This research evaluated the applicability of FeCl₃-based soil washing for Pb-contaminated soils collected from a military shooting range, focusing on stratigraphic differences. Through a systematic investigation of washing reagent type, concentration, liquid-to-solid ratio (L/S), agitation conditions, and magnetic separation intensity based on the subsoil (1.0-2.0 m), the optimal operating parameters were determined as FeCl₃ 0.1 M, L/S = 1:3, 20 min, 300 rpm, and 6,000 G. Under these conditions, the subsoil showed removal efficiencies of 74.2% in the 2.00-0.85 mm particle range and 88.8% in the 0.85-0.15 mm range, Pb concentrations below the remediation standard (200 mg·kg-¹). In contrast, when the same conditions were applied to the topsoil (0.0-0.6 m) and intermediate soil (0.6-1.0 m), high variability in removal efficiency was observed due to the presence of particulate lead bullets and metallic residues, and the target standard could not be met even after repeated washing. Additional washing following density separation improved the topsoil and intermediate soil by approximately 60%; however, final concentrations remained over three times higher than the regulatory threshold. Statistical analysis confirmed that the difference in washing efficiency between the subsoil and the upper layers was significant (p < 0.005). Therefore, this study demonstrates that FeCl₃ washing alone is applicable for subsoil remediation, while for topsoil and intermediate layers, combined advanced separation processes are required. These findings provide a scientific basis for developing stratified remediation strategies for Pb-contaminated military sites.

Keywords: FeCl₃ washing, Soil remediation, Heavy metal contamination, Pb removal