Solidification of Lead Contaminated Residual Soil

Treatment of lead contaminated soil in situ using cement based solidification/stabilization (S/S) technology is considered as a cost effective method. In this study, the efficiency in treating lead contaminated sedimentary residual soil was evaluated. Contaminated soils were prepared in the laboratory by spiking the residual soil with lead nitrate, Pb(N0₃)₂, to a concentration of 1,000 mg/kg. The contaminated soils were then treated with ordinary Portland cement with increasing cement content from 10% to 60%. Treated soils were also cured for 3, 7, 14, 28 and 56 days before subsequent strength, leaching and chemical testing. The results showed that all samples complied with the TCLP limit of 5 mg/L when extracted using deionized water. However, only samples treated with more than 40% cement complied with the TCLP criteria when extracted using standard TCLP leaching fluid i.e. acetic acid. This showed that acetic acid is an aggressive extractant compared to deionized water. Experimental results also showed that increasing the cement content would result in an increased in unconfined compressive strength and also reduced the leachability of lead. A regression model was also developed to predict the leaching of lead from solidified/stabilized contaminated soil using unconfined compressive strength data.