Multi-metal biosorption and bioaccumulation by Exiguobacterium sp. ZM-2

Abstract

The present work deals with the biosorption performance of dried and non-growing biomasses of Exiguobacterium sp. ZM-2, isolated from soil contaminated with tannery effluents, for the removal of Cd2+, Ni 2+, Cu2+, and Zn2+ from aqueous solution. The metal concentrations studied were 25 mg/l, 50 mg/l, 100 mg/l, 150 mg/l and 200 mg/l. The effect of solution pH and contact time was also studied. The biosorption capacity was significantly altered by pH of the solution. The removal of metal ions was conspicuously rapid; most of the total sorption occurred within 30 min. The sorption data have been analyzed and fitted to the Langmuir and Freundlich isotherm models. The highest Qmax value was found for the biosorption of Cd2+ at 43.5 mg/g in the presence of the non-growing biomass. Recovery of metals (Cd2+, Zn2+, Cu2+ and Ni2+) was found to be better when dried biomass was used in comparison to non-growing biomass. Metal removal through bioaccumulation was determined by growing the bacterial strain in nutrient broth amended with different concentrations of metal ions. This multi-metal resistant isolate could be employed for the removal of heavy metals from spent industrial effluents before discharging them into the environment. © 2012 Springer-Verlag Berlin Heidelberg and the University of Milan.