Kinetics and thermodynamic studies of adsorption of malachite green onto unmodified and EDTA-modified groundnut husk
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Date
2012
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Abstract
A batch experiment was applied to study the adsorption of malachite green from aqueous solution by
unmodified and ethylene diamine tetraacetic acid (EDTA)-modified groundnut husk. The effect of initial
dye concentration, temperature, contact time and pH on the sorption process was investigated. The
Langmuir and Freundlich adsorption isotherms were applied to test the experimental data. The
chemically modified groundnut husk agreed well with both the Langmuir and Freundlich models at the
temperature below the room temperature (25°C) and above the room temperature. Unmodified
groundnut husk showed poor agreement with the isotherm at temperature below the room temperature
but fits well into the model at higher temperature. Kinetics of the adsorption with respect to the initial
dye concentration and temperature was also investigated. The pseudo-first-order, pseudo-second-order
and intraparticle diffusion models were used to test the kinetic data. Obtained data were fitted properly
in the pseudo-second-order kinetic model. The thermodynamic parameters such as change in free
energy (∆G°), enthalpy (∆H°) and entropy (∆S°) were also determined and the results obtained confirmed
that the sorption process is feasible, spontaneous, and endothermic.