Water Treatment by Fast Oxygen Radical Flow With DC-Driven Microhollow Cathode Discharge

Water treatment with ozone has been utilized, but a higher oxidation technology is required to decompose persistent substances such as dioxin. In this paper, water treatment by a direct O radical injection method with dc-driven atmospheric microplasma and fast oxygen gas flow was examined. O radicals and OH radicals are able to realize stronger oxidation processes than those of the ozone method. The effect of water treatment by radical injection was observed by measurement of the acetic-acid (CH₃COOH) decomposition. This was examined while varying the discharge current and oxygen gas flow rates. The acetic acid was successfully decomposed by a direct radical flow into the solution; meanwhile, no decomposition was observed with ozone injection. A clear correlation was found between the decomposition rate and the gas-flow velocity estimated by the gas-flow rates. This result indicates that the rapid radical injection is crucial at the gas-liquid interface because a key radical, which is thought to be O, has a very short lifetime in atmospheric oxygen