Microbial solubilization of heavy metals from soil using indigenous sulfur oxidizing bacterium: Effects of sulfur/soil ratio

Abstract

Present study assesses efficiency of bioleaching to decontaminate heavy metal laden soil affected by tannery effluent employing sulfur oxidizing bacterium, Acidithiobacillus thiooxidans. Concentrations of predominant heavy metals were Cd, 9; Cu, 95; Cr, 11800; Pb, 85; and Zn, 238 mg/kg. Irrespective of sulfur/soil ratio (0.14, 0.21, 0.29, 0.43 and 0.57), pH dropped from near neutral to below 1 over a period of 28 days; drop in pH was rapid when the ratio was 0.57 and it took only 6 days for pH to drop from 7.12 to 0.94. Production of sulphate (22-45 g/l) increased with rise in sulfur/soil ratio. Solubilization of heavy metals was: Cd, 44-57; Cu, 60-92; Cr, 72-81; Pb, 39-56; and Zn, 55-94%.