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The kinetics of the adsorption of the protein BSA on the ion exchanger Q‐Sepharose FF were measured for several values of the pH and ionic strength, using several techniques. The measurements were best described with a model incorporating both surface and pore diffusion and with the chemical potential gradient as the driving force for diffusion. The surface‐diffusion coefficients from this model show an inverse exponential dependency on the binding strength. This dependency can be explained by an activated jump mechanism. The pore‐diffusion coefficient is much lower than that in free solution, which is probably caused by a combination of steric and electric exclusion.

The adsorption equilibrium of bovine serum albumin on Q‐sepharose, a strong union exchanger, was studied with batch equilibrium experiments at pH between 4 and 9 and ionic strengths between 5 and 440 mmol/L. Dependence of the adsorption equilibrium on the ionic strength was modeled as an ion exchange reaction. A simplified mechanism of this ion exchange reaction also yielded an expression for the dependence of the equilibrium on the charge of the protein. This model describes the measurements well, using fitted constants with physically realistic values.