Despite numerous advantages, fluidized bed adsorption is limited in commerc
ial applications due to a poor understanding of the relationships between m
ass transfer, hydrodynamics, and adsorption. To obtain a better understandi
ng of these parameters, we used two commercially available resins to compar
e the adsorption of lysozyme as a function of bed expansion and bulk-phase
viscosity using frontal analysis. Under static conditions adsorption was we
ll represented by a Langmuir isotherm. Dynamic capacities at breakthrough w
ere measured and normalized relative to the equilibrium capacity of each re
sin to facilitate direct comparison of resin performance under each conditi
on. To quantify the impact of resin characteristics in expanded bed adsorpt
ion, we carried out a comparison of mass-transfer effects using a macroporo
us resin, Streamline SP, and a hyper-diffusive resin, S-HyperD LS. Both res
ins are designed for fluidized bed adsorption of proteins. In this study th
e results of frontal analysis showed that breakthrough was due to mass-tran
sfer limitations of the adsorbing particles at expansions of 2 times the se
ttled bed height. At expansions of 3 and 4 times the settled bed height, ax
ial dispersion increased significantly; however mass-transfer limitations w
ere still the dominant mechanistic feature contributing to early breakthrou
gh at reduced dynamic capacity. Adsorption capacity under all conditions in
this study was poorer for the macroporous resin than for the hyper-diffusi
ve resin due to intraparticle mass-transfer limitations.