Oxidation of Organics using Mn(H2PO4)2 as a Catalyst for Rapid Determination of COD of Industrial Saline Effluents

Abstract

Abstract Chemical Oxygen Demand (COD) is a water quality parameter which indicates concentration of organic compounds as oxygen equivalents in aqueous effluent samples. Determination of COD is frequently done using APHA Standard Method which requires 2 h digestion time. There is need for improving the method to reduce analysis time. In this paper, we report the comparative study for determination of COD by Standard Method using Ag2SO4 and a rapid method using Mn(H2PO4)2 as a catalyst for different industrial effluent samples having different chloride concentration. A kinetic study has been carried out by varying time interval, HgSO4 dose and catalyst dose in different concentrated H3PO4:H2SO4 acid mixture ratio. The optimum conditions for industrial sample having low chloride concentration are 0.3g Mn(H2PO4)2, per 15 ml of 1:6 H3PO4: H2SO4, 0.2gm HgSO4 and digestion time of 5 min., whereas the sample having high chloride concentration requires 0.4 g of HgSO4 and digestion time of 20 min. The results obtained from the rapid COD determination method in this study and conventional method is found to be comparable. A water quality analyst would be able to save on digestion time by >90 %, if he chooses to perform the COD test as per the rapid method described herein.