater 2+ adsorption.

[0071] Example 2

[0072] Prepare electrolyte: Pb 2+ Dissolve in deionized water to obtain Pb 2+ The concentration of the solution is 20ppm. Place the prepared electrolyte in the electrolytic cell.

[0073] The MoO3 / PPy film electrode was used as the working electrode, the 2cm×2.5cm blank graphite paper was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode to form a three-electrode system. The system was inserted into the prepared electrolyte, and a reduction potential of -0.7V was applied to the working electrode through the power supply device to determine the Pb in the electrolyte. 2+ Changes in concentration over time (measured every 5 minutes at the beginning, and once every 10 minutes after reaching equilibrium). Experimental data can be found in Figure 2 .

[0074] like Figure 2 It can be seen that the adsorption reaches equilibrium in 120 minutes. At equilibrium, Pb 2+ The concentration of PbO3 / PPy membrane electrode prepared in this application is 0.008ppm, which meets the national drinking water standard. 2+ The maximum equilibrium adsorption capacity is 382~450mg·g -1 Among them, Pb 2+ Maximum equilibrium adsorption capacity q (mg·g -1 ) is calculated as follows:

[0075] q=(C0-C e )×V / m

[0076] Where V is the volume of the solution to be adsorbed (L), m is the mass of the active ingredient coated on the MoO3 / PPy membrane electrode (g); C o and C e The Pb content in the solution at the initial state and equilibrium state is 2+ Concentration (mg·L -1 ).

[0077] The electrolyte in the electrolytic cell is discarded and the electrolytic cell is cleaned.2+ The concentration of the electrolyte is 0.1 mol·L -1 The Na2SO4 solution was used as the regeneration solution and placed in the electrolytic cell. The MoO3 / PPy membrane electrode was used as the working electrode, the 2cm×2.5cm blank graphite paper was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode to form a three-electrode system. A closed loop was formed in the regeneration solution, and an oxidation voltage of 0.8V was applied to the working electrode through the power supply device. After 120 minutes, Pb was captured. 2+ The above adsorption and desorption steps were repeated 20 times, and the experimental results are shown in Figure 3 .

[0078] like Figure 3 As shown, in each cycle test, Pb 2+ The adsorption / release process is almost completely reversible, and even after the above 20 cycles, the regeneration efficiency of the membrane electrode is maintained above 90%.

[0079] In addition, by Figure 3 It can be seen that in 20 cycles, the adsorption capacity retention rate and regeneration efficiency curve of MoO3 / PPy electroactive membrane electrode fluctuated relatively little, indicating that the electroactive membrane electrode has a good adsorption performance for Pb 2+ It has a stable adsorption capacity.

[0080] Application Examples

[0081] The actual industrial wastewater produced by a fertilizer plant was used as the research object. The wastewater was the waste condensate produced when producing nitrophosphate fertilizer. 2+ The initial concentration was 19.09ppm. 40mL of industrial wastewater was placed in the electrolytic cell of this application. The MoO3 / PPy membrane electrode was used as the working electrode, the 2cm×2.5cm blank graphite paper was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode to form a three-electrode system. The three-electrode system was inserted into the industrial wastewater, and a reduction potential of -0.7V was applied to the working electrode through the power supply device to conduct the adsorption experiment. 100μL of water samples were collected at 0, 10, 20, 30, 40, 50, 60, 90, 120 and 180 minutes for Pb adsorption. 2+ The concentration test results showed that after 120 minutes, the treated wastewater Pb 2+ The concentration dropped to 0.007ppm, almost completely removing Pb from the wastewater. 2+ The removal rate is close to 100%. This shows that the metal vacancy-containing transition metal oxide prepared in this application can effectively adsorb trace Pb in wastewater when used as a membrane electrode. 2+ .

[0082] The reason for the above experimental results is that the present application speculates that in a complex system containing extremely low concentrations of heavy metal ions, the metal ions of transition metal oxides (TMOs) themselves have variable oxidation states and are easy to undergo redox reactions. By introducing defects, the charge distribution on the surface of the TMOs material can be reconfigured, thereby optimizing the electronic structure of the active sites, increasing the conductivity of TMOs and overcoming the defect of the limited number of active sites of TMOs. Therefore, after the transition metal oxides containing metal vacancies are used in the preparation of membrane electrodes, they have excellent removal effects in the treatment of heavy metal ions in wastewater treatment.

[0083] In addition, in MoO3 / PPy, TMOs containing metal vacancies can form a conductive microenvironment that satisfies material activation by virtue of the driving force transmitted within the composite material by the built-in electric field at the interface generated by the composite with PPy. Figure 4 As shown in (A), after the metal vacancy TMOs are combined with PPy, electrons are transferred from PPy to the surface of the metal vacancy TMOs, which can generate a built-in electric field from PPy to TMOs, thereby enhancing the overall electrical activity and causing the surface of the metal vacancy TMOs to be covered by a negative electron cloud, promoting cation capture. In addition, the electron transfer between the two phases causes the metal vacancy TMOs to transition to a metallic state, thereby effectively reducing the contact resistance and promoting ion mobility; and the reversible adsorption and desorption of heavy metal ions is achieved by adjusting the redox state of MoO3 / PPy to drive and control the directional flow of electrons.

[0084] like Figure 4 As shown in (B), the directional migration of electrons during the redox process of MoO3 / PPy forms a "switch" for ion adsorption and desorption. The reduced electrons flow from the inorganic substrate material to the conductive polymer, driving the heavy metal ions out of MoO3 / PPy, and the oxidized electrons flow from the conductive polymer to the inorganic substrate material. The metal vacancies provide an "electrostatic potential well" for capturing heavy metal ions. At this time, the heterogeneous heavy metal ions interact with the surrounding bimetallic vacancies and cleverly regulate the coordination state of the heterogeneous heavy metal ions by forming covalent bonds on the metal vacancies, thereby achieving ion capture.

[0085] like Figure 4 As shown in (C), under the action of the electric field formed by the charge balance between heavy metal ions and TMOs containing metal vacancies, a quasi-one-dimensional ion rapid migration "highway" is formed on the surface of TMOs containing metal vacancies, which is conducive to the rapid transport of ions and drives the efficient adsorption and desorption of target heavy metal ions in the environment where other competing ions exist.

[0086] The present application speculates that MoO3 / PPy achieves the effect of efficiently adsorbing extremely low concentration heavy metal ions in wastewater through the above-mentioned method.

[0087] It should be understood that the disclosed invention is not limited only to the specific method, scheme and material of description, because these all can change.It should also be understood that the terminology used herein is only for the purpose of describing specific embodiment scheme, rather than being intended to limit the scope of the present invention, and the scope of the present invention is only limited to the appended claims.

[0088] Those skilled in the art will also recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are also intended to be encompassed by the appended claims.

Claims

1. Use of a transition metal oxide containing metal vacancies in treating heavy metal ions in wastewater.

2. The use according to claim 1, wherein the transition metal oxide containing metal vacancies is used to prepare a membrane electrode in the process of treating heavy metal ions in wastewater.

3. The use according to claim 2, in the process of treating heavy metal ions in wastewater, the transition metal oxide containing metal vacancies supported by the conductive polymer is used to prepare a membrane electrode; wherein, A conductive polymer with excellent film-forming property is inserted into a transition metal oxide containing metal vacancies to obtain the conductive polymer-supported transition metal oxide containing metal vacancies.

4. The use according to claim 1, wherein the metal oxide in the metal vacancy-containing transition metal oxide comprises MoO3, TiO2 or CuO.

5. The use according to claim 1, wherein the heavy metal ions in the wastewater include Pb 2+ .

6. The use according to claim 2, wherein the preparation method of the transition metal oxide containing metal vacancies comprises: Step 1: mixing a transition metal oxide and a stripping agent to obtain a transition metal oxide flake; Step 2: passivating the transition metal oxide flakes with an encapsulant to obtain encapsulated flakes; Step 3: Create trace metal vacancies in the encapsulated thin slices through an electron beam-induced chemical etching method to obtain a transition metal oxide containing metal vacancies.

7. The use according to claim 6, wherein the method for preparing the transition metal oxide containing metal vacancies further comprises: The transition metal oxide containing metal vacancies is modified by plasma and / or dopants; wherein the dopant can be polybenzenesulfonic acid or sodium polystyrenesulfonate.

8. According to any one of claims 6-7, the method for preparing the membrane electrode comprises: (a) mixing and grinding a transition metal oxide powder containing metal vacancies, a binder and conductive carbon black, and then mixing with an N-methylpyrrolidone solvent, and stirring until the slurry is uniform to form a film-forming solution; (b) applying the membrane-forming solution onto a conductive substrate, and drying at 40-65° C. for 6-10 hours to obtain the membrane electrode.

9. The use according to claim 8, wherein the method for preparing the membrane electrode satisfies at least one of the following characteristics S1 to S4: S1. In step (a), the metal vacancy-containing transition metal oxide powder, the adhesive and the conductive carbon black are mixed in a mass ratio of (6-12):(0.5-3):1; S2, in step (b), drying at 50°C for 8h; S3, the adhesive is selected from at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose; S4. The conductive substrate is selected from one of stainless steel plate, carbon paper, platinum sheet, titanium plate, titanium mesh, graphite paper and carbon cloth.

10. The use according to claim 1, characterized in that The device for treating heavy metal ions in wastewater by using the transition metal oxide containing metal vacancies comprises: An electrolytic cell containing an electrolyte, a power supply device and a three-electrode system, wherein the three-electrode system is inserted into the electrolytic cell, the power supply device is used to supply power to the three-electrode system, and the three-electrode system comprises a working electrode, a counter electrode and a reference electrode; the working electrode is a transition metal oxide film electrode containing metal vacancies; During the process of treating heavy metal ions in wastewater, when a reduction potential is applied to the membrane electrode, the membrane electrode adsorbs the heavy metal ions in the wastewater; when an oxidation potential is applied to the membrane electrode, the membrane electrode desorbs the adsorbed heavy metal ions; wherein, -12V≤the reduction potential≤0V, and 0V≤the oxidation potential≤0.9V.

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