Evaluation of new high-density ion exchange adsorbents for expanded bed adsorption chromatography

Abstract

New adsorbents Q HyperZ and CM HyperZ composed of hydrogel-filled porous zirconium oxide particles were evaluated for expanded bed adsorption applications in the present work. The HyperZ adsorbents have wet density of 3.16 g ml −1, particle size of 44.5–100.8 μm and average sphere diameter of 67 μm. The bed expansion as the function of flow velocity and fluid viscosity was measured and correlated with Richardson–Zaki equation. The suitable expansion factor was considered less than 2.5, while the corresponding flow velocity was about 450 cm h −1. Liquid mixing in the bed was determined to evaluate the stability of expanded bed. The Bodenstein numbers tested were higher than 40 and the axial mixing coefficients ( D ax) were between 0.5 and 9.7 × 10 −6 m 2 s −1, which demonstrated that a stable expanded bed could be formed under suitable operation conditions. Bovine serum albumin (BSA) and lysozyme were used as model proteins to estimate the adsorption capacities of Q and CM HyperZ, respectively. The maximum equilibrium adsorption of Q and CM HyperZ could reach 45.7 and 27.2 mg g −1 drained adsorbents, respectively. It was found that yeast cells had little influence on the adsorption capacities of the two adsorbents tested. The dynamic adsorption capacity of BSA at 10% breakthrough with Q HyperZ was 35.9 mg g −1 drained adsorbent at flow velocity of 100 cm h −1 for packed bed adsorption. The values for expanded bed adsorption were 34.4 mg g −1 drained adsorbent at flow velocity of 200 cm h −1, 33.6 mg g −1 drained adsorbent at 300 cm h −1 and 31.7 mg g −1 drained adsorbent 400 cm h −1. The results demonstrated that Q HyperZ and CM HyperZ are suitable for expanded bed adsorption of biomolecules.