A cerium modified electrochemical catalyst suitable for use in high salt environments, and methods of making and using the same

Abstract

A cerium modified electrochemical catalyst suitable for a high salt environment, a preparation method and application thereof, comprising the following steps: (1) dissolving melamine, metal salt and citric acid in deionized water according to a mass ratio to form an A solution; (2) mixing beta-cyclodextrin, water and ethanol to form a B solution; (3) stirring the A solution, then adding the B solution dropwise into the A solution and stirring; (4) drying the AB mixed solution to obtain a dry powder; (5) calcining the dry powder under inert gas protection; (6) drying the obtained material after acid washing, alcohol washing and deionized water washing, to obtain an M@NCNTs-beta material. The M@NCNTs-beta material prepared by the application solves the agglomeration of carbon nanotubes, forms a composite shell structure, realizes "carbon double sealing" of metal elements, strengthens the performance of the catalyst, and promotes the stability of the catalyst in a high salt environment.

Description

Technical Field

[0001] This invention relates to the field of high-salt organic wastewater treatment, specifically to a cerium-modified electrochemical catalyst suitable for high-salt environments, its preparation method, and its application. Background Technology

[0002] High-salinity wastewater from industries such as chemical, pharmaceutical, petroleum, and food processing, containing various recalcitrant organic pollutants, has become a challenge in industrial wastewater treatment. In reality, high-salinity wastewater not only has a high salt content but also contains recalcitrant organic pollutants such as antibiotics, polycyclic aromatic hydrocarbons (PAHs), and dyes. With increasing demands for ecological protection, recalcitrant organic pollutants that pose serious health risks have attracted widespread global attention.

[0003] Bioelectrochemical technology, characterized by high degradation efficiency, no secondary pollution, and real-time adaptability, has gained popularity among researchers in recent years. However, high salt concentrations not only severely inhibit the metabolic activity and growth of anodic microorganisms but also corrode the electrodes. In bioelectrochemistry, cathodic electrochemical reactions are the catalysts for achieving cyclic reactions between the cathode and anode, enhancing the performance of anodic microorganisms. Therefore, developing a highly efficient and salt-resistant cathode catalyst is of great significance. However, in high-salt environments, the cathode electrode is easily deactivated. Therefore, designing a structure that protects the active sites of the catalyst and a catalyst capable of addressing the problem of rapid deactivation of these active sites is crucial. Summary of the Invention

[0004] Technical problem solved: Based on the practical problems of easy cathode deactivation, low catalytic performance and poor stability in the application of electrochemical or bioelectrochemical technologies in high-salt environments, this invention proposes a cerium-modified electrochemical catalyst suitable for high-salt environments, its preparation method and application.

[0005] Technical solution: A method for preparing cerium-modified electrochemical catalyst suitable for high-salt environments, comprising the following steps: (1) dissolving melamine, metal salt, and citric acid in deionized water at a mass ratio of (10-50):(1-10):(1-15) to form solution A; (2) mixing β-cyclodextrin, water, and ethanol at a mass ratio of (5-20):(2-5):(2-30) to form solution B; (3) adding solution B dropwise to solution A and stirring, wherein the volume ratio of solution A to solution B is (1-5):(1-3); (4) drying the mixed solution obtained in the previous step to obtain dry powder; (5) calcining the dry powder under nitrogen or inert gas protection; (6) drying the obtained material after acid washing, alcohol washing, and deionized water washing to obtain M@NCNTs-β material.

[0006] The metal salts mentioned above are at least two of cerium nitrate, ferric nitrate, and cobalt nitrate, with cerium nitrate being a fixed addition; the molar ratio of cerium nitrate to ferric nitrate or cobalt nitrate is (0.3-0.6):(1-1.5); there is no limit to the proportion of ferric nitrate or cobalt nitrate.

[0007] The mass ratio of the above-mentioned β-cyclodextrin, water and ethanol is 15:5:30.

[0008] The volume ratio of solution A to solution B is 5:3.

[0009] The drying temperature of the mixed solution in step (4) above is 50-80℃.

[0010] The roasting temperature is 700-900℃ and the roasting time is 1-3h.

[0011] The above method yields cerium-modified electrochemical M@NCNTs-β materials suitable for high-salt environments.

[0012] The above-mentioned cerium-modified electrochemical catalyst M@NCNTs-β material, suitable for high-salt environments, is used in the field of bioelectrochemistry for the treatment of high-salt organic wastewater.

[0013] The catalyst described above is used to remove total organic carbon and new pollutants from high-salt organic wastewater with a salinity of 1 wt.% to 4 wt.% and new pollutants being antibiotics or polycyclic aromatic hydrocarbons.

[0014] Beneficial effects: 1) The cerium-modified electrochemical catalyst prepared in this invention, suitable for high-salt environments, has a structure in which nitrogen-doped carbon nanotubes encapsulate multi-metal oxides. Furthermore, the β-cyclodextrin encapsulation effect alleviates the aggregation of carbon nanotubes, forming a "carbon double-encapsulation structure"; 2) The encapsulation effect of nitrogen-doped carbon nanotubes and the β-cyclodextrin encapsulation effect alleviate the leaching and passivation of metal oxides in high-salt environments, protecting the catalyst's activity. The addition of Ce further enhances the catalyst's stability in high-salt environments; 3) The composite incorporation of Ce enhances the electron transfer rate in the catalytic process, improves the stability of catalytic active sites, and enriches the catalyst's activity. 4) By controlling the amount of Ce added, this invention forms a structure in which Ce is partially encapsulated within carbon nanotubes and partially exposed and dispersed outside the carbon nanotubes. The Ce element encapsulated within the carbon nanotubes can interact with Co or Fe elements, increasing the content of active sites on the catalyst and promoting the stability of active sites in a high-salt environment. The Ce element exposed and dispersed outside the carbon nanotubes can alleviate or inhibit the invasion of chloride ions on active metal oxides from the outside. 5) The introduction of Ce element causes microcracks to be generated on the surface of carbon nanotubes while maintaining their own nanotube physical structure, providing abundant electron transport channels and improving the catalytic performance of the catalyst. Attached Figure Description

[0015] Figure 1 Catalyst morphology and structure diagram;

[0016] Figure 2 Degradation rates and COD removal rates of novel pollutants norfloxacin and phenanthrene in high-salt organic wastewater; Norfloxacin: Concentration of norfloxacin was determined by high-performance liquid chromatography (HPLC). Test conditions: column temperature 40℃, UV wavelength 205nm. Phenanthrene: Concentration of phenanthrene was determined by HPLC. Acetonitrile:water = 75%:25%, column temperature 30℃, UV wavelength 254nm. COD: Potassium dichromate method;

[0017] Figure 3 Power density of bioelectrochemical systems in high-salt organic wastewater environments under different cathode catalysts. Detailed Implementation

[0018] Example 1

[0019] The steps for preparing the cathode catalyst are as follows:

[0020] (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of 10:1:1 to form solution A;

[0021] (2) Mix β-cyclodextrin, water and ethanol in a mass ratio of 5:2:2 to form solution B;

[0022] (3) After stirring solution A for 6 hours, add solution B dropwise to solution A at a volume ratio of 1:1 and stir for 2 hours. Then dry at 50°C to obtain dry powder.

[0023] (4) The dry powder was roasted at 700℃ for 3 hours under N2 protection;

[0024] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain M@NCNTs-β material.

[0025] The metal salts are cerium nitrate and ferric nitrate, with a molar ratio of 0.3:1.

[0026] The prepared FeCe@NCNTs cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0027] Example 2

[0028] The steps for preparing the cathode catalyst are as follows:

[0029] (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of 25:3:4 to form solution A;

[0030] (2) Mix β-cyclodextrin, water and ethanol in a mass ratio of 10:5:15 to form solution B;

[0031] (3) After stirring solution A for 8 hours, add solution B dropwise to solution A at a volume ratio of 2:1 and stir for 3 hours. Then dry at 60°C to obtain dry powder.

[0032] (4) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0033] (5) The obtained material was washed with acid, alcohol and deionized water and then dried to obtain M@NCNTs-β material.

[0034] The metal salts are cerium nitrate and cobalt nitrate, with a molar ratio of 0.5:1.

[0035] The prepared CoCe@NCNTs cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0036] Example 3

[0037] The steps for preparing the cathode catalyst are as follows:

[0038] (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of 50:10:15 to form solution A;

[0039] (2) Mix β-cyclodextrin, water and ethanol in a mass ratio of 20:5:30 to form solution B;

[0040] (3) After stirring solution A for 12 hours, solution B is added dropwise to solution A at a volume ratio of 3:2 and stirred for 4 hours. Then, the solution is dried at 80°C to obtain dry powder.

[0041] (4) The dry powder was calcined at 900℃ for 1 hour under argon protection;

[0042] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain M@NCNTs-β material.

[0043] The metal salts are cerium nitrate, cobalt nitrate, and ferric nitrate, with a molar ratio of cerium nitrate to (cobalt nitrate + ferric nitrate) of 0.6:1.5.

[0044] The prepared CoFeCe@NCNTs cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0045] Example 4

[0046] The steps for preparing the cathode catalyst are as follows:

[0047] (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of 25:3:4 to form solution A;

[0048] (2) Mix β-cyclodextrin, water and ethanol in a mass ratio of 15:5:30 to form solution B;

[0049] (3) After stirring solution A for 8 hours, solution B is added dropwise to solution A at a volume ratio of 5:3 and stirred for 3 hours. Then, the solution is dried at 60°C to obtain dry powder.

[0050] (4) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0051] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain M@NCNTs-β material.

[0052] The metal salts are cerium nitrate, cobalt nitrate, and ferric nitrate, with a molar ratio of cerium nitrate to (cobalt nitrate + ferric nitrate) of 0.5:1.

[0053] The prepared CoCe@NCNTs cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0054] Control Experiment 1

[0055] The steps for preparing the cathode catalyst are as follows:

[0056] (1) Melamine and citric acid are dissolved in deionized water at a mass ratio of 25:4 to form solution A;

[0057] (2) Mix β-cyclodextrin, water and ethanol in a mass ratio of 20:5:30 to form solution B;

[0058] (3) After stirring solution A for 8 hours, solution B is added dropwise to solution A at a volume ratio of 5:3 and stirred for 3 hours. Then, the solution is dried at 60°C to obtain dry powder.

[0059] (4) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0060] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively and then dried to obtain NC-β material.

[0061] The prepared NC-β cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0062] Control Experiment 2

[0063] The steps for preparing the cathode catalyst are as follows:

[0064] (1) Melamine and citric acid are dissolved in deionized water at a mass ratio of 25:4 to form solution A;

[0065] (2) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0066] (3) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0067] (4) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain NC material.

[0068] The prepared NC cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0069] Control Experiment 3

[0070] The steps for preparing the cathode catalyst are as follows:

[0071] (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of 25:3:4 to form solution A;

[0072] (3) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0073] (4) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0074] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively and then dried to obtain M@NCNTs material.

[0075] The metal salts are cerium nitrate, cobalt nitrate, and ferric nitrate, with a molar ratio of cerium nitrate to (cobalt nitrate + ferric nitrate) of 0.5:1.

[0076] The prepared FeCoCe@NCNTs cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0077] Control Experiment 4

[0078] The steps for preparing the cathode catalyst are as follows:

[0079] (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of 25:3:4 to form solution A;

[0080] (3) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0081] (4) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0082] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively and then dried to obtain M@NCNTs material.

[0083] The metal salts are ferric nitrate and cobalt nitrate, with a molar ratio of ferric nitrate to cobalt nitrate of 0.5:1.

[0084] The prepared CoFe@NCNTs cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0085] Control Experiment 5

[0086] The steps for preparing the cathode catalyst are as follows:

[0087] (1) Dissolve cerium nitrate and cobalt nitrate in deionized water at a molar ratio of 0.5:1 to form solution A;

[0088] (2) Mix β-cyclodextrin, water and ethanol in a mass ratio of 20:5:30 to form solution B;

[0089] (3) After stirring solution A for 8 hours, solution B is added dropwise to solution A at a volume ratio of 5:3 and stirred for 3 hours. Then, the solution is dried at 60°C to obtain dry powder.

[0090] (4) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0091] (5) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain M@NCNTs-β material.

[0092] The prepared CoCe@NCNTs-β cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0093] Control Experiment 6

[0094] The steps for preparing the cathode catalyst are as follows:

[0095] (1) Dissolve ferric nitrate and cobalt nitrate in deionized water at a molar ratio of 0.5:1 to form solution A;

[0096] (2) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0097] (3) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0098] (4) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain FeCo material.

[0099] The prepared FeCo cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0100] Control Experiment 7

[0101] The steps for preparing the cathode catalyst are as follows:

[0102] (1) Dissolve cerium nitrate and ferric nitrate in deionized water at a molar ratio of 0.5:1 to form solution A;

[0103] (2) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0104] (3) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0105] (4) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain FeCe material.

[0106] The prepared FeCe cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0107] Control Experiment 8

[0108] The steps for preparing the cathode catalyst are as follows:

[0109] (1) Dissolve cerium nitrate and cobalt nitrate in deionized water at a molar ratio of 0.5:1 to form solution A;

[0110] (2) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0111] (3) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0112] (4) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain CoCe material.

[0113] The prepared CoCe cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0114] Control Experiment 9

[0115] The steps for preparing the cathode catalyst are as follows:

[0116] (1) Dissolve cerium nitrate and (ferric nitrate + cobalt nitrate) in deionized water at a molar ratio of 0.5:1 to form solution A;

[0117] (2) After stirring solution A for 8 hours, dry it at 60°C to obtain dry powder;

[0118] (3) The dry powder was roasted at 800℃ for 2 hours under N2 protection;

[0119] (4) The obtained material was acid-washed, alcohol-washed and deionized water-washed respectively, and then dried to obtain FeCoCe material.

[0120] The prepared FeCoCe cathode catalyst was applied to a bioelectrochemical system to treat high-salt organic wastewater with a salinity of 3.5%, a carbon source of 1 g / L glucose, and new pollutants of 10 mg / L norfloxacin antibiotic and 0.5 mg / L polycyclic aromatic hydrocarbon phenanthrene.

[0121] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. For those skilled in the art, after learning the contents described in the present invention, several equivalent changes and substitutions can be made without departing from the principle of the present invention. These equivalent changes and substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A method for preparing a cerium-modified electrochemical catalyst suitable for high-salt environments, characterized in that, The steps are as follows: (1) Melamine, metal salt and citric acid are dissolved in deionized water in a mass ratio of (10-50):(1-10):(1-15) to form solution A; (2) β-cyclodextrin, water and ethanol are mixed in a mass ratio of (5-20):(2-5):(2-30) to form solution B; (3) Solution B is added dropwise to solution A and stirred, and the volume ratio of solution A to solution B is (1-5):(1-3); (4) The mixed solution obtained in the previous step is dried to obtain dry powder; (5) The dry powder is calcined under nitrogen or inert gas protection; (6) The obtained material is dried after being washed with acid, alcohol and deionized water respectively to obtain M@NCNTs-β material.

2. The method for preparing cerium-modified electrochemical catalysts suitable for high-salt environments according to claim 1, characterized in that, The metal salt is at least two of cerium nitrate, ferric nitrate, and cobalt nitrate, with cerium nitrate being a fixed addition; the molar ratio of cerium nitrate to ferric nitrate or cobalt nitrate is (0.3-0.6):(1-1.5); there is no limit to the proportion of ferric nitrate or cobalt nitrate.

3. The method for preparing cerium-modified electrochemical catalysts suitable for high-salt environments according to claim 1, characterized in that, The mass ratio of β-cyclodextrin, water, and ethanol is 15:5:

30.

4. The method for preparing cerium-modified electrochemical catalysts suitable for high-salt environments according to claim 1, characterized in that, The volume ratio of solution A to solution B is 5:

3.

5. The method for preparing cerium-modified electrochemical catalysts suitable for high-salt environments according to claim 1, characterized in that, The drying temperature of the mixed solution in step (4) is 50-80℃.

6. The method for preparing cerium-modified electrochemical catalyst suitable for high-salt environments according to claim 1, characterized in that, The roasting temperature is 700-900℃, and the roasting time is 1-3 h.

7. Cerium-modified electrochemical M@NCNTs-β materials suitable for high-salt environments, prepared by the method described in any one of claims 1-6.

8. The application of the cerium-modified electrochemical catalyst M@NCNTs-β material, suitable for high-salt environments, as described in claim 7, in the field of bioelectrochemistry for the treatment of high-salt organic wastewater.

9. The application according to claim 8, characterized in that, The catalyst is used to remove total organic carbon and new pollutants from high-salt organic wastewater with a salinity of 1 wt.%-4 wt.% and the new pollutants being antibiotics or polycyclic aromatic hydrocarbons.

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