Determination Of COD And Reaction Kinetics Of Al/SnO₂-TiO₂ Electrode

In this paper,an Al/SnO2-TiO2 electrode was prepared by sol-gel method.The optimal conditions for electrode preparation and the optimal range of measured parameters were discussed.A three-electrode system was used to detemine COD by electrochemical method,and the surface dynamic behavior of the electrode during electrocatalytic oxidation was studied.Seven different organic solutions were selected and the instantaneous current value was measured by the chronoelectric method under different operating voltages.The recorded data was found to have a COD value proportional to the anodization current I in the linear range of 20 to 100 mg/L.The COD concentration is the same,and the oxidation currents of different organic substances are different,indicating that the electrocatalytic kinetic behavior of organic substances on the electrode surface is different.In order to further determine the linear relationship between the COD concentration of the organic compound solution and the oxidation current,we performed the analysis of the COD concentration and oxidation current of the two-component and three-component mixed solution.The conclusions reached are consistent with the single component.In order to explore the macroscopic kinetics of organic matter on the electrode surface,the kinetic catalytic mechanism was studied.The methylene blue and rhodamine B were selected as the target pollutants,and the Al/SnO2-TiO2 composite electrode was used as the working electrode.The three-electrode system was used to carry out the catalytic degradation of the target.The ln(C0/Ct)-t curve was found and found to have a good linear relationship with a correlation coefficient above 0.99.Therefore,the electrocatalytic reaction of organic compounds on the surface of Al/SnO2-TiO2 electrodes is a first-order kinetic reaction.The activation energy Ea of the electrode reaction of different organic compounds was calculated by the reaction rate constant k at no temperature,the methylene blue was 9.92 kJ/mol,and the rhodamine B was 14.7 kJ/mol.The magnitude of the activation energy reflects the difficulty of the catalysis.Explain that the dynamic behavior of different organic substances on the electrode surface is different.In addition,the experiment was repeated by simulating wastewater with potassium hydrogen phthalate.The correlation coefficient is very high,indicating a high degree of consistency between the electrochemical COD test method and the values obtained by the standard COD test method,and the Al/SnO2-TiO2 composite electrode test system has good reproducibility and stability.