Assessment of heavy metals retention in GCLs by column and batch tests

摘要

Heavy metals retention in a needle-punched GCL was evaluated by permeation column tests and batch sorption tests. The GCL was first permeated with water, followed by an acidic (pH=2.0) multispecies (Pb~(2+), Zn~(2+), Cu~(2+)) equimolar (25 mM) solution. The hydraulic conductivity to water was 1.5 × 10~(-9) cm/s, which increased to 1.6 ×10~(-8) cm/s upon permeation with the metals solution. Zn~(2+) was the most mobile, whereas Pb~(2+) was the most retarded metal. Batch sorption tests confirmed the highest uptake of Pb~(2+), whereas Cu~(2+)and Zn~(2+) had lower and very similar sorption. The release of exchangeable cations suggested that metals were actively retained in the soil by cation exchange. Precipitation of lead sulphate (PbSO_4) probably contributed to the retention of lead. The individual sorption isotherms of metal cations were strongly nonlinear.