Determination of diffusivity from mass transfer measurements in a batch dialyzer: numerical analysis of pseudo-steady state approximation

Abstract

The presented paper deals with the numerical analysis of pseudo-steady state conditions used in the modelling of the batch dialysis process. First, under specified conditions, time dependences of component concentrations and liquid volumes in both compartments were generated using a rigorous model based on Fick’s second law. From these data, the diffusion coefficient of the component in the membrane was calculated using a simplified model based on Fick’s first law. The specified coefficient was then compared with the calculated one. Numerical analysis revealed that in case of not too thick membranes, sufficiently high values of the diffusion coefficient, high intensity of mixing and considering the concentration and volume data in compartments I and II, the pseudo-steady state conditions can be considered as a good approximation of the real state.