Applicability of Simplified Models for the Estimation of Ion Exchange Diffusion Coefficients in Zeolites

Proposed Adsorption–Diffusion Model for Characterizing Chromium(VI) Removal Using Dried Water Hyacinth Roots

“…In order to establish the gross effectiveness of the proposed adsorption-diffusion model, the predictions of the proposed model was compared with two standard adsorption-diffusion models, namely, the diffusion model according to Vermeulen's approximation [37] and the parabolic diffusion model [38]. According to Vermeulen's approximation of impregnated diffusion model the plot of ln(1 À F 2 )…”

Removal of Cadmium By Natural and Surfactant-Modified Mexican Zeolitic Rocks in Fixed Bed Columns

“…Besides, the fact that the external surface of the zeolitic rock is modified with HDTMA-Br could affect the sorption process within the column, which needs a certain residence time for the diffusion of cadmium ions from the surface of the particle to the sorption sites. The diffusion coefficients (D s ) for cadmium on ZeNa and SMZ are 1.95 × 10 −8 and 1.42 × 10 −8 cm 2 /s, respectively, they were calculated from sorption kinetic data for the cadmium-ZeNa system that have been previously reported (Cortés-Martínez et al 2004), by solving the diffusion equation with the Paterson's approximation (Paterson 1947;Inglezakis and Grigoropoulou 2001). It can be noticed a lower D s for SMZ suggesting that the diffusion in this adsorbent is slower than the diffusion in ZeNa and this fact could explain the differences between the breakthrough curves of both materials.…”

Diffusion of alcohols and aromatics in a mesoporous MCM-41 material

“…Dyer and White [12] studied cation diffusion in a natural zeolite called clinoptilolite and compared three different approaches to determine diffusivities, including Fick's second law of diffusion, which was found to produce similar results with other approaches. The applicability of various models for the determination of ion exchange diffusivities in clinoptilolite was examined in another study [13]. Marecka and Mianowski [14] used Fick's second law to determine sorption of carbon dioxide and methane in a highly metamorphosed coal, and the results of the model were compared with the experimental kinetics of nitrogen sorption on type A zeolite.…”