Equilibrium, kinetics and thermodynamic studies on phosphate biosorption from aqueous solutions by Fe(III)-treated Staphylococus xylosus biomass: Common ion effect

The biosorption of phosphate from aqueous solutions using Fe(III)-treated Staphylococus xylosus cells was investigated. Langmuir and Freundlich isotherm models were applied to describe the adsorption equilibrium and found that Langmuir isotherm model fitted the equilibrium data better than Freundlich isotherm model. The biosorption capacity of Fe(III)-treated biomass for phosphate was found to be 70.92 mg/g at optimum conditions of pH 3.0, biomass concentration 0.5 g/L and equilibrium phosphate-biomass time 60 min respectively. The sorption efficiency at initial phosphate concentration of 50 mg/L was not influenced upon addition of SO42−, Cl−, CO32−, NO3−, Mg2+ and Ca2+ ions from 0 to 800 mg/L, whereas under the same conditions, phosphate sorption was increased with increase in concentration of Fe2+ ions. The kinetic models showed that phosphate sorption followed pseudo-second order kinetics. The calculated thermodynamic parameters indicated the spontaneous, exothermic and feasible nature of phosphate biosorption process. Phosphate was completely desorbed from 2.0 g/L of phosphate-loaded biomass using 0.14 M HCl and Fe(III)-treated biomass exhibited almost the same uptake capacities up to three subsequent biosorption/desorption cycles.