Electrochemical Oxidation of Acid Yellow and Acid Violet Dyes Assisted by Transition Metal Modified Kaolin

Electrochemical oxidation of some dyes making wastewater assisted by transition metal (Co, Cu) modified kaolin in an electrolytic cell with graphite plates as electrodes was investigated. H2O2, produced on the surface of porous graphite cathode reacts with the (Co, Cu) modified kaolin catalyst to form strong oxidant (hydroxyl radicals HO*) that can in turn degrade the pollutants adsorbed on the surface of kaolin. Series of experiments were done to prove the synergetic effect of the combined oxidation system and to find out the optimal operating conditions such as initial solution pH, current density, time of electrolysis, and amount of modified kaolin catalyst. It was found that when the initial pH was 3, current density of 40 mA/cm 2 , electrolysis time of 40 minutes and catalyst dose of 15 g/L, the COD (chemical oxygen demand) removal could reach up to about 100% for the two investigated dyes.