Equilibrium and thermodynamic studies on biosorption of Pb(II) onto Candida albicans biomass

Biosorption of Pb(II) ions from aqueous solutions was studied in a batch system by using Candida albicans. The optimum conditions of biosorption were determined by investigating the initial metal ion concentration, contact time, temperature, biosorbent dose and pH. The extent of metal ion removed increased with increasing contact time, initial metal ion concentration and temperature. Biosorption equilibrium time was observed in 30 min. The Freundlich and Langmuir adsorption models were used for the mathematical description of biosorption equilibrium and isotherm constants were also evaluated. The maximum biosorption capacity of Pb(II) on C. albicans was determined as 828.50 +/- 1.05, 831.26 +/- 1.30 and 833.33 +/- 1.12 mg g(-1), respectively, at different temperatures (25, 35 and 45 degrees C). Biosorption showed pseudo second-order rate kinetics at different initial concentration of Pb(II) and different temperatures. The activation energy of the biosorption (E-a) was estimated as 59.04 kJ mol(-1) from Arrhenius equation. Using the equilibrium constant value obtained at different temperatures, the thermodynamic properties of the biosorption (Delta G degrees, Delta H degrees and Delta S degrees) were also determined. The results showed that biosorption of Pb(II) ions on C. albicans were endothermic and spontaneous. The optimum initial pH for Pb(II) was determined as pH 5.0. FTIR spectral analysis of Pb(II) adsorbed and unadsorbed C. albicans biomass was also discussed. (C) 2008 Elsevier B.V. All rights reserved.