Effective diffusion coefficient determination within cylindrical granules of adsorbents using a direct simulation method

Analytical expressions for solute adsorption kinetics within porous carbon cylindrical granules of adsorbents with a one point formula for effective diffusion coefficient determination are available based on the assumption that solute transport is the rate limiting step and that it follows Fick's Second Law. Here the first practical application of this theory is provided with an initial, estimated diffusion coefficient refined by fitting calculated kinetic adsorption curves to experimental data determined for activated carbons. In an ideal experiment, experimental error (noise) is negligible, and no data refinement is needed. However, real experimental data are always more or less noise contaminated. Where such noise is significant, a simulation method offers the best value for effective diffusion coefficient. For this specific system, surface modification, pH and temperature effects on adsorption kinetics were analysed quantitatively as a basis of determining effective diffusion coefficients through the porous structure.

An apparent solute diffusion coefficient in cylindrical carbon granules is estimated with a middle point formula and refined by fitting a simulated adsorption curve to the experimental data.Figure optionsDownload as PowerPoint slide