Photocatalytic oxidation for determination of chemical oxygen demand using nano-TiO₂ film

A photocatalytic oxidation method for determination of chemical oxygen demand (COD) using nano-TiO₂ film, based on the use of a nano-TiO₂-Ce(SO₄)₂ system and electrochemical detection, was proposed. The technique was originated from the direct determination of the Ce(III) concentration change resulting from photocatalytic oxidation of organic compounds. Ce(III), which was produced by photocatalytic reduction of Ce(SO₄)₂, could be measured at a multi-walled carbon nanotubes (MWNT) chemically modified electrode (CME). The COD values by this method were calculated from the differential pulse voltammetry (DPV) current of Ce(III) at the CME. Under the optimal operation conditions, the detection limit of 0.5 mg·L^-1 COD with the linear range of 1-600 mg·L^-1 was achieved. This method was also applied to determination of various COD of ground water and wastewater samples. The results were in good agreement with those from the conventional COD methods, i.e., permanganate and dichromate ones.