Pore and surface diffusion in multicomponent adsorption and liquid chromatography systems

Chromatography of proteins on charge-variant ion exchangers and implications for optimizing protein uptake rates

“…The transport model can also account directly for the coupling between free and adsorbed protein via the chemical potential in what is sometimes referred to (inaccurately; [10]) as a Maxwell-Stefan formulation [11]. Alternative models include dual transport mechanisms that allow for separate diffusion of bound and unbound protein [12][13][14]. The flexibility afforded by the incorporation of additional parameters can make better fitting of experimental data possible but calls the effectiveness of model discrimination into question.…”

Preliminary Ion Exchange Modeling for Removal of Cesium from Hanford Waste Using Hydrous Crystalline Silicotitanate Material

“…The diffusional rates within each pore distribution could be significantly different. For example, in the larger pores created by the binding material diffusion rates might be larger than the diffusional rates within the smaller pores contained It has been observed by Ma et al (1996) and Robinson et al (1994) that for ion exchange materials with high capacities and affinities for certain ions (who generally have non-linear isotherms), parallel pore and surface diffusion is occurring. Based on equilibrium ion-exchange, Ma et.…”

“…Therefore, Fickian diffusion is acceptable and surface migration is considered to be small (or incorporated into the apparent pore diffusivity coefficient) when compared to pore diffusion. Unfortunately, for high affinity exchangers such as CST, which exhibit nonlinear isotherms, an apparent pore diffusivity coefficient is composition dependent as discussed by Ma et al (1996). As discussed in Chapter 7, in this report we assumed that a cesium composition independent pore diffusivity value can be adequately chosen.…”

Novel Simulated moving bed technologies

“…The resulting ODE's and algebraic equations are solved using an equation solver. The model equations and the numerical solution procedure can be found in the literature (Berninger et al, 1991;Ma et al, 1996). VERSE has been validated with many different systems and processes (e.g., Whitley 1990;Hritzko et al, 2000Hritzko et al, , 2002Xie et al, 2001Xie et al, , 2002.…”