A SIMULATION STUDY OF THE ADSORPTION CONCENTRATION POLARIZATION INTERPLAY IN PROTEIN ULTRAFILTRATION

A theoretical approach to study the adsorption-polarisation interplay in ultrafiltration is presented. The model is based on transient mass transfer in the boundary layer, with an appropriate ''source term'' to account for adsorption on the wall boundary of the membrane. The memb rane is assumed to be totally selective and of homogeneous surface por osity. Permeate flux is modelled as J = (DELTAP - DELTAPI)/(R(m) + R(a d)), where both DELTAPI, the osmotic term, and R(ad), the additional r esistance due to adsorption, are time-dependent. This approach is basi cally different from that of the semi-empirical models currently emplo yed. The transient mass transfer equation is solved numerically using a tridiagonal matrix algorithm. The evolution of flux and wall concent ration over time is obtained for selected values of the polarisation a nd adsorption parameters involved, particularly in reference to protei n ultrafiltration. However, the model can also be applied in a more ge neral way. The characteristic trend for the interplay of the two pheno mena, as the simulation results indicate, is for the wall concentratio n to increase initially for a very short time and then decrease toward s a steady-state or quasi-steady-state level in the long term. Prelimi nary experiments carried out yielded results in close agreement with t he model concerning flux as a function of time and steady-state flux a s a function of pressure.