A comparative Isothermal and Kinetic Study of the Adsorption of Lead (II) from Solution by Activated Carbon and Bentonite

Abstract

This work is aiming to study and compare the removal of lead (II) from simulated wastewater by activated carbon and bentonite as adsorbents with particle size of 0.32-0.5 mm. A mathematical model was applied to describe the mass transfer kinetic.

The batch experiments were carried out to determine the adsorption isotherm constants for each adsorbent, and five isotherm models were tested to choose the best fit model for the experimental data. The pore, surface diffusion coefficients and mass transfer coefficient were found by fitting the experimental data to a theoretical model. Partial differential equations were used to describe the adsorption in the bulk and solid phases. These equations were simplified and then solved using a technique with finite elements and orthogonal collection method for the bulk fluid and intraparticle phases, respectively. The results obtained from this work show that the equilibrium adsorption isotherms are favorable, and fitted well using the Freundlich model for activated carbon and bentonite. The activated carbon has a high value of pore diffusion coefficient, D_p, while bentonite has a high value of surface diffusion coefficient, D_s. This indicates that the pore diffusion controls the adsorption process for activated carbon, and the surface diffusion controls the adsorption process for bentonite. The activated carbon was more efficient than bentonite in removing of lead (II) from simulated industrial wastewater.