A laboratory treatability study for pilot-scale soil washing of Cr, Cu, Ni, and Zn contaminated soils



As part of this study, laboratory- and pilot-scale washing of soils contaminated with Cr, Cu, Ni, and Zn were performed. The soil washing agents used included strong acids (hydrochloric acid (HCl) and sulfuric acid (H2SO4)) and chelating agents (ethylenediaminetetraacetic acid calcium disodium salt (EDTA) and citric acid (CA)). A positive correlation was observed between the removal efficiency of the washing process and the concentration of the washing solution. Moreover, the effect of H2SO4 on metal removal with respect to concentration variations was more pronounced in the batch studies due mainly to acid dissolution of the heavy metals. Using H2SO4 concentrations of between 300 and 1000 mM, the removal efficiencies achieved when targeting Cr, Cu, Ni, Zn and the total metal content were 41–42, 38–68, 23–25, 47–53, and 42–55%. The removal efficiencies recorded during the engineering pilot scale washing of the field soils using H2SO4 are comparable to those obtained in the batch study. © 2011 American Institute of Chemical Engineers Environ Prog, 2011