Determination of solid-phase loading for the removal of metal ion from effluents using fixed-bed adsorbers

The sorption of cadmium and copper ions from aqueous solutions onto bone ch ar using fixed-bed adsorbers has been studied. A film-pore diffusion model has been utilized to predict theoretical breakthrough curves, which are com pared with experimental breakthrough curves by means of error analysis. The key parameters for correlating the theoretical model are the external film mass-transfer coefficient (k(f)), the effective diffusion coefficient (D-e ff), and the solid-phase loading (q). The k(f) is determined from fixed-bed empirical correlations, and D-eff is determined by a best-fit optimization routine. The q value has traditionally been determined using the equilibri um isotherm, which is applicable when the column adsorbent reaches equilibr ium, or using the breakthrough curve mass balance when the column does not reach equilibrium. The breakthrough curve mass balance method needs experim ental curves for each system and is not a practical solution for general de sign models. This paper presents two novel predictive equations for q in te rms of process variables. The accuracy of the equations is sufficient for a pplication in design models for nonequilibrium and equilibrium systems.