BIOSORPTION OF Cd(Ⅱ) IONS BY NORDMANN FIR CONES

摘要

The biosorption of Cd(Ⅱ) ions from aqueous solution was investigated by using Nordmann fir (Abies nordman-niana (Stev.) Spach. subsp. nordmanniana) cones, a natural biosorbent, in a batch biosorption system as a function of pH (1.5-7.0), initial metal concentration (5-150 mg/L), biomass dosage (1.0-8.0 g/L), contact time (0-480 min) and temperatures (15-45 ℃). The experimental data showed that the maximum pH for efficient biosorption of Cd (Ⅱ) was 6.5. The percentage removal increased from 76% to 84% with an increase in temperature from 15 to 45 ℃ at an initial Cd(Ⅱ) concentration of 5 mg/L. The data were analysed on the basis of pseudo-second-order kinetics, Elovich equation and intra-particle diffusion mechanism to determine the best fit model for Cd(Ⅱ) biosorption onto Nordmann fir cones. The pseudo-second-order kinetic model and Elovich equation provided the best correlation of the experimental data studied in comparison to the intra-particle diffusion mechanism. The experimental data were analysed using by Freundlich and Langmuir equation. The activation energy of biosorption (Ea) was calculated with Arhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of biosorption (ΔG°, ΔH° and ΔS°) were also evaluated.