Lime-based immobilization and leaching of Cr, Cd, Pb, and Ni as soil contaminants

Abstract EN

With rapidly expanding urban areas in the region, the need for the remediation and reclamation of contaminated and uncontrolled waste disposal sites is gaining an increasing sense of urgency.

Many of the contaminated sites involve sandy soils contaminated with heavy metals.

This paper reports the results of a study undertaken to demonstrate the effectiveness of metals immobilization for controlling the release of metals from contaminated sandy soils.

The study involved the use of sixteen combinations of lime alone and lime in combination with cement and a pozzolanic additive, to immobilize Cd2+, Ni2+, Pb2+, and Cr3* in soil samples contaminated with individual metals at 5000 mg/kg.

The effectiveness of immobilization was evaluated using single and repeated metals extraction protocols.

The single extraction protocol was achieved using the toxicity characteristic leaching procedure (TCLP).

The immobilized metals were also subjected to 21 repeated leaching cycles using 0.

In HC1 and 0.

IN EDTA solutions in 24 extraction columns.

The results confirmed that metals leaching decreased as the quantity of a particular additive or additive combination increased.

Stabilization using lime dosages in the range of 1% - 8% resulted in leaching reductions that exceeded 90% for Pb and 97% for Cd, Ni, and Cr.

Lime combined with cement was more effective than lime alone or lime combined with pozzolan in reducing metals leaching.

The results confirmed that metals immobilization using locally available materials can be effective in controlling the release of heavy metals from contaminated sandy soils.