Removal of Cadmium by Electrocoagulation and a Cost Evaluation

Abstract

The electrocoagulation method was selected for the removal of Cd+2. The effects of the parameters such as current density, pH, and supporting electrolyte concentration on this method were studied. The Cd+2 concentration, stirring speed, and temperature were 250 mg/L, 150 rpm, and 293 K in the determination of the optimum pH. The results obtained showed that a pH of 6 provided the highest Cd+2 removals. A pH of 6 was taken to be a constant optimum value while studying the effects of current density and supporting electrolyte concentration on removal. Current density values were chosen as 0.25, 0.50, 1.00, and 1.50 mA/cm 2 . Increasing current density increased Cd +2 removals significantly. Removal of 58%, 85%, 95%, and 99% were found for current densities of 0.25, 0.50, 1.00, and 1.50 mA/cm2 with an initial concentration of 250 mg/L with a reaction time of 30 minute, respectively. An increase in current density caused an extreme increase in energy consumption. Energy consumption was 0.363 kW-h/m3 for a current density of 0.25 mA/cm2 with a reaction time of 30 minutes while it was 1.575, 3.85, and 7.51 kWh/m3 for a current density of 0.50, 1.00 and 1.50 mA/cm2 at a pH of 6, respectively. It was found that the effect of supporting electrolyte concentration on removal efficiency was negative. As supporting electrolyte concentration increased, removal efficiency decreased and the energy consumption rate increased. It was determined, as a the result of the experiments, that Cd +2 ions can be removed at the rate of 99% with a pH of 6, a 250 mg/L Cd+2 concentration, a 150 rpm stirring speed, a temperature of 293 K and a current density of 1.50 mA/cm2 in an aqueous solution.