Examination of in situ Generation of Hydroxyl Radicals and Ozone in a Flow-through Electrochemical Reactor

Generation of hydroxyl radicals and ozone in a low ionic strength influent (0.001 M Na₂SO₄) treated in a continuous flow electrochemical (EC) reactor equipped with a cobalt-promoted lead dioxide anode was examined using p-chlorobenzoic acid (pCBA) and indigotrisulfonate (ITS) probes. EC generation of hydroxyl radicals via the oxidation of water was determined to precede that of ozone. OH· current yields were affected virtually solely by the current density, with almost negligible effects of variations of pH and carbonate concentrations. Absolute values of the current yields of EC generated OH· radicals were close to 1.0% for current densities > 30 mA/cm². The EC generation of ozone was suppressed in the presence of organic species, primarily due to the interception of OH· radicals that react with oxygen to form ozone. Apparent kinetic constants of major reactions associated with the EC generation of ozone were determined based on a steady-state model of an EC-controlled continuous flow reactor.