Comparison of solutions for the homogeneous surface diffusion model applied to adsorption systems

Abstract

Three solutions to the film surface diffusion mass transport model are discussed. The solutions are based on the homogenous surface diffusion model (HSDM) and are compared using three different adsorption systems. The mass transport solutions include a Crank–Nicholson implicit finite difference method, a semi-analytical solution method and a Cartesian collocation method. The three solutions are compared for accuracy, stability, convergence and computation CPU time. The experimental systems used two adsorbents, activated carbon, a mainly microporous material, and sorbsil silica, a mainly macroporous material. Two categories of adsorbates were selected for the study, phenol, a relatively small organic molecule, which does not ionise, and basic dyes, larger organic structures, which exist as ionisable salts. A range of initial adsorbate concentrations were studied. The range of material types and experimental conditions selected should be sufficient to test and compare the three models under a variety of conditions.