Parallel transport of BSA by surface and pore diffusion in strongly basic chitosan

TLDR: In this paper, the parallel transport of a protein by surface and pore diffusion within a highly porous ion exchanger is studied by measuring equilibria and uptake curves for adsorption of bovine serum albumin (BSA) on two different strongly basic chitosan ion exchangers (hard gels): Ch-2503 and ch-2507 at pH 6.9 and 298 K.

Abstract: The parallel transport of a protein by surface and pore diffusion within a highly porous ion exchanger is studied by measuring equilibria and uptake curves for adsorption of bovine serum albumin (BSA) on two different strongly basic chitosan ion exchangers (hard gels): Ch-2503 and Ch-2507 at pH 6.9 and 298 K. Experimenlal equilibrium isotherms are correlated by the Langmuir equation. Intraparticle effective diffusivities of BSA (D eff ) are determined from the homogeneous Fickian diffusion model, increasing with the bulk phase concentration increase of BSA (Co). It suggests the existence of parallel diffusion. The surface diffusivity D s for the parallel diffusion model is determined from the D eff , and D s =0.47X10 -13 m 2 /s (Ch-2507) and 2.4X10 -13 m 2 /s (Ch-2503) were obtained. Pore diffusivities based on the pore diffusion control (D' p ) are obtained by matching the shrinking core model with the experimental uptake curves. D' p decreases with increasing C 0 . Since D' p in Ch-2507 is constant when c 0 ≥1 kg/m 3 , the constant value 2.7X10 -11 m 2 /s is taken as the accurate pore diffusivity (D p ). As D' p in Ch-2503 does not approach a constant value, D p =1.0X10 -11 m 2 /s is determined by matching the parallel diffusion model with the uptake data, and the model calculated using experimental values of D s and D p agrees reasonably well with the uptake data for Ch-2507 and Ch-2503. This theoretical approach may be applied not only for intraparticle diffusion of proteions but any adsorbates in porous materials