Numerical and laboratory investigation on nano-silica and lime amended clay liner for heavy metal leachate control nano-silica clay liner for heavy metal leachate control
摘要
The originality of this study lies in integrating authentic multi-metal leachate derived from basic zinc sulfate filter-cake waste with a coupled laboratory and numerical evaluation of amended clay liners. The leachate contained high concentrations of cadmium (1220 mg/L), manganese (650 mg/L), zinc (91 mg/L), and nickel (95 mg/L), posing a significant risk to soil and groundwater. Clay mixtures amended with 0.8% nano-silica and 4% lime were experimentally evaluated through permeability, sorption, Atterberg limits, compaction, and unconfined compressive strength tests. Nano-silica reduced the hydraulic conductivity from 7.35 × 10−9 cm/s (natural clay) to 9.7 × 10−10 cm/s and achieved more than 99% removal of cadmium and lead. A one-dimensional diffusion–sorption model was calibrated using laboratory breakthrough data to simulate heavy-metal transport through a one-meter liner over 48 h. The model showed strong agreement with measured effluent concentrations and indicated a significant increase in retardation factors for nano-silica-treated clay. Overall, nano-silica demonstrated superior stabilization performance compared to lime and can effectively enhance the environmental safety of mining-waste landfill liners.