Effects of experimental parameters on phenol degradation by cathodic microarc plasma electrolysis

Cathodic microarc plasma electrolysis (CMPE) method was employed to degrade phenol in wastewater. The effects of electrode material, bath voltage, initial pH value and supporting electrolyte on phenol degradation were investigated. The plasma discharge was characterized by Optical emission spectroscopy (OES). The phenol concentration and its main intermediate products were determined by high performance liquid chromatography (HPLC). The chemical oxygen demand (COD) and its removal efficiency were also evaluated. The results illustrated that the Ti cathode degraded phenol more effectively than the Pt cathode due to the higher electron temperature in plasma discharge envelope and catalytic properties on Ti cathode. The electron temperature increased with increasing of bath voltage, which promoted the degradation of the phenol. Higher voltage enhanced the production and decomposition of intermediate products forward. For the pH value of electrolyte, alkaline condition was preferred to neutral and acidic conditions to improve degradation efficiency. Meanwhile, the chloride ion in the electrolyte promoted the ring-cleave reaction enormously.