Kinetic Modeling of Iron Electrocoagulation in Moderate to Slightly Acidic Media

Abstract

Electrocoagulation is an emerging process for water and wastewater treatment. However, there is a gap in understanding the effects of electrocoagulation operation (i.e., pH, applied current, electrode configuration) and the concentration dependencies of reactive species involved in the degradation of contaminants. Here, we show the development and validation of a batch reactor kinetic model for an electrocoagulation process in moderate to slightly acidic media for water treatment, guided by experimental data of electrocoagulation in synthetic wastewater at pH values of 5.0, 5.5, 6.0, and 6.5. The kinetic model uniquely predicts the full transient profile of the ferryl ion, a short-lived reactive oxygen species (ROS), coupling anode, cathode, and bulk Fenton chemistry in a single model validated against measured Fe(II), dissolved oxygen (DO), hydrogen peroxide (H2O2), and the sum of Fe(II) and Fe(III) concentrations. Our findings predict the rapid turnover and low concentration (<1.80 μg/L) of the ferryl ion as a reactive intermediate species. Interestingly, the kinetic model predicts that lower electrocoagulation currents yield higher ferryl ion concentrations. Further, increased electrocoagulation time results in faster consumption of the ferryl ion after the electrocoagulation step. The implication is that these results provide a guiding framework for designing electrocoagulation processes.