Removal of lead from aqueous solutions by electrocoagulation: isotherm, kinetics and thermodynamic studies

The present study provides an electrocoagulation process for the removal of lead from water using magnesium and galvanized iron as anode and cathode, respectively. The various operating parameters such as the effect of initial pH, current density, electrode configuration, inter-electrode distance, co-existing ions and temperature on the removal efficiency of lead were studied. The results showed that the maximum removal efficiency of 99.3 % at a pH of 7.0 was achieved at a current density 0.8 A/dm² with an energy consumption of 0.72 kWh/m³. The experimental data were fitted with several adsorption isotherm models to describe the electrocoagulation process. The adsorption of lead preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. In addition, the adsorption kinetic studies showed that the electrocoagulation process was best described using the second-order kinetic model at various current densities. Thermodynamic parameters, including the Gibbs free energy, enthalpy and entropy, indicated that the lead adsorption of water on magnesium hydroxides was feasible, spontaneous and endothermic.