RATE OF LIQUID-PHASE ADSORPTION ON ACTIVATED CARBON IN THE STIRRED TANK

Abstract

A method is developed to determine the dependence of surface diffusion coefficient on the amount adsorbed, derived for Freundlich adsorption isotherm, from adsorption rates in a finite bath. The adsorption rates on activated carbon of p-nitrophenol, benzoic acid and p-chIorophenol from dilute aqueous solutions are measured, where Freundlich adsorption isotherms are applicable, and the relations between surface diffusion coefficient and the amount adsorbed are determined for three adsorbates by this method. It is proved that the external mass transfer resistance in the stirred tank has a large influence on adsorption rate as well as intraparticle mass transfer resistance in finite bath adsorption. It is also clear from these relations that the ratio of activation energy for surface diffusion to adsorption energy is nearly equal to 0.5. The time-concentration curves predicted by this method coincide well with experimental data.