LEAD REMOVAL FROM SOILS VIA BENCH-SCALE SOIL WASHING TECHNIQUES

The retention and release of lead from eight different soils collected from the eastern United States were investigated. After characterization using well-established test procedures, the study soils were artificially contaminated with lead. Upon contamination, the lead-retention capacity of the study soils was statistically correlated with their physical and chemical properties. Lead capacity of the eight study soils was best correlated with the parameters of soil pH and the organic soil fraction. The efficiencies of six washing solutions in removing lead from the contaminated soils were then investigated via batch washing experiments. Unlike conventional field-scale soil washing, all particle size fractions were washed and recovered in these bench-scale experiments. HCl and EDTA obtained the best Pb-removal efficiencies. Removals tended to be independent of soil type and washing solution concentration. In addition to the physical/chemical properties of the washing solutions and of the study soils, the effects of the initial lead contamination level and washing solution concentration upon lead removals were examined. Lead-retention and release kinetic studies were performed to confirm equilibration between the aqueous and solid phases. Kinetics of both lead retention and release were very rapid for most study soils.