Thermodynamic, equilibrium and kinetic studies on biosorption of Pb +2 from aqueous solution by Bacillus pumilus sp. AS1 isolated from soil at abandoned lead mine

Abstract

Abstract In this study, a lead-resistant bacterium was isolated and used as an adsorbent to remove Pb+2 from aqueous solution. The strain was identified and designated as Bacillus pumilus sp. AS1 based on the morphology and 16S rRNA sequence analysis. Biosorption of Pb+2 from aqueous solutions using AS1 was investigated under various experimental conditions of pH, initial metal concentration, contact time and temperature. The optimum pH value was determined to be 4.0. Pseudo-second-order kinetic model was also found to be in good agreement with the experimental results. Thermodynamic parameters of the adsorption confirmed the endothermic nature of sorption process with positive heat of enthalpy, accompanied by a positive value of entropy change. The results of FTIR analysis suggested the involvement of carboxyl and hydroxyl groups during the biosorption process. Scanning electron microscopy and energy dispersive X-ray spectroscopy analyses showed that biosorption of B. pumilus sp. AS1 to Pb+2 involved surface adsorption and ion exchange. Desorption experiments by treating biomass with 0.1 M HNO3 solution resulted to more than 90% recovery of the adsorbed Pb+2 from AS1, thereby indicating that Pb+2 can be easily and quantitatively recovered from biomass.