LU501769B1

LU501769B1 - Carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof

Info

Publication number: LU501769B1
Application number: LU501769A
Authority: LU
Inventors: Hongbo Wang
Original assignee: Univ Yantai
Priority date: 2022-04-01
Filing date: 2022-04-01
Publication date: 2022-10-03

Abstract

The preparation method comprises the following steps: 1, removing impurities attached to the carbon felt and drying, and etching the dried carbon felt; 2. using the carbon felt pretreated in step 1 as raw material, loading iron, magnesium and chitosan on the surface of the carbon felt obtained in step 1 by hydrothermal method; 3. using the carbon felt-based iron/magnesium/nitrogen doped carbon catalytic electrode obtained in step 2 as raw material, loading the zirconium metal-organic frame structure on the surface of the carbon felt obtained in step 2 by hydrothermal method; then, oxidizing iron, magnesium and zirconium by calcination. The carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrode of the invention is applied to microbial fuel cells (MFC) and optimizes the treatment process, thus realizing the removal of radioactive ions in nuclear wastewater and the recovery of rare earth metals.

Description

DESCRIPTION LU501769 CARBON-BASED NITROGEN DOPED MIXED CRYSTAL CATALYTIC

ELECTRODE AND PREPARATION METHOD THEREOF

TECHNICAL FIELD The invention relates to a carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof, belonging to the technical field of sewage purification and waste water resource utilization.

BACKGROUND Microbial electrochemical system (MES), as a green technology that utilizes the metabolic activity of electricity-producing microorganisms to treat wastewater, has become the most promising wastewater treatment method. As a widely used MES, microbial fuel cell (MFC) consumes organic matter through the metabolic activity of anode electricity-producing microorganisms, generates electrons and transfers them to the cathode through an external circuit. In this process, organic matter is degraded and electricity is generated at the same time. Recently, Japan's discharge of nuclear waste water into the sea has aroused great concern. Traditional nuclear wastewater treatment methods mainly include adsorption, membrane filtration, etc. However, there is little research on electrochemical treatment of nuclear wastewater.

Recently, Japan's discharge of nuclear waste water into the sea has aroused great concern. Traditional nuclear wastewater treatment methods mainly include adsorption, membrane filtration, etc. However, there is little research on electrochemical treatment of nuclear wastewater. Among them, the cathode reduction efficiency of MFC affects the binding rate of terminal electron acceptor and electron in cathode chamber, which severely limits the overall performance of MFC. Although many scholars have optimized the cathode materials and surface catalysts, the problem has not been effectively solved. In order to improve the reduction efficiency of cathode electron acceptor, the doping of transition metal catalyst on cathode surface has attracted extensive attention.

The research on preparing the cathode of polycrystalline catalyst with carbon felt as substrate and iron/magnesium/zirconium composite oxide on the surface, improving the performance of MFC and treating and recovering cobalt, strontium, cesium, lanthanum and cerium in nuclear wastewater is still blank.

SUMMARY LU501769 The purpose of the present invention is to solve the shortcomings of the prior art, and provide a carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof. The carbon-based nitrogen doped mixed crystal catalytic electrode of the invention is applied to MFC and optimizes the treatment process, thus realizing the removal of radioactive ions in nuclear wastewater and the recovery of rare earth metals.

To achieve the above purpose, the present invention provides the following technical scheme: One of the aims of the invention is to provide a carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof, which is characterized by comprising the following steps: (1) pretreatment of carbon felt: removing impurities attached to the carbon felt and drying, and etching the dried carbon felt; (2) preparing carbon-based nitrogen catalytic electrode: using the carbon felt pretreated in step (1) as raw material, loading iron, magnesium and chitosan on the surface of the carbon felt obtained in step (1) by hydrothermal method, (3) preparing carbon-based nitrogen doped mixed crystal catalytic electrode: using carbon felt-based iron/magnesium/nitrogen-doped carbon catalytic electrode obtained in step (2) as raw material, loading zirconium metal-organic framework structure on the surface of carbon felt obtained in step (2) by hydrothermal method; then, oxidizing iron, magnesium and zirconium by calcination.

In the step (1), the specific steps of removing impurities attached to the carbon felt are as follows: immersing the carbon felt in the mixed solution of absolute ethyl alcohol and acetone for 24-48 h, and drying at 60-100°C with the mass ratio of absolute ethyl alcohol to acetone of 1: 2-2:1; In the step (1), the specific steps of etching treatment are as follows: immersing the dried carbon felt in dilute acid, etching for 12-24 hours and drying at 60-100°C to generate the attachment site of the catalyst; In the step (2), the specific steps of loading iron, magnesium and chitosan on the surface of the carbon felt obtained in the step (1) by hydrothermal method are as follows: firstly, dissolving chitosan in dilute acid, stirring for 12-24 hours to form a viscous solution, adding ferri¢/501769 trichloride hexahydrate and magnesium chloride hexahydrate in the process of stirring, and the mass ratio of chitosan, dilute acid, ferric trichloride hexahydrate and magnesium chloride hexahydrate is (18-20):(826-828):(2-4):(1-2); then, transferring the viscous solution to a reaction kettle, putting into the carbon felt obtained in step (1), hydrothermally treating in an oven at 180°C for 12 hours, and finally, cleaning the carbon felt with deionized water and dried at 60-100°C,; In the step (3), the specific steps of loading the zirconium metal-organic frame structure on the surface of the carbon felt obtained in the step (2) by hydrothermal method are as follows: firstly, dissolving zirconium tetrachloride and terephthalic acid in N,N-dimethylformamide (DMF), and the mass ratio of zirconium tetrachloride, terephthalic acid and DMF is (2-4):(1-2): (836-838); then, transferring the mixed solution to a 50 mL reaction kettle, putting it into the carbon felt-based iron/magnesium/chitosan catalytic electrode obtained in step (2), and carrying out hydrothermal treatment in an oven at 120°C for 24 hours; then, washing the carbon felt with absolute ethyl alcohol and DMF and dried at 60-100°C to remove unreacted substances; In the step (3), the specific steps of oxidizing iron, magnesium and zirconium by calcination are as follows: controlling the heating rate at 5 °C min’, and calcining at 600°C for 120 min; The second object of the present invention is the carbon-based nitrogen doped mixed crystal catalytic electrode prepared by the above preparation process.

The third purpose of the invention is the application of the carbon-based nitrogen doped mixed crystal catalytic electrode in the treatment of nuclear wastewater. The carbon-based nitrogen doped mixed crystal catalytic electrode of the invention realizes the removal of cobalt, strontium, cesium, lanthanum and cerium ions and the recovery of rare earth metals in radioactive wastewater.

The invention has the following beneficial effects: According to the invention, the carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrode for reducing noble metal ions such as cobalt, strontium, cesium, lanthanum and cerium is prepared, which can significantly improve the electrochemical performance of the cathode, further promote the accelerated metabolism of anode electricity-producing microorganisms and further improve the system voltage; at the same time,

as the reduction sites of cobalt, strontium, cesium, lanthanum and cerium ions, the catalytk&/501769 electrode can effectively reduce radioactive ions and realize efficient removal and recovery of radioactive ions. The catalytic electrode loaded with the reduced metal element on the surface can be used as the anode and released in the form of ions in the anode chamber, which shows that this electrode has the renewable performance. The anode chamber of MFC uses iron anode as the main anode and activated carbon/graphite particle bio-anode as the auxiliary anode, which increases the specific surface area of the anode and is conducive to the attachment of electricity-producing microorganisms, thus improving the performance of MFC.

BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is the cyclic voltammograms of carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrodes for reducing radioactive ions of Example 1 and Comparative Examples 1-3 (in the figure, the abscissa represents voltage in v; the ordinate represents the current in A; Fe (1) /Mg (1) /Zr@NC-CF-C corresponds to comparative example 1, Fe (1) /Mg (2) /Zr@NC-CF-C corresponds to comparative example 2, Fe (1) /Mg (2) /Zr@NC-CF-H corresponds to comparative example 3, Fe (1) /Mg (1) /Zr@NC-CF-H corresponds to Example 1); Fig. 2 shows the treatment performance of carbon-based nitrogen doped mixed crystal catalytic electrode for treating cerium with different concentrations (in the figure, the abscissa indicates the time in h; the left ordinate represents cerium ion concentration in mg L"!, and the right ordinate represents removal efficiency in %; the note on the right side of the figure represents the concentration of cerium in wastewater in mg L™).

DESCRIPTION OF THE INVENTION Next, the technical scheme in the embodiment of the invention will be clearly and completely described with reference to the drawings in the embodiment of the invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of the present invention.

Example 1

Preparing carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon (Fe (1) /MgJ501769 (1) /Zr@NC-CF-H) catalytic electrode comprises the following steps: (1) Pretreating carbon felt: immersing the carbon felt in the mixed solution of absolute ethyl alcohol and acetone according to the volume ratio of 1:1 for 48 hours and dry at 60°C; then, immersing the dried carbon felt in 10% acetic acid solution, etching for 24 hours and drying at 60°C.

(2) Preparing carbon-based nitrogen catalytic electrode: firstly, weighing 2 g of chitosan and dissolving it in 10% 80 mL acetic acid solution, stirring for 24 hours to form a viscous solution, and adding ferric trichloride hexahydrate and magnesium chloride hexahydrate with the molar ratio of iron to magnesium of 1:1 (1 mm:1 mm) during the stirring process; then, transferring the viscous solution to a 100 mL reaction kettle, putting into the carbon felt obtained in step (1), and hydrothermally treating in an oven at 180°C for 12 hours; and finally, cleaning the carbon felt with deionized water and drying at 60°C.

(3) Preparing carbon-based nitrogen doped mixed crystal catalytic electrode: firstly, weighing zirconium tetrachloride and terephthalic acid with a molar ratio of 1:1 (0.68 mm:0.68 mm) and dissolving in 50 mL of N,N- dimethylformamide (DMF); then, transfering the mixed solution to a 50 mL reaction kettle, putting it into the carbon felt-based iron/magnesium/chitosan catalytic electrode obtained in step (2), and carrying out hydrothermal treatment in an oven at 120°C for 24 hours; then, washing the carbon felt with anhydrous ethanol and DMF and dried at 60°C to remove unreacted substances; finally, calcining the dried catalytic electrode at 600°C for 120 min (the heating rate is 5°C min”, and the temperature is kept for 120 min), so that the iron, magnesium and zirconium supported on the electrode surface are oxidized.

Comparative example 1 Preparing carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon (Fe (1) /Mg (1) /Zr@NC-CF-C) catalytic electrode comprises the following steps: (1) Pretreating carbon felt: same as Example 1.

(2) Preparating carbon felt-based iron/magnesium/chitosan catalytic electrode: same as Example 1.

(3) Preparing carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrode: firstly, calcining the carbon felt-based iron/magnesium/chitosan catalytic electrode obtained in step (2) at 600°C for 120 min (the heating rate is 5°C min’, and the temperature i§)501769 kept for 120 min), so that the iron and magnesium loaded on the electrode surface are oxidized, then, weighing zirconium tetrachloride and terephthalic acid in the molar ratio of 1: 1 and dissolving them in 50 mL of N,N- dimethylformamide (DMF); then, transferring the mixed solution to a 50 mL reaction kettle, putting it into the calcined catalytic electrode, and carrying out hydrothermal treatment in an oven at 120°C for 24 hours; finally, washing the carbon felt with anhydrous ethanol and DMF and drying at 60°C to remove unreacted substances.

Comparative example 2 Preparing carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon (Fe (1) /Mg (2) /Zr@NC-CF-C) catalytic electrode comprises the following steps: (1) Pretreatment of carbon felt: same as Example 1.

(2) Preparation of carbon felt-based iron/magnesium/chitosan catalytic electrode: refer to Example 1, which is different from Example 1 in that ferric trichloride hexahydrate and magnesium chloride hexahydrate with the molar ratio of iron to magnesium of 1:2 (1 mm:2 mm) are added during stirring.

(3) Preparation of carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrode: same comparative example 1.

Comparative example 3 Preparation of carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon (Fe (1) /Mg (2) /Zr@NC-CF-H) catalytic electrode comprises the following steps: (1) Pretreatment of carbon felt: same as Example 1.

(2) Preparation of carbon felt-based iron/magnesium/chitosan catalytic electrode: same comparative example 2.

(3) Preparation of carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrode: same as Example 1.

Test 1 The catalytic electrodes obtained in Example 1 and Comparative Examples 1-3 are examined for redox.

The oxidation-reduction test of catalytic electrode is carried out by cyclic voltammetry at a scanning speed of 0.01 V/s, and the catalytic electrodes containing different catalysts are characterized by cyclic voltammetry in 1 mol L™! sodium sulfate solution. The results are shovk#/501 769 in Figure 1. As can be seen from Figure 1, the cyclic voltammetric curve has obvious redox peak, which shows that the catalyst can obviously promote the redox reaction of the electrode.

Test 2 The Fe (1) /Mg (1) /Zr@NC-CF-H catalytic electrode obtained in Example 1 is tested for its performance in treating radioactive wastewater.

The structure of dual-chamber MFC is mainly composed of anode chamber, cathode chamber and proton exchange membrane (PEM) separating the two polar chambers. In this double-chamber MFC, the iron anode is the main anode, and the graphite particles inoculated with Shiva dynamoelectric bacteria and activated carbon particles (mass ratio of 1:1) are the auxiliary anodes, which constitute the composite anode of MFC. While the carbon felt-based Fe/Mg/Zr/N doped carbon catalytic electrode Fe (1) /Mg (1) /Zr@NC-CF-H is used as the cathode of MFC, and the anode and cathode are connected by titanium wire and external resistor to form a complete loop. After the system is assembled, 100 mg L! COD of simulated wastewater is prepared and added into the anode chamber to provide the organic matter needed by the electricity-producing microorganisms for their own metabolism. Then, preparing a solution containing 1 g L! cobalt, strontium, cesium, lanthanum and cerium ions as nuclear wastewater, diluting it to different concentrations (5 mg L!, 10 mg L“ and 20 mg L* respectively) and adding it into the cathode chamber, and testing the performance of the system in treating cerium ions. The results are shown in Figure 2. It can be seen that the carbon felt-based iron/magnesium/zirconium/nitrogen doped carbon catalytic electrode of the invention can effectively reduce cerium ions and basically realize the complete removal of cerium.

Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that many changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

CLAIMS LU501769

1. À carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof, characterized by comprising the following steps: (1) pretreating carbon felt: removing impurities attached to the carbon felt, drying, and etching the dried carbon felt; (2) preparing carbon-based nitrogen doped catalytic electrode: using the carbon felt pretreated in step (1) as raw material, loading iron, magnesium and chitosan on the surface of the carbon felt obtained in step (1) by hydrothermal method; (3) preparing carbon-based nitrogen doped mixed crystal catalytic electrode: using the carbon felt-based iron/magnesium/nitrogen doped carbon catalytic electrode obtained in step (2) as raw material, loading the metal-organic framework structure of zirconium on the surface of the carbon felt obtained in step (2) by hydrothermal method; then, oxidizing iron, magnesium and zirconium by calcination.

2. The carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof according to claim 1, characterized in that in step (1), the steps of removing impurities attached to the carbon felt are as follows: immersing the carbon felt in the mixed solution of absolute ethyl alcohol and acetone for 24-48 hours, wherein the mass ratio of absolute ethyl alcohol to acetone is 1:2-2:1, and dry at 60-100°C.

3. The carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof according to claim 1, characterized in that in step (1), the steps of etching are as follows: immersing the dried carbon felt in dilute acid, etching for 12-24 hours and drying at 60-100°C to generate the attachment site of the catalyst.

4. The carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof according to claim 1, characterized in that in step (2), the steps of loading iron, magnesium and chitosan on the surface of carbon felt obtained in step (1) by hydrothermal method are as follows: firstly, dissolving chitosan in dilute acid, stirring for 12-24 hours to form a viscous solution, adding ferric trichloride hexahydrate and magnesium chloride hexahydrate in stirring, wherein the mass ratio of chitosan, dilute acid, ferric trichloride hexahydrate and magnesium chloride hexahydrate is (18-20): (826-828): (2-4): (1-2); then, transferring the viscous solution to a reaction kettle, putting the carbon felt obtained in step (1), carrying out hydrothermal treatment in an oven at 180°C for 12 hours, and finally, cleaning the carbon félU501769 with deionized water and drying it at 60-100°C.

5. The carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof according to claim 1, characterized in that in step (3), the steps of loading zirconium metal-organic frame structure on the surface of carbon felt obtained in step (2) by hydrothermal method are as follows: firstly, dissolving zirconium tetrachloride and terephthalic acid in N,N-dimethylformamide, wherein the mass ratio of zirconium tetrachloride, terephthalic acid and N,N- dimethylformamide is (2-4):(1-2):(836-838); then, transferring the mixed solution to a reaction kettle, putting the carbon felt-based iron/magnesium/chitosan catalytic electrode obtained in step (2), and carrying out hydrothermal treatment in an oven at 120°C for 24 hours; finally, washing the carbon felt with absolute ethyl alcohol and DMF and drying at 60-100°C to remove unreacted substances.

6. The carbon-based nitrogen doped mixed crystal catalytic electrode and preparation method thereof according to claim 1, characterized in that in step (3), the steps of oxidizing iron, magnesium and zirconium by calcination are as follows: controlling the heating rate at 5 °C min”, and calcining at 600°C for 120 min.

7. The carbon-based nitrogen doped mixed crystal catalytic electrode prepared by the preparation method of the carbon-based nitrogen doped mixed crystal catalytic electrode according to any one of claims 1-6.

8. An application of the carbon-based nitrogen doped mixed crystal catalytic electrode according to claim 7 in treating nuclear wastewater.