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Abstract
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Dye compounds is one of the most critical contaminant for natural ecosystems. The scope of this
study was to evaluate the feasibility application of eggshell as a sorbent for the removal of
Congo red as a typical of azo dyes from aqueous solution. The experiments were carried out in a
batch system to optimize operation variables such as adsorbent dosage, Congo red concentration,
pH and contact time. The Langmuir, Freundlich‚ Tempkin and Dubinin–Raduskovich (D–R)
adsorption isotherm models were studied and the best results were obtained by Langmuir
isotherm model. The maximum adsorption capacity was 5.02 mg g-1, indicating eggshell is a
good adsorbent for the adsorption of Congo red. The maximum absorption wave length of this
max) was determined by spectrophotometer. The adsorption kinetics was studied with the
pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. It was
found that the adsorption of Congo red on eggshell followed the pseudo-second order
equation which was studied in details. The thermodynamic parameters indicated that the
adsorption of Congo red onto eggshell was an exothermic and spontaneous process.
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