The kinetics of protein adsorption on porous particles

• Main Author: Ashmead, S. R.
• Published: Swansea University 1999
• Subjects: 572.072
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635802

The major aims of the research are to investigate the diffusional and mass transfer processes governing the adsorption kinetics of proteins and to develop detailed kinetic models for predicting the rate of adsorption of protein on recently developed adsorbents. Two different kinetic models are developed and tested. Firstly, a simple kinetic model that makes use of the diffusion equation and measurements on a 'differential bed'. This model allows the external liquid film and pore diffusion mass transfer coefficients to be estimated by concentration dependence of the overall coefficient. This model is tested for protein by studying the adsorption of bovine serum albumin (BSA) on Whatman cellulose anion exchange medium (DE52). Secondly, a more detailed two step model is developed which considers the polydispersity of the adsorbent and the non-uniformity of pore size. A series of differential equations are solved to produce concentration-time profiles that can be matched to experimental data. The various parameters employed in the model are determined experimentally or estimated from well defined correlations. The effective diffusivity is estimated from the predicted hindered diffusion coefficient, the tortuosity factor, being employed as a fitting parameter. The two-step model is validated by fitting the theoretical curves to experimental concentration-time profiles for both stirred cell and packed bed configurations. The model satisfactorily predicts the sensitivity of the profiles to variation in the number of pore volume groups, number of particle size bands, tortuosity and solute size. Any lack of fit can be explained in terms of the assumptions in the model development. Overall, better results are obtained by treating the effective diffusivity as the fitting parameter than by breaking down further into the hindered diffusion and tortuosity components.