Characterization of protein adsorption by composite silica-polyacrylamide gel anion exchangers .1. Equilibrium and mass transfer in agitated contactors

The uptake of proteins by composite porous silica-polyacrylamide gel ion exchangers known under the trade name HyperD, is investigated. These ion exchangers are found to have an exceptionally high static adsorption capacity, greater than about 200 mg/cm(3), and a rapid uptake kinetics. Being mechanically quite strong, they are suitable for chromatography applications at elevated mobile phase flow-rates. The uptake equilibrium of proteins by these ion exchangers is obtained experimentally and is found to follow the mass action law. Thus, reversible adsorption and desorption of proteins is obtained by varying the solution ionic strength. Batch mass transfer rates in an agitated contactor under favorable uptake conditions are also obtained. The uptake kinetics is controlled by the fluid phase mass transfer resistance for low protein concentrations, and by the intraparticle mass transfer resistance at high protein concentrations. In the latter case, the uptake is quite rapid and nearly complete saturation of particles 49-76 mu m in diameter can be obtained in 5 to 10 min. The parameters of a model describing the batch uptake kinetics in these ion exchangers are obtained by comparing experimental results with model predictions.