Fabrication by three-phase emulsification of pellicular adsorbents customised for liquid fluidised bed adsorption of bioproducts

A novel dense pellicular adsorbent, custom-designed for liquid fluidised bed adsorption of protein bioproducts, has been fabricated by coating zirconia-silica particles with agarose gel in a three-phase emulsification process. A slurry feedstock comprising solid zirconia-silica particles (120 mum average diameter) suspended in an aqueous solution of agarose was emulsified in an oil-surfactant mixture in a stirred vessel to yield composite droplets. These were subsequently stabilised by cooling to form spherical pellicular particles characterised by a porous, pellicular coat cast upon a solid core. The impact of agitation speed, surfactant concentration, oil viscosity and slurry composition upon the pellicle depth and overall particle diameter was investigated. Pellicle depth decreased with increasing impeller speed and decreased oil viscosity, whilst increased slurry viscosity enhanced that parameter. Initial increases from low concentrations of Span 80 surfactant (0.1% w/v oil) reduced the depth of the agarose pellicle, but the highest values investigated (1.5% w/v oil) promoted particle aggregation. The fluidisation behaviour of particles fabricated under various conditions was characterised by the measurement of expansion coefficients and axial dispersion coefficients for the liquid phase when operated in a standard fluidised bed contactor. Both parameters were found to be comparable or superior to those reported for conventional, composite fluidised bed adsorbents. The controlled coating of porous agarose upon a solid core to yield specific pellicular geometries is discussed in the context of the fabrication of adsorbents customised for the recovery of a variety of bioproducts (macromolecules, nanoparticulates) from complex particulate feedstocks (whole broths, cell disruptates and unclarified bio-extracts). Given the agreement between the size of the pellicular particles and the trends expected from theory, the large-scale manufacture of such particles for customised industrial use is recommended. (C) 2003 Society of Chemical Industry.