Ex-situ remediation of a metal-contaminated superfund soil using selective extractants

Abstract

Extractive processes can permanently and significantly reduce the volume, toxicity and mobility of contaminated materials at affected sites. Ethylenediaminetetraacetic acid (EDTA), N-2 (acetamido)iminodiacetic acid (ADA), pyridine2,6-dicarboxylic acid (PDA), and hydrochloric acid (HC1) were evaluated in batch studies for their ability to remove lead (Pb) and cadmium (Cd) from a Superfund soil. The extraction of Pb as a function of time was limited and the order of Pb removal was EDTA > ADA > PDA > HC1. Repeated extractions did not treat the soil below the Pb regulatory limit (1,000 mg/kg); however, the Pb remaining occurs in an immobile form. All extractants treated the soil below the proposed Cd regulatory limit (40 mg/kg) within 1 h. Lead recovery from solution was accomplished by hydroxide precipitation in the presence of excess calcium, and recovery at pH 11 was 70%, 98%, and 97% from the EDTA, ADA, and PDA complexes, respectively.