Surface diffusion in porous media: A critical review

Medveď, Igor; Černý, Robert

doi:10.1016/j.micromeso.2011.01.015

Cited by 186 publications

(131 citation statements)

References 95 publications

Supporting

Mentioning

128

Contrasting

Unclassified

Order By: Relevance

“…5) The mass transfer flux at the solid-liquid phase interface: Du et al, 2007;2008) To be continued A review of surface diffusion is available elsewhere (Medved and Cerny, 2011), which might provide some ideas to modify the intrapellet diffusion models.…”

Section: General Rate Modelsmentioning

confidence: 99%

Mathematically modeling fixed-bed adsorption in aqueous systems

Cai

Pan

2013

J. Zhejiang Univ. Sci. A

345

166

View full text Add to dashboard Cite

Adsorption is one of the widely used processes in the chemical industry environmental application. As compared to mathematical models proposed to describe batch adsorption in terms of isotherm and kinetic behavior, insufficient models are available to describe and predict fixed-bed or column adsorption, though the latter one is the main option in practical application. The present review first provides a brief summary on basic concepts and mathematic models to describe the mass transfer and isotherm behavior of batch adsorption, which dominate the column adsorption behavior in nature. Afterwards, the widely used models developed to predict the breakthrough curve, i.e., the general rate models, linear driving force (LDF) model, wave propagation theory model, constant pattern model, Clark model, Thomas model, Bohart-Adams model, Yoon-Nelson model, Wang model, Wolborska model, and modified dose-response model, are briefly introduced from the mechanism and mathematical viewpoint. Their basic characteristics, including the advantages and inherit shortcomings, are also discussed. This review could help those interested in column adsorption to reasonably choose or develop an accurate and convenient model for their study and practical application.

show abstract

Section: General Rate Modelsmentioning

confidence: 99%

Mathematically modeling fixed-bed adsorption in aqueous systems

Cai

Pan

2013

J. Zhejiang Univ. Sci. A

345

166

View full text Add to dashboard Cite

show abstract

“…In such a case, the diffusion mechanism can be ascribed to a surface diffusion process [74,75]. Surface diffusion can be treated as an independent flow in addition to pore diffusion in the bulk void of the adsorbent in contributing to the overall flux of the adsorbate [46,75], which will be more prominent in the micropores, where the motion of the adsorbate is more affected by the pore walls. The total flux ( ) in the micropores using Fick' theories can be expressed as follows:…”

Section: Pore and Surface Diffusionmentioning

confidence: 99%

“…A number of models in determining surface diffusion coefficients are given in the literature, based on molecular hopping, hydrodynamic, Fick's, or combined theories [46], most of which showed joint contribution of pore and surface diffusions in the intraparticle diffusion processes [47][48][49][50].…”

Section: Introductionmentioning

confidence: 99%

Adsorption of pyridine from aqueous solutions by polymeric adsorbents MN 200 and MN 500. Part 2: Kinetics and diffusion analysis

Zhu

Moggridge

D’Agostino

2016

Chemical Engineering Journal

View full text Add to dashboard Cite

Telephone: +44 (0)1223 334763Fax: +44 (0)1223 334796 2 AbstractThe adsorption kinetics of pyridine adsorption on Macronet adsorbents MN 200 and MN 500 from aqueous solution was investigated at various initial pyridine concentrations and temperatures. The Weber-Morris plots revealed the influence of both external film diffusion and intraparticle diffusion resistances. The two linear regions in Weber-Morris plots were attributed to macropore and micropore diffusion, which was associated to the bimodal pore size distribution of the adsorbents. New insights into the diffusion mechanisms were highlighted, with the proposed internal film diffusion resistance dominating into the macropore region, whereas homogeneous particle diffusion resistance describes diffusion in the micropore region. The importance of pore and surface diffusion in the micropores was noted in contributing to the observed diffusion kinetics. The pore diffusion coefficient was estimated from PFG (pulsedfield gradient) parameter and molecular diffusion coefficient of pyridine in bulk liquid. A greater contribution of the surface to the overall diffusion kinetics was found for MN 500 as inferred from a proposed calculation method, which agrees with its better adsorption performance. The overall findings highlight the effect of pore structure onto the diffusion mechanisms inside the pores and help to gain a better understanding into the adsorption kinetics of these Macronet adsorbents, which are promising materials for the removal of Nheterocyclic compounds from waste water.

show abstract

“…is the velocity of liquid water associated with surface diffusion of water, which may be significant at high temperatures (e.g., Kapoor et al, 1989;Medveď andČerný, 2011). Note that switching variables from ψ < 0 to ψ n produces ψ n > 0 and K n < 0.…”

Section: Conservation Equationsmentioning

confidence: 99%

“…The term ρ w V θ,surf in Eq. (2) represents the soil moisture movement caused by water molecules "hopping" or "skipping" along the surface of the water films due to a temperature gradient (e.g., Medveď andČerný, 2011). The present model for V θ,surf is adapted from the model of Gawin et al (1999) and is given as…”

Section: Functions Related To Liquid Water Transportmentioning

confidence: 99%

A non-equilibrium model for soil heating and moisture transport during extreme surface heating: the soil (heat–moisture–vapor) HMV-Model Version 1

Massman

2015

Geosci. Model Dev.

View full text Add to dashboard Cite

Abstract. Increased use of prescribed fire by land managers and the increasing likelihood of wildfires due to climate change require an improved modeling capability of extreme heating of soils during fires. This issue is addressed here by developing and testing the soil (heat-moisture-vapor) HMVmodel, a 1-D (one-dimensional) non-equilibrium (liquidvapor phase change) model of soil evaporation that simulates the coupled simultaneous transport of heat, soil moisture, and water vapor. This model is intended for use with surface forcing ranging from daily solar cycles to extreme conditions encountered during fires. It employs a linearized Crank-Nicolson scheme for the conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations, which were obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10 000 and 50 000 W m −2 . The Hertz-Knudsen equation is the basis for constructing the model's non-equilibrium evaporative source term. Some unusual aspects of the model that were found to be extremely important to the model's performance include (1) a dynamic (temperature and moisture potential dependent) condensation coefficient associated with the evaporative source term, (2) an infrared radiation component to the soil's thermal conductivity, and (3) a dynamic residual soil moisture. This last term, which is parameterized as a function of temperature and soil water potential, is incorporated into the water retention curve and hydraulic conductivity functions in order to improve the model's ability to capture the evaporative dynamics of the strongly bound soil moisture, which requires temperatures well beyond 150 • C to fully evaporate. The model also includes film flow, although this phenomenon did not contribute much to the model's overall performance. In general, the model simulates the laboratoryobserved temperature dynamics quite well, but is less precise (but still good) at capturing the moisture dynamics. The model emulates the observed increase in soil moisture ahead of the drying front and the hiatus in the soil temperature rise during the strongly evaporative stage of drying. It also captures the observed rapid evaporation of soil moisture that occurs at relatively low temperatures (50-90 • C), and can provide quite accurate predictions of the total amount of soil moisture evaporated during the laboratory experiments. The model's solution for water vapor density (and vapor pressure), which can exceed 1 standard atmosphere, cannot be experimentally verified, but they are supported by results from (earlier and very different) models developed for somewhat different purposes and for different porous media. Overall, this non-equilibrium model provides a much more physically realistic simulation over a previous equilibrium model developed for the same purpose. Current model performance strongly suggests that it is now ready for testing under field conditions.

show abstract

Surface diffusion in porous media: A critical review

Cited by 186 publications

References 95 publications

Mathematically modeling fixed-bed adsorption in aqueous systems

Mathematically modeling fixed-bed adsorption in aqueous systems

Adsorption of pyridine from aqueous solutions by polymeric adsorbents MN 200 and MN 500. Part 2: Kinetics and diffusion analysis

A non-equilibrium model for soil heating and moisture transport during extreme surface heating: the soil (heat–moisture–vapor) HMV-Model Version 1

Contact Info

Product

Resources

About