Experimental study on bioleaching of paddy soil in the vicinity of refinery site contaminated with copper, lead, and arsenic using sulfur-oxidizing bacteria

摘要

Applicability of bioleaching of Cu, Pb, and As from paddy soil in the vicinity of a refinery site was experimentally examined using a sulfur-oxidizing bacterium, Acidithiobacillus thiooxidans.As a result of aqua regia digestion, the concentrations of Cu (187 mg/kg), Pb (380 mg/kg), and As (107 mg/kg) in the studied soil exceeded the environmental criteria regulated by the Korean government. Batch experiments were performed to investigate the removal efficiency of the heavy metals according to various sulfur supply (0%, 0.1%, 0.5%, and 1%). All microbial experimental sets amended with sulfur showed the enhanced amount of heavy metals extracted, which showed the extraction processes require sulfur addition for proper metabolism of the bacterium. Among various amounts of sulfur addition, 1% (w/v) sulfur addition to the soil inoculated with bacterium led to the removal efficiencies of 67.6%, 25.8%, and 53.3% for Cu, Pb, and As, respectively. The relatively low removal efficiency of Pb resulted from formation of insoluble PbSO_4 precipitate. As a result of sequential extraction for the treated soil, most metals were found to exist as a highly stable fraction which is recalcitrant against change of the surrounding environment.