EFFECTIVENESS OF MODIFIED BENTONITE ON CD AND PB IMMOBILIZATION IN ARTIFICIALLY CONTAMINATED SOILS

The goal of this study was to know how the modified bentonite mineral can immobilize cadmium and lead in soils. Cadmium and lead chloride solutions were used to contaminate soils. Total levels of Cd were 31.12 and 39.80 mg kg^-1 corresponding to 63.83 and 146.87 mg kg^-1 of total Pb in experimentally contaminated clay and sandy loam soils. Clay soil had the highest total metal contents because of its highest adsorption capacity. Raw bentonite (RB), thermal activated bentonite (TB), acid activated bentonite (AB), and combination of acid thermal activated bentonite (ATB) were added to soils at rates of 0.5 and 1.0% (w/w) and incubated for 2, 14, 30, and 60 days at 25°C. The results indicate that, the extracted DTPA-Cd and Pb decreased with increasing incubation time, accompanied by decreases in EC due to the ATB-treatment. As the rate of the modified bentonite increased, the effectiveness of these treatments to immobilize Cd and Pb improved, and they can be organized in the following order: ATB > AB > TB> RB. ATB-treatment was the most efficient in decreasing DTPA-Cd and Pb with maximal immobilization efficiencies (E %) 91.42 and 90.99% for Cd and 98.46 and 97.85% for Pb in the clay and the sandy loam soils, respectively. RB-treatment exhibited the least ability among other treatments to immobilize these metals, reducing contents of DTPA-Cd and Pb by 79.25 and 90.61%, respectively. According to the statistical analysis utilizing the LSD test and in terms of practicality and cost, 1% ATB was the most effective treatment for immobilizing Cd and Pb in contaminated soils.