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Adsorption of cadmium ions from aqueous solutions using sesame as a low-cost biosorbent: kinetics and equilibrium studies
Cheraghi, E.; Ameri, E. & Moheb, A.
Abstract
Sesame leaf and stem, as a kind of useless
agricultural waste, was used as a sort of low-cost biosorbent
for the removal of cadmium ions from aqueous solutions
in batch and continuous modes. The biomass was
characterized by Fourier transform infrared spectroscopy,
scanning electron microscope and energy-dispersive X-ray
analysis before and after adsorption. There were hydroxyl
group, carboxyl group, etc. on the surface of the adsorbent
from Fourier transform infrared spectroscopy. A batch
study was employed as a function of the initial concentration,
adsorbent particle size, adsorbent dose, contact
time and the pH of the solution. Maximum sorption was
found to occur at an initial pH of 6. The equilibrium process
was satisfactorily described by the Langmuir isotherm
model with the maximum sorption capacity of
84.74 mg g-1
. Kinetic studies also indicated that both
pseudo-first-order and pseudo-second-order kinetic models
(with R2 values of 0.9929 and 0.9952, respectively) were
able to describe the process. A continuous study was carried
out, and the maximum uptake of cadmium ions in a
fixed-bed adsorption column was found to be
22.88 mg g-1
, where the initial concentration of cadmium
ions, bed height, flow rate and pH were 60 mg L-1
, 2 cm,
2.5 mL min-1 and 5.5, respectively.
Keywords
Agricultural waste; Biosorption; Heavy metals; Isotherm; Water treatment
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