Electrocoagulation efficiency probed using electrochemical impedance spectroscopy

In order to treat the polluted discharge from El-Jadida, Morocco, a method of electrocoagulation using aluminum electrodes was used. This approach was coupled for the first time with high-frequency electrochemical impedance spectroscopy (EIS). Significant pollutant abatement was observed after 30 min, at a current density of 190.5 A·m⁻², with a specific electrical energy consumption of 1.58 kW·h (per gram of eliminated carbon organic demand (COD)) and specific aluminum consumption of 0.11 g ·g⁻¹: electrocoagulation proved to be particularly effective, achieving 85.7% elimination of COD and a decrease of total dissolved solid (TDS) and electrical conductivity (EC) levels from 2430 mg·L⁻¹ to 1773 mg·L⁻¹ and from 4230 μS·cm⁻¹ to 3210 μS·cm⁻¹, respectively. As for USP and ORP, they decreased from 2.5 to 1.87 and from 244.6 mV to 51 mV, respectively. The inductance of the electrocoagulation system measured by EIS was modeled through an electrical equivalent circuit. When the applied intensity increased, the coagulation resistance increased suddenly when the applied electrical current reached 0.2 A (current density: 95.2 A·m⁻²). At this point, the rate of COD abatement versus SEEC (specific electrical energy consumption decreases which shows that the EC process should be combined with another process to improve its efficiency, such as ultrasound.