Abstract
The COD is a principal water quality index to manage water environment in Japan. However, much labor and large amounts of hazardous reagents are needed to measure by the conventional method in Japan Industrial Standard (JIS). In this study, we developed an improving method of JIS CODMn by colorimetry. This method was much easy procedure and could reduce amounts of the hazardous reagents and energy consumption to one twentieth of the conventional method.
Five ml of sample water and 0.50ml of 5.0mmol·l-1 KMnO4 were put into a test tube contained sulfuric acid and silver nitrate. It was heated at 100°C for 30 minutes with block heater. Since it was found that formed Mn2+ from MnO4- was reacted with residual MnO4- to Mn02 in the ratio of 3 : 2, we determined the residual concentration of MnO4- from absorbance at 525nm after filtration of Mn02, and calculated the CODMn.
It was confirmed that CODMn values by this developed method for 60 various water samples were equal to the values by the JIS method with r=0.998. The scatter of data and the measurable concentration range of this method were nearly equal to them of the JIS method.
