Ferula orientalis
L. stalks were used as an agricultural solid biomass waste for preparation of activated
carbon with zinc chloride activation using slow
pyrolysis in a fixed-bed reactor. The chemical characteristics
of the activated carbon obtained at 550 °C were
identified by elemental, fourier transform infrared spectroscopy,
Brunauer–Emmett–Teller, scanning electron
microscopy analyses and found to have a surface area of
1,476 m
2/g. The ability of the activated carbon to adsorb
methylene blue and crystal violet from aqueous solutions
has been investigated. Adsorption studies were performed
at different initial dye concentrations (200–800 ppm),
contact time (0.5–90 min) and temperature (25–45 °C).
Adsorption data were modeled with Langmuir, Freundlich
and Temkin adsorption isotherms. Equilibrium data of the
adsorption processes showed that adsorption of methylene
blue is fitted to the Langmuir and crystal violet to the
Freundlich isotherm. Pseudo-first-order, pseudo-secondorder
and Elovich kinetic models were used to analyze the
kinetic data obtained at different initial dye concentrations.
The adsorption kinetic data were very well described by the
pseudo-second-order model. The calculated thermodynamic
parameters such as change in free energy, enthalpy
and entropy showed that adsorptions of both dyes onto
activated carbon were spontaneous and endothermic under
the experimental conditions.
