Electrochemical Oxidation of Model Wastewater Contaminant Using Boron Doped Diamond Electrodes

In most scenarios, electricity and water do not mix. In the realm of advanced oxidation processes (AOPs), this is not the case - the exception to the rule is called electrochemical oxidation (EO). Research on the use of EO has become popular in recent years because the electrochemical mechanism’s non-selectivity towards oxidation is applicable to a wide range of wastewater contaminants. Using EO to treat persistent pollutants in wastewater has been shown to be more effective in completely removing organic contaminants than many existing methods of treatment. While EO is more effective, it is also more expensive to operate than existing processes. By researching the effect of the electrochemical system’s operating parameters on treatment performance, the cost can be reduced. Using novel boron doped diamond electrodes and Orange G as a model azo dye contaminant, experiments were performed to assess the effect of current density on dye mineralization. Three-hour tests in an undivided three-electrode cell were performed within a range of current densities. Zero order kinetics were observed at low current density while first order kinetics were observed at high current densities. The percent removal of contaminant peaked near a limiting current density, where transition between zero and first order kinetics occured. The applied current efficiency (ACE) was maximized when the reaction maintained zero order kinetics. As the reaction entered the mixed kinetic regime, an exponential rise in operating costs was identified by plotting electrical consumption per kg COD treated over time. When ACE was kept high, treatment was effective and economical, costing near 1.01 dollars per kg of COD treated. The resultant data from this research indicates a need to step down current in order to keep the reaction below the limiting current density thus enabling a more economical approach to EO.