Rapid determination of COD in industrial wastewater by mercury-free open-tube method

A reliable, simple and safe system to determine COD rapidly by a mercury free and open tube method was established The method employs K 2Cr 2O 7 as oxidant in a medium of H 2SO 4 H 3PO 4, with catalysis by Ag 2SO 4 and with addition of AgNO 3 and CrK(SO 4) 2·12H 2O to mask chloride Samples were digested in glass tubes and heated at 165℃ for 10min in an attemperator The residual dichromate was then determined by spectrophotometry or titration The results of the tests show that the detection limit for COD was 10 9 mg/L and in the range of 30(1500mg/L of COD the detected result was satisfied The advantage of this method avoids the use of toxic mercuride that could pollute the environment The developed method has been successfully applied to determine COD in large quantities of industrial wastewater samples