Remediation of Soils Contaminated with Tetraethyl Lead by Electric Fields

Four tests were conducted to investigate potential uses of electric fields for remediation of high buffering capacity soils contaminated with high lead concentrations (11 percent by dry weight). The soil samples were collected from a site in Louisiana where tetraethyl lead was used extensively for increasing the octane rating of leaded gasoline. Calcium was present at relatively high concentrations (9 percent by dry weight). Initial soil pH was basic (about 8.5). Two enhancement procedures were used: acetic acid for neutralizing the cathode and membranes to prevent migration of hydroxyl ions from the cathode. Current densities applied were in the order of 5 A/m² to 10 A/m². Tests were processed for up to 3,220 hours. Lead extraction rates were significantly affected by high calcium concentration. Energy expenditure was very high (up to 20 667 kWh/m³ in the unenhanced test). The study showed that the soil buffering capacity significantly affected energy requirements, cost-effectiveness, and success of the process. Efficient extraction of lead in soils will be controlled by the presence of high concentrations of soluble ions (such as calcium) in the soil.