Electrochemical Determination of Chemical Oxygen Demand Using Ti/TiO₂ Electrode

摘要

To overcome the shortcomings of the conventional potassium dichromate method (PDM) formonitoring chemical oxygen demand (COD) of waters, many efforts have been made on developingquick and environment-friendly techniques. Among all alternatives, electrochemical (EC) techniquesare very competitive due to their relatively simple devices and quickness. A number of electrodes havebeen fabricated to investigate electrochemical determination of COD. However, little work has beenreported on TiO2 based electrode for this purpose. In the present work, Ti/TiO2 electrode was simplyprepared by anodic oxidation of pure titanium. Aqueous solutions of potassium hydrogen phthalate andphenol were electrolyzed by chronocoulometry in a three-electrode system with Ti/TiO2 as workingelectrode (anode). Organic compounds were electrochemically oxidized on Ti/TiO2 electrode byhydroxyl radicals and the released electrons were recorded and transferred to currents. The electriccurrents were proportional to the COD values of the water samples being investigated. Based on dataof COD values and corresponding currents, a linear regression equation was obtained for a certain kindof waste water. With the regression equation, current of an unknown water sample was transferred toits COD value. Conditions for the presented EC method were set up as cell voltage 2.0V v.s. SCE andpH 7.0. The linear range of COD was of about 25~530 mg/L. COD values of real waste water sampleswere measured by Ti/TiO2 electrode and the relative errors were all in the range of % comparedwith data determined by conventional PDM. The electrochemicalmethodology was successfullyapplied to evaluate COD in waste water..