Kinetics of Zinc Ion Removal from Wastewater By Electrocoagulation

Abstract

In this work, the research focused on the removal of zinc ions from the synthetic wastewater by electrocoagulation (EC) with aluminum electrodes. The effects of current density, electrode spacing, initial concentration, wastewater pH and conductivity on the removal efficiency and energy consumption were systematically investigated. The results showed that the zinc removal efficiency increased with the increasing current density and residence time. With a relatively low energy consumption of 0.35 kWh/m3, all of zinc ions (50 mg/L) were removed from the synthetic wastewater within 20 minutes EC treatment, 8.3 mA/cm2 for current density, and 5.3 for pH. Later with an energy consumption of 0.88 kWh/m3, all of zinc ions (250 mg/L) were removed from the wastewater at EC time of 50 minutes. In addition, the kinetic study was applied to analyze the removal rate of zinc ions by EC at different current densities and initial concentrations. Different mechanisms of zinc removal were implied by comparing the results of the low initial concentration (≤ 250 mg/L) and the high one (≥ 500 mg/L). It was reasonable to conclude that, besides the co-precipitation effect of the aluminum hydroxide flocculation, the electrochemical reduction of zinc ions at the cathode also contributed to the zinc removal, especially at a high initial concentration.