Kinetic and thermodynamic studies of the biosorption of Cr(VI) by Pinus sylvestris Linn.

Abstract

Biosorption equilibrium, kinetics and thermodynamics of chromium(VI) ions onto cone biomass were studied in a batch system with respect to temperature and initial metal ion concentration. The biosorption efficiency of chromium ions to the cone biomass decreased as the initial concentration of metal ions was increased. But cone biomass of Pinus sylvestris Linn. exhibited the highest Cr(VI) uptake capacity at 45 °C. The biosorption efficiency increased from 67% to 84% with an increase in temperature from 25 to 45 °C at an initial Cr(VI) concentration of 300 mg/L. The Langmuir isotherm model was applied to experimental equilibrium data of Cr(VI) biosorption depending on temperature. According to Langmuir isotherm, the monolayer saturation capacity ( Q max) is 238.10 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data for initial Cr(VI). The pseudo-second-order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first-order kinetic model. The activation energy of biosorption ( E a) was determined as 41.74 kJ/mol using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of biosorption (Δ G° , Δ H° and Δ S°) were also evaluated.