The biosorption of Cd(II) ions from aqueous solution was investigated by
using Nordmann fir (Abies nordmanniana (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 degrees C). 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 degrees C 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 (Delta G degrees, Delta H degrees and Delta S
degrees) were also evaluated
