EX PERIMENTAL CHARACTERIZATION AND MODELLING OF MEMBRANE CHROMATOGRAPHY
Advancing the chemical engineering fundamentals
Membranes and Membrane Science - II (T2-8b)
Keywords: Membrane chromatography, Breakthrough curve, Langmuir adsorption, Orange G
Membrane chromatography has been studied as an alternative to conventional resin-based column chromatography for the isolation and purification of macromolecules. Membrane chromatography operates in convective mode, which can significantly reduce diffusion and pressure drop limitations commonly encountered in column chromatography. The development of mathematical models to describe membrane chromatography and the use of these models in computer programs to predict membrane performance are an engineering approach that can help to attain these bioprocess engineering tasks successfully.
In this study, a mathematical model has been developed to predict the performance breakthrough curves of these membranes. The model is based on the continuity equation from a mass balance over a section of the membrane and the adsorption mechanism between ligand and solute is described by Langmuir equation. The model depends on five dimensionless variables and permits to simulate the dimensionless solute concentration at the end of the membrane as a function of dimensionless time, which is defined as the ratio between time and process time (the average time taken by a fluid element to pass through the membrane). By one hand, three dimensionless variables are connected to time dependent processes (physical dispersion, Pe, solute–ligand adsorption, Kads, and solute–ligand desorption, r/Kads) and they are defined by the characteristic times of the process (tdisp/tprocess, tads/tprocess and tdes/tprocess, respectively). On the other hand, there are two dimensionless variables related to the adsorbent capacity (actual maximum adsorbent capacity, m, and limit adsorbent capacity, p) and defined by cs_eq_o and cs*.as characteristic concentrations. The parameters of Langmuir equation permit to calculate two dimensionless variables of the model: r and p. The rest of variables have to be determined by means of the adjustment of the calculated values to the experimental results.
Experimental work has been done in order to valid the model using Sartobind Membrane Adsorber. The breakthrough curves of Orange G (C.I.=16230) were obtained at different dye concentrations and ionic strengths. Adsorption isotherms were determined by plotting the adsorbed as a function of feed concentration at three ionic strengths and they were adjusted by Lagmuir equation. It has been observed that the adsorption is affected by the ionic strength. The adsorption capacity of Orange G was reduced by 2.8 folds with increasing the ionic strength from 0.1 to 0.5M.
The experimental and modeling results are in good agreement, although some model predictions differ a little of the experimental data. This could be due to the membrane may have some dead volume which cannot be reached by convective flow and diffusion of the solute become more significant.
See the full pdf manuscript of the abstract.
Presented Wednesday 19, 15:20 to 15:40, in session Membranes and Membrane Science - II (T2-8b).
