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CN-121449172-B - Co3O4Application of Ti composite electrode in electrolytic removal of nitrate nitrogen in water

CN121449172BCN 121449172 BCN121449172 BCN 121449172BCN-121449172-B

Abstract

The invention discloses an application of a Co 3 O 4 -Ti composite electrode in removing nitrate nitrogen in water by electrolysis, belonging to the technical field of sewage electrochemical treatment. In the application, an electrolytic reactor is used for electrolysis, the cathode of the electrolytic reactor is a Co 3 O 4 -Ti composite electrode, the current density of electrolysis is 45 mA/cm 2 ~55 mA/cm 2 , and the pH value of electrolyte in the electrolytic reactor is 5-6. The application of the Co 3 O 4 -Ti composite electrode in the electrolytic removal of nitrate nitrogen in water provided by the invention obviously improves the cyclic stability of the Co 3 O 4 -Ti composite electrode in the removal of nitrate nitrogen on the basis of ensuring the high removal rate of the nitrate nitrogen by improving the preparation method of the Co 3 O 4 -Ti composite electrode and cooperatively optimizing the application conditions.

Inventors

  • SU TING
  • WANG KUI
  • NIU CHAO
  • GAO WENWEN
  • LU CUIYING
  • GAO PINGQIANG

Assignees

  • 榆林学院
  • 陕西瑞必昂特环保科技有限公司

Dates

Publication Date
20260508
Application Date
20260106

Claims (10)

  1. 1. The application of the Co 3 O 4 -Ti composite electrode in removing nitrate nitrogen in water by electrolysis is characterized in that the cathode of the electrolysis reactor is the Co 3 O 4 -Ti composite electrode, the current density of electrolysis is 45 mA/cm 2 ~55 mA/cm 2 , the pH of electrolyte in the electrolysis reactor is 5-6, and the temperature of electrolysis is 25-35 ℃; The preparation method of the Co 3 O 4 -Ti composite electrode comprises the following steps: s1, putting a titanium sheet into etching solution for etching, and drying for later use after the etching is finished; s2, dissolving cobalt nitrate in an alcohol solvent to obtain an electrode solution; s3, dipping the electrode liquid prepared in the step S2, uniformly coating the electrode liquid on the surfaces of the two sides of the titanium sheet to be used in the step S1, and then drying; s4, repeating the operation of the step S3 for 2-4 times, and calcining at 300-600 ℃ for 3-7 min; s5, repeating the operation of the step S4 until the electrode liquid prepared in the step S2 is completely coated; And S6, calcining the coated titanium sheet at 300-600 ℃ for 2.5-3.5 hours, and cooling to room temperature to obtain the Co 3 O 4 -Ti composite electrode.
  2. 2. The use of the Co 3 O 4 -Ti composite electrode according to claim 1 for the electrolytic removal of nitrate nitrogen from water, wherein the difference between the temperatures of calcination in S4 and S6 is 50 ℃ or less.
  3. 3. The application of the Co 3 O 4 -Ti composite electrode in removing nitrate nitrogen in water by electrolysis according to claim 1, wherein the volume area ratio of the electrode liquid in the S2 to the titanium sheet is 1mL (0.8 cm 2 ~2cm 2 ), the concentration of cobalt nitrate in the electrode liquid is 0.1-0.3 mol/L, and the alcohol solvent is one or more selected from methanol, ethanol, propanol and butanol.
  4. 4. The application of the Co 3 O 4 -Ti composite electrode according to claim 1 in removing nitrate nitrogen in water by electrolysis, wherein the drying temperature in S3 is 60-80 ℃.
  5. 5. The application of the Co 3 O 4 -Ti composite electrode according to claim 1 in removing nitrate nitrogen in water by electrolysis, wherein the etching liquid in S1 is one or more selected from oxalic acid solution, hydrochloric acid solution, sulfuric acid solution, sodium hydroxide solution and potassium hydroxide solution, the mass percentage of the etching liquid is 10% -30%, and the etching temperature is 70 ℃ -90 ℃.
  6. 6. The application of the Co 3 O 4 -Ti composite electrode in removing nitrate nitrogen in water by electrolysis according to claim 1, wherein the pretreatment step is further included before the step S1, and comprises the steps of polishing a titanium sheet, putting an oxalic acid solution with the mass percent of 10% -30%, boiling for 20% -40 min, and cleaning.
  7. 7. The application of the Co 3 O 4 -Ti composite electrode according to claim 1 in removing nitrate nitrogen in water by electrolysis, wherein the mass concentration of the nitrate nitrogen is 15 mg/L-20 mg/L.
  8. 8. The use of Co 3 O 4 -Ti composite electrode according to claim 1 for the electrolytic removal of nitrate nitrogen in water, wherein the nitrate nitrogen comprises one or more of trinitrophenol, potassium nitrate, p-nitrophenol, o-nitrophenol.
  9. 9. The application of the Co 3 O 4 -Ti composite electrode in removing nitrate nitrogen in water by electrolysis according to claim 1, wherein the anode of the electrolytic reactor is a ruthenium iridium titanium electrode, and the electrode spacing between the cathode and the anode is 10-30 mm.
  10. 10. The preparation method of the Co 3 O 4 -Ti composite electrode is characterized by comprising the following steps of: s1, putting a titanium sheet into etching solution for etching, and drying for later use after the etching is finished; s2, dissolving cobalt nitrate in an alcohol solvent to obtain an electrode solution; s3, dipping the electrode liquid prepared in the step S2, uniformly coating the electrode liquid on the surfaces of the two sides of the titanium sheet to be used in the step S1, and then drying; s4, repeating the operation of the step S3 for 2-4 times, and calcining at 300-600 ℃ for 3-7 min; s5, repeating the operation of the step S4 until the electrode liquid prepared in the step S2 is completely coated; And S6, calcining the coated titanium sheet at 300-600 ℃ for 2.5-3.5 hours, and cooling to room temperature to obtain the Co 3 O 4 -Ti composite electrode.

Description

Application of Co 3O4 -Ti composite electrode in electrolytic removal of nitrate nitrogen in water Technical Field The invention belongs to the technical field of sewage electrochemical treatment, and particularly relates to application of a Co 3O4 -Ti composite electrode in electrolytic removal of nitrate nitrogen in water. Background With the rapid development of industry and agriculture, nitrate has become a common contaminant in surface and ground water. Nitrate itself is harmless, but is readily reduced to toxic nitrite by microorganisms in the human digestive system. Therefore, the removal of nitrate from drinking water and wastewater treatment is of paramount importance. In recent years, electrochemical reduction technology has been attracting attention because electrons can be used as a cleaning reducer to directly convert nitrate nitrogen, and the core research focuses on developing high-activity and high-selectivity non-noble metal cathode materials, such as cobalt, copper, silver and other catalysts, aiming at directionally converting nitrate nitrogen into harmless nitrogen instead of byproduct ammonium salt by regulating and controlling the electrode interface electronic structure and reaction path, and overcoming the problems of incomplete treatment, low removal rate, secondary pollution and the like in the traditional technology, and becomes an important development direction in the field. Cobalt is a functional material having a unique spinel structure and mixed valence state, and is receiving attention due to its excellent redox properties, stable electrochemical activity, and relatively low cost. The Co 3O4 -Ti coated electrode prepared from cobalt has good effect on removing inorganic nitrogen and organic nitrogen in electrochemical cathode reduction. The prior art with publication number CN110980888A discloses a preparation method of a Ti/Co 3O4 coating electrode, which has the advantages of simplicity, stable structure and high treatment efficiency on nondegradable organic wastewater. However, the preparation method adopts the traditional hydrothermal preparation process, the Co 3O4 -Ti coating formed on the surface of the titanium substrate is in a flaky loose structure, the binding force between an active component and a matrix is weak, and the active substance is easy to erode and fall off in the electrochemical circulation process, so that the stability of the electrode is obviously insufficient. Meanwhile, the active sites are unevenly distributed due to the non-uniformity of the hydrothermal reaction system, so that the removal rate of the refractory organic pollution can only reach 76.85%, and the byproduct nitrite accumulation phenomenon is serious. In order to solve the above problems, the laboratory publication "optimized preparation of Co 3O4 -Ti electrode and study on treatment of wastewater containing nitrophenol" (fresh in Bozhou [ D ]. Ulmin college, 2024.DOI: 10.44520/d.cnki.gyxy.2024.000002 ]) provides a preparation method of Co 3O4 -Ti electrode, and the removal rate of Co 3O4 -Ti electrode obtained by the preparation method to Total Nitrogen (TN) can reach 87.56%, but the stability of Co 3O4 -Ti electrode still needs to be improved, for example, the removal rate of nitrate nitrogen is reduced from 81.5% to 70% after 4 times of circulation, and is reduced to 60% after 5 times of circulation, which is probably due to the dissolution and peeling of Co 3O4 -Ti coating formed by coating on the surface of titanium substrate under acidic condition. The pH of the electrolyte is increased, the cycle performance is not obviously improved, and the removal rate of nitrate nitrogen is seriously reduced, for example, when the pH is 5, the removal rate of nitrate nitrogen is only 52%. And the laboratory finds that the removal rate of the Co 3O4 -Ti electrode to nitrate nitrogen is obviously different in summer and winter in subsequent researches. Therefore, on the basis of ensuring the high removal rate of the paranitronitrogen, how to improve the stability of the Co 3O4 -Ti electrode in removing the nitronitrogen in water by electrolysis is a technical problem to be solved. Disclosure of Invention 1. Problems to be solved Based on the technical problems, the first object of the invention is to provide a preparation method of a Co 3O4 -Ti composite electrode, wherein a Co 3O4 coating with compact structure and firm combination is successfully constructed on the surface of a substrate titanium sheet through repeated coating, predrying and precalcining processes for a plurality of times, and active components Co are uniformly distributed on the surface of the substrate titanium sheet; The second purpose of the invention is to provide the application of the Co 3O4 -Ti composite electrode in removing nitrate nitrogen in water by electrolysis, and the cycling stability of the Co 3O4 -Ti composite electrode in removing nitrate nitrogen by electrolysis is improved by controlling the tempera