Combined diffusion model for batch adsorption

Adsorption now plays a key role in environmental protection engineering and is used to remove pollutants from industrial effluents. The removal of acid dye by adsorption onto activated carbon and the removal of copper ions by sorption onto bone char have been studied using an agitated batch adsorber. Equilibrium studies have been carried out and rate processes have been investigated to study the effect of initial solute concentration and adsorbent mass. A diffusional mass transport model has been developed to predict the concentration versus time decay curves. The basis of the model is the shrinking core theory [1,5], which was originally applied to liquid phase systems [2,3,4] and based on determining a single effective diffusivity, D-eff. The model applied in the present paper analyses the role of D-eff in terms of pore, D-P, and surface, D-S, diffusion.