COLUMN LEACHING OF CADMIUM AND LEAD FROM A CONTAMINATED SOIL USING COMPOSITE LEACHING AGENT

Simulated soil column leaching experiment in laboratory using FeCl3 and organic acid( citric acid，malic acid， tartaric acid) were conducted to study the composite leaching agent concentration，dosage and the leaching times． And the chemical forms of Cd and Pb in the contaminated soil were determined before and after column leaching． The results showed， the optimum concentrations were 10 mmol /L ( FeCl3 ) and 20 mmol /L ( organic acid) ． And the removal rates of Cd and Pb were 72. 15% and 30. 26%，respectively． The efficency of composite leaching agent had increased substantially compared with using a single leaching agent． Composite leaching agent could effectively remove exchange status，carbonate status and oxide combination patterns of heavy metals，and the effect on organis status and residual status was not obvious． The removal of Cd was easier than Pb，which mainly due to the presence of Cd in contaminated soil was exchange status，carbonate status and iron manganese oxide status，while the existence of Pb was mainly the organic status and residual status． After leaching，Cd and Pb in the soil achieved the environmental quality standards．