TITLE:
Comparative Isotherms Studies on Adsorptive Removal of Congo Red from Wastewater by Watermelon Rinds and Neem-Tree Leaves
AUTHORS:
M. B. Ibrahim, S. Sani
KEYWORDS:
Adsorption Isotherms, Congo Red, Neem Leaves, Watermelon Rinds
JOURNAL NAME:
Open Journal of Physical Chemistry,
Vol.4 No.4,
October
15,
2014
ABSTRACT: Equilibrium adsorption
studies for detoxification of Congo Red (CR) dye from single component model
wastewater by powdered watermelon rinds and neem leaves adsorbents were carried
out with the view to test the applicability of the adsorption process to
Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Harkins-Jura isotherm
models. The values of correlation coefficient, R2 (0.9359 - 0.9998), showed that all the
experimental data fitted the linear plots of the tested isotherm models.
Dubinin-Radushkevich’s monolayer maximum adsorption capacity qD (20.72 - 26.06 mg/g) is better than Langmuir’s
qm (18.62 - 24.75
mg/g) for both adsorbents with the capacities higher for adsorption on
watermelon rind than on neem leaves. Values of Langmuir separation factor (RL)
suggest unfavourable adsorption processes (i.e. chemisorption) of the dye on both the
adsorbents, while Freundlich constant (nF) indicates unfavourable
process only for CR adsorption onto neem leaves. The Dubinin-Radushkevich’s
mean free energy of adsorption, E (0.29 - 0.32
kJ/mol), suggests physical adsorption processes. Values for Temkin’s heat of adsorption,
bT (-0.95 to 0.74
kJ/mol), also show physical adsorption process.