Efficacy of an electrochemical flow cell introduced into the electrochemical Fenton-type process using a Cu(I)/HOCl system.

Abstract

An electrochemical flow cell was introduced into the electrochemical Fenton-type process using a Cu(I)/HOCl system. The effects of the current density and the initial cupric ion (Cu2+) concentration on the process performance were discussed. The current efficiency of the process improved from 6.1% for an electrolytic tank system to 33% for the electrochemical flow cell system at a current density of 5.0 mA/cm2 and an initial Cu2+ concentration of 1.0 mM. The current efficiency increased to 58% for Cu2+ concentrations of 2.0 mM and beyond. The cathodic reduction of Cu2+ to the cuprous ion (Cu+) emerged as the rate-determining step in comparison to the anodic production of free chlorine. The introduction of the electrochemical flow cell enhanced the cathodic production of Cu+ by reinforcing the mass transfer of the Cu2+ to the cathode, and the detachment of micro bubbles generated electrochemically at the cathode surface. A decrease in the current density and an increase in the initial Cu2+ concentration also improved the current efficiency by promoting the cathodic production of Cu+. This involved the prevention of the cathodic reduction of protons to hydrogen gas and the elevation of the electrode potential of the cathodic reaction from Cu2+ to Cu+.