Study on determination of chemical oxygen demand in water with ion chromatography

A new method for determining chemical oxygen demand (COD) value in water using ion chromatography coupled with nano TiO₂-K₂S ₂O₈ co-existing system was described. The photocatalytic oxidation system and nano TiO₂-K₂S₂O ₈ co-existing system could degrade the organic compounds in water. All sulfur-containing species in the reactive solution were eventually transformed to sulfate which could be determined by conductivity detector in ion chromatography. The change of conductivity of sulfate was proportional to COD value. The optimal experimental conditions and the mechanism of the detection were discussed. The application range was 10.0-300.0 mg·L^-1 and the lowest limit of detection was 3.5 mg·L^-1. It was considered that the value obtained could be reliably correlated with the COD value obtained using the conventional methods.