Electrochemical hydrodehalogenation of chlorinated phenols in aqueous solutions - II. Effect of operating parameters

The effect of operating parameters on chloride ion release, current efficiencies, and energy consumptions of the electrochemical hydrodehalogenation (HDH) of dilute aqueous solutions of pentachlorophenol (PCP) and 2, 4-dichlorophenol (DCP) is reported. The parameters include the concentrations of PCP and DCP, applied current density, controlled cathode potential, temperature, and flow rate. Relatively high concentrations, high-temperature, and moderate current density (e.g., 10 mA cm(-2)) have the most beneficial effect on the HDH process. For example, the HDH of 20 mM DCP in an H-cell at 70degreesC gave current efficiencies up to 70% and an energy consumption of 2.6 kWh/kg DCP. Good results were also achieved in a solid polymer electrolyte zero gap flow cell, e. g., a current efficiency of 35% and an energy consumption of 4.5 kWh/kg. Encouragingly, the energy consumed for the HDH of 50 ppm PCP in water at ambient temperature is in a range of 28 and 80 kWh/kg PCP, which is much lower than previously reported. (C) 2002 The Electrochemical Society.