Improvement Of The Removal Of Heavy Metals From Porous Media By Modified Electrokinetic Remediation

Throughout this work several aspects of soil electrokinetic remediation (EKR) were explored. Inthis dissertation several technical aspects of EKR were evaluated. The first one was the effect ofelectrode configuration on the migration of heavy metals, the second was the optimization of pHcontrol during EKR, the third was the use of rotating and reciprocation electrodes in EKR, andfinally an estimation of the gas production at the electrodes during EKR was described. Theincreasing in the amount of migrated ions with the angle between the cathodes verified that electrodeconfiguration has a direct impact in the migration of Cu ions. With a60°angle between the twocathodes, the amount of Cu migrated ions was the highest. This was because the lower pHdistribution allowed Cu ions to migrate not only from the anode towards the cathodes but also in theopposite direction. By optimizing pH control during EKR it was possible to extract cadmium fromkaolin (98%recovery) and partially precipitate it at the catholyte (63%recovery). The pH level in thecatholyte was a function of the relationship between the HNO3concentration, the electrolyteconductivity, and time. It was also proven that reducing the quantity of acid used to control the pHsubstantially reduced energy consumption. The experiment with the rotating electrodes showed aclear relationship between the cathode rotation speed and the extraction rate of Cd, Cu, Ni and Zn.The highest rates of extraction rate were observed at1.25rpm when pH was not controlled and at0.6rpm when pH was controlled; by rotating the cathode at0.6rpm the extraction rate wasincreased1.4times for Cd,3.2times for Cu,2.2times for Ni, and2.0times for Zn. The experimentwith the reciprocating electrodes did not show significant changes in the migration of heavy metalsin the soil as the experiment with rotating electrodes did. A wide deflection angle of the orientationof the electric field diminished the effect of the reorientation of the electric field on theelectromigration of heavy metals in kaolin. A conceptual model was proposed to explain themigration of heavy metals under reoriented electrical field. Regarding the production of H2and O2at the membranes it was found a strong dependence on the type of soil. The presence of NO-3andSO4-in the soil hindered the production of oxygen at the anode. This problem could be solved bythe use of a cationic exchange membrane. An estimated maximum of14.2m3/month of H2and6.1m3/month of O2were produced with a silty clayey soil with the use of ion exchange membranes.