Abstract: A new photocatalytic method for the determination of chemical oxygen demand(COD) using nano ZnO-KMnO₄ co-existed system is described. The measuring principle is based on the fact that KMnO₄ acts as an acceptor of photogenerated electrons and then increases the rate of photocatalytic oxidation of organic compounds. The optimized operation conditions were selected and the photocatalytic oxidation mechanism was discussed. It is indicated that this method has mild operation conditions, it won′t cause secondary pollution, and can realize rapid and accurate determination of COD of surface water and drinking water. The application range is 1.5—10 mg/L and the lowest detection limit is 0.5 mg/L. The method was also applied to determining COD of real water samples. The results were in good agreement with those from the conventional methods(permanganate index method).

Key words: Chemical oxygen demand(COD), Photocatalytic oxidation, Nano-ZnO