Chemical Extraction of Arsenic and Heavy Metals from Contaminated Soils Under High Temperature and Pressure Conditions in Abandoned Mines in South Korea

The chemical extraction of As and heavy metals from contaminated soils, sampled from the Geopoong and Keumpoong mines in South Korea, was investigated under subcritical conditions. Soil samples from the abandoned mines were heavily contaminated with As, Cd, Cu, Pb, and Zn. The extent of metal removed from the contaminated soils by extractants varied according to the chemical forms of the metals in the soils. When temperature increased, the extraction of As increased accordingly, showing 92-100% removal with 100 mM of NaOH at 300°C. In contrast, the extraction of cationic metals by citric acid and ethylenediaminetetraacetic acid (EDTA) decreased markedly at 200–300°C because their chelating ability was decreased via decarboxylation and dehydration at high temperatures. Furthermore, the extraction of cationic metals was significantly affected by solution pH. Our results suggest that chemical extraction of cationic metals under subcritical conditions may be affected by several factors, including character of metal, type of extracting reagent, existing forms of metal in the soil, temperature, and soil pH.