Electrokinetic Remediation. I: Pilot-Scale Tests with Lead-Spiked Kaolinite

Abstract

The feasibility and efficiency of transporting lead under electric fields are investigated at pilot scale in three 1 t Georgia kaolinite specimens spiked with lead nitrate solution and at an electrode spacing of 72 cm. Enhancement methods such as cathode depolarization and/or catholyte neutralization techniques are not used in processing. A constant direct current density of 133 μmA/cm 2 is applied. Two of the tests are conducted on specimens spiked with lead at concentrations of 856 mg/kg and 1,533 mg/kg. The third test is conducted on a 1:1 mixture of compacted kaolinite/sand spiked with lead at a concentration of 5,322 mg/kg. Lead was transported toward the cathode and precipitated at its hydroxide solubility value within the basic zone in direct contact with the cathode compartment. Subsequent to 2,950 h of processing and an energy expenditure of 700 kWh/m 3, 55% of the lead removed across the soil was found precipitated within the last 2 cm close to the cathode, 15% was left in the soil before reaching this zone, 20% was found precipitated on the fabric separating the soil from the cathode compartment, and 10% was unaccounted. Heavy metals and species that are solubilized in the anodic acid front can be efficiently transported by electromigration under an electrical field applied across electrodes placed in soils.