Treatment of Phenol Wastewater Using Hydroxyl Radical Produced by Micro-Gap Discharge Plasma Technique

Hydroxyl radical produced by non-equilibrium plasma, which was induced by micro-gap dielectric barrier discharge, was used for the treatment of phenol wastewater. The advantage of this method was that chemicals and catalysts were not involved when hydroxyl radical was generated from water and oxygen. A proportional efficiency of phenol removal was observed with the hydroxyl radical increasing. The removal efficiency was higher in a basic condition than in an acidic condition, which was enhanced with the pH value of the solution increasing from 3.6 to 11.2. It was rational to adjust the pH value between 9.0 and 10.0. The removal efficiency of phenol was reduced when the conductivity of the solution increased from 0 to 200 µs.cm⁻¹; the highest was found in the solution without Na₂CO₃. The UV spectral absorption in the process indicated that few organic compounds with a conjugated structure were included in the treated wastewater.