The Process of Adsorption-Desorption of Heavy Metals in a Natural and a Contaminated Soil

Zinc adsorption and desorption processes have been studied in two simular soils, natural and contaminated (Zn > 3,000 mg kg−1). The adsorption mechanism is the same in both soils. Zn adsorption is accompanied by a decrease in pH. Desorption by CaCl2 removed only a small percentage (2%) of the adsorbed metal, but greater (>65%) quantities were extracted by EDTA, suggesting that soil cannot be considered as a permanent sink for heavy metals.