Evaluation of the adsorption kinetics and equilibrium for the potential removal of acid dyes using a biosorbent

The adsorption of Acid Red 14 (AR14) and Acid Blue 92 (AB92) onto the microporous and mesoporous egg shell membrane (ESM) was investigated in aqueous solution in a batch system with respect to initial dye concentration, pH, contact time, particle size and biosorbent doses at 20 +/- 1 degrees C. The surface area, Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) of ESM were obtained. The surface area of ESM was found to be 2.2098 m(2)/g. The pseudo-first-order, pseudo-second-order kinetics and the intraparticle diffusion models were used to describe the kinetics data. The rate constants at different pH values (2-12) were evaluated. The experimental data fitted well to the pseudo-second-order kinetics model at pH values of 2-8 and pseudo-first-order kinetics model at pH values of 10 and 12 for both dyes. Equilibrium isotherms were analyzed by Langmuir, Freundlich and Redlich-Peterson adsorption models. Maximum desorption of >= 89.6% was achieved for AR14 and 82.8% for AB92 in aqueous solution at pH 12. The results indicate that ESM could be fruitfully employed as effective biomaterial for the removal of residual color from effluents. (C) 2007 Elsevier B.V. All rights reserved.