Chromatographic performance of macroporous cellulose–tungsten carbide composite beads as anion-exchanger for expanded bed adsorption at high fluid velocity

Macroporous cellulose–tungsten carbide composite beads was designed and prepared as an anion-exchanger for expanded bed adsorption (EBA). The wet density of composite beads was adjusted at the range of 1.2–2.4 g/ml with the control of tungsten carbide addition, and optimized for EBA at high fluid velocity. The results indicated that the wet density of composite beads could increase linearly with the increase of tungsten carbide addition, meanwhile other physical properties, such as size, porosity, specific surface area, mean pore diameter, etc., were hardly or slightly influenced. The composite beads were coupled with diethylaminoethyl (DEAE) as an anion-exchanger for EBA. The expansion characteristics in expanded bed were investigated and sensitively changed as the wet density of composite beads, corresponding to tungsten carbide addition in the preparation. The relation among the operation fluid velocity, the ratio of tungsten carbide to cellulose viscose in the preparation and the expansion factor was found, which could be used to predict the operation velocity of composite beads with varying tungsten carbide addition. The liquid mixing in expanded bed was also tested and showed good bed stability for EBA processes. With the adsorption equilibrium experiments, the saturated adsorption capacity of bovine serum albumin could reach 68.7 mg/g adsorbents (equal to 97.1 mg/ml adsorbents). The ratio of Q10% (the dynamic adsorption at 10% breakthrough) in expanded bed to packed bed could reach more than 90% for the fluid velocity of 500 cm/h, even 77.1% for the fluid velocity as high as 900 cm/h. The chromatographic results demonstrated that the composite beads prepared are suitable for EBA applications at high fluid velocity.