Research On Determination Of COD With Al/TiO₂Film Electrode

COD is a dominant index for water pollution. To monitoring pollutant sources on-site and on-line is of great significance in pollution control and prevention. Being fast, simple and apt to achieve automation, thin film electrode method is promising method for on-line COD monitor. Possessing special chemical and optical performances, TiO2is attractive in waste water treatment and monitor.In the present thesis, sol-gel method was applied to prepare Al/TiO2thin film electrode. Based on catalytically electrical oxidation activity to potassium hydrogen phthalate, conditions for preparing Al/TiO2thin film electrode were determined, i.e., three dip-coatings, calcination temperature being500℃, calcination time being60min. The Al/TiO2thin film electrode was used in measuring COD values of standard potassium hydrogen phthalate solutions. The oxidation currents was linear with COD values, and the correlation coefficients were higher than0.99.CODs of seven water samples were measured by thin film electrode method. For the same samples, ratios of national standard method measured CODs to electrode method measured CODs were identical, while those for different samples were unlike.Water sample1#(brewing waste water) and water sample2#(domestic waste water) were diluted for4,6,8and10time, respectively. CODs of these diluted samples were measures by national standard method and Al/TiO2thin film electrode method, respectively. Similarity coefficients for the two investigated methods were lager than0.99, indicating that there was no significance difference between the two methods. For water sample3#to water sample7#,5parallel COD determinations by two methods were carried out for each sample. F-test was applied to check the difference between the two methods. The F-test showed that, on0.95confidence level, there was no significance difference between the two methods.Al/TiO2thin film electrode was used in measuring CODs of actual waste water samples, and the results were compared with CODs determined by national standard method. It showed that there was no significance difference between the two methods. In conclusion, Al/TiO2thin film method may be an alternate method to national standard method.