Investigation on the adsorption capability of egg shell membrane towards model textile dyes

Adsorption isotherms of Direct Red 80 (DR80) and Acid Blue 25 (AB25) on the egg shell membrane (ESM) were performed at 20 +/- 1 degrees C. Physical characteristics of ESM such as surface area and presence of functional groups were verified. The Fourier transform infra-red (FTIR) spectra proved the presence of factional groups such as hydroxyl, amine and carbonyl groups in ESM. The surface area of ESM was found to be 2.2098 m(2)/g. The effects of operational parameters such as initial dye concentration, pH(0), contact time, particle size and ESM doses were studied. The Langmuir, Freundlich, BET, Redlich-Peterson and Temkin adsorption models were applied to describe the equilibrium isotherms. The pseudo-first-order and pseudo-second-order kinetics models were examined to evaluate the kinetics data at different pH(0) values (2-12) and the rate constants were calculated. Maximum desorption of >= 81.8% was achieved for both dyes in aqueous solution at pH(0) 12. Also scanning electron micrographs (SEM) of the treated and untreated adsorbent were performed. Results indicate that ESM could be employed as a natural and Eco-Friendly adsorbent material for the removal of trace organics in solutions. (c) 2006 Elsevier Ltd. All rights reserved.