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pp.769-776
The objective of this study was to evaluate the immobilization of heavy metals (Cu, Pb, Zn and Cd) in an abandoned mine soil by applying both soluble phosphates and steel slag as stabilizers. The application rate of stabilizers to soils was determinated based on PO4/Pb molar ratio of 2.0 for phosphates and on weight/weight ratio of 2, 5, 10% for steel slag, respectively. Immobilization efficiency of heavy metals in the contaminated soils was evaluated by toxicity characteristics leaching procedure (TCLP). After adding both phosphate and slag, the immobilization efficiencies of Cu, Zn and Cd increased significantly (about 14% - 40%) compared to those of treatment with soluble phosphate alone. The increae in immobilization efficiencies of Cu was the greatest. Whereas, immobilization efficiency of Pb was not significantly different from those with soluble phosphate alone. Among the tested three phosphates (Na2HPO4 ·12H2O, Ca(H2PO4)2 ·H2O, (NH4)2HPO4), the immobilization efficiencies with Na2HPO4 ·12H2O increased more than those of other phosphates. Results of sequential extraction analysis indicated that fraction of reducible form (F3) and residual form (F5) increased, while mobile forms (F1, and F2) decreased after immobilization treatment with both stabilizers resulting in decrease in leachability of heavy meyals in the treated soils. Residual fraction of Cu after treatnment was the highest as 68.5%, it was followed by Cu > Pb > Zn > Cd.
