Kinetics and Thermodynamic Studies of Dextrin Adsorption on Modified Coal Surface

Abstract

The present paper deals with the adsorption kinetics of dextrin from an aqueous solution onto modified coal surface. The study explored the feasibility of improving coal surface with aluminium ion for easy adhering of dextrin as an adsorbate on coal under different experimental conditions. The rate constants for the adsorption of dextrin were determined using Lagergren kinetics rate equations and Intraparticle diffusion rate equation. From the kinetic models comparison applied to the adsorption of dextrin on coal samples, the experimental data fitted very well to pseudo second-order kinetic model and also followed by intraparticle diffusion, diffusion is not only the rate-controlling step. The results show that the sorption capacity increases with an increase in solution contact time from 30 to 150 minutes and temperature from 30 to 70 oC. The thermodynamic parameters were evaluated. The negative value of free energy change (?Go) reflects a more energetically favorable adsorption process (0.554-8.726 kJmol-1). ?Ho (57.32 kJmol-1) indicated that the adsorption of dextrin onto aluminium coated bituminous coal (ACB) was endothermic, which result was supported by the increasing adsorption of dextrin with temperature. The negative values of entropy ( ?So) confirmed a decrease in randomness of the adsorption process at the solid or solution interface (-187.23 kJmol-1) The results have established good potentiality for the modification of coal surface with aluminium sulfate for easy adsorption of dextrin on coal during processing.