title: Selective recovery of soil-borne metal contaminants through integrated solubilization by biogenic sulfuric acid and precipitation by biogenic sulfide.
abstract: A hybrid process combining solubilization via sulfuric acid produced by sulfur-oxidizing bacteria with precipitation via sulfide produced by sulfate-reducing bacteria was investigated to isolate soil-borne metal contaminants as purified metal-sulfides. The highly efficient two-step acidification process involved bioproduction of sulfuric acid in a culture medium containing 30% (v/v) of sludge filtrate (SF). Soil was added to the culture after maximum acid production. Solubilization efficiencies of 95% for Zn, 76% for Cu and 97% for Cd were achieved after 16 days. At pH 1.9, 3.0 and 4.0, 99% of Cu(2+), 96% of Cd(3+) and 93% of Zn(2+), respectively, were precipitated from the soil leachate by sulfide transported from sulfidogenic bioreactor via N(2) sparging, resulting in final effluent metal contents at the ppb-level. The introduction of SF did not affect the precipitation kinetics and purity of the recovered precipitates. Ultimately, 75% of Cu and 86% of Zn were recovered from the soil as pure CuS and ZnS (confirmed by SEM-EDS and XRD). These results demonstrate the potential of the integrated method for the selective production of valuable metals from metal contamination in soils.
authors.affiliation: Department of Environmental Engineering, Ocean University of China, Qingdao 266100, China. dfang@ouc.edu.cn
authors.forename: Di
authors.initials: D
authors.lastname: Fang
authors.forename: Ruichang
authors.initials: R
authors.lastname: Zhang
authors.forename: Xue
authors.initials: X
authors.lastname: Liu
authors.forename: Lixiang
authors.initials: L
authors.lastname: Zhou
mesh_terms: D003470:Culture Media; D019216:Metals, Heavy / Q000302:isolation & purification*; D008855:Microscopy, Electron, Scanning; D012989:Soil Pollutants / Q000302:isolation & purification*; D012995:Solubility; D013440:Sulfides / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D003470:Culture Media; D019216:Metals, Heavy; D012989:Soil Pollutants; D013440:Sulfides; D013464:Sulfuric Acids; C033158:sulfuric acid