A detailed study of the production of polysaccharide aerogel (bio-aerogel) particles from lab to pilot scale is surveyed in this article. An introduction to various droplets techniques available in the market is given and compared with the lab scale production of droplets using pipettes and syringes. An overview of the mechanisms of gelation of polysaccharide solutions together with non-solvent induced phase separation option is then discussed in the view of making wet particles. The main steps of particle recovery and solvent exchange are briefly described in order to pass through the final drying process. Various drying processes are overviewed and the importance of supercritical drying is highlighted. In addition, we present the characterization techniques to analyse the morphology and properties of the aerogels. The case studies of bio-aerogel (agar, alginate, cellulose, chitin, κ-carrageenan, pectin and starch) particles are reviewed. Potential applications of polysaccharide aerogel particles are briefly given. Finally, the conclusions summarize the prospects of the potential scale-up methods for producing bio-aerogel particles.

Ambient pressure dried resorcinol–formaldehyde (RF) organic aerogels are usually hard and brittle with Young's moduli in the range of 1–2 MPa, strengths of about 100 kPa and densities in the range of 0.2 to 0.4 g cm⁻³. Modifications of the classical sol–gel synthesis route transform these brittle materials into rubber- or cork-like flexible aerogels. We observed that in a small window of process parameters, the aerogel density decreases by an order of magnitude as well as the Young's moduli and the compression strengths. These new types of RF aerogels are elastically deformable by more than 40% in an almost reversible manner. In this paper we describe the effects of various sol–gel parameters on the flexibility, such as resorcinol to water and catalyst molar ratio and the pH of the initial solution. The aerogels are characterized with respect to the envelope density, stress–strain behavior and microstructure as observed from SEM fractographs. The chemical structure and structural differences arising between brittle and flexible RF aerogels were studied by recording ¹³C-NMR spectra.

This paper describes the synthesis of silica, titania, zirconia and mixed-metal-oxide aerogels by a new facile approach. The corresponding low cost and non-toxic chlorides instead of the well established but more expensive and deleterious alkoxy precursors were used as starting materials. Hydrolysis of the precursors led to wet gels. The strong exothermic reaction in the case of TiCl₄ or SiCl₄ as a gel precursor can be controlled by both cooling and immersing the needle of the syringe in the aqueous solution. Under optimal conditions a rapid formation of silica- and zirconia based hydrogels could be achieved even without additional amounts of an auxiliary agent. It is shown that in all other cases the hydrolysis reaction and gel formation can be controlled by adding agents with crosslinking properties like propylene oxide, dilution with alcohols or starting from water glass. Water glass not only has the function of a cheap network former but also allows the strict adjustment of the pH value via neutralization of the acid forming hydrolysis reactions. Supercritical drying of the wet alkogel in CO₂ delivered aerogels with BET surfaces up to 1390 m² g⁻¹, as determined by nitrogen adsorption measurements. In addition, the characterization includes XRD and SEM. These findings provide new physical insights into the hydrolysis of the gel precursors and lead to a significant reduction in production costs of inorganic aerogels.