Mass Transport Model for the Fixed Bed Sorption of Metal Ions on Bone Char

Abstract

The ability for the sorption of the three metals onto bone char was demonstrated by a series of equilibrium isotherm studies. The Sips isotherm equation was found to give the most accurate correlation of the equilibrium relationship between these metal ions and bone char, and the equilibrium adsorption capacities of bone char for copper, zinc, and cadmium ion were determined to be approximately 0.80, 0.50, and 0.55 mmol/g, respectively. A film surface diffusion model, which is based on the assumption that the sorbate penetration rate is controlled by the external film diffusion and surface diffusion within the sorbent, has been developed to simulate the fixed bed sorption of copper, zinc, and cadmium ions onto bone char. A computer program based on a numerical solution using the finite difference method has been constructed and successfully simulated the metal ion−bone char column behavior. A new external mass transfer correlation was proposed and applied in the model. The effect of axial dispersion was tested and found to be not significant in these systems.