Optimization Using Box-Behnken For Enhancement Of Electrokinetic Remediation For Pb And Cu Removal From Contaminated Soil

Abstract

Electrokinetic study was carried out to investigate the effect of concentration of heavy metals, voltage gradient and pH on the energy consumption and removal efficiencies of mixed heavy metals ( Pb and Cu) contaminated soil. Fifteen (15) experiments were conducted based on Box-Behnken Design, and each experiment lasted for five days. The results were used in modelling of heavy metals removal efficiencies and energy consumption of the process with the aid of Minitab. Numerical optimization reveals the optimum energy consumption of 156.3 kWh/m³ of treated soil and removal efficiency for Pb and Cu have arrived at 97.01 and 96.31 respectively at operating conditions of concentration of heavy metals of 100, 200 and 300, voltage gradient of 20, 25 and 30 and pH of 4, 6.5 and 9. Increase in concentration of heavy metals was found to decrease removal efficiency as a result of the increase in the current generated during the experiment due to an increase in soil electrical conductivity.

In contrast, increases in voltage gradient were found to increase the removal efficiency. Increase in both voltage gradient and concentration of heavy metals was found to increase the energy consumption but In terms of pH, the energy consumed is large at small pH values and in the presence of low concentrations of heavy metals, as well as the presence of low voltages. In contrast, the energy consumed increases with an increase in the pH at high concentrations of heavy metals, as well as at high voltages.