Mediated electrochemical oxidation is one of the suitable processes for the destruction of hazardous organic compounds and the dissolution of nuclear wastes at ambient temperature and pressure. The electrochemical oxidation of Co(II) was carried out in an undivided and divided electrochemical cell. The formation of Co(III) was studied in an divided electrochemical cell by varying conditions such as temperature and concentration of nitric acid in a batch type electrochemical reactor in recirculation mode. It was found that the formation of Co(III) increased with increasing nitric acid concentration and decreased with increasing temperatures. The produced Co(III) oxidant was then used for the destruction of phenol. It was noted that phenol could be mineralized to CO2 and water by Co(III) in nitric acid under different nitric acid concentrations and temperatures. The evolved CO2 was continuously measured and used for the calculation of destruction efficiency. The destruction was increased with increasing nitric acid concentration as well as the temperature. The maximum efficiency was observed to be 78% based on CO2 evolution for 5,000 ppm phenol solution at 60 oC in a continuous feed mode. The destruction efficiency was increased 28% by addition of silver at 25 ℃.