Polysaccharide aerogels are typically obtained through a process of hydrogel formation, solvent exchange and supercritical carbon dioxide drying, but freeze-drying may be a simpler and more versatile option
Bio-derived polysaccharide aerogels are highly porous materials fabricated from aqueous gels of a range of natural polysaccharides, such as starch, alginic acid and pectin. These materials have attracted increasing attention due to superior physical properties, which make them potential replacements for a number of petroleum-based products. Their applications range from catalytic supports, drug delivery agents and superinsulation to precursors for mesoporous carbons.
Polysaccharide aerogels are typically obtained through a process of hydrogel formation, solvent exchange and supercritical carbon dioxide drying. This process is long, solvent-intensive, and offers little control over meso- and macro-pore distribution. Work conducted by the University of York has demonstrated a simpler and more versatile alternative may be provided by freeze drying.
Freeze drying offers a number of unique benefits, including close control of process parameters and avoidance of the liquid-vapour interface, which overcomes surface tension issues. It is an accessible and scalable process which also enables recovery and potential reuse of solvents.
Polysaccharide aerogels produced by freeze drying from water tend to be low-density macroporous materials with large pores and very few mesopores. However with the aid of organic solvents, freeze drying was demonstrated to preserve the mesopores. The potential therefore exists to develop an industrial closed-loop process for production of aerogels with controllable meso and macropore structures.
The work at the University of York was carried out on an SP Scientific VirTis BTK freeze dryer.