Effects of Mass Action Equilibria on Fixed-Bed Multicomponent Ion-Exchange Dynamics

Abstract

A generalized parallel pore and surface diffusion model and associated dynamic simulation program have been developed for multicomponent fixed-bed ion-exchange processes. Both equilibrium and nonequilibrium mass action laws are used to describe stoichiometric ion exchange. Model equations are solved numerically for frontal, pulse, or sequential loading processes. Analytical solutions obtained from a local equilibrium theory for binary systems and experimental data of two multicomponent systems served as benchmarks for the numerical solutions. The results indicate that the parallel pore and surface diffusion model should be considered for nonlinear large-particle systems. A parametric study shows that a major difference in fixed-bed dynamics between mass action and Langmuir systems lies in the propagation of diffuse waves of multivalent ions. Generally, the higher the valence or mass action equilibrium constant, the more pronounced the tailing of diffuse waves, which results in apparent adsorption hysteresis in a loading and washing cycle. The apparently irreversibly adsorbed multivalent ions can be eluted by concentrated solutions of lower valence ions, as a result of the relative selectivities of the higher valence against lower valence ions decreasing with increasing total solution phase concentration. This can lead to changes from favorable to unfavorable isotherms and self-sharpening waves to diffuse waves, or vice versa. Other results show that elution order can be reversed for heterovalent ions in elution and displacement chromatography.

Modeling of Elution Curves in Preparative Chromatography Using Anion-Exchange Resin for Cobalt Purification

“…Other models [12][13][14][15][17][18][19][20][21][22][23] can calculate the elution curves or the breakthrough curves using practical values, such as the size of the resin bead and the diffusivity of the solute in the resin. In contrast, the model proposed in this paper, based on plate theory in multi-path mode, cannot predict these curves using practical parameters.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23] Most reports focus only on breakthrough curves. However, Ernest et al 12) calculated elution curves containing not only the breakthroughs but also the tailings. In addition, Dorsey et al 24) briefly summarized the modeling of ion-exchange chromatography.…”

State-of-arts in Multiscale Simulation for Process Development

“…(liquid-film mass transfer coefficient, k f )과 입자 내 확산계수(intraparticle diffusivity)으로 구할 수 있다 [65]. 또한, 입자 내 확산계수는 기공확산계수(macrospore diffusivity, D pore )와 흡착제 고체상 확산계 수(solid diffusivity, D solid )로 구분할 수 있다 [66,67]. …”

Modelagem do processo de troca iônica pela Lei da Ação das Massas e redes neurais artificiais

“…O processo de troca iônica é amplamente utilizado no tratamento de efluentes industriais e de usinas nucleares (Ernest et al, 1997), na purificação de fármacos, entre outras aplicações industriais. Materiais porosos (zeólitas ou resinas artificial) são empregados neste tipo de processo.…”

“…A seleção apropriada da isoterma de equilíbrio ou da equação cinética que caracterize a competição entre os íons é uma das etapas críticas que interferem diretamente na qualidade dos resultados da simulação e modelagem de processos de adsorção/troca iônica em colunas de leito fixo (Ernest et al, 1997).…”