Equilibrium, thermodynamic and kinetic studies on biosorption of Mn(II) from aqueous solution by Pseudomonas sp., Staphylococcus xylosus and Blakeslea trispora cells

Biosorption of Mn(II) from aqueous solutions using Pseudomonas sp., Staphylococcus xylosus and Blakeslea trispora cells was investigated under various experimental conditions of pH, biomass concentration, contact time and temperature. The optimum pH value was determined to 6.0 and the optimum biomass concentration to 1.0 g L−1 for all types of cells. Mn(II) biosorption was found to fit better to the Langmuir model for Pseudomonas sp. and B. trispora and to Freundlich model for S. xylosus. Langmuir model gave maximum Mn(II) uptake capacity 109 mg g−1 for Pseudomonas sp. and much lower, 59 mg g−1 and 40 mg g−1 for S. xylosus and B. trispora, respectively. 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. Interestingly, desorption experiments by treating biomass with 0.1 M HNO3 solution resulted to more than 88% recovery of the adsorbed Mn(II) from Pseudomonas sp. and almost 95% and 99% from S. xylosus and B. trispora cells respectively, thus indicating that Mn(II) can be easily and quantitatively recovered from biomass.