APPLICATION OF ZEOLITE AND BENTONITE FOR STABILIZING LEAD IN A CONTAMINATED SOIL

Lead is a toxic element, which is often incorporated into the trophic chain. It is resistant to migration into the soil profile and its presence in the upper layers of the soil is caused by anthropogenic factors. Zeolites are crystalline hydrated aluminosilicates containing a system of connected chambers and channels in their structure. The same properties apply to the bentonite which contains at least 75% montmorillonite. Both clay mineral / sorbents are characterised by high sorptive properties, which are greater in the case of the bentonite. Incorporation of these sorbents into the soil can effectively immobilize contaminants, especially heavy metals. The study evaluated the properties of zeolite and bentonite for stabilizing lead (Pb) in a contaminated soil. Sorbents were applied at different rates – 0, 0.25, 0.5, 1.0, 2.0, and 3.0% – to the contaminated soil and incubated for four months. Soil reaction (pH) and the electrical conductivity (EC) were measured. The total content of Pb and the reactive forms (extracted by 0.11 mol CH3HCOOH dm -3) were determined in the examined soil samples. Evaluation of the stabilization efficiency of Pb was performed on the basis of the fractions of the reactive lead. It was found that the addition of both zeolite and bentonite decreased the concentrations of the active forms of lead in soils. Thus, the two sorbents are characterized by a good stability and can be used for efficiently immobilizing lead in the soil contaminated through anthropogenic activity.