Mediated electrochemical oxidation of phenol in continuous feeding mode using Ag (II) and Ce (IV) mediator ions in nitric acid: A comparative study

Mediated electrochemical oxidation (MEO) process is one among the latest treatment technologies for the destruction of toxic organic pollutants under ambient temperatures and at atmospheric pressure. The process is a further extension of the conventional electrochemical treatment for the removal of toxic organics with powerful mediator oxidants in acidic medium. In this report the experimental results of using silver and cerium as mediator ions were compared with respect to their electro-oxidation behavior within the limitations of each mediator metal ion and their destruction efficiencies were compared for destructing phenol in continuous feeding mode. The following conclusions were drawn: (i) the optimum nitric acid concentration was found to be 8 and 3 M and the optimum temperature was found to be 60 and 80 °C for silver and cerium electro-oxidations, respectively; (ii) in the case of Ag (II)-MEO of phenol the maximum destruction efficiency achieved was 98% at 70 °C based on CO2 evolved; (iii) for Ce (IV)-MEO of phenol the maximum destruction efficiency achieved was 93% at 90 °C based on CO2. The results may provide baseline information on the use of suitable mediator metal ion in treating the target organic wastes by MEO process.