Fixed-bed ion exchange columns operating under non-equilibrium conditions: Estimation of mass transfer properties via non-equilibrium modeling

The paper considers a non-equilibrium poroelectroelastic theory of a polymer electrolyte under the conditions of water electrolysis with the purpose of further use for a theoretical description of mass transfer processes in l ayers of a membrane-electrode assembly. Moreover, this paper carries out the review and analysis of the models of electro- chemical and mass-exchange processes in the electrolyzers, and analyzes the problems of their physicochemical description. We make a conclusion about the need to use models of water sorption and scaling of polymer electrolyte and analyze the models of water sorption and swelling of the polymer electrolyte. It is concluded that the existing poroelectroelastic theory is the most suitable for its modification for use in non-equilibrium conditions during elec- trolysis. The basic equation of the balance of pressures of the classical equilibrium poroelectroelastic theory for polymer electrolyte is considered. A modification of the poroelectroelastic theory has been carried out in order to its use in non-equilibrium conditions of water electrolysis for the purpose of further modeling of mass transfer processes. Based on experimental data available in open sources, the paper makes an analysis of the properties and features of elastic forces in the polymer electrolyte, and then refines the dependencies of the elastic forces in the polymer electro- lyte from the swelling and temperature. Taking into account the existing experimental data on the permeability of gases in a polymer electrolyte and the feature of swelling of the polymer electrolyte in a contact with liquid water, parameters of the non-equilibrium poroelectroelastic theory have been obtained for the water electrolysis conditions.

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Application of microimaging to diffusion studies in nanoporous materials

Adsorption ◽

10.1007/s10450-020-00279-4 ◽

2020 ◽

Author(s):

Christian Chmelik ◽

Roger Gläser ◽

Jürgen Haase ◽

Seungtaik Hwang ◽

Jörg Kärger

Keyword(s):

Mass Transfer ◽

Direct Determination ◽

Multicomponent Diffusion ◽

Tracer Diffusion ◽

Interference Microscopy ◽

Direct Access ◽

Mixed Matrix Membranes ◽

Equilibrium Conditions ◽

Ir Microscopy ◽

Non Equilibrium

AbstractMicroimaging on the basis of, respectively, interference microscopy and IR microscopy permit the observation of the distribution of guest molecules in nanoporous solids and their variation with time. Thus attainable knowledge of both concentration gradients and diffusion fluxes provides direct access to the underlying diffusion phenomena. This includes, in particular, the measurement of transport diffusion under transient, i. e. under non-equilibrium conditions, and of self- or tracer diffusion on considering the rate of tracer exchange. Correlating the difference in guest concentration close to the external surface to its equilibrium value with the influx into the nanoporous solid, microimaging does as well allow the direct determination of surface resistances. Examples illustrating the variety of information thus attainable include the comparison of mass transfer under equilibrium and non-equilibrium conditions, single- and multicomponent diffusion and chemical reactions. They, finally, introduce into the potentials of microimaging for an in-depth study of mass transfer in mixed-matrix membranes. This tutorial review may serve as first introduction into the topic. Further references are linked for the interested reader.

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Dynamics of cyclic fixed bed ion exchange with counter-current regeneration: An analysis based on a linear mass transfer model

The Canadian Journal of Chemical Engineering ◽

10.1002/cjce.5450500516 ◽

1972 ◽

Vol 50 (5) ◽

pp. 651-657 ◽

Cited By ~ 3

Author(s):

K. S. Tan ◽

I. H. Spinner

Keyword(s):

Mass Transfer ◽

Ion Exchange ◽

Fixed Bed ◽

Transfer Model ◽

Mass Transfer Model ◽

Linear Mass ◽

Counter Current

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Modelling and simulation of the ion exchange process for Zn2+(aq) removal using zeolite NaY

Research Society and Development ◽

10.33448/rsd-v10i12.20362 ◽

2021 ◽

Vol 10 (12) ◽

pp. e310101220362

Author(s):

Andrezza de Araújo Silva Gallindo ◽

Reinaldo Alves da Silva Junior ◽

Meiry Gláucia Freire Rodrigues ◽

Wagner Brandão Ramos

Keyword(s):

Experimental Data ◽

Mass Transfer ◽

Ion Exchange ◽

Kinetic Modelling ◽

Fixed Bed ◽

Exchange Capacity ◽

Ion Exchange Capacity ◽

Saturation Time ◽

Capital Costs ◽

Film Mass Transfer

The treatment of water contaminated by toxic metals using ion exchange with zeolites is becoming attractive due to its low capital costs and high potential for removal capacity. Mathematical modelling of this process allows for operational control and estimation of the ability to remove these metals. In this work, the kinetic modelling was performed based on finite bath experimental data, with Intraparticle Diffusion (IPD) and External Liquid Film Mass Transfer (MTEF) models. The models Thomas (TH), Yoon-Nelson (YN) and Solid Film Mass Transfer (MTSF) were used to estimate the saturation time, ion exchange capacity and sizing variables of a fixed bed column. For the finite bath system, the results showed that the mass transfer was better represented by the IPD phenomenon. The breakthrough curve obtained by the Aspen Adsorption (MTSF) model presented the best fit, compared with experimental data, with R2≥0.9923. The average ion exchange capacities calculated for MTSF, TH and YN were respectively 2.22, 2.12 and 2.07 meq Zn2+(aq)/ g of zeolite. The model simulated with Aspen Adsorption was also used to analyze the continuous system behaviour, by varying the height of the bed. It was observed that increasing the height, the saturation time and ion exchange capacity also increase, while reducing the height makes axial dispersion the predominant mass transfer phenomenon, which reduces the diffusion of Zn2+(aq) ions.

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