Application of eggshell waste for the immobilization of cadmium and lead in a contaminated soil

Liming materials have been used to immobilize heavy metals in contaminated soils. However, no studies have evaluated the use of eggshell waste as a source of calcium carbonate (CaCO3) to immobilize both cadmium (Cd) and lead (Pb) in soils. This study was conducted to evaluate the effectiveness of eggshell waste on the immobilization of Cd and Pb and to determine the metal availability following various single extraction techniques. Incubation experiments were conducted by mixing 0-5% powdered eggshell waste and curing the soil (1,246 mg Pb kg(-1) soil and 17 mg Cd kg(-1) soil) for 30 days. Five extractants, 0.01 M calcium chloride (CaCl2), 1 M CaCl2, 0.1 M hydrochloric acid (HCl), 0.43 M acetic acid (CH3COOH), and 0.05 M ethylendiaminetetraacetic acid (EDTA), were used to determine the extractability of Cd and Pb following treatments with CaCO3 and eggshell waste. Generally, the extractability of Cd and Pb in the soils decreased in response to treatments with CaCO3 and eggshell waste, regardless of extractant. Using CaCl2 extraction, the lowest Cd concentration was achieved upon both CaCO3 and eggshell waste treatments, while the lowest Pb concentration was observed using HCl extraction. The highest amount of immobilized Cd and Pb was extracted by CH3COOH or EDTA in soils treated with CaCO3 and eggshell waste, indicating that remobilization of Cd and Pb may occur under acidic conditions. Based on the findings obtained, eggshell waste can be used as an alternative to CaCO3 for the immobilization of heavy metals in soils.