Equilibrium parameters for the single- and multicomponent biosorption of Cr(VI) and Fe(III) ions on R-arrhizus in a packed column

In this study, simultaneous biosorption of Cr(VI) and Fe(III) on free Rhizo pus arrhizus in a packed column operated in a continuous mode was investiga ted and compared to the single metal ion situation. The breakthrough curves were measured as a function of feed flow rate and different combinations o f metal ion concentrations in the feed solutions. Column competitive biosor ption data were evaluated in terms of the maximum (equilibrium) capacity of the column, the amount of metal loading on the R. arrhizus surface, the ad sorption yield, and the total adsorption yield. Since the maximum column ca pacity and the adsorption yield decreased with increasing concentrations of the other metal ion, the combined action of Cr(VI) and Fe(III) on R, arrhi zus was generally found to be antagonistic. In the single-ion situation, th e adsorption isotherms were developed for optimum conditions and it was see n that the adsorption equilibrium data fit the non-competitive Freundlich m odel. For the multicomponent adsorption equilibrium, the competitive adsorp tion isotherms were also developed. The empirical Freundlich model for bina ry metal mixtures represented satisfactorily most of the column adsorption equilibrium data of Cr(VI) and Fe(III) on R. arrhizus. (C) 2000 Elsevier Sc ience B.V. All rights reserved.