A surface-fluorinated-TiO2–KMnO4 photocatalytic system for determination of chemical oxygen demand

A new method for chemical oxygen demand (COD) determination has been developed, based on photocatalytic oxidative degradation by using a fluorinated-TiO2–KMnO4 system. In such a system, a linear correlation is observed between the amount of oxidizable dissolved organic matter and the amount of MnO4− consumed by the coupled reduction process. Thus, the COD determination is transformed to a simple and direct determination of the deletion of MnO4−. The surface fluorination of TiO2 nanoparticles can enhance the rate of photocatalytic oxidation of organic matter and the rate of coupled photocatalytic reduction of MnO4−. This makes the method be rapid, environment friendly and easy for operation. Under optimized conditions, this method can respond linearly to COD of potassium hydrogen phthalate (KHP) in the range of 0.1–280 mg L−1, with a detection limit of 0.02 mg L−1 COD. The COD in samples of tap water, lake water and paper industry sewage has been determined satisfactorily by using this method.