Advanced oxidation phenomena in electrocoagulation process: a myth or a reality?

This review discusses the advanced oxidation process (AOP) phenomena in electrocoagulation (EC) process. AOPs have been broadly defined as near ambient temperature treatment processes based on highly reactive radicals, especially the hydroxyl radical ((OH)-O-center dot) as the primary oxidant. In principle, as water-containing colloidal particulates, oils, or other contaminants move through the applied electric field, there may be ionisation, electrolysis, hydrolysis, and free-radical formation which may alter the physical and chemical properties of water and contaminants. Further, when the electrochemical reactors operate at a high cell potential and an anodic process occurs in the potential region of water discharge, hydroxyl radicals ((OH)-O-center dot) are generated. In order to get more probabilities to have free radicals formation in EC, ultrasound during EC may be very useful as discussed by some authors. Further, EC process at pH less than 3 has more chance to produce hydroxyl radicals formation. Finally, this review concludes that there is no proof of the presence of AOP phenomena in EC process and more research is needed here focusing on free radicals formation.